Submesoscale dynamics, with horizontal scales of O(1\u201310)~km, are ubiquitous in the surface ocean. Recent observations and simulations reveal enhanced sea surface temperature and velocity gradients at these scales, with sharpened buoyancy fronts attracting particular attention for their potential of energy transfer to link large-scale energy reservoirs to the small scales where dissipation occurs. This thesis addresses the following questions: How do the ocean and atmosphere interact at submesoscale? To what extent can balanced dynamics be applied to interpret submesoscale variability, and, given that, how well do balanced frameworks represent energy transfer at submesoscale fronts?
\r\n\r\nAir--sea interaction has been extensively studied at mesoscale, O(100)~km, but remains less well quantified at submesoscale. Mesoscale sea surface temperature and vorticity imprint their own spatial structure on wind stress gradients through thermal and current feedbacks (TFB and CFB). These feedbacks have typically been assessed separately, with limited attention to their collocation and potential joint impacts. Atmospheric wind stress modifications feed back on the ocean by altering surface vertical transports through Ekman dynamics. In submesoscale-resolving air--sea coupled simulations, examining TFB and CFB jointly reveals their combined influence on surface wind stress. The coupled effect produces anomalous wind stress curls an order of magnitude stronger than those at mesoscale. The resulting nonlinear Ekman velocities from wind stress curl changes reach magnitudes roughly ten times larger than at mesoscale, underscoring the potential importance of submesoscale air--sea coupling for vertical exchange in the surface ocean.
\r\n\r\nThe submesoscale range covers a transition from balanced to unbalanced motion as spatial scales decrease. This transition scale is critical for understanding energy transfers and tracer transport in the upper ocean, yet remains poorly constrained. Because balanced motions evolve on time scales much longer than Earth\u2019s rotation period, the temporal scale of submesoscale motions can indicate their dynamical regime. Spatio-temporal analyses in submesoscale-resolving simulations and surface mooring observations show that flow-following Lagrangian time scale of submesoscale flow is much longer than that registered by a fixed Eulerian observer, placing the transition to unbalanced dynamics at ~1 km, much shorter than suggested by Eulerian diagnostics. This implies that balanced theory remain applicable to submesoscale motions down to O(1)~km.
\r\n\r\nAlthough balanced quasi-geostrophic (QG) and semi-geostrophic (SG) theories reproduce submesoscale frontal development, the associated energy transfers under balanced conditions are less well understood. We derive and assess the full kinetic energy budget in spectral space and in physical space using coarse-graining for an isolated front in QG and SG frameworks. A geostrophic strain field by itself is sufficient to produce forward transfer of kinetic energy in QG frontogenesis. In SG, ageostrophic advection generates a dipole in energy transfer linked to the convergent--divergent surface flow structure, but this balanced ageostrophic circulation is too weak to overcome the dominant forward transfer from the strain field. These results demonstrate that balanced dynamics can generate surface convergence and drive downscale transfers, and that ageostrophic circulation is essential to produce the asymmetry of energy fluxes at submesoscale fronts.
" }, { "name": "Berne, Alexander C.", "degree": "PhD", "year": "2026", "title": "Tidal Dynamics of Laterally Heterogeneous Planetary Bodies", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:08022025-042237605", "creators": [ { "name": { "family": "Berne", "given": "Alexander C." }, "id": "Berne-Alexander-C", "orcid": "0000-0001-7857-8513", "display_name": "Berne, Alexander C." } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Stevenson", "given": "David J." }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David J." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." } ], "option_major": [ "geophys" ], "doi": "10.7907/8b21-dj47", "abstract": "Planetary bodies experience deformation in response to tidal forces from external gravitating objects. Changes to planetary gravity fields produced by this forcing depend on internal rheological structure. For example, a spherically symmetric body's response to tides depends on the presence, thicknesses, and effective shear moduli of internal layers (e.g., the core, an ocean) and follows the spatial pattern of driving gravitational potentials. However, bodies that exhibit substantial deviation from spherical symmetry can exhibit a more complicated response to forcing that includes power both at short (i.e., regional-scale) and long (i.e., global-scale) wavelengths. In this thesis, we explore the impact of lateral heterogeneities in internal rheological structure on the tidal responses of Enceladus, the second major moon of Saturn, and Earth's Moon.
\r\n\r\nWe begin by exploring the impact of faults and lateral variations in ice shell thickness on the long-wavelength gravitational response of Enceladus (Chapter 2). Using finite element models of Enceladus' crust, we demonstrate substantial deviation between the longest-wavelength components of response to tidal forcing (i.e., the diurnal degree-2 Love numbers) and those expected for a spherically symmetric model of Enceladus. We further show that structural heterogeneities predominantly produce deformation over spatial scales similar to the size of these features. Based on this finding, we develop a methodology to precisely characterize regional variations in crustal thickness using local observations of surface strain at Enceladus (Chapter 3). We demonstrate that this strain can be readily inferred using measurements of the motion of the surface over the tidal cycle (e.g., via interferometric synthetic aperture radar or InSAR). We then adapt our finite element models to explore relationships between slip on fault structures over Enceladus' south polar region (i.e., the Tiger Stripes) and geological activity observed for the body (Chapter 4). We find a close correspondence between the double-peaked and asymmetric timing of strike-slip motion and observed diurnal variations in the brightness of a large plume emanating from Encealdus' South Pole. Based on this finding, we suggest that rifts along the Tiger Stripes experience periodic localized extension to modulate cryovolcanic activity. Finally, we use observations of the spherical harmonic degree-3 variability in the lunar gravity field to infer the presence of a 2-3% internal hemispheric, near-to-far- side variation in shear modulus of the Moon's mantle (Chapter 5). We demonstrate that a 100-200K hemispheric difference in mantle temperature can explain this inferred shear modulus structure, and suggest that internal asymmetries may be a remnant of processes which formed surface mare basalts ~4 Gya. Our work demonstrates future potential for the use of tidal tomography to characterize the deep interior structure and geodynamics of planetary bodies throughout the solar system.
" }, { "name": "Bhattacharjee, Surjyendu", "degree": "PhD", "year": "2026", "title": "Aqueous Processes Across the Solar System: Isotopic Insights from Chondrites and Mars", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10102025-183957877", "creators": [ { "name": { "family": "Bhattacharjee", "given": "Surjyendu" }, "id": "Bhattacharjee-Surjyendu", "orcid": "0000-0002-3924-0357", "display_name": "Bhattacharjee, Surjyendu" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/xgd0-jk65", "abstract": "Since the birth of the solar system, volatiles have played a central role in shaping planetary environments and their habitability. They mediated the abiotic production of organic compounds, altered asteroidal bodies, and supplied liquid water and greenhouse gases to terrestrial planets, creating habitable conditions that are seen in the inner solar system. These cumulative processes ultimately set the stage for life\u2019s emergence on Earth. Despite decades of study, fundamental questions remain unresolved: the sources and distribution of volatiles across different reservoirs, their processing in the protoplanetary disk, and their operation on rocky planets. Progress has often been hindered by analytical limitations, necessitating the development of new approaches. This thesis addresses these gaps by investigating the origin and interaction of volatiles with rocks in two distinct solar system environments\u2014prebiotic chemistry in the early solar system and water\u2013rock interactions on early Mars.
\r\n\r\nThe first part focuses on volatile-driven prebiotic chemistry, using oxygen isotope ratios in organic compounds as tracers. In Chapter 2, I employed quantum mechanical calculations to model how organics fractionate oxygen isotopes from different volatile sources (H2O, CO, CO2). These models predict distinct isotopic compositions for organic molecules depending on their source and formation mechanism. In Chapter 3, I developed a novel electrospray ionization Orbitrap mass spectrometry method to quantify oxygen-exchange kinetics between organics and water, constraining rate constants and activation energies. Carboxylic acids were found to exchange isotopes more slowly than other organic classes, making them promising candidates for triple oxygen isotope measurements. In Chapter 4, I applied this novel method to measure the isotopic compositions of select organic acids from a chondritic meteorite. The results revealed distinct formation pathways and fluid sources that contributed to prebiotic chemistry in the early solar system. This represents the first such triple oxygen isotope measurement of meteoritic organics and establishes a new framework for probing their origin.
\r\n\r\nThe second part examines water\u2013rock interactions on Mars and their role in planetary climate and habitability. In Chapter 5, I used quantum mechanical calculations to quantify carbon, oxygen, and magnesium isotope fractionations between hydrous and anhydrous Mg- carbonates and aqueous fluids. These results demonstrate that hydrous and anhydrous carbonates produce distinct Mg isotope signatures, reflecting different reaction pathways. In Chapter 6, I developed a robust in situ ion microprobe protocol for measuring Mg isotope ratios in carbonates, validated by extensive accuracy and precision testing. This method enables direct investigation of water\u2013rock processes in planetary materials. Finally, in Chapter 7, I applied this technique to ALH84001 carbonates\u2014the oldest known Martian carbonates, formed when Mars was potentially habitable. The isotopic data show that the early Martian carbon cycle was modulated by silicate weathering, linking climate regulation to surface\u2013subsurface water cycling. These results indicate that Mars sustained episodic warm and aqueous environments and subsurface niches conducive to prebiotic chemistry far longer than previously thought.
" }, { "name": "Chen, Sihe", "degree": "PhD", "year": "2026", "title": "Polar Vortices and Aerosols in the Solar System", "advisor": "Yung, Yuk L.; Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04062026-211214699", "creators": [ { "name": { "family": "Chen", "given": "Sihe" }, "id": "Chen-Sihe", "orcid": "0000-0002-0901-3428", "display_name": "Chen, Sihe" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "chair", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Li", "given": "Cheng" }, "id": "Li-Cheng", "orcid": "0000-0002-8280-3119", "role": "member", "display_name": "Li, Cheng" } ], "option_major": [ "plansci" ], "doi": "10.7907/pcdd-5y77", "abstract": "Polar vortex is a ubiquitous phenomenon in atmospheres of rotating planets. Formed by the interplay of planetary rotation, radiative forcing, and meridional temperature gradients, these persistent, cyclonically rotating air masses are most pronounced in the stratosphere and troposphere of planets with significant atmospheric circulation. The strength and stability of a polar vortex depend on factors such as planetary obliquity, atmospheric composition, and seasonal variations. The polar vortices have strong implications for planetary habitability: a stable polar vortex can regulate heat distribution and maintain atmospheric stability, while excessive variability can lead to extreme climate shifts.
\r\n\r\nAerosols - suspended particles in a planetary atmosphere -play a crucial role in shaping the dynamics and chemistry of polar vortices. These particles, which can originate from volcanic eruptions, photochemical reactions, or external sources like meteoritic dust, influence radiative transfer and cloud formation. On Earth, stratospheric aerosols, particularly sulfuric acid droplets from volcanic eruptions, can enhance the stability of the polar vortex and contribute to ozone depletion through heterogeneous chemical reactions on their surfaces. Similarly, on Titan, complex organic aerosols accumulate in its polar vortex, forming thick hazes that drive seasonal temperature asymmetries, and the study of them has important implications for the early earth, where the atmosphere was as reducing.
\r\n\r\nChapters 2-4 of this thesis present both experimental and numerical approaches to studying polar vortices, while Chapters 5-6 focus on the development of observational methods for aerosol characterization. Chapters 7-8 investigate the interplay between aerosols and key atmospheric processes, including photochemistry and dynamics.
\r\n\r\nChapter 2 examines the dynamic regimes of polar vortices using a shallow-water system, identifying the conditions under which a Jupiter-like vortex crystal structure emerges, as opposed to the merging vortices observed on Saturn and Titan. Chapter 3 introduces a numerical approach utilizing a Riemann-solver-based cubed-sphere dynamical core, which eliminates the need for polar filters in general circulation models. This method significantly improves polar resolution, enabling a more detailed investigation of polar atmospheric physics.
\r\n\r\nChapter 4 applies a fast Fourier optics method to Pluto, generating synthetic stellar occultation light curves from global climate models. The analysis reveals that aerosol distribution influences the observed light curves, offering insights into Pluto's unobserved terrain. Chapter 5 develops a two-step neural network framework to characterize aerosol properties in satellite-based spectra of Earth's atmosphere, enhancing the accuracy of XCO2 quantification.
\r\n\r\nChapter 6 investigates the previously observed bimodal distribution of Pluto's haze by coupling a photochemistry-microphysics model with the solar insolation cycle. Chapter 7 examines the origin of an exotic form of \"aerosol\" - the plume activity on Enceladus. By coupling dynamical equations governing ice movement due to tidal stresses, water transport within subsurface channels, and vapor dynamics, the model reproduces the observed time variability of Enceladus' plume, supporting the existence of a subsurface ocean beneath its icy shell.
" }, { "name": "Conn, Scott", "degree": "PhD", "year": "2026", "title": "Interactions between Near-Inertial Waves and Ocean Turbulence", "advisor": "Callies, Joern", "url": "https://resolver.caltech.edu/CaltechTHESIS:11252025-215953680", "creators": [ { "name": { "family": "Conn", "given": "Scott" }, "id": "Conn-Scott", "orcid": "0000-0003-1404-0196", "display_name": "Conn, Scott" } ], "advisors": [ { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "advisor", "display_name": "Callies, Joern" } ], "committee": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "chair", "display_name": "Schneider, Tapio" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Thomas", "given": "Leif N." }, "id": "Thomas-L-N", "orcid": "0000-0002-0548-5786", "role": "member", "display_name": "Thomas, Leif N." }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" } ], "option_major": [ "envreng" ], "doi": "10.7907/z5n5-s931", "abstract": "When atmospheric storms sweep across the sea surface they excite near-inertial waves (NIWs) whose frequency sits close to the local Coriolis frequency. By generating shear-driven mixing in the upper ocean, NIWs mediate the storm\u2013ocean coupling and, in turn, influence climate. Oceanographers have long known that the fate of wind-generated NIWs hinges on how they interact with the background circulation -- especially with mesoscale eddies -- but observations show that this interaction ranges from negligible to dominant depending on location. Those regional contrasts matter: eddy-modified NIWs can dramatically reshape the pattern and intensity of mixing. My thesis uses a mix of theory, observations, and numerical modelling to better understand the dynamics that governs NIW-mesoscale interactions.
\r\n\r\nIn trying to understand how NIWs behave in the presence of mesoscale eddies, the work of theoreticians culminated in the YBJ (Young and Ben-Jelloul) equation which describes the evolution of NIWs, including the physics of advection and refraction of NIWs by mesoscale eddies. I test whether this equation, subject to observations of the wind stress, stratification and mesoscale eddy field, can capture the observed dynamics of NIWs. Simulations of the YBJ equation can be compared to observations from a mooring array in the North Atlantic. The simulation reproduces the amplitude, phase, and across-array structure of the waves, and it reveals strong concentration of NIWs in anticyclones. In contrast, the traditional slab model -- lacking mesoscale interaction physics -- performs poorly. Potential energy budget diagnostics further show that, in this region, the net NIW\u2013eddy energy exchange is small compared to other terms in the mesoscale energy budget.
\r\n\r\nGiven the utility of the YBJ equation in understanding observations, I next try to understand theoretically what governs the impact that mesoscale eddies have on NIWs. This analysis heavily leverages the connection between the YBJ equation and the Schr\u00f6dinger equation of quantum mechanics. The key governing parameter in the YBJ equation is the wave dispersiveness which quantifies the ratio of wave dispersion to wave refraction. Analytical calculations of the eigenmodes of the YBJ equation show that strongly dispersive waves are marginally affected by the eddies. However, eddies strongly imprint onto weakly dispersive NIWs. In the weak dispersion limit, the ray-tracing equations emerge from the YBJ equation, resolving some controversies regarding the applicability of ray-tracing to NIWs.
\r\n\r\nFinally, I try to understand how these different regimes may be distributed throughout the ocean. Observations from the Global Drifter Program can be used to calculate NIW spectra. Separating these spectra by vorticity reveals the impact of NIW-mesoscale interactions. NIW frequency shifts correlate strongly with vorticity, signalling weakly dispersive dynamics. Only a patch of the North Pacific shows a muted impact of mesoscale eddies. In high energy regions, such as western boundary currents and the Antarctic Circumpolar Current, NIWs exhibit a net negative frequency shift -- a potential sign of strongly dispersive waves. The true NIW signal is composed of many wave modes, each with a different dispersiveness, and each contributing to the observations. Idealised simulations of the YBJ equation are able to replicate the observed spectra from drifters well. The eigenmode approach is also useful in understanding the underlying physics that results in the observed spectral characteristics. The drifters confirm that trapping in anticyclones is common, but not universal.
" }, { "name": "Davis, M. Ryleigh", "degree": "PhD", "year": "2026", "title": "Spectroscopic Characterization of Icy Moon Surfaces: Compositions, Origins, and Implications from Jupiter to\r\nNeptune", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04262026-213125079", "creators": [ { "name": { "family": "Davis", "given": "M. Ryleigh" }, "id": "Davis-M-Ryleigh", "orcid": "0000-0002-7451-4704", "display_name": "Davis, M. Ryleigh" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "chair", "display_name": "de Kleer, Katherine R." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." } ], "option_major": [ "plansci" ], "doi": "10.7907/605z-1m76", "abstract": "The surfaces of icy satellites preserve a complex record of the processes that shape their formation and evolution, reflecting a combination of endogenic emplacement, exogenic delivery, and irradiation-driven modification. In this thesis, I use multi-wavelength spectroscopy to disentangle these competing processes and assess the extent to which surface compositions can be used to infer interior chemistry and system history across the outer solar system, from Jupiter to Neptune.
\r\n\r\nChapters 2 and 3 focus on Europa, whose surface may provide a window to the subsurface ocean composition, but is strongly altered by irradiation. Using VLT/SINFONI observations, I show that a 2.07 \u03bcm absorption feature on Europa\u2019s trailing hemisphere correlates with irradiation patterns but not with large-scale geology, indicating a predominantly exogenic origin and challenging models that invoke radiolytically altered ocean-derived salts to explain this band. I then use Galileo/NIMS observations of the young Pwyll and Manann\u2019an craters to constrain the equilibrium timescale of Europa\u2019s radiolytic sulfur cycle, finding that hydrated sulfuric acid is depleted in these regions and that equilibrium is reached on timescales \u22732\u20134 Myr\u2014orders of magnitude longer than laboratory estimates.
\r\n\r\nIn Chapter 4, I present near-global ultraviolet\u2013visible spectral mapping of Callisto with HST/STIS. These data reveal absorptions plausibly associated with iron-bearing silicates, organics, and potentially NaCl, and show little evidence for SO2 or other sulfur-bearing species. The spatial distribution of these spectral features reveals significant compositional heterogeneity, including localized features associated with major impact basins, challenging suggestions that Callisto\u2019s dark material is dominated by a thick (\u223c100 m) blanket of irregular satellite dust. Instead, these observations indicate that the dark material reflects a complex mixture of endogenic material excavated by impacts, delivered exogenic material, and radiolytic alteration.
\r\n\r\nIn Chapter 5, I use JWST/NIRSpec observations to show that Neptune\u2019s ring-moons exhibit a 2.72 \u03bcm absorption diagnostic of Mg-phyllosilicates, indicating extensive aqueous alteration within larger precursor bodies. These results suggest that Neptune\u2019s present-day moons are reaccreted fragments of differentiated satellites disrupted during Triton\u2019s capture, providing direct access to deep interior material from icy outer solar system bodies.
" }, { "name": "Deng, Ruolin", "degree": "PhD", "year": "2026", "title": "Tracking Cosmic Dust with Extraterrestrial Helium and Neon in Deep-Sea Sediments", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10142025-190548373", "creators": [ { "name": { "family": "Deng", "given": "Ruolin" }, "id": "Deng-Ruolin", "orcid": "0000-0001-5383-3039", "display_name": "Deng, Ruolin" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Tissot", "given": "Francois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "member", "display_name": "Tissot, Francois L. H." } ], "option_major": [ "geol" ], "doi": "10.7907/51e1-q145", "abstract": "Cosmic dust represents the dominant form of extraterrestrial material currently accreted by Earth, yet many fundamental aspects of its origin, composition, and impact remain poorly constrained. The past cosmic dust flux can be reconstructed by measuring extraterrestrial helium-3 in deep-sea sediments, which is retained in cosmic dust for millions of years, even through diagenetic processes. While cosmic dust flux through most of the times in the last 100 Myr is relatively constant, several short-lived helium-3 enhancement events have been identified and linked to asteroid disruptions in the asteroid belt. The cosmic dust sources of other similar events, however, remain uncertain. Moreover, the mineralogical carrier of solar wind helium and neon in marine sediments is still debated, and the broader influence of cosmic dust on terrestrial systems remains an open question. This thesis addresses these outstanding issues using noble gas geochemistry, trace metal analysis, paleomagnetism, stable isotope geochemistry, and dust dynamics modeling. Chapter II investigates the cosmic dust source and consequences of the K1 helium-3 enhancement event in the Late Cretaceous. Chapter III explores the source of cosmic dust through time, including the potential role of the Moon. Chapter IV evaluates the climatic significance of enhanced cosmic dust flux during the Late Eocene. Together, these studies provide new insight into the source, dynamic evolution, composition, and terrestrial impact of cosmic dust." }, { "name": "Fang, Jiaqi", "degree": "PhD", "year": "2026", "title": "Bridging Length and Time Scales of Plate Motions and Great Earthquakes", "advisor": "Gurnis, Michael C.; Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechTHESIS:04162026-011414705", "creators": [ { "name": { "family": "Fang", "given": "Jiaqi" }, "id": "Fang-Jiaqi", "orcid": "0000-0001-6369-4802", "display_name": "Fang, Jiaqi" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "co-advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" } ], "option_major": [ "geophys" ], "doi": "10.7907/c31c-fg36", "abstract": "Tectonic plates move at a steady velocity of several centimeters per year, which is intermittently interrupted by great megathrust earthquakes with rapid slip up to tens of meters. These large rupture events are driven by the slow tectonic loading and can substantially alter the deformation rate and state of stress in adjacent regions. With advances in computational algorithms, we develop cross-scale finite-element models that self-consistently integrate long-term motion of entire plates and the intervening space-time evolution associated with great earthquakes. The objectives are two-fold: firstly, to gain insight into the occurrence and magnitude of great earthquakes and their relationship with large-scale tectonic processes, and secondly, to constrain rheological properties of the solid Earth with multi-scale geophysical observations.
\r\n\r\nWe begin with formulating a generic subduction model that simultaneously resolves the dynamics of plate motions and megathrust seismic cycles (Chapter 2). Driven by internal buoyancy forces and governed by a nonlinear visco-elasto-plastic rheology, the predicted plate convergence and seismic cycle behavior align with observations in subduction zones. Using an efficient 2.5-dimensional approach, we show that the along-strike resistance arising from slip variations plays a key role in modulating the earthquake magnitude. In Chapter 3, we vary the rupture dimensions, rheological parameters and subduction characteristics to examine their influence on the plate velocity and coseismic slip. In Chapter 4, we build a three-dimensional model tailored to the Chilean Subduction Zone, and reproduce both the long-term motion of the Nazca Plate and post-seismic deformation in the adjacent non-ruptured segment after the 2010 Maule earthquake (Mw = 8.8). Combining these multi-scale geodetic observations as constraints significantly improves the uniqueness of inferred mantle viscosity structure. Following the previous work, we implement a margin-resolving global model of plate motions and earthquakes using the highly scalable finite-element code Rhea (Chapter 5). Constrained by both background plate motions and transient earthquake-related deformations, the model quantifies the sensitivity of different geodetic observations to the rheology of the megathrust, lithosphere and underlying mantle. In Chapter 6, we incorporate a true free surface and link plate motions, surface topography and off-megathrust stress state to Earth's nonlinear rheology within a unified cross-scale model. Our work demonstrates the potential for assimilating multi-scale geophysical observations in unified, physics-based models to better characterize Earth's internal structure and assess seismic hazards.
" }, { "name": "Hern\u00e1ndez-Montenegro, Juan David", "degree": "PhD", "year": "2026", "title": "As on Earth, So on Mars: Magmatic Records of Planetary Evolution", "advisor": "Asimow, Paul David; Bucholz, Claire E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03102026-203347374", "creators": [ { "name": { "family": "Hern\u00e1ndez-Montenegro", "given": "Juan David" }, "id": "Hern\u00e1ndez-Montenegro-Juan-David", "orcid": "0000-0001-7505-4650", "display_name": "Hern\u00e1ndez-Montenegro, Juan David" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "advisor", "display_name": "Asimow, Paul David" }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "advisor", "display_name": "Bucholz, Claire E." } ], "committee": [ { "name": { "family": "Tissot", "given": "Francois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "chair", "display_name": "Tissot, Francois L. H." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geol" ], "doi": "10.7907/p2m8-p097", "abstract": "Magmatic processes play a central role in the thermal, chemical, and hydrologic evolution of rocky planets by linking deep planetary interiors to their crusts and surface environments. This thesis integrates igneous and metamorphic petrology, stable isotope geochemistry, and thermodynamic modeling to investigate how magmatic rocks record the coupled evolution of planetary interiors and surface environments on both Earth and Mars. On Earth, I focus on sediment-derived magmas\u2014strongly peraluminous granites (SPGs) and associated pelitic migmatites\u2014which form by partial melting of metasedimentary crust and preserve geochemical signatures inherited from surface-processed materials. On Mars, I focus on primary and weakly evolved mafic magmas, which provide direct constraints on mantle temperatures, crustal differentiation, and the role of magmatism in sustaining subsurface water.
\r\n\r\nThe first part of the thesis examines how sedimentary signatures are transferred into granitic magmas during crustal anatexis and what these signatures reveal about Earth\u2019s long-term surface evolution. Iron isotope measurements and petrological modeling of the Neoarchean Ghost Lake Batholith show that partial melting largely homogenizes extreme sedimentary isotopic heterogeneity while preserving a resolvable record of bulk source composition, establishing SPGs as robust archives of secular iron isotope evolution in siliciclastic sediments. Building on this framework, triple-oxygen-isotope analyses of garnet in sediment-derived granites and migmatites are used to reconstruct weathering temperatures and meteoric water compositions from the Neoarchean to the Mesozoic, revealing discrete climate regimes linked to atmospheric oxidation, glaciation, and supercontinent cycles and demonstrating that sediment-derived magmas provide a lithology-integrated archive of Earth\u2019s surface environments.
\r\n\r\nThe second part of the thesis addresses how Martian magmatism records the thermal evolution of a stagnant-lid planet and its interaction with the hydrosphere. I introduce PRIMARSMELT, a new petrological modeling tool for reconstructing primary magma compositions and mantle potential temperatures from Martian meteorite and rover data. Application of this approach indicates that Martian mantle temperatures have remained nearly constant\u2014or may have increased\u2014through time, consistent with inefficient heat loss in the absence of plate tectonics. I further show that, although Martian magmas inevitably generate water-rich fluids during differentiation, fluid\u2013rock reactions rapidly seal permeability, implying that any present-day liquid water in the Martian crust must be continuously supplied by active magmatic degassing. Finally, mineral-scale observations from the Perseverance rover in Jezero crater demonstrate that ultramafic cumulates of the S\u00e9\u00edtah formation and basaltic lavas of the M\u00e1az formation formed within the same magmatic system, linking intrusive and extrusive processes and illustrating how crystal accumulation and differentiation generate lithologic diversity in the Martian crust.
\r\n \r\nTogether, these studies show how magmatic processes record the thermal evolution of planetary interiors and mediate their interactions with crustal and hydrologic systems, providing a comparative framework for understanding how rocky planets build crusts, cycle volatiles, and evolve toward\u2014or away from\u2014habitability.
" }, { "name": "Inglis, Julie Alanna", "degree": "PhD", "year": "2026", "title": "The Origins and Properties of Giant Planets on Extreme Orbits", "advisor": "Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09182025-175250684", "creators": [ { "name": { "family": "Inglis", "given": "Julie Alanna" }, "id": "Inglis-Julie-Alanna", "orcid": "0000-0001-9164-7966", "display_name": "Inglis, Julie Alanna" } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "chair", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Howard", "given": "Andrew W." }, "id": "Howard-Andrew-W", "orcid": "0000-0001-8638-0320", "role": "member", "display_name": "Howard, Andrew W." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." } ], "option_major": [ "plansci" ], "doi": "10.7907/wtg4-1c76", "abstract": "Over the past three decades we have discovered thousands of exoplanets orbiting nearby stars, greatly expanding our understanding of the galactic planet population. Most of these exoplanetary systems have properties that are markedly different from those of our own solar system. Some systems contain gas giant planets with masses comparable to or even larger than that of Jupiter orbiting only a few stellar radii from the surfaces of their host stars. In other systems, gas giants have been discovered with orbital separations more than 100 times the Earth-Sun distance. Both of these populations challenge our understanding of gas giant planet formation, and it has been suggested that they might have initially formed at intermediate orbital separations and then migrated to their present-day locations.
\r\n \r\nIn this thesis, I combine multiple observational techniques to characterize the properties of giant planets on extreme orbits in order to constrain their formation and migration histories. In Chapter 1, I fit both low- and high-resolution infrared spectra of the massive, widely separated, planetary-mass companion ROXs 42B b in order to measure the elemental abundances of carbon and oxygen in its atmosphere. In Chapter 2, I use two decades of astrometric monitoring to measure the mutual inclination between the orbital plane of ROXs 42B b and that of its host binary. In Chapter 3, I demonstrate how mid-infrared emission spectroscopy with JWST/MIRI LRS can be used to characterize the properties of both clouds and gas-phase absorbers in the atmosphere of HD 189733 b, a hot gas giant on a close-in orbit. In Chapter 4, I present a preliminary analysis of new high-resolution optical spectroscopy of the second hottest transiting planet currently known, TOI-2109 b. I use these optical high-resolution spectra to detect the presence of Fe, Mg, and Ti in this planet's atmosphere, and discuss how the relative abundances of refractory and volatile species can be used to constrain the solid-to-gas ratio of materials incorporated into the planet's envelope. In the conclusion, I discuss how the complementary techniques utilized in this thesis can be combined to develop a holistic view of the properties of gas giant planets on extreme orbits, which in turn allows us to test competing models for their origin.
" }, { "name": "Kalucha, Hemani", "degree": "PhD", "year": "2026", "title": "Geochemistry of Mars and Implications for Organic Carbon Preservation - Observations from Rover Data and Terrestrial Analogs", "advisor": "Fischer, Woodward W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08042025-230640580", "creators": [ { "name": { "family": "Kalucha", "given": "Hemani" }, "id": "Kalucha-Hemani", "orcid": "0009-0002-5953-3250", "display_name": "Kalucha, Hemani" } ], "advisors": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "advisor", "display_name": "Fischer, Woodward W." } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Ingalls", "given": "Miquela" }, "id": "Ingalls-Miquela", "orcid": "0000-0002-7451-2944", "role": "member", "display_name": "Ingalls, Miquela" } ], "option_major": [ "geobiol" ], "doi": "10.7907/w3ar-nz90", "abstract": "Curiosity and Perseverance rovers have been exploring ancient river and lake deposits in Gale Crater and Jezero Crater, Mars since 2012 and 2021, respectively. Understanding the geochemistry of these environments at small scales is key to assembling a thorough picture of the habitability of Mars through time. In Chapter 2, I proposed that the formation of certain sulfate minerals in Gale Crater is the result of pyrite oxidation as opposed to evaporation of lake water. This has significant implications for the ancient environment of Gale Crater since these deposits do not represent eras of the ancient lake drying out but rather extended continuity and stability of the aqueous system, which shows greater promise for habitability. Chapters 3-5 studied terrestrial analog sites for geochemical and textural characteristics of rock packages in Jezero crater in order to assess their biosignature preservation potential in the form of organic carbon. In the hyper arid river deposits of the Amargosa River in Death Valley, California, organic carbon persisted in fluvial deposits at low abundance despite oxidizing conditions and saturated sediments, and suggested that ancient river deposits on Mars may retain traces of organics in fine\u2010grained deposits if they are present during deposition. Comparing concretions found in the lake deposits of Jezero Crater to terrestrial concretions of similar mineralogy and formation mechanism, all three sites of terrestrial concretions contained significant concentrations of organic carbon (up to ~2 wt.%), which suggested that concretions at Jezero Crater reflect local sites of enhanced biosignature preservation potential. In the hypersaline sulfate and carbonate rich deposits of lakes in British Columbia, Canada, organic carbon is correlated with abundance of salt minerals specifically. The samples with the highest organic C content (up to ~23 wt. %) also have high salt content (up to ~75 wt. %). This designates hypersaline lakes as key preservers of organic carbon and salts as the highest priority mineral target for finding organic carbon on Mars. In summary, this PhD demonstrates that detailed analysis of the mineral deposits on Mars at the centimeter to micrometer scale reveal early Mars to be a highly habitable planet." }, { "name": "Kanine, Oak Arden", "degree": "PhD", "year": "2026", "title": "A Tale of Two Craters: Reconstructing Mars Paleoenvironment Using Orbital and Rover Data at Endeavour and Jezero", "advisor": "Ehlmann, Bethany L.; Lamb, Michael P.; Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10082025-035835147", "creators": [ { "name": { "family": "Kanine", "given": "Oak Arden" }, "id": "Kanine-Oak-Arden", "orcid": "0000-0002-9204-6107", "display_name": "Kanine, Oak Arden" } ], "advisors": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "co-advisor", "display_name": "Lamb, Michael P." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "co-advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "member", "display_name": "de Kleer, Katherine R." } ], "option_major": [ "gps", "geol" ], "doi": "10.7907/dry1-3w54", "abstract": "Understanding the evolution of planetary climates and corresponding changes to planetary surfaces involves the study of terrains of various ages and morphologies. Here, I study Endeavour and Jezero, two craters within the martian Noachian Highlands. I use multiple approaches \u2014 including sedimentology, stratigraphy, geomorphology, numerical modeling, and the quantitative study of geologic structures in 3D \u2014 and a combination of orbital images from satellites and on-the-ground or in-situ images from rover-based instruments to conduct detailed and ground-truthed studies at both craters. At each site, I characterize the role of water in shaping the surface and thus constrain the climate of ancient Mars. Also presented in this work is a methodological approach to optimize the usage of rover and orbital images for three-dimensional orientation of geologic structures.
\r\n\r\nIn Chapter 2, I find that rockfall is a potential source of erosion on Endeavour\u2019s crater rim. Repeated events of large clasts bouncing downslope and eroding bedrock could have generated incised landforms in the absence of flowing liquid water. Boulder deposits atop other crater-infilling units indicate the process of rockfall continued during or after the Noachian-Hesperian boundary (~2.5-2.7 Ga), potentially continuing to shape the crater rim morphology after regional surface desiccation. In contrast, the Jezero crater strata at Kodiak butte discussed in Chapter 3 are interpreted as either preserved fluvial bars in a braided river or mouth bars in a shallow lake, indicating water was abundant in the crater. Gravel- sized grains were transported by energetic flows, with minimal quiescent settling of fine-grained sediment. Deposits of such settings may have a lower biosignature preservation potential than those of Gilbert deltas, the previous depositional hypothesis. In Chapter 4, I performed traces of beds of the Jezero delta-fan structure in HiRISE and then used apparent dips of a given feature seen from multiple perspectives in rover images to estimate true surface orientations. I confirmed that the orientations of scarps, beds, or other quasi-planar surfaces measured from the highest-available resolution orbital datasets are accurate. However, it is challenging to distinguish hierarchical stratigraphic elements from each other and from erosional surfaces using orbital data, and therefore rover data adds key context for depositional interpretations that inform paleoenviroment. In particular, bedform internal structures could only be determined from rover datasets. In all, through a synthesis of methodological approaches and datasets, I find that the two studied craters potentially record disparate predominant morphology-shaping forces \u2014 dry rockfall in Endeavour, and fluvio-lacustrine activity at Jezero. These sites provide spatial and temporal snapshots of past surface conditions on Mars that can be used to build a more complete narrative of the planet\u2019s history.
" }, { "name": "Liu, Yuan-Kai", "degree": "PhD", "year": "2026", "title": "Space Geodetic Constraints on Plate Motion, Fault Creep, and Megathrust Coupling", "advisor": "Simons, Mark; Ross, Zachary E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12112025-041348554", "creators": [ { "name": { "family": "Liu", "given": "Yuan-Kai" }, "id": "Liu-Yuan-Kai", "orcid": "0000-0003-4032-9444", "display_name": "Liu, Yuan-Kai" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "advisor", "display_name": "Simons, Mark" }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-3213-9643", "role": "co-advisor", "display_name": "Ross, Zachary E." } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" } ], "option_major": [ "geophys" ], "doi": "10.7907/d6e6-q845", "abstract": "Earthquakes release centuries of accumulated elastic strain in seconds, yet where and how this strain builds up across fault systems remain only partly understood. The contrast between seismogenic asperities\u2014regions that lock and rupture in earthquakes\u2014and aseismic barriers that creep or remain stable defines the scale, frequency, and segmentation of major ruptures. Constraining the spatial extent and temporal persistence of these regions requires geodetic observations that resolve deformation from local fault zones to plate-wide strain fields.
\r\n\r\nIn this thesis, I use spaceborne geodesy, specifically Interferometric Synthetic Aperture Radar (InSAR), to complement sparse Global Navigation Satellite System (GNSS) networks in quantifying crustal deformation and inferring tectonic processes across a continuum of spatial and temporal scales. We strive to understand how strain accumulates, transfers, and is released along major plate boundary systems within a probabilistic framework that explicitly incorporates uncertainty and prior assumptions.
\r\n\r\nI begin with the central San Andreas Fault (Chapter 1), where locked, transitional, and creeping segments coexist within a narrow zone of complex mechanical interaction. By jointly analyzing geodetic coupling and seismicity, I find that the fraction of background earthquakes scales with the aseismic slip rate normalized by the plate rate, suggesting a phenomenological link between fault coupling and micro-earthquake clustering.
\r\n\r\nI then address a broader methodological challenge in InSAR geodesy\u2014the treatment of reference-frame motion and its influence on long-wavelength deformation gradients (Chapter 2). After applying refined tropospheric and ionospheric corrections and inversion of large-scale InSAR velocity fields, I show that the absolute Euler rotation of a tectonic plate can be directly estimated from InSAR data, offering an independent constraint on plate kinematics. This capability extends InSAR beyond local fault studies, enabling continental and even global mapping of tectonic deformation, which is a prospect that becomes increasingly viable with the advent of modern L-band radar missions capable of penetrating vegetation and maintaining coherence over wide spatial and temporal baselines.
\r\n\r\nNext, I examine the southern Dead Sea Transform and Gulf of Aqaba, where the Arabian and Nubian plates undergo transtensional motion as the transform transitions into the Red Sea rift (Chapter 3). By compiling a decade of Sentinel-1 data, I map along-strike variations in fault coupling and localized extension toward the rift triple junction, delineating the gradual shift from strike-slip shear to crustal rifting.
\r\n\r\nFinally, I combine InSAR and GNSS time series to construct a spatially continuous model of interseismic coupling along the Nazca-South America margin (Chapter 4). The results reveal strong spatial correlations between heterogeneity in fault coupling and subducted bathymetric highs, underscoring the mechanical role of subducted topography in segmenting megathrust behavior and strain accumulation.
\r\n\r\nThrough these studies, I demonstrate how integrating long-wavelength geodetic imaging allows one to map crustal deformation continuously from fault to plate scales with quantified confidence, while explicitly identifying regions where the data remain uninformative or ambiguous. In doing so, we aim to bridge observation and theory to connect the patterns we see from orbit to the physics that govern the accumulation of strain and seismic release of elastic strain within the Earth\u2019s dynamic lithosphere.
" }, { "name": "Marlin, Theresa", "degree": "PhD", "year": "2026", "title": "From Ocean Floor to Stratosphere: Investigating Astrobiologically Relevant Processes and Molecules on Solar System Bodies", "advisor": "de Kleer, Katherine R.; Cable, Morgan L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05242026-035435474", "creators": [ { "name": { "family": "Marlin", "given": "Theresa" }, "id": "Marlin-Theresa", "orcid": "0009-0003-0670-5474", "display_name": "Marlin, Theresa" } ], "advisors": [ { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "advisor", "display_name": "de Kleer, Katherine R." }, { "name": { "family": "Cable", "given": "Morgan L." }, "id": "Cable-Morgan-Leigh", "orcid": "0000-0002-3680-302X", "role": "co-advisor", "display_name": "Cable, Morgan L." } ], "committee": [ { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "chair", "display_name": "Newman, Dianne K." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "member", "display_name": "de Kleer, Katherine R." }, { "name": { "family": "Cable", "given": "Morgan L." }, "id": "Cable-Morgan-Leigh", "orcid": "0000-0002-3680-302X", "role": "member", "display_name": "Cable, Morgan L." } ], "option_major": [ "geobiol" ], "doi": "10.7907/dcap-p838", "abstract": "In astrobiology, the quest to understand the origin of life on Earth is often paired with an outward focus on whether life can be found elsewhere in the universe. The most accessible corner of the universe in which to search for extraterrestrial life is our own Solar System \u2014- the planets, their satellites, and the minor bodies present throughout. An examination of the essential elements for life on Earth returns three critical factors: liquid water, complex chemistry, and a source of energy. Searching for these three elements in bodies beyond Earth returns a suite of candidates: the ocean worlds of the outer Solar System. These moons, while too cold to harbor liquid water on their surfaces, are thought to have subsurface liquid water reservoirs which could potentially harbor life. Of particular note are two Saturnian satellites: Enceladus, with predicted hydrothermal activity and water-rock interactions, and\r\nTitan, with a dense atmosphere filled with complex organics with potential prebiotic significance. This thesis broadly addresses astrobiological questions on Earth, Enceladus, and Titan via laboratory chemistry and observational astronomy.
\r\n\r\n(I): Chemical gardens as analogs for hydrothermal vents on ocean worlds. This chapter probes laboratory-synthesized analogs of hydrothermal vents as reaction catalysts with alpha keto acids as reactants under various conditions. NMR spectroscopy results support the formation of prebiotically-relevant molecules including glycine (an amino acid) and maloyl formate (a precursor to alpha keto glutarate (AKG)).
\r\n\r\n(II): Propyne: determination of physical properties and unit cell parameters under Titan-relevant conditions. Many questions remain about the organic species that are photochemically produced in Titan\u2019s atmosphere. Propyne (CH3CCH) has been detected in gas phase and is a candidate for Titan\u2019s mixed-species ice clouds. This work presents a characterization of solid propyne using Raman spectroscopy, infrared spectroscopy, and X-ray diffraction.
\r\n\r\n(III):Zonal winds in Titan\u2019s middle atmosphere from a stellar occultation observed with Keck adaptive optics. Winds in Titan\u2019s atmosphere vary seasonally, and stellar occultations present a unique chance to probe them. This work presents spatially-resolved images of the refracted \u201clightspots\" visible around Titan\u2019s limb during an occultation, and discusses the zonal wind profile which best matches the observed data.
" }, { "name": "Milby, Zachariah", "degree": "PhD", "year": "2026", "title": "The Optical Aurora of Jupiter's Galilean Satellites; or, What They Do in the Shadows", "advisor": "de Kleer, Katherine R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05152026-163508815", "creators": [ { "name": { "family": "Milby", "given": "Zachariah" }, "id": "Milby-Zachariah", "orcid": "0000-0001-5683-0095", "display_name": "Milby, Zachariah" } ], "advisors": [ { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "advisor", "display_name": "de Kleer, Katherine R." } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "member", "display_name": "de Kleer, Katherine R." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/8ymw-rj97", "abstract": "When electrons from Jupiter's rapidly rotating magnetosphere collide with the thin atmospheres of the Galilean satellite\u2014Io, Europa, Ganymede and Callisto\u2014they create faint auroras like Earth's northern and southern lights. However, reflected sunlight from their icy surfaces overwhelms these faint auroral emissions at visible wavelengths. Fortunately, the satellites transit Jupiter's large shadow once per synodic orbit. When Jupiter is near elongation, we can view these transits from Earth and observe the satellites' faint auroral emissions in the absence of reflected sunlight. Over the past five years, we have used the High Resolution Echelle Spectrometer (HIRES) on the Keck I telescope at the summit of Maunakea to observe the optical wavelength auroras of these four satellites during the eclipse phase of their orbits. My analysis of the auroras and the modulation of their brightnesses over five- to ten-minute timescales has provided new insight into the composition and density of their atmospheres and how they interact with the local plasma environment.
\r\n\r\n\r\nAt Io, I found 13 auroral emissions not previously detected. I compared these detections to optical wavelength images taken through a variety of narrowband filters during the Cassini flyby to understand the morphology of the different auroral emissions. Using an auroral emission model, I showed that the oxygen emissions were consistent with electron impact on an atmosphere composed of O, SO and SO\u2082, disagreeing with prior studies which posited the oxygen emissions came from electron impact on its extended atomic oxygen corona. The brightest oxygen emissions did not vary with ambient upstream electron density, suggesting the electron flux into Io's atmosphere is more complex.
\r\n\r\n\r\nAt Europa, the oxygen emissions varied systematically with the upstream electron density, indicating a simpler electron precipitation process than that at Io. This allowed me to use the variability in the auroral emissions as a proxy to understand variability in Europa's plasma environment. I evaluated how the brightnesses changed on short timescales during single eclipses as well as systematically on longer timescales over the four years we made the observations. I validated the results by comparing to in situ measurements taken during the Galileo mission. I also considered the timescale under which a sublimated water atmosphere would need to freeze back onto the surface as Europa passed into Jupiter's shadow.
\r\n\r\n\r\nAt Ganymede, I showed the brightness had a hemispheric asymmetry that correlated with the geometry between the satellite and the centrifugal equator of Jupiter's magnetosphere. The brightness ratio between the northern and southern hemispheres suggested that its auroras are triggered by the bounce motion of electrons along Jovian magnetic field lines rather than by ram flux from the upstream plasma population. I compared the results to model simulations of Ganymede's O\u2082 and H\u2082O atmospheres at different times during the eclipse to understand the detectability of a sublimated water atmosphere which, like with Europa, would need to collapse rapidly at the onset of the eclipse.
\r\n\r\n\r\nFinally, at Callisto, detections of auroral emission have been challenging because of the very low magnetospheric electron densities at its orbital distance from Jupiter. However, through careful data processing I was able to retrieve brightnesses of the 630.0 nm [O I] emission from individual spectra, allowing for the first time-series analysis of Callisto's aurora. Like Europa, I found the brightness modulated with distance from the centrifugal equator as expected for excitation by the upstream ram electron flux. This indicated the absence of a substantial ionosphere and supported the paradigm that the ionosphere exists only over the trailing hemisphere when it is illuminated by sunlight. I did not detect enough emission lines to perform the atmospheric compositional analysis I did with the other satellites, but I forward-modeled the expected brightness of the O, O\u2082, H\u2082O and CO\u2082 atmospheres inferred or measured by other studies and found agreement with the aurora brightnesses and upper limits I observed with HIRES.
" }, { "name": "Rautela, Ojashvi", "degree": "PhD", "year": "2026", "title": "Thermo-Mechanical Properties of Earth\u2019s Crust and Mantle: From Surface Deformation to Lower Mantle Structures in the Present Day and the Geological Past", "advisor": "Avouac, Jean-Philippe; Jackson, Jennifer M.; Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09252025-124335004", "creators": [ { "name": { "family": "Rautela", "given": "Ojashvi" }, "id": "Rautela-Ojashvi", "orcid": "0000-0002-9567-8978", "display_name": "Rautela, Ojashvi" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "advisor", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "co-advisor", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "co-advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "chair", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." } ], "option_major": [ "geophys" ], "doi": "10.7907/gc13-j049", "abstract": "This thesis comprises three distinct studies, each drawing on multiple, diverse datasets and modeling approaches to investigate the thermo-mechanical behavior of Earth's crust and mantle in different tectonic regimes.
\r\n\r\nThe first study addresses the longstanding debate regarding the stratified rheological structure of the Tibetan lithosphere using constraints from postseismic deformation and climate-driven hydrological loading at a range of timescales. By leveraging multiple geodetic datasets and geological records of time-dependent surface deformation, with a focus on the postseismic deformation following the 2021 Mw 7.4 Maduo earthquake, this study proposes a regional model that can explain observations across spatial and temporal scales more consistently. Our results reveal a low-viscosity zone in the middle crust of Tibet (20\u201340 km depth), consistent with many previous studies. However, the viscosity we infer for this layer is sufficiently high to imply strong mechanical coupling between the upper and lower crust (or the under-thrusting Indian lithosphere).
\r\n\r\nThe second study assesses the role of hydrous material in seismic detectability of slabs in Earth's lower mantle from a mineral physics perspective. It highlights the need to consider both temperature and composition when interpreting seismic observations for identifying structures, such as paleoslabs. Recent experiments show that hydrous phases (e.g., δ-Fe13 and (Al,Fe)-phase H) can coexist with basaltic assemblages under lower mantle conditions, and can thus alter the aggregate properties of slab material. Using mineral physics modeling, which incorporates new experimental data for these hydrous phases, this study examines the thermo-elastic and geophysical properties of lower mantle petrologies, including hydrous slabs, in the context of recent observations of seismic scatterers and reflectors, geodynamical constraints, and global tomography. Most prominently, it shows that hydrous phases can render cold subducted slabs seismically \u201cinvisible\u201d, challenging the common assumption that slabs are distinctly faster than the ambient mantle at all mantle depths.
\r\n\r\nThe third study investigates the vertical motions of the Pacific seafloor in the Cretaceous using a newly developed Bayesian inversion method (InvoPlates) that constrains mantle thermal anomalies using lithosphere subsidence records over millions of years, present-day bathymetry, and paleo-carbonate compensation depths (CCD). The west-central Pacific\u2019s anomalously shallow bathymetry (\u201cPacific Superswell\u201d) and anomalous subsidence of atolls and guyots have been attributed to the \"Darwin Rise\", postulated to be a large superswell in the Cretaceous. This study constrains the spatio-temporal aspects of the Darwin Rise, which shows close correlation with the Ontong-Java Plateau formation, while de-tangling intrinsic plate cooling from lithosphere re-heating. It also challenges the traditional paleo-CCD reconstructions which link temporal CCD changes solely to changing ocean chemistry, key in models of long-term global carbon cycle, without considering time-varying plate-age independent vertical motions of the seafloor.
" }, { "name": "Wilner, Oliver David", "degree": "PhD", "year": "2026", "title": "Fluorinated Granitic Magmas: A Comprehensive Geochemical Study", "advisor": "Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:04142026-160416584", "creators": [ { "name": { "family": "Wilner", "given": "Oliver David" }, "id": "Wilner-Oliver-David", "orcid": "0000-0002-8172-4347", "display_name": "Wilner, Oliver David" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "chair", "display_name": "Bucholz, Claire E." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Goddard", "given": "William A., III" }, "id": "Goddard-W-A-III", "orcid": "0000-0003-0097-5716", "role": "member", "display_name": "Goddard, William A., III" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geol" ], "doi": "10.7907/pq7f-ad63", "abstract": "Fluorine, a highly reactive halogen, is understood to be responsible for the unusual behavior of elements in silicic magmas. Rare metals, including economically critical elements like Nb, Ta, and rare-earth elements (REEs), in particular deviate from their expected geochemistry in fluorinated systems, leading to a need to understand fluorine in granitic melts. The thesis presents many avenues of exploration into the interaction of F and the major, minor, and trace element geochemistry and mineralogy of granites. The first part of this work details a method to measure trace elements, including F, by pressing finely-ground powders into a cellulose-bound pellet, then analyzing by x-ray fluorescence (for F) and laser- ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS). This method overcomes previous in-house shortcomings by obviating the need to dissolve samples in strong acids, decreasing the dilution effects of fluxing, and removing the possibility of F volitization during high-temperature fusion. The second part presents studies of real granites, including the results of a global literature review of reported halogens in granitoids around the world, and a focused discussion of two specific rare-metal plutons from the Eastern Desert of Egypt. One of these, Abu Dabbab, is a world-class deposit of Ta, and is interpreted to be an isolated magmatic system that self-metasomatized. The other, Abu Rusheid, is highly enriched in U and REEs, and appears that the mineralization of this pluton occurred over an extended period of time as an open magmatic system. The final part of the thesis similarly presents a compilation and novel study of computational, molecular dynamics simulations of fluorinated magmas. The observed preferred F speciations (Al and Si) are not thermodynamically ideal, as the species are not charge neutral, but may be made into a neutral species as AlOF. The F-high field strength species are longer lived, but less common, which F-alkali species are abundant and short- lived." }, { "name": "Yu, Hongmin", "degree": "PhD", "year": "2026", "title": "Exploring Atmospheric Autoxidation of Organic Emission from Volatile Chemical Products", "advisor": "Wennberg, Paul O.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05182026-174822713", "creators": [ { "name": { "family": "Yu", "given": "Hongmin" }, "id": "Yu-Hongmin", "orcid": "0000-0001-5099-3950", "display_name": "Yu, Hongmin" } ], "advisors": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "advisor", "display_name": "Wennberg, Paul O." } ], "committee": [ { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "orcid": "0000-0001-5690-770X", "role": "chair", "display_name": "Flagan, Richard C." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "orcid": "0000-0001-6874-1137", "role": "member", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Kroll", "given": "Jesse H." }, "id": "Kroll-Jesse-H", "orcid": "0000-0002-6275-521X", "role": "member", "display_name": "Kroll, Jesse H." } ], "option_major": [ "envreng" ], "doi": "10.7907/gpy6-5p94", "abstract": "The atmospheric chemistry of organic peroxy radicals (RO\u2082), which are formed by the gas-phase oxidation of volatile organic compounds (VOCs), governs the chemical fate of VOCs in Earth\u2019s atmosphere. Upon formation, RO\u2082 react through bimolecular or unimolecular pathways to produce functionalized closed-shell products with lower volatility, which can partition into condensed phase and contribute to formation of secondary organic aerosol (SOA). While the major RO\u2082 bimolecular reactions (e.g. RO\u2082 + NO, RO\u2082 + HO\u2082) are well-known, the importance of RO\u2082 unimolecular chemistry, such as gas-phase autoxidation, is recognized more recently. Gas-phase autoxidation chemistry, which is initiated by a RO\u2082 intramolecular H-shift reaction, transforms VOCs into highly oxygenated organic molecules (HOMs) that are important SOA precursors. In this thesis, I investigate the atmospheric autoxidation chemistry of several classes of VOCs used as solvents or effective ingredients in consumer and industrial products - also known as volatile chemical products (VCPs) - which represents an emerging source of urban anthropogenic VOCs. Four simple molecules were selected as proxies from various VCP classes to probe the autoxidation chemistry of these compound classes (diethyl ether from simple ethers, 2-ethoxyethanol from glycol ethers, 1,2-diethoxyethane from diethers, and ethyl propionate from esters). Gas-phase oxidation experiments, together with computational analyses, were conducted to examine the H-shift reactions of RO\u2082 derived from those systems and evaluate how specific functional groups influence RO\u2082 H-shift rate coefficients. While H-shift processes in ether, glycol ether, and diether-derived RO\u2082 are accelerated and can compete with their bimolecular reactions with NOx species under modern urban atmospheric conditions, ester functionalities are found to suppress autoxidation chemistry and formation of HOMs. Overall, this work provides mechanistic insights into the ways in which functional groups modulate RO\u2082 autoxidation pathways and production of HOMs, thereby improving understanding of how VCP emissions may contribute to urban SOA formation." }, { "name": "Atterholt, James William", "degree": "PhD", "year": "2025", "title": "Fault Zone Structure and Rupture Behavior with Fiber-Optic Sensing and Second Moments", "advisor": "Zhan, Zhongwen; Ross, Zachary", "url": "https://resolver.caltech.edu/CaltechTHESIS:07232024-193557367", "creators": [ { "name": { "family": "Atterholt", "given": "James William" }, "id": "Atterholt-James-William", "orcid": "0000-0003-1603-5518", "display_name": "Atterholt, James William" } ], "advisors": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "advisor", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Ross", "given": "Zachary" }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "co-advisor", "display_name": "Ross, Zachary" } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/29nc-rd93", "abstract": "The structure of fault zones and the behavior of ruptures are indivisible. Fault structure is molded by the continued overprinting of slip events, and rupture propagation is highly sensitive to fault zone parameters. Observational constraints on both fault zone characteristics and the behavioral response of ruptures to fault variability are thus needed to understand earthquakes. Fault zones are narrow structures that are difficult to image in detail, particularly at depth. This means that fault structure is often oversimplified in rupture models and inversions. Earthquake source descriptions are frequently high dimensional. Fault slip distributions are often complicated and nonunique and seismicity catalogs can contain hundreds of thousands of events. This complexity can be difficult to reduce for the purpose of making clear conclusions on earthquake phenomenology. In this sense, observations of fault structure may benefit from a dimensionality expansion and observations of earthquakes may benefit from a dimensionality reduction. In Chapters 2-5 of this thesis I address the former problem. I show how an emergent technology, distributed acoustic sensing (DAS), that transforms fiber optic cables into dense arrays of strainmeters can be used to resolve fault zone characteristics with astonishing detail. This applies to small and large faults at shallow and deep depths. I define a framework for partitioning the seismic wavefield and show that scattered phases in earthquake wavefields encode information on the location and dimensions of small faults. I then investigate the Garlock Fault with an intersecting DAS array and uncover structural variability across the fault at shallow and seismogenic depths. I also use this array to investigate Moho topography, and find that the Garlock Fault offsets and, by extension, penetrates the mantle over a narrow width. In Chapters 6-8 of this thesis I address the latter problem. I show that second moments, both of source and seismicity distributions, can improve the clarity of observations and make drawing meaningful conclusions about rupture behavior possible. I first develop a framework to probabilistically invert for the second moments of source distributions and use it to investigate all large strike-slip events of the past three decades. These solutions show several patterns between faults and rupture behavior. I also create a seismicity catalog for the Ridgecrest earthquake sequence and use a second moment measure to constrain the evolution of fault orientation and the stress state." }, { "name": "Bonan, David Brooking", "degree": "PhD", "year": "2025", "title": "Explications of a Changing Climate", "advisor": "Schneider, Tapio; Thompson, Andrew F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06262024-011209069", "creators": [ { "name": { "family": "Bonan", "given": "David Brooking" }, "id": "Bonan-David-Brooking", "orcid": "0000-0003-3867-6009", "display_name": "Bonan, David Brooking" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "co-advisor", "display_name": "Schneider, Tapio" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "co-advisor", "display_name": "Thompson, Andrew F." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Zanna", "given": "Laure" }, "id": "Zanna-Laure", "orcid": "0000-0002-8472-4828", "role": "member", "display_name": "Zanna, Laure" }, { "name": { "family": "Rugenstein", "given": "Maria" }, "id": "Rugenstein-Maria", "orcid": "0000-0002-4541-3277", "role": "member", "display_name": "Rugenstein, Maria" } ], "option_major": [ "envreng" ], "doi": "10.7907/afb5-ns06", "abstract": "Climate models encode our collective knowledge about the climate system and are among the best tools available for estimating past and future climate change. However, in response to greenhouse gas forcing, climate models exhibit a large intermodel spread in various aspects of the climate system, adding considerable uncertainty to future climate projections. This dissertation introduces a series of conceptual models and frameworks to understand the behavior of climate models under greenhouse gas forcing and, consequently, Earth's changing climate.
\r\n\r\nA simple statistical model is used to explain and constrain the intermodel spread in Arctic sea ice projections across climate models. The probability of encountering seasonally ice-free conditions in the twenty-first century is also explored by systematically constraining components of the statistical model with observations.
\r\n\r\nA conceptual framework is introduced to understand controls on the strength and structure of the Atlantic meridional overturning circulation (AMOC) in climate models. This framework is used to explain why climate models suggest the present-day and future AMOC strength are related. This framework, in conjunction with observations, implies modest twenty-first-century AMOC weakening.
\r\n\r\nA simple energy budget framework is used to examine precipitation over a wide range of climates simulated by climate models. It is shown that in extremely hot climates, global-mean precipitation decreases despite increasing surface temperatures because of increased atmospheric shortwave absorption from water vapor, which limits energy available for surface evaporation. These results have large implications for understanding weathering rates in past climates as well as Earth's climate during the Hadean and Archaean eons.
\r\n\r\nFinally, a framework is introduced to reconcile two different approaches for quantifying the effect of climate feedbacks on surface temperature change. The framework is used to examine the influence of clouds on Arctic amplification in a climate model and an energy balance model. This work introduces an important non-local mechanism for Arctic amplification and shows that constraining the mid-latitude cloud feedback will greatly reduce the intermodel spread in Arctic warming.
\r\n\r\nThis dissertation advances our understanding of various aspects of Earth's changing climate and provides a series of conceptual frameworks that can be used to further constrain the behaviour of climate models in response to external forcing.
" }, { "name": "Camarca, Maria Noel", "degree": "PhD", "year": "2025", "title": "Fresh Eyes for an Old Moon: ALMA and JWST Perspectives of Callisto", "advisor": "de Kleer, Katherine R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05282025-033216413", "creators": [ { "name": { "family": "Camarca", "given": "Maria Noel" }, "id": "Camarca-Maria-Noel", "orcid": "0000-0003-3887-4080", "display_name": "Camarca, Maria Noel" } ], "advisors": [ { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "advisor", "display_name": "de Kleer, Katherine R." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Hallinan", "given": "Gregg W." }, "id": "Hallinan-G-W", "orcid": "0000-0002-7083-4049", "role": "member", "display_name": "Hallinan, Gregg W." }, { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "member", "display_name": "de Kleer, Katherine R." } ], "option_major": [ "plansci" ], "doi": "10.7907/y6t5-en36", "abstract": "As though its surface were frozen in time, Jupiter's moon Callisto has seemingly done little more than collect and degrade impact features since its formation some ~4.5 billion years ago. One outcome of Callisto\u2019s quiescence is that its geologic map retains only a few units, with large-scale landforms consisting of either enormous multi-ring impact basins or crater-laden plains. Despite this geologic simplicity, our knowledgebase of Callisto\u2019s material surface properties and volatile ice distributions is limited compared to the other icy Galilean moons. Understanding how Callisto localizes its thermal properties and delicate volatile ices is essential to understanding how long-term particle bombardment, solar insolation, and extended impact damage has sculpted its aged surface. While Callisto\u2019s much more active sibling satellites have scrubbed some or all of their surfaces free of the most ancient records, the oldest surface processes in the Galilean system remain visible today on Callisto. And with large telescope facilities such as the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Web Space Telescope, these surface properties are now accessible to Earth-based observers.
\r\n \r\nIn Chapters 2 and 3 of my dissertation, I complete the icy Galilean satellite ALMA catalogue with the full Callisto dataset which includes leading and trailing hemisphere images at ALMA Bands 7, 6, and 3, corresponding to 343, 223, and 97 GHz, respectively. At these frequencies, we sample the subsurface depths of order a few centimeters down to about half a meter. From these data, I demonstrate that Callisto\u2019s\u2019 subsurface thermal emission is much less susceptible to diurnal variation compared to the other icy satellites and that while Callisto\u2019s largest craters are thermally consistent with much smaller ones, the warm surface anomalies tell a story of impact bombardment not recorded in current geologic maps. Moreover, I identify several cold anomalies associated with large impacts, as well as one that might be relevant to Callisto's tenuous and patchy CO\u2082 atmosphere.
\r\n \r\nIn Chapter 4 of my dissertation, I present the results from a JWST NIRSpec 2.85\u20135.35 micron observing campaign that allowed us to inspect many of Callisto's volatile surface materials for the first time since the end of the Galileo mission in the early 2000s. In this work, I identify the Lofn/Heimdall impact region as Callisto's largest source of non-radiolytic CO\u2082. This particular crater suite may represent one of the best locations on Callisto to look for deep subsurface materials brought to the surface by the impact. Additionally, I propose Callisto's well-known radiolytic CO\u2082 trailing hemisphere bullseye is accompanied by a second bullseye in water ice exposure that may share a common origin.
\r\n\r\nLastly, in Chapter 5, I offer a brief synthesis of the icy moon ALMA survey, an endeavor that fulfills scientific promises that pre-date the array itself.
\r\n \r\nAltogether, this dissertation offers the community two of the key Callisto datasets of the 2020s era of research. Now that ESA\u2019s JUICE mission and NASA's Europa Clipper are en-route to the Jovian system, this research offers a timely complement to what is a blossoming era for Callisto and broader icy satellite exploration.
" }, { "name": "Christopoulos, Costa", "degree": "PhD", "year": "2025", "title": "Towards Hybrid Physics-Machine Learning Parameterizations: Employing Data Assimilation for Online Learning of Turbulence and Convection Closures in a Unified Scheme", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:12032024-211328064", "creators": [ { "name": { "family": "Christopoulos", "given": "Costa" }, "id": "Christopoulos-Costa", "orcid": "0000-0002-8552-465X", "display_name": "Christopoulos, Costa" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "chair", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." }, { "name": { "family": "Beucler", "given": "Tom" }, "id": "Beucler-Tom", "orcid": "0000-0002-5731-1040", "role": "member", "display_name": "Beucler, Tom" } ], "option_major": [ "envreng" ], "doi": "10.7907/ptr2-0r80", "abstract": "Despite advances in climate modeling, the spread in equilibrium climate sensitivity estimates has remained largely unchanged over generations of modeling, mainly due to uncertainties in cloud feedback mechanisms arising from subgrid-scale turbulence, convection, clouds, and the resulting cloud-radiation interactions. Misrepresentations of these processes affect both long-term climate projections and the simulation of short-term atmospheric phenomena, such as the diurnal cycle of precipitation. These limitations are most pronounced in regimes like stratocumulus clouds and their transition to cumulus over ocean basins---areas where climate models have the largest cloud biases in the historical record. This thesis aims to constrain the critical subgrid-scale physics of turbulence and convection by developing and calibrating a hybrid physics\u2013machine learning parameterization using the Eddy-diffusivity Mass-flux (EDMF) framework. By integrating machine learning components into the EDMF and employing data assimilation techniques for online learning, we attempt to directly target some of the processes responsible for uncertainties in cloud feedbacks.\r\n\r\nIn this thesis, we employ ensemble Kalman inversion within a single-column setup to simultaneously perform online calibration of parameters in empirical closures and embedded neural networks, targeting large-eddy simulations as ground truth. The online learning framework ensures stability and physical consistency, as machine learning components are trained within the context of the full model dynamics. By directly targeting poorly constrained processes like lateral entrainment/detrainment and turbulent mixing lengths, we improve the representation of subgrid-scale fluxes and resulting cloud properties across various atmospheric regimes. We uncover limitations of traditional semi-empirical closures, providing insights for future model development. The calibrated hybrid parameterization outperforms existing schemes, particularly in regions where climate models have historically underperformed, and maintains accuracy in out-of-sample forcings from a warmer climate. This work demonstrates that integrating machine learning with physics-based parameterizations through data assimilation offers a systematic and robust approach for reducing biases in climate models and understanding the physics of elusive subgrid-scale closures." }, { "name": "Dion-Kirschner, Hannah Henning", "degree": "PhD", "year": "2025", "title": "Carbon in Flux: Measuring the Climate Sensitivity of Terrestrial Greenhouse Gas Uptake", "advisor": "Sessions, Alex L.; Fischer, Woodward W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05312025-010337506", "creators": [ { "name": { "family": "Dion-Kirschner", "given": "Hannah Henning" }, "id": "Dion-Kirschner-Hannah-Henning", "orcid": "0000-0001-5978-5250", "display_name": "Dion-Kirschner, Hannah Henning" } ], "advisors": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "co-advisor", "display_name": "Sessions, Alex L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "co-advisor", "display_name": "Fischer, Woodward W." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/6pc2-ex86", "abstract": "The greenhouse gases carbon dioxide and methane exert a major control on Earth\u2019s climate, and their accumulation in the atmosphere is tempered by biological uptake. These biological uptake processes\u2014photosynthesis and methanotrophy\u2014are key contributors to the carbon-climate system, but their sensitivity to ongoing environmental change remains uncertain. In this thesis, I investigate how the ecophysiology of methanotrophy and photosynthesis dictate their response to perturbations in atmospheric composition, temperature, and other environmental variables. In Chapter 1, I present the first comprehensive compilation of kinetic measurements of methanotrophy in soils, and use this dataset to explore how kinetic properties may provide additional constraints to improve global models of the soil methane sink. Chapter 2 is a study of soil methane uptake rates in California dryland ecosystems and their relationship to local climate, ecology, and edaphic properties. This study reveals unique characteristics of dry climate regions that contradict typical assumptions about soil methane cycling. In Chapter 3, I present a novel method for position-specific carbon isotope analysis of submilligram glucose samples by Orbitrap mass spectrometry, and an application of this method to glucose standards isolated from C3 and C4 plants. In Chapter 4, I apply this new method to cellulose-derived glucose from tree-ring samples. Measurements of trees grown in climate chambers show how 13C-PSIA can disentangle changes in temperature, soil moisture, and tree carbon allocation. Finally, in two appendices, I describe methodological progress toward field-portable measurements of sedimentary porewater methane and the kinetics of soil methane uptake. Taken together, this work makes progress toward a more nuanced understanding of biological greenhouse gas uptake processes and their sensitivity to climate change." }, { "name": "Greklek-McKeon, Michael Christopher", "degree": "PhD", "year": "2025", "title": "The Compositional Diversity of Small Planets Orbiting Low-Mass Stars", "advisor": "Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-194525159", "creators": [ { "name": { "family": "Greklek-McKeon", "given": "Michael Christopher" }, "id": "Greklek-McKeon-Michael-Christopher", "orcid": "0000-0002-0371-1647", "display_name": "Greklek-McKeon, Michael Christopher" } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "chair", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Hallinan", "given": "Gregg W." }, "id": "Hallinan-G-W", "orcid": "0000-0002-7083-4049", "role": "member", "display_name": "Hallinan, Gregg W." }, { "name": { "family": "Howard", "given": "Andrew W." }, "id": "Howard-Andrew-W", "orcid": "0000-0001-8638-0320", "role": "member", "display_name": "Howard, Andrew W." } ], "option_major": [ "plansci" ], "doi": "10.7907/t2jp-m847", "abstract": "The Kepler and TESS missions have revealed that planets between the size of Earth and Neptune dominate our galaxy, showing a bimodal radius distribution that suggests distinct formation and evolution pathways. M dwarf stars offer the ideal opportunity to characterize these small planets due to their favorable planet-to-star size ratios. But M dwarf planets may differ fundamentally from those around Sun-like stars. Their cooler disk temperatures may result in more water-rich planet compositions, while their higher stellar activity rates may result in higher atmospheric mass loss rates. I investigate these questions by measuring planetary masses, radii, and bulk compositions with the first systematic transit timing variation survey of M dwarf planets discovered by the ongoing TESS survey, utilizing observations from Palomar Observatory and other small- to mid-sized telescopes. In this thesis, I present studies of four key systems from this survey: Kepler-289, where I improved planetary mass constraints by more than twofold and constrained the formation location of the outer gas giant companion; TOI-1266, where I characterized a potentially tidally heated planet with an inflated radius and a candidate water-world; LP 791-18, where I measured the bulk density of an Earth-sized planet and made predictions for its tidal heating rate that will be tested by upcoming JWST observations; and TOI-2267, a binary M dwarf system where I statistically validated a new Earth-sized planet with important implications for planet formation and migration. These systems have expanded our understanding of small planets around low-mass stars and provide valuable case studies for studies of atmospheric mass loss, the search for planets with water-rich envelopes, and the role of tidal heating in compact multi-planet systems." }, { "name": "Guo, Yongzhao", "degree": "PhD", "year": "2025", "title": "Exploring Versatility of Energy Metabolism and Dynamics of Anabolism and Growth in Anaerobic Methanotrophic Consortia", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-214449948", "creators": [ { "name": { "family": "Guo", "given": "Yongzhao" }, "id": "Guo-Yongzhao", "orcid": "0009-0005-3983-8382", "display_name": "Guo, Yongzhao" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "chair", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "envreng" ], "doi": "10.7907/fz82-xt77", "abstract": "Two main questions are asked in this thesis, how environmental microorganisms respond and persist in an energy-limiting condition, and how we can investigate and disentangle the dynamics of these microbes\u2019 activity and growth at a high spatiotemporal resolution. To the end, this thesis focuses on a symbiosis of methane oxidizing archaea (ANME) and sulfate reducing bacteria (SRB), who mediate the anaerobic oxidation of methane (AOM), an important process in the global methane cycle. For the former question, Chapter 2 first found that carbon monoxide (CO) was able to serve as an alternative electron donor for ANME-SRB, and notably CO can even reverse the direction of AOM in ANME archaea to produce methane by the reduction of CO\u2082. Chapter 3 then explored and verified from the other side the potential role of pyrite (nano)particles in supporting AOM via a predicted reaction at the pyrite-water interface to generate sulfate and iron oxides as electron sinks. For the latter question, Chapter 4 took advantage of stable isotopic probing combined with the high sensitivity and spatial resolution of nanometer-scale secondary ion mass spectrometry (nanoSIMS) approach, and proposed a pipeline of multi-isotope imaging to record and in situ read out the single cell activity in the past. Chapter 5 as an in progress work attempts to disentangle the native division process in the yet uncultured ANME archaea by means of serial block face electron microscopy (SBEM) and deep learning imaging analysis. Taken together, this work provides more evidence of the versatile energy metabolism for ANME-SRB symbiosis and at the same time offers solutions to capturing the dynamics of activity and growth in natural microorganisms for the field of environmental microbiology." }, { "name": "Khapikova, Polina", "degree": "PhD", "year": "2025", "title": "From Hadley Cells to Heat Extremes: Novel Physical and Statistical Frameworks for Evaluating Climate Models", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032025-003651371", "creators": [ { "name": { "family": "Khapikova", "given": "Polina" }, "id": "Khapikova-Polina", "orcid": "0000-0001-8142-5577", "display_name": "Khapikova, Polina" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Baldwin", "given": "Jane" }, "id": "Baldwin-Jane", "orcid": "0000-0002-4174-2743", "role": "member", "display_name": "Baldwin, Jane" } ], "option_major": [ "envreng" ], "doi": "10.7907/px1t-j224", "abstract": "As climate models become increasingly central to projecting future climate impacts and guiding adaptation strategies, understanding the sources of intermodel spread is critical. This thesis investigates key drivers of model uncertainty through a process-based lens grounded in fundamental climate physics. It focuses on two major contributors to model spread: atmospheric circulation and land-surface processes, which together shape regional hydrological extremes and human-relevant climate outcomes.
\r\n\r\nFirst, I develop a zonal-mean energetic framework to explain variations in the meridional extent of the Hadley Circulation (HC) across seasonal, interannual, and multidecadal timescales. I show that changes in tropical net energy input and eddy energy export can be used to explain HC migrations in a variety of contexts. For example, this framework can be used to explain the larger migrations of the ascending HC branch relative to the descending branch over the seasonal cycle, and the contrasting HC migration observed during El Nino events and in response to global warming. This approach provides a physically grounded method for interpreting both observed short-term variability and projected future changes in the tropical atmospheric circulation.
\r\n\r\nNext, I address uncertainty in terrestrial water storage (TWS) trends across CMIP6 models. To circumvent the limitations of short observational records, I introduce a novel method that compares the seasonal cycle of TWS using empirical orthogonal functions derived from GRACE satellite data. This approach enables the ranking of models based on their fidelity to observed seasonal variability. Models with stronger agreement with GRACE observations exhibit more consistent and often larger trends in TWS, and share features such as deeper soils and spatially distinct precipitation patterns. These insights can guide model selection and development efforts.
\r\n\r\nFinally, I explore model spread in the temperature-humidity combinations that produce extreme wet-bulb temperatures (WBTs), a key metric of human heat stress. While WBT projections are relatively consistent across models, the partitioning between temperature and humidity\u2014quantified using the \"stickiness\" metric\u2014varies substantially. I show that these differences lead to large uncertainty in the physiological impacts of heat stress at a given WBT. This work underscores the importance of accurately capturing surface energy partitioning to constrain present and future heat stress risks.
\r\n\r\nTogether, the chapters of this thesis offer several innovative approaches to evaluating uncertainty in climate projections. By applying simple theory, observational constraints, and novel metrics, this work demonstrates how physically grounded methods can identify more reliable models and improve the accuracy of future climate projections---particularly for hydrological extremes and human-centered impacts.
" }, { "name": "K\u00f6hne, Tobias", "degree": "PhD", "year": "2025", "title": "From Daily Deformation to Millennial Mechanics: Insights from Subduction Zone Earthquake Cycle Models", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:10302024-162816237", "creators": [ { "name": { "family": "K\u00f6hne", "given": "Tobias" }, "id": "K\u00f6hne-Tobias", "orcid": "0000-0002-8400-7255", "display_name": "K\u00f6hne, Tobias" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "chair", "display_name": "Ross, Zachary E." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/sn24-zn74", "abstract": "Subduction zones have hosted all the largest five earthquakes in the last one hundred years, including the 2011 Mw 9.1 Tohoku-oki earthquake on 11 March 2011, one of the largest natural disasters in history. While the general mechanism of these thrust-style earthquakes is well described by stress accumulation due to the locking between the incoming and the overriding tectonic plates, many questions remain as to the size and longevity of the asperities which host the coseismic rupture, the rheological models best describing the rock in and around the fault zone, and the effects of stress shadows and interactions between different asperities on the same plate interface. These questions are addressed by using large earthquakes as natural experiments, which we can observe using geodetic, seismic, and other techniques. However, ambiguities in the modeling results point to the inherent problem of non-uniqueness when interpreting surface observations of single events to infer complex processes at depth.
\r\n\r\nThis dissertation presents a new framework to study subduction zones and their rheological properties by extending both the time period modeled and the observations considered to all phases of the seismic cycle, on a fault interface that experiences earthquakes at multiple points in space and time. The motivating concept is that the recovery of rheological parameters could be greatly improved when considering that the constitutive laws for fault material must be able to reproduce all phases of the earthquake cycle, since it is the same physical material. Here, we (1) develop a timeseries analysis software that enables the efficient processing of large geodetic networks with long timeseries, allowing us to extract the relevant subduction-zone related signal in the observations, (2) formulate a forward model that, based on ancillary historical and seismic datasets as well as a candidate rheological model, simulates surface motion over multiple earthquake cycles, and (3) use a probabilistic inverse method to estimate the best-fitting rheological parameters given the postprocessed surface deformation timeseries and model uncertainties.
\r\n\r\nWe validate the timeseries analysis software on the transient volcanic deformation of Long Valley Caldera, California, USA, before extracting the megathrust component of the surface observations on Northern Honshu Island, Japan. We then estimate the rheological properties of the Northern Japanese subduction zone using our inversion method, simultaneously producing time-varying estimates of kinematic coupling, slip deficit, and surface deformation. Our model predictions match the pre- and postseismic displacement timeseries of the 2011 Tohoku-oki earthquake well. On the steadily creeping part of the plate interface, we infer rate-dependent frictional parameters generally increasing with depth, but with second-order along-strike variation. Finally, we discuss the potential impact of our cycle-spanning, probabilistic inversion method on the field of subduction zone studies, and present possible avenues for further improvements to our framework.
" }, { "name": "Liu, Weiyi", "degree": "PhD", "year": "2025", "title": "Insights Into the Core\u2019s Structure, Formation and Evolution from First-Principles Calculations", "advisor": "Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-184329081", "creators": [ { "name": { "family": "Liu", "given": "Weiyi" }, "id": "Liu-Weiyi", "orcid": "0000-0002-0044-2277", "display_name": "Liu, Weiyi" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Tissot", "given": "Francois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "member", "display_name": "Tissot, Francois L. H." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geochem" ], "doi": "10.7907/ps54-bx05", "abstract": "Understanding the formation, composition, and evolution of planetary cores is essential to unraveling the early history and internal dynamics of terrestrial planets. However, direct constraints on the physical and chemical properties of liquid metal under core-forming conditions remain limited due to the inaccessibility of the core and the challenges of reproducing its extreme pressures and temperatures in the laboratory. This thesis integrates first-principles molecular dynamics(FPMD)simulations with high-pressure experimental data to investigate the thermodynamics, chemical partitioning, and seismic implications of multicomponent metal liquids in the deep interiors of Earth and other differentiated bodies.
\r\n \r\nThis thesis focuses on two fundamental properties of the core: its thermodynamic behavior and its chemical interaction with the silicate mantle during differentiation. The first part of the thesis develops a thermodynamic model for multicomponent metallic liquids\u2014including Fe\u2013Ni systems with light elements such as O, S, Si, C, and H\u2013based on FPMD simulations and calibrated against experimental data. This model accurately reproduces pressure\u2013volume\u2013temperature relations and mixing behavior, and is consistent with both diamond anvil cell and shock wave measurements. The model forms the basis for a forward seismic modeling framework that allows direct comparison between core composition and observed density and velocity profiles in Earth\u2019s outer core. The second part of the thesis investigates the chemical partitioning of elements that record early planetary formation and evolution\u2014specifically Sm, Nd, I, and Pu\u2014between metal and silicate liquids at high temperatures. Two different approaches are employed to determine the partition coefficients: thermodynamic integration based on first-principles molecular dynamics for Sm and Nd, and two-phase FPMD simulations for I and Pu. With these partitioning behaviors quantified, the study further models core formation processes in differentiated planetesimals and Earth, providing new constraints on the extent of metal\u2013silicate chemical exchange and fresh insights into the isotopic and volatile evolution of planetary mantles.
" }, { "name": "Miaou, Emily Yishiuan", "degree": "PhD", "year": "2025", "title": "From Melting Dynamics to Medical Diagnostics: Studies in Geochemical Kinetics", "advisor": "Asimow, Paul David; Tissot, Fran\u00e7ois L. H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05162025-025853405", "creators": [ { "name": { "family": "Miaou", "given": "Emily Yishiuan" }, "id": "Miaou-Emily-Yishiuan", "orcid": "0000-0003-4688-3024", "display_name": "Miaou, Emily Yishiuan" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "advisor", "display_name": "Asimow, Paul David" }, { "name": { "family": "Tissot", "given": "Fran\u00e7ois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "co-advisor", "display_name": "Tissot, Fran\u00e7ois L. H." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Tissot", "given": "Fran\u00e7ois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "member", "display_name": "Tissot, Fran\u00e7ois L. H." } ], "option_major": [ "geochem" ], "doi": "10.7907/ck82-t059", "abstract": "This thesis investigates geochemical kinetics across different subfields, from isotope metallomics in the human body to melting dynamics in igneous petrology. Chapters II and III explore the chemical complexities of rapid mineral melting in igneous systems. An experimental-computational approach is used, with the experiments providing data that help calibrate the numerical model. This integrated strategy contributes to a comprehensive understanding of the kinetics of melting that could not be captured by either method alone. Chapter II outlines the experimental work, which includes both equilibrium and kinetic melting experiments performed on the ubiquitous igneous mineral series plagioclase. The kinetic experiments are designed to deliberately access a parameter space of disequilibrium behaviors rarely studied experimentally yet likely to be relevant in various natural settings where systems evolve too quickly to follow the predictions of equilibrium theory. Quantitative and qualitative analyses of the recovered experimental products allow us to observe unique textures and chemical gradients that arise from the interplay of thermal and chemical diffusion within the phases, coupled with phase boundary motion and associated surface reactions. Chapter III details the theory and computational methods used to develop a numerical model that describes chemical evolution of melt and crystal phases during two-component melting. Novel application of thermodynamic data is used to describe chemical behavior at the phase boundary, allowing for departure from traditional equilibrium assumptions. Results of the model bring us one step closer to the ultimate goal of understanding disequilibrium in multicomponent rock systems. Chapter IV investigates the kinetics of stable isotopes in biomedicine. Box modeling was used to simulate copper (Cu) stable isotope dynamics in the human body, allowing us to quantify the possible effects of various health conditions (e.g., cancer, liver disease) on isotopic compositions throughout different organs. In turn, we determine whether Cu isotopes can act as diagnostic or prognostic markers for certain diseases using detection by modern mass spectrometry and provide recommendations on their potential uses in the medical field." }, { "name": "Murphy, Sara Edinger", "degree": "PhD", "year": "2025", "title": "Elucidating the Products and Kinetics of Bimolecular Alkene-Derived Peroxy Radical Reactions in the Lab and in the Field", "advisor": "Wennberg, Paul O.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08052024-083837797", "creators": [ { "name": { "family": "Murphy", "given": "Sara Edinger" }, "id": "Murphy-Sara-Edinger", "orcid": "0000-0002-8226-9446", "display_name": "Murphy, Sara Edinger" } ], "advisors": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "advisor", "display_name": "Wennberg, Paul O." } ], "committee": [ { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "orcid": "0000-0001-6874-1137", "role": "chair", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "orcid": "0000-0003-1344-4068", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Sander", "given": "Stanley P." }, "id": "Sander-S-P", "orcid": "0000-0003-1424-3620", "role": "member", "display_name": "Sander, Stanley P." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." } ], "option_major": [ "envreng" ], "doi": "10.7907/q5bh-d327", "abstract": "Although peroxy radicals, reactive compounds formed in the atmospheric oxidation of hydrocarbons, are primary drivers of atmospheric composition, several uncertainties remain with respect to their fates in both low and high NO environments.\r\nThis thesis uses gas chromatography chemical ionization mass spectrometry (GC-CIMS) to identify and quantify the products of bimolecular peroxy radical reactions formed in both of these regimes in the lab and in the ambient environment. The\r\nfirst two chapters use laboratory experiments to probe the formation of a peroxide accretion product (ROOR) via peroxy radical self- and cross-reactions. In the first chapter, a method for studying the formation of the peroxide accretion product is developed and used to observe the formation of the accretion product of the ethene-derived hydroxy peroxy radical self-reaction. The self-reaction rate constant and the\r\nbranching to the formation of the accretion product are measured, and the identity of the accretion product is confirmed by comparison to a synthesized standard. In\r\nthe second chapter, the formation rate of the accretion product for a variety of small alkene-derived peroxy radical self-reactions is measured, and the observed relation-\r\nship between peroxy radical structure and accretion product formation is discussed. Finally, the third chapter presents observations of organic nitrogen compounds formed via the\r\nreactions of biogenic and anthropogenic hydrocarbons in the Los Angeles urban atmosphere. The identities of several of these organic nitrates are confirmed by comparison to laboratory oxidation experiments, and the role these compounds play in the local nitrogen budget is discussed." }, { "name": "Nghiem, Justin Anh-Khoa", "degree": "PhD", "year": "2025", "title": "Flocculation and Transport of Mud in Rivers and Deltas", "advisor": "Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-211248621", "creators": [ { "name": { "family": "Nghiem", "given": "Justin Anh-Khoa" }, "id": "Nghiem-Justin-Anh-Khoa", "orcid": "0000-0003-2772-9945", "display_name": "Nghiem, Justin Anh-Khoa" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Li", "given": "Gen K." }, "id": "Li-Gen-K", "orcid": "0000-0002-6300-3570", "role": "member", "display_name": "Li, Gen K." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/rh7k-x369", "abstract": "Mud (grains < 62.5 \u03bcm) dominates the sediment load of rivers from continents to the ocean and contributes to building coastal land and sequestering organic carbon. However, predicting mud transport is challenging because flocculation causes mud grains to aggregate into larger, faster settling particles called flocs, which dynamically respond to local flow, water, and sediment properties. In this thesis, I examined the factors controlling mud flocculation in rivers and deltas and the effects of enhanced floc settling velocity on mud accretion in a river delta using fieldwork and data compilations from the river sediment literature. Flocs have the potential to dictate mud deposition rates and transport patterns by effectively enhancing mud settling velocity. First, I developed a semi-empirical model to predict floc diameter and settling velocity in rivers using a global river data compilation (Chapter 2). Results show that turbulence, sediment concentration and mineralogy, organic matter concentration, and water chemistry are the key flocculation factors in rivers. I conducted fieldwork in the Wax Lake Delta, Louisiana, a river delta in the Mississippi River Delta complex. Based on floc measurements at the Wax Lake Delta, I validated the semi-empirical model and showed that a complementary physics-based floc settling velocity model relies on the permeability and fractal structure of flocs (Chapter 3). To better link floc settling velocity and mud transport, I used the Wax Lake Delta field data to demonstrate that flocculated mud might behave as bed-material load rather than washload (Chapter 4). This result implies that mud concentration and flux might be readily predictable from bed-material entrainment theory using local bed and flow measurements. Connecting mud transport to delta island sedimentation and delta resilience, I analyzed discharge and sediment flux in the Wax Lake Delta to understand how sediment is delivered to and transported in islands (Chapter 5). Field data and backwater modeling results show that tall levees can block flow, but intricate feedbacks between flow depth, velocity, and water surface slope set discharge and sediment flux into the island once primary channels overflow into islands. Suspended mud settles fast enough relative to island flow depth and velocity to settle out within the island rather than bypass. As such, mud can accrete and build up the island over time as evidenced by mud-rich island deposits in Wax Lake Delta. Finally, combining Wax Lake Delta data and a river data compilation on suspended sediment grain size and mineralogy, I showed that most suspended sediment in rivers is flocculated silt (Chapter 6). This silt likely flocculates due to physical trapping mechanisms rather than typically considered interactions between clay minerals and salinity because clay minerals compose a minority of the silt. Overall, this thesis informs how flocculation affects mud transport in rivers and deltas, encompassing the mechanisms of mud flocculation, predictions of floc settling velocity and mud concentration, and the significance of mud flocculation in shaping depositional landscapes.
" }, { "name": "Parra, Sergio Alexander", "degree": "PhD", "year": "2025", "title": "Location, Location, Location: Insights from Spatially-Resolved Observations of Marine Seep Carbonate Ecosystems and Carbonaceous Chondrite Surfaces", "advisor": "Orphan, Victoria J.; Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03052025-175659528", "creators": [ { "name": { "family": "Parra", "given": "Sergio Alexander" }, "id": "Parra-Sergio-Alexander", "orcid": "0000-0002-2637-7960", "display_name": "Parra, Sergio Alexander" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Meile", "given": "Christof" }, "id": "Meile-C", "orcid": "0000-0002-0825-4596", "role": "member", "display_name": "Meile, Christof" } ], "option_major": [ "geobiol" ], "doi": "10.7907/c0w0-ns76", "abstract": "Spatially heterogeneous, multi-component systems are prevalent topics of study in geobiology and planetary science. However, previous studies of these systems often represent limited measurements that abstract or separate the sample from its localized context, thereby obscuring or precluding insights into the drivers ultimately shaping these systems. This challenge motivates the work presented in this thesis, where we provide an extensive and spatially-resolved examination of two complex, heterogeneous systems in geobiology and planetary science: marine seep carbonates and carbonaceous chondrite surfaces, respectively. In marine seep systems worldwide, seep carbonates are a mineral byproduct of a microbial metabolism (the anaerobic oxidation of methane, or AOM) and can continue hosting metabolically active microbial communities, including methane-oxidizing microbes. However, much of our understanding of these endolithic microbial communities stems from bulk, centimeter-scale evaluations of microbial identity and/or metabolic activity across a limited number of samples. As such, the range of structural and environmental conditions that ultimately shape the degree and extent of microbial activity in seep carbonates, including AOM, remains relatively under-constrained. To address this gap, Chapters 1-3 investigate carbonate-hosted microbial communities at a methane seep site in Santa Monica. In Chapter 1, we explore carbonate \u2018nodules\u2019 from methane seep sediments at and below the sulfate-methane transition zone (SMTZ), analyzing their mineral composition, internal structures, and hosted microbial communities compared to their host sediment communities and porewater chemistry. We also discuss key implications of the connectivity of seep sediments to nodules over geologic timescales and the preservation of microbial \u2018thumbprints\u2019. Chapter 2 describes rare tripartite associations between two groups of anaerobic methanotrophic archaea (ANME-1 and ANME-2) and a bacterial partner within seep carbonate crusts and other substrates at the seafloor, with implications towards understudied diversity in the syntrophic interactions governing AOM beyond seep carbonates. Chapter 3 examines the impact of seep carbonate internal structure on endolithic communities from various carbonate crusts, revealing similarities and differences between surface and interior communities that may reflect the importance of pore networks in maintaining favorable local environments. In Chapter 4, we pivot to an extensive analysis of spectra from carbonaceous chondrite surfaces. Carbonaceous chondrites (CCs) are a group of meteorites that represent the oldest materials in the solar system, whose mineralogy preserves a record of early alteration processes thought to be shared with certain asteroids. However, most studies connecting specific CCs to specific asteroids have relied on spectroscopic measurements of bulk powder CCs, which are spatially unresolved and destroy textures, thereby hindering tying shared spectral features to particular phases, petrologic contexts, and alteration histories. As such, Chapter 4 presents an analysis of CCs measured using microimaging hyperspectral visible-and-shortwave-infrared (VSWIR) spectroscopy, where we capture chondrite surfaces features at high spatial resolution. We also compare CC spectral features with asteroids using the Expanded Bus-DeMeo taxonomy, which provides a systematic framework to examine and identify shared drivers of spectral diversity within this spectral range, including Fe-bearing minerals from both original and terrestrial alteration processes. Together, these studies emphasize the importance of spatially-resolved sampling across disciplines, specifically in geobiology and planetary science, thereby capturing and highlighting the heterogenous nature of key systems in these fields and bettering our understanding of the factors shaping them." }, { "name": "Peterson, Henry Grant", "degree": "PhD", "year": "2025", "title": "Mixing-Driven Abyssal Ocean Circulation over Sloping Topography", "advisor": "Callies, Joern", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032025-000538732", "creators": [ { "name": { "family": "Peterson", "given": "Henry Grant" }, "id": "Peterson-Henry-Grant", "orcid": "0000-0003-3491-7688", "display_name": "Peterson, Henry Grant" } ], "advisors": [ { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "advisor", "display_name": "Callies, Joern" } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Colonius", "given": "Tim" }, "id": "Colonius-T", "orcid": "0000-0003-0326-3909", "role": "member", "display_name": "Colonius, Tim" }, { "name": { "family": "Purkey", "given": "Sarah" }, "id": "Purkey-Sarah", "orcid": "0000-0002-1893-6224", "role": "member", "display_name": "Purkey, Sarah" }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" } ], "option_major": [ "envreng" ], "doi": "10.7907/94gy-cy80", "abstract": "The planetary-scale overturning circulation of the ocean is maintained by small-scale diapycnal mixing in the abyss. Recent theory and observations suggest that this turbulence is bottom-enhanced, confining the upwelling needed to close this circulation to thin bottom boundary layers (BLs) over sloping topography. Developing an understanding of how this mixing shapes the abyssal circulation, both locally and at the basin scale, is the unifying goal of this thesis.
\r\n\r\nThe local response of a water column to mixing has previously been understood using a one-dimensional model of a rotating, stratified fluid over a sloping seafloor. Canonically, this model assumes no cross- or along-slope variations of the flow, pressure, and buoyancy anomalies. At steady state, it predicts a peculiar form of the net cross-slope transport, however, failing to consider its coupling to the global circulation. For symmetric bathymetry without along-slope variations, for instance, this large-scale context implies that all cross-slope BL transport must be exactly returned in the interior. This interior downwelling is then turned by the Coriolis acceleration, rapidly spinning up along-slope flow in balance with a cross-slope barotropic pressure gradient. With these added physics, the one-dimensional model better captures the local response to mixing over an idealized ridge, for example. Using BL theory, we explicitly describe how the BL and interior communicate in this model. The up-slope transport of dense water in the bottom BL contributes a net downward flux of buoyancy, creating an effective bottom boundary condition on the interior. The coupling goes both ways, with the interior stratification at the top of the BL setting the strength of the BL transport. Variations across the slope then allow for BL--interior exchange.
\r\n\r\nUltimately, the net transport of the local response must conserve potential vorticity at the basin scale. To better understand this coupling for arbitrary topography, we develop a novel finite element model of the planetary geostrophic equations. Using a combination of simulations and BL theory, we then study the mixing-driven abyssal circulation in an idealized bowl-shaped basin. In the absence of wind forcing and the joint effect of baroclinicity and relief, the leading-order barotropic transport flows along f/H contours, where f is the Coriolis frequency and H is the depth. The local response to mixing is coupled to this barotropic circulation, simultaneously constrained by the barotropic circulation and forcing it via a bottom stress curl. For closed f/H contours, a strong along-contour barotropic circulation spins up, reminiscent of the local response described above. On the other hand, if these contours intersect the boundary, a case more typical in the real ocean, the barotropic transport is suppressed. This decouples the leading-order local response from the large-scale circulation and intensifies bottom BL upwelling. This work therefore suggests that the local abyssal stratification in the presence of bottom-enhanced mixing strongly depends on the large-scale context.
" }, { "name": "Ryan-Davis, Juliet Rose", "degree": "PhD", "year": "2025", "title": "Crystalline Records of Mafic Arc Magmas Across the Sierra Nevada Batholith, California", "advisor": "Bucholz, Claire E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-035505104", "creators": [ { "name": { "family": "Ryan-Davis", "given": "Juliet Rose" }, "id": "Ryan-Davis-Juliet-Rose", "orcid": "0000-0001-7048-5937", "display_name": "Ryan-Davis, Juliet Rose" } ], "advisors": [ { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "advisor", "display_name": "Bucholz, Claire E." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geol" ], "doi": "10.7907/y34m-jj74", "abstract": "Our planet Earth is unique among the rocky planets of the solar system in having compositionally evolved continental crust\u2014the reason for life as we know it. Processes that create continental crust occur at subduction zones where magmas differentiate, evolving from primary mantle-derived basalt to produce a diverse range of compositions that erupt at arc volcanoes and comprise the bulk of the continental crust. Many processes for differentiation have been proposed, yet, recognizing and evaluating the role of pre-existing crust in these processes remains challenging.
\r\n\r\nThis thesis includes two studies of mafic intrusions in the Sierra Nevada batholith\u2014the well-studied Mesozoic continental arc of the western North American Cordillera. The studies are grounded in field and petrographic observations. By targeting the intrusive record, they document the time-integrated effects of mafic magmatism over tens of millions of years within a volcanic arc.
\r\n\r\nChapter 2 is a petrologic study of the most primitive intrusive rocks of the batholith, exposed in the Emigrant Gap complex. The complex ranges compositionally from ultramafic cumulates to intermediate granodiorite. The petrology, geochemistry and field relationships of these plutonic rocks reveal that\u2014in addition to crystallization\u2014open-system processes (melt-mush reactions and hybridization between the mafic products and a crustally contaminated felsic magma) produced the distinctive geochemical and petrologic trends of the complex.
\r\n\r\nChapters 3 and 4 represent a broad study of mafic intrusions within a 250 km by 100 km swath of the central Sierra Nevada (37\u00b10.5\u00b0N latitude). This regional perspective on mafic magmatism spans ~110 million years and crosses several tectonically-assembled belts, each with distinctive geology. The two chapters document systematic differences in field relationships and geochemistry of the mafic intrusions that vary by geologic belt, as the mafic magmas interacted with heterogeneous crust. Chapter 3 presents field relationships, ages, and major and trace element chemistry. Chapter 4 presents isotopic compositions (O, Hf, Sr, and Nd), revealing that contamination of mafic magmas by ~10\u201320% assimilation of the local crustal column is inevitable, and that it occurs early during differentiation.
" }, { "name": "Seeger, Christina Hope", "degree": "PhD", "year": "2025", "title": "Surface Evolution on Basaltic Bodies: Tectonic, Geomorphic, and Diagenetic Modification on Io and Mars", "advisor": "Grotzinger, John P.; de Kleer, Katherine R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-233903333", "creators": [ { "name": { "family": "Seeger", "given": "Christina Hope" }, "id": "Seeger-Christina-Hope", "orcid": "0000-0003-4993-9724", "display_name": "Seeger, Christina Hope" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "co-advisor", "display_name": "Grotzinger, John P." }, { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "co-advisor", "display_name": "de Kleer, Katherine R." } ], "committee": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "chair", "display_name": "Lamb, Michael P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "member", "display_name": "de Kleer, Katherine R." } ], "option_major": [ "geol" ], "doi": "10.7907/4mfp-zx56", "abstract": "All planets and moons in the Solar System evolve over geologic timescales, though the processes affecting each body vary widely depending on gravity, atmosphere thickness and composition, volcanic activity, and perhaps most importantly, the presence of a hydrologic cycle. This dissertation investigates the surface evolution of two basaltic bodies in our Solar System: one that has barely changed in 3.5 billion years, and one that changes almost daily. Jupiter\u2019s moon Io is continually resurfaced by large-scale volcanic eruptions of low-viscosity lava and sulfur dioxide gas, driven by interior heating generated by diurnal tidal stresses. Such tidal stresses have been linked to eruptive activity and tectonic ridge formation on other moons like Titan and Europa; while they strongly influence Io, they are orders of magnitude weaker than the crustal subsidence stresses which control the expression of tectonic features on the surface (kilometers-tall mountains and caldera-like volcanic features called paterae). Chapter 2 investigates whether tidal stresses may have any influence on the formation of mountains and paterae. Though no global trends have been identified, I suggest that local correlations between patera orientations and the large volcanic center of Loki Patera may provide insight into the magma plumbing pathways of this unique volcano. As soon as tectonic mountains are uplifted on Io, they are subject to gravity- and seismicity-driven erosional processes tearing them down. In Chapter 3, I present the first regional geologic map of a trio of mountains named Cocytus Montes and identify a new geologic unit\u2014a blocky deposit composed of kilometer-scale slab-shaped blocks of crust\u2014that are visible thanks to the favorable resolution and near-terminator lighting conditions of new Junocam imagery. I explore several new erosional mechanisms for Io that could create these blocks, determining regolith creep-modified cliff collapse to be the most likely. The orders of magnitude higher resolution imagery collected by the Mars Science Laboratory Curiosity rover provides a backdrop for much closer analysis of how sediments moved, deposited, lithified, and were subsequently modified by diagenetic fluids on ancient Mars. Chapter 4 takes advantage of hand-sample scale data to categorize a diverse array of diagenetic fabrics (nodules, pits, color variations) that correlate with the stratigraphy in a region defined by a transition from clay-bearing rocks to sulfate-bearing rocks. I present several hypotheses to explain how the Mg sulfate detected in these nodules and pore-filling cements may have precipitated at depth, to complement current evaporite-driven models. These hypotheses could be tested in the coming years of Mars exploration by the rover, and will provide insights into the longevity of a groundwater system after surface water ceased to flow on ancient Mars. Overall, this work explores the well-studied terrestrial processes of surface modification, degradation, and diagenesis under distinctly alien conditions throughout the Solar System." }, { "name": "Silverman, Shaelyn Nicole", "degree": "PhD", "year": "2025", "title": "From Pure Cultures to Particles: Tracing Microbial Metabolism Through Amino Acid \u00b2H/\u00b9H Ratios", "advisor": "Sessions, Alex L.; Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05292025-055458332", "creators": [ { "name": { "family": "Silverman", "given": "Shaelyn Nicole" }, "id": "Silverman-Shaelyn-Nicole", "orcid": "0000-0001-9201-6904", "display_name": "Silverman, Shaelyn Nicole" } ], "advisors": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "advisor", "display_name": "Sessions, Alex L." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "co-advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "chair", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." } ], "option_major": [ "geobiol" ], "doi": "10.7907/5v12-1149", "abstract": "Microbial metabolisms exert profound impact on our planet\u2019s atmosphere and surface geochemistry. Most available tools to study microbial metabolism in the environment provide only snapshots of activity at the time of sampling. However, holistic understanding of microbial function requires the ability to quantitatively reconstruct their activities prior to sampling, for which tools are currently limited. The overarching research presented in this thesis addresses this challenge through development of a new isotopic tool, amino acid hydrogen isotope (\u03b42HAA) analysis, into a useful tracer of microbial metabolism in the environment. We begin by solving a major analytical challenge: correcting for contributions of exchangeable amine-bound hydrogen in derivatized amino acids, which unlocks the ability to accurately measure \u03b42HAA values in organisms via gas chromatography-pyrolysis-isotope ratio mass spectrometry. We demonstrate in aerobic heterotrophic bacteria and phytoplankton that \u03b42HAA values are controlled by metabolism (specifically, carbon flow in cells), and we apply this isotopic tool to natural samples of marine particulate organic matter (POM), demonstrating substantial potential turnover of photoautotrophic proteins into heterotrophic proteins (up to 57 \u00b1 18%) in POM with depth at different ocean sites. We further explore the microscale dynamics of marine bacteria on diatom aggregates to contextualize our understanding of controls on marine POM degradation. In particular, we find that both intra- and interspecies interactions profoundly shape microbial colonization dynamics, which in turn likely affect bulk particle degradation rates. Together, this body of work demonstrates the profound utility of \u03b42HAA analysis as a tracer of microbial metabolism\u2014a timely development given the need to trace and quantify the metabolic responses of microbial communities to ongoing environmental perturbations." }, { "name": "Strozewski, Benjamin Thomas", "degree": "PhD", "year": "2025", "title": "Crystal Chemistry and Seismic Wavespeeds of Dense Oxyhydroxides: Hydrogen Transport in Earth's Lower Mantle", "advisor": "Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05202025-040444350", "creators": [ { "name": { "family": "Strozewski", "given": "Benjamin Thomas" }, "id": "Strozewski-Benjamin-Thomas", "orcid": "0000-0003-2006-8160", "display_name": "Strozewski, Benjamin Thomas" } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "chair", "display_name": "Ross, Zachary E." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." } ], "option_major": [ "geophys" ], "doi": "10.7907/tejk-h629", "abstract": "In this thesis, I perform a thorough investigation of the electronic and elastic properties of the dense oxyhydroxide (Al,Fe)-phase H (Al0.84Fe3+0.07Mg0.02Si0.06OOH). This phase represents a realistic composition in a solid solution which has been hypothesized to carry 'water', in the form of hydrogen, to the lowermost depths of Earth's mantle. Its propensity for water storage and elastic properties are affected by hydrogen bond symmetrization and a high-low spin crossover of Fe3+ atoms, respectively. In order to determine changes in hydrogen bonding environment, I use synchrotron infrared spectroscopy and Raman spectroscopy, which identify O-H vibrational modes in the crystal structure and changes in their frequencies with pressure. These vibrational modes indicate that (Al,Fe)-phase H likely stores additional hydrogen as defects and that hydrogen bonds are disordered at ambient pressure due to the substitution of cations of different valence states. I find that hydrogen atoms become dynamically disordered across sites at 10 GPa and conclude that hydrogen bond symmetrization in (Al,Fe)-phase H takes place at 35 GPa. I use powder X-ray diffraction to constrain the equation of state of this phase, providing fundamental constraints on its incompressibility and density at high pressures. I complement this equation of state with study of the electronic environment around the Fe atoms via nuclear resonant forward scattering in order to constrain the spin crossover of Fe3+ atoms between 48 and 63 GPa. I use nuclear resonant inelastic X-ray scattering measurements to determine the seismic wavespeeds of (Al,Fe)-phase H to 120 GPa, the base of the lowermost mantle. The measured seismic wavespeeds are incorporated into whole-rock models which suggest that (Al,Fe)-phase H contributes to seismic heterogeneity in the mid-mantle and that hydrous metabasalt containing (Al,Fe)-phase H could contribute to seismic anomalies associated with the edges of large, low, shear velocity provinces in the lowermost mantle as it heats during descent in the lowermost mantle. The combined results of this thesis elucidate a complete compression pathway during transport of a dense oxyhydroxide into the lower mantle in the context of changes in its electronic and elastic properties. I offer several observables which may be used to detect the presence of this phase in subducted metabasalt and comment on the implications for hydrogen storage in the deep Earth." }, { "name": "Ward, Ryan Xavier", "degree": "PhD", "year": "2025", "title": "Observational and Computational Studies of Atmospheric Particle Formation", "advisor": "Seinfeld, John H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09062024-191128914", "creators": [ { "name": { "family": "Ward", "given": "Ryan Xavier" }, "id": "Ward-Ryan-Xavier", "orcid": "0000-0003-2317-3310", "display_name": "Ward, Ryan Xavier" } ], "advisors": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "orcid": "0000-0003-1344-4068", "role": "advisor", "display_name": "Seinfeld, John H." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "orcid": "0000-0001-5690-770X", "role": "member", "display_name": "Flagan, Richard C." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Ng", "given": "Nga L." }, "id": "Ng-Nga-L", "orcid": "0000-0001-8460-4765", "role": "member", "display_name": "Ng, Nga L." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "orcid": "0000-0003-1344-4068", "role": "member", "display_name": "Seinfeld, John H." } ], "option_major": [ "envreng" ], "doi": "10.7907/dham-e191", "abstract": "Aerosols are a ubiquitous component of the atmosphere, playing pivotal roles in air quality and climate. This thesis explores the way these particles come to be, and their roles in these atmospheric processes.
\r\n\r\nAerosols form from a variety of anthropogenic and biogenic activities, processes which are very prominent in urban settings. In Los Angeles, the last decade of research has been dominated by the role of summertime secondary organic aerosol (SOA) in contributing to particulate matter (PM). Here, we make observations in the equinox seasons and in the winter and detail the formation of atmospheric aerosols in these seasons. Using aerosol mass spectrometry, we demonstrate that ammonium nitrate persists as one of the dominant secondary aerosol components despite dramatic reductions in nitrogen oxide (NO\u2093) emissions. Further, we show that this ammonium nitrate is not measured by routine air quality measurements, biasing regulatory PM2.5 measurements. In the wintertime, similar techniques demonstrate that primary organic aerosol, as opposed to secondary, is an important component of the PM2.5, contrary to the prevailing narratives that SOA dominates the aerosol mass.
\r\n\r\nAt global scales, the role of these aerosols in cloud formation and climate processes is of primary interest. While a variety of physicochemical properties of aerosols are important in the formation of cloud droplets, we focus here on the specific process of organic surface-partitioning. It has been suggested that in phase-separated aerosol, organic-rich surface layers can depress the surface tension of the particles, lowering their barrier to activate into cloud droplets. We assess this propensity for surface tension depression in two SOA systems, \u03b1-pinene and \u03b2-caryophyllene. Synergizing laboratory measurements, a thermodynamic model, and field data, it is shown that surface-active organics in these SOA systems can impact their hygroscopicity, though perhaps not sufficiently to warrant inclusion of these processes in global-scale models.
" }, { "name": "Yang, Yan", "degree": "PhD", "year": "2025", "title": "Imaging the Earth\u2019s Near Surface with Dense Seismic Observation", "advisor": "Zhan, Zhongwen; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechThesis:07182024-175725823", "creators": [ { "name": { "family": "Yang", "given": "Yan" }, "id": "Yang-Yan", "orcid": "0000-0002-6105-2918", "display_name": "Yang, Yan" } ], "advisors": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "advisor", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "chair", "display_name": "Ross, Zachary E." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Fu", "given": "Xiaojing" }, "id": "Fu-Xiaojing", "orcid": "0000-0001-7120-704X", "role": "member", "display_name": "Fu, Xiaojing" } ], "option_major": [ "geophys" ], "doi": "10.7907/s4rx-6n15", "abstract": "Understanding the Earth's near surface is critical for assessing seismic hazards and ensuring environmental sustainability. In this thesis, I explore the use of advanced observation and analysis techniques for near-surface imaging with big seismic data.
\r\n\r\nChapters 2-6 focus on the applications of Distributed Acoustic Sensing (DAS). DAS is an emerging sensing technology that transforms fiber-optic cables into dense seismic arrays. In Chapter 2, I introduce a high-performance Python tool for computing seismic ambient noise cross-correlation with large volumes of DAS data. In Chapter 3, I perform ambient noise tomography using a DAS array in Ridgecrest, California, to resolve spatial variation of the near-surface structure, revealing its correlation with earthquake ground shaking amplification. In Chapter 4, I use surface wave scattering observed in the DAS noise cross-correlation for fault zone detection and characterization. In Chapter 5, I analyze three years of DAS noise cross-correlation to monitor seismic velocity changes, providing insights into vadose zone soil moisture dynamics and water resource management in the context of climate change. In Chapter 6, I use a DAS array at the South Pole to characterize firn structure for a better understanding of cryosphere mass balance.
\r\n\r\nChapters 7 and 8 focus on imaging geological structures in the urban Los Angeles region using dense arrays of geophones. Chapter 7 uses converted S-to-p phases recorded by a dense network of low-cost accelerometers to map the basin depth. Chapter 8 investigates shallow seismicity in the Long Beach area to illuminate complex fault structures.
\r\n\r\nIn Chapters 9 and 10, I apply a state-of-the-art machine learning framework known as a neural operator for solving seismic wave equations. The trained neural operator enables full seismic waveform modeling with substantial advancements over conventional numerical techniques including its fast speed, generalizability, and convenient differentiability for full waveform inversion.
" }, { "name": "Dallas, Brooke Hillary", "degree": "PhD", "year": "2024", "title": "Intermolecular and Intramolecular Stable Isotope Studies in Alanine", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05252024-201300283", "creators": [ { "name": { "family": "Dallas", "given": "Brooke Hillary" }, "id": "Dallas-Brooke-Hillary", "orcid": "0000-0002-1313-3270", "display_name": "Dallas, Brooke Hillary" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geol" ], "doi": "10.7907/xqdx-pp86", "abstract": "In Chapter 1 of this thesis, we give an introduction to this body of work, providing some background for context.
\r\n\r\nIn Chapter 2, we present a set of theoretical predictions for the carbon isotope distribution between equilibrated carbon sites of alanine and pyruvate. We start with the simplest possible theoretical treatment, and work progressively through higher levels of theory, showing consistency in the direction and magnitude of expected fractionation across these treatments.
\r\n\r\nIn Chapter 3, we present our experimental work to confirm the predictions made in Chapter 2 by measuring the \u03b413C of the \u03b1 carbon site in alanine that has undergone equilibration with the analogous carbon site in pyruvate via the alanine transaminase enzyme (ALT).
\r\n\r\nIn Chapter 4, we describe the process that led to our (re)discovery of \u03b2-hydrogen-deuterium exchange in amino acids catalyzed by transaminases. We then provide a literature review on the small body of historical work on this system, which took place primarily during the 1960s and 70s. This literature summary provides the background necessary for the reader to appreciate our experimental work presented in the next chapter.
\r\n\r\nIn Chapter 5, we present novel 1H NMR and 13C NMR experimental observations of intermolecular hydrogen isotope exchange between water and the \u03b1 and \u03b2 carbon sites of alanine, as well as intramolecular hydrogen isotope exchange between the \u03b1 and \u03b2 carbons, all of which is catalyzed by alanine transaminase (ALT). These experiments track the abundances of eight isotopically distinct alanine species varying in their position and/or number of hydrogen isotopes over a series of reactions differing in initial alanine isotopic composition and initial water isotopic composition. With the data collected we are able to determine up to thirteen rate constants and ten equilibrium constants describing the transfer of hydrogen and deuterium amongst these eight isotopic variants and water, as well as the thermodynamic equilibrium constants between them.
" }, { "name": "Dong, Guannan", "degree": "PhD", "year": "2024", "title": "Taking the Pulse of Life: Intramolecular and Clumped Isotopic Perspectives on the Origins and Evolution of Hydrocarbons in Geological and Prebiotic Systems", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012024-213407041", "creators": [ { "name": { "family": "Dong", "given": "Guannan" }, "id": "Dong-Guannan", "orcid": "0000-0002-6844-2492", "display_name": "Dong, Guannan" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "co-chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/yw0g-s893", "abstract": "Life\u2019s origins and fate are tightly intertwined. All life as we know it is composed of proteins, carbohydrates, lipids, and nucleic acids. These biomolecules are synthesized today by cellular machinery made of the same components, leaving open questions about the origins of life and prebiotic chemistry. After death, organic remnants are buried in sediments, undergoing microbial reworking, consolidation, and transformation into kerogen. As temperature and pressure increase with depth, kerogen matures, releasing oil and gas before ultimately transforming into graphite. The question remains: can we decipher the traces of life (and non-life) from somewhat altered organic matter from the past or on other planets? This thesis explores the origins and evolution of one of the most fundamental classes of compounds\u2014hydrocarbons\u2014across geological and prebiotic settings through novel applications of intramolecular and clumped isotope analysis.
\r\n\r\nChapter 2 delves into the evolution of isotopic signatures in methane, the simplest hydrocarbon, during the maturation process. By studying the clumped isotope effects of thermogenic methane formation through pyrolysis experiments, this chapter challenges previously held assumptions about abiotic and microbial signatures. The findings offer new opportunities to constrain the thermal maturation of sedimentary organic matter and have implications for the search for extraterrestrial life.
\r\n\r\nTo facilitate high-precision measurements of hydrocarbon isotopic structures, Chapter 3 presents hardware and software developments enabling automated, high-throughput analysis using Orbitrap mass spectrometry. Chapter 4 then introduces a novel method coupling gas chromatography and Orbitrap MS to simultaneously measure intramolecular \u00b9\u00b3C and \u00b2H distributions in n-alkanes, validating the technique for forensic fingerprinting and natural sample characterization.
\r\n\r\nTurning to the impact of thermal maturation, Chapter 5 examines how n-alkane intramolecular isotope patterns evolve through pyrolysis experiments. Kinetic isotope effects control residual n-alkane isotopic compositions, with minimal alteration to intramolecular distributions under the studied conditions, suggesting preservation of primitive signatures.
\r\n\r\nChapter 6 brings together these analytical developments to compare intramolecular isotope compositions of n-nonadecane from sedimentary, abiotic, and biological sources. Distinctive isotopic fingerprints are established for each source, with implications for interpreting organic matter histories and detecting potential signatures of extraterrestrial life.
\r\n\r\nCollectively, this thesis expands the \"molecular detective\" toolkit for tracing hydrocarbon origins across diverse environments, from deep petroleum systems to potential prebiotic reaction pathways. The findings illuminate key processes governing isotopic biosignatures and their preservation through geological time.
" }, { "name": "Hightower, Erin Jessica", "degree": "PhD", "year": "2024", "title": "From Tectonic Evolution to Intraplate Stress: The Role of Structural Inheritance and Long-Wavelength Loading", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11302023-021244845", "creators": [ { "name": { "family": "Hightower", "given": "Erin Jessica" }, "id": "Hightower-Erin-Jessica", "orcid": "0000-0002-4734-5159", "display_name": "Hightower, Erin Jessica" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." }, { "name": { "family": "Watkins", "given": "Michael M." }, "id": "Watkins-M-M", "role": "member", "display_name": "Watkins, Michael M." } ], "option_major": [ "geophys" ], "doi": "10.7907/xc1b-ke51", "abstract": "In this thesis, I present a multifaceted exploration of various aspects of deformation and stress in the Earth's lithosphere using a variety of methods in a range of tectonic environments. I begin by examining the evolution of a young subduction zone through a combination of gravity modeling and seismological observations. Chapter 2 details the development a linear 3-D gravity inversion method capable of modelling complex geological regions such as subduction margins. Our procedure inverts satellite gravity to determine the best-fitting differential densities of spatially discretized subsurface prisms in a least-squares sense. We use a Bayesian approach to incorporate both data error and prior constraints based on seismic reflection and refraction data. Based on these data, Gaussian priors are applied to the appropriate model parameters as absolute equality constraints. To stabilize the inversion and provide relative equality constraints on the parameters, we utilize a combination of first and second order Tikhonov regularization, which enforces smoothness in the horizontal direction between seismically constrained regions, while allowing for sharper contacts in the vertical. We apply this method to the nascent Puysegur Trench, south of New Zealand, where oceanic lithosphere of the Australian Plate has under-thrust Puysegur Ridge and Solander Basin on the Pacific Plate since the Miocene. These models provide insight into the density contrasts, Moho depth, and crustal thickness in the region. The final model has a mean standard deviation on the model parameters of about 17 kg/m-3, and a mean absolute error on the predicted gravity of about 3.9 mGal, demonstrating the success of this method for even complex density distributions like those present at subduction zones. The posterior density distribution versus seismic velocity is diagnostic of compositional and structural changes and shows a thin sliver of oceanic crust emplaced between the nascent thrust and the strike slip Puysegur Fault. However, the northern end of the Puysegur Ridge, at the Snares Zone, is predominantly buoyant continental crust, despite its subsidence with respect to the rest of the ridge. These features highlight the mechanical changes unfolding during subduction initiation.
Chapter 3 explores the earthquake interevent time distribution. Earthquakes are commonly assumed to result from a stationary Poisson (SIP) process. We reassess the validity of this assumption using the Quake Template Matching (QTM) catalog and the relocated SCSN catalog (HYS) for Southern California. We analyze the interevent time (IET) distribution and the Schuster spectra after declustering with the Zaliapin and Ben Zion (2013) method. Both catalogs exhibit fat-tails on the IET distribution, deviating from the expected exponential distribution. The Schuster spectra of the catalogs are also inconsistent with an SIP process. The QTM catalog shows a statistically significant seasonal signal and a drift in the Schuster probability at long periods, likely due to increased seismicity following the 2010 El Mayor-Cucapah earthquake. This increase is also evident in the yearly IET distributions of the catalog. In contrast, the HYS Schuster spectrum does not show seasonality, but the yearly IET distributions exhibit a decrease in seismicity rate over the duration of the catalog, likely due to seismic network upgrades around 1990. We use synthetic catalogs to test the origin and significance of the observed deviations from the Poisson model. Variations in the QTM annual seismicity rate, around 5.6%, are too small to generate a noticeable departure from an exponential distribution, and the SIP model can not be rejected at the 5% significance level. The synthetic catalogs also suggest the fat-tail is an artefact of incomplete declustering. Overall, variations in the IET distribution for southern California are probably the result of both 1) incomplete declustering and location uncertainty, and 2) transient non-stationarity of the background rate from viscoelastic effects of large earthquakes. However, the stationary Poisson model appears adequate for describing background seismicity at the scale of Southern California and the decadal time scale of the QTM catalog.
Chapters 4 and 5 cover the primary focus of this thesis, exploring the influence of long-wavelength loading on the stress field of continental interiors and intraplate seismicity. The continental interior of eastern North America in particular has hosted many significant historical earthquakes and is undergoing both glacial isostatic adjustment (GIA) and long-wavelength subsidence due to the sinking of the Farallon slab. The regional seismicity concentrates within ancient failed rift arms and other paleo-tectonic structures, which can act as weak zones in the crust where stress accumulates. Within some of these zones, focal mechanism stress inversion shows significant rotational deviation of the maximum horizontal stress (SHmax) direction from the regional NE-SW trend, which may be explained by long-wavelength stress perturbations in the presence of lithospheric weakness. We focus on two sources of intraplate stress perturbation and seismicity and test the hypotheses that 1) mantle-flow induced epeirogenic subsidence and 2) GIA contribute to intraplate seismicity in eastern North America via reactivation of pre-existing faults.
For the slab loading component of this work, we use high-resolution global, spherical finite-element flow models with CitcomS. To capture realistic temperature fields and the Farallon slab, we convert seismic tomography models to temperature using a mineralogically constrained depth-dependent scaling factor. We utilize laterally variable temperature-dependent viscosities, upon which we superimpose low-viscosity plate boundary weak zones, as well as lithospheric intraplate weak zones at the locations of failed rifts and other inherited structures in eastern North America. We parameterize the Farallon slab in terms of its buoyancy to determine the degree to which the flow induced by the sinking slab contributes to intraplate stress. Using the modeled stress tensors from instantaneous flow calculations, we compute SHmax, the stress magnitudes, and the Coulomb failure stress on mapped faults in several major seismic zones. Slab sinking drives localized mantle flow beneath the central-eastern U.S., leading to a stress amplification of 100-150 MPa across the region that peaks over the New Madrid Seismic Zone. This stress amplification introduces a pronounced continent-wide clockwise rotation of the predicted SHmax direction, reaching as much as 20\u00b0 in some seismic zones, particularly when lithospheric weak zones are included. In the New Madrid, Central Virginia, Charlevoix, and Lower Saint Lawrence Seismic Zones, the presence of weak zones loaded by the Farallon slab at depth can explain the pattern of clockwise rotation of the observed focal mechanism derived SHmax relative to the regional borehole derived SHmax as reported in previous studies. However, misfits on SHmax within many of the major seismic zones suggest other sources of stress are needed to properly reproduce the observed stress trends in some areas. We also find that in order for pre-existing lithospheric weak zones to exert appreciable control on intraplate stress under the influence of mantle flow, they must be shallow/sub-crustal and in contact with the crust. These stress perturbations and rotations ultimately bring faults in the NMSZ, the Western Quebec Seismic Zone (WQSZ), and the Lower Saint Lawrence and Charlevoix Seismic Zones closer to failure. In particular, inclusion of the Farallon slab and weak zones produces positive Coulomb failure stresses on some key faults associated with major historical earthquakes, including the Reelfoot Fault in the NMSZ and the Timiskaming fault in the WQSZ. Fault instability is even more likely when assuming weaker faults with lower coefficients of friction.
For the glacial unloading component of this work, we use the global, spherical finite element code CitcomSVE, which models dynamic deformation of a viscoelastic and incompressible planetary mantle in response to surface loading. We supply CitcomSVE with the same seismically constrained viscosity structures computed in the CitcomS models, including those with weak zones, and load the Earth model with the ICE-6G ice history. We perform the same suite of simulations and stress analyses as in the mantle loading problem, using the stress tensor output of the corresponding CitcomS model as the tectonic background stress. We compare the mantle flow and GIA induced stresses, with focus on the present day extant glacially derived stress field. GIA induced stress perturbations are small (~10 MPa), even in the presence of lithospheric weak zones. GIA induced SHmax alone exhibits a transition from clockwise to counterclockwise rotation moving northeast across the continent. We find that only by inclusion of the mantle flow derived background stress can we reproduce the continental scale clockwise stress rotation observed in stress data, suggesting the effect of mantle loading is more important for explaining these observations than is GIA. In the NMSZ, GIA helps promote stability on the Reelfoot Fault, in opposition to mantle flow, while promoting instability on more non-optimally oriented faults. GIA also helps localize higher Coulomb failure stress within the Charlevoix Seismic Zone and the western half of the WQSZ. In the WQSZ and LSLRS, GIA stress perturbations are large enough that even with only a small reduction in the coefficient of friction, faults that are not likely to fail under the background tectonic and geodynamic stresses alone could slip. Further investigation of the sensitivity of GIA stress to different 3D and 1D viscosity structures and the change in GIA stress with time since deglaciation is warranted to better understand how GIA affects intraplate seismicity. Ultimately, constraining how mantle flow and GIA affect stress and deformation in the presence of laterally variable viscosity is integral to quantifying how long-wavelength loading may alter the spatial distribution of seismic hazard.
" }, { "name": "Li, Haoyu", "degree": "PhD", "year": "2024", "title": "Revisiting U-Pb and \u00b2\u2076Al-\u00b2\u2076Mg Systematics of Calcium Aluminum-Rich Inclusions: Applications on Early Solar System Chronology and Evolution History", "advisor": "Tissot, Fran\u00e7ois L.H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05202024-220724726", "creators": [ { "name": { "family": "Li", "given": "Haoyu" }, "id": "Li-Haoyu", "orcid": "000-0002-7192-2470", "display_name": "Li, Haoyu" } ], "advisors": [ { "name": { "family": "Tissot", "given": "Fran\u00e7ois L.H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "advisor", "display_name": "Tissot, Fran\u00e7ois L.H." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Amelin", "given": "Yuri" }, "id": "Amelin-Y", "orcid": "0000-0001-6719-8937", "role": "member", "display_name": "Amelin, Yuri" }, { "name": { "family": "Krot", "given": "Alexander N." }, "id": "Krot-A-N", "role": "member", "display_name": "Krot, Alexander N." }, { "name": { "family": "Tissot", "given": "Fran\u00e7ois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "member", "display_name": "Tissot, Fran\u00e7ois L. H." } ], "option_major": [ "geochem" ], "doi": "10.7907/ahbv-8z61", "abstract": "Stable isotope systematics are powerful tools for understanding the evolution history of the earth and Solar system. In this thesis, I present applications of uranium (U) and magnesium (Mg) isotopes in both geochemistry and cosmochemistry.
\r\n\r\nUranium is a redox-sensitive to the dissolved oxygen level in aqueous environment, and these redox reactions are associated with resolvable isotopic fractionation. Thus, U isotopes are widely used in paleo-environment reconstruction as a proxy of marine anoxia. For this application, the work presented in this thesis includes (1) exploration of the potential of bioapatite as a novel paleoredox proxy. and (2) re-calibrate the U isotope composition of seawater. The U-Pb and Al-Mg systematics provide constraints on the time sequence and composition of the early Solar System. For this application, the work presented in this thesis includes (1) combined Pb-Pb and Al-Mg systematics on calcium-aluminum-rich inclusions (CAIs) to resolve the discrepancies between these two chronometers (2) Al-Mg systematics of bulk CAIs to understand their precursors. This thesis also presents the analytical techniques developed for the studies above and the development of a comprehensive uranium isotope database.
" }, { "name": "Li, Yida", "degree": "PhD", "year": "2024", "title": "I. Dynamics of Subduction Initiation and II. Constraining Sedimentary Basin Structure with Seismic Ambient Noise", "advisor": "Gurnis, Michael C.; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05302024-182513713", "creators": [ { "name": { "family": "Li", "given": "Yida" }, "id": "Li-Yida", "orcid": "0000-0003-0664-0247", "display_name": "Li, Yida" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/y3z2-z538", "abstract": "Subduction initiation, the inception of a subduction zone, heralds dramatic changes in tectonic plate kinematics and dynamics. In the first half of the thesis, I focus on understanding the dynamics of the subduction initiation process through a synthesis of numerical computations and theoretical frameworks. In Chapter 2, we employ force balance analysis and 2D geodynamic models to yield an analytical solution on the force evolution of the subducting plate. This formulation illuminates a pivotal phase in subduction initiation \u2014- the compression-to-extension transition of plate forces -\u2014 as a defining milestone. In Chapter 3, we extend this analytical framework into a sliced 3D context (2.5D) while incorporating the influence of strike-slip motion. Modified from Chapter 2, the analytical solution validates that strike-slip motion facilitates subduction initiation by accelerating the process of weakening. Chapter 4 ventures into 3D geodynamic modeling, focusing on the Puysegur trench -\u2014 a living example of subduction initiation. The models demonstrate a capability to match multiple geophysical and geological observations quantitatively with mechanical models. With a parametric search, we discover the best-fitting models require a relatively fast strain weakening rate, which can be explained by pore-pressure weakening at shallow depths and grain-size reduction at greater depths.
\r\n \r\n \r\nThe second part of this thesis transitions to ambient seismic noise correlation. In Chapter 5, we conduct an ambient noise tomography in northern Los Angeles basins with a newly obtained, dense seismic data set. The new shear wave velocity model exhibits a lower velocity in the basins than previous community models, which can potentially resolve the inconsistency between observed and calculated ground motions. In Chapter 6, we introduce a new method to identify the near-field noise sources from the spurious arrivals in ambient noise correlations. The correlation between the inverted noise sources and geological features in northern LA basins suggests the viability of this technique as a novel means of identifying geological structures, including faults.
" }, { "name": "Lim, Sujung", "degree": "PhD", "year": "2024", "title": "The Impact of Energy Availability and Substrate Complexity on Anaerobic Microbial Communities in Marine Sediment", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04172024-164449548", "creators": [ { "name": { "family": "Lim", "given": "Sujung" }, "id": "Lim-Sujung", "orcid": "0000-0001-6040-729X", "display_name": "Lim, Sujung" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/67j6-4885", "abstract": "This thesis probes the interplay of organic matter complexity (Chapters 1 and 2) and local redox gradients (Chapter 3) with the community structure and function of the anaerobic marine sediment microbiome. Deep marine sediments, despite being generally organic-poor, harbor a vast diversity of microorganisms that are critical to the global nutrient cycle. Transient nutrient inputs such as whale falls result in hotspots of microbial community activity in an environment that normally processes heavily degraded organic material from the upper ocean. These organic loading events result in transitions down redox gradients and dynamic shifts in the local energy availability of the microbial communities. Through in situ seafloor and laboratory microcosm experiments, we provide insights into the impact of energy availability and carbon complexity on maintaining hierarchical and complex community interactions, community activity, and systematic and functional diversity." }, { "name": "Marquez, Ren Thomas Caburnay", "degree": "PhD", "year": "2024", "title": "Primitive Stellar Remnants and their Signatures as Probes to the Nascent Solar System", "advisor": "Tissot, Fran\u00e7ois L. H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06042024-171635742", "creators": [ { "name": { "family": "Marquez", "given": "Ren Thomas Caburnay" }, "id": "Marquez-Ren-Thomas-Caburnay", "orcid": "0000-0002-8317-9397", "display_name": "Marquez, Ren Thomas Caburnay" } ], "advisors": [ { "name": { "family": "Tissot", "given": "Fran\u00e7ois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "advisor", "display_name": "Tissot, Fran\u00e7ois L. H." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Budde", "given": "Gerrit" }, "id": "Budde-Gerrit", "orcid": "0000-0003-0762-779X", "role": "member", "display_name": "Budde, Gerrit" }, { "name": { "family": "Tissot", "given": "Fran\u00e7ois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "member", "display_name": "Tissot, Fran\u00e7ois L. H." } ], "option_major": [ "geochem" ], "doi": "10.7907/ge1c-kj54", "abstract": "The confluence of eons of alteration, accretion, and a multitude of other planet-building processes present a tremendous challenge in studying the early Solar System through planetary materials. Mainly, pristine records of conditions in the nascent nebula are rare, and often pose significant analytical obstacles. Fine-grained (fg-) calcium-aluminum-rich inclusions (CAIs) offer a unique opportunity to investigate the earliest stages of nebular evolution, as these are (1) the most primitive condensates in the Solar System, and (2) have never seen melting unlike their coarse-grained counterparts. The main difficulty in working with these inclusions is their diminutive size. Central to the work presented here is the development of techniques that enable the analysis of ever-smaller extraterrestrial samples, mainly leachates from fine-grained CAIs, thereby allowing access to information often rendered unintelligable by bulk analysis.
\r\n\r\nFirst, I present a new software suite that optimizes mass-dependent isotope measurements on extraterrestrial materials (Chapter 1). This package, dubbed as COSMO, complements existing computational tools for optimizing the double spike technique (i.e., the double spike toolbox) by accounting for analytical artefacts from mass-independent effects (e.g., nucleosynthetic isotope anomalies). Specifically, the software aids in determining the ideal way to split a limited amount of materials between spiked and unspiked measurements. Such a tool should aid in extracting the most amount of information from rare and critical analytes (e.g., unique meteorites and returned samples).
\r\n\r\nNext, I discuss the nucleosynthetic barium isotope signatures in the various components of fine-grained CAIs (Chapter 3). These samples were derived via step-leaching of fine-grained CAIs from the Allende meteorite, which have previously been demonstrated to exhibit extreme nucleosynthetic 84Sr excesses. The barium isotope anomalies in these materials serve to potentially elucidate the stellar source(s) of these signatures, as Sr and Ba are documented to co-vary in known presolar materials and have similar geochemical behavior. However, our analyses revealed that these two elements are decoupled in these refractory leachates, pointing to nucleosynthetic sites that overproduce strontium such as electron-capture supernovae (ECSNe) and core-collapse (Type II) supernovae in massive rotating stars. In addition, the step-leaching procedure also reveals a strong congruence between L1-L3 isotopic variability and the anomalous signatures in presolar SiC grains.
\r\n\r\nLast, I demonstrate that the extreme strontium isotope anomalies in primitive condensates are hosted in oxides using a new protocol called intra-sample addition (ISA; Chapter 4). This experiment also reveals that 84Sr anomalies are heterogeneously distributed in these oxides, which is explained by the nugget effect via the presence of rare but highly anomalous grains. Such grains are interpreted here to be true presolar carriers, which we propose to have served as nucleation seeds of the earliest condensates in the nebula. These results are at-odds with the prevalent notion of a hot and homogeneous nebular gas from which early condensates form, and thus suggest an alternative mechanistic link between disk heterogeneity and the stellar building blocks of the Solar System.
" }, { "name": "Morris, Freya Kurt", "degree": "PhD", "year": "2024", "title": "Depositional and Structural History of the Pavian and Kudu Nappes in the Naukluft Mountains, Namibia", "advisor": "Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08132023-171059108", "creators": [ { "name": { "family": "Morris", "given": "Freya Kurt" }, "id": "Morris-Freya-Kurt", "orcid": "0000-0003-4765-9286", "display_name": "Morris, Freya Kurt" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Pico", "given": "Tamara" }, "id": "Pico-Tamara", "orcid": "0000-0002-3629-0922", "role": "member", "display_name": "Pico, Tamara" }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geol" ], "doi": "10.7907/ecfc-c202", "abstract": "The termination of the Marinoan Snowball Earth glacial epoch was one of the most extreme climate events in Earth history. Yet, the transition from global glaciation to an ice-free warmer climate is still poorly constrained. The Naukluft Nappe Complex of south-central Namibia contains several stratigraphic formations that record the environmental and tectonic transitions of the Neoproterozoic, including glaciogenic deposits and basal-Ediacaran cap carbonate of the Marinoan Snowball Earth. This stratigraphic record has the potential to provide a critical record of the climate, sea-level history, ocean chemistry, and time frames across the climate transition of the Marinoan Snowball deglaciation.
\r\n\r\nWe first show a detailed study of the sedimentology and stratigraphy of the upper Bl\u00e4sskranz Formation and Tsabisis Formation cap carbonate to develop an environmental and sequence stratigraphic history spanning and following the deglaciation. In downdip areas Marinoan diamictite transitions upward into dolostone intermixed with sandstone and extrabasinal clasts that is gradually overlain by fine grained laminated dolostone. Updip localities show the diamictite is overlain by intercalated sandstones, gravels, and shales before an abrupt change to laminated dolostone of the cap carbonate. A succession of stromatolites, which become strongly elongate upward, prograde into the laminated dolostone in the updip localities. The stromatolites are overlain by laminated dolostone that grades upward into rhythmite with intercalations of shale. Near the top of the cap, rhythmites may be reworked into tabular intraclast conglomerate, locally intercalated with hummocky cross stratified sandstone, which passes upward into the shale and limestone members of the Tsabisis Formation. The lateral and vertical distribution of facies indicate a retreat of the shoreline and glacially sourced siliciclastics near the base of the cap carbonate, a shallowing succession to fair-weather wave base at the top of the stromatolite facies, and a second shallowing succession to storm wave base near the top of the cap carbonate. Maximum flooding occurred soon after the initiation of carbonate deposition and two sequence boundaries mark higher stratigraphic levels within the cap carbonate. With a sea-level history and chronological framework inferred from the sequence stratigraphy we can consider different mechanisms of sea-level change, which may reflect the timescale and synchronicity of deglaciation.
\r\n\r\nNext, we consider the structural and stratigraphic relationships between the Neoproterozoic units of the Naukluft Mountains to define and contextualize the extent of the terminal Marinoan geologic record. We show that the Northern Pavian Nappe, which includes the Marinoan-associated Bl\u00e4sskranz and Tsabisis formations, is stratigraphically succeeded by the dolostone dominated Kudu Nappe and is not correlated or genetically related to the nearby Southern Pavian Nappe. Additionally, the modified stratigraphic and structural relationships allow for a simplified nappe emplacement history that reduces the magnitude of shortening associated with convergence along the Damara Orogen.
\r\n\r\nFinally, we use sea-level modeling of the Naukluft Marinoan record to constrain the duration of global deglaciation. Using a range of reconstructed synchronous and continuous deglaciation models, we evaluate if the observed sea-level patterns of the Naukluft can be fully explained by glacial isostatic mechanisms driven by the deglaciation. Short Snowball deglaciation durations, on the order of ~2 kyr, result in exclusive sea-level rise, or sea-level rise followed by sea-level fall, but cannot drive two distinct phases of sea-level fall. However, for longer duration snowball deglaciations, of ~10-30 kyr, we can drive two distinct intervals of sea-level rise and fall across much of the width of a continental margin, consistent with the stratal patterns observed in Naukluft Mountains cap carbonate succession. Our spatially varying sea-level predictions resulting from longer duration deglaciations may be applicable in interpreting stratal patterns of other cap carbonate successions. Furthermore, this work underlines the need for better constraints on the areal distribution and volume of Marinoan ice sheets, including improved understanding of plausible deglacial durations using updated global climate models.
" }, { "name": "Mueller, Elliott Patrick", "degree": "PhD", "year": "2024", "title": "Carbon Currencies: Isotopic Constraints on the Biogeochemistry of Organic Acids", "advisor": "Sessions, Alex L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05232024-200019160", "creators": [ { "name": { "family": "Mueller", "given": "Elliott Patrick" }, "id": "Mueller-Elliott-Patrick", "orcid": "0000-0002-6837-0409", "display_name": "Mueller, Elliott Patrick" } ], "advisors": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "advisor", "display_name": "Sessions, Alex L." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." } ], "option_major": [ "geobiol" ], "doi": "10.7907/qdbh-zr32", "abstract": "On both human and geologic timescales, the microbial degradation of organic carbon in anoxic environments significantly influences the Earth\u2019s climate. The rate-limiting step of this process is the initial breakdown of complex organic polymers (e.g. cellulose) into small organic acids (e.g. acetate), which are then rapidly converted into either carbon dioxide or methane. While the steady-state concentration of organic acids is kept low by microbial turnover, the flux of reactions producing and consuming them is large. In my doctoral work, I leveraged this dynamic pool of metabolites as a window into the broader carbon cycle. Specifically, I developed novel analytical and computational tools that quantify and interpret the isotope composition of organic acids. These techniques provide new information about the mechanism and rates of organic acid turnover in nature.
\r\n\r\nFirst, in Chapter 2, I adapted electrospray ionization (ESI) Orbitrap mass spectrometry (MS) to simultaneously measure the carbon and hydrogen isotope compositions of acetate. This approach is 50 to 1000-fold more sensitive than established techniques, making measurements of environmental samples feasible for the first time. This technique clearly distinguishes the metabolic sources of acetate (fermentation and acetogenesis). In Chapter 3, I developed a complementary computational tool to interpret this new isotopic information. Quantifying Isotopologue Reaction Networks (QIRN) builds numerical models of complex reaction networks, including metabolic pathways, and predicts the isotope composition of molecules produced by these networks. In Chapter 4, I combined my analytical and computational approaches to investigate the isotopic fractionations of the microbial metabolism that generate organic acids in nature, fermentation. I found that fermentation imposes a significant isotopic fractionation during the degradation of organic matter. By coupling flux-balance analysis and QIRN, I isolated the enzymes responsible for these fractionations. These results suggested that fermentation may have imprinted a carbon isotope trophic enrichment that is observable in the compound-specific carbon isotope composition of Proterozoic biomarkers. In Chapter 5, I used my Orbitrap method to quantify in situ acetate turnover rates based on the exchange of hydrogen atoms between water and acetate's methyl group. I took this tool to the environment, where I studied the biogeochemical drivers of carbon cycling in the deep continental subsurface. In Kidd Creek mine, which has subsurface fracture fluids that have been isolated for over a billion years, I found that acetate is being actively produced and consumed in the subsurface. My analyses of acetate's isotope composition suggested that turnover may be driven by low-temperature water-rock reactions with implications for the habitability of subsurface environments elsewhere in the Solar System. Chapter 6 is a second application of the Orbitrap and QIRN in natural systems. This time I expanded the Orbitrap technique to include not only acetate but also the organic acids propionate and butyrate. I investigated carbon turnover in the rumen fluid of cows, where microbial fermentation breaks down cellulose and transfers organic acids to the animal host. I found clear trends in the carbon and hydrogen isotope composition of acetate and propionate that may hold information about the metabolic strategies of fermenters in the rumen. Finally, in Chapter 7, I highlight the challenges and opportunities of transitioning Orbitrap MS isotopic applications from pure standards to compelx samples. These studies demonstrate bespoke strategies for isolating organic acids, and possibly other ESI-Orbitrap analytes, from environmental samples without fractionating their isotope ratios. Together, these chapters use a combination of novel analytical and computational tools to study the rate and mechanism of organic acid cycling in nature. Elucidating these drivers is necessary to understand the modern and ancient carbon cycle and to predict its response to climate change.
" }, { "name": "Nguyen, Newton Huy", "degree": "PhD", "year": "2024", "title": "From Source to Sink: Measuring and Modeling Processes Affecting Methane Emissions and Loss", "advisor": "Frankenberg, Christian", "url": "https://resolver.caltech.edu/CaltechTHESIS:08112023-233852985", "creators": [ { "name": { "family": "Nguyen", "given": "Newton Huy" }, "id": "Nguyen-Newton-Huy", "orcid": "0000-0002-9118-8672", "display_name": "Nguyen, Newton Huy" } ], "advisors": [ { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "advisor", "display_name": "Frankenberg, Christian" } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" } ], "option_major": [ "envreng" ], "doi": "10.7907/k2d1-rn95", "abstract": "Methane is a key target for climate change mitigation efforts. With a radiative forcing 85 times stronger than CO\u2082 over a 20-year period and an atmospheric lifespan of only a decade, mitigating methane emissions will slow climate change in the near-term. However, quantifying methane emissions from specific sectors accurately poses a significant challenge. This is because top-down estimations of methane emissions demand precise observations and constraints on a range of physical and chemical processes. In this thesis, I seek to enhance the accuracy of methane emissions calculations by resolving these processes in detail and advocating for an expansion of the methane monitoring network.
\r\n\r\nThe primary mechanism for atmospheric methane destruction is its oxidation by the Hydroxyl radical (OH). Chemical feedbacks due to temporal variations in OH availability can substantially influence the methane lifetime and, consequently, emissions trends over recent decades. In Chapter 2, I quantify the impact of this predominant chemical loss mechanism on methane emissions calculations.
\r\n\r\nMethane loss to the stratosphere represents the second most significant methane destruction mechanism, although the processes involved remain highly uncertain. Accurately quantifying methane loss via stratospheric-tropospheric exchange is crucial for improving the accuracy of methane emissions calculations. In Chapter 3, I utilize chemical tracers to determine how stratospheric-tropospheric exchange influences global methane emissions trends.
\r\n\r\nCurrent understanding of greenhouse gas fluxes from a top-down perspective typically relies on atmospheric inversions, which depend on spatial and temporal gradients in observed greenhouse gas concentrations. However, maintaining highly accurate ground-based measurements poses logistical and financial challenges, while satellites currently do not provide the requisite accuracy and spatial resolution for long-term monitoring. In Chapter 4, I explore the potential of frequency combs in measuring environmental impacts on greenhouse gas sensing and as tools to expand the observation network.
\r\n\r\nIn summary, this thesis contributes to a more profound understanding of the two primary methane sinks and how their variations affect methane emissions trends over recent decades. It also lays the groundwork for the next-generation greenhouse gas observation network using laser frequency combs by quantifying environmental impacts on greenhouse gas spectroscopy directly in the field. Future advances should focus on a more accurate understanding of methane sink processes, improved spectroscopy, and expanded measurement networks. This will require advances in both modeling and measurements.
\r\n\r\nUltimately, rapid and efficient mitigation of methane emissions remains the most feasible approach to curb anthropogenic climate change. To do this however, accurate assessments of methane trends and emissions necessitate bringing methane measurements and modeling of methane destruction processes closer to the real world.
" }, { "name": "Palfey, William Richard", "degree": "PhD", "year": "2024", "title": "Hydrogen Incorporation in Rutile- and Perovskite-Structured Minerals and Their Analogues", "advisor": "Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032024-221310680", "creators": [ { "name": { "family": "Palfey", "given": "William Richard" }, "id": "Palfey-William-Richard", "orcid": "0000-0002-9555-7877", "display_name": "Palfey, William Richard" } ], "advisors": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Goddard", "given": "William A., III" }, "id": "Goddard-W-A-III", "orcid": "0000-0003-0097-5716", "role": "member", "display_name": "Goddard, William A., III" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geochem" ], "doi": "10.7907/nbyx-6446", "abstract": "For several decades now, it has been known that large quantities of hydrogen can be stored in the earth\u2019s mantle. This hydrogen, which is disseminated as defect components in nominally anhydrous minerals (NAMs), can have an outsized influence on minerals\u2019 bulk properties, potentially impacting planetary-scale processes. However, a description of how this hydrogen is sequestered in NAMs \u2014 its distribution between phases, its inhomogeneity between different mantle regimes, and the variety of defects involved \u2014 has evolved significantly with time. Deciphering hydrogen\u2019s role in the deep earth requires a detailed understanding of how hydrogen incorporates into mantle phases, beginning at an atomistic and structural level. Unfortunately, for a variety of reasons, directly measuring the crystallographic positions of hydrogen in most NAMs represents an exceptionally high technical barrier. Thus, hydrogen\u2019s structural state is, in many phases, incompletely understood. One approach for addressing this is to incorporate the use of computational methods like density functional theory (DFT) in the interpretation of analytical methods that can provide indirect structural information, like Fourier transform infrared spectroscopy (FTIR). This is the methodology employed by the work outlined in subsequent chapters.
\r\n\r\nThis thesis focuses on two specific mineral structures found within the deep earth \u2014 the rutile and perovskite structures \u2014 and explores some of the many possible hydrogen defect states in these phases. These include not only the conventionally considered hydroxyl (OH\u207b) group, but also hydride (H\u207b), an anionic form of hydrogen whose role in the mantle has yet to be considered in detail. The predictive and interpretive capabilities of DFT are utilized in studies on stishovite, rutile-type TiO\u2082, SrTiO\u2083, and davemaoite to both elucidate hydrogen\u2019s incorporated state in these phases and make predictions about yet-to-be-observed hydrogen defects. Detailed spectroscopic studies on rutile-type TiO\u2082 and SrTiO\u2083 perovskite provide new insights into both hydrogen and non-hydrogen related defect structures in these materials, with implications for future studies of NAMs.
" }, { "name": "Peng, Shirui", "degree": "PhD", "year": "2024", "title": "Seismic Thermometry of the North Pacific and Equatorial Indian Oceans", "advisor": "Callies, Joern", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012024-234504692", "creators": [ { "name": { "family": "Peng", "given": "Shirui" }, "id": "Peng-Shirui", "orcid": "0000-0002-4616-4604", "display_name": "Peng, Shirui" } ], "advisors": [ { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "advisor", "display_name": "Callies, Joern" } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Colonius", "given": "Tim" }, "id": "Colonius-T", "orcid": "0000-0003-0326-3909", "role": "member", "display_name": "Colonius, Tim" }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "McPhaden", "given": "Michael J" }, "id": "McPhaden-Michael-J", "orcid": "0000-0002-8423-5805", "role": "member", "display_name": "McPhaden, Michael J" }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" } ], "option_major": [ "envreng" ], "doi": "10.7907/a814-nf75", "abstract": "The ocean absorbs the majority of excess heat in the climate system. Ocean mixing is also critical in setting Earth's thermal inertia. Over the course of the past few decades, conventional observations like Argo floats have drastically improved the coverage of the global ocean. However, their temporal and spatial resolutions are still limited. Resolving trends and patterns of temperature variations in the ocean under climate change remains a challenging sampling problem. This dissertation seeks to reduce such sampling errors by developing seismic thermometry. It is an acoustic method that measures large-scale ocean temperature changes using sound waves generated by repeating earthquakes. The chapters in this thesis attempt to combine physical understanding with statistical analysis to improve and implement seismic thermometry in several ways. First, acoustic waves generated by earthquakes along the Japan Trench and received at Wake Island are used to constrain temperature variation in the Kuroshio Extension region. An inversion that combines these measurements for the time and azimuth dependence of the range-averaged deep temperatures reveals lateral and temporal variations due to Kuroshio Extension meanders, mesoscale eddies, and decadal water mass rearrangements. Second, a comprehensive covariance structure is proposed to represent variabilities due to stochastic mesoscale, regional trend, and large-scale seasonality. It demonstrates statistical consistency between conventional float data and seismic measurements, and shows quantitatively that seismic thermometry reduces basin-scale temperature uncertainty when combined with conventional measurements. Finally, seismic data are compared with ocean models in the equatorial Indian Ocean to study the vertical structure of biweekly Yanai waves. The comparison indicates qualitative agreements in biweekly variations, and regression analysis confirms their origin as west-propagating Yanai waves. Yet quantitative differences in the biweekly variance magnitude demand further calibrations in both models and the seismic inversion." }, { "name": "Singer, Clare Emilie Elmendorf", "degree": "PhD", "year": "2024", "title": "The Role of Small-Scale Cloud, Aerosol, and Radiation Processes for Earth's Climate", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:05092023-230615398", "creators": [ { "name": { "family": "Singer", "given": "Clare Emilie Elmendorf" }, "id": "Singer-Clare-Emilie-Elmendorf", "orcid": "0000-0002-1708-0997", "display_name": "Singer, Clare Emilie Elmendorf" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" }, { "name": { "family": "Feingold", "given": "Graham" }, "id": "Feingold-Graham", "orcid": "0000-0002-0774-2926", "role": "member", "display_name": "Feingold, Graham" } ], "option_major": [ "envreng" ], "doi": "10.7907/bd4s-w586", "abstract": "What makes clouds ethereal and beautiful also makes them complex and challenging to understand and to model. The important (thermo)dynamical processes of clouds occur at scales from microns (cloud-aerosol interactions), to meters (turbulence), to thousands of kilometers (synoptic weather patterns), and every scale in between. In this thesis, I explore several facets of how clouds interact with, respond to, and shape Earth's climate. I focus on small-scale processes, using high-resolution models and theory, to understand phenomena that can have large-scale impacts.
\r\n \r\nIn the first three chapters of this thesis, I explore the idea of stratocumulus-cumulus transitions. Chapters 1 and 2 develop and demonstrate a conceptual model of a cloud-topped atmospheric boundary layer, which is rooted in mixed-layer theory. This model is able to concisely explain both the spatial stratocumulus-cumulus transition observed in the historical period, as well as a transition that has only been hypothesized by models, which may occur in the future as the direct effect of extreme concentrations of atmospheric CO2, or which may have occurred in the past. I use this conceptual model to show the importance of sea surface temperature variations for driving the climatological transition, and on sea surface warming as a positive feedback for the CO2-induced transition. Chapter 3 extends this work to understand the global response to CO2-induced stratocumulus-cumulus transitions and the role for spatial teleconnections by embedding this conceptual model of the boundary layer into a global climate model (GCM). In the GCM we see both a fast adjustment in low cloud cover to CO2, as well as a slower surface temperature-mediated feedback. Under CO2 quadrupling, the stratocumulus cloud regions shrink in extent as the cloud-top longwave cooling is inhibited by CO2 and surface temperatures also increase.
\r\n\r\nThe final two chapters diverge from the previous theme to present two studies using very high-resolution models to explore how clouds interact with i) aerosols and ii) radiation. In Chapter 4, using a particle-based cloud microphysics model, I find that aerosol hygroscopicity, determined by the chemical composition of the particles, can alter stratocumulus cloud macrophysical properties, like liquid water path by up to 25% (in the regime of small aerosol sizes). I compare these results to a more standard moment-based microphysics model and find that this model is overly sensitive to aerosol hygroscopicity in the regime of small aerosol sizes, but realistically represents the negative sensitivity for large aerosol sizes. Finally, in Chapter 5, I use a Monte Carlo 3D radiative transfer solver to estimate the global albedo bias introduced in models which make the standard assumption that photon fluxes in the horizontal are zero (the so-called Independent Column Approximation). I extrapolate globally from a set of resolved tropical cloud fields, using a learned empirical relation between top-of-atmosphere flux bias and cloud water path. I conclude that in a global model that resolves clouds at small-enough spatial scales, the tropical-mean, annual-mean bias may be on the order of 3 W m-2.
" }, { "name": "Sirorattanakul, Krittanon", "degree": "PhD", "year": "2024", "title": "Response of Earthquakes to Transient Stresses, in Laboratory and Nature", "advisor": "Avouac, Jean-Philippe; Rosakis, Ares J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05202024-162817936", "creators": [ { "name": { "family": "Sirorattanakul", "given": "Krittanon" }, "id": "Sirorattanakul-Krittanon", "orcid": "0000-0003-2310-8447", "display_name": "Sirorattanakul, Krittanon" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "advisor", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Rosakis", "given": "Ares J." }, "id": "Rosakis-A-J", "role": "co-advisor", "display_name": "Rosakis, Ares J." } ], "committee": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "chair", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Rosakis", "given": "Ares J." }, "id": "Rosakis-A-J", "orcid": "0000-0003-0559-0794", "role": "member", "display_name": "Rosakis, Ares J." } ], "option_major": [ "geophys" ], "doi": "10.7907/2fgg-0m89", "abstract": "Earthquake rates are known to fluctuate with time according to the changing state of stress in the Earth\u2019s crust. Studying the response of earthquakes to transient stresses provides a unique insight into the mechanisms controlling the earthquake nucleation process. Common sources of transient stresses include stress changes from fault slip during large earthquakes, spontaneous slow fault slip, fluid pressure diffusion, seasonal changes of water mass and snowpacks related to hydrological cycles, tidal stresses from changes of gravitational forces of the Sun and the Moon, and anthropogenic fluid injection and extraction related to geoenergy production. In this\r\nthesis, we first start in the laboratory-scale fault and conduct friction experiments to enhance our understanding of the underlying friction laws used for modeling earthquakes. We find that the traditional view of Coulomb friction, which postulates that there exists a threshold shear force called \u201cstatic friction,\u201d below which the frictional interface remains stationary, is incorrect. Our measurements have shown that such an interface is still sliding, albeit with extremely small decaying slip rates down to 10^{\u221212} m/s. This is consistent with a more recently developed friction law, which describes friction as dependent on slip rate and the state of the interface, e.g., time since the last earthquake. Next, we move beyond the laboratory and study natural faults. In one example, we study the response of earthquakes to transient stress induced by a spontaneous slow fault slip event that preceded the earthquake swarm\r\nsequence by approximately half a day. In another example, we study the response of earthquakes to seasonal stress perturbations as a result of seasonal changes in groundwater mass and snowpack between wet and dry seasons, using California as a case study. In both examples, we find that earthquake nucleation is not an instantaneous process. Rather the earthquake rates lag after the stress rates. Such behavior cannot be described by Coulomb friction but can be quantitatively explained by the rate- and state-dependent friction. In the final example, we document bursts of fast propagating swarms of induced earthquakes at the Groningen gas field in the Netherlands. While transient stress must exist to drive the sequence, we cannot explicitly quantify the sources. Overall, our work provides key insights into the earthquake nucleation process, allowing us to better understand how to model the response of earthquakes to transient stress, including earthquakes that are induced by anthropogenic activities related to geoenergy production." }, { "name": "Sosa, Emma Sofia", "degree": "PhD", "year": "2024", "title": "Composition, Structure, and Formation of the Lower Crust in Continental and Oceanic Arc Settings: Insights from the Xenolith Record", "advisor": "Bucholz, Claire", "url": "https://resolver.caltech.edu/CaltechTHESIS:05242024-181307541", "creators": [ { "name": { "family": "Sosa", "given": "Emma Sofia" }, "id": "Sosa-Emma-Sofia", "orcid": "0000-0002-1765-6191", "display_name": "Sosa, Emma Sofia" } ], "advisors": [ { "name": { "family": "Bucholz", "given": "Claire" }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "advisor", "display_name": "Bucholz, Claire" } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Tissot", "given": "Fran\u00e7ois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "member", "display_name": "Tissot, Fran\u00e7ois L. H." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." } ], "option_major": [ "geol" ], "doi": "10.7907/2arj-v665", "abstract": "The compositional variability of lavas erupted in subduction zone settings results from a multitude of deep crustal processes acting in concert, reflecting variations among arcs in source rock composition, water content, oxidation state (fO2), temperature, pressure, and crystallization sequence across arcs. Lower to mid-crustal xenoliths\u2014deeply sourced rock fragments entrained and brought to the surface by ascending melts\u2014provide a robust record of the chemistry and structure of their inaccessible source regions. This thesis combines a variety of laboratory techniques and modeling approaches to explore the origins of two xenolith suites from vastly different arc settings: the oceanic Aleutian Arc off the coast of Alaska and the continental Andean Arc in Colombia. While all samples are fully characterized in terms of their petrography and the major and trace element chemistry (of both minerals and whole-rock), special attention is given to stable Fe isotope ratios, which are particularly sensitive to the fractionation of important Fe-bearing minerals like olivine, magnetite, amphibole, and garnet. \t\r\n In the first chapter, we document the major and trace element compositions of 39 previously undescribed xenoliths from the Mt. Moffett and Mt. Adagdak volcanic centers on Adak Island, Central Aleutians. This data is then used to evaluate the P-T-fO2-H2O conditions under which the cumulates formed and interrogate the nature of their parental melts. The second chapter builds upon this first study, presenting Fe isotope data of whole-rock powders and mineral separates (spinel, clinopyroxene, olivine, amphibole, and magnetite) from the Adagdak xenoliths. Our data show that the Adak crust is stratified in terms of Fe isotopes, with an isotopically light lower-crust and an isotopically heavy middle to upper-crust. The implications of this compositional structure and its relation to the evolution of Adagdak magmas is then explored through mass-balance fractional crystallization modeling. In the final chapter, we apply the same methods used in the first two chapters to characterize a suite of lower to mid-crustal xenoliths from the Mercaderes region of Colombia in the Central Andean Cordillera. In contrast to Adagdak, the Mercaderes samples show a nearly constant whole-rock Fe isotope composition throughout our ~50 km crustal section. Through thermodynamic modeling, we show that the most likely explanation for this data is that the Mercaderes suite represents a prograde metamorphic sequence" }, { "name": "Swindle, Carl Raymond", "degree": "PhD", "year": "2024", "title": "Fluid-Rock Interactions from the Lithosphere to Earth\u2019s Surface", "advisor": "Farley, Kenneth A.; Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:09282023-195100516", "creators": [ { "name": { "family": "Swindle", "given": "Carl Raymond" }, "id": "Swindle-Carl-Raymond", "orcid": "0000-0002-8706-9398", "display_name": "Swindle, Carl Raymond" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "advisor", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "co-advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Tissot", "given": "Fran\u00e7ois L. H." }, "id": "Tissot-F-L-H", "orcid": "0000-0001-6622-2907", "role": "member", "display_name": "Tissot, Fran\u00e7ois L. H." } ], "option_major": [ "geol" ], "doi": "10.7907/5mbh-jw64", "abstract": "Fluids can cycle and migrate through planetary bodies, transporting soluble ions and influencing physical properties of the surrounding rock or magma, such as fracture toughness, seismic wave velocity, melting point, viscosity, and more. Precipitated minerals, fluids trapped in inclusions, and free pore fluids can be used to constrain fluid provenance, mixing relationships, and paleoenvironmental information such as temperature, pressure, redox conditions, salinity, and pH. In my thesis, I discuss my research on topics pertaining to the geochemistry associated with fluid-rock interactions that occur from the depths of the lithospheric mantle to Earth\u2019s surface. Broadly, these chapters address open questions pertaining to 1) the retention timescales and metasomatic overprinting of fluids sourced from the mantle in obducted peridotites, 2) the capacity for pedogenic Mg-carbonates to preserve palaeohydrological information with implications for Martian carbonates, and 3) the influences hydrous fluids have on lithospheric magmas and minerals.
\r\n\r\nHelium isotopes are arguably the best tracer for fluid sources in Earth materials at the planetary scale. \u00b3He/\u2074He ratios of the Earth\u2019s 1) continental crust, 2) atmosphere, 3) upper mantle, and 4) core or deep isolated mantle (mantle plume source) vary by over two orders of magnitude, offering considerable dynamic range compared to measurement precision. While helium isotope signatures in Earth\u2019s mantle have been determined almost exclusively by the analysis of helium retained in mantle xenoliths, phenocrysts, erupted glasses, and vent gases, this selection introduces a sampling bias towards fluids that have been transported to Earth\u2019s surface by eruptive processes. In contrast, residual mantle peridotites take much longer to arrive at Earth\u2019s surface and are therefore more susceptible to metasomatic processes that can overprint primary helium isotopic signatures. In Chapter 1, I use concentrations and isotopes of helium and argon along with concentrations of U and Th to place constraints on the sources and siting of helium retained in exhumed mantle peridotites collected from Twin Sisters Mountain of the Northern Cascades in Washington State, USA. Helium isotope ratios of peridotites from the Twin Sisters Mountain span from 0.8 to 6 times the atmospheric ratio (1RA=1.4*10\u207b\u2076 \u00b3He/\u2074He). Fluid inclusions in these peridotites capture a two-component mixture that included a mantle-like endmember (~6 RA) and a serpentinizing endmember (1.0 \u00b1 0.5 RA) that is consistent with a mixture of surface-derived groundwater, leached crustal radiogenic helium and reworked mantle helium. While these components are not effectively isolated by extraction using vacuum crushing and powder fusion, step-heating analysis reveals that the serpentinizing endmember is released at lower temperatures (<1000\u00b0C) and the mantle-like endmember is released at higher temperatures. Results demonstrate that helium signatures can be retained in lithospheric peridotites against both diffusive loss and radiogenic ingrowth over at least 10\u2078-year timescales but can be greatly modified by cryptic metasomatic processes during emplacement.
\r\n\r\nMg-carbonates have become increasingly relevant in the scientific community due to their orbital and in situ detection on the Martian surface. Like Ca-carbonate on Earth, Martian Mg-carbonates may preserve paleoenvironmental information associated with their formation on Mars billions of years ago, shedding light on habitability. Yet, unlike Ca-carbonates, the capacity for Mg-carbonates to preserve paleoenvironmental information through trace element signatures associated with their source fluids has not been well established for surficial magnesite samples on Earth. In Chapter 2, I 1) develop a digestion protocol to selectively digest Mg-carbonates (magnesite \u00b1 dolomite) while obviating influences of contaminant phases and ions adsorbed to mineral surfaces, 2) validate a method to analyze trace elements with Mg-matrix by solution ICP-MS, and 3) apply these procedures to determine trace element concentrations of pedogenic Mg-carbonates sampled along a depth profile in the Kunwarara open pit magnesite mine in Queensland, Australia. Results from this study confirm that the method we implemented selectively digests magnesite \u00b1 dolomite. A relationship between negative Ce anomaly in the carbonates and Fe/Mn-oxides/hydroxides in corresponding host sediment collected along the depth profile demonstrates that pedogenic magnesites can capture redox gradients in the soil column. This finding implies that Ce anomaly in carbonates can potentially be used to place constraints on the paleo-redox conditions associated with Mg-carbonate formation on ancient Mars.
\r\n\r\nNumerous questions in Earth science depend on quantitative understanding of how elements fractionate during melting and crystallization. To name a few: assessment of how lithospheric fluids influence geodynamical processes, constraining mechanisms that led to the formation of the Earth\u2019s continental crust, evaluation of elemental fluxes from the mantle to Earth's surface, calibration of a reliable crustal barometer, and gauging how magmatism and plate tectonics differed with the higher geothermal gradients of a younger Earth. MELTS thermodynamic software is a widely available free tool utilized by geoscientists to both test hypotheses and model the geochemistry of magmatic processes. However, minerals of the amphibole supergroup, although common in magmatic systems, rarely crystallize in MELTS simulations, even when well controlled experiments demonstrate that they should. The decrease in the Gibbs energy needed to stabilize amphibole in MELTS is often on the order of the configurational entropy contribution to the Gibbs energy associated with minor elements that are not present in any of the current amphibole solution models used in MELTS but are frequently incorporated in the amphibole crystal lattice. In Chapter 3, I outline a framework for a volume model for monoclinic amphiboles that can be used in an expanded amphibole solution model to be incorporated in MELTS software. A volume model is prerequisite to calibrating the other model terms because it accounts for differences in pressure among experimental constraints. The framework I develop extends the model to include minor components that are not present in existing versions of the MELTS amphibole models. I calibrate a preliminary model using a dataset composed of x-ray refinements that supply amphibole volume and site occupancy data. Results reveal regions in parameter space where data is limited and the sensitivity that model coefficients have to uncertainties in the data, suggesting that filtering the dataset to remove outliers may be necessary.
" }, { "name": "Wang, Ren\u00e9e Zurui", "degree": "PhD", "year": "2024", "title": "From Photosynthesis to Detoxification: Microbial Metabolisms Shape Earth\u2019s Surface Chemistry", "advisor": "Newman, Dianne K.; Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10102023-024622119", "creators": [ { "name": { "family": "Wang", "given": "Ren\u00e9e Zurui" }, "id": "Wang-Ren\u00e9e-Zurui", "orcid": "0000-0003-3994-3244", "display_name": "Wang, Ren\u00e9e Zurui" } ], "advisors": [ { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "co-advisor", "display_name": "Newman, Dianne K." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "co-advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Mazmanian", "given": "Sarkis K." }, "id": "Mazmanian-S-K", "orcid": "0000-0003-2713-1513", "role": "member", "display_name": "Mazmanian, Sarkis K." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/kf85-cq89", "abstract": "Earth\u2019s chemistry, through geologic time and in the present, is inextricably linked with biologically mediated reactions. All major elemental cycles on Earth\u2019s surface have arisen from two competing processes \u2013 life shaping its chemical environment through the evolution of key biochemical pathways, and the environment constraining metabolism by dictating which reactions will occur. Understanding this complicated interplay motivates the research presented in this thesis, which studies this phenomenon over two major elemental cycles \u2013 the modern Nitrogen (N) and ancient Carbon (C) cycle.
\r\n\r\nChapters One and Two focus on the evolution of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), the enzyme that catalyzes the key carbon fixation step in modern oxygenic photosynthesis. This reaction also imparts a large kinetic isotope effect (KIE) that causes the fixed carbon to be relatively depleted in natural abundance \u00b9\u00b3C compared to its substrate; this isotopic fingerprint can be seen in both the modern C cycle and in rock records recording the ancient C cycle. Therefore, this KIE has been used both in vitro (outside the cell) by biochemical models to rationalize rubisco\u2019s reaction mechanism, and in vivo (in the cell) as a proxy for environmental CO\u2082 concentrations in the past and present. However, both the in vitro and in vivo measurements are calibrated using modern organisms even though rubisco and oxygenic photosynthesis have undergone profound evolution over geologic time. Therefore, we measured the KIE in vitro and in vivo of a reconstructed ancestral Form IB rubisco dating to >> 1 Ga, and the KIE in vitro of a recently discovered Form I\u2019 rubisco that presents a modern analogue to ancestral Form I rubiscos prior to the evolution of the small subunit. Overall, we find that the KIEs of both rubiscos are smaller than their modern counterparts, which is surprising given that the rock record indicates overall carbon isotope fractionations in vivo are larger in the past. In addition, we find that models strictly based on modern organisms may not apply to the past, questioning the basic assumption that uniformitarianism can be readily applied to biological processes. However, these models can be rescued by accounting for other aspects of cell physiology.
\r\n\r\nChapter Three focuses on disentangling the source of key metabolites, like nitrous oxide (N\u2082O) in the modern N cycle. Like Chapters 1 and 2, an isotopic fingerprint that measures the \u2018preference\u2019 of \u00b9\u2075N for the central or outer nitrogen site in N\u2082O (\u201cSite Preference\u201d or \u201cSP\u201d) has primarily been calibrated using dissimilatory, or energy-generating, nitric oxide (NO) reductases (NORs). However, there exists a much larger and phylogenetically widespread class of NO-detoxifying enzymes; in particular, flavohemoglobin proteins (Fhp/Hmp) produce N\u2082O as a strategy to neutralize damaging NO-radicals in anoxic conditions. This enzyme, which generates N\u2082O in non-growing and anoxic conditions, may be more relevant to natural environments where N\u2082O production has been detected. Surprisingly, we found that Fhp imparts a distinct SP on N\u2082O that differs from both bacterial and eukaryotic NORs, and that this value better aligns with existing in situ measurements of N\u2082O from soils. In addition, we find that in strains with both Fhp and NOR, the Fhp signal dominates when cells are first exposed to high concentrations of NO in oxic conditions while growing before being shifted to an anoxic, non-growing state. Therefore, in addition to telling us \u2018Who\u2019s there,\u2019 the SP fingerprint may also be able to tell us something about cell physiology in vivo. We propose a new framework for interpreting the source of N\u2082O based on SP values.
" }, { "name": "Zeichner, Sarah Soojin", "degree": "PhD", "year": "2024", "title": "Fates of Carbon", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01022024-183348243", "creators": [ { "name": { "family": "Zeichner", "given": "Sarah Soojin" }, "id": "Zeichner-Sarah-Soojin", "orcid": "0000-0001-8897-7657", "display_name": "Zeichner, Sarah Soojin" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/vy9f-k705", "abstract": "This thesis investigates the organic matter relevant to the oldest rocks on the Earth and in the Solar System, along with novel methods for exploring the composition of that organic matter. Chapter II describes a novel method for using a gas chromatography-Orbitrap mass spectrometer system to simultaneously analyze multiple isotopic properties from multiple compounds within a complex mixture. This method is ideal for the study of environmental or extraterrestrial samples and was integral to the study described in Chapter III. Chapters III and IV highlight new isotopic properties that can be measured in extraterrestrial samples to constrain processes of abiotic organic molecule formation: These processes have direct implications for where the carbon on Earth comes from. Chapter III details the measurement of \u00b9\u00b3C, D, and double-\u00b9\u00b3C contents of five polycyclic aromatic hydrocarbons in samples returned by the Hayabusa2 spacecraft mission to the Ryugu asteroid. The findings of this study support the formation of aromatic hydrocarbons---arguably the most abundant molecules in the Milky Way galaxy and other galaxies---through low-temperature reactions within molecular clouds in the interstellar medium. Chapter IV characterizes the position-specific carbon isotopic compositions of three structurally-distinct amino acids-- \u03b1-alanine, \u03b2-alanine and aspartic acid--from the Murchison meteorite, which provide constraints for how they were synthesized abiotically within the meteorite parent body. Chapters V-VI of this thesis relate to organic molecules on the early Earth. Chapter V is a scholarly review of prior data documenting the carbon isotope contents of organic carbon in Archean rocks. It also includes a model for the evolution of the carbon isotopic composition of organic matter as it goes through the rock cycle (i.e., diagenesis, catagenesis, metagenesis and metamorphism), which is then used to re-interpret carbon isotope data based on extant biology and models of metabolic evolution. Chapter VI uses sedimentological experiments to demonstrate that water-soluble organic compounds may have led to the rise of mud deposition concurrent with the evolution of land plants." }, { "name": "Zhang, Qicheng", "degree": "PhD", "year": "2024", "title": "Sampling the Evolution of Solar System Cometoids", "advisor": "Hallinan, Gregg W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01012024-070706394", "creators": [ { "name": { "family": "Zhang", "given": "Qicheng" }, "id": "Zhang-Qicheng", "orcid": "0000-0002-6702-191X", "display_name": "Zhang, Qicheng" } ], "advisors": [ { "name": { "family": "Hallinan", "given": "Gregg W." }, "id": "Hallinan-G-W", "orcid": "0000-0002-7083-4049", "role": "advisor", "display_name": "Hallinan, Gregg W." } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "member", "display_name": "de Kleer, Katherine R." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Hallinan", "given": "Gregg W." }, "id": "Hallinan-G-W", "orcid": "0000-0002-7083-4049", "role": "member", "display_name": "Hallinan, Gregg W." } ], "option_major": [ "plansci" ], "doi": "10.7907/mjje-pc39", "abstract": "Comets are commonly defined to be planetesimals visibly losing mass through volatile sublimation. In the solar system, such behavior characterizes but a brief stage in the overall evolution of these objects, as limited by their supply of accessible volatile materials and the often short dynamical lifetimes of orbits sufficiently near the Sun for said volatiles to actually volatilize. In this thesis, I explore the characteristics of several different types of ``cometoids''---planetesimals visibly exhibiting comet-like mass loss sometime in their recent past, present, or near future---in both the outer and inner solar system at different stages in their physical and dynamical evolution. I first use stellar occultations---or rather, the lack thereof detected---to constrain their abundance of kilometer-scale objects in the Kuiper Belt, from which many comets are sourced. I then evaluate how the optical brightness, color, and polarization of dust ejected by a classical, currently active comet changes when exposed to the space environment in order to probe the material properties of its nucleus. Finally, I investigate an otherwise ordinary but active asteroid to explore how intense solar heating as it passes very near the Sun can volatilize its rocky surface to produce bright sodium emission explaining its comet-like behavior." }, { "name": "Adams, Danica Jeannine", "degree": "PhD", "year": "2023", "title": "Habitability Through Time: Photochemistry and Aerosols of Planetary Atmospheres", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032023-042339662", "creators": [ { "name": { "family": "Adams", "given": "Danica Jeannine" }, "id": "Adams-Danica-Jeannine", "orcid": "0000-0001-9897-9680", "display_name": "Adams, Danica Jeannine" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/za4k-hs94", "abstract": "The unique geologic preservation of much of Mars\u2019 ancient surface provides a window into its earliest history, and hence the early history of the solar system. Extensive geological and mineralogical evidence suggest that ancient Mars once had large volumes of surface liquid water, which likely persisted over timescales of 10\u2075 - 10\u2077 years during the Noachian era (e.g., Carr et al., 2003; Clifford et al., 2001; Barnhart et al., 2009; Schon et al., 2012). Explaining this evidence for surface liquid water is challenging, however, because of Mars\u2019s distant orbit and the lower luminosity of the young Sun 3-4 billion years ago. The faint young Sun paradox is an important problem in planetary science that challenges our ability to understand atmospheric evolution in general, including Earth, Mars, and rocky exoplanets (e.g., Sagan 1972).
\r\n\r\nThe precise composition and climate of the early atmosphere overtime largely remains an open question. In 2014, it was first recognized that early Mars could have been episodically warmed by the greenhouse effects of H\u2082 in a CO\u2082 atmosphere (e.g., Wordsworth et al., 2017); however, no sustained source of H\u2082 was identified in the literature (noting that volcanism would have been short lived). Chapter 2 presents a solution: crustal hydration (the loss of surface water to reduced iron and hydrated minerals) likely supplied large fluxes of H\u2082. Over a timescale of 10\u2077 years (the upper limit for the duration of large volumes of surface liquid water), crustal hydration provides a flux of H\u2082 into the atmosphere large enough to sustain a surface temperature >273 K in a \u2265 1 bar Noachian atmosphere. Importantly, Mars was likely warm over only a fraction of its early history, and cold early atmospheres likely also existed during early Mars\u2019 history. In cool climates, I find that a loss of atmospheric oxidants to the ground (to oxidize surface reduced iron) caused CO\u2082 to convert to CO in agreement with the results of Zahnle et al. (2008). Furthermore, a warm and wet climate suggests early Mars may have been similar to early Earth; however, the climate alone is not enough to suggest that early Mars may have been habitable. In Chapters 3 and 4, I investigate whether Mars may have had a nitrogen cycle, which would be important for nitrogen fixation. I used KINETICS, the Caltech-JPL 1D photochemical model, to explain present day deposits in Mars\u2019 soil samples. The Sample Analysis at Mars instrument onboard Mars Science Laboratory (MSL) has baked several volatile species out of the unique rock record at Mars, including nitrate (e.g., Sutter et al., 2017). The formation of these species would originate in the atmosphere as a result of photochemistry. In Chapter 3, I discover that nitrogen fixation in a warm and wet climate with lightning is able to explain the weight percent of nitrate measured by the MSL; lightning-induced NOx forms nitric acid in the atmosphere, and this nitric acid may dissolve in water, rain out to the surface, and undergo photoreduction in shallow surface waters. In Chapter 4, I discover a comparable amount of pernitric acid may be explained from formation in an icy climate; SEP-induced N(2D) attacks CO\u2082 to form NOx which reacts with HO\u2082 to form HO\u2082NO\u2082.
\r\n\r\nThe relatively new subfield of comparative planetology between Mars\u2019 evolution and exoplanet evolution (specifically, close-in super-Earths) will soon open, in the new era of the James Webb Space Telescope (JWST). I have prepared for this subfield by working with a suite of established numerical models to investigate the formation of prebiotic species in the reduced atmospheres of super-Earths (in Chapter 5) and the aerosols at warm gas Giants. In Chapter 6, I discover that aggregate hazes at warm sub-Neptunes, which result from methane photolysis, can explain the observed flat exoplanet spectra and muted spectral features, including the observations of GJ 1214b. In Chapter 7, I discover that the atmospheric dynamics of hot Jupiters cause patchy clouds of forsterite, iron, and titanium dioxide, and the 3D structure of the clouds helps explain the phase-integrated albedos of six worlds observed by HST.
" }, { "name": "Behmard, Aida", "degree": "PhD", "year": "2023", "title": "Planet Host Star Properties as Probes of Planet Formation and Evolution", "advisor": "Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05162023-173813482", "creators": [ { "name": { "family": "Behmard", "given": "Aida" }, "id": "Behmard-Aida", "orcid": "0000-0003-0012-9093", "display_name": "Behmard, Aida" } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Fuller", "given": "James" }, "id": "Fuller-J", "orcid": "0000-0002-4544-0750", "role": "member", "display_name": "Fuller, James" }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." } ], "option_major": [ "plansci" ], "doi": "10.7907/4mta-xt79", "abstract": "Over the past three decades, we have discovered over 5000 exoplanets that exhibit sizes, orbital architectures, and other properties that are often dramatically different from those of planets in our own Solar System. To understand the various processes that sculpted this diversity of planets, we can examine the stars they orbit. In the first project of my thesis, I modified a machine learning framework that models stellar spectra (The Cannon, Ness et al. 2015) to measure iron abundances for M dwarfs - small, cool stars that dominate the stellar population of our galaxy. Next, I combined Bayesian statistical methods and astrometric data that tracks the movements of stars to examine orbital alignment between planet host stars and their stellar companions. I discovered that close-in gas giant planet systems tend to be misaligned, which suggests that their dynamical histories include obliquity excitation through interactions with e.g., the protoplanetary disk and/or nearby stars. I then used Keck-HIRES spectroscopic observations and MESA stellar evolution models to uncover planet formation signatures encoded in host star elemental abundance patterns. I found that abundance differences between stars in binary systems may increase as a function of their separation, which has important implications for studies that rely on binary star chemistry. Most recently, I extended my abundance methodology to large spectroscopic samples to examine abundance patterns in planet host versus non-planet host stars, and thus explore planet formation signatures on a galactic scale." }, { "name": "Cheng, Rui", "degree": "PhD", "year": "2023", "title": "Remotely Evaluating the Seasonality of Gross Primary Production at High Latitudes", "advisor": "Frankenberg, Christian", "url": "https://resolver.caltech.edu/CaltechTHESIS:08112022-214313625", "creators": [ { "name": { "family": "Cheng", "given": "Rui" }, "id": "Cheng-Rui", "orcid": "0000-0002-3003-8339", "display_name": "Cheng, Rui" } ], "advisors": [ { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "advisor", "display_name": "Frankenberg, Christian" } ], "committee": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "chair", "display_name": "Schneider, Tapio" }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Bloom", "given": "A. Anthony" }, "id": "Bloom-A-Anthony", "role": "member", "display_name": "Bloom, A. Anthony" } ], "option_major": [ "envreng" ], "doi": "10.7907/3gnn-sy17", "abstract": "A warming trend larger than the global average is changing high-latitude terrestrial ecosystems. The impact of climate change at high latitudes is especially notable on the seasonality of vegetation photosynthesis, such as the Arctic greening, lengthened growing season, and increased peak production in the growing season. As a critical component of the global carbon cycle and land carbon sink, continuously monitoring the seasonal trajectory of ecosystem-level photosynthesis, Gross Primary Production (GPP), is much needed to better understand the climate change impacts and the sensitivity of high-latitude plant communities under global climate change. GPP has been estimated from both ground and space. However, sparsely distributed ground-level measurements are not representative of heterogeneous land cover and complex terrain in high latitudes. Remote sensing techniques provide extensive spatial coverage for comparing GPP at the regional scale. In this thesis, I carefully examine the advances in remote sensing for monitoring GPP at high latitudes, including using hyperspectral reflectance and Solar-Induced chlorophyll Fluorescence (SIF). We show that reflectance near 531 nm can track the seasonality of Light Use Efficiency (LUE), complementing conventional normalized difference vegetation index which is only a proxy of Absorbed Photosynthetic Active Radiation (APAR). Tracking both LUE and APAR is critical for improving GPP estimation, especially in evergreen forests with photosynthetic phenology but sustained canopy color -- a typical land cover type at high latitudes. Satellite-measured SIF can also track both LUE and APAR. Here, it is shown that the empirical model predicting GPP using SIF is land cover dependent. The presence of snow and surface, heterogeneous land cover, and complex terrains in the high latitudes further complicate the interpretation of the SIF-GPP relationship. To improve the accuracy of interpreting SIF in complex terrain, a geometric model is developed to account for variations in APAR on tilted slopes. The results of this thesis enhance the use of both reflectance and SIF to help improve terrestrial biosphere models simulating GPP and cope with model-data uncertainties. The results are also a useful reference for future satellite missions designing instruments and correcting topographic impacts. Overall, this thesis contributes to better evaluating GPP and constraining climate projection uncertainties.
" }, { "name": "Dong, Heng", "degree": "PhD", "year": "2023", "title": "Optimization of Electrodes Towards More Practical Electrochemical Water Treatment", "advisor": "Hoffmann, Michael R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03062023-153330120", "creators": [ { "name": { "family": "Dong", "given": "Heng" }, "id": "Dong-Heng", "orcid": "0000-0002-4168-7297", "display_name": "Dong, Heng" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Gray", "given": "Harry B." }, "id": "Gray-H-B", "orcid": "0000-0002-7937-7876", "role": "member", "display_name": "Gray, Harry B." }, { "name": { "family": "See", "given": "Kimberly" }, "id": "See-Kimberly", "orcid": "0000-0002-0133-9693", "role": "member", "display_name": "See, Kimberly" }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "member", "display_name": "Hoffmann, Michael R." } ], "option_major": [ "envreng" ], "doi": "10.7907/hkpg-je79", "abstract": "Due to water scarcity and water pollution, the world suffers from continuing water sanitation issues, which lead to billions of water-borne disease cases every year. Decentralized water treatment is regarded as an important supplement to the conventional wastewater treatment system to address the water sanitation and water pollution issues in rural, remote, and undeveloped regions. Electrochemical water treatment technology has been demonstrated to be feasible for decentralized water treatment systems because of the ambient operation conditions, robust performance, modular design, small footprint, and environmental compatibility. The performance of electrochemical water treatment systems relies heavily on the choice of electrodes. This thesis presents a comprehensive study towards understanding and optimizing the electrodes to enhance the performance and lower the cost of electrochemical water treatment systems. The research work on anodes followed an \u201cunderstanding \u2013 development\u201d approach and spanned both the scientific and engineering sides of the spectrum. Specifically, a comprehensive review was assembled through the analysis of existing literature on mixed metal oxide anodes. This review pointed towards potential future research directions. With the advancement of material sciences, it is important to focus not only on single catalytic metal elements, but also on the intermetallic electronic interaction to gain a deeper understanding of the catalytic activity of mixed metal oxides. The microscopic steric effects imposed by crystalline structures may also be a nonnegligible contributor to the catalytic properties.
\r\n\r\nFollowing the review, this thesis scrutinized the catalytic sites of crystalline CoSb\u2082O\u2086, an emerging anode for chlorine evolution reaction (CER) catalysis. It has been demonstrated to be a promising alternative for the conventional Ru- and Ir-based anodes based on its high activity and excellent stability, but its catalytic sites and mechanism are still unknown. By fabricating and testing a series of anodes with different Sb/Co ratios, it was discovered that the surface Sb/Co ratios in CoSb\u2082O\u2086 were ~50% higher than in the bulk. At the same time, it was surprising to find through scanning electrochemical microscopy (SECM) that Sb-rich samples showed higher catalytic activities, indicating that Sb sites may be even more active catalytic sites than the Co-sites. This was attributed to the electronic interaction between Co and Sb, as revealed by X-ray photoelectron spectroscopy (XPS).
\r\n\r\nOn the engineering side, a Ni\u2013Sb\u2013SnO\u2082 reactive electrochemical membrane (REM) was developed to treat primary effluent and greywater. In 30 min, the REM removed up to 78 \u00b1 2% COD and 94 \u00b1 0.6% turbidity from the primary effluent. The REM had ~100% COD removal and 89 \u00b1 4% turbidity removal from greywater, with the effluent meeting the NSF/ANSI 350 standard. Compared to the conventional plate-type electrodes under the same conditions, the REM had 36% lower energy consumption for primary effluent treatment and 22% lower energy consumption for greywater treatment while yielding better treatment results. The REM-based electrochemical system was demonstrated to be a promising solution for decentralized wastewater treatment and recycling for single households and for vehicles.
\r\n\r\nLast but not the least, this thesis presents the 3D-printing-derived carbon lattice as a monolithic electro-Fenton cathode. The Fenton reaction is one of the most important advanced oxidation processes (AOPs) that is widely used in water treatment to remove non-biodegradable pollutants, and heterogeneous electro-Fenton (HEF) process catalyzed by carbon-based cathodes has received considerable attention as an evolving branch due to its wide working pH range and independence from chemical dosing. However, the conventional carbon cathodes suffered from poorly controlled porosities, which hampered the mass transport and limited the overall catalytic performance. Three rationally-designed carbon lattice cathodes with different macroscopic porosities were fabricated and tested, showing that it was feasible to facilitate the mass transport by tuning the macroscopic electrode structure. Specifically, Grid-2% cathode, which had the largest macroscopic porosity, showed 157% higher specific activity for electrochemical H\u2082O\u2082 production and 256% higher specific activity for trimethoprim degradation than the Star-2%, the one with the smallest macroscopic porosity. Grid-2% achieved 97% aqueous trimethoprim removal in 60 min, demonstrating the potential of the carbon lattice cathode to be used for water treatment and remediation.
" }, { "name": "Douglas, Madison Marie", "degree": "PhD", "year": "2023", "title": "Mechanics of River Erosion and its Effects on Floodplain Biogeochemistry", "advisor": "Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012023-210614776", "creators": [ { "name": { "family": "Douglas", "given": "Madison Marie" }, "id": "Douglas-Madison-Marie", "orcid": "0000-0002-0762-4719", "display_name": "Douglas, Madison Marie" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "West", "given": "A. Joshua" }, "id": "West-A-Joshua", "orcid": "0000-0001-6909-1471", "role": "member", "display_name": "West, A. Joshua" }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/rwmn-hq80", "abstract": "Rivers transport water, sediment, and nutrients across Earth\u2019s surface. They shape landscapes, eroding mountain ranges and building floodplains, simultaneously providing important resources and posing a hazard to nearby communities. Here, I present field work, flume experiments, numerical models, and laboratory analyses addressing three main themes: permafrost river and floodplain dynamics, river meandering without plants, and rates of bedrock incision. Arctic rivers migrate rapidly across their floodplains and their migration rates are predicted to increase as permafrost thaws due to climate change. However, no mechanistic model is capable of predicting permafrost riverbank annual erosion rates. To address this knowledge gap, I developed a calibrated numerical model for permafrost riverbank erosion. A previously published theory assumes that permafrost erosion rates are limited by pore-ice thaw, but underestimates thaw rates due to bank roughness increasing heat transfer from the river to its banks (Chapter 3). Results indicate that thaw-limited erosion is orders of magnitude higher than observed erosion rates, and permafrost riverbank erosion must instead be limited by sediment entrainment and the collapse of overhanging blocks to match observed rates (Chapter 2). Based on experimental results, I developed a 1D numerical model that includes roughness-dependent permafrost thaw and sediment entrainment and tracks how heat transfer within the riverbank can form a thawed layer (Chapter 4). Results indicate that permafrost riverbank erosion rates respond to changes in river discharge due to climate change, which affect both bank thaw and entrainment rates, and are only sensitive to changes in water temperature via thawed layer failure. As a case study, I conducted fieldwork along the Koyukuk River in Alaska, which is located in discontinuous permafrost. I found that changes in riverbank erosion rates may more rapidly erase permafrost from floodplains (Chapter 7) and change the spatial patterns of floodplain methane emissions (Chapter 5). While riverbank erosion releases eroded organic carbon to be oxidized as greenhouse gases or transported downstream, a portion of this carbon is re-deposited in the floodplain, modulating the effects of river migration on regional carbon cycling (Chapter 6). To understand the effects of vegetation on river migration rates and fluvial stratigraphy, I conducted long-term monitoring of the unvegetated, ephemeral Amargosa River in Death Valley, California (Chapter 8). This study found that the Amargosa is actively meandering at very slow rates and frequently avulses, producing muddy stratigraphy with isolated sand bodies that is thought to be unique to vegetated meandering rivers. Sediment transport has also been proposed as a primary control on bedrock river incision rates, where saltating grains gradually abrade the channel bed over geologic timescales. However, uncertainty about long-term sediment supply and the frequency of floods that cause significant bedrock incision has prevented using saltation-abrasion to model landscape evolution. Using a global data compilation, I calculated a best-fit sediment supply-normalized flood intermittency parameter so that the saltation-abrasion model can be broadly applied (Chapter 9). Together, these studies advance understanding of how riverine sedimentary transport governs permafrost riverbank erosion, Arctic floodplain biogeochemistry, stratigraphic deposits of unvegetated rivers, and bedrock incision rates.
" }, { "name": "Dove, Lilian Aja", "degree": "PhD", "year": "2023", "title": "Impacts of Zonal Asymmetry on Southern Ocean Dynamics and Biogeochemistry", "advisor": "Thompson, Andrew F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05302023-201452585", "creators": [ { "name": { "family": "Dove", "given": "Lilian Aja" }, "id": "Dove-Lilian-Aja", "orcid": "0000-0001-8346-0034", "display_name": "Dove, Lilian Aja" } ], "advisors": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "advisor", "display_name": "Thompson, Andrew F." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Fu", "given": "Xiaojing" }, "id": "Fu-Xiaojing", "orcid": "0000-0001-7120-704X", "role": "member", "display_name": "Fu, Xiaojing" }, { "name": { "family": "Gray", "given": "Alison R." }, "id": "Gray-Alison-R", "role": "member", "display_name": "Gray, Alison R." }, { "name": { "family": "Gierach", "given": "Michelle Marie" }, "id": "Gierach-M-M", "role": "member", "display_name": "Gierach, Michelle Marie" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." } ], "option_major": [ "envreng" ], "doi": "10.7907/qnah-sc58", "abstract": "The Southern Ocean is a key region for the ventilation and formation of intermediate and deep water masses. Interactions of the Southern Ocean\u2019s Antarctic Circumpolar Current (ACC) with bathymetry can result in the diversion and compaction of frontal currents, resulting in standing meanders associated with enhanced mesoscale eddy kinetic energy (EKE) and submesoscale vertical velocities. As a result, standing meanders are thought to shape uptake and sequestration of heat and carbon across the ACC. In this thesis, I use observations from remote sensing and various autonomous underwater vehicles to investigate how physical mechanisms, from the submesoscale to the basin scale, shape the biogeochemical properties and tracer distributions of the Southern Ocean.
\r\n\r\nProcesses at the ocean's submesoscale can play a vital role in exchanging water across the base of the mixed layer, contributing to water mass ventilation. Data from over 20,000 profiles from biogeochemical-Argo floats across the ACC highlight that the high EKE regions associated with standing meanders have relatively reduced apparent oxygen utilization (AOU) values below the base of the mixed layer. This result, as well as larger AOU variance in deep potential density classes, suggests there is enhanced ventilation occurring in standing meanders. Further investigation suggests the observed increased ventilation is due to both along-isopycnal stirring and enhanced exchange across the base of the mixed layer by vertical velocities at the submesoscale, highlighting the importance of standing meanders in shaping temporal and spatial variability of biogeochemical cycles and air-sea exchange.
\r\n\r\nObservations with horizontal scales of 2-4 kilometers in the standing meander associated with Crozet Plateau show that submesoscale processes are indeed ubiquitous. In this region, processes on the submesoscale to mesoscale spectrum play a role in enhancing surface frontal gradients and heightening tracer variability at depth. A separate field program provided novel observations at the submesoscale in Drake Passage during wintertime. The Polar Front, one of the major fronts of the ACC, is shown to be eddy-suppressing, suggesting that along-isopycnal submesoscale processes contribute to ventilation at the front. These spatial variations in stratification may additionally impact carbon fluxes between the atmosphere, surface mixed layer, and interior ocean. This thesis presents evidence that ventilation is a heterogeneous process across the Southern Ocean, with contributions from processes at physical scales that are undersampled by current observational programs.
" }, { "name": "He, Liyin", "degree": "PhD", "year": "2023", "title": "Agriculture and Its Role in the Global Carbon Cycle", "advisor": "Frankenberg, Christian", "url": "https://resolver.caltech.edu/CaltechTHESIS:04152023-232107829", "creators": [ { "name": { "family": "He", "given": "Liyin" }, "id": "He-Liyin", "orcid": "0000-0003-4427-1438", "display_name": "He, Liyin" } ], "advisors": [ { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "advisor", "display_name": "Frankenberg, Christian" } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Schimel", "given": "David" }, "id": "Schimel-David", "orcid": "0000-0003-3473-8065", "role": "member", "display_name": "Schimel, David" } ], "option_major": [ "envreng" ], "doi": "10.7907/34d6-nj32", "abstract": "Crops not only feed the world's human population and livestock but also impact the global carbon cycle. The intensification of agriculture has allowed much greater crop yields by hybridization, irrigation, and fertilization in the five most recent decades. However, the increased frequency and severity of extreme weathers (e.g., heat wave, drought, flood) caused by global warming have led to large yield and economic losses. Thus, the monitoring of crop growth in a changing climate is of paramount importance to improve food security and alleviate poverty. It is via photosynthesis that crops use the energy of sunlight to reduce carbon dioxide (CO\u2082) into carbohydrates. An accurate quantification of plant photosynthesis is a key step towards estimating crop yield and understanding the carbon exchange between the biosphere and atmosphere. Satellite remote sensing has emerged as one promising solution for measuring photosynthesis from regional to global scales. In the thesis, first, we show the potential of solar-induced chlorophyll (SIF) signals emitted by the chlorophyll a of plants to track photosynthesis. Compared to traditional reflectance-based vegetation indices (VIs), SIF can better capture photosynthetic down-regulation under drought and heat stresses due to its physiological linkages with photosynthetic processes. Second, we demonstrate that SIF can be used to estimate crop yield. At field sites, we find a high correlation between SIF and crop photosynthesis measurements. Scaling up this relationship to the large scale, we show that crop yield estimates using satellite-derived SIF agree well with the United States Department of Agriculture (USDA) reported annual crop yield. Third, we examine how crops respond to climate change and air quality in China. We develop a crop yield prediction model, based on a large volume of historical crop data, as well as climate and pollution records. Our finding demonstrates the co-benefit of the recent air pollution control policy from an agriculture and food perspective. However, such a benefit will be significantly offset or even outweighed by continuing global warming. Fourth, we focus on how different ecosystems, especially intensified agriculture, has reshaped the seasonality of atmospheric CO\u2082. Our satellite-derived global terrestrial carbon fluxes capture the observed CO\u2082 seasonal cycle amplitude (SCA) trends at surface sites very well. We further find that CO\u2082 SCA trends at mid latitude sites around the Midwest United States are mainly impacted by intensified agriculture, whereas high latitude sites are mainly driven by increasingly productive natural ecosystems. The approaches, findings and datasets developed through the thesis will contribute to agro-ecosystems management in the face of climate change and contribute to equitable solutions to climate challenges.
" }, { "name": "Luo, Yangcheng", "degree": "PhD", "year": "2023", "title": "Tracer Transport in Three Dimensions: Dispersion of Methane on Mars, Coupled Chemistry and Dynamics on Exoplanets, and Submesoscale Mixing in the Ocean", "advisor": "Yung, Yuk L.; Callies, Joern", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302023-185542422", "creators": [ { "name": { "family": "Luo", "given": "Yangcheng" }, "id": "Luo-Yangcheng", "orcid": "0000-0003-0983-3650", "display_name": "Luo, Yangcheng" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "advisor", "display_name": "Callies, Joern" } ], "committee": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "chair", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" } ], "option_major": [ "plansci" ], "doi": "10.7907/91p7-gg59", "abstract": "One-dimensional (1D) modeling from a horizontally averaged perspective can oftentimes greatly simplify problems in atmospheric and oceanic sciences and thus capture leading-order physics. Meanwhile, 1D numerical models have great advantages such as numerical stability and time efficiency, hence they are widely used to gain insights into complex problems. However, oversimplification by 1D models may cause failures in finding solutions, revealing novel phenomena, and discovering scaling laws in the three-dimensional (3D) real world, and those are when 3D thinking proves its value. Also, the rise in computational power has allowed investigations using 3D numerical models. This thesis discusses three examples of how 3D modeling transcends the limitations of 1D modeling and reveals new solutions, phenomena, and scalings in planetary atmospheres and Earth\u2019s ocean.
\r\n\r\nChapter 2 is focused on the dispersion of methane plumes on Mars and how it can reconcile the discrepancy between observations. In the face of ostensibly inconsistent observational results of methane on Mars, we adopt a novel approach\u2014inverse Lagrangian modeling in 3D space\u2014to find the scenarios in which the inconsistency in the observations can be reconciled and locate the methane source. We find that the inconsistency between the results of the near-surface in situ methane measurements and the satellite remote sensing measurements can be reconciled if and only if an active methane emission hot spot is located in the immediate vicinity of the Curiosity rover in northwestern Gale crater, or unknown physical or chemical processes are rapidly removing methane.
\r\n\r\nChapter 3 presents a novel phenomenon that could exist on exoplanets\u2014self-sustained photochemical oscillations, which is only produced by 3D atmospheric models. We use a 3D, fully coupled, chemistry-radiation-dynamics model to simulate the ozone-NOx-HOx photochemistry in the atmosphere of a tidally locked Earth-like exoplanet in the circumstellar habitable zone, and calculate the transmission spectra during transits. We find that under certain conditions, biological nitrogen fixation like the one on the Earth can drive large-magnitude, self-sustained photochemical oscillations in the atmospheres of terrestrial exoplanets. The resulting large temporal variability in ozone abundance on exoplanets, if observed, may suggest a strong surface NOx emission source, which could signal extrasolar life participating in the nitrogen cycle on exoplanets. Fully coupled, three-dimensional atmospheric chemistry-radiation-dynamics models can reveal new phenomena that may not exist in one-dimensional models, and hence they are powerful tools for future planetary atmospheric research.
\r\n\r\nChapter 4 uses a 3D fluid dynamics model to study the vertical exchange in the upper part of Earth\u2019s ocean that potentially has great implications for the marine ecosystem. We develop scaling laws for the exchange rate between the surface ocean and the ocean interior which is critical to the rate of nutrient supply to phytoplankton near the ocean surface. These scaling laws could substitute the crude 1D parameterizations that are currently widely used in ocean models. We find that submesoscale turbulence energized by baroclinic instability in the ocean mixed layer can induce tracer exchange between the surface ocean and the ocean interior. Various environmental physical parameters affect the exchange rate. The exchange is stronger where the ocean mixed layer is thicker, the Richardson number (defined as the ratio of the squared buoyancy frequency to the squared vertical shear of the horizontal flow) of the thermocline is smaller, and the Richardson number of ocean mixed layer is larger. The associated nutrient supply from the ocean interior to the surface ocean is also expected to be stronger under these conditions.
" }, { "name": "L\u00f3pez G\u00f3mez, Ignacio", "degree": "PhD", "year": "2023", "title": "A Unified Data-Informed Model of Turbulence and Convection for Climate Prediction", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:11152022-215747755", "creators": [ { "name": { "family": "L\u00f3pez G\u00f3mez", "given": "Ignacio" }, "id": "L\u00f3pez-G\u00f3mez-Ignacio", "orcid": "0000-0002-7255-5895", "display_name": "L\u00f3pez G\u00f3mez, Ignacio" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "chair", "display_name": "Callies, Joern" }, { "name": { "family": "Stuart", "given": "Andrew M." }, "id": "Stuart-A-M", "orcid": "0000-0001-9091-7266", "role": "member", "display_name": "Stuart, Andrew M." }, { "name": { "family": "Teixeira", "given": "Joao" }, "id": "Teixeira-Joao", "role": "member", "display_name": "Teixeira, Joao" }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" } ], "option_major": [ "envreng" ], "doi": "10.7907/042m-9686", "abstract": "Resolving atmospheric turbulent and convective processes in global climate simulations is, and will remain for decades, an intractable computational problem. The strong influence of these processes on cloud formation and maintenance makes the task of modeling turbulence and convection one of the grand challenges in climate modeling, due to the outsized effect of clouds on climate. Current operational climate models fail to represent atmospheric turbulence and convection accurately and consistently across dynamical regimes and vertical levels; errors in the representation of these processes explain about half of the spread in climate projections. This dissertation seeks to reduce such representation errors by improving a recently proposed unified framework for modeling turbulence and convection, known as the extended eddy-diffusivity mass-flux scheme, in several ways. First, the framework is rederived by systematically coarse-graining the governing fluid equations, highlighting the assumptions about atmospheric motion that are necessary to yield the scheme. New terms related to turbulent entrainment processes are shown to arise from the derivation. Second, a generalized formulation of turbulent diffusion consistent with the framework is presented. This novel formulation is shown to accurately represent turbulent processes under statically stable and unstable conditions, including regimes with sharp lapse rate inversions such as the stratocumulus-topped boundary layer. Finally, a methodology to calibrate free parameters within the model from indirect data is proposed. The methodology, based on Kalman filtering, is shown to be efficient at calibrating imperfect black-box models from noisy data, and in its regularized unscented version approximately quantifies parametric uncertainty. The resulting unified data-informed model of turbulence and convection is shown to accurately represent a range of low-cloud regimes that are associated with the largest biases in current operational climate models. The response of the model to realistic climate perturbations is also shown to be consistent with the resolved climate response, although structural errors in the amount of condensate are still important at realistic vertical resolutions." }, { "name": "Osorio Rodr\u00edguez, Daniela", "degree": "PhD", "year": "2023", "title": "Microbial Transformations of Sulfur: Environmental and (Paleo) Ecological Implications", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06092023-201353115", "creators": [ { "name": { "family": "Osorio Rodr\u00edguez", "given": "Daniela" }, "id": "Osorio Rodr\u00edguez-Daniela", "orcid": "0000-0001-6676-4124", "display_name": "Osorio Rodr\u00edguez, Daniela" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "geobiol" ], "doi": "10.7907/9bn5-z794", "abstract": "This thesis is centered around the role that sulfur plays in the cycling of carbon and in microbial energetics. In the oceans, sulfate is the most important electron acceptor for the remineralization of organic matter after oxygen has been depleted, and sulfate reduction is particularly relevant in coastal environments and in marine and freshwater sediments. The opposite process, reduced sulfur oxidation, allows autotrophic microorganisms to fix carbon in environments where oxygen is scarce. Organic sulfur is also a relevant component of the sulfur cycle, since sulfur is the sixth most abundant element in biomass, it can protect organic matter from degradation, and it is composed of hundreds of molecules that are produced mainly by microorganisms, with potentially relevant ecological roles.
\r\n\r\nThis work has been divided into two parts. In the first one, we attempt to expand our understanding on different aspects of the sulfur cycle. In Chapter 2, published in Limnology and Oceanography, we focus on dimethylsulfoniopropionate (DMSP), the most abundant organic sulfur compound in the oceans with roles of UV, cryo, and osmoprotection, and involved in the formation of sulfate aerosols. We propose a framework to differentiate between the microbial degradation pathways of DMSP based on the sulfur isotope fractionations imprinted by each one of them. In Chapter 3, we perform a survey of sulfate, sulfide, and reduced sulfur intermediates, as well as redox-sensitive elements, in porewaters of a ~40 cm core from the San Clemente Basin (California) and three 1.2-2 m cores near Cocos Ridge (Costa Rica). We correlate these concentrations with the sediment microbial community composition to unveil the specifics of organic matter and sulfur cycling at these localities. In Chapter 4, we explore the utility of sulfur isotope fractionations to characterize different pathways involved in microbial sulfur oxidation (MSO), and examine the role of nutrient limitation and growth rates on the magnitude of the fractionation.
\r\n\r\nIn the second part of this thesis, we aim at understanding biomineralization by consortia between anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB), which comprise more than 90% of the microbial biomass in deep sea sediments around hydrocarbon seeps. In Chapter 5 (in review at Proceedings of the National Academy of Sciences) we establish that modern ANME-SRB aggregates precipitate amorphous silica in undersaturated solutions in sediments and carbonates, often in the form of rims, which pinpoints to a potentially new microbial biomineralization mechanism. In Chapter 6, we posit the use of this proxy, together with distinctive spectral and isotopic signals, to find potential microfossils of ANME-SRB aggregates in the rock record of the Earth and other planetary bodies where methane seepage has occurred throughout geologic time. This suite of tools is used in conjunction to identify ANME-SRB aggregates in the Tepee Buttes (Colorado, 75 Mya) seep carbonates.
" }, { "name": "Pardo, Olivia Sabine", "degree": "PhD", "year": "2023", "title": "The Elastic, Electronic, and Structural Properties of Hydrous, Sulfur-Bearing Minerals in Planetary Environments: from the Surface to Deep Interiors", "advisor": "Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06112023-090146049", "creators": [ { "name": { "family": "Pardo", "given": "Olivia Sabine" }, "id": "Pardo-Olivia-Sabine", "orcid": "0000-0003-3964-9272", "display_name": "Pardo, Olivia Sabine" } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geophys" ], "doi": "10.7907/yarz-tr12", "abstract": "In this thesis, a comprehensive investigation of the hydrous iron endmember sulfate szomolnokite (FeSO\u2084\u00b7H\u2082O) has been conducted using a suite of complementary techniques to measure its structural, elastic, electronic, and vibrational properties under extreme conditions. Through X-ray diffraction (XRD), nuclear resonant inelastic X-ray scattering (NRIXS), synchrotron M\u00f6ssbauer spectroscopy (SMS), and synchrotron Fourier transform infrared spectroscopy (FTIR) in the diamond anvil cell, the material properties of szomolnokite have been characterized under high pressures and low temperatures relevant to hydrous, sulfur-rich planetary environments. XRD measurements presented in this work have revealed two structural phase transitions occurring at pressures between 5.0 and 6.6 GPa and between 12.7 and 16.8 GPa, with the latter phase stable up to 80 GPa. The elastic parameters of each phase have been determined by fitting third-order Birch-Murnaghan equations of state. I compare our results with elastic parameters of other relevant sulfate\r\nphases, highlighting the importance of reporting and comparing these parameters at the pressures where the phases are stable. Using NRIXS and SMS, the lattice vibrational response and the effects on the iron electronic environments during the structural transitions are examined. The NRIXS and SMS data reveal distinct features and pressure-dependent behaviors that characterize alterations in both iron-site specific and bulk lattice properties associated with the phase transitions, including lattice softening and decreased iron-coordination environment symmetry. Utilizing both the NRIXS and XRD results, I discuss how the presence of sulfates in the ice-rich crusts of planetary bodies could affect tidal loading observations. Synchrotron FTIR measurements demonstrate that structurally bound H\u2082O is retained within the unit cell during the structural transitions and upon subsequent decompression, confirming the retention of water up to 23 GPa and temperatures as low as 20 K and indicating the reversibility of both structural transitions. Supported by our quantum mechanics molecular dynamics simulations, the existence of two vibrationally unique water sites in szomolnokite\u2019s crystal structure is proposed to explain the experimentally observed H2O-related features. I develop a spectral diagnostic for observing the high pressure structural transformations at ambient and low temperatures. The measured partial phonon density of states, predicted vibrational density of states, and measured FTIR spectrum are compared. Drawing from the insights gained, we emphasize the advantages of employing complementary experimental and computational techniques and discuss future research directions that can further enhance our knowledge of hydrous, sulfur-rich planetary environments." }, { "name": "Parker, Harrison Alexander", "degree": "PhD", "year": "2023", "title": "A Novel Algorithm for Inferring the Vertical Distribution of Trace Gases Using Remote Sensing Measurements", "advisor": "Wennberg, Paul O.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012023-170244182", "creators": [ { "name": { "family": "Parker", "given": "Harrison Alexander" }, "id": "Parker-Harrison-Alexander", "orcid": "0000-0002-0041-2764", "display_name": "Parker, Harrison Alexander" } ], "advisors": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "advisor", "display_name": "Wennberg, Paul O." } ], "committee": [ { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "chair", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "orcid": "0000-0001-6874-1137", "role": "member", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "orcid": "0000-0003-1344-4068", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." } ], "option_major": [ "envreng" ], "doi": "10.7907/xfkf-8t80", "abstract": "Remote sensing is a powerful tool that is used to diagnose sources, sinks, and fluxes of trace gases across different spatial and temporal scales. Ground-based remote sensing measurements of column-averaged dry mole fractions (DMF) of gases such as carbon dioxide (CO\u2082) and carbon monoxide (CO) made by the Total Carbon Column Observing Network (TCCON) are used to validate space-based measurements and better understand the carbon cycle. Surface signals of gas exchange can be masked in the total column values, however, limiting their use in assessment of local surface fluxes. Retrievals of the vertical distribution of trace gases can be used to obtain gas exchange information that is more directly related to changes at the surface but require high precision measurements with less temporal resolution than the TCCON total column measurements. In this thesis, I develop an algorithm, the Temporal Atmospheric Retrieval Determining Information from Secondary Scaling (TARDISS), that infers vertical information, or \u2018partial columns\u2019, from existing, quality-controlled total column data. The TARDISS algorithm does not fit the solar spectra but rather begins with trace gas column retrievals obtained from different spectral bands using the standard TCCON retrievals. TARDISS takes advantage of the fact that different bands have different sensitivities to the same trace gas as a function of altitude and solar zenith angle. We use the TARDISS partial column data to examine estimated surface fluxes in the North American boreal forest and compare them to surface fluxes estimated from tall tower in situ measurements. We also outline changes in air quality from the sudden change in traffic behavior from the COVID-19 lockdown which serves as motivation for the use of the TARDISS-derived lower partial column CO data to examine recent changes in air quality in the South Coast Air Basin." }, { "name": "Sanders, Cecilia Brooke", "degree": "PhD", "year": "2023", "title": "Geological and Geochemical Explorations of the Salitre Formation Phosphorite, Eastern Brazil", "advisor": "Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07202022-060317708", "creators": [ { "name": { "family": "Sanders", "given": "Cecilia Brooke" }, "id": "Sanders-Cecilia-Brooke", "orcid": "0000-0002-2663-164X", "display_name": "Sanders, Cecilia Brooke" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "chair", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geobiol" ], "doi": "10.7907/rd4m-7x08", "abstract": "This thesis documents my explorations of an ancient seafloor environment through sedimentary geology and stable isotope geochemistry. The geologic record of this seafloor \u2014 its life, environmental conditions, lithification, burial and exposure \u2014 consists of hundreds of meters of sedimentary rock, outcropping across Bahia and Minas Gerais, Brazil. Though it consists primarily of carbonate grains surrounded by carbonate cements, such as might be found forming in any shallow carbonate platform, this record also contains one of Brazil\u2019s most extensive sedimentary phosphate deposits. In these deposits, phosphate is concentrated as carbonate fluorapatite cements (CFA) in digitate stromatolites, distinctively finger-like, branching accretionary structures likely formed by the accumulation of sediment by microbial mats and biofilms. Chapter 1 introduces the broader motivations of this kind of paleoenvironmental and paleoecological research, for understanding the record of life on Earth and other worlds. Chapter 2 presents new sedimentological and stratigraphic data which interpret the depositional setting of a seafloor 600 million years ago on the rending supercontinent of Gondwana. Chapter 3 presents new carbon and oxygen isotopic measurements and clumped isotope measurements of structural carbonate in phosphatic and non-phosphatic textures of the rock, and uses them to constrain the alteration history of the rock and its effect on the record of primary depositional conditions. Chapter 4 presents new data on the sulfur isotope composition of specific minerals in the rock, combining several disparate analytical methods to draw conclusions about the metabolism of the stromatolites\u2019 microbial architects. Chapter 5 describes the distribution of organic material and style of fossilization, and presents preliminary data which suggest a possible mechanism by which microbial activity may have facilitated phosphate concentration and mineralization. As a whole, this thesis demonstrates the value of multidisciplinary analyses in the reconstruction and understanding of sedimentary phosphorite deposits throughout Earth history, improving our understanding of how and to what extent phosphorites may record the history of life and the environment." }, { "name": "Schulze, Benjamin Christopher", "degree": "PhD", "year": "2023", "title": "Insights into the Sources of Atmospheric Aerosols and Greenhouse Gases in California", "advisor": "Seinfeld, John H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012023-202236185", "creators": [ { "name": { "family": "Schulze", "given": "Benjamin Christopher" }, "id": "Schulze-Benjamin-Christopher", "orcid": "0000-0002-6405-8872", "display_name": "Schulze, Benjamin Christopher" } ], "advisors": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "advisor", "display_name": "Seinfeld, John H." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "orcid": "0000-0003-1344-4068", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "orcid": "0000-0001-5690-770X", "role": "member", "display_name": "Flagan, Richard C." }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" } ], "option_major": [ "envreng" ], "doi": "10.7907/zay2-1v59", "abstract": "A substantial fraction of atmospheric science research is motivated by uncertainties in the sources of urban particulate matter and greenhouse gases. Such a focus is justified, as particulate matter exposure is responsible for up to nine million annual premature deaths globally, while climate change is rapidly altering ecosystems across the world. Recognizing the urgency of these interrelated problems, regulatory agencies in the U.S. and elsewhere have sought to limit emissions contributing to air quality degradation and global warming.
\r\n \r\nIn this dissertation, we use a combination of ambient measurements, statistical models, and computational models to identify the sources of urban particulate matter and methane in multiple locations in California. In Los Angeles, we investigated the effects of reductions in mobile source pollutant emissions (i.e., on-road and off-road vehicles) on ambient aerosol concentrations. Mobile sources have historically accounted for the dominant fraction of urban particulate matter in Los Angeles, but despite notable reductions in their emissions over the last decade, ambient aerosol concentrations have not declined appreciably. Measurements using an Aerosol Mass Spectrometer demonstrate the complex interplay of direct (i.e., intended) and indirect effects of simultaneous reductions in organic aerosol (OA) precursor and nitrogen oxide emissions from these sources. Mobile sources are found to account for a modest and declining fraction of the total aerosol burden, while the contributions of non-traditional sources such as volatile chemical products (e.g., paints and coatings, cleaning products, adhesives and sealants) have increased. Simulations of organic and inorganic aerosol formation informed by in-situ measurements are developed to identify possible targets of future regulatory efforts.
\r\n\r\nIn the San Joaquin Valley, we used airborne measurements of methane fluxes to evaluate dairy emissions inventories used by state regulatory agencies for policy development. Dairy operations currently account for nearly half of the state\u2019s methane emissions, and recent legislation has mandated a 40% reduction in emissions by 2030. Observed methane fluxes align well with emission inventory predictions and demonstrate the utility of airborne flux measurements to track emission reduction progress in the future. Factor analysis of a combined dataset of greenhouse gas and volatile organic compound concentrations indicates dairy operations account for ~65% of total methane emissions in the southern San Joaquin Valley, with the remainder attributed to fugitive oil and gas emissions.
" }, { "name": "Stephenson, Oliver Laurent", "degree": "PhD", "year": "2023", "title": "Investigating the Earthquake Cycle on Multiple Temporal and Spatial Scales Using Satellites and Simulations", "advisor": "Simons, Mark; Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechTHESIS:08082022-055217161", "creators": [ { "name": { "family": "Stephenson", "given": "Oliver Laurent" }, "id": "Stephenson-Oliver-Laurent", "orcid": "0000-0002-5509-090X", "display_name": "Stephenson, Oliver Laurent" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "advisor", "display_name": "Simons, Mark" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "co-advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "chair", "display_name": "Ross, Zachary E." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/ha9m-4p17", "abstract": "The motion of the Earth's tectonic plates creates a gradual accumulation of stress at their boundaries, followed by a rapid release in earthquakes, a process known as the earthquake cycle. Studying this process is important because of the hazards earthquakes pose, but presents challenges due to the multi-scale nature of the problem\u2014stresses build up over hundreds to thousands of years, while earthquakes break narrow fault zones in a matter of seconds. In this thesis, we combine a variety of techniques to study the earthquake cycle on multiple temporal and spatial scales, including satellite-based interferometric synthetic aperture radar (InSAR) to observe the slow deformation of the Earth over wide areas, and high-performance computational simulations to model faults during earthquakes. We begin by presenting a method for removing the signal of plate-tectonic motion in large-scale InSAR measurements, allowing for better observation of small ground deformations. We then use these corrections to study the Makran subduction zone, on the Iran-Pakistan border. Our InSAR-derived ground velocity map can resolve motions at the level of millimeters per year over an area of nearly one million square kilometers, and we use it to place constraints on the degree of coupling on the subduction megathrust. Next, we show how InSAR can be combined with deep learning techniques to rapidly map earthquake damage in all weather conditions, day and night. Such products will hopefully prove useful in future disaster response. Finally, we present computational simulations of dynamic earthquake ruptures with enhanced dynamic weakening due to thermal pressurization. We apply our simplified model to the creeping section of the San Andreas Fault, which is generally thought to be a barrier to earthquake rupture. Our results show how thermal pressurization can allow earthquakes to propagate partially or completely through the creeping section for a range of physically reasonable parameters. Our work illustrates how results from multiple fields can be combined to deliver new insights into the earthquake cycle and the hazards that it poses." }, { "name": "Williams, Ethan Francis", "degree": "PhD", "year": "2023", "title": "Probing Solid-Earth, Ocean, and Structural Dynamics with Distributed Fiber-Optic Sensing", "advisor": "Zhan, Zhongwen", "url": "https://resolver.caltech.edu/CaltechTHESIS:11172022-023850059", "creators": [ { "name": { "family": "Williams", "given": "Ethan Francis" }, "id": "Williams-Ethan-Francis", "orcid": "0000-0002-6471-4497", "display_name": "Williams, Ethan Francis" } ], "advisors": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "advisor", "display_name": "Zhan, Zhongwen" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Kohler", "given": "Monica D." }, "id": "Kohler-M-D", "orcid": "0000-0002-4703-190X", "role": "member", "display_name": "Kohler, Monica D." }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/vehm-dd85", "abstract": "Observational geophysics conventionally relies on point sensors to document and monitor Earth\u2019s dynamic processes, from locating earthquakes and imaging subsurface structure with seismometers to forecasting coastal wave heights and detecting tsunamis with buoys. Distributed acoustic sensing (DAS) offers a fundamentally different paradigm: distributed instead of point sensing. DAS converts fiber-optic cables into dense arrays of broadband, linear strainmeters, with spatial resolution as fine as one meter and temporal resolution up to several thousand samples per second. The first four chapters of this thesis concern ocean-bottom DAS, repurposing pre-existing telecommunications and power cables as distributed seafloor sensing networks for seismology and physical oceanography. In Chapter 2, we analyze one of the first ocean-bottom DAS datasets, demonstrating that seismic and ocean waves observed on the same array are related by a classic theory of double-frequency microseism generation. We also extract the principal body-wave phases of a M8.2 deep earthquake, demonstrating the earthquake detection capabilities of DAS even in a shallow water environment. In Chapter 3, we apply ambient noise interferometry to a one-hour of ocean-bottom DAS data and derive a shallow shear-wave velocity model. We also isolate spurious arrivals in noise cross-correlations associated with nearby offshore wind turbines, suggesting potential for remote monitoring. In Chapter 4, we adapt ambient noise interferometry to the ocean surface gravity wavefield, and estimate the tidal current velocity along a short cable segment in the Strait of Gibraltar with a waveform stretching method. In Chapter 5, we explore the application of DAS as a temperature sensor at long periods, documenting temperature signals up to 4 K associated with internal wave and boundary layer dynamics. We demonstrate that while ocean-bottom DAS exhibits sufficient strain sensitivity to record seafloor geodetic processes, oceanic temperature transients may overprint such signals. The last part of this thesis concerns a different frontier in geophysical instrumentation: long time-series. With a 20-year continuous record of ambient vibrations from a single accelerometer located on the ninth floor of a concrete building, we document long-term, passive changes in the building\u2019s natural frequencies as well as complex, time-dependent nonlinear elasticity during earthquakes." }, { "name": "Zhang, Yi", "degree": "PhD", "year": "2023", "title": "Application of Heterojunction Ni-Sb-SnO\u2082 Anodes for Electrochemical Water Treatment", "advisor": "Hoffmann, Michael R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03132023-113800696", "creators": [ { "name": { "family": "Zhang", "given": "Yi" }, "id": "Zhang-Yi", "orcid": "0000-0002-9062-5201", "display_name": "Zhang, Yi" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "See", "given": "Kimberly" }, "id": "See-Kimberly", "orcid": "0000-0002-0133-9693", "role": "member", "display_name": "See, Kimberly" }, { "name": { "family": "Gschwend", "given": "Philip M." }, "id": "Gschwend-Philip-M", "orcid": "0000-0002-9497-4492", "role": "member", "display_name": "Gschwend, Philip M." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "member", "display_name": "Hoffmann, Michael R." } ], "option_major": [ "envreng" ], "doi": "10.7907/dmrd-w489", "abstract": "Clean water supply and adequate sanitation services are critical for public health as well as for food production. Small-scale decentralized treatment represents an attractive alternative that can provide necessary water treatment in many parts of the developing world where centralized wastewater treatment facilities are not practical owing to financial, geographical, or political constraints. Electrochemical oxidation (EO) is a suitable technique for decentralized treatment settings since it does not require the addition of auxiliary chemicals and offers fast reaction kinetics and modular treatment capacity. EO is considered a versatile technology since it can degrade a wide array of contaminants and inactivate waterborne pathogens. The chemical composition of the anode, where EO takes place, is a key factor that controls reactive species production and thus treatment efficiency and energy consumption. Ideal anodes for wastewater treatment should have high overpotential for oxygen evolution (\u201cnonactive\u201d anodes) and favor complete organics oxidation through direct electron transfer and/or reactions with potent oxidants such as hydroxyl radical and ozone. Common nonactive anodes including antimony-doped tin oxide (Sb-SnO\u2082), lead oxide (PbO\u2082), and boron-doped diamond (BDD) have attracted wide research interests. The work presented in this thesis centered around a newly designed heterojunction Ni-Sb-SnO\u20822-based anode (NAT/AT) and its various applications in decentralized water and wastewater treatment. Direct treatment using NAT/AT has proved to be efficient for chemical oxygen demand removal, trace organic compound degradation, and microbial disinfection. Detailed investigation into pharmaceutical degradation kinetics and transformation products further established NAT/AT as a potential treatment alternative for the control of pharmaceuticals and their metabolites in hospital wastewaters. NAT/AT is also capable of synthesizing ferrates (e.g., FeO\u2084\u00b2\u207b) in circumneutral conditions, the high oxidation state iron species that represents another group of powerful oxidants well-suited for decentralized treatment purposes. In an additional effort to tackle high concentrations of ammonium often present in latrine wastewaters, functionalized metal-organic framework (MOF), a class of materials featuring high porosity, abundant active sites, and highly tunable physical and chemical properties, was used to recover the ammonium nitrogen. Various modifications of MOF-808, a highly water stable MOF, were designed and synthesized to achieve urea hydrolysis, ammonium capture, and real-time ammonium sensing in sequence. In combination, the described works provide a powerful toolkit that can be used in treating various waste streams before discharge and/or reuse." }, { "name": "Castellanos, Jorge Alberto Castillo", "degree": "PhD", "year": "2022", "title": "Seismic Wavefield Imaging of the Earth: the Regional, the Local, and the Remote", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07192021-182024547", "creators": [ { "name": { "family": "Castellanos", "given": "Jorge Alberto Castillo" }, "id": "Castellanos-Jorge-Alberto-Castillo", "orcid": "0000-0002-0103-6430", "display_name": "Castellanos, Jorge Alberto Castillo" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/fm32-1t74", "abstract": "In this thesis, I use seismic wavefield methods to illuminate the interior structure and the dynamics of the Earth across different scales. First, I image the large-scale lithospheric structure at the eastern sector of the Trans-Mexican Volcanic Belt to constrain on the transition from flat to steeper subduction in central Mexico. Then, I move to a regional scale and image the dynamics of the Wallowa Mountain block in northeastern Oregon, where mantle-based stresses appear to have played an essential role in shaping the crustal structure. With the findings of this investigation, I was able to illuminate a deformation mechanism of mantle origin, which I also use here to explain other near-surface processes in different parts of the North America continent. After, I move to a local scale, where I use dense oil-industry instrumentation to image the sub-kilometer crustal structure of Long Beach, California. In the first part of this investigation, I use noise-derived surface waves to create a high-resolution shear wave velocity model of the first kilometer of the crust, which I use to numerically determine the variability in the expected ground shaking intensity of the area. In the second part, I move past the traditional surface wave analysis and use the body wave portion of the noise-derived Green's functions to create a high-resolution compressional wave velocity model beneath one of the surveys. Finally, I present a waveform-based method of analysis that shows great promise as a new way of investigating the seismic behavior and the physical conditions of isolated marine environments.
" }, { "name": "Chachan, Yayaati", "degree": "PhD", "year": "2022", "title": "A Journey with Dust: from Protoplanetary Disks to Planetary Atmospheres and Outflows", "advisor": "Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02282022-175350847", "creators": [ { "name": { "family": "Chachan", "given": "Yayaati" }, "id": "Chachan-Yayaati", "orcid": "0000-0003-1728-8269", "display_name": "Chachan, Yayaati" } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." } ], "option_major": [ "plansci" ], "doi": "10.7907/8dxy-2b79", "abstract": "Dust in astronomy is often perceived as a hindrance to true characterization of celestial bodies. However, it is the humble dust particles that often run the show in planet formation and evolution. In this thesis, I present four different observationally inspired problems, which span a vast chronological range from core formation to atmospheric escape, and show how dust holds sway over them. In Chapter 2, I demonstrate that protoplanetary disks that are capable of forming giant planets are also capable of hosting close-in super-Earths within the giant planet\u2019s orbit, in line with the observed correlation between the occurrence rates of these two sub-populations. In Chapter 3, I show how dust dynamics and differences in grain properties across the water ice line create a region at intermediate distances where gas accretion is rapid. This might explain the preponderance of giant planets at such distances from their host stars, independently or complementarily to prevalent ideas on where massive cores form. Subsequently, since our understanding of the simultaneous accretion of dust and gas during planet formation remains poor, I argue in Chapter 4 that atmospheric characterization of Neptune-class planets is valuable for advances in this area. In particular, I discuss my efforts to characterize one such planet (HAT-P-11b) that, as a low metallicity Neptune, serves as an instructive challenge for formation models. Finally, in Chapter 5, I substantiate the idea that dust in the form of photochemical hazes must be present in outflowing atmospheres of super-puffs (i.e. planets with super-Earth-like masses but giant planet-like radii) by using the transmission spectrum and bulk properties of the canonical super-puff Kepler-79d.
" }, { "name": "Dobrosavljevic, Vasilije V.", "degree": "PhD", "year": "2022", "title": "Exploring Earth's Core-Mantle Boundary with Multi-Technique Approaches", "advisor": "Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272022-200244272", "creators": [ { "name": { "family": "Dobrosavljevic", "given": "Vasilije V." }, "id": "Dobrosavljevic-Vasilije-V", "orcid": "0000-00002-3710-2188", "display_name": "Dobrosavljevic, Vasilije V." } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." } ], "option_major": [ "geophys" ], "doi": "10.7907/v5xy-mt19", "abstract": "Earth's core-mantle boundary (CMB) is the most extreme interface of the planet's interior. It regulates the flow of heat out of the core and in doing so influences the two internal engines of our dynamic habitable planet: convection in the solid mantle and the magnetic geodynamo in the core. Seismic observations of the CMB have revealed a complex landscape of heterogeneous multi-scale structures that likely play key roles in Earth's internal dynamics and may hold memory of Earth's ancient past. Many details of the compositions and properties of these structures, however, are essentially unknown. In this thesis, I deploy a suite of experimental techniques and interdisciplinary approaches to constrain the temperature and phase relations of the CMB, properties that affect dynamics of the mantle and core. In particular, I focus my study on ultralow velocity zones (ULVZs) - the most extreme and perhaps least well understood structures in the lowermost mantle. I first quantitatively show that these structures, originally posited to be areas of partial melt, can be well explained as solid FeO-rich formations given seismic, geodynamic, and mineralogical constraints. To further explore the viability of such solid FeO-rich structures, I develop a multi-technique approach combining two in-situ synchrotron-based methods, one sensitive to crystal structure and another to atomic dynamics, to study the high-pressure melting of iron-bearing materials. With this approach, I place new constraints on the core-mantle boundary temperature by measuring the melting temperature of a candidate core-forming alloy (Fe0.8Ni0.1Si0.1) at high pressures, finding that the addition of silicon to an Fe0.9Ni0.1 core can reduce CMB temperatures to ~3500 K. I then measure the melting of Fe0.94O, finding a melting temperature of 4140 \u00b1 110 K at CMB pressure, demonstrating the stability of solid FeO-rich ULVZs in the lowermost mantle. The melting experiments show strong agreement between the two independent techniques, helping to address sources of large discrepancies in previous high-pressure melting experiments. Reported high conductivity for iron-rich (Mg,Fe)O at CMB conditions may provide a mechanism for upwelling promoted by solid conductive ULVZs at roots of major hotspot plumes. As a whole, the thesis advances our understanding of the compositions and origins of ultralow velocity zones and, more broadly, the physical properties of Earth's core-mantle boundary region.
" }, { "name": "Hui, Katrina Lynn", "degree": "PhD", "year": "2022", "title": "Monsoonal Precipitation in a Model Hierarchy: Impact of Continental Geometry and Global Warming", "advisor": "Bordoni, Simona", "url": "https://resolver.caltech.edu/CaltechTHESIS:04192022-173428410", "creators": [ { "name": { "family": "Hui", "given": "Katrina Lynn" }, "id": "Hui-Katrina-Lynn", "orcid": "0000-0003-0325-8800", "display_name": "Hui, Katrina Lynn" } ], "advisors": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "advisor", "display_name": "Bordoni, Simona" } ], "committee": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "chair", "display_name": "Schneider, Tapio" }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Su", "given": "Hui" }, "id": "Su-Hui", "orcid": "0000-0003-1265-9702", "role": "member", "display_name": "Su, Hui" } ], "option_major": [ "envreng" ], "doi": "10.7907/k35s-mr12", "abstract": "Monsoon systems around the world vary in their onset timing and precipitation spatial extent, suggesting that continental geometry could play an important role in differentiating between different monsoons systems. Since over half the world's population is dependent on monsoonal precipitation, it is of crucial importance to understand what controls the strength, seasonal evolution, and spatial extent of the tropical circulation and its associated precipitation and how they will evolve in a warmer climate. Recent studies suggest that individual monsoon regions will respond differently to climate change, highlighting the potential influence continental geometry may have on the current and future monsoon. In this thesis, we study the response of monsoonal precipitation, in its precipitation intensity, pattern, and onset timing, to idealized continent and climate change using a model hierarchy. By progressively building up complexity, we can gain insight from the idealized cases to determine responsible mechanisms in the responses to warming found in individual monsoon regions within the full general circulation models (GCMs).
\r\n\r\nFirst, we study the influence of continental geometry on the timing and spatial distribution of monsoonal precipitation under our current climate using an idealized aquaplanet model run with different zonally symmetric configurations of Northern Hemispheric land. We show that having continent extending to the tropical latitudes is necessary to generate monsoons that feature a rapid migration of the convergence zone over the continent, similar to observed monsoons. Without these regions, the tropical circulation is not able to rapidly transition into an angular momentum conserving monsoon regime. Next, we focus only on the effect of climate warming on the monsoon by using a set of idealized aquaplanet simulations with uniform mixed-layer depth, run with different atmospheric longwave optical depths to simulate a large range of both colder and warmer climates than the current climate. We show that as the climate warms, during the spring the atmospheric energy storage increases, which compensates the thermal forcing and allows for the tropical circulation transitions to be delayed, resulting in a delay in monsoon onset. Furthermore, we find that in extremely warm climates, the compensating effect of the energy storage is limited due to complex changes in the surface temperature seasonality. As a result, eventually the monsoon onset delay with warming saturates. These results highlight the important role the surface, both in its physical conditions and energy balance, has on setting the monsoon.
" }, { "name": "Idini Zabala, Benjam\u00edn Rodo", "degree": "PhD", "year": "2022", "title": "Earthquakes and the New Paradigm of Diluted Cores in Gas Giant Planets", "advisor": "Stevenson, David John; Fuller, James", "url": "https://resolver.caltech.edu/CaltechTHESIS:05252022-055331911", "creators": [ { "name": { "family": "Idini Zabala", "given": "Benjam\u00edn Rodo" }, "id": "Idini-Zabala-Benjam\u00edn-Rodo", "orcid": "0000-0002-2697-3893", "display_name": "Idini Zabala, Benjam\u00edn Rodo" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "advisor", "display_name": "Stevenson, David John" }, { "name": { "family": "Fuller", "given": "James" }, "id": "Fuller-J", "orcid": "0000-0002-4544-0750", "role": "co-advisor", "display_name": "Fuller, James" } ], "committee": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "chair", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Fuller", "given": "James" }, "id": "Fuller-J", "orcid": "0000-0002-4544-0750", "role": "member", "display_name": "Fuller, James" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/hqtw-ka38", "abstract": "In this thesis, I present results on two distinct topics within geophysics: earthquake mechanics and the core of gas giant planets. A common element connecting this work is the similar research approach that I use to address each topic. Each chapter in this thesis attempts to provide a simple physical understanding on the fundamental aspects relevant to the system in question. Further, I use numerical models to expand my arguments in some cases, while in others I build up my case with mathematical modeling only.
\r\n\r\nChapters II-IV focus on the gravitational field of Jupiter and connect radio science observations from NASA's Juno mission to the structure of Jupiter's dilute core. In Chapter II, I use dynamical tides to interpret a nonhydrostatic component in Jupiter's degree-2 tidal response -- represented by the Love number k\u2082 -- observed by Juno at the mid-mission perijove (PJ) 17. The results presented here show how the Coriolis acceleration contributes with a dynamical effect to Jupiter's tidal response, providing a satisfactory fit to Juno's observed k\u2082. From these results, I conclude that Juno obtained the first unambiguous detection of the gravitational effect of dynamical tides in a gas giant planet.
\r\n\r\nIn Chapter III, I build a perturbation theory to show that the high-degree tidal gravitational field of Jupiter is dominated by spherical harmonic coupling promoted by Jupiter's oblate figure as forced by the centrifugal effect. Based on this novel understanding of Jupiter's high-degree tidal gravitational field, I establish that Juno observed a 7\u03c3 nonhydrostatic component in k\u2084\u2082 at mid-mission.
\r\n\r\nIn Chapter IV, I invoke a core-orbital resonance between internal gravity waves trapped in Jupiter's dilute core and the orbital motion of Io to explain the 7\u03c3 nonhydrostatic component in the high-degree tidal response of Jupiter as observed by Juno at mid-mission -- namely the Love number k\u2084\u2082. These results suggest that an extended dilute core in Jupiter (r \u2273 0.7RJup) reconciles the k\u2084\u2082 nonhydrostatic component. This explanation of Juno's observation requires two ingredients: a dilute core in Jupiter that becomes smoother or shrinks over geological time, alongside with a high amount of dissipation provided by resonantly excited internal gravity waves.
\r\n\r\nIn Chapter V, I connect observations of earthquake modes of propagation to the damaged rock often found around tectonic fault zones. Previous work showed that pulse-like rupture -- a propagation mode where slip propagates as a narrow pulse -- can be induced by the dynamic effect of seismic waves reflected at the boundary of a cavity formed by the damaged material in fault zones. My main result shows that pulses are easier to produce than previously thought; pulses can appear in a highly damaged fault zone even in the absence of reflected seismic waves. In addition, these results provide a new explanation for back-propagating rupture fronts recently observed during large earthquakes and the rapid-tremor-reversal slip patterns observed in Cascadia and Japan.
\r\n\r\nIn summary, the results contained in these four chapters advance our knowledge in fundamental problems related to geophysics. In relation to gas giant planets, my results include the development of a novel technique to reveal the structure of Jupiter's core using spacecraft observations of the tidal gravitational field. In relation to earthquakes, my results connect earthquake ruptures to observable fault zone properties.
" }, { "name": "Jia, Zhe", "degree": "PhD", "year": "2022", "title": "Resolving Earthquake Source Complexities in the Heterogeneous Earth", "advisor": "Zhan, Zhongwen; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05202022-003950365", "creators": [ { "name": { "family": "Jia", "given": "Zhe" }, "id": "Jia-Zhe", "orcid": "0000-0003-0652-2646", "display_name": "Jia, Zhe" } ], "advisors": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "advisor", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." } ], "option_major": [ "geophys" ], "doi": "10.7907/na72-6395", "abstract": "While the commonly used simple assumptions of sources and structures allows useful first-order approximation of earthquakes, they are increasingly insufficient in characterizing the complex earthquake ruptures and the seismic wave propagations. In this thesis, I present studies that address both the source and structural complexities, as well as their interactions, using flexible parameterizations and ideas.
\r\n\r\nFor large earthquakes, I develop a subevent inversion framework to determine their spatiotemporal rupture complexities, and applied it to multiple significant earthquakes. Our method does not assume a fault geometry and kinematic history, and incorporates Bayesian analysis for uncertainty assessments. In Chapter 2, I discovered that the 2018 Fiji Magnitude 8 deep earthquake doublet actually ruptured two slabs, which demonstrates local slab temperature as the critical factor for deep earthquakes, and reveals complex interactions between slabs. In Chapter 3, I determined that the 2019 Ridgecrest Magnitude 7 sequence coseismically ruptured orthogonal faults, and has superficially complex but in-depth simple fault geometries, which illustrates the fault geometrical control of the rupture behaviors which challenges traditional seismic hazard mapping. In Chapter 4, I found the 2021 South Sandwich Island Magnitude 8 earthquake consists of deep regular ruptures connected by a slow tsunamigenic event, which highlights the tsunami potential for deep initiations of megathrust earthquakes.
\r\n\r\nFor smaller earthquakes, I develop a Bayesian differential moment tensor inversion (diffMT) algorithm to remove the common earth structural effects, thus improving the earthquake focal mechanism resolvability. In Chapter 5, I demonstrated that diffMT reduces the moment tensor uncertainties substantially than traditional direct-inversion methods, and found that the North Korea nuclear tests in 2013-2016 are more dominated by explosive mechanism than previous understandings.
\r\n\r\nTowards high resolution mapping of the Earth structure, I expand the seismic tomography for high resolution basin structure by combining the wide aperture of seismic stations and high density of industrial arrays. In Chapter 6, I applied this approach on the densely populated Los Angeles Basin, and found improved mapping of small scale heterogeneities, which can potentially promote earthquake ground motion assessments.
\r\n\r\nIn summary, I have developed research tools and applied novel ideas on complex seismic events and heterogeneous earth environments. The results illustrate the diverse controlling factors of complex earthquake ruptures, and reveal the complex interactions between earthquakes and earth structure.
" }, { "name": "Jongramrungruang, Siraput", "degree": "PhD", "year": "2022", "title": "Towards Accurate and Automated Detection and Quantification of Localized Methane Point Sources on a Global Scale", "advisor": "Frankenberg, Christian", "url": "https://resolver.caltech.edu/CaltechTHESIS:08092021-200722718", "creators": [ { "name": { "family": "Jongramrungruang", "given": "Siraput" }, "id": "Jongramrungruang-Siraput", "orcid": "0000-0002-2477-2043", "display_name": "Jongramrungruang, Siraput" } ], "advisors": [ { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "advisor", "display_name": "Frankenberg, Christian" } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Thompson", "given": "David R." }, "id": "Thompson-David-R", "orcid": "0000-0003-1100-7550", "role": "member", "display_name": "Thompson, David R." }, { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "member", "display_name": "Ross, Zachary E." } ], "option_major": [ "envreng" ], "doi": "10.7907/ab33-7a98", "abstract": "Methane (CH4) is the second most important anthropogenic greenhouse gas with a significant impact on radiative forcing, tropospheric air quality, and stratospheric water vapor. Because methane has a much shorter lifetime compared to carbon dioxide (CO2), reduction in methane emission is deemed a key target for climate mitigation strategies in upcoming decades. One crucial step in emission reduction is determining the location and emission rate of localized methane sources. Remote-sensing instruments using absorption spectroscopy have emerged as one promising solution for measuring atmospheric CH4 concentration over large geographical areas. However, the identification and quantification of local point sources based on the observed methane column enhancement distribution has proven challenging due to uncertainties in the knowledge of local wind speed and retrieval errors arising from surface spectral interferences and instrument noise. In this thesis, it is shown how plume morphology based on a 2-D image of methane column enhancement can be used to quantify the source emission rate directly without relying on any ancillary data such as local wind speed measurements. Large eddies simulations (LES) are utilized to create realistic synthetic plume observations under various atmospheric conditions. Using this data, a deep learning model named MethaNet is trained to predict emission rates directly from 2-D methane plume images. The model achieves a level of performance for quantifying methane emission rates that is state-of-the-art for a method that does not rely on wind speed information. Obtaining methane column measurements with low precision error and bias is a key step for separating real plume enhancements from artefacts and enhancing the quantification performance. Here an instrument tradeoff analysis is presented to assess the effect of changing instrument specifications and retrieval parameters. It is shown how the retrieval errors can be mitigated with optimal spectral resolutions and a larger polynomial degree to approximate surface albedo variations in the retrieval process. The results in this thesis contribute towards building an enhanced monitoring system that can measure CH4 enhancement fields and determine methane sources accurately and efficiently at scale.
" }, { "name": "Kemeny, Preston Cosslett", "degree": "PhD", "year": "2022", "title": "A Fluvial Perspective on the Role of Sulfide Oxidation in the Global Carbon Cycle", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272022-003433646", "creators": [ { "name": { "family": "Kemeny", "given": "Preston Cosslett" }, "id": "Kemeny-Preston-Cosslett", "orcid": "0000-0003-1693-4142", "display_name": "Kemeny, Preston Cosslett" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "West", "given": "A. Joshua" }, "id": "West-A-Joshua", "orcid": "0000-0001-6909-1471", "role": "member", "display_name": "West, A. Joshua" } ], "option_major": [ "geochem" ], "doi": "10.7907/59hb-zp37", "abstract": "This thesis contains an introduction and five studies on the role of sulfide oxidation in regulating the relationship between chemical weathering and climate. Chapter I provides an overview of the key question \u2014 what stabilizes the global carbon cycle? \u2014 and motivates the specific questions addressed in each subsequent chapter. Chapter II describes a new numerical tool for inverting observations of dissolved river chemistry for information about chemical weathering reactions. Chapters III, IV, and V describe observations from field sites in Iceland, Nepal, and Alaska that address the fidelity of fluvial sulfur isotope ratios, the role of sulfide oxidation in Cenozoic cooling, and sulfur dynamics within permafrost landscapes, respectively. Using the tools and lessons of the preceding chapters, Chapter VI quantifies the impact of global chemical weathering on the concentration of atmospheric carbon dioxide." }, { "name": "Labedz, Celeste Ritter", "degree": "PhD", "year": "2022", "title": "Between Seismic Speed and Glacial Pace: Cryoseismic Observation of Intermediate-Scale Processes at Lemon Creek Glacier, Alaska", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012022-151808806", "creators": [ { "name": { "family": "Labedz", "given": "Celeste Ritter" }, "id": "Labedz-Celeste-Ritter", "orcid": "0000-0001-7339-2170", "display_name": "Labedz, Celeste Ritter" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/4y62-sd53", "abstract": "In this thesis, I present three studies in environmental seismology. First, I present an analysis of seismic tremor generated from subglacial water flow during the rapid drainage of an ice-marginal supraglacial lake, collected by an on-ice nodal seismic array. I find that seismic tremor indicates a partial pressurization of the subglacial hydrologic system that was not accompanied by the expected change in glacier surface velocity, suggesting that factors like glacier geometry play a significant role in whether pressurization necessarily leads to velocity change. Using seismometers in this way allows remote observation of active subglacial hydrologic systems as they vary over space and time, a vital parameter for understanding how liquid water affects glacier motion, melting, fracture, and hazards. Second, I present observations of glacier surface crevasse development over space and time, as detected by a dense array of seismometers atop the glacier. I find that icequakes associated with surface crevassing have a magnitude distribution that is swarm-like, rather than aftershock-like, and that the spatiotemporal distribution of events indicates that crevasses regularly widen, deepen, reactivate, and trigger activity at nearby crevasses through cryoseismicity. Understanding surface crevassing activity is valuable for constraining the degree to which glacier surface velocity measurements represent ice flow as a whole, and for interpreting how glacier flow responds to changes in forcing over time. Third, I present an investigation of changes in anthropogenic urban seismic noise in Los Angeles associated with changes in community behavior. I find that changes in human activity from the scale of hours to the scale of months create distinguishable differences in ambient seismic noise power that correlate well with other measures of community behavior. Characterizing anthropogenic seismic noise is beneficial for accurately interpreting measurements of transient seismic wave data collected in urban areas toward goals such as hazard mapping.
" }, { "name": "Larochelle, Stacy", "degree": "PhD", "year": "2022", "title": "Mechanical Interactions Between Water and the Solid Earth: from Quasi-Static Geodetic Deformation to Dynamic Fault Slip", "advisor": "Avouac, Jean-Philippe; Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechTHESIS:05302022-071239478", "creators": [ { "name": { "family": "Larochelle", "given": "Stacy" }, "id": "Larochelle-Stacy", "orcid": "0000-0001-6161-5605", "display_name": "Larochelle, Stacy" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "co-advisor", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "co-advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Ross", "given": "Zachary E." }, "id": "Ross-Z-E", "orcid": "0000-0002-6343-8400", "role": "chair", "display_name": "Ross, Zachary E." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" } ], "option_major": [ "geophys" ], "doi": "10.7907/2r5a-9277", "abstract": "Mechanical interactions between Earth's solid interior and its hydrosphere are central to many geophysical problems of crucial societal importance: Changing conditions in the global water cycle deform the solid Earth; the groundwater storage capacity of aquifer systems is controlled by its interaction with geological materials; and crustal water - either natural occurring or added through anthropogenic activities - affects earthquakes and fault slip processes. In this thesis, we investigate some of these interactions by harnessing recent developments in the fields of satellite geodesy, statistical data analysis and elastodynamic earthquake modelling. We start by developing a procedure to identify and extract seasonal deformation signals associated with hydrological loading of the solid Earth from geodetic time series in Chapter 1. In Chapters 2 and 3, we consider the examples of the Ozarks Plateau (central United States) and Sacramento Valley (California) to establish a methodology for characterizing poroelastic deformation arising from groundwater variations with space-based geodesy. Then, in Chapter 4, we develop a model to simulate fault slip due to crustal water injections and calibrate it against a well-instrumented field experiment on a natural fault. We conclude by deriving a theoretical understanding of these fault slip simulations by considering the simple case of a fixed-length pressurized zone in Chapter 5. Overall, our work provides key insights for extracting and using different sources of hydrogeodetic signals as well as for modeling and understanding fluid-induced fault slip processes, which is becoming increasingly important in a world faced with water scarcity, a changing climate and an increased reliance on groundwater and geoenergy resources.
" }, { "name": "Le, Tianhao", "degree": "PhD", "year": "2022", "title": "Radiation-Based Analytic Approaches to Investigate the Earth\u2019s Atmosphere", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01032022-071943237", "creators": [ { "name": { "family": "Le", "given": "Tianhao" }, "id": "Le-Tianhao", "orcid": "0000-0002-6600-8270", "display_name": "Le, Tianhao" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-Christian", "orcid": "0000-0002-0546-5857", "role": "member", "display_name": "Frankenberg, Christian" } ], "option_major": [ "envreng" ], "doi": "10.7907/1ck6-wx77", "abstract": "Radiation, propagating through Earth\u2019s atmosphere, plays an important role in the Earth system. Solar radiation is the major source of energy, followed by thermal infrared radiation emitted by the Earth. The total radiative energy budget affects dynamic, thermodynamics, photochemical and biological processes. In addition, by measuring the reflected and emitted radiation at a distance (e.g., satellite or aircraft), we can detect and monitor the physical characteristics of a region which can help researchers get a better understanding of Earth\u2019s atmosphere. Therefore, radiation-based analytic approaches are powerful tools in Earth Science. This thesis focuses on using radiation-based analytic tools to study the Earth\u2019s atmosphere and to understand human impacts on the Earth system.
\r\n\r\nFirst, we develop novel machine learning methods for hyperspectral radiative transfer simulations. Hyperspectral technique is one of the most popular and powerful methods for atmospheric remote sensing and is widely used for temperature, gas, aerosol, and cloud retrievals. However, accurate forward radiative transfer simulations are computationally expensive since they require a larger number of monochromatic radiative transfer calculations. We, therefore explore the feasibility of machine learning techniques for fast hyperspectral radiative transfer simulations that perform calculations at a small fraction of hyperspectral wavelengths and extend them across the entire spectral range. The machine learning-based approach achieves better performance than the traditional principal component analysis (PCA) method.
\r\n\r\nSecond, we evaluate modeled hyperspectral infrared spectra against satellite all-sky observations. The national weather centers obtain data from hyperspectral infrared sounders on a global scale. The cloudless scenario of this data is used to initialize weather forecasts, including temperature, water vapor, water cloud, and ice cloud profiles on a global grid. Although the data from these satellites are sensitive to the vertical distribution of ice and liquid water in the clouds, this information is not fully utilized. In this study, we evaluate how well the modeled spectra compare to AIRS observations using different cloud overlap models. We hope that this information can be used to verify clouds in the National Meteorological Center model and to initialize forecasts in the future.
\r\n\r\nIn the last chapter, we use radiation-based analytic approaches to study human impacts on the Earth system. In the first study case, we show that the radiative forcing due to geospatially redistributed anthropogenic aerosols mainly determined the spatial variations of winter extreme weather in the Northern Hemisphere during 1970-2005, which is a unique transition period for global aerosol forcing. In the second case, we review satellite and ground-based observations and conduct state-of-art atmospheric model simulations during the COVID-19 lockdown period. The halted human activities during the COVID-19 pandemic in China provided a unique experiment to assess the efficiency of air-pollution mitigation.
" }, { "name": "Li, Jiazheng", "degree": "PhD", "year": "2022", "title": "The Chemistry of Europa and Venus, and Characterization of Earth-Like Exoplanets", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05252022-004039193", "creators": [ { "name": { "family": "Li", "given": "Jiazheng" }, "id": "Li-Jiazheng", "orcid": "0000-0002-2563-6289", "display_name": "Li, Jiazheng" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "de Kleer", "given": "Katherine R." }, "id": "de-Kleer-K-R", "orcid": "0000-0002-9068-3428", "role": "chair", "display_name": "de Kleer, Katherine R." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/1q9j-y297", "abstract": "This thesis contains three parts of work, including oxidant sources on Europa, sulfur chemistry on Venus, and the characterization of Earth-like exoplanets. In the first part, we build two chemical-transport models to study the various oxidant-generation processes that occur in both Europa\u2019s atmosphere and surface ice. The atmospheric model focuses on the role that water plumes play in the formation of Europa\u2019s ionosphere. The simulation results, which show that the ionization reactions are initiated by electron-impact ionization and photoionization of water and continued by charge transfer between water and oxygen molecules, have successfully reproduced the observations. This model has also been used to study the dissociation processes of water molecules from the plumes, which can be regarded as an alternative source for the oxygen in the atmosphere. The chemical-transport model on Europa\u2019s surface ice is built to simulate chemical processes occurring in the ice during irradiation by electrons and to describe how the chemical species of interest (oxidants) are formed, transported, and distributed in the ice. This model also has implications for the chemical composition of Europa\u2019s subsurface ocean. Since the availability of oxidants could be the limiting factor for biologically useful chemical energy on Europa, the proposed research may give us insight into Europa\u2019s habitability.
\r\n\r\nThe second part of this thesis focuses on the unknown ultraviolet (UV) absorber(s) in the atmosphere of Venus. Ever since the detection of the enigmatic ultraviolet absorption in the upper atmosphere of Venus, questions have been raised about the identity of the unknown UV-visible absorber(s) and how it is formed on Venus. Our recent photochemical modelling study suggests that SO dimers may not be the major UV absorber(s) in Venus\u2019 upper atmosphere. However, SO dimers are important intermediaries in the formation of more complex S species (e.g., Sn (n = 1 to 7)). Polysulfur aerosol, which is formed from the nucleation process of Sn (n = 1 to 7), is a possible candidate for the unknown UV absorber(s). In this work, we compute that the mixing ratio of polysulfur aerosol is ~1.76\u00d710-14 in the upper atmosphere. By putting the polysulfur aerosol into the Spectral Mapping Atmospheric Radiative Transfer model (SMART), we find that the simulated spectrum of Venus agrees well with the observations. This result provides useful constraints for unraveling the identity(ies) of the unknown UV-visible absorber(s) on Venus.
\r\n\r\nThe third part of this thesis is devoted to the characterization of Earth-like exoplanets. In this part, we study the glints, a possible phenomenon on Earth-like exoplanets and the rotation period detection for Earth-like exoplanets. Small flashes of reflected light\u2014called glints\u2014are found in images taken by spacecraft observing the Earth and occur due to specularly reflected solar radiation. These glints have been found over both ocean and land. Using Deep Space Climate Observatory observations, we show that glints over land are due to specular reflection off horizontally oriented ice platelets floating in the air, while glints over ocean have contributions from reflection off either platelets floating above the ocean or a relatively smooth ocean surface. We use a radiative transfer model to simulate different kinds of glints and to explore their properties. This technique of comparing observations of terrestrial glints with model simulations may provide new information relevant to atmospheric dynamics and the search for habitable exoplanets. A terrestrial planet\u2019s rotation period is one of the key parameters that determines its climate and habitability. Here we demonstrate that, under certain conditions, the rotation period of an Earth-like exoplanet will be detectable using direct-imaging techniques. We use a global climate model that includes clouds to simulate reflected starlight from an Earth-like exoplanet and show that the rotation period of an Earth-like exoplanet is detectable using visible-wavelength channels with time-series monitoring at a signal-to-noise ratio (S/N) >20 with \u223c5\u201315 rotation periods of data, while the rotation period of a planet with full ocean coverage is unlikely to be detectable. To better detect the rotation period, one needs to plan the observation so that each individual integration would yield a S/N >10, while keeping the integration time shorter than 1/6 to 1/4 of the rotation period of the planet. Our results provide important guidance for rotation period detection of Earth-like exoplanets in reflected light using future space telescopes.
" }, { "name": "Markham, Stephen Robert", "degree": "PhD", "year": "2022", "title": "Gas Planet Seismology and Cooling", "advisor": "Batygin, Konstantin; Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:09242021-014822132", "creators": [ { "name": { "family": "Markham", "given": "Stephen Robert" }, "id": "Markham-Stephen-Robert", "display_name": "Markham, Stephen Robert" } ], "advisors": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "advisor", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "co-advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Fuller", "given": "James" }, "id": "Fuller-J", "orcid": "0000-0002-4544-0750", "role": "member", "display_name": "Fuller, James" }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/zb52-0517", "abstract": "In this thesis I advocate for the enhancement of interdisciplinary expertise between atmospheric and interiors sciences. I illustrate the intimate connection between atmosphere and interior with four projects involving two major topics: giant planet seismology, and convective inhibition by condensation. First I advance a heuristic to evaluate generic localized excitation sources for giant planet seismicity, concluding observed oscillations on Jupiter may be caused by highly energetic rock storms lurking deep beneath the visible clouds. Next I develop a method to use existing spacecraft data to probe for seismic activity on giant planets, applying the method to Cassini data. This method finds possible evidence of p-modes on Saturn, excited to staggering amplitudes warping the surface of Saturn with kilometer scale displacements. Next I explore the impact of convective inhibition on Uranus and Neptune, finding that condensation of methane and water produces non-negligible corrections to these planets' thermal histories. Finally I explore a similar mechanism operating in the limit where condensing species are highly abundant. I find that considering convective inhibition, super-Earths can retain their primordial heat for longer than the age of the universe.
" }, { "name": "Muir, Jack Broderick", "degree": "PhD", "year": "2022", "title": "Model Parameterization and Model Selection in Geophysical Inverse Problems. Designing Inverse Problems that Respect a priori Geophysical Knowledge", "advisor": "Tsai, Victor C.; Clayton, Robert W.; Zhan, Zhongwen", "url": "https://resolver.caltech.edu/CaltechTHESIS:10202021-003229377", "creators": [ { "name": { "family": "Muir", "given": "Jack Broderick" }, "id": "Muir-Jack-Broderick", "orcid": "0000-0003-2617-3420", "display_name": "Muir, Jack Broderick" } ], "advisors": [ { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "orcid": "0000-0003-1809-6672", "role": "advisor", "display_name": "Tsai, Victor C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "co-advisor", "display_name": "Zhan, Zhongwen" } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "orcid": "0000-0003-1809-6672", "role": "member", "display_name": "Tsai, Victor C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" } ], "option_major": [ "geophys" ], "doi": "10.7907/203d-yx49", "abstract": "The vast majority of the Earth system is inaccessible to direct observation. Consequently, the structure and dynamics of the Earth can only be determined indirectly, via geophysical sensing. These methods have the mathematical form of an inverse problem, in which the data and the unknowns are linked by a physical process, such as seismic wave propagation. From the possibly noisy data, we have indirect access to the unknowns. The vast majority of geophysical inverse problems are ill-posed, and require the provision of a priori knowledge to stabilize the solution. This thesis investigates methods for designing inverse problems to better take advantage of geophysical or geological constraints, to allow better resolution or more interpretability of the solutions. Four major themes are investigated: In Chapter 2, we study the collection of a novel dataset of Rayleigh wave horizontal-to-vertical ratios to provide stronger constraints on upper-crustal structure in Southern California. In Chapters 3 and 4, we develop a method for wavefield-reconstruction of sparse seismic data, including heterogeneous networks consisting of both displacement and strain instruments. This method amounts to an inversion in data-space, and promises to unlock the potential of wavefield based methods for complex datasets. In Chapters 5 and 6, we investigate a new structural parameterization based on a combination of Gaussian processes and the level-set method, that better models discontinuous geological features such as sedimentary basins. We test our method on a variety of synthetic and real datasets, culminating in a detailed study of the northeastern Los Angeles basin, which we found to be significantly deeper and steeper than in previous models. Finally, we develop a method of model selection for noisy historical datasets, which we investigate using the case study of correcting Oldham's data misinterpretation in the 1906 paper that \"discovered\" Earth's core.
" }, { "name": "Saper, Lee Michael", "degree": "PhD", "year": "2022", "title": "Experimental Studies on the Thermodynamics and Kinetics of Coexisting Olivine, Silicate Melt, and Vapor", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08242021-041734202", "creators": [ { "name": { "family": "Saper", "given": "Lee Michael" }, "id": "Saper-Lee-Michael", "orcid": "0000-0002-3995-9986", "display_name": "Saper, Lee Michael" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." } ], "option_major": [ "geol" ], "doi": "10.7907/f8qb-3g41", "abstract": "This thesis focuses on experiments run in 1 atm gas-mixing furnaces exploring the thermodynamics and kinetics of coexisting olivine, silicate melt, and vapor. Chapter 1 provides a high-level introduction and summary of the results for each of the following chapters. Chapter 2 and Chapter 3 both involve experiments run on natural olivines containing melt inclusions. Chapter 2 describes a set of homogenization and cooling rate experiments designed to characterize chemical zonation that develops across melt inclusions during cooling. A diffusion model for MgO in the inclusion liquid was calibrated based on these experiments and then used to calculate the syneruptive cooling rates of lavas on Earth and on Mars based on comparison of the model to experimental and natural diffusion profiles in melt inclusions. Chapter 3 presents the first co-determined measurements of S and Fe oxidation state in experimental silicate melts that were equilibrated with the oxygen fugacity of a gas-mixing furnace. The use of melt inclusions as sulfur-bearing experimental vessels is explored, as are implications for interpreting room temperature measurements of the oxidation state of multivalent elements. A set of natural melt inclusions are used as a case study to demonstrate that the temperature-dependence of sulfur-iron electron exchange in basaltic liquids is either weak or leads to the conversion of ferric iron to ferrous iron during cooling. Chapter 4 presents a new parameterization of the composition-dependence of the olivine-liquid Fe-Mg exchange coefficient, K\u1d05ol/liq,Fe2+-Mg, based on experiments at low oxygen fugacity where corrections for Fe3+ are minor. A quantitative thermodynamic model is fit to the data, showing that the K\u1d05 is a function of the Si, Al, Ti, Na+K contents of the liquid as well as olivine composition. Models of K\u1d05ol/liq,Fe2+-Mg that do not incorporate liquid compositional variables cannot account for the variability of K\u1d05 (~0.22-0.38) observed at low oxygen fugacity in a compilation of high-quality literature experiments. Lastly, in Appendix 1, the published version of Richter, Saper, et al. (2021), GCA 295 is included. For this chapter, I contributed MELTS calculations (Ghiorso and Sack 1995; Smith and Asimow 2005) which were used to model crystallization processes and to set boundary conditions for models elemental and isotopic diffusion of Mg and Li in lunar olivines and martian olivines and augites. The combined elemental and isotopic diffusion profiles were used to discriminate between zoning formed due to crystallization from that due to diffusion.
" }, { "name": "Scheller, Eva Linghan", "degree": "PhD", "year": "2022", "title": "A Multi-Disciplinary Approach: How Aqueous Minerals Hold the Key to Understanding the Climate and Habitability of Terrestrial Planets", "advisor": "Ehlmann, Bethany L.; Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05252022-013922276", "creators": [ { "name": { "family": "Scheller", "given": "Eva Linghan" }, "id": "Scheller-Eva-Linghan", "orcid": "0000-0002-9981-5802", "display_name": "Scheller, Eva Linghan" } ], "advisors": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "co-advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geol" ], "doi": "10.7907/8rj3-6k52", "abstract": "Understanding the interplay between geological processes and the climate within the ancient pasts of terrestrial planets holds the key to deciphering what makes terrestrial planets habitable. The climates of both Mars and Earth were drastically different in their ancient pasts. Liquid water once flowed on Mars ~3-4 Ga, creating fluvial valleys and aqueous minerals, until Mars dried out to the desert planet we know today. During the Pleistocene (~ 2.6 Ma \u2013 11.7 ka) and Neoproterozoic (640-710 Ma), Earth experienced widespread glaciations and even a global glaciated state, respectively. Aqueous minerals, such as clays and carbonates, record the history of their aqueous environments and can be used to track these dramatic changes in climate and environment. In Chapter 2, I use hyperspectral infrared imagery and high resolution images retrieved by the Mars Reconnaissance Orbiter to characterize the lithology of some of the oldest Noachian ~3.8-4.1 Ga crust exposed on Mars. I document eight geological units and features that will be studied with the Perseverance rover and record the presence of pyroxene-bearing igneous crustal materials, aqueous environments that led to widespread clay formation, and basin-forming impact processes that brecciated the crust. Associated younger Noachian-aged magnesium carbonate-bearing geological units will also be studied and sampled with the Perseverance rover. In Chapter 3, I review magnesium carbonate formation on Earth and Mars and find that textures of nodules, crusts, veins, sparry crystals, and thrombolites/stromatolites, their associated host lithologies and related secondary mineralogy can be used to distinguish between formation within weathering, lacustrine, hydrothermal, diagenetic, or microbially influenced aqueous environments, respectively, with rover analyses. Laboratory analysis of stable and radiogenic isotopes of returned samples will allow us to analyze the surface temperature and atmospheric isotopic composition of ancient Mars. In Chapter 4, I characterize the paragenesis of hydrated carbonates. In frigid environments, carbonates form in hydrated species known as monohydrocalcite (MHC) and ikaite that transform to calcite upon heating. Through petrographic analysis of Pleistocene ikaite pseudomorphs and a review of more ancient examples, I define a new carbonate microtexture, guttulatic calcite, which is diagnostic for carbonate dehydration and can be used to document frigid temperature conditions. In Chapter 5, I characterize the stable carbon, oxygen (\u03b4\u00b9\u2078OCARB), and clumped (\u0394\u2084\u2087) isotope systematics of hydrated carbonates. Through heating experiments of modern MHC, I measure and model change in \u03b4\u00b9\u2078OCARB and \u0394\u2084\u2087 signatures facilitated by equilibrium exchange as MHC is dehydrated. Using the determined correction for dehydration overprint allows reconstruction of precursor ikaite formation temperatures and isotopic signatures. The textural and isotopic proxies can now be used for reconstructing temperatures and isotopic signatures within Pleistocene and Neoproterozoic sedimentary deposits. In Chapter 6, I use the Perseverance rover\u2019s SHERLOC instrument\u2019s deep-UV Raman and fluorescence spectroscopy to discover evidence for two potentially habitable ancient aqueous environments that contain aromatic organic compounds. Spectral and textural observations of the olivinecarbonate assemblage within Jezero crater, Mars reveal carbonation of ultramafic protolith. A separate, later brine formed sulfate-perchlorate mixtures in void spaces. Fluorescence signatures consistent with multiple types of aromatic organic compounds occur throughout these samples, preserved in minerals related to both aqueous processes. These organic-mineral associations indicate that aqueous alteration processes led to the preservation and possibly formation of organic compounds on Mars. In Chapter 7, I model the global water budget and hydrogen isotopic composition (D/H) of Mars, using measured constraints from geomorphology, atmospheric escape rates, volcanic degassing processes, crust volatile content, and D/H. In my simulations, I find that chemical weathering sequestered a 0.1-1 km global equivalent layer of water, decreasing the volume of water participating in the hydrological cycle by 40 to 95% over the Noachian (~3.7-4 Ga) period, reaching present-day values by ~3 Ga. Between 30 and 99% of Martian water was sequestered through crustal hydration, demonstrating that irreversible chemical weathering can increase the aridity of terrestrial planets. In summary, this PhD thesis demonstrates that the formation of aqueous minerals is a major control on terrestrial planet climates and that aqueous minerals can be used to track the conditions of their formation environments.
" }, { "name": "Shen, Zhichao", "degree": "PhD", "year": "2022", "title": "Probing Water Below the Surface: Insights from Seismic Interferometry with Conventional and DAS Array", "advisor": "Zhan, Zhongwen", "url": "https://resolver.caltech.edu/CaltechTHESIS:05022022-204308721", "creators": [ { "name": { "family": "Shen", "given": "Zhichao" }, "id": "Shen-Zhichao", "orcid": "0000-0003-0458-5264", "display_name": "Shen, Zhichao" } ], "advisors": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "advisor", "display_name": "Zhan, Zhongwen" } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" } ], "option_major": [ "geophys" ], "doi": "10.7907/5vtn-1c34", "abstract": "Water is essential to our daily lives, yet its subsurface behavior remains challenging to track using remote observations. By extracting seismic waves traveling through the Earth, seismic interferometry is a powerful tool to image the Earth\u2019s interior, in particular the long-term and short-term behavior of water circulation. With conventional dense seismic networks and emerging distributed acoustic sensing (DAS), I demonstrate how seismic interferometry brings new insights on water below the surface ranging from the depths of the mantle transition zone (MTZ) to the subsurface aquifers of our planet.
\r\n\r\nBy applying a novel inter-source interferometry method that turns deep earthquakes into virtual seismometers, I not only present evidence for an intermediate-scale metastable olivine wedge and small-scale intra-slab scatterers in the MTZ beneath the Japan Sea, but also reveal their dimensions and velocity perturbations more accurately than before. Beyond the relative independent scales of slab structures, these results point toward a consistent picture of transformational faulting of metastable olivine as the initiation mechanism of deep earthquakes, petrologic processes associated with dehydration of subducting slabs, and an extremely dry slab core below 410-km. Borrowing the idea from inter-source interferometry, I develop a slab operator method by utilizing the waveform broadening due to the high-velocity anomaly. With synthetic tests and real data, I illustrate the feasibility of this method for accurately determining large-scale slab velocity perturbations.
\r\n\r\nShifting from the Earth\u2019s interior to the subsurface, I investigate the feasibility of vadose zone water monitoring with DAS. DAS provides an affordable and scalable solution for deploying ultra-dense seismic arrays by transforming existing optic-fiber cables into thousands of seismic sensors. With two years of ambient noise recorded on the Ridgecrest DAS array, the time-lapse images of seismic changes (dv/v) reveal an unprecedented high-resolution spatiotemporal evolution of water saturation in vadose zone. A striking correlation between the dv/v amplitude and the sedimentary thickness is observed, while the frequency analysis of dv/v measurements suggests an uppermost 10 m hydrologic source as the cause for dv/v temporal variability. The results demonstrate the great potential of DAS for long term subsurface water monitoring.
" }, { "name": "Vissapragada, Shreyas", "degree": "PhD", "year": "2022", "title": "The Irradiation-Driven Evolution of Gas-Giant Exoplanets", "advisor": "Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05172022-001822273", "creators": [ { "name": { "family": "Vissapragada", "given": "Shreyas" }, "id": "Vissapragada-Shreyas", "orcid": "0000-0003-2527-1475", "display_name": "Vissapragada, Shreyas" } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/73xn-xx35", "abstract": "Nearly thirty years after their initial discovery, we now know of over five thousand extrasolar planets. Intensive efforts have been made to characterize the sizes, masses, orbits, and compositions of these new worlds, and the resulting population challenges our intuition from the Solar System. One striking feature of the exoplanet census is that the vast majority of known planets reside quite close to their host stars, with orbital periods of less than a hundred days. Our galaxy is replete with hot Jupiters, sub-Neptunes, and super-Earths orbiting their stars more quickly than Mercury orbits the Sun. These close-in planets are bombarded by high-energy stellar radiation, which heats their upper atmospheres and triggers mass loss via hydrodynamic escape. This means that planetary sizes, masses, and compositions can be substantially altered from their values at formation. This thesis presents five studies aimed at elucidating the irradiation-driven evolution of close-in extrasolar planets." }, { "name": "Wallack, Nicole Lisa", "degree": "PhD", "year": "2022", "title": "The Planet-Disk Connection: from Protoplanetary Disks to Planetary Atmospheres", "advisor": "Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06052022-175041539", "creators": [ { "name": { "family": "Wallack", "given": "Nicole Lisa" }, "id": "Wallack-Nicole-Lisa", "orcid": "0000-0003-0354-0187", "display_name": "Wallack, Nicole Lisa" } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Mawet", "given": "Dimitri" }, "id": "Mawet-D", "orcid": "0000-0002-8895-4735", "role": "member", "display_name": "Mawet, Dimitri" }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/m484-et60", "abstract": "When gas giant planets form, they influence the structure of the surrounding gas disk, which in turn shapes the final compositions of their gas envelopes. My thesis work combines two distinct techniques in order to better understand planet formation and evolution. As a planet accretes its atmosphere, information about its formation history is encoded in its composition (metallicity and C/O ratio). Taking advantage of equilibrium chemistry expectations of carbon bearing molecules for cool (T<~1000K) planets, in Chapter 2 we probe the atmospheric metallicities of this population of planets using Spitzer secondary eclipses. Expanding this sample set to all short-period gas giant planets with Spitzer thermal emission detections in Chapter 3, we can further explore which system parameters had the most impact on the infrared spectral slopes of these objects. In parallel with these projects, I also carried out a search for planets in protoplanetary disks using direct imaging in Chapter 4. As these planets accrete gas, they also carve out gaps in the protoplanetary disk, leaving hints as to where in the disk they formed. We conducted a multi-year direct imaging survey of more than 40 stars hosting protoplanetary disks in order to detect embedded gas giant planets and better constrain planet-disk interactions. These two approaches represent two distinct, yet complementary, methods of studying the formation histories of giant planets." }, { "name": "Zhong, Minyan", "degree": "PhD", "year": "2022", "title": "High-Resolution Geophysical Images of Static Crustal Structure and Time-Dependent Glacier Flow", "advisor": "Simons, Mark; Zhan, Zhongwen", "url": "https://resolver.caltech.edu/CaltechThesis:10182021-162923917", "creators": [ { "name": { "family": "Zhong", "given": "Minyan" }, "id": "Zhong-Minyan", "orcid": "0000-0002-1382-7061", "display_name": "Zhong, Minyan" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "advisor", "display_name": "Simons, Mark" }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "co-advisor", "display_name": "Zhan, Zhongwen" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" } ], "option_major": [ "geophys" ], "doi": "10.7907/x1pa-p135", "abstract": "The emerging availability of high-quality geophysical observations motivates the development of new methodologies to better extract the key information contained in the datasets. In this thesis, I present methodological developments utilizing two types of geophysical data. Firstly, in Chapter 2, I make use of the observations recorded at the newly-available dense seismic arrays and propose a new method for estimating the seismic receiver functions (RFs). RFs have been widely used in global seismology to probe the structural discontinuities in the interior of the Earth. By exploiting the coherency in RFs at neighboring stations, the new method adds the RF coherency as a key constraint in RF estimation, which directly addresses issues such as non-uniqueness and over-fitting in conventional ways for RF estimations. I show a pilot application of this method to real data that demonstrates its advantages on obtaining high-quality RFs on short-term (e.g., one month) high-density seismic profiles. Secondly, in Chapter 3 and Chapter 4, I take advantage of the temporally dense Synthetic-Aperture-Radar (SAR) imagery. In these two main chapters of my thesis, I focus on understanding the temporal variations in the buttress stress of Antarctic ice shelves and develop new methodologies for observing tidally-induced ephemeral grounding of ice shelves on the sub-shelf bathymetric highs. This observational study provides new insights into the buttressing effect of ice shelves and improves our understanding of the dynamics of Antarctic ice flow including the short-term (days to weeks) response to tidal forcing and the long-term (tens to hundreds of years) response to changes in climate. Specifically, in Chapter 3, I illustrate the methodological development and an application to Rutford Ice Stream (RIS), West Antarctica; in Chapter 4, I further apply the new methods to Evans Ice Stream (EIS), an ice-stream-shelf system significantly larger than the RIS with multiple upstream tributaries and complex grounding line. At both RIS and EIS, I find abundant zones of ephemeral grounding in the vicinity of the grounding zone. These two studies provide direct evidence for the asymmetric response of ice flows to tidal forcing, which causes the observed strong fortnightly variation in horizontal flow. With the projected oceanic warming, our observations of ephemeral grounding will help quantify the increase in ice flow rate in the long-term caused by the loss of buttressing stress due to ice-shelf thinning.
" }, { "name": "de Oliveira Lobo, Ana Helena", "degree": "PhD", "year": "2022", "title": "Atmospheric and Ocean Dynamics of Water Worlds", "advisor": "Bordoni, Simona", "url": "https://resolver.caltech.edu/CaltechTHESIS:07262021-194514668", "creators": [ { "name": { "family": "de Oliveira Lobo", "given": "Ana Helena" }, "id": "de-Oliveira-Lobo-Ana-Helena-de-Oliveira", "orcid": "0000-0003-3862-1817", "display_name": "de Oliveira Lobo, Ana Helena" } ], "advisors": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "advisor", "display_name": "Bordoni, Simona" } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "member", "display_name": "Bordoni, Simona" } ], "option_major": [ "plansci" ], "doi": "10.7907/skh2-tp72", "abstract": "This dissertation explores the fundamental dynamics that control atmospheric and ocean circulation on water worlds. These planets are defined by the presence of liquid water, which is a minimum requirement for life as we know it, making them compelling targets in the search for extraterrestrial life. This work begins by examining the atmospheric features and surface climates of Earth-like planets with surface liquid water (Chapters I-III). These atmospheres are driven by top-of-atmosphere radiative imbalance. To further our understanding of planetary climate and of the atmosphere\u2019s dynamical controls, particularly with regards to seasonal behavior, we examine the circulation, energy budget, and hydrological cycle responses to changes in shortwave and longwave radiative forcings. This dissertation also explores icy worlds (Chapters IV-V), a type of water world where a liquid water ocean hides beneath a substantial icy shell. Processes occurring at the ocean boundaries can shape the circulation dynamics, stratification, and subsequent heat and salt distributions in the ocean interior. This work presents a new model for exploring these oceans, focusing on ocean-ice interactions and freshwater forcings on Enceladus.
" }, { "name": "Bailey, Elizabeth Ann", "degree": "PhD", "year": "2021", "title": "Interior and Orbital Dynamics at the Innermost and Outermost Reaches of Planetary Systems", "advisor": "Batygin, Konstantin; Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:07092020-150124576", "creators": [ { "name": { "family": "Bailey", "given": "Elizabeth Ann" }, "id": "Bailey-Elizabeth-Ann", "orcid": "0000-0002-4769-8253", "display_name": "Bailey, Elizabeth Ann" } ], "advisors": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "co-advisor", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "co-advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." } ], "option_major": [ "plansci" ], "doi": "10.7907/7nh2-g954", "abstract": "In contrast to the canonical planets of our solar system, with semimajor axes in the familiar range of ~ 0.3\u201330 au, exoplanets have been detected at considerably shorter and longer distances from their host stars. These planets, at the innermost and outermost reaches of planetary systems, have challenged many hitherto foundational ideas of planetary formation and evolution that were based solely on knowledge of our own solar system. This thesis addresses some of the emergent puzzles posed by the orbital and interior dynamics of planets orbiting very close and far away from their stars.
\r\n \r\nChapters II-III consider the origins of planets on very short-period orbits. Two and a half decades ago, the discovery of the first hot Jupiter marked the dawn of exoplanet detections around sunlike stars. The existence of these extremely irradiated Jovian planets (orbital periods \u227e 5 days) runs in stark contrast to the utter absence of material orbiting interior to Mercury in our own solar system. This striking discrepancy between the close-in planetary content of observed systems and our own \u2014 together with the notion that, interior to the \"snow lines\" of stars at stello-centric radii of several au, water ice is not available to contribute to the accretion of the several Earth-mass cores necessary for runaway core accretion \u2014 has led to many works aiming to explain how Jovian-mass (\u2273 0.1MJ) planets can migrate inward to become hot Jupiters after forming beyond the snow lines of their stars. One such migration mechanism, known as high-eccentricity migration, occurs when a Jovian planet is excited to extremely high eccentricity such that it experiences significant tidal dissipation at perihelion passage, promoting orbital decay to a short-period orbit. For cases such as the massive (~ 9MJ), eccentric (e ~ 0.5) hot Jupiter HAT-P-2b \u2014 for which the exterior perturber is characterized \u2014 the eccentric orbital state encodes information about the tidal history of the planet. In Chapter II, I outline a method for constraining the tidal dissipation rate in eccentric hot Jupiters such as HAT-P-2b and its analogues. In Chapter III, I consider the opposite limit of possibilities: local conglomeration. While observations of highly eccentric, tidally unstable hot Jupiters imply some hot Jupiters must form through high-eccentricity migration, I present a -2/7 power law prediction which naturally follows from a basic picture of viscous accretion and inner magnetic truncation of protoplanetary disks. This power law, combined with simple tidal corrections, agrees well with the observed period-mass distribution of hot Jupiters, possibly lending new credence to the hypothesis that hot Jupiters predominantly form in situ, near their observed close-in positions.
\r\n\r\nNext, with Chapter IV, we move on from the inner regions of planetary systems to address the interior dynamics of our furthest observed solar system planets, Uranus and Neptune. The so-called \"ice giants\" present a major challenge to interior modeling efforts due not only to a relative lack of spacecraft coverage compared to other solar system planets, but also because of a compositional degeneracy which inherently arises from their intermediate densities. An especially confounding issue surrounding these planets has been the extremely low heat flux of Uranus compared to Neptune. Chapter IV addresses these challenges with the application of novel thermodynamic constraints that follow in the case where hydrogen and water are taken to be immiscible major constituents. As discussed in Chapter IV, this model framework can satisfy the observed masses, radii, and gravitational harmonics of these planets \u2014 without being at odds with observations of the magnetic fields. Importantly, as Chapter IV shows, hydrogen-water immiscibility in the deep interiors of Uranus and Neptune can offer a natural explanation for the disparate heat fluxes \u2014 but characteristically similar magnetic fields \u2014 of Uranus and Neptune.
\r\n\r\nFollowing this discussion of the outermost directly observed planets in our solar system, Chapters V-VI delve into the orbital dynamics of planets on extremely wide (hundred-au) orbits, with a specific emphasis on the hypothesized Planet Nine. In our own solar system, the existence of a massive planet on such a wide orbit, with considerable eccentricity (e \u2273 0.1) and inclination (i ~ 20\u00b0), has been proposed to explain several dynamical features of the outer solar system. In Chapter V, I describe how this very distant planet could affect the dynamics down to the innermost reaches of the solar system, through secular modulation of the so-called \"invariable\" plane of the canonical planets, relative to the solar spin axis. Next, in Chapter VI, I numerically derive a prior distribution for the relative occupation of individual mean-motion resonances with this planet by eccentric small bodies, showing that assumption of low-order resonances with observed objects is not a viable means to determine the current true anomaly of Planet Nine.
\r\n\r\nFinally, in Chapter VII, concluding remarks are given, and the findings of this work are discussed in relation to the ongoing exploration of related topics in planetary system dynamics.
" }, { "name": "Biasi, Joseph Anthony", "degree": "PhD", "year": "2021", "title": "Paleomagnetism and Geochemistry of Basalts in the North American Cordillera, Davis Strait, and Antarctica", "advisor": "Asimow, Paul David; Kirschvink, Joseph L.; Bucholz, Claire E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022021-013516525", "creators": [ { "name": { "family": "Biasi", "given": "Joseph Anthony" }, "id": "Biasi-Joseph-Anthony", "orcid": "0000-0003-1196-7877", "display_name": "Biasi, Joseph Anthony" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "advisor", "display_name": "Asimow, Paul David" }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "advisor", "display_name": "Bucholz, Claire E." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "geochem" ], "doi": "10.7907/hbs7-aw47", "abstract": "Chapter 1 is an introduction to the thesis and contains a brief summary on how the chapters relate to each other. In Chapter 2, we present new whole-rock geochemical data from the Brooks Range Ophiolite (BRO) together with new mineral chemistry data from the BRO, South Sandwich forearc, Izu-Bonin forearc, and Hess Deep. In Chapter 3, we use a combination of paleomagnetic data and thermal modeling to create a magnetic geothermometer (MGT) that can constrain the active transport lifetime of magmatic conduits and igneous intrusions. In Chapter 4, we present new stratigraphic and paleomagnetic data from Paleocene flood basalts on Baffin Island. In Chapter 5, we present new paleomagnetic and paleointensity data from the James Ross Island volcanic group, located on the Antarctic Peninsula.
" }, { "name": "Chadwick, Grayson Lee", "degree": "PhD", "year": "2021", "title": "How to Beat Diffusion: Explorations of Energetics and Spatial Relationships in Microbial Ecosystems", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07182020-211405749", "creators": [ { "name": { "family": "Chadwick", "given": "Grayson Lee" }, "id": "Chadwick-Grayson-Lee", "orcid": "0000-0003-0700-9350", "display_name": "Chadwick, Grayson Lee" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/svrp-rb07", "abstract": "This thesis investigates four microbial systems, with a particular focus for how spatial considerations shape the behavior and evolution of microorganisms. After a general introduction in Chapter 1, Chapter 2 presents the results of experiments demonstrating how cellular activity varies through space within an anode-reducing biofilm. Chapter 3 presents a comprehensive comparative genomic analysis of all known marine anaerobic methanotrophic archaea, supporting the notion that these organisms share many energetic similarities with the anode reducing organisms in Chapter 2. These are interpreted as specific adaptations to life in highly structured microbial communities. Chapter 4 describes the enrichment and characterization of a new member of the purple sulfur bacteria, and the adaptations that may improve substrate acquisition beyond the normal limitations of diffusion. Chapter 5 describes the convergent evolution of novel Complex I gene clusters that have incorporated new proton pumping subunits, and the modifications made to the protein structure to facilitate the incorporation of these new subunits into the quaternary structure of the complex.
" }, { "name": "Chimiak, Laura Marie", "degree": "PhD", "year": "2021", "title": "Prebiotic Fingerprints", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01102021-045431757", "creators": [ { "name": { "family": "Chimiak", "given": "Laura Marie" }, "id": "Chimiak-Laura-Marie", "orcid": "0000-0002-5047-5421", "display_name": "Chimiak, Laura Marie" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geochem" ], "doi": "10.7907/0hvh-xz81", "abstract": "Meteorites contain organic compounds that occur in all known life. These compounds, commonly referred to as prebiotic compounds, include \u03b1-amino acids and are most prevalent on carbonaceous chondrites. As carbonaceous chondrites are pristine samples from early in the solar system that have not had living organisms on them, we can study the chemistry that produced \u03b1-amino acids on them to better understand the processes by which they might have formed on early Earth or on other bodies. Multiple syntheses have been put forth as routes to form amino acids on meteorites and include ice-grain chemistry on interstellar ices and Strecker synthesis in meteorite parent bodies. Prior measurements of molecular-average carbon isotope ratios (\u00b9\u00b3C/\u00b9\u00b2C) have found \u00b9\u00b3C enrichments of up to 53\u2030 in certain \u03b1-amino acids and molecular-average hydrogen isotope ratios (D/H) have found enrichments of 100s of \u2030. With this data, it has been suggested that Strecker synthesis\u2014a synthesis in which an aldehyde or ketone reacts with ammonia and cyanide to produce an \u03b1-aminonitrile that is hydrolyzed into an \u03b1-amino amide and then an \u03b1-amino acid\u2014is the primary pathway to produce \u03b1-amino acids on aqueously altered meteorites.
\r\n\r\nHere, we develop an instrument that can measure site-specific isotope ratios (SSIR) for carbon \u2014 that is the \u00b9\u00b2C/\u00b9\u00b3C at each site in a molecule \u2014 and use it to first constrain the site-specific isotope effects associated with Strecker synthesis and then the carbon SSIR of an alanine sample extracted from the Murchison meteorite. The instrument, the Q-Exactive Orbitrap, is a Fourier Transform Mass Spectrometer that has resolution of 240,000 full width-half maximum and can measure site-specific carbon isotope ratios on samples as small as 1 picomole. When we use it to measure the carbon SSIR in multiple samples of alanine produced by Strecker synthesis, we find a -20 \u2030 equilibrium isotope effect between the product alanine's C-2 site (amine carbon, \u00b9\u00b3C-depleted) reactant acetaldehyde\u2019s carbonyl carbon (\u00b9\u00b3C-enriched), a potential -15 \u2030 kinetic isotope effect on the C-1 site (eventual carboxyl carbon) for the first hydrolysis of \u03b1-aminopropanenitrile (\u00b9\u00b3C-enriched) into alaninamide (\u00b9\u00b3C-depleted), and a -15.4 \u2030 kinetic isotope effect on the C-1 carbon for the second hydrolysis step in which \u03b1-alaninamide (\u00b9\u00b3C-enriched) becomes alanine (\u00b9\u00b3C-depleted). Through conventional isotope ratio mass spectrometry, we also measure a +56.4 \u2030 equilibrium isotope effect between ammonia (\u00b9\u2075N-depleted) and the amine site on alanine (\u00b9\u2075N-enriched). When we measure the sample of alanine from the Murchison meteorite, we find site-specific carbon isotope ratios of -29 \u00b1 10 \u2030, 142 \u00b1 20 \u2030, and -36 \u00b1 20 \u2030 for the C-1, C-2, and C-3 (methyl) sites, respectively. This pattern agrees with the hypothesis that Strecker synthesis created alanine in Murchison. Combining these data with the isotope effects found for Strecker synthesis, we find initial site values of -7 \u00b1 10 \u2030, 162 \u00b1 20 \u2030, and 36 \u00b1 20 \u2030 for the C-1, C-2, and C-3 sites, respectively. With these values, we create a model of potential organic synthesis on the Murchison parent body that predicts the molecular-average \u03b4\u00b9\u00b3C values of 19 other prebiotic compounds.
\r\n\r\nFinally, we create a model that uses the previously measured molecular average carbon and deuterium isotope ratios for organics on Murchison to create models that predict site-specific and molecular average isotope ratios for organic compounds. This model finds that organic compounds with have methyl sites that are enriched in deuterium by up to 3000 \u2030 relative to other sites in the compound and that the degree of enrichment scales both with a compound class\u2019s solubility in water and with a sample\u2019s degree of aqueous alteration and terrestrial weathering. These patterns suggest that a primordial ISM-derived deuterium signal exchanges with water and that the methyl site hosts the highest amount of this enrichment due to its low acidity. The carbon model demonstrates that using only the aldehyde and cyanide values measured on Murchison and isotope effects inferred from other studies, we can predict 59 of 82 organic compounds on it (72%) that have \u03b4\u00b9\u00b3C values spanning over 149 \u2030 with an average residual of 6 \u2030. To achieve this level of prediction, the model combines Strecker synthesis, reductive amination, and oxidation of aldehydes to create straight-chain \u03b1-H hydroxy and amino acids, amines, and monocarboxylic acids with subsequent formaldehyde addition to these compounds to create branches.
" }, { "name": "Fan, Siteng", "degree": "PhD", "year": "2021", "title": "Planetary Atmospheres: Astrobiologically Relevant Icy Worlds and Earth as a Proxy Exoplanet", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12142020-085746258", "creators": [ { "name": { "family": "Fan", "given": "Siteng" }, "id": "Fan-Siteng", "orcid": "0000-0002-3041-4680", "display_name": "Fan, Siteng" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" } ], "option_major": [ "plansci" ], "doi": "10.7907/47nh-ze14", "abstract": "\"How did we get here?\" is a long-standing question in planetary science. Characterizing the pre-biotic atmospheric environment in which life may emerge is critical and increasingly urgent. Given the fact that the Earth provides the only ground truth of habitable worlds, most of the characterizations are based on the current Earth. However, life did not emerge on the modern Earth. It instead took place in a prebiotic environment, which includes a nitrogen-dominated, methane-abundant and oxygen-negligible reducing atmosphere. Therefore, this type of planetary atmospheres has great significance in the context of astrobiology and the search for life. Despite that real time observations can not be obtained for Early-Earth, spacecraft observations of the atmospheres of two icy worlds in the solar system, Titan and Pluto, can provide such valuable constraints. The theme of Chapter 2 and 3 of this thesis focus on this topic of investigating the atmospheres of Titan and Pluto using spectroscopic analysis. Chapter 4 studies the search for life also across the spectrum from a prospective the other way. It characterizes the Earth, the only known inhabited planet, as an exoplanet proxy, to derive observational benchmarks for habitability assessment.
\r\n\r\nChapter 2 studies Titan. It retrieves the hydrocarbon and nitrile species in Titan\u2019s upper atmosphere using stellar occultation observations obtained by Cassini UltraViolet Imaging Spectrograph (UVIS) during its Titan flybys. An innovative method is introduced to consider the pointing issue of the instrument, which prevents most of the previous spectral analyses. Combing an instrument simulator for handling the pointing motion and the Markov-Chain Monte Carlo (MCMC) method for parameter searching, species abundances in Titan\u2019s atmosphere are successfully retrieved during occultations with large pointing motions. The method also obtains the altitude range where the abundance of each species could be constrained.
\r\n\r\nChapter 3 studies Pluto. It investigates the morphology and microphysical processes of Pluto\u2019s haze particles in the lower 50km of its atmosphere using observations obtained by multiple instruments onboard the New Horizons spacecraft during its Pluto flyby in 2015. It suggests that Pluto\u2019s haze particles have a bimodal distribution: a large-size population of ~1\u03bcm fractal aggregates, which consists of ~20nm monomers, and a small-size one of ~80nm. This result successfully addresses the disagreement among the instruments, and provides important constraints on transport and dimensional transition of haze particles in Pluto\u2019s atmosphere.
\r\n\r\nChapter 4 studies exoplanets. It evaluates the observational baseline for Earth-like exoplanets using the Earth as a proxy. Observations of the Earth\u2019s images obtained by the Deep Space Climate ObserVatoRy (DSCOVR) are integrated to one single point to generate light curves of the \"proxy\" planet. Using the singular value decomposition (SVD) method, we found that the surface information of the \"proxy\" planet is in the second principal component (PC) of its light curves, while the first PC mainly consists of that of clouds. Using the strong linear correlation between the time series of the second PC and the corresponding land fraction, we constructed the first two-dimensional surface map of the Earth seen from a hypothetical distant observer, an observer who treats the Earth as an exoplanet.
" }, { "name": "Hayden, Alistair Thompson", "degree": "PhD", "year": "2021", "title": "Exhumed Fluvial Deposits: New Paleohydrological Tools Indicate Long-Duration Fluvial Activity on Early Mars", "advisor": "Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09072020-172907018", "creators": [ { "name": { "family": "Hayden", "given": "Alistair Thompson" }, "id": "Hayden-Alistair-Thompson", "orcid": "0000-0003-3540-7807", "display_name": "Hayden, Alistair Thompson" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/68ft-xm49", "abstract": "Fluvial sinuous ridges are common landforms on Mars that have been used for interpreting the history of ancient martian rivers. They are typically interpreted as eroded casts of an ancient river at a snapshot in time. However, some ridges might instead be channel belts that preserve river history, leading to significant differences in interpretation of paleohydrology, including flow direction, duration, and discharge. In this thesis, I used analog sites on Earth and techniques from fluvial sedimentology and fluvial geomorphology to determine that many ridges are exhumed channel belts, and to create and apply new tools for measuring bankfull discharge and duration of river flow from remote-sensing observations of these sedimentary deposits. I found evidence that rivers on ancient Mars were comparable in size to those on Earth today, and that they flowed for at least millions of years.
\r\n\r\nI examined sinuous ridges in three terrestrial sites to better understand ridges on Mars: the Cretaceous Cedar Mountain Formation and Jurassic Morrison Formation of Eastern Utah, and the Miocene Caspe Formation of Northeast Spain. Ridges at all sites are capped with sandy units rich with dune and bar strata atop a mudstone pedestal and they cross each other at different stratigraphic levels, observations that together indicate that ridges are channel belts exhumed from floodplain sediments \u2014 the most common arrangement of fluvial stratigraphy. By compiling measurements of hundreds of terrestrial channel belts and their associated channels, I found that the best methods to reconstruct paleochannel bankfull geometry from such deposits are to use thickness of channel belts (1-4 times paleochannel depth) or radius of curvature of lateral accretion sets (half the channel width). Ridge width and planview wavelength, common proxies for paleochannel width, are significantly more uncertain due to channel amalgamation and ridge erosion by scarp retreat, which I quantified with geometry and a new erosion model. Intermittency factor converts bankfull discharge to average discharge, enabling measurement of duration of river flow. I calculated the intermittency factor for 206 fluvial deposits and USGS streamgages, and found that it ranges between 0.003-0.7 with a median of 0.10, with values depending on the ratio of catchment-averaged erosion rate to average precipitation but independent of timescale, river size, climate, or grainsize.
\r\n\r\nThroughout the work, I applied the methods to sinuous ridges on Mars to demonstrate their applicability. I found that many ridges are likely channel belts, and that the ancient rivers they represent are likely smaller but longer than previously studies have indicated. Altogether, this contribution enables new quantitative analyses of ancient rivers on Earth and Mars, and provides evidence that ancient Martian climate was capable of supporting liquid water at many locations across the surface for at least millions of years.
" }, { "name": "Johnson, Daniel Lee", "degree": "PhD", "year": "2021", "title": "Sulfur Isotopic Insights into the Modern and Ancient Marine Sulfur Cycles", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10202020-173641319", "creators": [ { "name": { "family": "Johnson", "given": "Daniel Lee" }, "id": "Johnson-Daniel-Lee", "orcid": "0000-0002-7443-1546", "display_name": "Johnson, Daniel Lee" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Rosenthal", "given": "Yair" }, "id": "Rosenthal-Yair", "orcid": "000-0002-7546-6011", "role": "member", "display_name": "Rosenthal, Yair" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "geochem" ], "doi": "10.7907/vc71-ht05", "abstract": "The marine sulfur cycle plays a key role in regulating Earth's surface oxygen (O\u2082) levels through its interactions with the carbon and iron cycles. Our understanding of the sulfur cycle has traditionally come from measurements of the sulfur isotopic compositions of marine sulfate (SO\u2084\u00b2\u207b) and sulfur-bearing materials in marine sediments. Because the residence time of SO\u2084\u00b2\u207b in seawater is long (Myr) compared to the mixing time of Earth's oceans (kyr), the concentration and sulfur isotopic composition of marine SO\u2084\u00b2\u207b are homogeneous in modern seawater and are assumed to have been homogeneous throughout most of the Phanerozoic Eon (541 Ma to the present). This assumption of homogeneity, when combined with sulfur isotopic composition measurements, has enabled box model reconstructions of the relative fluxes of oxidized versus reduced sulfur leaving the oceans at times in Earth's past. Such reconstructions have informed our understanding of the interactions between Earth's tectonics, climate, and elemental cycles.
\r\n\r\nThis thesis tests some of the key assumptions made in sulfur cycle box models and attempts to better understand sulfur isotopic variability in geologic archives using a combination of measurements and modeling. Measurements of the sulfur isotopic composition (i.e., \u03b4\u00b3\u2074S) of SO\u2084\u00b2\u207b in Permo-Carboniferous brachiopod shells demonstrate that more precise records of SO\u2084\u00b2\u207b \u03b4\u00b3\u2074S may be generated via careful sampling that avoids diagenetically altered phases (Chapter II). Furthermore, measurements of heterogeneous carbonate associated sulfate (CAS) \u03b4\u00b3\u2074S within carbonates deposited across the End-Permian mass extinction (EPME) in South China show that a lack of careful sampling can substantially alter our understanding of the marine sulfur cycle at times in Earth's past (Chapter III). Simple models constructed in each of these studies indicate that changes in the \u03b4\u00b3\u2074S of the sulfur input to the ocean, the \u03b4\u00b3\u2074S offset (i.e., \u0394\u03b4\u00b3\u2074S) between the oxidized and reduced sulfur output fluxes, and the amount of SO\u2084\u00b2\u207b incorporated during diagenetic alteration - all assumed to be negligible in many studies of the marine sulfur cycle - may viably explain these data. Development of a sediment diagenesis model that includes sulfur isotopic species demonstrates that variations in organic matter rain rate, ferric iron input, sedimentation rate, bottom water O\u2082 concentration, and bottom water SO\u2084\u00b2\u207b concentration may all affect \u0394\u03b4\u00b3\u2074S in a given sedimentary environment (Chapter IV). Application of this model to pore water SO\u2084\u00b2\u207b and hydrogen sulfide H\u2082S \u03b4\u00b3\u2074S data from International Ocean Discovery Program (IODP) Expedition 361, IODP Expedition 363, and R.V. Knorr cruise KN223 sites shows that \u0394\u03b4\u00b3\u2074S is ubiquitously large in these deep ocean sedimentary environments (Chapter V). Cluster analysis of pore water [SO\u2084\u00b2\u207b] profiles collected during previous deep ocean cruises successfully extracts and groups profiles that are similar to those observed on these three cruises (Chapter VI). Comparison of cluster data to a compilation of recent marine pyrite (FeS\u2082) \u03b4\u00b3\u2074S data confirms that pyrite burial in shelf sediments constitutes the majority of pyrite burial occurring globally in the modern day. However, changes in sea level or in other variables that affect sediment deposition may plausibly force an increase in deep ocean pyrite burial and a corresponding change in the global \u0394\u03b4\u00b3\u2074S. Future studies of the modern and ancient marine sulfur cycles must carefully consider the geologic and geochemical context of sulfur isotopic measurements - including sea level changes, sedimentation rate changes, and measured or presumed concentrations of other redox-active species - if interpretations of such data are to be robust.
" }, { "name": "Lambert, Val\u00e8re R\u00e9gis Westbrooke", "degree": "PhD", "year": "2021", "title": "Constraining Earthquake Source Processes Through Physics-Based Modeling", "advisor": "Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechTHESIS:05202021-190145895", "creators": [ { "name": { "family": "Lambert", "given": "Val\u00e8re R\u00e9gis Westbrooke" }, "id": "Lambert-Valere-Regis-Westbrooke", "orcid": "0000-0002-6174-9651", "display_name": "Lambert, Val\u00e8re R\u00e9gis Westbrooke" } ], "advisors": [ { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "chair", "display_name": "Simons, Mark" }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "role": "member", "display_name": "Zhan, Zhongwen" } ], "option_major": [ "geophys" ], "doi": "10.7907/7s93-k485", "abstract": "Determining principles and conditions governing motion along faults is crucial for assessing how earthquake ruptures start and how large they may ultimately become. This thesis aims to shed light on the physics governing earthquake source processes by (i) developing physics-based numerical models that combine geological observations and laboratory insight with theoretical developments, and (ii) using these models to examine how different physical mechanisms and conditions are reflected in a range of geophysical observations taken together, from heat-flow constraints and seismologically determined properties of earthquakes to geodetic inferences and earthquake frequency-magnitude statistics.
\r\n\r\nWe examine the behavior and observable characteristics of numerically simulated sequences of earthquakes and aseismic slip in fault models designed to reproduce well-known features of mature faults that produce large destructive earthquakes. In part, the models are consistent with the inferred low-stress, low-heat operation of mature faults, which host large earthquakes at much lower levels of stress than their expected static strength. We explore two potential explanations for such behavior, one that faults are indeed quasi-statically strong but experience dramatic weakening during earthquakes, or that faults are persistently weak, e.g., due to fluid overpressure. We find that the two classes of fault models can, in principle, be distinguished based on the amount of seismic energy radiated from earthquake ruptures. Dynamic ruptures in the form of self-healing pulses, which occur on quasi-statically strong but dynamically weak faults, result in much larger radiated energy than inferred teleseismically for megathrust events, whereas crack-like ruptures on persistently weak faults are consistent with the seismological observations. The larger radiated energy of self-healing pulses is similar to limited regional inferences for crustal strike-slip faults. Our results suggest that re-evaluating estimates of radiated energy and static stress drop would provide substantial insight into the driving physics of large earthquakes and the absolute stress conditions on faults, with potential differences between tectonic settings.
\r\n\r\nThe results also have significant implications for seismic hazard, since our modeling shows that fault models that experience efficient dynamic weakening during ruptures tend to predominantly produce large earthquakes, at the expense of smaller earthquakes. Such behavior is consistent with some mature fault segments, such as several segments of the San Andreas Fault in California that have hosted large earthquakes but are currently nearly seismically quiescent. These considerations can provide physical basis for improving earthquake early warning systems. If mature faults in California are indeed governed by enhanced dynamic weakening, then our results suggest that the likelihood of an earthquake on these faults becoming substantially larger is much higher than typical expectations based on Gutenberg-Richter statistics.
\r\n\r\nBy considering average fault stress before simulated earthquake ruptures, we find that critical stress conditions for earthquake occurrence depend on the size and style of motion (e.g. the degree of slip acceleration at the rupture front) during individual ruptures. In particular, the stress conditions required to propagate large earthquake ruptures can be considerably lower than those required for rupture nucleation, and standard notions of quasi-static fault strength based on laboratory studies. Our results demonstrate that the critical stress for earthquake occurrence is not governed by a simple condition such as a certain level of Coloumb stress, as commonly used in studies of stress interactions among faults and earthquake aftershocks patterns. More robust criteria for critical stress conditions would depend on the strength evolution during dynamic rupture and can be explored in numerical simulations.
\r\n\r\nFinally, evaluating the predictive power of numerical earthquake models for future hazards is a topic of great importance for physics-based seismic hazard assessment. Towards that end, we investigate the sensitivity of outcomes from numerical simulations of sequences of earthquakes and aseismic slip, including the long-term interaction of fault segments, to choices in numerical discretization and treatment of inertial, wave-mediated effects. In particular, we find that the rate of earthquake ruptures that manage to jump between two fault segments, a parameter routinely used in seismic hazard studies, is highly sensitive to numerical and physical modeling choices. These results suggest the need for developing different parameterization of seismic hazard than currently used, a task for which numerical modeling is well-suited.
" }, { "name": "Lewis, Madeline Janine", "degree": "PhD", "year": "2021", "title": "Magmatic Differentiation in Arc and Mid Ocean Ridge Settings", "advisor": "Bucholz, Claire E.; Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022021-034345855", "creators": [ { "name": { "family": "Lewis", "given": "Madeline Janine" }, "id": "Lewis-Madeline-Janine", "orcid": "0000-0001-7968-2822", "display_name": "Lewis, Madeline Janine" } ], "advisors": [ { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "co-advisor", "display_name": "Bucholz, Claire E." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "co-advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geochem" ], "doi": "10.7907/a1ky-ab66", "abstract": "The compositional variation of igneous rocks and construction of Earth's crust is the result of magmatic differentiation -- crystallization, melting, and assimilation mechanisms that\r\ncause the composition of magmas to change over time. This thesis investigates magma generation and evolution at both convergent and divergent plate boundaries. The resulting magmatic arcs and mid-ocean ridges create the vast majority of Earth's crust, though the details of crustal construction and the specific processes that generate the observed magmatic and volcanic products are complex. Accordingly, this work uses the geochemical signatures encoded in rocks and minerals to explain magmatic differentiation histories in multiple tectonic settings.
\r\n\r\nHere, I present five main studies that utilize field and textural observations, geochemical analyses, and computational modeling to investigate the compositional structure of the crust beneath magmatic arcs and mid-ocean ridges. In addition, this work explores the pyroclastic and sedimentary products dispersed by magmatically heated hydrothermal fluids in submarine environments. Chapters 2 and 3 investigate the crystallization histories of mafic intrusions in the eastern-central Sierra Nevada batholith paleo-continental arc, California. This work has implications for the compositional and temporal generation of both mafic and evolved magmas throughout the batholith and in other continental arcs. Chapters 4 and 5 explore records of submarine volcanic ash deposits associated with explosive mid-ocean ridge eruptions from the East Pacific Rise and Pacific-Antarctic Ridge, as well as the effects that sea level change has on melting of the mantle, eruption styles, and the compositional evolution of mid-ocean ridge magmas. Chapter 6 examines the mineral hosting of rare earth elements (REEs) in the Wadi Karim banded iron formation, and the implications of element mobility on interpretations based on REE abundances.
" }, { "name": "Lingappa, Usha Farey", "degree": "PhD", "year": "2021", "title": "Manganese Through Time and Other Stories Concerning Cyanobacteria and the World Around Them", "advisor": "Fischer, Woodward W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012021-160326752", "creators": [ { "name": { "family": "Lingappa", "given": "Usha Farey" }, "id": "Lingappa-Usha-Farey", "orcid": "0000-0001-5691-6788", "display_name": "Lingappa, Usha Farey" } ], "advisors": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "advisor", "display_name": "Fischer, Woodward W." } ], "committee": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "chair", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." } ], "option_major": [ "geobiol" ], "doi": "10.7907/9ysw-jt52", "abstract": "This thesis is a collection of investigations concerning the interplay between Cyanobacteria and the inorganic/physical world. Chapters II-VI focus on manganese, an element Cyanobacteria have been\r\nintimately entangled with for billions of years. Chapter II is a review/perspective paper on the dynamics of\r\nmanganese in the environment through time and the many ways manganese interfaces with dioxygen.\r\nChapter III deciphers environmental and biological signatures recorded in ancient rocks from the pivotal\r\nmoment in Earth history when oxygenic photosynthesis first evolved. Chapter IV explores the ecology of\r\ndesert varnish, and provides an adaptive physiological mechanism underpinning manganese enrichment.\r\nChapter V examines the ability of modern Cyanobacteria to catalyze manganese oxidation. Chapter VI\r\nexplains as kindly as possible that the field of manganese aquatic chemistry has fundamentally\r\nmisunderstood the chemistry of Mn(III) and highlights how the current methods being used are\r\nproblematic because of this misunderstanding. Chapters VII and VIII are not about manganese and instead\r\nconcern other aspects of the physical world and their interface with Cyanobacteria. Chapter VII is about the\r\nimpact of Hurricane Irma on a cyanobacterial mat ecosystem. Chapter VIII is about the use of ooids as an\r\nenvironmentally friendly replacement for plastic microbeads in facial scrubs, in which Cyanobacteria\r\nmake a cameo as endoliths that facilitate ooid dissolution.
" }, { "name": "Metcalfe, Kyle Shuhert", "degree": "PhD", "year": "2021", "title": "Symbiotic Diversity and Mineral-Associated Microbial Ecology in Marine Microbiomes", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08122020-110818529", "creators": [ { "name": { "family": "Metcalfe", "given": "Kyle Shuhert" }, "id": "Metcalfe-Kyle-Shuhert", "orcid": "0000-0002-2963-765X", "display_name": "Metcalfe, Kyle Shuhert" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "chair", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/ve4r-k526", "abstract": "This thesis investigates ecological interactions in the seafloor between microbial taxa (Chapters 1 and 2) and between these microorganisms and their mineral hosts (Chapters 2 through 4). In seafloor sediments, electron acceptors are often limited, forcing microorganisms inhabiting these sediments to acquire symbiotic partners and/or perform extracellular electron transfer to insoluble electron acceptors. Seafloor methane seeps present an endmember case wherein extremely reducing fluids charged with methane advect through sediment. In these benthic ecosystems, anaerobic methanotrophic archaea (ANME) form symbiotic partnerships with sulfate-reducing bacteria (SRB), but it remained unclear if certain ANME exhibit a preference for certain SRB partners. In Chapter 1, I present results documenting such a pattern of partnership specificity in ANME-SRB consortia. In Chapter 2, I further examine these patterns in rare ANME taxa through development and application of a density-separation protocol refined from published work. This protocol exploits the co-association of microbial taxa on mineral surfaces to aid in the detection of novel symbioses, and further is useful to detect microbial interactions with certain minerals. In Chapter 3, I focus on the interaction between ANME-SRB consortia and authigenic silicates that have been observed on consortium exteriors, finding evidence to support that the precipitation of these silicates is actively mediated by ANME-SRB. In Chapter 4, I perform geochemical modeling benchmarked by synchrotron X-ray analysis to examine the imprint of extracellular electron transport by metal-reducing microorganisms on Precambrian manganese-rich sedimentary rocks." }, { "name": "Mullin, Sean William Alexander", "degree": "PhD", "year": "2021", "title": "Spatial and Temporal Dynamics of Microorganisms Living Along Steep Energy Gradients and Implications for Ecology and Geologic Preservation in the Deep Biosphere", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09232020-172452048", "creators": [ { "name": { "family": "Mullin", "given": "Sean William Alexander" }, "id": "Mullin-Sean-William-Alexander", "orcid": "0000-0002-6225-3279", "display_name": "Mullin, Sean William Alexander" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/f3k8-ck13", "abstract": "The deep biosphere represents a massive repository of life with unknown effects on global biogeochemical cycles. Even the fundamental life strategies of the endemic microorganisms that inhabit this biome remain enigmatic; some studies have indicated that subsurface organisms subsist in energetic regimes below the theoretical lower limit for life. A boom-bust life cycle, mediated by tectonic disturbances and subsurface fractures, may help explain these phenomena. This work addresses and expands on this question, first by exploring the response of continental deep biosphere microorganisms to an in situ organic matter amendment, then by analyzing the microbial community dynamics of the sediments and carbonate along a naturally-occurring energy gradient at a methane seep. Our experiments in the continental deep biosphere confirmed that mineralogical heterogeneity can drive differential colonization of the native microorganisms, implying that selection and adaptation to in situ conditions occurs, differentiating individual microbial niches. We also observed the formation of secondary framboidal iron sulfide minerals, a well-known phenomenon in marine sediments but not extensively observed in the deep subsurface, that were correlated to the presence of abundant sulfur-metabolizing microorganisms. Chapters 2 and 3 are instead focused on the microbial ecology of a methane seep on the Pacific margin of Costa Rica. Cold methane seeps themselves represent sharp boundaries between the generally low-energy background seafloor and abundant chemical energy in the form of methane. Chapter 2 describes that the microorganisms living at these seeps occupy a significantly narrower spatial scale than the endemic megafauna. In addition, by correlating community dissimilarity and geographic distance, the functional center of the seep was identified, allowing for insight into the ecological differentiation between clades of anaerobic methanotrophic archaea (ANME). Chapter 3 examines in greater detail the endolithic microbial community, principally composed of ANME-1. By conducting transplantation experiments of carbonates on the seafloor, we tested the response of the in situ endolithic communities and found that carbonates moved distinctly outside the active zone changed less than communities moved to regions of less activity.
" }, { "name": "Phillips, Alexandra Atlee", "degree": "PhD", "year": "2021", "title": "Sulfur Cycling in the Water Columns of Lakes and Oceans", "advisor": "Sessions, Alex L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06042021-142625243", "creators": [ { "name": { "family": "Phillips", "given": "Alexandra Atlee" }, "id": "Phillips-Alexandra-Atlee", "orcid": "0000-0001-5959-5238", "display_name": "Phillips, Alexandra Atlee" } ], "advisors": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "advisor", "display_name": "Sessions, Alex L." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." } ], "option_major": [ "geochem" ], "doi": "10.7907/tmxk-7f90", "abstract": "Sulfur is a critical bioelement central to many of Earth\u2019s biogeochemical cycles. Studies of sulfur have overwhelmingly focused on sediments, where transformations between organic and inorganic sulfur phases drive short-term biological reactions and long-term climate cycles. However, sulfur cycling in the water column is just as dynamic and exerts similar controls over biogeochemical cycles in lakes and oceans \u2013 although the exact dynamics are only beginning to be understood. This thesis provides new understanding of sulfur cycling in aquatic environments through three chapters that span laboratory developments and field observations. Chapter 1 presents a time-series in enigmatic Mono Lake, CA, where the temporal dynamics of sulfur cycling microbes was investigated. This study, published in Geobiology, highlights the dependency of sulfate reduction and oxidation on lake chemistry and the need for studies to move beyond \u201csnapshots\u201d of microbial diversity. Chapter 2, published in Rapid Communications in Mass Spectrometry, presents development of a highly sensitive (1-10 \u00b5g S) mass spectrometry technique that allows, for the first time, sulfur isotope measurements of amino acids. These new measurements permitted discovery of new connections between metabolism and sulfur isotope signatures. Chapter 3 further applies these novel methods, making the first sulfur isotope measurements of marine dissolved organic matter. The data indicated that marine organic sulfur is entirely produced by phytoplankton and implied that heterotrophic bacteria rapidly and efficiently recycle reduced sulfur compounds, even in the water column. Taken together, these three chapters significantly advanced available tools for studying sulfur in the environment and expanded our understanding of modern aquatic sulfur cycling. The final chapter represents a departure from oceans, lakes, mass spectrometry, and sulfur. Here, I evaluate the success and impacts of my outreach project, the popular Women Doing Science Instagram, in portraying diverse, international women scientists, noting the powerful potential for social media to bolster STEM identity for graduate students.
" }, { "name": "Roback, Kevin Patrick", "degree": "PhD", "year": "2021", "title": "Investigating Sand Transport and Landslides, and Implications for Past and Present Environments on Mars and Earth", "advisor": "Avouac, Jean-Philippe; Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05202021-183729767", "creators": [ { "name": { "family": "Roback", "given": "Kevin Patrick" }, "id": "Roback-Kevin-Patrick", "orcid": "0000-0001-5209-2873", "display_name": "Roback, Kevin Patrick" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "advisor", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/gykg-wz60", "abstract": "Wind-driven movement of sand and landslide activity are among the most important processes driving modern-day change on planetary surfaces. This thesis uses novel techniques and datasets to investigate the forces driving these processes on the surface of Mars, and also considers possible applications of the techniques described to Earth. Chapter 1 introduces past work done to understand these processes, and outstanding questions our work aims to answer. Chapter 2 presents and tests a new technique which aims to improve predictions of sand transport driven by wind on planetary surfaces by correcting coarse-resolution GCM predictions for the short-timescale fluctuations they miss. Chapter 3 presents new multiyear measurements of ripple migration at two dune fields on the surface of Mars, and applies these measurements, in conjunction with the new techniques described in Chapter 2, to investigate the dynamics of the Martian atmosphere, and test the accuracy of predictions made by Martian climate models. In Chapter 4, we study a large-scale natural sand trap in the Meroe Patera dune field on Mars, and estimate its trapped volume of sand in comparison to the volume of \"missing\" sand in a dune-free shadow zone downwind of the crater. The volume of trapped sand is far less than the missing volume, suggesting past escape of sand from the crater, despite a lack of obvious evidence for such escape in the present day. In Chapter 5, we change focus from sand transport to introduce an analysis of controls on the global distribution of Martian landslides. Chapter 6 discusses the limitations of applying the techniques of satellite image and climate model analysis described in Chapters 2-4 to terrestrial settings, as well as the possible utility of Chapter 5\u2019s method on other planets.
" }, { "name": "Sabbeth, Leah", "degree": "PhD", "year": "2021", "title": "Provenance, Structural Geology, and Sedimentation of the Miocene and Pliocene Californias", "advisor": "Stock, Joann M.; Wernicke, Brian P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09212020-084147468", "creators": [ { "name": { "family": "Sabbeth", "given": "Leah" }, "id": "Sabbeth-Leah", "orcid": "0000-0001-6615-7949", "display_name": "Sabbeth, Leah" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "co-advisor", "display_name": "Wernicke, Brian P." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Bucholz", "given": "Claire E." }, "id": "Bucholz-C-E", "orcid": "0000-0003-3252-7109", "role": "member", "display_name": "Bucholz, Claire E." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." } ], "option_major": [ "geol" ], "doi": "10.7907/gbcs-9289", "abstract": "The first chapter of this thesis documents a provenance study, in which orthoquartzite clasts deposited in the Miocene Sespe Formation are linked to the Mesoproterozoic Shinumo Quartzite. The Sespe Formation outcrops in the Santa Monica Mountains and the Santa Ana Mountains, both in California. The Shinumo Quartzite outcrops only in Grand Canyon. We determine that the Shinumo Quartzite can be distinguished from other sources that may feed the Sespe Formation through its unique combination of a moderate paleomagnetic inclination and 1.2, 1.4, and 1.7 Ga detrital zircon spectrum peaks. This provenance link places an important constraint on the drainage of a paleo-Colorado River from Grand Canyon during Miocene time.
\r\n\r\nThe second and third chapters of this thesis are hinged upon a geologic mapping project on Isla \u00c1ngel de la Guarda, a microcontinental block, in Baja California, Mexico. A plate reorganization at the end of the late Miocene andesitic arc marks the transfer of Baja California and the not-yet-rifted Isla \u00c1ngel de la Guarda to the Pacific plate from the North American plate. Between 3 and 2 Ma, the plate boundary jumped again, northward along the Ballenas Transform fault. In this Pliocene time, units mapped in this study were deposited.
\r\n\r\nThe oldest units mapped are Miocene-Pliocene volcanic flows, for which we have no lower age constraint. The oldest volcanic flow dated is a Pliocene andesite lava (3.916 \u00b1 0.088 Ma from 40Ar/39Ar). We map Miocene to Pliocene volcanic flows and Pliocene to Quaternary sedimentary units in two field areas. The sedimentary units are probably results of Pliocene rifting-related basin subsidence. Geochemical data from X-ray fluorescence indicate that lavas are compositionally similar to ~12 Ma arc-related rocks mapped in the Puertecitos Volcanic Province. In the southern field area, the sedimentary units are overlain by a Pliocene basaltic andesite with an 40Ar/39Ar age of 2.754 \u00b1 0.021 Ma. We map several NNE-striking faults throughout both field areas, which cut NNW-striking bedding in Pliocene units. The Pliocene volcanic flows and sedimentary units were probably tilted before faulting, and the faults are likely linked to the Northern Salsipuedes Basin, offshore of the island in the Ballenas Channel. Both of these events may be results of 3-2 Ma rifting.
" }, { "name": "Trumbo, Samantha Kathleen", "degree": "PhD", "year": "2021", "title": "Views of an Ocean World: The Signatures of Internal and External Processes on the Surface of Europa", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01082021-174930437", "creators": [ { "name": { "family": "Trumbo", "given": "Samantha Kathleen" }, "id": "Trumbo-Samanth-Kathleen", "orcid": "0000-0002-0767-8901", "display_name": "Trumbo, Samantha Kathleen" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." } ], "option_major": [ "plansci" ], "doi": "10.7907/d63b-y030", "abstract": "Beneath a comparatively thin ice shell, Europa harbors a global, salty, liquid-water ocean in contact with a rocky seafloor, making it an exciting target for exploring habitability in the Solar System. The potential habitability of Europa's ocean depends on its composition, which may be reflected in that of Europa's geologically young, fractured surface. However, two intertwined uncertainties are the degree to which the ocean and the surface are in contact, and the degree to which surface materials truly represent oceanic signatures. The latter is complicated by the fact that Europa\u2019s surface is continuously altered by sulfur plasma and particle irradiation due to its location within Jupiter\u2019s magnetosphere. In this thesis, I utilize a variety of multi-spectral, Earth-based observations of Europa to explore the balance and interplay of internal and external processes in shaping its surface.
\r\n\r\nChapters II and III focus on using visible-wavelength spectroscopy from the Hubble Space Telescope (HST) to understand the chemistry of Europa's surface salts. In Chapter II, I present the detection of irradiated sodium chloride (NaCl) and show that its distribution correlates with geologically disrupted chaos terrain, suggesting an ocean source. In Chapter III, I investigate multiple spectral features across Europa's sulfur-bombarded trailing hemisphere. In comparing their geographies with the distributions of large-scale geology, magnetospheric particle bombardment, and surface color, I identify some features as reflective of purely exogenous sulfur radiolysis products and others as indicative of radiolysis products formed from a mixture of endogenous material and magnetospheric sulfur.
\r\n\r\nChapters IV and V further consider the effects of radiolytic processing through the analysis of infrared spectra obtained with Keck NIRSPEC. In Chapter IV, I report a previously unseen spectral feature at 3.78 \u00b5m in disk-integrated spectra of the trailing hemisphere. Using Hapke spectral modeling, I demonstrate that it represents an unidentified radiolytic product of potential relevance to understanding the alteration of endogenic material. Chapter V considers a radiolytic species thought to be independent of endogenic material -- hydrogen peroxide (H\u2082O\u2082), a species relevant to the oxidation state and habitability of the ocean in the case of mutual exchange through the ice shell. Contrary to laboratory expectations, I observe the largest H\u2082O\u2082 absorptions within salty, low-latitude chaos terrain. I hypothesize that this distribution may reflect decreased hydrogen peroxide destruction due to electron scavenging by CO\u2082 within these same regions, which would suggest an internal carbon source.
\r\n\r\nFinally, Chapters VI and VII present preliminary studies of Europa's thermal emission using four images obtained with the Atacama Large Millimeter Array (ALMA) and a global thermophysical model developed to simulate Europa's expected thermal emission. In Chapter VI, I combine a single ALMA image with an observation from the Galileo Photopolarimeter Radiometer (PPR) to show that a thermal anomaly seen by the PPR and associated with two potential plume detections is better explained by a locally high thermal inertia than by geologic heating. Chapter VII considers all four ALMA images. While much of the large-scale thermal structure can be readily attributed to albedo variation, modeling of the images reveals a number of localized anomalies, which may indicate variations in geothermal heat flow, thermal inertia, or millimeter emissivity. In the absence of the additional observations needed to distinguish between such possibilities, I construct hypothetical maps presenting the ranges of possible thermal inertia and emissivity values.
" }, { "name": "Wang, Siwen", "degree": "PhD", "year": "2021", "title": "Photo- and Electro-Chemistry Methods for Waterborne Pathogen Treatment and Detection in Environmental Water", "advisor": "Hoffmann, Michael R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09182020-085441808", "creators": [ { "name": { "family": "Wang", "given": "Siwen" }, "id": "Wang-Siwen", "orcid": "0000-0002-8553-425X", "display_name": "Wang, Siwen" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "chair", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "member", "display_name": "Hoffmann, Michael R." }, { "name": { "family": "Tirrell", "given": "David A." }, "id": "Tirrell-D-A", "orcid": "0000-0003-3175-4596", "role": "member", "display_name": "Tirrell, David A." }, { "name": { "family": "Wang", "given": "Kaihang" }, "id": "Wang-Kaihang", "orcid": "0000-0001-7657-8755", "role": "member", "display_name": "Wang, Kaihang" } ], "option_major": [ "envreng" ], "doi": "10.7907/et9z-sz57", "abstract": "Waterborne disease is a global burden, which is mainly caused by waterborne pathogens disseminated through unsafe water, inadequate sanitation, and hygiene. Antibiotic resistance, which can also spread in water, has become an increasingly serious global health threat as it can prevent the effective treatment of infectious diseases. Improvements on water treatment and detection are the two critical strategies to control the surveillance of waterborne pathogens as well as antibiotic resistance bacteria and genes. The advancement in photo- and electro-chemical methods may provide more opportunities on decentralized water treatment and on-site pathogen monitoring under source-limited conditions. This thesis is dedicated to exploring the possible solutions to automatic, rapid, and easy-to-use in situ pathogen analysis for environmental water by adopting photo- or electro-chemical method, and to enhanced removal of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) from wastewater by combining photo- and electro-chemical techniques. These include removal of ARB and ARGs by UV-assisted electrochemical treatment, electrochemical cell lysis (ECL) for DNA extraction from bacteria, and sunlight-activated propidium monoazide (PMA) pretreatment for live/dead bacteria differentiation by quantitative real-time polymerase chain reaction (qPCR) detection. Both experimental approaches and computational modelling were used to evaluate the performance of the techniques and to bring more insights into the mechanism. Each study presents a demonstration on real environmental or wastewater to access the potential of their applications under complex environmental parameters.
\r\n\r\nUV-assisted electrochemical treatment for ARB and ARGs was conducted using a blue TiO\u2082 nanotube array (BNTA) anode. The inactivation of tetracycline- and SMX-resistant E. coli and the corresponding plasmid coded genes (tetA and sul1) damage was measured by plate counting on selective agar and qPCR, respectively. As a comparison of UV treatment alone, the enhanced reduction of both ARB and ARGs was achieved by UV-assisted electrochemical oxidation (UV-EO) without Cl\u207b and was further facilitated with the presence of Cl\u207b, which is attributed to the in-situ generated oxidants by electrochemical process. Significantly slower removal of ARG than ARB was observed for both UV irradiation alone and UV-EO treatment, wherein intracellular ARG generally reduced slower than extracellular ones, and short amplicons reduced significantly slower than long ones. The predominant nucleotide damage by UV irradiation and conformational change by UV-EO treatment was visualized by DNA gel electrophoresis for treated extracellular ARGs. The mechanism on ARB and ARGs damage was further understood by computational chemical modeling. The slower reduction was found for the native bacteria and genes, tetA and sul1, in the latrine wastewater than that in laboratory-prepared buffered samples. The result emphasizes that all the UV-based techniques may only apply after other treatments to avoid the impairment by the transmittance, color, and particulate material in environmental or wastewater.
\r\n\r\nA comprehensive investigation was conducted for ECL in terms of its performance on DNA extraction from gram-negative bacteria (Escherichia coli and Salmonella Typhi) and gram-positive bacteria (Enterococcus durans and Bacillus subtilis). A milliliter-output ECL device was developed based on the disruption of the cell membrane by OH\u207b that can be generated locally at the cathode and accumulated improvingly through a cation exchange membrane. Both gram-negative and gram-positive bacteria were successfully lysed within 1 min at a low voltage of ~5 V. To better understand the pH effects on cell lysis, the pH profile at the cathode surface and in bulk cathodic effluent was simulated via hydroxide transport in the cathodic chamber. The demonstration of ECL on various environmental water sample types (including pond water, treated wastewater, and untreated wastewater) showed its potential as a prelude to nucleic-acid based analyses of waterborne bacteria in the field.
\r\n\r\nPropidium monoazide (PMA), a nucleic acid-binding dye, has been used to distinguish live from dead cells prior to PCR-based detection. To explore the off-the-grid application of PMA, sunlight was investigated for PMA activation as an alternative light source to a typical halogen lamp. PMA was successfully activated by a solar simulator, and the pretreatment conditions were optimized with respect to the PMA concentration as 80 \u00b5M and the exposure time as 10 min. The optimal PMA pretreatment was tested on four different bacteria species (two gram-positive and two gram-negative), and the effects of sunlight intensity and multi-sequential treatment were studied. Sunlight-activated PMA pretreatment was eventually demonstrated on latrine wastewater samples with natural sunlight on both sunny and cloudy days. The results showed the potential of sunlight-activated PMA pretreatment to be integrated into a lab-on-a-chip (LOAC) PCR device for off-the-grid microbial detection and quantification.
" }, { "name": "Wu, Xunyi", "degree": "PhD", "year": "2021", "title": "Novel, Rapid and Cost-effective Methods for Concentration, Detection and Monitoring of Waterborne Pathogens in Resource-Limited Settings", "advisor": "Hoffmann, Michael R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06042021-184017139", "creators": [ { "name": { "family": "Wu", "given": "Xunyi" }, "id": "Wu-Xunyi", "orcid": "0000-0001-9710-6896", "display_name": "Wu, Xunyi" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "chair", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Tirrell", "given": "David A." }, "id": "Tirrell-D-A", "orcid": "0000-0003-3175-4596", "role": "member", "display_name": "Tirrell, David A." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "member", "display_name": "Hoffmann, Michael R." } ], "option_major": [ "envreng" ], "doi": "10.7907/fwhf-a510", "abstract": "Waterborne pathogenic organisms including bacteria, viruses, protozoa and helminths, are responsible for a series of diseases which is a major public health concern worldwide. This issue is extremely severe in developing regions due to the scarcity of clean water supply and poor sanitation. Therefore, point-of-use (POU) detection and quantification processes as well as a monitoring program of waterborne pathogens are needed to ensure the safety of water and protect human health. However, the polymerase chain reaction (PCR) technology and its related detection platforms rely on complicated thermal cycling, centralized laboratory equipment and trained personnel, thus making PCR-based systems incapable of POU testing of environmental waters. In this dissertation, we develop a portable 3D-printed system with super-absorbent polymer (SAP) microspheres for sample enrichment, and a membrane-based in-gel loop-mediated isothermal amplification (mgLAMP) system for absolute quantification of pathogens. We also explored the interactions between microbial indicator of Escherichia coli (E. coli) and waterborne pathogen Vibrio Cholerae (V. Cholerae). The main results are as follows:
\r\n\r\n1. The application of detection and quantification methods is often hindered by the low pathogen concentrations in natural waters. Rapid and efficient sample concentration methods are urgently needed. Here we present a novel method to pre-concentrate microbial pathogens in water using a portable 3D-printed system with super-absorbent polymer (SAP) microspheres, which can effectively reduce the actual volume of water in a collected sample. The SAP microspheres absorb water while excluding bacteria and viruses by size exclusion and charge repulsion. The 3D-printed system with optimally-designed SAP microspheres could rapidly achieve a 10-fold increase in the concentration of E. coli and bacteriophage MS2 within 20 minutes with concentration efficiencies of 87% and 96%, respectively. Fold changes between concentrated and original samples from qPCR and RT-qPCR results were found to be 11.34-22.27 for E. coli with original concentrations of 104-106 cell\u00b7mL-1; and 8.20-13.81 for MS2 with original concentrations of 104-106 PFU\u00b7mL-1. Furthermore, SAP microspheres can be reused 20 times without performance loss thereby significantly decreasing the cost of our concentration system.
\r\n\r\n2. Following sample concentration, accurate quantification methods for waterborne pathogens are needed, especially at the point of sample collection. The surge of COVID-19 in late 2019 called for a more urgent need for a rapid and cost-effective quantification of SARS-CoV-2 in environmental waters. Quantification results contribute to wastewater-based epidemiology (WBE) which helps the monitoring of prevalent infections within a community and early detections of contamination. Here we demonstrated the usage of our portable membrane-based in-gel loop-mediated isothermal amplification (mgLAMP) system for absolute quantification of SARS CoV-2 in wastewater samples within a one-hour timeframe for point-of-use (POU) testing and data management. The limit of detection (LOD) of mgLAMP for SARS-CoV-2 quantification in Milli-Q water was observed to be down to 1 copy/mL, and that in surface water collected from Kathmandu, Nepal was down to 100 copies/mL. Both were 100-fold lower than that of RT-qPCR in corresponding matrices. Compared to alternative detection methods, our platform has a very high level of tolerance against inhibitors thanks to the restriction of the hydrogel matrix. This enables the highly sensitive detection in either clinical or environmental samples.
\r\n\r\n3. Regular environmental surveillance of waterborne pathogens is key to ensure the safety of water and protect public health. Due to the diversity of pathogenic bacteria in environmental waters, regular monitoring of so many pathogens for individuality is impractical. Therefore, microbial indicators are used to gauge the total pathogen concentration; and manage waterborne health risks. In this study, the interactions of V. cholerae, the etiologic agent of reemerging cholera, with E. coli, the most commonly used indicator for waterborne pathogens. Specifically, we investigated through evaluating the survival and growth of both bacteria under different temperature and nutrition deprivation using plate culturing and real-time polymerase chain reaction (qPCR). During co-growth, it was challenging for V. Cholerae to maintain initial population advantages as E. coli consumes nutrition more effectively. Whereas during co-existence, V. Cholerae soon fell into a viable-but\u2013non-culturable state under environmental stress in 3-5 days while E. coli stay viable more than 14 days. We found that V. cholerae interacts with E. coli differently depending on the composition of the water that is sampled and analyzed. This suggests that bacterium-bacterium interactions influenced by the intrinsic chemical and biological parameters of ambient water will be a contributing mechanism in regulating the proliferation of V. cholerae.
\r\n\r\nIn summary, two platforms for environmental sample concentration and detection have been developed and tested using ambient and engineered waters. In addition, interactions between a microbial indicator, E. coli, and the pathogenic bacteria, V. Cholerae, were studied. The chapters in this thesis describe in detail: (1) A hand-pressed 3D-printed system to produce SAP microspheres was developed with the goal of achieving efficient concentrations of environmental microorganisms for subsequent analysis. The simplified concentration procedure and can be easily integrated into various detection platforms; (2) A portable membrane-based in-gel loop-mediated isothermal amplification (mgLAMP) system was developed for absolute quantification of SARS-CoV-2 in environmental water samples within one hour, enabling a 100-fold lower detection limit compared to the gold-standard of RT-qPCR; and (3) Differences in bacterium-bacterium interactions of V. cholerae and E. coli under as a function of water composition indicated that environmental stress presented in ambient water matrices should be taken into consideration while using a microbial indicator such as E. coli to estimate the risk of waterborne pathogens. These collective advances allow for the rapid and ultrasensitive POU testing of waterborne pathogens that should provide for more effective monitoring strategies in terms of the use of indicator microorganisms.
" }, { "name": "Xie, Hao", "degree": "PhD", "year": "2021", "title": "Road to Equilibrium: Stable Isotope Distribution in Gaseous Alkanes and Thermal History of Geological Hydrocarbons", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04012021-045507416", "creators": [ { "name": { "family": "Xie", "given": "Hao" }, "id": "Xie-Hao", "orcid": "0000-0001-5656-2035", "display_name": "Xie, Hao" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "chair", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Miller", "given": "Thomas F." }, "id": "Miller-T-F", "orcid": "0000-0002-1882-5380", "role": "member", "display_name": "Miller, Thomas F." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/neh6-6c82", "abstract": "Naturally occurring hydrocarbon fluids have economic, geological, and environmental significance. Most of the natural hydrocarbon on Earth is formed by thermal alteration of organic matter in the sedimentary basin. My dissertation study is motivated by this question: can we track generation, transformation, storage, and destruction of these subsurface hydrocarbon fluids with isotopic proxies? The conventional geochemical toolkit includes relative compositional abundances, such as wetness and C1/(C2+C3) ratio, and stable isotope ratios of 13C/12C and 2H/1H, on both the bulk (material-average) and compound-specific (molecular-average) levels. However, these signatures often rely on empirical categorizations and calibrations, so they can be prone to ambiguities, errors, and inconsistencies. This thesis presents a series of work that develops and refines stable isotope proxies of gaseous hydrocarbon (C1-C5) molecules. My approaches overcome the problems in mainly two ways. (1) I add new analytical techniques to acquire isotopologue ratios of compounds. I establish two new analytical proxies, multiply substituted isotopologues (clumped isotopes) of methane, and position-specific isotope ratios of propane, using recently advanced high-resolution isotope ratio mass spectrometry. (2) I use rigorous thermodynamic and kinetic constraints of isotope distribution in hydrocarbon molecules to interpret isotopic data in natural samples. These constraints are determined by theories and experiments. For thermodynamic control, I conducted catalytic exchange experiments to calibrate equilibrium isotope effect for propane position-specific hydrogen isotopes (Chapter 2) and compound-specific hydrogen isotope fractionation between alkanes (Chapter 4) and tested quantum chemical calculations. For expression of kinetic isotope effects, I implemented a statistical approach, the kinetic Monte Carlo method, to calculate the intramolecular and intermolecular stable isotope composition of alkanes generated by radical cracking mechanism in catagenesis (Chapter 6). I measured position-specific hydrogen isotopes of propane (Chapter 3) and methane clumped isotopes (Chapter 5) in natural gas samples from global reservoirs, and compiled compound-specific isotope data in the literatures (Chapter 5 and 6). Results show similarities in isotope ordering of these molecules, which is that gas formed at lower temperature/depth expresses kinetic isotope effects, but gas formed or buried at higher temperature for longer times is in equilibrium. The switch from kinetic control to thermodynamic control is likely a result of thermally-activated hydrogen exchange. This trend provides the foundation for tracking generation and thermal evolution of subsurface hydrocarbons with stable isotope proxies.
" }, { "name": "Anderson, Dana Eklund", "degree": "PhD", "year": "2020", "title": "Tracking Volatile Elements in Protoplanetary Disks and on Planetary Surfaces", "advisor": "Blake, Geoffrey A.", "url": "http://resolver.caltech.edu/CaltechTHESIS:09282019-173537468", "creators": [ { "name": { "family": "Anderson", "given": "Dana Eklund" }, "id": "Anderson-Dana-Eklund", "orcid": "0000-0002-8310-0554", "display_name": "Anderson, Dana Eklund" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "chair", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." } ], "option_major": [ "plansci" ], "doi": "10.7907/GZSA-DK98", "abstract": "The formation of planets begins with collisions of tiny, micron-sized, dust grains. These grains reside in structures known as protoplanetary disks, rotating disks consisting of gas and dust that encircle young protostars as a natural outcome of star formation. Although the processes of planet formation and evolution take place over millions and billions of years, in our limited view we can only see snapshots of the different stages. Many of the formative processes are difficult, if not impossible, to observe directly. However, evidence of these events exists in the chemical composition of the bulk material and surfaces of planets themselves, the gas and solid components of protoplanetary disks, and planetary debris such as asteroids and comets. This thesis utilizes modeling and observations of the carbon and nitrogen content of protoplanetary disks to shed light on key factors that control the formation and chemical composition of planets. In addition, this thesis advances techniques for the elemental analysis of planetary surfaces facilitating the detection of salts on the surface of Mars.
\r\n\r\nChapter 2 estimates the maximum potential destruction of solid, refractory carbon in protoplanetary disks in an effort to explain the lack of carbon found in meteorites and the bulk silicate Earth relative to the interstellar materials that seeded their formation. In a T-Tauri disk assuming uniform turbulence and passive heating from stellar photons destruction of refractory carbon sources via oxidation and UV photolysis is limited to the warm, photochemically-active disk surface layers. Exploration of distinct disk environments, considering non-idealized mass transport or enhanced disk heating due to active stellar mass accretion, is needed to explain the widespread lack of carbon in rocky solar-system bodies.
\r\n\r\nChapters 3 and 4 present spectral observations by the Atacama Large Millimeter/submillimeter Array (ALMA) of mature, 5-11 Myr-old, protoplanetary disks in the Upper Scorpius region that indicate diverging behavior of the key carbon and nitrogen species in the disk gas as disks evolve. Selective depletion of CO from the gas may cause disk gas masses to be underestimated if based on CO measurements alone and further investigation of additional gas tracers is warranted.
\r\n\r\nDepletion of CO from the gas in the outer regions of disks observed by ALMA may be the result of sequestration of carbon into less volatile species such as CO2 and CH3OH. Chapter 5 explores the fate of CO2 and CH3OH ices entering the inner regions of protoplanetary disks. Carbon returns to CO in unshielded transparent regions of the inner disk surface, consistent with infrared observations, but carbon reservoirs in the disk midplane may be distinct depending on the efficiency of mass transport in the disk.
\r\n\r\nChapter 6 examines the abilities of the Laser-Induced Breakdown Spectroscopy (LIBS) instrument ChemCam on the Mars rover Curiosity in regards to the detection of salts. LIBS analysis of a set of prepared sample pellets containing decreasing concentrations of salt identifies elemental emission lines of Cl, C, and S that are sensitive to changes in chloride, carbonate, and sulfate salt concentrations, respectively, and provides detection limits for ChemCam measurements of these salts.
" }, { "name": "Chadwick, Austin John", "degree": "PhD", "year": "2020", "title": "Mechanics of River Avulsions on Lowland River Deltas", "advisor": "Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02032020-134346875", "creators": [ { "name": { "family": "Chadwick", "given": "Austin John" }, "id": "Chadwick-Austin-John", "orcid": "0000-0002-2552-0083", "display_name": "Chadwick, Austin John" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/97C1-JG94", "abstract": "Lowland deltas are home to over 0.5 billion people and some of the most biodiverse ecosystems on Earth. Deltas are highly dynamic landscapes, and at the largest scale grow through repeated construction of depositional lobes punctuated by river avulsions \u2013 abrupt shifts in river course to the shoreline. River avulsions have been responsible for dangerous floods and civil unrest over human history, but also counter land loss due to sea-level rise and coastal subsidence by nourishing wetlands with sediment. Despite the central role avulsions play on lowland deltas, the processes controlling their location and frequency remain poorly understood compared to steeper environments such as alluvial fans. This thesis is focused on the mechanics of river avulsions on lowland deltas, and the factors controlling their location and frequency. Chapter 1 addresses the origin of a preferential avulsion site on river deltas, using a novel modeling framework that unites previous work to incorporate backwater hydrodynamics, river-mouth progradation, relative sea-level rise, variable flood regimes, and cycles of lobe construction, abandonment, and reoccupation. Chapter 2 focuses on changes to avulsion frequency caused by relative sea-level rise, incorporating a combination of theory, field data, and numerical modeling. Chapter 3 explores general model predictions for avulsion location and timing during climate change, including rising and falling sea level, imbalances in upstream water and sediment supply, and the magnitude and frequency of storm events. Finally, Chapter 4 presents a scaled laboratory experiment where models and theory for lowland delta avulsion mechanics were put to the test. The work presented in this thesis offers new tools to predict river avulsions on densely populated lowland deltas, and allows for comparison with existing models of coastal restoration that fail to account for river avulsion mechanics and the hydrodynamics of lowland rivers.
" }, { "name": "Finke, Cody Enslin", "degree": "PhD", "year": "2020", "title": "An Experimental and Economic Analysis of Electrochemical Technologies to Reduce Greenhouse Gas Emissions", "advisor": "Hoffmann, Michael R.", "url": "http://resolver.caltech.edu/CaltechTHESIS:07132019-171515484", "creators": [ { "name": { "family": "Finke", "given": "Cody Enslin" }, "id": "Finke-Cody-Enslin", "orcid": "0000-0002-1343-1737", "display_name": "Finke, Cody Enslin" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "member", "display_name": "Hoffmann, Michael R." }, { "name": { "family": "Gray", "given": "Harry B." }, "id": "Gray-H-B", "role": "member", "display_name": "Gray, Harry B." }, { "name": { "family": "Peters", "given": "Jonas C." }, "id": "Peters-J-C", "role": "member", "display_name": "Peters, Jonas C." } ], "option_major": [ "envreng" ], "doi": "10.7907/msvc-8t85", "abstract": "Global warming and the related problem of water scarcity are predicted to cause widespread environmental, humanitarian, and economic challenges. New technologies may be able to reduce greenhouse gas emissions enough to prevent many of the worst consequences of climate change However, in order to be competitive in the market, new, low emissions technologies much be affordable. In this thesis I present work on building a technology to lower the cost of decentralized, electrochemical wastewater treatment technologies by improving maintenance. I also show that atomic layer deposition of TiO2 can be used to tune the catalytic activity and stability of multiple electrocatalysts for both the chlorine and oxygen evolution reactions (two of the most widely used electrochemical reactions used to make chlorine gas and in electroplating metals respectively). With more development, this phenomenon has the potential to be used to reduce the cost of many electrochemical systems. I modeled the techno-economics of a low-cost industrial hydrogen production technology and found the first process, to my knowledge, which is able to make industrially relevant quantities of hydrogen at a large scale. I conclude by urging researchers who are trying to solve environmental problems to consider both the potential for the cost of the entire technology to be competitive with existing technologies and to determine what the most effective way to reduce costs are. Finally, I propose that cogeneration of hydrogen and other chemicals may be a viable strategy to producing large quantities of inexpensive, clean hydrogen.
" }, { "name": "Lai, Voon Hui", "degree": "PhD", "year": "2020", "title": "Seismic Waveform Modeling of Natural Hazards and Sharp Structural Boundaries", "advisor": "Helmberger, Donald V.; Zhan, Zhongwen", "url": "https://resolver.caltech.edu/CaltechTHESIS:01102020-152646406", "creators": [ { "name": { "family": "Lai", "given": "Voon Hui" }, "id": "Lai-Voon-Hui", "orcid": "0000-0002-0738-0187", "display_name": "Lai, Voon Hui" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "role": "co-advisor", "display_name": "Zhan, Zhongwen" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "role": "member", "display_name": "Zhan, Zhongwen" } ], "option_major": [ "geophys" ], "doi": "10.7907/5PQG-ST75", "abstract": "Seismic waveform modeling is a powerful tool for seismologists to learn about the Earth\u2019s dynamics, either how a natural hazard evolves with time, or the long-term deformation process governed by fine-scale structures along boundaries inside the Earth. Knowing that the recorded seismograms reflect the cumulative effects of the source, the earth structure, and the instrument response, I carefully study the characters of the seismograms such as the arrival time, amplitude, frequency content, and multipathing, for several settings, with the goal of improving our description of either the source or the structure.
\r\n\r\nPart 1 focuses on source characterization for non-earthquake natural hazards. I perform moment tensor inversions for the large seismic events at the Kilauea summit to infer the triggering mechanisms for the explosive eruptions and caldera collapse during the 2018 eruption sequence. The addition of infrasound data is crucial to resolve the uncertainties in the moment tensor solutions, particularly the depth and the necessity of the isotropic component. I also present a new mechanistic model to describe the seismic signal from debris flow and apply to the 2018 Montecito debris flow in which key parameters such as boulder size and flow rate and their evolution during the event can be determined using a single seismic station.
\r\n\r\nPart 2 consists of three studies spanning from the crust to the core, where forward waveform modeling is used to improve our understanding of the sharp structural boundaries and their role in observed ground motion and long-term dynamics. Numerical simulation and dense array analysis are used to model the direct effect of shallow basin structures in Los Angeles on shaking duration and reveal the importance of basin edges and attenuation model for predicting ground motion during large shallow ruptures. I also identify a strong velocity contrast in the lower crust \u2013 upper mantle structure across the San Andreas plate boundary system and, given velocity is a proxy to lithospheric strength, the sharp contrast can have a significant role in modulating the long-term plate deformation. Lastly, we observe strong waveform anomalies at the edge of the Pacific Large Low Shear Velocity Province (LLSVP) which have great importance in governing deep mantle convection. To fit the observation, I propose a model of ultra-low velocity zone (ULVZ), plume and slab interacting at the edge of the LLSVP. The configuration and location of this ULVZ-plume-slab interaction is important in inferring the mechanism behind plume generation which gives rise to the Hawaii-Emperor Seamount chain.
" }, { "name": "Leask, Ellen Kathleen", "degree": "PhD", "year": "2020", "title": "Investigating the Evolution of Surface Water on Mars through Spectroscopy of Secondary Minerals", "advisor": "Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02192020-182835054", "creators": [ { "name": { "family": "Leask", "given": "Ellen Kathleen" }, "id": "Leask-Ellen-Kathleen", "orcid": "0000-0002-3220-4003", "display_name": "Leask, Ellen Kathleen" } ], "advisors": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-C", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." } ], "option_major": [ "geol" ], "doi": "10.7907/TWR4-N128", "abstract": "Despite its current arid climate, Mars\u2019 surface preserves a wide variety of morphologies and minerals that point to a water-rich past. However, the mechanisms and timing of this environmental change are not yet well understood. In this dissertation, we explore a variety of water-related minerals through visible-shortwave infrared (VSWIR) reflectance spectroscopy to better understand the environmental conditions at the time of their formation, and trace the evolution of surface water on Mars over time. We also demonstrate the capabilities of VSWIR spectroscopy at laboratory and field scales in a Mars analogue environment (Samail Ophiolite, Oman)\u2014an emerging technique for use on future landed missions that enables us to differentiate between spectrally-similar minerals and spot rare minerals that help to constrain environmental conditions and better understand the geologic context of samples. On Mars, we use orbital datasets (predominantly CRISM, the Compact Reconnaissance Imaging Spectrometer for Mars) to investigate secondary minerals in the southern highlands of Mars, focusing on perchlorate, chloride, and sulphate minerals. We identify a previously unknown artifact in the CRISM dataset, which mimics perchlorate absorptions; previous orbital perchlorate detections (including those associated with recurring slope lineae) are not robust when data are reprocessed, suggesting that there may not be orbitally-detectable reservoirs of perchlorate on Mars, which would enable liquid brines to exist at the surface today. A detailed investigation of chloride deposits across the southern highlands of Mars points to an episodic surface-runoff water source rather than upwelling groundwater, a process which continued to create chloride deposits into the Amazonian era. Where chloride and sulphate deposits are in close proximity (Terra Sirenum, Mars), they do not appear to be genetically related as they often are on Earth; instead, they point to chemically distinct groundwater vs. surface water reservoirs in Terra Sirenum through the Hesperian and into the Amazonian. Together, these studies indicate that briny and/or acidic volumes of water at the surface capable of creating mineral deposits continued to exist \u2014 at least episodically \u2014 on Mars into the Amazonian, rather than ceasing much earlier in Mars\u2019 history.
" }, { "name": "Martin, Peter Eckels", "degree": "PhD", "year": "2020", "title": "Detection and Analysis of Martian Low-Temperature Geochemistry", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12112019-142555725", "creators": [ { "name": { "family": "Martin", "given": "Peter Eckels" }, "id": "Martin-Peter-Eckels", "orcid": "0000-0003-4243-2090", "display_name": "Martin, Peter Eckels" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geochem" ], "doi": "10.7907/EF7Y-D584", "abstract": "The history of Mars is encoded in the geochemistry of ancient sedimentary Martian rocks and secondary phases. Recent landed missions have provided unparalleled datasets with which to investigate this geochemistry. Accordingly, this thesis is concerned primarily with the in-situ analysis of low-temperature Martian geochemical processes by landed missions, and the attendant Earth-based studies which enrich those in-situ investigations. There are five main studies reported here. The first is an analysis of a Mars-analog environment on Earth. Datasets similar to those that will be produced by the upcoming Mars-2020 rover are used to evaluate the ability of the rover to reconstruct a known paleoenvironment, to identify reference datasets that require further development, and to suggest operational modes that most efficiently use the rover\u2019s resources. The second study is an in-situ noble gas analysis using the SAM instrument on the Curiosity rover to investigate a jarosite-containing sample using a two-step heating analysis for K-Ar dating. The jarosite likely formed at 2.12\u00b10.36 Ga while plagioclase in the sample formed at 4.07 \u00b1 0.63 Ga, indicating that liquid water interactions continued in Gale crater well past the end of the Hesperian period. The following chapter details another noble gas analysis, focusing on cosmogenic dating of surface exposure. In contrast to <100 Ma exposure ages observed at the floor of Gale crater, exposure ages exceeding 1 Ga are detected on the flanks of Mount Sharp. These ages indicate Mount Sharp formed during the Hesperian and has been largely unchanged in the intervening 3.1 Ga. The next study is a reevaluation of the data used to identify the presence of perchlorate in Gale crater. These data suggest that perchlorate is indeed present, but that it must be Amazonian in age, suggesting that rare surface wetting events have caused leaching of this soluble ion into the bedrock. The final study reports the development of a technique for measuring the isotopes in perchlorate using Orbitrap mass spectrometry on Earth, allowing investigation of the formation processes that impact the chlorine isotope ratio of this molecule on both Earth and Mars." }, { "name": "Naviaux, John David", "degree": "PhD", "year": "2020", "title": "Chemical and Physical Mechanisms of Calcite Dissolution in Seawater", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11062019-135828667", "creators": [ { "name": { "family": "Naviaux", "given": "John David" }, "id": "Naviaux-John-David", "orcid": "0000-0002-0681-3163", "display_name": "Naviaux, John David" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Menemenlis", "given": "Dimitris" }, "id": "Menemenlis-D", "role": "member", "display_name": "Menemenlis, Dimitris" }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "member", "display_name": "Hoffmann, Michael R." } ], "option_major": [ "envreng" ], "doi": "10.7907/DA32-MY55", "abstract": "Calcium carbonates are among the most abundant and reactive minerals on Earth, and their dissolution/preservation in the ocean helps to regulate changes in atmospheric pCO2. The chemistry of the oceans has varied significantly over the past several billion years, and it is changing at an unprecedented rate today in response to anthropogenic burning of fossil fuels. The excess CO2 from human activities is acidifying the oceans and decreasing the saturation state (\u03a9 = ([Ca2+][CO32-])/Ksp') of marine carbonates, increasing their propensity to dissolve. Despite its importance, the rate of carbonate dissolution in seawater is still described by a purely empirical expression, and the physical and chemical mechanisms setting the overall kinetics remain unknown. This stands in contrast to calcite dissolution in freshwater, where fully coupled surface-solution models have been identified. The lack of mechanistic understanding in seawater limits our ability to predict how carbonate dissolution kinetics, and therefore the buffering capacity of the ocean, are affected by changes in chemistry. This thesis advances our knowledge of the physical and chemical mechanisms responsible for carbonate dissolution by making new measurements in seawater both in the lab and in-situ.
\r\n \r\nI first probe the activation energy of the reaction in seawater by dissolving 13C-labeled CaCO3 across the full range of \u03a9 at 5, 12, 21, and 37\u00b0C. I find that a surface-based framework is required to explain the strong non-linearity of the data near equilibrium. In this framework, dissolution proceeds by the retreat of pre-existing steps for 0.9<\u03a9<1, defect-assisted etch pit formation for 0.75<\u03a9<0.9, and homogenous etch pit formation for 0<\u03a9<0.75. I provide the first seawater estimates of kinetic coefficients (\u03b2), nucleation site densities (ns), and step edge free energies (\u03b1) for each mechanism, as well as the activation energy for detachment from steps (\u03f5step) and the kinetic energy barrier to etch pit initiation (\u03f5init).
\r\n\r\nNext, I use a custom designed in-situ reactor to measure calcite dissolution rates across a transect of the North Pacific. I find that the same surface mechanisms and \"critical\" \u03a9s identified in lab also govern the dissolution of calcite in the open ocean. In-situ dissolution rates are ~4x slower than in the lab, but I use a combination of chemical spike experiments and measurements in archived seawater to show that this discrepancy can be explained by the presence of dissolved organic carbon in-situ. I propose an empirical rate equation that describes all previous in-situ measurements of inorganic calcite dissolution rates.
\r\n \r\nChanges in the relation between dissolution rate and \u03a9 can be explained by the activation of different surface processes, but the surface theory cannot account for much of the near-equilibrium dissolution behavior and temperature dependence. I therefore continue on in this thesis to combine the latest speciation models with dissolution measurements in artificial seawater of varying sulfate concentrations. I find that low sulfate solutions suppress dissolution rates by two orders of magnitude near equilibrium, while dissolution rates in the same solutions are enhanced far-from-equilibrium. Using these results, I fit a mechanistic model of dissolution that couples surface and solution processes. The model satisfies the principle of microscopic reversibility, provides an excellent estimate of calcite solubility product in seawater, and explains near equilibrium (\u03a9 > 0.75) dissolution rates in 0, 14, and 28 mM [SO42-] seawater at 21\u00b0C. The model cannot explain dissolution rates for \u03a9 < 0.75 when etch pits begin opening homogenously across the surface, so I suggest areas of improvement for future models.
\r\n\r\nPrevious work has demonstrated that calcite dissolution rates are enhanced in the presence of the enzyme carbonic anhydrase (CA). In the final chapter of this thesis, I evaluate the mechanism of CA rate enhancement by comparing the catalytic effects of freely dissolved CA, CA immobilized within hydrogels, and CA chemically bound onto porous silica beads. At the same time, I design and test a fluidized bed reactor and demonstrate its efficacy as a carbon capture device by attaching it directly to the Caltech cogeneration power plant smokestack. I find that dissolution rates within the reactor are only enhanced when CA is freely dissolved, strongly suggesting that the catalytic mechanism is direct proton transfer from the enzyme to the calcite surface.
" }, { "name": "Rooney, Brigitte Lee", "degree": "PhD", "year": "2020", "title": "Modeling the Impact of Biomass Combustion on Atmospheric Aerosol", "advisor": "Seinfeld, John H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012020-155204817", "creators": [ { "name": { "family": "Rooney", "given": "Brigitte Lee" }, "id": "Rooney-Brigitte-Lee", "orcid": "0000-0002-9725-9080", "display_name": "Rooney, Brigitte Lee" } ], "advisors": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "advisor", "display_name": "Seinfeld, John H." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "member", "display_name": "Flagan, Richard C." }, { "name": { "family": "Wang", "given": "Yuan" }, "id": "Wang-Yuan", "role": "member", "display_name": "Wang, Yuan" } ], "option_major": [ "envreng" ], "doi": "10.7907/adpa-0947", "abstract": "Biomass burning is a significant source of atmospheric particulate matter less than 2.5 micrometers in diameter (PM2.5) and encompasses a variety of activities, fuels, and emissions profiles. A significant portion of the world population relies on solid biofuels for cooking and other household activities. Residential use of solid biofuels can have negative impacts on human health, particularly in southeast Asia, and contribute to ambient air quality. In addition, wildfires are of increasing concern as climate changes and human activity expands further into the wildland-urban interface. Understanding the contributions of biomass combustion to air quality is critical for creating mitigation strategies.
\r\n\r\nIn this work, the impact of biomass burning on air quality is examined using numerical and observational methods. The Community Multiscale Air Quality modeling system (CMAQ) and the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) are used to study two biomass burning scenarios: the combustion of solid biofuels for cooking in rural India and the November 2018 Camp Fire in northern California. Model simulations are combined with surface and satellite observational data to evaluate their performance as well as their applicability to health and economic impact assessment studies. Additionally, discrepancies in methods used in laboratory experiments and field studies of cookstove emissions are investigated. Contributions of cookstove and wildfire emissions to PM2.5 are estimated, and climate and health co-benefits of residential solid biofuel use is assessed. This thesis strives to expand the current understanding of sources of PM2.5 and provide a base for future computational studies of biomass burning impacts on air quality, climate, and human health.
" }, { "name": "Stein, Nathaniel Thomas", "degree": "PhD", "year": "2020", "title": "Investigation of Past Habitable Environments through Remote Sensing of Planetary Surfaces", "advisor": "Grotzinger, John P.; Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06092020-122543624", "creators": [ { "name": { "family": "Stein", "given": "Nathaniel Thomas" }, "id": "Stein-Nathaniel-Thomas", "orcid": "0000-0003-3385-9957", "display_name": "Stein, Nathaniel Thomas" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "advisor", "display_name": "Grotzinger, John P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "chair", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." } ], "option_major": [ "plansci" ], "doi": "10.7907/cq9c-sg21", "abstract": "Planetary surfaces record a history of potentially habitable environments throughout the solar system. This dissertation focuses on the characterization of three planetary surfaces to inform their evolution and past habitability: Earth (Chapter 2), Mars (Chapters 3-4), and Ceres (Chapters 5-6). In chapter 1, we introduce major questions driving the work presented in this thesis. In Chapter 2, we use a combination of UAV-based images and in-situ observations to characterize the processes that control the texture and distribution of modern microbial mats in the Turks and Caicos. We find that the surface texture and distribution of the mats is controlled primarily by subtle differences in elevation that drive significant changes in subaerial exposure time. Sedimentation and mechanical weathering from storm events also play a key role in controlling the distribution of mats. In Chapter 3, we apply a PCA-based regression method to stereo Curiosity Mastcam images to measure the structural orientation of the Murray formation. We constrain the dip to be effectively horizontal, which indicates that the Murray formation predates the creation of Aeolis Mons and is consistent with flat strata being deposited on an equipotential surface in a lacustrine setting. In Chapter 4, we summarize the investigation of networks of reticulate ridges on the surface of several rock slabs in the Murray formation using data from the Curiosity rover. We find that the features are preserved mudcracks that were likely deposited during a lowstand in a lake ~3.2-3.6 Ga. The mudcracks are one of few definitive textural markers of drying in the Murray formation and suggest a history of oscillating lake levels that led to intermittent exposure. In Chapter 5, we catalog bright spots on Ceres and propose mechanisms for their formation. We identify hundreds of Na-carbonate-bearing regions on Ceres. We show with a Monte Carlo impact model that these deposits must have been exposed within the last few hundred Ma. In Chapter 6, we investigate the source of shallow subsurface Na-carbonate deposits. We show that the deposits must have been emplaced in the last ~1 Ga and that the solid-state mobilization of water ice and hydrated Na-carbonates could simultaneously explain the formation of domes and large crater rim Na-carbonate exposures. Chapter 7 synthesizes the major results of this thesis and avenues for future exploration." }, { "name": "Zhu, Yanzhe", "degree": "PhD", "year": "2020", "title": "3D Microfluidics for Environmental Pathogen Detection and Single-cell Phenotype-to-Genotype Analysis", "advisor": "Hoffmann, Michael R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06082020-172255300", "creators": [ { "name": { "family": "Zhu", "given": "Yanzhe" }, "id": "Zhu-Yanzhe", "orcid": "0000-0002-2260-1830", "display_name": "Zhu, Yanzhe" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "role": "chair", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Venkateswaran", "given": "Kasthuri Jhetty" }, "id": "Venkateswaran-K-J", "role": "member", "display_name": "Venkateswaran, Kasthuri Jhetty" }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "member", "display_name": "Hoffmann, Michael R." } ], "option_major": [ "envreng" ], "doi": "10.7907/vk3d-7212", "abstract": "The emergence of microfluidic technologies has enabled the miniaturization of cell analysis processes, including nucleic acid analysis, single cell phenotypic analysis, single cell DNA and RNA sequencing, etc. Traditional chip fabrication via soft lithography cost thousands of dollars just in personnel training and capital cost. The design of these systems is also confined to two dimensions limited by their fabrication. To address the needs of smooth transition from technology to adoption by end-users, less complexity is urgently needed for microfluidics to be applied in pathogen detection under low-resource settings and more powerful integration of analyses to understand single cells. This dissertation presents my explorations in 3D microfluidics involving simulation-aided design of pretreatment devices for pathogen detection, fabrication through 3D printing, utilization of alternative commercial parts, and the combination with hydrogel material to link phenotypic analysis with in situ molecular detection for single cells. The main outputs of this dissertation are as follows:
\r\n\r\n1) COMSOL Multiphysics\u00ae was used to aid the design and understanding of microfluidic systems for environmental pathogen detection. In the development of an asymmetric membrane for concentration and digital detection of bacteria, the quantification requires Poisson distribution of cells into membrane pores; the flow field and particle trajectories were simulated to validate the cell distribution in capturing pores. In electrochemical bacterial DNA extraction, the hydroxide ion generation, species diffusion, and cation exchange were modeled to understand the pH gradient within the chamber. To address the overestimated risk by polymerase chain reactions (PCR) that detects all target nucleic acids regardless of cell viability, we developed a microfluidic device to carry out on-chip propidium monoazide (PMA) pretreatment. The design utilizes split-and-recombine (SAR) mixers for initial PMA-sample mixing and a serpentine flow channel containing herringbone structures for dark and light incubation. Ten SAR mixers were employed based on fluid flow and diffusion simulation. High-resolution 3D printing was used for prototyping. On-chip PMA pretreatment to differentiate live and dead bacterial cells in buffer and natural pond water samples was experimentally demonstrated.
\r\n\r\n2) Water-in-oil droplet-based microfluidic platforms for digital nucleic acid analysis eliminates the need for calibration that is required for qPCR-based environmental pathogen detection. However, utilizing droplet microfluidics generally requires fabrication of sub-100 \u00b5m channels and complicated operation of multiple syringe pumps, thus hindering the wide adoption of this powerful tool. We designed a disposable centrifugal droplet generation device made simply from needles and microcentrifuge tubes. The aqueous phase was added into the Luer-Lock of the commercial needle, with the oil at the bottom of the tube. The average droplet size was tunable from 96 \u03bcm to 334 \u03bcm and the coefficient of variance (CV) was minimized to 5%. For droplets of a diameter of 175 \u03bcm, each standard 20 \u03bcL reaction could produce ~10\u2074 droplets. Based on this calculated compartmentalization, the dynamic range is theoretically from 0.5 to 3\u00d710\u00b3 target copies or cells per \u03bcL, and the detection limit is 0.1 copies or cells per \u03bcL.
\r\n\r\n3) Based on the disposable droplet generation device, we further developed a novel platform that enables both high-throughput digital molecular detection and single-cell phenotypic analysis, utilizing nanoliter-sized biocompatible polyethylene glycol (PEG) hydrogel beads. The crosslinked hydrogel network in aqueous phase adds additional robustness to droplet microfluidics by allowing reagent exchange. The hydrogel beads demonstrated enhanced thermal stability, and achieved uncompromised efficiencies in digital PCR, digital loop-mediated isothermal amplification (dLAMP), and single cell phenotyping. The crosslinked hydrogel network highlights the prospective linkage of various subsequent molecular analyses to address the genotypic differences between cellular subpopulations exhibiting distinct phenotypes. This platform has the potential to advance the understanding of single cell genotype-to-phenotype correlations.
\r\n\r\n4) For effective sorting of the hydrogel beads after single cell phenotyping, a gravity-driven acoustic fluorescence-based hydrogel beads sorter was developed. The design involves a 3D-printed microfluidic tube, two sequential photodetectors, acoustic actuator, and a control system. Instead of bulky syringe pumps used in traditional cell or droplet sorting, this invention drives beads suspended in heavier fluorinated oil simply by buoyancy force to have the beads float through a vertical channel. Along the channel, sequential photodetectors quantify the bead acceleration and inform the action of downstream acoustic actuator. Hydrogel beads with different fluorescence intensity level were led into different collection chambers. The developed sorter promises cheap instrumentation, easy operation, and low contamination for beads sorting, and thus the full establishment of the single cell phenotype-genotype link.
\r\n\r\nIn summary, the work in this dissertation established a) the simulation-aided design and 3D printing to reduce the complexity of microfluidics, and thus lowered its barrier for environmental applications, b) a simple and disposable device using cheap commercial components to produce monodispersed water-in-oil droplets to enable easy adoption of droplet microfluidics by non-specialized labs, c) a hydrogel bead-based analysis platform that links single-cell phenotype and genotype to open new research avenues, and d) a gravity-driven portable bead sorting system that may extend to a broader application of hydrogel microfluidics to point of care and point of sample collection. These simple-for-end-user solutions are envisioned to open new research avenues to tackle problems in antibiotic heteroresistance, environmental microbial ecology, and other related fundamental problems.
" }, { "name": "Bai, Kangchen", "degree": "PhD", "year": "2019", "title": "Dynamic Earthquake Source Modeling and the Study of Slab Effects", "advisor": "Ampuero, Jean-Paul; Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06142018-121935019", "creators": [ { "name": { "family": "Bai", "given": "Kangchen" }, "id": "Bai-Kangchen", "orcid": "0000-0002-9788-6404", "display_name": "Bai, Kangchen" } ], "advisors": [ { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "co-advisor", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "co-chair", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geophys" ], "doi": "10.7907/JVVW-M348", "abstract": "In this Thesis, I report my Ph.D. research on two major issues that are devoted towards constructing more realistic earthquake source model using computational tools: (1) constructing physically consistent dynamic rupture models that include complexities in fault geometry as well as heterogeneous stress and frictional properties inferred from observations; (2) study the effect of subducting slab structure on earthquakes that occur inside it with a special focus on the teleseismic waveforms.
\r\n\r\nFault step over is one of the most important geometric complexities that control the propagation and arrest of earthquake ruptures. In Chapter 2, we study the role of seismogenic depth and background stress on physical limits of earthquake rupture across fault step overs. We conclude that the maximum step over distance that a rupture can jump is approximately proportional to seismogenic depth. We also conclude that the pre-stress conditions have a fundamental effect on step over jump distance while the critical nucleation size has a secondary effect.
\r\n\r\nSeismic wave carries information of source as well as structures along the path it travels. It was found that seismic waves generated by shallow events in subduction zones whose ray path coincide with the down going slab structure display waveform complexities that feature multipathing. In Chapter 3, we study deep earthquakes whose depth phases sample the slab structure on their way up to the surface. Differential travel time sP-P analysis shows a systematic decrease of up to 5 seconds from Europe to Australia and then to Pacific which is indicative of a dipping high velocity layer above the source region. Finite-difference simulations showed that a slab shaped structure that follows the Benioff zone at shallow depth and steepens beyond 400 km produces a model that can account for the sP-P differential travel times of 5 seconds for oceanic paths. In Chapter 4, we design a slab operator that can be applied on the 1D synthetics to generate 2D synthetics with slab structure. We hope this operator can be used for generating more accurate Green's functions that could potentially serve earthquake source inversion.
\r\n\r\nIn Chapter 5, we design a dynamic rupture model of the Mw 7.8 Gorkha, Nepal earthquake. We employ a novel approach of integrating kinematic inversion results which provide low frequency stress distribution and stochastic high frequency stress motivated by earthquake cycle models and observations. By doing this, we are able to reproduce the observed frequency dependent rupture processes, in particular the concentration of high-frequency radiation in the down-dip part of the rupture.
\r\n\r\nIn Chapter 6, I report my on going work on the spectral element method based earthquake cycle simulator. Large scale earthquake cycle simulation with consideration of complicated velocity structure and fault geometry is a great challenge for numerical modeling. I tried to push forward this boundary by extending the existing spectral element earthquake cycle simulator to enable cycle simulations on bi-material faults. This chapter includes a benchmark test in 2D that demonstrates the correctness of this new algorithm and an application of this method on bi-material fault earthquake cycle modeling.
" }, { "name": "Chen, Sang", "degree": "PhD", "year": "2019", "title": "Understanding Geochemical Tracers in Deep-Sea Corals from a Biomineralization Perspective", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06072019-145745731", "creators": [ { "name": { "family": "Chen", "given": "Sang" }, "id": "Chen-Sang", "orcid": "0000-0001-8941-0791", "display_name": "Chen, Sang" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Lea", "given": "David W." }, "id": "Lea-David-W", "role": "member", "display_name": "Lea, David W." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "geochem" ], "doi": "10.7907/54TA-JK92", "abstract": "Deep-sea corals have been developed as a useful archive of the chemistry and circulation of intermediate and deep waters in past oceans over the last three decades. However, applications of traditional paleoceanographic tracers in deep-sea corals remain a challenge due to our incomplete understanding of the biomineralization mechanisms underlying the incorporation of these tracers and their variabilities in the coral skeletons (a.k.a. the \"vital effects\"). In this thesis, an effort was made to understand the vital effects associated with the stable isotope as well as minor and trace element compositions of the aragonitic skeletons of the deep-sea coral species Desmophyllum dianthus, through a combination of empirical observations and a numerical model of coral calcification. Observations of the chemical and isotopic compositions of the coral skeletons were performed on four different spatial scales in a suite of modern D. dianthus specimens: bulk samples, micromilled samples, SIMS and nanoSIMS. These observations reveal tracer correlations in deep-sea corals that are coherent over different spatial scales and point toward a universal mechanism of the incorporation of these tracers through the biomineralization process. A few tracers emerge as promising proxies for the temperature (Li/Mg, Sr/Ca) and carbonate chemistry (U/Ca, B/Ca, Ba/Ca) of the oceans. The numerical model for coral calcification explains the strong \u03b418O and \u03b413C vital effects in individual deep-sea corals with an updated physicochemical basis, and carbonic anhydrase is found to play a key role in setting the slopes of the strong \u03b418O-\u03b413C correlations in different biogenic carbonates. The model also constrains the key physical parameters in the biomineralization process and is extended to explain the observed minor and trace element variabilities and correlations in deep-sea corals. The model can qualitatively explain the observed correlation patterns between Mg/Ca, Li/Ca, B/Ca and Sr/Ca in the coral skeletons, but quantitative data-model comparison is limited by both deficiencies in high-quality data and a lack of a well-constrained inorganic reference frame for aragonite. Future improvements in the geochemical tracers in biogenic carbonates will benefit from more extended empirical calibrations as well as a more complete mechanistic understanding of the key physicochemical and biological processes underlying the incorporation of tracers.
" }, { "name": "Erickson, Zachary K.", "degree": "PhD", "year": "2019", "title": "Physical Processes Leading to Export of Fixed Carbon Out of the Surface Ocean", "advisor": "Thompson, Andrew F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06092019-160257514", "creators": [ { "name": { "family": "Erickson", "given": "Zachary K." }, "id": "Erickson-Zachary-K", "orcid": "0000-0002-9936-9881", "display_name": "Erickson, Zachary K." } ], "advisors": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "advisor", "display_name": "Thompson, Andrew F." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-C", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Gierach", "given": "Michelle Marie" }, "id": "Gierach-M-M", "role": "member", "display_name": "Gierach, Michelle Marie" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." } ], "option_major": [ "envreng" ], "doi": "10.7907/XDX7-8J36", "abstract": "The ocean sequesters carbon on long time scales by depositing it deep in the ocean, where it is no longer in contact with the atmosphere. This sequestration is also termed \"carbon export\", and is accomplished via a vertical flux of carbon into the interior of the ocean. Marine photosynthesis by phytoplankton, which consume carbon dioxide dissolved in the surface ocean and are transported to depth to be eventually remineralized or form sediments at the ocean surface, is a key component of this flux (the biological pump). This mechanism is primarily thought to occur via sinking of particulates. However, research over the past few decades has highlighted the role of instabilities at the \"submesoscale\", or 0.1--20 km, to induce large, O(100 m day-1) vertical velocities in the ocean. These vertical velocities can potentially subduct carbon from the surface ocean into the interior, where it would contribute to export. Observations of the ocean are, however, rarely made at scales which would detect these submesoscale instabilities. In this thesis, I use in situ observations from autonomous underwater vehicles, Seagliders, which make measurements in the upper 1000 m of the water column at horizontal scales of 1-3 km, to understand when and where submesoscale instabilities are present, and the extent to which they act to transport biologically fixed carbon out of the surface ocean. Three different types of instabilities are active in the surface mixed layer: baroclinic, gravitational, and symmetric. Each of these has potential to subduct material below the mixed layer; however, these instabilities are generally strongest during the winter, when biological production is at its minimum. An interesting exception is in southern Drake Passage, where interactions between the intense frontal system and the continental shelf result in subduction of water masses off the continental shelf during summer, when phytoplankton are photosynthesizing. In general, however, carbon export via submesoscale instabilities is expected to be largest during spring, when phytoplankton become more productive but conditions can still be ripe for submesoscale subduction. Scaling up these observations to the global ocean system is difficult because in situ observations at submesoscales are sparse. This thesis explores the ability of surface flux measurements, from reanalysis products and remote sensing measurements, to accurately depict carbon export via subduction processes by modeling the water profile in a one-dimensional model following Lagrangian floats in the ocean. This approach holds promise to advance the ultimate goal of determining the global effect of submesoscale-driven carbon export." }, { "name": "Hofmann, Florian", "degree": "PhD", "year": "2019", "title": "Iron-Oxide Geochronology to Constrain the Formation of Soils and Paleosols", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05312019-131059095", "creators": [ { "name": { "family": "Hofmann", "given": "Florian" }, "id": "Hofmann-Florian", "orcid": "0000-0002-9836-2338", "display_name": "Hofmann, Florian" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geol" ], "doi": "10.7907/PHV4-Y279", "abstract": "In this thesis, I show how iron-oxide geochronology can be applied to soils and paleosols and I explore new applications of the (U-Th)/He and cosmogenic 3He dating methods. In Chapters II and III, I apply the (U-Th)/He method to goethite pisoliths in paleosols and fissure fillings of the Bohnerz deposits, which are a widespread erosional lag deposit in Central Europe. I show that this deposit formed between ~55 Ma and 2 Ma and not in the late Cretaceous-early Eocene, as was previously claimed. A map compiled from published sources shows the paleo-extent of the Bohnerz deposit, which were developed on every limestone plateau in Central Europe. Concentrations of cosmogenic 3He measured on pisoliths in paleosols, demonstrate that ancient cosmic-ray exposure occurred over at least 5 Ma, possibly 10-20 Ma. This shows that the Bohnerz deposits represent surfaces, which were stable for tens of millions of years before burial. Even today, these surfaces experience extremely low erosion rates of ~0.1 m/Ma, comparable to some of the Earth's most stable surfaces in arid environments. The hiatus represented by the Bohnerz unconformity lasts 125-150 Ma, yet only 30-40% of that duration is recorded in Bohnerz deposits. Pisoliths of the Bohnerz deposits are a continuous record of Central European continental climate for most of the Cenozoic.
\r\n\r\nIn Chapter IV, I develop a laboratory technique to enable (U-Th)/He dating of hematite samples by the single-aliquot method. Highly retentive hematite samples have to be heated to >1000 \u00b0C to fully degas helium, but U is lost from the sample at around 980 \u00b0C. Through infrared spectroscopy and trace element analysis of heated samples, I show that U-loss correlates with a phase change from hematite to magnetite. Delaying this phase change to higher temperatures extends the usable range of temperatures to which samples can be safely heated without U-loss. This is achieved by degassing samples in a partial oxygen pressure of around 100 mbar, which permits degassing of samples up to 1150 \u00b0C without loss of U. I demonstrate that precise and accurate (U-Th)/He ages can be obtained for hematite samples, which agree with established two-aliquot ages. I show how this method can be implemented and automated.
\r\n\r\nIn Chapter V, I extend the use of 3He cosmogenic dating to fine-grained iron-oxide particles, which are abundant in most types of modern soils. Diffusion modeling predicts that hematite particles down to ~10 nm should quantitatively retain helium for at least 1 Ma at Earth-surface conditions. In order to test whether pedogenic iron-oxides can be used for geochronology, I study a vertical profile of a relict soil developed on a fanglomerate terrace at Whitewater Hill, California. Profiles of 10Be and 26Al in detrital quartz agree well with an exponential decrease in cosmogenic nuclide production and they yield an exposure age of 52.4\u00b12.2 ka assuming no erosion. The vertical profile of 3He concentrations in pedogenic iron-oxides shows a decrease with depth, but concentrations are higher than expected in the 40-100 cm depth range. This indicates vertical movement of iron-oxides in the soil, which is a well-known soil formation process. These observations are more consistent with a soil age of 208\u00b144 ka. This approach yields information on both age constraints and the formation and migration of pedogenic iron-oxides in the soil column.
" }, { "name": "Huang, Yuanlong", "degree": "PhD", "year": "2019", "title": "Development of Methods to Study Secondary Organic Aerosol", "advisor": "Seinfeld, John H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05232019-231457899", "creators": [ { "name": { "family": "Huang", "given": "Yuanlong" }, "id": "Huang-Yuanlong", "orcid": "0000-0002-6726-8904", "display_name": "Huang, Yuanlong" } ], "advisors": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "advisor", "display_name": "Seinfeld, John H." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "member", "display_name": "Flagan, Richard C." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "member", "display_name": "Hoffmann, Michael R." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." } ], "option_major": [ "envreng" ], "doi": "10.7907/783S-K686", "abstract": "Secondary organic aerosol (SOA) in the atmosphere contributes significantly to air pollution and has profound impacts on regional and global climate change, as well as human health. SOA, as opposed to directly emitted particles, refers to those particles formed from oxidation of gas-phase compounds followed by nucleation and/or gas-particle partitioning, as well as those modified by gas-phase oxidants (e.g., O3, OH radical, and NO3 radical) through heterogeneous reactions within their lifetime in the atmosphere. Investigations of SOA formation in the laboratory have been carried out in batch reactors (e.g., environmental smog chambers) and continuous flow reactors (e.g., oxidation flow reactors). Compared with the real atmosphere, the reactors in the laboratory have boundaries and defined residence times under different operation conditions. To better constrain the experimental results and derive reliable parameters for aerosol models (e.g., yields of volatile organic compounds), a full understanding of the role of the reactors on the gas-phase components and suspended particles is needed.
\r\n \r\nIn this thesis research, a number of studies were carried out to understand the role of the reactor itself on the behavior of SOA-forming systems. This includes the effect of the Teflon-walled Caltech Environmental Chamber on vapor molecules and characterization of the newly-built Caltech PhotoOxidation Flow Tube reactor (CPOT) for atmospheric chemistry studies.
\r\n \r\nVapor-wall interactions in Teflon-walled environmental chambers have been studied; however, conflicting results existed in the literature concerning the basic timescales of vapor-wall loss in environmental chambers. The competition between vapor-particle and vapor-wall interactions determines the fate of vapor molecules in the reactor. A unified theory and empirical equations have been developed in this thesis to explain the observed vapor-wall interaction timescales. About 100 compounds have been studied to verify this theory. In characterizing the flow reactor performance, computational fluid dynamics (CFD) simulations have been combined with residence time distribution (RTD) experiments, revealing, among others, the importance of the inlet design of the reactor and the effect of temperature gradients on radial mixing in the reactor. An axial-dispersed plug flow reactor (AD-PFR) model framework was developed as a basis on which to simulate photochemistry occurring in the CPOT. An analytical solution for the cumulative RTD, which uses data during the transition period to a steady state, can be applied to diagnose the dispersion condition inside the flow rector.
\r\n \r\nSince SOA formation involves interactions among gas-phase molecules, particle surfaces, and particle bulk phases, a state-of-the-art experimental technique (field-induced droplet ionization mass spectrometry, FIDI-MS) and a comprehensive model coupling gas-surface-aqueous multiphase transport and chemical reactions have been applied to investigate the gas-phase OH-initiated oxidation of pinonic acid (PA) at the air-water interface. The interfacial oxidation mechanism has been found to differ from that of homogeneous reactions, and the kinetics depend on both OH diffusion from gas-phase to the interface and aqueous-phase reaction of pinonic acid + OH. The model calculation shows that, under typical ambient OH levels, PA is oxidized exclusively at the air-water interface of droplets with a diameter of 5 \u00b5m, demonstrating the critical importance of air-water interfacial chemistry in determining the fate of surface-active species.
" }, { "name": "Mao, Xiaolin", "degree": "PhD", "year": "2019", "title": "Understanding Lithosphere and Mantle Dynamics with Numerical Models Constrained by Observations", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07012018-101034748", "creators": [ { "name": { "family": "Mao", "given": "Xiaolin" }, "id": "Mao-Xiaolin", "orcid": "0000-0002-8410-4629", "display_name": "Mao, Xiaolin" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "chair", "display_name": "Simons, Mark" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "role": "member", "display_name": "Zhan, Zhongwen" } ], "option_major": [ "geophys" ], "doi": "10.7907/59N8-H306", "abstract": "Numerical studies play an important role in understanding lithospheric and mantle dynamics. In this thesis, we first develop and use multiphysics geodynamic models to study the evolution of subduction. Our geodynamic models are constrained by different geological and geophysical observations, including topography. We then use 3D numerical simulations of dynamic rupture with off-fault inelastic deformation to study the scaling between damage zone thickness and fault width. Finally, we study the mechanical strength and anisotropy in the continental collision region with flexural models and gravity and topography data.
\r\n\r\nTopography is valuable data for investigating lithosphere and mantle dynamics and constraining numerical studies. Topography prediction with forward models is well established at plate interiors, while it is still difficult to predict realistic topography at subduction zones. We use multiphysics geodynamic models to tackle this problem. Our models incorporate a true free surface, phase changes, and elasto-visco-plastic rheology. We also include surface processes, water migration and water weakening. We study the influences of different geophysical, petrological, and geochemical processes on topography and subduction zone evolution and show that surface geometry, surface processes, elasticity, and oceanic crust all strongly influence the stress state and deformation within plates, water weakening decouples the overriding plate and the subducting slab at the mantle wedge region and contributes to the initiation of overriding plate failure, and oceanic crust has a similar effect with sediments lubricating the subduction interface. Free slip surface topography and free surface topography have substantial differences, and free surface topography is influenced by different processes by adjusting the force balance. Application to the New Hebrides subduction zone suggests that deformation within a detached slab segment caused by the impact of the slab segment on the strong lower mantle explains the origin of the isolated deep earthquakes in the transition zone beneath the North Fiji Basin, and the difference in the seismic intensities between northern and southern deep earthquake clusters is caused by transition from strong deformation to weak deformation after the impact.
\r\n\r\nWe apply our multiphysics approach to investigate the influence of inherited lithospheric heterogeneity on subduction initiation at the Puysegur Incipient Subduction Zone (PISZ) south of New Zealand. Our predictions fit the morphology of the Puysegur Trench and Ridge and the deformation history on the overriding plate. We show how a new thrust fault forms and evolves into a smooth subduction interface, and how a preexisting weak zone can become a vertical fault inboard of the thrust fault during subduction initiation, consistent with two-fault system at PISZ. The model suggests that the PISZ may not yet be self-sustaining. We propose that the Snares Zone (or Snares Trough) is caused by plate coupling differences between shallower and deeper parts, that the tectonic sliver between two faults experiences strong rotation, and that low density material accumulates beneath the Snares Zone.
\r\n\r\nWe then turn to the scaling between damage zone thickness and fault width. Field observations indicate that damage zone thickness scales with accumulated fault displacement at short displacements but saturates at a few hundred meters for displacements larger than a few kilometers. To explain this transition of scaling behavior, we conduct 3D numerical simulations of dynamic rupture with off-fault inelastic deformation on long strike-slip faults. We find that the distribution of coseismic inelastic strain is controlled by the transition from crack-like to pulse-like rupture propagation associated with saturation of the seismogenic depth. The yielding zone reaches its maximum thickness when the rupture becomes a stable pulse-like rupture. Considering fracture mechanics theory, we show that seismogenic depth controls the upper bound of damage zone thickness on mature faults by limiting the efficiency of stress concentration near earthquake rupture fronts. We obtain a quantitative relation between limiting damage zone thickness, background stress, dynamic fault strength, off-fault yield strength, and seismogenic depth, which agrees with first-order field observations. Our results help link dynamic rupture processes with field observations and contribute to a fundamental understanding of damage zone properties.
\r\n\r\nFinally, we investigate the interactions between mechanical strength and lithospheric deformations. Variation of lithospheric strength controls the distribution of stress and strain within plates and at plate boundaries. Simultaneously, deformation caused by localized stress and strain reduces the lithospheric strength. We calculate the effective elastic thickness, Te, which is a proxy of lithospheric strength, and its anisotropy at the Zagros-Himalaya belt and surrounding regions. Te varies from < 5 km to over 100 km, and shows good correlations with geological boundaries. Along plate boundaries, mountain belts, and major faults, Te is usually smaller than 30 km. In basins, Te is between 30 - 60 km. In stable cratons, Te is larger than 60 km. In the regions with low and intermediate strength (Te < 60 km), the extent of Te anisotropy is usually large, and the weak direction of Te anisotropy agrees well with the directions of GPS data and crustal stress. In stable cratons, the extent of Te anisotropy is usually small. Our results suggest that mechanical weakening is the dominant mechanism to reduce the lithospheric strength in regions where Te is smaller than 60 km. In stable cratons, the effects of mechanical weakening can be ignored, and only thermal weakening resulting from mantle processes can modify the lithospheric strength substantially.
" }, { "name": "Miller, Hayden Bryce Dutcher", "degree": "PhD", "year": "2019", "title": "Stable and Radiogenic Isotope Studies of Iron-oxides as Paleoenvironmental and Tectonic Archives", "advisor": "Farley, Kenneth A.; Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11072018-165610818", "creators": [ { "name": { "family": "Miller", "given": "Hayden Bryce Dutcher" }, "id": "Miller-Hayden-Bryce-Dutcher", "orcid": "0000-0001-7305-928X", "display_name": "Miller, Hayden Bryce Dutcher" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "co-advisor", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "co-advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Vasconcelos", "given": "Paulo" }, "id": "Vasconcelos-P", "role": "member", "display_name": "Vasconcelos, Paulo" } ], "option_major": [ "geochem" ], "doi": "10.7907/945X-R138", "abstract": "Geochemical records of continental weathering environments are limited despite their critical value to understanding how past climates functioned. This thesis seeks to address this limitation by drawing together innovative lines of research in geochronology, stable isotope geochemistry, and chemical weathering. Two distinct projects are described; each project designed to provide new insight into the paleoenvironmental and tectonic history of continental weathering environments. These projects, though distinct in their methods and samples, are unified by their goal: to use the stable, radiogenic, and nucleogenic isotopic composition of iron oxides to provide new constraints on the geologic history of continental weathering environments.
\r\n\r\nThe weathering of Fe-bearing rocks, coupled with the extreme insolubility of iron in moderately acidic to alkaline oxic waters, causes both goethite and hematite to be abundant chemical precipitates in near-surface environments. Goethite is favored in lower temperature and more acidic or alkaline conditions, while hematite precipitates more readily in near-neutral environments. These minerals are found in soils; spring, bog, and stream deposits; oxidized chemical sediments; and hydrothermal deposits. In many cases, substantial crystalline masses occur, which can take the form of nodules, pisoliths, botryoidal, stalactitic, and radiating masses, fibrous needles, pseudomorph, veneers, or as aggregates of flakes, tabular, or anhedral crystals. Time and temperature are arguably the two most fundamental variables we as geologists seek to constrain, and iron oxide deposits can provide a valuable archive of information on low-temperature, near-surface planetary processes.
\r\n\r\nThe first project investigates how the stable oxygen isotopic composition of goethite, when combined with direct He dating on the same texturally resolved scales as stable isotope analyses, can be used to interpret water sources (Chapter 1) and formation temperatures (Chapter 2). The first chapter creates a record of the paleolatitudinal gradient in the oxygen isotope composition of meteoric water. The major finding of this study is the consistency in this gradient over geologic time. This second chapter proposes a new geothermometer using the intracrystalline oxygen isotopic composition of goethite. While stable isotopic compositions of goethite have long been utilized as a tool for reconstructing paleoenvironmental conditions, previous studies have focused on the bulk concentration of stable isotopes within this phase. Since goethite has two structurally non-equivalent oxygen sites, we show it is possible to extract two isotopically unique populations of oxygen, the composition of which we interpret to be dependent on temperature at time of mineral formation. In combination with the ability to directly date goethite by the (U-Th)/He method, we may utilize goethite to constrain both the temperature and timing of goethite formation, providing a valuable archive for information on continental paleoenvironments.
\r\n\r\nThe second project utilized the paired He-Ne chronometer and 4He/3He method in hematite to produce thermal histories of the ancient Kaapvaal Craton over billion-year timescales. We applied these methods to hematite ore hosted within the Transvaal Supergroup in the Griqualand West (Chapter 3) and Transvaal Basin region (Chapter 4) of the ancient Kaapvaal Craton, South Africa. The application of hematite geo- and thermochronometry to these multi-billion year-old deposits represents the most challenging environments these methods have yet been applied to. We found, in some localities, hematite He-Ne ages provided further support of existing indirect age constraints on the timing of ore formation. In other localities, we found hematite He-Ne ages are uncorrelated with known tectono-thermal events. Modeled time-temperature histories indicate the Kaapvaal Craton has experienced exceptionally slow erosion rates over the last billion years, providing further evidence for the extreme tectonic stability of cratonic interiors over geologic timescales. This slow erosion took place over vast intervals of time, during which the craton was undergoing oxidative weathering, offering an additional constraint on understanding the history of atmospheric O2 during Proterozoic time.
" }, { "name": "Morrison, Rachel Ann", "degree": "PhD", "year": "2019", "title": "Equations of State, Sound Velocities, and Thermoelasticity of Iron-Nickel-Silicon Alloys in the Earth\u2019s Inner Core", "advisor": "Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10092018-192248653", "creators": [ { "name": { "family": "Morrison", "given": "Rachel Ann" }, "id": "Morrison-Rachel-Ann", "orcid": "0000-0003-3585-827X", "display_name": "Morrison, Rachel Ann" } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "chair", "display_name": "Tsai, Victor C." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." } ], "option_major": [ "geophys" ], "doi": "10.7907/YV5E-3125", "abstract": "The core of the Earth is predominately iron alloyed with approximately 5 wt% nickel along with some amount of light elements, e.g., Si, O, S, C, H, Mg. Mineral physics studies, in conjunction with seismological and cosmochemical observations, provide an opportunity to improve constraints on the composition of the core. In this thesis, we investigate the thermoelastic and vibrational properties of bcc- and hcp-structured Fe0.91Ni0.09 and Fe0.8Ni0.1Si0.1 (atomic percent) at high pressures.
\r\n\r\nWe present powder x-ray diffraction data on bcc- and hcp-structured Fe0.91Ni0.09 and Fe0.8Ni0.1Si0.1 at 300 K up to 167 GPa and 175 GPa, respectively. The alloys were compressed in diamond anvil cells, and their equations of state and axial ratios were measured with high statistical quality. These equations of state are combined with thermal parameters from previous reports to improve the extrapolation of the density, adiabatic bulk modulus, and bulk sound speed to the pressures and temperatures of Earth\u2019s inner core. We place constraints on the composition of Earth\u2019s inner core by combining these results with seismic observations and available data on other light-element alloys of iron. We find the addition of 4.3 to 5.3 wt% silicon to Fe0.95Ni0.05 alone can explain geophysical observations of density, adiabatic bulk modulus, and bulk sound speed at the inner core boundary, as can up to 7.5 wt% sulfur with negligible amounts of silicon and oxygen. Our findings favor an inner core with less than \u223c2 wt% oxygen and less than \u223c1 wt% carbon, although uncertainties in electronic and anharmonic contributions to the equations of state may shift these values.
\r\n\r\nSeismic studies provide evidence for an anisotropic inner core, which is suggested to be related to the ratio of the c- to a-unit cell parameters of hcp-structured materials. We demonstrate hcp-Fe0.91Ni0.09 and Fe0.8Ni0.1Si0.1 have measurably greater c/a axial ratios than those of hcp-Fe over the measured pressure range. We further investigate the relationship between the axial ratios, their pressure derivatives, and elastic anisotropy of hcp-structured materials.
\r\n\r\nNext, we present high pressure NRIXS data on bcc- and hcp-Fe0.91Ni0.09 and Fe0.8Ni0.1Si0.1 at 300 K with in situ x-ray diffraction. From these data, we determine the partial phonon density of states for each composition, and we systematically compare our results to iron. We constrain the Debye sound velocity from the low energy region of the phonon density of states. Using our previously determined equations of state for the same compositions, we constrain the compressional and shear sound velocities and shear moduli. At 300 K, we find that 9 at% nickel decreases the shear velocity of hcp-iron by \u223c6% and that silicon has a minimal effect on the shear velocity of hcp-Fe0.91Ni0.09. Thermal effects likely play a large role in the sound velocities of iron alloys at core conditions, so constraining these effects is critical to further constrain the composition of the core.
\r\n\r\nFrom the volume scaling of the phonon DOS, we find the 300 K vibrational components of the Gru\u0308neisen parameter for hcp-Fe0.91Ni0.09 and Fe0.8Ni0.1Si0.1 are very similar to that of hcp-Fe within uncertainties. We also constrain vibrational thermal pressure from the volume dependence of vibrational free energy, and we find negligible differences within uncertainty between the vibrational thermal pressures of hcp-Fe, Fe0.91Ni0.09, and Fe0.8Ni0.1Si0.1. By combining the vibrational component of thermal pressure with theoretical estimates of the anharmonic and electronic contributions, we provide an estimate for the total thermal pressure. We constrain a variety of additional parameters from the NRIXS data and phonon density of states, including the vibrational component of entropy, the vibrational thermal expansion, the vibrational kinetic energy, the Lamb-Mo\u0308ssbauer factor, and the vibrational specific heat.
" }, { "name": "Ruan, Xiaozhou", "degree": "PhD", "year": "2019", "title": "Oceanic Bottom Boundary Layers and Abyssal Overturning Circulation", "advisor": "Thompson, Andrew F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05302019-121137858", "creators": [ { "name": { "family": "Ruan", "given": "Xiaozhou" }, "id": "Ruan-Xiaozhou", "orcid": "0000-0003-1240-1584", "display_name": "Ruan, Xiaozhou" } ], "advisors": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "advisor", "display_name": "Thompson, Andrew F." } ], "committee": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "chair", "display_name": "Schneider, Tapio" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Callies", "given": "Joern" }, "id": "Callies-J", "orcid": "0000-0002-6815-1230", "role": "member", "display_name": "Callies, Joern" }, { "name": { "family": "McKeon", "given": "Beverley J." }, "id": "McKeon-B-J", "role": "member", "display_name": "McKeon, Beverley J." }, { "name": { "family": "Stewart", "given": "Andrew L." }, "id": "Stewart-A-L", "role": "member", "display_name": "Stewart, Andrew L." } ], "option_major": [ "envreng" ], "doi": "10.7907/6EZA-R251", "abstract": "The vast amount of carbon and heat exchange between the abyssal and upper ocean and subsequently the atmosphere is paced by the abyssal overturning circulation. A key component of the abyssal overturning circulation is the formation and consumption of the densest water mass on Earth, Antarctic Bottom Water (AABW), namely the conversion of North Atlantic Deep Water (NADW) to AABW and the consumption of AABW via small-scale diapycnal mixing. Yet, this pathway of AABW spanning thousands of kilometers has not been successfully reproduced in large-scale general circulation models (GCM). What is missing is essentially the understanding and resolution of small-scale physics involved in converting deep and bottom waters from one density class to another, the water mass transformation (WMT). In this thesis, we focus on small-scale (both in the horizontal and vertical directions) dynamics near the BBL, where enhanced shear, mixing and turbulence exist to facilitate effective WMT above the seafloor.
\r\n\r\nFrom high-resolution ocean glider observations around Antarctica, we find that a portion of Lower Circumpolar Deep Water, a branch of NADW, becomes lighter via mixing with light shelf water over the continental slope and shelf, instead of being converted into dense AABW under sea ice. This mixing is likely induced by submesoscale symmetric instability coming from a strong boundary current interacting with the sloping topography in the BBL. We then consider how to sustain the consumption of AABW in the global mid-ocean ridge system. Using numerical models, we show that submesoscale baroclinic eddies are crucial to maintaining strong stratification over the flanks of the mid-ocean ridges and thus permitting effective WMT. Lastly, we consider the interaction between external mean flows and stratified BBL over sloping topography. With the large-scale turbulence resolved in a large-eddy simulation model, we propose a new theoretical framework to describe the evolution of the BBL and the Eulerian advection of its associated stratification when external barotropic flows are present. This new framework can be used to parameterize bottom friction, important for closing the kinetic energy budget of the global ocean. We further extend this interaction to a horizontally-sheared and temporally-oscillating external mean flow and explore the response of the BBL and the BBL-interior mass exchange with simple turbulent parameterizations.
\r\n\r\nUsing a combination of different approaches, we confirm that the long-overlooked oceanic BBL is the key location for closing the abyssal overturning circulation. More importantly, without appropriate techniques to tackle the currently unresolved small-scale processes, they will likely remain a narrow bottleneck in understanding the abyssal overturning circulation.
" }, { "name": "Thomas, Nancy Helen", "degree": "PhD", "year": "2019", "title": "Remotely Sensing Aqueous Alteration on Mars: Innovative Statistical and Analytical Methods for Large Spectral Datasets", "advisor": "Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06072019-115333958", "creators": [ { "name": { "family": "Thomas", "given": "Nancy Helen" }, "id": "Thomas-Nancy-Helen", "orcid": "0000-0003-1989-4860", "display_name": "Thomas, Nancy Helen" } ], "advisors": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "plansci" ], "doi": "10.7907/8JFC-BY64", "abstract": "Liquid water once flowed on Mars and altered the crust. Aqueous minerals and salts record a rich history of aqueous processes and environmental changes. In this dissertation, I developed and applied innovative analytical and statistical methods to large spectral datasets to better characterize aqueous alteration on Mars. The Mars Science Laboratory (MSL) Curiosity rover is investigating the sedimentary sequence at Gale crater recording a potentially global transition from clay-enriched to sulfate-enriched rocks. Volatile elements like H and Cl are important for investigating aqueous processes but are difficult to quantify in the large ChemCam laser-induced breakdown spectroscopy (LIBS) dataset. In the first part of this dissertation, I measured aqueously altered samples with LIBS in the laboratory under Mars-relevant conditions to develop analytical methods for application to ChemCam. The Murray formation, the lowest exposed strata of the sedimentary sequence, contains 2.6 \u00b1 2.1 wt. % H2O. Carriers of H enrichment including clays, opal, Mg-sulfates, Ca-sulfates, hydrous Mn-oxides, akageneite, and jarosite are identified. Variability in the H content of the Murray formation records multiple aqueous alteration events as well as potential increases in salinity in the Gale crater lake. In the fourth chapter, I measured chlorine in Gale crater using multiple MSL instruments. Cl-enrichments correlated with increased Na2O are detected in the bedrock, in nodular textures, and at vein margins, indicating halite. The scattered, isolated occurrences of chlorides are consistent with late groundwater reworking and remobilization. Halite is concentrated in particular members of the Murray formation; the chlorides may have been emplaced as primary deposits in these members, consistent with varying salinity in the past lakewaters. In the second part of this dissertation, I adapted and applied semi-automated statistical methods called factor analysis and target transformation to the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) dataset to systematically search for hematite in stratified, candidate sedimentary outcrops. Few outcrops containing hematite are found and no obvious analogs to terrestrial iron formations are identified. Future studies will search for hematite in other geologic settings as well as other Fe-bearing phases such as Fe-phyllosilicates and Fe-sulfates to better characterize aqueous processes on Mars." }, { "name": "Viglione, Giuliana Augusta", "degree": "PhD", "year": "2019", "title": "Dynamics of Southern Ocean Mixed Layers", "advisor": "Thompson, Andrew F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06102019-132644524", "creators": [ { "name": { "family": "Viglione", "given": "Giuliana Augusta" }, "id": "Viglione-Giuliana-Augusta", "orcid": "0000-0002-2282-521X", "display_name": "Viglione, Giuliana Augusta" } ], "advisors": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "advisor", "display_name": "Thompson, Andrew F." } ], "committee": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "chair", "display_name": "Bordoni, Simona" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Sprintall", "given": "Janet" }, "id": "Sprintall-J", "role": "member", "display_name": "Sprintall, Janet" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." } ], "option_major": [ "envreng" ], "doi": "10.7907/CYRK-SB71", "abstract": "While it is often conceptualized in a spatially and/or temporally averaged sense, the mixed layer depth of the global ocean exhibits significant variability in both space and time. The mixed layer plays a key role in controlling the exchange of heat and gases between the atmosphere and the ocean interior; an inaccurate portrayal of mixed layer depths can be a major source of error in global climate models. In particular, the Southern Ocean, or the waters around Antarctica, take up a significant portion of anthropogenically released carbon dioxide and subduct it into the deep ocean, affecting global climate on both relatively short and glacial timescales. Variability in the mixed layer also affects the formation and subduction of mode waters, the partitioning of waters between the upper and lower overturning cells, and biological productivity. The stratification of the mixed layer is significantly modified by submesoscale dynamics, which are not resolved in current state-of-the-art climate models. The parameterization of these dynamics represents a large source of uncertainty, and better observations and a better understanding of the submesoscale can be used to improve climate predictions.
\r\n\r\nIn this work, the variability of Southern Ocean mixed layers is examined using both numerical and observational methods. General circulation model output is combined with a simple advection scheme to examine upwelling pathways, mixed layer residence times, and air-sea equilibrium in the Southern Ocean. Virtual Lagrangian drifters are released around the basin and tracked as they outcrop into the mixed layer, where they can exchange properties with the atmosphere. These studies are combined with high-resolution observations of mesoscale and submesoscale dynamics in the Southern Ocean, which play a leading order role in setting the stratification of the mixed layer. Seaglider data are used to construct potential vorticity fields, which are used to identify possible instances of different submesoscale instabilities in Drake Passage. Seasonal and zonal mixed layer variability are also examined using these observations. A second set of Seaglider observations are used to diagnose changes in ventilation and eddy stirring on sub-seasonal timescales at the Polar Front, one of the major fronts of the Southern Ocean. This thesis aims to expand current knowledge of mixed layer dynamics, especially at the submesoscale, and examine their implications for global circulation and climate.
" }, { "name": "Witkosky, Rebecca Amber", "degree": "PhD", "year": "2019", "title": "Tectonics in Nevada and Southern California: Subsidence of the Ediacaran Johnnie Formation, Cumulative Offset Along the Lavic Lake Fault, and Geomorphic Surface Development Along the Southern San Andreas Fault", "advisor": "Stock, Joann M.; Wernicke, Brian P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01172019-113222535", "creators": [ { "name": { "family": "Witkosky", "given": "Rebecca Amber" }, "id": "Witkosky-Rebecca-Amber", "display_name": "Witkosky, Rebecca Amber" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "advisor", "display_name": "Wernicke, Brian P." } ], "committee": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "chair", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geol" ], "doi": "10.7907/XTZX-X107", "abstract": "While we know the ages and tectonic histories of many critical geologic events in the history of the Earth, there are still questions regarding the timing of key events and structures that have and continue to influence life on this planet. This thesis includes three separate studies in Nevada and southern California: two potential new methods for measuring/organizing geologic time, and also an analysis of the long-term displacement along an active fault in the eastern California shear zone. In Chapter II, we used tectonic subsidence modeling to find that the Shuram carbon isotopic excursion in the Ediacaran Johnnie Formation likely occurred from 585-579 Ma, and that incision of the Rainstorm Member shelf occurred during the 579 Ma Gaskiers glaciation. The pre-Shuram-excursion chemostratigraphic carbon isotope profiles from the Khufai Formation in Oman and the type locality of the Johnnie Formation in Nevada are both generally positive and therefore possibly correlative. In Chapter III, we determined the cumulative tectonic offset along the Lavic Lake fault, an active structure that ruptured with >5 m of coseismic slip in the 1999 Mw 7.1 Hector Mine earthquake. We calculated a net slip of 960 +70/-40 m, based on the slip vector formed by a vertically separated lithologic contact and a horizontally separated older cross fault. The net slip we calculated is significantly less than a previous estimate that was based on an offset magnetic gradient, a disparity that may be explained by considering off-fault deformation, as well as the unknown depth and nature of the source of the magnetic contrast. In Chapter IV, we explored using a new method for the relative dating of Quaternary geomorphic surfaces, which is based on the positive correlation between increased spectral contrast in thermal hyperspectral airborne imagery and surface age. With field data, we found that desert varnish scores, desert pavement scores, and vegetation spacing estimates also correlate positively with surface age, implying that these factors could contribute to the increased spectral contrast in airborne remote sensing spectra. Additionally, the general increase in the band depth of airborne spectra at 9.16 \u03bcm could be due to increasing clay mineral abundance in progressively heavier desert varnish coatings on older surfaces. The positive correlation observed in this study between surface age and spectral contrast in airborne spectra can perhaps be used to develop a method for relative dating of varnished geomorphic surfaces elsewhere. All of the chapters in this thesis are broadly related by the concepts of geologic time and tectonic activity, which are two aspects of modern geology that are intrinsic to the science as a whole.
" }, { "name": "Bowden, Daniel Craig", "degree": "PhD", "year": "2018", "title": "The Propagation and Amplification of Surface Waves", "advisor": "Tsai, Victor C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04222018-154136913", "creators": [ { "name": { "family": "Bowden", "given": "Daniel Craig" }, "id": "Bowden-Daniel-Craig", "orcid": "0000-0003-3332-5146", "display_name": "Bowden, Daniel Craig" } ], "advisors": [ { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "orcid": "0000-0003-1809-6672", "role": "advisor", "display_name": "Tsai, Victor C." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "orcid": "0000-0003-1809-6672", "role": "member", "display_name": "Tsai, Victor C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9DR2SPR", "abstract": "The observation of surface waves from cross-correlations of ambient noise has proven to be an invaluable tool for the recovery of seismic travel times. Such techniques allow the construction of 3D velocity models and subsequent geologic interpretations in regions where tomography would otherwise be difficult due to the paucity of seismicity and short seismic array deployment times. One such model is developed here for offshore southern California using an array of Ocean Bottom Seismometers to better understand the tectonic history of the region.
\r\n\r\nHowever, for accurate hazard evaluation, characterizations of the spatial variability of ground motion amplitudes are also desired. Unfortunately, the amplitudes from noise cross-correlations are systematically biased by the spatial-, frequency- and temporal variability of noise sources. We demonstrate in this thesis that an ambient-noise based wavefront tracking technique using an array of stations can recover site-amplification and attenuation estimates successfully and robustly. This is applied on two different scales: to a very dense array of more than 5,000 geophones in the city of Long Beach, CA, and in a broader, continental scale to instruments from the USArray.
\r\n\r\nFinally, we discuss the propagation of surface waves in relation to seismic hazard and site characterization. We point out that the amplitude response and peak frequency of ground motion will be different for a given site, depending on the type of wave being considered. This work should be considered by any future seismic hazard evaluation where surface waves may cause damage.
\r\n" }, { "name": "Buhler, Peter Benjamin", "degree": "PhD", "year": "2018", "title": "Measuring and Modeling the Interplay between Planetary Orbits, Interiors, Surfaces, and Atmospheres", "advisor": "Ingersoll, Andrew P.; Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05312018-155112365", "creators": [ { "name": { "family": "Buhler", "given": "Peter Benjamin" }, "id": "Buhler-Peter-Benjamin", "orcid": "0000-0002-5247-7148", "display_name": "Buhler, Peter Benjamin" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "co-advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "chair", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "member", "display_name": "Tsai, Victor C." } ], "option_major": [ "plansci" ], "doi": "10.7907/MEXZ-2586", "abstract": "Typically, we only have access to observations that directly probe the instantaneous state of a planet. However, these instantaneous properties are often set by the long-term interplay between several aspects of the planet. I thus use quantitative models of the interactions between the orbital, interior, surface, and atmospheric evolution in the case of three planetary bodies (Mars, Pluto, and the extrasolar planet HAT-P-13b) to gain insight into the underlying physical processes that govern the evolution of planets.
\r\n\r\nIn chapter 2, the interplay between the interior structure and orbital evolution of the gas giant exoplanet HAT-P-13b allows measurements of its orbit to reveal its interior structure. I use telescopic observations of HAT-P-13b to measure its orbit and thus determine its core mass.
\r\n\r\nIn chapter 3, cell-shaped landforms on Sputnik Planitia, the surface of a vast deposit of nitrogen ice covering 5% of Pluto\u2019s surface, are the surface expression of convection within the nitrogen ice that is driven by heat flow from Pluto\u2019s interior. The cells have sublimation pits on them, with smaller pits near their centers and larger pits near their edges. Using a simple model, I calculate the sublimation rate of these pits, which allows the determination of a size-age relationship. I then use the spatial size distribution of pits on cells to calculate their convection rate, which constrains the plutonian heat flow and thus the interior properties of Pluto.
\r\n\r\nIn chapter 4, the interplay of condensation and sublimation between the surface and atmosphere of Mars create a baffling array of uniquely martian morphologies carved into the martian residual south polar CO2 cap (RSPC). Using a multi-year baseline of high-resolution observations to track the evolution of these morphologies, I build a self-consistent conceptual framework capable of explaining the basic mechanisms that give rise to the diversity of landforms that make up the RSPC.
\r\n\r\nIn chapter 5, the secular evolution of Mars' orbit drives the evolution of the equilibrium relationship between the martian atmospheric pressure and the large CO2 ice deposit on the martian south polar cap. I construct the first self-consistent conceptual framework capable of predicting the existence and form of the martian residual south polar cap and the buried CO2 deposit. I then use this framework to compute the secular pressure history of Mars.
\r\n\r\nTogether, the results of these investigations provide new perspective into the fundamental processes driving the formation and evolution of planetary bodies.
\r\n" }, { "name": "Buz, Jennifer", "degree": "PhD", "year": "2018", "title": "Macro Mars to Micro Mars: Mapping Minerals and Magnetization", "advisor": "Ehlmann, Bethany L.; Kirschvink, Joseph L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05242018-144308725", "creators": [ { "name": { "family": "Buz", "given": "Jennifer" }, "id": "Buz-Jennifer", "orcid": "0000-0002-0491-2686", "display_name": "Buz, Jennifer" } ], "advisors": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "co-advisor", "display_name": "Kirschvink, Joseph L." } ], "committee": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "chair", "display_name": "Lamb, Michael P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." } ], "option_major": [ "geol" ], "doi": "10.7907/Z6EH-M526", "abstract": "Combination of remote sensing data with in-situ measurements provides a fuller understanding of Mars phenomena. This dissertation focuses on integrating macroscopic and microscopic scales of measurement with regard to spectroscopy and magnetization. In the first chapter high resolution orbital spectroscopy (~18 m/px) and imagery (~30 cm/px) are used to identify potential sources for some of the sedimentary rocks investigated by the Curiosity rover and expand the accessible stratigraphy. While we find mineralogies in common outside and inside the crater as well as transport mechanisms, we conclude that additional sedimentary sources and/or modification after transport are required to explain chemical differences and that strata point to multiple episodes of a lake in Gale crater. In the third chapter we conducted a laboratory photometric study on candidate calibration target materials for the Mars-2020 rover. We characterized these target materials for proper calibration and monitoring of the Mastcam-Z instrument to enable mineral identification through reflectance spectroscopy. The fourth and fifth chapters focus on the microscopic magnetizations found within Martian meteorite ALH84001. Chapter four reports on paleomagnetic experiments conducted on isolated carbonate crystals which contain magnetite previously reported to be biogenic. We compare paleomagnetic test results which distinguish between biogenic and abiogenic origin hypotheses and find that the magnetization within the carbonates is most consistent with a shock processes. In chapter five we analyzed the distribution of dipoles within slices of ALH84001 and determined that they lie in a girdle distribution which could be interpreted as resulting from a true polar wander event on Mars. Looking at kilometer scale observations outside of Gale enlightened observations made along the rover transverse path. A high resolution laboratory analysis of calibration materials will enable future multispectral mineralogical explorations. Microscopic analyses of magnetization inform ancient surface processes on Mars and hint at large-scale global change. In each of these chapters our results were only made possible or greatly enhanced by the combination of data sources and scales.
" }, { "name": "Hines, Sophia Katharine Vizza", "degree": "PhD", "year": "2018", "title": "Glacial Ocean Dynamics: Insight from Deep-Sea Coral Reconstructions and A Time-Dependent Dynamical Box Model", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10242017-152242759", "creators": [ { "name": { "family": "Hines", "given": "Sophia Katharine Vizza" }, "id": "Hines-Sophia-Katharine-Vizza", "orcid": "0000-0001-9357-6399", "display_name": "Hines, Sophia Katharine Vizza" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "chair", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "geochem" ], "doi": "10.7907/Z9RF5S72", "abstract": "Glacial-interglacial cycles, occurring at a period of approximately 100,000 years, have dominated Earth's climate over the past 800,000 years. These cycles involve major changes in land ice, global sea level, ocean circulation, and the carbon cycle. While it is generally agreed that the ultimate driver of global climate is changes in insolation, glacial cycles do not look like insolation forcing. Notably, there is a highly non-linear warming response at 100,000 years to a relatively small forcing, implicating a more complicated system of biogeochemical and physical drivers. The ocean plays a pivotal role in glacial-interglacial climate through direct equator-to-pole transport of heat and its role in the carbon cycle. The deep ocean contains 60 times more carbon than the atmosphere, and therefore even small changes in ocean circulation can have a large impact on atmospheric CO2, a crucial amplifier in the climate system. In order to better understand the role that ocean circulation plays in glacial-interglacial climate we focus on the last glacial-interglacial transition. In this thesis, we present reconstructions of changes in intermediate water circulation and explore a new time-dependent dynamical box model. We reconstruct circulation using radiocarbon and clumped isotope measurements on U/Th dated deep-sea corals from the New England and Corner Rise Seamounts in the western basin of the North Atlantic and from south of Tasmania in the Indo-Pacific sector of the Southern Ocean. Our new time-dependent model contains key aspects of ocean physics, including Southern Ocean Residual Mean theory, and allows us to explore dynamical mechanisms which drive abrupt climate transitions during the last glacial period.
\r\n\r\nIn Chapter 2 we present a compilation of reconnaissance dated deep-sea corals from the Caltech collection. Reconnaissance dating facilitates sample selection for our high-precision radiocarbon and temperature time series and patterns in the depth distribution of deep-sea corals over time contain additional relevant climate information. In Chapter 3, we present a high-resolution radiocarbon record from south of Tasmania which highlights variability in Southern Ocean Intermediate Water radiocarbon during the deglaciation, particularly during the Antarctic Cold Reversal. We use our radiocarbon data, in combination with other deglacial climate records, to infer changes in overturning circulation configuration across this time interval. In Chapter 4 we present our time-dependent dynamical box model. Our model displays hysteresis in basin stratification and Southern Ocean isopycnal outcrop position as a function of North Atlantic Deep Water formation rate. In a dynamical system, hysteresis implies that there are multiple stable states, and switches between these states can lead to abrupt transitions, such as those observed during the middle of the last glacial period. In Chapter 5 we present paired radiocarbon and temperature time series from the North Atlantic and Southern Ocean spanning the late part of the last glacial. We explore the mechanisms driving trends in radiocarbon and temperature by looking at cross-plots of the data, and we make inferences about changes in circulation configuration using insight gained from our dynamical box model.
" }, { "name": "Kopparla, Pushkar", "degree": "PhD", "year": "2018", "title": "Exoplanetary Atmospheric Characterization Using Polarimetry and Other Radiative Transfer Modeling Problems", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04282018-222603635", "creators": [ { "name": { "family": "Kopparla", "given": "Pushkar" }, "id": "Kopparla-Pushkar", "orcid": "0000-0002-8951-3907", "display_name": "Kopparla, Pushkar" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/bc0z-ej27", "abstract": "This thesis deals with a pair of current problems with the remote sensing of planetary atmospheres. First is the modeling of polarization of scattered light from the atmospheres of exoplanets. With the first such observations becoming possible in the last year, there is a need to understand what these measurements actually mean. To that end, we developed families of radiative transfer models that simulate polarized phase curves for different atmospheric scenarios on hot Jupiters. These models were then used in the interpretation of scattered light from HD 189733b and WASP 12b, two hot Jupiter exoplanets, to determine their albedos and gauge what type of scattering particles might be present in their atmospheres. The last part of this half deals with observing oceans on distant Earth-like exoplanets using polarization from glint off the water surface. Though this measurement is not possible with current telescopes, but it may become accessible in the next decade with a slew of high powered ground and space telescopes in the pipeline.
\r\n\r\nThe second half of the thesis is devoted to the development of a fast radiative transfer model. The goal of this model is to be able to process the massive amounts of data coming in from Earth observing satellites such as GOSAT and OCO-2 in a timely and accurate manner. We refined the principal component analysis based fast radiative transfer model to be accurate enough to retrieve carbon dioxide concentrations to the part per million accuracy that is necessary to track spatial and temporal changes in this important greenhouse gas.
" }, { "name": "Lloyd, Max Kaufmann", "degree": "PhD", "year": "2018", "title": "Clumped and Intramolecular Isotopic Perspectives on the Behavior of Organic and Inorganic Carbon in the Shallow Crust and Deep Biosphere", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01312018-211454203", "creators": [ { "name": { "family": "Lloyd", "given": "Max Kaufmann" }, "id": "Lloyd-Max-Kaufmann", "orcid": "0000-0001-9367-2698", "display_name": "Lloyd, Max Kaufmann" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/Z96T0JV5", "abstract": "Although the upper crust is the most accessible swath of the subsurface, the geochemical processes therein are challenging to observe. Here, I use site-specific and \u2018clumped\u2019 isotope analyses (where multiple rare, heavy isotopes are bound in single molecules) of carbonates and organic solids to explore petrology, brittle tectonics, diagenesis, and biodegradation in the shallow crust. In carbonates, I employ contact aureoles, regional metamorphic terranes, thermal and geochemical models, and high-pressure experiments, to extract nuanced thermal and chemical histories. In the organic realm, I develop new methods to measure the clumped 13C \u2013 2H composition of methoxyl groups (R \u2013 O \u2013 CH3) from kerogen, lignin, and other complex organic substrates. This work expands the field of clumped isotope geochemistry into the realm of solid compounds, and enables new, site-specific isotopic perspectives on the shallow crustal transformations of organic carbon substrates and the microbial assemblages that live on them.
" }, { "name": "Luo, Yingdi", "degree": "PhD", "year": "2018", "title": "Earthquake Moment-Area Scaling Relations and the Effect of Fault Heterogeneity on Slow to Fast Earthquake Slip", "advisor": "Ampuero, Jean-Paul", "url": "https://resolver.caltech.edu/CaltechTHESIS:09062017-132833234", "creators": [ { "name": { "family": "Luo", "given": "Yingdi" }, "id": "Luo-Yingdi", "orcid": "0000-0002-1165-6107", "display_name": "Luo, Yingdi" } ], "advisors": [ { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "advisor", "display_name": "Ampuero, Jean-Paul" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9SQ8XMV", "abstract": "Earthquake moment-area scaling relations play a key role in both earthquake physics studies and earthquake hazard assessment. A three-stage moment-area relation, based on advances in earthquake source inversion, is currently in use in Japan. The second stage has a scaling exponent outside the range of commonly accepted models of small and very large earthquakes. We develop theoretical insight on the mechanical origin of this second-stage scaling. We utilize an analytical dislocation model, a numerical crack model and multi-cycle rate-and-state simulations of strike-slip faults with heterogeneous friction properties. We find that the second stage in earthquake moment-area scaling results from a combination of surface rupture effects, comprising an effective rupture elongation along-dip due to a mirror effect and systematic changes of the shape factor relating slip to stress drop. Based on this physical insight, we propose a simplified formula to account for these effects in moment-area scaling relations.
\r\n\r\nGeological, seismological, geodetic and experimental studies provide evidence of the heterogeneous structure of natural faults. To advance our understanding of the mechanical role of fault heterogeneity on the diversity of earthquake slip behavior, we conduct a theoretical and computational study of heterogeneous fault models. We consider faults with a mixture of frictionally stable and unstable materials and spatial contrasts of fault zone pore fluid pressure, akin to hydraulically sealed brittle asperities embedded in a ductile fault zone matrix. We first study faults with a regular alternation of materials, using linear stability analysis and quasi-dynamic rate-and-state simulations. We find transitions in fault behavior from fast to slow earthquakes to steady slip, and determine how these transitions depend on the composition and strength contrast of the material mixture. Based on these results, we develop rate-and-state models with stochastic distributions of brittle asperities in a ductile matrix to study slow slip and tremor phenomena. We focus on the hierarchical patterns of tremor migration observed in subduction zones, which feature distinct tremor propagation speeds in different directions. Our models are in quantitative agreement with observations of episodic slow slip and tremor events in Cascadia. We discovered that, in contrast to a common view, slow slip might well be a result of tremor activity rather than its cause. The collective interaction of asperities with a broad range of material properties, mediated by creep, is a novel and robust mechanism for the generation of slow slip events. We find that the hierarchical patterns of tremor migration and the nucleation locations of tremor swarms provide constraints on fault rheology. Our study also shows that, despite multiple asperity interactions, there is a close relation between tremor rate and the underlying slip rate which supports an approach to constrain slow slip rate via observed tremor rates.
" }, { "name": "Mai, Huajun", "degree": "PhD", "year": "2018", "title": "Scanning Electrical Mobility Methods for Aerosol Characterization", "advisor": "Flagan, Richard C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272018-093411980", "creators": [ { "name": { "family": "Mai", "given": "Huajun" }, "id": "Mai-Huajun", "orcid": "0000-0002-0616-1986", "display_name": "Mai, Huajun" } ], "advisors": [ { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "advisor", "display_name": "Flagan, Richard C." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "member", "display_name": "Flagan, Richard C." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" } ], "option_major": [ "envreng" ], "doi": "10.7907/9D4H-QS44", "abstract": "The scanning electrical mobility measurement is the most common tool used to characterize the size distribution of fine particles in the atmosphere. This thesis develops the methods for retrieving the particle size distribution from scanning electrical mobility measurement data for two systems: (1) the scanning electrical mobility spectrometer (SEMS; also known as the scanning mobility particle sizer, SMPS), which measures particle size distribution ranging from 15 - 1000 nm; (2) the scanning radial opposed migration ion and aerosol classifier (ROMIAC) system, which uses a two-stage condensation particle counter as particle detector to complete the 1 - 20 nm particle size distribution measurements.
\r\n\r\nSEMS / SMPS data have traditionally been inverted to determine the particle size distribution by solving a Fredholm integral equation in which the kernel function is based upon constant-voltage operation of the mobility classifier. The viscous boundary layer within the classifier renders that model invalid. This thesis determines, for the first time, the transfer function for a real differential mobility analyzer (DMA) that is operated in the scanning mode. The flow and electric fields within the instrument were obtained by finite element simulations taking into account its detailed geometry. Brownian dynamics simulations were then used to simulate diffusive particle trajectories within the instrument as the voltage was scanned. There results were coupled with empirically-derived response-time functions for the condensation particle counter that serves as a detector in the SEMS / SMPS to obtain integrated system transfer function that substantially improve the fidelity of the SEMS / SMPS data inversion.
\r\n\r\nThis approach was also applied to adaptation of the radial opposed migration ion/aerosol classifier (ROMIAC) for scanning-mode operation. The transfer function obtained through simulation of the scanning ROMIAC was used in the experimental validation of this new measurement method. This new instrument was then used to measure wall loss rates for 1.6 nm to 20 nm particles in the Caltech environmental chamber.
" }, { "name": "Perry, Stephen Michael", "degree": "PhD", "year": "2018", "title": "Analyzing Stress Change and Energy Budget of Earthquakes Through Physics-Based Modeling", "advisor": "Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechTHESIS:06062018-071106334", "creators": [ { "name": { "family": "Perry", "given": "Stephen Michael" }, "id": "Perry-Stephen-Michael", "orcid": "0000-0003-1748-1827", "display_name": "Perry, Stephen Michael" } ], "advisors": [ { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "chair", "display_name": "Tsai, Victor C." }, { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "role": "member", "display_name": "Zhan, Zhongwen" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" } ], "option_major": [ "geophys" ], "doi": "10.7907/ryht-eb75", "abstract": "Researchers use concepts such as stress drop, breakdown energy, and available energy to describe earthquakes sources and study earthquake physics. These quantities represent the spatially and temporally varying dynamic events by single, event-averaged values. They are inferred indirectly from observations, often based on simplified models. Thus, their relationship to fault constitutive properties, which are local on the fault, is not straightforward.
\r\n\r\nHere, we use simulations of earthquake sequences in fault models with friction laws motivated by laboratory experiments to examine how the event-averaged observables arise from spatially and temporally varying earthquake rupture. In particular, we consider whether several typically used fault mechanisms, such as rate-and-state friction, thermal pressurization of pore fluids, and flash heating, are consistent with common observations such as magnitude-invariant stress drop, increasing breakdown energy with the event size, and radiation efficiencies of ~0.5.
\r\n \r\nStress drops, observed to be magnitude invariant, are a key characteristic used to describe natural earthquakes. Theoretical studies and lab experiments indicate that dynamic weakening, such as thermal pressurization of pore fluids, may be present on natural faults. At first glance, these two observations seem incompatible, since larger events may experience greater weakening and should thus have lower final stresses. We hypothesize that dynamic weakening can be reconciled with magnitude-invariant stress drops due to larger events having lower average prestress when compared to smaller events. The additional weakening would allow the final stresses to also be lower, but the stress drops may be similar.
\r\n\r\nTo explore this hypothesis, we study long-term earthquake sequences on a rate-and-state fault segment with enhanced dynamic weakening due to thermal pressurization using a fully dynamic simulation approach with a seismogenic segment that has uniform friction properties. Our results show, for a range of event sizes, that such models can explain both observationally inferred stress drop invariance and breakdown energy increase with event magnitude. Smaller events indeed have larger average initial stresses than medium-sized events, and we get nearly constant stress drops for events spanning up to five orders of magnitude in seismic moment. Segment-spanning events have more complex behavior, which is dependent on the properties of the velocity-strengthening (VS) region at the edges of the fault. Models with large values of velocity strengthening in their boundary regions do not allow ruptures to propagate much into the velocity-strengthening region, thus containing the rupture area and leading to higher stress drops for a larger amount of slip. Decreasing the velocity strengthening of the boundaries leads to farther rupture propagation into the velocity-strengthening region and thus lower stress drops.
\r\n\r\nIn all models with the thermal pressurization of pore fluids that we have examined, both the smaller and segment-spanning events exhibit increases in breakdown energy consistent with observations. The breakdown energy is the portion of the dissipated energy that governs the event dynamics, analogous to the fracture energy concept of fracture mechanics. The increase in the breakdown energy is due to continuous weakening of the fault with slip, as hypothesized in previous analytical studies.
\r\n\r\nWe also examine the accuracy of seismically estimated breakdown energies GSE for a range of models, by comparing the values computed directly from our fault models and indirectly from seismically available observations. Observationally, GSE is typically obtained as the difference between the seismically estimated available energy \u0394W0 per unit area and radiated energy ER. This defines the available energy \u0394WA as the sum of the breakdown energy and radiated energy. However, the seismically estimated available energy \u0394W0 is obtained as one-half of the product of the (average) stress drop and (average) final slip, based on a simplified model. As such, we examine the relation between the actual available energy \u0394WA and its seismic estimate \u0394W0 in our models. We find that, as rupture mode changes from crack-like to pulse-like, the actual available energy \u0394WA, becomes increasingly larger that the seismically estimated available energy \u0394W0, due to significant and increasing stress undershoot characteristic of pulse-like ruptures. The extra available energy for more pulse-like ruptures either makes the breakdown energy much larger than its seismically estimated value, or makes the radiated energy much larger than the seismically estimated available energy \u0394W0, or both. In the two latter cases, the radiation ratio \u03b7 (sometimes called radiation efficiency) between the radiated energy and seismically estimated available energy increases beyond 1, consistent with some observations that were previously thought to be aphysical.
\r\n\r\nOverall, we find that models with rate-and-state friction and thermal pressurization of pore fluids, when resulting in continuous weakening of fault with slip and crack-like ruptures, produce events with magnitude-invariant stress drops, increases in breakdown energies with the event sizes consistent with observations, radiation ratios consistent with observations, and available energies similar to the ones inferred seismically. More pulse-like ruptures, which result occasionally in such models and reliably in models that incorporate more severe enhanced weakening motivated by flash heating, have increasingly more significant undershoot and hence extra energy available for breakdown and radiation compared with the seismically estimated available energy. Therefore, current seismic estimates of their breakdown energy and radiation ratio are not reliable. More work is needed to understand the energy budget of pulse-like events obtained in realistic fault models, especially since one of the common paradigms in earthquake physics is that many large events occur as pulse-like ruptures.
" }, { "name": "Piskorz, Danielle F.", "degree": "PhD", "year": "2018", "title": "Exploring Exoplanets' Spectroscopic Secrets: Clues on the Migration and Formation of Hot Jupiters", "advisor": "Knutson, Heather A.; Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09122017-074006746", "creators": [ { "name": { "family": "Piskorz", "given": "Danielle F." }, "id": "Piskorz-Danielle-F", "orcid": "0000-0003-4451-2342", "display_name": "Piskorz, Danielle F." } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "co-advisor", "display_name": "Knutson, Heather A." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "co-advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Hillenbrand", "given": "Lynne A." }, "id": "Hillenbrand-L-A", "role": "member", "display_name": "Hillenbrand, Lynne A." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9222RZX", "abstract": "Before the mid-90's, scientists' theories for planet formation were finely-tuned to explain the existence of our own Solar System. These theories were thrown into disarray when astronomers began to discover exoplanets, or planets in other solar systems. Forced to reconcile theory with observation, astronomers and planetary scientists have worked together for the past twenty years to solve the puzzles created by these thousands of exoplanets. One particularly intriguing group of newly-discovered planets were the hot Jupiters, planets the size of our Jupiter orbiting their host star every few days. This thesis details two observational campaigns that attempt to illuminate the origin and composition of hot Jupiters. Each project is powered by the NIRSPEC (Near-Infrared SPECtrometer) instrument located at Mauna Kea in Hawaii. The first project aims to determine the stellar multiplicity rate of hot Jupiter host stars. Such a metric can inform the migration histories of these planets. The second project treats a hot Jupiter and its host star as a spectroscopic binary. This treatment reveals the orbital elements and atmospheric composition of the hot Jupiter. The spectroscopic methods described in this thesis are small steps in the study of hot Jupiters and ultimately potentially habitable exoplanets." }, { "name": "Present, Theodore Michael", "degree": "PhD", "year": "2018", "title": "Controls on the Sulfur Isotopic Composition of Carbonate-Associated Sulfate", "advisor": "Adkins, Jess F.; Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04042018-153105432", "creators": [ { "name": { "family": "Present", "given": "Theodore Michael" }, "id": "Present-Theodore-Michael", "orcid": "0000-0002-4747-2174", "display_name": "Present, Theodore Michael" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "co-advisor", "display_name": "Adkins, Jess F." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "co-advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "orcid": "0000-0002-3174-5190", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geochem" ], "doi": "10.7907/6SFR-EX25", "abstract": "Sulfate in the modern ocean has a homogenous concentration and sulfur isotopic composition. It is well-mixed because rivers and mantle degassing deliver small amounts relative to its mass in the ocean. A similar small amount of sulfate is removed as biologic, sedimentary, and hydrothermal processes oxidize and reduce sulfur, carbon, and iron. These sulfur fluxes may have changed along with the carbon and oxygen cycles during ancient evolutionary, extinction, climatic, and tectonic transitions. The changing budget of marine sulfate is therefore key to understanding biogeochemical processes that control Earth\u2019s surface environment. The sulfur isotopic composition of marine sulfate reflects the proportion of sulfur partitioned into reduced minerals, especially pyrite, in marine sediments and weathering rocks.
\r\n\r\nIn this thesis, I examine how the sulfur isotopic compositions of ancient oceans is recorded in the sedimentary rock record and examine local and global effects on the sulfur isotopic composition of Paleozoic and the Mesoproterozoic sedimentary rocks. Carbonate minerals form in many depositional environments throughout Earth history and their chemical compositions relate to that of the fluid in which they formed. Much of my thesis focuses on the sulfur isotopic composition of minor amounts of sulfate incorporated into calcite, dolomite, and aragonite called carbonate-associated sulfate. Unpacking the local biogeochemical processes and global budgets affecting the sulfur isotopic composition of ancient carbonates enriches and clarifies the paleoenvironmental information preserved in the sedimentary record.
\r\n\r\nChapter 1 is a compilation and critical comparison of proxy records of the sulfur isotopic composition of Phanerozoic seawater sulfate. I compared data from marine evaporites, barite, and carbonate-associated sulfate and showed where each record is prone to biases and which processes create variance. Only carbonate-associated sulfate data fills critical periods of biogeochemical change, but it is the most susceptible to sources of variance other than passively recording the composition of ancient oceans. However, this additional variance reflects changes in the biogeochemical processes during early diagenesis in penecontemporaneous sediments, which are the locus of the pyrite burial and sulfide reoxidation fluxes pulling on the global sulfur budget.
\r\n\r\nChapter 2 utilizes a recently-developed analytical technique to compare the carbonate-associated sulfate of diagenetic carbonates and primary marine biogenic carbonates from latest Ordovician and earliest Silurian strata on Anticosti Island, Quebec. These samples span the duration of the Hirnantian Stage glaciation of Gondwana, which coincided with and possibly caused the Late Ordovician Mass Extinction. Much of the variance observed in bulk carbonate-associated sulfate is imparted during early diagenesis and burial diagenesis, and the best-preserved calcite from ancient brachiopods faithfully reflects seawater\u2019s sulfur isotopic composition. Seawater sulfate\u2019s isotopic composition did not change during the glaciation and extinction, supporting prior constraints on the mass of the marine sulfate reservoir and the magnitude of sulfur flux changes.
\r\n\r\nIn Chapter 3, we extended the record of seawater sulfate\u2019s sulfur isotopic composition from well-preserved brachiopod calcite from the Cincinnati Arch, Indiana-Ohio-Kentucky and Gotland, Sweden. We demonstrated that marine sulfate likely remained globally well-mixed with a constant isotopic composition for at least 30 Myr, from the earliest Late Ordovician through the late Silurian. The ocean\u2019s sulfur isotope composition likely changed little during multiple biotic crises, periods of basin restriction, oceanographic circulation changes, and sea level and climate changes. However, the first replicate carbonate-associated sulfate measurements of individual brachiopods indicate that even the best-preserved calcite is prone to diagenetic alteration that may obscure small changes in the ocean sulfate budget.
\r\n\r\nExquisitely-preserved biogenic calcite is rare in the rock record and absent in Precambrian strata, but bulk limestones and dolomites may record changes in the composition of ancient oceans. Chapter 4 compares the sulfur isotopic composition of carbonate-associated sulfate from limestones and dolostone deposited in peritidal to basinal environments on the Capitan Reef carbonate platform in the Guadalupe Mountains, west Texas. Rocks formed in different environments at the same time have carbonate-associated sulfate with different sulfur isotope compositions. Carbonate-associated sulfate is incorporated into bulk limestone and dolostone during early marine diagenesis, and its sulfur isotopic composition reflects the diagenetic and depositional environment. Carbonates recrystallizing in low-energy environments may incorporate marine pore fluids whose sulfur isotopic compositions evolved by the action of microbial sulfate reducing organisms. The sulfur isotopic composition of rocks deposited in high-energy environments, however, reflects that of seawater sulfate because the diagenetic fluid is open to the ocean and has the same sulfur isotopic composition of seawater. Later meteoric and burial diagenetic processes to which other geochemical tracers, such as carbon and oxygen isotopes, are sensitive do not greatly affect carbonate-associated sulfate. Thus, a record of the evolution of the sulfur, carbon, and oxygen isotopic composition of ancient oceans cannot come from the same sedimentary archives.
\r\n\r\nChapter 5 considers the range of hydrothermal and sedimentary reactions that fractionate sulfur isotopes to understand the origin of unusual millimeter-scale pyrite tubes associated with a Mesoproterozoic massive sulfide deposit in the Newland Formation, Belt Supergroup, Meagher County, Montana. The petrography and sedimentology of the tubes indicates that they formed on the seafloor or in the uppermost unlithified sediments from the effluence of metalliferous fluids into euxinic seawater. The texture-specific sulfur isotopic compositions of diagenetic barite, carbonate-associated sulfate, and diagenetic and hydrothermal pyrite indicates that there was an active microbial sulfate reducing community in the sediments and possibly colonizing the vents. A dynamic set of oxidation and reduction interactions between hydrothermal fluids and seawater were controlled by this community, leading to the novel morphology and texture of vent structures.
\r\n\r\nThis work indicates that combining sedimentological and petrographic observations with sulfur isotope data can constrain a wide range of biogeochemical processes. It guides future sulfur geochemical examination of parts of the rock record, especially the Precambrian, with few traditional archives of ancient seawater sulfate\u2019s chemistry. Information on both local and global controls on the sulfur isotopic composition of carbonate-associated sulfate, barite, and pyrite helps to resolve paleoenvironmental change.
" }, { "name": "Quinn, Daven Patel", "degree": "PhD", "year": "2018", "title": "Regional Structural Geology of Earth and Mars", "advisor": "Ehlmann, Bethany L.; Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05282018-115947263", "creators": [ { "name": { "family": "Quinn", "given": "Daven Patel" }, "id": "Quinn-Daven-Patel", "orcid": "0000-0003-1895-3742", "display_name": "Quinn, Daven Patel" } ], "advisors": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "advisor", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "co-advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geol" ], "doi": "10.7907/9enj-wn23", "abstract": "This thesis explores the geologic context around several key environmental transitions on Earth and Mars which are expressed at continental margins. Regional mapping techniques are applied to build links between methodologies used to explore rock samples and units \u2014 stratigraphy, structural geology, remote sensing, geochemistry, petrology, and geodynamic modeling. Four research projects are presented: Chapter 2 explores the tectonic context of xenoliths beneath the western margin of North America and illuminates the structural history of the lithospheric underpinnings of the California coast. In Chapter 3, we undertake a structural study of the southern Naukluft Mountains, Namibia, and re-interpret its tectonic context and age. Chapter 4 builds a new method for applying statistical errors to remotely measured planar orientations, and Chapter 5 applies this method to mapping the 3D structure of a globally significant stratigraphy on Mars. We find a long history of interaction with water at the margin of Isidis Basin. Together, these projects demonstrate the application of structural techniques to continental margins on Earth and Mars, and the creation of new techniques to support geological analysis from remotely-sensed data, where structural measurements may be poorly resolved." }, { "name": "Rollins, John Christopher", "degree": "PhD", "year": "2018", "title": "Using Heterogeneous 3D Earth Models to Constrain Interseismic and Postseismic Deformation in Southern California and Nepal", "advisor": "Avouac, Jean-Philippe", "url": "https://resolver.caltech.edu/CaltechTHESIS:11202017-145930076", "creators": [ { "name": { "family": "Rollins", "given": "John Christopher" }, "id": "Rollins-John-Christopher", "orcid": "0000-0002-5291-6956", "display_name": "Rollins, John Christopher" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "advisor", "display_name": "Avouac, Jean-Philippe" } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9X06572", "abstract": "We characterize interseismic strain accumulation across the Los Angeles basin and postseismic deformation following the 2010 Mw=7.2 El Mayor-Cucapah and 2015 Mw=7.8 Nepal earthquakes using geodetic data. These settings are all characterized by strong 3D heterogeneities of elastic structure, ductile properties, fault geometries, and fault slip behavior, and we use constaints from seismology, long-term tectonic modeling, geology, and other sources to construct detailed models of these heterogeneities. Postseismic surface displacements following the 2010 El Mayor-Cucapah earthquake indicate viscoelastic relaxation in the shallow Salton Trough mantle and possibly the lower crust, a process that would have been enhanced by high heat flow induced by crustal extension at the tip of the Gulf of California. We find that a dense and prolonged aftershock sequence in the Yuha Desert may have been driven by aseismic afterslip coupled with fluid flow. Our study of interseismic strain accumulation across the Los Angeles basin shows that the soft sedimentary basin has a first-order effect on the elastostatic Green\u2019s functions mapping fault creep and locking at depth to surface deformation, and therefore on the estimation of interseismic fault creep rates and strain accumulation at depth. We infer modest interseismic coupling on the three major thrust faults underlying the Los Angeles basin, corresponding to an annual seismic moment deficit buildup rate (to be presumably released in earthquakes) of 1.7 +1.2/-0.5 x 1017 Nm/yr. We estimate the long-term seismicity model needed to balance the rate of moment deficit accumulation assuming a truncated Gutenberg-Richter magnitude-frequency distribution of earthquakes. The long-term catalog is consistent with the instrumental rates of small and moderate earthquakes and tops out at a M~6.9 earthquake every ~430 years. Finally, we characterize the postseismic deformation following the 2015 Nepal earthquake using models of the thermal structure, state of stress, and rheology that are based on the long-term evolution and topography of the Himalaya. The rheological structure based on these models predicts negligible postseismic viscoelastic deformation. Afterslip on the downdip extension of the rupture cannot realistically explain the observed displacements either. We find that the postseismic deformation is well explained by a combination of afterslip on the downdip edge of the coseismic rupture (as well as a narrow zone in between the mainshock and a large aftershock) and, more prominently, transient viscoelastic relaxation in the hot Tibetan crust. These processes contribute to the stress loading of the Main Himalayan Thrust.
" }, { "name": "Spalding, Christopher", "degree": "PhD", "year": "2018", "title": "The Primordial Origin and Dynamical Sculpting of Close-In Planetary System Architectures", "advisor": "Batygin, Konstantin", "url": "https://resolver.caltech.edu/CaltechTHESIS:03202018-115359218", "creators": [ { "name": { "family": "Spalding", "given": "Christopher" }, "id": "Spalding-Christopher", "orcid": "0000-0001-9052-3400", "display_name": "Spalding, Christopher" } ], "advisors": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "advisor", "display_name": "Batygin, Konstantin" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9RB72TQ", "abstract": "For centuries, planet formation theories were tuned to reproduce the remarkable coplanarity of our Solar System. Specifically, the eight planetary orbital planes exhibit mutual inclinations limited to ~1\u22122 degrees. Furthermore, the misalignment between the Sun's spin axis and the orbital planes of the planets \u2013 the 'spin-orbit misalignment'\u2013 is only about 6 degrees. However, observational characterization of close-in extrasolar planetary systems has revealed an abundance of spin-orbit misalignments ranging all the way from 0 to 180 degrees (Winn et al. 2010). Particularly among the hot Jupiters (giant planets with orbital periods shorter than ~1 week), spin-orbit misalignments are more prevalent in systems hosted by stars with effective temperatures exceeding about 6200 K. Previous work has suggested that these misalignments arose from violent dynamical interactions that excited planets onto inclined and eccentric orbits, with subsequent tidal circularization generating the observed population (Albrecht et al. 2012). This hypothesis has had great difficulty explaining misaligned multi-planet systems, and misaligned orbits of planets that are too distant from their host stars for tidal circularization to act over a sufficiently short timescale. A new mechanism is required.
\r\n\r\nIn chapters II-VI, I present a theoretical framework referred to as \"disk-torquing,\" whereby spin-orbit misalignments arise through the tilting of protoplanetary disks themselves (Batygin 2012, Spalding and Batygin 2014, 2015). In this picture, gravitational torques from a companion star lead to the precession of the protoplanetary disk. When the disk is young and massive, gravitational star-disk coupling quenches misalignments between the stellar spin axis and disk plane. However, as the disk dissipates, a secular resonance is encountered that impulsively excites large stellar obliquities, ranging between 0 and 180 degrees, in accordance with the observations. In addition, I computed the magnetic torques between the star and disk, finding that a dipole field strength of ~1 kGauss is sufficiently strong to realign the star and disk within typical disk lifetimes (~3 million years). Magnetic fields of this magnitude are observed to persist throughout the disk-hosting stage only for stars less massive than ~1.2 solar masses (Gregory et al. 2012), corresponding to a main sequence effective temperature of 6200 K, i.e., coincident with the observed break between aligned and misaligned hot Jupiters. Cumulatively, the disk-torquing framework exhibits qualitative consistency with the observed dependence of spin- orbit misalignments upon stellar mass, leaving the theory ripe for a statistical comparison to observations within future work.
\r\n\r\nThe final three chapters change focus from spin-orbit misalignments toward the excitation of mutual inclinations between planetary orbits \u2013 orbit-orbit misalignments. Evaluation of the relative numbers of single to multi-transiting planetary systems within the Kepler space telescope\u2019s dataset has revealed a dichotomy whereby there exist two populations of planetary system \u2013 one with low orbit-orbit inclination, and a second that either possesses a single planet, or possesses multiple planets with large mutual inclinations, leaving only one detectable via transit (Johansen et al. 2012, Ballard and Johnson 2016). In separate but related observational work, it has become apparent that transiting hot Jupiters often appear without co-transiting, close-in planetary companions, wheres warm Jupiters often do (Steffen et al. 2012, Huang et al. 2016). I showed that both of these observations can naturally arise owing to secular perturbations from the host star (Spalding and Batygin 2016, 2017). Specifically, young stars rotate fast, becoming oblate. If the star\u2019s spin axis is misaligned with respect to the orbits of a multi-planet system, its quadrupole moment can disrupt the coplanarity of the system. Indeed, the stellar perturbations are often sufficient to completely destabilize the system (Chapter VI). In addition to constituting an entirely new mechanism of planetary instability, the origin of the required spin-orbit misalignment relates directly back to the discussion above \u2013 spin-orbit misalignments may drive the seemingly unrelated Kepler dichotomy.
\r\n\r\nFinally, I tied in the observation that hot Jupiters appear lonely by demonstrating that stellar contraction can give rise to a secular resonance that tilts exterior companions of hot Jupiters, taking them out of transit. Crucially, this resonance is encountered at an earlier time in systems hosting warm Jupiters, precisely owing to their slightly increased orbital distance. I found that the demarcation between a system undergoing secular tilting, and one where the disk quenches the tilting, coincides well with the relatively arbitrary dividing line between hot and warm Jupiters, usually set at orbital periods of about a week.
\r\n\r\nIn summary, I showed that spin-orbit misalignments and orbit-orbit misalignments, measured across a range of planetary size classes, can arise primordially owing to interactions with the host star and binary companions. The importance of the central star had most likely been missed in the previous literature owing to our solar system\u2019s peculiarly wide inner edge at ~0.4 AU, as opposed to the more typical ~0.1 AU within a galactic setting. In reality, through the wider lens of our galactic planetary census, a true understanding of planet formation demands a look at star-planet interactions wholly unknown from centuries of solar system exploration.
" }, { "name": "Wei, Ho-Hsuan", "degree": "PhD", "year": "2018", "title": "Dynamics of Seasonally-Varying Tropical Convergence Zones", "advisor": "Bordoni, Simona", "url": "https://resolver.caltech.edu/CaltechTHESIS:06082018-100127824", "creators": [ { "name": { "family": "Wei", "given": "Ho-Hsuan" }, "id": "Wei-Ho-Hsuan", "orcid": "0000-0002-6201-9810", "display_name": "Wei, Ho-Hsuan" } ], "advisors": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "advisor", "display_name": "Bordoni, Simona" } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Teixeira", "given": "Joao" }, "id": "Teixeira-Joao", "role": "member", "display_name": "Teixeira, Joao" }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "member", "display_name": "Bordoni, Simona" } ], "option_major": [ "envreng" ], "doi": "10.7907/GAPR-QY60", "abstract": "In the tropics, rain tends to be organized along concentrated rain bands, with the Intertropical Convergence Zone (ITCZ) over the ocean and monsoonal convergence zones over tropical land masses being particularly prominent features affecting hundreds of millions of people. What fundamentally controls the spatial and temporal distribution of these tropical rainbands remains an outstanding question in the literature. This thesis aims to enhance our understanding of the dynamics of seasonally migrating convergence zones over the ocean and in the South Asian monsoon region.
\r\n \r\nFirst, we explore to what extent energetic arguments that have provided insight into the position and shifts of the annual and zonal mean ITCZ can also be applied on shorter timescales. Idealized aquaplanet simulations show that the energy flux equator (EFE) always leads the ITCZ, leading to a breakdown of the commonly assumed anti-correlation between the ITCZ position and the cross-equatorial energy transport. At times during which the EFE and the ITCZ reside on opposite sides of the equator, the required energy transport is in fact achieved by the Hadley cell, in which the ITCZ is embedded, changing its vertical structure into one of negative gross moist stability. One way in which this is accomplished is through the development of a shallow return flow at levels near minimum moist static energy. While the relationship between the EFE and the ITCZ in the observed seasonal cycle is more complex than what is seen in the idealized simulations, the development of bottom-heavy circulations is a common feature both in the zonal mean and in individual longitudinal sectors at times when the EFE and the ITCZ are in opposite hemispheres.
\r\n \r\nIn the last chapter of this thesis, we explore changes in the South Asian monsoon as topography over Africa is removed in the full-physics GFDL AM2.1 GCM. Against expectations, the removal of the African topography is accompanied by a strengthening of the precipitation over India despite a weakening of the Somali jet. This counter-intuitive precipitation increase is associated with the development of a lower-level cyclonic wind anomaly, and associated meridional moisture flux convergence, over the Indian peninsula. Potential vorticity (PV) budget analyses following air parcel trajectories show that this cyclonic anomaly arises because, in the absence of the blocking effect of the African topography, air particles that reach the Arabian Sea originate at higher latitude and hence have a higher background planetary vorticity.
" }, { "name": "Wong, Ian Yu", "degree": "PhD", "year": "2018", "title": "Probing the Trojan-Hilda-KBO Connection: An Empirical Test of Dynamical Instability Models of Solar System Evolution", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03012018-170927159", "creators": [ { "name": { "family": "Wong", "given": "Ian Yu" }, "id": "Wong-Ian-Yu", "orcid": "0000-0001-9665-8429", "display_name": "Wong, Ian Yu" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9B856BX", "abstract": "In recent decades, the paradigm of solar system formation has undergone radical change. Many current models posit that a significant reorganization of the outer Solar System occurred after the end of planet formation. Specifically, it is hypothesized that Jupiter and Saturn crossed a mutual mean motion resonance, leading to a chaotic expansion of the ice giants' orbits that disrupted the large population of planetesimals situated further out. While the majority of these bodies were ejected from the Solar System, a fraction of them were retained as the present-day Kuiper Belt, while others were scattered inward and captured into resonances with Jupiter to become the Trojans and Hildas. These dynamical instability models invariably predict that the Trojans, Hildas, and Kuiper Belt objects (KBOs) were sourced from the same primordial body of outer solar system planetesimals. Therefore, a comparative exploration of these minor body populations serves as one of the definitive observational tests of our present understanding of solar system evolution. Over the past four-and-a-half years, I have carried out a diverse series of systematic studies aimed at synthesizing a detailed picture of Trojan, Hildas, and KBOs. By combining novel analyses of archival data with new photometric surveys, I have derived the first debiased color distributions of Trojans and KBOs and expanded our knowledge of their respective size distributions. In addition, I have explored the peculiar color bimodality attested in the all three asteroid populations, which indicates the presence of two sub-populations. Utilizing the full body of observations, I have formulated the first self-consistent hypothesis outlining the formation, composition, and dynamical/chemical evolution of the primordial outer solar system planetesimals, with special attention given to explaining the color bimodality, size distribution shapes, and collisional families. My results lay the groundwork for future studies with next-generation instruments and ultimately, the Trojan flyby mission Lucy.
" }, { "name": "Wong, Michael L.", "degree": "PhD", "year": "2018", "title": "A Planetary Perspective of Life", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06052018-220558731", "creators": [ { "name": { "family": "Wong", "given": "Michael L." }, "id": "Wong-Michael-L", "display_name": "Wong, Michael L." } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/KVBE-HJ52", "abstract": "Join me on my journey to Jupiter, Titan, Pluto, Earth, and Mars as I seek a deeper understanding of life through the lessons that I learn from each world. How should we define life? What does life do? Why does life exist, and how did it begin? And what do the answers to these questions mean for the prospect of life beyond Earth? No, you\u2019re not going to get any spoilers here. Yes, you actually have to read the manuscript. I spent a lot of time weaving this story together, adding supplementary material to each chapter, connecting the dots between the five planetary bodies that I\u2019ve chosen to tell this tale. There\u2019s a lot in here besides just my published work, including two essays on the origin of life (presented in the Interlude) and two scientific works in progress (presented in the Prologue and the Epilogue). I encourage you to follow the wending tale of my graduate school career from start to finish as I build a planetary perspective of life that I now proudly present to you.
" }, { "name": "Zhang, Xiyue", "degree": "PhD", "year": "2018", "title": "Dynamics of Resolved Polar Clouds", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:05312018-154833107", "creators": [ { "name": { "family": "Zhang", "given": "Xiyue" }, "id": "Zhang-Xiyue", "orcid": "0000-0002-6031-7830", "display_name": "Zhang, Xiyue" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "chair", "display_name": "Bordoni, Simona" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "orcid": "0000-0003-0322-4811", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Teixeira", "given": "Joao" }, "id": "Teixeira-Joao", "role": "member", "display_name": "Teixeira, Joao" }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "orcid": "0000-0003-1344-4068", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" } ], "option_major": [ "envreng" ], "doi": "10.7907/69E7-0Q10", "abstract": "The polar regions have been experiencing rapid warming and ice loss as greenhouse gas concentrations have risen. The projected warming in the Arctic varies significantly across climate models, part of which is attributed to polar cloud feedbacks. This thesis addresses the question of what drives the changes in polar clouds as the climate warms, using a large eddy simulation (LES) model. LES is a powerful high-resolution model that resolves the most energetic turbulence relevant for clouds. First, we focus on the Arctic boundary layer clouds through three observation based case studies. The cloud and boundary layer characteristics simulated by the LES agree reasonably well with observations and model intercomparisons. We found that during polar night over sea ice, cloud water path increases with temperature and free-tropospheric relative humidity, but it decreases with inversion strength across the cloud top. Most of these changes can be explained by a mixed-layer model. The strength of the estimated positive cloud longwave feedback largely depends on the cloud top inversion strength. Next, we extend the LES domain to cover the entire polar troposphere, and use output from an idealized GCM as forcing to drive the LES. This novel framework allows changes in the large-scale circulation to be parameterized in the LES. The simulated seasonal cycle of liquid clouds resembles observations. In a warmer climate, there is a significant decrease of the low-level liquid clouds during summer and autumn. In spring and winter, liquid clouds increase at all levels. Both the liquid and ice cloud tops rise as the climate warms. Offline radiative transfer calculations estimate a positive cloud feedback that is dominated by longwave feedback.\r\n" }, { "name": "Bischoff, Tobias", "degree": "PhD", "year": "2017", "title": "Dynamics of the Intertropical Convergence Zone", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:11122016-111133209", "creators": [ { "name": { "family": "Bischoff", "given": "Tobias" }, "id": "Bischoff-Tobias", "orcid": "0000-0003-3930-2762", "display_name": "Bischoff, Tobias" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Thompson", "given": "Frederick B." }, "id": "Thompson-F-B", "role": "chair", "display_name": "Thompson, Frederick B." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z97M05XR", "abstract": "Previous studies have shown that the latitude of the Intertropical Convergence Zone (ITCZ) is negatively correlated with cross-equatorial atmospheric energy transport and that the ITCZ shifts southward as the northern hemisphere cools and the northward cross-equatorial energy transport strengthens. However, it has remained unclear what controls the sensitivity of the ITCZ position to cross-equatorial energy transport, and what other factors may lead to shifts of the ITCZ position. In this thesis, it is shown how an energetic perspective using the vertically-integrated moist static energy balance of the atmosphere can be used to address this question. Climate states with a double-ITCZ around the equator also occur, for example, seasonally over the eastern Pacific, and frequently in climate models. Here it is shown how the ITCZ position is connected to the energy balance near the equator under a wide range of circumstances, including states with single and double ITCZs and using a Taylor expansion of the meridional energy transport around the equator quantitative estimates for the ITCZ location are derived. Simulations with an idealized aquaplanet general circulation model (GCM) confirm the quantitative adequacy of these relations. Using these ideas, an idealized precipitation model for the tropics is presented that is able to capture variations of paleoclimatological precipitation records on orbital time scales. The results provide a framework for assessing and understanding causes of common climate model biases and for interpreting tropical precipitation changes, such as those evident in records of climates of the past." }, { "name": "Cox, Stephen Ellis", "degree": "PhD", "year": "2017", "title": "New Techniques for Noble Gas Geochronometry and Thermochronometry", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12212016-095346656", "creators": [ { "name": { "family": "Cox", "given": "Stephen Ellis" }, "id": "Cox-Stephen-Ellis", "orcid": "0000-0002-8819-887X", "display_name": "Cox, Stephen Ellis" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" } ], "option_major": [ "geochem" ], "doi": "10.7907/Z9V69GKV", "abstract": "Noble gases were among the first species measured by mass spectrometry and interrogated for geochemical information about the solid Earth. The analytical challenge of measuring them has driven technological development in the field, and new applications have in turn followed from new developments. In the first chapter, I present developments that bolster an existing technique, the (U\u2013Th)/Ne system, by verifying the theoretical underpinnings of the method and by exploring its application in several minerals. In the second chapter, I show that the hematite (U\u2013Th)/Ne system is a sound geochronometer for use in the upper crust and a potent thermochronometer for exploring mid-crustal processes. In the third chapter I show significant advances toward using a quadrupole ion trap as a noble gas mass spectrometer, including the first static vacuum measurements. This technique provides new opportunities for low abundance noble gas measurements through its ultra low dark noise time of flight measurement approach and its high resolution, high mass range scanning capabilities. The quadrupole ion trap can measure lower concentrations of rare species like 3He and 21Ne on Earth, allowing us to make more precise determinations of cosmogenic exposure ages, and it can measure species with much higher resolution than is currently possible on most spaceflight instruments, allowing us to perform measurements on planetary surfaces and in deep space that are currently reserved to terrestrial laboratories. Finally, in the fourth chapter I demonstrate that an old, largely abandoned technique, (U\u2013Th)/He geochronometry, has useful applications now that we fully understand its limitations." }, { "name": "Gao, Peter", "degree": "PhD", "year": "2017", "title": "Clouds and Hazes in Planetary Atmospheres", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09302016-155917400", "creators": [ { "name": { "family": "Gao", "given": "Peter" }, "id": "Gao-Peter", "orcid": "0000-0002-8518-9601", "display_name": "Gao, Peter" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z99W0CGS", "abstract": "Clouds and hazes are found in every significant planetary atmosphere in the Solar System, from the sulfuric acid clouds of Venus and the water clouds of Earth and Mars, to the photochemical hazes that pervade the giant planets, ice giants, Titan, and even Pluto. Beyond the Solar System, transmission spectroscopy of exoplanets have found that many are also bound in clouds and hazes, though their higher temperatures give rise to clouds of salts, rocks, and metals, and hazes of soots and sulfurs. Understanding the behavior and role of clouds and hazes in planetary atmospheres is instrumental in understanding atmospheres as a whole, as they are strongly coupled to other atmospheric processes. For example, highly reflective clouds can reduce the effective temperature of a planet, while UV absorbing hazes can increase local atmospheric temperatures. Clouds and hazes also act as reservoirs for important trace species and can be crucial to atmospheric chemical cycles.
\r\n\r\nIn this Ph.D thesis, I use modeling and comparisons to observations to understand cloud and haze processes on multiple worlds within and beyond the Solar System. I use the Community Aerosol and Radiation Model for Atmospheres (CARMA) to simulate the sulfuric acid clouds of Venus in an attempt to find the cause of the spatial and temporal variability in the Venus upper haze, as observed by Venus Express. I show that the variability is likely caused by sustained updrafts lofting large cloud particles into the haze. I then modify CARMA to include fractal aggregate particles to investigate the properties of the photochemical haze on Pluto as observed by New Horizons, and find that the haze particles must be porous, and that they may act as nucleation cites for simple hydrocarbons. Finally, I add exotic condensates to CARMA to model clouds on exoplanets, where their existence has led to difficulties in finding the atmospheric compositions of these worlds. I show that not all species that can condense will, due to their material properties, and that the cloud optical depth is largely controlled by the rate of particle production via homogeneous nucleation. In addition, I investigate the effect a sulfur haze would have on the reflected light spectrum of giant exoplanets to prepare for upcoming direct imaging missions, and find that sulfur hazes significantly brighten these planets at long wavelengths, while darkening them at short wavelengths due to UV absorption. Finally, I retrieve the properties of water ice particles from Cassini observations of the plumes of Enceladus assuming that they are aggregates rather than spheres, and thereby unifying forward scattering observations with in situ measurements.
" }, { "name": "Inbal, Asaf", "degree": "PhD", "year": "2017", "title": "Seismogeodetic Imaging of Active Crustal Faulting", "advisor": "Ampuero, Jean-Paul", "url": "https://resolver.caltech.edu/CaltechTHESIS:10032016-142052951", "creators": [ { "name": { "family": "Inbal", "given": "Asaf" }, "id": "Inbal-Asaf", "orcid": "0000-0001-8848-7279", "display_name": "Inbal, Asaf" } ], "advisors": [ { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "advisor", "display_name": "Ampuero, Jean-Paul" } ], "committee": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "chair", "display_name": "Simons, Mark" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/Z92B8W02", "abstract": "Monitoring microseismicity is important for illuminating active faults and for improving our understanding earthquake physics. These tasks are difficult in urban areas where the SNR is poor, and the level of background seismicity is low. One example is the Newport-Inglewood fault (NIFZ), an active fault that transverses the city of Long-Beach (LB). The catalog magnitude of completeness within this area is M=2, about one order of magnitude larger than along other, less instrumented faults in southern California. Since earthquakes obey a power-law distribution according to which for each unit drop in magnitude the number of events increases by a tenfold, reducing the magnitude of completeness along the NIFZ will significantly decrease the time needed for effective monitoring. The LB and Rosecrans experiments provides a unique opportunity for studying seismicity along the NIFZ. These two array contain thousands of vertical geophones deployed for several-months periods along the NIFZ for exploration purposes. The array recordings are dominated by noise sources such as the local airport, highways, and pumping in the nearby oil fields. We utilize array processing techniques to enhance the SNR.We downward continue the recorded wave field to a depth of a few kilometers, which allows us to detect signals whose amplitude is a few percent of the average surface noise. The migrated wave field is back-projected onto a volume beneath the arrays to search for seismic events. The new catalog illuminates the fault structure beneath LB, and allows us to study the depth-dependent transition in earthquake scaling properties.
\r\n\r\nDeep aseismic transients carry valuable information on the physical conditions that prevail at the roots of seismic faults. However, due the limited sensitivity of geodetic networks, details of the spatiotemporal evolution of such transients are not well resolved. To address this problem, we have developed a new technique to jointly infer the distribution of aseismic slip from seismicity and strain data. Our approach relies on Dieterich (1994)'s aftershock model to map observed changes in seismicity rates into stress changes. We apply this technique to study a three month long transient slip event on the Anza segment of the San Jacinto Fault (SJF), triggered by the remote Mw7.2, 2010 El Mayor-Cucapah (EMC) mainshock.
\r\n\r\nThe EMC sequence in Anza initiated with ten days of rapid (\u2248100 times the longterm slip rate), deep (12-17 km) slip, which migrated along the SJF strike. During the following 80 days afterslip remained stationary, thus significantly stressing a segment hosting the impending Mw5.4 Collins Valley mainshock. Remarkably, the cumulative moment due to afterslip induced by the later mainshock is about 10 times larger than the moment corresponding to the mainshock and its aftershocks. Similar to sequences of large earthquakes rupturing fault gaps, afterslip generated by the two mainshocks is spatially complementary. One interpretation is that the stress field due to afterslip early in the sequence determined the spatial extent of the late slip episode. Alternatively, the spatial distribution is the result of strong heterogeneity of frictional properties within the transition zone. Our preferred model suggests that Anza seismicity is primarily induced due to stress transfer from an aseismically slipping principal fault to adjacent subsidiary faults, and that the importance of earthquake interactions for generating seismicity is negligible.
" }, { "name": "Lap\u00f4tre, Mathieu Gaetan Andre", "degree": "PhD", "year": "2017", "title": "Sedimentary Processes on Earth and Mars: Canyon Erosion, Sand-Ripple Formation, and Mineral Composition", "advisor": "Lamb, Michael P.; Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05152017-105730412", "creators": [ { "name": { "family": "Lap\u00f4tre", "given": "Mathieu Gaetan Andre" }, "id": "Lap\u00f4tre-Mathieu-Gaetan-Andre", "orcid": "0000-0001-9941-1552", "display_name": "Lap\u00f4tre, Mathieu Gaetan Andre" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "advisor", "display_name": "Lamb, Michael P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "co-advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "chair", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Golombek", "given": "Matthew P." }, "id": "Golombek-M-P", "role": "member", "display_name": "Golombek, Matthew P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9RF5S2T", "abstract": "Over the past few decades, orbiters, landers, and rovers have significantly expanded our understanding of Mars\u2019 hydrology and climate; however, significant knowledge gaps stand in the way of our quest for martian life. In particular, the global drying of the planet remains one of the grandest unsolved mysteries in planetary science. To help unravel this puzzle, we develop new quantitative theories for sedimentary processes with implications for both Earth and Mars. This thesis revolves around three main sedimentary processes \u2013 erosion, deposition, and sediment transport. First, we focus on the erosion of bedrock canyons by water on Earth and Mars. After showing that groundwater seepage erosion is only efficient at carving canyons in restricted conditions, we develop a new hydraulic theory for flow focusing upstream of horseshoe-shaped waterfalls and combine it with waterfall-erosion mechanics to constrain the discharge, duration, and volume of canyon-carving floods on Earth and Mars. We show that martian Hesperian floods were large but short-lived. Second, we investigate fluid and sediment controls on the equilibrium size of bedforms. We develop a comprehensive scaling relation to predict the size of ripples forming in various sedimentary environments, including martian brines and methane flows on Titan, and show that the scaling relation predicts the size of large wind ripples forming under a thin martian atmosphere. This new theory, combined with observations of large-ripple cross-strata in wind-blown sandstones of the Burns formation at Victoria crater, suggests that Mars had a thin atmosphere around the Noachian-Hesperian boundary. Finally, we use orbiter-based inferences of the mineralogy of sands of the Bagnold dunes of Gale crater to disentangle the magnitude of wind sorting and local sediment sources. We develop a new probabilistic framework to invert for surface mineralogy, groundtruth our predictions with compositional datasets provided by the Curiosity rover, and discuss the implications of our findings for mineral sorting by martian winds and paleoenvironmental interpretations of martian wind-blown sandstones. Collectively, these results provide new mechanistic and quantitative constraints on the past hydrology and climate of Mars that are key to assess Mars\u2019 astrobiological potential through space and time." }, { "name": "Li, Cheng", "degree": "PhD", "year": "2017", "title": "Convection in Planetary Atmospheres: Titan's Haze, Saturn's Storm and Jupiter's Water", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08172016-211741364", "creators": [ { "name": { "family": "Li", "given": "Cheng" }, "id": "Li-Cheng", "orcid": "0000-0002-8280-3119", "display_name": "Li, Cheng" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9R78C58", "abstract": "Atmospheric convection is a profound topic. Numerous books have been written on the consequences of convection. Yet, the picture of convection is still far from complete because of its high nonlinearity, multi-scale coupling and complex interactions with other systems. The theme of my dissertation is to investigate three aspects of atmospheric convection on three different planets. This dissertation is multi-disciplinary and includes scientific topics like photochemistry, dynamics and radiation, and methodologies like information retrieval, theoretical calculation and dynamic modeling.
\r\n\r\nChapter 1 and 2 study Titan. It focuses on how to infer the strength of convection from the vertical distribution of chemical species. In a photochemical model, convection is parameterized as eddy diffusion and the strength of convection is proportional to eddy diffusivity. We developed an inversion method to retrieve the vertical profile of eddy diffusivity directly from the Cassini observations and found out a stable layer in the atmosphere which may give rise to the detached haze layer on Titan. In addition, new observation from Cassini/CIRS limb sounding came a few month later. C3H6 was detected for the first time in the stratosphere. Our new photochemical model with the updated eddy diffusion profile successfully explained the observed vertical distribution of C3H6. Chapter 2 explains the modeling result and does a systematic study on all C3-hydrocarbons.
\r\n\r\nChapter 3 studies Saturn. It investigates the role of convection on regulating Saturn\u2019s giant storms. Six giant storms, called Great White Spots, have erupted on Saturn since 1876 at intervals of about 30 years. The most recent one occurred on Dec. 5th, 2010 at planetographic latitude 37.7\u00b0N. It produced intense lightning, created enormous cloud disturbances and wrapped around the planet in 6 months. We proposed the water-loading mechanism to explain the periodicity. Moist convection is suppressed for decades due to the larger molecular weight of water in a hydrogen-helium atmosphere. We show that this mechanism requires the deep water vapor mixing ratio to be greater than 1.0%, which implies Saturn\u2019s O/H to be at least 10 times the solar value.
\r\n\r\nChapter 4 studies Jupiter. It proposes an inversion strategy for the upcoming Juno microwave observation based on the modeling results and the theoretical arguments developed in Chapter 3. We extend the Juno/MWR\u2019s functionality by retrieving both the deep water mixing ratio and a few dynamic parameters representing subcloud meteorology. This proposition will contribute substantially to achieving the Juno/MWR objectives and shed light on the functioning of convection on planets with deep atmospheres.
" }, { "name": "Lui, Semechah Ka Yan", "degree": "PhD", "year": "2017", "title": "Earthquake Source Characterization Through Seismic Observations and Numerical Modeling", "advisor": "Lapusta, Nadia; Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11232016-044435496", "creators": [ { "name": { "family": "Lui", "given": "Semechah Ka Yan" }, "id": "Lui-Semechah-Ka-Yan", "orcid": "0000-0001-7801-3635", "display_name": "Lui, Semechah Ka Yan" } ], "advisors": [ { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "co-advisor", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "member", "display_name": "Tsai, Victor C." }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9QN64QM", "abstract": "In this thesis, I present a series of works on the characterization of source properties and physical mechanisms of various small to moderate earthquakes through both observational and numerical approaches. From the results, we find implications on a broader scheme of topics relating to larger earthquakes, shear zone structure, frictional properties of faults, and seismic hazard assessment.
\r\n\r\nPart I consists of two studies using waveform modeling. In Chapter 2, we present an in-depth study of a series of intraslab earthquakes that occurred in a localized region near the downdip edge of the 2011 Mw Tohoku-Oki megathrust earthquake. By refining source parameters of selected events, simulating their rupture properties and comparing their mechanisms to stress changes caused by the main shock in the region, we are able to identify the true rupture plane and the reactivation of a subducted normal fault, enhancing our understanding on the downdip shear zone. In Chapter 3, based on similar techniques, we further develop a systematic methodology to perform fast assessments on important source properties as an earthquake occurs. For two Mw 4.4 earthquakes in Fontana, moment magnitude and focal mechanism can be accurately estimated with 3 to 6 s after the first P-wave arrival, while focal depth can be constrained upon the arrival of S waves. Rupture directivity can also be determined with as little as 3 seconds of P waves. This study opens the opportunity to predict ground motions ahead of time and can potentially be useful for Earthquake Early Warning.
\r\n\r\nPart II involves the modeling of seismic source properties and physical mechanisms of interacting earthquakes in dynamic rupture simulations. In particular, we focus on small repeating earthquake sequences that trigger one another. In Chapter 4, we quantify the relative importance of physical mechanisms that contribute to earthquake interaction and identify that the stress change caused by post seismic slip is the dominating factor. Our findings introduce the possibility to constrain frictional properties of the fault based on earthquake interactions. We further apply this working model in Chapter 5 to reproduce the actual interacting repeating sequences in Parkfield. We are able to identify possible physical mechanisms that cause the inferred high stress drops of these repeating events, as well as reproduce their synchronized seismic cycles. Results from our simulations are consistent with the observed scaling relation between the recurrence time interval and the seismic moment of these events. Our findings indicate that the difference between the observed and the theoretical scaling relations can be explained by the significant aseismic slip in the rupture area.
" }, { "name": "Magyar, Paul Macdonald", "degree": "PhD", "year": "2017", "title": "Insights into Pathways of Nitrous Oxide Generation from Novel Isotopologue Measurements", "advisor": "Eiler, John M.; Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262017-143517395", "creators": [ { "name": { "family": "Magyar", "given": "Paul Macdonald" }, "id": "Magyar-Paul-Macdonald", "orcid": "0000-0003-0234-247X", "display_name": "Magyar, Paul Macdonald" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "co-advisor", "display_name": "Eiler, John M." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "co-advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/Z93776RJ", "abstract": "The accumulation of nitrous oxide (N2O) in the atmosphere is a significant manifestation of human perturbations of the nitrogen cycle. This thesis reports the development and first applications of a novel isotopic technique for characterizing nitrous oxide sources. Chapter 1 describes the development of methods to use the newly available technology of high- resolution dual-inlet multi-collector mass spectrometry to measure six isotopic parameters in nitrous oxide. It reports the standardization and initial biological application of these methods. Chapter 2 presents a model for the generation of isotope effects in an important N2O generating enzyme, the bacterial nitric oxide reductase; this model and published isotopic constraints are used to provide insights into the mechanism of that enzyme. Chapter 3 describes the six-dimensional isotopic characterization of nitrous oxide from bacterial denitrifiers, while Chapter 4 describes nitrous oxide generated by ammonia oxidizing bacteria.
" }, { "name": "Malatesta, Luca Claude", "degree": "PhD", "year": "2017", "title": "Impact of Climate and Tectonics on the Morphodynamics of Alluvial Piedmonts, Implications for Sediment Transfer and the Stratigraphic Record\r ", "advisor": "Avouac, Jean-Philippe; Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04072017-164424209", "creators": [ { "name": { "family": "Malatesta", "given": "Luca Claude" }, "id": "Malatesta-Luca-Claude", "orcid": "0000-0003-0983-715X", "display_name": "Malatesta, Luca Claude" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "advisor", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "co-advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9HD7SP4", "abstract": "Alluvial piedmonts encircle most of the Earth mountain ranges. The erosion product of these mountains must cross the piedmont domain before reaching the basins where they can enter the sedimentary record. The flux of sediment transfers environmental signals, e.g. tectonics and climate, from source to sink, their preservation is critical for the sedimentary record. Alluvial piedmonts are very reactive to external and internal forcing often incise by tens to hundreds of vertical meters over a few thousand years only to subsequently aggrade by roughly the same amount. In my thesis, I set to study the morphodynamics of alluvial piedmonts in two areas, Death Valley, California, and the Eastern Tian Shan.
\r\n\r\nIn Death Valley I show that cycles of aggradation and incision repeatedly bury active fault scarps and that leads to the accumulation of tectonic slip until the next incision episode when a tall waterfall is released in the catchment. This process links the release of tectonic offset to climatic periods and it also accounts for many unexplained 10 to 30 m waterfalls in the Death Valley area. In the Eastern Tian Shan, I establish that the northern alluvial piedmont, that is incised by 100 to 300 m in the Holocene, undergoes repeated cycles of aggradation and incision driven by fluctuations in Westerlies moisture and insolation at a 21 kyr period without the need for monsoonal moisture to drive the system. The varying extent of glacial overprint in the Eastern Tian Shan is responsible for the morphological contrast between the incised north and aggraded south piedmonts. I produce more terrace abandonment ages that show that all rivers of the northern piedmont incised since the last deglaciation but did so out of sync because of the geometry of the upstream glaciated valleys, and internal feedbacks with alluvial valley walls during river entrenchment. With new luminescence ages sampled in the stratigraphy I establish that sediments from the last 0.5 Myr are remobilized in the modern sediment flux by the alluvial incision. I develop a numerical tool that predicts locally the probability of sediment mixing based on the essential length- and timescales of the individual rivers of an alluvial piedmont.
" }, { "name": "Mui, Wilton", "degree": "PhD", "year": "2017", "title": "Development and Applications of Opposed Migration Aerosol Classifiers (OMACs)", "advisor": "Flagan, Richard C.; Seinfeld, John H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09062016-204048228", "creators": [ { "name": { "family": "Mui", "given": "Wilton" }, "id": "Mui-Wilton", "orcid": "0000-0003-3065-1296", "display_name": "Mui, Wilton" } ], "advisors": [ { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "advisor", "display_name": "Flagan, Richard C." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "co-advisor", "display_name": "Seinfeld, John H." } ], "committee": [ { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "chair", "display_name": "Flagan, Richard C." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Beauchamp", "given": "Jesse L." }, "id": "Beauchamp-J-L", "role": "member", "display_name": "Beauchamp, Jesse L." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9T72FF1", "abstract": "Particle electrical mobility classification has made important contributions in atmospheric and climate science, public health and welfare policy, and nanotechnology. The measurement of the particle size distribution is integral to characterization of the sub-micrometer aerosol particle population. The differential mobility analyzer (DMA) has been the primary instrument for such measurements. Aerosol particles are transmitted through the DMA on the condition that their migration time across an electrode separation distance is approximately equal to the advective transport time from the inlet to the outlet; these two travel times are induced by an electric field between the electrodes and an orthogonal particle-free carrier gas flow. However, scientific interest has increasingly shifted toward both the nanometer-scale particle size distribution and the miniaturization of instruments. The classical DMA suffers from severe resolution degradation and diffusional losses of nanometer-scale particles, as well as being ill-suited for lightweight, low-power applications. It is relatively recently that miniaturization of DMAs for portable applications has appeared in the scientific literature. Additionally, an abundance of efforts on DMA design have yielded instruments that can probe the nanometer-scale particle size regime, though their use is restricted to the laboratory as they require powerful pumps and operate at near-turbulent flow conditions.
\r\n\r\nThe opposed migration aerosol classifier (OMAC) is a novel concept for particle electrical mobility classification introduced about a decade ago. In contrast to the DMA, the OMAC transmits particles on the condition that their migration velocity in an electric field is approximately equal to the advective transport velocity by a particle-free flow; the migration velocity is induced by an electric field between two porous electrodes, through which a particle-free cross-flow moves in an anti-parallel direction to the electric field. Because of this flow field arrangement, the length scale over which diffusion must act to affect resolution is the entire electrode separation distance in the OMAC, whereas in the DMA it is smaller by about a factor of the sample-to-carrier gas flow rate ratio. As a result, resolution degradation due to diffusion occurs at a lower operating voltage in the OMAC compared to the DMA. Not only does this suggest a larger dynamic range for the OMAC, but also the capability to classify nanometer-scale particles with greater resolution and lower operating voltages and flow rates.
\r\n\r\nMotivated by the theoretical advantages of an OMAC compared to a DMA, this thesis details the design and characterization of OMAC classifiers to verify the performance of realized OMACs. The capabilities of prototype radial geometry OMACs were first investigated. They demonstrated sub-20 nm particle diameter classification at high resolution using modest flow rates, making them amenable to non-laboratory applications. Additionally, the delayed resolution degradation of OMACs was validated by the maintenance of resolution at operating voltages below those at which a DMA would have experienced severely degraded resolution.
\r\n\r\nVarious applications were then carried out to validate the use of OMACs in both nanometer-scale and sub-micrometer particle size regimes. The first OMAC application was in the field of biomolecule analysis, in which the radial OMAC was operated as an ion mobility spectrometer coupled to a mass spectrometer to resolve conformations of sub-2 nm biomolecules. The resolving power of the radial OMAC was high enough to differentiate peptide stereoisomers and populations of thermally-induced biomolecule conformations.
\r\n\r\nIn the aerosol measurement field, aerosol particle size distributions are typically obtained by passing the sample through an ionization source to impart charges on the sample particles, before mobility separation and detection. The detected signal must be inverted, using detector efficiencies, classifier transfer functions, and charge distributions, to obtain the true particle size distribution. While detector efficiencies and classifier transfer functions are typically well-quantified for the specific instruments used in the measurement, the charge distribution is almost never calculated for the specific measurement conditions. This is due both to the computational expense of, as well as the present impracticability of obtaining all the information needed for carrying out such calculations. Aerosol scientists typically use one parameterization of the charge distribution, regardless of the measurement conditions. Thus, the charge distribution represents the greatest source of bias in particle size distribution measurements. Having demonstrated high resolution of sub-2 nm ions, the radial OMAC was then used to obtain mobility distributions of gas ions formed in a bipolar aerosol charger. These ion mobility distributions were then used to quantify the particle size distribution bias due to the use of the common charge distribution parameterization.
\r\n\r\nIn atmospheric nucleation field, the radial OMAC was deployed as part of an airborne particle detection payload over a large cattle feedlot. Again, the radial OMAC demonstrated the ability to obtain nanometer-scale particle size distributions, that, when paired with a concurrently-deployed DMA, allowed for the measurement of ambient particle size distributions over the entire sub-micrometer size range. A spatially-dense set of such particle size distributions allowed for the calculation of particle growth rates from a clear nucleation event from cattle feedlot emissions.
\r\n\r\nFinally, OMACs were evaluated for their performance at low-flow rate operation to obtain sub-micron particle size distribution for deployment as portable exposure monitors, distributed network area monitors, and unmanned aerial vehicle instrumentation. The radial OMAC showed high fidelity to a reference instrument in reported ambient particle size distributions for nearly 48 hours of unattended operation. A planar geometry OMAC prototype was designed and characterized as well, indicating design and construction issues that caused deviations from ideal behavior. The planer OMAC qualitatively agreed with a reference instrument in reported ambient particle size distributions for about 12 hours of unattended operation. Both radial and planar OMACs were more compact, lower in weight, and less demanding in power consumption than a classical DMA, showing high potential for further miniaturized instrumentation development.
" }, { "name": "Ngo, Henry Hoang Khoi", "degree": "PhD", "year": "2017", "title": "Formation and Migration Histories of Giant Exoplanets in Multi-stellar Systems", "advisor": "Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262017-234026021", "creators": [ { "name": { "family": "Ngo", "given": "Henry Hoang Khoi" }, "id": "Ngo-Henry-Hoang-Khoi", "orcid": "0000-0001-5172-4859", "display_name": "Ngo, Henry Hoang Khoi" } ], "advisors": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Mawet", "given": "Dimitri" }, "id": "Mawet-D", "orcid": "0000-0002-8895-4735", "role": "member", "display_name": "Mawet, Dimitri" }, { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-K", "orcid": "0000-0002-7094-7908", "role": "member", "display_name": "Batygin, Konstantin" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9KD1VZW", "abstract": "The first planets discovered outside of our solar system were very different from the solar system planets. These discoveries raised new challenges to planet formation models, which were designed to explain the origin of the solar system planets. One particularly intriguing population, the \"hot Jupiters\" were some of the first planets discovered. These gas giant planets have masses similar to Jupiter and Saturn, however, they were found on orbits 100 times closer to their star than Jupiter is to the sun. Proposed formation scenarios involve models that argue for formation at presently observed locations, but these are challenged by the lack of planet-building materials so close to the host star. Other models assume these planets form at more moderate locations, perhaps in a manner similar to Jupiter and Saturn, followed by inward migration via some other mechanism. These models are challenged by the lack of a known migration mechanism.
\r\n\r\nThis dissertation compiles three studies conducted over the past five years to investigate the formation and migration histories of gas giant exoplanets. After the discovery of the first hot Jupiter, additional discoveries revealed some population characteristics that could provide evidence for certain formation or migration scenarios. A large fraction of hot Jupiters were found to have eccentric orbits and/or misaligned orbits relative to the star's spin axis. These properties suggest that a gravitational interaction with an additional massive object may have played a role in the dynamical history of these hot Jupiters. Studies of stellar multiplicity for nearby, sun-like stars have also revealed that multi-stellar systems are common.
\r\n\r\nThe studies presented in this dissertation investigate whether stellar companions to giant planet systems influence the planets. In the first and second study, we conduct a survey for stellar companions around stars that host hot Jupiters detected by the transiting method. The first study examines whether stars hosting misaligned planets are more likely to host a companion star. We found no such correlation, suggesting that stellar companions do not play a dominant role in causing planetary misalignment. In the second study, we look at the population of stellar companions as a whole to quantify the fraction of hot Jupiters that might have migrated due to stellar interactions. We find that less than 20% of hot Jupiters might have experienced this migration scenario. However, we do find that hot Jupiters are three times more likely to be in a wide multi-stellar system compared to nearby stars that do not host hot Jupiters, suggesting some other connection between the companion star and the giant planet.
\r\n\r\nIn the third study, we search for stellar companions around stars that host giant planets over a wide range of separations, from the close-in hot Jupiters to giant planets as far away as Jupiter is to our sun. These planets were found via the radial velocity method. We compare the giant planets' orbital properties for single- and multi-stellar systems to determine whether planets in multi-stellar systems show some evidence for star-planet interactions. With the current dataset, we find no evidence to support the hypothesis that planets in multi-stellar systems have a different set of orbital properties.
\r\n\r\nFinally, we present preliminary results of an ongoing survey to understand giant planet formation on the other extreme end. Instead of hot Jupiters on close-in orbits, this survey seeks to explain the origin of the very distant giant planetary mass objects found by direct imaging surveys. These objects are often found on separations that are ten to one hundred times farther away than Neptune is to our sun. Due to their distance and size, it's not certain if these objects are some of the biggest planets in existence or if they are the smallest stars. This new survey will search for planets to serve as the link between known giant exoplanets and these unknown directly imaged objects.
" }, { "name": "O'Rourke, Joseph Ghilarducci", "degree": "PhD", "year": "2017", "title": "The Divergent Evolution of Earth and Venus", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:03182017-212454688", "creators": [ { "name": { "family": "O'Rourke", "given": "Joseph Ghilarducci" }, "id": "O'Rourke-Joseph-Ghilarducci", "orcid": "0000-0002-1180-996X", "display_name": "O'Rourke, Joseph Ghilarducci" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "orcid": "0000-0002-2745-3240", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9JH3J6S", "abstract": "Venus and Earth are similar in terms of size and bulk composition, yet their surface conditions are radically different. Earth has hosted plate tectonics and a global magnetic field for billions of years, sustaining water oceans and allowing life to flourish. A thick atmosphere chiefly composed of carbon dioxide, in contrast, drives a greenhouse effect on Venus that would instantly reduce any terrestrial organism to ash. In this thesis, I present several contributions to the debate raging over whether Venus and Earth resembled each other in the past or if unique circumstances placed these celestial siblings on divergent paths from the start. First, I introduce a new process\u2014precipitation of magnesium-rich minerals\u2014that explains the apparent longevity of Earth's dynamo given plausible assumptions about how the core and mantle lose heat. This mechanism relies on high-temperature equilibration in the aftermath of giant impacts, meaning that Earth's violent birth enabled its clement present. The lack of a magnetic field thus indicates that Venus escaped savage bombardment or simply that sluggish mantle convection insulates the core. My analyses of the size and spatial distributions of impact craters suggest that volcanism proceeds planet-wide at gradual rates rather than as catastrophic resurfacing events, which supports a uniformitarian view of Venus. Modeling of enigmatic features called coronae on Venus also sheds light on the properties of the crust and lithosphere that yield a stagnant lid rather than plate tectonics. Finally, I present a thermal history for Venus that is consistent with these and other available constraints. Various uncertainties in my models highlight the pressing need to gather more data relevant to Earth's deep interior and from the most Earth-like planet in our solar system.
" }, { "name": "Pan, Lu", "degree": "PhD", "year": "2017", "title": "Insights into the Geologic History of Mars\u2019 Northern Lowlands from Near-Infrared Spectroscopy \r ", "advisor": "Ehlmann, Bethany L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04132017-163326100", "creators": [ { "name": { "family": "Pan", "given": "Lu" }, "id": "Pan-Lu", "orcid": "0000-0002-8151-2125", "display_name": "Pan, Lu" } ], "advisors": [ { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "advisor", "display_name": "Ehlmann, Bethany L." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z94747WX", "abstract": "Hydrated minerals, identified on Mars using near-infrared spectroscopy data, reveal new insights into the aqueous processes and evolution of climate in the history of Mars. Through investigations of the mineralogical record using near-infrared spectroscopy, this dissertation focuses on the geologic history and aqueous processes in the northern lowlands of Mars in order to assess the existence of a long-lived global ocean, the extent and volume of Noachian-Hesperian volcanic flows filling the northern lowlands, the nature of aqueous activity in the most recent Amazonian age, and the spectral variability of carbonates. The first chapter reports widespread and diverse mafic and hydrated mineralogy of units associated with impact craters across the northern lowlands. In the lowlands-wide survey, no pervasive carbonate or evaporative salts are found in support of a northern ocean, but we identify widespread phyllosilicates inferred to be Noachian basement materials excavated beneath 1-2 km of mafic lava flows. In the second and third chapters, combined analysis of imagery and spectral data is used to investigate local geologic processes related to liquid water in the knobby terrains of Acidalia and in the vicinity of Lyot crater. Phyllosilicates and hydrated silica are detected in the knobby terrains of Acidalia indicative of a declining prevalence of aqueous alteration through time. We also find diverse mineralogy in the vicinity of Lyot, probably formed in a hydrothermal system and later excavated by the Lyot impact. In contrast, we did not identify mineralization related to local channels that are syn- or post-impact. The fourth study analyzes the spectral properties of unshocked and impact-shocked carbonate rocks on Earth and found similar spectral characteristics between Mars carbonate detections and terrestrial carbonates in impact environments. Using near-infrared spectroscopy, we have identified and characterized the mineralogic record of Mars, and found past environments within the northern lowlands of Mars with varying style and intensity of aqueous alteration through time, with implications for the evolution of Mars climate.
" }, { "name": "Price, Jason Brian", "degree": "PhD", "year": "2017", "title": "I: Normal Faulting on the Austroalpine \u2018Overthrust\u2019 Constrained by Thermochronometry and Kinematic Analysis, Central Alps, Graub\u00fcnden Region, Switzerland. II: Clumped Isotope Thermometry of Carbonate Phases Associated with the Copper Deposits of Kennecott, Alaska", "advisor": "Wernicke, Brian P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05142017-011958758", "creators": [ { "name": { "family": "Price", "given": "Jason Brian" }, "id": "Price-Jason-Brian", "orcid": "0000-0001-9865-603X", "display_name": "Price, Jason Brian" } ], "advisors": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "advisor", "display_name": "Wernicke, Brian P." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9JM27NJ", "abstract": "I. A compilation of 362 cooling ages, including 52 newly reported in this study, from nine thermochronometric systems, 40K/39Ar amphibole, 40K/39Ar white mica, 87Rb/86Sr white mica, 40K/39Ar biotite, 87Rb/86Sr biotite, zircon and apatite fission track, zircon and apatite (U-Th)/He, indicate that the base of the Austroalpine allochthonous \u2018orogenic lid\u2019 was not in full thermal equilibrium with its Penninic substrate until at least the middle Oligocene, approximately 29-28 Ma, to allowably as late as the early Miocene, ca. 18 Ma. There is about a factor-of-five difference in cooling rates between the hanging wall (ca. 4\u00b0C/m.y.) and footwall (ca. 20\u00b0C/m.y.) during this period. In addition, there are demonstrably higher metamorphic grades, including blueschist- and eclogite-facies, in the Pennine footwall compared to lower greenschist-facies in the Austroalpine hanging wall. Together these two facts demonstrate that hot, high-pressure Penninic nappes were forced upward against the cold, low-pressure overriding Austroalpine plate in a very short time window of approximately 7-10 m.y. between the time of peak metamorphism during the Eocene and the time of thermal equilibration with the overriding plate during the Oligo-Miocene. The most likely mechanism to produce such a cold-on-hot juxtaposition is a normal fault, and therefore, we conclude that an important period of nappe emplacement in the Central Swiss Alps occurred concurrently with orogen-perpendicular normal fault motion at the base of the Austroalpine allochthon persisting well into the Oligocene and possibly into the early Miocene, post-dating the 32-30 Ma age of the Bergell intrusion.
\r\n\r\nMesoscopic structural measurements made at the top and bottom of the Pennine zone in eastern Switzerland indicate multiple, spatially heterogeneous directions of movement. At the top, in the Oberhalbstein Valley, movement directions vary from dominantly top-east to top-south-southeast a very minor top-north component within Pennine rocks of the Martegnas shear zone and no preferred movement direction within the Austroalpine hanging wall. Near Piz Toissa, a minimum of two kilometers of nearby structural section in the Err and Platta nappes have been faulted out. At the bottom of the Pennine zone in Val Lumnezia and the Chur Rhein Valley at Trimmis, we observe top-northwest, top-north, and top-northeast movements. In Val Lumnezia, the Sub-Penninic Scopi zone (Gotthard cover rocks) shows movement in a top-northwest direction; the superjacent Peidener imbricate fault zone, a relatively thin (ca. 50 to 100 m thick) structural zone consisting of Scopi zone lithologies, shows movement in a northeasterly direction; above that, the basal Penninic B\u00fcndnerschiefer shows no dominant movement direction. To the east, in the Chur Rhine Valley, movement is well defined as exclusively top-north. Therefore, movement directions in the lower B\u00fcndnerschiefer are broadly top-north but heterogeneous in direction along strike between Val Lumnezia and Chur Rhein Valley, and, as first suggested by Weh and Frotizheim (2001), it may be erroneous to regard the basal Pennine thrust as a simple through-going structure. In Val Lumnezia, the Scopi-Peidener-Pennine nappes resemble a \u201cjelly sandwich\u201d in which the thick Pennine mass utilized the Peidener zone to move in an oblique sinistral-normal slip sense past the southeast-dipping allochthonous Scopi zone and its east-dipping Gotthard \u201cmassif\u201d substrate. If the Peidener zone continues northeastward beneath alluvial cover of the Chur Rhein Valley, it may serve as a late, NE-directed shear zone that separates the Pennine nappes from European units. If so, it would explain the apparent truncation and progressive omission of allochthonous elements of European affinity along the zone from southwest to northeast beneath alluvium of the Chur Rhein Valley. We therefore infer that the direct juxtaposition of Penninic units to the east with the Helvetic autochthon to the west at the latitude of Trimmis records an episode of top-northeast, orogen-parallel strike-slip and extensional movement.
\r\n\r\nZircon (U-Th)/He (ZHe) cooling ages from the Oberhalbstein Valley indicate that the Austroalpine-Pennine contact was still active at ca. 27 Ma, and that the Martegnas shear zone was active, in part, between ca. 27 and 24 Ma. It is likely that the Piz Toissa klippe formed around this time during the late Oligocene. The pattern of much younger ZHe ages at the bottom of the Pennine zone is independent of any nappe boundaries, including the Peidener imbricate fault zone, but is consistent with the rise of the Aar massif during the Miocene. Tectonic movements, as recorded by the mesostructure in the Austroalpine, Penninic, and Sub-Penninic domains, and local ZHe cooling ages generally support the conclusion drawn strictly from cooling ages that the Pennine zone was emplaced en masse as a coherent \u2018piston\u2019 or \u2018mega-pip\u2019 during Oligocene to early Miocene time (approximately 29 to 18 Ma), well after juxtaposition of Apulia with cratonic Europe (continent-continent collision) and during the development of Alpine topography and the peripheral basins (viz. Molasse and Lombardi). Additional top-north movement and late uplift and flexure of the nappe stack, along with the Aar massif, occurred primarily in middle to upper Miocene time, following the post-collisional structural interposition of the Pennine zone between Europe and Apulia.
\r\n\r\nII. Nine carbonate phases at Kennecott, Alaska were measured for their clumped isotope (\u220647) equilibration temperatures. The total range for carbonate temperatures spans 38-164\u00b0C. Premineral phases are relatively cool (43-71\u00b0C); synmineral phases are relatively warm (89-157\u00b0C); late postmineral phases are the most cool (38-59\u00b0C) but overlap some premineral phases. Zebra dolomite precipitated in the range 130-163\u00b0C. Dedolomite, a hallmark alteration feature of the mineralizing fluids, falls into a narrow range of 98-109\u00b0C, consistent with the stability field for the low-temperature chalcocite polymorph. Except for one sample, none of the synmineral calcites crystallized within the stability field of djurleite, a volumetrically significant component of the main-stage ore, which suggests that intergrown djurleite may have been a somewhat later recrystallization product of chalcocite rather than a coeval phase.
\r\n\r\nCalculated compositions for \u03b418Owater vary from -4.2 to +11.0\u2030. The most depleted water precipitated hydrothermal baroque dolomite, whereas the most enriched water was associated with recrystallized limestone wallrock on the periphery of the orebody. Waters that precipitated calcite+copper vary from -1.1 to +9.3\u2030.
\r\n\r\nIntriguingly, rhythmic layering in zebra dolomite can be resolved in \u220647 space, and preliminary data indicate that the coarser-grained baroque dolomite bands precipitated at temperatures 5-10\u00b0C cooler than the surrounding, finer-grained dolomite wall rock bands.
\r\n\r\nThe calculated values of \u03b418Owater support a genetic model that invokes redox changes associated with fluid mixing as the likely mechanism responsible for copper deposition. In this model a sulfidic, basinal fluid having \u03b418O similar to seawater mixes with a cuprous fluid having heavier \u03b418O (5 to 8\u2030) which was derived from the Nikolai Greenstone during prehnite-pumpellyite-facies metamorphism.
" }, { "name": "Riel, Bryan Valmonte", "degree": "PhD", "year": "2017", "title": "Automatic Decomposition of Geodetic Time Series for Studies of Ground Deformation", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:10032016-210146623", "creators": [ { "name": { "family": "Riel", "given": "Bryan Valmonte" }, "id": "Riel-Bryan-Valmonte", "orcid": "0000-0003-1940-3910", "display_name": "Riel, Bryan Valmonte" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "member", "display_name": "Tsai, Victor C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9HD7SNP", "abstract": "Geodetic measurements of surface deformation have been used for several decades to study how the Earth's surface responds to a wide range of geophysical processes. Geodetic time series acquired over a finite spatial extent can be used to quantify the time dependence of surface strain for a wide range of spatial and temporal scales. In this thesis, we present a new method for automatically decomposing geodetic time series into temporal components corresponding to different geophysical processes. This method relies on constructing an overcomplete temporal dictionary of reference functions such that any geodetic signal can be described by a linear combination of the functions in the dictionary. By solving a linear least squares problem with sparsity-inducing regularization, we can limit the total number of dictionary elements needed to reconstruct a signal. In Chapter 2, we present the development of this method in the context of transient detection, where we define transient deformation as nonperiodic, nonsecular accumulation of strain in the crust. The sparsity regularization term automatically localizes the dominant timescales and onset times of any transient signals. We apply this method to Global Positioning System (GPS) data for a slow slip event in the Cascadia subduction zone while incorporating a spatial weighting scheme that filters for spatially coherent signals. In Chapter 3, we use a combination of unique space geodetic measurements and seismic observations to study the 2014 collapse of B\u00e1r\u00f0arbunga Caldera in Iceland associated with a major eruption event. The eruption sequence, which involved deflation of a magma chamber underneath the caldera and emplacement of a dike leading to lava flow, resulted in rapid subsidence of the glacier surface overlying the caldera and wide-scale ground deformation encompassing the rift zone associated with the dike emplacement. We present a model of the collapse that suggests that the majority of the observed subsidence occurs aseismically via a deflating sill-like magma chamber. In Chapter 4, we extend upon the transient detection framework presented in Chapter 2 to study complex surface deformation over groundwater basins near Los Angeles, California. We develop a distributed time series analysis framework based on the sparse estimation techniques of Chapter 2 and apply it to an 18-year interferometric synthetic aperture radar (InSAR) time series covering the Los Angeles area. We compare long- and short-term ground deformation signals to hydraulic head data from monitoring wells to understand the mechanical link between pressure variations in subsurface aquifers and observed ground deformation." }, { "name": "Saad, Katherine Michelle", "degree": "PhD", "year": "2017", "title": "Disentangling Spatiotemporal Signals in Global Atmospheric Methane Columns", "advisor": "Wennberg, Paul O.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06052017-164408423", "creators": [ { "name": { "family": "Saad", "given": "Katherine Michelle" }, "id": "Saad-Katherine-Michelle", "orcid": "0000-0002-2501-6223", "display_name": "Saad, Katherine Michelle" } ], "advisors": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "advisor", "display_name": "Wennberg, Paul O." } ], "committee": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "chair", "display_name": "Bordoni, Simona" }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Toon", "given": "Geoffrey C." }, "id": "Toon-G-C", "role": "member", "display_name": "Toon, Geoffrey C." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z97W697G", "abstract": "Methane is a major driver of atmospheric chemistry and a powerful radiative forcing agent. Thus, explaining tropospheric methane trends over the last two decades is critical for the scientific understanding of the global carbon cycle as well as the ability to predict future consequences on the climate and biosphere. Tropospheric concentrations of methane have been increasing, but the growth rate in the last two decades has been extremely variable. Long-term trends in atmospheric methane concentrations and short-term fluctuations in its growth rate are not well understood because its surface emissions and chemical loss are poorly constrained. The ranges of uncertainties for estimates of methane sources and sinks are considerably broad due to the complexity of both natural and anthropogenic fluxes and the heterogeneity of their timescales. This research takes a multifaceted approach to constraining methane fluxes and determining the causes of interannual and long-term variability by developing and synthesizing measurements, integrating methane observations with tracers of tropospheric advection, and assessing systematic biases in chemical transport models. This work synthesizes satellite, aircraft, and surface measurements, including a newly developed dataset of tropospheric column-averaged dry-air mole fractions from Fourier Transform Spectrometer (FTS) instruments within the Total Carbon Column Observing Network (TCCON). Assimilating measurements into the GEOS-Chem chemical transport model, the sensitivities of the temporal and spatial distributions of methane to changes in the distributions of sources and sinks are evaluated. We demonstrate that systematic biases in model stratospheres alias into assimilation of total column methane, masking measurement-model mismatch in tropospheric seasonality. This work also investigates the influence of large-scale transport to the spatial distribution, and in particular the interhemispheric and meridional gradients, of methane." }, { "name": "Schwantes, Rebecca Helen", "degree": "PhD", "year": "2017", "title": "Identifying Isoprene and Toluene Gas-Phase Oxidation Products to Better Constrain Ozone and Secondary Organic Aerosol Formation in the Atmosphere", "advisor": "Seinfeld, John H.; Wennberg, Paul O.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11022016-133509841", "creators": [ { "name": { "family": "Schwantes", "given": "Rebecca Helen" }, "id": "Schwantes-Rebecca-Helen", "orcid": "0000-0002-7095-3718", "display_name": "Schwantes, Rebecca Helen" } ], "advisors": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "advisor", "display_name": "Seinfeld, John H." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "co-advisor", "display_name": "Wennberg, Paul O." } ], "committee": [ { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "chair", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "member", "display_name": "Flagan, Richard C." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z92805K8", "abstract": "Anthropogenic pollutants such as NOx interact with volatile organic compounds (VOCs) such as isoprene and toluene to produce ozone (O3) and oxidized low volatility compounds that are responsible for forming secondary organic aerosol (SOA). Understanding the processes that form O3 and SOA from VOCs is important for understanding climate interactions and air quality. Both O3 and SOA are harmful air pollutants. O3 directly contributes to warming while the influence of aerosols is far more complicated, but ultimately leads to regional cooling. Understanding the chemistry that produces O3 and SOA will help better predict how future regulations will influence climate and air quality. A series of experiments using the Caltech chamber facility were designed and performed to better understand the influence of isoprene and toluene gas-phase oxidation products on O3 and SOA formation.
\r\n\r\nFirst, in order to conduct experiments, the new Caltech chamber facility was characterized. Second, to understand the oxidation products from isoprene in the presence of anthropogenic pollutants such as NOx, a chemical ionization mass spectrometer (CIMS) was used to identify the gas-phase products from the oxidation of isoprene by the nitrate radical (NO3). First-generation nitrates were identified to be predominantly δ-nitrates while first-generation nitrates formed from OH oxidation of isoprene in the presence of NO are predominantly β-nitrates. This has important consequences for NOx recycling and O3 generation because these β- and δ-nitrates react with O3 and OH at different rates and form different products. Photooxidation products from nitrooxy hydroperoxide, a product from isoprene + NO3 oxidation (in the presence of hydroperoxy radical-HO2), were identified to be predominantly propanone nitrate and nitrooxy hydroxy epoxide. Nitrooxy hydroxy epoxide undergoes reactive uptake to seed aerosol similar to isoprene dihydroxy epoxide, suggesting it may be important for SOA formation.
\r\n\r\nLastly, first- and later-generation photooxoidation products from cresol and benzaldehyde oxidation were identified. Cresol and benzaldehyde are products from toluene OH oxidation. Low volatility ring-retaining products produced from cresol oxidation were detected in the gas phase by the CIMS and in the particle phase using offline direct analysis in real time mass spectrometry (DART-MS). Products detected included polyols such as dihydroxy, trihydroxy, tetrahydroxy, and pentahydroxy toluenes and benzoquinones such as hydroxy, dihydroxy, and trihydroxy methyl benzoquinones. These results suggest that even though the cresol pathway only contributes ∼20% to gas-phase toluene oxidation, products from the cresol channel potentially generate a significant fraction ( ∼20-40%) of toluene SOA.
" }, { "name": "Solomatova, Natalia Viatcheslavovna", "degree": "PhD", "year": "2017", "title": "Iron-bearing Oxides, Silicate Glasses and Carbonates at Lower Mantle Pressures", "advisor": "Jackson, Jennifer M.; Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:05312017-162026972", "creators": [ { "name": { "family": "Solomatova", "given": "Natalia Viatcheslavovna" }, "id": "Solomatova-Natalia-Viatcheslavovna", "orcid": "0000-0002-2331-3427", "display_name": "Solomatova, Natalia Viatcheslavovna" } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "advisor", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "co-advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z99021TX", "abstract": "Iron is the fourth most abundant element in Earth\u2019s mantle and it affects geophysically observable properties, such as the density, sound velocities, viscosity and transport properties of mantle phases. Additionally, the concentration of iron in minerals and melts of the lower mantle dictates their structure and stability. Thus, understanding the effect of iron is important to interpret seismically observable complexities and understand their effect on processes in the deep Earth. In this thesis, I use experimental and theoretical methods to improve our understanding of the high-pressure behavior of iron-bearing periclase (\u201cferropericlase\u201d), silicate glasses and carbonates.
\r\n\r\nFerropericlase is thought to represent a significant fraction of Earth\u2019s lower mantle, and may explain the slow compressional and shear sound velocities of ultra-low velocity zones at the core-mantle boundary. To understand the effect of iron concentration on the (Mg,Fe)O solid solution, the equation of state and hyperfine parameters of (Mg,Fe)O with 48 mol% FeO were measured using X-ray powder diffraction and time-domain M\u00f6ssbauer spectroscopy, respectively, and the spin crossover behavior was compared to that of (Mg,Fe)O with 10 to 60 mol% FeO. I find that iron-rich ferropericlase at core-mantle boundary pressures likely contains a significant fraction of high-spin iron, contributing a positive buoyancy to promote topographic relief of ultra-low velocity zones in the lowermost mantle.
\r\n\r\nSome ultra-low velocity zones, particularly those at the base of the central parts of large low shear velocity provinces, may be best explained by the presence of iron-bearing silicate melts. The behavior of iron in silicate melts is poorly understood, but may be approximated by iron-bearing silicate glasses. I measured the hyperfine parameters of iron-bearing rhyolitic glass up to ~120 GPa and basaltic glasses up to ~90 GPa using time-domain M\u00f6ssbauer spectroscopy. Iron within these glasses experiences changes in coordination environment with increasing pressure without undergoing a high-spin to low-spin transition. Thus, ferrous iron in chemically\u2013complex silicate melts likely exists in a high-spin state throughout most of Earth\u2019s mantle.
\r\n\r\nDecomposition of carbonates may be responsible for creating silicate melts within the lower mantle by lowering the melting temperature of surrounding rock. Identifying and characterizing the stability of carbonate phases is therefore a necessary step towards understanding the transport and storage of carbon in Earth\u2019s interior. Dolomite is one of the major mineral forms in which carbon is subducted into the Earth\u2019s mantle. Although iron-free dolomite is expected to break down upon compression into single-cation carbonates, high-pressure polymorphs of iron-bearing dolomite may resist decomposition. Using a genetic algorithm that predicts crystal structures (USPEX), I have found a monoclinic phase with space group C2/c that has a lower energy than all previously reported dolomite structures at pressures above 15 GPa, and the substitution of iron for magnesium stabilizes monoclinic dolomite with respect to decomposition at certain pressures of the lower mantle.
\r\n\r\nIn this thesis, I demonstrate that iron undergoes a spin transition in (Mg,Fe)O, (Mg,Fe)CO3 and Ca(Mg,Fe)(CO3)2, while iron in basaltic and silicate glasses likely does not experience a spin transition up to lowermost mantle pressures. Additionally, I find that the amount of iron in (Mg,Fe)O and Ca(Mg,Fe)(CO3)2 dictates the dynamic and thermodynamic stabilities of those phases within Earth\u2019s lower mantle.
" }, { "name": "Subhas, Adam Vinay", "degree": "PhD", "year": "2017", "title": "Chemical Controls on the Dissolution Kinetics of Calcite in Seawater", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06092017-091849904", "creators": [ { "name": { "family": "Subhas", "given": "Adam Vinay" }, "id": "Subhas-Adam-Vinay", "orcid": "0000-0002-7688-6624", "display_name": "Subhas, Adam Vinay" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Berelson", "given": "William M." }, "id": "Berelson-W-M", "role": "member", "display_name": "Berelson, William M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "geochem" ], "doi": "10.7907/Z93X84P3", "abstract": "Calcium carbonate minerals are abundant on the earth\u2019s surface. Delivery of alkalinity to the oceans is balanced by the production and burial of calcium carbonate in marine sediments, which results in a large reservoir of sedimentary calcium carbonate both in the ocean and in terrestrial rocks. Alkalinity also provides oceanic buffering capacity, which today results in about 60 times more dissolved carbon dioxide in the world oceans than is present as carbon dioxide gas in the atmosphere. Because calcium carbonate formation removes alkalinity from the oceans, calcium carbonate precipitation leads to the outgassing of carbon dioxide from the ocean into the atmosphere. Likewise, the dissolution of calcium carbonate adds alkalinity to the oceans, leading to an increased buffering capacity and a drawdown of atmospheric carbon dioxide concentration.
\r\n\r\nCalcium carbonate precipitation in the form of calcite and aragonite is almost exclusively mediated by biological organisms such as corals, coccoliths, and foraminifera, which use these minerals as components in their shells. calcium carbonate is overproduced by organisms in the ocean relative to the flux of alkalinity delivered to the oceans by rivers. Thus, a significant portion of calcium carbonate must be dissolved back into seawater for the ocean alkalinity cycle to come into steady state. Because of the link between alkalinity and carbon dioxide, the ocean alkalinity cycle has a direct effect on atmospheric carbon dioxide concentration especially on timescales less than 100,000 years.
\r\n\r\nHow fast calcium carbonate dissolves back into seawater is thus a crucial rate in determining the response of the oceanic system to perturbations in either alkalinity or carbon dioxide input to the ocean-atmosphere system. We are testing the kinetics of this system with the large amount of carbon dioxide emitted from fossil fuel burning, about one third of which has dissolved into the surface ocean. This process is known as ocean acidification, as carbon dioxide is an acid, soaking up buffering capacity and dropping ocean pH. This carbon dioxide will eventually be neutralized through the dissolution of carbonate rich deep-sea sediments, but the process will take a long time. This thesis makes new measurements calcite dissolution in seawater, in an attempt to build an understanding of the chemical processes responsible for dissolution kinetics.
\r\n\r\nI first introduce the new method, in which carbon-13 labeled calcium carbonate is dissolved in undersaturated seawater. Mass loss is directly traced by measuring the appearance of carbon-13 in seawater over time. The dissolution rate of calcite is a highly nonlinear function of calcite saturation state.
\r\n\r\nNext, I show that this tracer can tell us about the balance of precipitation and dissolution at the mineral surface. I use this balance to constrain mass fluxes due to precipitation and dissolution as a function of saturation state. I also show that the enzyme Carbonic Anhydrase (CA), which rapidly equilibrates carbon dioxide and carbonic acid, greatly enhances the rate of calcite dissolution especially near equilibrium. A model of dissolution is presented in which CA is most effective in the region where dissolution proceeds via etch pit nucleation at surface defects.
\r\n\r\nThe dissolution behavior of biogenic carbonates is also investigated using the carbon-13 method. I cultured coccoliths, foraminifera, and soft corals in carbon-13-labeled seawater so that their skeletons incorporated the carbon-13 tracer. These skeletons were then used in dissolution experiments. I show that both magnesium and organic matter contained within the calcite lattice have large effects on the dissolution behavior of biogenic carbonates. Magnesium content generally increases dissolution rate, and it is hypothesized that highly soluble magnesium-rich phases are preferentially removed from dissolving carbonates. Organic content generally decreases dissolution rate. It is hypothesized that organic matrices within the calcite lattice promote re-precipitation reactions, due to the balance of dissolution and precipitation rates in our data, and their promotion of precipitation during biomineralization.
\r\n\r\nI then analyze in 2- and 3-dimensions dissolved foraminiferal tests to locate where and how mass is being lost. It is shown that dissolution proceeds along specific layers, that are consistent with the size and location of Mg-rich carbonate spherules that are initially deposited during chamber formation. Surface topography generation of foraminiferal tests shows that sub-micron features are formed rapidly and then quickly eroded into larger pits and channels. These larger channels then propagate and cover the test surface at higher amounts of mass loss.
\r\n\r\nFinally, the involvement of CA in carbonate dissolution necessitates the measurement of CA activity in the environment, especially in carbonate-rich ecosystems such as reefs, carbonate-rich sediments, and carbonate-rich marine particles. To this end, I survey a number of available techniques for measuring CA activity. In the end, it is shown that the most effective method is based on measuring the depletion of oxygen-18 from carbon-13- and oxygen-18-labeled DIC, as measured by membrane inlet mass spectrometry (MIMS). This method is promising and shows about 0.1 nM CA present in unfiltered surface seawater collected from San Pedro Basin.
" }, { "name": "Teng, Alexander Pai-Chung", "degree": "PhD", "year": "2017", "title": "Insights on the Formation and Fate of Organic Nitrates in the Atmosphere from Field and Laboratory Observations", "advisor": "Wennberg, Paul O.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06042017-134711204", "creators": [ { "name": { "family": "Teng", "given": "Alexander Pai-Chung" }, "id": "Teng-Alexander-Pai-Chung", "orcid": "0000-0002-6434-0501", "display_name": "Teng, Alexander Pai-Chung" } ], "advisors": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "advisor", "display_name": "Wennberg, Paul O." } ], "committee": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "chair", "display_name": "Seinfeld, John H." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Sander", "given": "Stanley P." }, "id": "Sander-S-P", "role": "member", "display_name": "Sander, Stanley P." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9RV0KRJ", "abstract": "Alkenes are oxidized rapidly in the atmosphere by addition of OH and subsequently O2, leading to the formation of peroxy radicals. These peroxy radicals react with NO to form organic nitrates through a minor radical-terminating branching pathway. Over large regions of the continental boundary layer, the formation of organic nitrates control tropospheric ozone and the lifetime of NOx. Laboratory investigations described herein show that the yield of nitrates through this pathway is larger than previously described for alkenes, and the yield increases with the number of heavy atoms. This result is used to interpret field observations taken over Houston in the summer of 2013. These measurements show that small alkenes still play a large role in ozone production more than a decade after they had been identified as a causal factor.\r\n\r\nIn further studies, measurements of isoprene hydroxy nitrates (ISOPN) and hydroperoxides, formed from the OH oxidation of isoprene, are used to diagnose the complexities of reversible O2 addition for allylic hydroxy isoprene radicals. It is shown that over most of the atmosphere, isoprene's peroxy radical isomers are in their equilibrium distribution. In this regime, hydroxy peroxy radical isomers comprise approximately 95% of the radical pool, a much higher fraction than in the nascent (kinetic) distribution. Intramolecular H-shift isomerization from the Z hydroxy peroxy radical isomers produced from OH addition to C4 is estimated to be 4s-1 at 297K. While the Z isomer is initially produced in low yield, it is continually reformed via decomposition of the hydroxy peroxy radicals. As a result, unimolecular chemistry from this isomer contributes as much as half of the atmospheric fate of the entire pool of peroxy radicals formed via addition of OH at C4. In contrast, unimolecular chemistry following OH addition at C1 is slower and less important. \r\n\r\nField observations of alkyl nitrates over the Southeastern United States during the summer over forested environments show that there are still gaps in our understanding of the organic nitrate budget. The formation of isoprene hydroxy nitrates (ISOPN) is shown to be a dominant NOx loss pathway during the day. " }, { "name": "Walker, Jennifer Marie", "degree": "PhD", "year": "2017", "title": "Seasonal and Interannual Variability in South Asian Monsoon Dynamics", "advisor": "Bordoni, Simona", "url": "https://resolver.caltech.edu/CaltechTHESIS:06052017-175613926", "creators": [ { "name": { "family": "Walker", "given": "Jennifer Marie" }, "id": "Walker-Jennifer-Marie", "orcid": "0000-0002-1709-0888", "display_name": "Walker, Jennifer Marie" } ], "advisors": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "advisor", "display_name": "Bordoni, Simona" } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Su", "given": "Hui" }, "id": "Su-Hui", "role": "member", "display_name": "Su, Hui" } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9513W8K", "abstract": "Recent theoretical advances indicate that the South Asian summer monsoon (SASM) should be viewed as an energetically-direct cross-equatorial Hadley circulation, with the monsoonal precipitation primarily occurring in its ascending branch, rather than its traditional interpretation as a large land-sea breeze circulation. Despite these developments, very few studies have explored the implications of these emerging theories for the observed variability of the SASM.
\r\n\r\nThis is the goal of this PhD thesis, which uses atmospheric reanalysis data from recent decades to investigate seasonal transitions and interannual variability of the SASM. Our approach differs from previous studies in its focus on the large-scale atmospheric dynamics of the SASM: more specifically, we analyze the tropical circulation throughout the SASM sector and its relationship with extratropical weather systems in both hemispheres that can affect transports of momentum and energy.
\r\n\r\nThe atmospheric moisture budget over the SASM region provides a crucial starting point for our work. We use this budget to introduce a novel objective index for the onset and retreat of the SASM, which robustly captures the expected seasonal transitions in precipitation and winds and eliminates the need for arbitrarily selected thresholds. Using this index, we show how the SASM onset and retreat are associated with a coherent set of seasonal transitions in circulation, jet streams, precipitation, energetics, and momentum balance throughout the SASM sector. These transitions closely resemble those of the zonal mean Hadley circulation, indicating that the SASM projects strongly onto the zonal mean and that the observed SASM is consistent with new theoretical interpretations.
\r\n\r\nWe also use the atmospheric moisture budget to define a new index for the SASM strength on interannual time scales. We show that interannual variability in SASM net precipitation is primarily caused by variations in winds rather than variations in humidity, highlighting the importance of understanding drivers of the large-scale circulation and its changes. We then use linear regression analysis to identify robust changes in the circulation associated with SASM year-to-year variability. We find that strong monsoons are associated with a northward expansion of the overturning circulation and a decreased near-surface land-sea thermal contrast, in disagreement with the traditional view of the SASM as a sea-breeze circulation. We also find teleconnections between SASM strength and temperatures, winds, and momentum and energy transports in the southern hemisphere extratropics. These interhemispheric teleconnections, which have not been previously identified, suggest new directions for future research to improve our understanding of the mechanisms involved in SASM variability.
\r\n\r\nImportant advances in modeling and predicting the SASM at all timescales require a deeper understanding of the fundamental processes driving this system. Through theoretically-guided analyses of the SASM observed variability, this dissertation work takes an important step in this direction and provides novel insight into long-standing open questions on the SASM, with crucial implications for its predictability.
\r\n" }, { "name": "Ward, Lewis Michael", "degree": "PhD", "year": "2017", "title": "Microbial Evolution and the Rise of Oxygen: The Roles of Contingency and Context in Shaping the Biosphere through Time", "advisor": "Fischer, Woodward W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012017-152345273", "creators": [ { "name": { "family": "Ward", "given": "Lewis Michael" }, "id": "Ward-Lewis-Michael", "orcid": "0000-0002-9290-2567", "display_name": "Ward, Lewis Michael" } ], "advisors": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "advisor", "display_name": "Fischer, Woodward W." } ], "committee": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "chair", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "McGlynn", "given": "Shawn E." }, "id": "McGlynn-S-E", "role": "member", "display_name": "McGlynn, Shawn E." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." } ], "option_major": [ "geobiol" ], "doi": "10.7907/Z9BZ642S", "abstract": "We are shaped by our environment, but we then shape it in turn. This interplay between life and the Earth, and how these interactions have shaped both parties through time, is the heart of the discipline of geobiology. My research is fundamentally motivated by a desire to understand how life and the Earth have changed together through time to reach the state that they\u2019re at today, and to understand from this history how the coevolution of planet and life may be different on other worlds. The focus of my work has been on how the structure and productivity of the biosphere across time and space has been shaped by the metabolic opportunities provided by the environment\u2014as a result of both biotic and abiotic factors\u2014and the metabolic pathways that are available to life, as a result of evolutionary contingency in the evolution of pathways and their inheritance and horizontal transfer.
\r\n\r\nThe biosphere on Earth today is incredibly productive due to the coupled dominant metabolisms of oxygenic photosynthesis and aerobic respiration, yet these can\u2019t always be assumed to have been present\u2014considering life more broadly, for instance in the context of the early Earth and other planets, we have to grapple with how evolutionary contingency and planetary environments interact to constrain the metabolic opportunities and rates of productivity available to the biosphere. In this dissertation, I broadly consider how the size and structure of Earth\u2019s biosphere has changed through time as surface environments evolve and metabolic innovations accumulate. These investigations make use of information gleaned from the rock record of the early Earth, as well as the biological record of the history of life as preserved in the genomes, biochemistry, and ecology of extant organisms. These coupled records provide opportunities for constraining estimates of the opportunities for life throughout Earth history and elsewhere in the universe.
\r\n" }, { "name": "Yu, Hang Hank", "degree": "PhD", "year": "2017", "title": "Understanding the Symbiosis in Anaerobic Oxidation of Methane Through Metabolic, Biosynthetic and Transcriptomic Activities", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechThesis:06082017-134458390", "creators": [ { "name": { "family": "Yu", "given": "Hang Hank" }, "id": "Yu-Hang-Hank", "orcid": "0000-0002-7600-1582", "display_name": "Yu, Hang Hank" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "chair", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9XD0ZQQ", "abstract": "Microorganisms provide essential ecological services to our planet. Their combined activities control and shape our environment as we know today. In the deep sea, a microbial mediated process known as anaerobic oxidation of methane (AOM) consumes large amounts of methane, a potent greenhouse gas and a valuable energy resource. How this symbiosis works is poorly understood.
\r\n\r\nIn this thesis, I tested current hypotheses on the symbiotic mechanisms in AOM microbial consortia, consisting of a partnership between anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB). Sediments collected from methane seeps offshore Oregon and California and dominated by AOM consortia were used in these investigations. A range of compounds were amended to sediment microcosms, and their effects on the metabolic activities of ANME or SRB were monitored by tracking the rates of methane oxidation or sulfate reduction on timescales varying from hours to months. A lack of stimulation or inhibition on the AOM consortia, combined with long-term community profiles, suggest that diffusible compounds are unlikely to be involved in the symbiosis in AOM. I further examine ANME genomes, focusing the role of sulfur in methane seep ecosystems. Phylogenetic analyses revealed multiple poorly characterized genes in the sulfur pathway, and comparisons with methanogenic archaea related to ANME provided a better understanding of their roles in the cell. Transcriptional responses combined with protein modeling were used to predict the potential substrate of a sulfite reductase related enzyme. These predictions were validated using genetics, and together point to an assimilatory rather than dissimilatory sulfur pathway in methane-utilizing archaea in general. Then, the AOM symbiosis was decoupled for the first time using soluble electron acceptors. ANME remained metabolically and biosynthetically active without their SRB partner, suggesting that the electrons are transferred directly in this partnership. This observation was investigated to a greater depth with transcriptomics. Membrane proteins and multiheme cytochromes critical in extracellular electron transfer in ANME and SRB were expressed. These results together illuminate the path electrons may take to exit or enter the AOM consortia. Overall, multiple activity analyses used here piece together a clearer view on how the symbiosis in AOM works, with potential applications in future energy generation from methane.
\r\n" }, { "name": "Zhang, Qiong", "degree": "PhD", "year": "2017", "title": "Accounting for Aerosol Scattering in the Remote Sensing of Greenhouse Gas", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06152016-152036651", "creators": [ { "name": { "family": "Zhang", "given": "Qiong" }, "id": "Zhang-Qiong", "orcid": "0000-0002-8762-0557", "display_name": "Zhang, Qiong" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Frankenberg", "given": "Christian" }, "id": "Frankenberg-C", "role": "member", "display_name": "Frankenberg, Christian" }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9XW4GRQ", "abstract": "This thesis includes three different projects related to the remote sensing of Earth's atmosphere. The first part, comprising Chapter 2 and Chapter 3, focuses on the retrieval of Level 1 product, particularly the effect of aerosol scattering in the remote sensing of greenhouse gases. In Chapter 2, we study the aerosol induced bias in the retrieval of column averaged CO2 mixing ratios (XCO2). Ground based remote sensing data from the California Laboratory for Atmospheric Remote Sensing Fourier Transform Spectrometer (CLARS-FTS) are used. We employ a numerical radiative transfer model to simulate the impacts of neglecting aerosol scattering on the CO2 and O2 slant column densities (SCDs) operationally retrieved from CLARS-FTS measurements. These simulations show that the CLARS-FTS operational retrieval algorithm likely underestimates CO2 and O2 abundances over the LA basin in scenes with moderate aerosol loading. The bias in the CO2 and O2 abundances due to neglecting aerosol scattering cannot be canceled by ratioing each other in the derivation of the operational product of XCO2. We propose a method for approximately correcting the aerosol-induced bias. Results for CLARS XCO2 are compared to the direct-sun XCO2 retrievals from a nearby Total Carbon Column Observing Network (TCCON) station.
\r\n\r\nIn Chapter 3, we explain why large XCO2 retrieval errors are found over deserts in the space borne Orbiting Carbon Observatory-2 (OCO-2) data. We argue that these errors are caused by the surface albedo being close to a critical surface albedo (\u03b1c). Over a surface with albedo close to \u03b1c, increasing the aerosol optical depth (AOD) does not change the continuum radiance. The spectral signature caused by changing the AOD is identical to that caused by changing the absorbing gas column. The degeneracy in the retrievals of AOD and XCO2 results in a loss of degrees of freedom (DOF) and information content (H). We employ a radiative transfer model to study the physical mechanism of XCO2 retrieval error over a surface with albedo close to \u03b1c. Based on retrieval tests over surfaces with different albedos, we conclude that over a surface with albedo close to \u03b1c, the XCO2 retrieval suffers from a significant loss of accuracy.
\r\n\r\nIn the Appendix, we put in a Chapter based on my work with Prof. Andrew Thompson on ocean The second part, mainly in Chapter 4, focuses on the application of Level 2 product. In this Chapter, we examine the uncertainties in middle atmospheric HOx chemistry by comparing the Aura Microwave Limb Sound (MLS) OH and HO2 measurements with the simulations of the Caltech-JPL KINETICS photochemical model. The model using the standard chemical kinetics underestimates OH and HO2 concentrations in the mesosphere. To resolve the discrepancies, we use MLS OH and HO2 measurements as benchmark to adjust the involved chemical rate coefficients within reasonable uncertainty ranges with an optimal estimation algorithm. The results show that four key reaction rate constants and the O2 cross section at Lyman-\u03b1 (121.6 nm) are the most sensitive parameters for determining the HOx profiles. We conclude that the rate coefficient of H + O2 + M \u2192 HO2 + M requires a very large adjustment beyond the uncertainty limits recommended in the NASA Data Evaluation, which suggests the need for future laboratory measurements. An alternative explanation is that radiative association plays a significant role in this process, i.e. H + O2 \u2192 HO2 + hv, which has never been measured or computed.
\r\n\r\nIn the Appendix, we put in a Chapter based on my work with Prof. Andrew Thompson on ocean submesoscale turbulence.
\r\n" }, { "name": "Case, David Hamilton", "degree": "PhD", "year": "2016", "title": "Carbonate-Associated Microbial Ecology at Methane Seeps: Assemblage Composition, Response to Changing Environmental Conditions, and Implications for Biomarker Longevity", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-170051580", "creators": [ { "name": { "family": "Case", "given": "David Hamilton" }, "id": "Case-David-Hamilton", "orcid": "0000-0002-1023-0040", "display_name": "Case, David Hamilton" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Levin", "given": "Lisa A." }, "id": "Levin-L-A", "role": "member", "display_name": "Levin, Lisa A." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geochem" ], "doi": "10.7907/Z9TD9V84", "abstract": "Methane seeps are globally distributed geologic features in which reduced fluid from below the seafloor is advected upward and meets the oxidized bottom waters of Earth\u2019s oceans. This redox gradient fuels chemosynthetic communities anchored by the microbially-mediated anaerobic oxidation of methane (AOM). Both today and in Earth\u2019s past, methane seeps have supported diverse biological communities extending from microorgansisms to macrofauna and adding to the diversity of life on Earth. Simultaneously, the carbon cycling associated with methane seeps may have played a significant role in modulating ancient Earth\u2019s climate, particularly by acting as a control on methane emissions.
\r\n\r\nThe AOM metabolism generates alkalinity and dissolved inorganic carbon (DIC) and at a 2:1 ratio, promoting the abiogenic, or authigenic, precipitation of carbonate minerals. Over time, these precipitates can grow into pavements covering hundreds of square meters on the seafloor and dominating the volumetric habitat space available in seep ecosystems. Importantly, carbonates are incorporated into the geologic record and therefore preserve an inorganic (i.e., d13C) and organic (i.e., lipid biomarker) history of methane seepage. However, the extent to which preserved biomarkers represent a snapshot of microorganisms present at the time of primary precipitation, a time-integrated history of microbial assemblages across the life cycle of a methane seep, or a view of the final microorganisms inhabiting a carbonate prior to incorporation in the sedimentary record is unresolved.
\r\n\r\nThis thesis addresses the ecology of carbonate-associated seep microorganisms. Chapters One and Two contextualize the extant microbial diversity on seep carbonates versus within seep sediments, as determined through 16S rRNA gene biomarkers. Small, protolithic carbonate \u201cnodules\u201d recovered from within seep sediments are observed to be capable of capturing surrounding sediment-hosted microbial diversity, but in some cases also diverge from sediments. Meanwhile, lithified carbonate blocks recovered from the seafloor host microbial assemblages demonstrably distinct from seep sediments (and seep nodules). Microbial 16S rRNA gene diversity within carbonate samples is well-differentiated by the extent of contemporary seepage. In situ seafloor transplantation experiments further demonstrated the microbial assemblages associated with seep carbonates to be sensitive to seep quiescence and activation on short (13-month) timescales. This was particularly true for organisms whose 16S rRNA genes imply physiologies dependent on methane or sulfur oxidation. With an improved understanding of the modern ecology of carbonate-associated microorganisms, Chapter Three applies intact polar lipid (IPL) and core lipid analyses to begin describing whether, and to what extent, geologically relevant biomarkers mimic short-term dynamics observed in 16S rRNA gene profiles versus archive a record of historic microbial diversity. Biomarker longevity is determined to increase from 16S rRNA genes to IPLs to core lipids, with IPLs preserving microbial diversity history on timescales more similar to 16S rRNA genes than core lipids. Ultimately, individual IPL biomarkers are identified which may be robust proxies for determining whether the biomarker profile recorded in a seep carbonate represents vestiges of active seepage processes, or the profile of a microbial community persisting after seep quiescence.
" }, { "name": "Chen, Jinqiang", "degree": "PhD", "year": "2016", "title": "Dynamics of the East Asian Summer Monsoon in Present and Future Climates", "advisor": "Bordoni, Simona", "url": "https://resolver.caltech.edu/CaltechTHESIS:09022015-090357274", "creators": [ { "name": { "family": "Chen", "given": "Jinqiang" }, "id": "Chen-Jinqiang", "display_name": "Chen, Jinqiang" } ], "advisors": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "advisor", "display_name": "Bordoni, Simona" } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9G44N60", "abstract": "This thesis aims at enhancing our fundamental understanding of the East Asian summer monsoon (EASM), and mechanisms implicated in its climatology in present-day and warmer climates. We focus on the most prominent feature of the EASM, i.e., the so-called Meiyu-Baiu (MB), which is characterized by a well-defined, southwest to northeast elongated quasi-stationary rainfall band, spanning from eastern China to Japan and into the northwestern Pacific Ocean in June and July.
\r\n\r\nWe begin with an observational study of the energetics of the MB front in present-day climate. Analyses of the moist static energy (MSE) budget of the MB front indicate that horizontal advection of moist enthalpy, primarily of dry enthalpy, sustains the front in a region of otherwise negative net energy input into the atmospheric column. A decomposition of the horizontal dry enthalpy advection into mean, transient, and stationary eddy fluxes identifies the longitudinal thermal gradient due to zonal asymmetries and the meridional stationary eddy velocity as the most influential factors determining the pattern of horizontal moist enthalpy advection. Numerical simulations in which the Tibetan Plateau (TP) is either retained or removed show that the TP influences the stationary enthalpy flux, and hence the MB front, primarily by changing the meridional stationary eddy velocity, with reinforced southerly wind on the northwestern flank of the north Pacific subtropical high (NPSH) over the MB region and northerly wind to its north. Changes in the longitudinal thermal gradient are mainly confined to the near downstream of the TP, with the resulting changes in zonal warm air advection having a lesser impact on the rainfall in the extended MB region.
\r\n\r\nSimilar mechanisms are shown to be implicated in present climate simulations in the Couple Model Intercomparison Project - Phase 5 (CMIP5) models. We find that the spatial distribution of the EASM precipitation simulated by different models is highly correlated with the meridional stationary eddy velocity. The correlation becomes more robust when energy fluxes into the atmospheric column are considered, consistent with the observational analyses. The spread in the area-averaged rainfall amount can be partially explained by the spread in the simulated globally-averaged precipitation, with the rest primarily due to the lower-level meridional wind convergence. Clear relationships between precipitation and zonal and meridional eddy velocities are observed.
\r\n\r\nFinally, the response of the EASM to greenhouse gas forcing is investigated at different time scales in CMIP5 model simulations. The reduction of radiative cooling and the increase in continental surface temperature occur much more rapidly than changes in sea surface temperatures (SSTs). Without changes in SSTs, the rainfall in the monsoon region decreases (increases) over ocean (land) in most models. On longer time scales, as SSTs increase, rainfall changes are opposite. The total response to atmospheric CO^2 forcing and subsequent SST warming is a large (modest) increase in rainfall over ocean (land) in the EASM region. Dynamic changes, in spite of significant contributions from the thermodynamic component, play an important role in setting up the spatial pattern of precipitation changes. Rainfall anomalies over East China are a direct consequence of local land-sea contrast, while changes in the larger-scale oceanic rainfall band are closely associated with the displacement of the larger-scale NPSH. Numerical simulations show that topography and SST patterns play an important role in rainfall changes in the EASM region.
" }, { "name": "Jiang, Junle", "degree": "PhD", "year": "2016", "title": "Probabilistic Imaging and Dynamic Modeling of Earthquake Source Processes", "advisor": "Lapusta, Nadia; Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:10142015-142502895", "creators": [ { "name": { "family": "Jiang", "given": "Junle" }, "id": "Jiang-Junle", "orcid": "0000-0002-8796-5846", "display_name": "Jiang, Junle" } ], "advisors": [ { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "co-advisor", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "co-advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "chair", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9639MQC", "abstract": "Investigation of large, destructive earthquakes is challenged by their infrequent occurrence and the remote nature of geophysical observations. This thesis sheds light on the source processes of large earthquakes from two perspectives: robust and quantitative observational constraints through Bayesian inference for earthquake source models, and physical insights on the interconnections of seismic and aseismic fault behavior from elastodynamic modeling of earthquake ruptures and aseismic processes.
\r\n\r\nTo constrain the shallow deformation during megathrust events, we develop semi-analytical and numerical Bayesian approaches to explore the maximum resolution of the tsunami data, with a focus on incorporating the uncertainty in the forward modeling. These methodologies are then applied to invert for the coseismic seafloor displacement field in the 2011 Mw 9.0 Tohoku-Oki earthquake using near-field tsunami waveforms and for the coseismic fault slip models in the 2010 Mw 8.8 Maule earthquake with complementary tsunami and geodetic observations. From posterior estimates of model parameters and their uncertainties, we are able to quantitatively constrain the near-trench profiles of seafloor displacement and fault slip. Similar characteristic patterns emerge during both events, featuring the peak of uplift near the edge of the accretionary wedge with a decay toward the trench axis, with implications for fault failure and tsunamigenic mechanisms of megathrust earthquakes.
\r\n\r\nTo understand the behavior of earthquakes at the base of the seismogenic zone on continental strike-slip faults, we simulate the interactions of dynamic earthquake rupture, aseismic slip, and heterogeneity in rate-and-state fault models coupled with shear heating. Our study explains the long-standing enigma of seismic quiescence on major fault segments known to have hosted large earthquakes by deeper penetration of large earthquakes below the seismogenic zone, where mature faults have well-localized creeping extensions. This conclusion is supported by the simulated relationship between seismicity and large earthquakes as well as by observations from recent large events. We also use the modeling to connect the geodetic observables of fault locking with the behavior of seismicity in numerical models, investigating how a combination of interseismic geodetic and seismological estimates could constrain the locked-creeping transition of faults and potentially their co- and post-seismic behavior.
" }, { "name": "Laraia, Anne Louise", "degree": "PhD", "year": "2016", "title": "Observations and Modeling of Tropical Planetary Atmospheres", "advisor": "Bordoni, Simona", "url": "https://resolver.caltech.edu/CaltechTHESIS:06252015-185841054", "creators": [ { "name": { "family": "Laraia", "given": "Anne Louise" }, "id": "Laraia-Anne-Louise", "display_name": "Laraia, Anne Louise" } ], "advisors": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "advisor", "display_name": "Bordoni, Simona" } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9J1012T", "abstract": "This thesis is a comprised of three different projects within the topic of tropical atmospheric dynamics. First, I analyze observations of thermal radiation from Saturn\u2019s atmosphere and from them, determine the latitudinal distribution of ammonia vapor near the 1.5-bar pressure level. The most prominent feature of the observations is the high brightness temperature of Saturn\u2019s subtropical latitudes on either side of the equator. After comparing the observations to a microwave radiative transfer model, I find that these subtropical bands require very low ammonia relative humidity below the ammonia cloud layer in order to achieve the high brightness temperatures observed. We suggest that these bright subtropical bands represent dry zones created by a meridionally overturning circulation.
\r\n\r\nSecond, I use a dry atmospheric general circulation model to study equatorial superrotation in terrestrial atmospheres. A wide range of atmospheres are simulated by varying three parameters: the pole-equator radiative equilibrium temperature contrast, the convective lapse rate, and the planetary rotation rate. A scaling theory is developed that establishes conditions under which superrotation occurs in terrestrial atmospheres. The scaling arguments show that superrotation is favored when the off-equatorial baroclinicity and planetary rotation rates are low. Similarly, superrotation is favored when the convective heating strengthens, which may account for the superrotation seen in extreme global-warming simulations.
\r\n\r\nThird, I use a moist slab-ocean general circulation model to study the impact of a zonally-symmetric continent on the distribution of monsoonal precipitation. I show that adding a hemispheric asymmetry in surface heat capacity is sufficient to cause symmetry breaking in both the spatial and temporal distribution of precipitation. This spatial symmetry breaking can be understood from a large-scale energetic perspective, while the temporal symmetry breaking requires consideration of the dynamical response to the heat capacity asymmetry and the seasonal cycle of insolation. Interestingly, the idealized monsoonal precipitation bears resemblance to precipitation in the Indian monsoon sector, suggesting that this work may provide insight into the causes of the temporally asymmetric distribution of precipitation over southeast Asia.
\r\n" }, { "name": "Li, Dunzhu", "degree": "PhD", "year": "2016", "title": "Some Advances in Computational Geophysics: Seismic Wave and Inverse Geodynamic Modeling", "advisor": "Helmberger, Donald V.; Gurnis, Michael C.; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-150442765", "creators": [ { "name": { "family": "Li", "given": "Dunzhu" }, "id": "Li-Dunzhu", "orcid": "0000-0003-3149-0236", "display_name": "Li, Dunzhu" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "co-advisor", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "co-advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9X63JW2", "abstract": "In this thesis, I develop computational methods that link theory with geophysical observations, with one part devoted to the development of forward models of seismic wave propagation through the mantle and core, and a second part devoted to the inversion of viscous flow in the mantle.
\r\n\r\nFirst order seismic structure of the earth has been well described radially since the PREM model was introduced. With the help of seismic tomography methods, many large-scale heterogeneous structures have become well imaged. Based on this progress, the information in seismic waveforms, which provides extra constraints, is becoming more important in determination of the detailed structure within the earth's interior. However, 3-D modeling of seismic wave propagation remains computationally expensive, especially at high frequency, because the computing cost scales with fourth power of frequency. Thus 2-D modeling is often used, and in many cases is sufficient for the problem. To use 2-D modeling in global seismology, several issues need to be considered: how to handle the differences in geometric spreading between 2-D and 3-D modeling, how to incorporate earthquake sources into a 2-D code, and how to handle the spherical geometry of the earth. In the first part of my thesis, we solve all three problems, using a 2-D staggered finite difference method with a post-processing step. The post-processing automatically corrects the geometric spreading difference between 2-D and 3-D wave propagation; the earthquake sources are added to the 2-D finite difference simulation using a momentum source and transparent box approaches; the earth-flattening is discussed, especially for the density transformation. Benchmarks of the new method against with 1-D and 3-D code demonstrates the the accuracy of the method.
\r\n\r\nWe then use the new code in a study of the interface between outer and inner core. Inner Core Boundary (ICB) is thought to be crucial in estimating the energy released in generating the geomagnetic field. One direct constraint on ICB properties is using reflected P wave from ICB, the PKiKP phase. Due to its small amplitude, near distance PKiKP is seldom observed. However, we find several events beneath Central American as having good set of PKiKP recordings from the USArray seismic network, as well as other core phases like P wave reflection with Core Mantle Boundary (CMB). The amplitude of the phases display large scatters across the stations, which are potentially caused by many factors, including site effects of the stations, upper mantle inhomogeneity, or a bumpy structure along either the CMB or ICB. After comparing amplitude ratio of between PKiKP and PcP phase, analyzing how this ratio changes for different nearby events, and computing forward models using our new method that investigate different factors influence the PKiKP phases, we attribute a stacked amplitude pattern as caused by ICB structure, in which PKiKP phase amplitude rapidly changes within a small range. Finally, we model this observed seismic pattern as a small dome-like anomalies above ICB, where the material changes from that of the outer core to that of inner core gradually.
\r\n\r\nThe final part of my thesis is on a geodynamic inversion problem for mantle convection. Mantle convection is an important process that determines plate motions and subduction. Numerous forward models indicate that the constitute relation (viscosity law) is of key importance for mantle convection. Despite substantial effort attempting to determine the viscosity structure of the mantle, either through forward and inverse geophysical models or through laboratory work, many first order questions remain. We assume the realistic viscosity structure, which is temperature and strain-rate dependent, can be parameterized using a set of scalar parameters. Given this set of viscosity parameters and an initial temperature, the mantle evolves following a set of partial differential equations (PDEs). Our goal with the inverse problem is to recover the viscosity parameters and initial temperature by fitting the observational data, which here includes plate motion history and the present day temperature distribution of the mantle. We formulate this inversion problem following a PDE constrained optimization framework. We first define the cost function we want to minimize; then, the derivative of the cost function with respect to viscosity parameters and initial temperature is calculated following the discrete adjoint equations; finally, a gradient-based optimization method, limited memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) approach is used to find the minimum. To accelerate the optimization process, we modified the traditional LBFGS by adding a preconditioner, and achieve a more rapid convergence. To test our method, we use two synthetic cases: a sinking cylinder within a viscous layer and a realistic subduction model. We find that in the initial temperature-only inversion, the initial temperature can be recovered well; in the joint inversion of initial temperature and viscosity parameters, the temperature, as well as effective viscosity, can also be recovered reasonably, but there are trade offs between viscosity parameters. Presumably, the trade off in viscosity parameters is related to the ill-posedness of the problem.
" }, { "name": "Ma, Yiran", "degree": "PhD", "year": "2016", "title": "Imaging the Earth with Ambient Noise and Earthquakes", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12192015-004219343", "creators": [ { "name": { "family": "Ma", "given": "Yiran" }, "id": "Ma-Yiran", "orcid": "0000-0002-8369-3310", "display_name": "Ma, Yiran" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "orcid": "0000-0003-1809-6672", "role": "chair", "display_name": "Tsai, Victor C." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/Z90Z7155", "abstract": "In this thesis, I develop the velocity and structure models for the Los Angeles Basin and Southern Peru. The ultimate goal is to better understand the geological processes involved in the basin and subduction zone dynamics. The results are obtained from seismic interferometry using ambient noise and receiver functions using earthquake- generated waves. Some unusual signals specific to the local structures are also studied. The main findings are summarized as follows:My focus in this thesis is to contribute to a more thorough understanding of the mechanics of ice and deformable glacier beds. Glaciers flow under their own weight through a combination of deformation within the ice column and basal slip, which involves both sliding along and deformation within the bed. Deformable beds, which are made up of unfrozen sediment, are prevalent in nature and are often the primary contributors to ice flow wherever they are found. Their granular nature imbues them with unique mechanical properties that depend on the granular structure and hydrological properties of the bed. Despite their importance for understanding glacier flow and the response of glaciers to changing climate, the mechanics of deformable glacier beds are not well understood.
\r\n\r\nOur general approach to understanding the mechanics of bed deformation and their effect on glacier flow is to acquire synoptic observations of ice surface velocities and their changes over time and to use those observations to infer the mechanical properties of the bed. We focus on areas where changes in ice flow over time are due to known environmental forcings and where the processes of interest are largely isolated from other effects. To make this approach viable, we further develop observational methods that involve the use of mapping radar systems. Chapters 2 and 5 focus largely on the development of these methods and analysis of results from ice caps in central Iceland and an ice stream in West Antarctica. In Chapter 3, we use these observations to constrain numerical ice flow models in order to study the mechanics of the bed and the ice itself. We show that the bed in an Iceland ice cap deforms plastically and we derive an original mechanistic model of ice flow over plastically deforming beds that incorporates changes in bed strength caused by meltwater flux from the surface. Expanding on this work in Chapter 4, we develop a more detailed mechanistic model for till-covered beds that helps explain the mechanisms that cause some glaciers to surge quasi-periodically. In Antarctica, we observe and analyze the mechanisms that allow ocean tidal variations to modulate ice stream flow tens of kilometers inland. We find that the ice stream margins are significantly weakened immediately upstream of the area where ice begins to float and that this weakening likely allows changes in stress over the floating ice to propagate through the ice column.
" }, { "name": "Nakajima, Miki", "degree": "PhD", "year": "2016", "title": "Origin of the Earth and Moon", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272016-122421111", "creators": [ { "name": { "family": "Nakajima", "given": "Miki" }, "id": "Nakajima-Miki", "display_name": "Nakajima, Miki" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9D798C0", "abstract": "According to the giant impact hypothesis, the Moon formed from a disk created by an impact between the proto-Earth and an impactor. Three major models for this hypothesis are (a) standard model: a Mars-sized impactor hit the Earth; (b) fast-spinning Earth model: a small impactor hit a rapidly spinning Earth; and (c) sub-Earths model: two half-Earth sized planets collided. These models have been supported because they can explain several observed features of the Earth-Moon system, such as the Moon's mass, angular momentum, and potentially geochemical measurements that suggest that the Earth and Moon have nearly identical isotopic ratios.
\r\n\r\nHowever, it is uncertain if these models are consistent with other geochemical constraints. For example, isotopic measurements of Earth's rocks indicate that the early Earth's mantle was chemically heterogeneous and this signature was preserved for billions of years. However, it is not clear if the giant impact hypothesis is consistent with this geochemical constraint because the giant impact could have been so energetic that the Earth's mantle could have completely mixed and homogenized. Furthermore, the fraction of the Earth's mantle that became molten by the impact is not well known, even though it is known to have significantly affected the subsequent evolutions of the Earth's interior and atmosphere. Additionally, the water and volatile content of the Moon may have an important implication for the lunar origin. Since the Moon-forming disk formed through a giant impact process, it must have been hot and partially vaporized. From this disk, a significant amount of water and volatiles may have escaped to space. However, this idea may contradict recent geochemical studies that indicate that Moon may not be as dry as previously thought.
\r\n\r\nFurthermore, moons of other planets may provide comprehensive pictures of the origin and evolution of the moons. For example, the Pluto-Charon system could have formed via a giant impact. Recent studies also suggest that Mars' satellites Phobos and Deimos could have formed in the same way. In contrast, satellites around the gas giants could have formed in situ from their proto-satellite disks and by gravitational capture. One of the Saturnian satellites, Enceladus has very unique geological and dynamical features. Cassini spacecraft observed that water plumes are emanating from cracks on the surface (so-called ``tiger stripes''). These plumes may originate from a few kilometer deep subsurface liquid ocean. Along the cracks, strong thermal emissions have been observed and these are thought to be related to the plume activities, but the connection has been still unclear.
\r\n\r\nIn my Ph.D. thesis, I aim to understand the origin and evolution of the Earth, Moon, and the Saturnian moon Enceladus.\r\nIn order to understand the initial state of the Earth's mantle and the Moon-forming disk, I perform giant impact simulations with a method called smoothed particle hydrodynamics (SPH). I show that the Earth's mantle becomes mostly molten by the impact and that the mantle remains unmixed in (a), but it may be at least partly mixed in (b) and (c). Therefore, (a) is most consistent with the preservation of the mantle heterogeneity. As for the Moon-forming disk, my calculations show that the disk of the standard model has a relatively low temperature (up to 4500 K) and low vapor mass fraction (~20-30%) while the disk formed by other models could be much hotter (6000-7000 K) and has a higher vapor mass fraction (80-90 %). Furthermore, I investigate the structure of the Moon-forming disk and estimated the extent of water escape. I show that escape is in the diffusion-limited regime and water escape from the disk to space is minor. This result could explain recent measurements on lunar water abundance. Furthermore, I develop a dynamical model that includes flow dynamics and flow-ice wall interaction that explains the Enceladus plume mass flux, heat flux, and several observed signatures. These studies will deepen comprehensive understanding of the origin of the moons in the solar system.
" }, { "name": "Newcombe, Megan Eve", "degree": "PhD", "year": "2016", "title": "Solubility and Diffusivity of Water in Lunar Basalt, and Chemical Zonation in Olivine-Hosted Melt Inclusions", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12212015-153532580", "creators": [ { "name": { "family": "Newcombe", "given": "Megan Eve" }, "id": "Newcombe-Megan-Eve", "orcid": "0000-0002-8450-768X", "display_name": "Newcombe, Megan Eve" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geol" ], "doi": "10.7907/Z9V985ZQ", "abstract": "I report the solubility and diffusivity of water in lunar basalt and an iron-free basaltic analogue at 1 atm and 1350 \u00b0C. Such parameters are critical for understanding the degassing histories of lunar pyroclastic glasses. Solubility experiments have been conducted over a range of fO2 conditions from three log units below to five log units above the iron-w\u00fcstite buffer (IW) and over a range of pH2/pH2O from 0.03 to 24. Quenched experimental glasses were analyzed by Fourier transform infrared spectroscopy (FTIR) and secondary ionization mass spectrometry (SIMS) and were found to contain up to ~420 ppm water. Results demonstrate that, under the conditions of our experiments: (1) hydroxyl is the only H-bearing species detected by FTIR; (2) the solubility of water is proportional to the square root of pH2O in the furnace atmosphere and is independent of fO2 and pH2/pH2O; (3) the solubility of water is very similar in both melt compositions; (4) the concentration of H2 in our iron-free experiments is <3 ppm, even at oxygen fugacities as low as IW-2.3 and pH2/pH2O as high as 24; and (5) SIMS analyses of water in iron-rich glasses equilibrated under variable fO2 conditions can be strongly influenced by matrix effects, even when the concentrations of water in the glasses are low. Our results can be used to constrain the entrapment pressure of the lunar melt inclusions of Hauri et al. (2011).
\r\n\r\nDiffusion experiments were conducted over a range of fO2 conditions from IW-2.2 to IW+6.7 and over a range of pH2/pH2O from nominally zero to ~10. The water concentrations measured in our quenched experimental glasses by SIMS and FTIR vary from a few ppm to ~430 ppm. Water concentration gradients are well described by models in which the diffusivity of water (D*water) is assumed to be constant. The relationship between D*water and water concentration is well described by a modified speciation model (Ni et al. 2012) in which both molecular water and hydroxyl are allowed to diffuse. The success of this modified speciation model for describing our results suggests that we have resolved the diffusivity of hydroxyl in basaltic melt for the first time. Best-fit values of D*water for our experiments on lunar basalt vary within a factor of ~2 over a range of pH2/pH2O from 0.007 to 9.7, a range of fO2 from IW-2.2 to IW+4.9, and a water concentration range from ~80 ppm to ~280 ppm. The relative insensitivity of our best-fit values of D*water to variations in pH2 suggests that H2 diffusion was not significant during degassing of the lunar glasses of Saal et al. (2008). D*water during dehydration and hydration in H2/CO2 gas mixtures are approximately the same, which supports an equilibrium boundary condition for these experiments. However, dehydration experiments into CO2 and CO/CO2 gas mixtures leave some scope for the importance of kinetics during dehydration into H-free environments. The value of D*water chosen by Saal et al. (2008) for modeling the diffusive degassing of the lunar volcanic glasses is within a factor of three of our measured value in our lunar basaltic melt at 1350 \u00b0C.
\r\n \r\nIn Chapter 4 of this thesis, I document significant zonation in major, minor, trace, and volatile elements in naturally glassy olivine-hosted melt inclusions from the Siqueiros Fracture Zone and the Galapagos Islands. Components with a higher concentration in the host olivine than in the melt (MgO, FeO, Cr2O3, and MnO) are depleted at the edges of the zoned melt inclusions relative to their centers, whereas except for CaO, H2O, and F, components with a lower concentration in the host olivine than in the melt (Al2O3, SiO2, Na2O, K2O, TiO2, S, and Cl) are enriched near the melt inclusion edges. This zonation is due to formation of an olivine-depleted boundary layer in the adjacent melt in response to cooling and crystallization of olivine on the walls of the melt inclusions concurrent with diffusive propagation of the boundary layer toward the inclusion center.
\r\n\r\nConcentration profiles of some components in the melt inclusions exhibit multicomponent diffusion effects such as uphill diffusion (CaO, FeO) or slowing of the diffusion of typically rapidly diffusing components (Na2O, K2O) by coupling to slow diffusing components such as SiO2 and Al2O3. Concentrations of H2O and F decrease towards the edges of some of the Siqueiros melt inclusions, suggesting either that these components have been lost from the inclusions into the host olivine late in their cooling histories and/or that these components are exhibiting multicomponent diffusion effects.
\r\n\r\nA model has been developed of the time-dependent evolution of MgO concentration profiles in melt inclusions due to simultaneous depletion of MgO at the inclusion walls due to olivine growth and diffusion of MgO in the melt inclusions in response to this depletion. Observed concentration profiles were fit to this model to constrain their thermal histories. Cooling rates determined by a single-stage linear cooling model are 150\u201313,000 \u00b0C hr-1 from the liquidus down to ~1000 \u00b0C, consistent with previously determined cooling rates for basaltic glasses; compositional trends with melt inclusion size observed in the Siqueiros melt inclusions are described well by this simple single-stage linear cooling model. Despite the overall success of the modeling of MgO concentration profiles using a single-stage cooling history, MgO concentration profiles in some melt inclusions are better fit by a two-stage cooling history with a slower-cooling first stage followed by a faster-cooling second stage; the inferred total duration of cooling from the liquidus down to ~1000 \u00b0C is 40 s to just over one hour.
\r\n\r\nBased on our observations and models, compositions of zoned melt inclusions (even if measured at the centers of the inclusions) will typically have been diffusively fractionated relative to the initially trapped melt; for such inclusions, the initial composition cannot be simply reconstructed based on olivine-addition calculations, so caution should be exercised in application of such reconstructions to correct for post-entrapment crystallization of olivine on inclusion walls. Off-center analyses of a melt inclusion can also give results significantly fractionated relative to simple olivine crystallization.
\r\n\r\nAll melt inclusions from the Siqueiros and Galapagos sample suites exhibit zoning profiles, and this feature may be nearly universal in glassy, olivine-hosted inclusions. If so, zoning profiles in melt inclusions could be widely useful to constrain late-stage syneruptive processes and as natural diffusion experiments.
\r\n" }, { "name": "Prancevic, Jeffrey Paul", "degree": "PhD", "year": "2016", "title": "Sediment Mobility in Steep Channels and the Transition to Landsliding", "advisor": "Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272016-111304491", "creators": [ { "name": { "family": "Prancevic", "given": "Jeffrey Paul" }, "id": "Prancevic-Jeffrey-Paul", "display_name": "Prancevic, Jeffrey Paul" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Hunt", "given": "Melany L." }, "id": "Hunt-M-L", "role": "member", "display_name": "Hunt, Melany L." }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "member", "display_name": "Tsai, Victor C." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9W66HRP", "abstract": "The mobility of sediment in steep mountain rivers controls the denudation rate and height of mountain ranges worldwide. Sediment movement within the steepest terrain often occurs as catastrophic shallow landsliding, posing significant hazards to those living downstream. Despite the importance of steep channels, our observations of sediment transport are mostly limited to rivers with slopes of less than 2\u00b0. This prevents us from predicting the runoff required to transport sediment throughout most of the drainage network and from knowing the mode of transport that should dominate (dilute river transport vs. landsliding). I performed a series of laboratory experiments in an artificial river with an adjustable slope to test the flow depths required to transport sediment on slopes up to the dry angle of repose. Counterintuitively, sediment becomes harder to move on steeper slopes by dilute river processes. Laboratory observations of flow hydraulics and field observations of cobble stability reveal that this reduced mobility is a hydraulic effect resulting from the shallow flows that are inherent to steep channels. In experiments that were conducted at slopes steeper than half of the dry angle of repose, sediment was more easily transported by shallow landsliding than dilute river processes. Within this landsliding regime, sediment was again observed to be more stable than predicted by traditional theory. Documentation of these experimental failures with high-speed video revealed that failures occur with a characteristic length scale that is shorter than predicted, and that these short failures experience a strong buttressing force at their downstream margin. These results suggest that landslide length scales consistently with width, and also provides new expectations for the saturation level required to initiate failures. Ultimately, these experiments provide us with expectations of the flow depth required to transport sediment throughout the entire drainage network, and also allow us to partition the drainage network into river-dominated and landslide-dominated regimes." }, { "name": "Raven, Morgan Reed", "degree": "PhD", "year": "2016", "title": "Organic Matter Sulfurization in the Modern Ocean", "advisor": "Sessions, Alex L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-125832967", "creators": [ { "name": { "family": "Raven", "given": "Morgan Reed" }, "id": "Raven-Morgan-Reed", "orcid": "0000-0003-4953-9966", "display_name": "Raven, Morgan Reed" } ], "advisors": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "advisor", "display_name": "Sessions, Alex L." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Lyons", "given": "Timothy W." }, "id": "Lyons-T-W", "role": "member", "display_name": "Lyons, Timothy W." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z91Z42B0", "abstract": "Only a tiny fraction of the carbon fixed by primary producers in the surface ocean is preserved in sediments, but this organic matter (OM) burial is one of the main processes linking the short and long-term carbon cycles, giving it important roles in global biogeochemistry. OM-rich deposits often contain abundant organic S (OS), and sulfur incorporation is thought to make OM less available for heterotrophs and more likely to be preserved. Still, we have few constraints on the significance of sulfurization for OM burial in the modern ocean, and fewer on how that flux might have differed in the past. This thesis applies a new generation of analytical tools for S-isotope analysis to investigate the timescales and mechanisms of OM sulfurization in the modern ocean. By measuring the \u03b434S values of minor S phases and individual S-bearing organic compounds as well as major sedimentary phases, we are able to make progress on long-standing questions about the distribution of S isotopes among organic and inorganic S phases in sediments.
\r\n\r\nChapters 2 and 3 focus on Cariaco Basin, where a large proportion of the OS in sediments appears to derive from OM sulfurization in particles sinking through the water column. Rapid sulfurization likely involves polysulfides and is associated with high primary productivity and OM export. In the sediments, low-molecular-weight organosulfur compounds accumulate over longer timescales and have low and distinctive \u03b434S values. Chapter 4 presents records from Santa Barbara Basin, where OS appears to be exchanging with less abundant porewater sulfide and controlling its \u03b434S value. As in many environments, pyrite in these sediments is more 34S-depleted than either OS or sulfide. We attribute this pattern to pyrite formation within sulfide-generating microenvironments prior to equilibration between OS and sulfide in porewater. Chapter 5 tests the feasibility of the proposed OS\u2013sulfide exchange and confirms that sulfide \u03b434S can reflect equilibrium with natural OM. We also find evidence that sulfurization of thiols may involve an interim polysulfide that includes the thiol S atom, providing a mechanism to mix biogenic S into proto-kerogen and potentially helping explain differences between the global pyrite and OS S-isotope records.
\r\n" }, { "name": "Scheingross, Joel Simon", "degree": "PhD", "year": "2016", "title": "Mechanics of Sediment Transport and Bedrock Erosion in Steep Landscapes", "advisor": "Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10092015-125804519", "creators": [ { "name": { "family": "Scheingross", "given": "Joel Simon" }, "id": "Scheingross-Joel-Simon", "orcid": "0000-0002-7220-8084", "display_name": "Scheingross, Joel Simon" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9B8562B", "abstract": "Erosion is concentrated in steep landscapes such that, despite accounting for only a small fraction of Earth\u2019s total surface area, these areas regulate the flux of sediment to downstream basins, and their rugged morphology records transient changes (or lack thereof) in geologic and climatic forcing. Steep landscapes are geomorphically active; large sediment fluxes and rapid landscape evolution rates can create or destroy habitat for humans and wildlife alike, and landslides, debris flows, and floods common in mountainous areas represent a persistent natural and structural hazard. Despite the central role that steep landscapes play in the geosciences and in landscape management, the processes controlling their evolution have been poorly studied compared to lower-gradient areas. This thesis focuses on the basic mechanics of sediment transport and bedrock incision in steep landscapes, as these are the fundamental processes which set the pace and style of landscape evolution. Chapter 1 examines the spatial distribution of slow-moving landslides; these landslides can dominate sediment fluxes to river networks, but the controls on their occurrence are poorly understood. Using a case-study along the San Andreas Fault, California, I show that slow-moving landslides preferentially occur near the fault, suggesting a rock-strength control on landslide distribution. Chapter 2 provides the first field-measurements of incipient sediment motion in streams steeper than 14% and shows a large influence of slope-dependent flow hydraulics and grain-scale roughness on particle motion. Chapter 3 presents experimental evidence for bedrock erosion by suspended sediment, suggesting that, in contrast to prevailing theoretical predictions, suspension-regime transport in steep streams can be the dominant erosion agent. Steep streams are often characterized by the presence of waterfalls and bedrock steps which can have locally high rates of erosion; Chapters 4 and 5 present newly developed, experimentally validated theory on sediment transport through and bedrock erosion in waterfall plunge pools. Finally, Chapter 6 explores the formation of a bedrock slot canyon where interactions between sediment transport and bedrock incision lead to the formation of upstream-propagating bedrock step-pools and waterfalls.\r\n \r\n" }, { "name": "Siebach, Kirsten Leigh", "degree": "PhD", "year": "2016", "title": "Formation and Diagenesis of Sedimentary Rocks in Gale Crater, Mars", "advisor": "Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032016-155530034", "creators": [ { "name": { "family": "Siebach", "given": "Kirsten Leigh" }, "id": "Siebach-Kirsten-Leigh", "orcid": "0000-0002-6628-6297", "display_name": "Siebach, Kirsten Leigh" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z97D2S4K", "abstract": "The history of surface processes on Mars is recorded in the sedimentary rock record. Sedimentary rock layers exposed in Gale Crater on the modern crater floor (Aeolus Palus) and on Mount Sharp (Aeolus Mons), which hosts one of the more complete records of transitions between major mineralogical eras on Mars, have been investigated by the Mars Science Laboratory Curiosity rover since landing in August 2012. This dissertation focuses on the formation and diagenesis of the sedimentary rocks in Gale crater in order to assess the compositional diversity of the volcanic sources around Gale crater, the effects of transport processes on the sediment grains, and the volumes and geochemistry of water that transported and cemented the sediments. The first study uses orbital mapping of a distinctive cemented boxwork layer on Mount Sharp to constrain a minimum volume of groundwater available to form this layer, 1 km above the modern floor of Gale, with implications for the formation of Mount Sharp. The other three studies use Curiosity rover imagery and geochemical data to investigate sedimentary rocks in Aeolus Palus and at the base of Mount Sharp. The second study identifies and describes diagenetic synaeresis cracks in the Sheepbed mudstone, at the lowest elevation in Aeolus Palus, with implications for the duration of water saturation of these lake sediments. The third and fourth studies identify and explain geochemical trends in the fluvio-deltaic Bradbury group, the Murray mudstone formation, and the eolian Stimson sandstone, focusing on geochemical diversity in the source regions for each of these units and how different depositional processes are reflected in the geochemical data. The sedimentary system in Gale crater has changed our understanding of Mars by expanding the known variety of igneous rocks, increasing estimates of the longevity of surface water lakes, and showing that there were once habitable environments on our neighboring planet." }, { "name": "Slotznick, Sarah Pearl", "degree": "PhD", "year": "2016", "title": "Coupling Textural, Magnetic, and Modeling Techniques to Understand Precambrian Paleoenvironments", "advisor": "Kirschvink, Joseph L.; Fischer, Woodward W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032016-150348563", "creators": [ { "name": { "family": "Slotznick", "given": "Sarah Pearl" }, "id": "Slotznick-Sarah-Pearl", "orcid": "0000-0001-8374-3173", "display_name": "Slotznick, Sarah Pearl" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "co-advisor", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "co-advisor", "display_name": "Fischer, Woodward W." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geobiol" ], "doi": "10.7907/Z9HT2M8X", "abstract": "The oxygenation of our planet is perhaps the greatest transition in its history, dramatically affecting geochemical cycles and the evolution of life. Major first-order questions still remain about late Archean and Proterozoic environments, even as newly developed geochemical techniques provide additional constraints and create subtle conundrums. I apply a new approach to classic localities to understand Precambrian redox character and paleoenvironmental conditions by combining textural observations from optical and electron microscopy, isotopic measurements, and (synchrotron-based) x-ray spectroscopy with scanning magnetic microscopy and bulk rock magnetic experiments. Models paired with data from the literature provide additional context for these measurement results.
\r\n\r\nThe first portion of this dissertation focuses on understanding the predominant microbial metabolism recorded in the 2.72 Ga Tumbiana Formation stromatolites. I proposed that these stromatolites formed in shallow, anoxic waters and record a global signature of unique autotrophy distinct from younger systems dominated by oxygenic photosynthesis. The next portion of this dissertation uses the redox sensitivity of iron as a tool to investigate paleoredox conditions of the 1.45 Ga lower Belt Supergroup during a potentially transitional time-period in surface environments. Observations of primary mineralogy in early diagenetic pyrite and detrital iron oxides suggest an oxygenated water-column overlying anoxic, sulfidic pore-fluids very similar to the modern. The final portion of this dissertation assesses the effects of prevalent secondary overprints on the use of iron as a paleoredox proxy. Theoretical data-driven models combined with trends from the Belt Supergroup highlight the mobility of iron during progressive burial metamorphism as well as in diagenetic transformations and reactions with infiltrating fluids. Applying coupled techniques, specifically including textural methods, is vital for untangling secondary alterations from primary records of environmental conditions during the Precambrian.
\u2003\r\n" }, { "name": "Sousa, Francis Joseph", "degree": "PhD", "year": "2016", "title": "Tectonics of Central and Eastern California, Late Cretaceous to Modern", "advisor": "Saleeby, Jason B.; Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05252016-090108907", "creators": [ { "name": { "family": "Sousa", "given": "Francis Joseph" }, "id": "Sousa-Francis-Joseph", "orcid": "0000-0003-1623-4023", "display_name": "Sousa, Francis Joseph" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9H41PD8", "abstract": "The Late Cretaceous to Modern tectonic evolution of central and eastern California has been studied for many decades, with published work generally focusing on specific geographic areas and time periods. The resulting literature leaves the reader, whether graduate student, faculty member, or layperson, wondering what a coherently integrated tectonic evolution might look like, or if it would be at all possible to undertake such a task. This question is the common thread weaving together the four studies presented in this work. Each of the individual chapters is targeted at a specific location and time period which I have identified as a critical yet missing link in piecing together a coherent regional tectonic story. In the first chapter, we re-discover a set of major west down normal faults running along the western slope of the southern Sierra, the western Sierra fault system (WSFS). We show that one of these faults was offset by roughly a kilometer in Eocene time, and that this activity directly resulted in the incision of much of the relief present in modern Kings Canyon. The second chapter is a basement landscape and thermochronometric study of the hanging wall of the WSFS. New data from this study area provide a significant westward expansion of basement thermochronometric data from the southern Sierra Nevada batholith. Thermal modeling results of these data provide critical new constraints on the early exhumation of the Sierra Nevada batholith, and in the context of the results from Chapter I, allow us to piece together a coherent chronology of tectonic forcings and landscape evolution for the southern Sierra Nevada. In the third chapter, I present a study of the surface rupture of the 1999 Hector Mine earthquake, a dextral strike slip event on a fault in the Eastern California Shear Zone (ECSZ). New constraints on the active tectonics in ECSZ will help future studies better resolve the enigmatic mismatch between geologic slip rates and geodetically determined regional rates. Chapter IV is a magnetostratigraphic pilot study of the Paleocene Goler Formation. This study provides strong evidence that continued investigation will yield new constraints on the depositional age of the only fossil-bearing Paleocene terrestrial deposit on the west coast of North America. Each of these studies aims to provide important new data at critical missing links in the tectonic evolution of central and eastern California." }, { "name": "Stevens, Victoria Louise", "degree": "PhD", "year": "2016", "title": "Reconciling Geodetic Strain and Seismicity Rate with Frequency-Magnitude Relation of the Largest Earthquakes", "advisor": "Avouac, Jean-Philippe", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-131105966", "creators": [ { "name": { "family": "Stevens", "given": "Victoria Louise" }, "id": "Stevens-Victoria-Louise", "orcid": "0000-0003-3174-9949", "display_name": "Stevens, Victoria Louise" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "advisor", "display_name": "Avouac, Jean-Philippe" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "member", "display_name": "Tsai, Victor C." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geol" ], "doi": "10.7907/Z9PN93K7", "abstract": "The aim of this thesis is to study how moment buildup rate on faults can be reconciled with moment release rate. We concentrate first on the Himalaya region and go on to look at faults worldwide. We first justify the extrapolation of GPS data in the Himalayan region over the approximate timescale of an earthquake cycle. To do this we show that GPS strain rates correlate with seismicity rates, and that the principal directions of strain found from GPS data are similar to those from earthquake moment tensors, showing that GPS data has been consistent at the timescale of earthquake strain-rate build-up, roughly 100-1000 years.
\r\n\r\nWe next use geodetic data to show that the Main Himalayan Thrust (MHT) is locked from the surface to roughly 100 km north along its entire length, with no creeping patches. We also find the long-term slip rate on the fault, and these values agree with values from geomorphic studies, showing that here the tectonic regime has been stable with time, and most of the deformation is elastic. However, we also find a correspondence between the pattern of uplift rate predicted from the model and the topography, suggesting that a small amount of permanent deformation (10%) may occur, and again suggesting that the pattern of coupling has been stable with time.
\r\n\r\nWe find the moment build-up rate on the MHT to be 15.1\u00b11.0x1019 Nm/yr and compare this rate with the rate of moment release estimated from large earthquakes that have occurred on this fault in the past 1000 years. We use the conservation of moment principal to model the most likely maximum magnitude earthquake that needs to occur to balance the moment budget, and find that we need an earthquake of magnitude 9 or more with a recurrence time of roughly 800 years.
\r\n\r\nWe extend this analysis to faults with no GPS data, and no long record of large earthquakes, by developing a method to find the expected maximum magnitude earthquake on faults assuming conservation of moment, and that the earthquakes follow the Gutenberg-Richter law. Our results compare well with historical catalogs where they are available.
" }, { "name": "Su, Zhan", "degree": "PhD", "year": "2016", "title": "High-Latitude Ocean Convection and Gyre Dynamics", "advisor": "Ingersoll, Andrew P.; Thompson, Andrew F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-174848616", "creators": [ { "name": { "family": "Su", "given": "Zhan" }, "id": "Su-Zhan", "orcid": "0000-0001-7603-7211", "display_name": "Su, Zhan" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "co-advisor", "display_name": "Thompson, Andrew F." } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Stewart", "given": "Andrew L." }, "id": "Stewart-A-L", "role": "member", "display_name": "Stewart, Andrew L." }, { "name": { "family": "Menemenlis", "given": "Dimitris" }, "id": "Menemenlis-D", "role": "member", "display_name": "Menemenlis, Dimitris" } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9H12ZZ3", "abstract": "High-latitude ocean deep convection substantially contributes to vertical mixing, vertical heat transport, deep-water formation, and sea-ice budget in the World Ocean. However, the extent of this contribution remains poorly constrained. The concept of ocean convective available potential energy (OCAPE) have been developed to improve the understanding and the prediction for these deep convection events. The kinetic energy (KE) budget of deep convection is explored analytically and numerically based on the observations in the Weddell Sea. OCAPE, which is derived from thermobaricity, is identified as a critical KE source to power ocean deep convection. Other significant contributions to the energetics of convection, including diabatic processes related to cabbeling and stratification, are also carefully quantified. An associated theory is developed to predict the maximum depth of convection. This work may provide a useful basis for improving the convection parameterization in ocean models.
\r\n\r\nAs an application of the theory above, basin-scale OCAPE is found to be significantly built up in the North Atlantic at the end of Heinrich Stadial 1 (~17,000 years ago). This OCAPE is ultimately released to power strong ocean deep convection in North Atlantic as simulated by numerical models. This causes a ~2 \u00b0C sea surface warming for the whole basin (~700 km) within a month and exposes a huge heat reservoir to the atmosphere. This may invigorate the Atlantic meridional overturning circulation and provide an important mechanism to explain the abrupt Bolling-Allerod warming.
\r\n\r\nMesoscale turbulence is another crucial process for high-latitude ocean dynamics. From the physical nature of baroclinic instability, the framework of eddy-size- constrained Available Potential Energy (APE) density is developed, which is capable of well-detecting individual eddies and local eddy kinetic energy (EKE) in the World Ocean. This new framework is likely useful in parameterizing mesoscale eddies in ocean GCMs. Mesoscale turbulence are found to be coupled to the wind-driven Ekman pumping in determining the temperature and salinity budgets in subpolar gyres such as the Weddell Gyre. A conceptual model of the evolution of isopycnals has been developed in which the isopycnal responds to a seasonal oscillation in the surface wind stress. The model accurately predicts the observed phases of the temperature and salinity variability in relationship to the surface wind stress. The model, despite its heavy idealization, also accounts for more than 50% of the observed oscillation amplitude, which depends on the strength of the seasonal wind variability and the parameterized eddy diffusivity. These results highlight the importance of mesoscale eddies in modulating the export of AABW in narrow boundary layers around the Antarctic margins.
" }, { "name": "Tan, Zhihong", "degree": "PhD", "year": "2016", "title": "Simulations and Mechanisms of Subtropical Low-cloud Response to Climate Change", "advisor": "Schneider, Tapio; Teixeira, Joao", "url": "https://resolver.caltech.edu/CaltechTHESIS:08192015-043550928", "creators": [ { "name": { "family": "Tan", "given": "Zhihong" }, "id": "Tan-Zhihong", "orcid": "0000-0002-7422-3317", "display_name": "Tan, Zhihong" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "advisor", "display_name": "Schneider, Tapio" }, { "name": { "family": "Teixeira", "given": "Joao" }, "id": "Teixeira-J", "role": "co-advisor", "display_name": "Teixeira, Joao" } ], "committee": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "orcid": "0000-0003-1344-4068", "role": "chair", "display_name": "Seinfeld, John H." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Teixeira", "given": "Joao" }, "id": "Teixeira-Joao", "role": "member", "display_name": "Teixeira, Joao" }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "orcid": "0000-0003-4771-3350", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9JS9NC9", "abstract": "This thesis focuses on improving the simulation skills and the theoretical understanding of the subtropical low cloud response to climate change.
\r\n\r\nFirst, an energetically consistent forcing framework is designed and implemented for the large eddy simulation (LES) of the low-cloud response to climate change. The three representative current-day subtropical low cloud regimes of cumulus (Cu), cumulus-over-stratocumulus, and stratocumulus (Sc) are all well simulated with this framework, and results are comparable to the conventional fixed-SST approach. However, the cumulus response to climate warming subject to energetic constraints differs significantly from the conventional approach with fixed SST. Under the energetic constraint, the subtropics warm less than the tropics, since longwave (LW) cooling is more efficient with the drier subtropical free troposphere. The surface latent heat flux (LHF) also increases only weakly subject to the surface energetic constraint. Both factors contribute to an increased estimated inversion strength (EIS), and decreased inversion height. The decreased Cu-depth contributes to a decrease of liquid water path (LWP) and weak positive cloud feedback. The conventional fixed-SST approach instead simulates a strong increase in LHF and deepening of the Cu layer, leading to a weakly negative cloud feedback. This illustrates the importance of energetic constraints to the simulation and understanding of the sign and magnitude of low-cloud feedback.
\r\n\r\nSecond, an extended eddy-diffusivity mass-flux (EDMF) closure for the unified representation of sub-grid scale (SGS) turbulence and convection processes in general circulation models (GCM) is presented. The inclusion of prognostic terms and the elimination of the infinitesimal updraft fraction assumption makes it more flexible for implementation in models across different scales. This framework can be consistently extended to formulate multiple updrafts and downdrafts, as well as variances and covariances. It has been verified with LES in different boundary layer regimes in the current climate, and further development and implementation of this closure may help to improve our simulation skills and understanding of low-cloud feedback through GCMs.
" }, { "name": "Trembath-Reichert, Elizabeth", "degree": "PhD", "year": "2016", "title": "Molecular and Geochemical Insights into Microbial Life Centimeters to Kilometers Below the Seafloor", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-132232540", "creators": [ { "name": { "family": "Trembath-Reichert", "given": "Elizabeth" }, "id": "Trembath-Reichert-Elizabeth", "orcid": "0000-0002-3979-8676", "display_name": "Trembath-Reichert, Elizabeth" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/Z96Q1V6Q", "abstract": "At the broadest scale, this thesis is an investigation of how life modulates the movement of essential elements (carbon, sulfur, nitrogen, and silicon) on modern and geologic timescales. Chapters 1 and 2 explore carbon and sulfur cycling microbial communities found centimeters below the seafloor in hydrocarbon-rich methane seep ecosystems. At the Hydrate Ridge methane seep, we investigated how microbial partnerships direct the flow of methane and sulfide in these benthic oases by using identity-based physical separation methods developed in our lab (Magneto-FISH) in conjunction with community profiling and metagenomic sequencing. This method explores the middle ground between single cell and bulk sediment analysis by separating target microbes and their physically associated community for downstream sequencing applications. Magneto-FISH captures were done at a range of microbial taxonomic group specificities and sequenced with both clone library and next-gen iTag 16S rRNA gene methods. Chapter 1 provides a demonstration of how FISH probe taxonomic specificity correlates to resultant Archaeal taxonomic diversity in Magneto-FISHed seep sediments, with specific attention to preparation of Archaea-enriched samples for downstream metagenomic sequencing. In Chapter 2, a Bacteria-focused parallel environmental isolation and sequencing effort was subjected to co-occurrence analyses which suggested there may be far more microbial associations in methane seep systems than are currently appreciated, including partnerships that do not involve the canonical anaerobic methane oxidizing archaea and sulfate reducing bacteria. With samples from IODP Expedition 337 Shimokita coalbed biosphere, Chapter 3 provides evidence for an active microbial assemblage kilometers below the sea floor in the deepest samples ever collected by marine scientific ocean drilling. Using in situ temperature Stable Isotope Probing (SIP) incubations and NanoSIMS, we investigated whole community activity (with the passive tracer D2O) and substrate specific activity with C1-carbon compounds methylamine and methanol. We found deuterium-based turnover times to be faster (years) than previous deep biosphere estimates (hundreds to thousands of years), but methylotrophy rates to be slower than previous carbon metabolic rates.
" }, { "name": "Wills, Robert Christopher", "degree": "PhD", "year": "2016", "title": "Stationary Eddies and Zonal Variations of the Global Hydrological Cycle in a Changing Climate", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:01202016-022601840", "creators": [ { "name": { "family": "Wills", "given": "Robert Christopher" }, "id": "Wills-Robert-Christopher", "display_name": "Wills, Robert Christopher" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "chair", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" } ], "option_major": [ "envreng" ], "doi": "10.7907/Z91V5BX8", "abstract": "This thesis advances our physical understanding of the sensitivity of the hydrological cycle to global warming. Specifically, it focuses on changes in the longitudinal (zonal) variation of precipitation minus evaporation (P - E), which is predominantly controlled by planetary-scale stationary eddies. By studying idealized general circulation model (GCM) experiments with zonally varying boundary conditions, this thesis examines the mechanisms controlling the strength of stationary-eddy circulations and their role in the hydrological cycle. The overarching goal of this research is to understand the cause of changes in regional P - E with global warming. An understanding of such changes can be useful for impact studies focusing on water availability, ecosystem management, and flood risk.
\r\n\r\nBased on a moisture-budget analysis of ERA-Interim data, we establish an approximation for zonally anomalous P - E in terms of surface moisture content and stationary-eddy vertical motion in the lower troposphere. Part of the success of this approximation comes from our finding that transient-eddy moisture fluxes partially cancel the effect of stationary-eddy moisture advection, allowing divergent circulations to dominate the moisture budget. The lower-tropospheric vertical motion is related to horizontal motion in stationary eddies by Sverdrup and Ekman balance. These moisture- and vorticity-budget balances also hold in idealized and comprehensive GCM simulations across a range of climates.
\r\n\r\nBy examining climate changes in the idealized and comprehensive GCM simulations, we are able to show the utility of the vertical motion P - E approximation for splitting changes in zonally anomalous P - E into thermodynamic and dynamic components. Shifts in divergent stationary-eddy circulations dominate changes in zonally anomalous P - E. This limits the local utility of the \"wet gets wetter, dry gets drier\u201d idea, where existing P - E patterns are amplified with warming by the increase in atmospheric moisture content, with atmospheric circulations held fixed. The increase in atmospheric moisture content manifests instead in an increase in the amplitude of the zonally anomalous hydrological cycle as measured by the zonal variance of P - E. However, dynamic changes, particularly the slowdown of divergent stationary-eddy circulations, limit the strengthening of the zonally anomalous hydrological cycle. In certain idealized cases, dynamic changes are even strong enough to reverse the tendency towards \"wet gets wetter, dry gets drier\u201d with warming.
\r\n\r\nMotivated by the importance of stationary-eddy vertical velocities in the moisture budget analysis, we examine controls on the amplitude of stationary eddies across a wide range of climates in an idealized GCM with simple topographic and ocean-heating zonal asymmetries. An analysis of the thermodynamic equation in the vicinity of topographic forcing reveals the importance of on-slope surface winds, the midlatitude isentropic slope, and latent heating in setting the amplitude of stationary waves. The response of stationary eddies to climate change is determined primarily by the strength of zonal surface winds hitting the mountain. The sensitivity of stationary-eddies to this surface forcing increases with climate change as the slope of midlatitude isentropes decreases. However, latent heating also plays an important role in damping the stationary-eddy response, and this damping becomes stronger with warming as the atmospheric moisture content increases. We find that the response of tropical overturning circulations forced by ocean heat-flux convergence is described by changes in the vertical structure of moist static energy and deep convection. This is used to derive simple scalings for the Walker circulation strength that capture the monotonic decrease with warming found in our idealized simulations.
\r\n\r\nThrough the work of this thesis, the advances made in understanding the amplitude of stationary-waves in a changing climate can be directly applied to better understand and predict changes in the zonally anomalous hydrological cycle.
" }, { "name": "Cho, Kangwoo", "degree": "PhD", "year": "2015", "title": "Wastewater Electrolysis Cell for Environmental Pollutants Degradation and Molecular Hydrogen Generation\r ", "advisor": "Hoffmann, Michael R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07312014-164509193", "creators": [ { "name": { "family": "Cho", "given": "Kangwoo" }, "id": "Cho-Kangwoo", "orcid": "0000-0002-1819-7687", "display_name": "Cho, Kangwoo" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "chair", "display_name": "Hoffmann, Michael R." }, { "name": { "family": "Goddard", "given": "William A., III" }, "id": "Goddard-W-A-III", "role": "member", "display_name": "Goddard, William A., III" }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9DZ0676", "abstract": "This study proposes a wastewater electrolysis cell (WEC) for on-site treatment of human waste coupled with decentralized molecular H2 production. The core of the WEC includes mixed metal oxides anodes functionalized with bismuth doped TiO2 (BiOx/TiO2). The BiOx/TiO2 anode shows reliable electro-catalytic activity to oxidize Cl- to reactive chlorine species (RCS), which degrades environmental pollutants including chemical oxygen demand (COD), protein, NH4+, urea, and total coliforms. The WEC experiments for treatment of various kinds of synthetic and real wastewater demonstrate sufficient water quality of effluent for reuse for toilet flushing and environmental purposes. Cathodic reduction of water and proton on stainless steel cathodes produced molecular H2 with moderate levels of current and energy efficiency. This thesis presents a comprehensive environmental analysis together with kinetic models to provide an in-depth understanding of reaction pathways mediated by the RCS and the effects of key operating parameters. The latter part of this thesis is dedicated to bilayer hetero-junction anodes which show enhanced generation efficiency of RCS and long-term stability.
\r\n\r\nChapter 2 describes the reaction pathway and kinetics of urea degradation mediated by electrochemically generated RCS. The urea oxidation involves chloramines and chlorinated urea as reaction intermediates, for which the mass/charge balance analysis reveals that N2 and CO2 are the primary products. Chapter 3 investigates direct-current and photovoltaic powered WEC for domestic wastewater treatment, while Chapter 4 demonstrates the feasibility of the WEC to treat model septic tank effluents. The results in Chapter 2 and 3 corroborate the active roles of chlorine radicals (Cl\u2022/Cl2-\u2022) based on iR-compensated anodic potential (thermodynamic basis) and enhanced pseudo-first-order rate constants (kinetic basis). The effects of operating parameters (anodic potential and [Cl-] in Chapter 3; influent dilution and anaerobic pretreatment in Chapter 4) on the rate and current/energy efficiency of pollutants degradation and H2 production are thoroughly discussed based on robust kinetic models. Chapter 5 reports the generation of RCS on Ir0.7Ta0.3Oy/BixTi1-xOz hetero-junction anodes with enhanced rate, current efficiency, and long-term stability compared to the Ir0.7Ta0.3Oy anode. The effects of surficial Bi concentration are interrogated, focusing on relative distributions between surface-bound hydroxyl radical and higher oxide.
\r\n" }, { "name": "Johnson, Jena Elaine", "degree": "PhD", "year": "2015", "title": "Manganese: Minerals, Microbes, and the Evolution of Oxygenic Photosynthesis", "advisor": "Fischer, Woodward W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05182015-162708844", "creators": [ { "name": { "family": "Johnson", "given": "Jena Elaine" }, "id": "Johnson-Jena-Elaine", "display_name": "Johnson, Jena Elaine" } ], "advisors": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "advisor", "display_name": "Fischer, Woodward W." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "orcid": "0000-0002-8836-3054", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Webb", "given": "Samuel M." }, "id": "Webb-S-M", "role": "member", "display_name": "Webb, Samuel M." } ], "option_major": [ "geobiol" ], "doi": "10.7907/Z9RF5S0X", "abstract": "Oxygenic photosynthesis fundamentally transformed our planet by releasing molecular oxygen and altering major biogeochemical cycles, and this exceptional metabolism relies on a redox-active cubane cluster of four manganese atoms. Not only is manganese essential for producing oxygen, but manganese is also only oxidized by oxygen and oxygen-derived species. Thus the history of manganese oxidation provides a valuable perspective on our planet\u2019s environmental past, the ancient availability of oxygen, and the evolution of oxygenic photosynthesis. Broadly, the general trends of the geologic record of manganese deposition is a chronicle of ancient manganese oxidation: manganese is introduced into the fluid Earth as Mn(II) and it will remain only a trace component in sedimentary rocks until it is oxidized, forming Mn(III,IV) insoluble precipitates that are concentrated in the rock record. Because these manganese oxides are highly favorable electron acceptors, they often undergo reduction in sediments through anaerobic respiration and abiotic reaction pathways.
\r\n\r\nThe following dissertation presents five chapters investigating manganese cycling both by examining ancient examples of manganese enrichments in the geologic record and exploring the mineralogical products of various pathways of manganese oxide reduction that may occur in sediments. The first chapter explores the mineralogical record of manganese and reports abundant manganese reduction recorded in six representative manganese-enriched sedimentary sequences. This is followed by a second chapter that further analyzes the earliest significant manganese deposit 2.4 billon years ago, and determines that it predated the origin of oxygenic photosynthesis and thus is supporting evidence for manganese-oxidizing photosynthesis as an evolutionary precursor prior to oxygenic photosynthesis. The lack of oxygen during this early manganese deposition was partially established using oxygen-sensitive detrital grains, and so a third chapter delves into what these grains mean for oxygen constraints using a mathematical model. The fourth chapter returns to processes affecting manganese post-deposition, and explores the relationships between manganese mineral products and (bio)geochemical reduction processes to understand how various manganese minerals can reveal ancient environmental conditions and biological metabolisms. Finally, a fifth chapter considers whether manganese can be mobilized and enriched in sedimentary rocks and determines that manganese was concentrated secondarily in a 2.5 billion-year-old example from South Africa. Overall, this thesis demonstrates how microbial processes, namely photosynthesis and metal oxide-reducing metabolisms, are linked to and recorded in the rich complexity of the manganese mineralogical record.
" }, { "name": "Kameel, Fathima Rifkha", "degree": "PhD", "year": "2015", "title": "Oxidation of Volatile Organic Compounds in Aqueous Solution and at the Air-water Interface of Aqueous Microdroplets", "advisor": "Hoffmann, Michael R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10262014-094813435", "creators": [ { "name": { "family": "Kameel", "given": "Fathima Rifkha" }, "id": "Kameel-Fathima-Rifkha", "display_name": "Kameel, Fathima Rifkha" } ], "advisors": [ { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "advisor", "display_name": "Hoffmann, Michael R." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Goddard", "given": "William A., III" }, "id": "Goddard-W-A-III", "role": "member", "display_name": "Goddard, William A., III" }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "role": "member", "display_name": "Hoffmann, Michael R." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z9MP5174", "abstract": "Isoprene (ISO),the most abundant non-methane VOC, is the major contributor to secondary organic aerosols (SOA) formation. The mechanisms involved in such transformation, however, are not fully understood. Current mechanisms, which are based on the oxidation of ISO in the gas-phase, underestimate SOA yields. The heightened awareness that ISO is only partially processed in the gas-phase has turned attention to heterogeneous processes as alternative pathways toward SOA.
\r\n\r\nDuring my research project, I investigated the photochemical oxidation of isoprene in bulk water. Below, I will report on the \u03bb > 305 nm photolysis of H2O2 in dilute ISO solutions. This process yields C10H15OH species as primary products, whose formation both requires and is inhibited by O2. Several isomers of C10H15OH were resolved by reverse-phase high-performance liquid chromatography and detected as MH+ (m/z = 153) and MH+-18 (m/z = 135) signals by electrospray ionization mass spectrometry. This finding is consistent with the addition of ·OH to ISO, followed by HO-ISO· reactions with ISO (in competition with O2) leading to second generation HO(ISO)2· radicals that terminate as C10H15OH via \u03b2-H abstraction by O2.
\r\n\r\nIt is not generally realized that chemistry on the surface of water cannot be deduced, extrapolated or translated to those in bulk gas and liquid phases. The water density drops a thousand-fold within a few Angstroms through the gas-liquid interfacial region and therefore hydrophobic VOCs such as ISO will likely remain in these relatively 'dry' interfacial water layers rather than proceed into bulk water. In previous experiments from our laboratory, it was found that gas-phase olefins can be protonated on the surface of pH < 4 water. This phenomenon increases the residence time of gases at the interface, an event that makes them increasingly susceptible to interaction with gaseous atmospheric oxidants such as ozone and hydroxyl radicals.
\r\n\r\nIn order to test this hypothesis, I carried out experiments in which ISO(g) collides with the surface of aqueous microdroplets of various compositions. Herein I report that ISO(g) is oxidized into soluble species via Fenton chemistry on the surface of aqueous Fe(II)Cl2 solutions simultaneously exposed to H2O2(g). Monomer and oligomeric species (ISO)1-8H+ were detected via online electrospray ionization mass spectrometry (ESI-MS) on the surface of pH ~ 2 water, and were then oxidized into a suite of products whose combined yields exceed ~ 5% of (ISO)1-8H+. MS/MS analysis revealed that products mainly consisted of alcohols, ketones, epoxides and acids. Our experiments demonstrated that olefins in ambient air may be oxidized upon impact on the surface of Fe-containing aqueous acidic media, such as those of typical to tropospheric aerosols.
\r\n\r\nRelated experiments involving the reaction of ISO(g) with ·OH radicals from the photolysis of dissolved H2O2 were also carried out to test the surface oxidation of ISO(g) by photolyzing H2O2(aq) at 266 nm at various pH. The products were analyzed via online electrospray ionization mass spectrometry. Similar to our Fenton experiments, we detected (ISO)1-7H+ at pH < 4, and new m/z+ = 271 and m/z- = 76 products at pH > 5.
\r\n" }, { "name": "Kammer, Joshua Andrew", "degree": "PhD", "year": "2015", "title": "Analyses of Planetary Atmospheres Across the Spectrum: From Titan to Exoplanets", "advisor": "Yung, Yuk L.; Knutson, Heather A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08312014-134619300", "creators": [ { "name": { "family": "Kammer", "given": "Joshua Andrew" }, "id": "Kammer-Joshua-Andrew", "orcid": "0000-0002-3441-3757", "display_name": "Kammer, Joshua Andrew" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "co-advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "role": "co-advisor", "display_name": "Knutson, Heather A." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "role": "member", "display_name": "Knutson, Heather A." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9GX48HD", "abstract": "Planetary atmospheres exist in a seemingly endless variety of physical and chemical environments. There are an equally diverse number of methods by which we can study and characterize atmospheric composition. In order to better understand the fundamental chemistry and physical processes underlying all planetary atmospheres, my research of the past four years has focused on two distinct topics. First, I focused on the data analysis and spectral retrieval of observations obtained by the Ultraviolet Imaging Spectrograph (UVIS) instrument onboard the Cassini spacecraft while in orbit around Saturn. These observations consisted of stellar occultation measurements of Titan's upper atmosphere, probing the chemical composition in the region 300 to 1500 km above Titan's surface. I examined the relative abundances of Titan's two most prevalent chemical species, nitrogen and methane. I also focused on the aerosols that are formed through chemistry involving these two major species, and determined the vertical profiles of aerosol particles as a function of time and latitude. Moving beyond our own solar system, my second topic of investigation involved analysis of infra-red light curves from the Spitzer space telescope, obtained as it measured the light from stars hosting planets of their own. I focused on both transit and eclipse modeling during Spitzer data reduction and analysis. In my initial work, I utilized the data to search for transits of planets a few Earth masses in size. In more recent research, I analyzed secondary eclipses of three exoplanets and constrained the range of possible temperatures and compositions of their atmospheres.
" }, { "name": "Kopf, Sebastian Hermann", "degree": "PhD", "year": "2015", "title": "From Lakes to Lungs: Assessing Microbial Activity in Diverse Environments ", "advisor": "Newman, Dianne K.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08182014-160835979", "creators": [ { "name": { "family": "Kopf", "given": "Sebastian Hermann" }, "id": "Kopf-Sebastian-Hermann", "display_name": "Kopf, Sebastian Hermann" } ], "advisors": [ { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "advisor", "display_name": "Newman, Dianne K." } ], "committee": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "chair", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." } ], "option_major": [ "geobiol" ], "doi": "10.7907/Z9HQ3WV6", "abstract": "All major geochemical cycles on the Earth\u2019s surface are mediated by microorganisms. Our understanding of how these microbes have interacted with their environments (and vice versa) throughout Earth's history, and how they will respond to changes in the future, is primarily based on studying their activity in different environments today. The overarching questions that motivate the research presented in the two parts of this thesis -- how do microorganisms shape their environment (and vice versa)? and how can we best study microbial activity in situ? -- have arisen from the ultimate goal of being able to predict microbial activity in response to changes within their environments both past and future.
\r\n\r\nPart one focuses on work related to microbial processes in iron-rich Lake Matano and, more broadly, microbial interactions with the biogeochemical cycling of iron. Primarily, we find that the chelation of ferrous iron by organic ligands can affect the role of iron in anoxic environmental systems, enabling photomixotrophic growth of anoxygenic microorganisms with ferrous iron, as well as catalyzing the oxidation of ferrous iron by denitrification intermediates. These results imply that the ability to grow photomixotrophically on ferrous iron might be more widespread than previously assumed, and that the co-occurrence of chemical and biological processes involved in the coupled biogeochemical cycling of iron and nitrogen likely dominate organic-rich environmental systems.
\r\n\r\nPart two switches focus to in situ measurements of growth activity and comprises work related to microbial processes in the Cystic Fibrosis lung, and more broadly, the physiology of slow growth. We introduce stable isotope labeling of microbial membrane fatty acids and whole cells with heavy water as a new technique to measure microbial activity in a wide range of environments, demonstrate its application in continuous culture in the laboratory at the population and single cell level, and apply the tool to measure the in situ activity of the opportunistic pathogen Staphylococcus aureus within the environment of expectorated mucus from cystic fibrosis patients. We find that the average in situ growth rates of S. aureus fall into a range of generation times between ~12 hours and ~4 days, with substantial heterogeneity at the single-cell level. These data illustrate the use of heavy water as a universal environmental tracer for microbial activity, and highlight the crucial importance of studying the physiology of slow growth in representative laboratory systems in order to understand the role of these microorganisms in their native environments.
" }, { "name": "Limaye, Ajay Brian Sanjay", "degree": "PhD", "year": "2015", "title": "Valley Evolution by Meandering Rivers", "advisor": "Lamb, Michael P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10272014-105243856", "creators": [ { "name": { "family": "Limaye", "given": "Ajay Brian Sanjay" }, "id": "Limaye-Ajay-Brian-Sanjay", "display_name": "Limaye, Ajay Brian Sanjay" } ], "advisors": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "advisor", "display_name": "Lamb, Michael P." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z9MG7MFJ", "abstract": "Fluvial systems form landscapes and sedimentary deposits with a rich hierarchy of structures that extend from grain- to valley scale. Large-scale pattern formation in fluvial systems is commonly attributed to forcing by external factors, including climate change, tectonic uplift, and sea-level change. Yet over geologic timescales, rivers may also develop large-scale erosional and depositional patterns that do not bear on environmental history. This dissertation uses a combination of numerical modeling and topographic analysis to identify and quantify patterns in river valleys that form as a consequence of river meandering alone, under constant external forcing. Chapter 2 identifies a numerical artifact in existing, grid-based models that represent the co-evolution of river channel migration and bank strength over geologic timescales. A new, vector-based technique for bank-material tracking is shown to improve predictions for the evolution of meander belts, floodplains, sedimentary deposits formed by aggrading channels, and bedrock river valleys, particularly when spatial contrasts in bank strength are strong. Chapters 3 and 4 apply this numerical technique to establishing valley topography formed by a vertically incising, meandering river subject to constant external forcing\u2014which should serve as the null hypothesis for valley evolution. In Chapter 3, this scenario is shown to explain a variety of common bedrock river valley types and smaller-scale features within them\u2014including entrenched channels, long-wavelength, arcuate scars in valley walls, and bedrock-cored river terraces. Chapter 4 describes the age and geometric statistics of river terraces formed by meandering with constant external forcing, and compares them to terraces in natural river valleys. The frequency of intrinsic terrace formation by meandering is shown to reflect a characteristic relief-generation timescale, and terrace length is identified as a key criterion for distinguishing these terraces from terraces formed by externally forced pulses of vertical incision. In a separate study, Chapter 5 utilizes image and topographic data from the Mars Reconnaissance Orbiter to quantitatively identify spatial structures in the polar layered deposits of Mars, and identifies sequences of beds, consistently 1-2 meters thick, that have accumulated hundreds of kilometers apart in the north polar layered deposits." }, { "name": "Piasecki, Alison Martha", "degree": "PhD", "year": "2015", "title": "Site-Specific Isotopes in Small Organic Molecules", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05292015-100107828", "creators": [ { "name": { "family": "Piasecki", "given": "Alison Martha" }, "id": "Piasecki-Alison-Martha", "display_name": "Piasecki, Alison Martha" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "chair", "display_name": "Sessions, Alex L." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9833PZP", "abstract": "Stable isotope geochemistry is a valuable toolkit for addressing a broad range of problems in the geosciences. Recent technical advances provide information that was previously unattainable or provide unprecedented precision and accuracy. Two such techniques are site-specific stable isotope mass spectrometry and clumped isotope thermometry. In this thesis, I use site-specific isotope and clumped isotope data to explore natural gas development and carbonate reaction kinetics. In the first chapter, I develop an equilibrium thermodynamics model to calculate equilibrium constants for isotope exchange reactions in small organic molecules. This equilibrium data provides a framework for interpreting the more complex data in the later chapters. In the second chapter, I demonstrate a method for measuring site-specific carbon isotopes in propane using high-resolution gas source mass spectrometry. This method relies on the characteristic fragments created during electron ionization, in which I measure the relative isotopic enrichment of separate parts of the molecule. My technique will be applied to a range of organic compounds in the future. For the third chapter, I use this technique to explore diffusion, mixing, and other natural processes in natural gas basins. As time progresses and the mixture matures, different components like kerogen and oil contribute to the propane in a natural gas sample. Each component imparts a distinct fingerprint on the site-specific isotope distribution within propane that I can observe to understand the source composition and maturation of the basin. Finally, in Chapter Four, I study the reaction kinetics of clumped isotopes in aragonite. Despite its frequent use as a clumped isotope thermometer, the aragonite blocking temperature is not known. Using laboratory heating experiments, I determine that the aragonite clumped isotope thermometer has a blocking temperature of 50-100\u00b0C. I compare this result to natural samples from the San Juan Islands that exhibit a maximum clumped isotope temperature that matches this blocking temperature. This thesis presents a framework for measuring site-specific carbon isotopes in organic molecules and new constraints on aragonite reaction kinetics. This study represents the foundation of a future generation of geochemical tools for the study of complex geologic systems. " }, { "name": "Stack, Kathryn Marie Morgan", "degree": "PhD", "year": "2015", "title": "Reconstructing Past Depositional and Diagenetic Processes through Quantitative Stratigraphic Analysis of the Martian Sedimentary Rock Record", "advisor": "Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12042014-212249920", "creators": [ { "name": { "family": "Stack", "given": "Kathryn Marie Morgan" }, "id": "Stack-Kathryn-Marie-Morgan", "orcid": "0000-0003-3444-6695", "display_name": "Stack, Kathryn Marie Morgan" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z9FN144M ", "abstract": "High-resolution orbital and in situ observations acquired of the Martian surface during the past two decades provide the opportunity to study the rock record of Mars at an unprecedented level of detail. This dissertation consists of four studies whose common goal is to establish new standards for the quantitative analysis of visible and near-infrared data from the surface of Mars. Through the compilation of global image inventories, application of stratigraphic and sedimentologic statistical methods, and use of laboratory analogs, this dissertation provides insight into the history of past depositional and diagenetic processes on Mars. The first study presents a global inventory of stratified deposits observed in images from the High Resolution Image Science Experiment (HiRISE) camera on-board the Mars Reconnaissance Orbiter. This work uses the widespread coverage of high-resolution orbital images to make global-scale observations about the processes controlling sediment transport and deposition on Mars. The next chapter presents a study of bed thickness distributions in Martian sedimentary deposits, showing how statistical methods can be used to establish quantitative criteria for evaluating the depositional history of stratified deposits observed in orbital images. The third study tests the ability of spectral mixing models to obtain quantitative mineral abundances from near-infrared reflectance spectra of clay and sulfate mixtures in the laboratory for application to the analysis of orbital spectra of sedimentary deposits on Mars. The final study employs a statistical analysis of the size, shape, and distribution of nodules observed by the Mars Science Laboratory Curiosity rover team in the Sheepbed mudstone at Yellowknife Bay in Gale crater. This analysis is used to evaluate hypotheses for nodule formation and to gain insight into the diagenetic history of an ancient habitable environment on Mars.
" }, { "name": "Swanson, Erika McGoldrick", "degree": "PhD", "year": "2015", "title": "Structural and Clumped-Isotope Constraints on the Mechanisms of Displacement Along Low-Angle Detachments", "advisor": "Wernicke, Brian P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10242014-133410215", "creators": [ { "name": { "family": "Swanson", "given": "Erika McGoldrick" }, "id": "Swanson-Erika-McGoldrick", "display_name": "Swanson, Erika McGoldrick" } ], "advisors": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "advisor", "display_name": "Wernicke, Brian P." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "member", "display_name": "Wernicke, Brian P." } ], "option_major": [ "geol" ], "doi": "10.7907/Z92F7KDC", "abstract": "Despite years of research on low-angle detachments, much about them remains enigmatic. This thesis addresses some of the uncertainty regarding two particular detachments, the Mormon Peak detachment in Nevada and the Heart Mountain detachment in Wyoming and Montana.
\r\n\r\nConstraints on the geometry and kinematics of emplacement of the Mormon Peak detachment are provided by detailed geologic mapping of the Meadow Valley Mountains, along with an analysis of structural data within the allochthon in the Mormon Mountains. Identifiable structures well suited to constrain the kinematics of the detachment include a newly mapped, Sevier-age monoclinal flexure in the hanging wall of the detachment. This flexure, including the syncline at its base and the anticline at its top, can be readily matched to the base and top of the frontal Sevier thrust ramp, which is exposed in the footwall of the detachment to the east in the Mormon Mountains and Tule Springs Hills. The ~12 km of offset of these structural markers precludes the radial sliding hypothesis for emplacement of the allochthon.
\r\n\r\nThe role of fluids in the slip along faults is a widely investigated topic, but the use of carbonate clumped-isotope thermometry to investigate these fluids is new. Faults rocks from within ~1 m of the Mormon Peak detachment, including veins, breccias, gouges, and host rocks, were analyzed for carbon, oxygen, and clumped-isotope measurements. The data indicate that much of the carbonate breccia and gouge material along the detachment is comminuted host rock, as expected. Measurements in vein material indicate that the fluid system is dominated by meteoric water, whose temperature indicates circulation to substantial depths (c. 4 km) in the upper crust near the fault zone.
\r\n\r\nSlip along the subhorizontal Heart Mountain detachment is particularly enigmatic, and many different mechanisms for failure have been proposed, predominantly involving catastrophic failure. Textural evidence of multiple slip events is abundant, and include multiple brecciation events and cross-cutting clastic dikes. Footwall deformation is observed in numerous exposures of the detachment. Stylolitic surfaces and alteration textures within and around \u201cbanded grains\u201d previously interpreted to be an indicator of high-temperature fluidization along the fault suggest their formation instead via low-temperature dissolution and alteration processes. There is abundant textural evidence of the significant role of fluids along the detachment via pressure solution. The process of pressure solution creep may be responsible for enabling multiple slip events on the low-angle detachment, via a local rotation of the stress field.
\r\n\r\nClumped-isotope thermometry of fault rocks associated with the Heart Mountain detachment indicates that despite its location on the flanks of a volcano that was active during slip, the majority of carbonate along the Heart Mountain detachment does not record significant heating above ambient temperatures (c. 40-70\u00b0C). Instead, cold meteoric fluids infiltrated the detachment breccia, and carbonate precipitated under ambient temperatures controlled by structural depth. Locally, fault gouge does preserve hot temperatures (>200\u00b0C), as is observed in both the Mormon Peak detachment and Heart Mountain detachment areas. Samples with very hot temperatures attributable to frictional shear heating are present but rare. They appear to be best preserved in hanging wall structures related to the detachment, rather than along the main detachment.
\r\n\r\nEvidence is presented for the prevalence of relatively cold, meteoric fluids along both shallow crustal detachments studied, and for protracted histories of slip along both detachments. Frictional heating is evident from both areas, but is a minor component of the preserved fault rock record. Pressure solution is evident, and might play a role in initiating slip on the Heart Mountain fault, and possibly other low-angle detachments.
\r\n" }, { "name": "Waszczak, Adam", "degree": "PhD", "year": "2015", "title": "Solar System Small-Body Demographics with the Palomar Transient Factory Survey", "advisor": "Kulkarni, Shrinivas R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05292015-134454898", "creators": [ { "name": { "family": "Waszczak", "given": "Adam" }, "id": "Waszczak-Adam", "display_name": "Waszczak, Adam" } ], "advisors": [ { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "advisor", "display_name": "Kulkarni, Shrinivas R." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Prince", "given": "Thomas A." }, "id": "Prince-T-A", "role": "member", "display_name": "Prince, Thomas A." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "member", "display_name": "Kulkarni, Shrinivas R." } ], "option_major": [ "plansci" ], "doi": "10.7907/Z91G0J73", "abstract": "Observational studies of our solar system's small-body populations (asteroids and comets) offer insight into the history of our planetary system, as these minor planets represent the left-over building blocks from its formation. The Palomar Transient Factory (PTF) survey began in 2009 as the latest wide-field sky-survey program to be conducted on the 1.2-meter Samuel Oschin telescope at Palomar Observatory. Though its main science program has been the discovery of high-energy extragalactic sources (such as supernovae), during its first five years PTF has collected nearly five million observations of over half a million unique solar system small bodies. This thesis begins to analyze this vast data set to address key population-level science topics, including: the detection rates of rare main-belt comets and small near-Earth asteroids, the spin and shape properties of asteroids as inferred from their lightcurves, the applicability of this visible light data to the interpretation of ultraviolet asteroid observations, and a comparison of the physical properties of main-belt and Jovian Trojan asteroids. Future sky-surveys would benefit from application of the analytical techniques presented herein, which include novel modeling methods and unique applications of machine-learning classification. The PTF asteroid small-body data produced in the course of this thesis work should remain a fertile source of solar system science and discovery for years to come." }, { "name": "Zhang, Dongzhou", "degree": "PhD", "year": "2015", "title": "Applications of Nuclear Resonant Scattering to Further Our Understanding of Earth\u2019s Interior", "advisor": "Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12152014-195321239", "creators": [ { "name": { "family": "Zhang", "given": "Dongzhou" }, "id": "Zhang-Dongzhou", "display_name": "Zhang, Dongzhou" } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z9SQ8XD5", "abstract": "The elastic and the thermodynamic properties of minerals under extreme P-T conditions are of general importance to the geodynamic modeling and the interpretation of seismic-wave observations. An accurate laboratory determination of these properties provides constraints to determine the composition and temperature of Earth's interior. In this thesis, I focus on the application of nuclear resonant scattering, an advanced synchrotron based spectroscopic technique, to further our understanding of candidate materials in Earth's interior. Specific examples include enstatite, which is an abundant mineral in the mantle, and iron-nickel alloy, which is believed to be the major component of the core. Our nuclear resonant scattering experiments is complemented with other synchrotron based techniques, such as diffraction.
\r\n\r\nNuclear resonant scattering is capable of detecting subtle changes in the mineral's hyperfine parameters, and can therefore be sensitive to the transitions occurring in minerals under pressure. For example, we explore the site-specific hyperfine behavior of iron in a 57Fe-enriched powdered enstatite sample using nuclear resonant scattering and diamond-anvil cells in two independent experiments. The (Mg0.980Fe0.020(5) )(Mg0.760Fe0.240)Si2O6 sample is pressurized up to 36 GPa at ambient temperature. In one experiment, NaCl is used as the pressure-transmitting medium, and in the other experiment, Ne surround the sample. Analyses of both data sets reveal a change in the trend or discontinuity in the hyperfine parameters around 10 GPa, indicative of a structural transformation in enstatite. However, the detailed behaviors of the iron sites with pressure appear to depend on the local stress conditions provided by the different pressure media.
\r\n\r\nNuclear resonant scattering is also used to measure the elastic properties of iron-bearing enstatite at high pressures. The behavior of synthetic powdered 57Fe-enriched (Mg0.980Fe0.020(5) )(Mg0.760Fe0.240)Si2O6 is explored by X-ray diffraction (XRD) and nuclear resonance inelastic X-ray scattering (NRIXS). The Pbca-structured enstatite sample is compressed in fine pressure increments for our XRD measurements. One structural transition between 10.1 and 12.2 GPa is identified from the XRD data. The XRD reflections observed for the high-pressure phase are best matched with space group P21/c. The partial phonon density of states (DOS) is derived from the raw NRIXS data up to 17 GPa, and from the low-energy region of the DOS, the Debye sound velocity is determined. We use the equation of state determined from XRD and Debye sound velocity to compute the isotropic compressional and shear wave velocities of enstatite at different pressures. We combine density-functional theory with nuclear resonant scattering to understand the local site symmetry of the Fe atoms in our sample. We compare our experimental results with seismic observations to understand large lateral variations in shear wave velocities in the upper mantle.
\r\n\r\nRecently, nuclear resonant scattering has been shown to be a powerful probe in determining the solid-liquid boundary of iron-bearing materials. To capture the sample's transient temperature fluctuations and reduce uncertainties in melting temperatures, we have developed a Fast Temperature Readout (FasTeR) spectrometer in-line with nuclear resonant scattering measurements under extreme conditions at Sector 3-ID-B of the Advanced Photon Source at Argonne National Laboratory. Dedicated to determining the sample's temperature near its melting point, FasTeR features a fast readout rate (about 100 Hz), high sensitivity, large dynamic range and well-constrained focus. FasTeR is capable of reading out temperatures about 1 to 2 magnitudes faster than the conventional CCD spectrometer, without sacrificing accuracy, and is especially suitable for dynamic measurements at extreme conditions.
\r\n\r\nBy combining nuclear resonant scattering with the laser heated diamond anvil cell and the FasTeR spectrometer, we have determined the melting temperatures of fcc-structured iron and iron-nickel alloy at high pressures. We find that the melting curve of Fe is slightly higher than the melting curve of Fe0.9Ni0.1, but the difference is smaller than the uncertainty. We calculate the fcc-hcp-l triple point of Fe0.9Ni0.1 to be 117\u00b13 GPa and 3285\u00b1200 K, and 111\u00b13 GPa and 3390\u00b1200 K for Fe. With the fcc-hcp-l triple points of Fe and Fe0.9Ni0.1, and the thermophysical parameters of hcp-Fe determined from a NRIXS measurement, we compute the high pressure melting curves of hcp-structured Fe and Fe0.9Ni0.1. We estimate the upper bound of Earth's inner core-outer core boundary temperature as ~5600\u00b1200 K, and we compute the upper bound of outer core temperature with an adiabatic model. We discuss the implications of these temperatures on the phase relations of deep Earth materials.
" }, { "name": "Dougherty, Sara Lyn", "degree": "PhD", "year": "2014", "title": "Seismic Structure along Transitions from Flat to Normal Subduction: Central Mexico, Southern Peru, and Southwest Japan", "advisor": "Clayton, Robert W.; Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05292014-181733885", "creators": [ { "name": { "family": "Dougherty", "given": "Sara Lyn" }, "id": "Dougherty-Sara-Lyn", "orcid": "0000-0002-5327-3286", "display_name": "Dougherty, Sara Lyn" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geophys" ], "doi": "10.7907/WHSR-VY75", "abstract": "The fine-scale seismic structure of the central Mexico, southern Peru, and southwest Japan subduction zones is studied using intraslab earthquakes recorded by temporary and permanent regional seismic arrays. The morphology of the transition from flat to normal subduction is explored in central Mexico and southern Peru, while in southwest Japan the spatial coincidence of a thin ultra-slow velocity layer (USL) atop the flat slab with locations of slow slip events (SSEs) is explored. This USL is also observed in central Mexico and southern Peru, where its lateral extent is used as one constraint on the nature of the flat-to-normal transitions.
\r\n\r\nIn western central Mexico, I find an edge to this USL which is coincident with the western boundary of the projected Orozco Fracture Zone (OFZ) region. Forward modeling of the 2D structure of the subducted Cocos plate using a finite-difference algorithm provides constraints on the velocity and geometry of the slab\u2019s seismic structure in this region and confirms the location of the USL edge. I propose that the Cocos slab is currently fragmenting into a North Cocos plate and a South Cocos plate along the projection of the OFZ, by a process analogous to that which occurred when the Rivera plate separated from the proto-Cocos plate 10 Ma.
\r\n\r\nIn eastern central Mexico, observations of a sharp transition in slab dip near the abrupt end of the Trans Mexican Volcanic Belt (TMVB) suggest a possible slab tear located within the subducted South Cocos plate. The eastern lateral extent of the USL is found to be coincident with these features and with the western boundary of a zone of decreased seismicity, indicating a change in structure which I interpret as evidence of a possible tear. Analysis of intraslab seismicity patterns and focal mechanism orientations and faulting types provides further support for a possible tear in the South Cocos slab. This potential tear, together with the tear along the projection of the OFZ to the northwest, indicates a slab rollback mechanism in which separate slab segments move independently, allowing for mantle flow between the segments.
\r\n\r\nIn southern Peru, observations of a gradual increase in slab dip coupled with a lack of any gaps or vertical offsets in the intraslab seismicity suggest a smooth contortion of the slab. Concentrations of focal mechanisms at orientations which are indicative of slab bending are also observed along the change in slab geometry. The lateral extent of the USL atop the horizontal Nazca slab is found to be coincident with the margin of the projected linear continuation of the subducting Nazca Ridge, implying a causal relationship, but not a slab tear. Waveform modeling of the 2D structure in southern Peru provides constraints on the velocity and geometry of the slab\u2019s seismic structure and confirms the absence of any tears in the slab.
\r\n\r\nIn southwest Japan, I estimate the location of a possible USL along the Philippine Sea slab surface and find this region of low velocity to be coincident with locations of SSEs that have occurred in this region. I interpret the source of the possible USL in this region as fluids dehydrated from the subducting plate, forming a high pore-fluid pressure layer, which would be expected to decrease the coupling on the plate interface and promote SSEs.
" }, { "name": "Huang, Yihe", "degree": "PhD", "year": "2014", "title": "Dynamic Rupture Simulation Integrated with Earthquake Observations", "advisor": "Ampuero, Jean-Paul", "url": "https://resolver.caltech.edu/CaltechTHESIS:05292014-144526425", "creators": [ { "name": { "family": "Huang", "given": "Yihe" }, "id": "Huang-Yihe", "display_name": "Huang, Yihe" } ], "advisors": [ { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "advisor", "display_name": "Ampuero, Jean-Paul" } ], "committee": [ { "name": { "family": "Tsai", "given": "Victor C." }, "id": "Tsai-V-C", "role": "chair", "display_name": "Tsai, Victor C." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" } ], "option_major": [ "geophys" ], "doi": "10.7907/VPJW-ZF69", "abstract": "Dynamic rupture simulations are unique in their contributions to the study of earthquake physics. The current rapid development of dynamic rupture simulations poses several new questions: Do the simulations reflect the real world? Do the simulations have predictive power? Which one should we believe when the simulations disagree? This thesis illustrates how integration with observations can help address these questions and reduce the effects of non-uniqueness of both dynamic rupture simulations and kinematic inversion problems. Dynamic rupture simulations with observational constraints can effectively identify non-physical features inferred from observations. Moreover, the integrative technique can also provide more physical insights into the mechanisms of earthquakes. This thesis demonstrates two examples of such kinds of integration: dynamic rupture simulations of the Mw 9.0 2011 Tohoku-Oki earthquake and of earthquake ruptures in damaged fault zones:
\r\n\r\n(1) We develop simulations of the Tohoku-Oki earthquake based on a variety of observations and minimum assumptions of model parameters. The simulations provide realistic estimations of stress drop and fracture energy of the region and explain the physical mechanisms of high-frequency radiation in the deep region. We also find that the overridding subduction wedge contributes significantly to the up-dip rupture propagation and large final slip in the shallow region. Such findings are also applicable to other megathrust earthquakes.
\r\n \r\n(2) Damaged fault zones are usually found around natural faults, but their effects on earthquake ruptures have been largely unknown. We simulate earthquake ruptures in damaged fault zones with material properties constrained by seismic and geological observations. We show that reflected waves in fault zones are effective at generating pulse-like ruptures and head waves tend to accelerate and decelerate rupture speeds. These mechanisms are robust in natural fault zones with large attenuation and off-fault plasticity. Moreover, earthquakes in damaged fault zones can propagate at super-Rayleigh speeds that are unstable in homogeneous media. Supershear transitions in fault zones do not require large fault stresses. In the end, we present observations in the Big Bear region, where variability of rupture speeds of small earthquakes correlates with the laterally variable materials in a damaged fault zone.
\r\n" }, { "name": "Lockwood, Alexandra Charlotte", "degree": "PhD", "year": "2014", "title": "Understanding Planet Formation through High Precision Photometry and Spectroscopy", "advisor": "Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05292014-141324161", "creators": [ { "name": { "family": "Lockwood", "given": "Alexandra Charlotte" }, "id": "Lockwood-Alexandra-Charlotte", "display_name": "Lockwood, Alexandra Charlotte" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "co-chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "orcid": "0000-0002-5375-4725", "role": "co-chair", "display_name": "Knutson, Heather A." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Johnson", "given": "John A." }, "id": "Johnson-J-A", "role": "member", "display_name": "Johnson, John A." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/7F1H-FG47", "abstract": "From studies of protoplanetary disks to extrasolar planets and planetary debris, we aim to understand the full evolution of a planetary system. Observational constraints from ground- and space-based instrumentation allows us to measure the properties of objects near and far and are central to developing this understanding. We present here three observational campaigns that, when combined with theoretical models, reveal characteristics of different stages and remnants of planet formation. The Kuiper Belt provides evidence of chemical and dynamical activity that reveals clues to its primordial environment and subsequent evolution. Large samples of this population can only be assembled at optical wavelengths, with thermal measurements at infrared and sub-mm wavelengths currently available for only the largest and closest bodies. We measure the size and shape of one particular object precisely here, in hopes of better understanding its unique dynamical history and layered composition.
\r\n\r\nMolecular organic chemistry is one of the most fundamental and widespread facets of the universe, and plays a key role in planet formation. A host of carbon-containing molecules vibrationally emit in the near-infrared when excited by warm gas, T~1000 K. The NIRSPEC instrument at the W.M. Keck Observatory is uniquely configured to study large ranges of this wavelength region at high spectral resolution. Using this facility we present studies of warm CO gas in protoplanetary disks, with a new code for precise excitation modeling. A parameterized suite of models demonstrates the abilities of the code and matches observational constraints such as line strength and shape. We use the models to probe various disk parameters as well, which are easily extensible to others with known disk emission spectra such as water, carbon dioxide, acetylene, and hydrogen cyanide.
\r\n\r\nLastly, the existence of molecules in extrasolar planets can also be studied with NIRSPEC and reveals a great deal about the evolution of the protoplanetary gas. The species we observe in protoplanetary disks are also often present in exoplanet atmospheres, and are abundant in Earth's atmosphere as well. Thus, a sophisticated telluric removal code is necessary to analyze these high dynamic range, high-resolution spectra. We present observations of a hot Jupiter, revealing water in its atmosphere and demonstrating a new technique for exoplanet mass determination and atmospheric characterization. We will also be applying this atmospheric removal code to the aforementioned disk observations, to improve our data analysis and probe less abundant species. Guiding models using observations is the only way to develop an accurate understanding of the timescales and processes involved. The futures of the modeling and of the observations are bright, and the end goal of realizing a unified model of planet formation will require both theory and data, from a diverse collection of sources.
" }, { "name": "Rosenburg, Margaret Anne", "degree": "PhD", "year": "2014", "title": "Interpretation of Lunar Topography: Impact Cratering and Surface Roughness", "advisor": "Aharonson, Oded", "url": "https://resolver.caltech.edu/CaltechTHESIS:05282014-080001211", "creators": [ { "name": { "family": "Rosenburg", "given": "Margaret Anne" }, "id": "Rosenburg-Margaret-Anne", "display_name": "Rosenburg, Margaret Anne" } ], "advisors": [ { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "advisor", "display_name": "Aharonson, Oded" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" } ], "option_major": [ "plansci" ], "doi": "10.7907/TGC6-8232", "abstract": "This work seeks to understand past and present surface conditions on the Moon using two different but complementary approaches: topographic analysis using high-resolution elevation data from recent spacecraft missions and forward modeling of the dominant agent of lunar surface modification, impact cratering. The first investigation focuses on global surface roughness of the Moon, using a variety of statistical parameters to explore slopes at different scales and their relation to competing geological processes. We find that highlands topography behaves as a nearly self-similar fractal system on scales of order 100 meters, and there is a distinct change in this behavior above and below approximately 1 km. Chapter 2 focuses this analysis on two localized regions: the lunar south pole, including Shackleton crater, and the large mare-filled basins on the nearside of the Moon. In particular, we find that differential slope, a statistical measure of roughness related to the curvature of a topographic profile, is extremely useful in distinguishing between geologic units. Chapter 3 introduces a numerical model that simulates a cratered terrain by emplacing features of characteristic shape geometrically, allowing for tracking of both the topography and surviving rim fragments over time. The power spectral density of cratered terrains is estimated numerically from model results and benchmarked against a 1-dimensional analytic model. The power spectral slope is observed to vary predictably with the size-frequency distribution of craters, as well as the crater shape. The final chapter employs the rim-tracking feature of the cratered terrain model to analyze the evolving size-frequency distribution of craters under different criteria for identifying \"visible\" craters from surviving rim fragments. A geometric bias exists that systematically over counts large or small craters, depending on the rim fraction required to count a given feature as either visible or erased." }, { "name": "Stolper, Daniel Aaron", "degree": "PhD", "year": "2014", "title": "New Insights into the Formation and Modification of Carbonate-Bearing Minerals and Methane Gas in Geological Systems using Multiply Substituted Isotopologues", "advisor": "Eiler, John M.; Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272014-225828922", "creators": [ { "name": { "family": "Stolper", "given": "Daniel Aaron" }, "id": "Stolper-Daniel-Aaron", "orcid": "0000-0003-3299-3177", "display_name": "Stolper, Daniel Aaron" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "co-advisor", "display_name": "Eiler, John M." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "co-advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "chair", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geobiol" ], "doi": "10.7907/Z9CF9N3Q", "abstract": "This thesis describes the use of multiply-substituted stable isotopologues of carbonate minerals and methane gas to better understand how these environmentally significant minerals and gases form and are modified throughout their geological histories. Stable isotopes have a long tradition in earth science as a tool for providing quantitative constraints on how molecules, in or on the earth, formed in both the present and past. Nearly all studies, until recently, have only measured the bulk concentrations of stable isotopes in a phase or species. However, the abundance of various isotopologues within a phase, for example the concentration of isotopologues with multiple rare isotopes (multiply substituted or 'clumped' isotopologues) also carries potentially useful information. Specifically, the abundances of clumped isotopologues in an equilibrated system are a function of temperature and thus knowledge of their abundances can be used to calculate a sample\u2019s formation temperature. In this thesis, measurements of clumped isotopologues are made on both carbonate-bearing minerals and methane gas in order to better constrain the environmental and geological histories of various samples.
\r\n\r\nClumped-isotope-based measurements of ancient carbonate-bearing minerals, including apatites, have opened up paleotemperature reconstructions to a variety of systems and time periods. However, a critical issue when using clumped-isotope based measurements to reconstruct ancient mineral formation temperatures is whether the samples being measured have faithfully recorded their original internal isotopic distributions. These original distributions can be altered, for example, by diffusion of atoms in the mineral lattice or through diagenetic reactions. Understanding these processes quantitatively is critical for the use of clumped isotopes to reconstruct past temperatures, quantify diagenesis, and calculate time-temperature burial histories of carbonate minerals. In order to help orient this part of the thesis, Chapter 2 provides a broad overview and history of clumped-isotope based measurements in carbonate minerals.
\r\n\r\nIn Chapter 3, the effects of elevated temperatures on a sample\u2019s clumped-isotope composition are probed in both natural and experimental apatites (which contain structural carbonate groups) and calcites. A quantitative model is created that is calibrated by the experiments and consistent with the natural samples. The model allows for calculations of the change in a sample\u2019s clumped isotope abundances as a function of any time-temperature history.
\r\n\t\r\nIn Chapter 4, the effects of diagenesis on the stable isotopic compositions of apatites are explored on samples from a variety of sedimentary phosphorite deposits. Clumped isotope temperatures and bulk isotopic measurements from carbonate and phosphate groups are compared for all samples. These results demonstrate that samples have experienced isotopic exchange of oxygen atoms in both the carbonate and phosphate groups. A kinetic model is developed that allows for the calculation of the amount of diagenesis each sample has experienced and yields insight into the physical and chemical processes of diagenesis.
\r\n\t\r\nThe thesis then switches gear and turns its attention to clumped isotope measurements of methane. Methane is critical greenhouse gas, energy resource, and microbial metabolic product and substrate. Despite its importance both environmentally and economically, much about methane\u2019s formational mechanisms and the relative sources of methane to various environments remains poorly constrained. In order to add new constraints to our understanding of the formation of methane in nature, I describe the development and application of methane clumped isotope measurements to environmental deposits of methane. To help orient the reader, a brief overview of the formation of methane in both high and low temperature settings is given in Chapter 5.
\r\n\t\r\nIn Chapter 6, a method for the measurement of methane clumped isotopologues via mass spectrometry is described. This chapter demonstrates that the measurement is precise and accurate. Additionally, the measurement is calibrated experimentally such that measurements of methane clumped isotope abundances can be converted into equivalent formational temperatures. This study represents the first time that methane clumped isotope abundances have been measured at useful precisions.
\r\n\t\r\nIn Chapter 7, the methane clumped isotope method is applied to natural samples from a variety of settings. These settings include thermogenic gases formed and reservoired in shales, migrated thermogenic gases, biogenic gases, mixed biogenic and thermogenic gas deposits, and experimentally generated gases. In all cases, calculated clumped isotope temperatures make geological sense as formation temperatures or mixtures of high and low temperature gases. Based on these observations, we propose that the clumped isotope temperature of an unmixed gas represents its formation temperature \u2014 this was neither an obvious nor expected result and has important implications for how methane forms in nature. Additionally, these results demonstrate that methane-clumped isotope compositions provided valuable additional constraints to studying natural methane deposits.
\r\n" }, { "name": "Thomas, Marion Y.", "degree": "PhD", "year": "2014", "title": "Frictional Properties of Fault: From Observations on the Longitudinal Valley Fault, Taiwan, to Dynamic Simulations", "advisor": "Avouac, Jean-Philippe; Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechTHESIS:09112013-133205322", "creators": [ { "name": { "family": "Thomas", "given": "Marion Y." }, "id": "Thomas-Marion-Y", "display_name": "Thomas, Marion Y." } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "advisor", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "co-advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geol" ], "doi": "10.7907/0AFX-WS57", "abstract": "Faults can slip either aseismically or through episodic seismic ruptures, but we still do not understand the factors which determine the partitioning between these two modes of slip. This challenge can now be addressed thanks to the dense set of geodetic and seismological networks that have been deployed in various areas with active tectonics. The data from such networks, as well as modern remote sensing techniques, indeed allow documenting of the spatial and temporal variability of slip mode and give some insight. This is the approach taken in this study, which is focused on the Longitudinal Valley Fault (LVF) in Eastern Taiwan. This fault is particularly appropriate since the very fast slip rate (about 5 cm/yr) is accommodated by both seismic and aseismic slip. Deformation of anthropogenic features shows that aseismic creep accounts for a significant fraction of fault slip near the surface, but this fault also released energy seismically, since it has produced five M_w>6.8 earthquakes in 1951 and 2003. Moreover, owing to the thrust component of slip, the fault zone is exhumed which allows investigation of deformation mechanisms. In order to put constraint on the factors that control the mode of slip, we apply a multidisciplinary approach that combines modeling of geodetic observations, structural analysis and numerical simulation of the \"seismic cycle\". Analyzing a dense set of geodetic and seismological data across the Longitudinal Valley, including campaign-mode GPS, continuous GPS (cGPS), leveling, accelerometric, and InSAR data, we document the partitioning between seismic and aseismic slip on the fault. For the time period 1992 to 2011, we found that about 80-90% of slip on the LVF in the 0-26 km seismogenic depth range is actually aseismic. The clay-rich Lichi M\\'elange is identified as the key factor promoting creep at shallow depth. Microstructural investigations show that deformation within the fault zone must have resulted from a combination of frictional sliding at grain boundaries, cataclasis and pressure solution creep. Numerical modeling of earthquake sequences have been performed to investigate the possibility of reproducing the results from the kinematic inversion of geodetic and seismological data on the LVF. We first investigate the different modeling strategy that was developed to explore the role and relative importance of different factors on the manner in which slip accumulates on faults. We compare the results of quasi dynamic simulations and fully dynamic ones, and we conclude that ignoring the transient wave-mediated stress transfers would be inappropriate. We therefore carry on fully dynamic simulations and succeed in qualitatively reproducing the wide range of observations for the southern segment of the LVF. We conclude that the spatio-temporal evolution of fault slip on the Longitudinal Valley Fault over 1997-2011 is consistent to first order with prediction from a simple model in which a velocity-weakening patch is embedded in a velocity-strengthening area." }, { "name": "Yang, Da", "degree": "PhD", "year": "2014", "title": "The Madden-Julian Oscillation: Observation, Modeling, and Theory", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05232014-112348842", "creators": [ { "name": { "family": "Yang", "given": "Da" }, "id": "Yang-Da", "display_name": "Yang, Da" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "chair", "display_name": "Bordoni, Simona" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." }, { "name": { "family": "Waliser", "given": "Duane E." }, "id": "Waliser-D-E", "role": "member", "display_name": "Waliser, Duane E." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "envreng" ], "doi": "10.7907/N1D7-1T85", "abstract": "The Madden-Julian Oscillation (MJO) is a pattern of intense rainfall and associated planetary-scale circulations in the tropical atmosphere, with a recurrence interval of 30-90 days. Although the MJO was first discovered 40 years ago, it is still a challenge to simulate the MJO in general circulation models (GCMs), and even with simple models it is difficult to agree on the basic mechanisms. This deficiency is mainly due to our poor understanding of moist convection\u2014deep cumulus clouds and thunderstorms, which occur at scales that are smaller than the resolution elements of the GCMs. Moist convection is the most important mechanism for transporting energy from the ocean to the atmosphere. Success in simulating the MJO will improve our understanding of moist convection and thereby improve weather and climate forecasting.
\r\n\r\nWe address this fundamental subject by analyzing observational datasets, constructing a hierarchy of numerical models, and developing theories. Parameters of the models are taken from observation, and the simulated MJO fits the data without further adjustments. The major findings include: 1) the MJO may be an ensemble of convection events linked together by small-scale high-frequency inertia-gravity waves; 2) the eastward propagation of the MJO is determined by the difference between the eastward and westward phase speeds of the waves; 3) the planetary scale of the MJO is the length over which temperature anomalies can be effectively smoothed by gravity waves; 4) the strength of the MJO increases with the typical strength of convection, which increases in a warming climate; 5) the horizontal scale of the MJO increases with the spatial frequency of convection; and 6) triggered convection, where potential energy accumulates until a threshold is reached, is important in simulating the MJO. Our findings challenge previous paradigms, which consider the MJO as a large-scale mode, and point to ways for improving the climate models.
" }, { "name": "Zhan, Zhongwen", "degree": "PhD", "year": "2014", "title": "Exploiting Seismic Waveforms of Ambient Noise and Earthquakes", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09272013-134450665", "creators": [ { "name": { "family": "Zhan", "given": "Zhongwen" }, "id": "Zhan-Zhongwen", "orcid": "0000-0002-5586-2607", "display_name": "Zhan, Zhongwen" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/NQHT-NA96", "abstract": "In this thesis, I apply detailed waveform modeling to study noise correlations in different environments, and earthquake waveforms for source parameters and velocity structure.
\r\n\r\nGreen's functions from ambient noise correlations have primarily been used for travel-time measurement. In Part I of this thesis, by detailed waveform modeling of noise correlation functions, I retrieve both surface waves and crustal body waves from noise, and use them in improving earthquake centroid locations and regional crustal structures. I also present examples in which the noise correlations do not yield Green's functions, yet the results are still interesting and useful after case-by-case analyses, including non-uniform distribution of noise sources, spurious velocity changes, and noise correlations on the Amery Ice Shelf.
\r\n\r\nIn Part II of this thesis, I study teleseismic body waves of earthquakes for source parameters or near-source structure. With the dense modern global network and improved methodologies, I obtain high-resolution earthquake locations, focal mechanisms and rupture processes, which provide critical insights to earthquake faulting processes in shallow and deep parts of subduction zones. Waveform modeling of relatively simple subduction zone events also displays new constraints on the structure of subducted slabs.
\r\n\r\nIn summary, behind my approaches to the relatively independent problems, the philosophy is to bring observational insights from seismic waveforms in critical and simple ways.
" }, { "name": "Ader, Thomas Joachim", "degree": "PhD", "year": "2013", "title": "Earthquakes of the Nepal Himalaya : Towards a Physical Model of the Seismic Cycle", "advisor": "Avouac, Jean-Philippe", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032013-180145987", "creators": [ { "name": { "family": "Ader", "given": "Thomas Joachim" }, "id": "Ader-Thomas-Joachim", "display_name": "Ader, Thomas Joachim" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "advisor", "display_name": "Avouac, Jean-Philippe" } ], "committee": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "chair", "display_name": "Simons, Mark" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geophys" ], "doi": "10.7907/z9c8276q", "abstract": "Home to hundreds of millions of souls and land of excessiveness, the Himalaya is also the locus of a unique seismicity whose scope and peculiarities still remain to this day somewhat mysterious. Having claimed the lives of kings, or turned ancient timeworn cities into heaps of rubbles and ruins, earthquakes eerily inhabit Nepalese folk tales with the fatalistic message that nothing lasts forever. From a scientific point of view as much as from a human perspective, solving the mysteries of Himalayan seismicity thus represents a challenge of prime importance. Documenting geodetic strain across the Nepal Himalaya with various GPS and leveling data, we show that unlike other subduction zones that exhibit a heterogeneous and patchy coupling pattern along strike, the last hundred kilometers of the Main Himalayan Thrust fault, or MHT, appear to be uniformly locked, devoid of any of the \u201ccreeping barriers\u201d that traditionally ward off the propagation of large events. The approximately 20 mm/yr of reckoned convergence across the Himalaya matching previously established estimates of the secular deformation at the front of the arc, the slip accumulated at depth has to somehow elastically propagate all the way to the surface at some point. And yet, neither large events from the past nor currently recorded microseismicity nearly compensate for the massive moment deficit that quietly builds up under the giant mountains. Along with this large unbalanced moment deficit, the uncommonly homogeneous coupling pattern on the MHT raises the question of whether or not the locked portion of the MHT can rupture all at once in a giant earthquake. Univocally answering this question appears contingent on the still elusive estimate of the magnitude of the largest possible earthquake in the Himalaya, and requires tight constraints on local fault properties. What makes the Himalaya enigmatic also makes it the potential source of an incredible wealth of information, and we exploit some of the oddities of Himalayan seismicity in an effort to improve the understanding of earthquake physics and cipher out the properties of the MHT. Thanks to the Himalaya, the Indo-Gangetic plain is deluged each year under a tremendous amount of water during the annual summer monsoon that collects and bears down on the Indian plate enough to pull it away from the Eurasian plate slightly, temporarily relieving a small portion of the stress mounting on the MHT. As the rainwater evaporates in the dry winter season, the plate rebounds and tension is increased back on the fault. Interestingly, the mild waggle of stress induced by the monsoon rains is about the same size as that from solid-Earth tides which gently tug at the planets solid layers, but whereas changes in earthquake frequency correspond with the annually occurring monsoon, there is no such correlation with Earth tides, which oscillate back-and-forth twice a day. We therefore investigate the general response of the creeping and seismogenic parts of MHT to periodic stresses in order to link these observations to physical parameters. First, the response of the creeping part of the MHT is analyzed with a simple spring-and-slider system bearing rate-strengthening rheology, and we show that at the transition with the locked zone, where the friction becomes near velocity neutral, the response of the slip rate may be amplified at some periods, which values are analytically related to the physical parameters of the problem. Such predictions therefore hold the potential of constraining fault properties on the MHT, but still await observational counterparts to be applied, as nothing indicates that the variations of seismicity rate on the locked part of the MHT are the direct expressions of variations of the slip rate on its creeping part, and no variations of the slip rate have been singled out from the GPS measurements to this day. When shifting to the locked seismogenic part of the MHT, spring-and-slider models with rate-weakening rheology are insufficient to explain the contrasted responses of the seismicity to the periodic loads that tides and monsoon both place on the MHT. Instead, we resort to numerical simulations using the Boundary Integral CYCLes of Earthquakes algorithm and examine the response of a 2D finite fault embedded with a rate-weakening patch to harmonic stress perturbations of various periods. We show that such simulations are able to reproduce results consistent with a gradual amplification of sensitivity as the perturbing period get larger, up to a critical period corresponding to the characteristic time of evolution of the seismicity in response to a step-like perturbation of stress. This increase of sensitivity was not reproduced by simple 1D-spring-slider systems, probably because of the complexity of the nucleation process, reproduced only by 2D-fault models. When the nucleation zone is close to its critical unstable size, its growth becomes highly sensitive to any external perturbations and the timings of produced events may therefore find themselves highly affected. A fully analytical framework has yet to be developed and further work is needed to fully describe the behavior of the fault in terms of physical parameters, which will likely provide the keys to deduce constitutive properties of the MHT from seismological observations." }, { "name": "Bergmann, Kristin Diane", "degree": "PhD", "year": "2013", "title": "Constraints on the Carbon Cycle and Climate During the Early Evolution of Animals", "advisor": "Grotzinger, John P.; Fischer, Woodward W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06102013-045943358", "creators": [ { "name": { "family": "Bergmann", "given": "Kristin Diane" }, "id": "Bergmann-Kristin-Diane", "display_name": "Bergmann, Kristin Diane" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "co-advisor", "display_name": "Grotzinger, John P." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "co-advisor", "display_name": "Fischer, Woodward W." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geol" ], "doi": "10.7907/KFJX-7S28", "abstract": "One of the greatest challenges in science lies in disentangling causality in complex, coupled systems. This is illustrated no better than in the dynamic interplay between the Earth and life. The early evolution and diversification of animals occurred within a backdrop of global change, yet reconstructing the potential role of the environment in this evolutionary transition is challenging. In the 200 million years from the end-Cryogenian to the Ordovician, enigmatic Ediacaran fauna explored body plans, animals diversified and began to biomineralize, forever changing the ocean's chemical cycles, and the biological community in shallow marine ecosystems transitioned from a microbial one to an animal one.
\r\n\r\nIn the following dissertation, a multi-faceted approach combining macro- and micro-scale analyses is presented that draws on the sedimentology, geochemistry and paleontology of the rocks that span this transition to better constrain the potential environmental changes during this interval.
\r\n\r\nIn Chapter 1, the potential of clumped isotope thermometry in deep time is explored by assessing the importance of burial and diagenesis on the thermometer. Eocene- to Precambrian-aged carbonates from the Sultanate of Oman were analyzed from current burial depths of 350-5850 meters. Two end-member styles of diagenesis independent of burial depth were observed.
\r\n\r\nChapters 2, 3 and 4 explore the fallibility of the Ediacaran carbon isotope record and aspects of the sedimentology and geochemistry of the rocks preserving the largest negative carbon isotope excursion on record---the Shuram Excursion. Chapter 2 documents the importance of temperature, fluid composition and mineralogy on the delta 18-O min record and interrogates the bulk trace metal signal. Chapter 3 explores the spatial variability in delta 13-C recorded in the transgressive Johnnie Oolite and finds a north-to-south trend recording the onset of the excursion. Chapter 4 investigates the nature of seafloor precipitation during this excursion and more broadly. We document the potential importance of microbial respiratory reactions on the carbonate chemistry of the sediment-water interface through time.
\r\n\r\nChapter 5 investigates the latest Precambrian sedimentary record in carbonates from the Sultanate of Oman, including how delta 13-C and delta 34-S CAS vary across depositional and depth gradients. A new model for the correlation of the Buah and Ara formations across Oman is presented. Isotopic results indicate delta 13-C varies with relative eustatic change and delta 34-S CAS may vary in absolute magnitude across Oman.
\r\n\r\nChapter 6 investigates the secular rise in delta 18-Omin in the early Paleozoic by using clumped isotope geochemistry on calcitic and phosphatic fossils from the Cambrian and Ordovician. Results do not indicate extreme delta 18-O seawater depletion and instead suggest warmer equatorial temperatures across the early Paleozoic.
\r\n " }, { "name": "Channon, Melanie Beth", "degree": "PhD", "year": "2013", "title": "Oxygen Isotopes and Volatiles in Martian Meteorite", "advisor": "Eiler, John M.; Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06032013-094453023", "creators": [ { "name": { "family": "Channon", "given": "Melanie Beth" }, "id": "Channon-Melanie-Beth", "display_name": "Channon, Melanie Beth" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "advisor", "display_name": "Eiler, John M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "co-advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." } ], "option_major": [ "geochem" ], "doi": "10.7907/HZ47-BJ39", "abstract": "Oxygen isotopes were measured in mineral separates from martian meteorites using laser fluorination and were found to be remarkably uniform in both \u03b418O and \u039417O, suggesting that martian magmas did not assimilate aqueously altered crust regardless of any other geochemical variations.
\r\n\r\nMeasurements of Cl, F, H, and S in apatite from martian meteorites were made using the SIMS and NanoSIMS. Martian apatites are typically higher in Cl than terrestrial apatites from mafic and ultramafic rocks, signifying that Mars is inherently higher in Cl than Earth. Apatites from basaltic and olivine-phyric shergottites are as high in water as any terrestrial apatite from mafic and utramafic rocks, implying the possibility that martian magmas may be more similar in water abundance to terrestrial magmas than previously thought. Apatites from lherzolitic shergottites, nakhlites, chassignites, and ALH 84001 (all of which are cumulate rocks) are all lower in water than the basaltic and olivine-phyric shergottites, indicating that the slow-cooling accumulation process allows escape of water from trapped melts where apatite later formed. Sulfur is only high in some apatites from basaltic and olivine-phyric shergottites and low in all other SNCs from this study, which could mean that cumulate SNCs are low in all volatiles and that there are other controlling factors in basaltic and olivine-phyric magmas dictating the inclusion of sulfur into apatite.
\r\n\r\nSulfur K\u03b1 X-rays were measured in SNC apatites using the electron probe. None of the peaks in the SNC spectra reside in the same position as anhydrite (where sulfur is 100% sulfate) or pyrite (where sulfur is 100% sulfide), but instead all SNC spectra peaks lie in between these two end member peaks, which implies that SNC apatites may be substituting some sulfide, as well as sulfate, into their structure. However, further work is needed to verify this hypothesis.
\r\n" }, { "name": "Chemtob, Steven Michael", "degree": "PhD", "year": "2013", "title": "The Origin and Evolution of Amorphous Silica Coatings on Young Hawaiian Basalts", "advisor": "Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:12192012-121428518", "creators": [ { "name": { "family": "Chemtob", "given": "Steven Michael" }, "id": "Chemtob-Steven-Michael", "display_name": "Chemtob, Steven Michael" } ], "advisors": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geochem" ], "doi": "10.7907/RGT1-NK93", "abstract": "Young basaltic lavas on the Big Island of Hawaii frequently feature brightly colored surface coatings. These coatings, the product of interaction of volcanically-derived acidic fluids with basaltic substrates, provide an opportunity to study the rates and mechanisms of early onset chemical weathering in a natural setting. Lava flows of various ages, from hours to ~40 years, at sites along Kilauea's southwest and east rift zones and at Mauna Loa were visited and sampled to determine the nature and extent of this alteration phenomenon. The coatings are composed of a layer of amorphous silica, 1-80 \u03bcm thick, capped in some cases by a 1 \u03bcm layer of Fe-Ti oxide. Raman, infrared, and
The silicon isotope compositions of silica coatings and basalts were measured to determine the degree of Si mobility during coating formation. Coatings are enriched in
The morphologic, spectroscopic and geochemical observations presented here are most consistent with a dissolution-reprecipitation mechanism for silica coating formation. Acidic solutions dissolved near-surface basalt, then precipitated
Marine stratocumulus clouds are generally optically thick and shallow, exerting a net cooling influence on climate. Changes in atmospheric aerosol levels alter cloud microphysics (e.g., droplet size) and cloud macrophysics (e.g., liquid water path, cloud thickness), thereby affecting cloud albedo and Earth\u2019s radiative balance. To understand the aerosol-cloud-precipitation interactions and to explore the dynamical effects, three-dimensional large-eddy simulations (LES) with detailed bin-resolved microphysics are performed to explore the diurnal variation of marine stratocumulus clouds under different aerosol levels and environmental conditions. It is shown that the marine stratocumulus cloud albedo is sensitive to aerosol perturbation under clean background conditions, and to environmental conditions such as large-scale divergence rate and free tropospheric humidity.
\r\n\r\nBased on the in-situ Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) during Jul. and Aug. 2011, and A-Train satellite observation of 589 individual ship tracks during Jun. 2006-Dec. 2009, an analysis of cloud albedo responses in ship tracks is presented. It is found that the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. Under closed cell structure (i.e., cloud cells ringed by a perimeter of clear air), with sufficiently dry air above cloud tops and/or higher cloud top heights, the cloud albedo can become lower in ship tracks. Based on the satellite data, nearly 25% of ship tracks exhibited a decreased albedo. The cloud macrophysical responses are crucial in determining both the strength and the sign of the cloud albedo response to aerosols.
\r\n\r\nTo understand the aerosol indirect effects on global marine warm clouds, multisensory satellite observations, including CloudSat, MODIS, CALIPSO, AMSR-E, ECMWF, CERES, and NCEP, have been applied to study the sensitivity of cloud properties to aerosol levels and to large scale environmental conditions. With an estimate of anthropogenic aerosol fraction, the global aerosol indirect radiative forcing has been assessed.
\r\n\r\nAs the coupling among aerosol, cloud, precipitation, and meteorological conditions in the marine boundary layer is complex, the integration of LES modeling, in-situ aircraft measurements, and global multisensory satellite data analyses improves our understanding of this complex system.
\r\n" }, { "name": "Dekas, Anne Elizabeth", "degree": "PhD", "year": "2013", "title": "Diazotrophy in the Deep: An Analysis of the Distribution, Magnitude, Geochemical Controls, and Biological Mediators of Deep-Sea Benthic Nitrogen Fixation", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12192012-141624638", "creators": [ { "name": { "family": "Dekas", "given": "Anne Elizabeth" }, "id": "Dekas-Anne-Elizabeth", "orcid": "0000-0001-9548-8413", "display_name": "Dekas, Anne Elizabeth" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "chair", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Howard", "given": "James B." }, "id": "Howard-J-B", "role": "member", "display_name": "Howard, James B." } ], "option_major": [ "geobiol" ], "doi": "10.7907/H9F5-T161", "abstract": "Biological nitrogen fixation (the conversion of N2 to NH3) is a critical process in the oceans, counteracting the production of N2 gas by dissimilatory bacterial metabolisms and providing a source of bioavailable nitrogen to many nitrogen-limited ecosystems. One currently poorly studied and potentially underappreciated habitat for diazotrophic organisms is the sediments of the deep-sea. Although nitrogen fixation was once thought to be negligible in non-photosynthetically driven benthic ecosystems, the present study demonstrates the occurrence and expression of a diversity of nifH genes (those necessary for nitrogen fixation), as well as a widespread ability to fix nitrogen at high rates in these locations. The following research explores the distribution, magnitude, geochemical controls, and biological mediators of nitrogen fixation at several deep-sea sediment habitats, including active methane seeps (Mound 12, Costa Rica; Eel River Basin, CA, USA; Hydrate Ridge, OR, USA; and Monterey Canyon, CA, USA), whale-fall sites (Monterey Canyon, CA), and background deep-sea sediment (off-site Mound 12 Costa Rica, off-site Hydrate Ridge, OR, USA; and Monterey Canyon, CA, USA). The first of the five chapters describes the FISH-NanoSIMS method, which we optimized for the analysis of closely associated microbial symbionts in marine sediments. The second describes an investigation of methane seep sediment from the Eel River Basin, where we recovered nifH sequences from extracted DNA, and used FISH-NanoSIMS to identify methanotrophic archaea (ANME-2) as diazotrophs, when associated with functional sulfate-reducing bacterial symbionts. The third and fourth chapters focus on the distribution and diversity of active diazotrophs (respectively) in methane seep sediment from Mound 12, Costa Rica, using a combination of 15N-labeling experiments, FISH-NanoSIMS, and RNA and DNA analysis. The fifth chapter expands the scope of the investigation by targeting diverse samples from methane seep, whale-fall, and background sediment collected along the Eastern Pacific Margin, and comparing the rates of nitrogen fixation observed to geochemical measurements collected in parallel. Together, these analyses represent the most extensive investigation of deep-sea nitrogen fixation to date, and work towards understanding the contribution of benthic nitrogen fixation to global marine nitrogen cycling.
" }, { "name": "Edgar, Lauren Ashley", "degree": "PhD", "year": "2013", "title": "Identifying and Interpreting Stratification in Sedimentary Rocks on Mars: Insight from Rover and Orbital Observations and Terrestrial Field Analogs", "advisor": "Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06072013-083424637", "creators": [ { "name": { "family": "Edgar", "given": "Lauren Ashley" }, "id": "Edgar-Lauren-Ashley", "display_name": "Edgar, Lauren Ashley" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "chair", "display_name": "Lamb, Michael P." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geol" ], "doi": "10.7907/RAGV-WT91", "abstract": "Sedimentary rocks on Mars provide insight into past aqueous and atmospheric processes, climate regimes, and potential habitability. The stratigraphic architecture of sedimentary rocks on Mars is similar to that of Earth, indicating that the processes that govern deposition and erosion on Mars can be reasonably inferred through reference to analogous terrestrial systems. This dissertation aims to understand Martian surface processes through the use of (1) ground-based observations from the Mars Exploration Rovers, (2) orbital data from the High Resolution Imaging Science Experiment onboard the Mars Reconnaissance Orbiter, and (3) the use of terrestrial field analogs to understand bedforms and sediment transport on Mars. Chapters 1 and 2 trace the history of aqueous activity at Meridiani Planum, through the reconstruction of eolian bedforms at Victoria crater, and the identification of a potential mudstone facies at Santa Maria crater. Chapter 3 uses Terrestrial Laser Scanning to study cross-bedding in pyroclastic surge deposits on Earth in order to understand sediment transport in these events and to establish criteria for their identification on Mars. The final chapter analyzes stratal geometries in the Martian North Polar Layered Deposits using tools for sequence stratigraphic analysis, to better constrain past surface processes and past climate conditions on Mars." }, { "name": "Hamecher, Emily A.", "degree": "PhD", "year": "2013", "title": "Studies of the Equation of State and Elasticity of Mantle Minerals", "advisor": "Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:03142013-132228957", "creators": [ { "name": { "family": "Hamecher", "given": "Emily A." }, "id": "Hamecher-Emily-A", "display_name": "Hamecher, Emily A." } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geol" ], "doi": "10.7907/7MZS-Y538", "abstract": "Because the Earth\u2019s upper mantle is inaccessible to us, in order to understand the chemical and physical processes that occur in the Earth\u2019s interior we must rely on both experimental work and computational modeling. This thesis addresses both of these geochemical methods. In the first chapter, I develop an internally consistent comprehensive molar volume model for spinels in the oxide system FeO-MgO-Fe2O3-Cr2O3-Al2O3-TiO2. The model is compared to the current MELTS spinel model with a demonstration of the impact of the model difference on the estimated spinel-garnet lherzolite transition pressure. In the second chapter, I calibrate a molar volume model for cubic garnets in the system SiO2-Al2O3-TiO2-Fe2O3-Cr2O3-FeO-MnO-MgO-CaO-Na2O. I use the method of singular value analysis to calibrate excess volume of mixing parameters for the garnet model. The implications the model has for the density of the lithospheric mantle are explored. In the third chapter, I discuss the nuclear inelastic X-ray scattering (NRIXS) method, and present analysis of three orthopyroxene samples with different Fe contents. Longitudinal and shear wave velocities, elastic parameters, and other thermodynamic information are extracted from the raw NRIXS data." }, { "name": "Levine, Xavier Josselin", "degree": "PhD", "year": "2013", "title": "Dynamics of Earth's Hadley Circulation", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:12062012-130125923", "creators": [ { "name": { "family": "Levine", "given": "Xavier Josselin" }, "id": "Levine-Xavier-Josselin", "display_name": "Levine, Xavier Josselin" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "chair", "display_name": "Bordoni, Simona" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." } ], "option_major": [ "envreng" ], "doi": "10.7907/Z25V-TA20", "abstract": "This thesis advances our understanding of the mechanisms controlling the Hadley circulation, and its interaction with eddies on planetary scales in particular. On Earth, and more generally in a rapidly rotating and differentially heated planet, planetary scale eddies in the extratropics interact with the mean flow in the tropics, contributing to the driving of the Hadley circulation. A hierarchy of numerical models is used to simulate and understand the relative importance of eddies in the driving of the Hadley circulation. In a global warming experiment, the Hadley circulation is found to strengthen in colder climates and weaken in warmer climates, with a maximum strength in a climate close to present-day Earth\u2019s. This nonmonotonicity is shown to be consistent with variations in the eddy activity in the midlatitudes. The cells are also found to widen over the entire range of this climate change. A criterion quantifying the importance of baroclinic waves in setting the depth of the troposphere, which is modified to account for the effect of convective adjustment on planetary Rossby waves activity, is used to explain the shifts in the terminus of the Hadley circulation for a wide range of climate scenarios. Additionally, by comparing simulations with and without ocean heat transport, it is shown that accounting for low-latitude ocean heat transport and its coupling to wind stress is essential to obtain Hadley circulations in a dynamical regime resembling Earth\u2019s. These changes in the strength and extent are found to be captured in a simple one-dimensional model that relies on standard assumptions about the thermodynamic properties of the atmosphere in the low-latitude regions and with a simple representation of eddy fluxes. Further work with this model, which may be amenable to analytical progress, could provide a quantitative understanding for the sensitivity of the Hadley circulation in comprehensive GCM simulations of 21st century global warming scenarios.
" }, { "name": "Li, King-Fai", "degree": "PhD", "year": "2013", "title": "Atmospheric Trace Gases as Probes of Chemistry and Dynamics", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08172012-154924604", "creators": [ { "name": { "family": "Li", "given": "King-Fai" }, "id": "Li-King-Fai", "orcid": "0000-0003-0150-2910", "display_name": "Li, King-Fai" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "envreng" ], "doi": "10.7907/EPJW-T613", "abstract": "This dissertation is a collection of empirical and modeling studies focusing on decadal and intraseasonal variabilities in atmospheric tracers. In Part I, a persistent discrepancy between the model and observed stratospheric O3 solar response is revisited using the Whole-Atmosphere Community Chemistry Model (WACCM). The model O3 simulated using UV irradiances measured from the latest spaceborne solar UV measurements by the Solar Radiation and Climate Experiment (SORCE) and that from the solar UV parametrization developed by the Naval Research Laboratory (NRL) are studied and compared with observations. None of the simulations using SORCE and NRL UV simultaneously agree with the observed O3 solar response in both upper and lower stratospheres, thus presenting a dilemma to our current understanding of stratospheric O3 response to UV perturbations. However, the simulation using the SORCE UV irradiance leads to a solar response in upper stratospheric/lower mesospheric OH column that agrees better than those derived from ground-based and satellite observations. Continuous long-term observations of solar UV, OH, O3, and other related chemical species through upcoming solar cycles are crucial for further investigations to solve the above puzzles. In Part II, intraseasonal variabilities in upper tropospheric/lower stratospheric (UTLS) O3 and mid-tropospheric carbon dioxide (CO2) related to the Madden-Julian oscillation (MJO) are studied using recent satellite observations. The UTLS O3 at mid-latitudes is shown to be modulated by the MJO through dynamical motions of the tropopause layer, supporting the conjecture proposed in previous studies. It is further shown that the UTLS O3 over the Arctic can be also modulated by the tropopause motions through MJO teleconnections. On the other hand, the distribution of tropical mid-tropospheric CO2 is modulated by the MJO through upward transport of surface CO2. The amplitude is of critical scale for identifying oceanic and land sources of CO2. The detailed structures of these MJO impacts are useful for diagnosing chemical transport models. These findings may be useful for improving air quality forecasts to weekly/monthly timescales, which help warn the public in advance and help authorities to take efficient emergency control actions." }, { "name": "Lin, Yunung Nina", "degree": "PhD", "year": "2013", "title": "Using Space Geodesy to Constrain Variations in Seismogenic Behavior on Subduction Megathrusts", "advisor": "Simons, Mark; Avouac, Jean-Philippe", "url": "https://resolver.caltech.edu/CaltechTHESIS:06042013-203949761", "creators": [ { "name": { "family": "Lin", "given": "Yunung Nina" }, "id": "Lin-Yunung-Nina", "display_name": "Lin, Yunung Nina" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "advisor", "display_name": "Simons, Mark" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "advisor", "display_name": "Avouac, Jean-Philippe" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "orcid": "0000-0002-4827-7987", "role": "member", "display_name": "Ampuero, Jean-Paul" } ], "option_major": [ "geol" ], "doi": "10.7907/0V1J-T074", "abstract": "The concept of seismogenic asperities and aseismic barriers has become a useful paradigm within which to understand the seismogenic behavior of major faults. Since asperities and barriers can be thought of as defining the potential rupture area of large megathrust earthquakes, it is thus important to identify their respective spatial extents, constrain their temporal longevity, and to develop a physical understanding for their behavior. Space geodesy is making critical contributions to the identification of slip asperities and barriers but progress in many geographical regions depends on improving the accuracy and precision of the basic measurements. This thesis begins with technical developments aimed at improving satellite radar interferometric measurements of ground deformation whereby we introduce an empirical correction algorithm for unwanted effects due to interferometric path delays that are due to spatially and temporally variable radar wave propagation speeds in the atmosphere. In chapter 2, I combine geodetic datasets with complementary spatio-temporal resolutions to improve our understanding of the spatial distribution of crustal deformation sources and their associated temporal evolution \u2013 here we use observations from Long Valley Caldera (California) as our test bed. In the third chapter I apply the tools developed in the first two chapters to analyze postseismic deformation associated with the 2010 Mw=8.8 Maule (Chile) earthquake. The result delimits patches where afterslip occurs, explores their relationship to coseismic rupture, quantifies frictional properties associated with inferred patches of afterslip, and discusses the relationship of asperities and barriers to long-term topography. The final chapter investigates interseismic deformation of the eastern Makran subduction zone by using satellite radar interferometry only, and demonstrates that with state-of-art techniques it is possible to quantify tectonic signals with small amplitude and long wavelength. Portions of the eastern Makran for which we estimate low fault coupling correspond to areas where bathymetric features on the downgoing plate are presently subducting, whereas the region of the 1945 M=8.1 earthquake appears to be more highly coupled." }, { "name": "Line, Michael Robert", "degree": "PhD", "year": "2013", "title": "Characterization of Exoplanet Atmospheres: Spectral Retrieval and Chemistry", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05212013-091653227", "creators": [ { "name": { "family": "Line", "given": "Michael Robert" }, "id": "Line-Michael-Robert", "display_name": "Line, Michael Robert" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Knutson", "given": "Heather A." }, "id": "Knutson-H-A", "role": "member", "display_name": "Knutson, Heather A." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/9VHA-2N67", "abstract": "The study of exoplanets is rapidly evolving into an important and exciting field of its own. My investigations over the past half-decade have focused on understanding just a small sliver of what they are trying to tell us. That small sliver is their atmospheres. Atmospheres are the buffer between the bulk planet and the vacuum of space. The atmosphere is an important component of a planet as it is the most readily observable and contains the most information about the physical processes that can occur in a planet. I have focused on two aspects of exoplanetary atmospheres. First, I aimed to understand the chemical mechanisms that control the atmospheric abundances. Second, I focused on interpreting exoplanet atmospheric spectra and what they tell us about the temperatures and compositions through inverse modeling. Finally, I interpreted the retrieved temperature and abundances from inverse modeling in the context of chemical disequilibrium in the planetary atmospheres. " }, { "name": "Meng, Lingsen", "degree": "PhD", "year": "2013", "title": "Navigating Earthquake Physics with High-Resolution Array Back-Projection", "advisor": "Ampuero, Jean-Paul", "url": "https://resolver.caltech.edu/CaltechTHESIS:08232012-003426663", "creators": [ { "name": { "family": "Meng", "given": "Lingsen" }, "id": "Meng-Lingsen", "display_name": "Meng, Lingsen" } ], "advisors": [ { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "orcid": "0000-0002-4827-7987", "role": "advisor", "display_name": "Ampuero, Jean-Paul" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "orcid": "0000-0002-4827-7987", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/Y2C6-YA15", "abstract": "Understanding earthquake source dynamics is a fundamental goal of geophysics. Progress toward this goal has been slow due to the gap between state-of-art earthquake simulations and the limited source imaging techniques based on conventional low-frequency finite fault inversions. Seismic array processing is an alternative source imaging technique that employs the higher frequency content of the earthquakes and provides finer detail of the source process with few prior assumptions. While the back-projection provides key observations of previous large earthquakes, the standard beamforming back-projection suffers from low resolution and severe artifacts. This thesis introduces the MUSIC technique, a high-resolution array processing method that aims to narrow the gap between the seismic observations and earthquake simulations.
\r\n\r\nThe MUSIC is a high-resolution method taking advantage of the higher order signal statistics. The method has not been widely used in seismology yet because of the nonstationary and incoherent nature of the seismic signal. We adapt MUSIC to transient seismic signal by incorporating the Multitaper cross-spectrum estimates. We also adopt a \u201creference window\u201d strategy that mitigates the \u201cswimming artifact,\u201d a systematic drift effect in back projection. The improved MUSIC back projections allow the imaging of recent large earthquakes in finer details which give rise to new perspectives on dynamic simulations. In the 2011 Tohoku-Oki earthquake, we observe frequency-dependent rupture behaviors which relate to the material variation along the dip of the subduction interface. In the 2012 off-Sumatra earthquake, we image the complicated ruptures involving orthogonal fault system and an usual branching direction. This result along with our complementary dynamic simulations probes the pressure-insensitive strength of the deep oceanic lithosphere. In another example, back projection is applied to the 2010 M7 Haiti earthquake recorded at regional distance. The high-frequency subevents are located at the edges of geodetic slip regions, which are correlated to the stopping phases associated with rupture speed reduction when the earthquake arrests.
" }, { "name": "Ortega Culaciati, Francisco Hernan", "degree": "PhD", "year": "2013", "title": "Aseismic Deformation in Subduction Megathrusts: Central Andes and North-East Japan", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:06102013-122003618", "creators": [ { "name": { "family": "Ortega Culaciati", "given": "Francisco Hernan" }, "id": "Ortega-Culaciati-Francisco-Hernan", "display_name": "Ortega Culaciati, Francisco Hernan" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geophys" ], "doi": "10.7907/BHDB-KH07", "abstract": "We aim to characterize fault slip behavior during all stages of the seismic cycle in subduction megathrust environments with the eventual goal of understanding temporal and spatial variations of fault zone rheology, and to infer possible causal relationships between inter-, co- and post-seismic slip, as well as implications for earthquake and tsunami hazard. In particular we focus on analyzing aseismic deformation occurring during inter-seismic and post-seismic periods of the seismic cycle. We approach the problem using both Bayesian and optimization techniques. The Bayesian approach allows us to completely characterize the model parameter space by searching a posteriori estimates of the range of allowable models, to easily implement any kind of physically plausible a priori information and to perform the inversion without regularization other than that imposed by the parameterization of the model. However, the Bayesian approach computational expensive and not currently viable for quick response scenarios. Therefore, we also pursue improvements in the optimization inference scheme. We present a novel, robust and yet simple regularization technique that allows us to infer robust and somewhat more detailed models of slip on faults. We apply such methodologies, using simple quasi-static elastic models, to perform studies of inter- seismic deformation in the Central Andes subduction zone, and post-seismic deformation induced by the occurrence of the 2011 Mw 9.0 Tohoku-Oki earthquake in Japan. For the Central Andes, we present estimates of apparent coupling probability of the subduction interface and analyze its relationship to past earthquakes in the region. For Japan, we infer high spatial variability in material properties of the megathrust offshore Tohoku. We discuss the potential for a large earthquake just south of the Tohoku-Oki earthquake where our inferences suggest dominantly aseismic behavior." }, { "name": "Osburn, Magdalena Rose", "degree": "PhD", "year": "2013", "title": "Isotopic Proxies for Microbial and Environmental Change: Insights from Hydrogen Isotopes and the Ediacaran Khufai Formation", "advisor": "Sessions, Alex L.; Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03202013-162430365", "creators": [ { "name": { "family": "Osburn", "given": "Magdalena Rose" }, "id": "Osburn-Magdalena-Rose", "display_name": "Osburn, Magdalena Rose" } ], "advisors": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "co-advisor", "display_name": "Sessions, Alex L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "co-advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "chair", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Lyons", "given": "Timothy W." }, "id": "Lyons-T-W", "role": "member", "display_name": "Lyons, Timothy W." } ], "option_major": [ "geobiol" ], "doi": "10.7907/KBAN-B073", "abstract": "Microbes have profoundly influenced the Earth\u2019s environments through time. Records of these interactions come primarily from the development and implementation of proxies that relate known modern processes to chemical signatures in the sedimentary record. This thesis is presented in two parts, focusing first on novel proxy development in the modern and second on interpretation of past environments using well-established methods. Part 1, presented in two chapters, builds on previous observations that different microbial metabolisms produce vastly different lipid hydrogen isotopic compositions. Chapter 1 evaluates the potential environmental expression of metabolism-based fractionation differences by exploiting the natural microbial community gradients in hydrothermal springs. We find a very large range in isotopic composition that can be demonstrably linked to the microbial source(s) of the fatty acids at each sample site. In Chapter 2, anaerobic culturing techniques are used to evaluate the hydrogen isotopic fractionations produced by anaerobic microbial metabolisms. Although the observed fractionation patterns are similar to those reported for aerobic cultures for some organisms, others show large differences. Part 2 changes focus from the modern to the ancient and uses classical stratigraphic methods combined with isotope stratigraphy to interpret microbial and environmental changes during the latest Precambrian Era. Chapter 3 presents a detailed characterization of the facies, parasequence development, and stratigraphic architecture of the Ediacaran Khufai Formation. Chapter 4 presents measurements of carbon, oxygen, and sulfur isotopic ratios in stratigraphic context. Large oscillations in the isotopic composition of sulfate constrain the size of the marine sulfate reservoir and suggest incorporation of an enriched isotopic source. Because this data was measured in stratigraphic context, we can assert with confidence that these isotopic shifts are not related to stratigraphic surfaces or facies type but instead reflect the evolution of the ocean through time. This data integrates into the chemostratigraphic global record and contributes to the emerging picture of changing marine chemistry during the latest Precambrian Era." }, { "name": "Philibosian, Belle", "degree": "PhD", "year": "2013", "title": "Characterization of Diverse Megathrust Fault Behavior Related to Seismic Supercycles, Mentawai Islands, Sumatra", "advisor": "Sieh, Kerry E.; Avouac, Jean-Philippe", "url": "https://resolver.caltech.edu/CaltechTHESIS:06072013-041618148", "creators": [ { "name": { "family": "Philibosian", "given": "Belle" }, "id": "Philibosian-Belle", "display_name": "Philibosian, Belle" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "co-advisor", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "co-advisor", "display_name": "Avouac, Jean-Philippe" } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geol" ], "doi": "10.7907/E0QH-YT77", "abstract": "Long paleoseismic histories are necessary for understanding the full range of behavior of faults, as the most destructive events often have recurrence intervals longer than local recorded history. The Sunda megathrust, the interface along which the Australian plate subducts beneath Southeast Asia, provides an ideal natural laboratory for determining a detailed paleoseismic history over many seismic cycles. The outer-arc islands above the seismogenic portion of the megathrust cyclically rise and subside in response to processes on the underlying megathrust, providing uncommonly good illumination of megathrust behavior. Furthermore, the growth histories of coral microatolls, which record tectonic uplift and subsidence via relative sea level, can be used to investigate the detailed coseismic and interseismic deformation patterns. One particularly interesting area is the Mentawai segment of the megathrust, which has been shown to characteristically fail in a series of ruptures over decades, rather than a single end-to-end rupture. This behavior has been termed a seismic \u201csupercycle.\u201d Prior to the current rupture sequence, which began in 2007, the segment previously ruptured during the 14th century, the late 16th to late 17th century, and most recently during historical earthquakes in 1797 and 1833. In this study, we examine each of these previous supercycles in turn.
\r\n\r\nFirst, we expand upon previous analysis of the 1797\u20131833 rupture sequence with a comprehensive review of previously published coral microatoll data and the addition of a significant amount of new data. We present detailed maps of coseismic uplift during the two great earthquakes and of interseismic deformation during the periods 1755\u20131833 and 1950\u20131997 and models of the corresponding slip and coupling on the underlying megathrust. We derive magnitudes of Mw 8.7\u20139.0 for the two historical earthquakes, and determine that the 1797 earthquake fundamentally changed the state of coupling on the fault for decades afterward. We conclude that while major earthquakes generally do not involve rupture of the entire Mentawai segment, they undoubtedly influence the progression of subsequent ruptures, even beyond their own rupture area. This concept is of vital importance for monitoring and forecasting the progression of the modern rupture sequence.
\r\n\r\nTurning our attention to the 14th century, we present evidence of a shallow slip event in approximately A.D. 1314, which preceded the \u201cconventional\u201d megathrust rupture sequence. We calculate a suite of slip models, slightly deeper and/or larger than the 2010 Pagai Islands earthquake, that are consistent with the large amount of subsidence recorded at our study site. Sea-level records from older coral microatolls suggest that these events occur at least once every millennium, but likely far less frequently than their great downdip neighbors. The revelation that shallow slip events are important contributors to the seismic cycle of the Mentawai segment further complicates our understanding of this subduction megathrust and our assessment of the region\u2019s exposure to seismic and tsunami hazards.
\r\n\r\nFinally, we present an outline of the complex intervening rupture sequence that took place in the 16th and 17th centuries, which involved at least five distinct uplift events. We conclude that each of the supercycles had unique features, and all of the types of fault behavior we observe are consistent with highly heterogeneous frictional properties of the megathrust beneath the south-central Mentawai Islands. We conclude that the heterogeneous distribution of asperities produces terminations and overlap zones between fault ruptures, resulting in the seismic \u201csupercycle\u201d phenomenon.
\r\n" }, { "name": "Phillips-Alonge, Kristin Eileen", "degree": "PhD", "year": "2013", "title": "Structure of the Subduction System in Southern Peru from Seismic Array Data", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11302012-163616170", "creators": [ { "name": { "family": "Phillips-Alonge", "given": "Kristin Eileen" }, "id": "Phillips-Kristin-Eileen", "display_name": "Phillips-Alonge, Kristin Eileen" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "orcid": "0000-0002-4827-7987", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/71A7-4211", "abstract": "Southern Peru represents a subduction transition region from normal subduction in the southernmost part of Peru to flat slab subduction in central Peru. In order to learn more about the structure of southern Peru, causes of flat slab subduction, and the nature of the transition from normal to flat slab subduction, we installed three seismic arrays utilizing a total of about 100 broadband stations. The first installed array samples the normal subduction region, while the second samples the transition from normal to flat subduction, and the third samples the flat slab region near where the Nazca Ridge is presently subducting. Data from teleseismic events greater than 30 degrees distance from Peru was analyzed using the receiver function method that makes use of P to S converted phases at interfaces such as the Moho to provide information about the structure directly beneath each station. A strong signal from the Moho was observed for each array and was found to have a maximum depth of around 75 km beneath the Altiplano. The average crustal Vp/Vs ratio was also estimated and was found to have an average value of around 1.75 beneath the Altiplano. The shape of the slab was also clarified for the three arrays. The transition from normal to flat slab subduction appears to be a contortion rather than a break in the slab. In addition to those signals, a positive impedance midcrustal signal at about 40 km depth was widely observed for stations on the eastern side of the arrays. The midcrustal signal is indicative of a velocity increase in the lower crust and is suggested to be an observation of the underthrusting Brazilian shield which would have implications for the timing of uplift in the Andes. Finite difference modeling with velocity models that include a midcrustal structure produces synthetics which are consistent with receiver function observations. Receiver function results and other related methods provide a simple way of making direct observations of key structural interfaces and the current state of the subduction system which has relevance in studies of the tectonic evolution of the region and estimations of causes of flat slab subduction." }, { "name": "Skinner, Steven Michael", "degree": "PhD", "year": "2013", "title": "Plate Tectonic Constraints on Flat Subduction and Paleomagnetic Constraints on Rifting", "advisor": "Clayton, Robert W.; Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06062013-151342444", "creators": [ { "name": { "family": "Skinner", "given": "Steven Michael" }, "id": "Skinner-Steven-Michael", "display_name": "Skinner, Steven Michael" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geol" ], "doi": "10.7907/G94S-Z109", "abstract": "Plate tectonics shapes our dynamic planet through the creation and destruction of lithosphere. This work focuses on increasing our understanding of the processes at convergent and divergent boundaries through geologic and geophysical observations at modern plate boundaries. Recent work had shown that the subducting slab in central Mexico is most likely the flattest on Earth, yet there was no consensus about what caused it to originate. The first chapter of this thesis sets out to systematically test all previously proposed mechanisms for slab flattening on the Mexican case. What we have discovered is that there is only one model for which we can find no contradictory evidence. The lack of applicability of the standard mechanisms used to explain flat subduction in the Mexican example led us to question their applications globally. The second chapter expands the search for a cause of flat subduction, in both space and time. We focus on the historical record of flat slabs in South America and look for a correlation between the shallowing and steepening of slab segments with relation to the inferred thickness of the subducting oceanic crust. Using plate reconstructions and the assumption that a crustal anomaly formed on a spreading ridge will produce two conjugate features, we recreate the history of subduction along the South American margin and find that there is no correlation between the subduction of a bathymetric highs and shallow subduction. These studies have proven that a subducting crustal anomaly is neither a sufficient or necessary condition of flat slab subduction. The final chapter in this thesis looks at the divergent plate boundary in the Gulf of California. Through geologic reconnaissance mapping and an intensive paleomagnetic sampling campaign, we try to constrain the location and orientation of a widespread volcanic marker unit, the Tuff of San Felipe. Although the resolution of the applied magnetic susceptibility technique proved inadequate to contain the direction of the pyroclastic flow with high precision, we have been able to detect the tectonic rotation of coherent blocks as well as rotation within blocks." }, { "name": "Thomas, Claire Waller", "degree": "PhD", "year": "2013", "title": "Liquid Silicate Equation of State: Using Shock Waves to Understand the Properties of the Deep Earth", "advisor": "Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:04162013-132730413", "creators": [ { "name": { "family": "Thomas", "given": "Claire Waller" }, "id": "Thomas-Claire-Waller", "display_name": "Thomas, Claire Waller" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geol" ], "doi": "10.7907/8JTY-MQ03", "abstract": "The equations of state (EOS) of several geologically important silicate liquids have been constrained via preheated shock wave techniques. Results on molten Fe2SiO4 (fayalite), Mg2SiO4 (forsterite), CaFeSi2O6 (hedenbergite), an equimolar mixture of CaAl2Si2O8-CaFeSi2O6 (anorthite-hedenbergite), and an equimolar mixture of CaAl2Si2O8-CaFeSi2O6-CaMgSi2O6(anorthite-hedenbergite-diopside) are presented. This work represents the first ever direct EOS measurements of an iron-bearing liquid or of a forsterite liquid at pressures relevant to the deep Earth (> 135 GPa). Additionally, revised EOS for molten CaMgSi2O6 (diopside), CaAl2Si2O8 (anorthite), and MgSiO3 (enstatite), which were previously determined by shock wave methods, are also presented.
\r\n\r\nThe liquid EOS are incorporated into a model, which employs linear mixing of volumes to determine the density of compositionally intermediate liquids in the CaO-MgO-Al2O3-SiO2-FeO major element space. Liquid volumes are calculated for temperature and pressure conditions that are currently present at the core-mantle boundary or that may have occurred during differentiation of a fully molten mantle magma ocean.
\r\n\r\nThe most significant implications of our results include: (1) a magma ocean of either chondrite or peridotite composition is less dense than its first crystallizing solid, which is not conducive to the formation of a basal mantle magma ocean, (2) the ambient mantle cannot produce a partial melt and an equilibrium residue sufficiently dense to form an ultralow velocity zone mush, and (3) due to the compositional dependence of Fe
This thesis describes the active structures of Myanmar and its surrounding regions, and the earthquake geology of the major active structures. Such investigation is needed urgently for this rapidly developing country that has suffered from destructive earthquakes in its long history. To archive a better understanding of the regional active tectonics and the seismic potential in the future, we utilized a global digital elevation model and optical satellite imagery to describe geomorphologic evidence for the principal neotectonic features of the western half of the Southeast Asia mainland. Our investigation shows three distinct active structural systems that accommodate the oblique convergence between the Indian plate and Southeast Asia and the extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Each of these active deformation belts can be further separated into several neotectonic domains, in which structures show distinctive active behaviors from one to another.
\r\n\r\nIn order to better understand the behaviors of active structures, we focused on the active characteristics of the right-lateral Sagaing fault and the oblique subducting northern Sunda megathrust in the second part of this thesis. The detailed geomorphic investigations along these two major plate-interface faults revealed the recent slip behavior of these structures, and plausible recurrence intervals of major seismic events. We also documented the ground deformation of the 2011 Tarlay earthquake in remote eastern Myanmar from remote sensing datasets and post-earthquake field investigations. The field observation and the remote sensing measurements of surface ruptures of the Tarlay earthquake are the first study of this kind in the Myanmar region.
\r\n" }, { "name": "Wicks, June Ki", "degree": "PhD", "year": "2013", "title": "Sound Velocities and Equation of State of Iron-Rich (Mg,Fe)O", "advisor": "Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06102013-152154645", "creators": [ { "name": { "family": "Wicks", "given": "June Ki" }, "id": "Wicks-June-Ki", "display_name": "Wicks, June Ki" } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." } ], "option_major": [ "geochem" ], "doi": "10.7907/Z94B2Z98", "abstract": "Ultralow-velocity zones (ULVZs) are small structures at the base of the mantle characterized by sound velocities up to 30% lower than those of surrounding mantle. In this thesis, we propose that iron-rich (Mg,Fe)O plays a key role in the observed sound velocities, and argue that chemically distinct, iron-enriched structures are consistent with both the low sound velocities and the measured shapes of ULVZs." }, { "name": "Williams, Nneka Njeri Akosua", "degree": "PhD", "year": "2013", "title": "Defining the Relationship between Seismicity and Deformation at Regional and Local Scales", "advisor": "Wernicke, Brian P.; Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09052012-110119932", "creators": [ { "name": { "family": "Williams", "given": "Nneka Njeri Akosua" }, "id": "Williams-Nneka-Njeri-Akosua", "display_name": "Williams, Nneka Njeri Akosua" } ], "advisors": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "advisor", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geol" ], "doi": "10.7907/CN29-YV40", "abstract": "In this thesis, I use source inversion methods to improve understanding of crustal deformation along the Nyainquentanglha (NQTL) Detachment in Southern Tibet and the Piceance Basin in northwestern Colorado. Broadband station coverage in both regions is sparse, necessitating the development of innovative approaches to source inversion for the purpose of studying local earthquakes.
\r\n\r\nIn an effort to study the 2002-2003 earthquake swarm and the 2008 Mw 6.3 Damxung earthquake and aftershocks that occurred in the NQTL region, we developed a single station earthquake location inversion method called the SP Envelope method, to be used with data from LHSA at Lhasa, a broadband seismometer located 75 km away. A location is calculated by first rotating the seismogram until the azimuth at which the envelope of the P-wave arrival on the T-component is smallest (its great circle path) is found. The distance at which to place the location along this azimuth is measured by calculating the S-P distance from arrivals on the seismogram. When used in conjunction with an existing waveform modeling based source inversion method called Cut and Paste (CAP), a catalog of 40 regional earthquakes was generated.
\r\n\r\nFrom these 40 earthquakes, a catalog of 30 earthquakes with the most certain locations was generated to study the relationship of seismicity and NQTL region faults mapped in Google Earth and in Armijo et al., 1986 and Kapp et al., 2005. Using these faults and focal mechanisms, a fault model of the NQTL Region was generated using GOCAD, a 3D modeling suite. By studying the relationship of modeled faults to mapped fault traces at the surface, the most likely fault slip plane was chosen. These fault planes were then used to calculate slip vectors and a regional bulk stress tensor, with respect to which the low-angle NQTL Detachment was found to be badly misoriented. The formation of low-angle normal faults is inconsistent with the Anderson Theory of faulting, and the presence of the NQTL Detachment in a region with such an incongruous stress field supports the notion that such faults are real.
\r\n\r\nThe timing and locations of the earthquakes in this catalog with respect to an anomalous increase in the eastward component of velocity readings at the single cGPS station in Lhasa (LHAS) were analyzed to determine the relationship between plastic and brittle deformation in the region. The fact that cGPS velocities slow significantly after the 2002-2003 earthquake swarm suggests that this motion is tectonic in nature, and it has been interpreted as only the second continental slow slip event (SSE) ever to be observed. The observation of slow slip followed by an earthquake swarm within a Tibetan rift suggests that other swarms observed within similar rifts in the region are related to SSEs.
\r\n\r\nIn the Piceance Basin, CAP was used to determine source mechanisms of microearthquakes triggered as a result of fracture stimulation within a tight gas reservoir. The expense of drilling monitor wells and installing borehole geophones reduces the azimuthal station coverage, thus making it difficult to determine source mechanisms of microearthquakes using more traditional methods. For high signal to noise ratio records, CAP produced results on par with those obtained in studies of regional earthquakes. This finding suggests that CAP could successfully be applied in studies of microseismicity when data quality is high.
" }, { "name": "Wolf, Aaron Samuel", "degree": "PhD", "year": "2013", "title": "Probing the Thermodynamic Properties of Mantle Rocks in Solid and Liquid States", "advisor": "Asimow, Paul David; Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06102013-170950875", "creators": [ { "name": { "family": "Wolf", "given": "Aaron Samuel" }, "id": "Wolf-Aaron-Samuel", "display_name": "Wolf, Aaron Samuel" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "co-advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/TJ86-C566", "abstract": "Our understanding of the structure and evolution of the deep Earth is strongly linked to knowledge of the thermodynamic properties of rocky materials at extreme temperatures and pressures. In this thesis, I present work that helps constrain the equation of state properties of iron-bearing Mg-silicate perovskite as well as oxide-silicate melts. I use a mixture of experimental, statistical, and theoretical techniques to obtain knowledge about these phases. These include laser-heated diamond anvil cell experiments, Bayesian statistical analysis of powder diffraction data, and the development of a new simplified model for understanding oxide and silicate melts at mantle conditions. By shedding light on the thermodynamic properties of such ubiquitous Earth-forming materials, I hope to aid our community\u2019s progress toward understanding the large-scale processes operating in the Earth\u2019s mantle, both in the modern day and early in Earth\u2019s history." }, { "name": "Yee, Lindsay Diana", "degree": "PhD", "year": "2013", "title": "Chemistry of Secondary Organic Aerosol Formation", "advisor": "Seinfeld, John H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03162013-090820386", "creators": [ { "name": { "family": "Yee", "given": "Lindsay Diana" }, "id": "Yee-Lindsay-Diana", "display_name": "Yee, Lindsay Diana" } ], "advisors": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "advisor", "display_name": "Seinfeld, John H." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Flagan", "given": "Richard C." }, "id": "Flagan-R-C", "role": "member", "display_name": "Flagan, Richard C." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" } ], "option_major": [ "envreng" ], "doi": "10.7907/BPKE-M777", "abstract": "The photooxidation of volatile organic compounds (VOCs) in the atmosphere can lead to the formation of secondary organic aerosol (SOA), a major component of fine particulate matter. Improvements to air quality require insight into the many reactive intermediates that lead to SOA formation, of which only a small fraction have been measured at the molecular level. This thesis describes the chemistry of secondary organic aerosol (SOA) formation from several atmospherically relevant hydrocarbon precursors. Photooxidation experiments of methoxyphenol and phenolic compounds and C12 alkanes were conducted in the Caltech Environmental Chamber. These experiments include the first photooxidation studies of these precursors run under sufficiently low NOx levels, such that RO2 + HO2 chemistry dominates, an important chemical regime in the atmosphere. Using online Chemical Ionization Mass Spectrometery (CIMS), key gas-phase intermediates that lead to SOA formation in these systems were identified. With complementary particle-phase analyses, chemical mechanisms elucidating the SOA formation from these compounds are proposed.
\r\n\r\nThree methoxyphenol species (phenol, guaiacol, and syringol) were studied to model potential photooxidation schemes of biomass burning intermediates. SOA yields (ratio of mass of SOA formed to mass of primary organic reacted) exceeding 25% are observed. Aerosol growth is rapid and linear with the organic conversion, consistent with the formation of essentially non-volatile products. Gas and aerosol-phase oxidation products from the guaiacol system show that the chemical mechanism consists of highly oxidized aromatic species in the particle phase. Syringol SOA yields are lower than that of phenol and guaiacol, likely due to unique chemistry dependent on methoxy group position.
\r\n\r\nThe photooxidation of several C12 alkanes of varying structure n-dodecane, 2-methylundecane, cyclododecane, and hexylcyclohexane) were run under extended OH exposure to investigate the effect of molecular structure on SOA yields and photochemical aging. Peroxyhemiacetal formation from the reactions of several multifunctional hydroperoxides and aldehyde intermediates was found to be central to organic growth in all systems, and SOA yields increased with cyclic character of the starting hydrocarbon. All of these studies provide direction for future experiments and modeling in order to lessen outstanding discrepancies between predicted and measured SOA.
" }, { "name": "Zhang, Xi", "degree": "PhD", "year": "2013", "title": "Aerosols and Chemistry in the Planetary Atmospheres", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12072012-233847443", "creators": [ { "name": { "family": "Zhang", "given": "Xi" }, "id": "Zhang-Xi", "display_name": "Zhang, Xi" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Stevenson", "given": "David J." }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David J." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/CS1E-F431", "abstract": "This dissertation is devoted to studying aerosols and their roles in regulating chemistry, radiation, and dynamics of planetary atmospheres. In chapter I, we provided a fundamental mathematical basis for the quasi-equilibrium growth assumption, a well-accepted approach to representing formation of secondary organic aerosols (SOAs) in microphysical simulations in the Earth\u2019s atmosphere. Our analytical work not only explains the quasi-equilibrium growth, which emerges as a limiting case in our theory, but also predicts the other types of condensational growth, confirmed by the recent laboratory and field experiments. In chapter II, we presented a new photochemical mechanism in which the evaporation of the aerosols composed of sulfuric acid or polysulfur on the nightside of Venus could provide a sulfur source above 90 km. Our model results imply the enhancements of sulfur oxides such as SO, SO2, and SO3. This is inconsistent with the previous model results but in agreement with the recent ground-based and spacecraft observations. In chapters III and IV, we developed a nonlinear optimization approach to retrieve the aerosol and cloud structure on Jupiter from the visible and ultraviolet images acquired by the Cassini spacecraft, combined with the ground-based near-infrared observations. We produced the first realistic spatial distribution of Jovian stratospheric aerosols in latitudes and altitudes. We also retrieved the stratospheric temperature and hydrocarbon species based on the mid-infrared spectra from the Cassini and Voyager spacecrafts. Based on the above information, the accurate and detailed maps of the instantaneous radiative forcing in Jovian stratosphere are obtained, revealing a significant heating effect from the polar dark aerosols in the high latitude region and therefore a strong modulation on the global meridional circulation in the stratosphere of Jupiter. In chapter V, we study the transport of passive tracers, such as aerosols, acetylene (C2H2) and ethane (C2H6) in the Jovian stratosphere, using both analytical and numerical approaches. We established several benchmark analytical solutions for the coupled photochemical-advective-diffusive system to understand its basic behaviors under different assumptions. A numerical two-dimensional chemical transport model is applied to Jupiter, and the effects of eddy mixing process and meridional circulation on the distributions of stratospheric species are discussed." }, { "name": "Alisic, Laura", "degree": "PhD", "year": "2012", "title": "Multi-Scale Dynamics and Rheology of Mantle Convection with Plates", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05092012-120619144", "creators": [ { "name": { "family": "Alisic", "given": "Laura" }, "id": "Alisic-Laura", "display_name": "Alisic, Laura" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/AXQP-0E85", "abstract": "Fundamental issues in our understanding of plate and mantle dynamics remain unresolved, including the rheology and state of stress of plates and slabs; the coupling between plates, slabs and mantle; the small-scale dynamics in subduction zones; the flow around slabs; and the cause of rapid changes in plate motions. To address these questions, models of global mantle flow with plates are computed using adaptive finite elements, and compared to a variety of observational constraints. These dynamically consistent instantaneous models include a composite rheology with yielding, and incorporate details of the thermal buoyancy field. Around plate boundaries, the local mesh size is 1 km, which allows us to study highly detailed features in a globally consistent framework. Models that best fit plateness criteria and plate motion data have strong slabs with high viscosities around 1024<\\sup> Pa s, and stresses of ~100 MPa. We find a strong dependence of global plate motions, trench rollback, net rotation, plateness, and strain rate on the stress exponent in the nonlinear viscosity; the yield stress is found to be important only if it is smaller than the ambient convective stress. Due to strong coupling between plates, slabs, and the surrounding mantle, the presence of lower mantle anomalies affect plate motions. The flow in and around slabs, microplate motion, and trench rollback are intimately linked to the amount of yielding in the subducting slab hinge, slab morphology, and the presence of high viscosity structures in the lower mantle beneath the slab. The lateral flow around slabs is generally trench-perpendicular, induced by the strongly coupled downward motion of the subducting slabs, and therefore our models do not account for the trench-parallel flow inferred from shear-wave splitting analysis. Flow models before and after the plate reorganization around 50 Ma are not able to reproduce the rapid change in Pacific plate motion from northwest to west that is associated with the bend in the Hawaiian-Emperor chain, despite a nonlinear rheology and the incorporation of detailed reconstructed paleo plate boundaries and age grids. In these models at 55 and 45 Ma, slab age is an impor- tant factor in the slab pull, determining the coupling between plates and slabs and between upper and lower mantle sections of slabs. The overall dynamics appear to be dominated by the characteristics of slab remnants in the lower mantle. Subducting slabs affect lateral flow in the upper mantle on a much smaller scale, and therefore we conclude that it is unlikely that the slabs in the western Pacific are responsible for the slowing of sub-Pacific flow after the initiation of their subduction around 50 Ma." }, { "name": "Batygin, Konstantin", "degree": "PhD", "year": "2012", "title": "Orbits and Interiors of Planets", "advisor": "Stevenson, David John; Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05202012-233257444", "creators": [ { "name": { "family": "Batygin", "given": "Konstantin" }, "id": "Batygin-Konstantin", "orcid": "0000-0002-7094-7908", "display_name": "Batygin, Konstantin" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "co-advisor", "display_name": "Stevenson, David John" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "co-advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/KQVW-GF86", "abstract": "The focus of this thesis is a collection of problems of timely interest in orbital dynamics and interior structure of planetary bodies.
\r\n\r\nThe first three chapters are dedicated to understanding the interior structure of close-in, gaseous extrasolar planets (hot Jupiters). In order to resolve a long-standing problem of anomalously large hot Jupiter radii, we proposed a novel magnetohydrodynamic mechanism responsible for inflation. The mechanism relies on the electro-magnetic interactions between fast atmospheric flows and the planetary magnetic field in a thermally ionized atmosphere, to induce electrical currents that flow throughout the planet. The resulting Ohmic dissipation acts to maintain the interior entropies, and by extension the radii of hot Jupiters at an enhanced level. Using self-consistent calculations of thermal evolution of hot Jupiters under Ohmic dissipation, we demonstrated a clear tendency towards inflated radii for effective temperatures that give rise to significant ionization of K and Na in the atmosphere, a trend fully consistent with the observational data. Furthermore, we found that in absence of massive cores, low-mass hot Jupiters can over-flow their Roche-lobes and evaporate on Gyr time-scales, possibly leaving behind small rocky cores. In systems where a transiting hot Jupiter is perturbed by a long-period companion, apsidal precession of the hot Jupiter that results from its tidal bulge plays an important, and often dominant role in determining the nature of the dynamical state onto which the system settles. This precession is in turn a strong function of the planet's degree of central concentration and is characterized by the planetary Love number. Utilizing this connection, we have shown that in tidally relaxed systems, measurement of the hot Jupiter's eccentricity directly yields the planetary Love number, which can then be used to place meaningful constraints on the physical structure of the planet with the aid of thermal evolution calculations.
\r\n\r\nChapters four through six focus on the improvement and implications of a model for orbital evolution of the solar system, driven by dynamical instability (termed the ``Nice\" model). Hydrodynamical studies of the orbital evolution of planets embedded in protoplanetary disks suggest that giant planets have a tendency to assemble into multi-resonant configurations. Following this argument, we used analytical methods as well as self-consistent numerical N-body simulations to identify fully-resonant primordial states of the outer solar system, whose dynamical evolutions give rise to orbital architectures that resemble the current solar system. We found a total of only eight such initial conditions, providing independent constraints for the solar system's birth environment. Next, we addressed a significant drawback of the original Nice model, namely its inability to create the physically unique, cold classical population of the Kuiper Belt. Specifically, we showed that a locally-formed cold belt can survive the transient instability, and its relatively calm dynamical structure can be reproduced. We developed a simple analytical model for dynamical excitation in the cold classical region and showed that comparatively fast apsidal precession and nodal recession of Neptune, during its eccentric phase, are essential for preservation of an unexcited state. Subsequently, we confirmed our findings with self-consistent N-body simulations, suggesting that the cold classical Kuiper belt's unique physical characteristics are a result of its remote formation site. Finally, we showed that the solar system may have initially hosted an additional ice-giant planet, that was ejected from the system during the transient phase of instability. Namely, we demonstrated that a large array of 5-planet (2 gas giants + 3 ice giants) multi-resonant initial states can lead to an adequate formation of the outer solar system, deeming the construction of a unique model of solar system's early dynamical evolution impossible.
\r\n\r\nThe last four chapters of this thesis address various aspects and consequences of dynamical relaxation of planetary orbits through dissipative effects as well as the formation of planets in binary stellar systems. Using octopole-order secular perturbation theory, we demonstrated that in multi-planet systems, tidal dissipation often drives orbits onto dynamical ``fixed points,\" characterized by apsidal alignment and lack of periodic variations in eccentricities. We applied this formalism towards investigating the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b is maintained in the face of tidal dissipation by a second planet in the system and computed a locus of possible orbits for the putative perturber. Following up along similar lines, we used various permutations of secular theory to show that when applied specifically to close-in low-mass planetary systems, various terms in the perturbation equations become separable, and the true masses of the planets can be solved for algebraically. In practice, this means that precise knowledge of the system's orbital state can resolve the sin(i) degeneracy inherent to non-transiting planets. Subsequently, we investigated the onset of chaotic motion in dissipative planetary systems. We worked in the context of classical secular perturbation theory, and showed that planetary systems approach chaos via the so-called period-doubling route. Furthermore, we demonstrated that chaotic strange attractors can exist in mildly damped systems, such as photo-evaporating nebulae that host multiple planets. Finally, we considered planetary formation in highly inclined binary systems, where orbital excitation due to the Kozai resonance apparently implies destructive collisions among planetesimals. Through a proper account of gravitational interactions within the protoplanetary disk, we showed that fast apsidal recession induced by disk self-gravity tends to erase the Kozai effect, and ensure that the disk's unwarped, rigid structure is maintained, resolving the difficulty in planet-formation. We also showed that the Kozai effect can continue to be wiped out as a result of apsidal precession, arising from planet-planet interactions in a mature planetary system. However, if such a system undergoes a dynamical instability, its architecture may change in such a way that the Kozai effect becomes operative, giving rise to the near-unity eccentricities, observed in some extrasolar planetary systems.
" }, { "name": "Beck, Anna Rose", "degree": "PhD", "year": "2012", "title": "Iron in the Ocean: Laboratory Experiments of Iron Geochemistry in the Presence of Marine Particles", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09282011-141454915", "creators": [ { "name": { "family": "Beck", "given": "Anna Rose" }, "id": "Beck-Anna-Rose", "display_name": "Beck, Anna Rose" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "role": "chair", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Berelson", "given": "William M." }, "id": "Berelson-W-M", "role": "member", "display_name": "Berelson, William M." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "envreng" ], "doi": "10.7907/0CAB-KF69", "abstract": "Iron (Fe) is an important micronutrient for primary productivity in the ocean. The Fe cycle in the ocean is relatively unconstrained, especially when it comes to quantifying sources and sinks related to exchange with particulate matter. This thesis attempts to constrain some of the kinetic and equilibrium particle interactions with Fe bound to the siderophore desferrioxamine B (DFB). Out of five inorganic particle types investigated, ferrihydrite, goethite, opal, foraminifera, and montmorillonite, ferrihydrite has the largest, extended impact on dissolved FeDFB. From experimental and modeling results, ferrihydrite has two primary exchange pathways, absorption, with a rate of 4 \u00b1 2 x 10-4 /(mg/L) per day, and dissolution, with a rate of 0.015 \u00b1 0.01 per day. Uptake appears irreversible and follows a colloidal pumping model. Isotopic fractionation is also the greatest in the presence of ferrihydrite with signals up to +1\u2030 or higher with excess ligand. Dry montmorillonite has the biggest initial impact on FeDFB, resulting in a nearly instantaneous equilibrium and little isotopic fractionation. Goethite, opal, and foraminifera all have a minimal impact on FeDFB and show slight enriched isotopic fractionation, +0.15\u2030, in the presence of large particle concentrations. DFB seems to induce heavy Fe desorption or dissolution, while particle uptake seems to favor transfer of lighter Fe. These isotopic and kinetic parameters are important constraints on the ability of particles to control dissolved Fe, since they fall through the water column faster than equilibrium will be obtained." }, { "name": "Bower, Daniel James", "degree": "PhD", "year": "2012", "title": "Geodynamics of Earth\u2019s Deep Mantle", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05282012-153935740", "creators": [ { "name": { "family": "Bower", "given": "Daniel James" }, "id": "Bower-Daniel-James", "display_name": "Bower, Daniel James" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "chair", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/E3FF-RC48", "abstract": "Seismic tomography and waveform modeling reveal several prominent structures in the Earth's lower mantle: (1) the D\" discontinuity, defined by a seismic velocity increase of 1-3% about 250 km above the core-mantle boundary (CMB), (2) Ultralow-velocity zones (ULVZs), which are thin, isolated patches with anomalously low seismic wavespeed at the CMB, and (3) two large, low-shear velocity provinces (LLSVPs) beneath Africa and the Pacific Ocean. The geodynamics of these structures are investigated using numerical convection models that include new discoveries in mineral physics and recent insight from seismology. In addition, I assess the influence of an iron spin transition in a major lower mantle mineral (ferropericlase) on the style and vigor of mantle convection.
\r\n\r\nA phase change model for the D\" discontinuity produces significant thermal and phase heterogeneity over small distances due to the interaction of slabs, plumes, and a phase transition. Perturbations to seismic arrivals are linked to the evolutionary stage of slabs and plumes and can be used to determine phase boundary properties, volumetric wavespeed anomaly beneath the discontinuity, and possibly the lengthscale of slab folding near the CMB.
\r\n\r\nI simulate convection within D\" to deduce the stability and morphology of a chemically distinct iron-enriched ULVZ. The chemical density anomaly largely dictates ULVZ shape, and the prescribed initial thickness (proxy for volume) of the chemically distinct layer controls its size. I synthesize the dynamic results with a Voigt-Reuss-Hill mixing model to provide insight into the inherent seismic trade-off between ULVZ thickness and wavespeed reduction.
\r\n\r\nThe dynamics of the LLSVPs are investigated using global 3-D models of thermochemical structures that incorporate paleogeographic constraints from 250 Ma to present day. The structures deform and migrate along the CMB, either by coupling to plate motions or in response to slab stresses. Slabs from Paleo-Tethys and Tethys Ocean subduction push the African structure further to the southwest than inferred from tomography. Dense and viscous slabs can severely compromise the stability of thermochemical structures with a high bulk modulus at the CMB.
\r\n\r\nFinally, I explore the consequences of the intrinsic density change caused by the Fe2+ spin transition in ferropericlase on the style and vigor of mantle convection. The transition generates a net driving density difference for both upwellings and downwellings that dominantly enhances the positive thermal buoyancy of plumes in 2-D cylindrical geometry. Although the additional buoyancy does not fundamentally alter large-scale dynamics, the Nusselt number increases by 5-10%, and vertical velocities increase by 10--40% in the lower mantle. Advective heat transport is more effective and temperatures in the CMB region are reduced by up to 12%.
" }, { "name": "Chapman, Alan Daniel", "degree": "PhD", "year": "2012", "title": "Late Cretaceous Gravitational Collapse of the Southern Sierra Nevada Batholith and Adjacent Areas Above Underplated Schists, Southern California", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07212011-115223871", "creators": [ { "name": { "family": "Chapman", "given": "Alan Daniel" }, "id": "Chapman-Alan-Daniel", "display_name": "Chapman, Alan Daniel" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "chair", "display_name": "Grotzinger, John P." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geol" ], "doi": "10.7907/NAQX-Y886", "abstract": "The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 \u00b0N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swing up to 90\u02da westward, taking on an east-west trend; 3) western zone rocks are truncated by eastern zone rocks along the proto-Kern Canyon fault, a Late Cretaceous oblique ductile thrust; and 4) fragments of shallow-level eastern SNB affinity rocks overlie deeper-level western zone rocks and subjacent subduction accretion assemblages (Rand, San Emigdio, and Sierra de Salinas schists) along a major Late Cretaceous detachment system. Integration of these observations with new and existing data reveals a temporal relationship between schist unroofing and upper crustal extension and rotation. I present a model whereby Late Cretaceous shallow subduction and subsequent trench-directed channelized extrusion of the schist triggered gravitational collapse of the overlying crustal column. This overarching model is based on several investigations summarized below.
\r\n\r\nThermobarometry, thermodynamic modelling and garnet diffusion modelling are presented that elucidate the tectonics of subduction and eduction of the San Emigdio Schist. I document an upsection increase in peak temperature (i.e. inverted metamorphism), from 590 to 700 \u00b0C, peak pressures ranging from 8.5 to 11.1 kbar, limited partial melting, microstructural evidence for large seismic events, rapid cooling (825\u2013380 \u00b0C/Myr) from peak conditions and an \u201cout and back\u201d P\u2013T path. Progressive cooling and tectonic underplating beneath an initially hot upper plate following the onset of shallow subduction provide a working hypothesis explaining high temperatures, inverted metamorphism, partial melting, and the observed P\u2013T trajectory calculated from the San Emigdio body.
\r\n\r\nNew geologic mapping and microstructural analysis indicate that the schist was transported to the SSW during structural ascent along a mylonitic contact (the Rand fault and Salinas shear zone) with upper plate assemblages. Crystallographic preferred orientation patterns in deformed quartzites reveal a decreasing simple shear component with increasing structural depth, suggesting a pure shear-dominated westward flow within the subduction channel and localized simple shear along the upper channel boundary. The resulting flow type within the channel is that of general shear extrusion.
\r\n\r\nStructural, thermobarometric, U-Pb geochronologic, and geochemical data from plutonic and metamorphic framework assemblages in the southern SNB also suggest SSW-directed transport of upper plate(s) along a major Late Cretaceous detachment system. The timing and pattern of regional dispersion of crustal fragments in the southern SNB is most consistent with Late Cretaceous collapse above the underplated schist. These observations imply a high degree of coupling between the shallow and deep crust during high magnitude extension. Zircon (U-Th)/He data presented herein reveal a rapid cooling event at 77 \u00b1 5 Ma, probably reflecting the time of large magnitude detachment faulting. A comparison of this dataset with existing apatite (U-Th)/He thermochronometry suggests that the development of modern landscape and arrangement of tectonic elements in southern California was greatly preconditioned by Late Cretaceous tectonics.
\r\n\r\nFinally, detrital and metamorphic zircon of the structurally highest and earliest subducted portions of the San Emigdio Schist constrain the depositional age to between ca. 102 and 98 Ma. Zircon oxygen isotope data from both lower plate schist and upper plate batholithic assemblages reveal a \u03b418O shift of ~ 1.5\u2030 between igneous (~ 5.5\u2030) and metamorphic (~ 7\u2030) domains. These results, taken with previous zircon and whole-rock \u03b418O measurements, provide evidence for massive devolatilization of the San Emigdio Schist and fluid traversal of upper plate batholithic assemblages, thereby altering the isotopic composition of overlying material. Furthermore, the timing of fluid-rock interaction in the southwestern SNB is coincident with eastward arc migration and an associated pulse of voluminous magmatism. I posit that during flattening of the Farallon slab the schist was rapidly delivered to the magmatic source, where ensuing devolatilization triggered a magmatic flare-up in the southeastern SNB. This short-lived (less than 15 Myr) high-flux event was followed by the termination of arc magmatism as the shallow subduction zone approached thermal equilibrium.
" }, { "name": "Chen, Ting", "degree": "PhD", "year": "2012", "title": "Part I: Structure of Central and Southern Mexico from Velocity and Attenuation Tomography. Part II: Physics of Small Repeating Earthquakes ", "advisor": "Clayton, Robert W.; Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechTHESIS:03262012-175814763", "creators": [ { "name": { "family": "Chen", "given": "Ting" }, "id": "Chen-Ting", "display_name": "Chen, Ting" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "orcid": "0000-0002-4827-7987", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geophys" ], "doi": "10.7907/REJW-YJ88", "abstract": "In part I, the 3D velocity and attenuation structure of the Cocos subduction zone in Mexico is imaged using earthquakes recorded by two temporary seismic arrays and local stations. Inversion results reveal low-attenuation and high-velocity Cocos slab. The slab dip angle increases from almost flat in central Mexico near Mexico City to about 30 degrees in southern Mexico near the Isthmus of Tehuantepec. High attenuation and low velocity in the crust beneath the Trans-Mexico Volcanic Belt correlate with low resistivity, and are probably related to dehydration and melting process. The most pronounced high-attenuation, low-Vp and high-Vp/Vs anomaly is found in the crust beneath the Veracruz Basin. A high-velocity structure dipping southward from the Gulf of Mexico near the Isthmus of Tehuantepec coincides with a discontinuity from a receiver functions study, and provides an evidence for the collision between the Yucatan Block and Mexico in the Miocene.
\r\n\r\n\r\nIn part II, we show that a model of small repeating earthquakes based on laboratory-derived rate and state friction laws reproduces the observed scaling between the recurrence time and seismic moment. In the model, a small fault patch governed by velocity-weakening friction is surrounded by a much larger velocity-strengthening region. For a fixed set of friction parameters, the observed scaling is reproduced by varying the size of the velocity-weakening patch. We further investigate the behavior of small repeating earthquakes in related models under different scenarios, including several forms of the state evolution equations in rate- and state-dependent friction laws, rectangular velocity-weakening patch geometries, quasi-dynamic vs. fully dynamic representation of inertial effects, and 2D vs. 3D simulations. We find that the simulated scalings between the recurrence time and seismic moment for these different scenarios are similar while differences do exist. We propose a theoretical model for the scaling between the recurrence time and seismic moment of small repeating earthquakes. The obtained theoretical insight is used to find the combinations of fault properties that allow the model to fit the observed scaling and range of the seismic moment and recurrence time.
" }, { "name": "Kidder, Steven Brooks", "degree": "PhD", "year": "2012", "title": "Microstructural, Metamorphic and Experimental Constraints on Differential Stress and Temperature in the Middle Crust", "advisor": "Avouac, Jean-Philippe", "url": "https://resolver.caltech.edu/CaltechTHESIS:03052012-150035418", "creators": [ { "name": { "family": "Kidder", "given": "Steven Brooks" }, "id": "Kidder-Steven-Brooks", "display_name": "Kidder, Steven Brooks" } ], "advisors": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "advisor", "display_name": "Avouac, Jean-Philippe" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geol" ], "doi": "10.7907/R9RS-1A13", "abstract": "Because shear stress drives plate tectonics and causes earthquakes, important objectives in the Earth Sciences include quantifying stress magnitudes and variability in space and time, and developing and improving tools to do so. This thesis addresses both objectives. In the first chapter I demonstrate that the Titanium-in-quartz thermobarometer (\"TitaniQ\") can be used to accurately record deformation temperatures under greenschist facies conditions. In the second chapter, an experimental study, I show that the relationship between recrystallized grain size and flow stress (the \u201crecrystallized grain size paleopiezometer\u201d) can be used to determine the stress history of dynamically recrystallized quartz under non steady state conditions. In the third chapter I apply the paleopiezometer in Taiwan\u2019s Hs\u00fcehshan range and compare results to independent constraints (e.g. critical taper theory and potential energy considerations). This analysis demonstrates: 1) the piezometer is accurate to within a factor of two or better under conditions at the brittle-ductile transition; 2) piezometric results are consistent with recent flow laws for quartz; 3) the activation energy of naturally deformed quartzite is >133 kJ/mol, consistent with experimental determinations; and 4) Peak differential stress in the Hs\u00fcehshan range was ~210 MPa at temperature ~300\u00b0C. Our results indicate hydrostatic fluid pressure and a low friction coefficient of ~0.38 within the Taiwan wedge. Integrated crustal strength in Taiwan is 1.5-2.1*1012 N/m, consistent with the force needed to support the topography of the range. The final chapter investigates stress levels on the Vincent thrust in the San Gabriel Mountains, California by constructing a numerical model of the initiation of flat slab subduction. A model inversion demonstrates that previously hypothesized high stresses are not required to explain inverted metamorphism along the fault." }, { "name": "Lebo, Zachary John", "degree": "PhD", "year": "2012", "title": "Computational Modeling Studies of Fundamental Aerosol-Cloud Interactions", "advisor": "Seinfeld, John H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03292012-204204319", "creators": [ { "name": { "family": "Lebo", "given": "Zachary John" }, "id": "Lebo-Zachary-John", "display_name": "Lebo, Zachary John" } ], "advisors": [ { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "advisor", "display_name": "Seinfeld, John H." } ], "committee": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "chair", "display_name": "Schneider, Tapio" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Li", "given": "Juilin F." }, "id": "Li-J-F", "role": "member", "display_name": "Li, Juilin F." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." } ], "option_major": [ "envreng" ], "doi": "10.7907/HH11-8N22", "abstract": "Basic questions regarding the interaction between changes in human activity and the atmosphere remain unanswered. Among these, the link between aerosol particles and cloud formation and development, especially in an altered climate, is a large point of uncertainty in recent climate projections. This should come as no surprise given the uncertainty in model parameters required to predict droplet activation, even in the most detailed models used for climate predictions. Here, a detailed spectral mixed-phase microphysics scheme and a state-of-the-art continuous two-dimensional (2-D) aerosol-droplet microphysics scheme have been developed and coupled to the Weather Research and Forecasting (WRF) model to more closely analyze the effects of aerosol perturbations on single clouds or cloud systems with the hope of ultimately improving numerical parameterizations used by microphysics schemes in general circulation models (GCMs).
\r\n\r\nThe continuous 2-D aerosol-droplet model is developed to explicitly treat the entire spectrum of aerosol, haze droplets, cloud droplets, and drizzle drops while allowing the solute mass spectrum to evolve within the droplets. In other words, the aerosol mass is conserved and regeneration of aerosol particles upon droplet evaporation is physically accurate without any a priori assumptions. The model is tested by performing simulations of marine stratocumulus and the results are compared with those from the aforementioned bin and bulk models. It is shown that microphysical processing of aerosols alone results in a large shift in the aerosol spectrum toward larger particles (via collision-coalescence of droplets). This could have potentially large effects on the activation of regenerated particles. Future studies with the model will address the need for better parameterizations of the aerosol regeneration process.
\r\n\r\nThe spectral mixed-phase microphysics scheme is used in conjunction with a two-moment bulk microphysics model to study the effect of aerosol perturbations on deep convective clouds. The bin model shows that with an increase in aerosol number concentration comes an invigoration and a decrease in precipitation. On the other hand, the bulk model suggests that the storm ought to weaken and precipitation will increase in a more polluted environment. The invigoration predicted by the bin model is a result of the suppression of the collision-coalescence process that permits more droplets to be lofted above the freezing level, hence increasing the bulk freezing rate aloft. The additional freezing and subsequent deposition acts to increase the latent heating and thus increase buoyancy. However, the cloud particles in the polluted cases are now smaller and more numerous and consequently have a shorter evaporation/sublimation timescale and a longer sedimentation time-scale. The ultimate result is for precipitation to decrease in conjunction with a moistening of the mid- to upper-troposphere. The difference in the sign of the aerosol effect between the two models is thought to be related to the saturation adjustment scheme used in the bulk model and is addressed by including an explicit treatment of condensation and activation within the bulk model, similar to the algorithm utilized in the bin model. The results of the inter-model comparison demonstrate the significance of the saturation adjustment assumption on the sign and magnitude of the aerosol effect on deep convective clouds.
" }, { "name": "Matzen, Andrew Keith", "degree": "PhD", "year": "2012", "title": "Fe-Mg and Ni Partitioning between Olivine and Silicate Melt", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04232012-061531097", "creators": [ { "name": { "family": "Matzen", "given": "Andrew Keith" }, "id": "Matzen-Andrew-Keith", "display_name": "Matzen, Andrew Keith" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Eiler", "given": "John M" }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geol" ], "doi": "10.7907/AB6Y-3374", "abstract": "The mineral olivine is abundant in a wide range of mafic igneous rocks from around the solar system. The fractionation, or accumulation, of olivine often exerts a major control on the observed variations in magma and whole-rock compositions. We performed experiments on a synthetic Hawaiian picrite and examined the olivine (ol)-liquid (liq) partitioning of Mg and Fe2+. These experiments show that the exchange coefficient, KD, Fe2+-Mg=(FeO/MgO)ol/(FeO/MgO)liq , by weight, is 0.345\u00b10.009 (1\u03c3) and is independent of temperature and liquid composition. Using this result, we estimate that parental liquids for tholeiites from Kilauea, Mauna Loa, and Mauna Kea have approximately 19-21 wt. % MgO. Published experiments on model Martian compositions suggest that for the Fe-enriched and Al-depleted Martian basalts a slightly higher KD,Fe2+-Mg of 0.36 is more appropriate. Using this value we conclude that the olivine-phyric shergottites Y 980459, NWA 5789, 2990, and EETA 79001 are possible liquid compositions (others are not); if the canonical KD,Fe2+-Mg of 0.30 were used, we would have concluded that none of the bulk meteorites represent liquids.
\r\n\r\nThe behavior of Ni is nearly unique among most other major and trace elements: it is compatible in olivine. This compatibility is useful in constraining the evolution of lavas, as their Ni contents will be very sensitive to the fractionation or accumulation of olivine. We performed experiments investigating the partitioning of Ni between a liquid and olivine of approximately constant composition over a range of temperatures and pressures. These experiments successfully separate the effects of composition from those of temperature and pressure, showing that, for our liquid with ~ 18 wt. % MgO, the ol-liq Ni partition coefficient (by wt.) decreases from 5.0 to 3.8 as the temperature and pressure increase from 1400 to 1550\u00b0C and 1-atm to 3.0 GPa, respectively. We show that this temperature and pressure effect may contribute to the generation of high-NiO olivines observed in Hawaiian and other ocean-island basalts.
\r\n" }, { "name": "Merlis, Timothy Moore", "degree": "PhD", "year": "2012", "title": "The General Circulation of the Tropical Atmosphere and Climate Changes", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:07012011-191902511", "creators": [ { "name": { "family": "Merlis", "given": "Timothy Moore" }, "id": "Merlis-Timothy-Moore", "display_name": "Merlis, Timothy Moore" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Thompson", "given": "Andrew F." }, "id": "Thompson-A-F", "role": "member", "display_name": "Thompson, Andrew F." } ], "option_major": [ "envreng" ], "doi": "10.7907/DH11-0926", "abstract": "I examine the general circulation of the tropical atmosphere and climate changes. First, the response of the zonal surface temperature gradients and zonally asymmetric tropical overturning circulations (Walker circulations) to substantial changes in the longwave optical depth of the atmosphere in an idealized general circulation model (GCM) is compared with scaling theories. Second, the response of the hydrological cycle and monsoonal Hadley circulations to changes in top-of-atmosphere insolation associated with orbital precession is examined in an idealized GCM.
\r\n\r\nZonal surface temperature gradients and Walker circulations are examined over a wide range of climates simulated by varying the optical thickness in an idealized atmospheric GCM with a climate-invariant zonally asymmetric ocean energy flux. The tropical zonal surface temperature gradient and Walker circulation generally decrease as the climate warms in the GCM simulations. A scaling relationship based on a two-term balance in the surface energy budget accounts for the changes in the zonally asymmetric component of the GCM-simulated surface temperature gradients. A scaling estimate for the Walker circulation based on differential changes (precipitation rates and saturation specific humidity) in the hydrological cycle accounts for the GCM simulations provided locally averaged quantities are used in the estimate.
\r\n\r\nThe results of atmospheric GCM simulations with varied top-of-atmosphere insolation are analyzed to constrain orbitally-forced changes in the tropical atmospheric circulations and precipitation. When the perihelion is varied between solstices, there is more annual-mean precipitation in the hemisphere in which perihelion occurs during the summer solstice. In aquaplanet simulations, this is primarily associated with thermodynamic changes: there is a correlation between the seasonal cycle of the perturbed water vapor and the seasonal cycle of the Hadley circulation convergence. The monsoonal Hadley circulation does not respond to insolation gradients in a simple manner, as the atmosphere\u2019s energy stratification changes. An idealized continent that has a simple treatment of land surface hydrology and inhomogeneous heat capacity allows an assessment of how land-sea contrasts can mediate the response to orbital precession. In these simulations, the response of precipitation to orbital precession depends on changes in the atmospheric circulation, which strengthens when perihelion occurs in the summer of the hemisphere with the land region. The changes in atmospheric circulation are related to changes in both the top-of-atmosphere energy balance and the thermodynamic properties of the surface.
" }, { "name": "Murphy, Caitlin Anne", "degree": "PhD", "year": "2012", "title": "Thermoelasticity of Hexagonal Close-Packed Iron from the Phonon Density of States", "advisor": "Jackson, Jennifer M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02162012-075245736", "creators": [ { "name": { "family": "Murphy", "given": "Caitlin Anne" }, "id": "Murphy-Caitlin-Anne", "display_name": "Murphy, Caitlin Anne" } ], "advisors": [ { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "advisor", "display_name": "Jackson, Jennifer M." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "role": "member", "display_name": "Jackson, Jennifer M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Fultz", "given": "Brent T." }, "id": "Fultz-B-T", "role": "member", "display_name": "Fultz, Brent T." } ], "option_major": [ "geophys" ], "doi": "10.7907/GQ17-GV90", "abstract": "Iron is the main constituent in Earth\u2019s core, along with ~5 to 10 wt% Ni and some light elements (e.g., H, C, O, Si, S). This thesis explores the vibrational thermodynamic and thermoelastic properties of pure hexagonal close-packed iron (\u03b5-Fe), in an effort to improve our understanding of the properties of a significant fraction of this remote region of the deep Earth and in turn, better constrain its composition.
\r\n\r\nIn order to access the vibrational properties of pure \u03b5-Fe, we directly probed its total phonon density of states (DOS) by performing nuclear resonant inelastic x-ray scattering (NRIXS) and in situ x-ray diffraction (XRD) experiments at Sector 3-ID-B of the Advanced Photon Source (APS) at Argonne National Laboratory. NRIXS and in situ XRD were collected over the course of ~14 days at eleven compression points between 30 and 171 GPa, and at 300 K. Our in situ XRD measurements probed the sample volume at each compression point, and our long NRIXS data-collection times and high-energy resolution resulted in the highest statistical quality dataset of this type for \u03b5-Fe to outer core pressures. Hydrostatic conditions were achieved in the sample chamber for our experiments at smaller compressions (P \u2264 69 GPa) via the loading of a neon pressure transmitting medium at the GeoSoilEnviroCARS (GSECARS) sector of the APS. For measurements made at P > 69 GPa, the sample was fully embedded in boron epoxy, which served as the pressure transmitting medium.
\r\n\r\nFrom each measured phonon DOS and thermodynamic definitions, we determined a wide range of vibrational thermodynamic and thermoelastic parameters, including the Lamb-M\u00f6ssbauer factor; vibrational components of the specific heat capacity, free energy, entropy, internal energy, and kinetic energy; and the Debye sound velocity. Together with our in situ measured volumes, the shape of the total phonon DOS and these parameters gave rise to a number of important properties for \u03b5-Fe at Earth\u2019s core conditions.
\r\n\r\nFor example, we determined the Debye sound velocity (vD) at each of our compression points from the low-energy region of the phonon DOS and our in situ measured volumes. In turn, vD is related to the compressional and shear sound velocities via our determined densities and the adiabatic bulk modulus. Our high-statistical quality dataset places a new tight constraint on the density dependence of \u03b5-Fe\u2019s sound velocities to outer core pressures. Via comparison with existing data for iron alloys, we investigate how nickel and candidate light elements for the core affect the thermoelastic properties of iron. In addition, we explore the effects of temperature on \u03b5-Fe\u2019s sound velocities by applying pressure- and temperature-dependent elastic moduli from theoretical calculations to a finite-strain model. Such models allow for direct comparisons with one-dimensional seismic models of Earth\u2019s solid inner core (e.g., the Preliminary Reference Earth Model).
\r\n\r\nNext, the volume dependence of the vibrational free energy is directly related to the vibrational thermal pressure, which we combine with previously reported theoretical values for the electronic and anharmonic thermal pressures to find the total thermal pressure of \u03b5-Fe. In addition, we found a steady increase in the Lamb-M\u00f6ssbauer factor with compression, which suggests restricted thermal atomic motions at outer core pressures. This behavior is related to the high-pressure melting behavior of \u03b5-Fe via Gilvarry\u2019s reformulation of Lindemann\u2019s melting criterion, which we used to obtain the shape of \u03b5-Fe\u2019s melting curve up to 171 GPa. By anchoring our melting curve shape with experimentally determined melting points and considering thermal pressure and anharmonic effects, we investigated \u03b5-Fe\u2019s melting temperature at the pressure of the inner\u2013core boundary (ICB, P = 330 GPa), where Earth\u2019s solid inner core and liquid outer core are in contact. Then, combining this temperature constraint with our thermal pressure, we determined the density of \u03b5-Fe under ICB conditions, which offers information about the composition of Earth\u2019s core via the seismically inferred density at the ICB.
\r\n\r\nIn addition, the shape of the phonon DOS remained similar at all compression points, while the maximum (cutoff) energy increased regularly with decreasing volume. As a result, we were able to describe the volume dependence of \u03b5-Fe\u2019s total phonon DOS with a generalized scaling law and, in turn, constrain the ambient temperature vibrational Gr\u00fcneisen parameter. We also used the volume dependence of our previously mentioned vD to determine the commonly discussed Debye Gr\u00fcneisen parameter (\u03b3D), which we found to be ~10% smaller than our vibrational Gr\u00fcneisen parameter at any given volume. Finally, applying our determined vibrational Gr\u00fcneisen parameter to a Mie-Gr\u00fcneisen type relationship and an approximate form of the empirical Lindemann melting criterion, we predict the vibrational thermal pressure and estimate the high-pressure melting behavior of \u03b5-Fe at Earth\u2019s core pressures, which can be directly compared with our previous results.
\r\n \r\nFinally, we use our measured vibrational kinetic energy and entropy to approximate \u03b5-Fe\u2019s vibrational thermodynamic properties to outer core pressures. In particular, the vibrational kinetic energy is related to the pressure- and temperature-dependent reduced isotopic partition function ratios (\u03b2-factors) of \u03b5-Fe and in turn, provide information about the partitioning behavior of solid iron in equilibrium processes. In addition, the volume dependence of vibrational entropy is directly related to the product of \u03b5-Fe\u2019s vibrational component of the thermal expansion coefficient and the isothermal bulk modulus, which we find to be independent of pressure (volume) at 300 K. In turn, this product gives rise to the volume-dependent thermal expansion coefficient of \u03b5-Fe at 300 K via established EOS parameters, and the vibrational Gr\u00fcneisen parameter and temperature dependence of the vibrational thermal pressure via thermodynamic definition.
" }, { "name": "Soto, Alejandro", "degree": "PhD", "year": "2012", "title": "Dynamical Paleoclimatology of Mars", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechTHESIS:01252012-143955675", "creators": [ { "name": { "family": "Soto", "given": "Alejandro" }, "id": "Soto-Alejandro", "display_name": "Soto, Alejandro" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Ehlmann", "given": "Bethany L." }, "id": "Ehlmann-B-L", "role": "member", "display_name": "Ehlmann, Bethany L." }, { "name": { "family": "Bordoni", "given": "Simona" }, "id": "Bordoni-S", "role": "member", "display_name": "Bordoni, Simona" } ], "option_major": [ "plansci" ], "doi": "10.7907/3D9Y-DC44", "abstract": "We investigated the dynamical paleoclimatology of Mars with a focus on three areas: large scale dynamics, atmospheric collapse, and controls on precipitation and aridity of a warm, wet Mars. We explored the changes, and lack of changes, in the large scale circulation over a range of atmospheric masses. We present the results here, with an emphasis on the response of the winds and the meridional transport.
\r\n\r\nThe conditions for continuous condensation of the CO2 atmospheres in the polar regions, often called 'atmospheric collapse', were explored by simulating the Martian atmosphere over a wide range of obliquities for a wide range of atmospheric thicknesses. As expected, atmospheric collapse occurs at low obliquities, but surprisingly, collapse occurs for high obliquities (up to 40\u25e6) for moderate atmospheric thicknesses (100's of millibars up to 1000 millibars). Using the MarsWRF model, we show that a competition between atmospheric heating feedbacks, including the greenhouse feedback and the heat transport feedback, and the condensation temperature feedback determines whether atmosphere collapse occurs.
\r\n\r\nFinally, we explored the precipitation and aridity of a warm, wet Mars with an active hydrological system. Even an extremely wet climate with a northern hemisphere ocean produces an extremely dry, desert climate in the southern hemisphere, with an equatorial band of rain and run off. Cross-equatorial flows deliver moist air from the northern ocean into the southern region, but topography and the distribution of land versus ocean limit the extent of the rainfall.
" }, { "name": "Thiagarajan, Nivedita", "degree": "PhD", "year": "2012", "title": "Using Clumped Isotopes and Radiocarbon to Characterize Rapid Climate Change During the Last Glacial Cycle", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05312012-104144486", "creators": [ { "name": { "family": "Thiagarajan", "given": "Nivedita" }, "id": "Thiagarajan-Nivedita", "display_name": "Thiagarajan, Nivedita" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M" }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "geochem" ], "doi": "10.7907/Z9CV4FR0", "abstract": "We generated records of carbonate clumped isotopes and radiocarbon in deep-sea corals to investigate the role of the deep ocean during rapid climate change events. First we calibrated the carbonate clumped isotope thermometer in modern deep-sea corals. We examined 11 specimens of three species of deep-sea corals and one species of a surface coral spanning a total range in growth temperature of 2\u201325\u00b0C. We find that skeletal carbonate from deep-sea corals shows the same relationship of \u039447 to temperature as does inorganic calcite. We explore several reasons why the clumped isotope compositions of deep-sea coral skeletons exhibit no evidence of a vital effect despite having large conventional isotopic vital effects.
\r\n\r\nWe also used a new dating technique, called the reconnaissance dating method to investigate the ecological response of deep-sea coral communities in the North Atlantic and Southern Ocean to both glaciation and rapid climate change. We find that the deep-sea coral populations of D. dianthus in both the North Atlantic and the Southern Ocean expand at times of rapid climate change. The most important factors for controlling deep-sea coral distributions are likely climatically driven changes in productivity, [O2] and [CO32-].
\r\n\r\nWe take 14 deep-sea corals that we had dated to the Younger Dryas (YD) and Heinrich 1 (H1), two rapid climate change events during the last deglaciation and make U-series dates and measure clumped isotopes in them. We find that temperatures during the YD and H1 are cooler than modern and that H1 exhibits warming with depth. We place our record in the context of atmospheric and marine benthic \u039414C, \u03b413C, and \u03b418O records during the deglaciation to understand the role of the deep North Atlantic during the deglaciation.
\r\n\r\nWe also investigated the role of climate change in the distribution of terrestrial megafauna. To help with this, we also developed a method for compound-specific radiocarbon dating of hydroxyproline extracted from bones in the La Brea Tar Pits. We find that the radiocarbon chronologies of megafauna from several locations around the world, including the La Brea Tar Pits, exhibit an increase in abundance of megafauna during Heinrich events.
\r\n" }, { "name": "Harrison, Benjamin Kimball", "degree": "PhD", "year": "2011", "title": "Microbial Colonization of Minerals in Marine Sediments \u2013 Method Development and Ecological Significance", "advisor": "Orphan, Victoria J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05262011-085126961", "creators": [ { "name": { "family": "Harrison", "given": "Benjamin Kimball" }, "id": "Harrison-Benjamin-Kimball", "display_name": "Harrison, Benjamin Kimball" } ], "advisors": [ { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "advisor", "display_name": "Orphan, Victoria J." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "role": "member", "display_name": "Orphan, Victoria J." }, { "name": { "family": "Edwards", "given": "Katrina J." }, "id": "Edwards-K-J", "role": "member", "display_name": "Edwards, Katrina J." } ], "option_major": [ "geochem" ], "doi": "10.7907/3891-QQ56", "abstract": "Interactions between microorganisms and minerals significantly impact microbial diversity and geochemical cycles in diverse settings. However, methodological difficulty has inhibited past study of microbe\u2013mineral interactions in fine-grained subsurface environments. Conventional sampling poorly resolves microbial diversity at the fine scale necessary to perceive overall community differences between mineral substrates that are thoroughly mixed. In particular, the importance of microbial attachment to minerals in unconsolidated marine sediments remains poorly constrained despite extensive geobiological research in these settings. This study presents an approach for characterizing microbial colonization patterns using mineral separation techniques. Differences in density and magnetic susceptibility are used to enrich target minerals from bulk environmental samples, selecting for those minerals which may have importance as substrates for metabolic activity.
\r\n \r\nThe application of this methodology to methane seep sediments of the Eel River Basin (ERB) on the California margin demonstrates that variations in microbial diversity between minerals are comparable to community differences across broad spatial scales and a range of porewater geochemistry. ERB colonization patterns determined by separation are shown to be reproducible and reflect in situ differences in the microbial community. Affinity of putative sulfide-oxidizing bacteria (primarily identified as Gammaproteobacteria) for mineral partitions enriched in authigenic sulfides suggests microbial attachment may reflect a metabolic role in sulfur cycling under reducing conditions. Mineral attachment is also shown to select between key archaeal phylotypes involved in the anaerobic oxidation of methane (AOM), providing insight into physiological differences between these uncultured groups. Preliminary results demonstrate that mineral attachment may be a significant factor in the microbial diversity of the marine subsurface, and that such community differences will be ecologically relevant.
\r\n" }, { "name": "Hayes, Alexander Gerard", "degree": "PhD", "year": "2011", "title": "Hydrocarbon Lakes on Titan and Their Role in the Methane Cycle", "advisor": "Aharonson, Oded", "url": "https://resolver.caltech.edu/CaltechTHESIS:05182011-100453420", "creators": [ { "name": { "family": "Hayes", "given": "Alexander Gerard" }, "id": "Hayes-Alexander-Gerard", "display_name": "Hayes, Alexander Gerard" } ], "advisors": [ { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "advisor", "display_name": "Aharonson, Oded" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" }, { "name": { "family": "Elachi", "given": "Charles" }, "id": "Elachi-C", "role": "member", "display_name": "Elachi, Charles" }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "plansci" ], "doi": "10.7907/14J8-7A73", "abstract": "Saturn's moon Titan is the only extraterrestrial body currently known to support standing bodies of liquid on its surface and, along with Earth and Mars, is one of only three places that we know to posses or have possessed an active hydrologic cycle. Understanding the nature of Titan's hydrologic system will teach us about the history of volatile compounds across the solar system and help define Earth's place within it. Titan's hydrologic cycle represents a simpler version of Earth's water cycle, lacking an ocean as a global sink of liquid and heat, and acts as a model for the evolution of planets around other stars, as its methane-based system may be more common than Earth's water-based system.
\r\n\r\nThis thesis combines several studies related to Titan's hydrologic system, particularly focusing on the role of lacustrine deposits. Following an introduction that discusses Titan's place in the solar system and the importance of studying its methane cycle, chapter two describes the lakes' geographic distribution and models interaction with a porous regolith. The chapter also discusses the implications of a hemispheric asymmetry in lake distribution, which has been attributed to an asymmetry in the intensity of Titan's seasons. The evolution of the orbital parameters that generate this asymmetry provide a mechanism for transferring not only methane, but also less volatile species such as ethane, from pole to pole over tens of thousands of years.
\r\n\r\nChapter three discusses lake properties through an examination of Ontario Lacus, the largest lake in Titan's southern pole. The complex dielectric properties of Ontario's near-shore region are derived through a combined analysis of radar altimetry and backscatter. The analysis is performed within multiple regions around Ontario's shore, producing a near-shore bathymetry map. The results of this study are then used to measure seasonal variation in chapter four. Shoreline recession at Ontario Lacus and smaller lakes which disappeared between repeat observations suggest an average meter-per-year loss rate between southern summer solstice and autumnal equinox. These observations demonstrate that Titan's surface plays an active role in its methane cycle and can be used to describe the evolution of its hydrologic system.
\r\n" }, { "name": "Kim, YoungHee", "degree": "PhD", "year": "2011", "title": "Properties of the Subduction System in Mexico", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04272011-150709139", "creators": [ { "name": { "family": "Kim", "given": "YoungHee" }, "id": "Kim-YoungHee", "display_name": "Kim, YoungHee" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Jackson", "given": "Jennifer M." }, "id": "Jackson-J-M", "orcid": "0000-0002-8256-6336", "role": "member", "display_name": "Jackson, Jennifer M." } ], "option_major": [ "geophys" ], "doi": "10.7907/BB7N-QP03", "abstract": "This thesis presents seismic imaging results of the structure of the Mexican subduction zone using receiver function (RF) based on teleseismic P-to-S converted waves, in order to gain insight into the physical and chemical factors associated with internal geodynamic processes. More specifically, this thesis investigates (1) the nature of tectonic processes involved in the buildup and subsequent modification of continental and oceanic lithosphere, and (2) the determination of mineralogy/petrology and fluidphase\r\nreactions in the subducting Cocos oceanic crust.
\r\n\r\nUtilizing the data acquired from two dense broadband seismic lines in Mexico, the geometries and seismic properties of the interface of the subducting Cocos plate beneath Mexico are determined from the RFs. The RF image for central Mexico shows that the subducting oceanic crust dips shallowly north at 15 degrees for a distance of 80 km from Acapulco at the Pacific coast, and then horizontally underplates the continental crust for approximately 200 km to the Trans-Mexican Volcanic Belt (TMVB). Modeling of the RF conversion amplitudes and timings of the underplated features reveals a thin very-low velocity zone between the plate and the continental crust that appears to absorb nearly all of the strain between the upper plate and the slab. The migrated image of the RFs shows that the slab dips steeply into the mantle at an angle of about 75 degrees beneath the TMVB.
\r\n\r\nThe RF results for southern Mexico in the Isthmus of Tehuantepec show an image of the Cocos slab down to about 100 km depth. The same cross-section image also reveals a slab-like south-dipping structure interpreted to be subducted from the Gulf of Mexico. This anomalous slab with the opposite dip direction of the Cocos slab appears to cut off the Cocos slab at 150 km depth. There is no tectonic explanation for the south-dipping slab under the current paradigm of Caribbean plate reconstructions. We present in this thesis the case for a new reconstruction of the Gulf of Mexico and propose that the slab may be due to the collision of the Yucatan Block into Mexico in the Miocene, and may also be responsible for the Cocos plate truncation imaged from previous tomography studies. This hypothesis explains the Chiapas Fold and Thrust Belt to the south of the Yucatan Block and may explain the unusual volcanic arc configuration in southern Mexico.
\r\n\r\nWe formulate and apply a new inversion technique based on the plane wave conversion to obtain the seismic parameters (S wave velocity, Vs, and density) of the oceanic crust. We use such parameters to infer mineralogical properties of subducting oceanic crust. From this effort, we provide tighter constraints on physical properties of the subducting Cocos oceanic crust, and explain the difference in the slab geometries betweeen central and southern Mexico from the mineral physics point of view. Anomalously low Vs (2.4\u22123.4 km/s) in the upper part of the flat oceanic crust in central Mexico points to elevated Poisson\u2019s and Vp/Vs ratios of the oceanic crust. This directly relates to the presence of water and hydrous minerals or high pore pressure; the mechanically weak hydrous layer may explain current subduction geometry at very shallow depth of about 45 km without strong coupling between the plates.
\r\n\r\nUsing Vp/Vs as a function of Vs in a range of likely pressure and temperature for candidate hydrous phases, we identify the major hydrous mineral phases present in the upper (3\u22125 km thickness) and lower parts (3\u22125 km thickness) of the subducted oceanic crust of central and southern Mexico. In central Mexico, the upper oceanic crust in the flat slab region is enriched with hydrous minerals such as talc over the normal oceanic crustal compositions such as MORB-like gabbro. Petrologically, the generation of talc during subduction of the oceanic crust is nearly impossible. One possible mechanism to produce such a low-velocity anomaly at the upper oceanic crust is that lower crustal rocks are hydrated with 15-20 percent of free water to reduce the seismic velocities significantly. We thus propose that the thin low-velocity, talc-rich layer in the upper oceanic crust is then generated from the mantle wedge side during the slab flattening process coupled with trench rollback. The talc-rich rocks at the slab interface can be formed in the mantle by the addition of silica transported by rising fluids via the dehydration reaction from the subducting oceanic crust and by mechanical mixing of mantle and siliceous rocks. The evolution of the thin low-strength zone, which decouples the horizontal slab from the continental crust, originating from the mantle wedge side rather than the trench side, has important implications for the dynamics of the subduction system, including the flattening process of the slab, as well as the geochemistry of the mantle wedge and arc in central Mexico. After passing through the flat segment, the major compositions of the steeply subducting oceanic crust underneath the TMVB are zoisite and lawsonite from 60 to 100 km in depth. The eclogitization occurs at the depth of about 100 km. The dominant mineral phase in the upper oceanic crust of southern Mexico from 45 to 120 km depth is amphibole on top of unaltered gabbroic oceanic crust.
" }, { "name": "Kuai, Le", "degree": "PhD", "year": "2011", "title": "I: Retrieval of Atmospheric Carbon Dioxide from High-Resolution Spectra. II: Interannual Variability of the Stratospheric Quasi-Biennual Oscillation", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05222011-150750020", "creators": [ { "name": { "family": "Kuai", "given": "Le" }, "id": "Kuai-Le", "display_name": "Kuai, Le" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/6821-E823", "abstract": "This thesis is devoted to an understanding of climate changes in the troposphere and the stratosphere from different aspects. In the troposphere, projecting future climate depends on our understanding of the exchange of CO\u2082 between the atmosphere, oceans, and terrestrial ecosystems. To understand the carbon cycle, it is important to estimate the sources and sinks of CO\u2082. The so-called inverse approach has been widely used to retrieve the abundances of atmospheric species, such as CO\u2082, from global surface networks and subsequently estimate their surface fluxes and variability. Understanding of the global distribution and temporal variability of atmospheric CO\u2082 thus helps constrain the surface carbon sources and sinks. In the stratosphere, the equatorial quansi-biennual oscillation (QBO) affects the polar stratosphere during winter, with the easterly phase of the QBO creating the condition for a more perturbed and warmer polar vortex. Therefore, the variation of the QBO period has additional significance, especially with respect to the timing of its phase relative to the Northern Hemisphere (NH) winter. The study of the interannual variability of the QBO improves our understanding of the climate system.
\r\n\r\nIn this thesis, a retrieval algorithm is developed to estimate both CO\u2082 column abundance and its profile using radiances in the near-infrared region. In addition, the interannual variability of QBO is explored by studying both observation data and the modeled results. The thesis includes two parts. Part I (chapters 1 and 2) is a summary of the work about the CO\u2082 retrievals. Part II (chapters 3 and 4) is devoted to the stratospheric dynamics.
\r\n" }, { "name": "Schwamb, Megan E.", "degree": "PhD", "year": "2011", "title": "Beyond Sedna: Probing the Distant Solar System", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07082010-134040468", "creators": [ { "name": { "family": "Schwamb", "given": "Megan E." }, "id": "Schwamb-Megan-E", "display_name": "Schwamb, Megan E." } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "member", "display_name": "Brown, Michael E." } ], "option_major": [ "plansci" ], "doi": "10.7907/W4B2-1B44", "abstract": "This thesis presents studies in observational planetary astronomy probing the structure of the Kuiper belt and beyond. The discovery of Sedna on a highly eccentric orbit beyond Neptune challenges our understanding of the solar system and suggests the presence of a population of icy bodies residing past the Kuiper belt. With a perihelion of 76 AU, Sedna is well beyond the reach of the gas-giants and could not be scattered onto its highly eccentric orbit from interactions with Neptune alone. Sedna\u2019s aphelion at \u223c1000 AU is too far from the edge of the solar system to feel the perturbing effects of passing stars or galactic tides in the present-day solar neighborhood. Sedna must have been emplaced in its orbit at an earlier time when massive unknown bodies were present in or near the solar system. The orbits of distant Sedna-like bodies are dynamically frozen and serve as the relics of their formation process.
\r\n\r\nWe have performed two surveys to search for additional members of the Sedna population. In order to find the largest and brightest Sedna-like bodies we have searched \u223c12,000 square degrees within +/- 30 degrees of the ecliptic to a limiting R magnitude of 21.3 using the QUEST camera on the 1.2m Samuel Oschin Telescope. To search for the fainter, more common members of this distant class of solar system bodies, we have performed an deep survey using the Subaru Prime Focus Camera on the 8.2m Subaru telescope covering 43 square degrees to a limiting R magnitude of 25.3. Searching over a two-night baseline, we were sensitive to motions out to distances of approximately 1000 AU.
\r\n\r\nWe present the results of these surveys. We discuss the implications for a distant Sedna-like population beyond the Kuiper belt and discuss future prospects for detecting and studying these distant bodies, focusing in particular on the constraints we can place on the embedded stellar cluster environment the early Sun may have been born in, where the location and distribution of Sedna-like orbits sculpted by multiple stellar encounters is indicative of the birth cluster size. These surveys were specifically designed to find the select members of a distant Sedna population but were also sensitive to the dynamically excited off ecliptic populations of the Kuiper belt including the hot classicals, resonant, scattered disk, and detached Kuiper belt populations. We present our observed latitude distributions and implications for the plutino population.
" }, { "name": "Selvans, Michelle Marie", "degree": "PhD", "year": "2011", "title": "Geophysical Investigations of Near-Surface Structure on the Earth and Mars", "advisor": "Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05252011-161906788", "creators": [ { "name": { "family": "Selvans", "given": "Michelle Marie" }, "id": "Selvans-Michelle-Marie", "display_name": "Selvans, Michelle Marie" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "chair", "display_name": "Simons, Mark" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "orcid": "0000-0001-9930-2495", "role": "member", "display_name": "Aharonson, Oded" }, { "name": { "family": "Plaut", "given": "Jeffrey J." }, "id": "Plaut-J-J", "orcid": "0000-0002-5367-1188", "role": "member", "display_name": "Plaut, Jeffrey J." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geophys" ], "doi": "10.7907/078P-0C05", "abstract": "I use remote sensing and active seismic methods to investigate near-surface structure on the Earth and Mars. These studies provide insight into styles of crustal deformation acting on continental margins in regions of extension, as well as paleoclimates that shaped the polar ice caps on Mars. I map the overall structure of the ice-rich Planum Boreum deposit at the north pole of Mars using 178 orbits of Mars Advanced Radar for Subsurface and Ionosphere Sounding data, and find no deflection of the lithosphere beneath the ice load. Bright, laterally extensive subsurface reflectors in the radargrams define the surface underlying Planum Boreum, as well as the interface between the two main units, the stratigraphically older Basal Unit and the stratigraphically younger North Polar Layered Deposits. The volumes of these units, and the overall edifice, are determined to the greatest accuracy possible to date. On Earth, I use a GPS campaign network in the state of Jalisco to investigate tectonic motion and interseismic deformation in the area. The consistent magnitude and direction of station velocities on the Jalisco Block suggest that it is moving rigidly with respect to North America. We constrain extension across the bounding fault zones of the block to values that are slow compared to relative rates of motion at nearby plate boundaries. I study another continental rift zone, in the Ross Sea, Antarctica, with refraction seismic data collected during research cruise NBP0701. I construct velocity models from 71 sonobuoys that detect deep structure in the oceanic crust of the Adare Basin and the crust of the Northern Basin, which lies to the south on the continental shelf. We demonstrate the importance of using multi-channel seismic data to correct for ocean currents and changes in ship navigation, the finite-difference modeling techniques necessary for accurately determining 1D velocity profiles for each sonobuoy, and for tying true velocities to the multi-channel seismic images of subsurface structure. We construct 2D velocity profiles using widely spaced sonobuoys in the Adare Basin, and using overlapping sonobuoys along some lines in both basins, and across the shelf break, to investigate crustal structure in the region. Detection of the Moho at 5.5 km below the seafloor by one sonobuoy suggests relatively thin oceanic crust in the Adare Basin, and flat velocity contours across the margin suggest continuity in crustal structure between the two basins." }, { "name": "Spasojevic, Sonja", "degree": "PhD", "year": "2011", "title": "Dynamics of Long-Term Sea-Level Change and Vertical Motion of Continents", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12012010-122030085", "creators": [ { "name": { "family": "Spasojevic", "given": "Sonja" }, "id": "Spasojevic-Sonja", "display_name": "Spasojevic, Sonja" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "chair", "display_name": "Simons, Mark" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Fischer", "given": "Woodward W." }, "id": "Fischer-W-W", "role": "member", "display_name": "Fischer, Woodward W." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/C7PG-QN55", "abstract": "We formulate and apply dynamic models to better understand mantle processes and evolution, the vertical motion of continents, and regional and global sea-level change since 100 Ma. We show that evolving mid-to-upper mantle upwellings explain observed anomalously shallow bathymetry, the negative geoid, and the low seismic shear velocity anomalies in the Ross Sea region of Antarctica. These upwellings create a long-lived dynamic topography high, and the Campbell plateau of New Zealand experienced excess subsidence as it moved away from this upwelling. We then use instantaneous models globally to demonstrate that upper-to-mid mantle upwellings, located in the Indian Ocean, Ross Sea, northeast Pacific, and west Atlantic, are the primary cause of high-amplitude geoid minima that are localized within the longer wavelength geoid trough created by Mesozoic slabs. We propose that these upwellings constitute an unrecognized mode of mantle upwellings, potentially developed in response to the ancient subduction zones.
\r\n\r\nIn an alternative approach, we apply inverse models to North America (NAM), and find that the vertical motion and relative sea level were controlled by Farallon slab subduction. The Farallon slab was flat-to-shallow lying in the Late Cretaceous and in turn controlled the marine inundation of the western NAM. During the Cenozoic, the Farallon slab sank into the lower mantle, while NAM moved westward in a mantle reference frame, resulting in the dynamic uplift of the western half and dynamic subsidence of the eastern half of NAM. We then use dynamic models and hypsometric analysis to show that the proposed dynamic subsidence potentially explains discrepancies between low-amplitude of sea-level fall inferred from subsidence analysis of New Jersey boreholes compared to sea-level curves based on global data sets.
\r\n\r\nFinally, we formulate dynamic models based on a hybrid approach, accounting for long-term sea-level change factors self-consistently. We infer the relative importance of dynamic topography versus other factors in controlling regional sea level and relative large-scale vertical motions, and calculate a global sea-level curve. We find that the eustatic sea-level fall since the Late Cretaceous is driven by changes in the age of the ocean floor, but is partially offset by dynamic topography.
" }, { "name": "Amidon, William Henry", "degree": "PhD", "year": "2010", "title": "Cosmogenic \u00b3He and \u00b2\u00b9Ne Dating in Accessory Mineral Phases", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05192010-102315391", "creators": [ { "name": { "family": "Amidon", "given": "William Henry" }, "id": "Amidon-William-Henry", "display_name": "Amidon, William Henry" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." } ], "option_major": [ "geol" ], "doi": "10.7907/R6JB-BW27", "abstract": "The development of terrestrial cosmogenic nuclide dating has led to applications as varied as the dating of glacial moraines, establishing slip-rates on faults, measuring the erosion rates of basins, and measuring rates of soil formation. Studies in many of these fields could greatly benefit from analysis of far more samples than can be easily dated using 10Be, 26Al, and 36Cl. The rapid preparation and analysis of samples for cosmogenic 3He often allows a greater number of samples to be analyzed, but has so far been applied primarily to olivine and pyroxene in mafic rocks. Because 3He is produced in all mineral phases, it can potentially be applied in almost any lithology. The goals of this thesis is to expand the range of target lithologies suitable for cosmogenic 3He dating by calibrating production rates of cosmogenic 3He in accessory mineral phases such as apatite, zircon, and garnet. Results are presented from three calibration studies: glacial moraine boulders in the Nepal Himalaya, young rhyolite surfaces from California\u2019s Coso volcanic field, and rhyolite surfaces scoured by the Bonneville flood near Twin Falls, Idaho. Both the Nepal and Coso studies compare 3He in zircon, apatite, and garnet against 10Be in quartz, finding that higher than expected 3He concentrations are likely due to anamolous elevation scaling in the Himalaya, and to production of 3He via neutron capture on 6Li at Coso. The Idaho calibration study is unique in that it is calibrated against the age of the Bonneville outburst flood (known by 14C dating), and uses a shielded sample to definitively document Li-produced 3He components in the deep sub surface. Collectively, these studies highlight several challenges associated with cosmogenic 3He dating of accessory phases: the difficulty in measuring small amounts of cosmogenic 3He in the presence of large amounts of radiogenic 4He, the importance of production of 3He via neutron capture on 6Li, and the redistribution of energetic 3He and 3H between adjacent mineral phases. Despite these challenges, adopting a 10Be production rate of 4.51 at g-1 a-1 in quartz (Balco et al., 2008), brings three independent 3He production rate estimates into good agreement with grand means of 103 \u00b1 3, 133 \u00b1 6, and about 134 \u00b1 13 at g-1 a-1 in zircon, apatite, and spessartine garnet respectively. Such agreement suggests that these phases are suitable for cosmogenic dating. 3He in accessory phases may enable a range of unique applications including the study of ancient sediments, paleo-altimetry, and rates of chemical weathering in soils." }, { "name": "Balta, Joseph Brian", "degree": "PhD", "year": "2010", "title": "1. Experimental Investigation of Hydrous Melting of the Earth\u2019s Upper Mantle, and 2. Olivine Abundances and Compositions in Hawaiian Lavas", "advisor": "Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechTHESIS:11062009-091851899", "creators": [ { "name": { "family": "Balta", "given": "Joseph Brian" }, "id": "Balta-Joseph-Brian", "display_name": "Balta, Joseph Brian" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geol" ], "doi": "10.7907/7NM9-AB40", "abstract": "(1) The presence of small amounts of water dissolved within nominally-anhydrous minerals in the earth has significant effects on the chemistry of melting in the Earth\u2019s mantle. Upwelling rock containing water will melt at greater depths than the same rock would if it were volatile-free, and the chemistry of these hydrous melts is expected to be quite different from that of anhydrous melts. We have developed new experimental techniques and applied them to melting under pressures where hydrous melting is of the greatest natural importance. We have also controlled the content of carbon, another volatile element, to produce melts from a range of compositions not previously sampled experimentally.
\r\n\r\nThe liquid composition shows a number of interesting properties. Compared to anhydrous melts from the same pressure, it shows decreased modal olivine and increased silica content. Compared to carbon-containing experiments, it suggests that carbon interacts with water when both volatiles are present, and may act to oppose the effects of water. The presence of a hydrous liquid also has an important effect on the coexisting solid chemistry. High-aluminum clinopyroxenes are commonly observed at this pressure in anhydrous systems. However, in all of our volatile-containing experiments, the clinopyroxenes show a substantial decrease in aluminum content and an increase in calcium content. Many elements, including water, enter into the clinopyroxene structure by coupled substitution with aluminum, and thus reduced clinopyroxene aluminum content during natural melting will decrease the partitioning of these elements during melting.
\r\n\r\n(2) Variations in the modal abundance of olivine are the main mineralogical differences amongst typical Hawaiian lavas. A large quantity of olivine must crystallize from the Hawaiian parental liquids prior to eruption to produce the erupted lavas. The chemistry and abundance of these olivines reflects the behavior of the magmatic system in a number of ways. We have used the chemistry of these olivines and lavas to estimate the parental liquid compositions in Hawaiian volcanoes, to infer the relationship between the olivines and the lavas that host them, and to probe the evolution of Hawaiian volcanoes over time.
\r\n" }, { "name": "Busch, Michael William", "degree": "PhD", "year": "2010", "title": "Shapes and Spins of Near-Earth Asteroids", "advisor": "Kulkarni, Shrinivas R.; Ostro, Steven J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04082010-125341638", "creators": [ { "name": { "family": "Busch", "given": "Michael William" }, "id": "Busch-Michael-William", "display_name": "Busch, Michael William" } ], "advisors": [ { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "co-advisor", "display_name": "Kulkarni, Shrinivas R." }, { "name": { "family": "Ostro", "given": "Steven J." }, "id": "Ostro-Steven-J", "role": "co-advisor", "display_name": "Ostro, Steven J." } ], "committee": [ { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "chair", "display_name": "Aharonson, Oded" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "member", "display_name": "Kulkarni, Shrinivas R." } ], "option_major": [ "plansci" ], "doi": "10.7907/ZVGV-8X89", "abstract": "Asteroids are diverse and numerous solar system objects, from the large number of objects in the main asteroid belt to the relatively small near-Earth population. Understanding their physical properties is essential to understanding the evolution of the solar system, and asteroid morphology is a complex field in its own right. The histories of individual asteroids, and particularly near-Earth objects, reflect continuous interaction among their shapes, rotation states, and orbits due to the effects of radiation pressure.
\r\n\r\nRadar astronomy has provided detailed information on the orbits, sizes, shapes, rotation states, and composition of many asteroids. To improve the capabilities of asteroid radar observations, I have developed the technique of radar speckle tracking. The echoes from different points on the surface of a radar target interfere with each other, producing a pattern of bright and dark speckles across the surface of the Earth. Using radio astronomy techniques, I track the motion of speckles between several ground stations during a radar experiment to accurately determine the rotation state of the target. Speckle tracking is a powerful tool to both determine the orbital evolution of near-Earth asteroids, particularly potential Earth impactors, and to survey the overall physical properties of the asteroid population.
\r\n\r\nIn addition, I have studied applying the techniques of adaptive optics and radio interferometry to asteroid science. These will become more useful with the next generation of asteroid-detecting surveys and the construction of large sub-millimeter interferometers. Interferometry in particular will soon be able to survey the entire asteroid belt.
\r\n" }, { "name": "DiCaprio, Christopher John", "degree": "PhD", "year": "2010", "title": "Measuring and Modeling Viscoelastic Relaxation of the Lithosphere with Application to the Northern Volcanic Zone, Iceland", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242010-103547444", "creators": [ { "name": { "family": "DiCaprio", "given": "Christopher John" }, "id": "DiCaprio-Christopher-John", "display_name": "DiCaprio, Christopher John" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "chair", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/5VWK-0T35", "abstract": "Viscoelastic relaxation of the stress perturbation caused by an earthquake or diking event can produce measurable ground deformation over 100 km away from the source. We consider the role of viscoelastic relaxation in two different contexts. First, we explore the role that post-seismic relaxation may play in loading a fault over the entire seismic cycle. Viscous relaxation recycles the stress that is shed by the co-seismic fault, acting to reload the fault with stresses in a non-linear fashion. Under conditions of rapid post-seismic relaxation and slow tectonic loading, stress recycling via viscoelastic relaxation can lead to clustering of earthquakes in time. The second context in which we consider viscoelastic relaxation involves the lithospheric response to a mid-ocean ridge rifting episode in Northern Iceland. The diking and subsequent relaxation act as a natural rock mechanics experiment, and in measuring and modeling the post-rifting response we aim to constrain the rheological properties of the Icelandic lithosphere. In order to use post-seismic or post-rifting relaxation to probe properties of the lithosphere, we must be able to precisely measure surface deformation. To that end, we have developed a couple of new interferometric synthetic aperture radar (InSAR) processing approaches: (1) Automatically producing multiple interferograms in a common coordinate system and (2) removing displacements caused by ocean tidal loading from InSAR observations. Both of these developments are essential as we begin to consider the systematic use of tens to hundreds of interferograms." }, { "name": "Heavens, Nicholas Gray", "degree": "PhD", "year": "2010", "title": "The Impact of Mesoscale Processes on the Atmospheric Circulation of Mars", "advisor": "Yung, Yuk L.; Richardson, Mark I.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04222010-152158923", "creators": [ { "name": { "family": "Heavens", "given": "Nicholas Gray" }, "id": "Heavens-Nicholas-Gray", "display_name": "Heavens, Nicholas Gray" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "co-advisor", "display_name": "Richardson, Mark I." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." } ], "option_major": [ "plansci" ], "doi": "10.7907/B693-EE28", "abstract": "The study of the modern martian atmosphere is (1) a key to the climate of Mars\u2019s past; (2) useful for comparison with other terrestrial planets such as the Earth; and (3) can support hazard analysis and weather forecasting for future exploration and habitation of the planet. Recently, it was found that middle atmospheric downwelling near the south pole during southern winter is much more vigorous than predicted by most Mars general circulation models. This underestimate may be due to models erroneously representing the radiative forcings in the atmosphere due to aerosol and/or the mechanical forcings due to wave breaking. Errors of this kind would influence middle atmospheric dynamics and likely would result from incomplete understanding of lower atmospheric processes such as dust transport. Here, retrievals of vertical profiles of temperature, pressure, dust, and water ice from the Mars Climate Sounder (MCS) on Mars Reconnaissance Orbiter (MRO) are used to characterize the atmospheric circulation of Mars and its forcings. First, I consider the annual cycle of the thermal structure and aerosol distributions of the lower and middle atmosphere and investigate the degree of coupling between the lower and middle atmospheric mean meridional circulations. To evaluate the role of wave breaking, I look for local convective instabilities in the Martian middle atmosphere: a key indicator of saturating vertically propagating waves such as the gravity waves and the thermal tides, which are important sources of wave drag in the Earth\u2019s mesosphere. I then characterize the vertical distribution of dust and its approximate radiative effects during northern spring and summer and show there is usually a maximum in dust mass mixing ratio at ~15\u201425 km above the tropics, which is not currently simulated by models. Next, I evaluate the relative importance of dust storm activity, pseudo-moist convection due to the solar heating of dust, orographic effects, and scavenging by water ice clouds in producing this maximum. Finally, I show that published models underestimate the thickness and altitude of water ice clouds in northern summer." }, { "name": "Hofmann, Amy Elizabeth", "degree": "PhD", "year": "2010", "title": "Micron- to Sub-Micron-Scale Trace Element Zonations in Zircon and Olivine", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272010-121809591", "creators": [ { "name": { "family": "Hofmann", "given": "Amy Elizabeth" }, "id": "Hofmann-Amy-Elizabeth", "display_name": "Hofmann, Amy Elizabeth" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geochem" ], "doi": "10.7907/24H9-0565", "abstract": "Sub-micron-scale zoning of Ti concentrations and correlations between concentrations of Ti and other trace elements (P, Ce, and Y) and cathodoluminescent (CL) banding is observed in natural zircons of both unknown (e.g., Jack Hills) and known (e.g., Toba and Bishop Tuffs) provenance. Ion images were made using the Caltech Microanalysis Center\u2019s CAMECA NanoSIMS 50L with an O- primary beam focused to ~400\u2013600 nm on the sample surface. The high spatial resolution of this technique allows for interrogation of chemical variations at or below the scale of CL banding in natural zircons. Images produced in this manner display several types of correlations among Ti, P, Ce, and Y (which appears to be a proxy for CL intensity): positive correlations between Ti concentrations, concentrations of some subset of the other trace elements (P, Ce, and Y), and cathodoluminescent (CL) zonations; Ti inversely correlated with P, Y, and Ce (all of which track oscillatory CL bands); no correlations between CL zones and either Ti or the other trace elements. Three possible causes for such correlations include: temperature-dependent equilibrium partitioning, trace-element partitioning limited by diffusion in the host melt, and surface-controlled, non-equilibrium growth. Comparison of our data with the expected results of these processes suggests that: 1) Ti partitioning in zircon is dependent upon non-equilibrium effects in addition to temperature and/or 2) the incorporation of elements that co-vary with Ti in zircon (e.g., Y, P and Ce) is also temperature-dependent.
\r\n\r\nTo explore these hypotheses, we performed a series of experiments on synthetic and natural granitic compositions (enriched in TiO2 and ZrO2) at temperatures of 1400, 1300, and 1200\u00b0C. All liquids were zircon-saturated and 6 of the 16 experimental glasses were also saturated in rutile. NanoSIMS measurements of Ti in zircon overgrowth rims in our experiments range from 760 to 112 ppm and show a positive correlation with TiO2 content of the quenched glass and run temperature. Our Ti-in-zircon values when \u201cadjusted\u201d for SiO2 and TiO2 melt activities (i.e., log(Ti-in-zircon, ppm)+log(\u03b1SiO2)-log(\u03b1TiO2) show a strong inverse correlation with 1/T; and least squares fits to the two sets of data generated in this study (synthetic bulk compositions and natural bulk compositions) yield equations with slopes that are statistically indistinguishable. This suggests that at temperatures above 1200\u00b0C other trace elements in the melt do not appear to have a substantial effect on Ti partitioning between zircon and silica-rich liquid. A weighted global fit to all of our experimental data is:
\r\nlog(Ti-in-zircon, ppm)+log(\u03b1SiO2)-log(\u03b1TiO2) = (6.21 \u00b1 0.43)-(5918 \u00b1 689)/T (K).
\r\nR2 for this equation is 0.85. Our Ti glass contents coupled with measured zircon Ti concentrations from the same experiments allow us to calculate a zircon-melt Ti partition coefficient. Our measured Dzre/meltTi values are 0.014 to 0.029 and are broadly consistent with values determined from natural-zircon glass pairs. We note that, in the cases for which zircon-independent temperature constraints are known for a parental liquid, neither of the current Ti-in-zircon thermometry calibrations can explain Ti variations in natural zircons as documented by the NanoSIMS.
In Chapter 4, we document spatially correlated P, Al, and Cr zoning in 36 of 40 Gorgona komatiitic olivines from three textural units: a jointed flow top, two random spinifex zones, and two oriented plate spinifex zones. P zoning is observed to be decoupled from or inversely correlated with Al and Cr zoning in some olivines from all three units; the type of zoning observed (e.g., oscillatory, sector) varies depending on textural type. Cooling-rate experiments were performed on a synthetic haplo-komatiite bulk composition in order to evaluate the physical parameters governing incorporation of P, Al, and Sc (as a proxy for Cr) in spinifex komatiitic olivines. Cation-cation plots of data from the natural olivines reveal strong linear trends between Al and Cr and suggest that Al and Cr enter the olivine crystal lattice in a 2:1 ratio. Trends in P-Al and P-Cr composition space differ depending on the olivine textural type. With one exception, oriented plate spinifex olivines define a sub-horizontal P-Al and P-Cr trend, which suggests that P is being accommodated into the olivine lattice via a substitution mechanism involving both Al and Cr. The outlier from this population is a rare preserved plate spinifex tip, which records much higher P at low Al and Cr concentrations compared to the other plate spinifex grains; we interpret these data as suggestive of P incorporation in excess of equilibrium values due to rapid crystal growth.
" }, { "name": "Kanda, Ravi V. S.", "degree": "PhD", "year": "2010", "title": "Mechanical Models for InterSeismic Deformation in Subduction Zones", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:06042010-144837173", "creators": [ { "name": { "family": "Kanda", "given": "Ravi V. S." }, "id": "Kanda-Ravi-V-S", "display_name": "Kanda, Ravi V. S." } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" } ], "option_major": [ "geophys" ], "doi": "10.7907/7WFR-GK09", "abstract": "Traditionally, interseismic deformation in subduction zones has been modeled using simple elastic dislocation models (EDMs). Such models have been extensively used over the past couple of decades as geodetic networks were being established around the world. However, with the availability of 3D (vector) velocity data with dense spatio-temporal coverage during the past decade, it becomes possible to explore more complex models of deformation. Such models may allow us to infer higher-order properties of the megathrust interface or the subducting plate from the observed deformation field. For instance, we show that it may be possible to infer the elastic plate thickness of the subducting plate (over the seismic cycle timescale) under certain conditions, especially if ocean-bottom geodetic measurements become routinely available in the near future. The plate thickness can affect surface deformation on the overriding plate if only a small fraction of the flexural stresses at the trench are continuously released over the seismic cycle time-scale. Another problem we address here is how the rheology of the megathrust interface affects the evolution of slip over the seismic cycle, and therefore, the seismic hazard inferred from geodetic data. We model such slip evolution on a realistic 3D fault surface having a frictional rheology. Assuming that seismic rupture zones (or \u201casperities\u201d) persist across several seismic cycles, we test the hypothesis that mechanical coupling on such asperities alone is sufficient to explain currently available geodetic observations in northern Japan. We find that it is not necessary to lock large portions of the megathrust between ruptures \u2013 unlike recent EDM predictions for northern Japan \u2013 resulting in potentially large future earthquakes. Instead, post-seismic slip around asperities immediately following seismic rupture can result in large \u201cstress-shadow\u201d regions, which experience negligible slip late in the cycle. Such stress-shadow regions can mimic the long-wavelength \u201clocked\u201d zones inferred from EDMs for the interseismic period, and account for most of the present day GPS velocities in northern Japan. The approach developed here can be extended to more complex models of deformation that include heterogeneities in crustal properties, multiple fault surfaces, and perhaps, even multiple rheologies over a single fault. " }, { "name": "Liu, Lijun", "degree": "PhD", "year": "2010", "title": "Linking Surface Evolution with Mantle Dynamic Processes Using Adjoint Models with Data Assimilation", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06022010-172250027", "creators": [ { "name": { "family": "Liu", "given": "Lijun" }, "id": "Liu-Lijun", "display_name": "Liu, Lijun" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "chair", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geophys" ], "doi": "10.7907/6VHZ-V130", "abstract": "Quantifying the relationship between subsolidus mantle convection and surface evolution is a fundamental goal of geophysics. Toward this goal progress has been slow due to incomplete knowledge of the earth\u2019s internal structure and properties. While seismic tomography reveals details on internal 3D structure of the present mantle, evolution of the subsolidus mantle during the geological past remains elusive. This thesis attempts to solve the time inversion of mantle convection using the adjoint method based on present-day seismic images and geological and geophysical observations dictating the past evolution of solid earth.
\r\n\r\nThe adjoint method, widely used in meteorological and oceanographic predictions, can be applied to mantle convection for the recovery of unknown initial conditions through the assimilation of present-day mantle seismic structure. We propose that an optimal first guess to the initial condition can be obtained through a simple backward integration (SBI) of the governing equations thus lessening the computational expense. By incorporating time-dependent surface dynamic topography in addition to present-day mantle structure, the adjoint method is improved so as to constrain uncertain mantle dynamic properties and initial condition simultaneously. The theory is derived from the governing equations of mantle convection and validated by synthetic experiments for a single- and two-layer viscosity mantle within regionally bounded spherical shells. For both cases, we show that the theory can constrain mantle properties with errors arising through the adjoint recovery of the initial condition. For the two-layer model, there is a trade-off between the temperature scaling and lower mantle viscosity.
\r\n\r\nBy assimilating seismic structure and plate motions in the inverse mantle convection model, we reconstruct Farallon plate subduction back to 100 Ma. We put constraints on basic mantle properties, including both the depth dependence of mantle viscosity and slab buoyancy, by predicting proxies of dynamic topography evident in the stratigraphy of the North American Cretaceous western interior seaway. Models that fit stratigraphy well require the Farallon slab to have been flat lying in the Late Cretaceous, consistent with geological reconstructions. The models predict an extensive zone of shallow-dipping subduction extending beyond the flat-lying slab farther east and north, while the limited region of subducting flat slab resembles an oceanic plateau. In order to test the hypothesis of oceanic plateau subduction and its relationship to the Laramide orogeny, we compare the inverse convection model with plate reconstructions. Two prominent seismic anomalies on the Farallon plate recovered from inverse models coincide with paleogeographically-restored positions of conjugates to the Shatsky and Hess plateaus when they subducted beneath North America. The distributed shortening of the Laramide orogeny closely tracked the passage of the Shatsky conjugate beneath North America, while the effects of Hess conjugate subduction were restricted to the northern Mexico foreland belt. We find that Laramide uplifts were consequences of the removal, rather than the emplacement, of the Shatsky conjugate, and we predict that these subducted plateaus should be detectable by the USArray seismic experiment.
\r\n\r\nThe inverse convection models predict a continuous vertical motion history of western U.S., which is further validated by constraints on the vertical motion of the Colorado Plateau since the Cretaceous. With the arrival of the flat-lying Farallon slab, dynamic subsidence swept from west to east over the western U.S., peaking at 86 Ma within the Colorado Plateau. This eastward migrating dynamic subsidence is consistent with a recently compiled backstripping study that shows a long-wavelength residual subsidence shifting to the east, coincident with the passage of the flat slab beneath North America in our inverse model. Two stages of uplift followed the removal of the Farallon slab below the Colorado Plateau: one in the latest Cretaceous, and the other in the Eocene, with a cumulative uplift of ~1.2 km; the former represents the Laramide uplift which also marks the initial uplift of the entire western U.S. Both the descent of the slab and buoyant upwellings raised the Colorado Plateau to its current elevation during the Oligocene. A locally thick lithosphere enhances coupling to the upper mantle so that the Colorado Plateau has a higher topography with sharp edges. Our models also predict that the plateau tilted downward to the northeast before the Oligocene, caused by northeast-trending subduction of the Farallon slab, and that this northeast tilting diminished and reversed to the southwest during the Miocene in response to buoyant upwellings.
\r\n\r\nOverall, this thesis shows that the adjoint models with data assimilation are useful in linking surface evolution to deep mantle processes both over North America and areas beyond. While more research is clearly needed to construct a more earth-like model, this thesis presents an important advance in data-oriented geodynamic models.
" }, { "name": "Marinova, Margarita M.", "degree": "PhD", "year": "2010", "title": "Inquiries into the Consequences of Planetary-Scale Impacts and the Implications of Carbonates in the Hyper-Arid Core of the Sahara", "advisor": "Aharonson, Oded", "url": "https://resolver.caltech.edu/CaltechTHESIS:05272010-184707226", "creators": [ { "name": { "family": "Marinova", "given": "Margarita M." }, "id": "Marinova-Margarita-M", "display_name": "Marinova, Margarita M." } ], "advisors": [ { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "advisor", "display_name": "Aharonson, Oded" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" } ], "option_major": [ "plansci" ], "doi": "10.7907/AA8Q-2954", "abstract": "This thesis focuses on the geophysical and morphological consequences of planetary-scale impacts \u2013 the last remnants of planetary accretion. In this size regime, the impact crater size is a significant fraction of the size of the planet, and the finite size of the target is important: its surface curvature, radial gravity, and large relative size of the impactor with respect to the target. A fully three-dimensional hydrodynamics model is used to simulate the events, thus capturing these finite-size effects. Simulated are a range of impact energies (0.02\u20135.89x10^(29) J), velocities (6\u201350 km/s), and angles (0\u00ba\u201375\u00ba) into a Mars-like planet. In addition, the variation in results with impactor type, for both single-material and differentiated impactors, is also examined. For this range of impact conditions, the crater size can span up to ~60% of the planetary circumference, and the ellipticity of the crater can be significant even for intermediate angle impacts. This is consistent with the observed large craters, which are commonly elliptical. Despite the large melt volumes produced, the planetary surface is preserved in most cases, as much of the melt is placed in the mantle. Antipodal crustal removal is common for the more energetic cases. For impacts with more than about three times the mutual impactor-target escape velocity, the impact has a net erosive effect, with more mass being removed than deposited. These large impacts are sufficiently massive that they can give an initially stationary Mars a rotation period of less than a day. The simulation results suggest that the Mars hemispheric dichotomy may have formed by a single, planetary-scale impact; the required impact conditions are consistent with accretion models.
\r\n\r\nThe last chapter of this thesis examines the paleoclimate implications of reef-like carbonate structures in the currently hyper-arid core of the Sahara (southwestern Egypt). The carbonates suggest a wetter epoch about 9,000\u201310,000 years ago, and the presence of long-term, standing water. Despite the higher precipitation, the chemical composition of the carbonates suggests that the vegetation cover was sparse.
" }, { "name": "Meltzner, Aron Jeffrey", "degree": "PhD", "year": "2010", "title": "Earthquake Recurrence, Clustering, and Persistent Segmentation near the Southern End of the 2004 Sunda Megathrust Rupture", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06012010-082222484", "creators": [ { "name": { "family": "Meltzner", "given": "Aron Jeffrey" }, "id": "Meltzner-Aron-Jeffrey", "orcid": "0000-0002-2955-0896", "display_name": "Meltzner, Aron Jeffrey" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geol" ], "doi": "10.7907/JHDG-MT86", "abstract": "The December 2004 moment magnitude (MW) 9.2 earthquake was the largest in the world in four decades. Rupture of the Sunda megathrust in that event produced broad regions of uplift and subsidence. We defined the pivot line separating these regions as a first step in defining the extent of the rupture, relying on the interpretation of satellite imagery and modeled water levels as well as on field measurements of emerged coral microatolls. Uplift in 2004 extended from the middle of Simeulue island, Sumatra, at ~2.5\u00b0N, to Preparis island, Myanmar (Burma), at ~14.9\u00b0N; thus the 2004 rupture was ~1600 km long.
\r\n\r\nThe Sunda megathrust ruptured again in March 2005 in an MW 8.6 earthquake. We focused our efforts on Simeulue, which straddles the boundary of these two ruptures and behaved as a barrier to both. We extracted records of relative sea-level change from coral microatolls on fringing reefs directly above the southern end of the 2004 rupture and the northern end of the 2005 rupture. These records provide a detailed history of tectonic strain accumulation and release.
\r\n\r\nAlong the coast of northern Simeulue, coral records reveal that predecessors of the 2004 earthquake occurred in the 10th and 14th\u201315th centuries AD. In the 14th\u201315th centuries, northern Simeulue experienced a cluster of large megathrust ruptures, associated with total uplift that was considerably more than in 2004. The strain released in 2004 under northern Simeulue took less than 250 years to accumulate if strain accumulation rates since 1948 can be extrapolated back in time. These observations suggest that re-rupture of at least the southernmost 100\u2013200 km of the 2004 patch is possible in the coming decades.
\r\n\r\nThe records from central-southern Simeulue indicate that none of the major uplifts known or inferred on northern Simeulue in the past 1100 years extended to southern Simeulue. In addition, the largest uplifts in the modern or paleogeodetic record in central-southern Simeulue apparently produced little or no uplift in northern Simeulue. These observations suggest that central Simeulue has behaved as a persistent barrier to rupture over at least the past 1100 years.
" }, { "name": "Metz, Joannah Marie", "degree": "PhD", "year": "2010", "title": "A Study of the Record of Ancient Sedimentary Rocks on Mars Using MER, HiRISE and CRISM Images", "advisor": "Grotzinger, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04102010-113856474", "creators": [ { "name": { "family": "Metz", "given": "Joannah Marie" }, "id": "Metz-Joannah-Marie", "display_name": "Metz, Joannah Marie" } ], "advisors": [ { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "advisor", "display_name": "Grotzinger, John P." } ], "committee": [ { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "orcid": "0000-0001-9930-2495", "role": "chair", "display_name": "Aharonson, Oded" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Lamb", "given": "Michael P." }, "id": "Lamb-M-P", "orcid": "0000-0002-5701-0504", "role": "member", "display_name": "Lamb, Michael P." }, { "name": { "family": "Milliken", "given": "Ralph E." }, "id": "Milliken-R-E", "role": "member", "display_name": "Milliken, Ralph E." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "plansci" ], "doi": "10.7907/8ZCD-SK38", "abstract": "Many processes that operate on a planetary surface have the potential to create sedimentary deposits which when preserved as rocks can provide clues that allow past environmental conditions to be reconstructed. This work combines several studies using data from the Mars Exploration Rover and Mars Reconnaissance Orbiter spacecraft to examine the structure and sedimentology of the sedimentary rock record of Mars. The first study supports the dune-interdune model proposed for the formation of the deposits at the Opportunity landing site in Meridiani Planum and provides evidence that liquid water was involved to a greater extent in the formation of outcrops in Erebus crater. The next study identifies two depositional fan complexes on the floor of southwestern Melas Chasma and suggests that they may be sublacustrine in origin, which suggests the former presence of a significant body of water stable for at least 100 to 10,000 years. Furthermore, the basin containing the fans may be a complete source-to-sink system. The third study examines the geomorphic channel patterns present on analogue terrestrial submarine fans and deltas. The last study characterizes the extent and styles of deformation of sedimentary rocks in Valles Marineris and finds that subaerial or subaqueous gravitational slumping or sliding and soft-sediment deformation are potential mechanisms that may have caused the deformation." }, { "name": "Minson, Sarah Ellen", "degree": "PhD", "year": "2010", "title": "A Bayesian Approach to Earthquake Source Studies", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechTHESIS:06062010-235315977", "creators": [ { "name": { "family": "Minson", "given": "Sarah Ellen" }, "id": "Minson-Sarah-Ellen", "orcid": "0000-0001-5869-3477", "display_name": "Minson, Sarah Ellen" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "chair", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Beck", "given": "James L." }, "id": "Beck-J-L", "role": "member", "display_name": "Beck, James L." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/3RT9-3215", "abstract": "Bayesian sampling has several advantages over conventional optimization approaches to solving inverse problems. It produces the distribution of all possible models sampled proportionally to how much each model is consistent with the data and the specified prior information, and thus images the entire solution space, revealing the uncertainties and trade-offs in the model. Bayesian sampling is applicable to both linear and non-linear modeling, and the values of the model parameters being sampled can be constrained based on the physics of the process being studied and do not have to be regularized. However, these methods are computationally challenging for high-dimensional problems.
\r\n\r\nUntil now the computational expense of Bayesian sampling has been too great for it to be practicable for most geophysical problems. I present a new parallel sampling algorithm called CATMIP for Cascading Adaptive Tempered Metropolis In Parallel. This technique, based on Transitional Markov chain Monte Carlo, makes it possible to sample distributions in many hundreds of dimensions, if the forward model is fast, or to sample computationally expensive forward models in smaller numbers of dimensions. The design of the algorithm is independent of the model being sampled, so CATMIP can be applied to many areas of research.
\r\n\r\nI use CATMIP to produce a finite fault source model for the 2007 Mw 7.7 Tocopilla, Chile earthquake. Surface displacements from the earthquake were recorded by six interferograms and twelve local high-rate GPS stations. Because of the wealth of near-fault data, the source process is well-constrained. I find that the near-field high-rate GPS data have significant resolving power above and beyond the slip distribution determined from static displacements. The location and magnitude of the maximum displacement are resolved. The rupture almost certainly propagated at sub-shear velocities. The full posterior distribution can be used not only to calculate source parameters but also to determine their uncertainties. So while kinematic source modeling and the estimation of source parameters is not new, with CATMIP I am able to use Bayesian sampling to determine which parts of the source process are well-constrained and which are not.
" }, { "name": "Pahlevan, Kaveh", "degree": "PhD", "year": "2010", "title": "Chemical and Isotopic Consequences of Lunar Formation via Giant Impact", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:06082010-072824369", "creators": [ { "name": { "family": "Pahlevan", "given": "Kaveh" }, "id": "Pahlevan-Kaveh", "display_name": "Pahlevan, Kaveh" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "plansci" ], "doi": "10.7907/YPP1-AQ73", "abstract": "There is near consensus in the planetary science community that the origin of the Moon can be traced to a massive interplanetary collision between a roughly Mars-sized object and the growing Earth towards the end of planetary accretion. Many in the geochemical community, however, have rightly expressed skepticism towards this hypothesis. The compositional signatures of the giant impact have never been clearly articulated, and no one has yet used the ideas of lunar origin to say something about the lunar composition that was not previously known, that is, to make a prediction. The work presented here seeks to develop the theory of lunar origin with two goals in mind: of reconciling the predictions of the dynamical scenario with the observed signatures in the lunar composition, and of making new predictions for the lunar chemical and isotopic composition that can test and further constrain the theory through comparison with observations." }, { "name": "Wang, Ying", "degree": "PhD", "year": "2010", "title": "Equilibrium \u00b2H/\u00b9H Fractionations in Organic Molecules ", "advisor": "Sessions, Alex L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10212009-213942982", "creators": [ { "name": { "family": "Wang", "given": "Ying" }, "id": "Wang-Ying", "display_name": "Wang, Ying" } ], "advisors": [ { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "advisor", "display_name": "Sessions, Alex L." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Goddard", "given": "William A., III" }, "id": "Goddard-W-A-III", "role": "member", "display_name": "Goddard, William A., III" } ], "option_major": [ "geochem" ], "doi": "10.7907/4MPX-MF10", "abstract": "\r\nCompound-specific H isotope analysis has become widespread over the past decade and stimulated a variety of studies using the H isotopic composition (\u03b4\u00b2H values) of sedimentary organic molecules as paleoenvironmental proxies. Since alkyl H can be affected by a variety of exchange processes that lead to \u03b4\u00b2H changes on geological timescales, interpretation of empirical \u03b4\u00b2H data must account for these changes, which requires quantitative knowledge regarding the endpoint of the isotopic exchange, i.e., equilibrium fractionation factor (\u03b1eq). Nevertheless, to date relevant data have been lacking for molecules larger than methane. This is because the conventional isotope exchange experiments suffer from the slow exchange rates of C-bound H (half-life ~ 105\u2013106 years), whereas theoretical calculations \u2014 a convenient way to cover many organic structures over wide temperature ranges \u2014 are restricted by systematic biases for the H isotope system.
\r\n\r\nTo remedy the situation, this project was proposed to use experimental equilibration data to calibrate ab initio calculations of \u03b1eq. To accurately measure the value of \u03b1eq within reasonable experimental timescale, I utilized the keto-enol tautomerism that leads to fast equilibration between H positions adjacent to carbonyl groups (denoted as H\u03b1) and water. By equilibrating ketones with waters of varying \u03b4\u00b2H values, the values of \u03b1eq were measured for H\u03b1 positions in a variety of acyclic and cyclic molecular structures at different temperatures. On the other hand, statistical thermodynamics and ab initio QM computations (B3LYP/6-311G**) were applied to calculate \u03b1eq values for the same ketone molecules. Comparison between experimental and theoretical results yields a temperature-dependent linear calibration curve for linear molecules with slope = 1.081\u22120.00376T and intercept = 8.404\u22120.387T (T is temperature in degrees Celsius). For cyclic structures, the calibration is slightly different with slope of 1.44\u00b10.05 and intercept of 32.8\u00b15.1. Application of these calibration curves to more ab initio calculations generates the \u03b1eq values for various H sites in alkanes, alkenes, ketones, carboxylic acids, esters, alcohols, and ethers, with the uncertainties estimated to be 10\u201325\u2030. The effects of functional groups were found to increase the value of \u03b1eq for H next to electron-donating groups, e.g., \u2212OR, \u2212OH or \u2212O(C=O)R, and to decrease the value of \u03b1eq for H next to electron-withdrawing groups, e.g., \u2212(C=O)R or \u2212(C=O)OR. It is analogous to the well-known substituent effects in the aromatic ring system.
\r\n\r\nOur results provide a modular dataset to calculate equilibrium \u00b2H/\u00b9H fractionations for common molecules found in sediments and oils. By summing over individual H positions, the equilibrium fractionation relative to water between 0 and 100\u00b0C is estimated to be \u221270\u2030 to \u221290\u2030 for n-alkanes, around \u2212100\u2030 for acyclic isoprenoids and \u221275 to \u2212100\u2030 for steroids and hopanoids. The temperature dependence of these molecular fractionations is very weak within the relevant temperature range. The results agree well with field data for thermally mature hydrocarbons (\u03b4\u00b2H values between -80\u2030 and -110\u2030 relative to water; Schimmelmann et al., 2006), suggesting that the observed \u03b4\u00b2H changes in sedimentary organic matter can be confidently attributed to H exchange towards an equilibrium state.
\r\n\r\nBecause of the need to accurately measure the widely-ranging \u03b4\u00b2H values encountered in natural and isotopically-exchanged samples, a side project was conducted to quantitatively investigate the isotopic memory effects in compound-specific \u00b2H/\u00b9H analysis by gas chromatography/pyrolysis/isotope-ratio mass spectrometry (GC/P/IRMS), i.e., the situation in which the \u00b2H/\u00b9H ratio of a given chromatographic peak affects that of the following peak(s). Through a series of experiments that employed synthesized esters with \u03b4\u00b2H varying by up to 1000\u2030, we were able to estimate the isotopic memory to be typically 2\u20134% of the nominal \u03b4\u00b2H difference between two adjacent peaks. It increases with decreasing time separation, increasing analyte abundance of the preceding peak, or increasing age of the pyrolysis reactor. Roughly half of the memory effect can be attributed to the H2-adsorption process in the pyrolytic reactor, and the other half to unknown processes within the GC. Finally, based on our experimental and model study, modifications in routine analyses were proposed to mitigate memory effects.
" }, { "name": "Choi, Eun-seo", "degree": "PhD", "year": "2009", "title": "Computational Approaches to Localized Deformation Within the Lithosphere and for Crust-Mantle Interactions", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09212008-122525", "creators": [ { "name": { "family": "Choi", "given": "Eun-seo" }, "id": "Choi-Eun-seo", "display_name": "Choi, Eun-seo" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/81QV-Q705", "abstract": "The thesis addresses selected problems related to localized deformation of the solid Earth\u2019s lithosphere that stem from non-uniform strengths or emerge from non-linear rheologies. A new code has been developed to model the spontaneous localization through strain-weakening plasticity. A code coupling technique is introduced as an attempt to efficiently solve multi-material and multi-physics problems like crust-mantle interactions.
\r\n\r\nWe first address a problem of localized deformation that is caused by pre-existing heterogeneities. Specifically, the effects of laterally varying viscous strength on the Cenozoic extension of the northern Basin and Range are investigated using numerical models. Three-dimensional viscous flow models with imposed plate motions and localized zones of low viscosity show that strain rates are concentrated in weak zones with adjacent blocks experiencing little deformation. This result can explain the geodetically discovered concentrated strain in the eastern part of the northern Basin and Range as the high strains are a response to far field plate motions within a locally less viscous mantle. The low viscosity of mantle is consistent with the low seismic velocities in the region.
\r\n\r\nAs an instance of spontaneously emergent localized deformations, brittle deformations in oceanic lithosphere are investigated next. We developed a Lagrangian finite difference code, SNAC, to investigate this class of problems. Brittle deformations are modeled as localized plastic strain. The detailed algorithm of SNAC is presented in Appendix A.
\r\n\r\nThe spacing of fracture zones in oceanic lithosphere is numerically explored. Numerical models represent a ridge-parallel cross-section of young oceanic lithosphere. An elasto-visco-plastic rheology can induce brittle deformation or creep according to the local temperature. The spacing of localized plastic zones, corresponding to fracture zones, decreases as crustal thickness increases. The stronger creep strength raises the threshold value of crustal thickness: If the crust is thinner than the threshold, the brittle deformation can evolve into primary cracks. Plastic flow rules are parametrized by the dilation angle. If the dilatational deformation is allowed in the plastic flow rules (dilation angle>0\u00b0), the primary cracks tend to be vertical; otherwise, a pair of primary cracks form a graben. The modeling results are compatible with the correlation between crustal thickness and the spacing of fracture zones found in different regions such as the Reykjanes ridge and the Australian Antarctic Discordance.
\r\n\r\nThree-dimensional (3D) numerical models are used to find the mechanics responsible for the various patterns made by the segments of the mid-ocean ridges and the structures connecting them. The models are initially loaded with thermal stresses due to the cooling of oceanic lithosphere and prescribed plate motions. The two driving forces are comparable in magnitude and the thermal stresses can exert ridge-parallel forces when selectively released by ridges and ridge-parallel structure. Represented by localized plastic strain, ridge segments interact in two different modes as they propagate towards each other: An overlapping mode where ridge segments overlap and bend toward each other and a connecting mode where two ridge segments are connected by a transform-like fault. As the ratio of thermal stress to spreading-induced stress (\u03b3) increases, the patterns of localized plastic strain change from the overlapping to connecting mode. Rate effects are taken into account by the spreading rate normalized by a reference-cooling rate (Pe\u2032) and the ratio of thermal stress to the reference spreading-induced stresses (\u03b3\u2032). The stability fields of the two modes are unambiguously defined by Pe\u2032 paired with \u03b3'.
\r\n\r\nCrust and mantle are distinct in terms of composition and rheology. To study the combined response of crust and mantle, it is necessary to solve multi-material and multi-physics problems that are numerically challenging. As an efficient way of solving such a problem, we introduce a code coupling technique. We adapt Pyre, a framework allowing distinct codes to exchange variables through shared interfaces, to the coupling of SNAC, a Lagrangian code for lithospheric dynamics, and CitcomS, an Eulerian code for mantle convection. The continuity of velocities and tractions and no-slip conditions are imposed on the interfaces. The benchmarks against analytic solutions to the bending of a thin plate verifies that SNAC gives an accurate solution for the given traction boundary condition. It is also shown that Pyre can correctly handle the data exchanges at the interfaces. In a preliminary high-resolution model, an elasto-visco-plastic lithosphere is coupled to a Newtonian viscous mantle. This coupled model shows a steady growth of dome in the lithosphere directly above a hot sphere placed in the mantle. However, the two coupled codes incur unnecessarily high numerical costs because they use different methods for time integration.
" }, { "name": "Downey, Nathan John", "degree": "PhD", "year": "2009", "title": "Tectonic History of the Osbourn Spreading Center and Dynamic Subsidence of the Congo Basin", "advisor": "Stock, Joann M.; Gurnis, Michael C.; Clayton, Robert W.; Simons, Mark", "url": "https://resolver.caltech.edu/CaltechETD:etd-08282008-093820", "creators": [ { "name": { "family": "Downey", "given": "Nathan John" }, "id": "Downey-Nathan-John", "display_name": "Downey, Nathan John" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "co-advisor", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "co-advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "chair", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "orcid": "0000-0002-2742-8299", "role": "member", "display_name": "Tromp, Jeroen" } ], "option_major": [ "geophys" ], "doi": "10.7907/MXQF-GY83", "abstract": "This is a thesis in two parts. First is the presentation of a new technique by which it is possible to constrain tectonic models of oceanic regions which are devoid of magnetic reversal anomalies. I applied this technique to the Osbourn region of the Southwest Pacific and determined the tectonic history of the Cretaceous Osbourn spreading center. The results of this analysis showed that the Osbourn Trough, although an extinct spreading center, was not part of the Cretaceous Pacific-Phoenix spreading center. The second part of this thesis involves study of the cratonic Congo sedimentary basin. I created instantaneous dynamic models of the Congo basin that are strongly constrained by observation and which demonstrate that the most recent subsidence event of the basin has a mantle dynamic origin. These models constrain the density structure of the upper mantle beneath the Congo. In addition, I examined geologic data that constrain the time-dependent history of the Congo basin in an attempt to determine the subsidence mechanism of cratonic sedimentary basins.\r\n" }, { "name": "Guo, Weifu", "degree": "PhD", "year": "2009", "title": "Carbonate Clumped Isotope Thermometry: Applications to Carbonaceous Chondrites and Effects of Kinetic Isotope Fractionation", "advisor": "Eiler, John M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12182008-115035", "creators": [ { "name": { "family": "Guo", "given": "Weifu" }, "id": "Guo-Weifu", "orcid": "0000-0002-1605-1019", "display_name": "Guo, Weifu" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "advisor", "display_name": "Eiler, John M." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/BWC2-RH54", "abstract": "'Clumped isotope' thermometry of carbonates in the carbonaceous chondrites (CM, CI, CR and Tagish Lake) demonstrates that aqueous alteration of their parent bodies occurred from -31 to 71\u00b0C and involved reaction with fluids having \u03b418OVSMOW values of -29.7\u2030 to 11.8\u2030 and \u03b417OVSMOW of -14.9\u2030 to 7.6\u2030. Estimated carbonate formation temperatures decrease in the order: calcite > dolomite > breunnerite. Based on independent constraints on the ages of these carbonates and models of the evolution of the oxygen isotope compositions of parent body waters, I estimate that carbonate precipitation during aqueous alteration of the carbonaceous chondrite parent bodies started within 1-2 million years after the accretion of those parent bodies, and that the alteration temperatures decreased from 34\u00b0C to 18\u00b0C in the first ~4 million years and further to -20\u00b0C after a total of ~6.5 million years. Our results provide the first direct measurements of the low-temperature cooling histories of C1 and C2 carbonaceous chondrite parent bodies. Within the CM chondrite group itself, I observe a negative correlation between the \u03b413C values of CM carbonates and the \u03b418O of their formation waters, suggesting formation and escape of 13C-depleted CH4 during aqueous alteration on the CM chondrite parent bodies.
\r\n\r\nI apply ab initio transition state and statistical thermodynamics theory to study the kinetic isotope fractionations of clumped isotopologues (i.e., multiply-substituted isotopologues; I also consider singly-substituted isotopologues) associated with phosphoric acid digestion of carbonate minerals and with the degassing of CO2 from aqueous solutions. Assuming that H2CO3 is the reaction intermediate during phosphoric acid digestion of carbonate minerals, I predict at 25\u00b0C that CO2 derived from acid digestion of carbonate minerals will be 10.72\u2030 and 0.220\u2030 higher, respectively, in 18O/16O ratios and 13C-18O clumped isotope anomaly than the reactant carbonate. These predicted kinetic isotope fractionations associated with phosphoric acid digestion and their temperature dependences (for both oxygen isotope and clumped isotopologues) compare favorably with independent experimental constraints for phosphoric acid digestion of calcite. I evaluate the effect of carbonate cation compositions on phosphoric acid digestion fractionations using cluster models in which disproportionating H2CO3 interacts with adjacent cations. These cluster models underestimate the magnitude of isotope fractionations, but do successfully reproduce the general trend of variations and temperature dependences of oxygen isotope acid digestion fractionations among different carbonate minerals (suggesting I have correctly identified the basic mechanism responsible for a dependence on cation chemistry, but not the exact structural model for cation\u2014H2CO3 clusters). I further integrate our acid digestion fractionation model with previous theoretical evaluations of abundances of 13C-18O bonds in carbonate minerals, and predict the relationship between \u039447 values for CO2 extracted from carbonate minerals and the growth temperatures of those carbonates, including witherite, calcite, aragonite, dolomite and magnesite. I observe reasonable agreement between these predictions and available experimental determinations (e.g., difference of less than 0.05\u2030 over 0-50\u00b0C, for calcite).
\r\n\r\nKinetic isotope fractionation associated with HCO3- dehydration and HCO3- dehydroxylation reactions (the two pathways of CO2 degassing from aqueous solutions) are estimated with ab initio transition state theory calculations. Coupled with models of isotopic fractionations accompanying carbonate precipitation, I predict that kinetic isotope fractionation associated with CO2 degassing reactions will increase the \u03b413C and \u03b418O but decrease the relative proportion of 13C-18O bonds in carbonate minerals that precipitate from degassing solutions. Furthermore, these kinetic isotope effects are correlated with each other. For example, I predict the 13C/12C ratio of carbonate increases by 1.1-3.2\u2030 and its \u039447 value decreases by 0.017-0.026\u2030 for every 1\u2030 kinetic enrichment in its 18O/16O at 25\u00b0C, with the exact values depending on the pathway for CO2 degassing (i.e., HCO3- dehydration vs. HCO3- dehydroxylation) and on the amount of carbonate formation that accompanies CO2 degassing. These predictions compare favorably with the experimental constraints from laboratory synthesized cryogenic carbonates and speleothem-like carbonates and with the isotopic compositions of natural modern speleothems.
" }, { "name": "Guo, Xin (Vincent)", "degree": "PhD", "year": "2009", "title": "Modeling Studies Related to Carbon Dioxide Phase Change on Mars", "advisor": "Richardson, Mark I.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05082009-120748", "creators": [ { "name": { "family": "Guo", "given": "Xin (Vincent)" }, "id": "Guo-Xin-Vincent", "display_name": "Guo, Xin (Vincent)" } ], "advisors": [ { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "advisor", "display_name": "Richardson, Mark I." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/E2R4-SS65", "abstract": "Carbon dioxide (CO\u2082) is the most abundant gaseous species in the atmosphere of Mars. Phase change of CO\u2082, predominantly between gas and solid, is the most eminent feature in the current Martian atmosphere. Correct and thorough understanding of the CO\u2082 cycle on Mars is crucial to the scientific research of Mars, including (but not limited to) climatology, meteorology, paleo-climatology, geomorphology, geology, and astrobiology.
\r\n\r\nThis dissertation focuses on modeling the CO\u2082 phase change and coupling the process with a Mars General Circulation Model (GCM) \u2015 the Mars Weather Forecast and Research (MarsWRF) model to study the climate of Mars. Two major forms of the CO\u2082 phase change are included: direct deposition/sublimation to/from the surface (exchange with surface frost) and atmospheric condensation/evaporation (exchange with \"snow\", which later will either precipitate to the ground and become a part of the surface reservoir, or evaporate before it reaches the surface).
\r\n\r\nThe first component has been historically simulated by a surface energy balance model. The energy balance calculations in MarsWRF, especially the physics module associated with subsurface heat conduction, are improved. The GCM is fine-tuned by changing the values of the seasonal ice cap albedos and emissivities and the total CO\u2082 mass in the system (later the heat conductivity of the polar soil). Resulted surface pressure cycle, which is a good indicator of the atmospheric reservoir of CO\u2082, matches the in situ measurements made by the Viking Landers extremely well. This fitting algorithm can be used for tuning of GCMs and for exploration of more complicated physical processes.
\r\n\r\nThe second component can be solved by a simple energy balance model in the atmosphere as well. However, it is widely accepted that sophisticated microphysics models may be required for more accurate simulations. A complete microphysics model, which calculates the nucleation process and ice particle growth process, is incorporated to MarsWRF. Preliminary simulation results show promising agreement with spacecraft observations.
\r\n\r\nWhen an insolation-dependent frost albedo is included, MarsWRF is able to produce a perennial CO\u2082 cap near the south pole of Mars. This is the first time that any GCM has successfully predicted a residual cap. This mechanism is necessary for a simple energy balance model to reproduce the perennial ice cap, and may shed some light on the ages and the cycles of the perennial caps.
\r\n\r\nA mass balance model is developed to simulate the non-condensable gas mass mixing ratio variation during the CO\u2082 phase change. When coupled with MarsWRF, the non-condensable gas cycle agrees qualitatively with the Gamma Ray Spectrometer data and other GCM results. It provides a benchmark check to the GCM itself and an independent way to study the dynamics of the Martian atmosphere.
\r\n" }, { "name": "Kaneko, Yoshihiro", "degree": "PhD", "year": "2009", "title": "Investigations of Earthquake Source Processes Based on Fault Models with Variable Friction Rheology", "advisor": "Lapusta, Nadia", "url": "https://resolver.caltech.edu/CaltechETD:etd-04282009-202026", "creators": [ { "name": { "family": "Kaneko", "given": "Yoshihiro" }, "id": "Kaneko-Yoshihiro", "orcid": "0000-0003-2342-0131", "display_name": "Kaneko, Yoshihiro" } ], "advisors": [ { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "advisor", "display_name": "Lapusta, Nadia" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Ampuero", "given": "Jean-Paul" }, "id": "Ampuero-J-P", "role": "member", "display_name": "Ampuero, Jean-Paul" }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/1WGT-6623", "abstract": "Ample experimental and observational evidence suggests that friction properties on natural faults vary spatially. In the lab, rock friction depends on temperature and confining pressure and it can be either velocity weakening or velocity strengthening, leading to either unstable or stable slip. Such variations in friction rheology can explain patterns of seismic and aseismic fault slip inferred from field observations.
\r\n\r\nThis thesis studies earthquake source processes using models with relatively simple but conceptually important patterns of velocity-weakening and velocity-strengthening friction that can arise on natural faults. Based on numerical and analytical modeling, we explore the consequences of such patterns for earthquake sequences, interseismic coupling, earthquake nucleation processes, aftershock occurrence, peak ground motion in the vicinity of active faults, and seismic slip budget at shallow depths. The velocity-dependence of friction is embedded into the framework of logarithmic rate and state friction laws.
\r\n\r\nIn addition to using existing boundary integral methods, which are accurate and efficient in simulating slip on planar faults embedded in homogeneous elastic media, the thesis develops spectral element methods to consider single dynamic ruptures and long-term histories of seismic and aseismic slip in models with layered bulk properties.
\r\n\r\nThe results of this thesis help to understand a number of observed fault slip phenomena, such as variability in earthquake patterns and its relation to interseismic coupling, seismic quiescence following decay of aftershocks at inferred rheological transitions, instances of poor correlation between static stress changes and aftershock occurrence, the lack of universally observed supershear rupture near the free surface, and coseismic slip deficit of large strike-slip earthquakes at shallow depths. The models, approaches, and numerical methods developed in the thesis motivate and enable consideration of many other earthquake source problems, such as the combined effect of two or more triggering mechanisms on aftershock rates, inferring friction properties on natural faults based on seismic and geodetic measurements, seismic hazard assessment based on observed interseismic coupling, and the effect of heterogeneous and/or nonelastic bulk properties on earthquake sequences.
\r\n\r\n" }, { "name": "Lewis, Kevin Wayne", "degree": "PhD", "year": "2009", "title": "The Rock Record of Mars: Structure, Sedimentology and Stratigraphy\r ", "advisor": "Aharonson, Oded", "url": "https://resolver.caltech.edu/CaltechETD:etd-06062009-150120", "creators": [ { "name": { "family": "Lewis", "given": "Kevin Wayne" }, "id": "Lewis-Kevin-Wayne", "orcid": "0000-0003-3412-803X", "display_name": "Lewis, Kevin Wayne" } ], "advisors": [ { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "advisor", "display_name": "Aharonson, Oded" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" } ], "option_major": [ "plansci" ], "doi": "10.7907/Y4JG-FZ60", "abstract": "This work combines several studies related to the sedimentary rock record of Mars. Data from several spacecraft are employed to ascertain the formation mechanisms and timescales of stratified outcrops exposed at the surface, In particular, high-resolution topographic data from stereo images are utilized to obtain quantitative estimates of geologic structure and stratigraphy. The first investigation focuses on a well-preserved fluvial distributary network exposed in Eberswalde crater. Geologic structure and basin topography are used to assess modes of formation and place limits on the deposition timescale. Chapter 3 describes an enigmatic feature studied by the Spirit rover, an 80 m diameter, intricately cross-bedded plateau known as Home Plate. Via combined analysis of the stratigraphy, structure, and sedimentology, a pyroclastic origin is proposed for the origin of this enigmatic sedimentary deposit. Finally, chapter 4 focuses on the occurrence of several rhythmically bedded sedimentary deposits across the surface of Mars. The strong quasiperiodicity seen in the stratigraphy at these locations is likely evidence of allogenic control on deposition from external climate cyclicity. Two scales of periodicity are demonstrated for one section at Becquerel crater. We propose a link to orbital forcing via the obliquity cycle of Mars. " }, { "name": "Petterson, Ryan", "degree": "PhD", "year": "2009", "title": "I. Glaciagenic and Related Strata of the Neoproterozoic Kingston Peak Formation in the Panamint Range, Death Valley Region, California. II. The Basal Ediacaran Noonday Formation, Eastern California, and Implications for Laurentian Equivalents. III. Rifting of Southwest Laurentia During the Sturtian-Marinoan Interglacial: The Argenta Orogeny", "advisor": "Wernicke, Brian P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05042009-102142", "creators": [ { "name": { "family": "Petterson", "given": "Ryan" }, "id": "Petterson-Ryan", "display_name": "Petterson, Ryan" } ], "advisors": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "advisor", "display_name": "Wernicke, Brian P." } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "geol" ], "doi": "10.7907/C9GZ-WE07", "abstract": "I. Glacigenic deposits in the Death Valley region occur within the Neoproterozoic Kingston Peak Formation. In the Panamint Range, immediately west of Death Valley, these strata are \u22651000 m thick and are continuously exposed for nearly 100 km along the strike of the range. Although these strata are variably metamorphosed and locally exhibit pronounced ductile strain, original sedimentary textures are well preserved throughout the range. Diamictic strata occur in two distinct intervals, a lower one comprising the Limekiln Spring and Surprise Members, and an upper one known as the Wildrose Sub-member of the South Park Member. Each of these intervals are succeeded by well defined cap carbonates, which, from oldest to youngest, are the Sourdough Member of the Kingston Peak and the Sentinel Peak Member of the overlying Noonday Formation. Between the two glacial successions, the Sourdough and sub-Wildrose South Park units comprise a ~300 m thick interglacial succession that includes platform carbonate deposition. Sparse lonestones and striated clasts, along with the impressive lateral continuity of diamictic units, support a glacial origin. Chemostratigraphic profiles of \u03b413C through the Sourdough (-3\u2030 to +2\u2030, increasing upward) and Sentinel Peak (-3\u2030 +/- 1\u2030) suggest correlation with the Sturtian and Marinoan caps, respectively. Potentially economic U deposits (secondary brannerite) occur in graphitic schists of the Limekiln Spring Member and sub-economic U and Th (hosted by detrital monazite) occur within quartz-pebble conglomerates in the South Park Member. The strata contain no fossils, radiometric age control, or primary magnetizations.
\r\n\r\nII. The Neoproterozoic-Cambrian succession in the Death Valley region of SW Laurentia is among the best exposed and easily accessible in the world, and comprises one of the most complete sections in Laurentia. The largest single exposure of these strata occurs in the Panamint Range on the west flank of Death Valley, but this area has received little attention in comparison to numerous exposures to the east of Death Valley, primarily because of structural complexity and metamorphism. The eastern strata, although unmetamorphosed, occur in isolated fault-bounded exposures and are relatively thin and incomplete compared to the Panamint stratigraphy. These factors, combined with a lack of fossil or radiometric age control, has hindered confident regional correlation, as well as placement in the context of hallmark Neoproterozoic events observed in the South Australian, Namibian and other successions around the globe. New geological mapping, measured sections and high-resolution C-isotope data reported here from the Noonday Formation in the Panamint Range delineate its regional stratigraphic architecture and establish its age through correlation with section with radiometric age control. Carbon isotopic trends in the Panamint Range match to within 1-2\u2030 reproducibility previous results obtained for correlative strata in the eastern sections, indicating that metamorphism did not significantly alter C isotopic ratios.
\r\n\r\nThe combined lithostratigraphic and chemostratigraphic data form the basis for a revised, more complete stratigraphic framework for the Noonday Formation. A composite section shows that, where most complete, the Noonday consists of three members, from the base upward, the Sentinel Peak, Radcliff, and Mahogany Flats members. New mapping and chemostratigraphic data permit robust regional correlation of a thin dolostone marker horizon at the base of the Noonday in the Panamint Range as little as 2 m thick (Sentinel Peak Member) with a tube-bearing microbial dolostone in the eastern Death Valley region more than 200 m thick. The data also reveal that the Radcliff Member is bounded by disconformable surfaces and their correlative conformities. These surfaces are recognizable throughout the region and are used to construct a regionally unified stratigraphic nomenclature.
\r\n\r\nA key finding of this study is the construction of a chemostratigraphic profile spanning most of Noonday time. This was greatly aided by the discovery of carbonatebearing strata in the lower part of the Radcliff Member in the Tucki Mountain area of the Panamints, and relating their stratigraphic position to upper Radcliff and younger Noonday strata in the Wildrose Canyon area. The chemostratigraphic profile is a remarkable match for the Maiberg cap carbonate sequence in Namibia, including the decline to a minimum at -5\u2030, a recovery to near 0\u2030, and then subsequent decline to -2\u2030. Globally, profiles through many post-Marinoan sequences are either too condensed or lack sufficient carbonate to record these features, including the sections in the eastern Death Valley region. (Halverson et al. 2005). As such, the Panamint profiles represent the first relatively complete record of the post-Marinoan C-isotopic recovery outside of southern Africa. Correlation of these curves (1) firmly places the Noonday at the base of the Ediacaran Period, (2) indicates deposition of ~200 m of Sentinel Peak and Radcliff strata occurred between 635 and 632 Ma, (3) supports the hypothesis that the Wildrose Diamictite of the Kingston Peak Formation, which lies in sharp contact below the Sentinel Peak Member, represents at least part of the Marinoan glacial interval; (4) helps identify correlative cap carbonate sequences in key Laurentian sections, which include the Ravensthroat Formation in the MacKenzie Mountains, dolostones capping the upper diamictite of the Pocatello Formation in eastern Idaho, and the middle part of the Mina el Mezquite Formation in Sonora. The Noonday C-isotopic profile confirms that the details of relatively rapid, complex variations in ocean chemistry observed in basal Ediacaran strata in Namibia are globally reproducible.
\r\n\r\nIII. The Kingston Peak Formation in the Panamint Range represents the stratigraphically most complete section of Cryogenian strata along the SW margin of Laurentia. Two glacigenic diamictites and their associated cap carbonates, the older Surprise Member and Sourdough Member and the younger Wildrose Member and Noonday Formation (Sentinel Peak Member), provide timing constraints to bracket the inter-glacial succession to between ca. 713 Ma and 635 Ma, the ages of inferred correlative glacial cap carbonate rocks dated elsewhere. This timing constraint is further strengthened by the presence of a sharp decline in C isotopes in the Thorndike Member, which occurs immediately beneath the Wildrose Member; this decline is readily correlated with the global Trezona anomaly.
\r\n\r\nWithin the inter-glacial succession, new mapping in the northern Panamints has documented the presence of a previously unrecognised suite of coarse sedimentary rocks herein defined as the Argenta Member of the Kingston Peak Formation. The Argenta consists largely of poorly-sorted breccias and conglomerates containing an assemblage of gravel-sized clasts dominated by granitic gneiss, schist, feldspar augens, vein quartz and quartzite fragments, and locally carbonate rocks. These compositions indicate derivation from a basement provenance and record deposition in alluvial-fan to coarse-braided fluvial settings; their textural and compositional immaturity implies relatively short distances of transport. Mapping shows that the Argenta defines wedge-shaped packages as much as 200 m thick and that the base of the Argenta is a significant angular unconformity. Combined, these features are evidence that deposition occurred during a phase of extensional tectonism interpreted as recording the initial dismemberment of the Rodinia supercontinent. Best estimates place the timing of this tectonism at ca. 650 \u2013 700 Ma.
\r\n" }, { "name": "Ragozzine, Darin Alan", "degree": "PhD", "year": "2009", "title": "Orbital Dynamics of Kuiper Belt Object Satellites, a Kuiper Belt Family, and Extra-Solar Planet Interiors", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05282009-164537", "creators": [ { "name": { "family": "Ragozzine", "given": "Darin Alan" }, "id": "Ragozzine-Darin-Alan", "orcid": "0000-0003-1080-9770", "display_name": "Ragozzine, Darin Alan" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "co-chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" } ], "option_major": [ "plansci" ], "doi": "10.7907/NRNC-XK21", "abstract": "This thesis discusses research into four different orbital dynamics problems, where the main goal of each chapter is to characterize the strongest non-Keplerian effect. These problems are introduced and discussed in Chapter 1, to help provide context for the subsequent chapters. In Chapter 2, I discuss a new technique for probing the interior density distributions of extra-solar planets by observing apsidal precession. Using a detailed theoretical and observational model of this precession, I conclude that NASA's Kepler mission will be able to detect the presence or absence of a massive core in very hot Jupiters with eccentricities greater than 0.003. The remaining chapters discuss the orbital dynamics of Kuiper belt objects (KBOs) orbiting the Sun beyond Neptune. The family of dwarf planet Haumea (2003 EL61) is characterized in Chapter 3, including a list of candidate family members sorted by dynamical proximity. Using a numerical integration of resonance diffusion, I also show that the Haumea family is at least 1 Gyr old and is probably primordial. In Chapter 4, I analyze and fit astrometric data for the two satellites of Haumea (Hi'iaka and Namaka) to determine their orbital properties and the masses of Haumea and Hi'iaka. The implications of the new orbital solution are discussed, including the exciting conclusion that Haumea and Namaka are currently starting a season of mutual events. A more general investigation of the orbital and tidal evolution of KBO binaries is given in Chapter 5. A new orbital evolution model is described that accounts for perturbations from the Sun, self-consistent tidal evolution, and non-hydrostatic quadrupoles of solid KBOs. Using this model, I find that the orbital parameters of KBO binaries may have been modified significantly over the age of the solar system. Applied to the Orcus-Vanth binary, this model shows that a short-period circular orbit does not necessarily imply a collisional formation. In all, the work in this thesis has sought to analyze observational data by using the theoretical tools of orbital dynamics. " }, { "name": "Salyk, Colette Vanessa", "degree": "PhD", "year": "2009", "title": "Molecular Spectroscopy of Planet-Forming Regions in Circumstellar Disks", "advisor": "Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05272009-151203", "creators": [ { "name": { "family": "Salyk", "given": "Colette Vanessa" }, "id": "Salyk-Colette-Vanessa", "orcid": "0000-0003-3682-6632", "display_name": "Salyk, Colette Vanessa" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Hillenbrand", "given": "Lynne A." }, "id": "Hillenbrand-L-A", "role": "member", "display_name": "Hillenbrand, Lynne A." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." } ], "option_major": [ "plansci" ], "doi": "10.7907/E4YF-FZ95", "abstract": "Planets, now known to be common companions of nearby stars, are believed to originate in circumstellar disks - disks of gas and dust that form around collapsing protostars. Because of their small angular size, disks in nearby star-forming regions are difficult to spatially resolve. However, since radial temperature gradients are set up by the luminous central star, the peak wavelength of blackbody emission is a proxy for disk location, and spectroscopic observations can thus be used to study disk structure. In this thesis, I present spectroscopic observations of circumstellar disks obtained with the Keck Near Infrared Spectrograph (NIRSPEC) and the Spitzer Space Telescope Infrared Spectrograph (IRS).
\r\n\r\nHigh-resolution (R ~ 25000) M-band spectra have been obtained with NIRSPEC for over 100 circumstellar disks. CO vibrational emission in the M-band is nearly ubiquitous from classical, optically thick disks, and can be used to examine the disks' inner structure and gas content. The emission is consistent with high temperatures and densities, and small emitting areas, suggesting that it originates at small disk radii - a few AU or less. An analysis of CO lineshapes shows that the CO gas is truncated at or near the dust sublimation radius for low and mid-mass stars but at larger radii for more luminous stars. CO emission is also present from many transitional disks - disks in which the inner regions have been depleted of small dust grains -demonstrating that many of their inner disks have significant quantities of gas. Although the formation mechanism for transitional disks is not yet known, gas-rich inner disks are consistent with formation via tidal clearing by a giant planet.
\r\n\r\nSpitzer-IRS spectra have been obtained for 82 disks, as part of the Cores to Disks (c2d) legacy program and other archived programs, and as part of a targeted IRS GO-5 survey at high S/N. Water vapor and other gaseous molecules, including OH, HCN, C2H2, and CO2, are detected from ~ 40% of disks. Excitation temperatures for the molecular species of ~ 500 K or higher and emitting radii of a few AU suggest an origin in the planet-forming regions of the disks. There are no strong correlations between detection rates or line equivalent widths and stellar or disk parameters. However, molecular detection rates are correlated with each other, and with disk color, suggesting a dependence on disk structure. Unlike for classical disks, transitional disks show no evidence for H2O, OH, or any organic molecules, perhaps because these molecules are easily photodissociated in the optically thin inner disk.
\r\n" }, { "name": "Sun, Daoyuan", "degree": "PhD", "year": "2009", "title": "Seismic Structure of the Lower Mantle", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06022009-012218", "creators": [ { "name": { "family": "Sun", "given": "Daoyuan" }, "id": "Sun-Daoyuan", "orcid": "0000-0003-4461-4664", "display_name": "Sun, Daoyuan" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geophys" ], "doi": "10.7907/BD11-ET49", "abstract": "The lower mantle plays an important role in the thermal and chemical evolution of the earth. Although recent advanced seismological imaging displays the heterogeneous nature of the lower mantle, most results are constrained to large scale and longer wavelength structures. This thesis involved waveform modeling studies of the detailed structures of the lower mantle, especially the African Superdome and D\" layer.
\r\n\r\nA simple uniform 3% shear velocity reduction model can explain the observed seismological anomalies for the African Superdome (also refer as Africa Large Low Shear Velocity Province or Africa Superplume), but it lacks small scale complexity inside. In parallel with the seismic model, a composition-dependent compressibility model with a high bulk modulus is developed to explain the African Superdome. To validate this dynamic model, we map the modeled chemistry and temperature into P and S velocity models. Synthetic seismogram sections generated for this 2D model are then compared directly with the corresponding seismic observations. These results explain the anti-correlation between the bulk velocity and shear velocity, as well as the sharpness of the edge.
\r\n\r\nA lower mantle S-wave triplication with a Scd branch occurring between S and ScS has been recognized for many years and has been interpreted in a variety of ways. The triplication is particularly strong when sampling regions beneath the circum-Pacific lower mantle fast velocity belt seen in global tomographic models, where it has been modeled with a 2\u20133% jump in S-velocity. The D\" discontinuity may arise from a phase change for Perovskite to Post-Perovskite. We model the phase boundary height by mapping S-wave tomography into temperature. A few adjustable parameters involving reference phase boundary height and velocity jump are determined from comparing synthetic seismogram predictions with densely sampled observations. Adding 3D propagational effects caused by these structures through Perovskite to Post-Perovskite velocity jump predicted from mineral physics appears to generate compatible results with Scd waveform observations.
\r\n\r\nIn the last chapter, we develop a new tool based on a decomposition referred to as a multi-path detector which can be used to distinguish between horizontal structure (in-plane multi-pathing) vs. vertical (out-of-plane multi-pathing) directly from processing array waveforms. A lateral gradient coefficient based on this detector provides a direct constraint on the sharpness of the boundaries and material properties. We demonstrate the usefulness of this approach by processing samples of both P and S data from the Kaapvaal array in Southern Africa. The results further validate the case for distinct chemistry inside the African Superdome. We also present evidence of a narrow plume-like feature coming off the top of the large African low-velocity structure in the lower mantle. The plume's diameter is less than 150 km and consistent with an iso-chemical, low-viscosity plume conduit.
\r\n" }, { "name": "Tape, Carl Harlan", "degree": "PhD", "year": "2009", "title": "Seismic Tomography of Southern California Using Adjoint Methods", "advisor": "Tromp, Jeroen", "url": "https://resolver.caltech.edu/CaltechETD:etd-05062009-183823", "creators": [ { "name": { "family": "Tape", "given": "Carl Harlan" }, "id": "Tape-Carl-Harlan", "orcid": "0000-0003-2804-7137", "display_name": "Tape, Carl Harlan" } ], "advisors": [ { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "advisor", "display_name": "Tromp, Jeroen" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "co-chair", "display_name": "Simons, Mark" }, { "name": { "family": "Hauksson", "given": "Egill" }, "id": "Hauksson-E", "role": "member", "display_name": "Hauksson, Egill" }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "member", "display_name": "Tromp, Jeroen" } ], "option_major": [ "geophys" ], "doi": "10.7907/B9KK-S206", "abstract": "A fundamental objective of seismology is to produce detailed tomographic images of Earth's interior by fitting simulated seismograms to recorded seismograms. The quality of the image depends on the quality of the observations and on the accuracy of the modeling tool. We present a seismic tomography approach that employs accurate numerical methods of seismic wave propagation. Our approach follows successive steps of a minimization problem. First, specify an initial tomographic model in terms of shear wave speed, compressional wave speed, and density. Next, collect a dataset of well-recorded earthquakes. Specify a misfit function that quantifies the difference between sets of recorded and simulated seismograms. For each earthquake, evaluate both the misfit function and the gradient of the misfit function. Adjoint methods are used to compute the gradient via the interaction of a \"forward wavefield,\" propagating from source to stations, with an \"adjoint wavefield,\" propagating from stations to source. Using the gradient for each earthquake, we then compute an update to the initial model. This procedure is then iterated to obtain a better model of Earth's interior structure.
\r\n\r\nWe iteratively improve a three-dimensional (3D) seismological model of the southern California crust. The resulting model is constructed from 16 tomographic iterations, which required 6800 wavefield simulations and a total of 0.8 million CPU-hours. The new crustal model reveals strong heterogeneity, including local changes of \u00b1 30% with respect to the initial 3D model provided by the Southern California Earthquake Center. The improved crustal model illuminates features at the surface that agree with geology, such as the southern San Joaquin basin. It also reveals crustal features at depth that aid in the tectonic reconstruction of southern California, such as possible Farallon oceanic crustal fragments beneath the western Transverse Ranges. The new model enables more accurate assessments of seismic hazard for scenario earthquakes.
\r\n" }, { "name": "Verdel, Charles Steven", "degree": "PhD", "year": "2009", "title": "I. Cenozoic Geology of Iran: An Integrated Study of Extensional Tectonics and Related Vulcanism. II. Ediacaran Stratigraphy of the North American Cordillera: New Observations from Eastern California and Northern Utah", "advisor": "Wernicke, Brian P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09182008-092505", "creators": [ { "name": { "family": "Verdel", "given": "Charles Steven" }, "id": "Verdel-Charles-Steven", "orcid": "0000-0003-2981-8570", "display_name": "Verdel, Charles Steven" } ], "advisors": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "advisor", "display_name": "Wernicke, Brian P." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "geol" ], "doi": "10.7907/4KPY-X114", "abstract": "I. The late Oligocene to Miocene collision of Arabia and Eurasia was preceded by ~175 My of subduction of Neotethyan oceanic crust. Associated magmatic activity includes late Triassic(?) to Jurassic plutons in the Sanandaj-Sirjan zone of southern Iran, limited Cretaceous magmatism in the Alborz Mountains of northern Iran, and widespread Eocene volcanism across central Iran. Metamorphic core complexes of Eocene age have recently been recognized in widely separated parts of Iran, suggesting that Tertiary volcanism was related to extension. Geochemical data indicate that Eocene volcanism was typical of continental arcs and was followed by less voluminous Oligocene basaltic volcanism of the type often associated with back-arc basins. This set of observations suggests that mid-Mesozoic plutons in southern Iran are the remnants of an original volcanic arc that was only weakly developed because of slow subduction rate. Magmatic activity largely ceased in southern and central Iran during the Cretaceous and shifted to the north, suggesting a period of flat slab subduction. Subsequent slab-rollback during the Eocene extended the overriding plate, forming metamorphic core complexes and inducing pressure-release melting of partially hydrated lithospheric mantle and upwelling of asthenosphere.
\r\n\r\nII. The Ediacaran Period spans from the base of cap carbonates overlying glacial deposits of the Marinoan \u201cSnowball Earth\u201d event to the Precambrian-Cambrian boundary, ~635 to 542 Ma. Sediments deposited during the rifting of southwest Laurentia, which are now exposed in a relatively narrow belt in the western US, are one of the best records on earth of the geological, geochemical, and geobiological events that occurred during this period. Evidence for one of the most significant of these, the final oxygenation of the oceans, is found within the upper Johnnie Formation in the southern Great Basin. C isotope data from thick, basinal facies of the Johnnie Fm. in the Panamint Range provide a more complete record of ocean chemistry associated with this event than previously determined from thinner, platformal facies. Strata in northern Utah of roughly the same age include a rift-related basalt, providing some of the youngest geologic evidence for the rifting of western Laurentia.
\r\n" }, { "name": "Wiktorowicz, Sloane John", "degree": "PhD", "year": "2009", "title": "Unambiguous Black Hole Mass from Polarimetry and Application to Hot Jupiters", "advisor": "Kulkarni, Shrinivas R.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03032009-092300", "creators": [ { "name": { "family": "Wiktorowicz", "given": "Sloane John" }, "id": "Wiktorowicz-Sloane-John", "orcid": "0000-0003-4483-5037", "display_name": "Wiktorowicz, Sloane John" } ], "advisors": [ { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "orcid": "0000-0001-5390-8563", "role": "advisor", "display_name": "Kulkarni, Shrinivas R." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Hillenbrand", "given": "Lynne A." }, "id": "Hillenbrand-L-A", "role": "member", "display_name": "Hillenbrand, Lynne A." }, { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "orcid": "0000-0001-5390-8563", "role": "member", "display_name": "Kulkarni, Shrinivas R." } ], "option_major": [ "plansci" ], "doi": "10.7907/3YVF-VE44", "abstract": "A novel technique for detecting light scattered by extrasolar planets is presented that has the potential to constrain orbital inclination and planet mass. To develop this technique, I have commissioned a high precision polarimeter on the Hale 5-m telescope at Palomar Observatory. The high mass X-ray binary Cygnus X-1 has been observed, which is a proxy for extrasolar planet studies. The single scattering model of Brown et al. (1978), widely used in the literature, predicts an orbital inclination for Cygnus X-1 that is inconsistent with the lack of observed X-ray eclipses to 4\u03c3 - 5\u03c3. Previous studies have hinted at this discrepancy, but data quality was such that the confidence in such a discrepancy was not statistically significant. My observations represent the highest precision study of this object, and they illustrate the overwhelming complexity of the supergiant/black hole system. They also call into question the validity of the Brown et al. (1978) formalism, widely used by the community, for inclination estimation in binary systems.
\r\n\r\nExtrasolar planet host stars have also been observed, and precision of order one part per million has been achieved on bright targets. Precision attained on fainter host stars is of order one part in 10^5 . While scattered light from extrasolar planets has not been conclusively detected, a planetary transit in the HD 189733 system may have been observed in polarized light. Such an event is observed to be 1,000 times weaker in polarized light than in photometry, and it indicates a planetary transit of the Southern Hemisphere of the host star. Such geometric information is difficult to determine by other methods.
\r\n\r\nThe integrated polarization of the debris disk surrounding \u03b3 Ophiuchi has been observed to high precision, and the position angle of net polarization is aligned with the disk major axis as seen by the Spitzer Space Telescope. This indicates the disk is primarily composed of forward scattering dust grains larger than the wavelengths of visible light.
\r\n\r\nFinally, Neptune-mass extrasolar planets orbiting close to their host stars have been modeled to be far too warm for liquid water oceans to exist in their upper atmospheres.
" }, { "name": "Barkume, Kristina Marie", "degree": "PhD", "year": "2008", "title": "Surface Properties of Kuiper Belt Objects and Centaurs", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05132008-202158", "creators": [ { "name": { "family": "Barkume", "given": "Kristina Marie" }, "id": "Barkume-Kristina-Marie", "display_name": "Barkume, Kristina Marie" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" } ], "option_major": [ "plansci" ], "doi": "10.7907/EQY1-NM23", "abstract": "The outer solar system is inhabited by a population of small solar system bodies called Kuiper belt Objects (KBOs) and Centaurs. I present a survey of visible and near infrared (NIR) spectra of the brightest KBOs and Centaurs. The visible spectra of 19 KBOs were obtained at Palomar Observatory. At the W.M. Keck Observatory, NIR spectra were obtained for 33 KBOs and 12 Centaurs. This data marks a significant leap in the available spectra, allowing for the population to be studied as whole.
\r\n\r\nThe spectra reveal that most KBOs are covered with a material with characteristics similar to irradiate ices rich in complex organic compounds. Water ice is also observed on some KBOs and Centaurs, though its abundance is variable across the samples. A two end member mixing model is found to describe the NIR spectral properties well, but poorly fits the visible-NIR data. This suggests that the non-water ice component is heterogeneous across the KBO and Centuar populations. To characterize the non-ice component better, the visible spectra are analyzed for signatures of both organic and mineralogical features. No evidence is found for the presence of minerals, but the spectra suggest complex organics are a dominant spectral component. The abundance of water is shown to directly correlate with diameter for KBOs, but not Centaurs, suggesting it is controlled by geophysical processes on KBOs.
\r\n\r\nThe analysis of these spectra has revealed an unusual population of KBOs that are now identified as mantle fragments from the large KBO 2003 EL61. The collision that spun-up 2003 EL61, formed its satellite system, and ejected the mantle fragments into the Kuiper belt is discussed. The unusual spectral properties of 2003 EL61, its brightest satellite, and the fragments are examined. Analysis suggests that the surfaces of all these objects can be composed of nearly pure water ice, suggesting that their volatile organic inventory has been lost. The discovery of crystalline water ice on these small KBOs suggests that crystallization is not an indication of recent surface activity as was previously suggested.
\r\n" }, { "name": "Chen, Min", "degree": "PhD", "year": "2008", "title": "Numerical Simulations of Seismic Wave Propagation in Anisotropic and Heterogeneous Earth Models: The Japan Subduction Zone", "advisor": "Tromp, Jeroen", "url": "https://resolver.caltech.edu/CaltechETD:etd-05302008-030851", "creators": [ { "name": { "family": "Chen", "given": "Min" }, "id": "Chen-Min-Geophysics", "orcid": "0000-0002-6970-7317", "display_name": "Chen, Min" } ], "advisors": [ { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "advisor", "display_name": "Tromp, Jeroen" } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/VDRB-Y055", "abstract": "This thesis involved studies of the seismic wave propagation in fully anisotropic and heterogeneous Earth models, and the seismic velocity structures in the Japan subduction zone derived from the observations, using both forward modeling and tomographic methods. All the simulations of seismic wave propagation in this thesis have been carried out using both 2-D finite-difference method (FDM) and 3-D spectral-element method (SEM).
\r\n\r\nWe extend the SEM code to incorporate three-dimensionally, fully anisotropic earth models. For weakly anisotropic media, we benchmark the numerical simulations against asymptotic, ray theoretical predictions for both surface waves and body waves. The numerical simulations and asymptotic predictions are in good agreement for anisotropy at the 5% level. Weakly anisotropic body-wave propagation involves all 21 independent elastic parameters. The code is capable of simulating the shear-wave splitting in terms of waveforms. Strong waveform distortions are observed when the seismic waves propagate through a simple and weakly anisotropic Earth model. Our results also further prove the anisotropic effects on body-wave traveltime are completely directional dependent.
\r\n\r\nFrom the high-density waveform data provided by Japanese data center (NIED), we observed a strong secondary SH arrival recorded in NE Japan. In order to explain this secondary arrival, a thin but strong low velocity layer (LVL) on top of the slab has to be introduced. Our 2-D model suggests the LVL extends down to a depth of 300 km with an S-wave velocity reduction of 14% if a thickness of 20 km is assumed. Further 3-D SEM simulations confirm that this model explains the strong secondary arrival. We interpret this deeply extended LVL as a zone composed of hydrated mafic and/or ultramafic rocks, and more likely ultramafic rocks (serpentinized peridotite) at depths greater than 150 km. The water released from the dehydration reactions in this hydrous zone could cause the abundant arc volcanism, the intermediate-depth intra-slab seismicity (70-30 km), and possible silent slip events.
\r\n\r\nIn order to obtain better 3-D seismic velocity models of the Japan subduction zone and the neighboring region beneath Eastern China, we use adjoint tomography to iteratively minimize the misfit between the synthetics and data from Hi-net, F-net, and Global Seismographic Network (GSN) stations. In this study, we are able to maximize the information obtained from three-component seismic records for tomographic inversion by using an automated windowing code. It selects not only the body-wave but also the surface-wave windows. With a dataset of 206 events in the Japan subduction zone, the frequency-dependent traveltime measurements are made in 44,709 windows for the period range of 24-120 s and 119,376 windows for the period range of 6-30 s. The combined adjoint sources are thus constructed based on these traveltime misfit measurements for all the receivers. Given the adjoint sources, we use the adjoint spectral-element method to calculate banana-doughnut kernels for the selected records. The weighted sums of the banana-doughnut kernels for all event-station pairs, with weights determined by the traveltime measurements, can be used to construct misfit kernels, which are the gradients required in a non-linear conjugate gradient algorithm to further refine the existing 3-D model.
" }, { "name": "Hebert, Laura Baker", "degree": "PhD", "year": "2008", "title": "(I) A Coupled Geochemical and Geodynamical Approach to Subduction Zone Modeling and (II) Development of Color in Greenish Quartz", "advisor": "Asimow, Paul David; Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02272008-172649", "creators": [ { "name": { "family": "Hebert", "given": "Laura Baker" }, "id": "Hebert-Laura-Baker", "display_name": "Hebert, Laura Baker" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "co-advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geochem" ], "doi": "10.7907/71YF-WH65", "abstract": "(I) We couple a petrological model with a 2D thermal and variable viscosity flow model to describe and compare fundamental processes occurring within subduction zones. We study the thermal state and phase equilibria of the subducting oceanic slab and mantle wedge and constrain fluid flux, presenting model results spanning normal ranges in subduction parameters. Coupling between the chemistry and the dynamics results in the development of a stable slab-adjacent low-viscosity region defined by hydrous phases and higher concentrations of water in nominally anhydrous minerals, bounded by the water-saturated solidus.
\r\n\r\nSubduction parameters are significant to the position of dehydration reactions within the slab and the geochemistry of fluids initiating flux melting. Modeling of fluid transport mechanisms and potential melt migration processes based on coupled modeling with the addition of fluid-mobile trace elements was performed. There is a progression of geochemical characteristics described in previous studies of arc lava datasets that can be duplicated with these models.
\r\n\r\nA localized low-viscosity, low-density geometry within the wedge, predicted by coupled modeling of the Izu-Bonin system, is required to match observations of topography, gravity, and geoid anomalies. Based on this, predictions can be made as to specific low-viscosity geometries associated with geophysical signals for other subduction zones based on regional subduction parameters.
\r\n\r\n(II) Naturally occurring greenish quartz found within the context of amethyst-bearing deposits is not simply the result of the exposure of amethyst to thermal bleaching. Rather, it can represent a set of distinct color varieties resulting from the changing chemical and thermal nature of the precipitating solution. Greenish quartz occurs at the Thunder Bay Amethyst Mine Panorama, Thunder Bay, Ontario, Canada, in several distinct varieties. Spectroscopic, irradiation, and controlled heating studies show that changes in salinity and temperature of the hydrothermal system that produced the deposit and changes in quartz growth rate are reflected in coloration. As the system evolved, a minor ferric component appears to change position from interstitial to substitutional within specific growth sectors. Greenish colors within the quartz are consistently correlated with the speciation of hydrous components.
\r\n" }, { "name": "Hudson, Troy Lee", "degree": "PhD", "year": "2008", "title": "Growth, Diffusion, and Loss of Subsurface Ice on Mars: Experiments and Models", "advisor": "Aharonson, Oded", "url": "https://resolver.caltech.edu/CaltechETD:etd-05022008-154254", "creators": [ { "name": { "family": "Hudson", "given": "Troy Lee" }, "id": "Hudson-Troy-Lee", "orcid": "0000-0002-5879-6633", "display_name": "Hudson, Troy Lee" } ], "advisors": [ { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "advisor", "display_name": "Aharonson, Oded" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." }, { "name": { "family": "Hecht", "given": "Michael H." }, "id": "Hecht-M-H", "role": "member", "display_name": "Hecht, Michael H." }, { "name": { "family": "Aharonson", "given": "Oded" }, "id": "Aharonson-O", "role": "member", "display_name": "Aharonson, Oded" } ], "option_major": [ "plansci" ], "doi": "10.7907/TGFK-MF98", "abstract": "Innovative experiments and models are used to explore the behavior of subsurface ice on Mars. Through communication with the atmosphere, the porous regolith of Mars hosts significant quantities of ice which grow, evolve, and are lost in response to climate changes. As a controlling property of rate of ice response to a changing equilibrium state, the diffusive properties of several regolith simulants are measured in Mars-like environments. Ice loss through a variety of particle sizes, particle size distributions, packing densities, and salt contents are examined and reveal that many unconsolidated media exhibit diffusion coefficients in the range of 2-6 cm2 s-1, indicating a response time on the order of several thousand years for ice within the upper meter of the regolith. Only high salt contents or mechanically packed micron-sized dust are observed to exhibit substantially lower coefficients, suggesting that strong diffusive barriers may not form as readily as previously invoked.
\r\n\t\r\nThe growth of ice directly from vapor under diffusive control is reproduced for Mars-like environmental conditions in the absence of the liquid phase. As predicted, ice deposits preferentially at grain contact points and the ice table interface is sharp and strongly controlled by near-surface temperature perturbations. The quantity of ice deposited as a function of depth and time accords well with new numerical models of vapor diffusion and ice deposition, though constriction of the pore space reduces the diffusion coefficient faster than originally expected.
\r\n\t\r\nA numerical model incorporating a fast solution to subsurface ice growth predicts near-surface ice contents for the last 300,000 years of Mars' history at high latitude locations, including specifically the Phoenix landing site. Several parameterizations of constriction developed from laboratory observations of ice growth are employed and compared. The thickness of the ice-free layer above the ice table has the strongest effect on the quantity of ice accumulated, though subsurface massive ice sheets and ice-free porosities also affect the ice profile. If predicted ice loss events have emptied the upper 0.5-1.0 m of regolith prior to 300,000 years ago, pore ice formed through diffusive processes will have been unable to fill the most rapidly accumulating depths with ice in this time unless ice-saturated regolith exists within ~0.5 m of the surface. Predictions of these experiments and models will be tested by the imminent arrival of the Phoenix Mars Lander and future Mars missions.
" }, { "name": "Konca, Ali Ozgun", "degree": "PhD", "year": "2008", "title": "Investigating Large Earthquake Rupture Kinematics from the Joint Analysis of Seismological, Geodetic and Remote Sensing Data", "advisor": "Helmberger, Donald V.; Avouac, Jean-Philippe", "url": "https://resolver.caltech.edu/CaltechETD:etd-05292008-113958", "creators": [ { "name": { "family": "Konca", "given": "Ali Ozgun" }, "id": "Konca-Ali-Ozgun", "orcid": "0000-0002-3198-7763", "display_name": "Konca, Ali Ozgun" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "co-advisor", "display_name": "Avouac, Jean-Philippe" } ], "committee": [ { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "chair", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/6B13-4M30", "abstract": "This thesis presents detailed studies of 4 large earthquakes. The 2006 Mw 8.6 Nias-Simeulue earthquake and 2007 Sumatra Mw 8.4 and 7.9 earthquake sequence which occurred on the Mentawai Island area of Sunda megathrust are studied using teleseismic, long period, GPS, and field data. Two crustal earthquakes, the 2005 Mw 7.6 Kashmir and the 1999 Mw 7.1 Duzce earthquakes, are studied using satellite image cross-correlation, seismic, GPS and SAR data.
\r\n\r\nThe 2005, Mw 8.6, Nias-Simeulue earthquake was caused by rupture of a portion of the Sunda megathrust offshore northern Sumatra. Based on the excitation of the normal modes and geodetic data, we put relatively tight constrains on the seismic moment and the fault dip, where the dip is determined to be 8o to10o with corresponding moments of 1.24 x 1022 to 1.00 x 1022 Nm, respectively. The geodetic constraints on slip distribution help to eliminate the trade-off between rupture velocity and slip kinematics. Our results indicate a relatively slow average rupture velocity of 1.5 to 2.5 km/s and long average rise time of up to 20 s.
\r\n\r\nOur study of the 2007 Mentawai Islands earthquakes shows the influence of permanent barriers on the extent of large megathrust ruptures, which can be a cause of some regularity of the seismic behavior, but also that the same portion of a megathrust can rupture in different patterns depending on whether asperities break as isolated seismic events or cooperate to produce a larger rupture. This variability arises mostly from the influence of nonpermanent barriers, probably zones with locally lower prestress due to the past earthquakes. The state of stress on that portion of the Sumatra megathrust was not adequate for the development of a single major large rupture at the time of this seismic crisis. However, the slip deficit that has accumulated since the 1833 and 1797 events remains large, and so is the potential for a large megahrust event in the Mentawai area.
\r\n\r\nWe analyzed the rupture process of 1999 Mw 7.1 Duzce earthquake using geodetic and seismic data. Applying subpixel cross-correlation of SPOT images acquired before and after the event, we mapped a continuous fault trace over 55 km; 15 km longer than the field reports. We investigated the spatiotemporal evolution of the earthquake using four-segment fault geometry with constraints on surface offsets based on satellite imagery, incorporated GPS and InSAR data and four strong-motion stations in the vicinity of the rupture. Our joint modeling shows a very stable slip distribution that does not depend on constraints imposed on rupture velocity. We show that no constant rupture velocity can explain the strong-motion data. Due to constraints from fault geometry and geodetic data, the rupture velocity has to vary rapidly. The rupture starts slow, accelerates to supershear speeds toward east and subsequently slows down. Supershear rupture is local and only toward the east of the hypocenter. Teleseismic data are consistent with the joint near-field model when 2 s time shifts are applied to their hand-picked arrivals. This implies that the weak beginning of the earthquake is not observable at teleseismic distances. This appears to be a common problem with teleseismic modeling and leads to more compact models with major slip around the hypocenter than the actual phenomenon. We performed teleseismic inversion models comparing four-segment fault geometry based on satellite imagery to one-segment geometry based on CMT solution. The four-segment model gives better predictions of near-field ground motions.
\r\n\r\nWe analyzed the Mw 7.6 Kashmir earthquake of October 8, 2005, using sub-pixel correlation of ASTER images to measure ground deformation, and modeling SAR imagery data along with seismic waveforms. The surface rupture is continuous over a distance of 75 km. The rupture lasted about 25 s and propagated up-dip and bilaterally by ~2 km/s, with a rise time of 2-5 s. The shallowness and compactness of the rupture, both in time and space, provide an explanation for the intensity of destructions. By comparing the teleseismic models with SAR data, we infer that satellite image correlation puts constraints on teleseismic models, which lead to more coherent models with the geodetic data. This kind of satellite image analysis could be achieved as soon as a postearthquake image is available, and would provide key information for early assessment of damages.
" }, { "name": "Nash, Cody Zane", "degree": "PhD", "year": "2008", "title": "Mechanisms and Evolution of Magnetotactic Bacteria", "advisor": "Kirschvink, Joseph L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05282008-140316", "creators": [ { "name": { "family": "Nash", "given": "Cody Zane" }, "id": "Nash-Cody-Zane", "display_name": "Nash, Cody Zane" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." } ], "committee": [ { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "chair", "display_name": "Newman, Dianne K." }, { "name": { "family": "Leadbetter", "given": "Jared R." }, "id": "Leadbetter-J-R", "orcid": "0000-0002-7033-0844", "role": "member", "display_name": "Leadbetter, Jared R." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/9M6S-MS85", "abstract": "Magnetotactic bacteria (MB) contain intracellular magnetic crystals of iron oxides and/or iron sulfides. These crystals and the membranes which enclose them are together known as magnetosomes. The crystals formed by MB fall into a narrow size range and have species-specific crystal morphologies. Magnetosomes are physically connected to the rest of the cell by actin-like filaments that are thought to allow the MB to take advantage of their passive orientation in the Earth\u2019s magnetic field to navigate more efficiently across chemical gradients. The large excess of crystals in most strains suggests that magnetosomes may also function as an iron reservoir or as a redox battery.
\r\n\r\nThis thesis describes a number of investigations of the MB. First, a set of genes was identified as being conserved uniquely among the MB by comparative genomics. This method was validated by finding many of the genes already known to be involved in magnetotaxis. Many additional genes were identified and some of these genes were found to cluster together. Three of these clusters were genetically interrupted to determine their role in magnetite biomineralization.
\r\n\r\nSecond, a transposon mutagenesis was undertaken to identify genes necessary for the magnetic phenotype of MB. Out of 5809 mutants screened, nineteen were found to be non- or partially magnetic. Fourteen of these have insertion sites in genes known to be involved in magnetotaxis. Five more were found to have insertions in previously unsuspected genes. The mutant phenotypes of the five mutants include the complete absence of magnetosomes, elongate crystals, reduced numbers of crystals and incomplete mineralization. These mutant strains were used to develop ferromagnetic resonance theory of isolated single-domain particles and biogenic particle identification.
\r\n\r\nThird, MB were discovered in hot springs and in hyper-saline, hyper-alkaline Mono Lake, CA. This extends the environmental range of MB to astro- and paleobiologically relevant environments. Magnetotactic Archaea were tentatively identified from Mono Lake, CA and are the first magnetotactic representatives of that domain.
\r\n" }, { "name": "Schaller, Emily Lauren", "degree": "PhD", "year": "2008", "title": "I. Seasonal Changes in Titan\u2019s Cloud Activity. II. Volatile Ices on Outer Solar System Objects", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05132008-173841", "creators": [ { "name": { "family": "Schaller", "given": "Emily Lauren" }, "id": "Schaller-Emily-Lauren", "display_name": "Schaller, Emily Lauren" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "member", "display_name": "Brown, Michael E." } ], "option_major": [ "plansci" ], "doi": "10.7907/YXFP-V230", "abstract": "This thesis presents studies in two distinct areas of observational planetary astronomy: studies of Saturn's moon Titan's seasonally varying tropospheric clouds, and studies of the surface compositions of Kuiper belt objects.
\r\n\r\nI. Understanding Titan's methane-based hydrological cycle and interpreting how and when the fluvial surface features seen by the Cassini Spacecraft were formed requires frequent long-term observations of Titan's clouds. Using nearly 100 adaptive optics images from the Keck and Gemini Telescopes from 2002-2006, we mapped the locations, frequencies, and magnitudes of Titan's clouds. We also developed a near-nightly cloud-monitoring program with the NASA Infrared Telescope Facility (IRTF). Nightly whole-disk infrared spectroscopy with IRTF allows us to determine Titan's total fractional cloud coverage, magnitudes, and altitudes, complementing and providing context for the relatively infrequent Cassini flybys. Taken together, the observations presented in this thesis have shown a striking seasonal change in the behavior of Titan's clouds as Titan has moved from southern summer solstice (October 2002) toward vernal equinox (August 2009) and indicate that seasonally varying insolation appears, to first order, to control Titan's cloud locations (Schaller et al. 2006a & 2006b).
\r\n\r\nII. Unlike Pluto and Eris, the vast majority of Kuiper belt objects (KBOs) are too small and too hot to retain volatile ices like CH4, N2, and CO on their surfaces to the present day. As a result, their infrared spectra are either dominated by involatile water ice or dark spectrally featureless material. To understand the dichotomy between volatile-rich and volatile-free surfaces in the outer solar system, we constructed a model of atmospheric escape of volatile ices over the age of the solar system (Schaller & Brown 2007a). We predicted that Quaoar, an object about half the size of Pluto, should be just capable of retaining methane ice to the present day. We observed Quaoar with the Keck Telescope, used Hapke theory to model its spectrum, and found that it contains a small amount of methane on its surface, indicating that it is a transition object between the dominant volatile-poor small KBOs and the few volatile-rich KBOs such as Pluto and Eris (Schaller & Brown 2007b).
" }, { "name": "Song, Teh-Ru Alex", "degree": "PhD", "year": "2008", "title": "Broad Band Modeling Earthquake Source and Upper Mantle Structure on Plate Boundary Zones", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05192008-121937", "creators": [ { "name": { "family": "Song", "given": "Teh-Ru Alex" }, "id": "Song-Teh-Ru Alex", "orcid": "0000-0003-3697-5881", "display_name": "Song, Teh-Ru Alex" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "chair", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geophys" ], "doi": "10.7907/K7RQ-MM41", "abstract": "Broadband seismic arrays have provided unprecedented data sets for seismologists to image the slips on faults and velocity structure beneath Earth's surface at all scales. In particular, plate boundary zones are the most complicated regions on the surface and full of complexities. Often that great earthquakes occur and rapid structural changes take place.
\r\n\r\nIn my thesis, one major effort is to use geophysical data and broadband seismic data to characterize the occurrences of great earthquakes at the subduction zone interface. Using gravity data from satellite and bathymetry model ETopo5, I recognized the strong correlation between gravity, topography and the occurrences of great earthquakes. Such a correlation gives a strong indication that lateral variations in the occurrences of great earthquakes at a given subduction zone are strongly linked to the fore-arc structure and topographic features such as basin and peninsulas. I also give robust estimates of the size and rupture extent of the recent 2004 Sumatra-Andaman giant earthquake using Earth's normal modes.
\r\n\r\nAnother part of my thesis consists of modeling waveform distortion and interference to study lithosphere and deep upper mantle structure. Modeling multi-pathing associated with sharp structure has become a very powerful method to delineate structure and explain the complicated behavior shown in the data recorded by dense arrays.
\r\n\r\nFuture research will focus on linking geodynamic models and seismic analysis of broadband waveform data as a way to further constrain the mantle structure and validate various geodynamic models.
" }, { "name": "Yang, Zhonghua", "degree": "PhD", "year": "2008", "title": "Constraining Global Carbon Budget Using Vertically-Integrated CO\u2082 Measurements", "advisor": "Wennberg, Paul O.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12132007-145150", "creators": [ { "name": { "family": "Yang", "given": "Zhonghua" }, "id": "Yang-Zhonghua", "display_name": "Yang, Zhonghua" } ], "advisors": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "advisor", "display_name": "Wennberg, Paul O." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "co-chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Toon", "given": "Geoffrey C." }, "id": "Toon-G-C", "role": "member", "display_name": "Toon, Geoffrey C." }, { "name": { "family": "Randerson", "given": "James T." }, "id": "Randerson-J-T", "role": "member", "display_name": "Randerson, James T." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" } ], "option_major": [ "geochem" ], "doi": "10.7907/3XR2-7185", "abstract": "I demonstrate that high precision measurements of the vertical-average dry volumn-mixing-ratio of atmospheric carbon dioxide (CO2 ) can be obtained from ground-based solar spectra. Oxygen measurements from the same spectra can be used to calibrate CO2 retrievals across different instruments, enabling a global network of column CO2 observations to be constructed. I also illustrate that this new type of data, together with aircraft pro\ufb01le CO2 observations, provide new constraints on global carbon \ufb02uxes.\r\n" }, { "name": "Hj\u00f6rleifsd\u00f3ttir, Vala", "degree": "PhD", "year": "2007", "title": "Earthquake Source Characterization Using 3D Numerical Modeling", "advisor": "Tromp, Jeroen", "url": "https://resolver.caltech.edu/CaltechETD:etd-03212007-170259", "creators": [ { "name": { "family": "Hj\u00f6rleifsd\u00f3ttir", "given": "Vala" }, "id": "Hj\u00f6rleifsd\u00f3ttir-Vala", "orcid": "0000-0003-3275-108X", "display_name": "Hj\u00f6rleifsd\u00f3ttir, Vala" } ], "advisors": [ { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "advisor", "display_name": "Tromp, Jeroen" } ], "committee": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "chair", "display_name": "Simons, Mark" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/M17S-7W40", "abstract": "To understand the physics of earthquakes, it is important to know what happens during individual events. Dissembling the information about the source process from the recorded seismograms is a difficult and non-unique process, as there are severe trade-offs between many of the source parameters. In this thesis we attempt to add information from frequencies not used during the initial modeling of individual events to put more constraints on the source process, to learn about specific source parameters important to the physics of earthquakes. We model earthquakes using a spectral element method for wave-propagation that accurately accounts for the Earth's 3D elastic structure. We study the rupture speed of the 2001 Kunlun, China earthquake, the continuity of slip during the 1998 Balleny Islands event and the duration of slip during the 2004 Sumatra-Andaman, Indonesia earthquake. Finally, we explore the feasibility of using adjoint methods to learn about the earthquake source." }, { "name": "Jiao, Yongqin", "degree": "PhD", "year": "2007", "title": "Physiological and Mechanistic Studies of Phototrophic Fe(II) Oxidation in Purple Non-sulfur Bacteria", "advisor": "Newman, Dianne K.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01242007-141030", "creators": [ { "name": { "family": "Jiao", "given": "Yongqin" }, "id": "Jiao-Yongqin", "orcid": "0000-0002-6798-5823", "display_name": "Jiao, Yongqin" } ], "advisors": [ { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "advisor", "display_name": "Newman, Dianne K." } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/XC8V-K304", "abstract": "Phototrophic Fe(II)-oxidizing bacteria use electrons from ferrous iron [Fe(II)] and energy from light to drive reductive CO\u2082 fixation. This metabolism is thought to be ancient in origin, and plays an important role in environmental iron cycling. It has been implicated in the deposition of Banded Iron Formations, a class of ancient sedimentary iron deposits. Consistent with this hypothesis, we discovered that hydrogen gas, a thermodynamically favorable electron donor to Fe(II), in an Archean atmosphere would not have inhibited phototrophic Fe(II) oxidation. To understand this physiology and the connection to BIF formation at the molecular level, the mechanisms of phototrophic Fe(II) oxidation were examined in two purple non-sulfur bacteria, Rhodopseudomonas palustris TIE-1 and Rhodobacter sp. SW2.
\r\n\r\nImportant advances were made in elucidating genes critical to phototrophic Fe(II) oxidation. In R. palustris TIE-1, the first genetically tractable phototrophic Fe(II) oxidizer isolated, transposon mutagenesis identified a putative integral membrane protein and a potential cobalamin (vitamin B\u2081\u2082) biosynthesis protein involved in Fe(II) oxidation.
\r\n\r\nIncreased expression of a putative decaheme c-type cytochrome, encoded by pioA, was observed when cells were grown under Fe(II)-oxidizing conditions. Two genes located immediately downstream of pioA in the same operon, pioB and pioC, encode a putative outer membrane beta-barrel protein and a putative high potential iron-sulfur protein, respectively. Deletion studies demonstrated that all three genes are involved in phototrophic Fe(II) oxidation.
\r\n\r\nIn Rhodobacter sp. SW2, a three-gene operon, foxEYZ, was found to be involved in phototrophic Fe(II) oxidation through heterologous expression in a close relative, Rhodobacter capsulatus SB1003. The first gene, foxE, encodes a novel c-type cytochrome located in the periplasm. Expression of foxE alone confers light-dependent Fe(II) oxidation activity to SB1003, but maximal activity is achieved when foxE is co-expressed with foxY and foxZ. FoxY appears to contain the redox cofactor pyrroloquinoline quinone and FoxZ a cytoplasmic membrane transporter. Recombinant PioC was overexpressed and partially purified from Escherichia coli.
\r\n\r\nThis research presents a detailed study of the physiology and genetics of phototrophic Fe(II) oxidation in two purple non-sulfur bacteria, and provides our first insight into the molecular mechanisms of this metabolism.
" }, { "name": "Kopp, Robert Evans, III", "degree": "PhD", "year": "2007", "title": "The Identification and Interpretation of Microbial Biogeomagnetism", "advisor": "Kirschvink, Joseph L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04122007-135320", "creators": [ { "name": { "family": "Kopp", "given": "Robert Evans, III" }, "id": "Kopp-Robert-Evans-III", "orcid": "0000-0003-4016-9428", "display_name": "Kopp, Robert Evans, III" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." } ], "committee": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "chair", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Grotzinger", "given": "John P." }, "id": "Grotzinger-J-P", "orcid": "0000-0001-9324-1257", "role": "member", "display_name": "Grotzinger, John P." } ], "option_major": [ "geobiol" ], "doi": "10.7907/83R3-VB23", "abstract": "Microbial activity plays a major role in the sedimentary iron cycle. Some microbes gain energy by reducing or oxidizing iron and thus induce changes in the sedimentary iron mineral assemblage. Magnetotactic bacteria engage in controlled, intracellular precipitation of magnetic iron minerals. These biological transformations are frequently a major influence on the magnetic properties of sediments. Understanding the biogeochemical iron cycle therefore facilitates the interpretation of sedimentary paleomagnetism; conversely, magnetic tools provide a non-destructive and rapid way of analyzing the biogeochemical iron cycle in modern and ancient environments.
\r\n\r\nFerromagnetic resonance (FMR) spectroscopy, a form of microwave spectroscopy, provides a rapid means of assessing internal fields generated in magnetic particles by interparticle interactions and particle anisotropy. It can therefore assess particle shape, arrangement, and heterogeneity. Because magnetotactic bacteria typically produce chains of crystals with narrow distributions of size and shape, FMR spectroscopy is well suited as a screening tool for identifying fossil magnetotactic bacteria (magnetofossils).
\r\n\r\nApplication of FMR and other techniques to modern carbonate sediments of the Triple Goose Creek region, Andros Island, Bahamas, reveals the contributions of magnetotactic bacteria, iron metabolizing bacteria, and sulfate reducing bacteria to the magnetization of carbonate sediments. In sediments above mean tide level, magnetofossils dominate sediment magnetism. Although stable remanent magnetization is preserved throughout the sediments, the quantity of biological magnetite diminishes by an order of magnitude in the iron reduction zone. Below this zone, the development of a sulfate reduction interval can lead to the authigenesis of magnetic iron sulfides. Supratidal portions of shallowing-upward parasequences in carbonate rocks therefore likely provide the most accurate record of syndepositional paleomagnetism.
\r\n\r\nAnomalous magnetic properties of clay deposited in the Atlantic Coastal Plain, New Jersey, during the Paleocene/Eocene Thermal Maximum (PETM) led previous authors to speculate that an extraterrestrial impact triggered the PETM. Reexamination of the clay using FMR and transmission electron microscopy reveals instead that the clay hosts abundant magnetofossils. The first identification of ancient biogenic magnetite using FMR indicates that the anomalous magnetic properties of PETM sediments were not produced by an impact, but instead reflect paleoenvironmental changes along the western North Atlantic margin.
" }, { "name": "Li, Liming", "degree": "PhD", "year": "2007", "title": "Dynamics of the Jovian Atmosphere from Observation and Theory", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02012007-204746", "creators": [ { "name": { "family": "Li", "given": "Liming" }, "id": "Li-Liming", "orcid": "0000-0002-5257-9849", "display_name": "Li, Liming" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "chair", "display_name": "Burnett, Donald S." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/6DAY-FJ03", "abstract": "The atmospheric dynamics of Jupiter is studied by the Cassini observations and numerical models.
\r\n\r\nThe multi-filter imaging data sets and the global thermal maps acquired by two instruments on Cassini--the Imaging Science Subsystem (ISS) and the Cassini Composite Infrared Spectrometer (CIRS) during the Jupiter flyby, are utilized to study atmospheric activities on Jupiter including small-scale spots, the Great Red Spot (GRS), the Dark Oval (DO), the vertical structure of zonal winds, and wave propagation. These new observations enrich the library of atmospheric activities and offer more clues and constraints on theoretical studies.
\r\n\r\nA reduced-gravity quasi-geostrophic (QG) model is combined with a parameterization of moist convections based on observations, to study the interaction between moist convection and zonal jets on Jupiter and Saturn. The numerical experiments support the idea that the zonal jets get their energy from moist convective events. Strong jets in Jupiter and Saturn, which violate the barotropic stability criterion, are reproduced by assuming westward flows in the deep underlying layer. Furthermore, our simulations suggest that the width and strength of jets on Jupiter and Saturn are controlled by the classical Rhines scale and a new velocity scale determined by characteristics of moist convection.
" }, { "name": "Miller, Sarah Ann", "degree": "PhD", "year": "2007", "title": "Alkaline Earth Element Partitioning in Simplified Magmatic Systems", "advisor": "Asimow, Paul David; Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05132007-103357", "creators": [ { "name": { "family": "Miller", "given": "Sarah Ann" }, "id": "Miller-Sarah-Ann", "display_name": "Miller, Sarah Ann" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "advisor", "display_name": "Asimow, Paul David" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geochem" ], "doi": "10.7907/90DK-3398", "abstract": "Trace element distributions between mineral and melt phases have proven to be important recorders of igneous differentiation histories, but this utility depends on thorough understanding of their partitioning behavior. We propose a theory for crystal-melt trace element partitioning that considers the energetic consequences of crystal-lattice strain, of multi component major-element silicate liquid mixing, and of trace element activity coefficients in melts. We demonstrate application of the theory using newly determined partition coefficients for Ca, Mg, Sr, and Ba between pure anorthite and seven CMAS liquid compositions at 1330 \u00b0C and 1 atm. By selecting a range of melt compositions in equilibrium with a common crystal composition at equal liquidus temperature and pressure, we have isolated the contribution of melt composition to divalent trace element partitioning in this simple system. The partitioning data are fit to Onuma curves with parameterizations that can be thermodynamically rationalized in terms of the melt major element activity product (aAl2O3)(aSiO22) and lattice strain theory modeling. Residuals between observed partition coefficients and the lattice strain plus major oxide melt activity model are then attributed to non-ideality of trace constituents in the liquids. The activity coefficients of the trace species in the melt are found to vary systematically with composition. Accounting for the major and trace element thermodynamics in the melt allows a good fit in which the parameters of the crystal lattice strain model are independent of melt composition.\r\n\r\nWe also present the first experimental measurements of mineral-melt radium partitioning. Ion probe analyses of coexisting anorthite and CMAS glass phases produce a molar DRa = 0.040 \u00b1 0.006 and DRa/DBa = 0.23 at 1400 \u00b0C and 1 atm. Our results indicate that lattice strain partitioning models fit the divalent (Ca, Sr, Ba, Ra) partition coefficient data of this study well, supporting previous work on crustal melting and magma chamber dynamics that has relied on such models to approximate radium partitioning behavior in the absence of experimentally determined values. " }, { "name": "Nadin, Elisabeth Sophia", "degree": "PhD", "year": "2007", "title": "Structure and History of the Kern Canyon Fault System, Southern Sierra Nevada, California", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05162007-094830", "creators": [ { "name": { "family": "Nadin", "given": "Elisabeth Sophia" }, "id": "Nadin-Elisabeth-Sophia", "display_name": "Nadin, Elisabeth Sophia" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" } ], "option_major": [ "geol" ], "doi": "10.7907/0WX9-S503", "abstract": "Results from field mapping and analyses of structural and petrochemical data from the southern Sierra Nevada batholith are presented to offer insight into the development of a major intra-arc fault system. The Kern Canyon fault system comprises an early ductile shear zone overprinted in its northern and central segments by a younger, recently active brittle fault. The divergence of these two faults at their middle latitudes poses a complex puzzle with regard to the physical and temporal evolution of deformation in the southern Sierra. Faulting began with ductile thrusting (the Proto-Kern Canyon fault zone) during emplacement of granitic plutons in the central to eastern part of the batholith at ca. 95 Ma. Early thrusting resulted in mismatched levels of pluton emplacement depths across the fault, truncation of significant regional geochemical markers in the batholith, and exhumation of the deepest level of the batholith in its southernmost region. Early ductile thrusting gave way to dextral strike-slip shearing by ca. 90 Ma. The youngest plutons in the batholith, emplaced along the fault between 90 and 80 Ma, are north-south elongate and reflect the dextral transpressional setting into which they were emplaced and deformed. Metamorphic country rocks were also highly sheared along the fault, and paleostress estimates from these deformed rocks suggest stresses along the middle segment of the Proto-Kern Canyon fault were 20\u201340 MPa, while strain rates were as high as 10-12 s-1 (comparable with other ductile faults). Strain studies and aspect ratios of igneous and metamorphic rocks strung out along the shear zone suggest ductile dextral displacement was 5\u201315 km. While ductile shearing ceased in the southern part of the batholith by ca. 85 Ma, it continued along the middle and northern segments of the Proto-Kern Canyon fault until ca. 80 Ma, when brittle deformation took over. This chronology suggests that the modern Kern Canyon fault, which shows ample evidence of activity into at least Quaternary time, initiated as a brittle structure in the southwestern part of the batholith, perhaps as early as 85 Ma, and shunted into the ductile shear zone at its middle latitudes ca. 5 Myrs later." }, { "name": "O'Leary, Julie Ann", "degree": "PhD", "year": "2007", "title": "Hydrogen Isotope Geochemistry of the Mantle: Constraints from Back Arc Basin Basalts and Mantle Xenoliths", "advisor": "Eiler, John M.; Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechETD:etd-12182006-072449", "creators": [ { "name": { "family": "O'Leary", "given": "Julie Ann" }, "id": "O'Leary-Julie-Ann", "display_name": "O'Leary, Julie Ann" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "advisor", "display_name": "Eiler, John M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." } ], "option_major": [ "geochem" ], "doi": "10.7907/6QQX-ED22", "abstract": "A new technique for measuring the hydrogen isotopic compositions of small quantities of hydrous and nominally anhydrous silicate materials was developed. The hydrogen isotopic composition of mantle derived basalts and nominally anhydrous minerals were measured to examine the systematics of the hydrogen isotope geochemistry of the mantle and to better constrain the mantle water cycle.
\r\n\r\nBack arc basin basalts (BABB) from the Mariana Trough are variably enriched in deuterium relative to mid ocean ridge basalts (MORBs). The \u03b4D values of 15 Mariana Trough BABB samples range from -74 \u2030 to -34 \u2030. High \u03b4D values in BABB lavas are associated with the trace element signature of H2O rich fluids derived from the altered oceanic crust that is subducting into the mantle. We calculate a mixing model to constrain the isotopic composition and trace element chemistry of the fluid infiltrating the back arc lava source region. The \u03b4D value of the infiltrating fluid is close to -30 \u2030. When the composition of the infiltrating fluid is compared to a forward calculation of the hydrogen isotopic evolution of altered oceanic crust it indicates that hydrous fluids in the back arc source region originate from the hydrated lithospheric mantle section of altered oceanic crust. Forward model calculations predict that hydrogen deeply subducted into the mantle may have an isotopic composition that is highly fractionated from the initial composition of altered oceanic crust.
\r\n\r\nPyroxenes from mantle xenoliths are deuterium depleted relative to all mantle materials, with \u03b4D values ~50 \u2030 lower than average MORB. Using continuous flow mass spectrometry we analyzed the hydrogen isotopic composition of clinopyroxene and orthopyroxene from mantle xenoliths. Our results confirm the previous observations of very low \u03b4D values for xenoliths from continental interiors but found \u03b4D values similar to MORB in Central American arc xenoliths. The relationship between \u03b4D and water content observed in pyroxenes suggests that most mantle xenoliths have undergone extensive degassing (40% \u2013 60%) and therefore the hydrogen content of upper mantle minerals may be higher than previously thought.
" }, { "name": "Yan, Zhimei", "degree": "PhD", "year": "2007", "title": "Regional Mapping of the Crustal Structure in Southern California", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06212006-181145", "creators": [ { "name": { "family": "Yan", "given": "Zhimei" }, "id": "Yan-Zhimei", "orcid": "0000-0002-2421-8296", "display_name": "Yan, Zhimei" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/K9B8-Y639", "abstract": "This thesis presents a study of the lateral variations of the crustal structure in Southern California from the waveform data recorded by the Southern California Seismic Network (SCSN) stations, the LARSE I and II surveys. The Receiver Function method is used to process the teleseismic waveform data to map the lateral variations of the crustal structure. A first arrival analysis of the LARSE II refraction data is used to determine the upper crustal velocity structure (less than 4 km).
\r\n\r\nA 2-D upper crustal structure with seven steeply dipping faults was constructed from the LARSE II seismic refraction survey. The regional upper plate complexes of the granitic and gneissic crystalline rocks are observed to yield consistently anomalous low velocities of 3.7-4.3 km/s as compared with the expected velocities for the constituent rock types, which is inferred to result from the extreme shearing, brittle fracturing and related retrogressive hydration reactions. The faults are identified from the distinctive features in the first arrivals and they correlate very well with the geologically mapped faults.
\r\n\r\nLateral variations of the crustal structure in Southern California are imaged from the back-azimuthal-grouped receiver functions (RFs) of the SCSN stations and the LARSE I, II passive stations. Large variations in the crustal structure are commonly observed beneath the San Gabriel Mountains (SGM), the western Peninsula Ranges, and the eastern Mojave Desert, such as the transition from 2-layered crustal structure to 3-layered from the eastern to the western SGM and the large offsets on the Moho among the different RF station groups. Deep Moho of 34-39 km is observed beneath the western Peninsula Ranges (WPR), Sierra Nevada and the San Bernardino Mountains and no regional root is observed beneath the San Gabriel Mountains.
\r\n\r\nSynthetic waveform modeling of the anomalous features in the RFs for two stations in the eastern San Gabriel Mountains indicates the existence of a flat-topped notch structure on the Moho. Moho is inferred to get shallowed from 37-39 km north of the San Andreas Fault, 33-35 km south of the San Gabriel Fault to a depth of ~29 km beneath the Mt. Baldy block.
" }, { "name": "Ai, Huirong (Anita)", "degree": "PhD", "year": "2006", "title": "Shock-Induced Damage in Rocks: Application to Impact Cratering", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05262006-173355", "creators": [ { "name": { "family": "Ai", "given": "Huirong (Anita)" }, "id": "Ai-Huirong-Anita", "display_name": "Ai, Huirong (Anita)" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "chair", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Ravichandran", "given": "Guruswami" }, "id": "Ravichandran-G", "role": "member", "display_name": "Ravichandran, Guruswami" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." } ], "option_major": [ "geol" ], "doi": "10.7907/39ZE-SY71", "abstract": "Shock-induced damage beneath impact craters is studied in this work. Two representative terrestrial rocks, San Marcos granite and Bedford limestone, are chosen as test target. Impacts into the rock targets with different combinations of projectile material, size, impact angle, and impact velocity are carried out at cm scale in the laboratory.
\r\n\r\nShock-induced damage and fracturing would cause large-scale compressional wave velocity reduction in the recovered target beneath the impact crater. The shock-induced damage is measured by mapping the compressional wave velocity reduction in the recovered target. A cm scale nondestructive tomography technique is developed for this purpose. This technique is proved to be effective in mapping the damage in San Marcos granite, and the inverted velocity profile is in very good agreement with the result from dicing method and cut open directly.
\r\n\r\nBoth compressional velocity and attenuation are measured in three orthogonal directions on cubes prepared from one granite target impacted by a lead bullet at 1200 m/s. Anisotropy is observed from both results, but the attenuation seems to be a more useful parameter than acoustic velocity in studying orientation of cracks.
\r\n\r\nOur experiments indicate that the shock-induced damage is a function of impact conditions including projectile type and size, impact velocity, and target properties. Combined with other crater phenomena such as crater diameter, depth, ejecta, etc., shock-induced damage would be used as an important yet not well recognized constraint for impact history.
\r\n\r\nThe shock-induced damage is also calculated numerically to be compared with the experiments for a few representative shots. The Johnson-Holmquist strength and failure model, initially developed for ceramics, is applied to geological materials. Strength is a complicated function of pressure, strain, strain rate, and damage. The JH model, coupled with a crack softening model, is used to describe both the inelastic response of rocks in the compressive field near the impact source and the tensile failure in the far field. The model parameters are determined either from direct static measurements, or from indirect numerical adjustment. The agreement between the simulation and experiment is very encouraging.
" }, { "name": "Basu, Shabari", "degree": "PhD", "year": "2006", "title": "Simulations of the Martian Dust Cycle with a General Circulation Model", "advisor": "Richardson, Mark I.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09232005-154100", "creators": [ { "name": { "family": "Basu", "given": "Shabari" }, "id": "Basu-Shabari", "display_name": "Basu, Shabari" } ], "advisors": [ { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "advisor", "display_name": "Richardson, Mark I." } ], "committee": [ { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "chair", "display_name": "Richardson, Mark I." } ], "option_major": [ "plansci" ], "doi": "10.7907/BDB8-Z423", "abstract": "The Martian seasonal dust cycle is examined with a General Circulation Model (GCM) that treats dust as a radiatively and dynamically interactive trace species. Dust injection is parameterized as being due to convective processes (such as dust devils) and model-resolved wind stresses. Multi-year Viking and Mars Global Surveyor mission air temperature data sets are used to quantitatively assess the quality of simulations. Varying the three free parameters for the two dust injection schemes (rate parameters for the two schemes and a threshold for wind-stress lifting), we find that northern spring and summer temperatures, which are observed to repeat very closely each year, can be reproduced by the model if the background dust haze is supplied by convective lifting. To obtain spontaneous and variable dust storms, dust injection due to high threshold and high rate stress lifting must be added. The convective scheme is found unable to generate a dust storm but is a good candidate for background dust (in agreement with imaging observations e.g., dust devils). Combining the convective scheme and high-threshold stress lifting, we obtain a \"best fit\" multi-year simulation, which includes simulation of both a realistic thermal state in northern spring and summer and, for the first time, the spontaneous generation of inter-annually-variable global dust storms. Our results support the idea that variable and spontaneous global dust storm behavior can emerge from a periodically forced system (the only forcing being the diurnal and seasonal cycles) when the dust injection mechanism involves an activation threshold. The general circulation model is also used to evaluate changes to the circulation and dust transport in the Martian atmosphere for simulations with a finite supply of dust on the surface. The focus is on changes to atmospheric temperatures and dust-related surface features, as these may potentially be verified by observations. In this work, the use of a finite surface dust supply increases the amount of inter-annual variability the system is capable of producing. This is due to a new set of initial conditions, in the form of available surface dust, being present at the beginning of each storm season." }, { "name": "Eltgroth, Selene Farrell", "degree": "PhD", "year": "2006", "title": "Unraveling Deep-Ocean Connections to Climate with Deep-Sea Coral Records of Radiocarbon and Cd/Ca", "advisor": "Adkins, Jess F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05262006-110220", "creators": [ { "name": { "family": "Eltgroth", "given": "Selene Farrell" }, "id": "Eltgroth-Selene-Farrell", "display_name": "Eltgroth, Selene Farrell" } ], "advisors": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "advisor", "display_name": "Adkins, Jess F." } ], "committee": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "chair", "display_name": "Eiler, John M." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Pasquero", "given": "Claudia" }, "id": "Pasquero-C", "role": "member", "display_name": "Pasquero, Claudia" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." } ], "option_major": [ "geochem" ], "doi": "10.7907/ZXHZ-EH83", "abstract": "We generated records of radiocarbon and trace metals in deep-sea corals to investigate the role of the deep ocean during episodes of rapid environmental change. Our record of radiocarbon ages measured in a modern deep-sea coral from the northeastern Atlantic shows the transfer of bomb radiocarbon from the atmosphere to the deep ocean. We detect bomb radiocarbon at the coral growth site starting in 1975\u20131979. Our record documents a Delta14C increase from \u201380 \u00b1 1\u2030 (average 1930\u20131979) to a plateau at \u201339 \u00b1 2\u2030 (average 1994\u20132001). From a suite of fossil deep-sea corals, variability in North Atlantic intermediate water Delta14C during the Younger Dryas (13.0\u201311.5 ka) supports a link between abrupt climate change and intermediate ocean circulation. We observe rapid shifts in deep-sea Delta14C that require the repositioning of large Delta14C gradients within the North Atlantic. The shifts are consistent with changes in the rate of North Atlantic Deep Water formation. We also observe a decadal scale event at 12.0 ka that is marked by the transient return of radiocarbon to the eastern and western basins of the North Atlantic.
\r\n\r\nTo develop a nutrient proxy for use in deep-sea corals, we measured Cd/Ca in 14 modern corals. Several of these corals had anomalously high Cd/Ca that we explain with a systematic bias in Cd/Ca obscuring the signal of seawater Cd/Ca. When these high Cd/Ca corals are removed from the calibration, the best-fit coral-water partition coefficient is 1.3 \u00b1 0.1. Examining Cd/Ca in fossil deep-sea corals, we find that our coral from the Younger Dryas (12.0 ka) resembles the high Cd/Ca corals of the modern calibration and probably does not reflect seawater Cd/Ca. The Cd/Ca record from a 15.4 ka coral resembles our low Cd/Ca calibration samples and probably reflects average seawater Cd/Ca.
\r\n" }, { "name": "Krakauer, Nir Yitzhak", "degree": "PhD", "year": "2006", "title": "Characterizing Carbon-Dioxide Fluxes from Oceans and Terrestrial Ecosystems", "advisor": "Schneider, Tapio", "url": "https://resolver.caltech.edu/CaltechETD:etd-05262006-111949", "creators": [ { "name": { "family": "Krakauer", "given": "Nir Yitzhak" }, "id": "Krakauer-Nir-Yitzhak", "orcid": "0000-0002-4926-5427", "display_name": "Krakauer, Nir Yitzhak" } ], "advisors": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "advisor", "display_name": "Schneider, Tapio" } ], "committee": [ { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "chair", "display_name": "Schneider, Tapio" }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Randerson", "given": "James T." }, "id": "Randerson-J-T", "role": "member", "display_name": "Randerson, James T." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "geochem" ], "doi": "10.7907/8B12-1G19", "abstract": "Understanding the processes that change the amount of carbon stored in the ocean and in the land biota, with their implications for future climate and ecology, is a fundamental goal of earth-system science. I have developed, refined, and applied several approaches that combine data analysis and modeling to better understand processes affecting carbon fluxes.
\r\n\r\n(1) Using a database of tree-ring widths from some 40,000 trees, I looked at the impact of large volcanic eruptions in the past millennium on tree growth globally. I found a decline in growth north of 45\u00b0 N lasting for several years after eruptions, presumably due to eruption-associated cooling, and no significant impact at lower latitudes. This argues against the hypothesis that the increased diffuse-light fraction due to volcanic aerosols greatly increased plant carbon uptake after the 1991 Pinatubo eruption, suggesting that other explanations are needed for the slow increase in atmospheric CO2 levels in the early 1990s.
\r\n\r\n(2) I applied generalized cross-validation (GCV) to the problem of estimating a regional CO2 source/sink pattern consistent with observed geographic variation in atmosphere CO2 levels. I showed that GCV works for selecting data and regional-flux uncertainty levels to assume for this inverse problem; these have usually been estimated rather arbitrarily, though they can have a large impact on the solution.
\r\n\r\n(3) The air-sea gas transfer velocity determines how fast the surface ocean adjusts to a change in atmospheric composition, and hence is important for understanding ocean CO2 uptake. By modeling the ocean\u2019s adjustment to fluctuations in atmospheric carbon isotope composition and analyzing a variety of atmosphere and ocean bomb-14C and 13C measurements, I estimated regional and global mean gas transfer velocities, concluding that there may be less latitudinal variation in the gas transfer velocity than usually thought \u2013 implying, for example, relatively low CO2 uptake in the Southern Ocean.
" }, { "name": "Liang, Mao-Chang", "degree": "PhD", "year": "2006", "title": "Chemical and Dynamical Processes in the Atmospheres of I. Ancient and Present-Day Earth, II. Jupiter and Galileo Satellite, III. Extrasolar \u201cHot Jupiters\u201d", "advisor": "Yung, Yuk L.; Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05032006-214832", "creators": [ { "name": { "family": "Liang", "given": "Mao-Chang" }, "id": "Liang-Mao-Chang", "orcid": "0000-0002-5294-9344", "display_name": "Liang, Mao-Chang" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Sari", "given": "Re'em" }, "id": "Sari-R", "orcid": "0000-0002-1084-3656", "role": "member", "display_name": "Sari, Re'em" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/8HSF-CA03", "abstract": "When exposed to stellar UV radiation, chemical processes will be governed not only by temperature/pressure but also the spectrum of the incoming dissociative photon flux; the system will approach kinetic, or photochemical, equilibrium, instead of thermochemical equilibrium. Over the previous decades, photochemistry has proven to be a powerful tool for predicting the chemical composition in the atmospheres of solar planets and their satellites. For example, the ozone layer in our own atmosphere (stratosphere) is a photochemical product of oxygen. In this thesis, I apply a photochemical model to the study of a variety of astronomical objects: the Earth, Jupiter, the Galilean satellite Callisto, and extrasolar \"hot Jupiters\" (HD 209458b). For the Earth, a method for utilizing the isotopic composition of CO2 and N2O to monitor global changes due to these two greenhouse gases is developed. For objects other than the Earth, the model facilitates in the interpretation of data acquired by remote (telescopic) and in situ (spacecraft) measurements. The ultimate goal is to understand the conditions of chemical and physical environments in protoplanetary nebulae, which will provide clues as to the formation of planetary systems; the synthesis of organic compounds which could lead to the appearance of life; and the evolution of planetary atmospheres such as the formation of Titan's nitrogen-rich atmosphere." }, { "name": "Liu, Junjun", "degree": "PhD", "year": "2006", "title": "Interaction of Magnetic Field and Flow in the Outer Shells of Giant Planets", "advisor": "Stevenson, David John; Goldreich, Peter Martin; Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05252006-223939", "creators": [ { "name": { "family": "Liu", "given": "Junjun" }, "id": "Liu-Junjun", "display_name": "Liu, Junjun" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "advisor", "display_name": "Stevenson, David John" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "advisor", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Sari", "given": "Re'em" }, "id": "Sari-R", "orcid": "0000-0002-1084-3656", "role": "member", "display_name": "Sari, Re'em" }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "orcid": "0000-0001-5687-2287", "role": "member", "display_name": "Schneider, Tapio" } ], "option_major": [ "plansci" ], "doi": "10.7907/4PVM-0G30", "abstract": "This study of the interaction of magnetic field and flow in the outer shells of giant planets consists of three parts.
\r\n\r\nPart one: The atmospheres of Jupiter and Saturn exhibit strong and stable zonal winds. Busse suggested that they might be the surface expression of deep flows on cylinders. However, the deep flow hypothesis experiences difficulty when account is taken of the electrical conductivity of molecular hydrogen as measured in shockwave experiments. The deep zonal flow of an electrically conducting fluid would produce a toroidal magnetic field, an associated poloidal electrical current, and Ohmic dissipation. In steady state, the total Ohmic dissipation cannot exceed the planet's net luminosity. If we assume that the observed zonal flow penetrates along cylinders until it is truncated to (near) zero at some spherical radius, the upper bound on Ohmic dissipation constrains this radius to be no smaller than 0.95 Jupiter radius and 0.87 Saturn radius. The truncation of the cylindrical flow in the convective envelope requires an appropriate force to break the Taylor-Proudman constraint. We have been unable to identify any plausible candidate. Thus we conclude that deep-seated cylindrical flows do not exist.
\r\n\r\nPart two: A fluid shell with sufficient electrical conductivity and azimuthal velocity shear outside of the dynamo generation region can attenuate the non-axisymmetric component of the magnetic field. However, the interaction of the axisymmetric component of the magnetic field and the zonal flow is able to reduce the magnitude of zonal flow. The dimensionless number characterizing this reduction is the Chandrasekhar number. The smaller Saturnian field may allow a larger velocity shear and a greater attenuation of the non-axisymmetric field, thereby providing a possible explanation for the nearly axisymmetric field.
\r\n\r\nPart three: Combining the study for the attenuation effect produced by the semi-conducting layer and the observation of the magnetic field by Galileo and Voyager, we find the possible outer boundary of the dynamo generation zone is at 0.86 Jupiter radius. The magnetic fields generated in the outer shell are dictated by a length scale comparable to the scale height of electrical conductivity, which is much smaller than the radius of the planet.
" }, { "name": "Liu, Qinya", "degree": "PhD", "year": "2006", "title": "Spectral-Element Simulations of 3-D Seismic Wave Propagation and Applications to Source and Structural Inversions", "advisor": "Tromp, Jeroen", "url": "https://resolver.caltech.edu/CaltechETD:etd-05262006-172954", "creators": [ { "name": { "family": "Liu", "given": "Qinya" }, "id": "Liu-Qinya", "orcid": "0000-0002-1071-2314", "display_name": "Liu, Qinya" } ], "advisors": [ { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "orcid": "0000-0002-2742-8299", "role": "advisor", "display_name": "Tromp, Jeroen" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "orcid": "0000-0002-2742-8299", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/JZ6J-0257", "abstract": "This thesis presents a concise introduction to the spectral-element method and its applications to the simulation of seismic wave propagation in 3-D earth models. The spectral-element method is implemented in the regional scale for a 3-D integrated southern California velocity model. Significantly better waveform fits are achieved for the 3-D synthetics calculated compare to the 1-D synthetics generated from the 1-D standard southern California model, especially for many basin stations where strong amplifications are observed due to the very low wave-speed sediments. A hypothetical earthquake rupturing from northeast to southwest at the southern end of the San Andreas fault is simulated to improve our understanding of the seismic hazards in the Salton Trough region.
\r\n\r\nWith the improved 3-D Green's function, we perform source inversions for both the source mechanisms and event depths of $M_w geq 3.5$ earthquakes in southern California. The inversion results generally agree well with the results obtained by other traditional methods, but with significantly more stations used in the inversions. Time shifts are generally required to align the data and the synthetics, which provides a great dataset for the improvement of the 3-D velocity models in southern California.
\r\n\r\nWe use the adjoint method to formulate the tomographic inverse problem based upon a 3-D initial model. We calculate the sensitivity kernels, a key component of the tomographic inversion, that relate the perturbations of observations to the perturbations of the model parameters. These kernels are constructed by the interaction of the regular forward wavefield and the adjoint wavefield generated by putting the time-reversed signals at the receivers as simultaneous adjoint sources. We compute the travel-time sensitivity kernels for typical phases in both regional and global problems for educational purposes, and outline the procedures of applying the conjugate-gradient method to solve both source and structural inversion problems.
" }, { "name": "Shyu, J. Bruce Hao-Te Hsu", "degree": "PhD", "year": "2006", "title": "A Neotectonic Model of Taiwan, with a Focus on the Longitudinal Valley Suture", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12252005-151244", "creators": [ { "name": { "family": "Shyu", "given": "J. Bruce Hao-Te Hsu" }, "id": "Shyu-J-Bruce-Hao-Te Hsu", "orcid": "0000-0002-2564-3702", "display_name": "Shyu, J. Bruce Hao-Te Hsu" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "chair", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geol" ], "doi": "10.7907/X1XD-SB94", "abstract": "The disastrous effects of the 1999 Chi-Chi earthquake in Taiwan demonstrated an urgent need for better knowledge of the island's potential earthquake sources as well as their neotectonic context. Toward this end, we have utilized digital elevation models of the island to prepare a neotectonic map of Taiwan and proposed a neotectonic model for the orogen. Taiwan's numerous active faults and folds reveal that the active orogen is a tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the Eurasian continental margin. The collision and suturing in the southern part of the orogen and the post-collisional collapse and extension in the island's northern and northeastern flanks have produced eleven distinct neotectonic domains. Each domain is defined by a distinctive suite of active structures. In most of the domains, the size of the principal active fault is large enough to produce future earthquakes with magnitudes in the mid-7 range.
\r\n\r\nIn order to further understand the suturing processes, we have focused the second part of our investigation on the Longitudinal Valley suture in eastern Taiwan. The earthquakes of November 1951 within this suture constitute one of the most destructive seismic episodes in Taiwan's history. The surface ruptures of the earthquakes consist of three distinct sections, two of which are along segments of the Longitudinal Valley fault. From fluvial terraces along the Hsiukuluan River, we have reconstructed a shallow listric geometry for the Longitudinal Valley fault. On the other hand, many uplifted lateritic fluvial terraces along the eastern flank of the Central Range indicate the presence of a west-dipping Central Range reverse fault. We believe the majority of the horizontal shortening across the Longitudinal Valley suture is accommodated by the slip on the Longitudinal Valley fault. The remaining horizontal convergence may be absorbed by a combination of slip on the Central Range fault and subsidence of the Longitudinal Valley floor. The along-strike difference in geometry of the two major faults along the Longitudinal Valley is likely the manifestation of the northward maturation of the suturing of the Luzon volcanic arc to the Central Range continental sliver.
" }, { "name": "Smith, Deborah Elaine", "degree": "PhD", "year": "2006", "title": "A New Paradigm for Interpreting Stress Inversions from Focal Mechanisms: How 3D Stress Heterogeneity Biases the Inversions Toward the Stress Rate", "advisor": "Heaton, Thomas H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05252006-191203", "creators": [ { "name": { "family": "Smith", "given": "Deborah Elaine" }, "id": "Smith-Deborah-Elaine", "orcid": "0000-0002-8317-7762", "display_name": "Smith, Deborah Elaine" } ], "advisors": [ { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "advisor", "display_name": "Heaton, Thomas H." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "orcid": "0000-0002-2742-8299", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Lapusta", "given": "Nadia" }, "id": "Lapusta-N", "orcid": "0000-0001-6558-0323", "role": "member", "display_name": "Lapusta, Nadia" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/42NY-WV90", "abstract": "Current stress studies often utilize stress inversions of earthquake focal mechanisms to estimate four parameters of the spatially uniform stress tensor, three principal stress orientations, and a ratio of the principal stresses. An implicit assumption in these studies is that earthquakes are good random samplers of stress; hence, the set of earthquake focal mechanisms within some region can be used to estimate the spatial mean stress state within the region. Numerical simulations indicate some regions, such as Southern California, have sufficient stress heterogeneity to bias the stress inversions toward the stress rate orientation and that stress studies using stress inversions need to be reinterpreted by taking this bias into account. An outline of how to subtract out this bias to yield the actual spatial mean stress is presented.
\r\n\r\nNumerical simulations demonstrate that spatially heterogeneous stress in 3D can bias stress inversions of focal mechanisms toward the stress rate tensor instead of the stress. Stochastic models of 3D spatially heterogeneous stress are created, synthetic earthquake focal mechanisms are generated using the Hencky-Mises plastic yield criterion, and results are compared with Hardebeck's Southern California earthquake catalog [Hardebeck, 2006]. The presence of 3D spatial stress heterogeneity biases which orientations are most likely to fail, a bias toward the stress rate tensor. When synthetic focal mechanisms are compared to real data, estimates of two stress heterogeneity parameters for Southern California are obtained: 1) A spatial smoothing parameter, \u03b1\u22480.8, where \u03b1 describes the spectral falloff of 1D cross sections through a 3D grid for the three principal stresses and three orientation angles. 2) A heterogeneity ratio, HR \u2248 1.25, which describes the relative amplitude of the spatial stress heterogeneity to the spatial mean stress. The estimate for \u03b1 is tentative; however, varying \u03b1 for \u03b1 \u2264 1.0 has little to no effect on the observation that spatially heterogeneous stress biases failures toward the stress rate. The estimate for HR is more robust and produces a bias toward the stress rate of approximately 40%. If the spatial mean stress and the stress rate are not aligned, the average focal mechanism failure mechanism should yield a stress estimate from stress inversions, approximately halfway between the two.
" }, { "name": "Tan, Eh", "degree": "PhD", "year": "2006", "title": "I. Multi-Scale Dynamics of Mantle Plumes, and II. Compressible Thermochemical Convection and the Stability of Mantle Superplumes", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05142006-210236", "creators": [ { "name": { "family": "Tan", "given": "Eh" }, "id": "Tan-Eh", "orcid": "0000-0002-1815-9613", "display_name": "Tan, Eh" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/ZQ5F-9823", "abstract": "The dynamic interaction of mantle plumes with subducted slabs and plate-scale flow is studied in Part I. We found that plumes preferentially develop on the edge of slabs and that a substantial amount of hot mantle can be trapped beneath slabs over long periods of time, leading to \"mega-plume\" formation. We used the solver-coupling technique to study the deflection of plume conduits and compare our result with the parameterized approach. The stability of mantle superplumes in compressible thermo-chemical convection is studied in Part II. The depth-dependent chemical density profile, caused by composition-dependent compressibility, is the preferred mechanism to stabilize the superplum" }, { "name": "Tan, Ying", "degree": "PhD", "year": "2006", "title": "Broadband Waveform Modeling Over a Dense Seismic Network", "advisor": "Helmberger, Donald V.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechETD:etd-06012006-174015", "creators": [ { "name": { "family": "Tan", "given": "Ying" }, "id": "Tan-Ying", "display_name": "Tan, Ying" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "orcid": "0000-0002-2742-8299", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "orcid": "0000-0001-6025-8925", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "geophys" ], "doi": "10.7907/F4DB-2K48", "abstract": "We developed a \"two-way\" calibration technique for studying clustered events, particularly their mechanisms and rupture directivities. First, we demonstrate that the magnitude 4 events with known source mechanisms can be used to calibrate the path effects on the short-period (0.5-2 sec) P waves, so that the corrected P waves can be modeled for determining focal mechanisms of the smaller events. The correction is formulated in terms of a station-specific \"Amplitude Amplification Factor\" (AAF), whose origin is mainly due to the site effect. Second, we show that the smaller events with radiation pattern corrections provide excellent empirical Green's functions (EGFs) for investigating the detailed rupture processes of the magnitude 4 events. In Chapter 2 of this thesis, we present the application of our methods to the 2003 Big Bear sequence.
\r\n\r\nA new technique CAPloc to retrieve full source parameters of small seismic events from regional seismograms is developed, which include origin time, epicenter location, depth, focal mechanism, and moment magnitude. In particular, we tested whether our new method could produce satisfactory results with as few as two stations, so that we can improve source estimates of poorly monitored events with sparse waveform data. We conducted the test in the Tibetan plateau. The focal mechanisms and locations determined from only two stations agree well with those from a well-distributed PASSCAL array.
\r\n\r\nWe use 49 Tonga-Fiji events recorded at the broadband TriNet array, southern California to develop a pure path upper-mantle shear velocity model. At the epicentral distances of 70-95 degree, multi-bounce S waves up to S5, including the guided waves, are observed and modeled to constrain the radial velocity structure. Our preferred model PAC06 contains a fast lid (Vsh=4.78 km/sec, Vsv=4.58 km/sec) ~60 km thick, and a prominent low velocity zone (LVZ) with the lowest velocities Vsh=4.34 km/sec, and Vsv=4.22 km/sec. Besides the 406 km and 651 km discontinuities, PAC06 also has a small (~1%) velocity jump at ~516 km. We consider these main features of PAC06 to be well determined, since PAC06 explains a large data set from various events. Therefore, it is ideally suited for comparing with mineralogical models.
" }, { "name": "Bosak, Tanja", "degree": "PhD", "year": "2005", "title": "Laboratory Models of Microbial Biosignatures in Carbonate Rocks", "advisor": "Newman, Dianne K.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12102004-144939", "creators": [ { "name": { "family": "Bosak", "given": "Tanja" }, "id": "Bosak-Tanja", "orcid": "0000-0001-5179-5323", "display_name": "Bosak, Tanja" } ], "advisors": [ { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "advisor", "display_name": "Newman, Dianne K." } ], "committee": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "chair", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Sessions", "given": "Alex L." }, "id": "Sessions-A-L", "orcid": "0000-0001-6120-2763", "role": "member", "display_name": "Sessions, Alex L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Newman", "given": "Dianne K." }, "id": "Newman-D-K", "orcid": "0000-0003-1647-1918", "role": "member", "display_name": "Newman, Dianne K." }, { "name": { "family": "Orphan", "given": "Victoria J." }, "id": "Orphan-V-J", "orcid": "0000-0002-5374-6178", "role": "member", "display_name": "Orphan, Victoria J." } ], "option_major": [ "geobiol" ], "doi": "10.7907/NJ3F-PJ25", "abstract": "Enigmatically shaped laminated carbonate rocks called stromatolites dominated shallow marine environments for the first 80% of Earth\u2019s history, and are potentially the oldest macrofossils. While these ancient rocky cones and domes occasionally resemble some modern microbial structures, it is unclear whether their formation required biological processes or they could have been produced abiotically. To develop criteria for assessing the biogenicity of ancient stromatolites, we precipitated calcium carbonate in the laboratory in the presence and absence of modern microorganisms under chemical conditions relevant for the early Earth. Using this novel approach, we disproved the paradigm that microbial sulfate reduction, a metabolism important for the formation of modern stromatolites, was responsible for the precipitation of their ancient counterparts. We also produced the first laboratory evidence that sub-micron and micron-sized pores occured in rapidly precipitating carbonate rocks only when microbes were present. Applying a set of experimentally established criteria to modern environmental samples and ancient stromatolites, we found similar biogenic microporosity in some modern fast-precipitating carbonates and in ancient stromatolites. In our abiotic laboratory precipitates, we observed calcite grains that resembled putatively biogenic features from the rock record called peloids. We explained their shape and growth pattern by purely inorganic parameters, underscoring the need for caution when interpreting seemingly biogenic fabrics in the rock record of Earth and other planets. Finally, we showed that active anoxygenic photosynthesis by Rhodopseudomonas palustris could stimulate the precipitation of calcite even in solutions that were well-buffered by a high concentration of dissolved inorganic carbon. Future studies of the relationship between photosynthetic biofilms, the environmental parameters such as light and currents, and the morphology of carbonate precipitates are key to recognizing potential biosignatures produced by similar organisms in the in situ precipitated stromatolites and other microbialites." }, { "name": "Dmochowski, Jane Ellen", "degree": "PhD", "year": "2005", "title": "Application of MODIS-ASTER (Master) Simulator Data to Geological Mapping of Young Volcanic Regions in Baja California, Mexico", "advisor": "Stock, Joann M.; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05262005-150027", "creators": [ { "name": { "family": "Dmochowski", "given": "Jane Ellen" }, "id": "Dmochowski-Jane-Ellen", "orcid": "0000-0003-4491-2258", "display_name": "Dmochowski, Jane Ellen" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geophys" ], "doi": "10.7907/DW9V-3831", "abstract": "Visible, near infrared, short-wave infrared, and thermal infrared multi-channel remote sensing data, MODIS-ASTER (MASTER), are used to extract geologic information from two volcanic regions in Baja California, Mexico: Tres Virgenes-La Reforma Volcanic Region and the volcanic island of Isla San Luis. The visible and near infrared and short-wave infrared data were atmospherically corrected and classified. The resulting classification roughly delineates surfaces that vary in their secondary minerals. Attempts to identify these minerals using ENVI's Spectral Analyst(TM) were moderately successful.
\r\n\r\nThe analysis of the thermal infrared data utilizes the shift to longer wavelengths in the Reststrahlen band as the mineralogy changes from felsic to mafic to translate the data into values of weight percent SiO2. The results indicate that the general approach tends to underestimate the weight percent SiO2 in the image. This discrepancy is removed with a \"site calibration,\" which provides good results in the calculated weight percent SiO2, with errors of a few percent. However, errors become larger with rugged topography or low solar angle at the time of image acquisition.
\r\n\r\nAnalysis of bathymetric data around Isla San Luis, and consideration of the island's alignment with the Ballenas transform fault zone to the south and volcanic seamounts nearby, suggest Isla San Luis is potentially volcanically active and could be the product of a \"leaky\" transform fault. The results from the image analysis in the Tres Virgenes-La Reforma Volcanic Region show the La Reforma and El Aguajito volcanic centers to be bimodal in composition and verify the most recent volcanism in the Tres Virgenes region to be basaltic-andesite. The results of fieldwork and image analysis indicate that the volcanic products of the central dome of La Reforma are likely a sequence of welded ash flow tuffs and lavas of varied composition, evidence of its origin as a caldera.
\r\n" }, { "name": "Keller, William R.", "degree": "PhD", "year": "2005", "title": "Cenozoic Plate Tectonic Reconstructions and Plate Boundary Processes in the Southwest Pacific", "advisor": "Clayton, Robert W.; Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01102005-223039", "creators": [ { "name": { "family": "Keller", "given": "William R." }, "id": "Keller-William-R", "display_name": "Keller, William R." } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "chair", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "co-chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/VB6N-HC69", "abstract": "The Australia-Pacific-Antarctic plate circuit has long been a weak link in global plate reconstruction models for Cenozoic time. The time period spanning chron 20 to chron 7 (43-25 Ma) is particularly problematic for global plate models because seafloor spreading was occurring in two poorly constrained regions in the Southwest Pacific - the Macquarie Basin southwest of New Zealand, and the Adare Basin north of the Ross Sea, Antarctica. I present a new shipboard dataset collected aboard several recent geophysical cruises which places important constraints on the tectonic evolution of these two regions. Utilizing multibeam bathymetry, magnetic, gravity, and seismic data in the Macquarie Basin, I am able to locate tectonic features and magnetic anomalies with greater accuracy than was previously possible. These tectonic features and magnetic anomalies are then used to calculate relative motion between the Australia and Pacific Plates for chrons 18-11 (40-30 Ma). I use revised locations of the rifted margins along the boundary of the Macquarie Basin to determine a best-fit pre-rift reconstruction for this region. During this same time period, seafloor spreading between East and West Antarctica was occurring along the Adare Trough, an extinct spreading center located north of the Ross Sea. Motion along the Adare Trough accounts for roughly 180 km of previously unrecognized motion between East and West Antarctica. I present multibeam and seismic data in the Adare Basin that place constraints on the timing and character of motion along this plate boundary." }, { "name": "Shuster, David Lawrence", "degree": "PhD", "year": "2005", "title": "Application of Spallogenic Noble Gases Induced by Energetic Proton Irradiation to Problems in Geochemistry and Thermochronometry", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06012005-135600", "creators": [ { "name": { "family": "Shuster", "given": "David Lawrence" }, "id": "Shuster-David-Lawrence", "display_name": "Shuster, David Lawrence" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "chair", "display_name": "Adkins, Jess F." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." } ], "option_major": [ "geochem" ], "doi": "10.7907/EXV3-GG18", "abstract": "Synthetic components of 3He, 4He, and 21Ne were generated within natural minerals via irradiation with 150 and 220 MeV proton beams. Fluences of ~10^14 and ~10^16 protons/cm2 induced 3He concentrations of ~10^8 and ~10^9 atoms/mg, respectively. Controlled degassing experiments on irradiated samples of terrestrial apatite (Ca5(PO4)3F), titanite (Ca(TiO)(SiO4)), olivine ((Mg,Fe)2SiO4), goethite (FeOOH), and quartz (SiO2) demonstrate that the proton-induced nuclides are spatially uniform across samples <= 1 mm in diameter and sequential degassing quantifies solid state diffusion kinetics of helium and neon. Diffusion kinetics of proton-induced 3He in Durango apatite (Ea = 147.9 \u00b1 1.3 kJ/mol; ln(Do/a2) = 16.0 \u00b1 0.3 ln(s-1)) and Fish Canyon tuff titanite (Ea = 183.7 \u00b1 2.7 kJ/mol; ln(Do/a2) = 13.3 \u00b1 0.5 ln(s-1)), are indistinguishable from those determined for natural radiogenic 4He in the same samples. Experiments indicate that lattice damage potentially introduced via proton irradiation did not significantly modify the natural 4He diffusion kinetics in the two samples, and that the proton-induced 4He component is relatively negligible in abundance. Therefore, sequentially measured 4He/3He ratios reflect the natural spatial distribution of radiogenic 4He. Combined with a (U-Th)/He age and helium diffusion kinetics, the distribution limits the time-temperature (t-T) path a mineral experienced through geologic time. This is the basis for a new methodology called 4He/3He thermochronometry, which for apatite constrains continuous t-T paths between 80 oC and 20 oC. Proton-induced 3He diffusion parameters in olivine are: Ea = 153.8 \u00b1 1.1 kJ/mol and ln(Do/a2) = 3.0 \u00b1 0.2 ln(s-1). At 25 oC, the helium diffusion kinetics in a goethite sample (Ea = 163 \u00b1 2.4 kJ/mol; ln(Do/a2) = 26.0 \u00b1 0.6 ln(s-1)) predict 90% 4He retention over 11.8 Ma, consistent with the observed deficit gas fraction and (U-Th)/He age of 10.7 Ma. This indicates that goethite (U-Th)/He dating is a viable weathering geochronometer. In quartz, the diffusion kinetics for proton-induced 21Ne and 3He (Ea = 153.7 \u00b1 1.5 (kJ/mol); ln(Do/a2) = 15.9 \u00b1 0.3 (ln(s-1)) and Ea = 84.5 \u00b1 1.2 (kJ/mol); ln(Do/a2) = 11.1 \u00b1 0.3 (ln(s-1), respectively), indicate that cosmogenic neon will be quantitatively retained in inclusion-free quartz at Earth surface temperatures whereas cosmogenic helium will not." }, { "name": "Wang, Zhengrong", "degree": "PhD", "year": "2005", "title": "Oxygen Isotope Studies of the Petrogenesis of Hawaiian Lavas and a Theoretical Study on Equilibrium Thermodynamics of Multiply-Substituted Isotopologues", "advisor": "Eiler, John M.; Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechETD:etd-05192005-000025", "creators": [ { "name": { "family": "Wang", "given": "Zhengrong" }, "id": "Wang-Zhengrong", "display_name": "Wang, Zhengrong" } ], "advisors": [ { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "advisor", "display_name": "Eiler, John M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "chair", "display_name": "Burnett, Donald S." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geochem" ], "doi": "10.7907/zrza-wc92", "abstract": "Temporal oxygen isotope variations have been discovered in both Mauna Kea and Koolau volcanoes after detailed studies of the Hawaiian Scientific Drilling Project (HSDP-phase II) and Koolau Scientific Drilling Project (KSDP). In both volcanoes, oxygen isotope compositions of olivine phenocrysts all converge to 'Mauna Loa-like' values from depleted or enriched composition, respectively and yet, the interpretations are totally different. In the studies of HSDP core, many lines of geochemical evidences strongly indicate that low-[delta18]O values characteristic of Kea trend Hawaiian lavas are the product of contamination by hydrothermally altered rocks in the volcanic edifice. In the studies of KSDP core and submarine Koolau landslides, a full diversity of [delta18]O values correlate with trace element and radiogenic isotope compositions of host lavas. These correlations are interpreted as reflecting mixing between partial melts of high-[delta18]O and normal-[delta18]O components. A magma mixing model has been constructed to simultaneously explain the oxygen isotope, major element, trace element and radiogenic isotope variations defined by these correlations. This model indicates that the Koolau shield-building lavas are mixtures of 75~100% melt of mantle peridotite with 0~25% eclogite melt, the protolith of which is Mid-Ocean Ridge Basalt (MORB) with Depleted Mantle Model (DMM) age of at least 1.8\u00b10.3 billions years. [delta18]O value of this eclogite component is predicted to be 11.3\u00b11.5\u2030, implying it is an upper crustal (layer 1 or 2) basalt or gabbro with a low-temperature alteration history; contains a small amount of sediment; and has experienced partial melting before forming eclogite.
\r\n\r\nI also derived a method for systematically evaluating clumped-isotope effects in the abundances of all isotopologues in thermodynamically equilibrated populations of O2, CO, N2, NO, CO2 and N2O between 1000 and 193 to 77 K. This method uses Urey-type algorithms to evaluate partition functions and equilibrium constants of isotope exchange reactions, and simultaneously solves for abundance of each isotopologue of a given molecule constrained by all independent equilibria. Calculation results show that, in most cases, multiply-substituted isotopologues of these mono-molecular gases are predicted to be enriched relative to stochastic (random) distributions by ca. 1 to 2 per mil at earth-surface temperatures.
" }, { "name": "Bouchez, Antonin Henri", "degree": "PhD", "year": "2004", "title": "Seasonal Trends in Titan\u2019s Atmosphere: Haze, Wind, and Clouds", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10272003-092206", "creators": [ { "name": { "family": "Bouchez", "given": "Antonin Henri" }, "id": "Bouchez-Antonin-Henri", "display_name": "Bouchez, Antonin Henri" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "member", "display_name": "Kulkarni, Shrinivas R." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/7KVP-D712", "abstract": "I present an analysis of visible and near-infrared adaptive optics images and spectra of Titan taken over 43 nights between October 1997 and January 2003 with the AEOS 3.6-m, Palomar Hale 5-m, and W.M. Keck 10-m telescopes. These observations reveal a seasonally changing stratospheric haze layer, two distinct regions of condensate clouds in the southern hemisphere, the albedo of Titan's surface, and the zonal wind field of the stratosphere.
\r\n\r\nTransient convective CH4 clouds are identified near Titan's south pole, rising to 16\u00b15 km above the surface. These clouds have been continuously present south of 70\u00b0S since at least December 2001, currently account for 0.5-1% of Titan's 2\u03bcm flux, and appear to be gradually brightening or thickening as the insolation of the south polar region increases. Above the polar clouds, an extensive but optically thin (\u03c4\u22480.05 at 2\u03bcm) cloud layer is noted near the tropopause south of 30\u00b0S. This cirrus-like structure has remained unchanged in extent and thickness since September 1999 despite seasonal changes in the underlying convective clouds and the overlying stratospheric haze. Aside from the convective CH4 clouds near the south pole, Titan's troposphere is free of aerosols with an upper limit of \u03c4<0.01 on the 2\u03bcm vertical optical depth in the 5-30 km altitude region.
\r\n\r\nThe albedo of Titan's surface at 2.0\u03bcm is derived from the radiative transfer analysis of spatially resolved spectra and images, and presented in the form of a ~600 km resolution global surface albedo map. At this resolution, the 2.0\u03bcm albedo ranges from 0.05 to 0.17, consistent with extensive exposure of clean water ice in some regions, while hydrocarbons and atmospheric sediments blanket others.
\r\n\r\nThe zonal wind field of Titan's stratosphere near southern summer solstice is derived from adaptive optics observations of the occultation of a binary star on 20 December 2001. Multiple refracted stellar images were detected on Titan's limb during the each successive occultation, allowing the angular deflection of the starlight at two altitudes over both hemispheres to be measured with an uncertainty of ~2 milliarcseconds. The zonal wind field derived from this measurement of the shape of Titan's limb exhibits strong but asymmetric high latitude jets, with peak wind speeds of 230\u00b120 m s-1 at 60\u00b0N and 160\u00b140 m s-1 at 40\u00b0S, and lower winds of 110\u00b140 m s-1 at the equator. The direction of the wind is not constrained.
" }, { "name": "Favela, Javier", "degree": "PhD", "year": "2004", "title": "Energy Radiation from a Multi-Story Building", "advisor": "Heaton, Thomas H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06032004-143147", "creators": [ { "name": { "family": "Favela", "given": "Javier" }, "id": "Favela-Javier", "display_name": "Favela, Javier" } ], "advisors": [ { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "advisor", "display_name": "Heaton, Thomas H." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Hall", "given": "John F." }, "id": "Hall-J-F", "role": "member", "display_name": "Hall, John F." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/SNYE-QG70", "abstract": "Damping limits the resonance of vibrating systems and thus higher anelastic damping is generally favored for engineered structures subjected to earthquake motions, because it means that a structure can dissipate a larger percentage of its energy per oscillation cycle. However, there are elastic processes that can mimic the effects of anelastic damping. In particular, buildings lose kinetic energy when their motion generates elastic waves in the Earth, which is referred to as radiation damping. Unlike anelastic damping, strong radiation damping may not always be desirable, as reciprocity can be used to show that buildings may be strongly excited by elastic waves of similar characteristics to those generated by the building's forced vibrations. As a result, it is important to quantify the radiation damping of structures to be able to improve their design.
\r\n\r\nSeveral experiments using Caltech's nine story Millikan Library as a controlled source were performed to investigate the radiation damping of the structure. The building was forced to resonate at its North-South and East-West fundamental modes, and seismometers were deployed around the structure in order to measure the waves generated by the library's excitation. From this \"local\" data set, we determine the elastic properties of the soils surrounding the structure and estimate what percentage of the total damping of the structure is due to energy radiation. Using Fourier transforms, we were also able to detect these waves at distances up to 400 km from the source using the broadband stations of the Southern California Seismic Network. This \"regional\" data set is used in an attempt to identify arrival times and to constrain the type of waves being observed at regional distances.
" }, { "name": "Huang, Xianglei", "degree": "PhD", "year": "2004", "title": "I. Variability of the Outgoing Thermal IR Spectra and Its Application in GCM Validation. II. The Detection of Cloud/Aerosol in the Outgoing Thermal IR Spectra", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05032004-150434", "creators": [ { "name": { "family": "Huang", "given": "Xianglei" }, "id": "Huang-Xianglei", "orcid": "0000-0002-7129-614X", "display_name": "Huang, Xianglei" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "chair", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." }, { "name": { "family": "Schneider", "given": "Tapio" }, "id": "Schneider-T", "role": "member", "display_name": "Schneider, Tapio" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/0J28-W457", "abstract": "The theme of this thesis is studying the outgoing thermal IR spectra of Earth and Mars. It is divided into two parts: the first part (Chapters 1-4) is focused on the variability seen in the outgoing thermal IR spectra and its application in validating model simulation, and the second part (Chapters 5-6) concentrates on the detection of cirrus (cirrus/dust aerosol) from terrestrial (Martian) outgoing thermal IR spectra.
\r\n\r\nIn Chapter 1, an example of climate change seen from two spectrometers seperated by 26 years is used to illustrate the singular importance of the outgoing thermal IR spectra in climate observations. The importance of testing the variability of models and the feasibility of using the outgoing thermal IR spectra in such tests are discussed.
\r\n\r\nIn Chapter 2, a study of the temporal variability at the tropical and midlatitude Pacific Oceans seen from IRIS (Infrared Interferometer Spectrometer) spectra and corresponding synthetic spectra based on simulations from two GCMs (UCLA GCM and NCAR CAM2) is presented. The discrepancies between modeled and observed temporal variability are substantial. The differences between two GCMs are also significant. Further examination shows that these discrepancies are insensitive to the parameterization of cloud optical properties and most likely due to deficiencies in simulating the seasonal and intraseasonal variations of the Walker Circulation in the tropical Pacific and the seasonal variations of boundary-layer temperature, low cloud, and stratospheric temperature in the midlatitude Pacific.
\r\n\r\nIn Chapter 3, a survey of the spatial variability seen from AIRS (Atmospheric Infrared Sounder) spectra and corresponding synthetic spectra based on NCAR CAM2 simulation is presented. To a large extent, the simulated spatial variability agrees well with the observed counterpart. The major discrepancies between model and observation can be attributed to the incorrect location of ITCZ in the western Pacific, the underrepresented dust aerosol at the Arabian Sea and off the Atlantic Coast of North Africa, and the overestimated spatial variation of stratospheric temperature in the model.
\r\n\r\nChapter 4 presents a comparative study of the temporal and spatial variability seen in the Martian outgoing thermal IR spectra collected by MGS-TES (Thermal Emission Spectrometer). Surface temperature variation is the dominant contributor to the temporal and spatial variability seen here. The variations of CO2 column abundance, dust aerosol and water ice cloud associated with topography, as well as the imprint of dust storms, can be also seen from such analysis. The negative correlation between dust and water ice spectral features seen from this analysis suggests that, to some extent, dust and water ice cloud are mutually exclusive of each other in the Martian atmosphere.
\r\n\r\nChapter 5 presents a sensitivity study of identifying optically thin cirrus from high-resolution (each individual absorption line is almost resolved) thermal IR spectra based on the line shapes of the residual spectra. This cirrus-detection approach is different from all previous cirrus-detection algorithms in the sense of making use of information content contained in the high-resolution measurements.
\r\n\r\nChapter 6 presents a tri-spectral algorithm to detect water ice cloud, dust, and surface anisothermality from low-resolution Martian outgoing thermal IR spectra, such as MGS-TES spectra. This algorithm is complementary to any more sophisticated retrieval scheme and can be used to screen large amounts of data to get a quick overview.
" }, { "name": "Lohman, Rowena Benfer", "degree": "PhD", "year": "2004", "title": "The Inversion of Geodetic Data for Earthquake Parameters", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechETD:etd-05022004-165305", "creators": [ { "name": { "family": "Lohman", "given": "Rowena Benfer" }, "id": "Lohman-Rowena-Benfer", "orcid": "0000-0001-7240-3165", "display_name": "Lohman, Rowena Benfer" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "chair", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" } ], "option_major": [ "geol" ], "doi": "10.7907/9FYH-HD84", "abstract": "The spatial and temporal coverage of geodetic data sets such as Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) is increasing to the point where we can constrain many aspects of the deformation associated with earthquakes and volcanic eruptions. As our understanding of the kinematics of deformation improves, we can begin to explore the dynamic processes that drive seismic and volcanic deformation in tectonically active regions around the world.
\r\n\r\nIn this thesis, I use InSAR data in inversions for earthquake source parameters for both small (4.0< Mw<5.5) and large (Mw>7) earthquakes. For small earthquakes, I focus on constraining the hypocenter location and seismic moment. I examine data for small earthquakes in the Basin and Range province of the Western United States, and in the Zagros mountains of Southern Iran. For large earthquakes, I place constraints on the coseismic slip distribution for a pre-determined fault plane geometry and explore how sensitive the inversion is to inadequacies in the fault plane parameterization. I perform inversions for both the 1999 Mw 7.1 Hector Mine earthquake in Southern California and the 1995 Mw 8.1 Antofagasta earthquake in Chile.
\r\n\r\nI also describe some advances in the technical details of using InSAR observations in inversions for deformation source parameters. I use the full noise covariance matrix in my inversions and compare inferred noise covariances for several interferograms covering the Mojave desert, Southern California, with GPS observations of tropospheric structure functions. I provide an algorithm for resampling (or averaging) InSAR data to minimize the computational burden by reducing the number of data points used as input to inversions. I also explore techniques for regularizing poorly determined inversions of geodetic data for coseismic fault slip.
" }, { "name": "Persaud, Patricia", "degree": "PhD", "year": "2004", "title": "Images of Early Continental Breakup in and around the Gulf of California and the Role of Basal Shear in Producing Wide Plate Boundaries", "advisor": "Clayton, Robert W.; Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12032003-113513", "creators": [ { "name": { "family": "Persaud", "given": "Patricia" }, "id": "Persaud-Patricia", "orcid": "0000-0003-3462-7023", "display_name": "Persaud, Patricia" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "co-advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Avouac", "given": "Jean-Philippe" }, "id": "Avouac-J-P", "orcid": "0000-0002-3060-8442", "role": "member", "display_name": "Avouac, Jean-Philippe" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/8K9G-SS73", "abstract": "Active faulting in the northern Gulf of California occurs over a broad zone, 70 x 200 km, affecting two-thirds of the width of new crust that has formed there starting at 6 Ma. This is an unusually wide plate boundary zone with a high density of faults and no evidence for the formation of normal oceanic crust. Over 3000 km of high-resolution, multichannel seismic data were used to map out this zone of distributed faulting and identify multiple basins within the broad rift zone. Previously, numerical models have shown that deformation shifts from one place to another by various mechanisms of strengthening of the active rift zone relative to adjacent regions. Models are presented here that for the first time, show the development of multiple active faults across the width of the plate boundary. These models do not rely on strengthening or weakening effects; rather they assume that shear at the base of the brittle crust is distributed and explore the effects of distributed shear on the style of deformation. Addiionally, the effect of obliquity on the style of deformation is studied and the styles of faulting produced in the models represent a wide range of geological structures, ranging from half-grabens to flower structures. The style of faulting in the northern Gulf of California is produced in a model with distributed shear using the published obliquity for this region.
\r\n\r\nOne mechanism for distributing shear at the base of the brittle crust is lower crustal flow. If a significant amount of lower continental crust exists within the Gulf, it may have flowed in the past. A study of the crustal thickness variations in the continental margins of the Gulf is presented here, that shows thinner crust in a ~50 km wide zone close to the Gulf, along the entire eastern Baja California peninsula. This thinned crust is associated with the eastern Peninsular Ranges batholith. In contrast, the western part of the batholith has a fairly uniform thickness of 35-40 km. It is possible that at the time of breakup, the lower crust was still behaving ductilely and that some of the lower continental crust from the margins now exists within the Gulf.
" }, { "name": "Savage, Brian Kirk", "degree": "PhD", "year": "2004", "title": "Regional Seismic Wavefield Propagation", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05262004-100247", "creators": [ { "name": { "family": "Savage", "given": "Brian Kirk" }, "id": "Savage-Brian-Kirk", "orcid": "0000-0002-9252-6282", "display_name": "Savage, Brian Kirk" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Tromp", "given": "Jeroen" }, "id": "Tromp-J", "role": "member", "display_name": "Tromp, Jeroen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/JQ8E-6387", "abstract": "Through the examination of local and regional seismic waveform data the crust and upper mantle of southern California are investigated. Using local and regional seismic phases such as Pn, Sn, PL, and surface waves, seismic wave velocities of interesting tectonic structures are determined. These structures include the southern Sierra Nevada, San Bernardino Mountains, and the Salton Trough / Imperial Valley. Detailed studies of how seismic waves propagate at local and regional distances are also undertaken. Knowledge of the seismic wave propagation through these tectonic provinces provides for a robust determination of their characteristics. Further, complex source and site-related propagation are included through an investigation of the Kursk submarine explosion and basin-related site amplification." }, { "name": "Wang, Huiqun Helen", "degree": "PhD", "year": "2004", "title": "Global Observations of Martian Clouds with the Mars Orbiter Camera of the Mars Global Surveyor Spacecraft", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04142004-151205", "creators": [ { "name": { "family": "Wang", "given": "Huiqun Helen" }, "id": "Wang-Huiqun-Helen", "orcid": "0000-0001-9722-9992", "display_name": "Wang, Huiqun Helen" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Danielson", "given": "Ed" }, "id": "Danielson-E", "role": "member", "display_name": "Danielson, Ed" }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." } ], "option_major": [ "plansci" ], "doi": "10.7907/CYNM-8830", "abstract": "We have studied the global cloud distribution on Mars using red and blue global map swaths taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC).
\r\n\r\nIn Chapters 1 and 4, we summarize the results for the first and second MGS mapping years, respectively. In Chapter 2, we investigate the mechanism for a new type of \"flushing\" dust storm first observed by MGS. These dust storms moved from the northern high latitudes southward across the equator, and led to a planet-encircling dust storm in the first MGS mapping year (1999). In Chapter 3, we track cloud motion to measure winds using images separated by 2 hours.
\r\n\r\nThe systematic daily global coverage of MGS not only provides us with detailed and coherent pictures of Martian cloud evolution, but also increases the number of cloud-tracked wind vectors by three orders of magnitude. Except for the global dust storm in the second MGS mapping year (2001), Martian weather is highly repeatable. When the 2001 global dust storm initiated, Hellas storms increased in frequency, transporting dust out of the basin daily. When the 1999 planet-encircling dust storm initiated, \"flushing\" storms also increased in frequency, transporting dust to the southern subtropics daily. These observations suggest that timely dust supply by local or regional storms could have a global impact.
" }, { "name": "Zeng, Lingsen", "degree": "PhD", "year": "2004", "title": "Non-Modal Partial Melting of Metasedimentary Pendants in the Southern Sierra Nevada and Implications for the Deep Origin of Within-Pluton Isotopic Heterogeneity", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10272003-131444", "creators": [ { "name": { "family": "Zeng", "given": "Lingsen" }, "id": "Zeng-Lingsen", "orcid": "0000-0001-7673-2847", "display_name": "Zeng, Lingsen" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "chair", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geol" ], "doi": "10.7907/5f6f-f677", "abstract": "Results from field mapping, structural analysis, major and trace element geochemistry, and radiogenic isotopic data from the Goat Ranch migmatite complex on the south shore of Lake Isabella, southern Sierra Nevada, California, are presented to (1) determine the major and trace element, Sr and Nd isotopic compositions of anatectic melts from pelitic sources; (2) investigate the structural and metamorphic responses of the Isabella pendant to the emplacement of the Goat Ranch pluton at ~100 Ma; and (3) evaluate the magnitude of assimilation of metasedimentderived melts by the Goat Ranch pluton at a mid-crustal level. Nd and Sr isotopic compositions were measured on the non-migmatitic distal wallrocks, leucosomes, migmatites, traverses into the Goat Ranch pluton, leucogranite dikes, and samples from the Rabbit Island, Heal Peak, and Bob Rabbit plutons. Major and trace element analyses were performed on selected samples of the leucosomes, migmatites and metapelites. Major and trace element analyses in addition to field and petrographic data demonstrate that leucosomes are products from partial melting of the pelitic protolith host. These data show that (1) contamination of Goat Ranch intrusion is restricted to the immediate proximity to migmatitic wallrocks. Isotopic heterogeneity of the Goat Ranch intrusion is not related to assimilation at or near the level of exposure, but from a deeper source; (2) as compared to the metapelites, leucosomes have higher Sr and lower Sm concentrations and lower Rb/Sr ratios. Sr and Nd isotope compositions of leucosomes, migmatites and metapelites suggesting a disequilibrium partial melting of the metapelite protolith; (3) based on their Sr, Nd and other trace element characteristics, two groups of leucosomes have been identified. Group A leucosomes show distinct positive Eu anomalies, relatively high Rb, Pb, Ba and K2O contents, and low Rb/Sr ratios. Group B leucosomes have negative Eu anomalies, relatively low Rb, Pb, Ba and K2O contents, and low Rb/Sr ratios as well; (4) the leucogranite dikes also can be subdivided into Group A (high 87Sr/86Sr(T) and low eNd(T)), and Group B (low 87Sr/86Sr(T)) and high eNd(T)); (5) H2O-fluxed melting of quartz + plagioclase with minor involvement of muscovite melting dominated the leucosome production; (6) Group A leucogranite dikes resulted from partial melting of the lower pelite, and Group B dikes from partial melting of the upper pelite; and (7) the Bob Rabbit pluton represents an extreme end-member case that was derived completely from melting of the upper pelite or its equivalent in depth in the I-SCR (strongly contaminated and reduced I-type pluton) zone. Strain analysis shows that progressive partial melting resulted in the loading framework transition in the upper pelite unit from LBF structure (the stronger phase forms a load-bearing framework) to IWL structure (the weaker phase forms an interconnected weak matrix) with proximity to the pluton. The presence of melts has greatly affected the strain partitioning within the migmatite zone.
\r\n\r\nBy incorporating accessory phase dissolution kinetics into non-modal partial melting of metasedimentary sources, theoretical modeling shows that non-modal partial melting of a pelitic source results in melts following two paths in eNd-87Sr/86Sr ratio space. Path 1 represents those partial melting reactions that favor muscovite/biotite dehydration and apatite but not monazite dissolution, leading to melts with elevated Rb/Sr, 87Sr/86Sr, Sm/Nd, and eNd values. In contrast, Path 2 represents those partial melting reactions in which muscovite/biotite dehydration plays an insignificant role, and favor monazite over apatite dissolution, and lead to melts with lower Rb/Sr, 87Sr/86Sr, Sm/Nd, and eNd values than their sources.
" }, { "name": "Akins, Joseph Albert", "degree": "PhD", "year": "2003", "title": "Dynamic Compression of Minerals in the MgO-FeO-SiO\u2082 System", "advisor": "Asimow, Paul David", "url": "https://resolver.caltech.edu/CaltechETD:etd-05302003-142219", "creators": [ { "name": { "family": "Akins", "given": "Joseph Albert" }, "id": "Akins-Joseph-Albert", "display_name": "Akins, Joseph Albert" } ], "advisors": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "advisor", "display_name": "Asimow, Paul David" } ], "committee": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "chair", "display_name": "Asimow, Paul David" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geol" ], "doi": "10.7907/NA1N-0B58", "abstract": "The first shock wave experiments performed on silicate materials were reported for quartz in 1962. The intervening forty years have allowed for extensive investigation of SiO\u2082 by dynamic, static and theoretical means. Previous studies have concluded that quartz transforms completely to stishovite at ~40 GPa and melts at ~115 GPa along its Hugoniot. Recent discoveries that SiO\u2082 transforms to phases slightly more dense than stishovite have led to a reexamination of the dynamic compression of SiO\u2082 in this thesis. Based on comparing calculated Hugoniots to data for multiple initial SiO\u2082 phases, it is proposed that, in addition to the stishovite and melt transitions, quartz is completely transformed to the CaCl2 structure at ~70 GPa. Coesite shows evidence of complete transformation to stishovite at ~ 50 GPa, and to the CaCl2 structure at ~65 GPa. Due to the higher temperature achieved in the quartz samples the slope of the stishovite-CaCl2 phase boundary is constrained to be ~180 K/GPa.
\r\n\r\nFrom a similar analysis of Hugoniot data collected for high quality MgSiO3 natural crystal and synthetic glass in this study, and existing data, it is concluded that along the crystal Hugoniot akimotoite is attained at ~70 GPa, perovskite structure at ~110 GPa and melt at ~ 170 GPa. It is found that the melt is 2-3 % denser than the solid at pressures greater than 100 GPa, after correcting for thermal differences in the two regimes. An important implication is a negative Clapeyron slope, leading to a decreasing melting temperature with increasing pressure, above ~ 100 GPa. These observations increase the possibility of the existence of a significant amount of partial melt in the lowermost mantle, e.g., the ultra low velocity zone.
" }, { "name": "Byrne, Shane", "degree": "PhD", "year": "2003", "title": "History and Current Processes of the Martian Polar Layered Deposits", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05292003-140024", "creators": [ { "name": { "family": "Byrne", "given": "Shane" }, "id": "Byrne-Shane", "orcid": "0000-0002-6735-4685", "display_name": "Byrne, Shane" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "plansci" ], "doi": "10.7907/XRZN-4T75", "abstract": "The Martian polar layered deposits constitute a detailed record of geologically recent environmental conditions. In this thesis I examine processes that have affected this history over timescales ranging from \u224810\u00b2 to \u224810\u2077 Martian years. To complete the work in this thesis I developed a geographic database of the Martian polar regions to enable comparisons of different datasets spread over different missions.
\r\n\r\nI report on the discovery of a large sand rich unit underlying the northern polar layered deposits. The presence of this unit suggests there once existed a radically different polar environment where there was no polar cap. A major new question now arises of where that water went during this time period and how the old polar cap (if there was one) was removed.
\r\n\r\nI describe analysis and modeling of evolving landforms on the southern residual CO\u2082 cap. This modeling suggests that these landforms are underlain by a water ice layer. THEMIS observations were used to confirm this hypothesis. This limits the size of the residual CO\u2082 cap reservoir to no more than 5% of the current atmosphere, which puts an important constraint on models of atmospheric evolution. Analysis of the size distribution coupled with this modeling indicates a uniform age for a large group of these features, implying some environmental change on the order of Martian centuries ago.
\r\n\r\nI examined geomorphologic evidence for flow processes at the margin of the south polar layered deposits. Indications of multiple episodes of previous flow are seen. However much evidence of brittle processes such as faulting, slumping and landsliding is also present. This leads to the conclusion that, during some periods, flow of the layered deposits is incapable of relieving the gravitationally generated stresses within the ice sheet. The evidence suggests that periods where flow was possible occurred intermittently and were separated by periods in which sublimation-based retreat of the ice dominated.
" }, { "name": "Fenton, Lori Kay", "degree": "PhD", "year": "2003", "title": "Aeolian Processes on Mars: Atmospheric Modeling and GIS Analysis", "advisor": "Brown, Michael E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03052003-124751", "creators": [ { "name": { "family": "Fenton", "given": "Lori Kay" }, "id": "Fenton-Lori-Kay", "orcid": "0000-0001-8116-4901", "display_name": "Fenton, Lori Kay" } ], "advisors": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "advisor", "display_name": "Brown, Michael E." } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." } ], "option_major": [ "plansci" ], "doi": "10.7907/C9V4-8050", "abstract": "Wind is currently the dominant geological agent acting on the surface of Mars. A study of Martian aeolian activity leads to an understanding of the forces that have sculpted the planet's face over the past billion years or more and to the potential discovery of climate shifts recorded in surface wind features that reflect ancient wind patterns. This work takes advantage of newly available tools and data to reconstruct the sedimentary history reflected in aeolian features on Mars. The thesis is divided into two main projects. In the first section, a widely accepted hypothesis, that oscillations in Martian orbital parameters influence atmospheric circulation patterns, is challenged. A Mars global circulation model is run at different obliquity, eccentricity, and perihelion states and the predicted surface wind orientations are correlated with observed aeolian features on the Martian surface. The model indicates that orbital parameters have little effect on wind patterns, suggesting that aeolian features not aligned with the current wind regime must have formed under atmospheric conditions unrelated to orbital parameters. In the second project, new spacecraft data and a mesoscale model are used to determine the sedimentary history of Proctor Crater, a 150 km diameter crater in the southern highlands of Mars. Using high-resolution imagery, topography, composition, and thermal information, a GIS was constructed to study the aeolian history of the crater, which was found to have a complex interaction of deposition and erosion. Surficial features include 450 m of sediments filling the crater basin, small bright bedforms, dust devil tracks, and a dark dunefield consisting of coarse, basaltic sand and containing slipfaces indicative of a multidirectional, convergent wind regime. All wind features, both ancient and contemporary, are coaligned, indicating that formative wind directions have changed little since the first aeolian features formed in this area. Mesoscale model runs over Proctor Crater indicate that two dune slipfaces are created by winter afternoon geostrophic westerlies and summer evening katabatic easterlies, and that dust devil tracks are created by summer noontime rotational westerlies. Using all available tools, this thesis begins the work of understanding how aeolian processes have influenced the Martian surface.\r\n" }, { "name": "Johnson, Elizabeth Ann", "degree": "PhD", "year": "2003", "title": "Hydrogen in Nominally Anhydrous Crustal Minerals", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05272003-165802", "creators": [ { "name": { "family": "Johnson", "given": "Elizabeth Ann" }, "id": "Johnson-Elizabeth-Ann", "orcid": "0000-0001-7244-6122", "display_name": "Johnson, Elizabeth Ann" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "chair", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" } ], "option_major": [ "geochem" ], "doi": "10.7907/EG6Q-8B56", "abstract": "Systematic infrared and nuclear magnetic resonance investigations of common crustal minerals were undertaken to better understand the geologic significance of minor components of structural hydrous species within these nominally anhydrous minerals.
\r\n\r\nThe absolute hydrogen concentration in three alkali feldspars and eight plagioclase samples was measured with \u00b9H nuclear magnetic resonance spectroscopy. The mid-infrared integral absorption coefficient was determined to be 15.3 \u00b1 0.7 ppm\u207b\u00b9cm\u207b\u00b2, allowing quantitative analysis of OH and H\u2082O in feldspars with infrared spectroscopy. A survey of hydrous species in igneous feldspars found that feldspars contain structural OH (0-512 ppm H\u2082O), H\u2082O (0-1350 ppm H\u2082O), and NH\u2084\u207a (0-1500 ppm NH\u2084\u207a) groups as well as fluid inclusions and alteration products. Composition and crystal structure influence the type of hydrous species that can be incorporated into feldspars, but the concentration and speciation of structural hydrogen is at least partially determined by the geologic environment. The diffusivity of H in OH-bearing plagioclase was determined at 800-1000\u00b0C (D0=5.7\u00b12.5x10\u207b\u2074 m\u00b2/sec and Q=224\u00b133 kJ/mol). A millimeter-sized volcanic feldspar phenocryst would be expected to lose a significant proportion of its OH concentration on the timescale of a typical eruption (hours to weeks).
\r\n\r\nThe structures and compositions of low albite and ussingite, Na\u2082AlSi\u2083O\u2088(OH), are similar. The strong hydrogen bonding in ussingite is found to be fundamentally different from the hydrogen bonding environment of OH in feldspars. Comparison of the infrared spectra of structural isomorphs reedmergnerite, NaBSi\u2083O\u2088, and low albite suggest that OH is incorporated in both structures through protonation of the most underbonded oxygen site.
\r\n\r\nThe concentration of structural OH in diopside was determined for four granulite facies siliceous marble samples from the Adirondacks, New York. Diopside OH concentration increases monotonically with increasing estimated water fugacity for each outcrop.
\r\n\r\nHydrogen concentration is correlated to Ti concentration in zoned grossular skarn garnets from Birch Creek, CA. Decrease of Ti and H from garnet cores to rims may be related to the solubility of Ti in the skarn-forming fluid. Skarn garnets from an Adirondacks, NY, wollastonite ore deposit exhibit a large range of OH concentrations broadly related to rock type that are due to recrystallization and partial dehydration.
" }, { "name": "Kuang, Zhiming", "degree": "PhD", "year": "2003", "title": "I: Remote Spectroscopic Measurements of Atmospheric HDO/H\u2082O and Column CO\u2082. II: Interannual Variations of the Earth\u2019s Reflectance", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechETD:etd-06022003-114148", "creators": [ { "name": { "family": "Kuang", "given": "Zhiming" }, "id": "Kuang-Zhiming", "display_name": "Kuang, Zhiming" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Seinfeld", "given": "John H." }, "id": "Seinfeld-J-H", "role": "member", "display_name": "Seinfeld, John H." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/Q9TP-RR97", "abstract": "The theme of this thesis is to apply remote sensing data on problems concerning the climate system. It is grouped into two parts. Part I (Chapters 1, 2) is devoted to spectroscopic measurements of HDO, H\u2082O and column CO\u2082, and Part II (Chapters 3-5) is devoted to variations in the Earth's reflectance.
\r\n\r\nIn Chapter 1, we derive the first simultaneous measurements of HDO and H\u2082O in the tropical upper troposphere and lower stratosphere. This is made possible by extending the retrievals of the Atlas-3 Atmospheric Trace Molecule Spectroscopy (ATMOS) data deeper into the troposphere. The derived HDO/H\u2082O ratio demonstrates that convection has a major influence on the moisture budget and the dehydration processes in this region.
\r\n\r\nThe objective of Chapter 2 is to determine the precision to which column averaged CO\u2082 volume mixing ratio (VMR) can be measured by near-infrared (NIR) spectrometry of reflected sun light. The key idea in this study is the simultaneous use of the CO\u2082 (1.58-\u00b5m and 2.06-\u00b5m) and O\u2082 (0.76-\u00b5m) bands. This approach allows small changes in the spectrum arising from variations of column CO\u2082 VMR to be distinguished from those arising from variations of other atmospheric/surface parameters. Using prototype retrieval simulations based on a practical satellite instrument design, we show that the 3-band, high-resolution, spectrometric approach using NIR reflected sunlight has the potential for highly accurate column CO\u2082 VMR measurements.
\r\n\r\nIn Chapters 3-5, we examine the interannual variations in the Earth's reflectance. Chapter 3 introduces the Nimbus-7 TOMS reflectance measurements and provides an overview on the interannual variability of the Earth's reflectance. Variations in the globally averaged reflectance are also used to examine a postulated cosmic ray-cloud-climate connection.
\r\n\r\nIn Chapter 4, we relate interannual reflectance variations over the summertime polar icy areas to variations in the microwave-derived sea ice concentration. The results provide independent confirmation on sea ice variations observed by microwave instruments, and quantify the role of clouds in shielding the reflectance effect of sea ice variations. An interesting hemispheric asymmetry is found: a 1% change in the sea ice concentration is related to a significantly larger reflectance change in the Antarctic than in the Arctic icy areas.
\r\n\r\nChapter 5 is devoted to interannual reflectance variations over the northern midlatitude oceans. We find that interannual reflectance variations in these regions are, to a large extent, related to variations in the large scale circulation, mostly through variations in the storms tracks. The findings in this chapter suggest that the response of clouds to climate change may be better viewed from a large-scale circulation perspective, other than a purely thermodynamic one (such as in the cloud-temperature relations), a stand many previous investigations have taken.
" }, { "name": "Lane, Benjamin Frederick", "degree": "PhD", "year": "2003", "title": "High-Precision Infra-Red Stellar Interferometry", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03122003-112232", "creators": [ { "name": { "family": "Lane", "given": "Benjamin Frederick" }, "id": "Lane-Benjamin-Frederick", "orcid": "0000-0002-8006-0243", "display_name": "Lane, Benjamin Frederick" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Colavita", "given": "M. Mark" }, "id": "Colavita-M-M", "role": "member", "display_name": "Colavita, M. Mark" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Kulkarni", "given": "Shrinivas R." }, "id": "Kulkarni-S-R", "role": "member", "display_name": "Kulkarni, Shrinivas R." } ], "option_major": [ "plansci" ], "doi": "10.7907/618C-6550", "abstract": "This dissertation describes work performed at the Palomar Testbed Interferometer (PTI) during 1998-2002. Using PTI, we developed a method to measure stellar angular diameters in the 1-3 milli-arcsecond range with a precision of better than 5%. Such diameter measurements were used to measure the mass-radius relations of several lower main sequence stars and hence verify model predictions for these stars. In addition, by measuring the changes in Cepheid angular diameters during the pulsational cycle and applying a Baade-Wesselink analysis we are able to derive the distances to two galactic Cepheids (eta Aql and zeta Gem) with a precision of order 10%; such distance determinations provide an independent calibration of the Cepheid period-luminosity relations that underpin current estimates of cosmic distance scales.
\r\n\r\nSecond, we used PTI and the adaptive optics facility at the Keck Telescope on Mauna Kea to resolve the low mass binary systems BY Dra and GJ 569B, resulting in dynamical mass determinations for these systems. GJ 569B most likely contains at least one substellar component, and as such represents the first dynamical mass determination of a brown dwarf.
\r\n\r\nFinally, a new observing technique - dual-star phase referencing - was developed and demonstrated at PTI. Phase referencing allows interferometric observations of stars previously too faint to observe, and is a prerequisite for large-scale interferometric astrometry programs such as the one planned for the Keck Interferometer; interferometric astrometry is a promising technique for the study of extra-solar planetary systems, particularly ones with long-period planets.
" }, { "name": "Liu, Jing", "degree": "PhD", "year": "2003", "title": "Part I. Slip Behavior of the San Andreas Fault Through Several Earthquake Cycles Part II. A Structural Interpretation of the Aftershock \"Cloud\" of the 1992 Mw 7.3 Landers Earthquake", "advisor": "Kirschvink, Joseph L.; Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05272003-095416", "creators": [ { "name": { "family": "Liu", "given": "Jing" }, "id": "Liu-Jing", "display_name": "Liu, Jing" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "chair", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geol" ], "doi": "10.7907/A2P1-VB75", "abstract": "Part 1 of this thesis addresses the question of how variable fault slip per event is through time. This question is important, because progress in understanding and forecasting large earthquakes depends critically on precise reconstruction of the variation of rupture magnitude with time. Well-documented examples of slip measurements of successive past earthquakes rarely span more than three earthquake cycles. The dearth of accurate measurements of serial slip is partly due to the obliteration of piercing lines that we can use to separate the offsets associated with individual earthquakes.
\r\n\r\nThe special configuration of a series of channels offset across the San Andreas fault, near Wallace Creek has enabled me to determine the styles and the magnitudes of slip of the most recent 6 events at this locality. At the site, a feeder channel cuts a Pleistocene alluvial fan on the upstream side of the fault. On the downstream side, several small channels were offset dextrally from the source and sequentially abandoned. We opened a latticework of trenches across the offset channels on both sides of the fault. The trenches across the mouth of the upstream feeder channel exposed a set of nested channels; downstream trenches revealed several singular channels. The elevations, shapes, stratigraphy and ages of channels provide reliable information for correlating channels across the fault. 3-D excavations have allowed me to locate accurately the offset channel pairs and to determine the amounts of motion with small uncertainties. The dextral slips associated with the latest 6 events are, from the youngest to oldest, ~ 8 m, ~ 7.5 m, ~5.5 m, ~ 1.5 m, ~ 8.0 m, and ~ 5.5 m. The high occurrence of events with slip of about 7.5 m suggests that the magnitude of slip at a point along the fault does not result from a random process. But the slip is not as regular as predicted by characteristic models either. Thus, data at the site do not support perfectly characteristic behavior, but do show a significant degree of regularity.
\r\n\r\nPart II of the thesis demonstrates that Landers aftershocks constituted primarily a several-km-wide damage zone centered on the mainshock rupture plane. Most aftershocks probably did not occur on the same surfaces that had moved during the mainshock. Rather, the aftershock populations revealed the nature of the fractured medium around the principal faults, and the general structure of a fault zone.
" }, { "name": "Luo, Sheng-Nian", "degree": "PhD", "year": "2003", "title": "I. The Heterogeneities at the Core-Mantle and Inner-Core Boundaries from PKP Phases. II. The Static and Dynamic Behavior of Silica at High Pressures", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05302003-174154", "creators": [ { "name": { "family": "Luo", "given": "Sheng-Nian" }, "id": "Luo-Sheng-Nian", "display_name": "Luo, Sheng-Nian" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Ravichandran", "given": "Guruswami" }, "id": "Ravichandran-G", "role": "member", "display_name": "Ravichandran, Guruswami" }, { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-P-D", "role": "member", "display_name": "Asimow, Paul David" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." } ], "option_major": [ "geophys" ], "doi": "10.7907/D8HB-A439", "abstract": "Waveform and differential travel-time (DTT) of various PKP phases have been utilized to study the velocity variations at the core-mantle boundary (CMB) and the inner-core boundary (ICB). The spatial concentration of events and stations, and the significant variations in PKPab-PKPdf DTT and waveform of PKPab, indicate localized sharp lateral variation of velocity at the CMB as supported by simulations. Modeling of DTT's among PKiKP, PKIKP and PKP-B-diffracted (Bdiff) phases, and waveform of Bdiff supports that the ratio of relative velocity variations of S- and P-wave at the CMB is larger than 2, and that hemispheric P-wave velocity variations exist at the top of the inner core, and that D' structure is related to the ICB via core dynamics.
\r\n\r\nThe equation of state of stishovite is obtained by direct shock wave loading up to 235 GPa as K0T=306 \u00b1 5 GPa and K0T' = 5.0 \u00b1 0.2 where K0T is ambient bulk modulus and K0T' its pressure derivative. Phase diagram of silica (including melting curve) up to megabar pressure regime is established based on molecular dynamics (MD) simulations and dynamic and static experiments. Calculations show that perovskite is thermodynamically stable relative to the stishovite and periclase assemblage at lower mantle conditions. A detailed and quantitative examination is conducted on the thermodynamics and phase change mechanisms (including amorphization) that occur upon shock wave loading and unloading of silica. The systematics of maximum undercooling and superheating, are established by incorporating normalized energy barrier for nucleation and heating (cooling) rate, and validated at the atomic level with systematic MD simulations. By considering superheating in shock wave experiments, high-pressure melting curves for silica, alkali halides and transition metals are constructed based on the Lindemann law and the $ln2$ rule for the entropy of melting.
" }, { "name": "Natawidjaja, Danny Hilman", "degree": "PhD", "year": "2003", "title": "Neotectonics of the Sumatran Fault and Paleogeodesy of the Sumatran Subduction Zone", "advisor": "Saleeby, Jason B.; Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05222003-155554", "creators": [ { "name": { "family": "Natawidjaja", "given": "Danny Hilman" }, "id": "Natawidjaja-Danny-Hilman", "orcid": "0000-0002-3870-9184", "display_name": "Natawidjaja, Danny Hilman" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "chair", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Adkins", "given": "Jess F." }, "id": "Adkins-J-F", "role": "member", "display_name": "Adkins, Jess F." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geol" ], "doi": "10.7907/KBXR-5B89", "abstract": "Under the Sumatran plate boundary the Australian-Indian plate is subducting at about 60 mm/yr in the direction N11\u00b0E. The oblique convergence is partitioned into trench-parallel slip - accommodated largely by the Sumatran fault zone and trench-perpendicular slip - accommodated by the subduction zone. Our detailed map of the Sumatran fault zone (SFZ) shows that the Sumatran fault is highly segmented. The influence of these fault segmentations on historical seismic source dimensions suggests that the dimensions of future events will also be influenced by fault geometry. The largest geomorphic offsets along the Sumatran fault zone are about 20 km, and may represent the total offset across the fault. The shape and location of the Sumatran fault and the active volcanic arc are highly correlated with the shape and character of the underlying subducting oceanic lithosphere.
\r\n\r\nWe utilize coral microatolls in west Sumatra to document evidence for deformation of the underlying subduction interface. Microatolls are very sensitive to fluctuations in sea level, and thus act as natural tide gauges. They record not only the magnitude of vertical deformation associated with earthquakes (paleoseismic data), but also continuously track long-term aseismic deformation that occurs during intervals between earthquakes (paleogeodetic data). Numerous microatolls from the region around the equator record a simple pattern of tilt away from the trench axis in 1935 related to an Mw7.7 earthquake. About 115 km from the trench axis, uplift was nil. Nearer to the trench, uplift progressively increased trench-ward to at least 90 cm. Farther than 115 km from the trench, submergence of up to 35 cm occurred. We model these paleogeodetic data by a 2.3 m slip event on the interface between 88 and 125 km from the trench axis. A large aseismic event or ?silent earthquake? in 1962 is among the most interesting phenomena discovered in the coral record, and is the second largest short-lived event recorded throughout the equatorial region. Furthermore, paleogeodetic data reveal that the interseismic deformation rates have varied both temporally and spatially.
" }, { "name": "Pritchard, Matthew Earl", "degree": "PhD", "year": "2003", "title": "Recent Crustal Deformation in West-Central South America", "advisor": "Simons, Mark", "url": "https://resolver.caltech.edu/CaltechETD:etd-06022003-105512", "creators": [ { "name": { "family": "Pritchard", "given": "Matthew Earl" }, "id": "Pritchard-Matthew-Earl", "orcid": "0000-0003-3616-3373", "display_name": "Pritchard, Matthew Earl" } ], "advisors": [ { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "advisor", "display_name": "Simons, Mark" } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/XADN-C411", "abstract": "I use interferometric synthetic aperture radar (InSAR) to create maps of crustal deformation along the coast and within the volcanic arc of central South America. I image deformation associated with six subduction zone earthquakes, four volcanic centers, at least one shallow crustal earthquake, and several salt flats. In addition, I constrain the magnitude and location of post-seismic deformation from the afore-mentioned subduction zone earthquakes. I combine InSAR observations with data from the Global Positioning System (GPS) and teleseismic data to explore each source of deformation. I use the observations to constrain earthquake and volcanic processes of this subduction zone, including the plumbing system of the volcanoes and the decadal along strike variations in the subduction zone earthquake cycle.
\r\n \r\nI created interferograms of over 900 volcanoes in the central Andes spanning 1992-2002, and found four areas of deformation. I constrained the temporal variability of the deformation, the depth of the sources of deformation assuming a variety of source geometries and crustal structures, and the possible cause of the deformation. I do not observe deformation associated with eruptions at several volcanoes, and I discuss the possible explanations for this lack of deformation. In addition, I constrain the amount of co-seismic and post-seismic slip on the subduction zone fault interface from the following earthquakes: 1995 Mw 8.1 Antofagasta, Chile; 1996 Mw 7.7 Nazca, Peru; 1998 Mw 7.1 Antofagasta, Chile; and 2001 Mw 8.4 Arequipa, Peru. In northern Chile, I compare the location and magnitude of co-seismic slip from 5 Mw > 7 earthquakes during the past 15 years with the post-seismic slip distribution. There is little post-seismic slip from the 1995 and 1996 earthquakes relative to the 2001 event and other recent subduction zone earthquakes.
\r\n" }, { "name": "Weiss, Benjamin Paul", "degree": "PhD", "year": "2003", "title": "Martian Paleomagnetism with the SQUID Microscope", "advisor": "Kirschvink, Joseph L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02032003-104251", "creators": [ { "name": { "family": "Weiss", "given": "Benjamin Paul" }, "id": "Weiss-Benjamin-Paul", "display_name": "Weiss, Benjamin Paul" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "plansci" ], "doi": "10.7907/87T4-9E64", "abstract": "Rocks should preserve natural remanent magnetizations with stable directional and intensity information at levels ~1000 times below that of the noise level on today's best moment magnetometers. The superconducting quantum interference device (SQUID) Microscope is a new, high-resolution magnetometer that can now detect such weak signals. It maps the magnetic fields above samples with a spatial resolution of <100 \u00b5m and a moment sensitivity of <10\u207b\u00b9\u2075 Am\u00b2. It therefore provides data with a resolution directly comparable with that of other common petrographic techniques. This thesis describes applications of SQUID microscopy to a variety of problems in the planetary sciences.
\r\n\r\nA SQUID microscope paleomagnetic conglomerate test demonstrates that ALH84001 has been cooler than ~40\u00b0C since before its ejection from the surface of Mars at 15 Ma. Because this temperature cannot sterilize most bacteria or eukarya, these data support the hypothesis that meteorites could transfer life between planets in the solar system. These and other data on panspermia demand a re-evaluation of the long-held assumption that terrestrial life evolved in isolation on Earth.
\r\n\r\nSubsequent magnetic and textural studies of the meteorite show that 4 Ga ALH84001 carbonates containing magnetite and pyrrhotite carry a stable natural remanent magnetization. \u2074\u2070Ar/\u00b3\u2079Ar thermochronology demonstrates that this magnetization originated at 3.9-4.1 Ga on Mars. This magnetization is the oldest known for a planetary rock, and its strong intensity suggests that Mars had generated a geodynamo at or before 4 Ga. The intensity of the field that magnetized ALH84001 was roughly within an order of magnitude of that at the surface of the present-day Earth, sufficient for magnetotaxis by the bacteria whose magnetofossils have been reported in ALH84001 and possibly for the production of the strong crustal anomalies.
\r\n\r\n\u2074\u2070Ar/\u00b3\u2079Ar thermochronology calculations also provide an explanation for why ALH84001 contains a sample of an apparently ancient martian atmosphere. Because this gas is enriched in light isotopes of H and N relative to that on present-day Mars, this supports the hypothesis that the planet has experienced significant atmospheric loss since 4 Ga. These calculations also suggest that for the last 4 Gyr, average surface temperatures on Mars may not have been much higher than the present cold conditions.
" }, { "name": "Billen, Magali Isabelle", "degree": "PhD", "year": "2002", "title": "I. Seafloor Morphology of the Osbourn Trough and Kermadec Trench and II. Multiscale DynamiCS of Subduction Zones", "advisor": "Stock, Joann M.; Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11012001-142941", "creators": [ { "name": { "family": "Billen", "given": "Magali Isabelle" }, "id": "Billen-Magali-Isabelle", "orcid": "0000-0002-7316-1791", "display_name": "Billen, Magali Isabelle" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/W46E-ZY34", "abstract": "This thesis aims to demonstrate that integration of detailed observations of deformation at short to long length scales with carefully formulated numerical modeling is an effective method for simulating the complex multiscale nature of mantle-lithosphere dynamics. In Part I, marine geophysical observations are used to determine the origin of the Osbourn Trough, a long linear depression within the Pacific Plate seaward of the Tonga-Kermadec Trench, and to determine the elastic strength of the subducting plate within the Kermadec Trench. Based on the morphology of the seafloor from swath bathymetry mapping and modeling of magnetic data, we conclude that the Osbourn Trough is an extinct spreading center which stopped spreading about 72 million years ago. Swath bathymetry mapping within the Kermadec Trench reveals extensive faulting within the trench on the subducting plate, with oblique grabens aligned perpendicular to the absolute plate motion direction. Using isostatic flexural response methods, we find that the flexural rigidity (1e19-1e20 Nm) is smaller than normally found for old oceanic lithosphere reflecting a local reduction in the strength of the plate.
\r\n\r\nIn Part II, regional 3-D dynamic models of the Tonga-Kermadec and Aleutian subduction zones are used to constrain lateral variations in viscosity in the upper mantle. Modeling of the dynamic topography of the overriding plate for the Tonga-Kermadec subduction zone requires a low viscosity and low density (-20 kg/m\u00b3) region within the wedge above the slab to decouple the slab-induced flow from. These efforts lead to a good fit to the observed shallow bathymetry on the overriding plate for a model with a slab density anomaly due to temperature of ~80 kg/m\u00b3. However, the geoid anomaly above the subduction zone is too large by 20-40 m at length scales of 100-1000 km. A reduction of the slab density by a factor of 1.5 is needed to match both the geoid and topography, suggesting the density anomaly of the slab due to temperature is compensated within the upper mantle (~100-300 km). Similar modeling for the Aleutians including a narrower low viscosity region and smaller density anomaly (-10 kg/m\u00b3) in the wedge is able to fit the geoid and topography without reducing the slab density.
" }, { "name": "Dyudina, Ulyana Anatolyevna", "degree": "PhD", "year": "2002", "title": "Light Scattering in the Clouds on Jupiter", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04242012-142706141", "creators": [ { "name": { "family": "Dyudina", "given": "Ulyana Anatolyevna" }, "id": "Dyudina-Ulyana-Anatolyevna", "display_name": "Dyudina, Ulyana Anatolyevna" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "chair", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "co-chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/N7JD-N925", "abstract": "We construct maps of jovian cloud properties from images taken simultaneously by the Galileo solid state imaging system (SSI) and the near-infrared mapping spectrometer (NIMS) at 26 visible and near infrared wavelengths, ranging from 0.41 to 5.2 \u00b5m. Three regions - the Great Red Spot (GRS), a 5-micron Hot Spot, and one of the White Ovals - are studied. We perform a principal component analysis (PCA) on the multispectral images. PCA shows that the pixel-to-pixel variations at the different wavelengths are highly correlated, and that 91% of the variance in the data can be summarized using only three maps. The three maps are combined into one color map, which indicates different 26-wavelength spectra as different colors. Using the representative spectra for each color we compare different areas on the map qualitatively. We find that in the GRS there is a red chromophore which is associated with clouds that block 5-\u00b5m emission. At the hot spot and white oval regions there is no chromophore associated with clouds. Most of the bright, optically thick clouds blocking thermal emission are also extended vertically to the upper troposphere. Some of the bright, optically thick clouds blocking thermal emission are deep and do not extend vertically to the upper troposphere. A small convective stormlike cloud to the northwest of the GRS is unusually reflective at long wavelengths (4\u00b5m) and might indicate large particles.
\r\n\r\nWe study lightning on Jupiter and the clouds illuminated by the lightning. The Galileo SSI lightning images have a resolution of 25 km/pixel and are able to resolve the diffuse spots of light scattered in the clouds, which have full widths at half maximum in the range 90-160 km. We compare the lightning images with the images produced by our 3D Monte Carlo light scattering model. The model reproduces non isotropic non-conservative scattering of the photons in the non-homogeneous opacity distribution. We derive that some of the observed scattering patterns are produced in a 3D cloud rather than in a plane-parallel cloud layer, suggesting deep convection. For the six flashes studied, the clouds above the lightning are optically thick (\u0393 > 5). Lightning is as deep as the bottom of the water cloud. Jovian flashes are more regular\r\nand circular than the largest terrestrial flashes observed from space.
" }, { "name": "Ji, Chen", "degree": "PhD", "year": "2002", "title": "Analysis of Complex Faulting: Wavelet Transform, Multiple Datasets and Realistic Fault Geometry", "advisor": "Helmberger, Donald V.; Anderson, Don L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02172012-155442347", "creators": [ { "name": { "family": "Ji", "given": "Chen" }, "id": "Ji-Chen", "display_name": "Ji, Chen" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Anderson", "given": "Don L." }, "id": "Anderson-D-L", "role": "co-advisor", "display_name": "Anderson, Don L." } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "chair", "display_name": "Anderson, Donald L." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Simons", "given": "Mark" }, "id": "Simons-M", "orcid": "0000-0003-1412-6395", "role": "member", "display_name": "Simons, Mark" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/XYM3-4718", "abstract": "This thesis presents the studies of two recent large and well-recorded earthquakes,\r\nthe 1999 Hector Mine and Chi-Chi earthquakes. A new procedure for the determination\r\nof rupture complexity from a joint inversion of static and seismic data was\r\nfirst developed. This procedure applies a wavelet transform to separate seismic information\r\nrelated to the spatial and temporal slip history, then uses a simulated\r\nannealing algorithm to determine the finite-fault model that minimizes the objective\r\nfunction described in terms of wavelet coefficients. This method is then applied to\r\nsimultaneously invert the slip amplitude, slip direction, rise time and rupture velocity\r\ndistributions of the Hector Mine and Chi-Chi earthquakes with both seismic and\r\ngeodetic data. Two slip models are later verified with independent datasets.
\r\n\r\n\r\nResults indicate that the seismic moment of the Hector Mine earthquake is 6.28 x\r\n10^(19) Nm, which is distributed along a \"Y\" shape fault geometry with three segments.\r\nThe average slip is 1.5 m with peak amplitudes as high as 7 m. The fault rupture has\r\nan average slip duration of 3.5 sec and a slow average rupture velocity of 1.9 km/ sec,\r\nresulting in a 14 sec rupture propagation history. The rise time appears to be roughly\r\nproportional to slip, and the two branches of \"Y\" shape fault rupture together. The\r\nChi-Chi earthquake is the best-recorded large earthquake so far. Its seismic moment\r\nof 2.7 x 10^(20) Nm is concentrated on the surface of a \"wedge shaped\" block. The rupture\r\nfront propagates with a slow rupture velocity of about 2.0 km/ sec. The average slip\r\nduration is 7.2 sec. Four interesting results are obtained: (1) The sinuous fault plane\r\nstrongly affects both spatial and temporal variation in slip history; (2) Long-period\r\npeak slip velocity increases as the rupture propagates; (3) The peak slip velocity\r\nnear the surface is in general higher than on the deeper portion of the fault plane as\r\npredicted by dynamic modeling [e.g., Oglesby et al., 1998]; and (4) the complex fault\r\ngeometry and slip distribution are related to the two transfer zones obliquely across\r\nTaiwan, which separate Taiwan into three regions with different tectonic activity. The transfer zone in the north can be explained by the slab breakoff mechanism proposed\r\nby Teng et al. [2000] recently.
\r\n" }, { "name": "Kessel, Ronit", "degree": "PhD", "year": "2002", "title": "The Activity of Chromite in Multicomponent Spinels: An Experimental Study with Implications for the Metamorphic History of Equilibrated Ordinary Chondrites", "advisor": "Stolper, Edward M.; Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:02172012-143736224", "creators": [ { "name": { "family": "Kessel", "given": "Ronit" }, "id": "Kessel-Ronit", "display_name": "Kessel, Ronit" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "co-advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geochem" ], "doi": "10.7907/0774-JM48", "abstract": "An experimental technique for evaluating the activity of chromite in\r\nmulticomponent spinels was developed by equilibrating the spinel of interest with a Pt-alloy\r\nunder a controlled temperature and oxygen fugacity. The thermodynamic\r\nproperties of the ternary Pt-Fe-Cr system was evaluated, such that activities of Cr and Fe\r\nin an equilibrated Pt-alloy can be used to calculate the activity of chromite in the spinel of\r\ninterest.
\r\n\r\nThe ternary activity model formulation used is based on the characterization of\r\neach bounding binary system, Pt-Fe, Pt-Cr, Fe-Cr, with the addition of ternary interaction\r\nterms. The Pt-Fe and Pt-Cr systems are described as asymmetric regular solutions with\r\ninteraction parameters of W_(PtFe)=-138.0\u00b13.3, W_(FePt)=-90.8\u00b124.0, and W_(PtCr)=-129.1\u00b11.2,\r\nW_(CrPt)=-80.9\u00b14.4, and D_(PtCr)=+94.4\u00b12.5 kJ/mol (1\u03c3), respectively. Combined with\r\nliterature thermodynamic properties for the Fe-Cr system, the ternary interaction\r\nparameters in the Pt-Fe-Cr system were found to be C_(Cr)=0, C_(Pt)=+ll5.7, and C_(Fe)=-68.6\r\nkJ/mol.
\r\n\r\nUsing this technique, the metamorphic history of equilibrated ordinary chondrites\r\nwas evaluated by examining the compositions and textures of olivines, pyroxenes,\r\nspinels, and alloys. Equilibrium temperatures based on Fe-Mg exchange between olivine\r\nand spinel exhibit a range of 680-796\u00b0C in H, L, and LL ordinary chondrites spanning\r\npetrographic type 4 to 6. Type 4 chondrites in all groups record variable temperatures\r\nthat are lower than or equal to those of types 5 and 6 chondrites, implying decoupling of\r\nmetamorphic temperature from petrographic type. Cooling rates near 800\u00b0C were found to be 1-3 K/Ma, slow enough to allow continous re-equilibration of spinel grains from\r\npeak metamorphic temperatures to the olivine-spinel equilibration temperature.
\r\n\r\nThe temperature-oxygen fugacity relationships in equilibrated H chondrites were\r\nconstrained from spinel-alloy and olivine-pyroxene-alloy phase assemblages based on the\r\nmineral compositions and activity-composition models. Log_(10)f_(02) values based on the\r\nassemblage olivine-pyroxene-alloy are -1.75\u00b10.02 log units below Iron-W\u00fcstite (IW)\r\nbuffer, regardless of petrographic type. The log_(10)f_(02) values calculated based on the\r\nspinel-alloy coexistence are at least ~1.5 log units more oxidizing than those based on the\r\nolivine-pyroxene-alloy if olivine-spinel equilibration temperatures (728-820\u00b0C) are\r\nassumed. This probably indicates that closure for spinel-alloy equilibria occurred under\r\nretrograde conditions at temperatures below 700\u00b0C.
" }, { "name": "Mukhopadhyay, Sujoy", "degree": "PhD", "year": "2002", "title": "I. Extraterrestrial \u00b3He in the Sedimentary Record. II. Geochemistry of Shield Stage Lavas from Kauai, Hawaii", "advisor": "Farley, Kenneth A.; Wyllie, Peter J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02232012-115811346", "creators": [ { "name": { "family": "Mukhopadhyay", "given": "Sujoy" }, "id": "Mukhopadhyay-Sujoy", "display_name": "Mukhopadhyay, Sujoy" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "advisor", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "co-advisor", "display_name": "Wyllie, Peter J." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." } ], "option_major": [ "geochem" ], "doi": "10.7907/XPM2-1Q79", "abstract": "(I) Extraterrestrial ^3He in the sedimentary record:
\r\n\r\nAnalyses of ^3He, a tracer of interplanetary dust particles (IDPs), in marine\r\ncarbonates from the Italian Apennines exclude large, long-lived enhancement in the IDP\r\nflux between 75 Ma and 39 Ma, These data in combination with previous ^3He\r\nmeasurements preclude recurrent comet showers with periods less than 38 Myrs. The IDP\r\naccretion rate at the K-T boundary (65 Ma) is invariant and has, therefore, been used as a\r\nchronometer to estimate the duration of the K-T extinction event. Our calculation\r\nsuggests that the duration of the boundary event is 10000 \u00b1 2000 years, and the\r\ndeposition time of the impact ejecta layer is less than 60 years. These results indicate that\r\nthe mass-extinction at the K-T boundary was catastrophic, ruling out volcanism and sea\r\nlevel changes as important factors and requiring an extremely rapid faunal turnover rate.
\r\n\r\nBecause extraterrestrial ^3He is preserved in the sedimentary record for at least 480\r\nMa, the ^3He carrier phase(s) must be chemically stable on the seafloor and resist diffusion\r\nover geologic time, Our chemical leaching and step-heating experiments indicate that the\r\ncarrier phase(s) may be magnetite or more probably associated with magnetite, The\r\nassociation may be in the form of composite grains or nanometer thick rims.
\r\n\r\n(II) Geochemistry of shield stage lavas from Kauai, Hawaii:
\r\n\r\nWe measured He, Sr, Nd, Pb, and Os isotope ratios and major and trace element\r\nconcentrations in shield lavas from Kauai, Hawaii. The range of ^3He/^4He ratios (17-28\r\nR_A) measured from the Kauai shield is similar to that reported from Loihi Seamount and is clearly distinct from other Hawaiian shield volcanoes. These results challenge the\r\nprevailing notion that high ^3He/^4He ratios are restricted to the pre-shield stage of\r\nHawaiian volcanism. ^3He/^4He ratios in Kauai shield lavas vary erratically with\r\nstratigraphic position and on timescales of 100 years. These variations in ^3He/^4He ratios\r\nare correlated with variations in radiogenic isotope ratios, suggesting rapid changes in\r\nparental magma composition with time.
\r\n\r\nOur new geochemical data from Kauai shield lavas require the involvement of a\r\ndepleted mantle component that is normally sampled only during the post-shield and\r\npost-erosional stages of Hawaiian volcanism. In addition, the Kauai data support the\r\nexistence of a single high ^3He^4He reservoir in the Earth's mantle and suggest that the\r\nproportion of the high ^3He/^4He component in the Hawaiian plume has varied significantly\r\nwith time. The long-term evolution of the Hawaiian plume and the temporal variability\r\nrecorded in Kauai lavas cannot be explained by a steady-state cylindrically zoned plume\r\nand require more complex time-varying heterogeneities.
\r\n\r\n" }, { "name": "Nazareth, Julie Jeannine", "degree": "PhD", "year": "2002", "title": "The Structure of the Crust and Distribution of Earthquakes in Southern California", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02152012-100334523", "creators": [ { "name": { "family": "Nazareth", "given": "Julie Jeannine" }, "id": "Nazareth-Julie-Jeannine", "display_name": "Nazareth, Julie Jeannine" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Hauksson", "given": "Egill" }, "id": "Hauksson-E", "orcid": "0000-0002-6834-5051", "role": "member", "display_name": "Hauksson, Egill" }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geophys" ], "doi": "10.7907/6KNK-GG47", "abstract": "The lithologically and tectonically complex crust of southern California and the current broad deformation zone accommodating the relative motion between the Pacific and North American plates, result in significant variations in style, depth distribution, and rate of earthquakes, and thus also in the seismic hazard across southern California.\r\nAlthough the thickness of the seismogenic crust is an important parameter in seismic hazard analysis, it has never been determined systematically for southern California. Seismogenic thickness can be predicted by the depth distribution of the moment release of regional seismicity. The seismogenic thickness of southern California is highly variable, ranging from less than 10 km in the Salton Trough to greater than 25 km at the southwestern edge of the San Joaquin Valley. On average, the seismogenic thickness of southern California is 15.0 km. Seismogenic thickness along the major strike slip systems of southern California can vary significantly along strike. Fault segmentation based upon surface features does not correspond to the variation in seismogenic thickness and thus the potential down-dip width of the fault. A model of the broad scale features of the crust and upper mantle structure of the borderland-continent transition zone adjacent to Los Angeles constrains the crustal thickness and the location and width of the transition zone. The data require the Moho to deepen significantly to the north, dramatically increasing the crustal thickness over a relatively short distance of 20-25 km. The Moho is coherent and laterally continuous beneath the Inner California Borderland and transition zone. The Inner Borderland seems to be modified and thickened oceanic crust, with the oceanic upper mantle intact beneath it. The static stress change triggering model has some validity and can be useful in explaining apparently triggered seismicity within one fault length of a large mainshock. However, because its applicability varies between different sequences, its general application to seismic hazard evaluation requires more refinement and the inclusion of parameters such as tectonic regime, regional stress state, and fault strength." }, { "name": "Niemi, Nathan Alan", "degree": "PhD", "year": "2002", "title": "Extensional Tectonics in the Basin and Range Province and the Geology of the Grapevine Mountains, Death Valley Region, California and Nevada", "advisor": "Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09122001-155631", "creators": [ { "name": { "family": "Niemi", "given": "Nathan Alan" }, "id": "Niemi-Nathan-Alan", "orcid": "0000-0002-3380-3024", "display_name": "Niemi, Nathan Alan" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." } ], "option_major": [ "geol" ], "doi": "10.7907/1HWM-JP59", "abstract": "Geologic mapping provides structural and stratigraphic observations which lead to new insights into the magnitude, timing, and rate of Cenozoic extensional tectonism in the Death Valley region of the Basin and Range province in the western United States. Detailed mapping of the Grapevine Mountains, in northeastern Death Valley, yields new information on the structural evolution of the Titus Canyon anticline, a west-vergent fold of the Cordilleran thrust belt. The Grapevine Mountains contain the longest exposure of west-vergent folding in the Death Valley region, and detailed mapping supports previous interpretation of this structure as a piece of a single, laterally continuous fold, whose extensionally dismembered fragments form a key marker in reconstructions of Basin and Range extension. Such an interpretation suggests >100 km of west-north-west translation of the Grapevine Mountains away from the Sheep Range in late Cenozoic time. Correlation and re-interpretation of Cenozoic sedimentary and volcanic strata between the Sheep Range and the Grapevine Mountains indicate that this extension occurred on two separate extensional systems, the Sheep Range detachment system, and the Northeastern Death Valley detachment system. The former was active from 16-14 Ma, while the latter was active from 12.5-8 Ma. In contrast, stratigraphic and sedimentological data from the Eagle Mountain Formation suggests that, although extension across the central Death Valley region accommodated a similar magnitude of extension as the northern Death Valley region, ~100 km, extension across this region occurred post-11 Ma, and largely between 8-6 Ma. New geodetic and paleoseismic data are also presented from the eastern Basin and Range. These data indicate that slow (~4 mm/yr), long term (100s ka) strain accumulation is accommodated, geologically, by short (1000s yr) periods of fast (>1cm/yr) strain release, suggesting that the appearance of diffuse deformation across the eastern Basin and Range is likely due to time-averaging of many temporally discrete high-strain release earthquake clusters. These observations together suggest that the diffuse nature of intra-continental extension in the Basin and Range province may be the result of the summation of many spatially and temporally distinct extensional events, which, when active, progress at very high rates" }, { "name": "Oskin, Michael Eugene", "degree": "PhD", "year": "2002", "title": "Part I. Tectonic Evolution of the Northern Gulf of California, Mexico, Deduced from Conjugate Rifted Margins of the Upper Delf\u00edn Basin. Part II. Active Folding and Seismic Hazard in Central Los Angeles, California", "advisor": "Stock, Joann M.; Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11252001-103911", "creators": [ { "name": { "family": "Oskin", "given": "Michael Eugene" }, "id": "Oskin-Michael-Eugene", "orcid": "0000-0002-6631-5326", "display_name": "Oskin, Michael Eugene" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "chair", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." } ], "option_major": [ "geol" ], "doi": "10.7907/4TQK-NH19", "abstract": "Part I of this thesis addresses the tectonic evolution of the Pacific-North America plate boundary through northwest Mexico and its implications for rifting processes. Offset ignimbrites support 255\u00b110 km of opening across the Upper Delf\u00edn basin of the northern Gulf of California. Additional deformation from the continental margins supports 296\u00b117 km total plate boundary displacement between coastal Sonora and the Main Gulf Escarpment in Baja California, of which at least 276\u00b113 km occurred since ~6 Ma. This strain history requires that the plate boundary localized into the the northern Gulf of California during latest Miocene time. Only a narrow width of upper continental crust foundered into the Upper Delf\u00edn basin, such that most of the crust between Isla Tibur\u00f3n and Baja California must be new transitional oceanic crust and possibly lower continental crust contributed by inflow from the rift flanks. Extension of the margins of the Upper and Lower Delf\u00edn basins is <40% in most places, though the whole crustal column may have been thinned by a factor of two, further supporting that lower crustal flow has operated here. Opening of the Upper Delf\u00edn basin was accompanied by a steady or increased strain rate on its continental margins, contrary to the expected rheology of a narrow continental rift. Reevaluation of a critical deposit of marine rocks on Isla Tibur\u00f3n indicates that initial marine incursion in the northern Gulf of California also occurred during latest Miocene time. Together, these records suggest that opening of the Upper Delf\u00edn basin was an abrupt event, accompanied by a localized zone of intense extension, marine incursion, and a rapid increase in strain rate. Continental rupture in the Upper Delf\u00edn basin does not appear to have been a response to crustal weakening by intracontinental extension, but rather may have resulted from a significant increase in strain rate, brought on by a change in boundary forces. Part II of this thesis develops methods to estimate seismic hazard from blind reverse faults by analysis of fault-related folding of Late Quaternary strata, with application to the Elysian Park anticline of Los Angeles, California.
" }, { "name": "Schauble, Edwin Arthur", "degree": "PhD", "year": "2002", "title": "I. Predicting Equilibrium Stable Isotope Fractionations of Iron, Chlorine, and Chromium. II. Oxygen-Isotope Investigation of Mesozoic and Cenozoic Granitoids of the Northeastern Great Basin, Nevada and Utah", "advisor": "Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04102012-131908152", "creators": [ { "name": { "family": "Schauble", "given": "Edwin Arthur" }, "id": "Schauble-Edwin-Arthur", "display_name": "Schauble, Edwin Arthur" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "chair", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Eiler", "given": "John M." }, "id": "Eiler-J-M", "orcid": "0000-0001-5768-7593", "role": "member", "display_name": "Eiler, John M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geol" ], "doi": "10.7907/4sdq-m548", "abstract": "Theoretical studies of the stable isotope geochemistry of iron, chlorine, and chromium are presented, with the goal of providing a framework to aid interpretations of\r\nnew measurements and to identify promising areas for future study. In addition, new oxygen-isotope measurements of Mesozoic and Cenozoic granitoids from the northeastern Great Basin are used to constrain the temporal evolution of magmatic sources in the region.
\r\n\r\nThe stable isotope compositions of elements heavier than sulfur (atomic no. 16) are generating great geochemical interest, now that new mass-spectrometry techniques\r\nmake it possible to measure their isotopic abundances with high precision. Theoretical calculations for three of these elements (iron, chlorine, and chromium) are made using\r\npublished infrared, Raman, and inelastic neutron scattering measurements of vibrational frequencies, in combination with empirical and ab initio force-field estimates of unknown frequencies. The calculations suggest that a number of natural processes can drive significant stable isotope fractionations of heavy elements, including oxidation/reduction during the precipitation or dissolution of dissolved metals (inorganically or organically),\r\nand bond-partner exchange during hydrothermal alteration, or degradation of Cl-bearing organic compounds. At equilibrium and 25\u00b0C, ^(56)Fe/^(54)Fe will be ~5\u2030 higher in\r\n[Fe(H_2O)_6]^(3+) than in coexisting [Fe(H_2O)_6]^(2+), ^(53)Cr/^(52)Cr will be ~6-7\u2030 higher in [CrO_4]^(2-) than in coexisting [Cr(H_2O)_6]^(3+) or Cr_2O_3, and aqueous Cl- will be ~2-3\u2030 lighter than coexisting alteration minerals like mica and amphibole.
\r\n\r\nOxygen isotope measurements of whole-rock samples from granitoid plutons in the northeastern Great Basin suggest that two or three different types of source rocks were melted in varying proportions during the three stages of magmatism in this region in the Late Jurassic, Late Cretaceous, and mid-Cenozoic. Radiogenic-isotope measurements were previously made on the same samples. Late Cretaceous (90-70 Ma) granites have high \u03b4^(18)O (+9.3 to + 12.1) and ^(87)Sr/^(86)Sr_i (0.711 to 0.734), and low \u03b5Nd\r\n(-13 to -23) indicating that their source was dominated by evolved crustal sediments and basement. However, late Jurassic plutons in this region span a larger range of \u03b4^(18)O values (+7.2 to + 13.2), despite having Sr and Nd isotopic compositions that are much less suggestive of an ancient crustal component (^(87)Sr/^(86)Sr_i = 0.705 to 0.711, \u03b5Nd = -2.5 to -6.5) than the Late Cretaceous plutons, suggesting moderate to extensive mixing or\r\nassimilation of high-\u03b4^(18)O sedimentary rocks into a more mafic parent melt. The 40-25 Ma Cenozoic plutons (\u03b4^(18)O = +7.0 to + 9.7, ^(87)Sr/^(86)Sr_i = 0.707 to 0.717, \u03b5Nd= -13.2 to -26.3) probably have a source dominated by continental basement. The Cenozoic plutons can be subdivided into a higher \u03b4^(18)O (+8.6 to + 9.7) southern group and a lower \u03b4^(18)O (+7.0 to + 8.2) northern group across a Crustal Age Boundary (CAB) at roughly 40\u00b0 40'\r\nN; this CAB coincides with a radiogenic isotope boundary defined with the same samples, as well as with the approximate southern limit of exposure of Archean\r\nbasement. The low \u03b4^(18)O values and depleted lead isotope compositions of the Lower Array (northern) samples indicate that Archean age basement is present beneath a large\r\narea of the most northeasterly part of the Great Basin. A further, speculative conclusion is that \u03b4^(18)O of the (meta)sedimentary source region may have dropped by 2-3\u2030 as a result of fluid-rock interaction sometime between the Jurassic and Late Cretaceous magmatic episodes.
" }, { "name": "Stewart, Sarah Toby", "degree": "PhD", "year": "2002", "title": "Collisional Processes Involving Icy Bodies in the Solar System", "advisor": "Ahrens, Thomas J.; Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09242008-095607", "creators": [ { "name": { "family": "Stewart", "given": "Sarah Toby" }, "id": "Stewart-Sarah-Toby", "orcid": "0000-0001-9606-1593", "display_name": "Stewart, Sarah Toby" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "co-advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" } ], "option_major": [ "plansci" ], "doi": "10.7907/0V4Q-VF61", "abstract": "1. The Shock Hugoniot of Solid Ice:
\r\n\r\nWe present a complete description of the solid ice Hugoniot based on new shock wave experiments conducted at an initial temperature of 100 K and previously published data obtained at 263 K. We identify five regions on the solid ice Hugoniot: (1) elastic shock waves, (2) ice Ih deformation shocks, transformation shocks to (3) ice VI, (4) ice VII, and (5) liquid water. In each region, data obtained at different initial temperatures are described by a single Us - Δup shock equation of state. The dynamic strength of ice Ih is strongly dependent on temperature. The Hugoniot Elastic Limit varies from 0.05 to 0.62 GPa, as a function of temperature and peak shock stress. We estimate the entropy and temperature along the 100 and 263 K Hugoniots and derive the critical pressures for shock-induced incipient (IM) and complete (CM) melting upon release. On the 100 K Hugoniot, the critical pressures are about 4.5 and between 5-6 GPa for IM and CM, respectively. On the 263 K Hugoniot, the critical pressures are 0.6 and 3.7 GPa for IM and CM, lower than previously suggested. Shock-induced melting of ice will be widespread in impact events.
\r\n\r\n2. Rampart Crater Formation on Mars:
\r\n\r\nWe present a model for the fluidization of Martian rampart crater ejecta blankets with liquid water based on the shock physics of cratering onto an ice-rich regolith. We conducted simulations of crater formation on Mars, explicitly accounting for the equations of state and shock-induced melting criteria for both the silicate and ice components and using strength models constrained by the observed transition diameter DTr from simple to complex craters on Mars, where DTr = 8 km corresponds to an effective yield strength of 107 Pa.
\r\n\r\nFor the observed size range of rampart craters (diameters D ≾ 30 km) and typical asteroidal impact conditions (silicate impactors, D ≾ 1 km, at 10 km s-1), we find that the hemispherical volume where subsurface ice is partially melted by the impact shock has a radius of about 15 projectile radii (rp), much larger than previous predictions of about 6 rp. The radius of the final crater is comparable to the radius of partial melting and more than half the ice within the excavated material is melted. Thus, the amount of shock-melted water incorporated into the continuous ejecta blanket is within a factor of two of the near-surface ground ice content.
\r\n\r\nWe find that fluidized ejecta blankets may form in the current climate with mean surface temperatures of 200 K. Decreasing the effective yield strength of the modeled materials, e.g., by increasing the ice content or porosity, modifies the impact-induced flow in the excavated cavity, resulting in deeper projectile penetration, steeper ejection angles, higher crater rim uplift, and reduced final crater diameter. The volume fraction of shock-melted water in the ejecta blanket increases with distance from the crater rim. The horizontal flow velocities during emplacement of fluidized ejecta (~ 10 - 1000 m s-1) is nearly constant in the continuous ejecta blanket and within the range of large terrestrial landslides. Therefore, ground-hugging debris flow conditions are achieved. The ejecta blanket properties from impacts into a Martian regolith containing 20-40%vol near-surface ice are consistent with the fraction of liquid water inferred from models of ejecta flow rheologies which produce rampart morphologies, about 10-30% liquid water by volume [Ivanov, B. A., Solar System Research, 30, 43-58, 1996].
\r\n\r\nWe present a model for the formation of different rampart ejecta morphologies which may be used in conjunction with an ejecta blanket debris flow model to map the distribution of ground ice. In addition, we find that formation of single or multiple-rampart ejecta blankets does not require pre-existing liquid water in the Martian crust. We estimate the minimum water content in observed rampart ejecta blankets to be equivalent to a global layer of water 0.6 m thick. Based on the crater sampling efficiency, the implied global Martian ice content, within the upper 2 km of the crust, is equivalent to a global layer of water 100 m deep. This result is comparable to other estimates of HM2O content in the Martian crust.
\r\n" }, { "name": "Venkataraman, Anupama", "degree": "PhD", "year": "2002", "title": "Investigating the Mechanics of Earthquakes Using Macroscopic Seismic Parameters", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechETD:etd-06132002-094224", "creators": [ { "name": { "family": "Venkataraman", "given": "Anupama" }, "id": "Venkataraman-Anupama", "display_name": "Venkataraman, Anupama" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Rosakis", "given": "Ares J." }, "id": "Rosakis-A-J", "orcid": "0000-0003-0559-0794", "role": "member", "display_name": "Rosakis, Ares J." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/JS1E-X675", "abstract": "To understand the physics of earthquake rupture mechanics, we have to relate seismologically observable parameters to the dynamics of faulting. One of the key seismological parameters that will help us achieve this objective is radiated energy. In this work, we develop a new method of estimating radiated energy from regional data using an empirical Green's functions; we also modify existing methods of estimating radiated energy from teleseismic data by improving the corrections applied to the observed seismic data for attenuation and directivity effects. \r\n\r\nWe compute teleseismic estimates of radiated energy for 23 large subduction zone earthquakes recorded between 1992 and 2001; most of these earthquakes have a magnitude, Mw > 7.5, but we also include some smaller (Mw~6.5) well-studied subduction zone earthquakes and 6 crustal earthquakes. We compile the static stress drop estimates for these 29 earthquakes from published literature. We then determine radiation efficiency of these earthquakes using a stress relaxation model that relates measurable and macroscopic seismological parameters to the physical processes on the fault zone via fracture energy. We also determine the rupture velocity of these earthquakes from published literature. A comparison of radiation efficiencies and rupture velocities of these earthquakes with the expected theoreticial values for different modes of crack propagation validates the use of the stress relaxation model to understand earthquake rupture mechanics.\r\n\r\nFrom our calculations, we observe that most earthquakes have radiation efficiencies between 0.25 and 1 and are hence efficient in generating seismic waves, but tsunami earthquakes and two deep earthquakes, the 1994 deep earthquake that occurred in Bolivia and the 1999 Russia-China border earthquake, have very small radiation efficiencies (<0.25) and hence dissipate a large amount of energy on the fault plane. We suggest that the difference in the radiation efficiencies of the different types of earthquakes could be due to fundamental differences in the rupture mechanics of different events. In case of deep events, the energy is probably dissipated in thermal processes on the fault zone, while it is possible that the morphology of the trench causes branching and bifurcation of rupture resulting in the large energy dissipation during the rupture process of tsunami earthquakes." }, { "name": "Brodsky, Emily Elizabeth", "degree": "PhD", "year": "2001", "title": "Studies in Fluid Dynamics as Applied to Seismology and Volcanology", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08152001-152200", "creators": [ { "name": { "family": "Brodsky", "given": "Emily Elizabeth" }, "id": "Brodsky-Emily-Elizabeth", "orcid": "0000-0002-6855-6860", "display_name": "Brodsky, Emily Elizabeth" } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "geophys" ], "doi": "10.7907/XF8B-3F65", "abstract": "This thesis addresses three problems in seismology and volcanology by applying fluid dynamical theories that have been developed for engineering applications.
\r\n\r\nFault zones are proposed to operate analogously to journal bearings. A quantitative assessment of the physical regimes in which faults behave as lubricated systems is made using elastohydrodynamic theory. Elastohydrodynamic lubrication with typical parameters explains the following observable phenomenon: (1) a reduction in the frictional stress by 50% during large earthquakes, (2) a decrease in high-frequency (>1 Hz) radiation above a critical slip distance of a few meters and (3) a two orders of magnitude variation in scaled radiated energy between small (Mw < 4) and large earthquakes (Mw > 6).
\r\n\r\nRegionally triggered seismicity often occurs in geothermal areas. It is documented here that the 1999 Mw=7.4 Izmit, Turkey, earthquake was followed by widespread seismicity in Greece over a study region extending from 400 km to nearly 1000 km away from the epicenter. The increase in cataloged earthquakes is statistically significant at the 95% level. A related phenomenon is the regional triggering of volcanic eruptions. A model for triggering eruptions based on rectified diffusion is formulated and evaluated. The excess pressure from rectified diffusion in a typical basaltic system following a regional M\u22658 earthquake is between 0.001 and 0.02 MPa. Strong constraints on the porosity, size of the bubbly region, velocity structure and permeability must be imposed for rectified diffusion to be effective.
\r\n\r\nA fluid dynamical model based on supersonic nozzle flow is used to link observed seismic waves with the mass discharge rate of an explosive volcanic eruption. The method is tested by calculating the vertical mass discharge rate from Mount St. Helens for the beginning of the May 18, 1980 eruption. The observed seismic sources are modeled as thrusts due to a combination of the momentum flux of the erupted products and the pressure of the eruptive jet. The momentum discharge rate is converted to a mass discharge rate. The calculated mass ejected in the first 100 s is 1.6x10\u00b9\u00b9-4.6x10\u00b9\u00b9 kg. Since the total blast deposit is ~3.2x10\u00b9\u00b9-4.1x10\u00b9\u00b9 kg, one interpretation is that the directed blast had a significant (\u226540%) vertical component.
" }, { "name": "Eisner, Leo", "degree": "PhD", "year": "2001", "title": "A Reciprocity Method for Multiple Source Simulations", "advisor": "Clayton, Robert W.; Stock, Joann M.; Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08302001-030958", "creators": [ { "name": { "family": "Eisner", "given": "Leo" }, "id": "Eisner-Leo", "display_name": "Eisner, Leo" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "co-advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geophys" ], "doi": "10.7907/Y9S0-0S33", "abstract": "This thesis develops and applies the reciprocity method to assess the seismic site and path effects at a chosen location of interest. To do this, we show that the reciprocity theorem is valid for this application, and develop a technique to represent velocity models of sedimentary basins. Using these tools we test the accuracy of synthetic seismograms computed for southern California. Finally, we apply the reciprocity technique to evaluate the site and path effects for three selected sites in southern California.
\r\n\r\nThe first chapter describes the reciprocity method for simulating seismograms due to multiple earthquake sources at a site of interest. It shows a theoretical proof of the method and discusses the practical implementation and accuracy for the finite difference technique. The numerical tests show that the reciprocal simulations can be performed with the same level of accuracy as the forward calculations.
\r\n\r\nThe second chapter develops a new methodology to represent models of sedimentary basins with extremely low near surface velocities by replacing these velocities with equivalent medium parameters for a finite frequency signal. The new model has a higher minimum velocity, which makes the numerical simulations feasible, and minimizes the difference between the seismograms from the original and new model.
\r\n\r\nThe third chapter validates the velocity model by comparing synthetics and data. It applies the reciprocity method and compares the full waveform synthetic seismograms with a large number of weak motion data. The discrepancies between the predicted waveforms and the data are interpreted by analyzing the attributes of seismograms to find regions of the model that are in error.
\r\n\r\nFinally the reciprocity technique is applied to calculate site and path effects in the Los Angeles area for three selected sites by simulating 75 source scenarios on 5 major southern California faults. The largest amplitudes at the selected sites are obtained from earthquakes on local faults rather than an earthquake on the San Andreas fault.
" }, { "name": "Goreva, Julia S.", "degree": "PhD", "year": "2001", "title": "Origin of Th/U Variations in Chondritic Meteorites", "advisor": "Burnett, Donald S.; Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:04252014-150216789", "creators": [ { "name": { "family": "Goreva", "given": "Julia S." }, "id": "Goreva-Julia-S", "display_name": "Goreva, Julia S." } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geochem" ], "doi": "10.7907/hfsz-ym11", "abstract": "Isotope dilution thorium and uranium analyses of the Harleton chondrite show a\r\nlarger scatter than previously observed in equilibrated ordinary chondrites (EOC). The\r\nlinear correlation of Th/U with 1/U in Harleton (and all EOC data) is produced by\r\nvariation in the chlorapatite to merrillite mixing ratio. Apatite variations control the U\r\nconcentrations. Phosphorus variations are compensated by inverse variations in U to\r\npreserve the Th/U vs. 1/U correlation. Because the Th/U variations reflect phosphate\r\nampling, a weighted Th/U average should converge to an improved solar system Th/U.\r\nWe obtain Th/U=3.53 (1-mean=0.10), significantly lower and more precise than previous\r\nestimates.
\r\n\r\nTo test whether apatite also produces Th/U variation in CI and CM chondrites, we\r\nperformed P analyses on the solutions from leaching experiments of Orgueil and\r\nMurchison meteorites.
\r\n\r\nA linear Th/U vs. 1/U correlation in CI can be explained by redistribution of\r\nhexavalent U by aqueous fluids into carbonates and sulfates.
\r\n\r\nUnlike CI and EOC, whole rock Th/U variations in CMs are mostly due to Th\r\nvariations. A Th/U vs. 1/U linear correlation suggested by previous data for CMs is not\r\nreal. We distinguish 4 components responsible for the whole rock Th/U variations: (1) P\r\nand actinide-depleted matrix containing small amounts of U-rich carbonate/sulfate phases\r\n(similar to CIs); (2) CAIs and (3) chondrules are major reservoirs for actinides, (4) an\r\neasily leachable phase of high Th/U. likely carbonate produced by CAI alteration.\r\nPhosphates play a minor role as actinide and P carrier phases in CM chondrites.
\r\n\r\nUsing our Th/U and minimum galactic ages from halo globular clusters, we\r\ncalculate relative supernovae production rates for 232Th/238U and 235U/238U for different\r\nmodels of r-process nucleosynthesis. For uniform galactic production, the beginning of the\r\nr-process nucleosynthesis must be less than 13 Gyr. Exponentially decreasing production is also\r\nconsistent with a 13 Gyr age, but very slow decay times are required (less than 35 Gyr),\r\napproaching the uniform production. The 15 Gyr Galaxy requires either a fast initial\r\nproduction growth (infall time constant less than 0.5 Gyr) followed by very low decrease (decay\r\ntime constant greater than 100 Gyr), or the fastest possible decrease (\u22488 Gyr) preceded by slow in fall\r\n(\u22487.5 Gyr).
\r\n" }, { "name": "Hardebeck, Jeanne Louise", "degree": "PhD", "year": "2001", "title": "The Crustal Stress Field in Southern California and its Implications for Fault Mechanics", "advisor": "Kanamori, Hiroo; Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242013-095637288", "creators": [ { "name": { "family": "Hardebeck", "given": "Jeanne Louise" }, "id": "Hardebeck-Jeanne-Louise", "display_name": "Hardebeck, Jeanne Louise" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "co-advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "chair", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Hauksson", "given": "Egill" }, "id": "Hauksson-E", "orcid": "0000-0002-6834-5051", "role": "member", "display_name": "Hauksson, Egill" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "geophys" ], "doi": "10.7907/198c-1e38", "abstract": "A high-resolution image of crustal stress orientation, determined from the inversion of earthquake focal mechanisms, provides insights into the mechanics and evolution of faulting in southern California. The plate boundary region is a wide, complex zone of deformation, and the stress field also appears to be spatially heterogeneous. Temporal variations in stress orientation are observed as well. The observed stress rotations due to the 1992 Landers earthquake are used to make an order of magnitude estimate of the deviatoric stress magnitude at seismogenic depths. The inferred deviatoric stress is on the order of 100 bar, an order of magnitude less than the fault strength predicted from laboratory experiments, implying that active faults in southern California are weak. The San Andreas Fault does not appear to be weaker than other faults, as it is well-oriented for failure in the stress field of its immediate surroundings. Earthquakes both modify and respond to the stress field. The 1992 Landers and 1994 Northridge earthquakes caused observable rotations of the stress axes, and the mainshock-induced static stress changes appear to have triggered some aftershocks. The number of aftershocks consistent with static stress triggering in each sequence is significantly greater than the number that would be expected to appear consistent by chance. Since small earthquakes are a response to the stress field, one might expect their stress drops to scale with effective normal stress. However, the stress drops of a set of small events do not appear to scale with depth, and therefore normal stress, in most of the seismogenic crust." }, { "name": "Lee, Yuan-Tai", "degree": "PhD", "year": "2001", "title": "Atmospheric Chemistry and Transport Modeling in the Outer Solar System", "advisor": "Murray, Bruce C.; Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01252013-101859233", "creators": [ { "name": { "family": "Lee", "given": "Yuan-Tai" }, "id": "Lee-Yuan-Tai", "display_name": "Lee, Yuan-Tai" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/y7ep-g464", "abstract": "This thesis consists of 1-D and 2-D photochemical dynamical modeling in the upper atmospheres of outer planets. For 1-D modeling, a unified hydrocarbon photochemical model has been studied in Jupiter, Saturn, Uranus, Neptune, and Titan, by comparing with the Voyager observations, and the recent measurements of methyl radicals by ISO in Saturn and Neptune. The CH_3 observation implies a kinetically sensitive test to the measured and estimated hydrocarbon rate constants at low temperatures. We identify the key reactions that control the concentrations of CH_3 in the model, such as the three-body recombination reaction, CH_3 + CH_3 + M \u2192 C_(2)H_6 + M, and the recycling reaction H + CH_3 + M \u2192CH_4 + M. The results show reasonable agreement with ISO values. In Chapter 4, the detection of PH_3 in the lower stratosphere and upper troposphere of Jupiter has provided a photochemical-dynamical coupling model to derive the eddy diffusion coefficient in the upper troposphere of Jupiter. Using a two-layers photochemical model with updated photodissociation cross-sections and chemical rate constants for NH_3 and PH_3, we find that the upper tropospheric eddy diffusion coefficient <10^5 cm^2 sec^(-1) and the deeper tropospheric value >10^6 cm^2 sec^(-1) are required to match the derived PH_3 vertical profile by the observation. The best-fit functional form derivation of eddy diffusion coefficient in the upper troposphere of Jupiter above 400 mbar is K = 2.0 x 10^4 (n/2.2 x 10^19)^(-0.5)cm^2 sec^(-1). On the other hand, Chapter 5 demonstrates a dynamical-only 2-D model of C_(2)H_6 providing a complete test for the current 2-D transport models in Jovian lower stratosphere and upper troposphere (270 to 0.1 mbar pressure levels). Different combinations of residual advection, horizontal eddy dispersion, and vertical eddy mixing are examined at different latitudes.
\r\n" }, { "name": "Moyer, Elisabeth Jeanne Bailey", "degree": "PhD", "year": "2001", "title": "Tracers of Rapid Transport in the Lower Stratosphere", "advisor": "Webster, Chris; Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02122013-103240444", "creators": [ { "name": { "family": "Moyer", "given": "Elisabeth Jeanne Bailey" }, "id": "Moyer-Elisabeth-Jeanne-Bailey", "display_name": "Moyer, Elisabeth Jeanne Bailey" } ], "advisors": [ { "name": { "family": "Webster", "given": "Chris" }, "id": "Webster-C", "role": "advisor", "display_name": "Webster, Chris" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "member", "display_name": "Hoffmann, Michael R." }, { "name": { "family": "Webster", "given": "Chris" }, "id": "Webster-C", "role": "member", "display_name": "Webster, Chris" }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/snq4-db56", "abstract": "This thesis consists of three parts, each related to the use of tracer measurements to\r\ndiagnose the small-scale structure and mechanisms by which air is transported, both\r\nvertically and horizontally, in the lower stratosphere.
\r\n\r\n1. I demonstrate that the isotopic composition of water vapor can diagnose rapid convective\r\ntransport across the tropopause. I use data from the space shuttle- and balloon-borne\r\nFourier transform solar occultation spectrometers ATMOS (Atmospheric Trace\r\nMOlecule Spectrometer) and Mark-IV to reconstruct the mean deuterium isotopic composition\r\nof water entering the stratosphere. Initial \u03b4D is -670 per mil (33% of deuterated\r\nwater retained). I construct a one-dimensional model simulating isotopic fractionation\r\nduring ascent to the tropopause and demonstrate that for all but the most rapid ascent.\r\nvirtually all deuterated water is stripped from an air parcel in the last few kilometers of\r\nthe uppermost troposphere. The observed stratospheric \u03b4D is then far heavier than modeled\r\ndepletions under most conditions. I conclude that the observations can be matched\r\nonly by substantial evaporation of lofted condensate or by ascent in highly-supersaturated\r\nconditions, and infer that mean stratospheric air must have experienced rapid convection\r\nto at least near-tropopause altitudes. This study serves to demonstrate that the isotopic\r\ncomposition of water vapor is a valuable tracer that can be used to constrain mechanisms\r\nof stratosphere-troposphere transport.
\r\n\r\n\r\n2. I use in-situ tunable diode laser measurements of CO, H_2O, and N_2O taken over\r\nFairbanks, AK to show rapid transport by streamers of air in the lower stratosphere. I\r\nwas part of a team that used ALIAS and JPL-H2O, two tunable diode laser spectrometers built by the Webster group of the Jet Propulsion Laboratory, to obtain data in the upper troposphere and lower stratosphere on 21 ER-2 flights between April and September, 1991, during the POLARIS (Photochemistry of Ozone Loss in the Arctic Region In Summer) mission. I use this dataset to identify episodes of rapid polewards advection in the lowermost stratosphere in which filaments of air move from tropics to 65 N latitude\r\nin weeks. I find that the lowermost stratosphere is a region of intense filamentary activity,\r\nbut that tropical filamentation is absent above the 420 K surface, in contradiction\r\nto the results of previous trajectory simulations. Individual filaments extend from the\r\n\u201coverworld\u201d stratosphere to the local tropopause, showing that the boundary between\r\n\u201coverworld and \u201cmiddleworld\u201d is not a true dynamical barrier. The filamentation is\r\nstrongly seasonal, in agreement with previous trajectory results, but with a longer period\r\nof activity. I conclude that the tropopause transition layer extends to 420 K \u019f, and that\r\ntransport in this layer is coupled to changes in the tropospheric subtropical jet.
\r\n\r\n\r\n3. I describe the design and construction of a new lightweight open-path tunable-diode-\r\nlaser instrument for measurements of water, vapor isotopic composition from aircraft\r\nplatforms. I initiated and led an effort to design and build an instrument capable\r\nof resolving transport issues such as those mentioned in (1). WISP (Water Isotope SPectrometer) is a 3-channel tunable-diode-laser spectrometer, with two mid-infrared and one\r\nnear-infrared laser sources. Light is injected into a 94-pass Herriott cell for a total of 94\r\nmeters of pathlength. The expected threshold sensitivity is a few parts in 10^5 absorption.\r\nDetection of HDO has an expected SNR >10 up to near-tropopause altitudes. All isotopomers\r\nof water vapor, and methane, are detected in a single scan, allowing improved\r\naccuracy as common systematics drop out of the ratio. I led the integration of the instrument on NASA\u2019s WB-57 aircraft as part of the ACCENT mission. The instrument can\r\nprovide a versatile tool for t racer measurements in the tropopause region.
\r\n" }, { "name": "Ni, Sidao", "degree": "PhD", "year": "2001", "title": "2D Modeling of Lower Mantle Structure with WKM Synthetics", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03252014-144322918", "creators": [ { "name": { "family": "Ni", "given": "Sidao" }, "id": "Ni-Sidao", "orcid": "0000-0003-2988-4850", "display_name": "Ni, Sidao" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "geophys" ], "doi": "10.7907/J8XC-TF53", "abstract": "The Earth is very heterogeneous, especially in the region close to the surface of the\r\nEarth, and in regions close to the core-mantle boundary (CMB). The lowermost\r\nmantle (bottom 300km of the mantle) is the place for fast anomaly (3% faster S\r\nvelocity than PREM, modeled from Scd), for slow anomaly (-3% slower S velocity than\r\nPREM, modeled from S,ScS), for extreme anomalous structure (ultra-low velocity\r\nzone, 30% lower inS velocity, 10% lower in P velocity). Strong anomaly with larger\r\ndimension is also observed beneath Africa and Pacific, originally modeled from travel\r\ntime of S, SKS and ScS. Given the heterogeneous nature of the earth, more accurate\r\napproach (than travel time) has to be applied to study the details of various anomalous\r\nstructures, and matching waveform with synthetic seismograms has proven effective\r\nin constraining the velocity structures. However, it is difficult to make synthetic\r\nseismograms in more than 1D cases where no exact analytical solution is possible.\r\nNumerical methods like finite difference or finite elements are too time consuming\r\nin modeling body waveforms. We developed a 2D synthetic algorithm, which is\r\nextended from 1D generalized ray theory (GRT), to make synthetic seismograms\r\nefficiently (each seismogram per minutes). This 2D algorithm is related to WKB\r\napproximation, but is based on different principles, it is thus named to be WKM, i.e.,\r\nWKB modified. WKM has been applied to study the variation of fast D\" structure\r\nbeneath the Caribbean sea, to study the plume beneath Africa. WKM is also applied\r\nto study PKP precursors which is a very important seismic phase in modeling lower\r\nmantle heterogeneity. By matching WKM synthetic seismograms with various data,\r\nwe discovered and confirmed that (a) The D\" beneath Caribbean varies laterally, and\r\nthe variation is best revealed with Scd+Sab beyond 88 degree where Sed overruns\r\nSab. (b) The low velocity structure beneath Africa is about 1500 km in height, at\r\nleast 1000km in width, and features 3% reduced S velocity. The low velocity structure\r\nis a combination of a relatively thin, low velocity layer (200 km thick or less) beneath\r\nthe Atlantic, then rising very sharply into mid mantle towards Africa. (c) At the\r\nedges of this huge Africa low velocity structures, ULVZs are found by modeling the\r\nlarge separation between S and ScS beyond 100 degree. The ULVZ to the eastern\r\nboundary was discovered with SKPdS data, and later is confirmed by PKP precursor\r\ndata. This is the first time that ULVZ is verified with distinct seismic phase." }, { "name": "Okin, Gregory Stewart", "degree": "PhD", "year": "2001", "title": "Wind, Driven Desertification: Process Modeling, Remote Monitoring, and Forecasting", "advisor": "Murray, Bruce C.; Farley, Kenneth A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05022014-104651690", "creators": [ { "name": { "family": "Okin", "given": "Gregory Stewart" }, "id": "Okin-Gregory-Stewart", "orcid": "0000-0002-0484-3537", "display_name": "Okin, Gregory Stewart" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "co-advisor", "display_name": "Farley, Kenneth A." } ], "committee": [ { "name": { "family": "Randerson", "given": "James T." }, "id": "Randerson-J-T", "orcid": "0000-0001-6559-7387", "role": "chair", "display_name": "Randerson, James T." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Schlesinger", "given": "William H." }, "id": "Schlesinger-W-H", "role": "member", "display_name": "Schlesinger, William H." } ], "option_major": [ "geochem" ], "doi": "10.7907/7ND2-DH05", "abstract": "Arid and semiarid landscapes comprise nearly a third of the Earth's total land surface. These areas are coming under increasing land use pressures. Despite their low productivity these lands are not barren. Rather, they consist of fragile ecosystems vulnerable to anthropogenic disturbance.
\r\n\r\nThe purpose of this thesis is threefold: (I) to develop and test a process model of wind-driven desertification, (II) to evaluate next-generation process-relevant remote monitoring strategies for use in arid and semiarid regions, and (III) to identify elements for effective management of the world's drylands.
\r\n\r\nIn developing the process model of wind-driven desertification in arid and semiarid lands, field, remote sensing, and modeling observations from a degraded Mojave Desert shrubland are used. This model focuses on aeolian removal and transport of dust, sand, and litter as the primary mechanisms of degradation: killing plants by burial and abrasion, interrupting natural processes of nutrient accumulation, and allowing the loss of soil resources by abiotic transport. This model is tested in field sampling experiments at two sites and is extended by Fourier Transform and geostatistical analysis of high-resolution imagery from one site.
\r\n\r\nNext, the use of hyperspectral remote sensing data is evaluated as a substantive input to dryland remote monitoring strategies. In particular, the efficacy of spectral mixture analysis (SMA) in discriminating vegetation and soil types and detennining vegetation cover is investigated. The results indicate that hyperspectral data may be less useful than often thought in determining vegetation parameters. Its usefulness in determining soil parameters, however, may be leveraged by developing simple multispectral classification tools that can be used to monitor desertification.
\r\n\r\nFinally, the elements required for effective monitoring and management of arid and semiarid lands are discussed. Several large-scale multi-site field experiments are proposed to clarify the role of wind as a landscape and degradation process in dry lands. The role of remote sensing in monitoring the world's drylands is discussed in terms of optimal remote sensing platform characteristics and surface phenomena which may be monitored in order to identify areas at risk of desertification. A desertification indicator is proposed that unifies consideration of environmental and human variables.
" }, { "name": "Pankine, Alexey Anatolyevich", "degree": "PhD", "year": "2001", "title": "Low Order Model of Martian Circulation and Interannual Variability of Global Dust Storms", "advisor": "Ingersoll, Andrew P.; Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechETD:etd-11072001-160517", "creators": [ { "name": { "family": "Pankine", "given": "Alexey Anatolyevich" }, "id": "Pankine-Alexey-Anatolyevich", "display_name": "Pankine, Alexey Anatolyevich" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "co-advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/MGSA-ZT98", "abstract": "The main theme of this work is the development of a simplified model of the martian circulation suitable for conducting computationally fast long term simulations of the martian climate system. In particular, we are looking for causes of the irregular occurrence of the martian global dust storms (GDSs). The low-order model (LOM) is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting low-order model consists of twelve coupled nonlinear ordinary differential equations (ODEs). The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit output of the NASA Ames GCM.
\r\n\r\nThe model performance is examined for different seasons and dust opacities and it is found that the simulated mean meridional circulation and temperature fields compare well with the more sophisticated GCM. The time of occurence and duration of the global dust storms produced by the model compare well with observations by Viking Landers (VLs). The intensity of the meridional circulation as simulated by the LOM during northern summer is stronger than that predicted by the GCM. The situation can be improved if the Rayleigh friction varies seasonally. The LOM uncoupled from the dust source can be further simplified to form the Lorenz system with forcing.
\r\n\r\nThe model is applied to the problem of interannual variability of martian global dust storms. Basic hypotheses of the intrinsic and of the extrinsic irregularity of the martian climate system are tested. The intrinsic irregularity hypothesis implies that the system under consideration is chaotic, so that small variations in initial conditions make the behavior of the system essentially unpredictable. Different paths taken by the system in state space would correspond to years with and without a GDS. The extrinsic irregularity hypothesis, on the other hand, implies that without noise the system behaves periodically, but stochastic forcing of the system causes it to behave irregularly. It is concluded that the observed variability of GDSs is more easily explained by extrinsic irregularity. The stochastic forcing (``noise') could be provided by transient weather systems or some surface process, like size sorting or redistribution of the sand particles in the ``active' (i.e., storm generating) zones on the surface. The results are very sensitive to the value of the saltation threshold, which hints at the possible feedback between saltation threshold and dust storm activity. According to this hypothesis, the saltation threshold has adjusted its value so that dust storms are barely able to occur.
" }, { "name": "Qi, Chunhua", "degree": "PhD", "year": "2001", "title": "Aperture Synthesis Studies of the Chemical Composition of Protoplanetary Disks and Comets", "advisor": "Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11302001-000213", "creators": [ { "name": { "family": "Qi", "given": "Chunhua" }, "id": "Qi-Chunhua", "display_name": "Qi, Chunhua" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "chair", "display_name": "Brown, Michael E." }, { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "orcid": "0000-0002-4633-5098", "role": "member", "display_name": "Sargent, Anneila Isabel" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/VNV1-8B86", "abstract": "Improvements in observational methods have now made it possible to directly observe planet-forming environments around young stars and to better characterize the most primitive relics of planetary growth in our own solar system. This thesis describes one such method, aperture synthesis imaging using the Owens Valley Radio Observatory (OVRO) Millimeter Array, and its application to the chemical composition of circumstellar accretion disks and comets.
\r\n\r\nThe observations presented in this thesis concentrate on [lambda]~3 mm transitions of HCN/HCO+ and {13}CO/CN in LkCa 15, GM Aur, MWC 480, and HD 163296. These disks were chosen based on their large spatial extent, Keplerian kinematic patterns, and strong CO emission.
\r\n \r\nEven at a resolution of 2\" (or a linear scale of ~300 AU at the distance of Taurus and Ophiuchus), the OVRO observations show that the chemistry in circumstellar disks is sensitive to both the central stellar luminosity and the degree of dust settling toward the disk midplane. Abundance ratios such as CN/HCN and HCO+/CO serve as unique probes of pivotal processes such as photoevaporation or cosmic ray induced ionization. The observed lower limit to the fractional ionization of 10{-10} is sufficient to support magnetorotational instabilities that are likely to dominate the transport mechanisms in the outer reaches of protoplanetary disks. CN/HCN gradients in the T Tauri and Herbig Ae star disks appear to be correlated with the local UV radiation field and with the degree of dust settling as judged by recent fits to their spectral energy distributions, illustrating the important role of photochemistry at large disk radii.
\r\n\r\nThe disk emission toward LkCa 15 is particularly intense, with many molecules being detected, including HCN/HCO+ and their {13}C-isotopomers, DCN, CN, HC_3N, CH_3OH, CS, {13}CO, and C{18}O. The overall abundance patterns are consistent with recent models of photon-dominated chemistry in the near surface regions of flaring circumstellar disks that also provide a natural explanation for the mid- and far-infrared properties of the disk spectral energy distribution.
\r\n\r\nDirect ties between accretion disks and the formation of planetary systems can be tested by examining primitive solar system bodies such as comets. Comet Hale-Bopp was observed at OVRO from 1997 March 29 to April 2 in a variety of spectroscopic settings between 3.4 and 1.2 mm. The resulting aperture synthesis millimeter-wave continuum and molecular line images reveal in great detail the inner coma. The millimeter-wave continuum brightness of Hale-Bopp is dominated by emission from dust grains in the coma. By subtracting a spherically symmetric coma model from the continuum visibilities, the millimeter-wave flux from the nucleus has been isolated, and leads to an estimated radius of 19-22.5 km.
\r\n\r\nThe large size of comet Hale-Bopp accounts for its extraordinary outgassing rates, which permitted the aperture synthesis observations of over 18 millimeter transitions of HCN, DCN, HDO, HC_3N, HNC, HNCO, CS, H_2S}, SO, OCS, CO, CH_3OH and CH_3OCH_3. The OVRO Millimeter Array was able to image, for the first time, molecular analogs of the dust jets commonly observed at optical and infrared wavelengths. This is particularly significant for investigating the true composition of comets, since jets are known to lift off large, icy grains from which direct sublimation can occur as they are exposed to the Sun. The production rates derived from the aperture synthesis images are similar to those found by other researchers, and reveal a marked similarity between the composition of Hale-Bopp and that derived for dense molecular clouds, in particular the hot cores observed near massive young stars. In addition, quite substantial D/H fractionations, comparable to the OVRO DCN/HCN measurement in LkCa 15, are found in the jets. While this clearly suggests an evolutionary history in which cometary materials remain at very low temperatures throughout their assemblage and for the bulk of their lives, the complex, kinetically controlled chemistry revealed in the OVRO images of the cold, outer regions of disks around young stars means that it is difficult to characterize cometary volatiles as being primarily \"interstellar\" or \"nebular\" in origin.
" }, { "name": "Toigo, Anthony Domenick", "degree": "PhD", "year": "2001", "title": "Behavior of Dust in the Martian Atmosphere", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242013-112821494", "creators": [ { "name": { "family": "Toigo", "given": "Anthony Domenick" }, "id": "Toigo-Anthony-Domenick", "display_name": "Toigo, Anthony Domenick" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Richardson", "given": "Mark I." }, "id": "Richardson-M-I", "role": "member", "display_name": "Richardson, Mark I." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "plansci" ], "doi": "10.7907/7v06-j640", "abstract": "Two aspects of the dust cycle on Mars are examined: the seasonal variation of dust aerosols\r\nin the atmosphere as observed by spacecraft and dust lifting by high wind stress at the south\r\npole during late spring employing a specially developed mesoscale atmospheric model. Reanalysis\r\nof Viking mission optical depth measurements shows that the visible to infrared\r\nratio of total extinction opacity varies with season, and is due to seasonally varying water\r\nice haze. The Martian atmosphere is clearer of dust, especially during northern spring and\r\nsummer, than previously thought. Water ice hazes can provide roughly 50% of the total\r\nvisible opacity in these seasons, and that they represent only 1-5% of the total water column.\r\nNext, the conversion for use on Mars of a terrestrial mesoscale atmospheric model\r\n(the Mars MM5) is presented and described. Validation of the Mars MM5 is conducted\r\nby comparison with a general circulation model on scales of a few hundred kilometers and\r\nwith Martian surface landers (Viking Lander 1, Viking Lander 2, and Mars Pathfinder)\r\non scales of a few kilometers, and in both cases there is good agreement in the meteorological\r\nvariables of temperature, pressure, and wind. Tides are found to be at least as\r\nimportant as slopes in generating the diurnal cycle of winds at the lander sites, in contrast\r\nto previous one-dimensional studies. Finally, assuming that dust injection is related to the\r\nmovement of sand-sized grains or aggregates, the Mars MM5 predicts wind stresses of sufficient\r\nstrength to initiate movement of sand-sized particles, and hence dust lifting, during\r\nlate southern spring in the south polar region. It is found that the direct cap edge thermal\r\ncontrast provides the primary drive for high surface wind stresses at the cap edge at this season\r\nwhile sublimation flow is not found to be particularly important. Comparison between\r\nsimulations, in which dust is injected when wind stresses are high and those with inactive\r\ndust injection, show no signs of consistent feedback due to dust clouds on the surface wind stress fields during the late spring season examined here.\r\n" }, { "name": "Zhang, Hui", "degree": "PhD", "year": "2001", "title": "Spectroscopic Studies of N\u20820 and HNO\u2084: A Window into the Global Biogeochemistry of Nitrogen", "advisor": "Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302013-092114374", "creators": [ { "name": { "family": "Zhang", "given": "Hui" }, "id": "Zhang-Hui", "display_name": "Zhang, Hui" } ], "advisors": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "orcid": "0000-0001-6874-1137", "role": "member", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Sander", "given": "Stanley P." }, "id": "Sander-S-P", "role": "member", "display_name": "Sander, Stanley P." }, { "name": { "family": "Wennberg", "given": "Paul O." }, "id": "Wennberg-P-O", "orcid": "0000-0002-6126-3854", "role": "member", "display_name": "Wennberg, Paul O." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." } ], "option_major": [ "plansci" ], "doi": "10.7907/2ts6-9d87", "abstract": "Nitrogen is an essential nutrient for all living organisms. This thesis focuses on the spectroscopic studies of two species that participate in the global biogeochemical cycle of nitrogen: N_2O and HNO_4. Both play important roles in the radiative and chemical processes in the terrestrial atmosphere.
\r\n\r\nIn terms of experimental instrumentation, this thesis takes great advantage of the recent\r\nadvances in both Optical Parametric Oscillator (OPO) and high power, narrow-linewidth\r\npulsed laser technology. Chapter 1 describes a \u03b2-BaB_2O_4 (BBO) OPO pumped by a high\r\nrepetition rate Nd:YAG laser (Coherent Infinity^(TM). This combination provides a unique\r\nlight source with wide tunability and high average output power, making it ideally suited\r\nfor the photochemical and spectroscopic studies carried out in this thesis.
\r\n\r\nN_2O is a prominent greenhouse gas and the major natural source of NO that initiates the\r\ncatalytic NO_x ozone destruction cycles in the stratosphere. It has been suggested (Yung\r\nand Miller 1997, Science 78, 1778, referred to as YM97 hereafter) that N_2O should be\r\nisotopically fractionated as a result of photolysis in the upper atmosphere, which represents\r\nthe primary sink of N_2O. Chapter 2 studies the photolytic fractionation of N_2O in an\r\nattempt to test the YM97 model. These measurements have consistently shown large heavy\r\nenrichment of the residual N_2O isotopomers. The magnitude of the observed fractionation,\r\nhowever, is significantly larger than predicted but in accord with the sizable fractionation\r\nobserved in the stratosphere. An attempt to reconcile the differences is given which notes\r\nthe existence of vibrationally \"hot\" N_2O molecules at room temperature and the possible\r\ninvolvement of more than two electronic states in the photolysis. A fully quantitative test\r\nof YM97 theory will require accurate wavelength and temperature dependent differential\r\ncross sections for each of the N20 isotopomers that are not yet available.
\r\n\r\nHNO_4 is an important reservoir species coupling the HO_x and NO_x families in the upper\r\ntroposphere and lower stratosphere. Chapter 3 investigates the cleavage of the HOO-NO_2\r\nbond in HNO_4 via absorption of red/near infrared (NIR) solar radiation. Experiments are\r\ndesigned to determine the cross sections and quantum yields for gas phase HN04 photodissociation.\r\nHN04 is found to dissociate at wavelengths as long as 1600 nm. It is argued\r\nthat molecular internal energy available for thermal excitation in addition to the photon energy\r\ncan explain the observed dissociation of HN04 beyond its thermodynamic dissociation\r\nthreshold. Accordingly, a temperature-dependent quantum yield is predicted. The 1st OH\r\nstretching overtone is found to be partially dissociative. Because it is significantly brighter\r\nthan the 2nd overtone, it contributes significantly to the photodissociation of HNO_4. Based\r\non these experimental results, the strength of the HOO-NO_2 bond is constrained and compared\r\nto literature values. The atmospheric significance of the NIR photodissociation of\r\nHNO_4 is then discussed.
" }, { "name": "Holt, Elizabeth Warner", "degree": "PhD", "year": "2000", "title": "\u00b9\u2078O/\u00b9\u2076O Studies of Short-Lived (10-25 Year), Fumarolic (>500\u00b0C) Meteoric-Hydrothermal Events in the Outflow Sheets of Ash-Flow Tuffs", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11282022-190922104", "creators": [ { "name": { "family": "Holt", "given": "Elizabeth Warner" }, "id": "Holt-Elizabeth-Warner", "display_name": "Holt, Elizabeth Warner" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "chair", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geochem" ], "doi": "10.7907/8vdb-7r67", "abstract": "\u00b9\u2078O/\u00b9\u2076O data from the 0.76 Ma Bishop Tuff outflow sheet provide evidence\r\nfor a vigorous, short-Jived (\u224810-25 years), high-temperature (400\u00b0-650\u00b0C), fumarolic\r\nmeteoric-hydrothermal event immediately following eruption. This is proved by: (1) the\r\njuxtaposition in the upper, partially welded Bishop Tuff of low-\u00b9\u2078O groundmass/glass\r\n(\u03b4\u00b9\u2078O = -5 to +3) with coexisting quartz and feldspar phenocrysts having magmatic \u03b4\u00b9\u2078O values (+8.4 \u00b1 0.3; +7.2 \u00b1 0.3); and (2) the fact that these types of \u00b9\u2078O/\u00b9\u2076O signatures\r\ncorrelate very well with the morphological features and mapped zones of fumarolic activity.\r\nTen detailed \u03b4\u00b9\u2078O-depth profiles in various parts of the Bishop Tuff outflow sheet show\r\nevidence for two types of fumarolic meteoric-hydrothermal circulation systems in the upper\r\npart of the tuff; there is a broadly based, stratigraphically bound, 20- to 40-m-thick Upper\r\nLow-\u00b9\u2078O Zone (ULZ) that straddles the contact between the Tableland Unit and the Gorges\r\nUnit, and there is also a set of localized, 40- to 80-m-thick zones in the partially welded tuff\r\nin which extremely \u00b9\u2078O-depleted rock (\u03b4\u00b9\u2078O as low as -6.5) characterizes a Deep\r\nFumarolic System (DFS). This DFS is spatially associated with steep fissures, tubular\r\nconduits, and shallow-dipping columnar joints in cylindrical volumes of rock lying beneath\r\nmore than 1000 fumarolic mounds scattered across the surface of the tuff. Both of these\r\n\u00b9\u2078O-depleted zones are concentrated over areas where the underlying Densely Welded Zone\r\n(DWZ) is particularly thick, namely above pre-Bishop Tuff paleodrainages. The DWZ\r\nremained largely hot, ductile, and impermeable during fumarolic activity, which prevented\r\nthe heated meteoric fluids from penetrating the densely welded tuff until it cooled\r\nsufficiently so that throughgoing vertical fractures provided access to the base of the ash-flow\r\nsheet (at which time the fumarolic activity appears to have rapidly terminated).\r\nWhole-rock \u03b4\u00b9\u2078O values of samples collected from the surface of the 1912 ash-flow sheet\r\nat the Valley of Ten Thousand Smokes (VTTS), Alaska show analogous \u00b9\u2078O/\u00b9\u2076O\r\nsystematics and a similar range in \u03b4\u00b9\u2078O values (-0.1 to +12.6) to surface samples collected\r\nfrom the Bishop Tuff outflow sheet (+2.5 to +16.7)." }, { "name": "Ivanov, Anton Borisovich", "degree": "PhD", "year": "2000", "title": "Some aspects of the Martian climate in the Mars Orbiter Laser Altimeter (MOLA) investigation. Part I. Evolution of the polar residual ice caps. Part II. Polar night clouds. Part III. Interpretation of the MOLA reflectivity measurement in terms of the surface albedo and atmospheric opacity", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302013-163300566", "creators": [ { "name": { "family": "Ivanov", "given": "Anton Borisovich" }, "id": "Ivanov-A-B", "display_name": "Ivanov, Anton Borisovich" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/9mv8-hz72", "abstract": "The spacecraft exploration of the planet Mars in the last two decades provided scientists\r\nwith an enormously rich data base. This work presents some aspects of the\r\nMars Orbiter Laser Altimeter investigation related to the issues in the Martian climatology.\r\nThe instrument continues to function on board of the Mars Global Surveyor\r\nSpacecraft.
\r\n\r\nThe polar ice caps on Mars are the largest reservoirs of water on the planet.\r\nTheir formation and evolution are not understood very well at this point. Ice flow,\r\nsublimation and wind erosion are believed to be the most important processes that\r\nshape the caps. We have developed a model to understand the role of sublimation\r\nfor the formation of the ice caps and attempted to constrain the time scale for the\r\nformation of the observed ice caps. The model has been justified using the precise\r\ntopography of the ice caps and the layered terrains that have been measured by the\r\nMOLA instrument. We argue that sublimation is a very important process for the\r\nformation of the caps, especially on the time scales greater than 10 million years.
\r\n\r\nWe report the direct observations of CO_2 clouds, forming during the polar winter\r\ntimes over both poles. These clouds are similar over both poles and possibly represent\r\na CO_2 snowfall. On the basis of the reflective properties and spatial occurrence, we\r\ncan distinguish two major classes of clouds. We will discuss some hypotheses on the\r\nmechanisms of their formation.
\r\n\r\nTotal atmospheric opacity of the Martian atmosphere at 1\u00b5m can be derived\r\nfrom the MOLA reflectivity measurement. Opacity estimates for the period from\r\nL_S = 105\u00b0 to L_S = 220\u00b0 are found to be consistent with the Viking Lander and\r\nPathfinder values. Opacity measured in the polar regions displays storms and polar\r\nhood activity. Aerosol scale heights can be inferred from the opacity changes on some\r\nlarge scale topographic features. Dust scale heights are found to be lower than the\r\natmospheric scale height. Water ice cloud scale heights are found to be consistent with the atmospheric scale height. Comparison of the MOLA derived opacity with\r\nthe TES derived opacity yields information on the aerosol particle size distribution.\r\nWe discuss an algorithm to derive 1\u00b5m normal albedo of the surface. 9\u00b5m dust\r\nopacity from the Thermal Emission Spectrometer (TES) is employed to remove an\r\natmospheric attenuation from the MOLA reflectivity measurements. We will present\r\nsome initial results on the calculation of the surface albedo.
\r\n" }, { "name": "Roulston, Mark Stephen", "degree": "PhD", "year": "2000", "title": "Construction of low dimensional models of El Ni\u00f1o-southern oscillation using empirical orthogonal functions ", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242013-112006606", "creators": [ { "name": { "family": "Roulston", "given": "Mark Stephen" }, "id": "Roulston-M-S", "display_name": "Roulston, Mark Stephen" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/32fe-ag39", "abstract": "The main theme of this thesis is the construction and analysis of low dimensional dynamical models of El Nino-Southern Oscillation (ENSO). Low dimensional models of ENSO have been constructed [Val86, WF96, Jin97b] but all the models were built on ad hoc assumptions and simplifications. The low dimensional models in this thesis were constructed from a higher dimensional intermediate coupled model (ICM) by Galerkin projection on truncated basis sets of empirical orthogonal functions (EOFs), a method that has previously been applied to atmospheric models and models of turbulence [Sel95, HLB96]. This\r\nmethod makes no simplications to the physics of the ICM but instead projects it into a lower dimensional subspace of its full state space that has been empirically shown to\r\ncontain the maximum amount of variance of any subspace of the same dimension.
\r\n\r\nAnalysis of the reduced models shows that the variability of the full model can be explained by three types of mode; I. self-sustaining. II. linearly stable but nonlinearly coupled to a self-sustaining mode, III. linearly stable and excited by noise. When driven by noise the stable modes can couple to the primary modes, and this provides an additional pathway for noise to perturb these leading modes.
\r\n\r\nThe implication is that the behavior of the model without stochastic forcing can be well reproduced by the low dimensional models obtained by projection onto the leading EOFs but that many more EOFs are required to properly model the response to stochastic forcing.
\r\n\r\nExperiments with the full model also indicate that the model is not efficient at transferring power from high (intraseasonal) frequencies to low (interannual) frequencies. In particular the impact of a Madden-Julian type oscillation in the 30-60 day frequency range on the interannual ENSO variability is negligble compared to the impact of the interannual component of atmospheric variability.
\r\n" }, { "name": "Abolins, Mark Joseph", "degree": "PhD", "year": "1999", "title": "I. Stratigraphic constraints on the number of discrete neoproterozoic glaciations and the relationship between glaciation and ediacaran evolution. II. The Kwichup Spring thrust in the northwestern Spring Mountains, Nevada : implications for large-magnitude extension and the structure of the Cordilleran thrust belt", "advisor": "Wernicke, Brian P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04202006-152208", "creators": [ { "name": { "family": "Abolins", "given": "Mark Joseph" }, "id": "Abolins-Mark-Joseph", "display_name": "Abolins, Mark Joseph" } ], "advisors": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "advisor", "display_name": "Wernicke, Brian P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/SZ62-KD58", "abstract": "Part I: Stratigraphic constraints on the number of discrete neoproterozoic glaciations and the relationship between glaciation and ediacaran evolution.\r\n\r\nStratigraphic and structural observations in the Death Valley region provide new insights into two topical problems. First, stratigraphic observations provide a better understanding of the number of discrete Neoproterozoic glaciations and the relationship between glaciation and the diversification of the first animals. Detailed stratigraphic investigations reveal incised valleys within the Neoproterozoic Johnnie Formation. The size (>150 m) and regional extent of the valleys, and the carbon isotope signature of underlying carbonates show that the valleys are probably glacioeustatic in origin. The incised valleys help to complete the Neoproterozoic glacial record in the western United States. The incised valleys and a pair of glacial diamictites in the underlying Kingston Peak Formation represent two to three discrete Neoproterozoic glaciations. This record of two to three glaciations matches the global Neoproterozoic glacial record. The incised valleys provide the youngest evidence for large-scale Neoproterozoic glaciation in the western United States. Correlation of the Johnnie valleys with incised valleys in the uppermost Caddy Canyon Formation of Idaho and Utah shows that this glaciation occurred before 580 Ma. These findings suggest that diverse Ediacaran faunas post-date the youngest major Neoproterozoic glaciation by tens of millions of years.\r\n\r\nSecond, structural and stratigraphic observations provide new constraints on the magnitude of extension in the Death Valley extended domain. These observations reveal a thrust fault in the northwestern Spring Mountains, NV. Correlation of this thrust fault with thrusts in other ranges constrains the translation of those ranges relative to the Spring Mountains. While these correlations are not unique, the most plausible correlations require large-magnitude extension in the Death Valley area and north of Las Vegas Valley.\r\n\r\nCorrelation of contractile structures in the northwestern Spring Mountains and Specter Range with Permo-Triassic structures in the Cottonwood Mountains may provide a link between the Permo-Triassic thrust belt in the Cottonwood Mountains and the Central Nevada thrust belt. The Central Nevada thrust belt may be at least in part Permo-Triassic in age, and may represent a foreland fold and thrust belt which developed inboard of the Golconda allochthon during its emplacement.\r\n\r\nPart II: The Kwichup Spring thrust in the northwestern Spring Mountains, Nevada : implications for large-magitude extension and the structure of the Cordilleran thrust belt.\r\n\r\nApproximately 170 km(2) of new mapping in the northwestern Spring Mountains reveals contractile structures related to a regional thrust fault called the Kwichup Spring thrust. The Kwichup Spring thrust involves at least 1.4 km of stragraphic throw. Along much of its length, the Kwichup Spring thrust has been reactivated or excised by a normal fault.\r\n\r\nStratigraphic and structural evidence suggest that the Kwichup Spring thrust correlates with the Montgomery thrust in the Montgomery Mountains. Correlation of these two thrusts requres a reappraisal of the geometry of the Cordilleran thrust belt in Nevada and southeastern California. The Kwichup Spring - Montgomery thrust probably correlates with either the Clery thrust in the Funeral Mountains or the Panamint thrust in the Panamint Mountains. Both possible correlations require large (>115 km) west-northwest translation of the Panamint and Cottonwood Mountains with respect to the Spring Mountains during Neogene extension.\r\n\r\nBefore this large-scale translation, the Panamint and Cottonwood Mountains were positioned along the southern projection of the Central Nevada thrust belt of Taylor and others (1993). Since contractile structures in the Cottonwood Mountains are Permo-Triassic, the Central Nevada thrust belt may be at least in part Permo-Triassic.\r\n" }, { "name": "Holland, Kathleen Gabrielle", "degree": "PhD", "year": "1999", "title": "Phase Changes and Transport Properties of Geophysical Materials Under Shock Loading", "advisor": "Ahrens, Thomas J.; Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10062023-181634008", "creators": [ { "name": { "family": "Holland", "given": "Kathleen Gabrielle" }, "id": "Holland-Kathleen-Gabrielle", "display_name": "Holland, Kathleen Gabrielle" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." } ], "option_major": [ "geophys" ], "doi": "10.7907/cbd3-mk54", "abstract": "The lower mantle of the Earth is believed to be largely composed of (Mg, Fe)O (magnesiowiistite) and (Mg,Fe)SiO\u2083 (perovskite); thus the high pressure phase of (Mg,Fe)\u2082SiO\u2084 (olivine), which is believed to be perovskite plus magnesiowiistite is of geophysical interest. Radiative temperatures of single-crystal olivine starting material [(Mg_(0.9), Fe_(0.1))\u2082SiO\u2084] decreased abruptly from 7040 \u00b1 315 to 4300 \u00b1 270 K upon shock compression above 80 GPa. The data indicate that an upper bound to the solidus of the magnesiowiistite and perovskite assemblage at 4300 \u00b1 270 K is 130 \u00b1 3 GPa. These conditions correspond to those for partial melting at the base of the mantle, as has been suggested to occur within the recently discovered ultra-low-velocity zone (ULVZ) beneath the Central Pacific. We construct speculative high pressure phase diagrams for the MgO - SiO\u2082 system using experimental data from our work, and other mineral physics experiments.
\r\n\r\nIn separate experiments, time dependent shock temperatures were measured for stainless steel (SS) films sandwiched between two transparent Al\u2082O\u2083 anvils. The anvil material was the same as the driver material so that there would be symmetric heat flow from the sample. Inferred Hugoniot temperatures, T_h, of 5000 - 8500\u00b1500 Kat 222- 321 GPa are consistent with previous measurements in SS. Temperatures at the film\u00ad anvil interface (T_i), which are directly measured (rather than T_h) indicate that T_i did not decrease measurably during the approximately 250 ns that the shock wave took to traverse the Al\u2082O\u2083 anvil. Thus an upper bound is obtained for the thermal diffusivity of Al\u2082O\u2083 at the metal/anvil interface of K \u2264 14 \u00b1 5 cm\u00b2/s at 208 GPa and 2110 K. This is a factor of 1.6 lower than previously calculated values, resulting in a decrease of the inferred T_h by at least 400 K. The observed shock temperatures are combined with temperatures calculated from measured Hugoniots and are used to calculate the thermal conductivity of Al\u2082O\u2083. There was no measurable radiant-intensity decrease during the time when the shock wave propagated through the anvil; we infer from this that Al\u2082O\u2083 remained transparent while in the shocked state. Thus an Al\u2082O\u2083 anvil is sufficiently transparent for shock temperature measurements for metals, to at least 240 GPa.
\r\n\r\nFinally, shock temperature experiments employing a six-channel pyrometer were conducted on 200, 500, and 1000 \u00c5 thick films of Fe sandwiched between 3 mm thick anvils of Al\u2082O\u2083 and LiF, to measure the thermal diffusivity ratios of Al\u2082O\u2083/Fe and LiF/Fe, at high temperatures and pressures. Temperature decays of 3000 \u00b1 800 K in 250 ns were observed at Fe pressures of 194 - 303 GPa, which reflect the conduction of heat from the thin metal films into the anvil material. These results were achieved in experiments employing LiF anvils at 164 - 166 GPa and 4190 - 4220 K, and Al2O3 anvils at 196 - 303 GPa and 1410 - 2750 K. Thermal modeling of interface temperature versus time yields best fit thermal diffusivity ratios ranging from 15 \u00b1 30 to 80 \u00b1 20 (Fe/anvil) over the pressure and temperature range of the experiments. Calculated thermal conductivities for Fe, using electron gas theory, of 110 - 212 W /mK are used to calculate thermal conductivities for the anvil materials ranging from 6 to 12 W/mK. Debye theory predicts higher values of 8 to 34 W/mK. Data from previous experiments on thick (\u2265 100\u00b5m) films of Fe and stainless steel are combined with our present results from experiments on thin (\u2264 1000 \u00c5) films to infer a 5860 \u00b1 390 K Hugoniot temperature for the onset of melting of iron at 243 GPa. Our results address the question of whether radiation observed in shock temperature experiments on metals originates from the metal at the metal/ anvil interface or from the shocked anvil. We conclude that the photon flux from the shocked iron/anvil sandwich recorded in all experiments originates from the metal. Within the uncertainties of the shock temperature data, the uncertainties in shock temperatures resulting from the radiation from the anvils is negligible. This is in direct disagreement with previous conclusions of Kondo.
" }, { "name": "Jackson, Miriam", "degree": "PhD", "year": "1999", "title": "Dynamics of the shear margin of Ice Steam B, West Antarctica", "advisor": "Kamb, W. Barclay; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08032006-130753", "creators": [ { "name": { "family": "Jackson", "given": "Miriam" }, "id": "Jackson-Miriam", "display_name": "Jackson, Miriam" } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/8254-RC11", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe ice streams in the West Antarctica Ice Sheet flow at several hundred metres per year. The lateral increase in speed from typical inland ice sheet speeds of a few metres per year to ice stream speeds of several hundred metres per year occurs over a short distance (~ 2 km) in the outer part of the ice stream known as the marginal shear zone (MSZ). The ice in this zone is highly crevassed and chaotically jumbled. This thesis is an effort to understand the dynamics of the MSZ and to find out whether the velocity of the ice stream is controlled primarily by the stresses in its MSZs or by stresses at the base. This is done by determining the marginal shear stress in one of the marginal shear zones using the ice itself as a stress meter. The observed marginal shear strain rate of 0.14 a(-1) is used to calculate the marginal shear stress from the flow law of ice determined by creep tests on ice cores from a MSZ. The test specimen orientation relative to the stress axes in the tests is chosen on the basis of c-axis fabrics so that horizontal shear across vertical planes parallel to the margin is applied to the ice specimens in the test. The resulting marginal shear stress is (2.2 \u00b1 0.3) x 10(5) Pa. This implies that 63 to 100% of the ice stream's support against gravitational loading comes from the margins and only 37 to 0% from the base, so that the margins play an important role in controlling the ice stream motion. The marginal shear stress value is twice that given by the ice-stream model of Echelmeyer et al. (1994), and the corresponding strain-rate enhancement factors differ greatly (E [...] 1 - 2 from the creep tests vs. E [...] 10 - 12.5 from the model of Echelmeyer et al. (1994)). This large discrepancy may possibly be explained by recrystallization of the ice during or shortly after coring. Estimates of the expected recrystallization time scale range widely but include the ~ 1-hour time scale of coring and leave the likelihood of recrystallization uncertain. However, the observed two-maximum fabric type is not what is expected for annealing recrystallization from the sharp single-maximum fabric that would be expected in situ at the high shear strains involved ([gamma] ~ 20). Experimental data from Wilson (1982) suggest that if the core did recrystallize, the prior fabric was a two-maximum fabric not substantially different from the observed one, which implies that the measured flow law and derived marginal shear stress are applicable to the in-situ situation.\r\n\r\nAn ice-stream flow model was developed to explore the discrepancy in enhancement factors. Using this model, which is similar to the model of Echelmeyer et al. (1994), it is possible to match the observed surface velocity profile across the ice stream using a strain rate enhancement factor of 5. This is more than four times the value found in the experimental work but half the value from the modelling results of Echelmeyer et al. The flow model suggests that the lateral shear stress integrated over the margins is larger than the basal shear stress integrated over the base, so that the ice stream is controlled at the sides rather than at the base.\r\n\r\nIt was thus not possible to reconcile fully the results from the experimental work and from modelling, since the modelling still suggests that there is substantial flow enhancement in the MSZ. There may be variation of the enhancement factor with depth, so that at 300 m depth the enhancement factor is close to 1, but increases at greater depths.\r\n\r\nc-axis measurements in ice from the middle of the MSZ reveal that there is an asymmetrical two-maxima fabric, as expected for ice under simple shear. 600 m away, between the middle of the MSZ margin and its outer edge, there is still a two-maxima fabric but the secondary maximum is much smaller and the primary maximum is much bigger. 500 m further, right at the boundary between the shear margin and the ice stream, there is only a single maximum. Outside the ice stream the fabrics show a single, very diffuse maximum.\r\n" }, { "name": "Kass, David M.", "degree": "PhD", "year": "1999", "title": "Change in the Martian Atmosphere", "advisor": "Ingersoll, Andrew P.; Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242013-162910396", "creators": [ { "name": { "family": "Kass", "given": "David M." }, "id": "Kass-David-M", "display_name": "Kass, David M." } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/1mbp-xd62", "abstract": "There are several lines of evidence that the atmosphere of Mars has significantly\r\nevolved over the history of the planet. Because Mars does not have a strong intrinsic\r\nmagnetic field, the atmosphere is eroded by interactions with the solar wind. Conditions\r\nin the early solar-system significantly enhanced this loss, notably the component\r\ndue to solar-wind induced sputtering away. Modeling indicates that, integrated over\r\nthe last 3.5 billion years, 0.8 bars of CO_2 have been sputtered. This is accompanied by\r\nthe loss of 50 m of water. The loss of CO_2 is a significant loss when compared to the\r\nestimates of the thickness of the early atmosphere. A simple model of the behavior of\r\nthe atmospheric \u03b4^(13)C, based on the expected Martian carbon \"cycle\" constrains the\r\nsize the current CO_2 reservoirs by putting the sputtering loss into the context of the\r\nevolution of the atmosphere. In order to balance the isotopic effects of the sputtering\r\nloss, it is necessary for there to be ~ 100 mbars of CO_2 trapped in the planet. This\r\nis quite reasonable given the ability of the regolith to hold adsorbed CO_2.
\r\n\r\nUsing a modified form of Optimal Interpolation, it is possible to assimilate Thermal\r\nEmission Spectrometer (TES) observations from the Mars Global Surveyor (MGS)\r\nspacecraft into the Ames Mars General Circulation Model (MGCM). The method is\r\noptimized for the assimilation of the irregular data obtained during the aerobraking\r\nphase of the mission. Based on 25 sols of data at L_s \u2248 200, the assimilation process\r\nreveals several interesting features of the Martian atmosphere. The assimilation indicates\r\nthat the lower atmosphere (up to ~ 0.1 mbar) in the northern polar regions is\r\nvery cold-probably at or close to the CO_2 condensation temperature. Furthermore,\r\nthe data imply that the midlatitudinal westerly jets extend poleward of the indicated\r\nMGCM locations. In addition to correcting the phasing of the Northern baroclinic\r\nstorm belt, the data indicate that the amplitude of the waves are stronger than expected\r\nand possibly with a lower zonal wavenumber. Thus the data and assimilation\r\nallows the MGCM to create the 1997 Martian Fall instead of a random Fall.
\r\n" }, { "name": "Liu, Cangli", "degree": "PhD", "year": "1999", "title": "I. Rigid Body Penetration into Brittle Material. II. Phase Change Effect on Shock Wave Propagation", "advisor": "Ahrens, Thomas J.; Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04232013-084302487", "creators": [ { "name": { "family": "Liu", "given": "Cangli" }, "id": "Liu-Cangli", "display_name": "Liu, Cangli" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Ravichandran", "given": "Guruswami" }, "id": "Ravichandran-G", "orcid": "0000-0002-2912-0001", "role": "co-chair", "display_name": "Ravichandran, Guruswami" }, { "name": { "family": "Ustundag", "given": "Ersan" }, "id": "Ustundag-E", "role": "co-chair", "display_name": "Ustundag, Ersan" } ], "option_major": [ "geophys" ], "doi": "10.7907/w8gc-n615", "abstract": "Part I.
\r\n\r\nWe have developed a technique for measuring the depth time history of rigid body penetration into brittle materials (hard rocks and concretes) under a deceleration of ~ 105 g. The technique includes bar-coded projectile, sabot-projectile separation,\r\ndetection and recording systems. Because the technique can give very dense data on penetration depth time history, penetration velocity can be deduced. Error analysis shows that the technique has a small intrinsic error of ~ 3-4 % in time during penetration, and 0.3 to 0.7 mm in penetration depth. A series of 4140 steel projectile penetration into G-mixture mortar targets have been conducted using the Caltech 40 mm gas/ powder gun in the velocity range of 100 to 500 m/s.
\r\n\r\nWe report, for the first time, the whole depth-time history of rigid body penetration into brittle materials (the G-mixture mortar) under 105 g deceleration. Based on the experimental results, including penetration depth time history, damage of recovered target and projectile materials and theoretical analysis, we find:
\r\n\r\n1. Target materials are damaged via compacting in the region in front of a projectile and via brittle radial and lateral crack propagation in the region surrounding the penetration path. The results suggest that expected cracks in front of penetrators may be stopped by a comminuted region that is induced by wave propagation. Aggregate erosion on the projectile lateral surface is < 20% of the final penetration depth. This result suggests that the effect of lateral friction on the penetration process can be ignored.
\r\n\r\n2. Final penetration depth, Pmax, is linearly scaled with initial projectile energy per unit cross-section area, es , when targets are intact after impact. Based on the experimental data on the mortar targets, the relation is Pmax(mm) 1.15es (J/mm2 ) + 16.39.
\r\n\r\n3. Estimation of the energy needed to create an unit penetration volume suggests that the average pressure acting on the target material during penetration is ~ 10 to 20 times higher than the unconfined strength of target materials under quasi-static loading, and 3 to 4 times higher than the possible highest pressure due to friction and material strength and its rate dependence. In addition, the\r\nexperimental data show that the interaction between cracks and the target free surface significantly affects the penetration process.
\r\n\r\n4. Based on the fact that the penetration duration, tmax, increases slowly with es and does not depend on projectile radius approximately, the dependence of tmax on projectile length is suggested to be described by tmax(\u03bcs) = 2.08es (J/mm2 + 349.0 x m/(\u03c0R2), in which m is the projectile mass in grams and R is the projectile radius in mm. The prediction from this relation is in reasonable agreement with the experimental data for different projectile lengths.
\r\n\r\n5. Deduced penetration velocity time histories suggest that whole penetration history is divided into three stages: (1) An initial stage in which the projectile velocity change is small due to very small contact area between the projectile and target materials; (2) A steady penetration stage in which projectile velocity continues to decrease smoothly; (3) A penetration stop stage in which projectile deceleration jumps up when velocities are close to a critical value of ~ 35 m/s.
\r\n\r\n6. Deduced averaged deceleration, a, in the steady penetration stage for projectiles with same dimensions is found to be a(g) = 192.4v + 1.89 x 104, where v is initial projectile velocity in m/s. The average pressure acting on target materials during penetration is estimated to be very comparable to shock wave pressure.
\r\n\r\n7. A similarity of penetration process is found to be described by a relation between normalized penetration depth, P/Pmax, and normalized penetration time, t/tmax, as P/Pmax = f(t/tmax, where f is a function of t/tmax. After f(t/tmax is determined using experimental data for projectiles with 150 mm length, the penetration depth time history for projectiles with 100 mm length predicted by this relation is in good agreement with experimental data. This similarity also predicts that average deceleration increases with decreasing projectile length, that is verified by the experimental data.
\r\n\r\n8. Based on the penetration process analysis and the present data, a first principle model for rigid body penetration is suggested. The model incorporates the models for contact area between projectile and target materials, friction coefficient, penetration stop criterion, and normal stress on the projectile surface. The most important assumptions used in the model are: (1) The penetration process can be treated as a series of impact events, therefore, pressure normal to projectile surface is estimated using the Hugoniot relation of target material; (2) The necessary condition for penetration is that the pressure acting on target materials is not lower than the Hugoniot elastic limit; (3) The friction force on projectile lateral surface can be ignored due to cavitation during penetration. All the parameters involved in the model are determined based on independent experimental data. The penetration depth time histories predicted from the model are in good agreement with the experimental data.
\r\n\r\n9. Based on planar impact and previous quasi-static experimental data, the strain rate dependence of the mortar compressive strength is described by \u03c3f/\u03c30f = exp(0.0905(log(\u03ad/\u03ad_0) 1.14, in the strain rate range of 10-7/s to 103/s (\u03c30f and \u03ad are reference compressive strength and strain rate, respectively). The non-dispersive\r\nHugoniot elastic wave in the G-mixture has an amplitude of ~ 0.14 GPa and a velocity of ~ 4.3 km/s.
\r\n\r\nPart II.
\r\n\r\nStress wave profiles in vitreous GeO2 were measured using piezoresistance gauges in the pressure range of 5 to 18 GPa under planar plate and spherical projectile impact. Experimental data show that the response of vitreous GeO2 to planar shock loading\r\ncan be divided into three stages: (1) A ramp elastic precursor has peak amplitude of 4 GPa and peak particle velocity of 333 m/s. Wave velocity decreases from initial longitudinal elastic wave velocity of 3.5 km/s to 2.9 km/s at 4 GPa; (2) A ramp wave with amplitude of 2.11 GPa follows the precursor when peak loading pressure is 8.4 GPa. Wave velocity drops to the value below bulk wave velocity in this stage; (3) A shock wave achieving final shock state forms when peak pressure is > 6 GPa. The Hugoniot relation is D = 0.917 + 1.711u (km/s) using present data and the data of Jackson and Ahrens [1979] when shock wave pressure is between 6 and 40 GPa for \u03c10 = 3.655 gj cm3 . Based on the present data, the phase change from 4-fold to 6-fold coordination of Ge+4 with O-2 in vitreous GeO2 occurs in the pressure range of 4 to 15 \u00b1 1 GPa under planar shock loading. Comparison of the shock loading data for\r\nfused SiO2 to that on vitreous GeO2 demonstrates that transformation to the rutile structure in both media are similar. The Hugoniots of vitreous GeO2 and fused SiO2 are found to coincide approximately if pressure in fused SiO2 is scaled by the ratio of fused SiO2to vitreous GeO2 density. This result, as well as the same structure, provides the basis for considering vitreous Ge02 as an analogous material to fused SiO2 under shock loading. Experimental results from the spherical projectile impact demonstrate: (1) The supported elastic shock in fused SiO2 decays less rapidly than a linear elastic wave when elastic wave stress amplitude is higher than 4 GPa. The supported elastic shock in vitreous GeO2 decays faster than a linear elastic wave; (2) In vitreous GeO2 , unsupported shock waves decays with peak pressure in the phase transition range (4-15 GPa) with propagation distance, x, as \u03b1 1/x-3.35 , close to the prediction of Chen et al. [1998]. Based on a simple analysis on spherical wave propagation, we find that the different decay rates of a spherical elastic wave in fused SiO2 and vitreous GeO2 is predictable on the base of the compressibility variation with stress under one-dimensional strain condition in the two materials.
\r\n\r\n" }, { "name": "Melbourne, Timothy Ian", "degree": "PhD", "year": "1999", "title": "I. Rupture Properties of Large Subduction Earthquakes. II. Broadband Upper Mantle Structure of Western North America", "advisor": "Helmberger, Donald V.; Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09122016-121754817", "creators": [ { "name": { "family": "Melbourne", "given": "Timothy Ian" }, "id": "Melbourne-Timothy-Ian", "display_name": "Melbourne, Timothy Ian" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "co-advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geophys" ], "doi": "10.7907/87nd-p040", "abstract": "This thesis contains two studies, one of which employs geodetic data bearing on large\r\nsubduction earthquakes to infer complexity of rupture duration, and the other is a\r\nhigh frequency seismological study of the upper mantle discontinuity structure under\r\nwestern North America and the East Pacific Rise. In the first part, we present\r\nGlobal Positioning System and tide gauge data which record the co-seismic deformation\r\nwhich accompanied the 1995 Mw8.0 Jalisco event offshore central Mexico, the\r\n1994 Mw7.5 Sanriku event offshore Northern Honshu, Japan, and the 1995 Mw8.1\r\nAntofagasta earthquake offshore Northern Chile. In two of the three cases we find\r\nthat the mainshocks were followed by significant amounts of rapid, post-seismic deformation\r\nwhich is best and most easily explained by continued slip near the co-seismic\r\nrupture patch. In Jalisco, we find that the post-seismic deformation which occurred\r\nduring the two weeks following the mainshock amounted to as much 70% of the co-seismic\r\ndeformation, from which we estimate an additional moment release of 40%,\r\nwhile in the Sanriku event an additional 30% moment release followed in the 10 days\r\nafter the mainshock. Because of the favorable geometry of the Jalisco network, we infer\r\nthat the post-seismic faulting occurred predominantly down-dip of the co-seismic\r\nrupture plane. This is the first documented case of rapid slip migration following\r\na large earthquake, and is pertinent to earthquake prediction based on precursory\r\ndeformation. Following the Antofagasta mainshock there was no rapid post-seismic\r\ndisplacement within the resolution of the GPS measurements, which equals roughly\r\n1% of the co-seismic displacement. As the three GPS data sets represent the best\r\nobservations of large subduction earthquakes to date and two of them show significant\r\namounts of aseismic energy release, they strongly suggest silent faulting may\r\nbe common in certain types of subduction zones. This, in turn, bears on estimates\r\nof global moment release, seismic coupling, and our understanding of the natural\r\nhazards associated with convergent margins.
\r\n\r\nThe second part of this dissertation utilizes high frequency body waves to infer\r\nthe upper mantle structure of western North America and the East Pacific Rise.\r\nAn uncharacteristically large Mw5.9 earthquake located in Western Texas provided a\r\nvivid topside reflection off the 410 Km velocity discontinuity (\"410\"), which we model\r\nto infer the fine details of this structure. We find that, contrary to conventional\r\nwisdom, the 410 is not sharp, and our results help reconcile seismic observations\r\nof 410 structure with laboratory predictions. By analyzing differences between our\r\nstructure and seismic 410 structure estimates under the nearby Gulf of California, we\r\nattempt to extract differences in temperature and mineralogy between subcontinental\r\nand suboceanic 410 structures.
\r\n\r\nExtending this analysis, we utilize teleseismic events from East Pacific Rise transform\r\nfaults to model multiple S upper mantle triplications. We find that for raypaths\r\ntraversing the rise crest the 1-D model TNA [Grand and Helmberger (1984)] derived\r\nfor the western US accurately predicts differential SnS-S travel times and triplication\r\nwaveform structure, implying that there is little velocity heterogeneity along the\r\nridge crest along nearly its entire length. We find that for energy traversing paths\r\nincreasingly away from the ridge axis there is no discernible change in the apparent\r\ndepth of the 410 and 670 Km discontinuities. In the shallowest mantle (uppermost 75\r\nKm), there is a strong lateral shear velocity gradient amounting to 3% over roughly\r\n150 Km. The LID, nonexistent at the ridge crest, grows slowly in thickness beyond\r\n150 Km from the axis. The compatible geodynamic model of these two results is that\r\nthe East Pacific Rise is not fed from the local lower mantle, rather, upper mantle\r\nmaterial must be transported laterally to supply the ridge axis spreading center, and\r\nthe LID reflects the source region of the East Pacific Rise magma supply.
" }, { "name": "Polet, Jascha", "degree": "PhD", "year": "1999", "title": "Seismological observations of upper mantle anisotropy [pt. 1] ; Source spectra of shallow subduction zone earthquakes and their tsunamigenic potential [pt. 2]", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:02092011-083952190", "creators": [ { "name": { "family": "Polet", "given": "Jascha" }, "id": "Polet-J", "display_name": "Polet, Jascha" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "display_name": "Anderson, Donald L." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/yd79-j825", "abstract": "One of the most important developments in observational seismology in the last 10 years\r\nis the worldwide increase in the number of broadband instruments and seismic networks,\r\nas well as the improved access to the data-set that these seismometers provide. A data-set\r\nof this magnitude offers nearly unlimited possibilities for research into earthquake source\r\nprocesses and Earth structure. The work presented in this thesis involves the application of\r\ndifferent methods to seismological recordings, as well as an interpretation and discussion\r\nof the results.\r\nIn Chapter I, I take advantage of the very broadband nature and small spacing of the\r\nstations of TERRAscope, one of the first digital broadband seismic networks, to determine\r\ndispersion curves for long period surface waves. This enables us to invert for an upper\r\nmantle S-wave velocity model for southern California. The Rayleigh wave, SV, model is\r\nabout 4% slower than the model developed for tectonic north America. If the correction for\r\nhigher modes I performed on our Love wave data measurements is accurate, the resulting\r\nSH velocity model shows about 5% anisotropy (transverse isotropy) in the upper mantle\r\nbeneath southern California.\r\nIn Chapter 2, I perform measurements of shear-wave splitting on a unique data-set\r\nobtained from temporary arrays located above the Nazca subduction zone in South\r\nAmerica. Data from SKS, and local S-wave data from deep and intermediate depth\r\nearthquakes, were used to develop a model of the anisotropy in this region. The above slab\r\ncomponent of anisotropy in the western region, where the slab is at a depth of about 300\r\nkm and up is oriented NS and its delay time is limited to about 0.3 sec. This direction\r\nagrees with the shortening direction of the Andes and is orthogonal to that predicted by a\r\ncomer flow model. To the east, the stations have EW aligned fast directions and possibly\r\nsample the Brazilian craton. The below slab component samples a zone of EW aligned\r\nanisotropy, as well as trench parallel aligned anisotropy. The trench parallel directions can\r\nbe explained by the retrograde motion of the slab in south America, and I speculate that the\r\nEW direction could suggest a tear in the slab, or a local EW orientation because of local\r\nbuckling of the slab under NS compression.\r\nIn Chapter 3 I use this same method for the data of the TriNet array. Here I find an overall\r\npattern of consistent directions of the polarization direction of the fast SKS waves, the\r\nfastest P-wave velocities and the World Stress Map maximum horizontal compressive\r\nstress directions. This suggest that the pattern of anisotropy is generally uniform in the\r\ncrust and lithospheric mantle, in a layer with an overall thickness of 100 to 150 km. The\r\nalignment of most fast directions can be explained by plate-tectonic, extensional and compressional\r\nevents. We also examine the detailed lateral and vertical variations of anisotropy\r\nin this region.\r\nChapter 4 is focussed on the differences in source spectra and tectonic setting between\r\ntsunami earthquakes, which excite anomalously great tsunamis and 'regular' shallow\r\nsubduction earthquakes. We find that these unusual events have several characteristics in\r\ncommon: low energy release at short periods, centroid location close to the trench, updip\r\nrupture, relatively small accretionary prism, sediment subduction and a well-developed\r\nhorst and graben structure of the oceanic plate close to the trench. We speculate that these\r\nevents can nucleate in an unusually shallow part of the subduction zone, where sediments\r\nnormally exhibit stable sliding behavior, because of the contacts between the horsts and the\r\noverriding plate. Because the earthquakes are so shallow, and there is some sediment being\r\nsubducted, part of the rupture goes through sediments, making the source process slow.\r\nThe true displacement (and thus the tsunami height) of these events may be underestimated\r\nbecause the elastic constants of the fault zone are not taken into account when converting\r\nseismic moment into displacement.\r\n" }, { "name": "Showman, Adam Peter", "degree": "PhD", "year": "1999", "title": "I. Dynamics at the Galileo Probe Site on Jupiter and II. Orbital and Thermal Evolution of Ganymede", "advisor": "Ingersoll, Andrew P.; Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:11292022-160931702", "creators": [ { "name": { "family": "Showman", "given": "Adam Peter" }, "id": "Showman-Adam-Peter", "display_name": "Showman, Adam Peter" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "co-advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "orcid": "0000-0002-8255-0545", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" } ], "option_major": [ "plansci" ], "doi": "10.7907/q4n0-9s68", "abstract": "The low abundances of water and H\u2082S measured by the Galileo probe at Jupiter sug\u00adgest that the probe entered a downdraft where dry air from above cloud top advects to 10 bars or deeper. I use basic physical constraints to extract dynamical informa\u00adtion from three aspects of Galileo probe data. First, I suggest that to remain dry, the downdraft must be underlain by a stable layer which inhibits mixing of volatiles from below; this requires the downdraft to be mechanically forced. Second, on rapidly rotating planets, the Coriolis and centripetal forces caused by winds usually balance the horizontal pressure-gradient force (which gives information about horizontal den\u00adsity differences). Therefore, I use the known winds versus depth at the probe site to infer horizontal density differences between the probe site and its surroundings. Under reasonable assumptions, these densities are consistent with a downdraft at the probe site. Third, I use ideas of horizontal mixing and column stretching to explain how the observed vertical profiles of ammonia, H\u2082S, and water vapor can be produced in a downdraft. Finally, I discuss some apparent inconsistencies between these sim\u00adple models. I also describe preliminary efforts to explore the origin, stability, and evolution of the downdrafts using the shallow water equations.
\r\n\r\nThe differences between Ganymede and Callisto have led to speculation that Gany\u00admede's history was shaped by tidal heating from an orbital resonance. Using the numerical model developed by Malhotra (1991, Icarus 94, 399), I demonstrate that Io, Europa, and Ganymede could have passed through either of two (previously un\u00adexplored) Laplace-like resonances en route to the current Laplace resonance. Un\u00adder reasonable conditions, these resonances produce great enough tidal heating in Ganymede to be geophysically significant. I also coupled the orbital evolution to an internal model of Ganymede to explore the effect of the resonance on Ganymede's interior. If Ganymede's tidal Q decreases strongly with temperature, the coupling can lead to massive, short-lived heating episodes which can melt much of the icy interior. Such heat pulses require the initial ice temperature to be extremely cold (>200 K), however, so they may be unlikely.
" }, { "name": "Sidorin, Igor A.", "degree": "PhD", "year": "1999", "title": "Dynamically consistent interpretation of the seismic structure at the base of the mantle", "advisor": "Gurnis, Michael C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11042005-150916", "creators": [ { "name": { "family": "Sidorin", "given": "Igor A." }, "id": "Sidorin-Igor-A", "display_name": "Sidorin, Igor A." } ], "advisors": [ { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "role": "advisor", "display_name": "Gurnis, Michael C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/v5ch-c986", "abstract": "There is increasing evidence of large degrees of heterogeneity in the seismic structure of the lowermost 200-300 km of the mantle constituting the D\" layer. The region is believed to play an important role in the dynamics of the mantle and the Earth as a whole. This is the place where hot plumes, reaching the Earth's surface may originate. This is also the region where most of the lithosphere subducted from the surface may ultimately settle. The interface between the two largest structural domains of the Earth, the core-mantle boundary, is also a zone of active chemical reactions.\r\n\r\nOne of the most diagnostic seismologically observed features in the D\" region is an apparent seismic velocity discontinuity 200-300 km above the core-mantle boundary, generally referred to as the D\" discontinuity. The primary evidence for the discontinuity comes from the observed seismic triplication with phases Scd or Pcd arriving between the direct arrival, S or P, and the core-reflected, ScS or PcP, in the 65\u00b0-85\u00b0 distance range. The cause of this abrupt velocity increase is unknown and various explanations have been advanced, including sharp thermal gradients, a chemical interface, or a solid-solid phase transition. However, neither seismology nor geodynamics alone can distinguish between the alternatives. In addition, no satisfactory explanation has yet been given to the apparent intermittance of the D\" discontinuity, as the triplication is strong in some regions (such as Alaska or Central America) but weak or missing in other regions (such as Central Pacific).\r\n\r\nWe use a combination of dynamic and seismic waveform modeling to provide tighter constraints on this structural feature of D\" and reduce the tradeoffs that exist in both seismological studies and dynamic modeling. The dynamic models are based on the adiabatic model that is computed in Chapter 2 by integrating available mineral physics data. The temperature field, chemical heterogeneity, and the distribution of phases computed from convection models are mapped to seismic velocities which are then used to compute synthetic seismic waveforms. By comparing these waveforms with data, we rule out some classes of dynamic models in favor of others. In particular, in Chapter 3 we demonstrate that a model with a chemical layer at the base of the mantle does not provide a consistent explanation for the seismological observations of the D\" discontinuity. We propose that the strength of the triplication is conditioned by both the abrupt velocity increase at the D\" discontinuity and the local velocity structure accompanying the discontinuity. Variations of the local structure strongly modulate the strength of the observed triplication and provide a natural explanation for the apparent intermittance. We also show that purely thermal gradients computed from convection models do not produce a sufficiently strong Scd phase. In Chapter 4 we suggest that the observed regional patterns in the strength of the D\" triplication are most compatible with a phase change model of the D\" discontinuity. In Chapter 5 a variety of convection models with a basal phase transition are tested to obtain the characteristics of the phase transition most compatible with observations. We find that the best value for the ambient elevation above the core-mantle boundary is about 150 km and the best value for the Clapeyron slope is about 6 MPa/K. In Chapter 6 this model is further tested by placing a discontinuity in context of the global shear velocity structure recovered by Grand's [1994] tomography model. We find that such a synthetic velocity model with a phase change characterized by a shear velocity contrast of 1.5%, ambient elevation ~ 200 km and Clapeyron slope ~ 6 MPa/K predicts the observed differential travel times patterns for the D\" triplication beneath Alaska, Eurasia and Central America. The model also provides an explanation for the apparent intermittance of the D\" discontinuity by predicting very weak triplication for Central Pacific and north-eastern Caribbean where convincing evidence for the D\" triplication is lacking.\r\n" }, { "name": "Spotila, James Anthony", "degree": "PhD", "year": "1999", "title": "The neotectonics of the San Bernardino Mountains and adjacent San Andreas Fault : a case study of uplift associated with strike-slip fault systems", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10232007-155443", "creators": [ { "name": { "family": "Spotila", "given": "James Anthony" }, "id": "Spotila-James-Anthony", "display_name": "Spotila, James Anthony" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "chair", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geol" ], "doi": "10.7907/z7g7-eb63", "abstract": "The San Bernardino Mountains have uplifted over the last few million years at the hub of structural systems along the southern San Andreas fault zone and represent an excellent opportunity to study the interplay between orogeny and transpressive strike-slip faulting. To attain a better understanding of the complex architecture of deformation in this range, I have constrained several basic kinematic aspects of its development. First, the timing and magnitude of rock uplift and exhumation of fault blocks have been constrained using the thermochronometry of radiogenic helium in apatite (Chapter 2). This has shown that small crustal slivers within the San Andreas fault zone were exhumed several kilometers over the last few million years, due to slip-partitioning along geometrically-complex, high-angle faults. Second, a detailed constraint on the vertical deformation field of the largest fault block in the range has been determined using a deeply weathered granite surface as a structural datum (Chapter 3). A structural analysis of this deformation pattern has provided the total displacements, slip rates, and subsurface geometries of the major thrust faults within the range (Chapter 4). As a whole, the San Bernardino Mountains appear to have uplifted within a complex system of both high and low-angle faults. The total horizontal plate motion accommodated by this uplift is on the order of 6 km and is focused tightly about a restraining bend in the San Andreas fault zone at San Gorgonio Pass. This suggests the entire range has been built due to convergence associated with a small geometric perturbation of a major strike-slip system.\r\n\r\nTo acquire a different perspective on the relationship of strike-slip faulting and uplift, I have also studied the deformation pattern around a restraining bend resulting from a single fault rupture. Structural analysis of surficial breaks at a slip gap during the 1992 Landers earthquake has revealed how complex, secondary thrust and normal faulting were induced to accommodate simple strike-slip motion where a through-going connection between two dextral fault segments has yet to develop (Chapter 5). This illustrates a single episode in the incremental evolution of a transpressive orogenic system." }, { "name": "Tulaczyk, Slawek M.", "degree": "PhD", "year": "1999", "title": "Basal mechanics and geologic record of ice streaming, West Antarctica", "advisor": "Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechETD:etd-03092004-155058", "creators": [ { "name": { "family": "Tulaczyk", "given": "Slawek M." }, "id": "Tulaczyk-Slawek-M", "display_name": "Tulaczyk, Slawek M." } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "chair", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Engelhardt", "given": "Hermann" }, "id": "Engelhardt-H", "role": "member", "display_name": "Engelhardt, Hermann" }, { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "member", "display_name": "Scott, Ronald F." } ], "option_major": [ "geol" ], "doi": "10.7907/N04E-S040", "abstract": "Piston coring in boreholes drilled at the UpB camp through Ice Stream B, West Antarctica, provided the first samples of sediments ever recovered from beneath an active ice stream. Sedimentological analyses indicate that the samples come from the layer of weak, subglacial till underlying this ice stream (the UpB till). Textural properties of the till and the Tertiary diatoms found in it suggest that the UpB till is recycled from the sediments of the inferred eastern subglacial extension of the Ross Sea sedimentary basin. Geotechnical tests show that the UpB till can be modeled as a compressible, Coulomb-plastic material whose strength is practically independent of deformation rate but is determined by effective stress which also determines the water content. Simulations of the subglacial behavior of such till have successfully reproduced fundamental features of the observed, subglacial till kinematics, e.g., viscous-like vertical distribution of strain and oscillations in tilt rates. The compressible-Coulomb-plastic till model offers a framework for understanding and modeling of ice stream motion and ice-till interactions. The high porosity of the UpB till ([approximately] 0.4) suggests that effective stress is consistently very low, ca. 0.1 to 30 kPa, in the subglacial zone of Ice Stream B. These conditions are explained by the 'undrained-bed' model of sub-ice-stream hydrology that includes only local exchange of water between the water stored in the till pore space and the water stored as basal ice. In this model, there is a negative feedback effect between the basal melting rate and till strength which forces a steady-state in which the basal melting rate is zero and the till is water-rich and weak. Coupling of the undrained-bed model with an equation for the velocity of ice stream sliding yields the undrained plastic-bed model of ice streaming (the UpB model). In accordance with the existing observations, the physics of the UpB model produces two stable modes: an active 'ice-stream' mode and an 'ice-sheet' mode. The model may experience thermally-triggered switches between the two modes and it can be used to test the hypothesis that the West Antarctic Ice Sheet will become unstable in the near-future." }, { "name": "Wasylenki, Laura Eileen", "degree": "PhD", "year": "1999", "title": "Partial Melting of Depleted Peridotite in the Earth's Upper Mantle and Implications for Generation of Mid-Ocean Ridge Basalts", "advisor": "Stolper, Edward M.; Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:10242019-141223855", "creators": [ { "name": { "family": "Wasylenki", "given": "Laura Eileen" }, "id": "Wasylenki-Laura-Eileen", "orcid": "0000-0003-0333-3567", "display_name": "Wasylenki, Laura Eileen" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "co-advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "co-chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." } ], "option_major": [ "geol" ], "doi": "10.7907/9rx0-fn74", "abstract": "Peridotite in the earth's upper mantle undergoes polybaric, fractional melting as it rises adiabatically beneath mid-ocean spreading ridges. As liquid is continually extracted, peridotite becomes increasingly depleted in incompatible components. The amounts and compositions of partial melts of depleted peridotite are important parameters in models of MORB petrogenesis, but have not been well-constrained previously. I present partial melting experiments on a depleted peridotite composition at 10 kbar and 1250\u20131390\u00b0C. My experiments make use of small aggregates of glassy carbon particles into which partial melt is extracted at high temperature. I have been able to analyze low degree partial melts (<10%) and quantify the effects of incompatible element depletion on the melting behavior of peridotite. Special tests of the approach to equilibrium in this study confirm the validity of the aggregate melt extraction technique, which has sparked much debate in the literature (see Chapters 2 and 3 for details).
\r\n\r\nMelts of depleted peridotite differ in important ways from melts of fertile peridotite, mostly due to lower alkali contents and chemical consequences thereof. At low melt fractions, melts of depleted peridotite have less SiO\u2082, more CaO, and higher CaO/Al\u2082O\u2083 than melts of fertile peridotite at the same melt fraction. According to these results and others in the literature, solidus temperature is a linear function of incompatible major element content. Melt fraction at cpx-out is proportional to normative cpx in source peridotite.
\r\n\r\nLiquid compositions from this study are in good agreement with calculations using the quantitative models of Kinzler and Grove (1992a), Langmuir et al. (1992), and Ghiorso and Sack (1995). Calculations of polybaric, fractional melting of primitive mantle using the models of Langmuir et al. (1992) and Asimow (1997) indicate that about half of all liquid contributed to MORB is formed by partial melting of depleted peridotite.
\r\n\r\nThe data presented in this thesis provide information about amounts and compositions of partial melts formed from depleted peridotite, an important upper mantle constituent beneath mid-ocean ridges, and can be used to improve quantitative models of MORB primary magma formation and further our understanding of MORB petrogenesis.
" }, { "name": "Brady, Robert John", "degree": "PhD", "year": "1998", "title": "The Geology of the Gold Butte Breakaway Zone and the Mechanical Evolution of Normal Fault Systems", "advisor": "Wernicke, Brian P.; Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02012019-101059213", "creators": [ { "name": { "family": "Brady", "given": "Robert John" }, "id": "Brady-Robert-John", "display_name": "Brady, Robert John" } ], "advisors": [ { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "advisor", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "co-advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "chair", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." } ], "option_major": [ "geol" ], "doi": "10.7907/715q-hm18", "abstract": "The Gold Butte breakaway zone is the easternmost and oldest of the major Tertiary normal fault systems in the central Basin and Range province of the southwestern U.S. The normal faults of the breakaway zone crop out across the South Virgin Mountains (SVM), and define a narrow boundary zone between the Colorado Plateau and the highly extended central Basin and Range Province. Geochronologic data, including 40Ar/39Ar muscovite ages, (U-Th)/He apatite ages, and (U-Th)/Pb monazite ages, suggest that extension within the breakaway zone occurred rapidly at ~15 Ma, consistent with earlier work (Fitzgerald, 1991). Approximately 400 km2 of the SVM was mapped at a scale of 1:12 000. This mapping shows that extension initiated on a set of steeply west dipping normal faults. Later faults soled into the earlier faults rather than cutting them, requiring motion to continue on both fault sets, with the earlier faults remaining active to dips of less than 30\u00b0. Total extension across the SVM is at least ~21 km. The latest deformation to affect the region was isostatic uplift of the footwall to the Lakeside Mine Fault Zone, with resultant formation of a basement dome and associated folding and late stage faulting adjacent to the dome. Seismic reflection data suggest that the crustal thickness of the region is 30 to 35 kilometers. When combined with the high average elevation of the denuded basement block, this suggests that extension of the upper crust has been compensated by emplacement of fluid mid to lower crust. The lower crust and Moho are seismically transparent, so the lower crust is probably not made up of basaltic intrusions; rather, it has probably flowed in from surrounding areas. A mechanical model has been developed which considers the behavior of an elastic upper crust isostatically compensated by flow in the lower crust. This model shows that gradual isostatic upwarping of the thinning region should generate compressional flexural stresses near the base of the elastic upper crust. These stresses may shut down the active faults and force new normal faults to root outside of the extended region.
" }, { "name": "Ducea, Mihai Nicolae", "degree": "PhD", "year": "1998", "title": "A petrologic investigation of deep-crustal and upper-mantle xenoliths from the Sierra Nevada, California ; constraints on lithospheric composition beneath continental arcs and the origin of cordilleran batholiths", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05022006-165209", "creators": [ { "name": { "family": "Ducea", "given": "Mihai Nicolae" }, "id": "Ducea-Mihai-Nicolae", "display_name": "Ducea, Mihai Nicolae" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/HCEX-DQ60", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThere are few direct observations constraining the vertical extent of the large Cordilleran granitic batholiths and their composition at depths greater than 30 km. I present evidence for a ~ 100 km thick sequence of cogenetic rocks which together comprise the Sierra Nevada batholith of California (SNB). The SNB magmatism produced tonalitic and granodioritic magmas which reside in the Sierra Nevada upper- to mid-crust as well as deep crust/upper mantle mafic-ultramafic cumulates. Samples of the mafic-ultramafic sequence are preserved only as xenoliths in Miocene volcanics which erupted through the central part of the batholith. Sm-Nd and Rb-Sr mineral geochronologic analyses were performed on fresh, cumulate textured, garnet pyroxenite, eclogite and gabbroic xenoliths with large grainsize. All samples equilibrated between ~35 and 100 km beneath the batholith and yield Sm-Nd mineral ages between 81 and 136 Ma, broadly coincident with the previously established period of most voluminous batholithic magmatism in the Sierra Nevada.\r\n\r\nThe whole rock initial [...] and the [...] ratios of the igneous xenoliths are similar to the ratios published for the outcrops of the central SNB. I interpret these xenoliths to be magmatically related to the upper- and mid-crustal granitoids, as cumulates and/or restites. This more complete view of the vertical dimension in a batholith demonstrates that a large mass of mafic-ultramafic residue at depth complements the predominantly granitic batholiths, as predicted by mass balance calculations and experimental studies. The SNB magmatism was a large scale process responsible for efficiently segregating a ~30-35 km thick column consisting predominantly of granitoids from a ~ 70 km mafic-ultramafic, mainly eclogite facies root.\r\n\r\nTrace element data indicate that these garnet-rich assemblages were in equilibrium at depths of 45 km or more with SNB-like tonalitic-granodioritic melts. I propose that the petrologic mechanisms responsible for \"distillation\" of large scale granitoids in the central Sierra Nevada are similar to the ones which led to the extraction of the voluminous granitoids that make up the cratonic nucleii of the continents. The large magnitude isotopic heterogeneity observed in the xenoliths, and the similar range of isotopic ratios measured in surface granitoids, suggest that the compositional variability observed in the surface granitods is primarily inherited from the source rocks in the deeper parts of the lithosphere. The isotopic ratios of the deep-seated residues/cumulates require the existence of three source components for the batholith: (1) a young supracrustal component, represented by Mesozoic accreted arc rocks, (2) a Proterozoic lower crustal (+old lithospheric mantle) component, and (3) a Phanerozoic depleted mantle component. Xenolith data support the hypothesis of lithospheric scale thrusting of accreted masses over the autochtonous crust of western North-America prior to the generation of large volume granitic magmatism in the Sierra Nevada region.\r\n\r\nBatholith cumulates/residues resided under the batholith as eclogite facies rocks for at least 70 My after magmatism shutoff. However, mantle xenoliths sampled in younger, Pliocene volcanic rocks contain spinel peridotites which equilibrated over the same depth interval as the garnet pyroxenite assemblages from Miocene pipes. Futhermore, no garnet-bearing samples have been recovered from the Pliocene volcanics. Silica-rich glass inclusions, trapped along grain boundaries of peridotites from Pliocene volcanics, have isotopic compositions similar to the eclogitic keel. These geologic observations as well as geophysical constraints suggest that the thick and dense \"eclogitic\" root may have foundered in the mantle between Mid- Miocene and Pliocene.\r\n" }, { "name": "Evans, David Aspinwall Dai", "degree": "PhD", "year": "1998", "title": "I. Neoproterozoic-Paleozoic Supercontinental Tectonics and True Polar Wander. II. Temporal and Spatial Distributions of Proterozoic Glaciations", "advisor": "Kirschvink, Joseph L.; Stock, Joann M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11152012-083234968", "creators": [ { "name": { "family": "Evans", "given": "David Aspinwall Dai" }, "id": "Evans-David-Aspinwall-Dai", "orcid": "0000-0001-8952-5273", "display_name": "Evans, David Aspinwall Dai" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "co-advisor", "display_name": "Stock, Joann M." } ], "committee": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "chair", "display_name": "Stock, Joann M." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." } ], "option_major": [ "geol" ], "doi": "10.7907/grbc-aa41", "abstract": "The Proterozoic Eon, occupying nearly half of Earth history from 2.5 to 0.5 billion\r\nyears ago, is marked at its beginning and end by dramatic events in the tectonic,\r\npaleoclimatic, chemical, and biological evolution of the planet. The onset of the\r\nProterozoic Eon witnessed the emergence of continents and perhaps the introduction of\r\nplate tectonics, Earth's first extensive ice ages, oxygenation of the hydro-atmosphere, and\r\ndevelopment of eukaryotes. The end of the Proterozoic Eon is characterized by\r\nsupercontinental turnover and very rapid continental drift rates, a series of glaciations\r\nwhich left their marks on every continent, the rise of atmospheric oxygen to sustain\r\nmulticelled organisms, and an evolutionary \"explosion\" of animal life.
\r\n\r\nEstablishment of coherent paleogeographies of these important intervals is a crucial\r\nprerequisite for describing the events and understanding the underlying processes.\r\nPaleomagnetism is the most direct quantitative method for charting continental drift through\r\ntime. The purpose of this dissertation is to use paleomagnetism to constrain tectonic and\r\npaleoclimatic processes at the beginning and end of the Proterozoic Eon.
\r\n\r\nA paleomagnetic study of Early Cambrian rocks in western Mongolia finds somewhat\r\nambiguous results and addresses tectonic models of the Paleo-Asian Ocean. Review of the\r\nmost reliable studies among the Proterozoic-Cambrian global paleomagnetic database\r\npermits the hypothesis that an episode of inertial interchange true polar wander (TPW)\r\noccurred in Early Cambrian time. The Cambrian TPW event and a previously hypothesized\r\nOrdovician-Devonian TPW migration share a common axis and suggest the existence of\r\nlong-lived mantle mass anomalies inherited from the previous supercontinent, Rodinia.\r\nThe breakup of Rodinia and subsequent amalgamation of Gondwanaland appear analogous\r\nin several ways to the Gondwanaland-Super-Asia supercontinental transition, suggesting a\r\n500-600-Myr cyclicity.
\r\n\r\nAn exhaustive review of paleomagnetic and geochronological constraints upon\r\nNeoproterozoic glaciogenic deposits fails to find a convincing high-paleolatitude\r\noccurrence. Detailed study of one of these deposits in South China reveals a reliable\r\npaleomagnetic pole implying a paleolatitude of 34\u00b12\u00b0, with both paleoclimatic and\r\npaleogeographic implications. A reliable estimation of 11\u00b15\u00b0 depositional paleolatitude for\r\n2.2-billion-year-old lavas directly overlying a glaciogenic formation in South Africa,\r\nextends the occurrence of low-latitude continental ice sheets further back into the\r\nPrecambrian.
\r\n\r\n" }, { "name": "Herman, Robert Laird", "degree": "PhD", "year": "1998", "title": "In Situ Measurements of Chemical Tracers in the Stratosphere: CO, N\u2082O, and CH\u2084", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07272023-210618418", "creators": [ { "name": { "family": "Herman", "given": "Robert Laird" }, "id": "Herman-Robert-Laird", "display_name": "Herman, Robert Laird" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/y3yr-cv21", "abstract": "Stratospheric transport is studied with measurements of long-lived tracers. The Aircraft Laser Infrared Absorption Spectrometer II (ALIAS II) was designed and built to make in situ measurements of atmospheric trace gases at altitudes ranging from 7 km to 30 km. With this spectrometer, nitrous oxide (N\u2082O) and methane (CH\u2084) mixing ratios were measured on six high\u00ad altitude balloon flights from the tropics (7\u00b0S), mid-latitudes (34\u00b0N), and high latitudes (65\u00b0N). Comparisons of measured mixing ratios with model predictions are used to quantify meridional transport rates in the stratosphere. The mean time scale for entrainment of mid-latitude stratospheric air into the tropics is estimated to be 7\u207a\u00b9\u2070\u208b\u2087 months for altitudes between the tropical tropopause and 20 km, and 16\u207a\u00b9\u2078\u208b\u2088 months for 20 to 28 km. These results suggest that most of the stratospheric entrainment into the tropics occurs at altitudes roughly below 20 km, and that the tropical stratosphere is dynamically isolated from the mid-latitude stratosphere at altitudes between 20 and 28 km.
\r\n\r\nFaster transport in the lower stratosphere was studied with measurements of atmospheric carbon monoxide (CO) by the ALIAS instrument, predecessor to ALIAS II. This instrument measured CO on fifty eight flights of the NASA ER-2 high-altitude aircraft from October, 1995, to September, 1997, during two aircraft campaigns: Stratospheric Tracers of Atmospheric Transport (STRAT) and Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS). These flights covered altitudes up to 22 km and latitudes from 3\u00b0S to 90\u00b0N. CO has a photochemical lifetime of only several months in the upper troposphere and lower stratosphere, so its mixing ratio is sensitive to rapid transport. These measurements indicate that quasi-horizontal poleward outflow from the tropical stratosphere occurs on rapid time scales of roughly one month for altitudes between 16 and 20 km.
" }, { "name": "Mills, Franklin Perry", "degree": "PhD", "year": "1998", "title": "I. Observations and Photochemical Modeling of the Venus Middle Atmosphere. II. Thermal Infrared Spectroscopy of Europa and Callisto", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11222004-140151", "creators": [ { "name": { "family": "Mills", "given": "Franklin Perry" }, "id": "Mills-Franklin-Perry", "display_name": "Mills, Franklin Perry" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Brown", "given": "Michael E." }, "id": "Brown-M-E", "role": "member", "display_name": "Brown, Michael E." }, { "name": { "family": "Okumura", "given": "Mitchio" }, "id": "Okumura-M", "role": "member", "display_name": "Okumura, Mitchio" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" } ], "option_major": [ "plansci" ], "doi": "10.7907/NWPG-E852", "abstract": "The evolution of our solar system remains one of the most fascinating questions since ancient astronomers first realized that the \"stars\" which do not twinkle are planets. In the modern era, the future evolution of the Earth has become a topic that may arise even in lay conversations. For example, the effects of changes in the earth's climate and the ozone layer are debated in policy and economic discussions as well as in scientific forums. One method for assessing our understanding of the Earth's atmosphere is to examine the atmospheres of the other terrestrial planets. The atmospheres of Venus and Mars share some common features with that of the Earth, but there are important differences. These differences are important because they force us to examine the often implicit assumptions that lie within the tunable parameters that exist in all models. Consequently, studies of the atmospheric chemistry on Venus and Mars can provide a test of the degree to which our understanding of the fundamental physical and chemical principles that govern the Earth's atmosphere is correct.
\r\n\r\nThe chemistry of the Martian atmosphere has been \"solved\" to the extent that modern photochemical models [e.g., Nair et al. 1994] can reproduce the primary observable characteristics to within a factor of 2 - 3 using the results from laboratory studies of photochemical reaction rates. The chemistry of the Venus atmosphere, however, remains an \"unsolved\" problem in that the differences between the most recent generation of models [Yung and DeMore 1982] and some of the existing observations are greater than a factor of 10. The first part of this dissertation (Chapters 1, 2, and 3) combines several lines of research that focused on how the discrepancy between models and observations of the Venus atmosphere can be reduced. (The appendices for Chapter 2 are in Chapter 5.) The results provide a better understanding of the current photochemical processes in the Venus atmosphere and can serve as a baseline for future studies of its evolution.
\r\n\r\nThe intervening chapter reports observations of Europa and Callisto in the 8-l3μm wavelength region. Those observations provide constraints on the composition and/ or physical state of the surficial material on the two satellites.
\r\n\r\nPart I (Observations and Photochemical Modeling of the Venus Middle Atmosphere)
\r\n\r\nThe primary photochemical cycle of the Venus middle atmosphere (within and above the upper cloud layer) is the photolysis of C02 to form CO and oxygen atoms on the dayside followed by the reformation of C02 from CO and oxygen, primarily via catalytic reactions. Previous photochemical models-using ClOx, SOx, NOx, and HOx radicals to catalyze the reformation of C02-could qualitatively explain the stability of Venus' C02 atmosphere. Despite the powerful catalytic reactions introduced, however, none of the previous models could quantitatively explain either the low column abundance of molecular oxygen or the intense nightside air glow in the 02(a1Δ) band. The most comprehensive of the previous models, that by Yung and DeMore [1982], predicted a column abundance of molecular oxygen that was a factor of ~30 larger than the upper limit obtained the following year [Trauger and Lunine 1983], and it predicted a nightside airglow that was about three-quarters of the observed intensity. These discrepancies suggested that significant gaps remained in our understanding of the dominant chemical processes in the Venus middle atmosphere.
\r\n\r\nIn the fifteen years since these studies, new observations have provided further insight into the current state of the Venus atmosphere, and our understanding of chlorine and sulfur chemistry has improved as a result of laboratory and field studies related to the terrestrial stratosphere. One idea that had been proposed is that the abundance of 02 in the Venus atmosphere might vary by as much as a factor of 10 over time scales of years. This proposal was based on observations of S02 and SO at the top of the Venus clouds which showed a monotonic decrease in the abundances of both species from 1980 to 1995 with S02 declining by a factor of 10 and SO by a factor of 5. An alternate proposal was that rapid reactions on aerosol particles, such as
\r\n\r\nHOCl + HCl +aerosol-+ H20 + Cl2 + aerosol
\r\n\r\nwhich converts Cl from a relatively nonreactive form, HCl, to a potentially highly reactive form, Cl2, could greatly enhance the effectiveness of the chlorine catalytic reactions that oxidize CO to C02.
\r\n\r\nThis project has attempted to reconcile the differences between observations and photochemical models with regard to the oxygen budget of the Venus middle atmosphere. To examine the potential temporal variability of the 02 abundance, we attempted to detect molecular oxygen on the dayside of Venus using the Ultra-High Resolution Facility at the Anglo-Australian Telescope on 23 January 1995. We observed the 763.6325 and 763.2165 nm 02 lines at a spectral resolving power, λ⁄⁄λ, of 600000 with a square, 1.5 arc-second field of view. These observations reveal no evidence for 02 above the Venus cloud tops within our detection limit which is equivalent to a uniform vertical mixing ratio of 3 ppm. Our upper limit on the abundance of 02 in the Venus middle atmosphere is comparable to that obtained by Traub and Carlton [1974] and is a factor of ten larger (less stringent) than that obtained by Trauger and Lunine [1983] (2σ = 0.3 ppm). Within the obvious limitations imposed by the relative sensitivities of the non-detections, we find no evidence for an increase in the abundance of 02 in association with the observed decreases in S02 and SO abundances.
\r\n\r\nThe parallel branch to new observations was development of a new photochemical model for the Venus middle atmosphere that incorporates the most recent chemical kinetic rates and photoabsorption cross sections. Our one-dimensional, steady-state photochemical model can reproduce (within measurement uncertainty and temporal⁄spatial variability) the retrieved SO profile [Na et al. 1994], the retrieved S02 abundance and scale height at the cloud top [Na et al. 1994], the retrieved CO profile [Clancy and Muhleman 1991], and the observed \"global average\" 02 (a1Δ) airglow [Crisp et al. 1996] using only gas-phase chemistry if we adjust key reaction rates within their assessed one standard deviation uncertainties. Our predicted column abundance for 02 is a factor of 10 smaller than than from previous models. Our results suggest SClx and ClSOx compounds may be important in the chemistry of the upper cloud layer, and we find that Reaction G10 is not an important source of Cl2 above the cloud top.
\r\n\r\nThe current observational upper limit can be reconciled with the predictions from our photochemical model if one examines the absorption produced by our predicted 02 distribution instead of the column abundance. Our model predicts that most of the 02 in the Venus atmosphere will be located between 85 and 95 km altitude, several scale heights above the cloud top (~70-75 km altitude) and, thus, above the region in which multiple scattering is important. Radiative transfer model calculations indicate that the absorption due to our predicted 02 distribution is equivalent to that produced for a uniform vertical distribution of 02 with mixing ratio of 0.3 ppm, the two standard deviation upper limit from the observations. If the equilibrium constant for ClCO is adjusted by two standard deviations and the temperatures at 85 - 95 km altitude are decreased by ~15-20 K (two standard deviations), the predicted 02 absorption will lie below the observed one standard deviation upper limit.
\r\n\r\nPart II (Thermal Infrared Spectroscopy of Europa and Callisto)
\r\n\r\nThe trailing hemispheres of Europa and Callisto were observed and a 9- 13 μm spectrum of Europa with better spectral resolution and better signal-to-noise than was previously possible has been derived. The ratio spectrum of the two satellites has a signal-to-noise ratio of approximately 30 and spectral resolving power of approximately 50. The ratio spectrum was combined with the average Voyager 1 spectrum of Callisto from Spencer [1987a] to obtain a 9- 13 μm spectrum of Europa with signal-to-noise that is a factor of 10 better than that in the average Voyager spectrum of Europa in Spencer [1987a]. No emissivity features due to water ice are apparent at the 3% level in our Europa spectrum. The disk-integrated, effective color temperature ratio for the two satellites is consistent with previous ground-based, broadband, thermal infrared photometry. One possible explanation for the absence of features in the thermal infrared spectra of Europa (at the 3% level) and Callisto (at the 1% level) is if the surfaces of both satellites have significant abundances of small particles (≲50 micrometer in size). This explanation is consistent with most of the published observations by Galileo.
\r\n" }, { "name": "Scrivner, Craig William", "degree": "PhD", "year": "1998", "title": "Analysis and Modeling of Seismic Ground Motions in Heterogeneous Structures in Southern California", "advisor": "Helmberger, Donald V.; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07142023-185900244", "creators": [ { "name": { "family": "Scrivner", "given": "Craig William" }, "id": "Scrivner-Craig-William", "display_name": "Scrivner, Craig William" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "geophys" ], "doi": "10.7907/m61x-wq81", "abstract": "This thesis contains studies of seismic data from the 1995-1996 Ridgecrest earthquake sequence, an aftershock of the 1987 Whittier Narrows earthquake and the 1991 Sierra Madre mainshock, and aftershocks of the 1994 Northridge earthquake. The Ridgecrest data set spans southern California, including stations in the Los Angeles area basins. The Whittier Narrows/Sierra Madre and Northridge data sets consist of stations in the Los Angeles and San Fernando Valleys, respectively, and record earthquakes occurring directly adjacent to these sedimentary basins. The studies examine the variability of ground motions in the crust and details of seismic propagation from the crust into sedimentary basins. In the Ridgecrest study, amplitudes of synthetic waveforms from a 1D model are compared with data amplitudes at rock, soil, and basin sites. At rock sites, the data amplitudes are within a factor of 2 of the synthetic amplitudes. At basin and soil sites, the data are within a factor of 3 of the synthetic amplitudes. Stations beyond the trailing edge of sedimentary basins are affected by leaked basin surface waves. In the Whittier Narrows/Sierra Madre study, waveform phases generated by the edge of the Los Angeles basin are identified and modeled with a 2D structure. In the data, multiples of the direct shear wave, reflected from the surface and turned by the basin edge, are up to two times the amplitude of the direct arrival. A simple, smooth, 2D basin edge model produces the correct timing and relative amplitude of basin-trapped phases. In the Northridge study, we contrast waveforms from a shallow and a deep event. The waveforms from the shallow event include basin-generated surface waves in the basin, and a phase-shift in the direct shear wave outside the basin. A model with a strong velocity contrast at about 1 km depth in the upper basin, a depth for the entire basin just above the shallow source depth, and a gradient beneath the basin produces synthetic waveforms that match the distinctive features in the data set." }, { "name": "Tsitas, Steven R.", "degree": "PhD", "year": "1998", "title": "I. The effect of volcanic aerosols on ultraviolet radiation in Antarctica. II. A novel method for enhancing subsurface radar imaging using radar interferometry", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302013-102418285", "creators": [ { "name": { "family": "Tsitas", "given": "Steven R." }, "id": "Tsitas-S-R", "display_name": "Tsitas, Steven R." } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/fc8p-nd23", "abstract": "The theory of radiative transfer is used to explain how a stratospheric aerosol layer\r\nmay, for large solar zenith angles, increase the flux of UV-B light at the ground. As\r\nprevious explanations are heuristic and incomplete, I first provide a rigorous and complete\r\nexplanation of how this occurs. I show that an aerosol layer lying above Antarctica during\r\nspring will decrease the integrated daily dose of biologically weighted irradiance, weighted\r\nby the erythema action spectrum, by only up to 5%. Thus after a volcanic eruption, life in\r\nAntarctica during spring will suffer the combined effects of the spring ozone hole and\r\nozone destruction induced by volcanic aerosols, with the latter effect only slightly offset by aerosol scattering.
\r\n\r\nI extend subsurface radar imaging by considering the additional information that\r\nmay be derived from radar interferometry. I show that, under the conditions that temporal\r\nand spatial decorrelation between observations is small so that the effects of these\r\ndecorrelations do not swamp the signature expected from a subsurface layer, the depth of\r\nburial of the lower surface may be derived. Also, the echoes from the lower and upper\r\nsurfaces may be separated. The method is tested with images acquired by SIR-C of the area\r\non the Egypt/Sudan border where buried river channels were first observed by SIR-A.\r\nTemporal decorrelation between the images, due to some combination of physical changes\r\nin the scene, changes in the spacecraft attitude and errors in the processing by NASA of the\r\nraw radar echoes into the synthetic aperture radar images, swamps the expected signature\r\nfor a layer up to 40 meters thick. I propose a test to determine whether or not simultaneous\r\nobservations are required, and then detail the radar system requirements for successful\r\napplication of the method for both possible outcomes of the test. I also describe in detail the possible applications of the method. These include measuring the depth of burial of ice in the polar regions of Mars, enhancing the visibility of buried features and, most importantly, the ability to map soil moisture in arid regions of the earth at high spatial resolution.
\r\n" }, { "name": "Vasavada, Ashwin R.", "degree": "PhD", "year": "1998", "title": "I. Temperatures of polar ice deposits on mercury and the moon. II. Jovian atmospheric dynamics from Galileo imaging", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01282013-083854060", "creators": [ { "name": { "family": "Vasavada", "given": "Ashwin R." }, "id": "Vasavada-Ashwin-R", "orcid": "0000-0003-2665-286X", "display_name": "Vasavada, Ashwin R." } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/ps1y-d710", "abstract": "Locations on Mercury that produce ice-like radar responses lie within\r\nimpact craters that have very cold, permanently shaded floors. The retention of\r\npossible ice deposits is determined largely by their temperature. We present model-\r\ncalculated temperatures of flat surfaces and surfaces within bowl-shaped and flatfloored\r\npolar impact craters. Our model includes appropriate insolation cycles,\r\nrealistic crater shapes, multiple scattering of sunlight and infrared radiation, and\r\ndepth and temperature-dependent regolith thermophysical properties. Unshaded\r\nwater ice deposits are rapidly lost to sublimation on Mercury and the Moon.\r\nMeter-thick deposits of water ice are stable to evaporation over the age of the\r\nsolar system if located in the permanently shaded portions of flat-floored craters\r\nwithin 10\u00b0 latitude of the poles of either planet. Results for craters associated with\r\nradar features on Mercury are consistent with stable water ice deposits if a thin\r\nregolith layer thermally insulates the lowest latitude deposits, reducing sublimation\r\nrates. A regolith cover also is a diffusion barrier, reduces losses from sputtering,\r\nimpact vaporization, and exposure to H Ly\u03b1, and is implied independently by the\r\nradar observations. Impact craters near the lunar poles contain colder permanently\r\nshaded regions than those on Mercury.
\r\n\r\nDuring the first six orbits of the Galilee spacecraft's prime mission, the\r\nSolid State Imaging system acquired multispectral image mosaics of Jupiter's\r\nGreat Red Spot, an equatorial belt/zone boundary, a \"5-\u00b5m hotspot\" similar to the\r\nGalilee Probe entry site, and two of the classic White Ovals. We present mosaics\r\nof each region approximating their appearance at visible wavelengths and showing\r\ncloud height and opacity variations. The local wind field is derived by tracking\r\ncloud motions between multiple observations of each region with time separations\r\nof roughly one and ten hours. Vertical cloud structure is derived in a companion\r\npaper by Banfield et al.(1998). Galilee's brief, high-resolution observations\r\ncomplement Earth-based and Voyager studies, and offer local meteorological\r\ncontext for the Galileo Probe results. Images taken one hour apart reveal small,\r\nrapidly changing, high cloud features possibly analogous to terrestrial\r\nthunderstorms. Our results show that the dynamics of the zonal jets and large\r\nvortices have changed little since Voyager, with a few exceptions. We detect a\r\ncyclonic current within the center of the predominantly anticyclonic Great Red\r\nSpot. The zonal velocity difference between 0\u00b0s and 6\u00b0S has increased by 20 m s^(-1).\r\nWe measure a strong northeast flow approaching the hotspot. This flow indicates\r\neither massive horizontal convergence or the presence of a large anticyclonic\r\nvortex southeast of the hotspot. The current compact arrangement of two White\r\nOvals and a cyclonic structure greatly perturbs the zonal jets in that region.
" }, { "name": "Wen, Lianxing", "degree": "PhD", "year": "1998", "title": "Plate Tectonics, Mantle Convection and D\" Seismic Structures", "advisor": "Anderson, Donald L.; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12012022-215809006", "creators": [ { "name": { "family": "Wen", "given": "Lianxing" }, "id": "Wen-Lianxing", "orcid": "0000-0002-5344-6212", "display_name": "Wen, Lianxing" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "geophys" ], "doi": "10.7907/mn9a-ve49", "abstract": "This thesis is directed at understanding dynamics of the Earth's mantle. I adopt multidisciplinary approaches toward the problem: geodynamical and seismological.
\r\n\r\nMy approach in geodynamics is directed at understanding the relationship between large scale surface observables (geoid, topography, plate motions) and mantle rheology and convection of the present-day Earth. In chapter 2, I do best-fit correlations of shallow mantle structure with various tectonic features and remove them to generate what we call \"residual tomography.\" In chapter 3, I show that the pattern, spectrum and amplitude of the \"residual topography\" are consistent with shallow origin of the \"Earth surface dynamic topography;\" the very long wavelength geoid and topography (l = 2 - 3) are successfully explained by density models inferred from the \"residual tomography,\" assuming layered mantle convection stratified at the \"920 km seismic discontinuity.\" In chapter 4, I develop a new method to calculate mantle flow in the spherical coordinates with lateral variation of viscosity. The viscosity contrast between continental and oceanic regions is identified to have dominating effects on both the observed poloidal/toroidal ratio and pattern of toroidal motions at long wavelengths. I show convection models with lateral variation of viscosity are capable of producing long wavelength plate motions observed in plate tectonics.
\r\n\r\nMy approach in seismology is focused on exploring fine structures near the core\u00ad mantle boundary and developing new techniques for computing synthetic seismo\u00adgrams. I discuss the method development and strategies to explore fine structures near the core-mantle boundary region in the following chapters. In chapter 5, I develop a hybrid method which can handle the seismic wave propagation in heterogeneous regions at large distances. The hybrid method is a combination of analytical and numerical methods, with numerical methods applied in heterogeneous regions only and analytical methods outside. In chapter 6, I discuss wave propagation of SKS and SPdKS phases through ultra-low velocity zones near the core-mantle boundary and constrain the general structures of ultra low velocity zones near the core-mantle boundary under Fiji subduction zone and Iceland. The long period SKS-SPdKS data are explained by ultra low velocity zones with P velocity reduction of 10% and horizontal length scales of about 250 km and height of about 40 km. S velocity reduction of 30% is consistent with the data, although the trade-offs between S velocity reduc\u00adtion and height of the structure exist. In chapter 7, I discuss wave propagation of PKP and its precursors and constrain the detailed structures of the ultra low velocity zones near the core-mantle boundary from observed broadband PKP precursors. The observed long period precursors are explained by the existence of ultra low velocity zones with P velocity reduction of at least 7% and horizontal length scales of 100-300 km and height of about 60-80 km, whereas short period precursors suggest that the structures have smooth edges and structures with smaller scale are adjacent to these large Gaussian-shaped structures. These fine structures may be indicatives of vigor\u00adous small-scale convection or the instabilities of the bottom thermal boundary layer of the mantle.
" }, { "name": "Xiaoming, Ding", "degree": "PhD", "year": "1998", "title": "High Resolution Studies of Deep Earth Structure", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08032023-144000226", "creators": [ { "name": { "family": "Xiaoming", "given": "Ding" }, "id": "Xiaoming-Ding", "display_name": "Xiaoming, Ding" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/z21r-bk54", "abstract": "Recent advances in seismic tomography has imaged major deep structure in the lower mantle. The ring of fast velocities originally derived from global long-period inver\u00adsions has been resolved into interspersed sheet-like structure which appears to be old slabs. Beneath some of the structure, there are high velocity zones (HVZ) with variable thickness approaching the core mantle boundary (CMB). Detailed broadband modeling of waveforms produced by seismic paths sampling one of these zones yields a picture of D\" zone, with one thermal negative above the layer and one positive approaching the CMB, which would seem to be quite compatible with pancaked slab debris. In contrast, modeling waveforms produced by sampling the slowest velocity regions along the CMB reveals a thin ultra low velocity zone (ULVZ). The dimensions of these zones range from a few hundred km beneath Iceland to a few thousand km beneath Africa.
\r\n\r\nSeismic data recorded on TERRAscope and Berkeley Digital Seismic Network are used to study the HVZ beneath Central America. Modeling these waveforms (P, SV and SH) constitutes a major portion of this thesis. Two modeling strategies were employed in the thesis: (1) Assume a \"Lay type\" D\" with a sharp velocity discontinuity; (2) Assume an upper transition zone approaching D\", and a lower transition zone approaching the CMB (old slabs). Our preferred model following strategy (1) (Chapter 2) has an S discontinuity 200 km above the CMB with 3% jump and a negative gradient in the D\" layer. It fits S, SKS, Scd on radial component and\r\nS and Scd phase on tangential component in the distance range of 78\u00b0 to 92\u00b0. A 2D model with decreasing thickness of D\" layer toward North is also investigated. It fits the data better at the distances beyond 90\u00b0 and produces reasonable good fit of the S and Scd phases. This suggests that the typical negative gradient in the \"Lay type\" D\" may not be necessary as in SDH. P waveform modeling, on the other hand, shows no indication of a corresponding Ped phase. The PREM model fits the P travel time and waveform well. Our preferred model following strategy (2) (Chapter 3) has a positive gradient initiated 350 km above the CMB with a sharper increase near 200 km and a strong negative radient begins at about 100 km. This model can explain both P and S waveforms.
\r\n\r\nIn Chapter 4 the ULVZ beneath Iceland and Africa are addressed. The major phases used to study the ULVZ are SKS and S_[P_(diff)]KS which travels along the CMB as P at both the core entry (S_[P_(diff)]KS) and exit (SK_[P_(diff)]S) locations. A major structure beneath Iceland (SK_[P_(diff)]S) as identified from data recorded on stations in Northern Europe appears to be shaped like a dome, 80 km high, 200 km wide with a 10% drop in P and S velocities. The data for Africa is less complete but highly anomalous. Shear wave record sections across Africa and Europe containing the cross-over from S to SKS and extended core-phases (75\u00b0 to 120\u00b0) are presented from deep South American events. These are compared against corresponding synthetics for various tomography models computed with a new 2D synthesizing technique (Appendix A). Some of the most recent models, Grand [1994], explain the observation for African data better than lD models. However, considerable fine tuning is required in D\" to explain abrupt changes in S and ScS waveforms and the extreme cases in SKS-S travel times. Essentially, Grand's anomaly needs to be increased to -4% with evidence for a strong plume (1500 km of vertical structure with -4% velocity drop) to explain the SKS travel times and waveform data. The plume is located along the eastern edges of the basal low velocity region.
\r\n\r\nBy studying the various branches of the core phases PKP, it has become quite\r\nclear that North-South paths in the inner-core appear faster than East-West paths. Moreover, the broadband seismograms associated with these paths are distinct. The reason for this difference is not known but suggests a lower (anisotropic) inner-core with an upper (isotropic) inner-core which may have variable thickness. Modeling of long period and broadband data for such structures is, also, addressed in Chapter 5 of this thesis.
" }, { "name": "Yen, Albert Shih-Yueh", "degree": "PhD", "year": "1998", "title": "Effects of the Martian environment on its surface materials: experimental studies", "advisor": "Murray, Bruce C.; Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:01282013-130210960", "creators": [ { "name": { "family": "Yen", "given": "Albert Shih-Yueh" }, "id": "Yen-Albert-Shih-Yueh", "display_name": "Yen, Albert Shih-Yueh" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/g71q-2569", "abstract": "The past and present weathering processes active at the martian surface\r\ncontrol the chemical and mineralogical nature of the soils. Determining the\r\ncurrent characteristics of martian surface materials can, therefore, provide clues\r\nabout the surface history of Mars. The research in this thesis is based on three\r\nsets of experiments. First, reflectance spectra are collected from Mars analog\r\nmineral samples in the laboratory and compared with spacecraft data. The results\r\nindicate that the water content of the martian soil is consistent with the 2% value\r\nobtained by the Viking Lander analyses, and this suggests a drier, more\r\ndehydrated soil than implied by much modeling of early Mars conditions.\r\nSecond, ultraviolet radiation-induced dehydration of minerals is investigated as a\r\npossible method to convert the postulated large initial supply of hydrated mineral\r\nphases on Mars to the current, relatively anhydrous state. These experiments\r\nindicate that water adsorbed onto the surfaces of mineral grains can be ejected by\r\nincident ultraviolet photons, but that the removal of bound water from minerals is\r\nunlikely to be a significant weathering process on Mars. Thus, the inventory of\r\nhydrous minerals at the surface today is likely representative of the quantity that\r\nformed in the past. Finally, the possibility that ultraviolet radiation can stimulate\r\nthe oxidation of materials on the martian surface is studied experimentally. The\r\ndata show that the oxidation rate of metallic iron increases upon exposure to UV\r\nphotons but that this process is unlikely to be an effective way to oxidize minerals\r\non Mars. Suggestions for future laboratory experiments and spacecraft\r\ninstruments which can further test the conclusions of this thesis are described." }, { "name": "Zachariasen, Judith Ann", "degree": "PhD", "year": "1998", "title": "Paleoseismology and Paleogeodesy of the Sumatran Subduction Zone: A Study of Vertical Deformation Using Coral Microatolls", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04112005-132058", "creators": [ { "name": { "family": "Zachariasen", "given": "Judith Ann" }, "id": "Zachariasen-Judith-Ann", "display_name": "Zachariasen, Judith Ann" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "chair", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." } ], "option_major": [ "geol" ], "doi": "10.7907/YYWJ-R395", "abstract": "Corals from Western Sumatra retain stratigraphic records of relative sea-level change that can be used to infer vertical displacement rates in the hanging wall block of the Sumatran subduction zone. The upward growth of the coral \"microatolls\" is limited by low water levels, and fluctuations in water level produce measurable changes in the coral morphology. Furthermore, the corals contain annual growth rings, which act as an internal chronometer of coral growth history. The microatolls, which are widespread and can live for decades or centuries, can serve as natural long-term tide gauges, recording sea-level variations over wide intervals of space and time.
\r\n\r\nRelative sea-level records from living corals from the outer-arc islands and mainland coast constrain the nature of recent vertical deformation over the subduction zone. Emerged fossil corals from the islands, dated with U-Th geochronometry, constrain the paleoseismic and paleogeodetic history of the region.
\r\n\r\nStratigraphic analysis of cross-sectional slabs cut from living coral heads reveals that the islands have been submerging at rates of 4-10 mm/yr over the last four or five decades, while the mainland has remained relatively stable. Many fossil corals died in the early 1800's. Their age and morphological signature indicate they died as a result of coseismic uplift of more than lm during the last great subduction-zone earthquake in this region, in 1833, following decades of interseismic submergence at rates similar to modern rates.
\r\n\r\nOther sampled corals died at earlier times throughout the late to mid-Holocene. Their presence in the intertidal zone suggests that little permanent vertical deformation has occurred here over the past several thousand years, and, therefore, most of the accumulated interseismic strain is recovered during earthquakes. The temporal distribution of coral deaths suggests an average earthquake recurrence interval for subduction zone events of about 230 years. Combining sea-level histories from modern, 1833, and older corals yields partial records of co- and interseismic vertical displacement for multiple earthquake cycles. Such displacement records from the hanging wall of a major plate boundary can help constrain models of subduction-zone deformation.
" }, { "name": "Zajac, Blair J.", "degree": "PhD", "year": "1998", "title": "The State of Stress as Inferred from Deviated Boreholes: Constraints on the Tectonics of Offshore Central California and Cook Inlet, Alaska", "advisor": "Stock, Joann M.; Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06072010-160325894", "creators": [ { "name": { "family": "Zajac", "given": "Blair J." }, "id": "Zajac-Blair-J", "display_name": "Zajac, Blair J." } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geophys" ], "doi": "10.7907/S3V0-3M43", "abstract": "This thesis introduces a new method of constraining the vector directions of the three principal stresses and their relative magnitudes, by using borehole breakouts in non-vertical drill holes. Unlike older stress state measurements from breakouts, this work does not presume that one of the principal stresses is Vertical. This method has important uses in complicated three-dimensional structures, such as in the Los Angeles basin, and in oil drilling applications.
\r\n\r\nChapter 1 discusses why knowledge of the three-dimensional stress tensor is relevant to today's science and examines the applications of the stress state determination technique discussed herein. The history of previous work is also described.
\r\n\r\nIn Chapter 2 I discuss the techniques of determining the stress tensor from borehole breakouts, examining the physics of borehole breakouts, the theory of the inversion technique used, and data processing issues. The theory and data processing issues are not discussed separately in this work, since data processing issues often prompted new theoretical techniques. I first examine the physics of borehole breakouts and how the orientation of breakouts on the borehole wall relates to the local stress field. A new borehole breakout selection scheme which takes into account highly non-vertical boreholes is then presented along with a discussion of the real world problems of data gathering, identification, and processing. Having selected a borehole breakout data set using the criteria, I invert for the best fitting stress state using a new technique combining genetic algorithms and non- differential function optimizers. Finally, I present a way in which 95% confidence limits can be placed on the resulting stress tensor.
\r\n\r\nWith all of the technical and theoretical pieces in place, I now examine several different data sets. Chapter 3 examines a borehole breakout data set publish by Qian and Pedersen [1991] from the Siljan Deep Drilling Project in Sweden and demonstrates that even for simple borehole breakout data sets, the stress state inversions assuming a vertical principal stress direction may fall outside of the 95% confidence limits of an inversion allowing non-vertical principal stress directions. My technique of displaying the borehole breakout data makes the data quality more obvious as compared to the way Qian and Pedersen [1991] plotted the data.
\r\n\r\nChapter 4 examines a borehole breakout data set from the offshore Santa Maria Basin, California. This analysis presents vertical borehole breakout data that represent a maximum horizontal principal stress direction of N7\u00b0E, roughly consistent with other earthquake focal mechanism, GPS, and borehole breakout studies in the area. However, the stress state inversion of breakouts identified in the vertical and a limited number of nearly horizontal boreholes suggests a stress state very different from any other stress state results. This could imply that the three dimensional stress in the Santa Maria Basin is very complicated. However, given the limited amount of borehole breakouts identified in nearly horizontal wells, the stress state results from this data set are inconclusive.
\r\n\r\nChapter 5 examines the largest data set used in this study, from a series of oil wells in Cook Inlet, Alaska. These are borehole caliper arm data from 21 different wells reaching a maximum deviation of 54\u00b0 and 3,223 m true vertical depth. Stress state inversions of 31 different subsets of the borehole breakout data were performed. Inversion of breakouts identified in the top two of three marker beds analyzed in wells drilled from the Baker platform identified nearly degenerate thrust faulting stress states with the maximum principal stress axis, S_1, oriented horizontally WNWESE, perpendicular to the NNE-trending anticlinal structures. The stress state from the deepest marker is also a nearly degenerate thrust faulting stress state with S_1 oriented NNW\u2014SSE, aligned with the regional direction of relative plate motion between the North American and Pacific plates. In between the shallow and deep stress state is an apparent normal faulting stress state with S_2 oriented subhorizontally ENE\u2014WSW. This clockwise rotation of the stress tensor as a function of depth suggests that the stress field changes with depth, from a shallow stress state responsible for the local NNE-trending structures to a deeper one from the North American and Pacific plates' collision zone. The observed normal faulting stress state between the two thrust faulting stress states is anomalous and may represent some sort of transition from the shallow to the deep stress state. Stress state profiles in 500 m true vertical depth (TVD) intervals show consistently oriented thrust faulting stress regimes with NNW\u2014SSE trending S_1 azimuths. The thrust faulting S_3 principal stress direction is consistently within 30\u00b0 of vertical, suggesting that while the assumption of a purely vertical principal stress direction is not valid, the stress tensor does not significantly rotate away from the surface conditions that require a purely vertical stress tensor. The nearly degenerate thrust faulting stress states determined from the Granite Point and the 10.8 km distant Baker platform breakouts are nearly identical, implying that the technique of using deviated borehole breakouts to invert for the regional stress is valid. The orientations of the maximum horizontal stress determined from the Cook Inlet borehole breakouts are consistent with other stress indicators in south-central Alaska and consistent with the direction of relative plate motion between the North American Plate and the Pacific plate. The S_1 axis for the Cook Inlet field trends due south plunging 3\u00b0. The 95% confidence limits allow the S_1 azimuth to vary from N156\u00b0E to N195\u00b0E and the plunge to vary from 10\u00b0 to -4\u00b0. This stress state does not appear representative of the stress field for each subset of breakouts. The Granite Point S1 axis trends N19\u00b0W plunging 3\u00b0; the 95% confidence limits allow the azimuth to vary from N42\u00b0W to N7\u00b0E and the plunge to vary from 1\u00b0 to 6\u00b0. The Baker platform S_1 axis trends N170\u00b0E plunging 8\u00b0; the 95% confidence limits on S_1 allow its azimuth to vary from N139\u00b0E to N191\u00b0E and its plunge to vary from 1\u00b0 to 15\u00b0. Finally, the Dillon platform S_1 axis trends N69\u00b0W plunging 2\u00b0; the 95% confidence limits constrain the S_1 azimuth from N268\u00b0E to N324\u00b0E and the plunge from 8\u00b0 to -4\u00b0. The more westerly orientation of S_1 at the Dillon platform may be related to the local NNE-trending anticlinal structures in the Cook Inlet Basin.
\r\n\r\nChapter 6 concludes and summarized the results and conclusions from the thesis.
\r\n\r\nThe first appendix contains in minute detail some of the mathematics describing the boreholes, breakouts, and coordinate system rotations used to perform this work. The second appendix contains the individual discussion and plots of the raw dipmeter data from all of the Cook Inlet, Alaska wells.
" }, { "name": "Zhu, Lupei", "degree": "PhD", "year": "1998", "title": "Broadband waveform modeling and its application to the lithospheric structure of the Tibetan plateau", "advisor": "Helmberger, Donald V.; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12072006-152420", "creators": [ { "name": { "family": "Zhu", "given": "Lupei" }, "id": "Zhu-Lupei", "display_name": "Zhu, Lupei" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Anderson", "given": "Don L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Don L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/EWXK-PQ59", "abstract": "This thesis presents a study of the lithospheric structure of the Tibetan Plateau. The data are broadband seismic waveforms recorded during the 1991-1992 Sino-US Tibet PASSCAL experiment. Several techniques are developed to retrieve the structural information from these waveforms at ranges from near-field to teleseismic distances.\r\n\r\nFirst, a 1-D average crustal velocity model is derived from regional earthquakes, based on travel times of various phases and modeling waveforms of Love waves. The source mechanisms and depths of 62 events in Tibet and surrounding areas are determined using this 1-D model. The result is that most earthquakes occur at shallow depths, between 5 and 15 km. Thrust faulting source mechanisms are dominant on the margins of the plateau. Within the plateau but at locations with surface elevation less than 5 km, source mechanisms are a mixture of strike-slip and thrust. In areas with surface elevation higher than 5 km, all events show consistently normal faulting, which indicates that a large portion of the high plateau is under EW extension. I also found three sub-crustal earthquakes at depth range between 70 and 80 km in southern Tibet. Their existence suggests relatively cold uppermost mantle in the region.\r\n\r\nThe lateral variations are investigated using teleseismic waveforms. Crustal thickness and Vp/Vs ratio at each station are estimated using receiver function analysis. I found crustal Vp/Vs ratios to range from 1.75 to 2.0 and crustal thicknesses from 55 to 80 km. On average the northern Tibetan crust is 20 km thinner and has a higher Vp/Vs ratio than the southern part. Teleseismic P and S arrival delays exhibit strong azimuthal and lateral variation. The uniform surface elevation of Tibet coupled with large variations of crustal thickness and upper mantle velocity suggest that the north-central plateau is supported partly by a hot upper mantle. A low velocity layer is found in the mid-crust of northern Tibet. Modeling the anomalous \"double-pulse\" P waveform at the northernmost station reveals a 15 to 20 km Moho offset between the plateau and the Qaidam Basin." }, { "name": "Asimow, Paul David", "degree": "PhD", "year": "1997", "title": "A Thermodynamic Model of Adiabatic Melting of the Mantle", "advisor": "Stolper, Edward M.; Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11202003-144820", "creators": [ { "name": { "family": "Asimow", "given": "Paul David" }, "id": "Asimow-Paul-David", "orcid": "0000-0001-6025-8925", "display_name": "Asimow, Paul David" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Gurnis", "given": "Michael C." }, "id": "Gurnis-M-C", "orcid": "0000-0003-1704-597X", "role": "member", "display_name": "Gurnis, Michael C." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geol" ], "doi": "10.7907/93RY-AN70", "abstract": "Mid-ocean ridge basalts (MORB) are mixtures of melts produced over a range of pressure and temperature in a nearly adiabatic open system undergoing changes in composition as melting proceeds. Interpretation of the compositional variations observed in MORB and their correlation with geophysical aspects of the ridge therefore requires complex forward models to connect experimental observations of isothermal, isobaric batch melting of peridotite to natural compositions. Previous attempts to construct such models have relied on parameterizations of melt composition or partition coefficients and extent of melting in pressure-temperature space from experimental batch melting data. This thesis undertakes the examination of an alternative approach using thermodynamic models of silicate minerals and melts to predict equilibria under quite arbitrary constraints, including variable bulk composition and constant entropy. The liquids predicted from the thermodynamic models along polybaric paths can then be integrated to produce comprehensive forward models of MORB genesis.
\r\n \r\nChapter 1 introduces the nature of the MORB modeling problem and the motivation of the thermodynamic approach in greater detail. Chapter 2 illustrates the thermodynamic approach by demonstrating that the effect of the garnet-spinel and spinelplagioclase peridotite transitions, which retard or reverse isentropic melting, can be easily understood. Chapter 3 looks at the variables affecting isentropic melt productivity (i.e., the increment of additional melting per decrement of pressure at constant entropy). I find that this quantity is likely to increase during progressive melting, punctuated by drops where phases are exhausted from the residuum. Chapter 4 extends this approach to issues of melt transport in one dimension and steady state; I evaluate the magnitude of entropy production due to gravitational dissipation and thermal interactions with migrating fractional melts and examine the effect of focused melt flow. Finally, chapter 5 deals with the compositions and mean properties of MORB obtained by integrating the compositions and melt fractions predicted by our models. We compare our results to published models of MORB compositions and consider the implications. The algorithms and source code, including subsolidus capability, added to the MELTS package of Ghiorso and Sack for these calculations are included as appendices.
" }, { "name": "Haldemann, Albert Frank Christian", "degree": "PhD", "year": "1997", "title": "Interpreting Radar Scattering: Circular-Polarization Perspectives from Three Terrestrial Planets", "advisor": "Muhleman, Duane Owen; Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04222010-100328955", "creators": [ { "name": { "family": "Haldemann", "given": "Albert Frank Christian" }, "id": "Haldemann-Albert-Frank-Christian", "display_name": "Haldemann, Albert Frank Christian" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" } ], "option_major": [ "plansci" ], "doi": "10.7907/YQ6F-ZS42", "abstract": "Planetary radar astronomy has used circular polarization radar signals to probe the surfaces of many solar system targets. However the trend for terrestrial observations has been toward greater use of linearly polarized imaging radars. Fortunately the latest generation of imaging radars has been developed with a multi-polarization capability. This should allow a synergy of the two research communities to occur.
\r\n\r\nOne of the unresolved debates on planetary radar astronomy is the nature of the scattering processes from cold planetary ices. This question recently received input from a terrestrial source: Greenland (Rignot et al. 1993). In this thesis a survey is made of high altitude sites to discover if the Greenland percolation zone scattering behavior is wide-spread on the Earth. The survey was carried out with the enormous, publicly available dataset from the 1994 missions of Shuttle Imaging Radar payload. This instrument (SIR-C) obtained full-polarization information with its linear-polarization system. These data allow reconstruction of circular polarizations for comparison to planetary results. The search proved fruitful. Hundreds of square kilometers in western Tibet's Kunlun Shan, and in the Central Andes at the latitude of Santiago display radar scattering behavior quite similar to that in Greenland where internal reflections of the radar waves within icy inclusions in the firn enhance scattering in the same sense of circular polarization.
\r\n\r\nA separate unresolved issue in the planetary radar astronomy is the question of the nature of the highlands of Venus that exhibit high radar reflectivity and low emissivity. These so-called anomalous radar behavior in these regions have alternately been ascribed to high-dielectric doping or low dielectric volume scatterinig. We present new dual circular-polarization radar maps of the western hemisphere of Venus. The results are from a 1993 experiment to image Venus with 3.5 cm radar. Maps of Venusian radar albedo were made for each of two days of observation in both OS (echo principally due to specular reflection) and SS (diffuse echo) channels. On both days, the sub-earth longitude was near 300E. The SS maps are dominated by a significant component of diffuse backscatter from the 285E longitude highlands: Beta, Phoebe, and Themis Regiones. Beta Regio includes previously observed radar-anomalous regions. The nature of these altitude-related electrical properties on Venus is one of the outstanding surface process questions that remain after the Magellan mission. Our experiment provides the first full-disk polarization ratio (\u00b5_c) maps. The data show that different geology determines different radar scattering properties within Beta. Diffuse scattering is very important in Beta, and may be due to either surface or volume scattering. We find a strong correlation of the SS albedo \u03c3_(SS) with altitude R_p (km) in Beta, \u03c3_(SS) \u221d0.3R_p. Also, \u03c3_(OS) \u221d0.7 R_p. The onset of this relationship is at the R_p~6054 km planetary radius contour. The nature and morphology of the highland radar anomalies in Beta is consistent with a diffuse scattering mechanism. In Beta Regio we find \u00b5_c > 0.5 in general, with \u00b5_c as high as 0.8 between Rhea and Theia Montes, to the west of Devana Chasma. These values are compatible with measurements of blocky terrestrial lava flows if surface scattering dominates. If volume scattering is important, the high RCP cross-sections may indicate an important decrease in embedded scatterer size with altitude, which could be related to enhanced weathering.
\r\n\r\nFinally, the techniques of planetary radar astronomy were used in an applied sense. Results are presented of 3.5-cm delay-Doppler and Doppler-only (continuous wave or CW) radar experiments to assess three potential Mars Pathfinder landing sites: Ares Vallis, Tritonis Lacus, and northwest (NW) Isidis. The regional relief at all of the landing sites is appropriate for a Pathfinder landing sequence: east-west slopes do not exceed 3\u00b0 at any of the sites. We find that Ares Vallis has a Hagfors rms slope of \u03b8_(rms)=4.8\u00b0\u00b11.1\u00b0 as measured by delay-Doppler radar, and \u03b8_(rms)=6.4\u00b0\u00b10.6\u00b0 measured by CW radar. These values are similar to, or less than the previous measurements of the Viking Lander 1 region (\u03b8_(rms)=6\u00b0, Tyler et al. 1976, Harmon 1997). The Tritonis Lacus landing site is rougher with delay- Doppler, \u03b8_(rms)=5.6\u00b0\u00b10.6\u00b0, while the NW Isidis landing site is very smooth, both in a regional sense (slopes < 0.7\u00b0) and in a Hagfors rms slope sense: \u03b8_(rms)=1.8\u00b0\u00b10.2\u00b0. Reflectivities at all of the sites should be sufficient to allow the radar altimeter on Pathfinder to function properly.
\r\n" }, { "name": "Holk, Gregory James", "degree": "PhD", "year": "1997", "title": "The Role of Water in the Magmatic and Tectonic Evolution of Metamorphic Core Complexes: A stable Isotope Study of the Southern Omineca Crystalline Belt, British Columbia, Canada", "advisor": "Taylor, Hugh P., Jr.; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10252022-202940570", "creators": [ { "name": { "family": "Holk", "given": "Gregory James" }, "id": "Holk-Gregory-James", "display_name": "Holk, Gregory James" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P., Jr." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P., Jr." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "co-advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Taylor", "given": "Hugh P., Jr." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P., Jr." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." } ], "option_major": [ "geol" ], "doi": "10.7907/pkn3-p364", "abstract": "The oxygen isotope data in this study delineate 2 major episodes of water-rock interaction related to the metamorphic, plutonic, and tectonic development of the metamorphic core complexes in the southern Omineca belt. Episode 1 is a Paleocene pre\u00ad-extensional metamorphic/magmatic-hydrothermal event. The occurrence of isotopically uniform quartz (\u03b4\u00b9\u2078O = 12.5 \u00b1 0.5\u2030) and feldspar (10.9 \u00b1 0.7\u2030) throughout different rock types indicates that much of a 6-km-thick section of the mid-crustal Selkirk allochthon underwent internally buffered \u00b9\u2078O/\u00b9\u2076O homogenization during Paleocene melting and decompression as it moved up the Monashee decollement thrust ramp. Areas of uniform \u03b4\u00b9\u2078O are those with the most leucogranite or those subjected to severe anatexis. Only locally, in the most impermeable (or refractory) zones did 180 exchange among the rocks, leucogranite melts, and aqueous fluids fail to go to completion (i.e., in the deepest parts of the section, in a marble-rich zone, around some thick amphibolites, and in most garnets). Evidence for \u00b9\u2078O/\u00b9\u2076O heterogeneity in the protoliths of these rocks is observed in stratigraphically correlative lower-grade units elsewhere in British Columbia, as well as in garnets that coexist with isotopically homogeneous quartz. A model is introduced utilizing water as a petrologic catalyst: fluids evolved during muscovite breakdown and partial melting of pelites produce \u00b9\u2078O/\u00b9\u2076O homogenization with only minor influx of external H\u2082O; this is followed by release of magmatic H\u2082O from these melts as they crystallize (triggering further melting of adjacent feldspathic assemblages) during and after the ~20 km uplift that occurred in the thrusting event that took place just prior to detachment faulting.
\r\n \r\nEpisode 2 is a series of Eocene synextensional meteoric-hydrothermal events affecting the shallow crust along all of the major detachment faults in the region, and along some parts of the Monashee decollement; these effects were locally enhanced by added heat from some synextensional alkaline intrusions (the Coryell plutons). Very large quartz-feldspar \u00b9\u2078O/\u00b9\u2076O disequilibrium effects were imprinted upon the rocks during exchange with hot meteoric waters (initial \u03b4\u00b9\u2078O ~ -15); the mineral most affected was feldspar (\u03b4\u00b9\u2078O down to -5.0). In the Valhalla core complex, the hanging wall rocks above the Slocan Lake fault are sufficiently uniform to allow us to apply open-system kinetic oxygen isotope exchange modeling, thereby placing constraints on the duration (1-3 Ma) and integrated fluid flux (\u2265 10\u2077 cm\u00b3H\u2082O/cm\u2082rock) for this hydrothermal metamorphism.
" }, { "name": "Holt, John William", "degree": "PhD", "year": "1997", "title": "I. Detailed Records of Geomagnetic Field Behavior from Death Valley and Hawaii. II. An Age Constraint on Gulf of California Rifting from Santa Rosal\u00eda, Baja California", "advisor": "Kirschvink, Joseph L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09072023-170005385", "creators": [ { "name": { "family": "Holt", "given": "John William" }, "id": "Holt-John-William", "display_name": "Holt, John William" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." } ], "committee": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "chair", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." } ], "option_major": [ "geol" ], "doi": "10.7907/y9sj-ca84", "abstract": "Detailed records of geomagnetic field behavior were produced and analyzed from Plio/Pleistocene sedimentary rocks of Death Valley, California and from Pleistocene/Holocene volcanic rocks of Hawaii. These records provide new information about geomagnetic field polarity reversals, excursions, secular varia\u00adtion, and the paleomagnetic recording process in sediments. In addition, a magnetostratigraphic and geochronlogic study of Mio/Pliocene marine sedimen\u00adtary rocks in Baja California, Mexico was performed in order to provide a new age constraint on Gulf of California rifting.
\r\n\r\nThe paleomagnetic studies in Death Valley were undertaken on siltstones, sand\u00ad stones, and evaporites exposed along the southern Death Valley fault zone in the Confidence Hills. These rocks contain multiple records of the R\u00e9union and Olduvai normal-polarity subchrons (2.15 - 2.13 Ma and 1.95 - 1.79 Ma, respec\u00adtively) within rocks formed as a result of deposition in different subenvironments of a saline ephemeral lake, with an average deposition rate of ~ 30 cm/kyr. Variations in bedding attitudes between the exposed sections allow a fold test of paleomagnetic directions. Two records of the upper Olduvai polarity reversal were obtained which agree despite differences of lithology, depositional environ\u00adment, and structural tilting. These records indicate several phases of polarity shifts during the transition of the geomagnetic field from normal to reversed polarity. Transitional virtual geomagnetic poles (VGP's) lie in longitudinal bands ~ 90\u00b0 away from the sampling site longitude, vastly different from VGP's pro\u00adduced by studies in other locations around the world but consistent with site\u00ad dependent trends of VGP paths observed in global data compilations. Studies of the anisotropy of anhysteritic remanence conclude that inclination shallowing in sediments during periods of low ambient magnetic field intensity is a possible cause for this site dependence of VGP paths. However, some aspect of the transitional geomagnetic field is recorded by the sedimentary rocks of Death Valley whether or not inclination shallowing took place.
\r\n\r\nA detailed record of the R\u00e9union normal-polarity subchron was obtained from one of the sections in the Confidence Hills. This record shows that the R\u00e9union subchron was a single normal-polarity event of ~ 20 kyr duration, which is a significant finding due to the lack of previous data in this time interval. The pres\u00adence of a lithofacies which contains disruptive anhydrite crystals dispersed throughout the matrix creates two small gaps in the record just prior to the nor\u00admal-polarity R\u00e9union interval. Remagnetizations within this lithofacies facilitate the interpretation of the depositional environment responsible for growth of the disruptive evaporites.
\r\n\r\nSamples of the 1 km core produced by the Hawaii Scientific Drilling Project (HSDP) provided the basis for a study of geomagnetic field excursions and secular variation during the past 400 kyr at Hawaii. This core consists of over 200 lava flows erupted from Mauna Loa and Mauna Kea volcanoes. In contrast to previous hypotheses that the non-dipole field has been anomalously low in the central Pacific region for the past few hundred kyrs, the results of this study show that secular variation, and hence, the non-dipole field component, at Hawaii is consistent with secular variation elsewhere on the globe for the past 400 kyr. In addition, the data show evidence for a persistent axial quadrupole in the time\u00ad averaged field. This research also resulted in the first records of geomagnetic field excursions in the central Pacific which may be correlated with those found elsewhere on the globe, lending support to the hypothesis that these are global events rather than local perturbations of the geomagnetic field.
\r\n\r\nPaleomagnetic and geochronologic studies of marine sedimentary rocks in the Santa Rosal\u00eda basin, Baja California Sur, show that despite the presence of local copper ore deposition, primary magnetic remanence directions may be obtained from most of the marine sandstones overlying the basement in that area. Using preliminary magnetostratigraphy and an \u2074\u2070Ar/\u00b3\u2079Ar isotopic age of 6.76 \u00b1 0.45 Ma (1\u03c3) obtained for a volcanic unit interbedded with the sandstones, a correla\u00adtion with the geomagnetic polarity time scale was made possible, yielding an age of 7.1 \u00b1 0.05 Ma for the base of the marine section. This provides a new age constraint on Gulf of California rifting and may help to refine models of North America - Pacific plate boundary interactions during the period 12 - 3.5 Ma.
" }, { "name": "Hsieh, Jean Chia Chin", "degree": "PhD", "year": "1997", "title": "An Oxygen Isotopic Study of Soil Water and Pedogenic Clays in Hawaii", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:05192023-221323734", "creators": [ { "name": { "family": "Hsieh", "given": "Jean Chia Chin" }, "id": "Hsieh-Jean-Chia-Chin", "display_name": "Hsieh, Jean Chia Chin" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/xcze-bj98", "abstract": "Soils result from complex interactions amongst the biosphere, atmosphere, hydrosphere, and lithosphere. In this project oxygen isotopes were used to trace the movement of water in soils and to determine the conditions of mineral formation during pedogenesis. Incoming rainwater and soil-water \u03b4\u00b9\u2078O values were monitored for two seasonal cycles in a series of soils along an arid-to-humid transect in Hawaii. The \u03b4\u00b9\u2078O values of halloysite separated from the soil profiles was related to depth profiles of soil\u00ad water \u03b4\u00b9\u2078O values. This is the first oxygen isotopic investigation of soil water and pedogenic clays from the same soil profiles.
\r\n\r\nA direct CO\u2082 equilibration method was developed to measure the \u03b4\u00b9\u2078O value of soil water. This method also has the advantage of requiring only one step compared with two steps for existing methods. Reproducibility of measurements using this method is as good as existing methods. Tests designed to investigate factors controlling equilibration determined that biological respiration, water content, and soil type were important. Samples should be irradiated to eliminate CO\u2082-respiring organisms. These results imply that water in soils can be partitioned into compartments such as bulk liquid water and adsorbed water and that these compartments may have unique isotopic compositions.
\r\n\r\nApplication of this method to the soils in Hawaii showed that seasonal wetting and drying cycles affected the \u03b4\u00b9\u2078O value of soil water. During the dry season, the soil-water \u03b4\u00b9\u2078O values decrease with depth in the soil profile due to evaporation of water from the surface. During the rainy season, they increase with depth as water infiltrates through the surface from storms. The \u03b4\u00b9\u2078O values of rainwater and soil-water generally increased as annual rainfall increased. Rainwater \u03b4\u00b9\u2078O values were 5%o more negative soil-water \u03b4\u00b9\u2078O values at low rainfall sites and about 2\u2030 to 3\u2030 more negative at high rainfall sites. These trends are consistent with the current understanding of parameters that influence these \u03b4\u00b9\u2078O values.
\r\n\r\nThe chemical treatments used to separate halloysite from bulk soil material did not alter the \u03b4\u00b9\u2078O values. Halloysite \u03b4\u00b9\u2078O values at low rainfall sites ranged between +20.4\u2030 to +23.6\u2030 and the two values at a high rainfall site ranged from +18.0\u2030 to +18.7\u2030. The data suggest halloysite formation in isotopic equilibrium with its environment and imply that it forms in a restricted range of conditions. A straightforward comparison of these data to soil-water \u03b4\u00b9\u2078O values suggests that halloysite formed between 50\u00b0C and 60\u00b0C, obviously an unrealistic circumstance. It is possible that independently calibrated mineral-water fractionation factors for low-temperature systems are incorrect or that climatic conditions in Hawaii are poorly constrained.
" }, { "name": "Jiang, Yibo", "degree": "PhD", "year": "1997", "title": "Decadal evolution of atmospheric ozone and remote sensing of tropospheric ozone", "advisor": "Yung, Yuk L.; Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242013-141747377", "creators": [ { "name": { "family": "Jiang", "given": "Yibo" }, "id": "Jiang-Yibo", "orcid": "0000-0001-6711-7260", "display_name": "Jiang, Yibo" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/40ec-pk63", "abstract": "Monitoring and preservation of the Earth's ozone layer has engaged scientists intensively\r\nin the 20th century especially after the discovery of the Antarctic ozone hole by\r\nFarman et al. (1985). There is increasing evidence that ozone depletion occurs on a\r\nglobal scale such as in the Arctic and at midlatitudes. Following the understanding\r\nof the the catalytic destruction of ozone in the stratosphere by chlorine derived from\r\nchlorofluorocarbons (CFC's), there is a growing realization that the consequences of\r\nanthropogenic pollution can be felt in unpredictable ways in near and faraway places.
\r\n\r\nThe atmosphere is a complex mixture of more than a thousand trace chemicals\r\nthat are constantly reacting and redistributing. The need to understand the sources\r\nand distribution of these chemicals, along with the mechanisms by which they are\r\ntransformed, transported, and ultimately removed from the atmosphere, has grown in\r\nparallel with the increased concern about air pollution and its consequences. Therefore,\r\nthe exploration of the mechanism controlling both spatial and temporal variation of\r\nthe atmosphere is a key component of the atmosphere science research (as part\r\nof the global change) and it requires an interdisciplinary approach and innovative\r\napplication of the traditional techniques of chemistry, physics, and meteorology.
\r\n\r\nMonitoring the composition of the troposphere and stratosphere globally is particularly\r\ninteresting in this context for ozone which is the key component regulating\r\nthe photochemistry of the atmosphere.
\r\n\r\nIn chapter 1, the decadal evolution of the Antarctic ozone hole is studied by using\r\nozone column amounts obtained by the total ozone mapping spectrometer (TOMS) in\r\nthe southern polar region during late austral winter and spring (Days 240 - 300) for\r\n1980 - 1991 using area-mapping techniques and area-weighted vortex averages. The\r\nvortex here is defined using the -50 PVU (1 PVU = 1.0 x 10^(-6)K kg^(-1) m^2 s^(-1)) contour\r\non the 500 K isentropic surface. The principal result is that there is a distinct change\r\nafter 1985 in the vortex averaged column ozone depletion rate during September and\r\nOctober, the period of maximum ozone loss. The mean ozone depletion rate in the\r\nvortex between Day 240 and the day of minimum vortex-averaged ozone is about 1\r\nDU/day at the beginning of the decade, increasing to about 1.8 DU /day by 1985,\r\nand then apparently saturating thereafter. The vortex-average column ozone during\r\nSeptember and October has declined at the rate of 11.3 DU / yr (3.8%) from 1980\r\nto 1987 (90 DU over 8 yrs), and at a smaller rate of 2 DU / yr (0.9%) from 1987 to\r\n1991 (10 DU over 5 years, excluding the anomalous year 1988). We interpret the\r\nyear-to-year trend in the ozone depletion rate during the earlier part of the decade\r\nas due to the rise of anthropogenic chlorine in the atmosphere. The slower trend at\r\nthe end of the decade indicates saturation of ozone depletion in the vortex interior, in\r\nthat chlorine amounts in the mid-80s were already sufficiently high to deplete most of\r\nthe ozone in air within the isolated regions of the lower stratospheric polar vortex. In\r\nsubsequent years, increases in stratospheric chlorine may have enhanced wintertime\r\nchemical loss of ozone in the south polar vortex even before major losses during the\r\nAntarctic spring.
\r\n\r\nIn chapter 2, we will show that standard deviation of column ozone from the zonal\r\nmean (COSDZ) provides a measure of the longitudinal inhomogeneity in column ozone\r\nand dynamical wave activities in the atmosphere. We point out that simulation of this\r\nquantity by three-dimensional (3-D) models could provide a sensitive check on the\r\nwave activities in the stratosphere that are responsible for ozone transport. Analysis\r\nof the Total Ozone Mapping Spectrometer (TOMS) data shows a profound secular\r\nchange in COSDZ from 1979 to 1992. The changes are not symmetric between the\r\nsouthern and northern atmospheres. In the southern higher latitudes, COSDZ shows\r\na significant increase around 65\u00b0 in August and September, while the changes are\r\nmuch smaller in the northern higher latitudes in the boreal spring. We interpret most\r\nof the observed changes to be caused by enhanced ozone losses in the polar vortices in\r\nthe springtime of the two respective hemispheres. There is also evidence for secular\r\ndynamical changes at mid-latitudes.
\r\n\r\nIn chapter 3, an estimate of tropospheric ozone levels over tropical pacific south\r\nAmerica is obtained from the difference in the TOMS (Total Ozone Mapping Spectrometer)\r\ndata between the high Andes and the Pacific Ocean. From 1979 to 1992\r\ntropospheric ozone apparently increased by 1.47 \u00b1 0.40 %/yr or 0.21 \u00b1 0.06 DU / yr\r\nover South America and the surrounding oceans. An increase in biomass burning in\r\nthe Southern Hemisphere can account for this trend in tropospheric ozone levels.
\r\n\r\nDue to larger multiple scattering effects in the troposphere compared to that in\r\nthe stratosphere, the optical path of tropospheric ozone is markedly enhanced (as\r\ncompared with that of stratospheric ozone) in the Huggins bands from 310 nm to\r\n345 nm. By using this principle, we model the direct and diffuse solar fluxes on the\r\nground shows differences between tropospheric and stratospheric ozone in chapter 4.\r\nThe characteristic signature of tropospheric ozone enables us to distinguish a change\r\nin tropospheric ozone from that of stratospheric ozone. A simple retrieval algorithm\r\nis used to recover the tropospheric column ozone from simulated data.
\r\n\r\nLight reflected or transmitted by a planetary atmosphere contains information\r\nabout the particles and molecules in the atmosphere. Therefore, accurately calculating\r\nthe radiation field is necessary. In the appendix, the doubling-adding method for\r\nplane-parallel polarized radiative transfer model is studied in detail. A special Fourier\r\nexpansion leading to a compact notation is developed for the azimuth-dependent\r\nquantities. The multi-layer model for a vertically inhomogeneous atmosphere is implemented and several numerical results are presented for verification and comparison.\r\nPreliminary runs from this model in the Huggins bands show the distinct features of\r\nlinear polarization in the reflection spectrum due to the multiple Rayleigh scattering\r\nin the troposphere.
\r\n\r\n" }, { "name": "Kursinski, Emil Robert", "degree": "PhD", "year": "1997", "title": "The GPS Radio Occultation Concept: Theoretical Performance and Initial Results", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:01282013-095417825", "creators": [ { "name": { "family": "Kursinski", "given": "Emil Robert" }, "id": "Kursinski-Emil-Robert", "display_name": "Kursinski, Emil Robert" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "chair", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." } ], "option_major": [ "plansci" ], "doi": "10.7907/HPMZ-6524", "abstract": "Implementation of the Global Positioning System (GPS) network of satellites and\r\nsmall, high performance instrumentation to receive GPS signals have created an\r\nopportunity for low cost, active remote sounding of Earth's atmosphere by radio\r\noccultation. The first goal of the present research is to estimate the spatial coverage,\r\nresolution and accuracy expected for atmospheric profiles derived from GPS occultations.\r\nTypically, vertical resolution ranges from 0.5 km in the lower troposphere to 1.4 km in the\r\nmiddle atmosphere. Useful profiles of refractivity should be derivable from ~60 km\r\naltitude to the surface with the exception of regions less than 250 m in vertical extent\r\nassociated with high vertical humidity gradients. Above the 250 K altitude level in the\r\ntroposphere, where the effects of water are negligible, sub-Kelvin temperature accuracy is\r\npredicted up to ~40 km depending on the phase of the solar cycle. Predicted accuracy of\r\ngeopotential heights of constant pressure levels is ~10 m or better between 10 and 20 km\r\naltitudes. Deep in the warm troposphere the contribution of water to refractivity becomes\r\nsufficiently large for the accurate retrieval of water vapor given independent temperatures\r\nfrom weather analyses. We discuss several applications of the unique qualities of the\r\ntechnique including numerical weather prediction and long term monitoring of Earth's\r\nclimate.
\r\n\r\nThe second goal is to demonstrate some features using data from the prototype\r\nGPS-MET occultation investigation. We demonstrate ~1 km vertical resolution and\r\ntemperature consistency with global weather analyses generally at the 0.5 to 1 K level.\r\nWe discuss some initial observations of equatorial waves in the lower stratosphere and\r\npossible implications for exchange between the troposphere and stratosphere. During the\r\nJune-July 1995 period, occultations typically extend to within 1 to 3 km of the surface and\r\nare used to derive a brief climatology of water vapor in latitude versus height, the first\r\ntruly global view of water vapor at ~1 km vertical resolution. A low latitude bias structure\r\nin the weather analyses is revealed centered near 2 km altitude where analysis humidities\r\nare larger than those derived from the occultations in the subtropics but smaller in the\r\ntropics apparently associated with a systematic error in the boundary layer height in the\r\nanalyses.
" }, { "name": "Nagy, Elizabeth Ann", "degree": "PhD", "year": "1997", "title": "Extensional Deformation and Volcanism Within the Northern Puertecitos Volcanic Province, Sierra Santa Isabel, Baja California, Mexico", "advisor": "Stock, Joann M.; Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01132010-093747416", "creators": [ { "name": { "family": "Nagy", "given": "Elizabeth Ann" }, "id": "Nagy-Elizabeth-Ann", "display_name": "Nagy, Elizabeth Ann" } ], "advisors": [ { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "advisor", "display_name": "Stock, Joann M." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "co-advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "geol" ], "doi": "10.7907/znpy-3311", "abstract": "Geologic features at the western edge of the Gulf Extensional Province (GEP) in northeastern Baja California, Mexico, record details of Pacific-North American (PAC-NAM) plate boundary history prior to and during its establishment within the Gulf of California. Methods of study in Santa Isabel Wash (SIW) (informally named) in the northern Sierra Santa Isabel include geologic mapping of ~140 km^2 (1:20000 scale) along the northern margin of the Miocene-Pliocene Puertecitos Volcanic Province (PVP), ^(40)Ar/^(39)Ar geochronology, electron microprobe analysis, paleomagnetic study, and petrography. Local Neogene stratigraphy (spanning ~17-6 Ma) includes volcaniclastic breccias, basaltic to dacitic lava flows, and rhyolitic pyroclastic flow deposits. The completeness of the lithologic package improves stratigraphic correlations between the PVP and nearby regions.
\r\n\r\nHigh-angle extension-related faults cut all rocks in SIW. The southeastward projection of the pre-6 Ma Matorni accommodation zone, which separates a northern region of greater and more prolonged extension from a less extended southern zone, may pass on the north side of SIW. Paleomagnetic analysis indicates no vertical axis rotations in SIW since 6 Ma. This contrasts with regions north of the Matomi accommodation zone where clockwise rotation has accompanied extensional deformation since 3-6 Ma. About 500 meters of post-6 Ma, E-side-down displacement occurs across two major, NNW-striking normal faults on the west side of SIW. These, and smaller synthetic and antithetic faults in the hanging walls, accommodate up to 4% E- to ENE-directed extension. Quaternary deformation is also documented.
\r\n\r\nA new model developed to explain ENE-directed extension in northeastern Baja California partitions present-day PAC-NAM plate motion between NNW-striking, sinistral dip-slip faults and N- to NNW-striking, dextral (oblique?) strike-slip fault(s) in the northernmost Gulf of California. The model offers explanations for the geometry of plate motion accommodation between the latitudes of the Agua Blanca fault and the PVP, bathymetric features near Wagner and Consag basins, the position and jumps of nearby spreading centers since 6 Ma, the greater width and bend in coastline of the northernmost Gulf of California, the incorporation of the PVP into the GEP 2-3 Ma, and suggests a transitional tectonic scenario between oceanic spreading centers and continental transforms (\"Wagner Transition Zone\").
" }, { "name": "Song, Xi", "degree": "PhD", "year": "1997", "title": "High Resolution Modeling of Regional Phases", "advisor": "Anderson, Donald L.; Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08302023-200342752", "creators": [ { "name": { "family": "Song", "given": "Xi" }, "id": "Song-Xi", "display_name": "Song, Xi" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "chair", "display_name": "Anderson, Donald L." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "orcid": "0000-0002-7659-8358", "role": "member", "display_name": "Wernicke, Brian P." } ], "option_major": [ "geophys" ], "doi": "10.7907/qjr7-9471", "abstract": "It has been a long-time goal of seismologists to decouple source phenomena from propagation effects. This thesis elaborates on our effort towards this goal.
\r\n\r\nWe start by representing earthquakes as point-sources in space and using 1-D synthetics to resolve point-source parameters. Our trial-and-error approach to ob\u00adtain 1-D crustal models is summarized in a set of sensitivity tests, where regional seismograms are decomposed into segments, i.e., the Pnl segment, the SV waves, the Love wave and the Rayleigh wave, so that the impact of model parameters on each segment is the most direct. In these tests, broadband waveform data is studied in a forward modeling approach, with synthetics computed using the reflectivity method and the generalized ray theory. Applying these tests to paths sampling the Basin and Range province, we find that a simple two-layer crustal model is effective in explaining regional seismograms. Our sensitivity tests also serve to help understand, and inter\u00ad pret, the many results of a source estimation method we use to obtain point-source parameters. This method desensitizes the source mechanism result from the crustal model used to generate the 1-D synthetics, by allowing relative time shifts between the various segments. With this method, we obtain source mechanisms and seismic moments for a selection of Northridge aftershocks using broadband and long-period waveform data recorded by the TERRAscope array. The source duration of these earthquakes is measured by comparing the short-period to long-period energy ratio in the data to that in the synthetics. The seismic moment and source-duration are used to estimate the relative stress drop. The depth distribution of the relative stress drop indicates that the largest stress drops are in the depth range of 5-15 km for the 24 Northridge aftershocks in our study.
\r\n\r\nTo obtain more detailed information about large earthquakes, such as fault di\u00admension and rupture directivity, we develop a new method of using empirical Green's functions (eGf). As an example, the January 17, 1994 Northridge mainshock is studied with one of its aftershocks as an eGf. The source duration of the mainshock, as seen from the regional surface waves observed at various stations, is obtained by searching for the trapezoidal far-field source-time function for each station which, when convolved with the aftershock data, best simulates the mainshock data. Sta\u00adtions to the north see shorter source durations than those to the south. Modeling these with theoretical predictions of rupture on a square fault, we constrain the ef\u00adfective fault dimension to be 14 km with rupture along the direction of the average\r\nrake vector. A moment of (1.4 \u00b1 0.9) x 10\u00b2\u2076 dyne\u2022cm with a stress drop of ~120 bars is obtained for the mainshock from our eGf study.
\r\n\r\nWhen empirical Green's functions are not available due to a difference in the source mechanisms or in the source locations, theoretical modeling plays an important role. Our approach to develop high resolution Green's functions is to convert eGfs to pseudo Green's functions (pGf). This is done by modeling the eGfs with the generalized ray theory and consists of two major steps.
\r\n\r\nThe first step is to shift individual ray responses to account for a difference in source location.\tThis ray-shifting technique has its own use in fast generation of synthetic seismograms for finite sources. To study the directivity for a finite source, we discretize the fault region into a set of elements represented as point-sources. We then generate the generalized ray responses for the best-fitting point-source location, and derive for each separate ray the response for neighboring point-sources using power series expansions. The response for a finite fault is then a summation over rays and fault elements. If we sum over the elements first, we obtain an effective far\u00ad field source-time function for each ray, which is sensitive to the direction of rupture. These far-field source-time functions are convolved with the corresponding rays and the results summed to form the total response. A simple application of the above method is demonstrated with the tangential motions observed from the 1991 Sierra Madre earthquake. For this event, we constrain the fault dimension to be about 3 km with rupture towards the west, which is compatible with other more detailed studies.
\r\n\r\nThe second step in the modeling of the eGfs and the development of pseudo Green's functions is to account for variations in model structure by perturbing individual generalized ray responses calculated from a 1-D model. The model is divided into blocks and velocities in the blocks are allowed to vary, which shifts the arrival time of the individual rays. The amplitudes of the rays are perturbed independently to accom\u00admodate local velocity variations in the structure. For eGfs that are moderate-sized earthquakes with known source mechanism and time history, the velocity variation in each block and the amplification factor for individual rays can be optimized using a simulated annealing algorithm. The usefulness of the pGfs is demonstrated with the 1991 Sierra Madre earthquakes as examples. The pGf technique is also useful in retrieving 2-D structure, which is essentially waveform tomography. This is demonstrated with a study of a Tibetan profile.
" }, { "name": "Wolf, Richmond Andrew", "degree": "PhD", "year": "1997", "title": "The development of the (U-Th)/He thermochronometer", "advisor": "Farley, Kenneth A.; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10112005-111913", "creators": [ { "name": { "family": "Wolf", "given": "Richmond Andrew" }, "id": "Wolf-Richmond-Andrew", "display_name": "Wolf, Richmond Andrew" } ], "advisors": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "advisor", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "role": "co-chair", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "co-chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geol" ], "doi": "10.7907/kz3w-5t57", "abstract": "(U-Th)/He dating of apatite provides a tool for recording the low temperature (<100\u00b0C) history of the crust. A model based on stopping distances in apatite relates the fraction of alpha particles emitted from the crystal during U and Th decay to crystal size. Helium ages for different sized apatite aliquots are indistinguishable when corrected for the effects of alpha emission. Diffusion coefficients were measured by the incremental outgassing of helium from apatite. The measured range of diffusion parameters is nearly identical for apatites of different chemical composition, grain size, and grain morphology. Isothermal experiments are consistent with spherical diffusion domains which are smaller than the physical grain size.
\r\n\r\nHelium ages may reflect complex thermal histories where samples spend considerable amounts of time in the region where helium is only partially retained. Therefore, the solution to the full radiogenic helium diffusion/production equation is used to interpret helium ages instead of Dodson's (1973) closure temperature formulation. The time required to achieve a steady state between helium production and diffusion at various temperatures can be determined, as well as the range of temperatures defining the helium partial retention zone (the region where helium retentivity is most sensitive to temperature). In general, this zone resides at ~40-80\u00b0C (~2±1 km depth for typical continental geothermal gradients). This is ~35\u00b0C cooler than the analogous apatite fission track partial annealing zone.
\r\n\r\nApplication of the (U-Th)/He method to natural systems has provided consistent results and useful geologic information. Helium ages from the Cajon Pass Drillhole decline from 41.1 to 0.3 Ma between 526 and 2018 m depth, and appear to be in equilibrium with the present thermal gradient. This is in contrast to the previous assertion that the region is in a thermal transient resulting from recent erosion. Helium ages from Mt. San Jacinto, California, decrease monotonically from 79 to 17 Ma with sample elevation, and suggest a modest (~7\u00b0) westward tilting of the block with no evidence of rapid exhumation during this period. Helium ages from Mt. San Jacinto and Cajon Pass are younger than other available thermochronometric techniques, consistent with predictions from laboratory diffusion data.
" }, { "name": "Wood, David Judson", "degree": "PhD", "year": "1997", "title": "Geology of the Eastern Tehachapi Mountains and Late Cretaceous-Early Cenozoic tectonics of the southern Sierra Nevada Region, Kern County, California", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12122006-135618", "creators": [ { "name": { "family": "Wood", "given": "David Judson" }, "id": "Wood-David-Judson", "display_name": "Wood, David Judson" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "chair", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Wernicke", "given": "Brian P." }, "id": "Wernicke-B-P", "role": "member", "display_name": "Wernicke, Brian P." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geol" ], "doi": "10.7907/M8Z7-0W45", "abstract": "Many geologic studies have inferred that the California continental margin in the vicinity of the western Mojave Desert was tectonically disrupted after emplacement of the Cretaceous Cordilleran batholith and prior to Neogene displacements on the San Andreas fault system. The causes of this regional deformation, however, are poorly understood. Located along the northern margin of this disrupted region at the southern end of the comparatively little deformed Sierra Nevada batholith, the eastern Tehachapi Mountains are ideally situated to study the possible mechanisms of this disruption. In view of this, the geology and structure of the eastern Tehachapi Mountains were investigated using geologic field mapping at scales of 1:6,000 through 1:24,000, detailed petrographic studies, and structural and kinematic analysis of deformation fabrics and structures in the field and in the lab. The study area is divided by a generally N trending shallowly SE dipping ductile-cataclastic fault zone called the Blackburn Canyon fault into the eastern Tehachapi gneiss complex in the footwall and the Oak Creek Pass complex in the hangingwall.\r\n\r\nThe eastern Tehachapi gneiss complex is composed of two different sequences of metasedimentary rocks that have been intruded by three generations of plutonic rocks. The Brite Valley group metasedimentary rocks consist largely of pelites and graphitic quartzite with subordinate marble. The Antelope Canyon group metasedimentary rocks consist of a lower section composed mostly of thinly laminated dirty quartzite overlain by an upper section of marble. The earliest intrusive rocks in the area (group I orthogneisses) are lithologically diverse and include granite augen gneiss, garnetiferous hornblende diorite gneiss, and hornblende biotite quartz diorite gneiss. Both groups of paragneiss and the group I orthogneisses are intruded by group II plutons of the Tehachapi Intrusive Complex. The Tehachapi Intrusive Complex is composed of comagmatic gabbro, quartz diorite, and tonalite and it is inferred to be continuous with the large ~100 Ma Bear Valley Springs tonalite pluton exposed to the west. The group III intrusives are small bodies and thin sheets of leucocratic biotite granite which intrude all of the other lithologies.\r\n\r\nThe rocks in the gneiss complex have had a complex deformational history. The metasedimentary rocks are folded into map-scale N to NW trending SW vergent isoclinal F1 folds. Later (?) intrusion of the group I orthogneisses was accompanied (?) and followed by amphibolite facies metamorphism and the localized formation of NE trending shallow plunging open to tight F2 folds. During (?) and after intrusion of the ~100 (?) Ma Tehachapi Intrusive Complex the gneiss complex was metamorphosed at amphibolite facies and deformed by map-scale open to tight NW trending SW vergent F3 folds. After much of the F3 folding the basement rocks in the Tehachapi Valley area appear to have been folded into a regional dextral-sense convex-west F4 oroclinal fold. In the later stages of F4 folding part of the southwest limb of the Tehachapi Valley orocline is inferred to have been transposed into a NW trending shallow NE dipping noncoaxial ductile shear zone called the eastern Tehachapi shear zone. The shear zone has a structural thickness of ~1 km, top to the S-SW shear sense, and most shearing appears to have occurred during greenschist facies retrograde metamorphism. The shear zone appears to continue to the north across Tehachapi Valley where it is inferred to merge with the steeply E dipping dextral-slip proto-Kern Canyon fault. Motion on the shear zone is inferred to have ended at about the time when the Late Cretaceous (?) group III leucogranites intruded. Following shear zone activity rocks in the gneiss complex locally were folded in gentle NE trending subhorizontal F5 folds. Late top to the NE shearing in the upper structural levels of the gneiss complex suggests that a normal fault may be concealed beneath the alluvium of Tehachapi Valley.\r\n\r\nThe lithologies and deformation history of the Oak Creek Pass complex are very different from the eastern Tehachapi gneiss complex. The Oak Creek Pass complex is composed mostly of granodioritic plutonic rocks (group IV intrusives) which commonly are cataclastically deformed and metamorphosed at greenschist and lower grade. Arkosic sandstones and conglomerates of the Late Cretaceous (?)-Eocene (?) Witnet Formation locally are unconformable above the granodiorite. Emplacement of the Oak Creek Pass complex above the eastern Tehachapi gneiss complex along the Blackburn Canyon fault took place after most of the activity along the eastern Tehachapi shear zone. Shear sense along the Blackburn Canyon fault is top to the S or SE. The Oak Creek Pass complex is divided into a number of structural plates by low-angle (?) ductile-cataclastic fault zones one of which is the NE trending Mendiburu Canyon fault. Synclinal F6 folding of the Witnet Formation and NW vergent overthrusting of the Witnet Formation by granitic rocks along the Mendiburu Canyon fault are interpreted to postdate motion along the Blackburn Canyon fault. Deformation of the Witnet Formation is inferred to be pre-Miocene in age based on correlation with a similar deformation across Tehachapi Valley.\r\n\r\nThe Brite Valley group metasedimentary rocks are suggested to correlate with the western facies of the Triassic-Jurassic age Kings sequence and the Antelope Canyon group rocks may correlate with the eastern facies of the Kings sequence or possibly with Late Proterozoic-Cambrian age rocks of the miogeocline. Juxtaposition of the two groups of metasedimentary rocks may have been along a cryptic structure that was active prior to intrusion of some of the group I plutons which are inferred to be mid-Cretaceous in age. Formation of the NE trending F2 folds between ~117 Ma and ~100 Ma is suggested to have resulted from the local reorientation of the regional stress field in the vicinity of a weak strike-slip (?) fault such that the direction of maximum compressive stress during the deformation was oriented subparralel to the trend of the Sierra Nevada batholith. The F3 folds, F4 folds, and the eastern Tehachapi shear zone are interpreted to have formed more or less sequentially during a protracted period of contractional deformation in the middle to lower crust of the southern Sierra Nevada batholith from ~100 Ma to ~80 Ma. Top to the S-SW motion along the shear zone may reflect the and underthrusting of Rand schist beneath the batholith at lower structural levels during low-angle Laramide subduction.\r\n\r\nThe Blackburn Canyon fault and a number of other previously identified low-angle faults in the southern Sierra Nevada region are suggested to be extensional faults along which part of the southern Sierra Nevada batholith was unroofed. The source region for the out of place Oak Creek Pass complex and other inferred allochthonous rocks is suggested to be the area in the Sierra Nevada east of the proto-Kern Canyon fault and south of South Fork Valley. Exposures of Witnet Formation may be the remnants of a synextensional sedimentary deposit that accumulated in a supradetachment basin. This inferred extensional exhumation of the southeastern Sierra Nevada may have begun as early as ~85-90 Ma and ended at ~80 Ma or later based on data from previous studies in the region. Thus, contractional deformation in the middle crust of the southern Sierra Nevada region may have been coeval with upper crustal extensional deformation in Late Cretaceous time.\r\n\r\nCorrelation of the Cretaceous structural histories of the eastern Tehachapi gneiss complex and the northern Salinian block in the Coast Ranges of central California supports previous suggestions that the two areas may have evolved in close proximity to one another. The relative westward offset of the Salinian block from the Sierra Nevada prior to the Neogene may in part be the result of Late Cretaceous-early Cenozoic (?) westward extrusion of wedges of middle to lower crust bounded by thrust faults below and E dipping extensional faults above in a manner analogous to recent models for deformation in the Himalayas. The upper plate rocks of the Blackburn Canyon fault appear to be rotated about 90\u00b0 clockwise relative to their inferred source region and the F4 folds in the Tehachapi area appear to have dextral vergence. The vergence of the folding and the sense of rotation both are consistent with Late Cretaceous dextral-oblique convergence indicated by plate motion models and with the presence of Late Cretaceous synbatholithic dextral transpressional and strike-slip shear zones in the Sierra Nevada to the north." }, { "name": "Anbar, Ariel David", "degree": "PhD", "year": "1996", "title": "I. Rhenium and Iridium in Natural Waters. II. Methyl Bromide: Ocean Sources, Ocean Sinks, and Climate Sensitivity. III. CO\u2082 Stability and Heterogeneous Chemistry in the Atmosphere of Mars", "advisor": "Wasserburg, Gerald J.; Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:01202022-231109666", "creators": [ { "name": { "family": "Anbar", "given": "Ariel David" }, "id": "Anbar-Ariel-David", "orcid": "0000-0002-6015-7750", "display_name": "Anbar, Ariel David" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Farley", "given": "Kenneth A." }, "id": "Farley-K-A", "orcid": "0000-0002-7846-7546", "role": "member", "display_name": "Farley, Kenneth A." }, { "name": { "family": "Morgan", "given": "James J." }, "id": "Morgan-J-J", "role": "member", "display_name": "Morgan, James J." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "geochem" ], "doi": "10.7907/rrjq-k179", "abstract": "Part I: Rhenium and iridium were measured in natural waters by isotope dilution and negative thermal ionization mass spectrometry, following clean chemical separation from 200 mL (Re) and 4 L (Ir) samples. In the Pacific\r\nOcean, Re is well-mixed in the water column, confirming predictions of conservative behavior. The Re concentration is 7.42 \u00b1 0.04 ng kg\u207b\u00b9. The concentration of Ir in the oceans is fairly uniform with depth and location, ranging from 2.9 to 5.7 x 10\u2078 atoms kg\u207b\u00b9. Pristine river water contains \u2248 20 x 10\u2078 atoms kg\u207b\u00b9 while polluted rivers have 50 - 100 x 10\u2078 atoms kg\u207b\u00b9. Concentrations in the Baltic Sea are much lower than expected from conservative estuarine mixing, indicating rapid removal of \u224875% of riverine Ir. Under oxidizing conditions, Ir is scavenged by Fe-Mn oxyhydroxides. Ir is enriched in anoxic waters relative to overlying oxic waters, indicating that anoxic sediments are not a major Ir sink. The residence time of dissolved Ir in the oceans is 10\u00b3 - 10\u2074 years, based on these and other observations. The amount of Ir in Ktr boundary sediments is \u224810\u00b3 times the total quantity in the oceans.
\r\n\r\nPart II: The biogeochemistry of methyl bromide (CH\u2083Br) in the oceans was studied using a steady-state mass-balance model. CH\u2083Br concentrations are sensitive to temperature and the rate of CH\u2083Br production. Model production rates correlate strongly with chlorophyll concentrations, indicating CH\u2083Br biogenesis. This correlation explains discrepancies between two observational studies, and supports suggestions that the ocean is a net sink for atmospheric CH\u2083Br. The Southern Ocean may be a CH\u2083Br source.
\r\n\r\nPart III: High resolution, temperature-dependent CO\u2082 cross sections were incorporated into a 1-D photochemical model of the Martian atmosphere. The calculated CO\u2082 photodissociation rate decreased by as much as 33% at some\r\naltitudes, and the photodissociation rates of H\u2082O and O\u2082 increased by as much as 950% and 80%, respectively. These results minimize or even reverse the sense of the CO\u2082 chemical stability problem due to increased production of HO\u2093 species which catalyze CO oxidation. The effect of heterogeneous chemistry on the abundance and distribution of HO\u2093 was assessed using observations of dust and ice aerosols and laboratory adsorption data.\r\nAdsorption of HO\u2082 can deplete OH in the lower atmosphere enough to significantly reduce the CO/CO\u2082 ratio.
" }, { "name": "Gurwell, Mark Andrew", "degree": "PhD", "year": "1996", "title": "Planetary atmospheres: probing structure through millimeterwave observations of carbon monoxide", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:02052013-152025528", "creators": [ { "name": { "family": "Gurwell", "given": "Mark Andrew" }, "id": "Gurwell-M-A", "display_name": "Gurwell, Mark Andrew" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/wbs1-8j46", "abstract": "This thesis consists of inteferometric observation of carbon monoxide from\r\nthree planetary atmospheres. The observations address specific questions about the\r\nstate and structure of each atmosphere. The analysis and results for each planetary\r\nbody are contained within individual chapters of the thesis and the abstract for each\r\nis reproduced below.
\r\n\r\nTitan: Evidence for Well-Mixed Vertical Profile
\r\n\r\nWe report on new millimeter heterodyne observations of the ^(12)CO J(1 - 0)\r\nrotational transition from the stratosphere of Titan made in October 1994 with the\r\nOwens Valley Radio Observatory Millimeter Array. The spectrum obtained clearly\r\nexhibits a strong emission core over the ~600 MHz bandwidth of the upper sideband\r\nspectrometer. The lineshape, referenced to the flat spectrum simultaneously observed\r\nin the lower sideband was inverted to determine a best fit CO mixing ratio profile\r\nconsistent with the observations. The bet fit profile is a constant mixing ratio of 5 \u00b1 1 x 10^(-5) over the altitude range of 60- 200 km. Combined with IR observation\r\nof tropospheric CO (\u0192co = 6 x 10^(-5), Lutz et al. 1983) this provides strong evidence\r\nthat CO is well mixed from the surface to at least 200 km in Titan\u2019s atmosphere.
\r\n\r\nMars: Thermal Structure from 0-70 km
\r\n\r\nMillimeter-wave heterodyne observations of the ^(12)CO J (l - 0) rotational transition\r\nfrom the atmosphere of Mars were made on three dates in February 1993 with\r\nthe Owens Valley Radio Observatory Millimeter Array. These observations yielded\r\nhigh-quality spectra with a spatial resolution of 4.2\" on a 12.5\" diameter Mars. The\r\nspectra were numerically inverted for profiles of the local atmospheric temperature\r\nfrom 0 to 70 km, assuming a constant CO mixing ratio for the atmosphere. The\r\nderived average low latitude atmospheric temperature profile is approximately 20 K\r\ncooler than reference temperature profiles compiled during the Viking era. This new\r\ntemperature profile is well-matched by cooler profiles determined from whole disk CO\r\nmeasurements, suggesting very little dust loading of the atmosphere at the time of\r\nthe observations (Clancy et al. 1990). In addition, the revealed thermal structure\r\nshows variation with latitude, and these temperature profiles compare well with profiles\r\nderived from Mariner 9 IRIS observations (Leovy 1982, Santee and Crisp 1993) and calculated thermal structure from the Mars General Circulation Model (Haberle\r\net al.. 1993). The temperature profiles were averaged in local time and the resulting\r\ncross-section of temperature as a function of pressure and latitude used to infer the\r\nmean zonal circulation of the atmosphere. These wind results are somewhat compromised\r\nby the relatively low spatial resolution of the observation but do qualitatively\r\nmatch both inferred zonal winds from the Mariner 9 IRIS observations and Mars\r\nGCM calculations. These initial observations point toward the desirability of further\r\ninterferometric measurements.
\r\n\r\nVenus: Temporal Variations of the Mesophere
\r\n\r\nMillimeter-wave heterodyne observations of the ^(12)CO J(1-0) rotational transition\r\nfrom the mesosphere of Venus were made in early November and early December\r\n1994 with the Owens Valley Radio Observatory Millimeter Array. The spatial resolute ion for each day was about 1000 km at the sub-earth point. The high quality CO\r\nspectra were numerically inverted for profiles of the local CO mixing ratio from 80\r\nto 105 km, assuming a Pioneer Venus mean temperature profile for the atmosphere.\r\nFor each day the revealed CO distribution shows a nightside maximum centered at\r\nlow latitudes and shifted from the anti-solar point toward the morning terminator.\r\nBoth clays show a clear latitudinal falloff in the CO abundance. In November the\r\nmaximum was centered at roughly 2^h local time at 100 km, while in December the\r\nmaximum was at roughly 4 \u2013 4.5^h local time at 100 km. In addition, CO abundances\r\nwere slightly higher in November. The changes in the CO distribution are\r\nexamined in the context of the mesospheric circulation model of Clancy and Muhleman\r\n(1985b). The increased shift away from the anti-solar point and decreased CO\r\nabundance for the December observations both point toward increased zonal and/or\r\ndecreased sub-solar to anti-solar circulation within the mesosphere during the month\r\nbetween observations.
\r\n" }, { "name": "Kedar, Sharon", "degree": "PhD", "year": "1996", "title": "The origin of harmonic tremor at Old Faithful geyser", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-01262009-133713", "creators": [ { "name": { "family": "Kedar", "given": "Sharon" }, "id": "Kedar-S", "display_name": "Kedar, Sharon" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/X1RD-ZV73", "abstract": "Volcanic tremor, the seismic signal which is often associated with eruptions, is among the least understood phenomena in seismology. Large variations in the physical properties of volcanic rocks and fluids along with the complex geological structure make it difficult to obtain reliable source models. Old Faithful geyser, Yellowstone National Park, was chosen as a laboratory for studying fluid-flow-induced seismicity. The geyser's cyclic behavior on an hourly time scale, and its accessibility, make it suitable for a detailed study of seismic behavior between eruptions simultaneously with underwater pressure measurements inside the geyser.
\r\n\r\nWe observe that sharp pressure pulses inside the water-column attributed to steam bubble collapse are followed by distinct seismic events, with a sharp onset and a harmonic horizontal motion whose frequency varies spatially but not temporally. A superposition of these events creates the appearance of continuous harmonic tremor. Since the pressure in the water column exhibits no sign of resonance, the harmonic motion must be caused by elastic waves reverberating in the solid medium. A near-surface soft layer is demonstrated to be a possible elastic model.
\r\n\r\nThe harmonic tremor observed at Old faithful seems analogous to some examples of shallow volcanic tremor.
\r\n\r\n" }, { "name": "Lee, Woh-jer", "degree": "PhD", "year": "1996", "title": "Experimental Study on Liquid Immiscibility in Silicate-Carbonate Systems with Applications to Carbonatites", "advisor": "Wyllie, Peter J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09192023-212841699", "creators": [ { "name": { "family": "Lee", "given": "Woh-jer" }, "id": "Lee-Woh-jer", "display_name": "Lee, Woh-jer" } ], "advisors": [ { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "advisor", "display_name": "Wyllie, Peter J." } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geol" ], "doi": "10.7907/vpan-h802", "abstract": "Phase equilibrium experiments have been conducted in several silicate-carbonate systems to 2.5 GPa in order to understand the magmatic processes involved in the generation of carbonatite complexes. The studied phase fields were intersected by SiO\u2082-CaCO\u2083, NaAlSi\u2083O\u2088-CaCO\u2083, NaAlSiO\u2084-NaAlSi\u2083O\u2088-CaCO\u2083 and primitive nephelinite\u00ad (Na,Ca,Mg) carbonate, which along with the analyzed liquid and solid compositions were used to define the positions of the silicate-carbonate miscibility gap and liquidus field boundaries on various compositional projections. These boundaries exert controls on the evolution of silicate-CO\u2082 and carbonatitic magmas, and vary strongly with temperature, composition and pressure. The size of the miscibility gap decreases with increasing temperature and Mg/Ca of liquids. The extent of the Mg-free miscibility gap decreases with decreasing pressure, whereas the magnesian one shows an opposite trend. The immiscible carbonate-rich liquids could dissolve at most ~80 wt% CaCO\u2083 while still containing significant amounts of silicate and alkalis. The position of the silicate-calcite coprecipitation boundary becomes more carbonate-rich as pressure decreases, and as composition becomes more magnesian and aluminous. Calcite grew remarkably rounded in many experiments. A variety of liquid paths are compared with the field boundaries at different conditions. Partial melting of carbonated peridotite produces dolomitic carbonatites along the coprecipitation boundary, to CO\u2082-bearing, silica-undersaturated liquids in the primary silicate field. Both types of magmas could potentially ascend to the surface of the earth without much modification. None of them would reach the miscibility gap at mantle conditions. Within the crust, carbonated silicate liquids could either intersect the miscibility gap after substantial crystallization to exsolve alkali-bearing to alkalic carbonatitic liquids, or reach the coprecipitation boundary and evolve towards alkali-enrichment and silicate\u00ad depletion without immiscibility. Alkali-bearing, CaCO\u2083-rich immiscible liquids, when separating from their silicate parents, first precipitate silicate minerals during cooling until calcite is joined, and the residual liquids become more alkalic by further crystallization of calcite. It appears that most calciocarbonatites are cumulates from liquids along the coprecipitation boundary, whereas the natrocarbonatites at Oldoinyo Lengai are produced directly by immiscibility." }, { "name": "Lyons, James Richard", "degree": "PhD", "year": "1996", "title": "Atmospheric chemistry in the outer solar system: from 40 K to 4000 K", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01252013-094647944", "creators": [ { "name": { "family": "Lyons", "given": "James Richard" }, "id": "Lyons-J-R", "display_name": "Lyons, James Richard" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/D9MH-G975", "abstract": "This thesis consists of four papers on the general subject of atmospheric chemistry\r\nin the outer solar system. Although all are reducing environments, the atmospheres differ\r\nwidely in the ranges of temperature and pressure they encompass. Individual abstracts are\r\ngiven below.
\r\n\r\nPhotochemistry of the Atmosphere and Ionosphere of Triton
\r\n\r\nA one-dimensional photochemical model of the atmosphere and ionosphere of\r\nTriton was constructed to evaluate the significance of CO and CO_2, detected as surface\r\nices (Cruikshank et al. 1993), to the gas phase chemistry. For a CO mixing ratio of 10(^-4),\r\nconsistent with the observed fraction of CO ice, the model yields several interesting\r\nresults. Gas phase production of CO_2 is slow, but may, with the help of heterogeneous\r\nreactions on aerosols, be capable of producing a detectable layer of CO_2 ice over the age\r\nof the solar system; however, we consider this unlikely. Atomic nitrogen, produced in the\r\nionosphere, diffuses to the lower atmosphere and recombines to form N_2 in a cycle in\r\nwhich C acts as a catalyst. In a model with solar radiation only, the model predicts N\r\ndensities a factor of two smaller than reported by Krasnopolsky et al. (1993). Atomic\r\ncarbon is produced in the ionosphere primarily by dissociative recombination of CO^+. For\r\nan assumed rate coefficient for charge exchange from N_2^+ and CO^+ to C of 1x10^(-10) cm^3\r\nsec^(-1), Triton's ionosphere is dominated by C^+ and can be accounted for entirely by solar\r\nradiation. For a rate coefficient 10 times smaller, magnetospheric electron precipitation\r\nis needed to account for the observed electron density, but C^+ is still the principal ion.\r\nElectron precipitation is necessary to explain the observed N abundances. Measurements\r\nof the rate coefficients for ion-molecule reactions involving neutral C are needed.
\r\n\r\nMetal Ions in the Atmosphere of Neptune
\r\n\r\nMicrowave propagation experiments performed with Voyager 2 at Neptune\r\nrevealed sharp layers of electrons with densities \u223c10^4 cm^(-3) in Neptune's lower ionosphere.\r\nThese layers are reminiscent of terrestrial sporadic-E layers, and, when taken together\r\nwith data from the other giant planets, confirm the importance of the magnetic field in\r\nlayer formation. A photochemical model which incorporates species produced by\r\nmeteoroid ablation predicts that Mg^+ is the most likely metal comprising the layers,\r\nalthough laboratory data on the kinetics of metallic atoms and ions in reducing\r\nenvironments are lacking. The metal chemistry discussed here is directly relevant to the\r\nabundant metals observed at the impact site of the G fragment of Comet Shoemaker-Levy\r\n9 on Jupiter.
\r\n\r\nMeteoroidal Influx into the Upper Atmospheres of Uranus and Neptune
\r\n\r\nResults from a recent analysis of meteoroid ablation rates in the atmosphere of\r\nNeptune have been coupled with photochemical models of the upper atmospheres of\r\nNeptune and Uranus to yield estimates of stratospheric water profiles as a function of\r\nmeteoroid influx. Because water has never been detected in the upper atmospheres of the\r\ngiant planets, the tangential column opacities of the model water profiles were compared\r\nwith UV absorption measurements made by Voyager to determine maximum water\r\ninfluxes. For Uranus an upper limit is obtained which is consistent with an Oort-family\r\nparticle population, but not with a large population of planet-family dust particles. For\r\nNeptune the model water profile is strongly dependent on the still uncertain eddy\r\ncoefficient, making it difficult to rule out a large planet-family of IDP's. However, an IDP\r\npopulation sufficiently large to account for the CO observed in Neptune's atmosphere can\r\nbe ruled out.
\r\n\r\nA Chemical Kinetics Model for the Comet Impact with Jupiter
\r\n\r\nA chemical kinetics code was developed for gas phase species comprised of the\r\nelements H,C,N,O,S and Si. The code is valid at high temperatures and for H-dominated\r\ncompositions. The kinetics model was tested by running it to steady state equilibrium and\r\ncomparing the results with a thermochemical model. Model runs for pressure-temperature\r\nhistories relevant to the comet Shoemaker-Levy 9 impacts with Jupiter were made for\r\nC > O and C less than O compositions and for a variety of temperatures. Results indicate that the\r\nplume gas must have C > O, in agreement with Zahnle et al. (1995), implying a greater\r\nthan 50:1 mix of Jupiter gas to vaporized comet.
" }, { "name": "Nair, Hari", "degree": "PhD", "year": "1996", "title": "Photochemical processes in the atmospheres of Earth and Mars", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08192010-151207728", "creators": [ { "name": { "family": "Nair", "given": "Hari" }, "id": "Nair-H", "display_name": "Nair, Hari" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/p4n5-3x10", "abstract": "Part I:
\r\n\r\nThis thesis consists of two chapters concerning photochemical processes in the atmospheres of earth and Mars. The first chapter is a comprehensive study of the photochemistry of the martian atmosphere. Classical models of the Mars atmosphere have neglected an important property of carbon dioxide, namely that the photoabsorption cross section decreases with lower temperature. Accounting for this effect yields a smaller photolysis rate for CO_2 and more importantly, an enhanced photolysis rate for water vapor. Both effects combine to yield carbon monoxide mixing ratios smaller by a factor of four than observations indicate. We propose modifications in the rate coefficients for two key reactions, CO + OH and OH + HO_2, in order to resolve this discrepancy. We note that similar revisions have been proposed to reconcile models and observations of ozone in the terrestrial mesosphere. Other investigators have proposed a heterogeneous sink of odd hydrogen radicals on aerosols; we find that such a sink is unnecessary. Finally, we have performed the first time dependent calculation to examine the mechanism by which the escape of atomic oxygen controls the escape flux of hydrogen from the atmosphere. We show that this coupling operates over a time scale of 10^5 years.
\r\n\r\nIn chapter two we investigate the formation and evolution of low ozone anomalies in the northern winter stratosphere using a Lagrangian photochemical model. The UARS spacecraft has observed pockets of low ozone in the 6 to 10 millibar altitude range, where the effects of dynamics and chemistry on the ozone budget are comparable. We employ the Lagrangian model to compute the ozone loss rate within an isolated parcel of air as it travels along a specified trajectory. Since we have decoupled the dynamics and chemistry, disagreement between the model and observations should reflect deficiencies in the chemistry. We find that the model consistently overestimates the ozone loss rate above about 7 millibars altitude, which is a common feature of most current photochemical models. Below 10 millibars altitude, the model is in good agreement with the observations, indicating that the description of chemistry is valid in the low to mid stratosphere.
\r\n\r\nPart II:
\r\n\r\nPhotochemical models have historically overestimated ozone loss rates in the upper stratosphere and lower mesosphere, where ozone is photochemically controlled. Thus it is evident that there is some missing chemistry in current models. Current understanding of the factors controlling ozone in the low to mid stratosphere is that dynamical influences play a large role in determining the ozone abundance. It is difficult to test the chemistry in the models at these altitudes since the contributions from transport and chemistry must be separated.
\r\n\r\nThe Microwave Limb Sounder (MLS) aboard the Upper Atmosphere Research Satellite (UARS) has observed pockets of low ozone in the winter polar stratosphere outside the polar vortex. These pockets occur in the 6 to 10 millibar altitude range, where the effects of dynamics and chemistry on the ozone budget are comparable. The formation and evolution of these anomalies are investigated using a Lagrangian photochemical model, where the chemistry within an isolated parcel of air is simulated as it travels along a specified trajectory. Since we have decoupled the dynamics and chemistry, disagreement between the model and observations should reflect deficiencies in the chemistry.
\r\n\r\nWe find that the model consistently overestimates the ozone loss rate above about 7 millibars, where the ozone deficit tends to manifest itself. Below 10 millibars altitude, the model is in good agreement with the observations, indicating that the description of chemistry is valid in the low to mid stratosphere. Individual trajectories have many uncertainties associated with them; in order to present more quantitative conclusions the results computed along many trajectories should be taken together to minimize errors.
\r\n\r\n" }, { "name": "Thio, Hong Kie", "degree": "PhD", "year": "1996", "title": "1. Using Short-Period Surface Waves to Study Seismic Source and Structure. 2. Source Complexity of Large Strike-Slip Earthquakes", "advisor": "Kanamori, Hiroo; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10102023-192037999", "creators": [ { "name": { "family": "Thio", "given": "Hong Kie" }, "id": "Thio-Hong-Kie", "display_name": "Thio, Hong Kie" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "orcid": "0000-0003-3363-2197", "role": "member", "display_name": "Heaton, Thomas H." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geophys" ], "doi": "10.7907/s8s1-f531", "abstract": "The availability of high dynamic range very broad band seismic data in recent years has greatly increased the level of detail and the speed with which we can study the seismic source. The work presented in this thesis draws heavily on the deployment of broad-band seismometers, both on a worldwide scale, with networks like IRIS, IRIS/IDA and GEOSCOPE, as well as on a local scale, using data from the TERRAscope network.\r\nThe routine study of seismicity in Southern California, like in other seismically active regions, has traditionally been carried out using dense arrays of high-gain short-period seismometers. With the addition of the very broad band instrumentation of TERRAscope we can improve this pursuit in several ways, one of which being the use of short period surface waves to study local earthquakes as described in chapter 1 of this thesis. Over the years, surface waves have proved to be very reliable and stable for moment tensor inversions. The method is very rapid, and because of the longer periods used they are more reliable for consistent estimation of earthquake moment. At short distances the surface waves arrive within a few minutes after an event has occurred at the stations, and with real-time telemetry we can obtain the size and mechanism for local earthquakes within minutes. The propagation corrections for surface waves are very straightforward so that this procedure can be made completely automatic. Armed with the results from above procedure, we can determine travel time residuals for a dense distribution of raypaths across Southern California. In chapter 2 we present tomographic inversions of these resid\u00aduals, for Love and Rayleigh waves at periods between 10 and 50 seconds. The results indicate that lateral variations of phase velocity of up to 10% exist in the area, and that these anomalies can have relatively short wavelengths.
\r\n\r\nThe 1994 Northridge earthquake provided a wealth of data to apply our moment tensor inversion to, and in chapter 3 we present a detailed analysis of the aftershock mechanisms in relation to the source complexity of the mainshock. We show that the orientation of the aftershock mechanisms changes away from the zone where rupture took place. We suggest that this change in mechanism reflects changes in fault geometry which have limited the extent of the Northridge rupture, leading to a high static stress drop.
\r\n\r\nThe issue of source complexity is discussed further in chapter 4, where we present a systematic study of the rupture of three large strike-slip earthquakes and compare these results with observation on the surface rupture. We find a very good correlation which suggests that the source complexity can be attributed to fault geometry, which tends to become simpler as slip accumulates along a fault. This provides an explanation for the high stress drops that are observed for earthquakes which occur along faults with low strain rates.
\r\n\r\nFinally, in chapter 5 we compiled energy and moment estimates for earthquakes in Southern California, based on the results in the previous chapters. We find that the radiated seismic energy is not linearly related to the seismic moment, but that instead the\r\nenergy-moment ratio increases as a function of moment. We provide some suggestions as to the cause of this relationship, including a moment dependence of the specific fracture energy and a non-similarity of the frictional stress between different size earthquakes.
" }, { "name": "Weisstein, Eric W.", "degree": "PhD", "year": "1996", "title": "Millimeter/submillimeter fourier transform spectroscopy of Jovian planet atmospheres", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:02062013-163011023", "creators": [ { "name": { "family": "Weisstein", "given": "Eric W." }, "id": "Weisstein-E-W", "display_name": "Weisstein, Eric W." } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/R90F-8A53", "abstract": "A new Fourier transform spectrometer, built for use at the Caltech Submillimeter\r\nObservatory, has been used to observe all four of the jovian planets (Jupiter,\r\nSaturn, Uranus, and Neptune) in the millimeter-submillimeter wavelength range (0.3-\r\n3.0 mm). The observations have resulted in the detection of the PH_3 1 - 0 rotational\r\nline (266.9 GHz) in Saturn. and the PH_3 3 - 2 ( 800.5 GHz) line in both Jupiter and\r\nSaturn. Because PH_3 is a disequilibrium species, it is an important tracer of vertical\r\nmixing and upper atmospheric photochemistry, and can therefore be used to derive\r\ndynamical and chemical properties of the jovian atmospheres. A jovian planet radiative transfer code has been used to model the observed PH_3 lineshapes. Using the\r\nFTS, a spectral line survey covering the entire range of submillimeter frequencies observable from the ground has also been performed on Jupiter at Saturn at a resolution\r\nof 200 MHz. This survey has yielded the tentative detection of HCl (and possibly\r\nHCN) in Saturn and, again with the aid of radiative transfer modeling, provided a\r\ngreat number of improved upper limits on the concentrations of many other species.\r\nFinally, Uranus and Neptune have been observed in the 1300 \u00b5m atmospheric window\r\nwhich contains the CO 2 - 1 transition. This line was not detected in either planet,\r\nplacing upper limits on the tropospheric CO mole fraction of 0.5 ppm in Uranus and\r\n1.4 ppm in Neptune.\r\n" }, { "name": "Yule, John Douglas", "degree": "PhD", "year": "1996", "title": "Geologic and tectonic evolution of jurassic marginal ocean basin lithosphere, Klamath Mountains, Oregon", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02262010-073813373", "creators": [ { "name": { "family": "Yule", "given": "John Douglas" }, "id": "Yule-John-Douglas", "display_name": "Yule, John Douglas" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/AZ70-V587", "abstract": "This study examines the geologic and tectonic history of the westernmost lithotectonic belt of the Klamath Mountains province, known as the western Jurassic belt (WJB). In Oregon the WJB exposes one of the world's best preserved examples of ancient marginal ocean basin lithosphere, including a complete ophiolite sequence, an arc volcano- plutonic complex, and older fragments of oceanic lithosphere that occur as screens within the ophiolite and which form the basement constructs of the arc. As such, the region provides an exceptional opportunity to directly examine the structural framework and geologic features of marginal ocean basins. Geologic mapping in the central Illinois River drainage area, Curry and Josephine Counties, Oregon has resulted in the following changes to previously reported work: 1) the discovery of a 5 x 45 km fragment of rocks correlative with the Rattlesnake Creek terrane; rocks previously known only to occur within the overthrust lithotectonic belt to the east, the western Paleozoic and Triassic belt , 2) the discovery of an intra-peridotite boundary separating pre-175 Ma serpentinized harzburgite and dunite from relatively unaltered peridotite associated with the Josephine ophiolite (166162 Ma), and 3) a re-interpretation of the region as a fold and fault belt rather than an imbricate thrust stack of separate subterrane units. Collectively, these relations confirm the prediction of a previous model for the Jurassic tectonic evolution of the region that invokes rifting of a Middle Jurassic arc and arc basement terrane to form a paired, Late Jurassic inter-arc basin ophiolite and volcanic arc. Radiometric ages determined from rocks in the map area and from arc plutons exposed to the east, in combination with a wealth of preexisting geochronometric data, indicate that the Klamath Mountains province experienced a continuum of arc-related magmatism from ~175-135 Ma, distinct episodes of thrusting at ~165 and ~155 Ma, and a prolonged episode of ophiolite genesis and extension from ~170- 160 Ma. These features characterize the province as a batholithic belt constructed in an entirely oceanic setting and represent an archetypal example of a long-lived oceanic arc system generated at a loosely coupled ocean/ocean convergent plate boundary." }, { "name": "Dissly, Richard William", "degree": "PhD", "year": "1995", "title": "Laboratory Studies of Astrophysical Ices", "advisor": "Anicich, Vincent G.; Allen, Mark Andrew", "url": "https://resolver.caltech.edu/CaltechETD:etd-10312007-083146", "creators": [ { "name": { "family": "Dissly", "given": "Richard William" }, "id": "Dissly-Richard-William", "display_name": "Dissly, Richard William" } ], "advisors": [ { "name": { "family": "Anicich", "given": "Vincent G." }, "id": "Anicich-V-G", "role": "advisor", "display_name": "Anicich, Vincent G." }, { "name": { "family": "Allen", "given": "Mark Andrew" }, "id": "Allen-M-A", "role": "advisor", "display_name": "Allen, Mark Andrew" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/c0mj-np35", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis thesis reports the results of three laboratory studies, each concerned with some aspect of ices in an astrophysical environment, presented as independent papers:\r\n\r\n1. Molecular hydrogen is the most abundant molecule in interstellar space, and is therefore of central importance to the physics and chemistry of that environment. Experiments simulating the codeposition of molecular hydrogen and water ice on interstellar grains demonstrate that amorphous water ice at 12 K can incorporate a substantial amount of H2, up to a mole ratio of H2/H2O = 0.53. We find that the physical behavior of ~80% of the hydrogen can be explained satisfactorily in terms of an equilibrium population, thermodynamically governed by a wide distribution of binding site energies. Such a description predicts that gas phase accretion could lead to mole fractions of H2 in interstellar grain mantles as high as 0.3. Accretion of gas phase H2 onto grain mantles, rather than photochemical production of H2 within the ice, could be a general explanation for recent observations of frozen H2 in interstellar ices. The possibility of interstellar grains that are rich in H2 could strongly affect our understanding of grain surface chemistry and gas-grain interactions.\r\n\r\n2. Photochemical models of Triton's atmosphere predict ethylene (C2H4) as a primary product of methane photodissociation, formed at a high enough level that it should be readily observable as a surface condensate in [...] years, yet it has not been observed. Ultraviolet photolysis experiments on C2H4 ice were done to simulate its irradiation on Triton's surface. Our results show that C2H4 ice is readily dissociated by radiation of wavelengths [...], with C2H4 ice as a primary product. Dilution in an inert N2 matrix does not affect the photochemical yield of C2H4, suggesting that the reaction C2H4 [...] C2H2 is unimolecular. Quantum yields for both the destruction of C2H4 and the formation of C2H2 are discussed, as functions of both irradiation wavelength and dilution in N2 ice. Applying these results to Triton, we find that the ambient UV flux reaching Triton's surface is more than adequate to prevent the build-up of an ethylene ice layer.\r\n\r\n3. Thermal models of icy satellite surfaces that allow the scattering and absorption of incident sunlight at significant depths predict an enhancement of subsurface temperatures over the mean surface temperature known as the solid-state greenhouse effect. We verify that a solid-state greenhouse can readily be produced in a bed of evacuated glass beads, used as a crude analog for the surface of an icy body. Measurements of the thermal and radiative properties thought to govern the size of this temperature enhancement confirm that it can be reasonably predicted from these parameters.\r\n" }, { "name": "Gazis, Carey Alice", "degree": "PhD", "year": "1995", "title": "An isotopic study of the fluid flow and thermal history of the 2.8 Ma Chegem ash-flow caldera and related intrusive rocks (Caucasus Mountains, Russia)", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11022007-110943", "creators": [ { "name": { "family": "Gazis", "given": "Carey Alice" }, "id": "Gazis-C-A", "display_name": "Gazis, Carey Alice" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "chair", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." } ], "option_major": [ "geol" ], "doi": "10.7907/mjb1-6r66", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe 2.8 Ma Chegem caldera, an 11x15 km ash-flow caldera located in the Caucasus Mountains, presents a unique opportunity to study silicic magma systems because of its combination of youth, exposure and simplicity. Rapid uplift and erosion in the region has exposed over 2 km of flatlying caldera fill, consisting of densely welded tuff (rhyolitic to dacitic), overlain by glacial deposits and andesite flows and cut by a granodiorite porphyry intrusion. The Eldjurta Granite, whose age and composition are similar to the Chegem volcanics, is exposed in an adjacent river valley 10 km to the northeast. Major Mo-W deposits located in nearby skarns have prompted mineral-exploration drillholes (to 4 km depth) in the granite. An isotopic study of the rocks of the Chegem caldera and the Eldjurta Granite has been performed to examine their petrogenesis, fluid flow and thermal histories.\r\n\r\nBiotite and sanidine [...] ages for 8 Chegem Tuff samples and the granodiorite intrusion are analytically indistinguishable at 2.82 \u00b1 0.02 Ma. Thus, the Chegem Tuff was erupted, cooled and intruded by the granodiorite within < 50,000 yrs. In the nearby Eldjurta Granite, biotite and K-feldspar [...] ages for 11 samples, including 8 from the deep drillhole (to 3970m depth) yield ages between 0.83 \u00b1 0.29 Ma and 2.78 \u00b1 0.09 Ma. A decrease in biotite ages from 1.90 \u00b1 0.24 Ma near the roof of the granite to 0.83 \u00b1 0.29 Ma at 3970m depth, apparently records the uplift and cooling history of this pluton. The ages of the upper 10 samples imply an isotherm migration rate of 13 mm/yr, probably due to a combination of downward migration of isotherms and regional uplift.\r\n\r\nOxygen isotope studies of the intracaldera tuff, including 38 samples from a continuous 1405m-stratigraphic section, reveal a striking caldera-wide stratigraphic horizon of [...]-depleted rocks in which there is extreme disequilibrium between phenocrysts and groundmass (sometimes still glassy). All quartz and feldspar phenocrysts have \"normal\" igneous [...] values of [...]8.5 and [...]7.0, respectively. Whole-rock and groundmass [...] values are as low as -4.0 and -7.7, respectively. Infrared spectroscopic analyses of glassy pumices reveal that they contain 3.3 to 4.8 wt% water. The [...] and water speciation of these glasses reflects low-temperature hydration by meteoric water, whereas some of their [...] values require higher temperature water-glass interaction.\r\n\r\nPronounced disequilibrium between coexisting feldspar and groundmass or glass has never been observed before on this scale. It requires a hydrothermal event involving large amounts of low-[...] H2O at sufficiently high temperatures and short enough time that glass exchanges thoroughly but feldspar does not. The most likely process responsible for the [...] depletions at Chegem is a high-temperature (500-600\u00b0C), short-lived (10-25 years), vigorous meteoric-hydrothermal event similar to that which occurred at the Valley of Ten Thousand Smokes, Alaska. Mass balance calculations indicate fluid fluxes of [...] mol/[...]-sec over that time period. Sr isotopic studies reveal that this hydrothermal event caused increases in whole-rock [...], possibly because the hydrothermal waters attained radiogenic Sr from crystalline rocks which were incorporated in the caldera fill during caldera collapse.\r\n\r\n[...] ratios of unaltered Chegem volcanic and intrusive rocks range from 0.7044 to 0.7060, significantly lower than values for surrounding country rock (0.7070 to 0.7319). Thus, the Chegem magmas were probably derived from the mantle or lower crust. The [...] ratios correlate with major- and trace-element trends, indicating that the Chegem magma chamber was both isotopically and compositionally zoned. Compared to the Chegem rocks, the Eldjurta Granite has higher [...] (0.7069), [...] and [...], and so must have evolved separately at some time.\r\n" }, { "name": "Gerstell, Marguerite F.", "degree": "PhD", "year": "1995", "title": "Part 1. Two radiative transfer models with terrestial applications. Part 2. Testing the porcupine plate hypothesis", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03302010-131151765", "creators": [ { "name": { "family": "Gerstell", "given": "Marguerite F." }, "id": "Gerstell-Marguerite-F", "display_name": "Gerstell, Marguerite F." } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." } ], "option_major": [ "plansci" ], "doi": "10.7907/e7ex-9x13", "abstract": "Paper I: Goody's convolution theorem for obtaining the cumulative k-distribution of a gas mixture requires stronger assumptions than the multiplicative property of band transmission; thus new experimental investigations of its effectiveness were undertaken. The convolution was found to be a useful speed optimization of k-distribution calculations at high pressures. For low pressures a variety of mixing methods were compared, all taking advantage of the idea that stratospheric lines are too narrow to overlap.\r\n\r\nAppendix I discusses the context and application of k-distribution calculations.\r\n\r\nPaper II: We used a \"quasi-random\" radiative transfer model to estimate stratospheric radiative perturbations produced by SO_2 gas, silicate ash, and H_2SO_4 aerosols after the 1982 El Chichon eruptions. One week after the last eruption, net radiative heating perturbations exceeding 20 K/day were modeled at altitudes near 26 km. Silicate ash heating may have been balanced by global enhancement of stratospheric meridional circulation, with upward velocities of 1 cm/s near Chichon's latitude. Radiative forcing by silicate ash and SO_2 gas should be included in more comprehensive models of plume evolution. Particle size distributions inferred from ash fallout rates could be wrong if radiative heating is neglected.\r\n\r\nPaper III: Uncertainties in the solar spectrum can affect modeled net heating rates in the upper stratosphere by a factor of several. Variation among Antarctic surface albedo values in common use can affect modeled net heating rates in the lower stratosphere by tens of percent. Large uncertainties in polar cloud cover are less important to stratospheric heating models. I join Marcel Nicolet in urging support for a continuous solar observation program, and recommend that future intercomparisons of stratospheric radiation models prescribe a solar spectrum, to reveal other differences.\r\n\r\nAppendix 2 gives the details of some further validation and sensitivity tests for the quasi-random model.\r\n\r\nPaper IV: The Porcupine Plate was postulated in 1986 to explain difficulties in reconstructing anomalies 21 and 24 in the North Atlantic. Its main feature was thought to be a transpressive Eocene plate boundary along Charlie-Gibbs Fracture Zone. Eliminating data that could have been affected by subsequent movements of Greenland relative to North America leads to a picture that casts doubt on the Porcupine Plate hypothesis.\r\n" }, { "name": "Huang, Weishi", "degree": "PhD", "year": "1995", "title": "Seismic Strain Rates and the State of Tectonic Stress in the Southern California Region", "advisor": "Kanamori, Hiroo; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11022007-093001", "creators": [ { "name": { "family": "Huang", "given": "Weishi" }, "id": "Huang-Weishi", "display_name": "Huang, Weishi" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "chair", "display_name": "Anderson, Donald L." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geol" ], "doi": "10.7907/P2W6-3155", "abstract": "I determine 505 fault plane solutions from the first motions of P-waves for the\r\nbackground seismicity (3.0≤ M≤6.0, 1981-1991) and collect mechanisms of major\r\nearthquakes (M≥6.0, 1927-1994) from the literature in the southern California region.\r\nThen I study the seismic strain and tectonic stress fields in individual domains (ten in\r\ntotal) by analyzing these mechanism data. The seismic strain tensors are obtained by\r\ntensorial summation of individual seismic moment tensors. The tectonic stress tensors\r\nare determined by performing numerical inversions of the slip vector data, using\r\nAngelier's (1990) method. The findings are summarized as follows:
\r\n\r\n(1) Of the 505 fault plane solutions for the 1981-1991 background seismicity, 54%\r\nare strike-slip (SF), 21 % reverse (RF), 17% normal (NF), and 8% oblique-slip\r\nfaulting (OS) events. The catalog of the major earthquakes for the period 1927-\r\n1994 also displays similar proportions of the faulting mechanisms;
\r\n\r\n(2) The similarity of the focal mechanisms can be measured by a parameter, seismic\r\nconsistency (Sc) introduced by Apperson (1991). It is defined as the ratio of the\r\nscalar moment of the total moment tensor to the sum of the scalar moments of\r\nindividual moment tensors. In southern California, the Brawley fault (BYF)\r\ndomain shows the highest Sc (0.70), whereas the White Wolf fault (WWF)\r\ndomain displays the lowest Sc (0.44). Sc values in other domains vary between\r\nthe above two values;
\r\n\r\n(3) The depths of possible low-angle faults inferred from the fault plane solutions\r\nvary from 20 km in the Transverse ranges where N-S convergence dominates, to\r\nonly 1 km in the southern Sierra Nevada fault (SSNF) domain where E-W divergence\r\ndominates. Our current data do not show the existence of a sigle unified\r\nseismically-active master detachment in the seismogenic zone;
\r\n\r\n(4) The axes of the maximum principal stress, \u03b41. are oriented N6\u00b0E \u00b111\u00b0, whereas\r\nthose of the maximum principal strain, \u03b51 are oriented N5\u00b0E \u00b121\u00b0;
\r\n\r\n(5) The strain and stress tensors are similar to each other in the Mojave (MVE), San\r\nJacinto (SJF), Elsinore (ESF), BYF, western and eastern Transverse Ranges\r\n(WTR, ETR) domains, but dissimilar in the central Transverse Ranges (CTR),\r\nNewport-Inglewood fault (NIF), WWF, and SSNF domains. Areas with small\r\nvalues of \u03a6 = (\u03b42 - \u03b43)/(\u03b41 - \u03b43) (<0.35) such as the WTR, CTR, and NIF domains are associated with more than 40% of RF events. Areas with \u03a6 values around 0.5\r\nsuch as the SJF, ETR, WWF, ESF, BYF, and MVE domains are associated with\r\nmore than 47% of SF events. The SSNF domain has a large \u03a6 (>0.65) and\r\nshows 49% of NF events, Variation of the state of stress appears to be in the\r\nTransverse Ranges where hypocenters are generally deep. Other areas show a\r\nrelatively stable state of stress throughout the seismogenic depth;
\r\n\r\n(6) Seismic fraction of deformation, \u03b7, is a measure of the deformation mode. It is\r\ndefined as the ratio of seismic strain rate to the total deformation rate. Because of\r\nthe limited seismic data, we can usually estimate the apparent instead of the real\r\nseismic fraction of deformation. Therefore, caution must be exercised in applying\r\nthe values of \u03b7 to evaluations of seismic potential, In southern California, there\r\nare some indications that areas in which seismic deformation nearly accounts for\r\nthe total deformation are typically associated with cold and rigid batholithic rocks\r\nor high seismic velocity anomalies such as in the SJF, south central MVE, WWF,\r\nand possibly the ETR domains. However, areas with low seismic velocity\r\nanomalies are not free of earthquakes as seen, for example, in the BYF domain,\r\nwhich shows \u03b7 = 0.6-1.0. Other domains show \u03b7 < 0.4. The problem of whether the\r\nmissing deformation is being released aseismically or has accumulated elastically\r\nremains to be resolved.
" }, { "name": "Jones, Laura Ellen", "degree": "PhD", "year": "1995", "title": "Part I. Broadband modeling of aftershocks from the Joshua Tree, Landers, and Big Bear sequences, southern California. Part II. Characteristics of the June 28, 1992, Big Bear mainshock from TERRAscope data: evidence for a multiple-event source", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11302011-093359502", "creators": [ { "name": { "family": "Jones", "given": "Laura Ellen" }, "id": "Jones-L-E", "display_name": "Jones, Laura Ellen" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/r040-cd43", "abstract": "The Joshua Tree, Landers and Big Bear earthquake sequences recorded on the broadband TERRAscope array in Southern California provide an unusually large data set of\r\nhigh-quality three-component broadband waveforms from small to moderately sized earthquakes. This data set offers the opportunity of detailed large-scale studies of these smaller but nonetheless potentially damaging earthquakes. What follows is a detailed study of over sixty M > 3.8 aftershocks in three regions: north and south of the\r\nPinto Mountain fault in the Mojave desert (associated with the Joshua Tree and Landers sequences), and within the San Bernardino mountains block (associated with the Big Bear sequence). Source parameters, including depths, moments, and durations, for sixty M_w > 3.8 earthquakes from the Joshua Tree, Landers, and Big Bear sequences are\r\npresented here. These events occurred between April of 1992 and November of 1994; the list of events comprises nearly every aftershock above M3.8 for which we could obtain\r\ncoherent TERRAscope data and accurate timing and location information.
\r\n\r\nChoice of velocity model affects the accuracy of the source estimations and the error associated with estimations of moment, though it appears that for Landers events recorded at stations within or near the Mojave region, a simple one-dimensional velocity model is adequate. To minimize model-associated error, however, a velocity model for the Mojave region is developed and presented. This model is used in the computation of the synthetic Green's functions used in estimates of source parameters for many of the earthquakes presented here.
\r\n\r\nThe existence of such a large data set from events in the same region (the Mojave desert) also allows systematic investigation of station effects for the five TERRAscope\r\nstations used in this study; Goldstone (GSC), Isabella (ISA), Pasadena (PAS) , Pinyon Flats (PFO), and Seven Oaks Dam (SVD). For each event, moments and durations are\r\ncomputed for each station, and these examined for systematic variations of moment with azimuth and with source-receiver distance.
\r\n\r\nMoments and durations are computed for each aftershock we study, and stress-drops inferred from these appear to vary with location, with respect to previous seismic\r\nactivity, and proximity to previous (i.e., Landers) rupture. A strong correlation of increased stress-drop with depth is noted for the Big Bear region; the same is not\r\nobserved for Mojave aftershocks.
\r\n\r\nThe June 28, 1992, Big Bear earthquake is commonly considered to be an aftershock of the earlier M_w = 7.3 Landers mainshock, and as such has been perhaps overlooked.\r\nHowever, it is a significant and enigmatic event in its own right. Its rupture history was obscured by controversy over epicentral location, lack of observed surface rupture,\r\nand the complexity of source suggested by the mainshock waveforms themselves. From overall pat terns of seismicity and long-period focal studies, rupture is generally assumed\r\nto have propagated northeast. However, mainshock locations from both strong-motion and TERRAscope data are consistent and do not lie on this assumed fault plane. Further,\r\ndirectivity analysis suggests significant energy propagating northwest along the presumed antithetic fault-plane .A combination of directivity analysis, point-source empirical Green's function analysis, and line-source directivity analysis together indicate that a two-fault event is necessary to produce the waveforms observed during the Big Bear mainshock. These results suggest that the Big Bear earthquake comprised at least two substantial subevents, with the initial subevent rupturing towards the northwest on the presumed antithetic fault plane. Several seconds later, rupture initiated on the northeast striking plane.
" }, { "name": "Koerner, David", "degree": "PhD", "year": "1995", "title": "The kinematics of circumstellar disks around T Tauri stars", "advisor": "Sargent, Anneila Isabel", "url": "https://resolver.caltech.edu/CaltechETD:etd-10312007-162008", "creators": [ { "name": { "family": "Koerner", "given": "David" }, "id": "Koerner-David", "display_name": "Koerner, David" } ], "advisors": [ { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "role": "advisor", "display_name": "Sargent, Anneila Isabel" } ], "committee": [ { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "role": "chair", "display_name": "Sargent, Anneila Isabel" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Beckwith", "given": "Steve V. W." }, "id": "Beckwith-S-V-W", "role": "member", "display_name": "Beckwith, Steve V. W." } ], "option_major": [ "plansci" ], "doi": "10.7907/css3-2v20", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nAperture synthesis images of molecular gas around the T Tauri stars, GM Aurigae, RY Tauri, DL Tauri, DO Tauri, and AS 209 are interpreted with the aid of a kinematic model of a circumstellar disk. The velocity structure and morphology of the gas strongly suggest that circumstellar disks with radii of a few hundred AU are present around all five stars. Explicit identification of kinematic patterns in the spectral line maps is achieved for the two largest disks, GM Aur and DO Tau.\r\n\r\nMaps of the relatively old T Tauri star, GM Aur, in the [...] line at 4\" resolution reveal compact gas associated with the stellar position and at the core of a larger rotating gaseous disk, 950 x 530 AU in extent. The mean velocity gradient across the disk, which is oriented along [...], is consistent with rotation about an axis at [...]. The structure observed in [...] aperture synthesis maps agrees well with synthetic maps of the gas emission generated from a model. For a disk that is inclined [...] from face on, in Keplerian rotation, a 0.80 [...] central mass (star + disk), a systemic velocity, [...], of 15.38 km [...] and a mass, 0.1 [...] is derived.\r\n\r\nA survey of T Tauri stars for circumstellar molecular gas also yields evidence for rotating disks. RY Tau, DL Tau, DO Tau, and AS 209 are detected in CO[...] emission elongated along [...], respectively, with deconvolved half-maximum radii of 110, 250, 350, and 290 AU in aperture synthesis images at [...] resolution. Three of these, RY Tau, DL Tau, and AS 209, exhibit velocity gradients parallel to this direction in first moment velocity maps, suggesting rotation of the circumstellar gas. Spectra of RY Tau and AS 209 exhibit a characteristic double-peaked shape, but that of DO Tau is dominated by the presence of high-velocity blue-shifted gas. DL Tau's spectrum has a linewidth that is too narrow [...] to be resolved into double peaks. Position-Velocity Diagrams (PVDs) constructed parallel and perpendicular to the axis of elongation imply rotation and infall or outflow, respectively. Those for RY Tau, DL Tau, and AS 209 show predominantly rotation, but some evidence of an orthogonal gradient (infall or outflow) is seen for RY Tau and AS 209. In contrast, the PVDs for DO tau suggest that its molecular emission originates predominantly from outflow or infall.\r\n\r\nRecent evidence of infall in circumstellar gas around T Tauri stars has motivated construction of a kinematic model of molecular emission from a disk of rotating and infalling gas. The velocity structure of the model disk assumes that infalling gas obeys angular momentum conservation on ballistic trajectories until it reaches the radial value, [...], where the magnitude of the rotational velocity component reaches the Keplerian value. For [...], gas is assumed to be in circular Keplerian orbits. Synthetic spectral line maps are generated by the model and cross-correlated with aperture synthesis maps for a range of the free parameters, including [...]. The best-fit value of [...] for RY Tau, DL Tau, and AS 209, approximately matches that of the outer radius of their emission, indicating these disks are predominantly in Keplerian rotation. However, emission from these stars is marginally resolved and uncertainties in the best-fit parameters are correspondingly high. In contrast, kinematic patterns are well-resolved in emission from DO Tau found in maps within a narrow, near-systemic velocity range. These are best matched by simulations from a model disk with [...] = 350 AU and an outer radius of 500 AU. This result strongly suggests that, in this case, infall from the molecular cloud onto a rotating disk is still in progress.\r\n" }, { "name": "Kohler, Monica Diane", "degree": "PhD", "year": "1995", "title": "Three-Dimensional Seismic Velocity Structure of the Earth's Outermost Core and Mantle", "advisor": "Tanimoto, Toshiro; Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10312007-090136", "creators": [ { "name": { "family": "Kohler", "given": "Monica Diane" }, "id": "Kohler-Monica-Diane", "orcid": "0000-0002-4703-190X", "display_name": "Kohler, Monica Diane" } ], "advisors": [ { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "advisor", "display_name": "Tanimoto, Toshiro" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "member", "display_name": "Tanimoto, Toshiro" } ], "option_major": [ "geophys" ], "doi": "10.7907/q3fd-fd26", "abstract": "Obtaining an accurate, detailed picture of deep-Earth structure is of fundamental importance in a wide range of geophysical applications such as fluid dynamic, magnetohydrodynamic, and mineral physics models of the Earth which incorporate properties determined from seismology. Because it is such a drastic chemical and thermal boundary layer, the nature of the core-mantle boundary has important implications for deep-Earth processes, particularly those which have their origin in the lower mantle or outer core. Seismic data provide the most direct method of sampling the Earth's interior and are, therefore, useful for determining deep-Earth material properties.
\r\n\r\nThe goal of this work has been to present models of three-dimensional, shear and compressional velocity structure which are self-consistent with the data and which can be used in other geophysical applications. The numerical inversions consisted of determining the three-dimensional structure of the outermost core and mantle of the Earth from long-period seismic waveforms. This approach is distinct from other global models of deep-Earth heterogeneity because it accounts for possible lateral heterogeneity in an outermost core layer whose properties are constrained by seismic phases which travel through the core-mantle boundary region.
\r\n\r\nThis method is different from previous core studies in several important ways: synthetic seismograms are constructed using short-period normal modes for the entire set of body-wave phases which travel through the interior of the Earth (e.g., P, PP, S, SS, SKS). Over 5000 seismograms from global digital seismic networks were collected and processed. First-order perturbations in P-wave velocities in one outermost core layer and S-wave velocities within 11 mantle layers of varying thicknesses comprised the least-squares solutions to the inverse problem. Spheroidal modes with periods between 33 and 100 sec were selected to model the body-wave portion of seismograms recorded from earthquakes which occurred globally.
\r\n\r\nThe preferred model is a 12-layered model incorporating data weighted by inverse data variance. This model produces velocity anomalies in the mantle and outermost core which are acceptable for first-order perturbation methods. The results of one-layer inversions also point to the possible existence of lateral variations in the outermost core, most likely between \u00b10.5% but not as large as \u00b15%. This model suggests that outermost core P-wave velocity perturbations accompany S-wave velocity perturbations in the lowermost mantle to produce observed variations in SKS-S and SKKS-SKS travel times. In addition, the patterns of structure vary smoothly and exhibit both large and small scale features. The spectral amplitudes fall off more rapidly for the lower mantle layers than for the upper mantle. The depth resolution displayed by the c\u2070\u2080 spherical harmonic term is 200-300 km for upper mantle layer midpoints and increases to 500-600 km for lower mantle layer midpoints.
\r\n\r\nThe data variance reduction of entire body-wave portions as well as SnKS portions of seismograms are slightly better for the 12-layered model than for the 11-layered model; however, the total variance reductions were never very large. The results of the F ratio suggest that lateral velocity variations in the outermost core layer are not zero and that the deepest layer is statistically significant. This test does not require that the extra layer lie in the outermost core (as opposed to the lowermost mantle).
\r\n\r\nThe results of pattern retrieval resolution tests support the conclusion that structure of the outermost core has been obtained independently from the mantle. Multiplicative factors have been calculated from the resolution tests using synthetic Earth models to place constraints on the amount of power leakage suspected from one region to another due to incomplete data coverage. An upper bound of 84% and a lower bound of 68% of the power of outermost core structure is, in fact, due to heterogeneity in the outermost core. By the same analysis, less than 100% of the power of structure initially placed in the lowermost mantle was retrieved in that layer after the resolution inversion. An upper bound of 60% and a lower bound of 53% of the power of lowermost mantle structure is, in fact, due to D\" heterogeneity. Almost no leakage occurred from structure initially placed in the uppermost mantle layer.
\r\n\r\nSeveral possible sources of lateral velocity anomalies for the lowest layers are explored. Invoking thermal coupling between the mantle and core, one explanation is that the fluid surfaces are deformed due to cold downwellings of lower mantle, and as a result, outermost core fluid. This will give the appearance of lateral velocity anomalies. If lateral velocity anomalies indeed exist, they are likely to be due to a combination of lateral temperature variations and chemical inhomogeneity, suggested by mineral physics relationships.
\r\n" }, { "name": "Leshin, Laurie Ann", "degree": "PhD", "year": "1995", "title": "The Abundance and Hydrogen Isotopic Composition of Water in SNC Meteorites: Implications for Water on Mars", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-091745", "creators": [ { "name": { "family": "Leshin", "given": "Laurie Ann" }, "id": "Leshin-Laurie-Ann", "display_name": "Leshin, Laurie Ann" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "geochem" ], "doi": "10.7907/36AJ-NW91", "abstract": "The water in the current martian atmosphere contains ~5 times more deuterium (D) than water on Earth (corresponding to a \u03b4D value of ~+4000) resulting from preferential loss of hydrogen relative to deuterium from the martian atmosphere. This thesis places constraints on the D/H of other martian water reservoirs by measuring the D/H of water in hydrous phases within the SNC meteorites, thought to be samples of martian igneous rocks.
\r\n\r\nResults from vacuum extractions of volatiles from bulk SNC samples by stepwise heating show the water yields to decrease and \u03b4D values to increase to well above terrestrial values with increasing temperature, indicative of mixing between terrestrial ~+2000 for Shergotty, the most Denriched sample. However, even the highest \u03b4D values measured may represent lower limits on the true values due to partial exchange with lighter terrestrial water.
\r\n\r\nD/H and water contents of individual amphibole, biotite and apatite grains in several SNC meteorites were measured using an ion microprobe. The amphiboles contain an order of magnitude less water than previously assumed, suggesting that SNC parent magmas may have been less hydrous than previously proposed. The \u03b4D values of the phases range from ~+500 to +4300. The variability and D-enriched nature of these values imply that the primary igneous phases have not retained a martian magmatic water signature. Rather, the high and variable D/H of the water in these phases, like that released at high temperatures from bulk SNC samples, is concluded to result from the interaction of the samples with D-enriched martian crustal fluids after crystallization, probably in an environment similar to terrestrial magmatic hydrothermal systems.
\r\n\r\nThe data presented in this thesis represent the first direct evidence for ubiquitous crustal water-igneous rock interaction on another planet. Moreover, the results imply that a large amount of water must have been lost from the martian system since water in the martian crust, in addition to the atmosphere, appears to reflect D-enrichment processes.
" }, { "name": "McMuldroch, Stuart", "degree": "PhD", "year": "1995", "title": "The Circumstellar Environments of FU Orionis Stars", "advisor": "Sargent, Anneila Isabel; Blake, Geoffrey A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10312007-094538", "creators": [ { "name": { "family": "McMuldroch", "given": "Stuart" }, "id": "McMuldroch-Stuart", "display_name": "McMuldroch, Stuart" } ], "advisors": [ { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "orcid": "0000-0002-4633-5098", "role": "advisor", "display_name": "Sargent, Anneila Isabel" }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "co-advisor", "display_name": "Blake, Geoffrey A." } ], "committee": [ { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "chair", "display_name": "Westphal, James A." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "co-chair", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Sargent", "given": "Anneila Isabel" }, "id": "Sargent-A-I", "orcid": "0000-0002-4633-5098", "role": "member", "display_name": "Sargent, Anneila Isabel" }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" } ], "option_major": [ "plansci" ], "doi": "10.7907/14NE-ZW09", "abstract": "Extensive observations were made of six FU Orionis objects (RNO 1B/1C, V1057 Cygni, Elias 1-12, V1515 Cygni and FU Orionis) and one pre-outburst candidate (V1331 Cygni) using the Owens Valley millimeter-wave array and the Caltech Submillimeter Observatory (CSO). Aperture synthesis maps of CO (1\u21920), \u00b9\u00b3CO (1\u21920), \u00b9\u00b3CO (2\u21921), \u00b9\u2078CO (1\u21920), and \u00b3CO (2\u21921) molecular lines and associated dust continuum emission trace the masses, kinematics and morphology of FU Orionis disks, envelopes, and outflows. Maps from the CSO delineate outflowing gas at larger spatial scales while line strengths, when input into radiative transfer models, yield column densities and fractional chemical abundances.
\r\n\r\nUnresolved 1.3 mm continuum emission from Vl331 Cygni and V1057 Cygni reveal massive circumstellar disks of 0.5 and 0.09 M\u2609, respectively. Maps of the 2.6 and 3.1 mm continuum emission reveal that RNO 1C is surrounded by a flattened dusty envelope, 5000 AU in size, with mass \u2a7e 1.1 M\u2609. No evidence is seen for multiple systems with orbital periods \u2273 4 x 10\u2074 years years.\r\n\r\nAll sources, with the exception of RNO 1B/1C are surrounded by large molecular gas envelopes between 2000-7500 AU in size, with masses ranging from 2 x 10\u207b\u00b3 to 0.36 M\u2609. Aperture synthesis maps suggest the envelopes are asymmetrically distributed. Gas kinematics around V1057 Cygni and Elias 1-12 suggest, but do not demand, that this material is rotating and possibly infalling.
\r\n\r\nOf the seven sources observed, all but FU Orionis show signs of outflowing molecular gas. No high velocity clumps or \"bullets\" are seen towards any of the sources. V1331 Cygni, V1057 Cygni, and V1515 Cygni possess arc or ring-like outflow morphologies, while emission from RNO 1B/1C and Elias 1-12 delineates filled outflow shells. All emission patterns are consistent with outflow shells being viewed at different angles. Although based on the statistics of small numbers, observations suggest shells are seen more frequently around FUors than T Tauri stars. Shell formation may therefore be caused by time-dependent events in the outflow. Cross-cutting arcs within the shell structure, seen towards RNO 1B/1C and Elias 1-12, are probably ridges of gas swept-up by the most recent outbursts, confirming the repetitive nature of FUor outbursts. Estimates of the dynamical ages of the arcs suggest that the interval between outbursts is ~5 x 10\u00b3 and 1.3 x 10\u2074 years for RNO 1B/1C and Elias 1-12 respectively, consistent with previous estimates of FUor cycling times.
\r\n\r\nComparable envelopes and shell-like outflow structure are seen towards embedded sources while envelopes surrounding T Tauri stars are smaller and less massive. This suggests FU Orionis objects are transition sources between deeply embedded and optically visible stars. The strength of the molecular outflow emission is correlated with the mass of the extended envelope; the outflow has evacuated molecular gas leaving less to be swept-up by subsequent outbursts, while envelope masses are smaller since less material is available for accretion.
\r\n\r\nChemically, fractional abundances of SiO and methanol are enhanced towards RNO 1B/1C by over an order of magnitude. Methanol is enhanced relative to HCN and H2CO towards Elias 1-12. Such large changes in fractional abundances must be caused by chemical processing. The SiO enrichments may be produced by sputtering or evaporation of dust grains in regions of directly shocked material or by chemical reactions of SiH4 after sublimation from grain surfaces. Methanol enrichments are difficult to produce in strong shocks, and may be caused by low velocity grain-grain collisions. For RNO 1B/1C, evaporation of the entire methanol rich grain mantles seems to be required; while for Elias 1-12 mantle phase changes from an amorphous ice to a clathrate hydrate can be invoked, expelling the methanol, with smaller molecules remaining trapped in the clathrate. Such low velocity collisions probably occur in the turbulent shear zones surrounding the outflowing gas.
" }, { "name": "Ray, Terrill Wylie", "degree": "PhD", "year": "1995", "title": "Remote monitoring of land degradation in arid/semiarid regions", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-083125", "creators": [ { "name": { "family": "Ray", "given": "Terrill Wylie" }, "id": "Ray-T-W", "display_name": "Ray, Terrill Wylie" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Blom", "given": "Ron" }, "id": "Blom-R", "role": "member", "display_name": "Blom, Ron" } ], "option_major": [ "plansci" ], "doi": "10.7907/65EA-Y568", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nLand degradation is a serious and growing problem on a world-wide scale -- 11% of the Earth's vegetated surface having suffered serious damage in the last 45 years. Human activity, especially sprinkler irrigation agriculture, can cause dramatic changes in arid regions as the fragile natural plant cover is stripped off and its root system destroyed in the process of cultivation. Satellite and airborne remote sensing data covering the Manix Basin of Eastern California over the last two decades shows that abandoned fields there suffered progressive degradation, as the topsoil eroded due to the lack of protective plant cover. Blowing sand buried and disrupted the downwind plant cover, which caused the downwind area to lose its protection against wind erosion and expanded the region of damage.\r\n\r\nBecause the amount and kind of plant cover is an important marker both of where wind erosion has occurred and where it is likely to occur in the future, especially designed satellite monitoring systems should be able to sense to signatures of undisturbed and disturbed vegetation cover in arid regions. However, this problem cannot be addressed by standard vegetation indices, because of the adaptation of arid region plants to the scarcity of water. Furthermore, weekly to monthly sampling will be necessary because blowing sand visible to satellite remote sensing is highly dependent on the local weather, and this can change within a few months. A new vegetative index suitable for arid regions is proposed for the wavelength region from 0.4-1.0 [...].\r\n\r\nThe detection and identification of arid region plant communities requires a highly calibrated remote sensing system with higher spectral resolution than that currently offered by Landsat Thematic Mapper. The way in which regions of blowing sand can appear and disappear with rapidity demonstrates the need for a remote monitoring system that can survey large areas on a regular basis. Such a system must be supported by focused ground observations and a continuing analysis of the satellite data.\r\n" }, { "name": "Stephens, Stuart Keller", "degree": "PhD", "year": "1995", "title": "Carbonate formation on Mars : experiments and models", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechETD:etd-11052007-080036", "creators": [ { "name": { "family": "Stephens", "given": "Stuart Keller" }, "id": "Stephens-S-K", "display_name": "Stephens, Stuart Keller" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "plansci" ], "doi": "10.7907/PSFY-MZ22", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe experiments reported in this thesis were motivated by a desire to explain the small present [...] pressure in the Martian atmosphere, given the hypothesis that Mars once possessed a much denser [...] atmosphere. We adopted the premise that carbonate production on the surfaces of regolith particles, mediated by small amounts of [...], might explain the decline in the surface pressure over geologic timescales.\r\n\r\n\tWe exposed powders [...] of basalt glass, and of monominerallic diopside, olivine, plagioclase, and quartz, to conditions simulating the past and present surface of Mars ([...], and [...] contents equivalent to <1 to >5000 monolayers on particle surfaces). A sensitive manometer was used to acquire precise measurements of pressure over periods of [...] days. Initial pressure drops were attributed to adsorption of [...] on particle surfaces and dissolution of [...]. Continuing uptake of gas in most experiments suggested that [...] reacted with powders to form carbonate. Fits to [...] after [...] day gave [...], implying logarithmic reaction kinetics (i.e., reaction rate, [...]. Subsequent fits to [...], incorporating adsorption and dissolution, gave rates of D = 0.01-2 monolayers [...] per [...], with [...] day. Reaction amounts totaled [...] monolayers. Parabolic kinetics, arising from diffusion through a product layer, probably did not exceed P(t) [...]\r\n\r\nRates varied with sample composition (basalt and diopside > olivine > plagioclase and quartz). Basalt glass was not more reactive than diopside. Basalt powder pretreated with weak acid displayed rates reduced by over an order of magnitude (although diopside did not), suggesting something removed by acid contributes to [...] uptake. Rates increased with [...] content, temperature, and CO2 pressure, vA fit to data for basalt at 295 K gave [...], where H is [...] content in monolayers and D is in monolayers [...] per log [...]t; at 248-263 K, the-effect of [...] is stronger: [...]. [...] for \"dry\" experiments; no lower limit was put on [...] required for reaction.\r\n\r\nReflectance spectra at mid-infrared wavelengths [...] were obtained for all \"dry\" and \"vapor\" experimental powders, and ratioed to starting spectra for maximum sensitivity to added phases. Prominent spectral features near [...] in basalt and diopside coincided with [...] absorptions at 6.9 [...] for calcite. Additional absorptions near 6.1 [...] in basalt and 4.0 [...] in diopside were also consistent with the presence of calcite. Absorption ratios near 7 [...] ranged from [...] (corresponding to perhaps 3 wt% added calcite) to as little as [...], below which we were unable to identify added phases. There was a clear positive correlation between absorption ratios and experimental [...] uptakes (and hence [...] content), strengthening the conclusion that carbonate--probably calcite but perhaps magnesite or dolomite--formed in pressure-drop experiments.\r\n\r\nOur experiments suggested that this process does occur, but modeling and application to Mars indicated that it may be insufficient to explain the carbonate production required to reduce atmospheric pressure by [...] bar over geologic time. The principal difficulty lies in the lack of evidence for the reaction proceeding easily beyond one monolayer of product. Although some experiments displayed evidence for the growth of more than a monolayer, they also showed that this arises in a regime of logarithmic reaction kinetics, where [...] uptake is limited by declining surface area available for reaction. For a global layer of basalt powder, only high specific surface area [...], a deep regolith (>100 m), or plentiful [...] (equivalent to films >5 monolayers thick) allow total [...] stored as carbonate to exceed [...] mb. Diffusion-limited kinetics were not ruled out for timescales much longer than experimental durations, and models with thicker carbonate growths show that this could account for storage of an early Martian atmosphere.\r\n\r\nOther mechanisms for the loss of [...] may also contribute in the transition to the present surface pressure. Or, Mars may simply never have had a dense, [...] atmosphere, although this requires explanations other than a [...] greenhouse for the morphological features used to support the hypothesis of a warm, wet early Mars. If large amounts of carbonate minerals do represent a sink for atmospheric [...], the question of their location on the surface still remains since they have not been confirmed spectroscopically.\r\n" }, { "name": "Takata, Toshiko", "degree": "PhD", "year": "1995", "title": "Three-dimensional analysis of impact processes on planets", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11012007-084634", "creators": [ { "name": { "family": "Takata", "given": "Toshiko" }, "id": "Takata-T", "display_name": "Takata, Toshiko" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/2jtf-x438", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis thesis consists of four chapters. The first chapter describes the numerical method known as Smoothed Particle Hydrodynamics (SPH), that is used in present calculations relating to oblique impact on a planet with an atmosphere. Numerical test results are presented to demonstrate the validity of the present computer code. The SPH code is applied to Comet Shoemaker-Levy 9 impact on Jupiter, particularly the disintegration of the comet in the Jovian atmosphere and the evolution of the vapor plume. These calculations are described in chapter II. In order to interpret the phenomena observed in the impacts, numerical predictions are compared with the observational data. These comparisons are summarized in chapter III. Chapter IV considers analytical models of the formation of radar dark and/or bright halos surrounding impact craters discovered on Venus as a result of the Magellan mission. The surface features caused by the atmospheric shock waves associated with impacts are modeled and applied to the observed Venusian radar features.\r\n\r\nPaper I:\r\n\r\nThe SPH method used for a series of impact calculations is tested. From the performance tests, we infer that the tree structure method for a vectorizing computer code can be applied when the number of particles, N, [...]. Most of the calculations are performed using a CRAY-YMP at Jet Propulsion Laboratory or a CRAY-C90 at Goddard Space Flight Center. Tests for one-dimensional shock propagation show that the developed code yields an error of less than several percent in density and pressure, upon comparison with the analytical impedance-match solution. For spherical, three-dimensional impact of a projectile upon a silicate half-space, the shock wave attenuation of pressure and density calculated by the SPH code is very similar to the results obtained with a finite-difference Lagrangian continuum code (previously obtained by Ahrens and O'Keefe, [1977]). For example, the shock pressures in the near field agree within 15 % differences, whereas the shock pressure in the far field, at 10 projectile radii, differs by a factor of 2 from that calculated previously using a two-dimensional axisymmetric Lagrangian code.\r\n\r\nPaper II:\r\n\r\nThe impact of fragments of Comet Shoemaker-Levy 9 on Jupiter and the resulting vapor plume expansion are investigated by conducting three-dimensional numerical simulations using the Smoothed Particle Hydrodynamics (SPH) method. An icy body, representing the cometary fragments, with a velocity of 60 km/sec and a diameter of 2 km can penetrate to 350 km below the 1-bar pressure level in the atmosphere. Most of the initial kinetic energy of the fragment is transferred to the atmosphere between 50 km and 300 km below the 1-bar pressure level. The shock-heated atmospheric gas in the wake is totally dissociated and partially ionized. Scaling our SPH results to other sizes indicates that fragments larger than [...] 100 m in diameter can penetrate to below the visible cloud decks. The energy deposited in the atmosphere is explosively released in the upward expansion of the resulting plume. The plume preferentially expands upward rather than horizontally due to the density gradient of the ambient atmosphere. It rises ...] km in [...] seconds. Eventually the total atmospheric mass ejected to above 1 bar is [...] 40 times the initial mass of the impactor. The plume temperature at a radius ~ [...] km is > [...] K for [...] seconds, for a 2-km fragment. We predict that impact-induced plumes will be observable with the remote sensing instruments of the Galileo spacecraft. As the impact site rotates into the view of the earth some 20 minutes after the impact, the plume expansion will be observable using the Hubble Space Telescope and from visible and infrared instruments on ground-based telescopes. The rising plume reaches ~ 3000 km altitude in ~ ten minutes and will be visible from the earth.\r\n\r\nPaper III:\r\n\r\nPreliminary observational data from the impact of fragments of Comet Shoemaker-Levy 9 (SL9) are compared with smoothed particle hydrodynamic (SPH) and radiative calculations to determine the energies of individual SL9 fragments and the equivalent diameter of the SL9 progenitor. The Hubble Space Telescope (HST) images of the G impact-induced plume demonstrate that it achieved a height of ~3300 km [Hammel et al., 1994]. This is in close agreement with the SPH calculations for a 7 x [...] erg or 2 km \u00b1 0.3 km diameter solid ice impactor at 60 km/sec. Comparison of the R fragment impact-induced plume brightness in the 8 to 12 [...] band, as recorded by the NASA Infrared Telescope Facility (Mauna Kea, HI) [Orton et al. 1994], with our radiative predictive calculations yields a kinetic energy of 4 x [...] ergs or a diameter of 1.6 \u00b1 0.3 for the R fragment. Using the G and R impacts to calibrate Weaver et al.'s [1994] detailed photometric determination of the relative diameters of pre-Jovian impact projectiles in the SL9 chain from HST images yields revised values for the 11 largest fragment diameters. Adding the inferred masses from the plume and radiative calibration of Weaver et al.'s catalog yields an SL9 progenitor equivalent (ice) diameter of 4.1 \u00b1 0.6 and 3.5 \u00b1 0.5 km, respectively. This compares to a 7.7 km diameter progenitor inferred by Weaver et al. and a 2 km diameter progenitor obtained using tidal break-up modeling by Scotti and Melosh [1993] and Asphaug and Benz [1994]. We also examined the inferred position of Jupiter derived H2O impact ejecta from the hypothetical (3 to 5 bar) cloud deck and find that although Jupiter derived impact induced plumes having radius of > [...] km and achieved altitudes of 3 x [...] km, the contained Jovian water ejecta is restricted to the interior of the plume and would be masked from Earth observations by the surprisingly opaque plume. On the basis of Bjorker et al.'s [1994] observations of thirty minutes' water emissions from the plumes of the impact sites of fragments G and K Field and Ferraro's [1994] analysis which indicates that even if SL9 fragments are 50% porous, upon being subjected to entry, the ram pressures, upon reaching the level of 1 bar, squeeze-out virtually all porosity and the present, self-consistent kinemetric and radiative coupling of the SL9 impactor, we conclude: 1) there is no evidence that SL9 was anything but a comet as first suggested by the coma, 2) penetration of 2 km diameter fragments occurs to depths of ~ 300 km, even for a porous comet, as calculated by the present SPH method and by other groups using finite difference methods [Zahnle and MacLow, 1993, Boslough et al., 1994].\r\n\r\nPaper IV:\r\n\r\nA paraboloidal bow shock model was developed in order to estimate the surface distribution of gas shock-induced modifications surrounding venusian impact craters. We applied two-dimensional oblique shock dynamics to describe a three-dimensional paraboloidal - shaped bow shock impinging upon an assumed incompressible venusian surface. The effects of the hypersonic atmospheric shock acting on the venusian surface are considered in terms of maximum gas pressure, the density, the particle velocity, and the temperature, for varying angles and velocities of impact. The maximum boulder size that can be saltated by the shockwave induced gas flow and the degree of mutual collision of the surface materials are also considered. The present calculations quantitatively predict the areal extent of the gas shock perturbed surface for normal and oblique impact as a function of impact angle and velocity, and radii of impactors. For a 1 km-radius stony meteorite impacting at 20 km/s, the radius of the disturbed area extends ~ 10-17 times the 3-5 km crater radius. The perturbed surface affects the surface radar properties and the present results can provide an explanation of the wide \"dark/bright halos\" surrounding some of venusian impact craters observed via Magellan imagery. For example, a ~ 50 km radius bright halo within a ~ 20 km dark halo is observed around the 3.1 km-radius crater located at 16.5\u00b0 north latitude and 334.4\u00b0 longitude. The average value of the radar backscatter cross section of the ~ 20 km radius dark halo indicates that ~ 50 cm-thick layer of porous lithologic material is superimposed upon the undisturbed surface. The occurrence of the bright halo indicates that the surface roughness in this region is ~ 30% greater than that of the surrounding original surface. The present model can relate the observed crater halo radii to the impact parameters, such as impact velocity and angle, and the impactor radius.\r\n" }, { "name": "Tryka, Kimberly A.", "degree": "PhD", "year": "1995", "title": "Nitrogen on Triton and Pluto", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-10302007-142312", "creators": [ { "name": { "family": "Tryka", "given": "Kimberly A." }, "id": "Tryka-K-A", "display_name": "Tryka, Kimberly A." } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/rpj9-kj04", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nNitrogen has been detected on the surfaces of two objects in the solar system, Triton and Pluto. To better understand the surfaces of these two bodies I have made measurements of the spectrum of solid nitrogen at temperatures applicable to Triton and Pluto, over a wavelength region which encompasses both the fundamental vibrational transition of N2, at 4.294 [...], and its first overtone, at 2.148 [...]. These measurements show that the appearance of the N2 bands is a function of temperature. I have used this temperature dependence, in conjunction with observational data and spectral modeling techniques, to determine the temperature of N2 on Triton and Pluto. The temperature I derive for Triton, 38\u00b11 K, is in agreement with measurements made by the Voyager 2 spacecraft. The temperature determined for Pluto is 40\u00b12 K, slightly warmer than for Triton. Observations of Pluto's thermal flux have not been able to constrain Pluto's temperature well; estimates in the literature run from 30 to 60 K. To determine if the spectroscopically derived temperature for nitrogen on Pluto is consistent with the published thermal fluxes of Pluto I have modeled the expected thermal flux assuming that the N2 is contained in symmetric polar caps and that the equatorial region is bare of nitrogen. With these assumptions I find that the modeled flux of Pluto fits all the published thermal flux measurements if the polar caps extend to \u00b120\u00b0 latitude, and if the equatorial region has a bolometric albedo [...] 0.2.\r\n" }, { "name": "Watada, Shingo", "degree": "PhD", "year": "1995", "title": "Part I. Near-source acoustic coupling between the atmosphere and the solid earth during volcanic eruptions. Part II. Nearfield normal mode amplitude anomalies of the Landers earthquake", "advisor": "Kanamori, Hiroo; Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10302007-082547", "creators": [ { "name": { "family": "Watada", "given": "Shingo" }, "id": "Watada-S", "display_name": "Watada, Shingo" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "geophys" ], "doi": "10.7907/JSE5-G397", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis thesis consists of two chapters. In the first chapter the normal mode theory of a spherical Earth model is extended to include the atmosphere and the theory is applied to understand the observation of air-ground acoustic coupling during volcanic eruptions and to construct synthetic ground motions. In chapter II, the fully developed normal mode theory of 3D Earth is applied to the nearfield amplitude anomalies of the surface waves of the Landers rearthquake. Synthetic seismograms for the recently-available three dimensional seismic global Earth models are constructed using the normal mode theory and compared with observations. The horizontal scale and the location of lateral seismic velocity variations which caused the amplitude anomalies are examined in detail.
\r\n\r\nPart I:
\r\n\r\nLong-period harmonic Rayleigh waves were observed by worldwide seismographic networks during the eruption of Mt. Pinatubo in 1991. It has been suggested that these Rayleigh waves were excited, through atmospheric-solid Earth coupling, by atmospheric oscillations set off by the eruption. We investigated this problem using the Earth's normal modes computed for a spherically symmetric Earth model with the solid (elastic) Earth, ocean and atmosphere. These normal modes represent Rayleigh waves in the solid Earth, tsunamis in the ocean, and Lamb waves, internal acoustic waves and internal gravity waves in the atmosphere. Since the atmosphere has a low sound velocity channel below the thermosphere (altitude 90 km), two characteristic acoustic modes with periods of 230 and 270 s exist. The energy coupling between atmospheric acoustic waves and Rayleigh waves is efficient because of the proximity of the horizontal phase velocities of these waves. The energy distribution suggests that a low altitude volcanic eruption would excite the 230 s mode more strongly than the 270 s mode. This is consistent with the observation for the Pinatubo eruption. In contrast, the internal gravity mode has a period of 300 s. The barographic oscillation at a period of 300 s observed for the 1980 Mt. St. Helens eruption is probably this mode. However, because of its slow phase velocity, it would not couple to Rayleigh waves efficiently, and cannot be detected with seismographs.
\r\n\r\nPart II-A:
\r\n\r\nThe 1992 Landers earthquake ([...]=7.3) occurred in the middle of the TERRAscope network. Long-period Rayleigh waves recorded at TERRAscope stations [...] after travelling around the Earth show large amplitude anomalies, one order of magnitude larger than spherical Earth predictions up to a period of about 600 s. The ground motions over the epicentral region at and after the arrival of R4-5 are in phase at all stations. These observations are inconsistent with the nearly vertical strike slip mechanism of the Landers earthquake. Synthetic seismograms for a rotating, elliptic and laterally heterogeneous Earth model calculated by the variational method agree well with the observed waveforms. Calculations for various 3D Earth models demonstrate that the amplitudes are very sensitive to the large scale aspherical structure in the crust and the mantle. The anomalies for modes shorter than 300 s period can be explained by lateral heterogeneity shallower than the upper mantle. Rotation of the Earth and lower mantle heterogeneity are required to explain mode amplitudes at longer periods. Current whole mantle seismic tomographic models can fully explain the observed amplitudes longer than 300 s. To assess the effect of the high order lateral heterogeneity in the mantle, more precise estimate of the crustal correction is required.
\r\n\r\nPart II-B:
\r\n\r\nWe modeled the interaction of the source mechanism and the station location with large-scale lateral heterogeneity using the splitting matrix of an isolated multiplet and the 'source-receiver function' whose spherical harmonic coefficients are given by [...] where s and t are angular and azimuthal order numbers respectively. For a short period of time waveform perturbation is proportional to the integral of products of the splitting function with harmonic coefficients [...] and the 'source-receiver' function. For the Landers earthquake and TERRAscope stations source-receiver geometry, the 'source-receiver function' is dominated by the low-order components, paticularly l = 2, m = \u00b12 in the epicentral coordinates. This beach-ball like pattern is the same for all the near-source stations located in different quadrants of the strike-slip mechanism. The two maxima of the 'beach ball' pattern coincide with the locations of the degree 2 maxima of the splitting functions; western Pacific and east of South America. These features explain the weak dependence of the waveforms on higher order lateral heterogeneity and similarity of waveforms over the epicentral region. The location and the source mechanism of the Landers earthquake relative to the large scale lateral heterogeneity l = 2, including the variations of the cruatal structures, are responsible for the cause of amplitude anomalies near the epicenter. However, the amplitude near the epicenter of an earthquake with a thrust fault type mechanism, for example the Northridge earthquake, is explained well with a spherical Earth model.
\r\n" }, { "name": "Banfield, Donald J.", "degree": "PhD", "year": "1994", "title": "A dynamical history of the inner Neptunian satellites and Martian weather : Viking observations and M.O. data assimilation techniques", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03022006-132818", "creators": [ { "name": { "family": "Banfield", "given": "Donald J." }, "id": "Banfield-Donald-J", "display_name": "Banfield, Donald J." } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/07dr-qq38", "abstract": "We examine a scenario involving the capture origin of Triton, and infer the dynamical history of the Neptune satellite system. Triton's post-capture orbit forced chaotic perturbations on the original inner satellites of Neptune, leading to their mutual collisions and self-destruction. Neptune's current inner satellite system re-formed equatorially after Triton's orbital circularization. The 4.7\u00b0 inclination of 1989N6 is probably due to a temporary inclination resonance. The 2:1 secondary resonance of the 1989N6-1989N3 12:10 resonance would eject 1989N6 at 4.7\u00b0, matching the observations. We have established limits for Neptune's Q: 12,000 < QN < 330,000.\r\n\r\nWe examine a steady-state scheme for data assimilation in the context of a single, sun-synchronous, polar-orbiting satellite. The optimal (Wiener) gains are steady in time, and equivalent to those of a Kalman filter. The gains are computed by iteration using prior estimates to assimilate simulated observations of one model run ('Truth') into another run. The resulting prediction errors then form the next estimate of the gains. In model tests, the scheme works well even if only the mass field is observed. Although the scheme was developed for Mars Observer, it should be applicable to data retrieved from Earth atmosphere satellites, e.g., UARS.\r\n\r\nSpring and fall Viking IRTM T15 observations are used to estimate the Martian weather correlation length scale in the range 0.5-1 mbar. The results are important in providing a benchmark for validating Martian GCMs, determining the optimal placement of a network of landers, and guiding data assimilation efforts. Atmospheric temperature observations are used to compute an atmospheric mean state, which is subtracted from the observations to yield weather temperature residuals. These residuals are correlated with each other to determine the weather temperature correlation length scale (~ 1500km) and the weather temperature variance (~ 4-11K2). This work suggests that ~110 landers are needed to globally observe Mars' weather." }, { "name": "Betts, Bruce Harold", "degree": "PhD", "year": "1994", "title": "Thermal and visible studies of Mars using the Termoskan data set", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02112013-110255064", "creators": [ { "name": { "family": "Betts", "given": "Bruce Harold" }, "id": "Betts-B-H", "display_name": "Betts, Bruce Harold" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "chair", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Paige", "given": "David" }, "id": "Paige-P", "role": "member", "display_name": "Paige, David" } ], "option_major": [ "plansci" ], "doi": "10.7907/M9T5-G181", "abstract": "In February and March, 1989, the Termoskan instrument on board the Phobos '88\r\nspacecraft of the USSR acquired the highest spatial resolution thermal data ever obtained\r\nfor Mars, ranging in resolution from 300 m to 3 km per pixel. It simultaneously obtained\r\nbroad band visible channel data. The panoramas cover a large portion of the equatorial\r\nregion from 30\u00b0S to 6\u00b0N. New and unique analyses facilitated by Termoskan are\r\npresented here. In addition, this thesis describes the instrument, data, and validation.\r\nTermoskan thermal data shows good temperature agreement with Viking IRTM.\r\nHowever, conversion of Termoskan visible data to bolometric albedo is problematic.
\r\n\r\nUtilizing the Termoskan data, I recognized a new feature on Mars: ejecta blanket\r\ndistinct in the thermal infrared (EDITH). Virtually all of the more than 100 such features\r\ndiscovered in the Termoskan data are located on the plains near Valles Marineris. I\r\ncompiled a data base of 110 EDITH and non-EDITH craters ranging in diameter from 4.2\r\nkm to 90.6 km. EDITHs have a startlingly clear dependence upon terrains of Hesperian\r\nage, and show almost no other correlations within the data base. The Hesperian terrain\r\ndependence cannot be explained by either atmospheric or impactor variations. Wind\r\npatterns or locally available aeolian material cannot provide a single overall explanation for\r\nthe observed variations. I postulate that most of the observed EDITHs are due to\r\nexcavation of thermally distinctive Noachian age material from beneath a relatively thin\r\nlayer of younger, more consolidated Hesperian volcanic material. The plausibility of this\r\ntheory is supported by much geological evidence for relatively thin near-surface Hesperian\r\ndeposits overlying massive Noachian megabreccias on the EDITH-rich plains units. I\r\nsuggest that absence of thermally distinct ejecta blankets on Noachian and Amazonian\r\nterrains is due to absences of distinctive near-surface layering. Thermally distinct ejecta blankets are excellent locations for future landers and remote sensing because of relatively dust free surface exposures of material excavated from depth.
\r\n\r\nAlso included in the thermal images are observations of several major channel and\r\nvalley systems including significant portions of Shalbatana, Ravi, Al-Qahira, and Ma'adim\r\nValles, the channel south of Hydraotes Chaos, channel material in Eos Chasma, and small\r\nportions Simud, Tiu, and Ares Valles and channel material in Gangis Chasma.\r\nSimultaneous broad band visible data exists for all but Ma'adim Vallis. I find that most of\r\nthe channels and valleys have higher inertias than their surroundings, consistent with\r\nprevious thermal studies of martian channels. I show for the first time that thermal inertia\r\nboundaries closely match all flat channel floor boundaries. Using Viking albedos,\r\nTermoskan temperatures, and thermal modelling, I derive lower bounds on typical channel\r\nthermal inertias ranging from 8.4 to 12.5 (10^(-3) cal cm^(-2) s^(-1/2) K^(-1). Lower bounds on\r\ninertia differences with the surrounding heavily cratered plains range from 1.1 to 3.5.\r\nAtmospheric and geometric effects are not sufficient to cause the inertia enhancements. I\r\nagree with previous researchers that localized, dark, high inertia areas within channels are\r\nlikely aeolian in nature. However, thermal homogeneity and strong correlation of thermal\r\nboundaries with the channel floor boundaries lead me to favor non-aeolian overall\r\nexplanations. Small scale aeolian deposition or aeolian deflation may, however, play some\r\nrole in the inertia enhancement Channel floor inertia enhancements are strongly\r\nassociated with channels showing fretted morphologies such as wide, flat floors and steep\r\nscalloped walls. Therefore, I favor fretting processes over catastrophic flooding for\r\nexplaining the inertia enhancements. Fretting may have emplaced more blocks on channel\r\nfloors or caused increased bonding of fines due to increased availability of water.\r\nAlternatively, post-channel formation water that may have been preferentially present due\r\nto the low, flat fretted floors may have enhanced bonding of original fines or dust fallout\r\nThe coupling of both EDITHs and channel inertias to morphology is unlike most sharp\r\nMartian inertia variations which are decoupled from observed surface morphology.
\r\n\r\nTermoskan observed morning limb brightening in the thermal channel, but not in\r\nthe visible channel. The thermal morning limb brightening is likely due to a water ice or\r\ndust haze that is warmer than the surface at the time of the observations. A water ice haze\r\nwith a scale height of 5 km could match the observations. Visible scattering is observed to\r\nbe significant on morning and evening limbs out to 60 or 70 km. Localized high altitude\r\nstratospheric clouds are observed in the visible channel.
\r\n\r\nThe Termoskan data show that the highland-lowland boundary in the Aeolis\r\nQuadrangle appears strongly correlated with a high-low thermal inertia boundary. The\r\nsharpness of that boundary varies from less than 4 km to more than 50 km. In all cases,\r\ninertias continue to decrease gradually for many tens of km into the lowlands. Several\r\nother large scale thermal boundaries are also observed in the data.
\r\n\r\nTermoskan observed fine thermal structure on the flanks of Arsia Mons and\r\nelsewhere, which represent examples of interesting and significant thermal variations seen\r\nat the limit of Termoskan's spatial resolution. Sharp variations and boundaries imply there\r\ncannot be global scale dust blanketing deeper than about one centimeter, if that.
\r\n\r\nTermoskan obtained the first ever thermal images of Phobos' shadow on the\r\nsurface of Mars, along with simultaneous visible images. The best observed shadow\r\noccurrence was on the flanks of Arsia Mons. For this occurrence, I combined the\r\nobserved decrease in visible illumination of the surface with the observed decrease in\r\nbrightness temperature to calculate thermal inertias of the Martian surface. Most of the\r\nderived inertias fall within the range 0.9 to 1.4, corresponding to 5 to 10 micron dust\r\nparticles for a homogeneous surface. Dust at the surface is consistent with previous\r\ntheories of Tharsis as a current area of dust deposition. Shadow derived inertias are\r\nsensitive to mm depths, whereas diurnally derived inertias are sensitive to cm depths. The\r\nshadow derived inertias are very similar to Haberle and Jakosky [1991] atmospherically\r\ncorrected Palluconi and Kieffer [1981] Viking IRTM diurnally derived inertias. Thus, if\r\nnear surface layering exists at all in this region, it is not very significant.
\r\n\r\n\r\n" }, { "name": "Butler, Bryan Jay", "degree": "PhD", "year": "1994", "title": "3.5-cm radar investigation of Mars and Mercury : planetological implications", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:01252013-144953787", "creators": [ { "name": { "family": "Butler", "given": "Bryan Jay" }, "id": "Butler-B-J", "display_name": "Butler, Bryan Jay" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/MSRK-FF90", "abstract": "Bistatic radar observations have been made using the\r\ncombined VLA/Goldstone radar instrument at X-Band wavelength (near 8500\r\nMHz). This thesis contains a description of the instrument, observations, data\r\nreduction, and implications of some of the measurements. While the instrument\r\nhas been used to probe many objects, discussion will be restricted to the data sets\r\nfor Mercury and Mars. This technique has provided the first unambiguous radar\r\ncross section maps of both planets, with surface resolutions as good as 150 km for\r\nMercury, and 100 km for Mars. The analysis of the radar cross section maps has\r\nprovided a rich harvest of new information about the surface and near-surface of\r\nboth planets.
\r\n\r\nMars was observed twice during the opposition of 1988, and 3 times during the\r\nopposition of 1992/93. During the 1988 observations, the subearth latitude was\r\n\u223c -24\u00b0, providing a good view into the south polar regions. The Martian season\r\nat the time was mid southern summer (L_s \u223c 295\u00b0), and thus the seasonal CO_2\r\nice cap had sublimated away, exposing the residual south polar ice cap (RSPIC).\r\nThe RSPIC was the area with the highest cross section on the planet in 1988,\r\nwith a peak normalized cross section of 0.716. This is incredibly high, especially\r\nconsidering that it was at an incidence angle of \u223c 66\u00b0 at the time. The RSPIC\r\nalso exhibited the odd characteristic that throughout much of its extent, more echo\r\nenergy was received in the same sense circular (SS) polarization as that transmitted\r\nthan in the opposite sense (OS), a so-called polarization inversion. This is a\r\ncharacteristic which has also been observed on the Galilean satellites, and on a\r\nportion of Greenland, and may be true for all cold, clear icy regions. This seems\r\nto be a result of the radar wave penetrating into a relatively lossless medium containing\r\nmany volume scatterers. In the case of the RSPIC, the lossless medium is\r\nice, whether CO_2 or H_2O, and the scattering centers are most probably cracks and\r\nvoids in the ice. Simulations indicate that the radar wave penetrates down to 10's\r\nof meters into the ice layer, implying that at the time the RSPIC was very clean,\r\ni.e., less than \u223c 1% volume fraction of contaminating dust, to that depth.
\r\n\r\nDuring the 1992/93 observations, the subearth latitude was \u223c +6\u00b0 to \u223c +9\u00b0,\r\nproviding a tolerable view into the north polar regions. The Martian season at the\r\ntime was early northern spring (L_s \u223c20\u00b0), and thus much of the seasonal CO_2 cap\r\nwas present, which covered the residual north polar ice cap (RNPIC). No regions\r\nwith enhanced cross section were found in the north polar regions, in stark contrast\r\nto the south. Fits to a sensible backscatter function provide an indication of slight\r\ncross section enhancements near the Chasma. Borealis, but the reliability of the fits\r\nremains in question due to the restricted incidence angle range of the data. There\r\nare at least 3 possible reasons for the fact that the north polar regions show no\r\ncross section enhancements: 1 - there is some fundamental difference in the structure\r\nand/or composition (amount of dust contaminant) of the two residual caps,\r\n2 - the seasonal CO_2 cap which was present during the north polar experiments\r\nabsorbed enough of the incoming radar energy to obscure the RNPIC, and 3 - the\r\nnorth polar regions were imaged with slightly poorer geometry. Some combination\r\nof the three is most likely.
\r\n\r\nMany other regions with anomalous cross sections were found on the surface of\r\nMars. The large volcanic provinces of Tharsis and Elysium have very high cross\r\nsections associated with them. These are most probably a result of the extremely\r\nrough surfaces of the large volcanoes and their associated flows. One of the most\r\nintriguing features in the Mars data set is a region which extends west from Tharsis\r\nfor over 2000 km, which displays no cross section distinguishable from the noise\r\nin either polarization, which we have termed \"Stealth.\" The surface and near surface\r\n(to depths of meters) must be composed of very underdense material, with\r\nan absence of volume scatterers (rocks). The proximity of Stealth to Arsia and\r\nPavonis Montes suggests that it may be comprised of pyroclastic materials which\r\nwere blown westward after eruptions from these two large shield volcanoes.
\r\n\r\nMercury was observed twice during the conjunction in August of 1991, once\r\nduring the conjunction in November of 1992, and twice during the conjunction in\r\nFebruary of 1994. The data in 1992 were compromised by transmitter problems\r\nand will thus only be very briefly discussed. The 1994 data will be only briefly\r\nmentioned, as well, since the data reduction has not been fully completed, and\r\nthus all results are very preliminary. During the 1991 observations, the subearth\r\nlatitude was \u223c + 10\u00b0, providing nearly as good a view of the north polar regions\r\nof Mercury as is obtainable via earth based remote sensing. The feature with the\r\nhighest SS cross section (.079) in either of the radar images was near the nominal\r\npolar position. This feature also exhibits a polarization inversion throughout much\r\nof its extent, similar to the RSPIC on Mars. This feature is probably the signature\r\nof water ice deposits in permanently shadowed regions near the pole, which\r\nexplains the reduced cross section when compared to the Martian RSPIC. The ice\r\nmay be covered by a thin layer of dust, which would protect the ice from erosion\r\nfrom energetic sources as well as contributing to the reduced cross section. Other\r\nregions with anomalous cross sections exist on the surface, most notably five large\r\nquasi-circular regions, which we refer to as \"basins.\" It is clear from the 1992\r\ndata that the Caloris basin has no such cross section enhancement in its interior,\r\nand so our \"basins\" are different from Caloris in some manner. During the 1994\r\nobservations, the subearth latitude was \u223c -10\u00b0, providing nearly as good a view\r\nof the south polar regions of Mercury as is obtainable from earth. Preliminary\r\nresults indicate that there is a region of enhanced cross section near the south\r\npole, similar to that near the north pole.
" }, { "name": "Chamberlin, Laurinda Ann", "degree": "PhD", "year": "1994", "title": "Pd-oxide equilibration: a new experimental method for the direct determination of the activities of oxide components in melts and minerals", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10102011-082937068", "creators": [ { "name": { "family": "Chamberlin", "given": "Laurinda Ann" }, "id": "Chamberlin-L-A", "display_name": "Chamberlin, Laurinda Ann" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Beckett", "given": "John R." }, "id": "Beckett-J-R", "role": "member", "display_name": "Beckett, John R." } ], "option_major": [ "geol" ], "doi": "10.7907/v11m-fr06", "abstract": "A new technique, Pd-oxide equilibration, has been developed for the experimental determination of the\r\nactivities of oxide components in melts and minerals using the equilibrium between Pd alloy, oxygen, and the oxide component in the sample of interest. Due to the\r\nextraordinary stability of dilute alloys of Pd with Mg, AI, and Si, these metals dissolve into Pd in equilibrium with oxide-based materials in amounts easily measured with the electron microprobe at f_O_2's that can be achieved with conventional gas-mixing techniques. Activity-composition relations for Pd-Mg, -Al, and -Si alloys were determined by equilibrating Pd at fixed f_O_2 and T with periclase,\r\ncorundum, and cristobalite (a_(oxide)\u22611). Because Mg, Al, and Si have constant activity coefficients in Pd at low concentrations, the activity of the oxide of each metal is a\r\nsimple function of the ratio of the concentration of the metal in Pd in equilibrium with the sample to that in Pd in equilibrium with the pure oxide. Therefore, if Pd plus a\r\nmelt or mineral and Pd plus pure oxide standards are equilibrated simultaneously at fixed T and f_O_2 the\r\nprecision of the analytical technique is the major limitation on the determination of oxide activities. With Pd-oxide equilibration, all measurements of thermodynamic properties reflect equilibration at the temperature of interest, so no phase, ordering, or structural changes upon quenching influence the results. In addition, the method can be precise, since the only measurements involved in the determination of activities are the concentrations of various metals in the Pd, and there is no need for accurate knowledge of T or f_O_2.
\r\n\r\nThe technique of Pd-oxide equilibration was used to determine activities of MgO and Al_2O_3 and \u2206G_f\u00b0's in stoichiometric MgAl_2O_4 spinel at 1150 to 1400\u00b0C. The results are in good agreement with those of JANAF (1985) but are distinct at the 1\u03c3 level from the \u2206G_f\u00b0's of Helgeson et al. (1978), Holland and Powell (1990), Berman (1988), and Hallstedt (1992), and at the 2\u03c3 level from Robie et al. (1978). This implies a larger residual entropy upon quenching than is accounted for by most compilations of\r\nthermodynamic data. These differences were accounted for by applying Landau theory corrections to the calorimetric heat contents (Bonnickson, 1955) using neutron diffraction measurements of the equilibrium amount of disorder in spinel as a function of temperature (Peterson et al., 1991). The corrected heat contents and measured \u2206G_f\u00b0's have been used to produce a new, self-consistent C_p function that can account for all experimental data. The results imply that nonconfigurational entropy contributions\r\nare important in spinel.
\r\n\r\nPd-oxide equilibration was also used to measure the activities of MgO, Al_2O_3, and SiO_2 In melts in the five-component system CaO-MgO-Al_2O_3-SiO_2-TiO_2\r\n(CMAST). Five bulk compositions were studied, including synthetic analogs of Type B, Type C, and forsterite-bearing Ca-Al-rich inclusions (CAls) and one synthetic analog\r\nof an average Group 2 plagioclase-olivine inclusion (POI) from carbonaceous chondrites. Correlated variations between activity coefficient and liquid composition are observed in the melts, which may give insight into the relationships between thermodynamics and structure. The measured activities agree to within 10-35% of those calculated using Berman's (1983) model and are therefore generally consistent with known phase equilibrium data in CMAS. Measured activities indicate that liquids of CAl and POI composition would be out of equilibrium with a solar gas and should volatilize Mg, SiO, and lesser Ca if they melt in such a gas.
\r\n\r\nThe technique of Pd-oxide equilibration was also used to measure the activities of MgO and Al_2O_3 in spinel solid solutions in the MgAl_2O_4-Al_(8/3)O_4 compositional system at 1400\u00b0C. Eight compositions were studied, ranging from stoichiometric MgAl_2O_4 to corundum-saturated spinel. Activities of MgAl_2O_4 and \u03b3-Al_(8/3)O_4 were calculated from the experimental values of a_(Mg)O and a_(Al)_2O_3 using the free energy expressions of Chamberlin et al. (l993b) and Navrotsky et al. (1986). The MgAl_2O_4\r\nactivities are approximately Raoultian, whereas the \u03b3-Al_(8/3)O_4 activities show a strong positive deviation from ideality. A plausible model for spinel solid solution at 1400\u00b0C based on Landau theory (Carpenter et al., 1993a,b) is set forth, with an assumed cation and vacancy distribution. The similarity between the free energies of mixing calculated from the activities and the enthalpies of mixing measured by Navrotsky et al. (1986) imply that entropies of mixing are virtually zero and that the solid solution is affected by significant short-range order. The \u2206G_f\u00b0 of spinel increases with increasing alumina content, indicating that excess alumina does not increase the condensation temperature of spinel in the solar nebula. However, the high P_(Al) in the solar nebula and the fact that \u2206G_f\u00b0 remains relatively constant at low alumina contents imply that the first spinel condensates would be somewhat aluminous.
\r\n\r\nFinally, Pd-oxide equilibration was used to measure the activities of MgO and SiO_2 in forsterite and protoenstatite. Four compositions were studied: nominally pure forsterite, forsterite in equilibrium with\r\nprotoenstatite, and forsterites that crystallized from liquids of two different bulk compositions in the system CMAST (POI and FOB). Measured oxide activities and \u2206G_f\u00b0's vary systematically with Ca content. The \u2206G_f\u00b0's are consistent with the literature values of Robie et al. (1978), Berman (1988), JANAF (1985), and Gillet et al. (1991) in this temperature range except in FOB, where they are lower. The free energy of formation (\u2206G_f\u00b0) of protoenstatite from the oxides determined from the MgO and SiO_2 activities agrees with that of Berman (1988) to 1 kJ/mole. Low levels of Ca dissolved in forsterite may increase the number of point defects in the lattice and thereby decrease the mechanical strength of the mineral. The Pd-oxide equilibration technique, with its potential for directly and precisely determining oxide activities in melts and mineral solutions and free energies of formation of minerals, could be of considerable value in refining the existing thermodynamic data base.
\r\n\r\n" }, { "name": "Garnero, Edward James", "degree": "PhD", "year": "1994", "title": "Seismic structure above and below the core-mantle boundary", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05242013-114249496", "creators": [ { "name": { "family": "Garnero", "given": "Edward James" }, "id": "Garnero-E-J", "display_name": "Garnero, Edward James" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/zsct-z181", "abstract": "Seismic structure above and below the core-mantle boundary (CMB) has been studied\r\nthrough use of travel time and waveform analyses of several different seismic\r\nwave groups. Anomalous systematic trends in observables document mantle heterogeneity\r\non both large and small scales. Analog and digital data has been utilized,\r\nand in many cases the analog data has been optically scanned and digitized prior to\r\nanalysis.
\r\n\r\nDifferential travel times of S - SKS are shown to be an excellent diagnostic of\r\nanomalous lower mantle shear velocity (V s) structure. Wavepath geometries beneath\r\nthe central Pacific exhibit large S- SKS travel time residuals (up to 10 sec), and\r\nare consistent with a large scale 0(1000 km) slower than average V_s region (\u22653%).\r\nS - SKS times for paths traversing this region exhibit smaller scale patterns and\r\ntrends 0(100 km) indicating V_s perturbations on many scale lengths. These times are\r\ncompared to predictions of three tomographically derived aspherical models: MDLSH\r\nof Tanimoto [1990], model SH12_WM13 of Suet al. [1992], and model SH.10c.17\r\nof Masters et al. [1992]. Qualitative agreement between the tomographic model\r\npredictions and observations is encouraging, varying from fair to good. However,\r\ninconsistencies are present and suggest anomalies in the lower mantle of scale length\r\nsmaller than the present 2000+ km scale resolution of tomographic models. 2-D\r\nwave propagation experiments show the importance of inhomogeneous raypaths when\r\nconsidering lateral heterogeneities in the lowermost mantle.
\r\n\r\nA dataset of waveforms and differential travel times of S, ScS, and the arrival\r\nfrom the D\" layer, Scd, provides evidence for a laterally varying V_s velocity discontinuity\r\nat the base of the mantle. Two different localized D\" regions beneath\r\nthe central Pacific have been investigated. Predictions from a model having a V_s\r\ndiscontinuity 180 km above the CMB agree well with observations for an eastern\r\nmid-Pacific CMB region. This thickness differs from V_s discontinuity thicknesses\r\nfound in other regions, such as a localized region beneath the western Pacific, which\r\naverage near 280 km. The \"sharpness\" of the V_s jump at the top of D\", i.e., the\r\ndepth range over which the V_s increase occurs, is not resolved by our data, and our\r\ndata can in fact may be modeled equally well by a lower mantle with the increase in\r\nV_s at the top of D\" occurring over a 100 krn depth range. It is difficult at present to\r\ncorrelate D\" thicknesses from this study to overall lower mantle heterogeneity, due to\r\nuncertainties in the 3-D models, as well as poor coverage in maps of D\" discontinuity\r\nthicknesses.
\r\n\r\nP-wave velocity structure (V_p) at the base of the mantle is explored using the\r\nseismic phases SKS and SPdKS. SPdKS is formed when SKS waves at distances\r\naround 107\u00b0 are incident upon the CMB with a slowness that allows for coupling with\r\ndiffracted P-waves at the base of the mantle. The P-wave diffraction occurs at both\r\nthe SKS entrance and exit locations of the outer core. SP_dKS arrives slightly later in\r\ntime than SKS, having a wave path through the mantle and core very close to SKS.\r\nThe difference time between SKS and SP_dKS strongly depends on V_p at the base\r\nof the mantle near SK Score entrance and exit points. Observations from deep focus\r\nFiji-Tonga events recorded by North American stations, and South American events\r\nrecorded by European and Eurasian stations exhibit anomalously large SP_dKS -\r\nSKS difference times. SKS and the later arriving SP_dKS phase are separated by\r\nseveral seconds more than predictions made by 1-D reference models, such as the\r\nglobal average PREM [Dziewonski and Anderson, 1981] model. Models having a\r\npronounced low-velocity zone (5%) in V_p in the bottom 50-100 km of the mantle\r\npredict the size of the observed SP_dK S-SKS anomalies. Raypath perturbations\r\nfrom lower mantle V_s structure may also be contributing to the observed anomalies.
\r\n\r\nOuter core structure is investigated using the family of SmKS (m=2,3,4) seismic\r\nwaves. SmKS are waves that travel as S-waves in the mantle, P-waves in the\r\ncore, and reflect (m-1) times on the underside of the CMB, and are well-suited for\r\nconstraining outermost core V_p structure. This is due to closeness of the mantle\r\npaths and also the shallow depth range these waves travel in the outermost core.\r\nS3KS - S2KS and S4KS - S3KS differential travel times were measured using\r\nthe cross-correlation method and compared to those from reflectivity synthetics created\r\nfrom core models of past studies. High quality recordings from a deep focus\r\nJava Sea event which sample the outer core beneath the northern Pacific, the Arctic,\r\nand northwestern North America (spanning 1/8th of the core's surface area), have\r\nSmKS wavepaths that traverse regions where lower mantle heterogeneity is pre-\r\ndieted small, and are well-modeled by the PREM core model, with possibly a small\r\nV_p decrease (1.5%) in the outermost 50 km of the core. Such a reduction implies\r\nchemical stratification in this 50 km zone, though this model feature is not uniquely\r\nresolved. Data having wave paths through areas of known D\" heterogeneity (\u00b12%\r\nand greater), such as the source-side of SmKS lower mantle paths from Fiji-Tonga\r\nto Eurasia and Africa, exhibit systematic SmKS differential time anomalies of up\r\nto several seconds. 2-D wave propagation experiments demonstrate how large scale\r\nlower mantle velocity perturbations can explain long wavelength behavior of such\r\nanomalous SmKS times. When improperly accounted for, lower mantle heterogeneity\r\nmaps directly into core structure. Raypaths departing from homogeneity play\r\nan important role in producing SmKS anomalies. The existence of outermost core\r\nheterogeneity is difficult to resolve at present due to uncertainties in global lower\r\nmantle structure. Resolving a one-dimensional chemically stratified outermost core\r\nalso remains difficult due to the same uncertainties. Restricting study to higher\r\nmultiples of SmKS (m=2,3,4) can help reduce the affect of mantle heterogeneity\r\ndue to the closeness of the mantle legs of the wavepaths. SmKS waves are ideal in\r\nproviding additional information on the details of lower mantle heterogeneity.
\r\n\r\n" }, { "name": "Keszthelyi, L\u00e1szl\u00f3 P.", "degree": "PhD", "year": "1994", "title": "On the Thermal Budget of Pahoehoe Lava Flows", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03182013-160237674", "creators": [ { "name": { "family": "Keszthelyi", "given": "L\u00e1szl\u00f3 P." }, "id": "Keszthelyi-L\u00e1szl\u00f3-P", "display_name": "Keszthelyi, L\u00e1szl\u00f3 P." } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Denlinger", "given": "Roger" }, "id": "Denlinger-R", "role": "member", "display_name": "Denlinger, Roger" }, { "name": { "family": "Stock", "given": "Joann M." }, "id": "Stock-J-M", "orcid": "0000-0003-4816-7865", "role": "member", "display_name": "Stock, Joann M." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geol" ], "doi": "10.7907/G5V5-T293", "abstract": "In this thesis I investigate some aspects of the thermal budget of pahoehoe lava\r\nflows. This is done with a combination of general field observations, quantitative\r\nmodeling, and specific field experiments. The results of this work apply to pahoehoe\r\nflows in general, even though the vast bulk of the work has been conducted on the lavas\r\nformed by the Pu'u 'O'o - Kupaianaha eruption of Kilauea Volcano on Hawai'i. The field\r\nobservations rely heavily on discussions with the staff of the United States Geological\r\nSurvey's Hawaiian Volcano Observatory (HVO), under whom I labored repeatedly in\r\n1991-1993 for a period totaling about 10 months.
\r\n\r\nThe quantitative models I have constructed are based on the physical processes\r\nobserved by others and myself to be active on pahoehoe lava flows. By building up these\r\nmodels from the basic physical principles involved, this work avoids many of the pitfalls of\r\nearlier attempts to fit field observations with \"intuitively appropriate\" mathematical\r\nexpressions. Unlike many earlier works, my model results can be analyzed in terms of the\r\ninteractions between the different physical processes. I constructed models to: (1) describe\r\nthe initial cooling of small pahoehoe flow lobes and (2) understand the thermal budget of\r\nlava tubes.
\r\n\r\nThe field experiments were designed either to validate model results or to constrain\r\nkey input parameters. In support of the cooling model for pahoehoe flow lobes, attempts\r\nwere made to measure: (1) the cooling within the flow lobes, (2) the amount of heat\r\ntransported away from the lava by wind, and (3) the growth of the crust on the lobes.\r\nField data collected by Jones [1992], Hon et al. [1994b], and Denlinger [Keszthelyi and\r\nDenlinger, in prep.] were also particularly useful in constraining my cooling model for\r\nflow lobes. Most of the field observations I have used to constrain the thermal budget of\r\nlava tubes were collected by HVO (geological and geophysical monitoring) and the Jet\r\nPropulsion Laboratory (airborne infrared imagery [Realmuto et al., 1992]). I was able to\r\nassist HVO for part of their lava tube monitoring program and also to collect helicopterborne\r\nand ground-based IR video in collaboration with JPL [Keszthelyi et al., 1993].
\r\n\r\nThe most significant results of this work are (1) the quantitative demonstration that\r\nthe emplacement of pahoehoe and 'a'a flows are the fundamentally different, (2)\r\nconfirmation that even the longest lava flows observed in our Solar System could have\r\nformed as low effusion rate, tube-fed pahoehoe flows, and (3) the recognition that the\r\natmosphere plays a very important role throughout the cooling of history of pahoehoe lava\r\nflows. In addition to answering specific questions about the thermal budget of tube-fed\r\npahoehoe lava flows, this thesis has led to some additional, more general, insights into the\r\nemplacement of these lava flows. This general understanding of the tube-fed pahoehoe\r\nlava flow as a system has suggested foci for future research in this part of physical\r\nvolcanology.
" }, { "name": "Leroy, Stephen Sylvain", "degree": "PhD", "year": "1994", "title": "Convectively generated internal gravity waves in Venus's middle atmosphere : momentum transport and radio scintillations", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06182008-135507", "creators": [ { "name": { "family": "Leroy", "given": "Stephen Sylvain" }, "id": "Leroy-Stephen-Sylvain", "display_name": "Leroy, Stephen Sylvain" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" } ], "option_major": [ "plansci" ], "doi": "10.7907/msgs-7b48", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis work is divided into two papers. Firstly, we theoretically calculate how gravity waves are emitted from the neutrally buoyant dry convection in Venus's middle atmosphere and investigate whether such waves play a significant role in supporting the superrotation of Venus's atmosphere. Secondly, we attempt to explain the radio scintillations seen in the occultations of many spacecraft, particularly Pioneer Venus, as caused by convectively generated gravity waves. Below are the abstracts of the two papers presented in this thesis.\r\n\r\nPaper I:\r\n\r\nWe calculate the emission of internal gravity waves from neutrally buoyant dry convection embedded within a stable atmosphere with static stability and zonal winds varying in height. We apply this theory to Venus's middle atmosphere to investigate whether these waves can help support the superrotation of Venus's atmosphere. Furthermore, we model the radio scintillation data obtained for Venus as caused by such internal gravity waves. The emission mechanism is similar to that suggested for driving the gravity modes of the Sun. We assume a background atmosphere on which we have superimposed linear wave propagation. Waves are damped by reabsorption by the convection, wavebreaking in the stable atmosphere, critical layer absorption, and by wave radiation to space. Wavebreaking is imposed wherever the waves become convectively unstable. Inertial effects are neglected and plane parallel geometry is assumed. Propagation of the waves is handled using a second order WKBJ approximation. A complete three dimensional ensemble of waves is retained.\r\n\r\nWe show that both westward and eastward propagating waves exert strong accelerations on the mean flow. The westward propagating carry enough momentum to support the westward superrotation between the convection and the cloud-tops; however, the bulk of the wave momentum flux is critically absorbed and deposited within a kilometer of the convection because most of the waves propagate slowly in the horizontal. The eastward propagating waves are found to exert large decelerations above the zonal wind maximum. The decelerations are larger than 20 m [...] day [...], similar to wave drag in the Earth's mesosphere.\r\n\r\nIn the course of evaluating our model, we have found that dry convection must have \"penetrative\" mixed layers above and below it. This arises from wavebreaking of gravity waves immediately after their generation. The effect of the penetrative layer is to filter wave emission and to create a discontinuity in the background temperature lapse rate dT/dz. The latter may be observable in atmospheres.\r\n\r\nPaper II:\r\n\r\nWe simulate radio scintillations as they would appear in Pioneer Venus radio occultation data assuming that the index of refraction fluctuations in Venus's atmosphere responsible for the scintillations are directly caused by gravity wave fluctuations. We assume that the gravity waves are created by a global convection layer between 50 and 55 km altitude in Venus's atmosphere and propagate vertically. Associated with the gravity waves are density fluctuations which create the index of refraction variations. We compare the simulated scintillations with data and argue that this theory for the radio scintillations is preferable to the theory that the scintillations are caused by clear air turbulence in Venus's atmosphere.\r\n\r\nWe show that these gravity waves can explain the shape and amplitude of the radio scintillation variance spectra in frequency. The shape of the simulated radio scintillation variance spectra in frequency is nearly a direct result of a saturated spectrum of breaking gravity waves. This saturated spectrum is the spectrum of breaking gravity waves in the vertical wavenumber. On the other hand, the overall amplitude is subject to parameters such as the intensity of the convection, the angle between the zonal winds and the beam path, and the zonal wind profile at polar latitudes. Limits can be placed, though, on the intensity of the convection which generates the waves and on the angle between the radio beam path and the winds in Venus's atmosphere. We find that the convection in Venus's middle atmosphere, even in polar regions, must transport 1 W/[...] to create gravity waves strong enough to break. This result is dependent on the amplitude of the zonal winds at polar latitudes.\r\n" }, { "name": "Song, Xiaodong", "degree": "PhD", "year": "1994", "title": "Structure of the earth's core and lowermost mantle from seismic PKP waves", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05312013-094528303", "creators": [ { "name": { "family": "Song", "given": "Xiaodong" }, "id": "Song-Xiaodong", "display_name": "Song, Xiaodong" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/k5gh-th50", "abstract": "This thesis addresses the fine structure, both radial and lateral, of compressional wave velocity and attenuation of the Earth's core and the lowermost mantle using waveforms, differential travel times and amplitudes of PKP waves, which penetrate the Earth's core.
\r\n\r\nThe structure near the inner core boundary (ICB) is studied by analyzing waveforms of a regional sample. The waveform modeling approach is demonstrated to be an effective tool for constrainning the ICB structure. The best model features a sharp velocity jump of 0.78km/s at the ICB and a low velocity gradient at the lowermost outer core (indicating possible inhomogeneity) and high attenuation at the top of the inner core.
\r\n\r\nA spherically symmetric P-wave model of the core, is proposed from PKP differential times, waveforms and amplitudes. The ICB remains sharp with a velocity\r\njump of 0. 78km/ s. A very low velocity gradient at the base of the fluid core is demonstrated to be a robust feature, indicating inhomogeneity is practically inevitable. The model also indicates that the attenuation in the inner core decreases with depth. The velocity at D\" is smaller than PREM.
\r\n\r\nThe inner core is confirmed to be very anisotropic, possessing a cylindrical symmetry around the Earth spin axis with the N-S direction 3% faster than the E-W\r\ndirection. All of the N-S rays through the inner core were found to be faster than the E-W rays by 1.5 to 3.5s. Exhaustive data selection and efforts in insolating\r\ncontributions from the region above ensure that this is an inner core feature.
\r\n\r\nThe anisotropy at the very top of the inner core is found to be distinctly different from the deeper part. The top 60km of the inner core is not anisotropic. From 60km\r\nto 150km, there appears to be a transition from isotropy to anisotropy.
\r\n\r\nPKP differential travel times are used to study the P velocity structure in D\". Systematic regional variations of up to 2s in AB-DF times were observed, attributed primarily to heterogeneities in the lower 500km of the mantle. However, direct comparisons with tomographic models are not successful.
\r\n" }, { "name": "Tackley, Paul James", "degree": "PhD", "year": "1994", "title": "Three-dimensional models of mantle convection : influence of phase transitions and temperature-dependent viscosity", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:05222013-080427740", "creators": [ { "name": { "family": "Tackley", "given": "Paul James" }, "id": "Tackley-P-J", "display_name": "Tackley, Paul James" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/541t-s191", "abstract": "Two of the most important questions in mantle dynamics are investigated in three separate studies: the influence of phase transitions (studies 1 and 2), and the influence of\r\ntemperature-dependent viscosity (study 3).
\r\n\r\n(1) Numerical modeling of mantle convection in a three-dimensional spherical shell incorporating the two major mantle phase transitions reveals an inherently three-dimensional flow pattern characterized by accumulation of cold downwellings above the 670 km discontinuity, and cylindrical 'avalanches' of upper mantle material into the lower mantle. The exothermic phase transition at 400 km depth reduces the degree of layering. A region of strongly-depressed temperature occurs at the base of the mantle. The temperature field is strongly modulated by this partial layering, both locally and in globally-averaged\r\ndiagnostics. Flow penetration is strongly wavelength-dependent, with easy penetration at long wavelengths but strong inhibition at short wavelengths. The amplitude of the geoid is not significantly affected.
\r\n\r\n(2) Using a simple criterion for the deflection of an upwelling or downwelling by an endothermic phase transition, the scaling of the critical phase buoyancy parameter with the important lengthscales is obtained. The derived trends match those observed in numerical\r\nsimulations, i.e., deflection is enhanced by (a) shorter wavelengths, (b) narrower up/downwellings (c) internal heating and (d) narrower phase loops.
\r\n\r\n(3) A systematic investigation into the effects of temperature-dependent viscosity on mantle convection has been performed in three-dimensional Cartesian geometry, with a factor of 1000-2500 viscosity variation, and Rayleigh numbers of 10^5-10^7. Enormous differences in model behavior are found, depending on the details of rheology, heating mode, compressibility and boundary conditions. Stress-free boundaries, compressibility,\r\nand temperature-dependent viscosity all favor long-wavelength flows, even in internally heated cases. However, small cells are obtained with some parameter combinations.\r\nDownwelling plumes and upwelling sheets are possible when viscosity is dependent solely on temperature. Viscous dissipation becomes important with temperature-dependent\r\nviscosity.
\r\n\r\nThe sensitivity of mantle flow and structure to these various complexities illustrates the importance of performing mantle convection calculations with rheological and thermodynamic properties matching as closely as possible those of the Earth.
" }, { "name": "Woods, Bradley Brett", "degree": "PhD", "year": "1994", "title": "Regional surface wave magnitude and moment determination methods applied to nuclear explosions at the Nevada test site : implications for yield estimation and seismic discrimination", "advisor": "Harkrider, David G.; Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04212006-165925", "creators": [ { "name": { "family": "Woods", "given": "Bradley Brett" }, "id": "Woods-Bradley-Brett", "display_name": "Woods, Bradley Brett" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "co-chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "co-chair", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/P212-Q044", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis thesis examines the use of regional surface-wave data to measure the long-period source spectrum of underground nuclear explosions for the purposes of yield determination and seismic discrimination. It is demonstrated that regional (D < 2500 km) fundamental-mode Rayleigh and Love waveforms can be modeled with considerable accuracy. The procedure for modeling regional earth structure for such seismograms by inverting surface-wave dispersion data is described. This technique is a hybrid of preexisting surface-wave analysis and inversion methods. Theoretical path corrections are determined from the Green's function for a given modeled path. A method is described to obtain consistent, stable, time-domain surface-wave magnitude ([...]) or seismic moment ([...]) measurements from poorly dispersed regional Rayleigh waves. Source parameters for 190 Nevada Test Site explosions are determined using these methods. Observations demonstrate that the measurement/detection threshold for regional surface-waves is [...] > 4.0 (Yield = 1 kt)--a significant improvement over classical teleseismic [...] measurements. The results indicate that the [...] (or log [...]) - yield scaling relationship is near unity and constant for explosions of all measurable sizes. Site effects are also investigated to determine the portability of such surfacewave measurements. Spectral-domain moment estimates also were performed on the digital portion of the data set. Besides obtaining an average scalar moment from Rayleigh wave amplitudes, the isotropic (explosive source) and deviatoric moment (double-couple source generated by tectonic release) components were determined by a joint inversion of Rayleigh and Love wave amplitude and phase data. Although in the most general case the inversion solution is non-unique, constraining the depth of the deviatoric source to be equal to that of the explosion and assuming a vertical strike-slip orientation yields a unique linear inversion solution. The spectral moment estimates are similar to the time-domain values, although the spectral-domain moment variances are appreciably smaller than the time-domain ones. A regional short-period vs. long-period seismic discriminant is developed using the ratio of the seismic moment to local magnitude ([...]). This discriminant successfully separates the explosion and earthquake populations at all measurable source sizes, so that for a given seismic moment source level, an explosion has an [...] 0.5 magnitude units larger than a comparable-sized earthquake.\r\n" }, { "name": "Bell, David Ronald", "degree": "PhD", "year": "1993", "title": "Hydroxyl in mantle minerals", "advisor": "Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechETD:etd-04102008-142715", "creators": [ { "name": { "family": "Bell", "given": "David Ronald" }, "id": "Bell-David-Ronald", "display_name": "Bell, David Ronald" } ], "advisors": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/RDF1-8761", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis thesis is an investigation of the infrared spectroscopic characteristics, abundance, stability and partitioning behavior of hydroxyl (OH) in minerals from the Earth's upper mantle. Using manometric and nuclear reaction analysis techniques to calibrate intensities of OH bands in the mineral IR spectra, the following ranges in OH concentration (expressed as ppm H2O by weight) were determined for natural samples: clinopyroxene 150 - 1080; orthopyroxene 50 - 460; olivine <1 - 245; garnet < 0.1 - 330; kyanite 55 - 222; zircon 28 - 74.\r\n\r\nSystematics of OH distribution in garnets from various mantle rock types indicate a connection with petrogenetic environment, illustrating qualitative use of OH as an indicator of the activity of hydrous components (e.g., water) in the mantle. Applications to specific mantle assemblages are discussed. Heterogeneous distribution of H in the mantle on local and regional scales is indicated.\r\n\r\nTrace structural OH in mantle rocks ranges from 30 to 600 ppm H2O in samples examined, implying that nominally anhydrous minerals in peridotite could store all the water (about 100 - 200 ppm) in the depleted upper mantle (MORB source). These minerals also provide a mechanism to recycle water into the mantle in subduction zones.\r\n\r\nPartitioning behavior of H was investigated in a suite of co-magmatic kimberlite megacryst minerals. Fugacities of water calculated from OH in olivine are compatible with mantle conditions and yield an estimate of ~1 wt.% H2O in the parental megacryst magma. OH concentrations in garnet, pyroxenes and olivine are influenced by water activity, crystal chemistry (particularly Ti substitution) and possibly temperature, resulting in substantial variations in inter-mineral [...] involving garnet, but relatively constant [...] among pyroxenes and olivine and illustrating the complications of quantitative hydrobarometry in nature.\r\n\r\nExperiments on the thermal stability of OH in garnet and other minerals were conducted at atmospheric, crustal and mantle pressures. These demonstrate slow equilibration of OH in synthetic pyrope. Rapid mobility of H, redox processes and necessity for structural changes in the host crystal are important factors in determining the behavior of H in natural mineral systems.\r\n\r\nRelatively deuterium-depleted isotopic compositions are indicated for this form of H.\r\n" }, { "name": "Blank, Jennifer Glee", "degree": "PhD", "year": "1993", "title": "An experimental investigation of the behavior of carbon dioxide in rhyolitic melt", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05302007-075656", "creators": [ { "name": { "family": "Blank", "given": "Jennifer Glee" }, "id": "Blank-J-G", "display_name": "Blank, Jennifer Glee" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/tq3x-2059", "abstract": "The nature and behavior of CO2 in rhyolitic melt at low to moderate pressures was examined using a variety of experimental and analytical techniques. The results are applicable to and critical for understanding the inventory of carbon in the mantle, the growth and evolution of atmospheres, and the processes governing magma degassing. In this study, Fourier transform infrared (FTIR) spectroscopy was calibrated against vacuum extraction/manometry and used to measure solubilities and diffusivities of CO2 in rhyolitic glasses. The difference in 13C/12C ratios between coexisting CO2 vapor and CO2 dissolved as CO2 molecules in rhyolitic melt was also determined experimentally and measured using vacuum extraction and mass spectrometry. Together, these data establish a basis with which to interpret the interaction of carbon dioxide with silicic systems.\n\nThe solubility behavior of CO2 in rhyolitic melt, studied at 750-850\u00b0C and pressures up to ~ 1500 bars, obeys Henry's Law. Only molecular CO2 was observed in the glasses under these conditions, but both CO2 molecules and CO3(2-) ions have been detected in a single CO2-bearing rhyolitic glass quenched from much higher pressure (25 kbars) by other workers, suggesting that the reaction CO2 (melt) + O2- (melt) = CO3(2-) (melt) is favored in rhyolitic melts as pressure increases. Using the CO2 solubility data, a thermodynamic model was developed to describe CO2 solubility in rhyolitic melt as a function of temperature and pressure. The solubility of CO2 in rhyolite is approximately 30% lower than that in basalt, in which all dissolved CO2 has been detected as CO3(2-). CO2 and water solubility data can be used to interpret volatile contents of silicic eruption products. Modeled CO2-H2O vapor saturation curves permit estimation of minimum entrapment pressures of rhyolitic melt inclusions.\n\nThe diffusive behavior of CO2 in rhyolitic melt was examined through a set of experiments conducted at 450-1050\u00b0C and 550-1050 bars in which the silicate glasses were not allowed to fully equilibrate with CO2 vapor. CO2 concentration profiles, determined by FTIR spectroscopy, were fit to an analytical solution of the diffusion equation assuming constant DCO2. DCO2 has a strong, direct correlation with temperature but is only weakly responsive to changes in pressure. The observed Arrhenius relation between diffusivities and temperature over a 600\u00b0C interval was used to calculate the activation energy for CO2 diffusion. The relation between the size of a CO2 molecule and its activation energy derived from the experimental results mimics the positive correlation reported for noble gases, suggesting that the diffusive behavior of CO2 in the melt is similar to that of other neutral species. CO2 diffusivity in rhyolitic melt is lower than bulk water diffusivity (at 0.2 wt% total water) for temperatures below 1050\u00b0C but is higher at higher temperatures. CO2 diffusivity in rhyolitic melt is similar to that in basaltic melt, but the activation energy for CO2 diffusion in rhyolite is somewhat lower. These diffusion results can be applied to an evaluation of diffusive transport of CO2 in magmas, diffusional fractionation of CO2 and H2O, and growth rates of CO2-rich bubbles in magmas.\n\nThe effect of increasing water content on CO2 solubility in rhyolite was examined through another set of experiments involving variable proportions of CO2 and H2O in the vapor phase. Under the conditions of the experiments, which are relevant to degassing of common silicic magmas near the earth's surface, Henry's law is obeyed for both water and carbon dioxide in rhyolitic melts. Thus, the amount of CO2 dissolved in a rhyolitic melt saturated with H2O-CO2 vapor at a given pressure and temperature will be lower than if the vapor were pure CO2 by a factor equal to the ratio of the fugacity of CO2 in the mixed vapor to the fugacity of CO2 in pure CO2 vapor at the same conditions. This is essentially a dilution effect. The same is true for the amount of water dissolved in the melt, except that it is the amount of molecular water that is lowered proportionately to the fugacity of water by this dilution effect. There is no evidence of an enhancement of CO2 solubility in mixed H2O-CO2 systems over systems in which only CO2 is present, as has been reported previously for significantly higher pressures. Further work will be needed to confirm reported non-Henrian behavior at elevated pressures and the implied significance for solubility mechanisms under these conditions, but in the meantime, it appears that efforts to model high level crustal and volcanic phenomena are considerably simplified by the validity of Henry's law for the major volatile species.\n\nThe isotopic partitioning of 13C between CO2 vapor and coexisting dissolved CO2 was measured through rhyolite-CO2 experiments at 800-1200\u00b0C and 250-1444 bars. The abundance and isotopic composition of CO2 dissolved in the glass were determined by stepped heating and the yields were checked against IR spectroscopic analysis. The 13C/12C of coexisting vapor was determined by direct sampling. No detectable isotopic fractionation between CO2 vapor and CO2 molecules dissolved in rhyolitic melt was observed. These results are very different from those for the system basalt-CO2, in which degassing leaves behind CO3(2-) depleted in 13C dissolved in the melt. The 13C/12C ratios of natural rhyolitic samples offer potential for a direct measurement of the carbon composition of the source region of this magma type." }, { "name": "Burt, Emelia Anna", "degree": "PhD", "year": "1993", "title": "Oxygen isotope studies of some sedimentary and metasedimentary rocks of the central and northern Appalachian Mountains, the Colorado Plateau, and the Ouachita Mountains", "advisor": "Taylor, Hugh P.; Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:11292012-100814038", "creators": [ { "name": { "family": "Burt", "given": "Emelia Anna" }, "id": "Burt-E-A", "display_name": "Burt, Emelia Anna" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." } ], "option_major": [ "geol" ], "doi": "10.7907/qgxa-rq43", "abstract": "Terrigenous sedimentary rocks from the Colorado Plateau show a relatively\r\nuniform bulk silicate \u03b4^(18)O of +14.8 with an SEM of 0.32. Shales and calcilutites in this\r\nregion have a mean bulk silicate \u03b4^(18)O of +17.7 which is significantly heavier than the\r\nmean for interbedded sandstones and siltstones. Bulk silicate \u03b4^(18)O is decoupled from\r\ncarbonate \u03b4^(18)O due to differences in mode of deposition and diagenetic behavior.
\r\n\r\nCentral Appalachian terrigenous sedimentary rocks show a surprisingly uniform\r\nbulk silicate \u03b4^(18)O of +14.8 with an SEM of 0.1. The mean bulk silicate \u03b4^(18)O for all\r\nshales (+15.2) is only 0.3 per mil heavier than the mean for all sandstones and siltstones\r\n(+14.9). The oxygen isotope uniformity of Central Appalachian sedimentary rocks is\r\nmainly a primary depositional feature that is the result of thorough, grand-scale mixing of\r\nterrigenous sediment in the Appalachian geosyncline, probably involving several cycles of\r\nsedimentation, uplift, erosion, and reworking extending over hundreds of millions of years\r\nduring the Paleozoic era. The bulk silicate \u03b4^(18)O of siltstones and shales shows a\r\nsignificant (P \u02c2 0.05) correlation with conodont color alteration index, which is a measure of\r\ndiagenetic temperature. As a result of isotopic exchange with porewater during diagenesis,\r\nthe bulk silicate \u03b4^(18)O of shales and siltstones can apparently be lowered by as much as 2.5\r\nto 4.0 per mil. These diagenetic effects contributed to the overall homogeneity of these\r\nsedimentary rocks because the shales started out at higher \u03b4^(18)O.
\r\n\r\nA reconnaissance ^(18)O/^(16)O study of 14 samples of terrigenous sedimentary rocks\r\nfrom the Ouachita Mountains suggests more inherent isotopic variation in these samples,\r\nperhaps in part as a result of greater heterogeneity of source regions. Some of the isotopic\r\nvariation also seems clearly attributable to diagenetic effects. A significant (P \u02c2 0.05)\r\ncorrelation was found between mean vitrinite reflectance, also a measure of diagenetic\r\ntemperature, and the bulk silicate \u03b4^(18)O difference between shale-sandstone pairs in three\r\ndifferent sedimentary formations.
\r\n\r\nNorthern Appalachian metasedimentary rocks show a decrease in bulk\r\nsilicate \u03b4^(18)O at garnet grade and higher. The terrigenous facies metamorphic rocks have\r\nbeen depleted in ^(18)O by about two per mil relative to their unmetamorphosed counterparts\r\nin the Central Appalachians, except where they are adjacent to carbonate-rich sections.\r\nCarbonate facies metasedimentary rocks are 5 to 6 per mil higher than interbedded\r\nterrrigenous facies rocks, but at the margins of that formation there is a distinct lowering of\r\nbulk silicate \u03b4^(18)O and carbonate \u03b4^(18)O due to influx of metamorphic hydrothermal fluids\r\nfrom the adjacent terrrigenous rocks. This is attributed to the involvement of isotopically\r\nlight fluids during metamorphism. Further work is need to elucidate the differences\r\nbetween metamorphic processes in pelitic and calcareous sediments.
\r\n\r\n\r\n" }, { "name": "Dreger, Douglas S.", "degree": "PhD", "year": "1993", "title": "Modeling earthquakes with local and regional broadband data", "advisor": "Helmberger, Donald V.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:02172011-095833318", "creators": [ { "name": { "family": "Dreger", "given": "Douglas S." }, "id": "Dreger-D-S", "display_name": "Dreger, Douglas S." } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "co-advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/es5j-ag55", "abstract": "Waveform modeling techniques are applied to several recent, moderate sized earthquakes\r\nrecorded by the broadband TERRAscope array in southern California. A\r\nmethod for the determination of source parameters at regional distances with three-component,\r\nsparse network data is described. The sensitivity of the method to source\r\nmislocations and velocity model is investigated. The method is relatively insensitive\r\nto source mislocation. The choice of velocity model can affect the inversion results,\r\nbut it appears that for a number of paths throughout southern California, a simple\r\nplane layered velocity model derived from travel-time studies explains much of the\r\nobserved waveforms.\r\nThe broadband waveforms of two small earthquakes that occurred in 1988 near\r\nUpland, California are forward modeled to determine Green's functions for the path\r\nto Pasadena, California. The effects of near surface gradients, crustal interface sharpness,\r\nand two-dimensional basin-ridge structures were studied. This analysis resulted\r\nin a simple plane layered velocity model that best fit the data. The Green's functions\r\nare then used to study the source characteristics of the 1990 Upland mainshock (M_L = 5.2). The long-period body waves are inverted to determine the orientation\r\nand seismic moment. Comparisons of the 1990 mainshock with the 1988 events revealed\r\nthat the mainshock was a relatively complicated event. Multi-point source\r\nand distributed finite slip models show that the mainshock ruptured down dip (6\r\nkm to 9km) with a non-uniform slip distribution in which 30 % of the total seismic\r\nmoment was released from a relatively small area at 9 km depth. The overall area\r\nof the mainshock was found to be significantly smaller than the aftershock zone.\r\nThe source process of the June 28, 1991 Sierra Madre earthquake (M_L = 5.8)\r\nis investigated using the broadband data recorded at 6 TERRAscope stations. The\r\nlong-period body waves are inverted to determine the orientation and seismic moment.\r\nRatios of the peak amplitudes of simulated short-period Wood-Anderson and\r\nlong-period Wood-Anderson seismograms are compared for the mainshock and the\r\ntwo largest aftershocks. The ratios show that stations southwest of the epicenter\r\nhave elevated levels of short-period energy relative to stations to the east suggesting\r\nthe presence of directivity. The displacement waveforms were forward modeled using\r\ndistributed finite slip models. The best fitting model consists of an updip rupture\r\ntoward the west. This model fails however to explain the amplitudes of the short-period\r\nwaves. A non-uniform slip model was developed that better explains the\r\nshort-period amplitudes. The results of this analysis indicate that the shorter-period\r\nenergy is controlled more by the patches on the fault that experience the greatest\r\nslip, rather than the accumulative motions due to slip on the whole fault surface." }, { "name": "Eluszkiewicz, Janusz B.", "degree": "PhD", "year": "1993", "title": "I. Microphysics of frost metamorphism : applications to Triton and Mars. II. A global analysis of the ozone deficit in the upper stratosphere and lower mesosphere. III. The diabatic circulation in the stratosphere as diagnosed from microwave limb sounder data", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechETD:etd-08032006-131846", "creators": [ { "name": { "family": "Eluszkiewicz", "given": "Janusz B." }, "id": "Eluszkiewicz-Janusz-B", "display_name": "Eluszkiewicz, Janusz B." } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/YN0R-AM36", "abstract": "The present thesis reflects work I have done as a graduate student at Caltech. It is devoted to two broad subjects, planetary frost metamorphism and the terrestrial middle atmosphere, and consists of three papers.\r\n\r\nPaper I considers frost metamorphism on the surfaces of Triton and Mars. Based on an analysis of the microphysical processes involved in pressureless sintering, it is concluded that fine-grained nitrogen and carbon dioxide frosts can undergo seasonal metamorphism into semitransparent layers on the surface of Triton and in the martian seasonal polar caps, respectively. The presence of such layers explains a host of facts about Triton's surface and about the martian seasonal caps. The Triton portion of the paper has been published in the Journal of Geophysical Research, while the Mars portion has been submitted to Icarus.\r\n\r\nPaper II is devoted to elucidating a long-standing issue in the terrestrial middle atmosphere chemistry, the so-called \"ozone deficit problem.\" Based on an analysis of data acquired by the Limb Infrared Monitor of the Stratosphere (LIMS) instrument between October 1978 and May 1979, it is concluded that current photochemical models systematically underestimate observed ozone abundances in the upper stratosphere and lower mesosphere. Three modifications to the accepted photochemical scheme, capable of providing a global solution to this problem, are proposed and discussed. This paper is in press by the Journal of Geophysical Research.\r\n\r\nPaper III differs from the other two in that it reports on results from an ongoing research effort. It considers the diabatic circulation in the stratosphere and lower mesosphere, using ozone and temperature measurements acquired by the Microwave Limb Sounder (MLS) instrument onboard the Upper Atmosphere Research Satellite (UARS). The present study extends past analyses of the diabatic circulation by considering a full annual cycle November 1991 - November 1992 and by taking advantage of the high vertical resolution of MLS data. In the tropical upper stratosphere and lower mesosphere, a semiannual oscillation (SAO) is observed in the computed circulation, with the region of downwelling reaching maximum spatial extent ~1 month before the equinox. The projected lifetime of UARS should enable the present analysis to be extended to several SAO cycles.\r\n" }, { "name": "Grant, Lisa Baugh", "degree": "PhD", "year": "1993", "title": "Characterization of Large Earthquakes on the San Andreas Fault in the Carrizo Plain: Implications for Fault Mechanics and Seismic Hazard", "advisor": "Sieh, Kerry E.; Silver, Leon T.; Brooks, Norman H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01072013-092342447", "creators": [ { "name": { "family": "Grant", "given": "Lisa Baugh" }, "id": "Grant-Lisa-Baugh", "display_name": "Grant, Lisa Baugh" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." }, { "name": { "family": "Brooks", "given": "Norman H." }, "id": "Brooks-N-H", "role": "advisor", "display_name": "Brooks, Norman H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/zs8s-9j51", "abstract": "Despite the widespread use of geomorphic offset measurements for\r\ncalculating earthquake probabilities, little attention has been paid to either the\r\nuncertainties in the interpretation of offset geomorphic features, or the effects\r\nof these uncertainties on fault models and estimates of seismic hazard.\r\nInterpretation of offsets along the San Andreas fault in the Carrizo Plain have\r\nbeen the basis of hypotheses of a strong Carrizo fault segment which regularly\r\nbreaks in great earthquakes several centuries apart with dextral surface slip on\r\nthe order of 10 m per event.
\r\n\r\nThe smallest geomorphic offset measurements along a 6 km stretch of\r\nthe fault southeast of Wallace Creek vary between ~6.5 m and ~10m. A 3-D\r\nexcavation of alluvial deposits at the Phelan fan shows that at least 6.6 to 6.9\r\nm of dextral slip occurred during the 1857 Fort Tejon earthquake, and that the\r\npenultimate earthquake occurred several centuries prior to 1857. Thus, either\r\nthe amount of surface slip varied several meters over a 2-3 km stretch of the\r\nfault in 1857, or 2 to 3 meters of slip in a penultimate earthquake was\r\nfollowed by ~7 m of slip in 1857.
\r\n\r\nTwo monuments from an 1855 survey which spans the San Andreas\r\nfault in the Carrizo Plain have been displaced 11.0 \u00b1 2.5m right-laterally by the\r\ngreat earthquake of 1857. This magnitude of offset is consistent with\r\ngeomorphic indications that slip across the fault during the 1857 earthquake\r\nand associated foreshocks and aftershocks varied from 6.6 to 10 m over 2.6 km\r\nalong this section. Comparison of recent geodetic measurements with the\r\nlate Holocene slip rate at Wallace Creek shows that fault slip rates determined\r\nfrom short-term wide aperture measurements are indistinguishable from\r\nrates determined from long-term narrow aperture measurements. Using\r\nradiocarbon dates of the penultimate large earthquake and measurements of\r\nslip in 1857, we calculate an average slip rate for the last complete earthquake\r\ncycle that is at least 25% lower than the late Holocene slip rate on the main\r\nfault trace. This suggests that variation in fault slip during the 1857\r\nearthquake left a slip deficit in at least the upper 1km of crust at Wallace\r\nCreek. Slip in future earthquakes may compensate this deficit.
\r\n\r\nThree trenches across the San Andreas fault on the Bidart fan in the\r\nCarrizo Plain record evidence of 7 previous earthquakes. Radiocarbon dating\r\nindicates five earthquakes, including the 1857 earthquake, have occurred\r\nsince A.D. 1218. The penultimate earthquake, event B, occurred between 1405\r\nand 1510 A.D. Several centuries before 1857, events B, C, D and E occurred in\r\na temporal cluster after approximately 1218 A.D. and prior to 1510 A.D. The\r\naverage recurrence interval within this cluster ranges from 73 to 116 years,\r\ndepending on assumptions. Events B and D may correlate with prehistoric\r\nearthquakes recorded in sediments elsewhere along the southern San\r\nAndreas fault. Events C and E appear to have ruptured locally in smaller\r\nmagnitude earthquakes. Surface slip from either event B, or events B and C\r\ncombined, totals 7 to 11 m.
\r\n\r\nIf fault strength is defined by long earthquake repeat time, then the\r\nCarrizo segment of the San Andreas is not inherently stronger than the\r\nMojave segment. The temporal and spatial distribution of large earthquakes\r\non the San Andreas fault is difficult to reconcile with slip-based theories of\r\nsegmentation of strike-slip faults. Temporal patterns of seismicity may be\r\nmore robust than spatial trends. Clusters of large earthquakes analogous to\r\nsequences of foreshocks, mainshocks and aftershocks may occur on longer\r\ntime scales of seismic \"supercycles.\"
\r\n" }, { "name": "LaTourrette, Thomas", "degree": "PhD", "year": "1993", "title": "Experimental Determination of U and Th Partitioning Between Clinopyroxene, Garnet, Olivine, and Natural and Synthetic Silicate Melt", "advisor": "Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01072013-160430261", "creators": [ { "name": { "family": "LaTourrette", "given": "Thomas" }, "id": "LaTourrette-Thomas", "display_name": "LaTourrette, Thomas" } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/4ww8-x445", "abstract": "The distribution of U and Th between crystals and quenched silicate melt has been measured in experimentally crystallized natural and synthetic starting compositions. Clinopyroxene was crystallized from two natural basalts and a synthetic composition on the diopside-anorthite join, olivine from one of the natural basalts, and garnet from a synthetic andesite. Clinopyroxene and olivine were crystallized at atmospheric pressure under controlled oxygen fugacity and U and Th distributions were determined by particle track radiography. Garnet crystals were grown at 27 Kbars and actinide distributions were determined by secondary ion mass spectrometry. Crystals were grown by slow cooling in an effort to maintain chemical equilibrium at the crystal-melt interface.
\r\n\r\nClinopyroxene- and olivine-melt partition coefficients (Dixtl/liq = Cixtl/Ciliq) were calculated from track distributions by correcting for chemical zoning in the crystals (a result of fractional crystallization) and particle range differences between the crystals and glass. Over the range of \u0192O2s and compositions studied, DUcpx/liq = 0.0021 - 0.0093, = DThcpx/liq = 0.0047- 0.021, and DU;Thol/liq < 0.00005. Garnet-melt partition coefficients are DUgt/liq = 0.0013 and DThgt/liq = 0.0122. In order to study the effect of the U valence state distribution on U-Th fractionation, clinopyroxene crystallization experiments were run at oxygen fugacities corresponding to the Ni-NiO (NNO), Fa-Mt-Qz (FMQ) and 1 log unit more oxidizing than Fe-FeO (IW+ 1) oxygen buffers. All compositions show an increase in DUcpx/liq with decreasing \u0192O2, presumably from the increasing proportion of U4+ in the melt. DThcpx/liq displays little variation with \u0192O2, consistent with the fact that Th is solely tetravalent DThcpx/liq does show an apparent small decrease with decreasing \u0192O2 in one composition, and this is interpreted to be due to compositional changes stemming from variable amounts Na-loss with \u0192O2. A limited compositional analysis indicates that actinides may be incorporated into clinopyroxene by means of a (U,Th)4+ + 2Na+,\u21d4 3Ca2+ coupled substitution in the M2 site. This mechanism predicts a positive dependence of the actinide partition coefficients on (DCacpx/liq)3 / (DNacpx/liq)2.
\r\n\r\nWhile there is evidence for deviations from interfacial equilibrium during crystal growth, DThxtl/liq and DUxtl/liq are affected similarly. This results in DThxtl/liq/DUxtl/liq, which gives a measure of the degree of U-Th fractionation possible by crystal-melt partitioning, being insensitive to these deviations. DThcpx/liq/DUcpx/liq is well behaved, approximately independent of composition, and decreases by a factor of 2 - 3 as the \u0192O2 decreases from NNO to IW+1. This indicates that U-Th fractionation by crystal-melt partitioning is \u0192O2 dependent.
\r\n\r\nThese results indicate that U-Th fractionation by clinopyroxene-melt partitioning during partial melting will result in a melt with Th/U less than the clinopyroxene, U-Th fractionation by olivine will be insignificant for physically realistic melt fractions, and U-Th\r\nfractionation by garnet will result in a melt with ThiU greater than the garnet. The observed pattern of 238U-230Th disequilibrium in oceanic basalts (MORB and OIB) requires a net UTh fractionation that is large, ubiquitous, and results in (238U-230Th) < 1. With these constraints, fractionation by partial melting of spinel lherzolite is ruled out. The sense of U-Th fractionation by garnet is consistent with oceanic basalts, but the magnitude of fractionation is much smaller than the entire range in observed fractionations. Since partial melts of neither spinel nor garnet lherzolite can match the sense and magnitude of 238U-230Th disequilibrium in MORB and OIB, partial melting is considered unimportant in generating 238U-230Th disequilibrium in oceanic basalts. 238U-230Th disequilibrium in MORB and OIB must therefore result from some process other than partial melting, and possible alternative mechanisms are presented.
\r\n" }, { "name": "Ma, Kuo-Fong", "degree": "PhD", "year": "1993", "title": "The origin of tsunamis excited by local earthquakes. Broadband waveform observation of local earthquakes", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:01092013-102744893", "creators": [ { "name": { "family": "Ma", "given": "Kuo-Fong" }, "id": "Ma-Kuo-Fong", "display_name": "Ma, Kuo-Fong" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/dkgr-2k53", "abstract": "The origins of tsunamis excited by the 1989 Lorna Prieta, the 1906 San Francisco, and 1975 Kalapana, Hawaii, earthquakes were examined in part I. Since tsunamis are mainly caused by vertical deformation under the sea-floor, the tsunami data allows us to constrain the vertical motion of the sea-floor during the earthquake and to determine the excitation mechanism of the tsunami.
\r\n\r\nThe first arrival of the observed tsunami from the 1989 Lorna Prieta, California, earthquake observed at Montery was about 10 min. after the origin time of the earthquake.\r\nThe synthetic tsunami computed for the uniform dislocation model determined from seismic data can explain the arrival time, polarity, and amplitude of the beginning of the tsunami but the period is too long. We tested other fault models with more localized slip distribution. None of the models could explain the observed period. The residual waveform, the observed minus the synthetic waveform, begins as a downward motion at about 18 min. after the origin time of the earthquake, and could be interpreted as due to a secondary source near Moss Landing. The volume of sediments involved in the slumping is approximately 0.012 km^3. We conclude that the most likely cause of the observed tsunami\r\nis the combination of the vertical uplift of the sea floor due to the main faulting and a localized slumping near Moss Landing.
\r\n\r\nThe observation of tsunami excited by the 1906 San Francisco earthquake is curious because this earthquake is generally believed to be a strike-slip earthquake for which\r\ntsunamis are not usually expected. We show that the tsunami was caused by a local subsidence associated with a bend of the San Andreas fault offshore from the Golden Gate; no vertical fault motion was involved during the 1906 San Francisco earthquake.
\r\n\r\nThe 1975 Kalapana, Hawaii, earthquake was accompanied by large tsunamis which were well recorded at several tide-gauge stations around the Hawaii islands. To examine\r\nthe source of the tsunamis associated with the earthquake, we computed synthetic tsunamis for three tide-gage stations, Hilo, Honolulu and Kahului, using various dislocation models, Hilina fault models and slump models. Crustal deformation data were used to constrain the\r\ndislocation models. We could find a combination of a dislocation model for the earthquake and a Hilina fault model which can explain the observed crustal deformation inland fairly well. However, the tsunamis computed for this combined model are too early in first arrivals and too small in amplitudes. The residual tsunamis, observed synthetic, are not very different from the observed tsunamis and can be interpreted with a slump model which\r\ninvolves an uplift of 100-110 cm over an area of about 2500-3000 km^2 offshore. The total volume of displaced water associated with the slumping is about 2.5~3 Km^3.
\r\n\r\nThe recent deployment of TERRAscope, a broadband and wide dynamic range seismic network in Southern California, provided us with a capability of recording complete\r\nwaveforms of nearby earthquakes. These waveform data allow us to determine the overall faulting mechanisms, seismic moments, depths, stress drops, and the attenuation characteristics of the crust In part II. I investigated the waveforms of local earthquakes recorded at TERRAscope stations to understand the characteristics of the earthquake\r\nsequences.
\r\n\r\nThe Pasadena earthquake (M_L=4.9) of 3 December, 1988, occurred at a depth of 16 km, probably on the Santa Monica-Raymond fault. Prior to this event, no earthquake larger\r\nthan magnitude 4 had been recorded in this area since 1930. We determined the focal mechanisms and seismic moment of 9 aftershocks by combining the first-motion data and the waveform data of P, SV, and SH waves recorded at Pasadena TERRAscope station, since the first-motion data for most of the aftershocks are too sparse to determine the mechanism. The average orientations of the P and T axes of the aftershocks are consistent with the strike of the Raymond fault. The ratio of cumulative seismic moment of the\r\naftershocks to the seismic moment of the main shock is significantly smaller than commonly observed.
\r\n\r\nThe mechanisms and seismic moments of the Sierra Madre earthquake (M_L=5.8) of 28 June, 1991, sequence were determined using the same techniques that was applied in the\r\n1988 Pasadena earthquake sequence. Most events located within 5 km west of the mainshock are similar to the mainshock in waveform. The mechanisms thus determined are\r\nthrust. Some events have high stress drops between 100 to 1000 bars; the mainshock is one of them. For other larger events, including the two largest aftershocks, the stress\r\ndrops are between 10 to 100 bars. A few events located east of the mainshock have waveforms different from the mainshock and have strike-slip mechanisms. The ratio of\r\ncumulative seismic moments of the aftershocks to seismic moment of the mainshock is smaller than that of most events in California. The average Q_\u03b2 values along the paths from the hypocenters of the Sierra Madre and the Pasadena earthquake to PAS are about 130 and 80 respectively.
\r\n\r\nThe 1992 Landers earthquake is the largest event to have occurred in Southern California since 1952. We examined the waveforms of the aftershocks recorded at PFO\r\nTERRAscope station to see the correlation of the waveform and mechanisms determined from surface wave inversion. Since the depths of the events are usually not determined\r\nvery well, the amplitude ratio of surface wave to body wave was used to examine the accuracy of the depths determined with various methods. Most of the events which occurred to the south of the mainshock epicenter have similar waveforms and mechanisms. Only a few events occurred to the north of the mainshock epicenter where large slip occurred during the mainshock. These events have dissimilar waveforms and mechanisms. A near vertical distribution of the aftershock extending to a depth of 15 km, or even deeper is found at about 18 km to the south of the Landers earthquake epicenter. About 72% of the total energy of the aftershocks were released from the region to the south of the mainshock\r\nepicenter. The ratio of cumulative seismic moment of the aftershock to that of mainshock is less than 1/100.
\r\n" }, { "name": "Rowan, Linda Rose", "degree": "PhD", "year": "1993", "title": "Equation of state of molten mid-ocean ridge basalt. Structure of Kilauea volcano.", "advisor": "Ahrens, Thomas J.; Stolper, Edward M.; Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01142013-104747074", "creators": [ { "name": { "family": "Rowan", "given": "Linda Rose" }, "id": "Rowan-L-R", "display_name": "Rowan, Linda Rose" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "display_name": "Stolper, Edward M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "display_name": "Clayton, Robert W." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "display_name": "Rossman, George Robert" }, { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "display_name": "Westphal, James A." } ], "option_major": [ "geol" ], "doi": "10.7907/J6D0-GV56", "abstract": "Basalts are the most ubiquitous rocks erupting at the earth's surface at the present\r\ntime and they provide an important probe of the subsurface processes occurring\r\nwithin planetary interiors. Recent advances in both mineral physics and seismic\r\nanalysis have allowed me to undertake two independent studies related to the genesis\r\nand eruption of basaltic magmas. Chapters 1 and 2 are part of an experimental study\r\nconducted in the shock wave laboratory on the equation of state of molten mid-ocean\r\nridge basalt and the chemical interactions of the shocked liquid with its Mo container.\r\nMy advisors for this project were Thomas Ahrens and Edward Stolper. Chapter 3 is a\r\ntravel time tomography study of the three-dimensional structure of Kilauea Volcano,\r\nHawaii in collaboration with Robert Clayton. Chapter 3 is currently in press in the\r\nJournal of Geophysical Research.
\r\n\r\nThe EOS of molten MORB to 20 GPa was accomplished using the innovative silicate\r\nliquid shock wave measurement technique on the 40 mm propellant gun developed\r\nby Rigden [1986] and Miller [1990). This technique has been used to determine\r\nthe EOS for four synthetic melts and this thesis applies the technique to a natural\r\nmelt, a MORB dredged from the Juan de Fuca ridge. The resulting EOS indicates\r\nthat the MORB liquid is very compressible and therefore has a low bulk modulus of\r\n11.7 GPa. These results are consistent with low pressure static compression experiments\r\non similar basalts, but are not consistent with the results of ultrasonic interferometry.\r\nThe compressible nature of the MORB liquid is related to its composition\r\nand this may be expressed best by comparing the MORB Hugoniot to the Hugoniot\r\ndetermined for An_(36)Di_(64) and komatiite. The MORB and An_(36)Di_(64) Hugoniots show\r\nsignificant increase in density at low pressure followed by a stiffening at high pressures\r\nwhere the liquid Hugoniot approaches its respective dense oxide high pressure\r\ncomposition. This may be related to gradual coordination changes from four-fold to\r\nsix-fold for the Si^(+4) and Al^(+3) which are essentially complete at the high pressure\r\nwhere the curve stiffens. The MORB is much more compressible than the komatiite\r\nand overtakes the komatiite in density at a low pressure of 2.5 GPa. This is a\r\ncompositional effect caused by the enrichment of the MORB in Al_2O_3 and SiO_2 and\r\ndepletion in MgO compared to komatiite. The compressible nature of the MORB\r\nallows it to become denser than the surrounding mantle near the base of the low\r\nvelocity zone and therefore it is unlikely that MORB can be derived from very deep\r\nin the earth's upper mantle.
\r\n\r\nFor most shock wave experiments, the sample is not recovered and nothing can\r\nbe determined about its structure or composition due to the passage of the shock\r\nwave. In a few of my EOS experiments on molten MORB, however, the shocked sample\r\nwas recovered and could be studied in detail. Observations of impact-induced\r\ninteractions between the silicate liquid and its Mo container provide insight into\r\nplanetary impact and differentiation processes involving metal-silicate partitioning.\r\nThe shocked liquids showed extreme reduction and with increasing pressure the FeO\r\ncontent of the initial melt was reduced to almost nothing by reaction with the Mo.\r\nThese reactions produced metallic particles enriched in Mo, Fe and Si. These particles\r\nshow a similar texture as those found at impact sites on the earth and moon\r\nand provide clues to the impact origin of metallic particles.
\r\n\r\nA travel time tomography study of local P wave data from Kilauea Volcano,\r\nHawaii, was undertaken to determine the lateral heterogeneities produced by its intricate\r\nmagmatic and tectonic environment. The technique proved to be a powerful\r\nprobe of the volcano's intrusive plumbing because the presence of a dense seismic\r\narray and many local earthquakes allowed for excellent coverage of complex subsurface\r\nfeatures. Analysis and interpretation of the tomographic images leads to the\r\nfollowing inferrred model. The main shallow magma reservoir is delineated by a\r\nslow anomaly centered 2 km southeast of Halemaumau caldera. There is a distinct\r\nhigh velocity region centered northwest of the summit from 0 to 2 km depth that\r\nmay represent a dense wall and/or cap of intrusive rock that acts as a barrier or\r\ncontainment structure for the northern part of the reservoir. We suggest that the\r\nshallow reservoir is a narrow, compartmentalized region of sills and dikes because of\r\nthe closely spaced high and low velocity anomalies near the summit. The rift zones\r\nof Kilauea are imaged as major, high velocity entities, widening to the south with\r\ndepth until 6 km. These fast anomalies may be related to the sheeted dike complexes\r\nalong the rifts. On a finer scale, magma pockets centered at 0-2 km depth have been\r\ninferred beneath Makaopuhi, Mauna Ulu and Puu Oo, along the east rift zone. The\r\nHilina and Kaoiki fault zones, are imaged as slow features at shallow depths (less than 6\r\nkm), related to their tensional structures that produce the open fractures and cracks\r\nin the basaltic edifice. The Koae fault system is imaged as a slightly fast shallow\r\nstructure (less than 6 km) possibly related to intrusive diking from the adjacent rift zones.\r\nContinued inversions with the immense amount of seismic data collected for Hawaiian\r\nevents will allow the detailed development of a three-dimensional velocity model\r\nfor Kilauea. Such a model will be extremely useful to seismologists and petrologists\r\nalike for understanding the tectonic growth and magmatic evolution of this dynamic\r\nshield volcano.
\r\n\r\n" }, { "name": "Santee, Michelle", "degree": "PhD", "year": "1993", "title": "The thermal structure, dust loading, and meridional transport in the Martian atmosphere during late southern summer", "advisor": "Murray, Bruce C.; Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01092013-102520560", "creators": [ { "name": { "family": "Santee", "given": "Michelle" }, "id": "Santee-Michelle", "display_name": "Santee, Michelle" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/5qzc-4127", "abstract": "This thesis consists of two papers, both of which investigate the state of the Martian\r\natmosphere during a relatively clear period in late southern summer. The first paper\r\ndescribes a new technique for the simultaneous retrieval of atmospheric temperatures\r\nand dust abundances from thermal emission spectra. The second paper describes a\r\ndiagnostic stream function model which is used with the temperature and dust results\r\nof the first paper to solve for the meridional and vertical components of the diabatic\r\ncirculation simultaneously. The abstracts for the two papers are reproduced below.
\r\n\r\nPAPER I:
\r\n\r\nThe temperature structure and dust loading of the Martian atmosphere are investigated\r\nusing thermal emission spectra recorded by the Mariner 9 infrared interferometer\r\nspectrometer (IRIS). The analysis is restricted to a subset of the IRIS data\r\nconsisting of approximately 2400 spectra in a 12-day period extending from L_s = 343\u00b0\r\nto L_s = 348\u00b0, corresponding to late southern summer on Mars. Simultaneous retrieval\r\nof the vertical distribution of both atmospheric temperature and dust optical depth\r\nis accomplished through an iterative procedure which is performed on each spectrum.\r\nThe inclusion of dust opacity in the retrieval algorithm causes the retrieved\r\ntemperatures to change by more than 20 K in some atmospheric layers. The largest\r\ncolumn-integrated 9 \u00b5m dust optical depths (~ 0.4) occur over the equatorial regions.\r\nThe highest atmospheric temperatures (> 260 K) are found at low altitudes\r\nnear the sub-solar latitude (~ 6\u00b0 s), while the coldest temperatures (\u02c2 150 K) are\r\nfound at levels near 1.0 mbar over the winter pole. A comparison of temperature\r\nmaps for 2 PM and 2 AM indicates diurnal temperature variations as large as 80 K\r\nat low altitudes near the sub- solar latitude, whereas diurnal temperature changes at\r\npressures less than 1.0 mbar are typically about 10 K. Both dayside and nightside\r\ntemperatures above about 0.1 mbar (~ 40 km) are warmer over the winter (north)\r\npolar region than over the equator or the summer (south) polar region. This thermal\r\nstructure suggests the existence of a net zonally-averaged meridional circulation with\r\nrising motion at low latitudes, poleward flow at altitudes above 40 km, and subsidence\r\nover the poles. Because a meridional circulation transports atmospheric constituents\r\nas well as heat, it has significant implications for the net flux of dust and water into\r\nthe polar regions.
\r\n\r\nPAPER II:
\r\n\r\nThe circulation of the Martian atmosphere during late southern summer is calculated\r\ndiagnostically from the observed atmospheric temperature distribution. We use global\r\nmaps of temperature and dust optical depth (~ 0-60 km) retrieved from a subset of\r\nthe Mariner 9 IRIS thermal emission spectra spanning L_s = 343\u00b0- 348\u00b0 [Santee and\r\nCrisp, 1992]. This thermal structure is characterized by a reversed meridional temperature\r\ngradient (temperatures increasing poleward) at altitudes above about 40 km.\r\nZonal- mean zonal winds are derived from the zonally-averaged temperatures assuming\r\ngradient wind balance and zero surface zonal wind. Both hemispheres have intense\r\nmid- latitude westerly jets (with velocities of 80- 90 m/s near 50 km); in the southern\r\ntropics the winds are strongly easterly (with velocities of 100 m/s near 50 km).\r\nThe north-south atmospheric transport includes contributions from the zonal- mean\r\nmeridional circulation and large-scale waves. Their net effect can be approximated\r\nby the diabatic circulation, which is that circulation needed to maintain the observed\r\ntemperature distribution (warm winter pole, cool tropics) in the presence of the radiative\r\nforcing. A radiative transfer model [Crisp, 1990] which accounts for absorption,\r\nemission and multiple scattering by particles and non- grey gases is used to compute\r\nthe solar heating and thermal cooling rates from diurnal averages of the retrieved\r\nIRlS temperature and dust distributions. At pressures below 4 mbar, there are large\r\nnet heating rates (up to 8 K/ day) in the equatorial region and large net cooling rates\r\n(up to 20 K/ day) in the polar regions. These net heating rates are used in a diagnostic\r\nstream function model which solves for the meridional and vertical components of\r\nthe diabatic circulation simultaneously. We find a two-cell circulation, with upwelling\r\nover the equator(~ 1.5 cm/s), poleward motion in both hemispheres(~ 2 m/s), and\r\nsubsidence over the poles (1-2 cm/ s). This circulation is sufficiently vigorous that the\r\nmeridional transport time scale is ~ 13 days. Vertical transport is primarily advective\r\nin nature, except in the high-altitude winter polar regions, where diffusive processes\r\ndominate. Water vapor desorbed from the low-latitude regolith during late northern\r\nwinter/ early northern spring may be transported upward by the ascending branch of\r\nthis circulation, where it would be transported poleward by the high-altitude meridional\r\nwinds. This process could provide a high-altitude source of water vapor for the\r\npolar hood.
\r\n\r\n\r\n\r\n\r\n" }, { "name": "Wald, David Jay", "degree": "PhD", "year": "1993", "title": "Rupture characteristics of California earthquakes", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01152013-161612475", "creators": [ { "name": { "family": "Wald", "given": "David Jay" }, "id": "Wald-D-J", "display_name": "Wald, David Jay" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/0efb-ty71", "abstract": "The rupture characteristics of the 1987 Superstition Hills (M_s = 6.6), the 1989\r\nLoma Prieta (M_s = 7.1), and the 1991 Sierra Madre (M_L = 5.8) earthquakes were\r\ndetermined using a constrained, damped, least-squares inversion of strong motion and\r\nteleseismic waveforms. Extension of the modeling procedure to employ teleseismic,\r\nempirical Green's functions allowed determination of faulting details of a fourth\r\nearthquake, the great 1906 San Francisco event.
\r\n\r\nThe 1987 Superstition Hills earthquake was the second and larger of two significant\r\nearthquakes that occurred on conjugate faults in the western Imperial Valley.\r\nThe first event (M_s = 6.2), located on the Elmore Ranch Fault, had a geometry and\r\nmechanism favorable for triggering the larger event on the Superstition Hills Fault\r\nsome 12 hours later. The Superstition Hills event was modeled as three independent\r\nsubevents, each nucleating from a common location near the intersection of the two\r\nfaults. This required rerupturing of one fault region on the time scale of several seconds.\r\nSlip was quite heterogeneous along strike, but fairly systematic as a function\r\nof depth. Substantial differences between the source process as observed from strong\r\nmotion data and from teleseismic data were observed.
\r\n\r\nThe 1989 Loma Prieta Earthquake began with a small (magnitude 4.5 to 5.0)\r\nprecursor, which preceded the main part of the rupture by about 2 sec. Rupture was\r\nbilateral, with the overall radiation greater from the northwest portion of the fault.\r\nSeparate inversions of the teleseismic data (periods 3-30 sec) and strong motion data\r\n(periods 1-5 sec) resulted in similar models, indicating a close correspondence of\r\nlong- and short-period radiation. Forward predictions of the local strong motions\r\nfrom the teleseismic rupture model matched the distribution, duration and overall\r\nfrequency content of the recordings, suggesting that constraints on strong motions\r\ncan be made with teleseismic broadband recordings.
\r\n\r\nShort period and broadband teleseismic waveform data and three-component\r\nstrong-motion records were analyzed to obtain the source rupture history of the\r\n1991 Sierra Madre earthquake. The near-field, shear-wave displacement pulse from\r\nthis event had a relatively short duration (about 1 sec) for the magnitude of the\r\nevent, requiring a particularly high-average stress drop (175 bars). The ground-motion\r\nvariations in the Los Angeles region were controlled predominantly by source\r\ndirectivity. Rupture was updip and southwestward, resulting in strong motions and\r\nheavier damage in regions to the southwest of the epicenter and near the updip fault\r\nprojection.
\r\n\r\nThe rupture process of the 1906 San Francisco earthquake was analyzed, using\r\nall high-quality, teleseismic recordings archived in the 1908 Carnegie Report of the\r\nState Earthquake Investigation Commission. The recordings are relatively simple\r\nconsidering the great rupture length in 1906, requiring that substantial portions of\r\nthe fault, while having large slips, radiated little 5-25 sec energy. Two regions of the\r\nfault, one near the epicenter south of San Francisco, and one between Point Reyes\r\nand Fort Ross were responsible for generating the greater part of the energy observed\r\non the teleseismic recordings. By comparison of our model for 1906 with modern,\r\nwell-studied, large strike-slip events, we found similarities in rupture style with the\r\nrelatively simple 1990 Philippines earthquake (M_s = 7.8), but contrasts with the\r\ncomplexity of the 1976 Guatemala earthquake (M_s = 7.5).
\r\n\r\nThe rupture characteristics of these events when analyzed with previous finite-fault\r\nstudies over the past decade indicate several common features. Variations\r\nin slip are more pronounced along strike than downdip. Vertical strike-slip faults\r\nshow a systematic slip variation with depth, consistent with both shallow and deep\r\nzones with velocity-strengthening frictional resistance; nucleation is usually at the\r\nbase of the seismogenic zone. Oblique and dip-slip events show much more depth\r\nvariation in slip, indicative of thicker, more complex seismogenic zones associated\r\nwith tectonic regimes involving crustal thickening or extension. The Superstition\r\nHills, Loma Prieta and Sierra Madre strong-motion data sets all require short rise\r\ntimes, so only a small portion of the fault is slipping at a particular time, in agreement\r\nwith the \"self-healing\" model described by Heaton [1990] and in conflict with long\r\nslip durations required by many crack-like models of dynamic rupture. With the\r\nexception of the Superstition Hills earthquake, seismic moments and slip distributions\r\ndetermined from the strong-motion data concur with moments and slips derived\r\nfrom geodetic and longer-period waveforms. This indicates that the higher-frequency\r\ndata are sufficient for estimating the total slip, and therefore, the rupture durations\r\ninferred represent the entire coseismic slip duration. The agreement between longand\r\nshort-period source models makes it possible to estimate ground motions for\r\nimportant historical events from source models determined using longer-period (5-15\r\nsec), teleseismic body waves.
" }, { "name": "Achterberg, Richard Karl", "degree": "PhD", "year": "1992", "title": "Numerical Simulation of Baroclinic Jovian Vortices", "advisor": "Ingersoll, Andrew P.; Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09262011-111706613", "creators": [ { "name": { "family": "Achterberg", "given": "Richard Karl" }, "id": "Achterberg-Richard-Karl", "display_name": "Achterberg, Richard Karl" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "co-advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci", "astronomy" ], "doi": "10.7907/0pjs-sb11", "abstract": "This thesis consists of two papers on the dynamics of Jovian planet atmospheres. The first paper discusses the uses of a normal-mode expansion in the vertical for modeling\r\nthe dynamics of Jupiter's atmosphere. The second paper uses a non-linear numerical model based on the normal-mode expansion of the first paper to study the dynamics\r\nof baroclinic vortices. The abstracts for the two papers are reproduced below.
\r\n\r\nPaper 1:
\r\n\r\nWe propose a non-linear, quasi-geostrophic, baroclinic model of Jovian atmospheric dynamics, in which vertical variations of velocity are represented by a truncated sum over a complete set of orthogonal functions obtained by a separation of variables of the linearized quasi-geostrophic potential vorticity equation. A set of equations for the time variation of the mode amplitudes in the non-linear case is then derived. We show that for a planet with a neutrally stable, fluid interior instead of a solid lower boundary, the barotropic mode represents motions in the interior, and is not affected by the baroclinic modes. One consequence of this is that a normal mode model with one baroclinic mode is dynamically equivalent to a one layer model with solid lower topography. We also show that for motions in Jupiter's cloudy lower troposphere, the stratosphere behaves nearly as a rigid lid, so that the normal-mode model is applicable to Jupiter. We test the accuracy of the normal-mode model for Jupiter using two simple problems: forced, vertically propagating Rossby waves, using two and three baroclinic modes, and baroclinic instability, using two baroclinic modes. We find that the normal-mode model provides qualitatively correct results,\r\neven with only a very limited number of vertical degrees of freedom.
\r\n\r\nPaper 2:
\r\n\r\nWe examine the evolution of baroclinic vortices in a time dependent, nonlinear numerical model of a Jovian atmosphere. The model uses a normal-mode expansion in the vertical, using the barotropic and first two baroclinic modes (Achterberg and Ingersoll 1989). Our results for the stability of baroclinic vortices on an \u0192-plane in the absence of a mean zonal flow are consistent with previous results in the literature, although the presence of the deep fluid interior on the Jovian planets appears to shift the stability boundaries to smaller length scales. The presence of a mean zonal shear flow acts to stabilize vortices against instability, significantly modifies\r\nthe finite amplitude form of baroclinic instabilities, and combined with internal barotropic instability (Gent and McWilliams 1986) produces periodic oscillations in the\r\nlatitude and longitude of the vortex as observed at the level of the cloud tops. This instability may explain some, but not all, observations of longitudinal oscillations of\r\nvortices on the outer planets. Oscillations in aspect ratio and orientation of stable elliptical vortices in a zonal shear flow are observed in this baroclinic model, as in\r\nsimpler two-dimensional models (Kida 1981). The meridional propagation and decay of vortices on a \u03b2-plane is inhibited by the presence of a mean zonal flow. The direction of propagation of a vortex relative to the mean zonal flow depends upon the sign of the meridional potential vorticity gradient; combined with observations of vortex drift rates, this may provide a constraint on model assumption for the flow in the deep interior of Jupiter.
\r\n" }, { "name": "Dixon, Jacqueline Eaby", "degree": "PhD", "year": "1992", "title": "Water and carbon dioxide in basaltic magmas", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09302011-113009730", "creators": [ { "name": { "family": "Dixon", "given": "Jacqueline Eaby" }, "id": "Dixon-J-E", "display_name": "Dixon, Jacqueline Eaby" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Holloway", "given": "John" }, "id": "Holloway-J", "role": "member", "display_name": "Holloway, John" }, { "name": { "family": "Clague", "given": "David" }, "id": "Clague-D", "role": "member", "display_name": "Clague, David" } ], "option_major": [ "geol" ], "doi": "10.7907/KPWW-6M36", "abstract": "Experiments were conducted in which basaltic melts were equilibrated with a vapor phase consisting of pure water, pure carbon dioxide, and water-carbon dioxide mixtures at\r\n1200\u00b0C and 200 to 980 bars in order to develop a basis for interpreting the behavior of these volatiles during the evolution and degassing of submarine magmas. Molar\r\nabsorptivities for the 4500 cm^(-1) band for hydroxyl groups and for the 5230 and 1630 cm^(-1) bands of molecular water were calibrated to be 0.67 \u00b1 0.04, 0.62 \u00b1 0.08, and 25 \u00b1 3 l/mole-cm, respectively. The solubility of water in MORE liquid was determined from the experiments in which MORB melt was equilibrated with pure H_20 vapor. Results are in agreement with the higher-pressure results of Hamilton et al. (1964) on Columbia River basalt. Trends observed in the concentrations of molecular water and hydroxyl groups with respect to total water concentration in the quenched, experimental, basaltic glasses are\r\nsimilar to those observed in albitic glasses (Silver and Stolper, 1989). Moreover, the concentration of molecular water measured in the quenched basaltic glasses is\r\napproximately proportional to water fugacity in all samples regardless of the composition of the vapor (X_CO_2), demonstrating that molecular water solubility in basaltic melts is closely approximated by Henry's law at pressures less than 1 kbar. Total water concentrations and\r\nthe speciation of water in vapor-saturated basaltic melt are fit by a regular ternary solution model with the coefficients for albitic glasses (Silver and Stolper, 1989), where the activity of water in the melt is given by Henry's law for molecular water. At pressures higher than\r\nabout 1 kbar, the effect of the molar volume of water in the melt (V^(0,m)_(H_2O)) on the activity of water in vapor-saturated melts is no longer negligible; a (V^(0,m)_(H_2O)) ~12 cm^3/mole fits the data of Hamilton et al. (1964).
\r\n\r\nConcentrations of CO_2 dissolved as carbonate in the experimental glasses range from 63 to 315 ppm CO_2. Carbonate was the only species of dissolved carbon observed.\r\nThe mole fraction of CO_2 in the vapor varied from 0.39 to 0.93. Concentrations of CO_2 dissolved as carbonate in the melt for all the experiments are proportional to fCO_2. The\r\ndata for pure CO_2-saturated and mixed H_2O-CO_2-saturated experiments are fit with a straight line through the origin with a slope of 40 ppm/100 bar fCO_2 (equivalent to 47\r\nppm/km water depth). These results suggest Henrian behavior for CO_2; that is, the solubility of CO_2 in the basaltic melt is essentially proportional to the fugacity of CO_2 with the same constant of proportionality whether the vapor contains pure CO_2 or H_2O + CO_2. These results do not support the widely held view that water enhances the solubility of carbon dioxide in basaltic melts.
\r\n\r\nResults of degassing calculations show that the vapor phase in equilibrium with MORB magmas at typical midoceanic eruption depths is CO_2 -rich and that the dissolved\r\nCO_2 contents should vary linearly with depth of eruption. Basaltic magmas containing < 1.0 wt. % H_2O will not degas significant quantities of water until pressures < 100 bars are reached. As water contents increase either through fractional crystallization or variations in the initial water contents. an inverse correlation is predicted between dissolved CO_2 and H_20 contents in melts saturated with a mixed H_2O-CO_2 vapor phase. These predictions were tested by examining the water and carbon dioxide concentrations in suites of basaltic glasses from the Juan de Fuca Ridge and Hawaii.
\r\n\r\nConcentrations of dissolved H_2O and CO_2 were measured in a suite of basaltic glasses from the Juan de Fuca Ridge. CO_2 contents dissolved as carbonate range from about 45 to 360 ppm by weight. In contrast to the predictions based on vapor-saturated degassing samples empted at a given depth exhibit a large range in dissolved CO_2 contents that we interpret to be the result of variable amounts of degassing. The lowest CO_2 contents at each depth are in reasonable agreement with the experimentally determined CO_2\r\nsolubility curve for basalt at low pressures. All glasses with CO_2 values higher than the experimentally determined solubility at the emption depth are oversaturated because of\r\nincomplete degassing. The highest CO_2 contents are spatially associated with the local topographic highs for each ridge segment. Lavas from relatively deep areas may have had greater opportunity to degas duIing ascent from a relatively deeper magma chamber or during late ral flow in dikes or seatloor lava flows. The highest observed CO_2\r\nconcentrations are from the axial seamount and lead to an estimate of a minimum depth to the magma chamber of 2.7 kilometers beneath the ridge axis. Water contents were not\r\nmodified during degassing and were found to behave incompatibly duIing partial melting and crystal fractionation. Variations in ratios of water to other incompatible elements suggest that water has a bulk partition coefficient similar to La duIing partial melting\r\n(~D0.010).
\r\n\r\nMajor, minor, and dissolved volatile element concentrations were measured in tholeiitic glasses from the submarine portion (puna Ridge) of the east lift zone of Kilauea Volcano, Hawaii. Dissolved H_2O and S concentrations display a wide range relative to nonvolatile incompatible elements at all depths. This range cannot be readily explained by fractional crystallization, degassing of H_2O and S during eruption on the seafloor, or source region heterogeneities. Dissolved CO_2 concentrations, in contrast, show a positive correlation with eruption depth and typically agree within error with the solubility at that\r\ndepth. Magmas along the Puna Ridge can be modelled as resulting from (1) mixing of a relatively volatile-rich, undegassed component with magmas that experienced low pressure (perhaps subaerial) degassing during which substantial H_2O, S, and CO_2 were lost, followed by (2) fractional crystallization of olivine, clinopyroxene, and plagioclase from this mixture to generate a residual liquid; and (3) further degassing, principally of CO_2 for\r\nsamples erupted deeper than 1000 m, during eruption on the seafloor. The degassed end member may form at upper levels of the summit magma chamber (assuming less than lithostatic pressure gradients), during residence at shallow levels in the crust, or during sustained summit eruptions. The final phase of degassing during eruption on the seafloor\r\noccurs slowly enough to achieve melt/vapor equilibrium during exsolution of the typically CO_2-rich vapor phase. According to the model, an average Kilauean primary magma with 16.0 % MgO should contain ~0.47 wt. % H_20 and ~900 ppm S. The model predicts that submarine lavas from wholly submarine volcanoes (i.e., Loihi), for which there is no opportunity to generate the degassed end member by low pressure degassing, will be enriched in volatiles relative to those from volcanoes whose summits have breached the sea surface (i.e., Kilauea and Mauna Loa).
\r\n" }, { "name": "Donnellan, Andrea", "degree": "PhD", "year": "1992", "title": "A geodetic study of crustal deformation in the Ventura Basin region, Southern California", "advisor": "Hager, Bradford H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09282011-105846249", "creators": [ { "name": { "family": "Donnellan", "given": "Andrea" }, "id": "Donnellan-Andrea", "display_name": "Donnellan, Andrea" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." } ], "option_major": [ "geol" ], "doi": "10.7907/ejva-6672", "abstract": "The Ventura basin lies within the north-south compressive western Transverse Ranges in southern California. The basin is characterized by rapid north-south convergence on geologic time-scales, with Quaternary rates of convergence across the basin estimated to be approximately 20 mm/yr. Global Positioning System (GPS) observations carried out over a period of 2.7 years suggest rapid rates of convergence of 7 \u00b1 2 mm/yr on geodetic time scales. The deformation corresponds to a maximum shear strain rate of 0.6 \u00b1 0.1 \u03bcrad/yr with the azimuth of maximum\r\ncompression oriented 16\u00b0 \u00b1 8\u00b0 W. The dilatation rate of 0.3 \u00b1 .1 x 10^(-6)yr^(-1) indicates that a significant amount of compression is occurring. The strain rates of\r\n0.1 \u00b1 0.1 \u03bcrad/yr south of the basin are much lower. Strain rates calculated from the GPS measurements are consistent with those calculated from comparisons between GPS and historical triangulation data. The deformation in the basin region cannot be modeled as a megashear zone, which best describes much of California.
\r\n\r\n\r\nThe observed deformation can be modeled by creep on detachment faults both north and south of the basin. Faults near the surface are most likely locked. Rupture of the San Cayetano fault within the next 200 years is possible, resulting in an earthquake of moment magnitude 6.0-6.8. Based on the fault models, the south side of the basin is capable of producing a magnitude 5.5-6.0 earthquake. The models of the short-term deformation suggest that the observed rate is consistent with the geologic record, but that the observations have taken place over a small fraction of the earthquake cycle.
\r\n" }, { "name": "Duffy, Thomas Sheehan", "degree": "PhD", "year": "1992", "title": "Elastic Properties of Metals and Minerals under Shock Compression", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05172007-104609", "creators": [ { "name": { "family": "Duffy", "given": "Thomas Sheehan" }, "id": "Duffy-Thomas-Sheehan", "display_name": "Duffy, Thomas Sheehan" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/m63k-zj81", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nComparison of laboratory elasticity data with seismic measurements of the Earth provides a means to understand the deep interior. The effect of pressure and temperature on elastic properties must be well understood for meaningful comparisons. In this work, elastic wave velocities have been measured under shock compression to 80 GPa in an Fe-Cr-Ni alloy, to 27 GPa in polycrystalline MgO, and to 81 GPa in molybdenum preheated to 1400\u00b0C. These measurements were made by recording particle velocity histories at a sample surface using the method of velocity interferometry. In addition to elastic properties, these experiments provide information on the constitutive and equation of state (EOS) properties of the sample as well as the unloading adiabats.
\r\n\r\nCompressional and bulk wave velocities in Fe-Cr-Ni alloy are consistent with third-order finite strain theory and ultrasonic data. Thermal effects on the wave velocities are less than 2% at 80 GPa. Second pressure derivatives of velocity were constrained along the Hugoniot to be: (\u22022CL/\u2202P2)H = -0.16 (0.06) GPa-1 and (\u22022KS/\u2202P2)H = -0.17 (0.08) GPa-1. The measured wave profiles can be successfully reproduced by numerical simulations utilizing elastic-plastic theory modified by a Bauschinger effect and stress relaxation. Material strength was found to increase by a factor of at least 5 up to 80 GPa and to be 2-3% of the total stress.
\r\n\r\nCompressional and bulk velocities in Fe-Cr-Ni define linear velocity-density trends and can be modeled by averaging properties of Fe, Cr, and Ni. The effect of alloying ~4 wt.% Ni with Fe would change both VP and VB by less than 1% under core conditions. Compressional velocities in Fe-Ni are compatible with inner core values when corrected for thermal effects. Shear velocities in Fe, determined from a combination of VP and VB data, are ~3.6 km/s at P=150-200 GPa. Low values are most likely caused by a weak pressure dependence of the rigidity and imply that partial melting is not required in the inner core.
\r\n\r\nWave profile and EOS measurements in polycrystalline MgO define its EOS: US = 6.77(0.08) + 1.27(0.04)up. Compressional sound velocities to 27 GPa yield the longitudinal modulus and its pressure derivative: CLo = KoS + 4/3G = 335 \u00b1 1 GPa and C'Lo = 7.4 \u00b1 0.2, which are in good agreement with ultrasonic determinations. The unloading wave profiles can be modeled using a modified elastic-plastic constitutive response originally developed for metals. Thermal expansivities in MgO have been determined to be 12 \u00b1 4 x 10-6 K-1 at P=174-200 GPa and T=3100-3600 K from shock temperature and EOS data. These results imply that the lower mantle is enriched in Si and/or Fe relative to the upper mantle.
\r\n\r\nWave profiles in molybdenum at 1400\u00b0C are the first wave profile determinations at significantly high initial temperature. The EOS determined from these measurements agrees well with previous data. The compressive yield strength of Mo is 0.79-0.94 GPa at 1400\u00b0C, and the HEL stress is 1.5-1.7 GPa. The temperature coefficient of compressional velocity, (\u2202Vp/\u2202T)p, is found to vary from -0.35(0.13) m/s/K at 12 GPa to -0.18(0.14) m/s/K at 81 GPa and compares with an ambient pressure value of -0.26 m/s/K. It is inferred that (\u2202Vp/\u2202T)p decreases with pressure, and data for Mo are shown to be consistent with trends defined by other metals.
" }, { "name": "Hofstadter, Mark David", "degree": "PhD", "year": "1992", "title": "Microwave observations of Uranus", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:09222011-102938775", "creators": [ { "name": { "family": "Hofstadter", "given": "Mark David" }, "id": "Hofstadter-Mark-David", "orcid": "0000-0002-3208-3918", "display_name": "Hofstadter, Mark David" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/9RTG-Q786", "abstract": "This thesis explores the atmosphere of Uranus using microwave observations at wavelengths from 1 to 20 cm, with primary emphasis on high resolution VLA data at wavelengths\r\nof 2 and 6 cm. While radio maps of Uranus have been published previously, this is the first detailed analysis and interpretation of such observations. Atmospheric\r\nstructures are mapped to depths greater than has been seen on any giant planet. Several features of the data are immediately clear. First, there are strong horizontal and vertical gradients in the atmospheric properties that control the radio brightness. Polar regions are much brighter than lower latitudes, and the deep troposphere (pressures greater than a few tens of bars) appears much dimmer than would be expected based on the upper troposphere.\r\n(Both these results had been postulated in previous works, but older observations lacked the resolution to confirm them.) A second important feature of the data is that the\r\nintrinsic latitudinal brightness variations determined in this work at 2 cm and 6 cm are highly correlated with each other and with Voyager infrared measurements, suggesting a\r\ncommon cause. Because these data sets probe different altitudes between 50 and 0.1 bar, the cause must be acting over this altitude range of about 250 km. Another immediate\r\nresult, independent of atmospheric modeling, is that the radio brightness features have not changed significantly in the 8 years between 1981 and 1989.
\r\n\r\nSince radio brightness is a function of temperature and composition, the observations can be used to map these properties as a function of latitude and height. Arguments are presented that indicate compositional gradients are the dominant factor controlling the brightness variations, and these compositional changes are used as a tracer to infer the general circulation and some of the chemical processes of the atmosphere. The most likely interpretation of the data is that the Southern Hemisphere is dominated by a single meridional circulation cell, with an upwelling centered near -25\u00b0 latitude that brings absorber rich air parcels from 50 bars up to the 0.1 bar region. As parcels rise, the absorber mixing ratio drops by a factor of about 100 between 25 and 10 bars, and then a further factor of 2 at higher altitudes. These depletions are probably due to condensation. The absorber depleted parcels then move poleward and descend, dominating the atmospheric\r\ncomposition over the pole down to 50 bars, but not deeper. This circulation is consistent with the zonal winds and upper atmospheric temperatures observed by Voyager in the\r\ncontext of a simple, linear, dynamical model. The model suggests that the forcing driving these motions occurs within the upper few hundred bars of the atmosphere. The species most likely to be responsible for microwave absorption in the atmosphere is NH_3, and at depth it appears to have a molar mixing ratio within an order of magnitude of 1.4 x 10^(-4), the solar value. The formation of an NH_4SH cloud above 30 bars can account for the\r\nprimary depletion of NH_3, while NH_3 ice condensation at 5 bars accounts for the rest. Most of the results discussed here, however, are independent of what the absorbing\r\nspecies actually is.
\r\n\r\nSuperimposed on the large scale brightness pattern are smaller brightness oscillations, less than about 15\u00b0 wide in latitude. These long lasting features are reminiscent of the zones and belts of Jupiter, and could be the result of variations in either cloud altitudes or the depth of penetration of subsiding air parcels. A more extensive analysis is needed, however, to understand these small scale structures. The final point addressed in this\r\nwork is the seasonal variability of the atmosphere. While no variations exist in the current high resolution data set, which covers about 10 years of the mid-summer season,\r\nit is expected that detectable changes will occur over 20 to 40 year time scales (each season on Uranus lasts 21 years). The magnitude of the variations, however, cannot be\r\ndetermined from the available data.
" }, { "name": "Knott, Diane Clemens", "degree": "PhD", "year": "1992", "title": "Geologic and isotopic investigations of the early Cretaceous Sierra Nevada Batholith, Tulare Co., CA, and the Ivrea Zone, NW Italian Alps: examples of interaction between mantle-derived magma and continental crust", "advisor": "Taylor, Hugh P.; Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04222011-143434002", "creators": [ { "name": { "family": "Knott", "given": "Diane Clemens" }, "id": "Knott-D-C", "display_name": "Knott, Diane Clemens" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "co-advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "chair", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geol" ], "doi": "10.7907/AA6N-EY25", "abstract": "Two igneous suites containing layered ultramafic-mafic cumulates were investigated with the intent to characterize the parental magma and to identify processes significant to the petrogenesis of these rocks. In both study areas, the early Cretaceous Sierra Nevada batholith and the Ivrea Zone, isotopic systematics of the cumulates were found to preserve the characteristics of the mantle-derived parental magma and to record the effects of fractional crystallization and assimilation. Modeling the relative importance of these processes and characterization of the material derived from the mantle are necessary to understanding the growth of the continental crust.
\r\n\r\nGeologic mapping of 110 mi2 of the 125 to 110 Ma Stokes Mountain region reveals the presence of layered cumulate megaxenoliths and two coeval ring dike complexes. Petrographic analysis and geochemical modeling of 125 dominantly mafic and intermediate samples demonstrate the comagmatic nature of this suite. Combined oxygen, strontium and neodymium analysis of 22 samples indicates, however, that each ring complex was fed by an isotopically distinct parental magma (\u03b5Nd(115) = +6.1, Sri = 0.70338, \u03b418O = 6.6\u2030 ; (\u03b5Nd(115) = +5.7, Sri = 0.70372, \u03b418O = 6.7\u2030) both of which were derived from a variably contaminated, depleted mantle source. Minor assimilation of continentally-derived metasediments and mafic-ultramafic material of the Kings-Kaweah ophiolite further affected the isotopic evolution of the two subsuites. Hydrothermal alteration in the subvolcanic environment is recorded only by rare stoped xenoliths of 120 Ma hypabyssal intrusives.
\r\n\r\nLate Hercynian (\u2248300 - 270 Ma) magmatism produced the 10 km thick Mafic Complex lying at the base of the Ivrea-Strona-Ceneri crustal cross section. \u03b418O analysis of 237 whole rock samples and 26 mineral separates reveals that presumably early intrusions into the cool crust preserve the depleted mantle signature of the modeled parental magma (\u03b5Nd(115) = +7, Sri = 0.703, \u03b418O = 6.5\u2030) while later intrusions assimilated significant amounts of the 10 - 12\u2030 metapelite. Subsequent intrusion of voluminous basaltic magma fonned a large, convecting magma chamber in which assimilation was concentrated within boundary layers. Such lower crustal production of high-18O (\u03b418O = 8 - 10\u2030) mafic magmas is suggested as contributing to the petrogenesis of upper crustal Permian granites.
\r\n" }, { "name": "McGill, Sara Hanley Fagerson", "degree": "PhD", "year": "1992", "title": "Paleoseismology and neotectonics of the central and eastern Garlock Fault, California", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03192007-132452", "creators": [ { "name": { "family": "McGill", "given": "Sara Hanley Fagerson" }, "id": "McGill-Sara-Hanley-Fagerson", "display_name": "McGill, Sara Hanley Fagerson" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/N2KZ-NH42", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Garlock fault is one of the major active faults in California. Although it has not produced any large earthquakes during historic times, abundant fault scarps in Holocene deposits and offset geomorphic features attest to the occurrence of large, prehistoric earthquakes on this fault. In an effort to better characterize the seismic hazard associated with the Garlock fault, I have measured the slip rate of the fault in southeastern Searles Valley, documented the left-lateral displacement associated with past earthquakes on the central and eastern portions of the fault, estimated the size and frequency of those earthquakes, and constrained the age of the most recent large earthquake on the portion of the fault in Searles Valley.\r\n\r\nA latest-Pleistocene shoreline at the overflow-level of Searles Lake has been offset 82 to 106 meters (best estimate = 90 m) along the Garlock fault, in southeastern Searles Valley. Radiocarbon dates from both surface and subsurface units indicate that the most recent highstand of Searles Lake ended sometime between 10,000 and 13,800 radiocarbon years ago (Stuiver and Smith, 1979; Benson and others, 1990; Bard and others, 1990). The maximum slip rate of the Garlock fault in southeastern Searles Valley is thus 10.6 mm/[...]-yr. If part of the offset of the shoreline is a remnant from older lakestands, then the slip rate may be somewhat less, but a channel that incised after the most recent highstand is offset 69 \u00b1 2 m, indicating that the minimum slip rate is 5 mm/[...]-yr. Subjective evaluation of the constraints on the offset and on the age of the shoreline suggest that the slip rate is most likely between 6 and 8 mm/[...]-yr at this site. If Bard and others' (1990) calibration of the radiocarbon timescale is correct, then the true slip rate of the Garlock fault is between 4 and 9 mm/yr and most likely between 5 and 7 mm/yr.\r\n\r\nThis slip rate is consistent with the [...] rate determined by Clark and Lajoie (1974) at Koehn Lake. Considering the Quaternary, west-northwestward extension that has occurred north of the Garlock fault, one might expect the slip rate of the Garlock fault to decrease eastward (Davis and Burchfiel, 1973). The slip rate determined in southeastern Searles Valley indicates that no eastward decrease in the Garlock fault slip rate is required between Koehn Lake and Searles Lake, but an eastward decrease of up to 3 mm/yr is plausible.\r\n\r\nGeomorphic features offset along the central and eastern Garlock fault record the amount of left-lateral surface slip associated with prehistoric earthquakes. Along the easternmost 90 km of the fault, the smallest offsets cluster around 2-3 m, apparently associated with the most recent rupture of this portion of the fault. Larger offsets along this part of the fault, especially in Pilot Knob Valley, cluster around values consistent with 2 to 4 m of slip in each of the past several events. Farther west, south of El Paso Mountains, offset geomorphic features suggest that each of the past two earthquakes on this stretch of the Garlock fault was produced by about 7 m of slip, whereas the third event back resulted from about 4 m of slip.\r\n\r\nVertical displacements of geomorphic features range from 0% to 30% of the left-lateral offsets. Within Pilot Knob Valley (along the southern side of the Slate Range) vertical displacements are consistently up on the northern side, whereas within the Avawatz Mountains both north- and south-side-up displacements are present.\r\n\r\nOn the basis of the geomorphic offsets, the geometry of the Garlock fault, and the precedents set by historical strike-slip earthquakes elsewhere, a number of different rupture patterns are plausible. These range from rupture of the entire Garlock fault in a single event with a maximum magnitude of about [...]M=7.8, to separate rupture of the western segment and of the central and eastern segments combined, with approximate magnitudes of M[...]<7.7 and M[...]=7.5, respectively, to separate rupture of even shorter segments, producing earthquakes of magnitudes M[...]=6.6 to M[...]=7.5.\r\n\r\nIn conjunction with available slip rates for the Garlock fault, the geomorphic offsets suggest that average recurrence intervals are probably within the range of 600-1200 yr south of El Paso Mountains, about 200-750 yr in Searles Valley, about 200-1300 yr in Pilot Knob Valley, and about 200-3000 yr near Leach Lake and in the Avawatz Mountains.\r\n\r\nStratigraphic relations exposed in two trenches across the Garlock fault in Searles Valley provide clear evidence for several Late Holocene, prehistoric faulting events. A radiocarbon date on detrital charcoal from one of the trenches indicates that the most recent surface-faulting event on this portion of the Garlock fault occurred no more than 530 years ago. This earthquake probably had a magnitude in the range of M[...] = 7.2 to M[...] <= 7.8. Historical evidence suggests that this event occurred more than about 90 years ago. Consideration of these constraints and of the average recurrence interval for this portion of the fault (200-750 yr) suggests that the next large earthquake on the Garlock fault in Searles Valley will occur within the next 660 yr and could, in fact, be overdue.\r\n" }, { "name": "Shah, Kathryn Pierce", "degree": "PhD", "year": "1992", "title": "Interferometric observations of the J(0,1) CO line on Venus: upper Mesospheric winds and CO abundance", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:10042011-095138905", "creators": [ { "name": { "family": "Shah", "given": "Kathryn Pierce" }, "id": "Shah-K-P", "display_name": "Shah, Kathryn Pierce" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "plansci" ], "doi": "10.7907/qkzq-0655", "abstract": "In 1988, we observed Venus with the millimeter\r\ninterferometer at the Owens Valley Radio Astronomy\r\nObservatory at 115.2712 GHz, the first rotational transition\r\nof ^(12)CO. The 33.\"4 diameter disk was spatially resolved by a synthesized beam with a full-width-half-maximum of 2.\"8. Local time ranged from afternoon on the planetary eastern limb, 2 PM, to just past local midnight on the western limb, 12:30 AM. Venus' millimeter continuum emission was measured in a 400 MHz broadband channel. More\r\nimportantly, the CO absorption line was measured and finely resolved in frequency by two 32-channel filterbanks having channel widths of 50 kHz and 1 MHz.
\r\n\r\nThe 400 MHz broadband channel visibility data yielded a continuum brightness map of Venus. Brightness variations across the disk were primarily caused by sidelobe beam effects associated with the incomplete (u,v) coverage of the OVRO array. However, after radial averaging, the\r\ncontinuum brightness map continued to show one significant trend - a nightside limb cooler than the dayside limb. The\r\ncontinuum channel has a weighting function which samples a wide layer in the atmosphere between 40-60 km at normal incidence and 55-75 km along the planet limb. A radiative transfer model roughly reproduced the increased nightside limb-darkening, when given a mesospheric temperature profile 40 K cooler than the nominal Pioneer Venus nightside temperature profile between 60-85 km. The strength of this result is undercut-by strong uncertainties associated with the continuum map's absolute intensity values due to the small number of baselines in the OVRO array.
\r\n\r\nThe 50 KHz filterbank resolved the inner core of the CO absorption line. This yielded the first measurement of doppler shifts across Venus due to strong winds in the\r\nupper mesosphere. It is the most important result presented in the thesis. Calculated weighting functions showed\r\nsampling of the mesosphere over a 12 km layer centered\r\nat roughly 99 km. The doppler shifts have a signature which matches westward, horizontal winds - being strongly \"blue\" on the east/dayside limb, zero near the center and strongly \"red\" on the west/nightside limb of the planet. Smoothed wind measurements were best fitted in a least squares sense for a mean zonal flow of 132\u00b110 ms^(-1). A smaller (\u226440 ms^(-1))subsolar-to-antisolar flow may have been superimposed on the dominant zonal flow in 1988. These measurements indicate either a reversal of the mesospheric cyclostrophic breakdown inferred by Pioneer Venus or the influence of uninvestigated dynamical forces.
\r\n\r\nThe 1 MHz and 50 kHz filter bank spectra were merged to look at the entire 115 GHz CO line. These 1988 CO spectra show a decided local time dependency, becoming progressively deeper from the afternoon to the evening hours. A constrained least-squares inversion algorithm was used to solve for the local CO mixing ratio profile over local time and latitude. The resultant CO mixing ratio remains constant with height at a value of several 10^(-5) in the late afternoon hours but increases from 10^(-4) at 80 km to 10^(-3) at 100 km in the night hours. The highest CO abundances occurred after local 10 PM and centered about the equator between 40\u00b0N and 40\u00b0S. This distribution of CO abundance fulfills predictions from research based on disk-average CO spectra and photochemical models. Only the late afternoon profiles are surprising, showing essentially little CO rather than an expected moderate CO abundance from dayside photodissociation of CO_2.
\r\n" }, { "name": "Sheng, Yuntai Jack", "degree": "PhD", "year": "1992", "title": "Origin of plagioclase-olivine inclusions", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10042011-103334484", "creators": [ { "name": { "family": "Sheng", "given": "Yuntai Jack" }, "id": "Sheng-Y-J", "display_name": "Sheng, Yuntai Jack" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/cjkd-xe14", "abstract": "Plagioclase-Olivine Inclusions (POIs) are an abundant group of chondrule-like objects found in carbonaceous chondrites. Despite textural evidence of a molten or partially molten origin, approximately half of the POls studied exhibited variations in Mg isotope composition of up to 11 %/amu between spinel and coexisting silicates. Equilibrium crystallization experiments performed to study the crystallization behavior of melts of POI compositions showed that the phase assemblages predicted on the basis\r\nof phase equilibria are generally consistent with those observed in POIs. Spinel is the liquidus phase for most of the inclusions that contain spinel with fractionated Mg\r\nisotopes, and therefore these spinels could be preserved if melting was below the liquidus temperature for the bulk composition of the inclusion. The presence of resorbed spinels in some inclusions whose bulk composition does not permit spinel in its phase assemblage requires that these spinels were relict. The petrographic and chemical properties of POIs indicate that they are not condensates or evaporative residues, but formed by melting or partial melting of pre-existing solids that had originated from isotopically distinct reservoirs. The presence of isotopically heterogeneous spinel in the POIs requires that\r\nthe maximum temperature experienced by these objects was low enough, the duration of heating short enough, and the subsequent cooling rate fast enough to prevent\r\nhomogenization of Mg isotopes by diffusive transport. The self-diffusion rate of Mg was measured in spinel and coexisting melt using isotope tracers. For spinel, the activation energy of 384\u00b17 kJ for Mg and pre-exponential factor of 7791.9\u00b11.3 cm^2/s is obtained. The temperatures of melting of POIs is estimated to be in the range of 1350-1500\u00b0C, the duration of the heating events were < 2 hr, and the initial cooling rate was > 25\u00b0/hr. The melting occurred after most ^(26)Al had decayed and possibly subsequent to the extensive oxygen isotopic exchange between solids and nebula gas. The melting of POIs\r\nis probably by flash heating or impact melting in a hot parcel or region of the nebula. These refractory objects (including CAIs) are believed to be the result of repetitive\r\nheating events that had frequently generated or reprocessed refractory residues over a prolonged timescale of very early solar system history.\r\n" }, { "name": "Smither, Catherine Louise", "degree": "PhD", "year": "1992", "title": "Stress-relief displacements induced by drilling and three-dimensional modeling of planetary impacts", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09282011-151807180", "creators": [ { "name": { "family": "Smither", "given": "Catherine Louise" }, "id": "Smither-C-L", "display_name": "Smither, Catherine Louise" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." } ], "option_major": [ "geophys" ], "doi": "10.7907/49fn-dg49", "abstract": "The holographic stressmeter uses double-exposure holographic interferometry to record the displacements induced by the drilling of a sidehole into the borehole wall. The local stresses, which are the result of the far-field stresses, concentrated at the borehole, cause deformation of the surface of the borehole wall near the sidehole. To interpret the data, it is essential to understand this deformation. The initial model used a thin infinite elastic plate subjected to plane stress at infinity. Two-dimensional finite element analysis showed that the displacement depends on the depth of the\r\nsidehole. We then developed a new model for the analysis of stress-relief displacements. For holes with a depth/diameter ratio greater than unity, the simple plane\r\nstress elastic plate solution breaks down. The revised model, which gives a more exact solution of displacements near the hole, does a better job of fitting the observed\r\ndata.
\r\n\r\nA three-dimensional smoothed particle hydrodynamics code was used to model normal and oblique impacts of silicate projectiles on planetary bodies. The energy of the system is partitioned after impact into internal and kinetic energy of the both bodies. These simulations show that, unlike the case of impacts onto a half-space, up to 70% of the initial energy remains in the kinetic energy of the impactor, as parts of it travel past the main planet and escape the system. More oblique impacts retain more kinetic energy in the impactor: 6 to 75% versus 4 to 30% for the normal impacts. Higher velocity collisions also show this trend, as the kinetic energy of the impactor is 2 to 50% of the total for 5 km/s impacts, and 13 to 75% for 20 km/s\r\nimpacts. Impacts at 20 km/s with an impactor 60% the size of the target completely melted both targets. Three to 4 times more vaporization of the target material occurred on the larger targets. The amount of target material ejected at velocities greater than the escape velocity is found to be higher than that predicted by studies of impact onto a half-space, and slightly less than the amount predicted by theories of catastrophic breakup of asteroids.
\r\n" }, { "name": "Svitek, Tomas", "degree": "PhD", "year": "1992", "title": "Martian water frost : control of global distribution by small-scale processes", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03112009-141429", "creators": [ { "name": { "family": "Svitek", "given": "Tomas" }, "id": "Svitek-T", "display_name": "Svitek, Tomas" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "chair", "display_name": "Murray, Bruce C." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/EDK8-3457", "abstract": "This thesis analyzes the small\u2014scale physical processes occurring in the Martian water polar frosts. The small\u2014scale processes are considered from the point of view of how they control the global distribution and behavior of water on Mars. The analysis of the small\u2014scale properties of the surface frost is essential in efforts to find solutions for some outstanding, contradictory observations, to interpret correctly remote sensing observations, to model the surface\u2014frost thermal balance, and to implement the boundary conditions and parameterizations used in the global models of the volatiles' behavior on Mars. Two different problems are investigated in this thesis:\r\n\r\nThe effect of surface roughness on frost temperature and morphology is studied in Chapter 2 and 3. The investigation of the temperature/roughness feedback leads to the following suggestion: There is a natural tendency of volatile surfaces to develop spontaneously small-scale roughness in a sublimation\u2014dominated environment. The evidence for this claim consists of the model of a rough\u2014surface thermal balance, and of the terrestrial analogs of differential sublimation structures. Such a phenomenon can be tested by the Mars Observer and has important implications for the behavior of water frost on Mars.\r\n\r\nViking Lander 2 winter\u2014frost observations are described in Chapter 4. This study suggests that winter water frost occurred there in two forms: a) thin, almost continuous, early frost, and b) much thicker, patchy, later frost with local cold\u2014trapping of water vapor playing the crucial role. This conclusion is based on the correlation of multiple data sets (from both Viking Orbiter and Lander) and on the combined models of the physical processes occurring on a small scale \u2014 below the resolution of remote sensing. The evidence consists of the frost\u2014surface coverage and color transitions, and of the calculation of the vertical and horizontal water\u2014vapor transport near the surface. Again, this phenomenon can be confirmed or rejected by a set of observations from the Mars Observer.\r\n\r\nThe inherent rough\u2014surface morphology and the frost cold\u2014trapping must be a general property of at least some forms of the seasonal and residual frosts. Both effects must be considered in order to understand the global observations of the Martian frost and the surface environment of Mars in general.\r\n" }, { "name": "Wolf, Michael Bennett", "degree": "PhD", "year": "1992", "title": "Amphibolite-tonalite relationships: Part I. Experimental investigation of the phase relationships and textural development of amphibolite dehydration-melting. Part II. The geology, petrology and geochronology of a tonalitic and mafic dike swarm (southwestern foothills terrane, California)", "advisor": "Wyllie, Peter J.; Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-07072006-112717", "creators": [ { "name": { "family": "Wolf", "given": "Michael Bennett" }, "id": "Wolf-Michael-Bennett", "display_name": "Wolf, Michael Bennett" } ], "advisors": [ { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "advisor", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/B45Z-4N34", "abstract": "PART I: Phase relationships have been determined for the dehydration-melting of a (powdered and solid) calcic, low-K, olivine tholeiitic amphibolite (hornblende 70%, plagioclase 30%), in runs at 10 kbar, 750 to 1000\u00b0C,fO2 ~= Ni-NiO, and for 1 to 21 days. Hornblende is involved in a sliding reaction: hornblende + anorthitic plagioclase -> clinopyroxene + liquid + aluminous hornblende + calcic hornblende + orthopyroxene + garnet. The liquid fraction varies from <1% at 750\u00b0C to ~47% at 1000\u00b0C, with the big increase occurring above 875\u00b0C. Liquids are tonalitic but have very high Al2O3 contents (18-21 wt.%). At high liquid fractions (~0.5), liquids are high-alumina basaltic. Liquids become more sodic with increasing temperature, but the compositional trends reverse direction, and liquids become more calcic above 975\u00b0C, where garnet is unstable. The water contents of liquids range from over 7 wt.% at low liquid fractions to 2 wt.% at high liquid fractions. In the solid amphibolite runs, liquid interconnectivity may be attained at 875\u00b0C with only 2 vol.% liquid and dihedral angles less than 60\u00b0. The removal of water-rich tonalitic liquids from a substantially melted amphibolitic source could help generate a relatively dry mafic granulite terrane, with densities up to 3.5 gm/cm3. Delamination of this dense lower crust is possible.\r\n\r\nPART II: A cogenetic and coeval tonalitic and mafic dike swarm has been identified within a southern fragment (the Owens Mountain area) of the western Foothills terrane (Sierra Nevada, California). The swarm was mylonitized and transposed during emplacement, from 155 to 148 m.y. (U-Pb zircon data), at an estimated depth of 10 km. Steeply SE-plunging fold axes and S-fold geometries indicate a left-lateral sense of shear. The Late Jurassic Nevadan orogeny is a manifestation of dramatic changes in magnitude and direction of North American motion. The Cordilleran dike swarms record a complex pattern of sinistral-sense transtension-transpression that developed during this period of change, at the J2 (~150 m.y.) apparent polar wander cusp, and during subsequent, rapid northwestward acceleration of North America.\r\n\r\nEXTENDED ABSTRACT (PART I): Phase relationships and morphologies and reaction kinetics have been determined for the dehydration-melting of a natural amphibolite (mode: hornblende 70%, plagioclase 30%) with no added water, at 10 kbar and 750 to 1000\u00b0C, and for durations of l to 21 days, using both finely-powdered and solid starting materials. The amphibolite composition is equivalent to a calcic, low-K, olivine tholeiite. Experimental conditions simulated the dehydration-melting of deep mafic continental crust and hot, subducted oceanic crust. Experiments were conducted in unbuffered Au capsules at oxygen fugacities probably just above the Ni-NiO buffer.\r\n\r\nHornblende is involved in the following sliding reaction (the order of the product phases represents the order of appearance with increasing temperature): hornblende + anorthitic plagioclase -> clinopyroxene + liquid + aluminous hornblende + calcic hornblende + orthopyroxene + garnet. The liquid fraction ranges from <1% at 750\u00b0C to ~47% at 1000\u00b0C, with most of the increase occurring above 875\u00b0C. The liquids are generally tonalitic but have very high Al2O3 contents (18-21 wt.%). At high liquid fractions (~0.5), the liquids have a composition of high-alumina basalt. Fractionation of the plagioclase would be necessary to reduce both the CaO and Al2O3 contents of the liquids to calc-alkaline compositions. The liquid compositions become more sodic with increasing temperature, but the compositional trends reverse direction, and the liquid compositions become more calcic above 975\u00b0C, as garnet disappears. The water contents of the liquids range from over 7 wt.% at low liquid fractions to 2 wt.% at high liquid fractions. The high-temperature mineral assemblage that coexists with the liquid is clinopyroxene, orthopyroxene and plagioclase \u00b1 garnet \u00b1 aluminous hornblende. Thus, dehydration-melting of the amphibolite can reproduce natural granulite and garnet pyroxenite mineral assemblages. The removal of the water-rich tonalitic liquids from a substantially melted amphibolitic source would help generate a relatively dry granulite terrane. The stability of garnet plays a major role in determining the REE composition of the liquids. Garnet modes from these runs are consistent with REE patterns of Archean tonalites. Delamination of the garnet clinopyroxenite restite is possible due to the very high densities (up to 3.5 gm/cm3) of these assemblages after liquid segregation. Garnet phenocrysts show syn-growth compositional zoning. The total alumina in hornblende geobarometer appears to work for this mafic mineral assemblage.\r\n\r\nThe solid amphibolite runs indicate that anisotropic crystal structures and rock texture control liquid morphology and distribution during dehydration-melting. The shapes of most liquid pockets are crystallographically-controlled, with many corners having angles greater than 60\u00b0. Few crystal/liquid triple-junctions develop the interfacial energy-controlled dihedral angles ([theta]), which form in experiments using finely-ground powders of minerals with poor cleavage. Liquid interconnectivity probably is attained at 875\u00b0C with only 2 vol.% liquid, indicating that dihedral angles less than 60\u00b0 may not be necessary to achieve interconnectivity in partially melted metamorphic rocks. The surfaces between elongated grains in lineated rocks can become pathways for the migration of liquid or the diffusion of components.\r\n\r\nEXTENDED ABSTRACT (PART II): The geology, petrology and geochronology (U-Pb zircon) of a southern fragment of the western Foothills terrane has been studied (the Owens Mountain area of the western Sierra Nevada foothills, northeast of Fresno, California). A previously unrecognized dike swarm/shear zone is identified within the steeply dipping, Callovian to Kimmeridgian metavolcanic and metasedimentary strata. The dike swarm consists predominantly of cogenetic tonalitic and mafic dikes and tonalitic tabular bodies. Mutually cross-cutting relationships indicate that the tonalitic and mafic dikes also were coeval. Some of the tonalitic dikes range up to ~100 m in thickness, and individual dikes of both tonalitic and basaltic composition can be followed for up to 3 km. The dike swarm is sheeted in places, comprising almost 100% of some outcrops. Textures and fabrics within the dike swarm range from partially recrystallized igneous to strongly deformed S and L metamorphic tectonites, implying that dike emplacement occurred during ductile deformation. Hot subsolidus mylonitization has transposed layering parallel to foliation and has greatly thinned many of the dikes to centimeter to meter thicknesses. Layering and parallel foliation dip subvertically and strike NNW-SSE. Post-tectonic annealing has destroyed most microscopic shear indicators, but macroscopic intrafolial folds are common and have steeply SE-plunging fold axes and S-fold geometries that indicate a left-lateral sense of shear. The geochronological data on the tonalite dikes reveal that emplacement and crystallization of the coeval tonalitic and mafic magmas at Owens Mountain occurred over an 8 m.y. period, from 155 to 148 Ma, at an estimated depth of 10 km. Thus the beginning of intrusion occurred within 5 m.y. of deposition of the metavolcanic and metasedimentary strata into which the dikes were emplaced. A correlation between age and degree of deformation and recrystallization of the tonalites implies syntectonic dike emplacement. Undeformed granitic dikes that cut the strata are younger than 124 Ma.\r\n\r\nThe regional tectonics of the Owens Mountain and other Cordilleran dike swarms can be related in a broad dynamic sense to the absolute motion of North America by using the apparent polar wander (APW) analysis of May and Butler (1986). The Late Jurassic Nevadan orogeny is the manifestation of the drastic changes in magnitude and direction of North American motion (from ~45 km/m.y. to the NNE to ~200 km/m.y. to the NW; May and Butler, 1986). The Late Jurassic dike swarms record a complex pattern of sinistral-sense transtension-transpression that developed at the J2 (~150 Ma) APW cusp and during subsequent, rapid northwestward acceleration of North America.\r\n" }, { "name": "Worden, Charles Bruce", "degree": "PhD", "year": "1992", "title": "Interactive seismic imaging on a multicomputer and application to the Hosgri fault", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09302011-112951758", "creators": [ { "name": { "family": "Worden", "given": "Charles Bruce" }, "id": "Worden-C-B", "display_name": "Worden, Charles Bruce" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Seitz", "given": "Charles L." }, "id": "Seitz-C-L", "role": "member", "display_name": "Seitz, Charles L." } ], "option_major": [ "geol" ], "doi": "10.7907/arcb-zc42", "abstract": "We present a system designed to change the manner in which seismic reflection data is imaged, by enabling interactive response to user input. This approach greatly\r\neases the effort required to produce a seismic image and gives the analyst the flexibility to explore a wide range of models. We also argue that the ability to interact with the image can greatly aid in the interpretation process, and that the structural geologist charged with interpreting the image should be directly involved in the imaging\r\nprocess. Our approach differs from current seismic\r\nprocessing techniques that limit the ability of the seismic analyst to fully explore the imaging parameters. Current methods also provide the seismic interpreter with little information as to the robustness or reliability of the imaged structure.
\r\n\r\nThe interactive imaging system is implemented on a heterogeneous, medium-grained multicomputer. This machine is configured to provide the substantial performance required by the interactive imaging task. We discuss the\r\nimplementation of the system as four separate, but\r\ninterrelated tasks: data I/O, computation, image display, and user interface. Each of these functions is supported by hardware specifically suited to the task. The system software is designed to conceal as much of the parallel implementation as possible from a programmer wishing to add processing functions.
\r\n\r\nThe interactive system is applied to a portion of EDGE seismic refection profile RU-3 that crosses the Hosgri fault, offshore central California. From the imaged\r\nstructure we infer that the Hosgri is a near-vertical fault, with relatively recent strike-slip displacement. We see no evidence, however, of recent thrust faulting.
\r\n" }, { "name": "Zhang, Yu-Shen", "degree": "PhD", "year": "1992", "title": "Three-dimensional modeling of upper mantle structure and its significance to tectonics", "advisor": "Tanimoto, Toshiro", "url": "https://resolver.caltech.edu/CaltechTHESIS:10132011-095958731", "creators": [ { "name": { "family": "Zhang", "given": "Yu-Shen" }, "id": "Zhang-Yu-Shen", "display_name": "Zhang, Yu-Shen" } ], "advisors": [ { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "advisor", "display_name": "Tanimoto, Toshiro" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/1fgz-mq89", "abstract": "A global model was constructed for shear wave velocity structure, expanded up to degree and order 36 in spherical harmonic expansion, and down in 500 km of the Earth's upper mantle. The data set included about 18,000 seismograms associated with 971 events with magnitude larger than\r\nabout 5.5.
\r\n\r\nAssuming that the errors in data space and model space are both Gaussian random distributed, we used the Akaike Bayesian information criterion (ABIC) method and the Akaike information criterion (AIC) method to determine the optimal damping parameters and the optimal regularization of the\r\nunknown continuous model, respectively. Both the spherical harmonic expansion and the block parametrization approaches have been tested. The equal area block regularization approach gave a more accurate result than the spherical harmonic expansion approach, and it was adopted.
\r\n\r\nAge-Love wave phase velocity variations were retrieved for the Pacific, Atlantic and Indian Oceans, respectively. Simple forward modeling showed that seismic phase velocity variation with a continuous thickening of lithosphere\r\nup to about 150 Ma fits the present observation, disagreeing with the conventional model, which changes the age-depth curve at about 60-80 Ma. The age-Love wave phase velocity variations in different oceans showed systematic\r\ndifferences at younger ages, and convergence beyond 100 Ma. Age-seismic phase velocity relationships on each side of ridges were also examined and asymmetric velocity variations were found. The average age-phase velocity\r\nrelations were subtracted from Love wave phase velocity variation maps and \"residual\" maps were produced. The results indicated broad, low velocity regions in the south Pacific (super-swell region), the south and west Indian\r\nOcean, and high velocity regions east of the East Pacific Rise and in the north to northeast Indian Ocean.
\r\n\r\nIn the S-wave velocity results under global mid-ocean ridges, low velocity anomalies were resolved but were limited in the 100 km below the surface. The minimum velocities were at depth about 50 km. The horizontal width of the low velocity anomaly, which crossed over ridges, increased with the spreading rate. The S-wave velocities under ridges were strongly correlated with spreading rates at shallow depth, but the correlation decreased for deeper\r\nresults and almost disappeared at 100 km. Several major hotspots were associated with low-velocity anomalies of about 1-2 percent and diameters larger than 1000 km. But the depths of the low velocity anomalies were between\r\n100-200 km, which were different from those of ridges and expressed the mechanism differences between ridges and hotspots. The velocity structures under the East African Rift Valley and the Baikal Rift Valley were inspected.\r\nAn active mechanism was suggested with the East African Rift Valley, and a different mechanism was connected with the Baikal Rift Valley.
\r\n\r\n" }, { "name": "Zhao, Lian-She", "degree": "PhD", "year": "1992", "title": "Seismic waveform modeling of regional phases and wavefields from an off-center explosion", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10032011-142032525", "creators": [ { "name": { "family": "Zhao", "given": "Lian-She" }, "id": "Zhao-Lian-She", "display_name": "Zhao, Lian-She" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "display_name": "Harkrider, David G." } ], "option_major": [ "geophys" ], "doi": "10.7907/thvj-vd30", "abstract": "This thesis consists of two parts. Part I (Chapter 1) is a theoretical study of wavefields radiated from an off-center explosion in an embedded solid sphere, while Part II (Chapters 2, 3 and 4) deals with seismic waveform modeling of regional phases.
\r\n\r\nChapter 1 investigates the effects of asymmetric source regions on the excitation of seismic body waves of\r\nexplosions. We give an analytic formulation for determining the wave fields from an off-center explosion in an embedded\r\nsolid sphere in an elastic whole-space. It is shown that SH wave amplitudes can be ten times larger than the P wave amplitudes if the source is properly located.
\r\n\r\nChapter 2 discusses the strategies of modeling regional Broadband recordings with the application to Harvard station recordings of November 25, 1988 Saguenay earthquake. We demonstrate that the longer period motions\r\n(WWSSN) preceding the direct S arrival can be modeled reasonably well with a crustal model consisting of a layer over half-space. While a generic model assumed to be the same everywhere can be used to model the P_nl waveshape, HeImberger and Engen (1980), some adjustments are required\r\nto fit the absolute timing of P_n and S_n for specific paths. In particular, path from the Saguenay event to Harvard is slower than expected for a shield environment and is associated with the roots of the Appalachian\r\nThrust Belt.
\r\n\r\nChapters 3 and 4 concern the velocity structures of the Tibetan Plateau and surrounding regions. A fast shield-like velocity model, TIP, is proposed for the structure beneath the Tibetan Plateau as suggested by modeling SH waveforms in Chapter 3. The crustal model is determined by modeling\r\nLove waveforms and P_nl waveforms in the time domain while the upper mantle is constrained with S and SS waveform data. Relocations of Tibetan earthquakes are discussed in Chapter 4, assuming model TIP at source\r\nregion and model JB at receiver regions. A detailed\r\ninvestigation of 100 such events yields a distinctly different picture from a random distribution of events down to a depth of about 50 kms given by ISC. Waveform modeling\r\nof depth phases such as _pP indicates that only three or four events from of this population is actually deeper than 25 km. These few events occur near the edges of the Plateau where active subduction is occurring as suggested by the thrust-like nature of their mechanisms. The events occurred earlier than indicated by the ISC by 3 seconds on average which leads to about a 1.5% and 0.5% over estimation of P_n and S_n velocities respectively applying ISC tables and standard flat-layered models.
\r\n" }, { "name": "Erel, Yigal", "degree": "PhD", "year": "1991", "title": "Transport of Natural Lead and Cadmium in Rivers: Global Flux Implications", "advisor": "Patterson, Clair C.; Morgan, James J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04112011-111843025", "creators": [ { "name": { "family": "Erel", "given": "Yigal" }, "id": "Erel-Yigal", "display_name": "Erel, Yigal" } ], "advisors": [ { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "advisor", "display_name": "Patterson, Clair C." }, { "name": { "family": "Morgan", "given": "James J." }, "id": "Morgan-J-J", "role": "advisor", "display_name": "Morgan, James J." } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "member", "display_name": "Patterson, Clair C." }, { "name": { "family": "Morgan", "given": "James J." }, "id": "Morgan-J-J", "role": "member", "display_name": "Morgan, James J." } ], "option_major": [ "geochem" ], "doi": "10.7907/1RX3-W586", "abstract": "Lead and cadmium concentrations in marine and terrestrial ecosystems, in\r\nsurfaces of soils, and in the atmosphere have been highly elevated on a global scale due\r\nto industrial pollution. In order to ascertain the natural (rock-derived) levels of lead and\r\ncadmium in streams, pristine mountain watersheds in the Sierra Nevada, California were\r\nstudied for their lead and cadmium contents, and the transport of lead and cadmium was\r\nrelated to metal relatively uninfluenced by pollution that share similar transport patterns.\r\nIn addition, rock and unpolluted water samples from granodiorite, basalt and carbonate\r\nterrains were analyzed for the concentrations of lead, iron and other elements. Wholerock\r\nsamples as well as biotite and feldspar mineral separates were used for laboratory\r\nleaching and adsorption-desorption experiments to investigate the relationship between\r\nlead and iron chemistry under controlled conditions.
\r\n\r\nThe concentrations of lead and cadmium in the late-summer drainage are shown\r\nto be close to the natural levels that are controlled by the weathering of bedrock and soil.\r\nThis is demonstrated by measurements of 1) lead isotopic composition, and Fe/Pb ratios\r\nin stream water, ground water, soil and bedrock, and 2) the removal rate of excess\r\natmospheric lead and cadmium from the water as it flows downstream.
\r\n\r\nAfter the spring snow-melt runoff, most of the lead in alpine streams originates\r\nfrom ground water, and has isotopic ratios that are consistent with values expected from\r\nbedrock and soil sources, indicating that this lead is not anthropogenic in origin. The\r\nlead found in unpolluted ground waters is more radiogenic than the lead in the bedrock\r\ndrained by these waters. A preferential release of radiogenic lead into waters and\r\nleached phases of rock and soil can be explained by the preferential weathering of\r\nradiogenic accessory minerals and to a lesser extent by a preferential release of U and Th\r\ndecay products due to the recoil effect.
\r\n\r\nThe lead uptake mechanism is proposed to be adsorption on oxy-hydroxide\r\nsurfaces. In contrast, the uptake of cadmium in the stream water is erratic and cannot\r\nbe explained by the same mechanism. Adsorption-desorption experiments suggest that\r\nlead coprecipitates and is adsorbed on particle surfaces, mainly ferric iron hydroxides.\r\nDue to a similar transport mechanism and comparable rate of release from common rock\r\nand soil minerals, the ratio between natural (rock-derived) lead and iron in rivers should\r\nbe similar to their average upper continental crustal molar ratio of 1:6,500.
\r\n\r\nExperiments and speciation models indicate that complexation of lead by manmade\r\norganic compounds decreases the fraction of lead bound to surface sites. Such an\r\nindirect pollution effect mobilizes lead and decreases the Fe/Pb ratio in rivers regardless\r\nof any direct addition of anthropogenic lead.
\r\n\r\nMany trace metals maintain their average upper continental crustal ratio with iron\r\nin unpolluted river water, river sediments and soils; However, large excesses of most\r\ntrace metals relative to iron are found in deep-ocean water. At the transition from fresh\r\nwater to saline ocean water, two processes take place: 1) rapid removal of iron (and\r\nother particle-forming elements) from the water column due to coagulation and settling;\r\nand 2) partial desorption of trace metals from particle surfaces. While more than 99% of\r\nthe riverborne iron settles to the sediment within the continental shelf, some of the trace\r\nmetals are released to solution as dissolved chloro-complexes and are further transported\r\nto the open sea. In addition, some of the trace metals attached to airborne and recycled\r\nsea-floor particles may desorb when these particles are in contact with sea water.
\r\n\r\nThe adsorption/desorption process in sea water account for the relative\r\nabundances of many trace metals in deep-sea water (not including REE). Furthermore,\r\nit is suggested that the observed concentrations of these trace metals in deep-ocean water\r\nare relatively unaffected by pollution and are largely determined by natural processes.
\r\n" }, { "name": "Fahnestock, Mark Allen", "degree": "PhD", "year": "1991", "title": "Hydrologic control of sliding velocity in two Alaskan glaciers : observation and theory", "advisor": "Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechETD:etd-07182006-134101", "creators": [ { "name": { "family": "Fahnestock", "given": "Mark Allen" }, "id": "Fahnestock-Mark-Allen", "display_name": "Fahnestock, Mark Allen" } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/41WM-7B96", "abstract": "Short term variations in the velocities of glaciers reflect changes in the processes which determine sliding velocity. The role of water in these processes is considered for certain types of variable behavior observed on two glaciers in Alaska.\r\n\r\nPulses of increased velocity on Variegated Glacier (mini-surges) prior to its 1982-83 surge have been attributed to pulses of water at the glacier bed. Our field program in 1986 demonstrated that mini-surges still occurred following the surge; the propagation of two such disturbances over part of the upper reach of the glacier was documented. The mini-surges of 1986 had substantially lower peak velocities but only slightly lower propagation velocities than the pre-surge mini-surges. The first of the mini-surges observed in 1986 originated in the tributary, the second originated in the upper reach of the main glacier.\r\n\r\nA model of the basal water system with pressure dependent conductivity and storage is developed to investigate the conditions necessary for propagation of a pulse of water. The response of this system to the introduction of a localized increase in input is followed with a finite difference formulation. The extra input of water produces a downglacier propagating front, which, for reasonable values of porosity and pre-event conditions, moves at speeds similar to those observed for mini-surges.\r\n\r\nThe relation between the non-linearity of the pressure dependence in this model and the shape and history of the propagating disturbances is investigated using conductivity relations which have linear, quadratic, and cubic dependence on pressure, and one with an inverse dependence on the effective pressure. The modeling indicates that a system with a non-linear change of conductivity in response to a change in water pressure (suggestive of a cavity system) is required to match the field observations.\r\n\r\nThe shapes of waves which propagate with unchanging form in this system can be found theoretically; the numerical model generates these waves when the input rate is held constant. The constant form shapes are calculated for the conductivity relations mentioned above; for conductivities with higher-than-linear dependence on pressure the waves reach a plateau upglacier; the linear case increases without bound.\r\n\r\nModeling of a Rothlisberger tunnel system with the addition of a storage term indicates that such a system will propagate a disturbance, but will not match the abrupt rise times seen in boreholes as a mini-surge wave passes. The pressure dependent conductivity model does a better job of matching observations. \r\n\r\nColumbia Glacier, a large tidewater glacier in southern Alaska, experiences noteworthy velocity fluctuations during the melt season in response to storms and increased ablation, and also displays a well developed diurnal cycle in velocity. A 1987 field project involving the University of Colorado, tbe USGS, and Caltech collected detailed time series of surface velocity, water input and discharge, and basal water pressure. These data show a complex pattern of behavior which is highly correlated with variations in hydrologic parameters. Basal water pressures near the floatation level are related to the rapid surface motion (4-8 m/d) of this glacier. A series of at least four velocity events accompanied elevated inputs of water to the glacier. These speed-ups did not have a strong coincident peak in basal water pressure, but were followed by an increase in outflow discharge from the glacier.\r\n\r\nAn estimate of the change in the volume of water stored in the glacier is made by relating input to the glacier (estimated from the filling rate of an ice-marginal lake and also from meteorological records) to discharge. This calculation shows that variations in velocity on time scales longer than one day can be explained by changes in the volume of water stored in or under the ice. The first velocity event was followed by a slowdown of the glacier which was coincident with a drop in stored water volume of about 0.1 m3/m2 averaged over the ice surface. The peak in velocity for the largest velocity event is accompanied by a large peak in stored water volume.\r\n\r\nA model of the basal water system which consists of co-existing linked cavity and tunnel components is proposed to explain the melt season behavior of Columbia Glacier. In this hybrid cavity/tunnel system the distributed input of water reaches the bed and flows through the cavities to reach large tunnels which are responsible for the downglacier transport of water. The cavity part of this system is responsible for the correlation between stored water volume and velocity, while the tunnel system is responsible for the seasonal variation of velocity and the localized upwelling of water discharged from the terminus of the glacier.\r\n\r\nA model based on a simple sliding law, an effective pressure distribution at the bed which is determined by the discharge through a tunnel system, and continuity for the ice is used to look at the role of effective pressure in the difference between winter and summer glacier-flow behavior. This model produces the late-melt-season pulse in velocity at the terminus which is related to an annual increase in calving rate. This may explain the previously discovered correlation between calving rate and outflow discharge, as well as the connection between the location of calving activity and the location of upwelling at the terminus.\r\n\r\nThe results of this work suggest that the complicated behavior of these glaciers can be understood at a simple level from the variations in hydrologic systems.\r\n" }, { "name": "Graves, Robert Wilson", "degree": "PhD", "year": "1991", "title": "Modeling seismic wave propagation using paraxial extrapolators", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04112011-093820974", "creators": [ { "name": { "family": "Graves", "given": "Robert Wilson" }, "id": "Graves-R-W", "display_name": "Graves, Robert Wilson" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." } ], "option_major": [ "geophys" ], "doi": "10.7907/10tz-eh38", "abstract": "The development of a paraxial extrapolation system to simulate seismic wave\r\nfield propagation in complex three-dimensional (3-D) media results in a practical\r\napproach to address modeling problems that require large computer memory.\r\nThe paraxial approach applies to wave propagation problems in which most of the\r\nenergy is traveling within a restricted angular cone about a principle axis of the\r\nproblem. To set up the paraxial system, the equations of motion are initially cast\r\nas a first-order extrapolation system. Approximating the exact one-way extrapolation\r\noperator for this system with a truncated series expansion yields a sequence\r\nof paraxial extrapolation operators. Using the second-order operator results in a\r\nparaxial system which is accurate for propagation angles out to 60\u00b0 with respect to\r\nthe extrapolation axis. The acoustic formulation of this system produces excellent\r\nresults as compared to a full wave field calculation. Formulating an appropriate\r\nsystem for the elastic case is more difficult due to the coupling between P and\r\nS energy. Specifying media variations as small perturbations to a homogeneous\r\nreference medium leads to a useful formulation of the paraxial system for the 2-D elastic\r\ncase.\r\nUsing the acoustic system to model path effects for local earthquakes recorded\r\nat two southern California stations indicates the strong influence that the 3-D\r\ncrustal basins of this region have on the propagation of seismic energy. Although\r\nthe simulation tracks only acoustic waves, the method is capable of modeling effects\r\ndue to focusing, diffraction and the generation of multiple reflections and\r\nrefractions. The modeling results show that the 3-D structure of the Los Angeles,\r\nSan Fernando and San Gabriel basins create strong patterns of focusing and defocusing\r\nfor propagation paths coming into the stations located at Pasadena (PAS)\r\nand the University of Southern California (USC). These simulations compare well\r\nwith earthquake data recorded at both stations.\r\n" }, { "name": "Hwang, Lorraine Joyce", "degree": "PhD", "year": "1991", "title": "Teleseismically determined source parameters of several large collision-zone earthquakes", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-06292005-161026", "creators": [ { "name": { "family": "Hwang", "given": "Lorraine Joyce" }, "id": "Hwang-Lorraine-Joyce", "display_name": "Hwang, Lorraine Joyce" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/k0nd-yv62", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nUnderstanding earthquake hazards begins with the understanding of the earthquake process itself and its effects in the near source region. Here both ends of the problem are explored. First, source parameters and rupture models for several earthquakes around the circum-Pacific are studied. Second, acceleration spectra are compared to teleseismic data. It is hoped that the extensive teleseismic data base can be used to scale acceleration spectra for large future, earthquakes.\r\n\r\nThe 7 May 1986 Andreanof Islands earthquake was a large (1.3 x [...] dyne-cm) thrust event (strike 257\u00b0, dip 18\u00b0, rake 116\u00b0) that ruptured a 220 km segment of the Aleutian Arc. The earthquake ruptured bilaterally with the largest moment releasing subevent nucleating 75-90 km west of the epicenter in a region of low aftershock seismicity. At a distance of 100 km, the acceleration spectrum had the same amplitude as that from teleseismic data.\r\n\r\nThe 20 May (6.4 M[...], NEIC) and 14 November (7.3 M[...], 1.7 x [...] dyne-cm) 1986 Hualien earthquakes occurred on two steeply dipping, reverse faulting events near the Eurasian-Philippine Sea plate boundary. The amplitude of the observed spectra at a distance of 70-80 km is 5 times that from teleseismic data. This is consistent with previous observations. Comparisons between hard and soft rock recording sites indicate that the alluvial valley amplified the strong ground motion between 0.15-1.8 Hz.\r\n\r\nThe 24 November 1987 Superstition Hills earthquake (8 x [...] dyne-cm) consisted of two spatially distinct subevents with different focal mechanisms at depths between 4 to 8 km. Rupture models along with aftershock, afterslip and geologic data suggest that the northern and southern segments of the Superstition Hills fault behaved differently during this event.\r\n\r\nThe 1987-88 Gulf of Alaska earthquake sequence consisted of three large, intraplate, strike-slip earthquakes (7.2, 7.8, 7.7 Mw), whose depths extended to 25 km. The data are modeled with multiple subevents with different focal mechanisms. In comparison with other large events, the short durations and rupture lengths of the two largest events illustrate the difference in strength between oceanic and continental lithosphere. Moment release is confined to the epicentral region and/or regions of apparent structural complexities where seismicity trends intersect." }, { "name": "Ihinger, Phillip Dean", "degree": "PhD", "year": "1991", "title": "An experimental study of the interaction of water with granitic melt", "advisor": "Stolper, Edward M.; Epstein, Samuel; Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:03012011-153233991", "creators": [ { "name": { "family": "Ihinger", "given": "Phillip Dean" }, "id": "Ihinger-P-D", "display_name": "Ihinger, Phillip Dean" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "advisor", "display_name": "Stolper, Edward M." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "co-advisor", "display_name": "Epstein, Samuel" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "co-advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/1ds0-5n95", "abstract": "The nature of water in granitic melt is investigated through a variety of experimental\r\nand analytical techniques. The knowledge of the presence of two dissolved melt species\r\n(hydroxyl and molecular water groups), and the precise determination of their\r\nconcentrations with infrared spectroscopy, is used in conjunction with vacuum extraction\r\nand hydrogen isotopic techniques to determine, (1) the solubility of water in granitic melts\r\nas a function of pressure at 850\u00b0C, (2) the speciation of water in granitic melt as a function\r\nof temperature, and (3) the fractionation factors which govern the partitioning of hydrogen\r\nisotopes between water vapor and granitic melt.\r\n\r\nNatural obsidian starting materials were held at 850\u00b0C and pressures ranging from\r\n200 to 1600 bars in the presence of excess vapor. Samples were rapidly quenched to\r\nglasses and their water contents were determined using vacuum manometry and infrared\r\nspectroscopy. The results of these experiments demonstrate a progressive increase in\r\nsolubility with pressure, but suggest that increasing dissolution of water has no influence\r\non the total volume of the melt (the partial molar volume of water in these low pressure\r\nmelts is near zero). The solubility measurements can be used to model shallow level\r\neruptive cycles which involve crystal fractionation, volatile saturation, onset of eruption,\r\nand influx of new magma to repeat the cycle. Preliminary experiments on the temperature\r\ndependence of water solubility suggest a dependence as high as 1 wt % per 200\u00b0C at 1600\r\nbars. This result supports the suggestion that mafic intrusion into silicic magma chambers\r\ninduces supersaturation of the felsic liquid and subsequent explosive eruption.\r\n\r\nHydrated obsidian chips were held at temperatures ranging from 450 to 600\u00b0C to\r\ndetermine the equilibrium speciation of water in the melt. These data show distinct nonideal\r\nbehavior, In K_(eq) decreases with increasing water content (K_(eq) = the equilibrium\r\nconstant for the reaction involving dissolved water species). Relaxation analyses are used\r\nto demonstrate that these rapidly-quenched glasses preserve their high-temperature\r\nspeciation. This analysis has been used to demonstrate that melts held at 850\u00b0C do not\r\npreserve their equilibrium speciation on quench. Intersection of the equilibrium isotherms\r\nwith the fictive temperature curve recorded by the 850\u00b0C samples provides identification of\r\nthe last-equilibrated temperature for the quenched glasses. This information, coupled with\r\nthe speciation recorded in glasses quenched at a slower rate, is used to extract the viscosity\r\nof hydrous rhyolitic liquids as a function of temperature. This formulation is compared to\r\nempirical methods for determining melt viscosities. The equilibrium speciation data is used\r\nto formulate a regular solution model to determine the speciation of water in rhyolitic melts\r\nat any temperature and water content.\r\nThe hydrogen isotopic composition of water evolved from quenched granitic melts\r\nis compared to the isotopic composition of their equilibrium vapors. The bulk partitioning\r\nof hydrogen isotopes between melt and vapor varies as a regular function of the total\r\ndissolved water content, suggesting that two independent fractionation factors control their\r\nequilibrium. The fractionation factor between vapor and hydroxyl groups (\u22481.040 \u00b1 0.05\r\n\u2030) is significantly greater than the fractionation between vapor and the molecular water\r\nspecies (\u22481.00 \u00b1 0.10 \u2030). These fractionation factors can be used to explain the\r\ndegassing trends measured in natural igneous environments. The magma chamber beneath\r\nMono Craters, CA may have experienced a significant amount of closed system degassing\r\nbefore undergoing open system degassing late in its history.\r\n" }, { "name": "Kiefer, Walter Scott", "degree": "PhD", "year": "1991", "title": "Models for the formation of highland regions on Venus", "advisor": "Hager, Bradford H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12032004-155735", "creators": [ { "name": { "family": "Kiefer", "given": "Walter Scott" }, "id": "Kiefer-Walter-Scott", "display_name": "Kiefer, Walter Scott" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/6KQ8-MM86", "abstract": "The unifying theme of this thesis is an attempt to understand the origin of several major highland units on Venus. Chapters 1 and 2 develop numerical models of mantle plumes. In Chapter 1, I discuss the numerical methods used in calculating the geoid anomalies, topographic uplifts, and heatflow associated with upwelling plumes. Because plumes are a likely cause of at least some terrestrial hotspot swells, Chapter 1 also examines how the numerical models compare with observations of terrestrial hotspots. In Chapter 2, I compare the plume model results with observations of geoid anomalies and topography from the Equatorial Highlands of Venus. Chapter 3 examines another model, in which parts of the Equatorial Highlands are interpreted as spreading centers analogous to terrestrial mid-ocean ridges. Chapter 4 develops a crustal convergence and mantle downwelling model for the Ishtar Terra region of Venus.\r\n\r\nTerrestrial hotspot swells are regions of elevated topography and high rates of volcanism. A variety of evidence suggests that at least some hotspots, such as Hawaii, are formed by quasi-cylindrical mantle plumes upwelling from deep in the mantle. I model such plumes using a finite element code in cylindrical, axisymmetric geometry with a depth-dependent Newtonian viscosity. Many previous workers have modeled plumes using a sheet-like, Cartesian geometry, but I find that cylindrical and sheet-like upwellings have significantly different geoid and topography signatures. However, Rayleigh number-Nusselt number systematics in the two geometries are quite similar. Increasing the Rayleigh number or including a low-viscosity asthenosphere decrease the geoid anomaly and the topographic uplift of a plume. For comparison with observations, the models are scaled with the assumptions of whole-mantle convection and a temperature contrast of about 300 \u00b0C between the center of a plume and normal mantle. The models are able to explain the amplitudes of the observed geoid anomalies and topographic uplifts at Cape Verde and Hawaii, provided that the Earth's mantle has a low viscosity zone in the asthenosphere and upper mantle similar to that previously inferred by Hager and colleagues on the basis of long-wavelength geoid modeling. However, for aspect ratio 1, the models predict swell widths that are about twice as wide as observed. This discrepancy may be due in part to terrestrial plumes having aspect ratios of less than 1. Alternatively, inclusion of temperature-dependent rheology may lead to narrower swells.\r\n\r\nThe Equatorial Highlands of Venus consist of four main structures, Atla, Beta, Ovda, and Thetis Regiones. Each of these features has a circular to ovalshaped planform and rises 4 to 6 km above the mean planetary radius. These highland units are also long-wavelength geoid highs, with amplitudes ranging from 35 meters at Ovda to 120 meters at Atla. These features also contain topographic valleys, interpreted as extensional rift zones, and Beta is known to contain shield volcanoes. These characteristics are all consistent with the Equatorial Highlands being formed by upwelling mantle plumes. In order to compare results for Venus and Earth, I assume that the two planets have similar mantle heat flows. With this assumption, I find that in order to satisfy the observed geoid and topography for the Equatorial Highlands, the asthenosphere and upper mantle viscosity must be higher on Venus than on Earth. This conclusion is consistent with modeling of the long-wavelength admittance spectrum of Venus and with the observed differences in the slopes of the geoid spectra of the two planets. One possible explanation for the different viscosity structures of the two planets is that the mantle of Venus is drier than the Earth's mantle.\r\n\r\nAn alternative model for Ovda and Thetis Regiones, proposed by Crumpler, Head, and colleagues, is that these features are terrestrial-type spreading centers. The strong positive correlation between the geoid and topography observed in Ovda and Thetis is unlike that observed for terrestrial spreading centers. The maximum elevation expected for spreading centers on Venus is 1.5 km, and a cooling plate thermal model predicts a maximum geoid anomaly of 8 meters, both much less than observed. Thus, even if a spreading center is operative in Ovda and Thetis, most of the geoid and topography must be due to other mechanisms. Crumpler et al. also proposed the existence of \"cross-strike discontinuities,\" which they interpreted as transform fault zones, but the evidence for these structures is not conclusive.\r\n\r\nThe Ishtar Terra region of Venus contains the highest topography known on the planet, over 10 km above the mean planetary radius, as well as abundant tectonic features, many of which are apparently compressional in origin. These characteristics suggest that Ishtar is a crustal convergence zone overlying a region of downwelling mantle. In order to explore quantitatively the implications of this hypothesis for Ishtar's origin, I present models of the viscous crustal flow driven by gradients in lithostatic pressure. For reasonable bounds on the mantle convective velocity, I find that if the crustal convergence hypothesis is correct, then the crustal thickness in the plains surrounding Ishtar can be no more than about 25 km thick. This result is in good agreement with several independent estimates of crustal thickness on Venus based on modeling of the spacing of tectonic features and of impact crater relaxation, but is much less than the estimated crustal thickness derived from an Airy isostasy model of Ishtar's gravity anomaly. Much of the observed gravity anomaly must be due to density anomalies in the mantle beneath Ishtar. Although I treat Ishtar as a crustal convergence zone, the crustal flow model results show that under some circumstances near-surface material may actually flow away from Ishtar, providing a possible explanation for graben-like structures in Fortuna Tessera.\r\n" }, { "name": "King, Scott David", "degree": "PhD", "year": "1991", "title": "The interaction of subducting slabs and the 670 kilometer discontinuity", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04132011-101632415", "creators": [ { "name": { "family": "King", "given": "Scott David" }, "id": "King-S-D", "display_name": "King, Scott David" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/pme7-gx03", "abstract": "The subduction of oceanic lithosphere plays a major role in the dynamics of the Earth. The dynamics of subduction are influenced both by variations in density (due to phase changes or compositional changes), and variations in viscosity encountered by the slab; the rheology of the slab and the coupling of the slab with the oceanic lithosphere also play important roles. Geoid and topography place fundamental constraints on subduction, and observations can be used to test various mantle models.\r\n\r\nThe effects of the rheology of slabs are considered using finite element convection calculations with Newtonian (linear) and non-Newtonian (power-law) temperature-dependent\r\nrheology. Newtonian temperature-dependent fluids do not exhibit slab-like features without weakening the thermal boundary layer. Weak zones are imposed at the trench and ridge, and the effects of varying the size, location, and strength of the weak zones are studied. Non-Newtonian rheology provides a self-consistent mechanism for weakening the thermal boundary layer without imposing a weak zone at the trench. This self-consistency is not proof or confirmation of the importance of power-law deformation in the Earth. Even with non-Newtonian rheology, a weak\r\nzone at the ridge is necessary for plate-like behavior.\r\n\r\nThe geoid and topography for slabs with a density discontinuity and a viscosity discontinuity are compared. Weak slabs deform rapidly by spreading out along the density discontinuity with little deformation of the boundary, while strong slabs deform slowly and locally depress the density boundary. However, the long wavelength\r\ncomponents of the geoid and topography are independent of the lateral variations in viscosity from the slab. Finite deformations of a compositional boundary are compared with an undeformable boundary approximation; the long wavelength components of the geoid and topography are indistinguishable for boundary deformations up to several hundred kilometers.\r\n\r\nSubduction calculations are computationally intensive and high resolution is required to resolve deformation at the trench. The solutions are time-dependent, and a temperature-dependent rheology is required. Faster and more powerful numerical techniques are needed. A fast implementation of the finite element method is presented. Applied to creeping flow, this formulation allows large viscosity variations,\r\nbut is still efficient on a vector supercomputer.\r\n" }, { "name": "Larsen, Shawn Christian", "degree": "PhD", "year": "1991", "title": "Geodetic measurement of deformation in southern California", "advisor": "Sieh, Kerry E.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechETD:etd-03102008-095117", "creators": [ { "name": { "family": "Larsen", "given": "Shawn Christian" }, "id": "Larsen-Shawn-Christian", "display_name": "Larsen, Shawn Christian" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/SPH1-EV56", "abstract": "The Global Positioning System (GPS) has rapidly become one of the most important geodetic tools for studying tectonic deformation. With potential 3-dimensional relative positioning accuracies better than 1 cm, GPS can monitor secular deformation as well as rapid strain fluctuations due to seismic and volcanic activity. A 1970/1971 trilateration survey and 1987/1988 GPS observations suggest uniaxial convergence of 6.4 mm/yr oriented N25.1 \u00b0E in the eastern third of the Santa Barbara channel, and a combination of convergence and left-lateral shear to the west. GPS surveys have been conducted in the Imperial Valley during 1986, 1988, 1989, and 1990. About 5 \u00b1 1 cm/yr plate-boundary displacement is observed across the valley, somewhat larger than rates obtained through conventional geodesy. These GPS observations have been influenced by the 1987 Superstition Hills earthquake sequence, the first occurrence of a large earthquake within a preexisting GPS network. The measurements suggest 130 cm right-lateral slip along the northwest trending Superstition Hills fault, and 30 cm left-lateral slip along the conjugate northeast trending Elmore Ranch fault. Imperial Valley leveling surveys conducted in 1931, 1941, 1974, 1978, and 1980, are integrated with seismic, geomorphic, and sub-surfacial structural data, to suggest the northern segment of the Imperial fault formed within the last 80,000 years, and support the hypothesis that the Gulf of California rift system is propagating northwestward into the North American continent." }, { "name": "Moses, Julianne Ives", "degree": "PhD", "year": "1991", "title": "I. Phase Transformations and the Spectral Reflectance of Solid Sulfur: Possible Metastable Sulfur Allotropes on Io's Surface. II. Photochemistry and Aerosol Formation in Neptune's Atmosphere", "advisor": "Yung, Yuk L.; Westphal, James A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08012006-093137", "creators": [ { "name": { "family": "Moses", "given": "Julianne Ives" }, "id": "Moses-Julianne-Ives", "orcid": "0000-0002-8837-0035", "display_name": "Moses, Julianne Ives" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "co-advisor", "display_name": "Westphal, James A." } ], "committee": [ { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "chair", "display_name": "Westphal, James A." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." } ], "option_major": [ "plansci" ], "doi": "10.7907/S8F2-V423", "abstract": "This thesis consists of two independent papers:
\r\n\r\nPAPER I:
\r\n\r\nThe spectral reflectance of elemental sulfur is examined in a set of laboratory experiments to determine the factors that affect the transformation rate of monoclinic (\u03b2) sulfur and various other sulfur allotropes into orthorhombic (\u03b1) sulfur. The laboratory data have implications for the spectral variation and physical behavior of freshly solidified sulfur, if any exists, on Jupiter's satellite Io. Depending on its thermal history, molten sulfur on Io would initially solidify into a glassy solid or a monoclinic crystalline lattice; these forms might contain polymeric sulfur molecules as well as the more abundant S8 molecules. If freshly frozen sulfur on Io could lose heat rapidly and approach ambient dayside Io temperatures within several hours, then some of the metastable sulfur allotropes could be maintained on Io virtually indefinitely. Small droplets of sulfur ejected during plume eruptions might cool quickly enough to preserve these allotropes, but sulfur in large volcanic flows or lakes would probably remain warm long enough for phase transformations to proceed at a visible rate.
\r\n\r\nPAPER II:
\r\n\r\nPhotodissociation of methane at high levels in Neptune's atmosphere leads to the production of more complex hydrocarbon species such as ethane, acetylene, methylacetylene, propane, diacetylene, ethylacetylene, and butane. These gases diffuse to the lower stratosphere where temperatures are low enough to allow all seven of the aforementioned species to condense. Particle formation may not occur readily, however, as the vapor species become supersaturated. We present a theoretical analysis of particle formation mechanisms at conditions relevant to Neptune's troposphere and stratosphere and show that hydrocarbon nucleation is very inefficient under Neptunian conditions: saturation ratios much greater than unity are required for aerosol formation by either heterogeneous, ion-induced, or homogeneous nucleation. Thus, stratospheric hazes may form far below their saturation levels. We compare nucleation models with detailed atmospheric photochemical models in order to place realistic constraints on the altitude levels at which we expect hydrocarbon hazes or clouds to form on Neptune.
\r\n" }, { "name": "Pickett, David Alan", "degree": "PhD", "year": "1991", "title": "An isotopic and petrologic study of an exposure of the deep Sierra Nevada batholith, Tehachapi Mountains, California", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11032005-074035", "creators": [ { "name": { "family": "Pickett", "given": "David Alan" }, "id": "Pickett-David-Alan", "display_name": "Pickett, David Alan" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/XN66-1508", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Tehachapi Mountains, southernmost Sierra Nevada, California, are composed of variably deformed Cretaceous batholithic intrusive rocks and their high-grade framework. The purpose of this study is to 1) establish stronger constraints on the apparently great depths of exposure, and 2) characterize isotopically and chemically the petrogenesis of the intrusive rocks.\r\n\r\nThe Al contents of hornblendes imply igneous pressures from 3.2 kbar in the extreme north of the study area to around 8 kbar in the south. The southern values are the highest yet determined for the entire Sierra Nevada. The rocks commonly show subsolidus recrystallization and metamorphism producing local, fluid-related, garnet-bearing assemblages. Pressures based on garnet-hornblende-plagioclase-quartz and garnet-biotite-plagioclase-quartz equilibria in these metaigneous rocks and framework rocks (7-8 kbar at 670-760[degrees]C) confirm the igneous results. There is also recorded in one area a lower-pressure event (4 kbar, 600[degrees]C) which apparently occurred after uplift which quickly followed initial crystallization of the magmas. The recognition of deformed quartz-bearing rocks at such great depths implies that the young, warm, deep batholith may represent a site favorable for major delamination of the crust.\r\n\r\nInitial [...] of the igneous rocks of the main study area generally ranges from 0.7041 to 0.7054, with [...]. Lower [...] and higher [...] values are found in the tonalite of Bear Valley Springs to the north. Combined with Pb and published O results, the isotopic data are most consistent with a model of mixing between mantle derived magmas and metasedimentary rocks of chiefly continental provenance. (Two granites from the older suite deviate from this pattern, probably due to fluid interaction.) However, isotopic ratios do not show coherent variation trends consistent with this model when combined with chemical data. The chemical data suggest that lithologic variation among the intrusive rocks results from fractional crystallization acting on mafic to intermediate parent magmas which obtained their diverse isotopic characteristics at a deeper level (>25-30 km). This study reveals the deep Sierra Nevada batholith to be more heterogeneous and somewhat more mafic than analogous portions of the higher batholith, and suggests that isotopic hybridization of batholith magmas takes place in its deepest levels." }, { "name": "Rubin, Charles Martin", "degree": "PhD", "year": "1991", "title": "Structural, stratigraphic, and geochronologic analysis of the Alexander-Taku terrane boundary and the overlapping upper Jurassic to lower Cretaceous gravina sequence, southeast Alaska", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04132011-115331837", "creators": [ { "name": { "family": "Rubin", "given": "Charles Martin" }, "id": "Rubin-C-M", "display_name": "Rubin, Charles Martin" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "chair", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geol" ], "doi": "10.7907/ZQ82-2077", "abstract": "An imbricate thrust belt that extends along strike for over 2000 km overprints the tectonic boundary between two of the largest allochthonous crustal fragments (Intermontane and Insular superterranes) in the North American Cordillera and affects rocks west of the Coast Plutonic Complex in southeast Alaska, western British Columbia and northern Washington. Deformation was broadly coeval with mid-Cretaceous magmatism and involved the emplacement of west-directed thrust nappes over a structurally intact and relatively unmetamorphosed basement. The Paleozoic and lower Mesozoic Alexander terrane forms structural basement for much of the thrust belt, along a moderately northeast-dipping ramp.
\r\n\r\nThe western metamorphic belt of the Coast Plutonic Complex consists of the Alexander and Taku terranes, and the Upper Jurassic and Lower Cretaceous Gravina sequence. The Alexander terrane consists of lower Paleozoic metavolcanic and metasedimentary rocks (Descon Formation) and dioritic plutons that are unconformably overlain by Lower Devonian clastic strata (Karheen Formation). These rocks are overlain locally by Upper Triassic basalt rhyolite and marine clastic strata (Hyd Group). The Taku terrane consists of polydeformed and metamorphosed strata that are divided into anupper Paleozoic and lower Mesozoic assemblage (Alava sequence) and a lower Paleozoic assembtage (Kah Shakes sequence). The lower Paleozoic Kah Shakes sequence consists of Devonian orthogneiss, quartz-rich metasedimentary rocks, metabasalt, meta-silicic tuff, marble, cate-silicate, and quartzite. The quartz-rich metasedimentary rocks may be correlative with the lower Paleozoic and mid-Paleozoic Yukon-Tanana terrane, which represents an east-Pacific fringing arc complex built on continental slope and rise deposits. The upper Paleozoic and lower Mesozoic Alava sequence consists of crinoidal and argillaceous marble, carbonaceous phyllite, argillite, mafic flows, pillow breccia, pyroclastic tuff, and minor quartz-rich metasedimentary rocks. The upper Paleozoic part of the Alava sequence is probably correlative with the mid- to late Paleozoic portion of the Yukon-Tanana terrane. The Middle and Upper Triassic portion of the Alava sequence may represent a metamorphiC vestige of the Stuhini Group, now exposed on the western flank of the Coast Batholitic belt.
\r\n\r\nUpper Jurassic and Lower Cretaceous metavolcanic and metasedimentary strata of the Gravina sequence unconformably overlie both the Alexander and Taku terranes. These rocks form two distinct lithotectonic units in southern southeast Alaska. The lower unit consists of coarse marine pyroclastic and volcaniclastic strata, mafic flows, breccia, and fine-grained tuff which are locally intruded by hypabyssal bodies of diorite and quartz diorite. Fine- to coarse-grained turbidites and related channel-fill deposits comprise the epiclastic part of the Gravina sequence. Conglomerate units contain mostly volcanic and plutonic lithic clasts that suggest they were derived from a composite igneous source. Clasts from the channel-fill deposits yield Pb-U zircon ages of 154 to 158 Ma. The pyroclastic and volcaniclastic rocks represent remnants of a Late Jurassic oceanic arc system that was constructed on a composite basement consisting of the Alexander and Taku terranes; the Taku terrane is inferred to represent the westernmost extent of the Stikine and Yukon-Tanana terranes. These data suggest that the Intermontane (Stikine and Yukon-Tanana terranes) and Insular (Alexander terrane) superterranes were juxtaposed prior deposition of the Upper Jurassic and Lower Cretaceous Gravina sequence.
\r\n\r\nThe lower Paleozoic to Early Cretaceous rocks were deformed in the mid-Cretaceous and tectonism was broadly coeval with arc magmatism. Deformation involved the emplacement of west-directed thrust nappes over a structurally intact and relatively unmetamorphosed basement. Mid-Cretaceous tonalite, granodiorite, and quartz diorite intrude rocks of the thrust belt and were locally affected by the deformation. Mid-Cretaceous deformation occurred during two episodes that were contemporaneous with the emplacement of sill-like plutonic bodies. Older structures record ductile southwest-vergent folding and faulting, regional metamorphism and contain a well developed axial-planar foliation. The second generation structures developed during the later stages of southwest-directed reverse faulting that juxtaposes rocks of contrasting metamorphic pressures and temperatures. The presence of syntectonic kyanite-staurolite-garnet-biotite assemblages in the more eastern high-strain zones indicates that at least some of the reverse faults were generated at depths in excess of 20 km during the later stages of thrust faulting and associated uplift.
\r\n\r\nPaleocene and younger (?) deformation has also affected rocks on the western margin of the Coast Plutonic Complex. Younger fabrics are dominated by low to moderate west-dipping foliation surfaces that are axial planar to asymmetric east-vergent folds. The east-verging fabrics have transposed earlier mid-Cretaceous fabrics . Late Paleocene pegmatite dikes are highly deformed and are affected by the west-dipping structures. Exposure of mid-crustal level rocks might be related to a reversal in vergence during Paleocene time, in which deep levels of the mid-Cretaceous thrust system were transported upward along east-vergent structures. A swarm of hornblende-bearing diabase dikes cross-cut all structures and fabrics. These dikes trend northeast and mark a regional change in the overall regional strain patterns during Miocene time.
\r\n\r\nStructural, stratigraphic and geochronologic data suggest that regional-scale deformation in southeast Alaska occurred between 113 Ma and 89 Ma. Rocks in the thrust belt were regionally uplifted by 70 Ma, at an average minimum rate of \u2248 0.9 mm/yr. Mid-Cretaceous deformation involved the collapse of marginal basin(s) and a magmatic arc, overprinting the older tectonic boundary between the Insular superterrane and the late Mesozoic western margin of North America (i.e., the Intermontane superterrane). Contractional deformation along the length of the thrust belt was broadly coeval with arc magmatism, and thus records intra-arc tectonism. Late Paleocene to Early Eocene deformation and uplift may mark the transition from contractional to extensional tectonism, and perhaps records the collapse of tectonically thickened crust.
" }, { "name": "Shaller, Philip John", "degree": "PhD", "year": "1991", "title": "Analysis and implications of large Martian and terrestrial landslides", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08112004-132513", "creators": [ { "name": { "family": "Shaller", "given": "Philip John" }, "id": "Shaller-Philip-John", "display_name": "Shaller, Philip John" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/SNME-K738", "abstract": "I address two long-standing scientific problems in this thesis: the mechanism(s) of long-runout in large landslides; and the activity of water on the surface of Mars late in its history. Long-runout landslides form significant geologic risks. My research has aimed at understanding the factors that control the initiation and runout of large landslides wherever they occur. A second objective of this research has been to use martian landslides to gauge the activity of liquid water on Mars' surface over the past quarter of its history. To achieve these objectives, I made field observations of six moist and dry landslides in the western United States, I studied all the high-resolution Viking Orbiter images for large landslides on Mars and I collated all the available literature data on large landslides, to develop the clearest view possible of the nature of the large landslide process. I then used this information to evaluate all the previously published models of long runout, and to develop my own theory when I found that none of the existing theories provided an adequate explanation of the observations.\r\n\r\nI conclude that large landslides primarily slide and spread into place over fluidized natural basal lubricants. This concept follows upon the air-layer lubrication theory of Shreve, but does not call upon a gas lubricant, a possibility ruled out by the presence of Blackhawk-like long-runout landslides on Mars. Rather, the lubricants appear to be fine-grained materials from the substrate or from the landslide debris itself that deform plastically at the high shear stresses and strain rates present beneath large rapid landslides. Large dry landslides grade into moist debris flows as water becomes incorporated into their fine-grained component. Moist and dry landslides differ markedly in sedimentology and morphology, but not in a variety of quantitative relations. Seven landslide events on Mars appear to have involved water during runout, based on comparisons with water-bearing landslides of similar morphology and volume on Earth. These deposits occur primarily in Valles Marineris and indicate that liquid water has been sporadically available on Mars at various times over the last ~1 billion years of its history.\r\n" }, { "name": "Webb, Francis H.", "degree": "PhD", "year": "1991", "title": "Geodetic measurement of deformation in the offshore of southern California", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04142011-131740440", "creators": [ { "name": { "family": "Webb", "given": "Francis H." }, "id": "Webb-F-H", "display_name": "Webb, Francis H." } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/ztnn-4v90", "abstract": "Geodetic surveys using signals from satellites of the Global Positioning System (GPS) have allowed for the reoccupation of historical triangulation markers for crustal deformation studies and the recovery of a long history of geodetic data that date to the late 1800's. From June 1986 to May 1988, six GPS experiments were conducted in California that incorporated more than 50 first-order triangulation stations on the channel islands of southern California and the mainland into a precise GPS network. Interstation vectors were calculated from the GPS observables using the National Geodetic Survey's (NGS) GPS22 software. The results of these analyses provided baseline component precisions better than several pans in 10^7. The vectors from all of the GPS surveys were combined and used with historic triangulation observations to estimate shear-strain rates across the Santa Barbara Channel and Oxnard plain, and across the southern California Continental Borderland. Simultaneous reduction was used to evaluate the shear-strain rates from the combination of these data. Shear-strain rates across the Santa Barbara channel are from 0.2 to 0.4 \u00b5rad/yr with a direction of maximum contraction of from N23W to N20E, averaged over a hundred years of geodetic data. For networks that cross the Continental Borderland, the data were insufficient to reliably estimate strain rates.\r\n\r\nThe direction of shortening implied by the geodetic data agrees with that inferred from the trends of late Quaternary and Holocene faults and folds in the Santa Barbara channel. When the shear-strain rates across the channel are modeled as uniaxial convergence, this indicates shortening from 13\u00b15 mm/yr at N23W\u00b15 across the western part of the channel to 18\u00b15 mm/yr at N20E\u00b15 across the eastern part. By adding the western channel velocity to the geodetic velocity of the Vandenberg VLBI site with respect to North America, a velocity path across the Pacific-North American plate boundary can be constructed to the offshore islands of 56\u00b14 mm/yr at N38W\u00b14, exceeding the NUVEL-1 plate-model velocity for Pacific North American plate motion in California by 7 mm/yr.\r\n" }, { "name": "Anderson, William Wyatt", "degree": "PhD", "year": "1990", "title": "High Pressure States in Condensed Matter: I. High Pressure Behavior of the Iron-Sulfur System with Applications to the Earth's Core. II. Empirical Equation of State for Organic Compounds at High Pressures", "advisor": "Ahrens, Thomas J.; Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:03182015-092735941", "creators": [ { "name": { "family": "Anderson", "given": "William Wyatt" }, "id": "Anderson-William-Wyatt", "display_name": "Anderson, William Wyatt" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "co-advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" } ], "option_major": [ "plansci" ], "doi": "10.7907/7dsx-ed25", "abstract": "Part I:
\r\n\r\nThe earth's core is generally accepted to be composed primarily of iron, with an admixture of other elements. Because the outer core is observed not to transmit shear waves at seismic frequencies, it is known to be liquid or primarily liquid. A new equation of state is presented for liquid iron, in the form of parameters for the 4th order Birch-Murnaghan and Mie-Gr\u00fcneisen equations of state. The parameters were constrained by a set of values for numerous properties compiled from the literature. A detailed theoretical model is used to constrain the P-T behavior of the heat capacity, based on recent advances in the understanding of the interatomic potentials for transition metals. At the reference pressure of 105 Pa and temperature of 1811 K (the normal melting point of Fe), the parameters are: \u03c1 = 7037 kg/m3, KS0 = 110 GPa, KS' = 4.53, KS\" = -.0337 GPa-1, and \u03b3 = 2.8, with \u03b3 \u221d \u03c1-1.17. Comparison of the properties predicted by this model with the earth model PREM indicates that the outer core is 8 to 10 % less dense than pure liquid Fe at the same conditions. The inner core is also found to be 3 to 5% less dense than pure liquid Fe, supporting the idea of a partially molten inner core. The density deficit of the outer core implies that the elements dissolved in the liquid Fe are predominantly of lower atomic weight than Fe. Of the candidate light elements favored by researchers, only sulfur readily dissolves into Fe at low pressure, which means that this element was almost certainly concentrated in the core at early times. New melting data are presented for FeS and FeS2 which indicate that the FeS2 is the S-hearing liquidus solid phase at inner core pressures. Consideration of the requirement that the inner core boundary be observable by seismological means and the freezing behavior of solutions leads to the possibility that the outer core may contain a significant fraction of solid material. It is found that convection in the outer core is not hindered if the solid particles are entrained in the fluid flow. This model for a core of Fe and S admits temperatures in the range 3450K to 4200K at the top of the core. An all liquid Fe-S outer core would require a temperature of about 4900 K at the top of the core.
\r\n\r\nPart II.
\r\n\r\nThe abundance of uses for organic compounds in the modern world results in many applications in which these materials are subjected to high pressures. This leads to the desire to be able to describe the behavior of these materials under such conditions. Unfortunately, the number of compounds is much greater than the number of experimental data available for many of the important properties. In the past, one approach that has worked well is the calculation of appropriate properties by summing the contributions from the organic functional groups making up molecules of the compounds in question. A new set of group contributions for the molar volume, volume thermal expansivity, heat capacity, and the Rao function is presented for functional groups containing C, H, and O. This set is, in most cases, limited in application to low molecular liquids. A new technique for the calculation of the pressure derivative of the bulk modulus is also presented. Comparison with data indicates that the presented technique works very well for most low molecular hydrocarbon liquids and somewhat less well for oxygen-bearing compounds. A similar comparison of previous results for polymers indicates that the existing tabulations of group contributions for this class of materials is in need of revision. There is also evidence that the Rao function contributions for polymers and low molecular compounds are somewhat different.
" }, { "name": "Bent, Allison Lyn", "degree": "PhD", "year": "1990", "title": "Source Characteristics of Recent and Historic Earthquakes in Central and Southern California: Results from Forward Modeling", "advisor": "Helmberger, Donald V.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:03202015-092027205", "creators": [ { "name": { "family": "Bent", "given": "Allison Lyn" }, "id": "Bent-Allison-Lyn", "display_name": "Bent, Allison Lyn" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "co-advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "member", "display_name": "Tanimoto, Toshiro" } ], "option_major": [ "geophys" ], "doi": "10.7907/wyry-7c13", "abstract": "The long- and short-period body waves of a number of moderate earthquakes occurring in central and southern California recorded at regional (200-1400 km) and teleseismic (> 30\u00b0) distances are modeled to obtain the source parameters-focal mechanism, depth, seismic moment, and source time history. The modeling is done in the time domain using a forward modeling technique based on ray summation. A simple layer over a half space velocity model is used with additional layers being added if necessary - for example, in a basin with a low velocity lid.
\r\n\r\nThe earthquakes studied fall into two geographic regions: 1) the western Transverse Ranges, and 2) the western Imperial Valley. Earthquakes in the western Transverse Ranges include the 1987 Whittier Narrows earthquake, several offshore earthquakes that occurred between 1969 and 1981, and aftershocks to the 1983 Coalinga earthquake (these actually occurred north of the Transverse Ranges but share many characteristics with those that occurred there). These earthquakes are predominantly thrust faulting events with the average strike being east-west, but with many variations. Of the six earthquakes which had sufficient short-period data to accurately determine the source time history, five were complex events. That is, they could not be modeled as a simple point source, but consisted of two or more subevents. The subevents of the Whittier Narrows earthquake had different focal mechanisms. In the other cases, the subevents appear to be the same, but small variations could not be ruled out.
\r\n\r\nThe recent Imperial Valley earthquakes modeled include the two 1987 Superstition Hills earthquakes and the 1969 Coyote Mountain earthquake. All are strike-slip events, and the second 1987 earthquake is a complex event With non-identical subevents.
\r\n\r\nIn all the earthquakes studied, and particularly the thrust events, constraining the source parameters required modeling several phases and distance ranges. Teleseismic P waves could provide only approximate solutions. P\u2099\u2097 waves were probably the most useful phase in determining the focal mechanism, with additional constraints supplied by the SH waves when available. Contamination of the SH waves by shear-coupled PL waves was a frequent problem. Short-period data were needed to obtain the source time function.
\r\n\r\nIn addition to the earthquakes mentioned above, several historic earthquakes were also studied. Earthquakes that occurred before the existence of dense local and worldwide networks are difficult to model due to the sparse\r\ndata set. It has been noticed that earthquakes that occur near each other often produce similar waveforms implying similar source parameters. By comparing recent well studied earthquakes to historic earthquakes in the same\r\nregion, better constraints can be placed on the source parameters of the historic events.
\r\n\r\nThe Lompoc earthquake (M=7) of 1927 is the largest offshore earthquake to occur in California this century. By direct comparison of waveforms and amplitudes with the Coalinga and Santa Lucia Banks earthquakes, the focal\r\nmechanism (thrust faulting on a northwest striking fault) and long-period seismic moment (10\u00b2\u2076 dyne cm) can be obtained. The S-P travel times are consistent with an offshore location, rather than one in the Hosgri fault zone.
\r\n\r\nHistoric earthquakes in the western Imperial Valley were also studied. These events include the 1942 and 1954 earthquakes. The earthquakes were relocated by comparing S-P and R-S times to recent earthquakes. It was found that only minor changes in the epicenters were required but that the Coyote Mountain earthquake may have been more severely mislocated. The waveforms as expected indicated that all the events were strike-slip. Moment estimates were obtained by comparing the amplitudes of recent and historic events at stations which recorded both. The 1942 event was smaller than the 1968 Borrego Mountain earthquake although some previous studies suggested the reverse. The 1954 and 1937 earthquakes had moments close to the expected value. An aftershock of the 1942 earthquake appears to be larger than previously thought.
" }, { "name": "Blum, Joel David", "degree": "PhD", "year": "1990", "title": "Geochemistry and Resonance Ionization of Platinum-Group Elements", "advisor": "Wasserburg, Gerald J.; Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09042014-150651827", "creators": [ { "name": { "family": "Blum", "given": "Joel David" }, "id": "Blum-Joel-David", "display_name": "Blum, Joel David" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "co-advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "chair", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "co-chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geochem" ], "doi": "10.7907/KXRF-AQ49", "abstract": "Experimental studies were conducted with the goals of 1) determining the origin of Pt-group element (PGE) alloys and associated mineral assemblages in refractory inclusions from meteorites and 2) developing a new ultrasensitive method for the in situ chemical and isotopic analysis of PGE. A general review of the geochemistry and cosmochemistry of the PGE is given, and specific research contributions are presented within the context of this broad framework.
\r\n\r\nAn important step toward understanding the cosmochemistry of the PGE is the determination of the origin of POE-rich metallic phases (most commonly \u03b5Ru-Fe) that are found in Ca, AJ-rich refractory inclusions (CAI) in C3V meteorites. These metals occur along with \u03b3Ni-Fe metals, Ni-Fe sulfides and Fe oxides in multiphase opaque assemblages. Laboratory experiments were used to show that the mineral assemblages and textures observed in opaque assemblages could be produced by sulfidation and oxidation of once homogeneous Ni-Fe-PGE metals. Phase equilibria, partitioning and diffusion kinetics were studied in the Ni-Fe-Ru system in order to quantify the conditions of opaque assemblage formation. Phase boundaries and tie lines in the Ni-Fe-Ru system were determined at 1273, 1073 and 873K using an experimental technique that allowed the investigation of a large portion of the Ni-Fe-Ru system with a single experiment at each temperature by establishing a concentration gradient within which local equilibrium between coexisting phases was maintained. A wide miscibility gap was found to be present at each temperature, separating a hexagonal close-packed \u03b5Ru-Fe phase from a face-centered cubic \u03b3Ni-Fe phase. Phase equilibria determined here for the Ni-Fe-Ru system, and phase equilibria from the literature for the Ni-Fe-S and Ni-Fe-O systems, were compared with analyses of minerals from opaque assemblages to estimate the temperature and chemical conditions of opaque assemblage formation. It was determined that opaque assemblages equilibrated at a temperature of ~770K, a sulfur fugacity 10 times higher than an equilibrium solar gas, and an oxygen fugacity 10\u2076 times higher than an equilibrium solar gas.
\r\n\r\nDiffusion rates between -\u03b3Ni-Fe and \u03b5Ru-Fe metal play a critical role in determining the time (with respect to CAI petrogenesis) and duration of the opaque assemblage equilibration process. The diffusion coefficient for Ru in Ni (DRuNi) was determined as an analog for the Ni-Fe-Ru system by the thin-film diffusion method in the temperature range of 1073 to 1673K and is given by the expression:
\r\n\r\nDRuNi (cm\u00b2 sec\u207b\u00b9) = 5.0(\u00b10.7) x 10\u207b\u00b3 exp(-2.3(\u00b10.1) x 10\u00b9\u00b2 erg mole\u207b\u00b9/RT) where R is the gas constant and T is the temperature in K. Based on the rates of dissolution and exsolution of metallic phases in the Ni-Fe-Ru system it is suggested that opaque assemblages equilibrated after the melting and crystallization of host CAI during a metamorphic event of \u2265 10\u00b3 years duration. It is inferred that opaque assemblages originated as immiscible metallic liquid droplets in the CAI silicate liquid. The bulk compositions of PGE in these precursor alloys reflects an early stage of condensation from the solar nebula and the partitioning of V between the precursor alloys and CAI silicate liquid reflects the reducing nebular conditions under which CAI were melted. The individual mineral phases now observed in opaque assemblages do not preserve an independent history prior to CAI melting and crystallization, but instead provide important information on the post-accretionary history of C3V meteorites and allow the quantification of the temperature, sulfur fugacity and oxygen fugacity of cooling planetary environments. This contrasts with previous models that called upon the formation of opaque assemblages by aggregation of phases that formed independently under highly variable conditions in the solar nebula prior to the crystallization of CAI.
\r\n\r\nAnalytical studies were carried out on PGE-rich phases from meteorites and the products of synthetic experiments using traditional electron microprobe x-ray analytical techniques. The concentrations of PGE in common minerals from meteorites and terrestrial rocks are far below the ~100 ppm detection limit of the electron microprobe. This has limited the scope of analytical studies to the very few cases where PGE are unusually enriched. To study the distribution of PGE in common minerals will require an in situ analytical technique with much lower detection limits than any methods currently in use. To overcome this limitation, resonance ionization of sputtered atoms was investigated for use as an ultrasensitive in situ analytical technique for the analysis of PGE. The mass spectrometric analysis of Os and Re was investigated using a pulsed primary Ar\u207a ion beam to provide sputtered atoms for resonance ionization mass spectrometry. An ionization scheme for Os that utilizes three resonant energy levels (including an autoionizing energy level) was investigated and found to have superior sensitivity and selectivity compared to nonresonant and one and two energy level resonant ionization schemes. An elemental selectivity for Os over Re of \u2265 10\u00b3 was demonstrated. It was found that detuning the ionizing laser from the autoionizing energy level to an arbitrary region in the ionization continuum resulted in a five-fold decrease in signal intensity and a ten-fold decrease in elemental selectivity. Osmium concentrations in synthetic metals and iron meteorites were measured to demonstrate the analytical capabilities of the technique. A linear correlation between Os\u207a signal intensity and the known Os concentration was observed over a range of nearly 10\u2074 in Os concentration with an accuracy of ~ \u00b110%, a millimum detection limit of 7 parts per billion atomic, and a useful yield of 1%. Resonance ionization of sputtered atoms samples the dominant neutral-fraction of sputtered atoms and utilizes multiphoton resonance ionization to achieve high sensitivity and to eliminate atomic and molecular interferences. Matrix effects should be small compared to secondary ion mass spectrometry because ionization occurs in the gas phase and is largely independent of the physical properties of the matrix material. Resonance ionization of sputtered atoms can be applied to in situ chemical analysis of most high ionization potential elements (including all of the PGE) in a wide range of natural and synthetic materials. The high useful yield and elemental selectivity of this method should eventually allow the in situ measurement of Os isotope ratios in some natural samples and in sample extracts enriched in PGE by fire assay fusion.
\r\n\r\nPhase equilibria and diffusion experiments have provided the basis for a reinterpretation of the origin of opaque assemblages in CAI and have yielded quantitative information on conditions in the primitive solar nebula and cooling planetary environments. Development of the method of resonance ionization of sputtered atoms for the analysis of Os has shown that this technique has wide applications in geochemistry and will for the first time allow in situ studies of the distribution of PGE at the low concentration levels at which they occur in common minerals.
" }, { "name": "Brigham, Cheryl A.", "degree": "PhD", "year": "1990", "title": "Isotopic Heterogeneity in Calcium-Aluminum-Rich Meteoritic Inclusions", "advisor": "Wasserburg, Gerald J.; Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:04282010-113920823", "creators": [ { "name": { "family": "Brigham", "given": "Cheryl A." }, "id": "Brigham-Cheryl-A", "display_name": "Brigham, Cheryl A." } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "co-advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "chair", "display_name": "Epstein, Samuel" }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "member", "display_name": "Wasserburg, Gerald J." } ], "option_major": [ "geochem" ], "doi": "10.7907/TYS3-HQ41", "abstract": "Calcium-Aluminum-rich inclusions (CAI), found in meteorites, are among the oldest known solids identified in the solar system. Analyses of CAI have provided constraints on physical and chemical conditions that existed just prior to, and during planetary formation. A few rare inclusions, called FUN (for Fractionation and Unknown Nuclear effects), exhibit large isotopic anomalies and have provided insight into nucleosynthetic and nebular processes.
\r\n\r\nIn this thesis, data obtained on the petrography, chemistry and isotopic compositions of CAI, identified in the carbonaceous chondrite Allende, are used as tracers to address several specific questions: 1) What are the relationships between fine and coarse-grained CAI? 2) What are the differences, in composition and origin, between FUN inclusions and isotopically normal CAI? 3) What was the role of volatility-controlled processes, such as distillation and condensation, in the evolution of CAI? 4) What was the role of chemical alteration and isotopic reequilibration in the evolution of CAI?
\r\n\r\nIsotopic data were obtained by thermal ionization and ion microprobe mass spectrometry for individual grains within both fine and coarse-grained CAI, and correlated with petrographic and chemical observations. Evidence is presented for the enrichment of fine-grained inclusions in the lighter isotopes of Mg, in contrast to coarse-grained CAI, which are enriched in the heavier isotopes. Isotopic heterogeneity was observed within both fine and coarse-grained inclusions. Heterogeneity is discussed in the context of primary and secondary phases, mineral alteration processes, and isotopic reequilibration.
\r\n\r\nA new class of coarse-grained inclusion, characterized by a distinct purple color and high spinel contents (\u226550%), were identified and found to exhibit a high frequency (20%) of FUN isotopic anomalies. Four new FUN inclusions were identified and studied in detail. The correlated isotopic fractionation for Mg, Si, and Cr in these inclusions, suggests the importance of volatility-controlled formation processes. A model is presented for the evolution of FUN inclusions, involving distillation of ordinary chondritic material, with a mass loss of around 70%, followed by exchange with isotopically normal reservoirs. The high spinel contents and large isotopic fractionation of these inclusions, may indicate that they formed at higher temperatures than isotopically normal CAI.
" }, { "name": "Davies, John Huw", "degree": "PhD", "year": "1990", "title": "Some Problems in Mantle Structure and Dynamics. Part 1. Inversion for Depth Variation of Spectra of Mantle Compressional and Shear Velocity Heterogeneity. Part 2. Physical Model of Source Region of Subduction Zone Volcanism", "advisor": "Clayton, Robert W.; Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:09242010-084738829", "creators": [ { "name": { "family": "Davies", "given": "John Huw" }, "id": "Davies-John-Huw", "display_name": "Davies, John Huw" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." } ], "option_major": [ "geophys" ], "doi": "10.7907/1pkp-t397", "abstract": "Part 1. The scatter in ISC P- and S-wave travel-time residuals was inverted to give a measure of the data-set's incoherent noise and the depth variation of the spectra of the Earth's seismic heterogeneity. The P- and S-wave models are similar in pattern with most of their power shallower than 400km. The power generally decreases with depth and is lowest around 1500-2600km depth. Both models show a slight increase locally below the 670km discontinuity. The long-wavelength half-width (l<50) is around 500km through the upper mantle increasing to around 1200km in the lowermost mantle. The variance in the travel-time residuals requires that (\u03b41nV\u209b/ \u03b41n V\u209a) \u2248 2, if they are correlated. Our results suggest values as high as 5 from 60-1400km; these could be correct but our preferred explanation is that it's a result of poor depth resolution of the shallowest layer and a difference in the spectral resolution of the two studies.
\r\n\r\nPart 2. Thermal modeling of a generic subduction zone suggests that the oceanic crust does not melt extensively to be the source of subduction zone magmas. The slab dehydrates and the water is transported laterally into the wedge by a mechanism involving transport fixed in amphiboles and vertical porous flow when free. This water generates melting at the amphibole saturated solidus. Melting reaches a maximum at the hottest geotherm, which also caps the source region. Melts depart the source region in cracks whose direction of propagation is perpendicular to the least compressive stress. For a corner flow regime this leads to focusing of melt towards the wedge corner. The model correctly predicts the location of, the volcanic front. The melt and residue provide buoyancy that leads to local flow reversal and modulates the volcanism with a period of \u2248 1Ma. Estimates suggest more water is subducted than reappears in extrusive volcanics. We suggest the excess water is stored in melts trapped deeper in the section that later become the precursors of granitic and tonalitic plutons.
" }, { "name": "Grossman, Arie William", "degree": "PhD", "year": "1990", "title": "Microwave imaging of Saturn's deep atmosphere and rings", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechETD:etd-10302008-151649", "creators": [ { "name": { "family": "Grossman", "given": "Arie William" }, "id": "Grossman-Arie-William", "display_name": "Grossman, Arie William" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/svtf-j306", "abstract": "This work presents an analysis of microwave images of Saturn's atmosphere and rings. Interferometer observations at wavelengths of 0.27, 2.01, 3.53, 6.17, and 20.13 centimeters and precise application of synthesis imaging techniques yielded brightness and polarization maps of unsurpassed resolution and sensitivity. Linear polarization is detected from the ring ansea, and brightness variations in the deep atmosphere and the rings are revealed for the first time.\r\n\r\nThe disk-integrated spectrum of Saturn is interpreted within the context of a radiative transfer model that requires the NH3 mixing ratio to take on a value of 0.9 to 1.1 x10[superscript -4] (0.5-0.6 times solar) directly below the ammonia ice cloud at a pressure of 1.4 bar. The NH[subscript 3] mixing ratio increases with depth to a value of 5.0 to 6.5 x10[superscript -4] (2.9-3.7 times solar) at a pressure of 6 bar. The variation of NH3 with depth can be entirely accounted for by the presence of 11-14 times solar abundance of H[subscript 2]S, which reacts with NH[subscript 3] to produce a substantial NH[subscript 4]SH cloud.\r\n\r\nLatitudinal variations in brightness temperature indicate that the saturated vapor abundance of ammonia decreases by 50% from equator to pole within the cloud deck. At greater depths the latitudinal variations of ammonia are consistent with alternating zones of concentration and depletion caused by vertical motions. An apparent depletion in northern mid-latitudes is well-correlated with a decrease in infrared opacity and depressed cloud top levels, indicating deep-seated downwelling.\r\n\r\nThe size, composition, and shape of particles comprising the rings of Saturn are constrained by modeling the emission, scattering, and extinction of radiation by the rings. The observations can be fit by a incremental power-law particle size distribution with exponent in the range 2.6-3.0 for the combined A and B rings, assuming a classical many-particle-thick layer. The wavelength dependence of the optical depths places a strict lower limit of 1 cm on particle sizes in the classical rings. Observations of thermal emission from the rings further constrain the mass fraction of uniformly mixed silicate impurities to be less than 1%. Azimuthal variations in brightness and linear polarization rule out the possibility that the particles are smooth, convex objects, and favor a model in which the particles are irregularly shaped.\r\n" }, { "name": "Gudmundsson, Olafur", "degree": "PhD", "year": "1990", "title": "Some problems in global tomography: modeling the core-mantle boundary and statistical analysis of travel-time data", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09202010-080853201", "creators": [ { "name": { "family": "Gudmundsson", "given": "Olafur" }, "id": "Gudmundsson-O", "display_name": "Gudmundsson, Olafur" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/qneg-nb47", "abstract": " Core-mantle boundary (CMB) structure is mapped with travel-time data in the International Seismological Centre (ISC) catalog. Different subsets of ISC data yield inconsistent results for CMB topography. Correlations of anomalies in well covered areas indicate a common source of signal above the CMB. Allowing for heterogeneity above the CMB yields models of 4 km peak-to-peak CMB topography and 2.5% velocity variations in the D\" layer. The models contain a large degree-two, zonal component. This agrees with the results of a stacking procedure employed in search of an axisymmetric pattern in the ISC data. It is concluded that the axisymmetric pattern in antipodal PKIKP data must at least in part be explained by CMB structure.\r\n\r\n A method is developed to extract estimates of random data-errors and statistical measures of the earth's structure from global, travel-time data. Application of this method to teleseismic P-wave data yields an estimate of the signal-to-noise ratio in excess of unity. Heterogeneity is found to be strongly concentrated near the earth's surface. It extends over a wide range of scales in the upper mantle, but is restricted to relatively large scales in the lower mantle. The root-mean-square level of heterogeneity is found to be of the order of 0.1% in the lower mantle, but several times higher at its top and bottom.\r\n\r\n Synthetic (2D) tests of lower-mantle and CMB travel-time inversions indicate only partial success for the lower mantle and a 5 to 10 km uncertainty in CMB mapping. This is consistent with the inconsistencies in the ISC data, when mapped onto the CMB, and suggests that the above results pertaining to CMB structure may be obscure." }, { "name": "LeFevre, L. Victoria", "degree": "PhD", "year": "1990", "title": "I. A seismotectonic study of the Middle America Subduction Zone. II. Lithosphere and upper mantle structure of the Canadian Shield and Eastern North America", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:07152014-110952725", "creators": [ { "name": { "family": "LeFevre", "given": "L. Victoria" }, "id": "LeFevre-L-V", "display_name": "LeFevre, L. Victoria" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/20tk-sb77", "abstract": "This thesis consists of two separate parts. Part I (Chapter 1) is\r\nconcerned with seismotectonics of the Middle America subduction zone.\r\nIn this chapter, stress distribution and Benioff zone geometry are\r\ninvestigated along almost 2000 km of this subduction zone, from the\r\nRivera Fracture Zone in the north to Guatemala in the south.\r\nParticular emphasis is placed on the effects on stress distribution of\r\ntwo aseismic ridges, the Tehuantepec Ridge and the Orozco Fracture\r\nZone, which subduct at seismic gaps. Stress distribution is determined\r\nby studying seismicity distribution, and by analysis of 190 focal\r\nmechanisms, both new and previously published, which are collected\r\nhere. In addition, two recent large earthquakes that have occurred\r\nnear the Tehuantepec Ridge and the Orozco Fracture Zone are discussed\r\nin more detail. A consistent stress release pattern is found along\r\nmost of the Middle America subduction zone: thrust events at\r\nshallow depths, followed down-dip by an area of low seismic activity, followed\r\nby a zone of normal events at over 175 km from the trench and 60 km\r\ndepth. The zone of low activity is interpreted as showing decoupling\r\nof the plates, and the zone of normal activity as showing the breakup\r\nof the descending plate. The portion of subducted lithosphere\r\ncontaining the Orozco Fracture Zone does not differ significantly, in\r\nBenioff zone geometry or in stress distribution, from adjoining\r\nsegments. The Playa Azul earthquake of October 25, 1981, Ms=7.3,\r\noccurred in this area. Body and surface wave analysis of this event\r\nshows a simple source with a shallow thrust mechanism and gives\r\nMo=1.3x1027 dyne-cm. A stress drop of about 45 bars is calculated;\r\nthis is slightly higher than that of other thrust events in this\r\nsubduction zone. In the Tehuantepec Ridge area, only minor differences\r\nin stress distribution are seen relative to adjoining segments. For\r\nboth ridges, the only major difference from adjoining areas is the\r\ninfrequency or lack of occurrence of large interplate thrust events.
\r\n\r\nPart II involves upper mantle P wave structure studies, for the\r\nCanadian shield and eastern North America. In Chapter 2, the P wave\r\nstructure of the Canadian shield is determined through forward waveform\r\nmodeling of the phases Pnl, P, and PP. Effects of lateral\r\nheterogeneity are kept to a minimum by using earthquakes just outside\r\nthe shield as sources, with propagation paths largely within the\r\nshield. Previous mantle structure studies have used recordings of P\r\nwaves in the upper mantle triplication range of 15-30\u00b0; however, the\r\nlack of large earthquakes in the shield region makes compilation of a\r\ncomplete P wave dataset difficult. By using the phase PP, which\r\nundergoes triplications at 30-60\u00b0, much more information becomes\r\navailable. The WKBJ technique is used to calculate synthetic\r\nseismograms for PP, and these records are modeled almost as well as the\r\nP. A new velocity model, designated S25, is proposed for the Canadian\r\nshield. This model contains a thick, high-Q, high-velocity lid to 165\r\nkm and a deep low-velocity zone. These features combine to produce\r\nseismograms that are markedly different from those generated by other\r\nshield structure models. The upper mantle discontinuities in S25 are\r\nplaced at 405 and 660 km, with a simple linear gradient in velocity\r\nbetween them. Details of the shape of the discontinuities are not well\r\nconstrained. Below 405 km, this model is not very different from many\r\nproposed P wave models for both shield and tectonic regions.
\r\n\r\nChapter 3 looks in more detail at recordings of Pnl in eastern\r\nNorth America. First, seismograms from four eastern North American\r\nearthquakes are analyzed, and seismic moments for the events are\r\ncalculated. These earthquakes are important in that they are among the\r\nlargest to have occurred in eastern North America in the last thirty\r\nyears, yet in some cases were not large enough to produce many good\r\nlong-period teleseismic records. A simple layer-over-a-halfspace model\r\nis used for the initial modeling, and is found to provide an excellent\r\nfit for many features of the observed waveforms. The effects on Pnl of\r\nvarying lid structure are then investigated. A thick lid with a\r\npositive gradient in velocity, such as that proposed for the Canadian\r\nshield in Chapter 2, will have a pronounced effect on the waveforms,\r\nbeginning at distances of 800 or 900 km. Pnl records from the same\r\neastern North American events are recalculated for several lid\r\nstructure models, to survey what kinds of variations might be seen.\r\nFor several records it is possible to see likely effects of lid\r\nstructure in the data. However, the dataset is too sparse to make any\r\ngeneral observations about variations in lid structure. This type of\r\nmodeling is expected to be important in the future, as the analysis is\r\nextended to more recent eastern North American events, and as broadband\r\ninstruments make more high-quality regional recordings available.
" }, { "name": "Liu, Wei", "degree": "PhD", "year": "1990", "title": "Paleomagnetism of miocene sedimentary rocks in the Transverse ranges: the implications for tectonic history", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09142010-081708512", "creators": [ { "name": { "family": "Liu", "given": "Wei" }, "id": "Liu-Wei", "display_name": "Liu, Wei" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "geol" ], "doi": "10.7907/W9W2-VR83", "abstract": " Reconstructions of the offset history of the San Andreas fault in southern California have relied mainly on the correlation of rocks and structures within the Central Transverse Ranges. Only a few Miocene basins exposed along the fault zone in this area are associated closely with the early activity of the San Andreas system. The age of these sedimentary rocks is therefore critical for constraining the early activity, and helping understand the history, of the San Andreas fault. This study refines the ages of three Miocene sedimentary rock units, the Cajon, Crowder, and type Punchbowl, and Mill Creek formations, along the San Andreas fault in the Central Transverse Ranges by paleomagnetic methods, in order to provide age constraints on structures and tectonic events in the area. In addition, these data can be used to determine the magnitude of net tectonic rotations that may have occurred in these rocks.\r\n\r\n Magnetic polarity stratigraphies have been developed for the top three units of the Cajon Formation and for the entire Crowder Formation in the Cajon Valley. By matching the magnetic polarity stratigraphies with the standard magnetic polarity time scale, the ages of the Cajon and the Crowder formations are constrained to range from at least 17 Ma to 12.7 Ma and from 17 Ma to 9 Ma, respectively. Although deposition of these two formations began at nearly the same time (about 17 Ma), the youngest rocks preserved in each unit differ in age by nearly 4 million years. In conjunction with their distinct sedimentary features, source areas, and geographic extent, this indicates that they were deposited in different basins. Hence, the offset along the Squaw Peak fault that now separates the units was probably on the order of at least several tens of kilometers.\r\n\r\n Because unit 6 of the Cajon Formation (ca. 13 Ma) and unit 5 of the Crowder Formation (9.0 Ma) are the youngest units obviously truncated by the Cajon Valley and Squaw Peak faults, respectively, and the 4.2 Ma Phelan Peak Formation is not offset by these faults, these two faults were active sometime between 13 and 9 Ma, respectively and 4.2 Ma. As the San Gabriel and Liebre Mountain faults were also active during these intervals of time, our results are compatible with the theory that the Cajon Valley and the Squaw Peak faults are the offset extensions of the San Gabriel and Liebre Mountain faults, respectively. This further supports the proposal that the total offset along the modern San Andreas fault during Pliocene and Pleistocene time has been 150 - 160 kilometers.\r\n\r\n A similar paleomagnetic stratigraphic study was conducted on the late Miocene Punchbowl Formation at the Devil's Punchbowl County Park of California. The magnetic polarity pattern obtained from the Punchbowl Formation can be matched unambiguously to the geomagnetic reversal time scale from chrons 5Ar to 4Br, which implies that the formation was deposited from about 12.5 to 8.5 Ma. Combined with our age constraints on the Cajon Formation, this demonstrates that the Cajon and Punchbowl formations were deposited during completely different periods of time. This confirms the interpretation of Woodburne and Golz (1972) that the two formations do not correlate. Hence, the distance between these two formations cannot be used to constrain the total offset along the San Andreas fault.\r\n\r\n The age of the Punchbowl Formation also constrains the activity of the Fenner fault, which may be an old strand of the early San Andreas system. The Punchbowl Formation is the oldest unit that is not offset by the Fenner fault. Although the Paleocene San Francisquito Formation is the youngest unit offset by the fault at Devil's Punchbowl, early Miocene rocks were offset by the San Francisquito and Clemens Well faults, which were suggested as offset portions of the Fenner fault (Powell, 1980). Hence, the Fenner fault was probably active between early Miocene time and 12.5 Ma. Timing of another strand of the early San Andreas system, the Punchbowl fault, is also constrained by our result. Based on the geologic data, the Punchbowl fault has had two episodes of activity, one immediately before the deposition of the Punchbowl Formation, another after its deposition. Therefore, our results constrain these two episodes to start at about 12.5 Ma and after 8.5 Ma, respectively.\r\n\r\n Tectonic rotations determined by anomalies in the paleomagnetic declination of these formations are quite different. In Cajon Valley, the Cajon Formation shows clockwise rotations of up to 26\u00b0, whereas rotation in the Crowder Formation is much less (at most 4\u00b0 clockwise). Rotations in the Cajon Formation were probably caused by differential thrusting along the Squaw Peak thrust system, complicated further by small contributions from drag on \"tear\" segment of the Squaw Peak and the San Andreas faults.\r\n\r\n Abnormal counterclockwise rotations (27.5\u00b0 \u00b1 4.3\u00b0) were found in the Punchbowl Formation, which are compatible with those interpreted in the Mint Canyon Formation (13\u00b0 \u00b1 30\u00b0) 40 to 50 km to the west. This suggests that the entire San Gabriel block between the San Andreas and San Gabriel faults may have been rotated counterclockwise. The rotation probably occurred as the San Gabriel block moved adjacent to the preexisting bent segment of the San Andreas fault, aided by the Mojave Desert block acting as a \"backstop.\" After correcting for this rotation, the Punchbowl and Fenner faults would be parallel to the San Andreas fault in this area. This supports the proposal that the Fenner and Punchbowl faults were strands of the early San Andreas system during Miocene time.\r\n\r\n There is little or no rotation in the Mill Creek Formation, which was exposed in an elongated block between two (or three) strands of the San Andreas fault. As the Mill Creek block is a long sliver in, and parallel to the strike of, the fault zone, it is thus difficult to rotate.\r\n\r\n Our results do not agree with the prediction that the entire Transverse Ranges have been rotated clockwise in Neogene time. They also suggest that the geometry of major faults along which rigid blocks move is critical for producing the rotation and for determining the sense of the rotation. If our interpretation is correct, it implies that the San Andreas fault has had its abnormal geometry since it formed, and that the fault itself and the San Bernardino Mountains have not been rotated since Miocene time. \r\n" }, { "name": "Magistrale, Harold William", "degree": "PhD", "year": "1990", "title": "I. The Superstition Hills, California, earthquakes of 24 November 1987. II. Three-dimensional velocity structure of southern California.\r ", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:03192015-141811420", "creators": [ { "name": { "family": "Magistrale", "given": "Harold William" }, "id": "Magistrale-H-W", "display_name": "Magistrale, Harold William" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/CVA7-Z091", "abstract": "Part 1 of this thesis is about the 24 November, 1987, Superstition Hills earthquakes. The Superstition Hills earthquakes occurred in the western Imperial Valley in southern California. The earthquakes took place on a conjugate fault system consisting of the northwest-striking right-lateral Superstition Hills fault and a previously unknown Elmore Ranch fault, a northeast-striking left-lateral structure defined by surface rupture and a lineation of hypocenters. The earthquake sequence consisted of foreshocks, the M_s 6.2 first main shock, and aftershocks on the Elmore Ranch fault followed by the M_s 6.6 second main shock and aftershocks on the Superstition Hills fault. There was dramatic surface rupture along the Superstition Hills fault in three segments: the northern segment, the southern segment, and the Wienert fault.
\r\n\r\nIn Chapter 2, M_L\u22654.0 earthquakes from 1945 to 1971 that have Caltech catalog locations near the 1987 sequence are relocated. It is found that none of the relocated earthquakes occur on the southern segment of the Superstition Hills fault and many occur at the intersection of the Superstition Hills and Elmore Ranch faults. Also, some other northeast-striking faults may have been active during that time.
\r\n\r\nChapter 3 discusses the Superstition Hills earthquake sequence using data from the Caltech-U.S.G.S. southern California seismic array. The earthquakes are relocated and their distribution correlated to the type and arrangement of the basement rocks. The larger earthquakes occur only where continental crystalline basement rocks are present. The northern segment of the Superstition Hills fault has more aftershocks than the southern segment.
\r\n\r\nAn inversion of long period teleseismic data of the second mainshock of the 1987 sequence, along the Superstition Hills fault, is done in Chapter 4. Most of the long period seismic energy seen teleseismically is radiated from the southern segment of the Superstition Hills fault. The fault dip is near vertical along the northern segment of the fault and steeply southwest dipping along the southern segment of the fault.
\r\n\r\nChapter 5 is a field study of slip and afterslip measurements made along the Superstition Hills fault following the second mainshock. Slip and afterslip measurements were started only two hours after the earthquake. In some locations, afterslip more than doubled the coseismic slip. The northern and southern segments of the Superstition Hills fault differ in the proportion of coseismic and postseismic slip to the total slip.
\r\n\r\nThe northern segment of the Superstition Hills fault had more\r\naftershocks, more historic earthquakes, released less teleseismic energy, and had a smaller proportion of afterslip to total slip than the southern segment. The boundary between the two segments lies at a step in the basement that separates a deeper metasedimentary basement to the south from a shallower crystalline basement to the north.
\r\n\r\nPart 2 of the thesis deals with the three-dimensional velocity structure of southern California. In Chapter 7, an a priori three-dimensional crustal velocity model is constructed by partitioning southern California into geologic provinces, with each province having a consistent one-dimensional velocity structure. The one-dimensional velocity structures of each region were then assembled into a three-dimensional model. The three-dimension model was calibrated by forward modeling of explosion travel times.
\r\n\r\nIn Chapter 8, the three-dimensional velocity model is used to locate\r\nearthquakes. For about 1000 earthquakes relocated in the Los Angeles basin, the three-dimensional model has a variance of the the travel time residuals 47 per cent less than the catalog locations found using a standard one-dimensional velocity model. Other than the 1987 Whittier earthquake sequence, little correspondence is seen between these earthquake locations and elements of a recent structural cross section of the Los Angeles basin. The Whittier sequence involved rupture of a north dipping thrust fault bounded on at least one side by a strike-slip fault. The 1988 Pasadena earthquake was deep left-lateral event on the Raymond fault. The 1989 Montebello earthquake was a thrust event on a structure similar to that on which the Whittier earthquake occurred. The 1989 Malibu earthquake was a thrust or oblique slip event adjacent to the 1979 Malibu earthquake.
\r\n\r\nAt least two of the largest recent thrust earthquakes (San Fernando and Whittier) in the Los Angeles basin have had the extent of their thrust plane ruptures limited by strike-slip faults. This suggests that the buried thrust faults underlying the Los Angeles basin are segmented by strike-slip faults.
\r\n\r\nEarthquake and explosion travel times are inverted for the three-dimensional velocity structure of southern California in Chapter 9. The inversion reduced the variance of the travel time residuals by 47 per cent compared to the starting model, a reparameterized version of the forward model of Chapter 7. The Los Angeles basin is well resolved, with seismically slow sediments atop a crust of granitic velocities. Moho depth is between 26 and 32 km.
\r\n" }, { "name": "Miller, Gregory Hale", "degree": "PhD", "year": "1990", "title": "The Equation of State and Petrogenesis of Komatiite", "advisor": "Ahrens, Thomas J.; Stolper, Edward M.; Rossman, George Robert; Goddard, William A., III", "url": "https://resolver.caltech.edu/CaltechTHESIS:03272015-161328191", "creators": [ { "name": { "family": "Miller", "given": "Gregory Hale" }, "id": "Miller-G-H", "display_name": "Miller, Gregory Hale" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "co-advisor", "display_name": "Stolper, Edward M." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "role": "co-advisor", "display_name": "Rossman, George Robert" }, { "name": { "family": "Goddard", "given": "William A., III" }, "id": "Goddard-W-A-III", "role": "co-advisor", "display_name": "Goddard, William A., III" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/r0pt-2227", "abstract": "(1) Equation of State of Komatiite
\r\n\r\nThe equation of state (EOS) of a molten komatiite (27 wt% MgO) was detennined in the 5 to\r\n36 GPa pressure range via shock wave compression from 1550\u00b0C and 0 bar. Shock wave velocity,\r\nUS, and particle velocity, UP, in km/s follow the linear relationship US = 3.13(\u00b10.03) + 1.47(\u00b10.03)\r\nUP. Based on a calculated density at 1550\u00b0C, 0 bar of 2.745\u00b10.005 glee, this US-UP relationship\r\ngives the isentropic bulk modulus KS = 27.0 \u00b1 0.6 GPa, and its first and second isentropic pressure\r\nderivatives, K'S = 4.9 \u00b1 0.1 and K\"S = -0.109 \u00b1 0.003 GPa-1.
\r\n\r\nThe calculated liquidus compression curve agrees within error with the static compression\r\nresults of Agee and Walker [1988a] to 6 GPa. We detennine that olivine (FO94) will be neutrally\r\nbuoyant in komatiitic melt of the composition we studied near 8.2 GPa. Clinopyroxene would also\r\nbe neutrally buoyant near this pressure. Liquidus garnet-majorite may be less dense than this komatiitic\r\nliquid in the 20-24 GPa interval, however pyropic-garnet and perovskite phases are denser than\r\nthis komatiitic liquid in their respective liquidus pressure intervals to 36 GPa. Liquidus perovskite\r\nmay be neutrally buoyant near 70 GPa.
\r\n\r\nAt 40 GPa, the density of shock-compressed molten komatiite would be approximately equal\r\nto the calculated density of an equivalent mixture of dense solid oxide components. This observation\r\nsupports the model of Rigden et al. [1989] for compressibilities of liquid oxide components.\r\nUsing their theoretical EOS for liquid forsterite and fayalite, we calculate the densities of a spectrum\r\nof melts from basaltic through peridotitic that are related to the experimentally studied komatiitic\r\nliquid by addition or subtraction of olivine. At low pressure, olivine fractionation lowers the density\r\nof basic magmas, but above 14 GPa this trend is reversed. All of these basic to ultrabasic liquids\r\nare predicted to have similar densities at 14 GPa, and this density is approximately equal to the bulk\r\n(PREM) mantle. This suggests that melts derived from a peridotitic mantle may be inhibited from\r\nascending from depths greater than 400 km.
\r\n\r\nThe EOS of ultrabasic magmas was used to model adiabatic melting in a peridotitic mantle.\r\nIf komatiites are formed by >15% partial melting of a peridotitic mantle, then komatiites generated\r\nby adiabatic melting come from source regions in the lower transition zone (\u2248500-670 km) or the\r\nlower mantle (>670 km). The great depth of incipient melting implied by this model, and the melt\r\ndensity constraint mentioned above, suggest that komatiitic volcanism may be gravitationally hindered.\r\nAlthough komatiitic magmas are thought to separate from their coexisting crystals at a temperature\r\n=200\u00b0C greater than that for modern MORBs, their ultimate sources are predicted to be\r\ndiapirs that, if adiabatically decompressed from initially solid mantle, were more than 700\u00b0C hotter\r\nthan the sources of MORBs and derived from great depth.
\r\n\r\nWe considered the evolution of an initially molten mantle, i.e., a magma ocean. Our model\r\nconsiders the thermal structure of the magma ocean, density constraints on crystal segregation, and\r\napproximate phase relationships for a nominally chondritic mantle. Crystallization will begin at the\r\ncore-mantle boundary. Perovskite buoyancy at > 70 GPa may lead to a compositionally stratified\r\nlower mantle with iron-enriched mangesiowiistite content increasing with depth. The upper mantle\r\nmay be depleted in perovskite components. Olivine neutral buoyancy may lead to the formation of\r\na dunite septum in the upper mantle, partitioning the ocean into upper and lower reservoirs, but this\r\nseptum must be permeable.
\r\n\r\n(2) Viscosity Measurement with Shock Waves
\r\n\r\nWe have examined in detail the analytical method for measuring shear viscosity from the\r\ndecay of perturbations on a corrugated shock front The relevance of initial conditions, finite shock\r\namplitude, bulk viscosity, and the sensitivity of the measurements to the shock boundary conditions\r\nare discussed. The validity of the viscous perturbation approach is examined by numerically solving\r\nthe second-order Navier-Stokes equations. These numerical experiments indicate that shock instabilities\r\nmay occur even when the Kontorovich-D'yakov stability criteria are satisfied. The experimental\r\nresults for water at 15 GPa are discussed, and it is suggested that the large effective viscosity\r\ndetermined by this method may reflect the existence of ice VII on the Rayleigh path of the\r\nHugoniot This interpretation reconciles the experimental results with estimates and measurements\r\nobtained by other means, and is consistent with the relationship of the Hugoniot with the phase\r\ndiagram for water. Sound waves are generated at 4.8 MHz at in the water experiments at 15 GPa.\r\nThe existence of anelastic absorption modes near this frequency would also lead to large effective\r\nviscosity estimates.
\r\n\r\n(3) Equation of State of Molybdenum at 1400\u00b0C
\r\n\r\nShock compression data to 96 GPa for pure molybdenum, initially heated to 1400\u00b0C, are\r\npresented. Finite strain analysis of the data gives a bulk modulus at 1400\u00b0C, K'S. of 244\u00b12 GPa and\r\nits pressure derivative, K'OS of 4. A fit of shock velocity to particle velocity gives the coefficients of\r\nUS = CO+S UP to be CO = 4.77\u00b10.06 km/s and S = 1.43\u00b10.05. From the zero pressure sound speed, CO, a bulk modulus of 232\u00b16 GPa is calculated that is consistent with extrapolation of ultrasonic elasticity measurements. The temperature derivative of the bulk modulus at zero pressure, \u03b8KOS\u03b8T|P, is\r\napproximately -0.012 GPa/K. A thermodynamic model is used to show that the thermodynamic\r\nGr\u00fcneisen parameter is proportional to the density and independent of temperature. The Mie-Gr\u00fcneisen\r\nequation of state adequately describes the high temperature behavior of molybdenum\r\nunder the present range of shock loading conditions.
" }, { "name": "Ripperdan, Robert Lowell", "degree": "PhD", "year": "1990", "title": "Magnetostratigraphic investigations of the lower paleozoic system boundaries, and associated paleogeographic implications", "advisor": "Kirschvink, Joseph L.; Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:03082012-091130735", "creators": [ { "name": { "family": "Ripperdan", "given": "Robert Lowell" }, "id": "Ripperdan-R-L", "display_name": "Ripperdan, Robert Lowell" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "chair", "display_name": "Epstein, Samuel" }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "member", "display_name": "Patterson, Clair C." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geol" ], "doi": "10.7907/hvxy-nh76", "abstract": "Continued refinement of a global Geologic Timescale solely through increased precision\r\nof biostratigraphic correlations philosophically suffers from the inherent lack of a\r\nuniversal reference frame. Geomagnetic polarity reversals, which occur relatively rapidly\r\nand simultaneously on a global scale, can provide the necessary universal reference frame,\r\nprovided the polarity reversals are correlated within a well-defined biostratigraphic framework\r\nand occur with a fairly distinctive pattern.
\r\n\r\nMagnetostratigraphic correlations across the Cambrian-Ordovician boundary interval\r\nindicate that normal polarity zones correlative to Late Cambrian conodont zones occur\r\nwithin sections from Texas, northern China, western Newfoundland, central Australia, and\r\npossibly Kazakhstan. These correlations strongly suggest that temporal differences may\r\nexist between sections in the absolute time value of key biostratigraphic horizons. There\r\nmay also be very brief normal polarity zones correlative with Early Ordovician conodont\r\nand graptolite zonations, but those relationships have not yet been well-established.
\r\n\r\nMagnetostratigraphic correlations allow polarity to be unambiguously determined\r\nfor the relevant continental unit, even in the absence of previous paleomagnetic investigation.\r\nExtension of this to Late Cambrian and Early Ordovician paleogeographic problems\r\nindicate that North China, and probably also South China, underwent approximately 90\u00b0\r\ncounterclockwise rotation during the Cambrian, and were most likely attached to or very\r\nnear the present northern margin of Australia during that time.
\r\n\r\nPaleomagnetic results from Upper Silurian through Middle Devonian carbonates of\r\nthe Barrandian area, Czechoslovakia have at least three components of magnetization preserved\r\nwithin them. Two of the components appear to pass the fold test, indicating that\r\nthey pre-date the deformation creating the basin, constrained to be not later than Late\r\nCarboniferous. Differences between the two components probably correspond to different\r\ntimes of acquisition, and may record rapid plate motion of the Bohemian Massif during the\r\nMiddle Paleozoic.
\r\n\r\nPaleomagnetic results from Upper Ordovician to Lower Silurian carbonates from\r\nAnticosti Island, Quebec are not reliable because of the extremely weak magnetization of\r\nthese rocks. Sharp increases in intensity during thermal demagnetization experiments may\r\nprovide insight into the chemical changes which occur within carbonate rocks during thermal\r\ndemagnetization, but at the present time those phenomenon are not well understood.
" }, { "name": "Stead, Richard J.", "degree": "PhD", "year": "1990", "title": "Finite differences and a coupled analytic technique with applications to explosions and earthquakes", "advisor": "Helmberger, Donald V.; Clayton, Robert W.; Harkrider, David G.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:03192015-141813901", "creators": [ { "name": { "family": "Stead", "given": "Richard J." }, "id": "Stead-R-J", "display_name": "Stead, Richard J." } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "co-advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "co-advisor", "display_name": "Harkrider, David G." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "co-advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/gsvf-5426", "abstract": "An analytic technique is developed that couples to finite difference calculations\r\nto extend the results to arbitrary distance. Finite differences and the\r\nanalytic result, a boundary integral called two-dimensional Kirchhoff, are\r\napplied to simple models and three seismological problems dealing with data.\r\nThe simple models include a thorough investigation of the seismologic effects\r\nof a deep continental basin. The first problem is explosions at Yucca Flat, in\r\nthe Nevada test site. By modeling both near-field strong-motion records and\r\nteleseismic P-waves simultaneously, it is shown that scattered surface waves\r\nare responsible for teleseismic complexity. The second problem deals with\r\nexplosions at Amchitka Island, Alaska. The near-field seismograms are investigated\r\nusing a variety of complex structures and sources. The third problem\r\ninvolves regional seismograms of Imperial Valley, California earthquakes\r\nrecorded at Pasadena, California. The data are shown to contain evidence of\r\ndeterministic structure, but lack of more direct measurements of the structure\r\nand possible three-dimensional effects make two-dimensional modeling of\r\nthese data difficult." }, { "name": "Zhou, Hua-wei", "degree": "PhD", "year": "1990", "title": "Travel time tomographic studies of seismic structures around subducted lithospheric slabs", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10102013-155017222", "creators": [ { "name": { "family": "Zhou", "given": "Hua-wei" }, "id": "Zhou-Hua-wei", "display_name": "Zhou, Hua-wei" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/57m9-s813", "abstract": "The nature of the subducted lithospheric slab is investigated seismologically by tomographic inversions of ISC residual travel times. The\r\nslab, in which nearly all deep earthquakes occur, is fast in the seismic images because it is much cooler than the ambient mantle. High resolution three-dimensional P and S wave models in the NW Pacific are obtained using regional data, while inversion for the SW Pacific slabs includes teleseismic arrivals. Resolution and noise estimations show the models are generally well-resolved.
\r\n\r\nThe slab anomalies in these models, as inferred from the seismicity, are generally coherent in the upper mantle and become contorted and decrease in amplitude with depth. Fast slabs are surrounded by slow regions shallower than 350 km depth. Slab fingering, including segmentation and spreading, is indicated near the bottom of the upper mantle. The fast anomalies associated with the Japan, Izu-Bonin, Mariana and Kermadec subduction zones tend to flatten to sub-horizontal at depth, while downward spreading may occur under parts of the Mariana and Kuril arcs. The Tonga slab appears to end around 550 km depth, but is underlain by a fast band at 750-1000 km depths.
\r\n\r\nThe NW Pacific model combined with the Clayton-Comer mantle model predicts many observed residual sphere patterns. The predictions indicate that the near-source anomalies affect the residual spheres less than the teleseismic contributions. The teleseismic contributions may be removed either by using a mantle model, or using teleseismic station averages of residuals from only regional events. The slab-like fast bands in the corrected residual spheres are are consistent with seismicity trends under the Mariana Tzu-Bonin and Japan trenches, but are inconsistent for the Kuril events.
\r\n\r\nThe comparison of the tomographic models with earthquake focal mechanisms shows that deep compression axes and fast velocity slab anomalies are in consistent alignment, even when the slab is contorted or flattened. Abnormal stress patterns are seen at major junctions of the arcs. The depth boundary between tension and compression in the central parts of these arcs appears to depend on the dip and topology of the slab.
\r\n" }, { "name": "Bursik, Marcus Ivan", "degree": "PhD", "year": "1989", "title": "Late Quaternary Volcano-Tectonic Evolution of the Mono Basin, Eastern California", "advisor": "Sieh, Kerry E.; Allen, Clarence R.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03282006-103736", "creators": [ { "name": { "family": "Bursik", "given": "Marcus Ivan" }, "id": "Bursik-Marcus-Ivan", "display_name": "Bursik, Marcus Ivan" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "co-advisor", "display_name": "Allen, Clarence R." } ], "committee": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "chair", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Sturtevant", "given": "Bradford" }, "id": "Sturtevant-B", "role": "member", "display_name": "Sturtevant, Bradford" } ], "option_major": [ "geol" ], "doi": "10.7907/mv55-ah24", "abstract": "The Mono Basin of eastern California provides an ideal laboratory in which to study the interaction of volcanic and tectonic processes. The late Quaternary geological record of volcanic activity and range-front faulting is relatively complete in the basin. Range-front faults of the Sierra Nevada offset dateable late Pleistocene glacial moraines, thus affording the opportunity to estimate range-front slip rates. The first two chapters concern dating of moraines that are offset by range-front faults.
\r\n\r\nIn Chapter One, I discuss the ages of the glacial moraines of the Mono Basin and their correlation between canyons. I dated the moraines by studying their morphology and the relative weathering of granitic boulders atop their crests, and by use of the clast-sound velocity (CSV) dating technique. The CSV technique consists of measuring the p-wave speed (V\u209a) in morainal boulders. V\u209a decreases with age as boulders weather. Clast-sound velocities enabled statistical division of moraines in each canyon into differently weathered deposits. Relative weathering features of boulder surfaces further helped discern age differences between moraines in a single canyon. Finally, CSV, relative weathering and moraine morphology, considered together, allowed correlation of moraines to an established glacial sequence, and therefore, correlation between canyons. Regression of mean V\u209a against best estimates of glaciation ages within the glacial sequence provided a further check on the validity of the correlations.
\r\n\r\nMoraines in all major canyons from Lee Vining south were correlative with the standard late Pleistocene sequence of Tioga, Tenaya, Tahoe and Mono Basin deposits. At Lundy Canyon, however, Tahoe and Tenaya moraines are poorly, if at all, preserved. The prominent moraines extending into the basin are probably of Tioga age. Poor preservation of Tenaya and Tahoe deposits may be due to the narrow, steep-sided morphology of Lundy Canyon, and rapid down-dropping on the range-front fault.
\r\n\r\nIn Chapter Two, I discuss the application of a new quantitative dating technique to the moraines of Lee Vining Canyon. At Lee Vining Canyon, I measured cross-sectional profiles of lateral moraines of different ages to determine whether the degree to which they have been degraded could be used as a relative-dating method. Correlation of the degree of moraine degradation against an independent measure of age suggested that relative ages of late Pleistocene lateral moraines can be inferred from moraine profiles.
\r\n\r\nAnalysis of the degradation of moraine profiles with a diffusion model resulted in equations that relate profile width and maximum slope angle to age. In accordance with the diffusion model, the functional relationship between profile width and estimated age was found to be nearly linear for the moraines of Lee Vining Canyon. Fits of model to data were good, despite evidence of transport of material by non-linear diffusive processes along some of the profiles.
\r\n\r\nMaximum slope angle is inversely proportional to age according to the diffusion model. Regression of mean maximum slope angle against inverse age for the group of moraines from Lee Vining Canyon suggested that the relationship between the two variables is expressed by the diffusion model.
\r\n\r\nDeviations of model profile shapes from true shapes suggested that in addition to moraine age, initial profile shape and non-diffusive degradation processes are important in controlling the relationship between slope parameters and age over spans of 10\u2074 years.
\r\n\r\nIn Chapter Three, I use moraine ages determined in Chapter One to estimate slip rates of range-front faults. For Chapter Three, I measured fault-scarp profiles on the dated lateral moraines of the Mono Basin to determine fault slip rates. I compared these data with what can be deduced about the extension rate due to dike intrusion underneath the Mono Craters. I then considered extension rates in the context of regional strain patterns to infer the mode of deformation and strain relief in the Mono Basin during late Quaternary time.
\r\n\r\nThe extension-rate data indicate that dikes are being intruded underneath the Mono Craters in response to crustal stretching, and because of this, are now accommodating elastic strain that was once accommodated by range-front normal faulting. The section of the range front near the craters accommodated as much as 1 mm/yr of extension until 40,000 to 70,000 years ago. For the past 40,000 to 70,000 years, this section of range front has become inactive, even though extension along the range front to north and south has continued at up to 0.9 mm/yr. Dikes have been intruding underneath the Mono Craters for the past 40,000 years. Depending upon the assumptions used to calculate dike intrusion rates, the dikes accommodate 1 mm/yr of tectonic extension that was previously accommodated by range-front faulting.
\r\n\r\nConsideration of the extension rates in the context of regional tectonic strain patterns suggests that the Mono Craters are forming along one of the extensional boundary structures of a pull-apart basin, the other extensional boundary of which is the deactivated range-front segment.
\r\n\r\nIf the Mono Craters represent an early stage of caldera formation, then their formation within a pull-apart zone may indicate that this is an ideal tectonic environment in which to form certain types of calderas.
" }, { "name": "Dowling, Timothy Edward", "degree": "PhD", "year": "1989", "title": "A Dynamical Study of Jupiter's Great Red Spot", "advisor": "Ingersoll, Andrew P.; Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechETD:etd-05302007-084208", "creators": [ { "name": { "family": "Dowling", "given": "Timothy Edward" }, "id": "Dowling-Timothy-Edward", "display_name": "Dowling, Timothy Edward" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "co-advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "chair", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Leonard", "given": "Anthony" }, "id": "Leonard-A", "role": "member", "display_name": "Leonard, Anthony" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Zurek", "given": "Richard W." }, "id": "Zurek-Richard-W", "role": "member", "display_name": "Zurek, Richard W." } ], "option_major": [ "plansci" ], "doi": "10.7907/whc3-mh91", "abstract": "This work is presented in the form of two related papers. In the first paper we investigate layer thickness variations in Jupiter's atmosphere by tracking absolute vorticity (\u03b6 + f) along streamlines of the Great Red Spot (GRS) and White Oval BC. The ratio of absolute vorticity to layer thickness, called the potential vorticity, is conserved following the motion. By observing Lagrangian variations of absolute vorticity, we may infer variations in layer thickness. The data thus obtained are a useful diagnostic that will help differentiate between models of Jovian vortices. We interpret the observed layer thickness variations using a simple \"1-1/2\" layer model in which a thin upper weather layer, which contains the vortices, overlies a much deeper layer, which is meant to model the deep atmosphere. In this model, layer thickness variations are directly coupled to motions in the deep atmosphere, and we use the data to infer the deep motions. In the first paper we interpret the data, using the quasi-geostrophic equations. In the second paper we reinterpret the data, using the more general shallow water equations. Most current models of the GRS are cast in terms of the 1-1/2 layer model, and they start by prescribing the motions in the deep atmosphere. Here we are able to derive the deep motions using the same 1-1/2 layer model assumptions, up to a constant that depends on the unknown static stability of Jupiter's troposphere. None of the current prescriptions for the deep motions are in qualitative agreement with the observations over the full range of latitudes observed. We study the 1-1/2 layer model numerically, using both the derived deep motions and the prescribed deep motions of current models. Only the present model, based on observations, yields Lagrangian absolute vorticity profiles that agree with those obtained in the first paper. A model run that starts with the observed zonally averaged cloud-top winds and derived deep motions shows instability, which naturally leads to the genesis and maintenance of a large, isolated vortex similar to the GRS.
" }, { "name": "Herkenhoff, Kenneth Edward", "degree": "PhD", "year": "1989", "title": "Quantitative Studies of the Martian South Polar Region Using Spacecraft Images", "advisor": "Albee, Arden Leroy; Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechETD:etd-06072007-141923", "creators": [ { "name": { "family": "Herkenhoff", "given": "Kenneth Edward" }, "id": "Herkenhoff-Kenneth-Edward", "display_name": "Herkenhoff, Kenneth Edward" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "co-advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "member", "display_name": "Westphal, James A." } ], "option_major": [ "plansci" ], "doi": "10.7907/bty4-vk56", "abstract": "Spacecraft observations must be calibrated absolutely in order to investigate the photometric properties of the Martian surface and atmosphere. The accuracy of the Mariner 9 and Viking Orbiter television system calibration was evaluated by comparing the two data sets with each other and with Earth-based spectrophotometry of Mars and Phobos. The Viking imaging data are consistent with published estimates of the geometric albedo of Phobos, which is uncertain by about 20%. Mariner 9 data are calibrated to within about \u00b120% by comparing Phobos images with Viking data. Better photometric observations of Phobos are necessary to improve the calibration of the Viking Orbiter and Mariner 9 television systems. Similarly, inflight Phobos observations should be used to calibrate imaging systems on future Mars missions.
\r\n\r\nMariner 9 images were processed for comparison with nearly simultaneous infrared spectra of the south polar cap of Mars recorded in 1971-72. Combined analysis of these observations indicates that the southern residual cap was covered by carbon dioxide frost throughout the summer, in agreement with Viking Orbiter measurements made three Mars years later. Thermal modeling of the spectra shows that areas of intermediate albedo are cooled to the sublimation temperature of CO2, suggesting that frost is present but not visible. Topographic roughness may shade the CO2 from the sun and produce the variegated appearance of the residual cap.
\r\n\r\nFive color/albedo units, including polar frost, have been recognized and mapped in the southern layered deposits on Mars. Atmospheric dust scattering was measured in shadows and modeled in order to remove the component of brightness due to the atmosphere and quantify the albedo and color of the surface. The layered deposits appear to be mantled by red dust, except where eolian stripping has exposed the underlying bedrock. Frost and bare ground are mixed below the resolution of the images in many areas adjacent to the polar cap, some of which appear to be younger than the surrounding layered terrain. Dark material has been deposited in topographic depressions in much of the south polar region, including the layered deposits. The available observational data suggest that the layered deposits are composed of bright dust, ice, and a small amount of dark material. If the dark material is sand, a periodic change in polar winds seems required in order to transport the sand poleward into the layered terrain. In any case, the observations are not consistent with the layered deposits being composed only of bright dust and ice.
\r\n\r\nMaximum slopes of 10-20 degrees occur on an exposure of layered deposits within the south polar residual cap of Mars. A new photoclinometric technique is used to produce profiles of slope and albedo using high resolution Mariner 9 images. Stereophotogrammetry is also used to constrain the photoclinometric solutions, which resolve layer thicknesses of 100-300 meters. The results are limited by the ~200 meter resolution of the images, and thinner (unresolved) layers are likely. The ~25% maximum albedo variations are correlated with slope, indicating that frost is present on level areas. There is evidence for temporal changes in frost distribution in the 7 days (4\u00b0 of Ls) between the two images used in this study, demonstrating that future photoclinometric studies of the polar regions must be attempted carefully. The magnitude of the slopes derived here suggest that the layers are competent, perhaps due to the presence of a weathering rind.
\r\n\r\nWeathering of the layered deposits by sublimation of water ice can account for the data presented here and previous observations of the north polar deposits. The non-volatile component of the layered deposits appears to consist mainly of bright red dust, with small amounts of dark dust or sand. Deposition of sand in the layered deposits is problematical, so inclusion of dark dust is preferred. The dark dust may be similar to the magnetic material found at the Viking Lander sites, and may therefore preferentially form ~ 100\u00b5 filamentary residue particles upon weathering. Once eroded from the layered deposits, these particles may then saltate to form the dark sand dunes found in both polar regions. Eventual destruction of the particles could allow recycling of the dark dust into the layered deposits via atmospheric suspension.
" }, { "name": "Maher, Kevin A.", "degree": "PhD", "year": "1989", "title": "Geology of the Jackson Mountains, Northwest Nevada", "advisor": "Saleeby, Jason B.; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06282007-082748", "creators": [ { "name": { "family": "Maher", "given": "Kevin A." }, "id": "Maher-Kevin-A", "display_name": "Maher, Kevin A." } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "co-advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." } ], "option_major": [ "geol" ], "doi": "10.7907/DE6N-4051", "abstract": "The Jackson Mountains are located in the western Great Basin in Humboldt County, northwest Nevada. The range contains a late Paleozoic to Mesozoic depositional sequence. This sequence records sedimentation, volcanism and deformation in a back-arc setting. The Mississippian to late Early Permian McGill Canyon Formation was deposited in basinal to slope to distal shelf environments, dominated by hemipelagic and turbiditic facies. In the Permian there was an volcanic arc andesite component, and a nearby contemporaneous carbonate platform shed olistostromes into the unit. The McGill Canyon was laid down in an area between the McCloud arc and the Havallah back-arc basin. The late Middle Triassic to middle Norian Bliss Canyon Formation was laid down in basinal to fore-reef to carbonate platform to lagoonal to terrigenous littoral environments. Both of these formations are of flap sequences deposited on an east-facing, back-arc margin. The Bliss Canyon represents the western margin of the Early Mesozoic marine basin of the western Great Basin. From the late Norian to the Bathonian, several stages of subearial volcanism and alluvial epiclastic sedimentation laid down the Happy Creek Formation, a thick arc andesite volcanic pile. The Happy Creek is part of the Early Mesozoic Cordilleran magmatic arc province. In the Bathonian, this volcanic pile was cut by a conjugate sinistral high-angle wrench fault system as volcanism waned. During the Callovian, sediments of the King Lear Formation filled in and then overlapped the wrench basins. These sediments were derived from the east, where a west-vergent thrust system was active. This phase of thrusting ceased by the Oxfordian. Arc-related silicic volcanism and alluvial to fluvial sedimentation within the King Tear continued into the Aptian, when the thrusts were reactivated during a second phase. Both phases of thrusting verged both east and west. Stocks, dikes and sills of the Early Mesozoic Intrusive suite are comagmatic with the volcanism in the Happy Creek and King Lear, and intrude the sedimentary units. This suite both plugs and is truncated by the wrench faults and the first phase of thrusting, but is cut by the second phase. The Jackson Mountains are part of the Black Rock terrane in northwest Nevada. Within this terrane, the rocks share a common tectonic history and stratigraphy distinct from the neighboring terranes, and are separated from them by Mesozoic thrust and strike-slip faults.
" }, { "name": "Michelangeli, Diane Vera", "degree": "PhD", "year": "1989", "title": "I. Impact of Volcanic Aerosols on Stratospheric Chemistry. II. O\u2082(\u00b9\u03a3g\u207a) and O\u2082(\u00b9\u0394g\u207a) in the H + O\u2082 Reaction System. III. Barotropic Instability of Zonal Jets on Mars, Earth and Venus", "advisor": "Yung, Yuk L.; Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06112007-132024", "creators": [ { "name": { "family": "Michelangeli", "given": "Diane Vera" }, "id": "Michelangeli-Diane-Vera", "display_name": "Michelangeli, Diane Vera" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "co-advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Blake", "given": "Geoffrey A." }, "id": "Blake-G-A", "orcid": "0000-0003-0787-1610", "role": "member", "display_name": "Blake, Geoffrey A." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Leu", "given": "Ming-Taun" }, "id": "Leu-Ming-Taun", "role": "member", "display_name": "Leu, Ming-Taun" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/6s4a-6e87", "abstract": "In order to fully understand an atmospheric system, we must answer questions in radiative transfer (Paper I), dynamics (Paper II), and chemistry (Paper I). The adequacy of the chemical models at reproducing the atmosphere depends on the fundamental knowledge of rate constants and absorption cross sections, which are determined in laboratory experiments (Paper III). All these issues are investigated in the three independent papers of this thesis. While seemingly unrelated, they all attempt to explain observations of terrestrial atmospheres. Paper I focuses on the chemical effects, in the Earth's stratosphere, of a volcanic eruption. Paper II reports experimental results important for the understanding of nightglow emissions on Earth. And finally, Paper III discusses barotropic instabilities as a possible explanation for thermal waves on Mars.
" }, { "name": "Navon, Oded", "degree": "PhD", "year": "1989", "title": "Chemical and Mineralogical Characterization of Micro-Inclusions in Diamonds", "advisor": "Wasserburg, Gerald J.; Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10232013-113130725", "creators": [ { "name": { "family": "Navon", "given": "Oded" }, "id": "Navon-Oded", "display_name": "Navon, Oded" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "co-advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "chair", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Armstrong", "given": "John T." }, "id": "Armstrong-John-T", "role": "member", "display_name": "Armstrong, John T." }, { "name": { "family": "Hutcheon", "given": "Ian D." }, "id": "Hutcheon-Ian-D", "role": "member", "display_name": "Hutcheon, Ian D." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." } ], "option_major": [ "geol" ], "doi": "10.7907/A88J-S465", "abstract": "Secondary-ion mass spectrometry (SIMS), electron probe analysis (EPMA), analytical scanning electron microscopy (SEM) and infrared (IR) spectroscopy were used to determine the chemical composition and the mineralogy of sub-micrometer inclusions in cubic diamonds and in overgrowths (coats) on octahedral diamonds from Zaire, Botswana, and some unknown localities.
\r\n\r\nThe inclusions are sub-micrometer in size. The typical diameter encountered during transmission electron microscope (TEM) examination was 0.1-0.5 \u00b5m. The micro-inclusions are sub-rounded and their shape is crystallographically controlled by the diamond. Normally they are not associated with cracks or dislocations and appear to be well isolated within the diamond matrix. The number density of inclusions is highly variable on any scale and may reach 10\u00b9\u00b9 inclusions/cm\u00b3 in the most densely populated zones. The total concentration of metal oxides in the diamonds varies between 20 and 1270 ppm (by weight).
\r\n\r\nSIMS analysis yields the average composition of about 100 inclusions contained in the sputtered volume. Comparison of analyses of different volumes of an individual diamond show roughly uniform composition (typically \u00b110% relative). The variation among the average compositions of different diamonds is somewhat greater (typically \u00b130%). Nevertheless, all diamonds exhibit similar characteristics, being rich in water, carbonate, SiO\u2082, and K\u2082O, and depleted in MgO. The composition of micro-inclusions in most diamonds vary within the following ranges: SiO\u2082, 30-53%; K\u2082O, 12-30%; CaO, 8-19%; FeO, 6-11%; Al\u2082O\u2083, 3-6%; MgO, 2-6%; TiO\u2082, 2-4%; Na\u2082O, 1-5%; P\u2082O\u2085, 1-4%; and Cl, 1-3%. In addition, BaO, 1-4%; SrO, 0.7-1.5%; La\u2082O\u2083, 0.1-0.3%; Ce\u2082O\u2083, 0.3-0.5%; smaller amounts of other rare-earth elements (REE), as well as Mn, Th, and U were also detected by instrumental neutron activation analysis (INAA). Mg/(Fe+Mg), 0.40-0.62 is low compared with other mantle derived phases; K/AI ratios of 2-7 are very high, and the chondrite-normalized Ce/Eu ratios of 10-21 are also high, indicating extremely fractionated REE patterns.
\r\n\r\nSEM analyses indicate that individual inclusions within a single diamond are roughly of similar composition. The average composition of individual inclusions as measured with the SEM is similar to that measured by SIMS. Compositional variations revealed by the SEM are larger than those detected by SIMS and indicate a small variability in the composition of individual inclusions. No compositions of individual inclusions were determined that might correspond to mono-mineralic inclusions.
\r\n\r\nIR spectra of inclusion- bearing zones exhibit characteristic absorption due to: (1) pure diamonds, (2) nitrogen and hydrogen in the diamond matrix; and (3) mineral phases in the micro-inclusions. Nitrogen concentrations of 500-1100 ppm, typical of the micro-inclusion-bearing zones, are higher than the average nitrogen content of diamonds. Only type IaA centers were detected by IR. A yellow coloration may indicate small concentration of type IB centers.
\r\n\r\nThe absorption due to the micro-inclusions in all diamonds produces similar spectra and indicates the presence of hydrated sheet silicates (most likely, Fe-rich clay minerals), carbonates (most likely calcite), and apatite. Small quantities of molecular CO\u2082 are also present in most diamonds. Water is probably associated with the silicates but the possibility of its presence as a fluid phase cannot be excluded. Characteristic lines of olivine, pyroxene and garnet were not detected and these phases cannot be significant components of the inclusions. Preliminary quantification of the IR data suggests that water and carbonate account for, on average, 20-40 wt% of the micro-inclusions.
\r\n\r\nThe composition and mineralogy of the micro-inclusions are completely different from those of the more common, larger inclusions of the peridotitic or eclogitic assemblages. Their bulk composition resembles that of potassic magmas, such as kimberlites and lamproites, but is enriched in H\u2082O, CO\u207c\u2083, K\u2082O, and incompatible elements, and depleted in MgO.
\r\n\r\nIt is suggested that the composition of the micro-inclusions represents a volatile-rich fluid or a melt trapped by the diamond during its growth. The high content of K, Na, P, and incompatible elements suggests that the trapped material found in the micro-inclusions may represent an effective metasomatizing agent. It may also be possible that fluids of similar composition are responsible for the extreme enrichment of incompatible elements documented in garnet and pyroxene inclusions in diamonds.
\r\n\r\nThe origin of the fluid trapped in the micro-inclusions is still uncertain. It may have been formed by incipient melting of a highly metasomatized mantle rocks. More likely, it is the result of fractional crystallization of a potassic parental magma at depth. In either case, the micro-inclusions document the presence of highly potassic fluids or melts at depths corresponding to the diamond stability field in the upper mantle. The phases presently identified in the inclusions are believed to be the result of closed system reactions at lower pressures.
" }, { "name": "Nourse, Jonathan Alan", "degree": "PhD", "year": "1989", "title": "Geological Evolution of Two Crustal Scale Shear Zones. Part I: The Rand Thrust Complex, Northwestern Mojave Desert, California. Part II: The Magdalena Metamorphic Core Complex, North Central Sonora, Mexico", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02112014-112136459", "creators": [ { "name": { "family": "Nourse", "given": "Jonathan Alan" }, "id": "Nourse-Jonathan-Alan", "display_name": "Nourse, Jonathan Alan" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "geol" ], "doi": "10.7907/S427-2704", "abstract": "The geology and structure of two crustal scale shear zones were studied to understand the partitioning of strain within intracontinental orogenic belts. Movement histories and regional tectonic implications are deduced from observational data. The two widely separated study areas bear the imprint of intense Late Mesozoic through Middle Cenozoic tectonic activity. A regional transition from Late Cretaceous-Early Tertiary plutonism, metamorphism, and shortening strain to Middle Tertiary extension and magmatism is preserved in each area, with contrasting environments and mechanisms. Compressional phases of this tectonic history are better displayed in the Rand Mountains, whereas younger extensional structures dominate rock fabrics in the Magdalena area.
\r\n\r\nIn the northwestern Mojave desert, the Rand Thrust Complex reveals a stack of four distinctive tectonic plates offset along the Garlock Fault. The lowermost plate, Rand Schist, is composed of greenschist facies metagraywacke, metachert, and metabasalt. Rand Schist is structurally overlain by Johannesburg Gneiss (= garnet-amphibolite grade orthogneisses, marbles and quartzites), which in turn is overlain by a Late Cretaceous hornblende-biotite granodiorite. Biotite granite forms the fourth and highest plate. Initial assembly of the tectonic stack involved a Late Cretaceous? south or southwest vergent overthrusting event in which Johannesburg Gneiss was imbricated and attenuated between Rand Schist and hornblende-biotite granodiorite. Thrusting postdated metamorphism and deformation of the lower two plates in separate environments. A post-kinematic stock, the Late Cretaceous Randsburg Granodiorite, intrudes deep levels of the complex and contains xenoliths of both Rand Schist and mylonitized Johannesburg? gneiss. Minimum shortening implied by the map patterns is 20 kilometers.
\r\n\r\nSome low angle faults of the Rand Thrust Complex formed or were reactivated between Late Cretaceous and Early Miocene time. South-southwest directed mylonites derived from Johannesburg Gneiss are commonly overprinted by less penetrative north-northeast vergent structures. Available kinematic information at shallower structural levels indicates that late disturbance(s) culminated in northward transport of the uppermost plate. Persistence of brittle fabrics along certain structural horizons suggests a possible association of late movement(s) with regionally known detachment faults. The four plates were juxtaposed and significant intraplate movements had ceased prior to Early Miocene emplacement of rhyolite porphyry dikes.
\r\n\r\nIn the Magdalena region of north central Sonora, components of a pre-Middle Cretaceous stratigraphy are used as strain markers in tracking the evolution of a long lived orogenic belt. Important elements of the tectonic history include: (1) Compression during the Late Cretaceous and Early Tertiary, accompanied by plutonism, metamorphism, and ductile strain at depth, and thrust driven? syntectonic sedimentation at the surface. (2) Middle Tertiary transition to crustal extension, initially recorded by intrusion of leucogranites, inflation of the previously shortened middle and upper crustal section, and surface volcanism. (3) Gravity induced development of a normal sense ductile shear zone at mid crustal levels, with eventual detachment and southwestward displacement of the upper crustal stratigraphy by Early Miocene time.
\r\n\r\nElucidation of the metamorphic core complex evolution just described was facilitated by fortuitous preservation of a unique assemblage of rocks and structures. The \"type\" stratigraphy utilized for regional correlation and strain analysis includes a Jurassic volcanic arc assemblage overlain by an Upper Jurassic-Lower Cretaceous quartz pebble conglomerate, in turn overlain by marine strata with fossiliferous Aptian-Albian limestones. The Jurassic strata, comprised of (a) rhyolite porphyries interstratified with quartz arenites, (b) rhyolite cobble conglomerate, and (c) intrusive granite porphyries, are known to rest on Precambrian basement north and east of the study area. The quartz pebble conglomerate is correlated with the Glance Conglomerate of southeastern Arizona and northeastern Sonora. The marine sequence represents part of an isolated arm? of the Bisbee Basin.
\r\n\r\nCrosscutting structural relationships between the pre-Middle Cretaceous supracrustal section, younger plutons, and deformational fabrics allow the tectonic sequence to be determined. Earliest phases of a Late Cretaceous-Early Tertiary orogeny are marked by emplacement of the 78 \u00b1 3 Ma Guacomea Granodiorite (U/Pb zircon, Anderson et al., 1980) as a sill into deep levels of the layered Jurassic series. Subsequent regional metamorphism and ductile strain is recorded by a penetrative schistosity and lineation, and east-west trending folds. These fabrics are intruded by post-kinematic Early Tertiary? two mica granites. At shallower crustal levels, the orogeny is represented by north directed thrust faulting, formation of a large intermontane basin, and development of a pronounced unconformity. A second important phase of ductile strain followed Middle Tertiary? emplacement of leucogranites as sills and northwest trending dikes into intermediate levels of the deformed section (surficial volcanism was also active during this transitional period to regional extension). Gravitational instabilities resulting from crustal swelling via intrusion and thermal expansion led to development of a ductile shear zone within the stratigraphic horizon occupied by a laterally extensive leucogranite sill. With continued extension, upper crustal brittle normal faults (detachment faults) enhanced the uplift and tectonic denudation of this mylonite zone, ultimately resulting in southwestward displacement of the upper crustal stratigraphy.
\r\n\r\nStrains associated with the two ductile deformation events have been successfully partitioned through a multifaceted analysis. Rf/\u00d8 measurements on various markers from the \"type\" stratigraphy allow a gradient representing cumulative strain since Middle Cretaceous time to be determined. From this gradient, noncoaxial strains accrued since emplacement of the leucogranites may be removed. Irrotational components of the postleucogranite strain are measured from quartz grain shapes in deformed granites; rotational components (shear strains) are determined from S-C fabrics and from restoration of rotated dike and vein networks. Structural observations and strain data are compatable with a deformation path of: (1) coaxial strain (pure shear?), followed by (2) injection of leucogranites as dikes (perpendicular to the minimum principle stress) and sills (parallel to the minimum principle stress), then (3) southwest directed simple shear. Modeling the late strain gradient as a simple shear zone permits a minimum displacement of 10 kilometers on the Magdalena mylonite zone/detachment fault system. Removal of the Middle Tertiary noncoaxial strains yields a residual (or pre-existing) strain gradient representative of the Late Cretaceous-Early Tertiary deformation. Several partially destrained cross sections, restored to the time of leucogranite emplacement, illustrate the idea that the upper plate of the core complex bas been detached from a region of significant topographic relief. 50% to 100% bulk extension across a 50 kilometer wide corridor is demonstrated.
\r\n\r\nLate Cenozoic tectonics of the Magdalena region are dominated by Basin and Range style faulting. Northeast and north-northwest trending high angle normal faults have interacted to extend the crust in an east-west direction. Net extension for this period is minor (10% to 15%) in comparison to the Middle Tertiary detachment related extensional episode.
" }, { "name": "Polanskey, Carol Ann", "degree": "PhD", "year": "1989", "title": "I. Impact Spallation Experiments: Fracture Patterns and Spall Velocities. II. Craters in Carbonate Rocks: An Electron Paramagnetic Resonance Analysis of Shock Damage", "advisor": "Ahrens, Thomas J.; Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10172013-085025235", "creators": [ { "name": { "family": "Polanskey", "given": "Carol Ann" }, "id": "Polanskey-Carol-Ann", "display_name": "Polanskey, Carol Ann" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "co-advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "member", "display_name": "Westphal, James A." } ], "option_major": [ "plansci" ], "doi": "10.7907/3rgr-f070", "abstract": "This work is divided into two independent papers.
\r\n\r\nPAPER 1.
\r\n\r\nSpall velocities were measured for nine experimental impacts into San Marcos gabbro targets. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles were iron, aluminum, lead, and basalt of varying sizes. The projectile masses ranged from a 4 g lead bullet to a 0.04 g aluminum sphere. The velocities of fragments were measured from high-speed films taken of the events. The maximum spall velocity observed was 30 m/sec, or 0.56 percent of the 5.4 km/sec impact velocity. The measured velocities were compared to the spall velocities predicted by the spallation model of Melosh (1984). The compatibility between the spallation model for large planetary impacts and the results of these small scale experiments are considered in detail.
\r\n\r\nThe targets were also bisected to observe the pattern of internal fractures. A series of fractures were observed, whose location coincided with the boundary between rock subjected to the peak shock compression and a theoretical \"near surface zone\" predicted by the spallation model. Thus, between this boundary and the free surface, the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.
\r\n\r\nPAPER 2.
\r\n\r\nCarbonate samples from the nuclear explosion crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron paramagnetic resonance, EPR. The first series of samples for OAK Crater were obtained from six boreholes within the crater, and the second series were ejecta samples recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to spectra of Solenhofen limestone, which had been shocked to known pressures.
\r\n\r\nThe results of the OAK borehole analysis have identified a thin zone of highly shocked carbonate material underneath the crater floor. This zone has a maximum depth of approximately 200 ft below sea floor at the ground zero borehole and decreases in depth towards the crater rim. A layer of highly shocked material is also found on the surface in the vicinity of the reference bolehole, located outside the crater. This material could represent a fallout layer. The ejecta samples have experienced a range of shock pressures.
\r\n\r\nIt was also demonstrated that the EPR technique is feasible for the study of terrestrial impact craters formed in carbonate bedrock. The results for the Meteor Crater analysis suggest a slight degree of shock damage present in the \u03b2 member of the Kaibab Formation exposed in the crater walls.
" }, { "name": "Prentice, Carol Seabury", "degree": "PhD", "year": "1989", "title": "Earthquake Geology of the Northern San Andreas Fault Near Point Arena, California", "advisor": "Sieh, Kerry E.; Allen, Clarence R.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01192007-104328", "creators": [ { "name": { "family": "Prentice", "given": "Carol Seabury" }, "id": "Prentice-Carol-Seabury", "display_name": "Prentice, Carol Seabury" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "co-advisor", "display_name": "Allen, Clarence R." } ], "committee": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "chair", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geol" ], "doi": "10.7907/7Y6G-DE19", "abstract": "The northern segment of the San Andreas fault last ruptured in 1906, producing the great San Francisco earthquake. This study involves the collection and interpretation of geologic data from the segment of the northern San Andreas fault near Point Arena, California, to determine the recurrence interval and slip rate of this segment of the fault.
\r\n\r\nHolocene sediments deposited on an alluvial fan preserve a record of prehistoric earthquakes near Point Arena, California. Excavations into the fan provided exposures of the sediments across the San Andreas fault zone. At least five earthquakes were recognized in the section. All of these occurred since the deposition of a unit that is approximately 2000 years old. Because deposition in this setting was intermittent and deposition of younger units involved the erosion of underlying units, it is likely that events occurred that were not recorded in the section. Radiocarbon dating of units in the section allows constraints to be placed on the dates of the earthquakes recognized. A buried Holocene (2356-2709 years old) channel has been offset a maximum of 64 \u00b1 2 meters. This implies a maximum slip rate of 25.5 \u00b1 2.5 mm/yr. These data suggest that the average recurrence interval for great earthquakes on this segment of the San Andreas fault is long - between about 200 and 400 years.
\r\n\r\nOffset marine terrace risers near Point Arena and an offset landslide near Fort Ross provide estimates of the average slip rate across the San Andreas fault since Late Pleistocene time. Near Fort Ross, a landslide has been offset approximately 1.7 km across the San Andreas fault. Radiocarbon analysis of charcoal from this deposit indicates that the landslide is older than 43,700 years. This implies a slip rate of less than 39 mm/yr. Correlation of two marine terrace risers across the San Andreas fault near Point Arena suggests offsets of approximately 1.5 and 2.5 km. The U-series age of a solitary coral, altitudinal spacing and correlation with known global high sea-level stands suggest ages of 83,000 and 133,000 years for these surfaces, indicating slip rates of about 18-19 mm/yr since Late Pleistocene time.
\r\n\r\nTentative correlation of the Pliocene Ohlson Ranch Formation in northwestern Sonoma County with deposits 50 km to the northwest near Point Arena, provides piercing points to use in calculation of a Pliocene slip rate for the northern San Andreas fault. A fission-track age of 3.3 \u00b1 0.8 Ma was determined for zircons separated from a tuff collected from the Ohlson Ranch Formation. The geomorphology of the region, especially of the two major river drainages, supports the proposed 50 km Pliocene offset. This implies a Pliocene slip rate of at least 12-20 mm/yr.
\r\n\r\nThese rates for different time periods imply that the slip rate of the northern San Andreas fault has not changed by more than a factor of two since Pliocene time. The rates also imply that much of the Pacific-North American plate motion must be accommodated on other structures at this latitude.
" }, { "name": "Salyards, Stephen Lowell", "degree": "PhD", "year": "1989", "title": "Dating and Characterizing Late Holocene Earthquakes Using Paleomagnetics", "advisor": "Sieh, Kerry E.; Kirschvink, Joseph L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10172013-145007953", "creators": [ { "name": { "family": "Salyards", "given": "Stephen Lowell" }, "id": "Salyards-Stephen-Lowell", "display_name": "Salyards, Stephen Lowell" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "advisor", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "co-advisor", "display_name": "Kirschvink, Joseph L." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "geophys" ], "doi": "10.7907/68QC-3J13", "abstract": "In this thesis I apply paleomagnetic techniques to paleoseismological problems. I investigate the use of secular-variation magnetostratigraphy to date prehistoric earthquakes; I identify liquefaction remanent magnetization (LRM), and I quantify coseismic deformation within a fault zone by measuring the rotation of paleomagnetic vectors.
\r\n\r\nIn Chapter 2 I construct a secular-variation reference curve for southern California. For this curve I measure three new well-constrained paleomagnetic directions: two from the Pallett Creek paleoseismological site at A.D. 1397-1480 and A.D. 1465-1495, and one from Panum Crater at A.D. 1325-1365. To these three directions I add the best nine data points from the Sternberg secular-variation curve, five data points from Champion, and one point from the A.D. 1480 eruption of Mt. St. Helens. I derive the error due to the non-dipole field that is added to these data by the geographical correction to southern California. Combining these yields a secular variation curve for southern California covering the period A.D. 670 to 1910, with the best coverage in the range A.D. 1064 to 1505.
\r\n\r\nIn Chapter 3 I apply this curve to a problem in southern California. Two paleoseismological sites in the Salton trough of southern California have sediments deposited by prehistoric Lake Cahuilla. At the Salt Creek site I sampled sediments from three different lakes, and at the Indio site I sampled sediments from four different lakes. Based upon the coinciding paleomagnetic directions I correlate the oldest lake sampled at Salt Creek with the oldest lake sampled at Indio. Furthermore, the penultimate lake at Indio does not appear to be present at Salt Creek. Using the secular variation curve I can assign the lakes at Salt Creek to broad age ranges of A.D. 800 to 1100, A.D. 1100 to 1300, and A.D. 1300 to 1500. This example demonstrates the large uncertainties in the secular variation curve and the need to construct curves from a limited geographical area.
\r\n\r\nChapter 4 demonstrates that seismically induced liquefaction can cause resetting of detrital remanent magnetization and acquisition of a liquefaction remanent magnetization (LRM). I sampled three different liquefaction features, a sandbody formed in the Elsinore fault zone, diapirs from sediments of Mono Lake, and a sandblow in these same sediments. In every case the liquefaction features showed stable magnetization despite substantial physical disruption. In addition, in the case of the sandblow and the sandbody, the intensity of the natural remanent magnetization increased by up to an order of magnitude.
\r\n\r\nIn Chapter 5 I apply paleomagnetics to measuring the tectonic rotations in a 52 meter long transect across the San Andreas fault zone at the Pallett Creek paleoseismological site. This site has presented a significant problem because the brittle long-term average slip-rate across the fault is significantly less than the slip-rate from other nearby sites. I find sections adjacent to the fault with tectonic rotations of up to 30\u00b0. If interpreted as block rotations, the non-brittle offset was 14.0+2.8, -2.1 meters in the last three earthquakes and 8.5+1.0, -0.9 meters in the last two. Combined with the brittle offset in these events, the last three events all had about 6 meters of total fault offset, even though the intervals between them were markedly different.
\r\n\r\nIn Appendix 1 I present a detailed description of my standard sampling and demagnetization procedure.
\r\n\r\nIn Appendix 2 I present a detailed discussion of the study at Panum Crater that yielded the well-constrained paleomagnetic direction for use in developing secular variation curve in Chapter 2. In addition, from sampling two distinctly different clast types in a block-and-ash flow deposit from Panum Crater, I find that this flow had a complex emplacement and cooling history. Angular, glassy \"lithic\" blocks were emplaced at temperatures above 600\u00b0 C. Some of these had cooled nearly completely, whereas others had cooled only to 450\u00b0 C, when settling in the flow rotated the blocks slightly. The partially cooled blocks then finished cooling without further settling. Highly vesicular, breadcrusted pumiceous clasts had not yet cooled to 600\u00b0 C at the time of these rotations, because they show a stable, well clustered, unidirectional magnetic vector.
" }, { "name": "Solomon, George Cleve", "degree": "PhD", "year": "1989", "title": "An \u00b9\u2078O/\u00b9\u2076O Study of Mesozoic and Early Tertiary Granitic Batholiths of the Southwestern North American Cordillera", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01192007-082647", "creators": [ { "name": { "family": "Solomon", "given": "George Cleve" }, "id": "Solomon-George-Cleve", "display_name": "Solomon, George Cleve" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geol" ], "doi": "10.7907/T831-NP65", "abstract": "Abundant evidence from previous studies indicates that, as long as samples are collected well away from pluton margins, the whole-rock \u03b4\u00b9\u2078O value of an unaltered granitic pluton is not likely to vary by more than \u00b10.5 per mil from the original \u00b9\u2078O/\u00b9\u2076O composition of its source rocks. Therefore, granitic plutons may be viewed as \"remote-sensing probes\" which sample deep portions of the continental crust or upper mantle, and \u00b9\u2078O/\u00b9\u2076O studies of such plutons can provide detailed information on lithologic boundaries at depth. This thesis presents approximately 350 new \u00b9\u2078O/\u00b9\u2076O analyses of whole-rock and quartz powders from Mesozoic and Cenozoic granitic plutons in the Northern Great Basin (NGB) and Southern Basin and Range (SBR) provinces of the western United States. The samples were collected along two broad, regional traverses eastward from the Sierra Nevada Batholith (SNB) and the Peninsular Ranges Batholith (PRB) in California: (1) the NGB traverse from western Nevada, near Carson City, eastward to the area around Salt Lake City, Utah; (2) the SBR traverse in southeastern California (SECA), eastward from the Central and Eastern Transverse Ranges across the Mojave Desert to the Colorado River, and then southeastward into southern Arizona. Where available, wholerock major-element geochemistry, [\u03b5Nd, and (\u2078\u2077Sr/\u2078\u2076Sr)i analyses of the same samples by other workers are integrated with these \u00b9\u2078O/\u00b9\u2076O analyses. In addition, several hundred whole-rock \u00b9\u2078O/\u00b9\u2076O analyses and, where available, Nd and Sr isotopic data, have been taken from the literature and combined with the new results to compile a data base that provides virtually complete reconnaissance coverage of the batholithic terranes in the Cordillera of southwestern North America.
\r\n\r\nSamples in the southern Arizona part of the SBR traverse were collected from Jurassic, late Cretaceous, and early Tertiary granitic plutons emplaced well within mapped boundaries of the > 1.5 Ga craton. The Jurassic plutons are metaluminous, alkali-calcic, epizonal syenites, monzodiorites and granodiorites (avg. whole-rock \u03b4\u00b9\u2078O: +6.7 to +7.4). The late Cretaceous plutons are metaluminous hornblende-bearing monzogranites and granodiorites (+7.4 < \u03b4\u00b9\u2078O < +9.9). The early Tertiary (Laramide) plutons are all peraluminous, leucocratic, two-mica granites (+8.2 < \u03b4\u00b9\u2078O < +9.0), which exhibit synkinematic and post-kinematic features. The Cretaceous suite is sliqhtly more \u00b9\u2078O-enriched and less oxidized than the Jurassic suite. The peraluminous two-mica granites, which are mineralogically closest to typical S-type plutons (as defined in SE Australia), have distinctly lower \u03b4\u00b9\u2078O values than most S-type granitic rocks throughout the world. We therefore classify all of these Arizona granites as basically I-type; there is no isotopic evidence for a major, pelitic, S-type source in southern Arizona. The two-mica granites probably represent highly fractionated \"first-melts\" of cratonal basement, while the epizonal Jurassic and Cretaceous plutons probably formed from \"drier\" melts that originated deeper in the crust.
\r\n\r\nThe samples in the Transverse Ranges and the SECA part of the SBR traverse were obtained from Triassic monzonites and syenogranites, Jurassic granodiorites and monzogranites, and late Cretaceous granodiorites, monzogranites, and two-mica granites. Most of these plutons are alkalicalcic to alkalis and were intruded upward through Precambrian basement rocks, with the exception of Cretaceous calc-alkaline monzogranites and rare two-mica granites emplaced west of cratonal basement rocks in the San Bernardino Mountains (SBM) and San Gabriel Mountains (SGM). The Triassic plutons (e.g. Mt. Lowe pluton) have uniformly low \u03b4\u00b9\u2078O values (+6.7 to +8.0). The Jurassic and Cretaceous magmas had \u03b4\u00b9\u2078O values between +6.7 and +9.3, including the two-mica granites of the Old Woman Mountains (+7.2 to +9.3), Cadiz Valley Batholith (+7.7 to +9), Chemehuevi Mountains (+7.8), and eastern SBM (+8.8 to +8.9). As in southern Arizona, these \"cratonal\" two-mica granites have lower \u03b4\u00b9\u2078O values than typical S-type plutons. In contrast, the Cretaceous plutons emplaced west of mapped cratonal basement in the SBM and SGM have high \u03b4\u00b9\u2078O values, between +8.5 and +10.8. This east-west change in primary whole-rock \u03b4\u00b9\u2078O marks a fundamental, regional \u00b9\u2078O/\u00b9\u2076O boundary, which we believe can be used to map the western edge of the craton in the Cordillera of the southwestern USA. The whole-rock \u03b4\u00b9\u2078O values of the plutons in the fault-reconstructed SGM terrane, the SBM terrane, and in the Little San Bernardino Mountains (LSB) can be contoured in a systematic fashion, and these contours are subparallel to the aforementioned regional \u00b9\u2078O/\u00b9\u2076O boundary.
\r\n\r\nNearly all of the Jurassic plutons in the SBR traverse were emplaced into shallow volcanic centers, and they show characteristics related to calderas, including hydrothermal alteration by heated low-\u00b9\u2078O meteoric waters. The altered plutons have \u03b4\u00b9\u2078O values ranging from -3.4 to +5.7, and where sampling density permits, contouring of \u03b4\u00b9\u2078O values reveals map patterns similar to those found at other meteoric-hydrothermal centers throughout the world. The best-studied of these Jurassic centers in this work is the Rodman-Ord Mountains (ROM) area, where the distinctive \u00b9\u2078O/\u00b9\u2076O map patterns produced by the Jurassic hydrothermal events have been used to estimate approximately 3 to 4 km of left-lateral strike-slip displacement along the late Cenozoic Camp Rock Fault. These SBR calderas are apparently part of a major Jurassic rift-system that extends from southeastern Arizona to the California-Nevada border. The low \u03b4\u00b9\u2078O values of the altered Jurassic plutons in SECA indicate that the paleoclimate in that portion of the rift was typical of mountainous regions today.
\r\n\r\nThe Oligocene to Jurassic plutons in the NGB traverse in Nevada and Utah are the same samples analyzed by Farmer and DePaolo (1983) in their Nd-Sr isotopic study of NGB plutonism: (1) calc-alkaline, metaluminous granodiorites and monzogranites intrude eugeoclinal Paleozoic allochthonous terranes between the SNB and the Roberts Mountain Thrust; (2) calc-alkaline, metaluminous to peraluminous granodiorites, monzogranites and two-mica granites intrude miogeoclinal terranes between the Roberts Mountain Thrust and the first outcrops of > 1.5 Ga cratonal basement going east; (3) alkali-calcic monzodiorites, granodiorites, and monzogranites intrude cratonal shelf sediments deposited on > 1.5 Ga craton in northeastern Nevada and western Utah. The primary, whole-rock \u03b4\u00b9\u2078O values in the first of the above groups exhibit the same geographic systematics discovered by Taylor and Silver (1978) for the PRB in southern and Baja California. There is a sharp, north-trending \u00b9\u2078O/\u00b9\u2076O boundary in western Nevada, analogous to the longitudinal \"\u00b9\u2078O-step\" down the center of the PRB. West of this boundary, the NGB plutons have \u03b4\u00b9\u2078O values that are uniformly lower than +8.5, and east of this boundary the plutons have \u03b4\u00b9\u2078O > +8.5, ranging up to +13.2. The highest \u00b9\u2078O/\u00b9\u2076O areas coincide with the second of the above groups, particularly where two-mica granite plutons occur. Just east of the Utah border, the third group of plutons exhibits \u03b4\u00b9\u2078O values < +9, and farther inland, \u03b4\u00b9\u2078O decreases to values as low as +6.7. This eastern boundary is inferred to be the same one we observe in the eastern Transverse Ranges in SECA.
\r\n\r\nWe use the \u00b9\u2078O/\u00b9\u2076O data from the NGB and SBR traverses, combined and augmented with literature-derived data on the PRB, SNB, and Idaho Batholith to provide a framework for viewing the subcrustal distribution of petrotectonic assemblages in much of the western United States. In conjunction with the Nd-, Pb- and Sr-isotopic signatures, the \u00b9\u2078O/\u00b9\u2076O data are used to map isotopic variations in the source regions of these plutons. This method yields a well-constrained model for the continental crust (especially when compared with earlier models that do not take into account the \u00b9\u2078O/\u00b9\u2076O values). Such studies are particularly helpful in constraining rock-types in these source regions, because \u00b9\u2078O/\u00b9\u2076O variations in rocks arise in a totally different manner than do the radiogenic isotope variations, which are mostly dependent upon age and upon various trace element concentrations.
\r\n\r\nAs discovered in the PRB by Taylor and Silver (1978), the \u03b4\u00b9\u2078O values of granitic rocks in the western United States define a series of sharp isotopic boundaries, independent of pluton lithologies, between different geographic groupings of granitic plutons. These are extremely well defined for the Cretaceous magmatic arc, for which three north-trending belts of plutons exist: (1) a Western Zone (WZ) of low-\u00b9\u2078O plutons with +5.5 < \u03b4\u00b9\u2078O < +8.5; (2) a Central Zone (CZ) of high-\u00b9\u2078O plutons with \u03b4\u00b9\u2078O between +8.5 and +13.2; and (3) an Eastern Zone (EZ) with variable \u03b4\u00b9\u2078O, typically lower than +9.0, but locally exhibiting plutonic centers with \u03b4\u00b9\u2078O > +9.0 (commonly associated with metamorphic core complexes). When (\u2078\u2077Sr/\u2078\u2076Sr)i values are taken into account, the Central Zone in the NGB must be divided into two geographic and geochemical entities; one lying west of a north-trending (\u2078\u2077Sr/\u2078\u2076Sr)i \"step\" (< 0.7080 to the west and > 0.7100 to the east), and one between this \u2078\u2077Sr/\u2078\u2076Sr \"step\" and the CZ-EZ boundary. The westernmost part is here termed the Central V-type subzone (CZ-V), and the eastern part is termed the Central S-type subzone (CZ-S). The CZ-S subzone is not present (except on a very small, local scale) south of approximately latitude 37\u00b0N, but it makes up approximately half of the Central Zone in the NGB, and dominates the CZ in the Idaho Batholith, north of the NGB. In contrast, the CZ-V subzone extends along the entire length of the Cordillera in the western USA, although it is very narrow north of 40\u00b0N latitude in the western portions of the Idaho Batholith.
\r\n\r\nThe three geographic \u00b9\u2078O/\u00b9\u2076O zones have boundaries coincident with several fundamental geologic features. The WZ occurs west of the quartz diorite line of Moore (1959) while the CZ is centered on the thickest portions of the late Precambrian-early Phanerozoic (0.3 to 1.5 Ga) Cordilleran geosyncline. The CZ in general lies east of the quartz diorite line, and west of the western limits of > 1.5 Ga Precambrian crystalline basement. The CZ-V subzone lies within the area of the geosyncline characterized by accreted terranes and dominated by eugeoclinal lithologies, whereas the CZ-S subzone appears to be associated with late Proterozoic miogeoclinal metasedimentary rocks. The EZ is located east of the western limit of older (> 1.5 Ga) crystalline basement and east of the thick geosynclinal sedimentary section. The EZ hosts most of the major porphyry copper deposits of the region, whereas the CZ hosts the known tungsten-skarn deposits.
\r\n\r\nThe isotopic data suggest that the Cordilleran granitic plutons are derived from varying proportions of the following major end-member components (largely by simple two-component mixing): (1) upper mantle and/or subducted oceanic crust, either an Oceanic Island Arc (OIA), or MORB-type source, with \u03b4\u00b9\u2078O = +6 to +7, (\u2078\u2077Sr/\u2078\u2076Sr)i ~ 0.702 to 0.704, and \u03b5Nd ~ +2 to +7; (2) \"eugeosynclinal\" sediments and altered volcanic rocks (SAV-type sources) with \u03b4\u00b9\u2078O = +10 to +13.5, (\u2078\u2077Sr/\u2078\u2076Sr)i ~ 0.705 to 0.710, and \u03b5Nd = -2 to -9; (3) \"miogeosynclinal\" continental margin sediments (MCM), with \u03b4\u00b9\u2078O > +10, (\u2078\u2077Sr/\u2078\u2076Sr)i > 0.715, and \u03b5Nd < -9; (4) some type of \"model lithospheric component\" in the lower continental crust (LCC, > 1.5 Ga) and/or upper mantle (SCL), having evolved, crustal characteristics and (\u2078\u2077Sr/\u2078\u2076Sr)i of about 0.705 to 0.710, with \u03b4\u00b9\u2078O values of +6.0 to +8.0 in the SBR and +7.5 to +9 in the NGB, and \u03b5Nd = -6 and -12 in the NGB and -4 and -10 in the SBR; and (5) mid-level continental crust of the craton (MCC) with \u03b4\u00b9\u2078O = +8 to +10, (\u2078\u2077Sr/\u2078\u2076Sr)i > 0.715, and \u03b5Nd < -12 to as low as -20. The latter values depend on the age of the crust.
\r\n\r\nThe simplest way to characterize each geographic \u00b9\u2078O/\u00b9\u2076O zone is by simple two-component melt-solid or solid-solid mixing of source-region materials, although the lack of specific isotopic data on the actual end-members precludes a rigorous evaluation of the relative importance of assimilation-fractional crystallization (AFC) processes. Western Zone: OIA-SAV with OIA dominant. Central V-type subzone: OIA-SAV with SAV dominant. Central S-type subzone: dominantly MCM with minor SAV, LCC, and OIA(?). Eastern Zone: dominantly LCC/SCL with widely varying proportions of some other end-members, such as MCC and/or a modified OIA mantle component (i.e., one that is older and more LIL-enriched than Cretaceous OIA or MORB, and thus one with a relatively high Sr content and high \u2078\u2077Sr/\u2078\u2076Sr ratio).
\r\n\r\nPrevious workers place the \"edge of the craton\" beneath the -0.706 (Kistler and Peterman, 1978) or -0.708 (Farmer and DePaolo, 1983) (\u2078\u2077Sr/\u2078\u2076Sr)i boundaries. However, we suggest that, in the NGB the (\u2078\u2077Sr/\u2078\u2076Sr)i \"step\" (0.708) is not the edge of the craton, but instead is probably a structural discontinuity that has juxtaposed an accreted terrane of eugeosynclinal volcanic and volcanogenic sedimentary rocks on the west against a late Precambrian sedimentary terrane on the east. The sharpness of this boundary implies that it is either the edge of an ancient rift-zone (Kistler and Peterman, 1978), a strike-slip fault, or a suture zone. The hypothetical late Precambrian metasedimentary basin that we infer east of the \u2078\u2077Sr/\u2078\u2076Sr \"step\" could represent an in-filled pull-apart basin, which opened during southward transport of the \"Mojavia\" terrane of Bennett and DePaolo (1987), thus explaining the east-trending boundary between the CZ and EZ that extends all the way across south-central Nevada.
\r\n\r\nThe isotopic differences inferred for the deep continental crustal sources (LCC/SCL) in the NGB (\u03b4\u00b9\u2078O = +7 to +9) and SBR (\u03b4\u00b9\u2078O = +6 to +8) bear on the structure of the craton. The \u03b4\u00b9\u2078O of the LCC/SCL component in SECA is similar to that in southern Arizona, implying that the \u00b9\u2078O/\u00b9\u2076O composition of LCC/SCL in the SBR was acquired after any of the hypothetical tectonic movements that shifted \"Mojavia\" from the NGB southward into southeastern California (Bennett and DePaolo, 1987). This means that: (1) a relatively low-\u00b9\u2078O source could have underplated the SBR (including Mojavia) after tectonic emplacement of \"Mojavia\" athwart the southern Arizona region; or (2) previous fusion events at 1.4 Ga and 1.1 Ga could have modified the SBR deep sources, such that the \u03b4\u00b9\u2078O of the LCC/SCL underneath the SBR was lowered relative to the equivalent zone in the NGB.
" }, { "name": "Chang, Shih-Bin Robin", "degree": "PhD", "year": "1988", "title": "Bacterial Magnetite in Sedimentary Deposits and its Geophysical and Paleoecological Implication", "advisor": "Kirschvink, Joseph L.; Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechETD:etd-05232007-103731", "creators": [ { "name": { "family": "Chang", "given": "Shih-Bin Robin" }, "id": "Chang-Shih-Bin-Robin", "display_name": "Chang, Shih-Bin Robin" } ], "advisors": [ { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "advisor", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "co-advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Hoffmann", "given": "Michael R." }, "id": "Hoffmann-M-R", "orcid": "0000-0001-6495-1946", "role": "member", "display_name": "Hoffmann, Michael R." }, { "name": { "family": "Awramik", "given": "Stanley M." }, "id": "Awramik-Stanley-M", "role": "member", "display_name": "Awramik, Stanley M." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" } ], "option_major": [ "geochem" ], "doi": "10.7907/2ema-0m34", "abstract": "In the past two decades, natural remanent magnetization carried by marine sediments and sedimentary rocks has been used extensively to monitor the history of the geomagnetic field and to constrain motion of crustal plates. But the origin of the magnetic minerals contributing to observed remanent magnetization is only now being resolved. The main reason behind that is that representative magnetic extracts are hard to obtain from marine sediments for direct observation. Previous attempts to separate the magnetic carriers in sediments and to examine their granulometry under the scanning electron microscope (SEM) have revealed the existence of large detrital, diagenetic, and meteoritic magnetite particles. These studies, however, have been limited in their ability to recognize the more magnetically stable and smaller single-domain fraction (<0.1 micron in size) of magnetite particles. Meanwhile, the existence of single-domain magnetite grains as a major remanence carrier in a variety of marine sedimentary deposits has been shown by various rock magnetic methods, but the origin of these grains was not revealed. The major part of this thesis is devoted to the development of better extraction techniques, employing the higher resolution transmission electron microscope (TEM) to identify the presence and to study the origin of these ultrafine-grained magnetite particles in marine sediments. Special emphasis is paid to search for the existence of magnetite precipitated by magnetotactic bacteria and to determine its role as the remanence carrier in certain sediments.
\r\n\r\nSeveral new occurrences of living magnetotactic bacteria have been discovered and investigated. Among them, the organic-rich mud from a shallow marine basin off the California coast (the Santa Barbara Basin) and the carbonate ooze from Sugarloaf Key, Florida are of particular interest. The former demonstrates that magnetotactic bacteria are able to live and flourish at depth in an open marine environment similar to that present over most of the world ocean floors; if the local marine sediments are able to preserve the bacterial magnetite particles, then they have an excellent chance for recording a stable remanent magnetization. The latter implies that there is a good chance for using magnetostratigraphy study on shallow water carbonates to unravel the history of their formation. In addition, the occurrences of magnetotactic bacteria and bacterial magnetite at a hypersaline lagoon (Laguna Figueroa) in Baja California, Mexico, a well-known and well-studied present-day analog of Precambrian stromatolites, suggest that stromatolites would be a good place to search for bacterial magnetofossils in Precambrian.
\r\n\r\nThe magnetotactic organisms from all the newly studied occurrences have been isolated and examined. The magnetite crystals in them are similar in size and morphology to those previously found in magnetotactic bacteria from other environments. Three basic shapes of bacterial magnetite are cuboid, hexagonal prism, and tear-drop, which are all quite distinguishable from that (typical octahedra) of inorganically formed magnetite. In addition, all of the measured sizes of bacterial magnetite crystals fall well within the single-domain stability field of magnetite. It is this characteristic size and shape distribution of bacterial magnetite particles that enables the search for their occurrences in modern and fossil sedimentary records.
\r\n\r\nA set of calcite, aragonite, and recrystallized dolomite samples from Bahama Bank and a core sample from Laguna Figueroa that displays interlayers of flood derived sediments and laminated mats are studied to determine the possible diagenetic effects on bacterial magnetite. Euhedral bacterial magnetite crystals have been found in all three types of sediments from Bahama Bank. Apparently, the recrystallization process does not change or alter the identity of bacterial magnetite. In Laguna Figueroa core samples, the bacterial magnetite has only been observed in the surface layer (where the living magnetotactic bacteria were found) and flood derived sediments. No bacterial magnetite was detected from laminated mat samples, and rock magnetic study shows the disappearance of a significant portion of ultrafine-grained magnetite through depth in them. Iron reduction coupled with the oxidation of organic materials, which are rich in laminated mats and relatively scarce in flood derived sediments, is one possible explanation for these observations.
\r\n\r\nNumerous deep sea core samples have been examined to identify the presence of bacterial magnetite particles. To date, the oldest undoubtedly bacterial magnetite assemblage detected in deep sea core materials is from Miocene ODP Leg 101 sample 633A-023X-03. Some bacterial magnetite-like crystals have also been isolated from Oligocene DSTP Leg 73 samples, but they are not aligned in a chain or clumped together like bacterial magnetite particles extracted from modern environments are. Among varieties of deep sea sediments being studied, bacterially formed single-domain magnetite grains are found to be most abundant in calcareous sediments with high sedimentation rate, which might reflect the enhancement of preservation potential of ultrafine-grained magnetite during the period when massive carbonate deposition diluted the concentration of organic materials.
\r\n\r\nSome possible implications of surveying the fossil occurrences of bacterial magnetite were explored. One of them is using the presence of bacterial magnetite as an independent magnetic stability indicator. It seems clear that bacterial magnetite crystals should preserve their spatial orientations and magnetic remanence directions relative to the rock matrix, unless they are disrupted by major events of thermal, chemical, or physical alteration, which would result in producing a strong secondary component in the sample. Several sets of samples that have been shown by conventional paleomagnetic or rock magnetic techniques to contain either one single primary component or one main primary component plus a weak secondary component are analyzed to test this possibility. Bacterial magnetite has been found well preserved in some of them (e.g., Neogene carbonate samples from the Bahamas, Miocene Potamida Clay of Crete, Cambrian Sinskian Formation of Siberian Platform, etc.). On the other hand, no bacterial magnetite was detected from samples with well-documented overprinting records (e.g., materials from the Great Basin, Morocco, and Newfoundland).
\r\n\r\nBecause bacterial magnetite formation requires iron-mediating enzymes and certain amounts of free oxygen, to trace back the earliest occurrence of bacterial magnetite in Precambrian would support constraints on some important biochemical evolutional sequences. Stromatolitic carbonate and chert samples with ages ranging from middle Archaean to late Proterozoic are studied. Euhedral bacterial magnetite chain has been found from Nama sedimentary rocks of South Africa (approximately 700-600 My) which represents the oldest bacterial magnetofossils reported to date. A chain composed of single-domain magnetite particles with fuzzy outlines has also been detected from the 2000 My Gunflint deposit. These findings support the currently accepted hypothesis about the timing of abrupt Precambrian atmospheric oxygen buildup. They also reflect the necessity for organisms to develop mechanisms for acquiring and storing extracellular iron after the Global Ocean \"Rusting\" event drastically reduced the availability of dissolved iron (normally in the ferrous state) in the hydrosphere. The geologic record shows this event probably occurred around Early Proterozoic as represented by worldwide-spread Banded Iron Formation deposition at that time.
" }, { "name": "Edwards, Richard Lawrence", "degree": "PhD", "year": "1988", "title": "High Precision Thorium-230 Ages of Corals and the Timing of Sea Level Fluctuations in the Late Quaternary", "advisor": "Wasserburg, Gerald J.; Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10112005-103528", "creators": [ { "name": { "family": "Edwards", "given": "Richard Lawrence" }, "id": "Edwards-Richard-Lawrence", "display_name": "Edwards, Richard Lawrence" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "co-advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "geochem" ], "doi": "10.7907/S2FW-0463", "abstract": "Mass spectrometric techniques for the measurement of \u00b2\u00b3\u2070Th and \u00b2\u00b3\u2074U have been developed. These techniques have made it possible to reduce the analytical errors in \u00b2\u00b3\u2070Th dating of corals using very small samples. Samples of 8 x 10\u2077 atoms of \u00b2\u00b3\u2070Th can be measured to an accuracy of \u00b1130% (2 sigma), 6 x 10\u2078 atoms of \u00b2\u00b3\u2070Th can be measured to an accuracy of \u00b129%, and 3 x 10\u00b9\u2070 atoms of \u00b2\u00b3\u2070Th can be measured to an accuracy of \u00b12%. The time range over which useful data on corals can now be obtained ranges from 15 to 500,000 years. The error in age (based on analytical error) for a sample that is 18 years old \u00b13 years (2 sigma). The error is \u00b15 years at 180 years, \u00b144 years at 8294 years, and \u00b11 ky at 123.1 ky. For young corals, this approach may be preferable to \u00b9\u2074C dating.
\r\n\r\nFluctuations in climate result in changes in sea level because the ice stored in continental glaciers is ultimately derived from the ocean. Certain species of coral grow close to the sea surface. Fossils of these species therefore record the former height of the sea surface. The precision with which the age of a coral can now be determined makes it possible to determine, with some precision, the timing of sea level fluctuations in the late Quaternary. This record will allow a critical test of the Milankovitch hypothesis, which predicts the timing of Pleistocene climate fluctuations from changes in the distribution of solar insolation that result from changes in the earth's orbital geometry. Analyses of a number of corals that grew during the last interglacial period yield ages of 122 to 130 ky. The ages coincide with or slightly postdate the summer solar insolation high at 65\u00b0N latitude, which occurred 128 ky ago. This supports the idea that changes in Pleistocene climate can be the result of orbital forcing.
\r\n\r\nApparent fluctuations in sea level recorded on tectonically active shorelines are the result of both sea level change and vertical tectonic movement. If the record of sea level change is known (e.g., from the coral record in a stable area), this record can be subtracted from the record of apparent sea level change, in the tectonically active area, to yield a record of vertical tectonic movement. The precision with which coral ages can now be determined may allow us to resolve the ages of individual coseisimic uplift events and thereby date prehistoric earthquakes.
\r\n\r\nThis possibility has been examined at two localities, northwest Santo Island and north Malekula Island, Vanuatu. Previous work (Taylor et al., 1980, 1985a, 1987) showed (using the counting of annual growth bands to determine ages) that the tops of partially emerged coral heads at each locality died at the same time as the last major earthquake at each locality (MS = 7.5, 1973, on northwest Santo; and MS = 7.5, 1965, on north Malekula). It was concluded that the tops of these coral heads were killed by coseismic uplift. At each locality, there were also completely emerged coral heads, which were inferred to have been killed by earlier coseismic uplift events. These could not be dated by growth band counting because the coral heads were completely dead.
\r\n\r\nThe accuracy of \u00b2\u00b3\u2070Th ages of very young corals was tested by dating portions of three corals whose ages were known from the counting of growth bands. Within analytical error, the \u00b2\u00b3\u2070Th ages were the same as the growth band ages for all three samples (dates of growth by counting growth bands - A.D. 1971 to 1973, A.D. 1935 to 1939, and A.D. 1804 to 1810; dates of growth from \u00b2\u00b3\u2070Th measurements - A.D. 1969 \u00b1 3, A.D. 1932 \u00b1 5, and A.D. 1806 5 [2 sigma \u00b11) demonstrating that the \u00b2\u00b3\u2070Th ages were accurate.
\r\n\r\nThe \u00b2\u00b3\u2070Th growth dates of the surfaces of adjacent emerged coral heads, collected from the same elevation (1.2 m) on northwest Santo Island, were, within analytical error, identical (A.D. 1866 \u00b1 4 and A.D. 1864 \u00b1 4). This indicates that the corals died at the same time and is consistent with the idea that they were killed by coseismic uplift. Similar adjacent coral heads on north Malekula Island yielded \u00b2\u00b3\u2070Th growth dates of A.D. 1729 \u00b1 3 and A.D. 1718 \u00b1 5. The ages are similar but analytically distinguishable. The difference may be due to erosion of the outer, younger, portion of the latter coral head. Using the date of the large historical earthquake at each locality and the \u00b2\u00b3\u2070Th growth date of the emerged corals at each locality, recurrence intervals of 108 years for northwest Santo and 236 years for north Malekula are calculated.
\r\n\r\nThis experiment has shown that it is possible to date corals that grew in the past several centuries to accuracies of \u00b13 to \u00b15 years (2 sigma). The main problems with applying this approach to determine seismic histories will be associated with the preservation of fossil corals that have been killed by coseimic uplift and the ability to identify such features in the field.
" }, { "name": "Ho-Liu, Phyllis Hang-Yin", "degree": "PhD", "year": "1988", "title": "I. Attenuation Tomography. II. Modeling Regional Love Waves: Imperial Valley to Pasadena", "advisor": "Kanamori, Hiroo; Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03192013-112511014", "creators": [ { "name": { "family": "Ho-Liu", "given": "Phyllis Hang-Yin" }, "id": "Ho-Liu-Phyllis-Hang-Yin", "display_name": "Ho-Liu, Phyllis Hang-Yin" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "co-advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geophys" ], "doi": "10.7907/fb8j-fs65", "abstract": "Abstract to Part I
\r\n\r\nThe inverse problem of seismic wave attenuation is solved by an iterative back-projection method. The seismic wave quality factor, Q, can be estimated approximately by inverting the S-to-P amplitude ratios. Effects of various uncertain ties in the method are tested and the attenuation tomography is shown to be useful in solving for the spatial variations in attenuation structure and in estimating the effective seismic quality factor of attenuating anomalies.
\r\n\r\nBack-projection attenuation tomography is applied to two cases in southern California: Imperial Valley and the Coso-Indian Wells region. In the Coso-Indian Wells region, a highly attenuating body (S-wave quality factor (Q\u03b2 \u2248 30) coincides with a slow P-wave anomaly mapped by Walck and Clayton (1987). This coincidence suggests the presence of a magmatic or hydrothermal body 3 to 5 km deep in the Indian Wells region. In the Imperial Valley, slow P-wave travel-time anomalies and highly attenuating S-wave anomalies were found in the Brawley seismic zone at a depth of 8 to 12 km. The effective S-wave quality factor is very low (Q\u03b2 \u2248 20) and the P-wave velocity is 10% slower than the surrounding areas. These results suggest either magmatic or hydrothermal intrusions, or fractures at depth, possibly related to active shear in the Brawley seismic zone.
\r\n\r\nNo-block inversion is a generalized tomographic method utilizing the continuous form of an inverse problem. The inverse problem of attenuation can be posed in a continuous form , and the no-block inversion technique is applied to the same data set used in the back-projection tomography. A relatively small data set with little redundancy enables us to apply both techniques to a similar degree of resolution. The results obtained by the two methods are very similar. By applying the two methods to the same data set, formal errors and resolution can be directly computed for the final model, and the objectivity of the final result can be enhanced.
\r\n\r\nBoth methods of attenuation tomography are applied to a data set of local earthquakes in Kilauea, Hawaii, to solve for the attenuation structure under Kilauea and the East Rift Zone. The shallow Kilauea magma chamber, East Rift Zone and the Mauna Loa magma chamber are delineated as attenuating anomalies. Detailed inversion reveals shallow secondary magma reservoirs at Mauna Ulu and Puu Oo, the present sites of volcanic eruptions. The Hilina Fault zone is highly attenuating, dominating the attenuating anomalies at shallow depths. The magma conduit system along the summit and the East Rift Zone of Kilauea shows up as a continuous supply channel extending down to a depth of approximately 6 km. The Southwest Rift Zone, on the other hand, is not delineated by attenuating anomalies, except at a depth of 8-12 km, where an attenuating anomaly is imaged west of Puu Kou. The Ylauna Loa chamber is seated at a deeper level (about 6-10 km) than the Kilauea magma chamber. Resolution in the Mauna Loa area is not as good as in the Kilauea area, and there is a trade-off between the depth extent of the magma chamber imaged under Mauna Loa and the error that is due to poor ray coverage. Kilauea magma chamber, on the other hand, is well resolved, according to a resolution test done at the location of the magma chamber.
\r\n\r\nAbstract to Part II
\r\n\r\nLong period seismograms recorded at Pasadena of earthquakes occurring along a profile to Imperial Valley are studied in terms of source phenomena (e.g., source mechanisms and depths) versus path effects. Some of the events have known source parameters, determined by teleseismic or near-field studies, and are used as master events in a forward modeling exercise to derive the Green's functions (SH displacements at Pasadena that are due to a pure strike-slip or dip-slip mechanism) that describe the propagation effects along the profile. Both timing and waveforms of records are matched by synthetics calculated from 2-dimensional velocity models. The best 2-dimensional section begins at Imperial Valley with a thin crust containing the basin structure and thickens towards Pasadena. The detailed nature of the transition zone at the base of the crust controls the early arriving shorter periods (strong motions), while the edge of the basin controls the scattered longer period surface waves. From the waveform characteristics alone, shallow events in the basin are easily distinguished from deep events, and the amount of strike-slip versus dip-slip motion is also easily determined. Those events rupturing the sediments, such as the 1979 Imperial Valley earthquake, can be recognized easily by a late-arriving scattered Love wave that has been delayed by the very slow path across the shallow valley structure.
\r\n\r\n\r\n" }, { "name": "Manduca, Cathryn Clement Allen", "degree": "PhD", "year": "1988", "title": "Geology and Geochemistry of the Oceanic Arc-Continent Boundary in the Western Idaho Batholith near McCall", "advisor": "Silver, Leon T.; Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02042005-111245", "creators": [ { "name": { "family": "Manduca", "given": "Cathryn Clement Allen" }, "id": "Manduca-Cathryn-Clement-Allen", "display_name": "Manduca, Cathryn Clement Allen" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "co-advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" } ], "option_major": [ "geol" ], "doi": "10.7907/JP15-KC07", "abstract": "A major lithospheric boundary is preserved within the western Idaho Batholith. The juxtaposition of two suites of supracrustal rocks, exposed as sheets within intrusive rocks, is the expression of this boundary at the level of exposure. The western suite of mafic layered gneisses are inferred to be metamorphosed oceanic arc rocks; the eastern suite of biotite schist, quartzite and calc-silicate gneiss are inferred to be metamorphosed continental sedimentary rocks. Three broadly Cretaceous, plutonic and meta-plutonic complexes record the presence of the boundary at greater depth. The Hazard Creek complex, west of the supracrustal boundary, is comprised of epidote-bearing intrusives. The Little Goose Creek complex is comprised primarily of the porphyritic orthogneiss that intruded the supracrustal boundary. The Payette River complex, east of the supracrustal boundary, is comprised of large bodies of tonalite and granite.
\r\n\r\nEach complex has a distinct geochemical character. The Hazard Creek complex is dominantly a tonalite-trondhjemite suite characterized by Ri less than .7045, \u03b4\u00b9\u2078O less than 8.4, high Sr, Na\u2082O and Al\u2082O\u2083 concentrations and low MgO, Rb and K\u2082O concentrations. Porphyritic orthogneiss in the Little Goose Creek complex has a remarkable range in Ri and \u03b4\u00b9\u2078O (.7042-.7097, 8.0-10.7). The porphyritic orthogneiss is interpreted as dominated by two components: one similar in composition to the Hazard Creek complex and a second, modeled as Precambrian sedimentary material, with high Ri, \u03b4\u00b9\u2078O and K\u2082O concentrations and lower Sr concentration. The Payette River complex has generally high Ri (.7076-.7100) and variable \u03b4\u00b9\u2078O (7.2-10.4). The geochemical changes indicate that the supracrustal boundary is the surface expression of a steeply-dipping structure which juxtaposes oceanic-arc lithosphere against continental lithosphere. An abrupt geochemical discontinuity preserved within the porphyritic orthogneiss, near the change in supracrustal rocks, may reflect an abrupt discontinuity at depth or may be due to the juxtapositon of portions of a stratified pluton. The juxtaposition of lithospheric blocks must have occured prior to intrusion of the porphyritic orthogneiss approximately 111 Ma, and most probably, occured before 118 Ma, prior to the beginning of plutonism. No structural evidence for the initial formation of the boundary is recognized; it is proposed to form by transform faulting or by rifting followed by convergence.
\r\n\r\nEpisodic or continuous deformation along the boundary began prior to 118 Ma and produced four sets of structures. The oldest structures are foliation and isoclinal folding of crystalloblastic gneisses which may have formed during rapid burial of oceanic-arc rocks west of the boundary. Compressive deformation, forming north-south striking steeply-dipping foliations and steeply-plunging lineations in the eastern portion of the Hazard Creek complex, was broadly coeval with its emplacement. Igneous foliation and lineation with similar orientation formed during emplacement of the Payette River complex around 90 Ma. The youngest penetrative deformation formed similarly oriented, mylonitic fabrics in a 10 km wide zone centered on the boundary. All but the oldest structures are inferred to have formed by flattening and vertical flow in response to east-west compression. Deformation is interpreted to represent the response of a preexisting lithospheric boundary to compressive stresses related to subduction of material to the west.
" }, { "name": "Ojakangas, Gregory Wayne", "degree": "PhD", "year": "1988", "title": "I. Episodic Volcanism of Tidally Heated Satellites with an Application to Io. II. Thermal State of an Ice Shell on Europa. III. Polar Wander of a Synchronously Rotating Satellite with Application to Europa", "advisor": "Stevenson, David John; Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10162009-112521312", "creators": [ { "name": { "family": "Ojakangas", "given": "Gregory Wayne" }, "id": "Ojakangas-Gregory-Wayne", "display_name": "Ojakangas, Gregory Wayne" } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "advisor", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "co-advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/RMD6-XM66", "abstract": "Two examples of planetary bodies that may have coupled thermal and dynamical evolutions are investigated. The work is presented in three individual papers.
\r\n\r\nThe first example is that of a tidally heated satellite in an orbital resonance, for which the tidal dissipation rate is a strongly increasing function of the internal temperature. For such a satellite, a feedback mechanism exists between the orbital and thermal energies, which may lead to periodic variations in tidal heating within the satellite and its orbital eccentricity. A simple model of this mechanism is presented in the first paper and is applied specifically to Io.
\r\n\r\nThe second example is that of an ice shell on Europa, which is decoupled from the silicate core by a layer of liquid water. In the second paper, the spatially varying thickness that such a shell would have in thermal equilibrium with tidal dissipation within it, surface solar insolation and heat flow from the core is calculated for reasonable rheological laws for ice. The contribution of these variations in ice thickness to Europa's inertia tensor is estimated, and the implications for nonsynchronous rotation of Europa are discussed. In the third paper, a detailed dynamical model is developed, which demonstrates that such a shell may exhibit large\u2014scale polar wander as it approaches thermal equilibrium, because of the destabilizing effect of the variations in ice thickness on the inertia tensor of the shell.
\r\n\r\nThe abstracts of the three papers are reproduced below.
\r\n\r\nEpisodic Volcanism of Tidally Heated Satellites with Application to Io
\r\n\r\nA simple model of the coupled thermal and orbital evolution of a tidally heated satellite in an orbital resonance is presented and applied specifically to Io. The model quantitatively demonstrates how a feedback mechanism between the orbital and thermal energy of such a satellite can lead to periodic variations in surface heatflow and orbital eccentricity. The convective heatflow and (k/Q) of the satellite are parameterized as local power laws of the temperature, where Q is the quality factor and k is the second-degree tidal potential Love number. The time evolution of the model is determined by two nonlinear equations: an equation governing the orbital eccentricity, and a simple heat-balance equation determining the temperature. A linear stability analysis reveals that the time-independent solution is unstable if n > m + p, where n and m are the exponents in the power laws for (k/Q) and convective heatflow, respectively, and p is the ratio of the convective cooling time scale to the time scale for equilibration of the eccentricity. Numerical integration of the nonlinear equations reveals behavior in qualitative agreement with this relation. Laboratory data on near-solidus peridotites suggest 20 \u227e n \u227e 30, and parameterized convection schemes suggest m ~ 10. Since p is of order unity, it follows that tidally heated satellites are probably in the unstable regime if they are operating near the solidus. It is thus probable that Io has no thermal steady state. The model is made more realistic by (1) arresting the reduction of (k/Q) at low temperature, and (2) arresting the growth of temperature at the mantle solidus and allowing volcanism to remove the excess heat. When the second modification is included, the unstable regime becomes periodic. In addition, a global k substantially larger than the elastic value is possible for a mostly solid Io because the body may begin to behave viscously when the tidal period is longer than, or comparable to, the Maxwell time. This requires a solid-state viscosity of \u227e 4 x 10\u00b9\u2075 Pa s, which may be achievable with a small amount of partial melt. The model can easily be adjusted to pass through Io's current observed heatflow (1-2 W m\u207b\u00b2) and eccentricity (~ 0.004) for reasonable choices of parameters (Q/k)min ~ 100, (Q/k)max ~ few x 10\u00b3 solidus viscosity ~ 10\u00b9\u2075\u201310\u00b9\u2077 Pas, and QJ within the required dynamical bounds. The periods of high heatflow and acceptable eccentricity typically have duration of ~ 20-20 myr, separated in time by ~ 80-100 myr. Spatial heterogeneities in Io's thermal structure are likely to make the behavior more complicated. The model predicts that Io's mean motion may be currently increasing, a possibility suggested by recent estimates of \u1e45\u2081 from eclipse data. Since Europa's eccentricity mimics that of Io, the model also implies that the tidal stresses in Europa's ice shell may have recently been large enough to produce the observed fracturing. The episodic heating mechanism may be responsible for the resurfacing of Enceladus < 10\u2079 years ago.
\r\n\r\nThermal State of an Ice Shell on Europa
\r\n\r\nWe consider a model of Europa consisting of an ice shell that is decoupled from a silicate core by a layer of liquid water. The thickness of the shell is calculated as a function of colatitude and longitude, assuming that a state of conductive equilibrium exists with the incident annual average solar insolation, tidal dissipation within the shell, and heat flow from the core. Ice thickness profiles are calculated for each of two plausible rheological behaviors for ice: the Maxwell rheology and the generalized flow law rheology. In both cases the strong temperature\u2014dependence of the dissipation rate is explicitly included as well as the temperature\u2014dependence of the thermal conductivity of ice. Because of the strong temperature dependence of the dissipation rate, nearly all of the tidal dissipation is concentrated in the lowermost few kilometers of the shell. Even though the effective Q of the greater part of the shell is >> 100 in our models, average shell thicknesses do not exceed 25 km. Thus, if the total thickness of H\u2082O which mantles Europa is \u2273 25 km, none of the models admit the possibility of a completely frozen H\u2082O layer. The total dissipation rates in our models are comparable to those of a constant Q model with Q ~ 10. The thickness profiles are relatively insensitive to heat flow from the core. The second degree spherical harmonic components of the ice thickness are given and the resulting contributions to the quantities (B-A)/C and (B-C)/A of Europa are estimated. Although the contribution to (B-A)/C is perhaps larger than the permanent value needed to prevent nonsynchronous rotation, its dependence on the shell's orientation relative to synchroneity suggests that very slow nonsynchronous rotation will persist, with reorientation of the shell relative to the satellite-planet direction occurring on a timescale \u2273 the thermal diffusion timescale for the shell (~10\u2077 yr). The existence of a significant \"fossil\" bulge on the shell due to long-term elastic behavior of its outer, coldest regions would eliminate nonsynchronous rotation. Since the contribution to ((B-C)/A) of the thickness variations in most of our models is > 0, Europa may experience polar wander as thermal equilibrium is approached, if the above is the most important permanent contribution to ((B-C)/A). The magnitudes of the principal moment differences are insensitive to the details of the parameterization of the tidal dissipation.
\r\n\r\nPolar Wander of a Synchronously Rotating Satellite with Application to Europa
\r\n\r\nAn ice shell on Europa that is decoupled from the silicate core by a layer of liquid water has a thermal-equilibrium thickness profile that varies with position over its surface, because of spatial variations in the surface temperature and tidal dissipation within the ice (see previous paper). The second spherical harmonic degree components of these thickness variations and of any fossil rotational and tidal bulges present on the shell contribute to the inertia tensor of the body. The problem is that of a planetary elastic lithosphere that is topographically loaded from below. Following the development of Willemann and Turcotte (1981) we develop equations describing the variations in the inertia tensor of a body, which are caused by the addition of second harmonic degree topography to the base of the crust. Applied to the case of an ice shell on Europa, it is found for many choices of parameters that a state of thermal equilibrium for the shell will involve an orientation of Europa's principal axes of inertia (when the hydrostatic bulges are relaxed), which is unusual for a synchronously rotating satellite. Specifically, the intermediate and maximum principal moments are reversed. To reach the preferred orientation for synchronous satellites, a thermal equilibrium ice shell must execute a net reorientation of ninety degrees about the satellite\u2014planet direction. We present a simple model of a rigid, synchronously rotating satellite in a circular orbit for which the difference between the intermediate and maximum principal moments is linear in time, passing through zero when t = 0. The model demonstrates that the expected reorientation is indeed dynamically favored.
\r\n\r\nWe then consider a more realistic model, including the effects of various torques which act to couple the motions of the core, shell, and liquid water layer, as well as the effect of viscous dissipation which arises in the shell due to the predicted polar wander. It is found that the Poincar\u00e9 torque, gravitational coupling, and the torque due to viscous shear in the liquid water layer are unable to induce significant motion of the core during polar wander of the shell. However, the Poincar\u00e9 torque exerted on the liquid water layer by the shell is believed to cause the liquid water layer to reorient in coincidence with the shell. The model suggests that viscous friction in the shell eliminates the possibility that polar wander will occur unless preexisting fractures (e.g., due to tidal stresses (Crawford and Stevenson, 1988)) extend from the surface to a depth where the ice behaves viscously on the polar wander time scale. If the temperature Tf at the base of the fractured region is as high as ~ 140-145 K, the model indicates that polar wander occurs on a time scale of 10\u2076-10\u2075 y (shorter as Tf increases) after the sign of the difference between the maximum and intermediate principal moments reverses. In the absence of dissipation, polar wander would occur in ~ few x 10\u00b3 y. Polar wander must occur on a time scale significantly shorter than ~ 10\u2077 y, or the thickness profile of the ice will be in continuous equilibrium with its thermal environment regardless of its orientation, and the mechanism driving the polar wander will be virtually eliminated. It is likely that events of large scale polar wander occur episodically, separated in time by periods on the order of the time scale for thermal diffusion through the shell (~ 10\u2077 y), although a state of slow, continuous drifting of the pole is also possible. The time scale of viscous flow of topography at the base of the ice is also near 10\u2077 y. If dissipation in the shell due to polar wander is a few orders of magnitude smaller than our simple model suggests, polar wander as described here is a much more effective means for fracturing the ice than is tidal flexing, and it may contribute to producing the observed global fracture systems in Europa's ice.
\r\n" }, { "name": "Silver, Lynn Alison", "degree": "PhD", "year": "1988", "title": "Water in Silicate Glasses", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03212013-080648923", "creators": [ { "name": { "family": "Silver", "given": "Lynn Alison" }, "id": "Silver-Lynn-Alison", "display_name": "Silver, Lynn Alison" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "chair", "display_name": "Burnett, Donald S." }, { "name": { "family": "Eckert", "given": "Hellmut" }, "id": "Eckert-Hellmut", "role": "member", "display_name": "Eckert, Hellmut" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geol" ], "doi": "10.7907/z336-zw46", "abstract": "The speciation of water in a variety of hydrous silicate glasses, including simple and rhyolitic compositions, synthesized over a range of experimental conditions with up to 11 weight percent water has been determined using infrared spectroscopy. This technique has been calibrated with a series of standard glasses and provides a precise and accurate method for determining the concentrations of molecular water and hydroxyl groups in these glasses.
\r\n\r\nFor all the compositions studied, most of the water is dissolved as hydroxyl groups at total water contents less than 3-4 weight percent; at higher total water contents, molecular water becomes the dominant species. For total water contents above 3-4 weight percent, the amount of water dissolved as hydroxyl groups is approximately constant at about 2 weight percent and additional water is incorporated as molecular water. Although there are small but measurable differences in the ratio of molecular water to hydroxyl groups at a given total water content among these silicate glasses, the speciation of water is similar over this range of composition. The trends in the concentrations of the H-bearing species in the hydrous glasses included in this study are similar to those observed in other silicate glasses using either infrared or NMR spectroscopy.
\r\n\r\nThe effects of pressure and temperature on the speciation of water in albitic glasses have been investigated. The ratio of molecular water to hydroxyl groups at a given total water content is independent of the pressure and temperature of equilibration for albitic glasses synthesized in rapidly quenching piston cylinder apparatus at temperatures greater than 1000\u00b0C and pressures greater than 8 kbar. For hydrous glasses quenched from melts cooled at slower rates (i.e., in internally heated or in air-quench cold seal pressure vessels), there is an increase in the ratio of molecular water to hydroxyl group content that probably reflects reequilibration of the melt to lower temperatures during slow cooling.
\r\n\r\nMolecular water and hydroxyl group concentrations in glasses provide information on the dissolution mechanisms of water in silicate liquids. Several mixing models involving homogeneous equilibria of the form H\u2082O + O = 2OH among melt species have been explored for albitic melts. These models can account for the measured species concentrations if the effects of non-ideal behavior or mixing of polymerized units are included, or by allowing for the presence of several different types of anhydrous species.
\r\n\r\nA thermodynamic model for hydrous albitic melts has been developed based on the assumption that the activity of water in the melt is equal to the mole fraction of molecular water determined by infrared spectroscopy. This model can account for the position of the water-saturated solidus of crystalline albite, the pressure and temperature dependence of the solubility of water in albitic melt, and the volumes of hydrous albitic melts. To the extent that it is successful, this approach provides a direct link between measured species concentrations in hydrous albitic glasses and the macroscopic thermodynamic properties of the albite-water system.
\r\n\r\nThe approach taken in modelling the thermodynamics of hydrous albitic melts has been generalized to other silicate compositions. Spectroscopic measurements of species concentrations in rhyolitic and simple silicate glasses quenched from melts equilibrated with water vapor provide important constraints on the thermodynamic properties of these melt-water systems. In particular, the assumption that the activity of water is equal to the mole fraction of molecular water has been tested in detail and shown to be a valid approximation for a range of hydrous silicate melts and the partial molar volume of water in these systems has been constrained. Thus, the results of this study provide a useful thermodynamic description of hydrous melts that can be readily applied to other melt-water systems for which spectroscopic measurements of the H-bearing species are available.
" }, { "name": "Stork, Christof", "degree": "PhD", "year": "1988", "title": "Ray Trace Tomographic Velocity Analysis of Surface Seismic Reflection Data", "advisor": "Clayton, Robert W.; Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08232012-133835865", "creators": [ { "name": { "family": "Stork", "given": "Christof" }, "id": "Stork-Christof", "display_name": "Stork, Christof" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "co-advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Keller", "given": "Herbert Bishop" }, "id": "Keller-H-B", "role": "member", "display_name": "Keller, Herbert Bishop" }, { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "member", "display_name": "Tanimoto, Toshiro" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/73RH-5N25", "abstract": "Recent development of two technologies allows application of a generalized formulation of travel time inversion to very large data sets, such as the surface reflection surveys collected for oil exploration. This generalized formulation uses very small cell sizes, effectively eliminating discretization effects. Inversion of an effective continuum that has no built-in a priori constraints is what places this technique in the category of tomography.
\r\n\r\nIn reflection surveys, the generalized formulation investigated here treats the continuous velocity field independently from the reflector locations. The a priori assumption, common with travel time inversions in seismic exploration data, is thus not made: that the velocity field is defined as a series of layers with constant or smoothly varying velocity. This assumption restricts significant velocity variations to occur only at reflector locations. Velocity parameterized as layers is merely one of many geologic constraints that can be added optionally in tomographic inversion.
\r\n\r\nThe technologies that enable this generalized approach to travel time inversion are: 1) a computer program capable of tracing rays through a 2-dimensional grid of points and off reflectors with structure, and 2) iterative schemes that efficiently perform damped, constrained generalized matrix inversions over a user-specified wide eigenvalue range for very large model and data sizes. An argument is presented that a variation of Richardson's iteration is preferred to the Conjugate Gradient Iterative Method for performing the matrix inversion.
\r\n\r\nWith this generalized formulation, Ray Trace Tomography is a first approach to tomographic transmission analysis. Travel times and ray paths are a valid approximation to the wave equation for broad velocity variations. The method efficiently addresses the characteristics of more general but much more expensive transmission techniques. For example, Ray Trace Tomography demonstrates that an iterative application of a transmission velocity analysis technique, tomography, and a scattering reflector location technique, migration, do not necessarily converge to the optimal solution. To resolve the ambiguity between velocity-reflector depth, velocity and reflector locations must be coupled in one inversion technique. Ray Trace Tomography is able to couple the two. Using it to indicate the absolute resolution between velocity and reflector depth, we find that for certain geometries, reflector depths cannot be resolved where most recorded energy travels within 45\u00b0 of vertical.
\r\n\r\nPoor resolution of the velocity-reflector depth ambiguity and other problems are inherent to reflection surveys. These problems also exist for other transmission techniques and can be solved only through use of inversion constraints. Ray Trace Tomography can test constraints for possible use in other transmission techniques efficiently.
\r\n\r\nRay Trace Tomography has difficulty with non-linearities caused by some types of starting model errors, such as small-scale reflector structure. Improved performance with non-linearities is an objective we should seek in other transmission techniques.
\r\n\r\nNot only is Ray Trace Tomography a useful intellectual exercise as a preliminary analysis of transmission inversion, but in many cases it is a viable technique for addressing serious problems with surface seismic reflection data. It can determine an accurate two-dimensional velocity field for migration, such as in the case of gas pockets or fault blocks. In addition, it can resolve between certain velocity and reflector ambiguities such as those occuring in the permafrost region of Alaska.
\r\n\r\nAs a comparatively efficient technique, Ray Trace Tomography can serve as a tool for interactive interpretation. The geologist can use the ray tracing to compare various geologic models with the data and then use the inversion to fine-tune the models. The inversion enables the geologist to formulate his geologic knowledge as constraints in the inversion. By analyzing the inversion results, the interpreter will develop an understanding of the validity of the various models and the resolution amoung them.
" }, { "name": "Svendsen, Robert Frederik, Jr.", "degree": "PhD", "year": "1988", "title": "Optical Radiation from Shock-Compressed Materials", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:04192010-095015524", "creators": [ { "name": { "family": "Svendsen", "given": "Robert Frederik, Jr." }, "id": "Svendsen-Robert-Frederik-Jr", "display_name": "Svendsen, Robert Frederik, Jr." } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Corngold", "given": "Noel Robert" }, "id": "Corngold-N-R", "role": "member", "display_name": "Corngold, Noel Robert" }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "geophys" ], "doi": "10.7907/m809-aq12", "abstract": "Recent observations of shock-induced radiation from oxides, silicates and metals of geophysical interest constrain the shock-compressed temperature of these materials. In these experiments, a projectile impacts a target consisting of a metal driver plate, metal film or foil layer, and transparent window. We investigate the relationships between the temperature inferred from the observed radiation and the temperature of the shock-compressed film or foil and/or window. Changes of the temperature field in each target component away from that of their respective shock-compressed states occur because of: 1) shock-impedance mismatch between target components, 2) thermal mismatch between target components, 3) surface roughness at target interfaces, and 4) conduction within and between target components. In particular, conduction may affect the temperature of the film/foil-window interface on the time scale of the experiments, and so control the intensity and history of the dominant thermal radiation sources in the target. We use this type of model to interpret the radiation emitted by a variety of shock-compressed materials and interfaces.
\r\n\r\nIn a series of experiments on films (~ 1 \u03bcm thick) and foils (~ 10-100 \u03bcm thick) of Fe in contact with Al\u2082O\u2083 and LiF windows, Fe at Fe-Al\u2082O\u2083 interfaces releases from experimental shock-compressed states between 245 and 300 GPa to interface states at pressures between 190 and 230 GPa, respectively, and temperatures between 4000 and 8000 K, respectively. These temperatures are \u2248 200-1500 K above model calculations for Fe experiencing no reshock at ideal (smooth) Fe-Al\u2082O\u2083 interfaces. We attribute this discrepancy to localized dissipation at the Fe-Al\u2082O\u2083 interface, producing higher interface temperatures than uniform compression and energy transfer. This behavior is observed for both Fe foils and films. Both 190 GPa, localized heating due to gaps or interface-surface roughness does not apparently affect the temperature of Fe-Al\u2082O\u2083 interfaces. In contrast, from the same range of shock states, Fe at Fe-LiF interfaces releases to states between 130 and 160 GPa (because it has a lower shock impedance than Al\u2082O\u2083); both the data and model imply that Fe-LiF interfaces respond ideally to shock-compression up to 140 GPa (where the data end). Both the Fe-Al\u2082O\u2083 data and the model suggest that the degree of reshock and localized heating is strongly pressure-dependent above the solid Fe-liquid Fe phase boundary. LiF appears to be a more ideal window than Al\u2082O\u2083 also because it is a poorer thermal inertia (i. e., k\u03c1cP, where k is the thermal conductivities, \u03c1 is the mass density, and cP is the specific heat at constant pressure) match to Fe than is Al\u2082O\u2083.
\r\n\r\nIn the absence of energy sources and significant energy flux from other parts of the target, the rate of change of the film/window or foil/window, interface temperature, dTINT(t)/dt, is proportional to -\u03bcexp(-\u03bc\u00b2), where \u03bc \u2261 \u03b4FW/2\u221a(\u03baFt), \u03b4FW is the thickness of the high-temperature (reshocked) zone in the film/foil layer at the film/foil-window interface, \u03baF, is the thermal diffusivity of the film/foil material, and 0 \u2264 t \u2264 texp (texp is the time scale of the experiment, 200- 400 ns). On this basis, the temperature of a thin (\u03b4FW << 2\u221a(\u03baFtexp) reshocked layer relaxes much faster than that of a thick (\u03b4FW >> 2\u221a(\u03baFtexp)) layer. We estimate \u221a(\u03baFtexp) ~ 10 \u03bcm for Fe under the conditions of Fe-Al\u2082O\u2083 and Fe-LiF interfaces at high pressure. In this case, a 100-\u03bcm-thick reshocked Fe layer would relax very little, remaining near TINT(0) on the time scale of the experiment, while a 1-\u03bcm-thick reshocked Fe layer would relax on a time scale of \u227e 10 nsec, which is much less than texp, to a temperature just above TINT(\u221e), i.e., the temperature of the ideal (smooth) interface.
\r\n\r\nGreybody model fits to radiation from an Fe film-Al\u2082O\u2083 interface resolve a gradually increasing effective greybody emissivity, \u03b5̂gb(t), and a gradually decreasing greybody temperature, Tgb(t). This behavior is characteristic of most Fe-Al\u2082O\u2083 interface experiments. The decrease of Tgb(t) can be explained in terms of the reshock model for the film/foil-window interface temperature, TINT(t). For this experiment, the model implies that the thickness of the reshocked film layer, \u03b4FW, is approximately equal to the conduction length scale in the film, \u221a(\u03baFtexp) (~10 \u03bcm for Fe). Further, assuming 1) Tgb(t) = TINT(t), 2) the thermal inertia of the film is an order of magnitude less than the window, and \u03b4FW \u227e 2\u221a(\u03baFtexp), the greybody constrains the temperature rise due to localized heating through reshock \u0394TFW to \u227e 2000K. A slight decrease of the Al\u2082O\u2083 absorption coefficient upon shock compression can explain the slight increase of \u03b5̂gb(t) with time; this may be consistent with the low-pressure observation that the refractive index of Al\u2082O\u2083 seems to decrease with pressure.
\r\n\r\nIn contrast to the Fe-Al\u2082O\u2083 results, greybody fits to radiation from an Fe foil-LiF interface show a relatively constant greybody temperature, and a decreasing greybody emissivity. The constant greybody temperature implies a constant interface temperature, as expected for an interface experiencing minimal reshock, while the decaying \u03b5̂gb(t) is consistent with a shock-induced increase in the absorption coefficient of LiF. Setting TINT(0) = Tgb(0), we fit a simplified version of the full radiation model to these data and obtain an estimate of the absorption coefficient (~100 m\u207b\u00b9) of LIF shock-compressed to 122 GPa.
\r\n\r\nShock-compressed MgO radiates thermally at temperatures between 2900 and 3700 K in the 170-200 GPa pressure range. A simple energy-transport model of the shocked-MgO-targets allows us to distinguish between different shock-induced radiation sources in these targets and to estimate spectral absorption-coefficients, a\u03bbMgO, for shocked MgO (e.g., at 203 GPa, a\u03bbMgO ~ 6300, 7500, 4200 and 3800 m\u207b\u00b9, at 450, 600, 750 and 900 nm, respectively). The experimentally inferred temperatures of the shock-compressed states of MgO are consistent with temperatures calculated for MgO, assuming that 1) it deforms as an elastic fluid, 2) it has a Dulong-Petit value for specific heat at constant volume in its shocked-state, 3) it undergoes no phase transformation below 200 GPa, and 4) the product of the equilibrium thermodynamic Gruneisen's parameter, \u03b3, and the mass density, \u03c1, is a constant and equal to 4729.6 kg/m\u00b3.
\r\n\r\nOptical radiation from shock-compressed crystal CaMgSi\u2082O\u2086 (diopside) constrains crystal CaMgSi\u2082O\u2086 Hugoniot temperatures of 3500-4800 K in the 150-170 GPa pressure range, while glass CaMgSi\u2082O\u2086, with a density 87% of that of crystal CaMgSi\u2082O\u2086, achieves Hugoniot temperatures of 3600-3800 K in the 105-107 GPa pressure range. The radiation history of each of these materials implies that the shock-compressed states of each are highly absorptive, with effective absorption coefficients of \u2273 500-1000 m\u207b\u00b9. Calculated Hugoniot states for these materials, when compared to the experimental results, imply that crystal CaMgSi\u2082O\u2086 Hugoniot states in the 150-170 GPa range represent a high-pressure phase (HPP) solid (or possibly liquid) phase with an STP density of \u2248 4100 \u00b1 200 kg/m\u00b3, STP Gr\u00fcneisen's parameter of \u2248 1.5 \u00b1 0.5 and STP HPP-LPP specific internal energy difference, \u0394ei\u03b2-\u03b1, of 0.9 \u00b1 0.5 MJ/kg. These results are consistent with a CaSiO\u2083-MgSiO\u2083 perovskite high-pressure phase assemblage. For glass CaMgSi\u2082O\u2086, we have the same range of HPP properties, except that \u0394ei\u03b2-\u03b1, is 2.3 \u00b1 0.5 MJ/kg, a strong indication that the glass CaMgSi\u2082O\u2086 Hugoniot states occupy the liquid phase in the system CaMgSi\u2082O\u2083. Comparison of the pressure-temperature Hugoniot of crystal CaMgSi\u2082O\u2086 with the Hugoniots of its constituent oxides (i.e., SiO\u2082, CaO and MgO) demonstrates the primary influence of the HPP STP density of these materials on the magnitude of the temperature in their shock-compressed states. The crystal Di pressure-temperature Hugoniot constrained by the experimental results lies at 2500-3000 K between 110 and 135 GPa, within the plausible range of temperature profiles in the mantle near the core-mantle boundary.
\r\n\r\nIn the context of the above model considerations, we constrain the Hugoniot temperature of Fe shock-compressed to 300 GPa via thermal radiation from the Fe film/foil-window interfaces discussed above. The temperature of the film/foil-window interface is obtained from measurements of the spectral radiance of the interface, for the duration of the shock transit through the window, using a 4-wavelength optical radiometer. The model indicates that the experimental observations constrain the interface temperature, rather than the the temperature of the Al\u2082O\u2083 or LiF windows. Our results further imply that Al\u2082O\u2083 remains at least partially transparent to at least 230 GPa and ~ 9,000 K. Without correcting the Hugoniot temperatures inferred from the interface temperatures for the effects of reshock, we infer a melting temperature of Fe along its Hugoniot of 6700 \u00b1 400 K at 243 GPa. Combining these estimates with the lower-pressure (\u2264 100 GPa) static Fe melting data of Williams and Jeanloz (1986), we infer a melting temperature for Fe of approximately 7800 \u00b1 500 K at the pressure of the Earth's outer-inner boundary. Assuming that Fe or an Fe-light element alloy is forming the inner core from an Fe-light element mixture in the liquid outer core, this temperature also represents an upper bound to the temperature at the outer-inner core boundary.
\r\n\r\nLiquid-state and solid-state model fits to melting data for Fe, FeS and FeO provide constraints for calculating ideal phase relations in Fe-FeS and Fe-FeO systems in the pressure range corresponding to the earth's outer core. The liquid-state model fit to the Fe melting data of Williams and Jeanloz (1986) places constraints on the temperature and other properties along the liquidus above the range of their data. The temperature along the best-fit Fe liquidus is 5000 K at 136 GPa and 7250 K at 330 GPa, which is somewhat lower than that implied by the Hugoniot results (~ 7800 K). This discrepancy may be due to the reshock effect discussed above, or some inaccuracy in the extrapolation, presuming the Hugoniot results represent the equilibrium melting behavior of Fe. Constraints on the solidi of FeS and FeO from the comparison of data and solid-state model calculations imply that FeS and FeO melt at approximately 4610 K and 5900 K, respectively, at 136 GPa, and approximately 6150 K and 8950 K, respectively, at 330 GPa. Calculations for the equilibrium thermodynamic properties of solid and liquid Fe along the coincident solidus and liquidus imply that the entropy of melting for Fe is approximately independent of pressure at a value of approximately R (where R is Ryberg's constant), while the change in the molar heat capacity across the transition increases with pressure from approximately 0.5 R to 4R between standard pressure and 330 GPa. We use these constraints to construct ideal-mixing phase diagrams for Fe-FeS and Fe-FeO systems at outer core pressures, assuming that Fe and FeS, or Fe and FeO, respectively, are the solid phases in equilibrium with the liquid Fe-FeS or Fe-FeO mixtures, respectively.
\r\n\r\nThe composition of the Fe-X (X = 0 or S) liquid mixture relative to the eutectic composition of the Fe-FeX system determines whether Fe or FeX will solidfy at the liquidus. For these ideal mixing calculations, the eutectic composition is controlled by the ratio of the end-member (i.e., Fe and FeX) melting temperatures at a given pressure. If Fe and FeX have the same melting temperature, for example, the eutectic composition is 25 mole % X; if the melting temperature of FeX is greater or less than Fe, the eutectic composition will be displaced to more Fe or FeX rich compositions, respectively. Since, as quoted above, the melting temperature of FeO is about 1500 K greater than that of Fe at 330 GPa, which is in turn about 1000 K greater than that of FeS at this pressure, we note that calculated Fe-FeO eutectic compositions at 330 GPa (15-20 mole % O) are less than 25 mole % O, while calculated Fe-FeS eutectic compositions at 330 GPa (23-30 mole % S) are generally greater than 25 mole % S. The mass density of the Earth's outer core just above the inner core boundary is approximately 12160 kg/m\u00b3, and we note that this is also the density of an ideal mixture of 93 mole % Fe and 7 mole % S (i.e., 14 mole % FeS), and a similar mixture of approximately 72 mole % Fe and 28 mole % 0 (56 mole % FeO). Consequently, these calculations and considerations imply that an O-rich outer core is more likely to lie on the FeO-rich side of the Fe-FeX eutectic, while an S-rich outer core is more likely to lie on the Fe-rich side of the Fe-FeX eutectic.
\r\n\r\nThe temperature of the Fe-FeS eutectic is lower than the Fe-FeO eutectic, being approximately 5000 K at 330 GPa. Note that the eutectic temperature represents a lower bound to temperatures at the outer-inner core boundary under the hypothesis that this boundary represents the liquidus in an Fe-X mixture. Eutectic and end-member melting temperatures in both the Fe-FeS and Fe-FeO systems imply, in the context of the outer-inner core boundary-phase boundary hypothesis, that previous widely-accepted temperature profiles for the outer core, ranging from \u227e 3000 K at the 136 GPa, the core-mantle boundary, to \u227e 4200 K at 330 GPa, the outer-inner core boundary, are about 1000-1500 K too low. This possibility implies that at least one boundary layer of 1000-1500 K exists in the mantle, possibly at its base in the D\" region.
" }, { "name": "Zhang, Jiajun", "degree": "PhD", "year": "1988", "title": "Determination of Source Finiteness and Depth of Large Earthquakes", "advisor": "Hager, Bradford H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03202013-144322900", "creators": [ { "name": { "family": "Zhang", "given": "Jiajun" }, "id": "Zhang-Jiajun", "display_name": "Zhang, Jiajun" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." } ], "committee": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Lorenz", "given": "Jens" }, "id": "Lorenz-Jens", "role": "member", "display_name": "Lorenz, Jens" } ], "option_major": [ "geophys" ], "doi": "10.7907/jnbk-0b27", "abstract": "In this thesis, a method to retrieve the source finiteness, depth of faulting, and the mechanisms of large earthquakes from long-period surface waves is developed and applied to several recent large events.
\r\n\r\nIn Chapter 1, source finiteness parameters of eleven large earthquakes were determined from long-period Rayleigh waves recorded at IDA and GDSN stations. The basic data set is the seismic spectra of periods from 150 to 300 sec. Two simple models of source finiteness are studied. The first model is a point source with finite duration. In the determination of the duration or source-process times, we used Furumoto's phase method and a linear inversion method, in which we simultaneously inverted the spectra and determined the source-process time that minimizes the error in the inversion. These two methods yielded consistent results. The second model is the finite fault model. Source finiteness of large shallow earthquakes with rupture on a fault plane with a large aspect ratio was modeled with the source-finiteness function introduced by Ben-Menahem. The spectra were inverted to find the extent and direction of the rupture of the earthquake that minimize the error in the inversion. This method is applied to the 1977 Sumbawa, Indonesia, 1979 Colombia-Ecuador, 1983 Akita-Oki, Japan, 1985 Valparaiso, Chile, and 1985 Michoacan, Mexico earthquakes. The method yielded results consistent with the rupture extent inferred from the aftershock area of these earthquakes.
\r\n\r\nIn Chapter 2, the depths and source mechanisms of nine large shallow earthquakes were determined. We inverted the data set of complex source spectra for a moment tensor (linear) or a double couple (nonlinear). By solving a least-squares problem, we obtained the centroid depth or the extent of the distributed source for each earthquake. The depths and source mechanisms of large shallow earthquakes determined from long-period Rayleigh waves depend on the models of source finiteness, wave propagation, and the excitation. We tested various models of the source finiteness, Q, the group velocity, and the excitation in the determination of earthquake depths.
\r\n\r\n\r\nThe depth estimates obtained using the Q model of Dziewonski and Steim (1982) and the excitation functions computed for the average ocean model of Regan and Anderson (1984) are considered most reasonable. Dziewonski and Steim's Q model represents a good global average of Q determined over a period range of the Rayleigh waves used in this study. Since most of the earthquakes studied here occurred in subduction zones Regan and Anderson's average ocean model is considered most appropriate.
\r\n\r\nOur depth estimates are in general consistent with the Harvard CMT solutions. The centroid depths and their 90 % confidence intervals (numbers in the parentheses) determined by the Student's t test are: Colombia-Ecuador earthquake (12 December 1979), d = 11 km, (9, 24) km; Santa Cruz Is. earthquake (17 July 1980), d = 36 km, (18, 46) km; Samoa earthquake (1 September 1981), d = 15 km, (9, 26) km; Playa Azul, Mexico earthquake (25 October 1981), d = 41 km, (28, 49) km; El Salvador earthquake (19 June 1982), d = 49 km, (41, 55) km; New Ireland earthquake (18 March 1983), d = 75 km, (72, 79) km; Chagos Bank earthquake (30 November 1983), d = 31 km, (16, 41) km; Valparaiso, Chile earthquake (3 March 1985), d = 44 km, (15, 54) km; Michoacan, Mexico earthquake (19 September 1985), d = 24 km, (12, 34) km.
\r\n\r\nIn Chapter 3, the vertical extent of faulting of the 1983 Akita-Oki, and 1977 Sumbawa, Indonesia earthquakes are determined from fundamental and overtone Rayleigh waves. Using fundamental Rayleigh waves, the depths are determined from the moment tensor inversion and fault inversion. The observed overtone Rayleigh waves are compared to the synthetic overtone seismograms to estimate the depth of faulting of these earthquakes. The depths obtained from overtone Rayleigh waves are consistent with the depths determined from fundamental Rayleigh waves for the two earthquakes. Appendix B gives the observed seismograms of fundamental and overtone Rayleigh waves for eleven large earthquakes.
" }, { "name": "Astiz Delgado, Luciana Maria de Los Angeles", "degree": "PhD", "year": "1987", "title": "I. Source Analysis of Large Earthquakes in Mexico. II. Study of Intermediate-Depth Earthquakes and Interplate Seismic Coupling", "advisor": "Hager, Bradford H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08222012-144207263", "creators": [ { "name": { "family": "Astiz Delgado", "given": "Luciana Maria de Los Angeles" }, "id": "Astiz-Delgado-Luciana-Maria-de-Los-Angeles", "display_name": "Astiz Delgado, Luciana Maria de Los Angeles" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." } ], "committee": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "chair", "display_name": "Hager, Bradford H." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geophys" ], "doi": "10.7907/278K-HZ75", "abstract": "Along the coast of Mexico and Central America several seismic gaps were defined by the timing, location and extent of large earthquakes. Among these regions with high seismic potential, the Ometepec and Michoacan gaps have broken since 1980. The 1982 Ometepec doublet and the 1981-1986 Michoacan sequence are studied in detail in Part I.
\r\n\r\nThe seismic moment of each of the Ometepec doublet events is 2.8 x 1026 dyne cm. The first event involved a deeper asperity (at 20 km) that caused an incremental stress change large enough to trigger the second event at shallower depth. The second event is best modeled by two sources at 15 and 10 km depth. T he largest event of the Michoacan sequence occurred on September 19, 1985 (Mw = 8.0) and caused extensive structural damage and death to over ten thousand people in Mexico City. The first event of the sequence was the 1981 Playa Azul event, which broke the central part of the gap. It is 27 km deep and has a seismic moment of 7.2 x 1027 dyne cm. The seismic moment of the September 19, 1985 earthquake was released in two distinct events with the rupture starting in the northern portion of the seismic gap and propagating 95 km to the southeast with low moment release through the area already broken by the 1981 Playa Azul earthquake. The rupture propagated 125 km further southeast with an Mw = 7.5 event on September 21, 1985. Another aftershock occurred on April 30, 1986, 50 km to the northwest of the September 19 mainshock. The most recent Michoacan events are shallower, 17-22 km, than the Playa Azul earthquake, which has a higher stress drop suggesting a higher stress level at greater depths in the Michoacan gap. The slip vectors of these events are consistent with the convergence direction of the Cocos and North American plates.
\r\n\r\nPart II investigates the relation of intermediate-depth earthquakes to the shallower seismicity, especially since these events may reflect the state of inter-plate coupling at subduction zones. A catalog of earthquake focal mechanisms was gathered, which includes all events listed by NOAA and ISC catalogs with M > 6 and depth between 40 to 200 km, that occurred between 1960 and 1984. The final catalog includes a total of 335 events; 47 were determined by this study. Focal mechanism solutions for intermediate-depth earthquakes with M > 6.8 can be grouped into four : 1) Normal-fault events (44%), and 2) reverse-fault events (33%), both with a strike nearly parallel to the trench axis. 3) Normal or reverse fault events with a strike significantly oblique to the trench axis (10%) and 4) tear faulting events (13%).
\r\n\r\nSimple models of plate coupling and geometry suggest that Type 1 events occur at strongly coupled plate boundaries where a down-dip extensional stress prevails in a gently dipping plate. Continental loading may be another important factor. In contrast, large normal fault earthquakes occur at shallow depths in subduction zones that are decoupled. Type 2 events with strike subparallel to the subduction zone, most of them with near vertical tension axis, occur mainly in regions that have partially coupled or uncoupled subduction zones and the observed continuous seismicity\r\nis deeper than 300 km. In terms of our simple model, the increased dip of the downgoing slab associated with weakly coupled subduction zones and the weight of the slab may induce near vertical tensional stress at intermediate depth and, consequently, the change m focal mechanism from Type 1 to Type 2 events. Events of Type 3 occur where the trench axis bends sharply, causing horizontal extensional or compressional intraplate stress. Type 4 are hinge faulting events.
\r\n\r\nWe also investigate the temporal variation of the mechanism of large intraplate earthquakes at intermediate depths in relation to the occurrence of large underthrusting earthquakes in Chile. Focal mechanisms were determined for three large events (March 1, 1934: M = 7.1, d = 120 km, April 20, 1949: M = 7.3, d = 70 km and May 8, 1971: Mw = 7.2, d = 150 km), which occurred down-dip of the great 1960 Chilean earthquake (Mw = 9.5) rupture zone. The 1971 event is down-dip compressional, whereas the 1949 and the 1934 earthquake focal mechanisms are consistent with a down-dip te nsional mechanism. Published fault plane solutions of large intermediate-depth earthquakes (March 28, 1965 and November 7, 1981), which occurred down-dip of the Valparaiso earthquakes of 1971 (Mw = 7.8) and 1985 (Mw = 8.0) are also down-dip tensional. These results suggest that before a major thrust earthquake, the interplate boundary is strongly coupled and the subducted slab is under tension at intermediate depths; after the occurrence of an interplate thrust event, the displacement on the thrust boundary induces transient compressional stress at intermediate depth in the downgoing slab. This interpretation is consistent with the hypothesis that temporal variations of focal mechanisms of outer-rise events are due to changes of interplate coupling.
\r\n\r\nThe variation of intermediate-depth earthquake focal mechanisms with M \u2265 6 is examined region by region in relation to local variations of the strength of interplate coupling. In summary, regions that are mostly uncoupled present down-dip tensional stresses in a steeply-dipping slab probably induced by the negative buoyancy of the subducted lithosphere (e.g., North Scotia arc). Double seismic zones may be present in\r\npartially coupled regions in response to un bending of the downgoing slab (e.g., Northeast Japan). Lateral bending or tearing of the slab influences the stress distribution within the subducted plate (e.g., New Ireland). Subduction of topographic highs may also change the interplate coupling locally (e.g., Louiville ridge in T onga). Regions that are mostly coupled are generally shallow dipping and the observed continuous seismicity is at most 300 km deep. In these regions normal faulting events occur at the base of the coupled region (e. g. South America). In contrast, normal faulting events occur at the trench axis at uncoupled regions where the strains due to bending of the plate are largest. Temporal variations in the interplate coupling due to the occurrence of large thrust events at the plate boundary are suggested in several regions such as Middle America and Chile.
" }, { "name": "Brugman, Melinda Mary", "degree": "PhD", "year": "1987", "title": "Water Flow at the Base of a Surging Glacier", "advisor": "Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechETD:etd-07192006-093757", "creators": [ { "name": { "family": "Brugman", "given": "Melinda Mary" }, "id": "Brugman-Melinda-Mary", "display_name": "Brugman, Melinda Mary" } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "co-chair", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "co-chair", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Meier", "given": "Mark" }, "id": "Meier-M", "role": "member", "display_name": "Meier, Mark" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geol" ], "doi": "10.7907/VSHG-G674", "abstract": "Water tracing experiments were successfully conducted over a distance of ten kilometers along the base of Variegated Glacier for the purpose of characterizing the water drainage system of the glacier in the surging as compared to the non-surging state. Three tracing experiments were conducted, and fluorescent dyes, Rhodamine WT and Tinopal AMS, were injected into boreholes at separate locations. The two Rhodamine WT experiments were conducted over a 10 km distance, both during the most rapid surging motion of the glacier, and after its cessation.
\r\n\r\nIn each experiment, the terminus streams were monitored for stream discharge, sediment content and tracer concentration. Rhodamine WT tracer was significantly adsorbed on the suspended sediment, particularly during the surge. The adsorption behavior followed the Langmuir model, and calculated distribution coefficients of Kd = 100 to 1000 ml/g were measured for during the glacier surge. The Kd values measured after the surge were lower than during the surge by a factor of 10 to 1000. The much higher Kd values in the surging as compared to non-surging glacier states can be best explained by a factor of 10 to 1000 decrease in the modal and/or mean grain-size of the suspended sediment. The abundance of fine-grained sediment during the surge is probably due to increased grinding of rock material at the glacier bed.
\r\n\r\nTheoretical models of tracer dispersion in a single tunnel, were compared to models of dispersion in linked-cavity systems to infer the details of water flow at the glacier bed. The broad, roughly symmetrical, dye-return curve measured during the glacier surge conforms to diffusive dispersion theory, and differs sharply from the highly asymmetrical dispersion curve measured after the surge. Results indicate the dispersion behavior, and calculated Manning roughness, of the post-surge Variegated Glacier is similar to those of glaciers that do not surge. The drainage system of the Variegated Glacier in the surging state is consistent with a model of tracer dispersion in an interconnecting network of conduits and cavities, and is strikingly different from the tunnel system indicated for the non-surging state.
\r\n" }, { "name": "Friedson, Andrew James", "degree": "PhD", "year": "1987", "title": "I. Meridional Energy Balance of Uranus. II. Viscosity of Rock-Ice Mixtures. III. The Thermosphere of Titan", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01292013-151449809", "creators": [ { "name": { "family": "Friedson", "given": "Andrew James" }, "id": "Friedson-Andrew-James", "display_name": "Friedson, Andrew James" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/65ch-hj35", "abstract": "Part I:
\r\n\r\nThe seasonal meridional energy balance and thermal structure of the atmosphere of Uranus is investigated using a two-dimensional radiative-convective-dynamical model. Diurnal-average temperatures and heat fluxes are calculated as a function of pressure, latitude, and season. In addition to treating radiation and small-scale convection in a manner typical of conventional radiative-convective models, the dynamical heat fluxes due to large-scale baroclinic eddies are included and parameterized using a mixing length formulation (Stone, 1972; Ingersoll and Porco, 1978). The atmosphere is assumed to be bounded below by an adiabatic, fluid interior with a single value of potential temperature at all latitudes. The internal heat flux is found to vary with latitude and season. The total internal power and the global enthalpy storage rate are seen to oscillate in phase with a period of 1/2 Uranian year. On an annual-average basis, equatorward heat transport can take place in both the atmosphere and the convective interior. For a weak internal heat source, the meridional transport takes place predominantly in the atmosphere. If the internal heat source is larger, a greater share of the transport is taken up by the interior. For a value of the internal heat near the current upper limit for Uranus (~27% of the absorbed sunlight), about 1/3 of the equatorward heat transport at mid-latitudes occurs in the interior. For a given internal heat source, placing the peak of the solar heating at high altitudes or depositing the solar energy into a narrow altitude range favors heat transport by the atmosphere over the interior. Deep penetration of sunlight favors transport by the interior. For the time corresponding to the Voyager 2 Uranus encounter, the effective temperature at the south (sunlit) pole is calculated to be ~1.5 K higher than that at the equator. Horizontal contrasts of the mean 450-900 mbar temperature are found to be less than \u2264 1.5 K, in fair agreement with Voyager 2 IRIS results (Hanel et al., 1986), but the model fails to reproduce the local minimum in this temperature seen at 30\u00b0S. Nevertheless, it is concl uded that meridional heat transport in the atmosphere is efficient in keeping seasonal horizontal temperature contrasts below those predicted by radiative-convective models (Wallace, 1983).
\r\n\r\nPart II:
\r\n\r\nTheory and experiments are used to establish lower and upper bounds on the ratio of actual viscosity to pure ice viscosity for a suspension of rock particles in a water ice matrix. For typical conditions encountered in icy satellites, this ratio is of order ten or possibly larger, depending on unknown factors such as the particle size distribution. It is shown that even this modest increase in viscosity may be enough to have caused a failure of solidstate convective self-regulation early in the evolution of a homogeneous, rock-water ice satellite, provided the satellite is large enough and sufficiently silicate-rich. The criteria for this failure are satisfied by Ganymede and are marginal for Callisto, if the silicates are hydrated. Failure of self-regulation means that the viscosity is too high for the interior to remain completely solid and eliminate the heat production of long-lived radioisotopes by solid state convection. Partial melting of the ice then occurs. It is further shown that satellites of this size may then undergo runaway differentiation into a rock core and almost pure ice mantle, because the gravitational energy release is sufficient to melt nearly all the ice, and the Rayleigh-Taylor instability time scale is short. (Although the high pressure phases of ice melt, the resulting water quickly refreezes at a higher level.) We conjecture that these results explain the striking surface dissimilarity of Ganymede and Callisto, if these satellites accreted cold and undifferentiated. Ganymede may have gone supercritical (melted and differentiated) because of a failure of self-regulation, whereas Callisto remained undifferentiated to the present day. Like all proposed explanations for the Ganymede-Callisto dichotomy, this conjecture cannot be quantified with confidence, because of inadequate or incomplete observations, theory and experimental data.
\r\n\r\nPart III:
\r\n\r\nThe diurnal variation of the vertical structure of Titan's thermosphere is calculated through simultaneous solution of the equations of heat transfer and hydrostatic equilibrium. The temperature and density profiles are found above the mesopause. The dynamical response of the thermosphere to heating is for the most part neglected. Nevertheless, we are able to draw some interesting qualitative and quantitative conclusions regarding the vertical structure. Heating of the upper thermosphere occurs primarily through absorption of solar Lyman \u03b1 radiation by methane, with an additional amount of heating (\u2264 20%) due to low-energy magnetospheric electron precipitation. The heat is conducted downward to the mesopause, where it is removed by IR cooling due principally to acetylene. The mesopause is found to occur where the density is 2.2 x 1012 cm-3 (736 km) and has a temperature of ~110 K. The exospheric temperature is unlikely to exceed 225 K in the course of a Titan day. The diurnally averaged exospheric temperature is in the range 187-197 K, depending on the amount of magnetospheric electron heating that is included in the model. The amplitude of the diurnal variation is found to be \u2264 28 K. We find that the vertical extent of the hydrogen cloud is too large to be explained in terms of simple thermal escape of hydrogen from a ~225 K exosphere and conclude that other processes must be important for populating or heating the neutral torus.
" }, { "name": "Houston, Heidi Beth", "degree": "PhD", "year": "1987", "title": "Source Characteristics of Large Earthquakes at Short Periods", "advisor": "Clayton, Robert W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04162019-172034832", "creators": [ { "name": { "family": "Houston", "given": "Heidi Beth" }, "id": "Houston-Heidi-Beth", "display_name": "Houston, Heidi Beth" } ], "advisors": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "advisor", "display_name": "Clayton, Robert W." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/mqta-6t98", "abstract": "In Chapter 1, we analyzed short-period body waves recorded at teleseismic distances from great earthquakes. They provide information about source rupture processes and strong motions. First, we examined records of 19 earthquakes of moment magnitude MW of 6.5 to 9.5. Four parameters were measured from the short-period P-wave train: the maximum amplitude, the period at maximum amplitude, the time between the first arrival and when the maximum amplitude is attained, and coda length. An extension, m̂b, of the teleseismic body-wave magnitude, mb, was defined using the maximum amplitude of the entire short-period P wave rather than the amplitude achieved in the first few P-wave cycles. m̂b increases as MW increases. The time from the first arrival until the maximum amplitude is achieved and the coda length are roughly proportional to MW, but were further interpreted by a simple asperity model of the rupture process. These data support that 1 to 2 sec waves are on average generated preferentially in the same regions of the fault plane as 10 to 50 sec waves.
\r\n\r\nAn application to strong motion modeling is presented in which a 1971 San Fernando teleseismic short-period record is summed up to simulate teleseismic records produced by five great earthquakes. The summation procedure matches the moment of the event to be simulated, and includes rupture propagation, fault plane roughness, and randomness. The m̂b data provide an important constraint on the summation procedure. Thus constrained, this summation procedure can be more confidently used with near-field strong motion records as Green's functions to predict strong motions from great earthquakes.
\r\n\r\nIn Chapter 2, we analyzed the spectra of short- and intermediate-period teleseismic GDSN (digital) records for seven large earthquakes and hand-digitized short-period analog records of the 1971 San Fernando earthquake. To obtain the source or moment-rate spectrum at periods between 1 and 30 sec, we Fourier-transformed the P waves, corrected for instrument response, attenuation, geometrical spreading, and radiation pattern (including the depth phases), and then averaged the records for each event. Significant differences exist between the spectra of different events, presumably due to variations in tectonic setting or seismic coupling. Using the digital data, we also investigated the relationship between time-domain amplitude and spectral amplitude for short-period P waves. From our empirical relation between spectral amplitude and time-domain amplitude, we estimated the spectral amplitudes implied by the m̂b data. We compared our results to the \u03c9-2 and Gusev source spectral models. Neither model can completely represent the data. Nevertheless, we consider the \u03c9-2 model a useful reference model for comparing different events. The average source spectrum of six large events with MW's of 7.4 to 7.8 does not have the spectral structure suggested by Gusev.
\r\n\r\nIn Chapter 3, source characteristics of the Sept. 19, 1985 Michoacan, Mexico earthquake and its aftershock on Sept. 21 are inferred from broadband and short-period teleseismic GDSN records. We obtained the teleseismic source spectrum from 1 to 30 sec. The Michoacan source spectrum is enriched at 30 sec and depleted at 1 to 10 sec relative to an average source spectrum of large interplate subduction events. Source spectra for the Sept. 21 aftershock, 1981 Playa Azul, 1979 Petatlan, and 1978 Oaxaca events follow a trend similar to that of the 1985 Michoacan event. This spectral trend may characterize the Mexican subduction zone.
\r\n\r\nA station-by-station least-squares inversion of the Michoacan earthquake records for the source time function yields three source pulses, which we interpreted as events on the fault plane. The first two are similar in moment, and the third contains only 20% of the moment of the first. Directivity is evident in the timing. At each station, we measured the time differences between the pulses, and performed a least-squares nonlinear estimation of the strike, distance, and time separation between the events to locate them relative to one another. The second event occurred 26 sec after the first, and 82 km southeast of it, indicating southeastward rupture along the trench. The two large events are also seen in the near-field strong motions.
\r\n\r\nThe mainshock records, spectrum, and time functions contain less high frequency radiation than those of the 1985 Valparaiso, Chile earthquake. Apparently, the Michoacan earthquake ruptured two relatively smooth, strong patches which generated large 30 sec waves, but small 1 to 10 sec waves. Such behavior contrasts with the Valparaiso event which had a more complex rupture process and generated more 1 to 5 sec energy. This difference is consistent with the higher near-field accelerations recorded for the Valparaiso event.
\r\n\r\nIn Chapter 4, time functions and rupture processes of 4 recent large subduction zone earthquakes were determined from broadband teleseismic GDSN records using the iterative inversion technique of Kikuchi and Fukao. The method inverts the records simultaneously by determining the location, time, and seismic moment of a single point source that best explains the records, then subtracting the synthetics for that point source from the records, and repeating the procedure for the residual records. Using this technique with the high-quality GDSN intermediate-band records provides more details of the rupture process than have been obtained previously.
\r\n \r\nUsing the inversion, we produced maps of the spatial and temporal distribution of seismic moment release at periods of 3 to 30 sec for the 1985 Michoacan, Mexico, 1983 Akita-Oki, Japan, 1985 Valparaiso, Chile, and 1986 Andreanof Islands, Alaska earthquakes. These are four of the largest earthquakes that occurred from 1983 to 1986. Comparing the source spectra of these events yields complementary information at periods of 1 to 30 sec. These four earthquakes have distinct rupture styles.
\r\n\r\nIn Chapter 5, we compared strong motion spectra of the 1985 Michoacan, Mexico and the 1983 Akita-Oki, Japan earthquakes with their teleseismic spectra. The spectral levels of the Michoacan strong motions, which were recorded by a high-quality digital array, agree to within a factor of 2 with those predicted by the Michoacan teleseismic records. The Michoacan teleseismic spectrum is lower than that of Akita-Oki. This relationship also holds for their strong motion spectra. This consistency means that teleseismic records, which are relatively more abundant, can be used to predict properties of strong motions from large earthquakes.
" }, { "name": "Kirk, Randolph Livingstone", "degree": "PhD", "year": "1987", "title": "I. Thermal Evolution of Ganymede and Implications for Surface Features. II. Magnetohydrodynamic Constraints on Deep Zonal Flow in the Giant Planets. III. A Fast Finite-Element Algorithm for Two-Dimensional Photoclinometry", "advisor": "Goldreich, Peter Martin", "url": "https://resolver.caltech.edu/CaltechETD:etd-11142006-131417", "creators": [ { "name": { "family": "Kirk", "given": "Randolph Livingstone" }, "id": "Kirk-Randolph-Livingstone", "display_name": "Kirk, Randolph Livingstone" } ], "advisors": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "advisor", "display_name": "Goldreich, Peter Martin" } ], "committee": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "chair", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." } ], "option_major": [ "plansci" ], "doi": "10.7907/T5PT-S948", "abstract": "The work is divided into three independent papers:
\r\n\r\nPAPER I:
\r\n\r\nThermal evolution models are presented for Ganymede, assuming a mostly differentiated initial state of a water ocean overlying a rock layer. The only heat sources are assumed to be primordial heat (provided by accretion) and the long-lived radiogenic heat sources in the rock component. As Ganymede cools, the ocean thins, and two ice layers develop, one above composed of ice I, and the other below composed of high-pressure polymorphs of ice. Subsolidus convection proceeds separately in each ice layer, its transport of heat calculated using a simple parameterized convection scheme and the most recent data on ice rheology. The model requires that the average entropy of the deep ice layer exceed that of the ice I layer. If the residual ocean separating these layers becomes thin enough, then a Rayleigh-Taylor-like (\"diapiric\") instability may ensue, driven by the greater entropy of the deeper ice and merging the two ice mantles into a single convective layer. This instability is not predicted by linear analysis but occurs for plausible finite amplitude perturbations associated with large Rayleigh number convection. The resulting warm ice diapirs may lead to a dramatic \"heat pulse\" at the surface and to fracturing of the lithosphere, and may be directly or indirectly responsible for resurfacing and grooved terrain formation on Ganymede. The timing of this event depends rather sensitively on poorly known rheological parameters but could be consistent with chronologies deduced from estimated cratering rates. Irrespective of the occurrence or importance of the heat pulse, we find that lithospheric fracturing requires rapid stress loading (on a timescale \u227e 104) years). Such a timescale can be realized by warm ice diapirism, but not directly by gradual global expansion. In the absence of any quantitative and self-consistent model for the resurfacing of Ganymede by liquid water, we favor resurfacing by warm ice flows,which we demonstrate to be physically possible, a plausible consequence of our models, compatible with existing observations, and a hypothesis testable by Galileo. We discuss core formation as an alternative driver for resurfacing, and conclude that it is less attractive. We also consider anew the puzzle of why Callisto differs so greatly from Ganymede, offering several possible explanations. The models presented do not provide a compelling explanation for all aspects of Ganymedean geological evolution, since we have identified several potential problems, most notably the apparently extended period of grooved terrain formation (several hundred million years), which is difficult to reconcile with the heat pulse phenomenon.
\r\n\r\nPAPER II:
\r\n\r\nThe observed zonal flows of the giant planets will, if they penetrate below the visible atmosphere, interact significantly with the planetary magnetic field outside the metalized core. The appropriate measure of this interaction is the Chandrasekhar number Q = (H2)/(4\u03c0\u03c1\u03bd\u03b12\u03bb) (where H = radial component of the magnetic field, \u03bd = eddy viscosity, \u03bb = magnetic diffusivity, \u03b1-1 = lengthscale on which \u03bb varies); at depths where Q \u2273 1 the velocity will be forced to oscillate on a small lengthscale or decay to zero. We estimate the conductivity due to semiconduction in H2 (Jupiter, Saturn) and ionization in H2O (Uranus, Neptune) as a function of depth; the value \u03bb \u2243 1010 cm2s-1 needed for Q = 1 is readily obtained well outside the metallic core (where \u03bb \u2243 102 cm2s-1).
\r\n\r\nThese assertions are quantified by a simple model of the equatorial zonal jet in which the flow is assumed uniform on cylinders concentric with the spin axis, and the viscous and magnetic torques on each cylinder are balanced. We solve this \"Taylor constraint\" simultaneously with the dynamo equation to obtain the velocity and magnetic field in the equatorial plane. With this model we reproduce the widely differing jet widths of Jupiter and Saturn (though not the flow at very high or low latitudes) using \u03bd = 2500 cm2s-1, consistent with the requirement that viscous dissipation not exceed the specific luminosity. A model Uranian jet consistent with the limited Voyager data can also be constructed, with appropriately smaller \u03bd, but only if one assumes a two-layer interior. We tentatively predict a wide Neptunian jet.
\r\n\r\nFor Saturn (but not Jupiter or Uranus) the model has a large magnetic Reynolds number where Q = 1 and hence exhibits substantial axisymmetrization of the field in the equatorial plane. This effect may or may not persist at higher latitudes. The one-dimensional model presented is only a first step. Variation of the velocity and magnetic field parallel to the spin axis must be modeled in order to answer several important questions, including: 1) What is the behavior of flows at high latitudes, whose Taylor cylinders are interrupted by the region with Q \u2273 1? 2) To what extent is differential rotation in the envelope responsible for the spin-axisymmetry of Saturn's magnetic field?
\r\n\r\nPAPER III:
\r\n\r\nIt is shown that the problem of two-dimensional photoclinometry (PC) -- the reconstruction of a surface z(x,y) from a brightness image B(x,y) -- may be formulated in a natural way in terms of finite elements. The resulting system of equations is underdetermined as a consequence of the lack of boundary conditions for z, but a unique solution may be chosen by minimizing a function S expressing the \"roughness\" of the surface. An efficient PC algorithm based on this formulation is presented, requiring ~ 10.66 (four-byte) memory locations and ~104 floating multiplications/additions per pixel, and incorporating: 1) Minimization of the roughness by the penalty method, which yields the smallest set of equations. 2) Iterative solution of the nonlinear equations by Newton's method. 3) Solution of the linearized equations by an inner iterative cycle of successive over-relaxation, which takes advantage of the extreme sparseness of the system. 4) Multigridding, in which the solutions to the smaller problems obtained by reducing the resolution are used recursively to greatly speed convergence at the higher resolutions, and 5) A rapid noniterative initial estimate of z obtained by exploiting the special symmetry of the equations obtained in the first linearization.
\r\n\r\nThe algorithm is extensively demonstrated on 200 by 200 pixel synthetic \"images\" generated from digital topographic data for northern Utah over a range of phase angles. Rms error in the solution is ~ 22 m, out of ~ 660 m total relief. The error is dominated by \"stripes\" with the same azimuth as the light source, resulting from use of the roughness criterion in lieu of boundary conditions; the rms error along profiles parallel to the stripes is only ~ 2-8 m, depending on the phase angle. Satisfactory solutions are obtained even in the presence of quantization error, noise, and moderate blur in the image.
\r\n\r\nApplications of the PC algorithm to both remote sensing and photomicrography are sketched; a photoclinometric map of a low-relief Precambrian era fossil is presented as an example of the latter. Prospects for dealing with photometrically inhomogeneous surfaces, and an extension of the method to the analysis of side-looking radar data (\"radarclinometry\") are also discussed.
" }, { "name": "Louie, John Nikolai", "degree": "PhD", "year": "1987", "title": "Seismic Reflection Experiments Imaging the Physical Nature of Crustal Structures in Southern California", "advisor": "Allen, Clarence R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10092013-141757161", "creators": [ { "name": { "family": "Louie", "given": "John Nikolai" }, "id": "Louie-John-Nikolai", "display_name": "Louie, John Nikolai" } ], "advisors": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." } ], "committee": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "chair", "display_name": "Allen, Clarence R." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geophys" ], "doi": "10.7907/e3d2-8b93", "abstract": "Seismic reflection methods have been extensively used to probe the Earth's crust and suggest the nature of its formative processes. The analysis of multi-offset seismic reflection data extends the technique from a reconnaissance method to a powerful scientific tool that can be applied to test specific hypotheses. The treatment of reflections at multiple offsets becomes tractable if the assumptions of high-frequency rays are valid for the problem being considered. Their validity can be tested by applying the methods of analysis to full wave synthetics.
\r\n\r\nThree studies illustrate the application of these principles to investigations of the nature of the crust in southern California. A survey shot by the COCORP consortium in 1977 across the San Andreas fault near Parkfield revealed events in the record sections whose arrival time decreased with offset. The reflectors generating these events are imaged using a multi-offset three-dimensional Kirchhoff migration. Migrations of full wave acoustic synthetics having the same limitations in geometric coverage as the field survey demonstrate the utility of this back projection process for imaging. The migrated depth sections show the locations of the major physical boundaries of the San Andreas fault zone. The zone is bounded on the southwest by a near-vertical fault juxtaposing a Tertiary sedimentary section against uplifted crystalline rocks of the fault zone block. On the northeast, the fault zone is bounded by a fault dipping into the San Andreas, which includes slices of serpentinized ultramafics, intersecting it at 3 km depth. These interpretations can be made despite complications introduced by lateral heterogeneities.
\r\n\r\nIn 1985 the Calcrust consortium designed a survey in the eastern Mojave desert to image structures in both the shallow and the deep crust. Preliminary field experiments showed that the major geophysical acquisition problem to be solved was the poor penetration of seismic energy through a low-velocity surface layer. Its effects could be mitigated through special acquisition and processing techniques. Data obtained from industry showed that quality data could be obtained from areas having a deeper, older sedimentary cover, causing a re-definition of the geologic objectives. Long offset stationary arrays were designed to provide reversed, wider angle coverage of the deep crust over parts of the survey. The preliminary field tests and constant monitoring of data quality and parameter adjustment allowed 108 km of excellent crustal data to be obtained.
\r\n\r\nThis dataset, along with two others from the central and western Mojave, was used to constrain rock properties and the physical condition of the crust. The multi-offset analysis proceeded in two steps. First, an increase in reflection peak frequency with offset is indicative of a thinly layered reflector. The thickness and velocity contrast of the layering can be calculated from the spectral dispersion, to discriminate between structures resulting from broad scale or local effects. Second, the amplitude effects at different offsets of P-P scattering from weak elastic heterogeneities indicate whether the signs of the changes in density, rigidity, and Lame's parameter at the reflector agree or are opposed. The effects of reflection generation and propagation in a heterogeneous, anisotropic crust were contained by the design of the experiment and the simplicity of the observed amplitude and frequency trends. Multi-offset spectra and amplitude trend stacks of the three Mojave Desert datasets suggest that the most reflective structures in the middle crust are strong Poisson's ratio (\u03c3) contrasts. Porous zones or the juxtaposition of units of mutually distant origin are indicated. Heterogeneities in \u03c3 increase towards the top of a basal crustal zone at ~22 km depth. The transition to the basal zone and to the mantle include increases in \u03c3. The Moho itself includes ~400 m layering having a velocity higher than that of the uppermost mantle. The Moho maintains the same configuration across the Mojave despite 5 km of crustal thinning near the Colorado River. This indicates that Miocene extension there either thinned just the basal zone, or that the basal zone developed regionally after the extensional event.
\r\n" }, { "name": "Regan, Janice", "degree": "PhD", "year": "1987", "title": "Numerical Studies of Propagation of Lg Waves Across Ocean Continent Boundaries Using the Representation Theorem", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10232019-124415442", "creators": [ { "name": { "family": "Regan", "given": "Janice" }, "id": "Regan-Janice", "display_name": "Regan, Janice" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "member", "display_name": "Tanimoto, Toshiro" } ], "option_major": [ "geophys" ], "doi": "10.7907/vc5q-tp40", "abstract": "The methods for Representation Theorem (RT) coupling of finite element (FE) or finite difference calculations and Harkrider's (Harkrider 1964, 1970) propagator matrix method calculations to produce a hybrid method for propagation of SH mode sum seismograms across paths that contain regions of non plane-layered structure are explained and developed. The coupling methods explained in detail use a 2-D Cartesian FE formulation. Analogous methods for the 3-D method follow directly. Extensive tests illustrating the validity and accuracy of the implementation of these coupling methods are discussed. These hybrid techniques are developed to study the propagation of surface waves across regional transition zones or other heterogeneities that exist in part of a longer, mostly plane-layered, path. The effects of a thinning or thickening of the crustal layer on the propagation of Lg mode sum seismograms have been examined in this study. The thinning or thickening of the crustal layer is used as a simple model of ocean continent transitions. The Lg phase is of particular interest since it is used in several important applications such as mapping the extent of continental crust, magnitude determination, and discrimination between explosive and earthquake sources. The understanding of the observations that Lg wave is attenuated completely when the propagation path includes an oceanic portion of length greater than one hundred to two hundred kilometers or a region of complex crustal structure is not complete, and a clear explanation of these phenomena could have important consequences for all these types of studies. The transition model calculations done in this study show that passage through a region of thinning crustal thickness, the model for a continent to ocean transition, increases the amplitude and coda length of the Lg wave at the surface, and allows much of the modal energy trapped in the crust, which forms the Lg phase, to escape in to the subcrustal layers as body waves or other downgoing phases. The magnitude of both these effects increases as the length of the transition increases or the slope of the layer boundaries decrease. The passage of the wavefront exiting the continent to ocean transition region through the oceanic structure allows further energy to escape from the crustal layer, and produces a decrease in Lg amplitude at the surface as the length of the oceanic path increases. The amplitude decrease is maximum near the transition region and decreases with distance from it. Passage through a region of thickening crust, the model of a ocean to continent transition, causes a rapid decrease in the Lg amplitude at the surface of the crust. The energy previously trapped in the oceanic crustal layer spreads throughout the thickening crustal layer, and any amplitude which has been traveling through the subcrustal layer but has not reached depths below the base of the continental crust is transmitted back into the continental crust. The attenuation of Lg at the crustal surface along a partially oceanic path occurs in the oceanic structure and in the ocean to continent transition region . The attenuation at the surface depends in part on the escape of energy at depth through the continent to ocean transition region into the underlaying half-space. The total attenuation of Lg due to propagation through a forward transition followed by a reverse transition is at most a factor of four to six. This is inadequate to explain the observed attenuation of Lg. Thus, additional effects, other than geometry must be considered to provide a complete explanation of the attenuation of Lg.
" }, { "name": "Rudy, Donald James", "degree": "PhD", "year": "1987", "title": "Mars: High Resolution VLA Observations at Wavelengths of 2 and 6 cm and Derived Properties", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02202013-103037890", "creators": [ { "name": { "family": "Rudy", "given": "Donald James" }, "id": "Rudy-Donald-James", "display_name": "Rudy, Donald James" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" } ], "option_major": [ "plansci" ], "doi": "10.7907/3g59-p796", "abstract": "Observations of Mars at wavelengths of 2 and 6cm were made using the VLA in its A configuration. Two seasons were observed; late spring in the northern hemisphere (LS ~ 60\u00b0) and early summer in the southern summer (LS ~ 300\u00b0). The sub-earth latitudes were 25\u00b0N and 25\u00b0S, for each of these seasons respectively. So the geometry for viewing the polar region was optimal in each case. Whole-disk brightness temperatures were estimated to be 193.2 K \u00b1 1.0 at 2 cm and 191.2 K \u00b1 0.6 at 6 cm for the northern data set and 202.2 K \u00b1 l.0 at 2 cm and 195.4 K \u00b1 0.6 at 6 cm for the southern data set (formal errors only). Since measurements of the polarized flux were taken at the same time, whole-disk effective dielectric constants could be estimated and from these, estimates of sub-surface densities could be made. The results of these calculations at 2cm yielded whole-disk effective dielectric constants of 2.34 \u00b1 0.05 and 2.02 \u00b1 0.03 which imply sub-surface densities of 1.24 g cm-3 \u00b1 0.06 and 1.02 g cm-3 \u00b1 0.05 for the north and south, respectively. The same calculations at 6 cm yielded effective densities of 1.45 g cm-3 \u00b1 0.10 and 1.31 g cm-3 \u00b1 0.07 from effective dielectric constants of 2.70 \u00b1 0.09 and 2.48 \u00b1 0.06 for the north and south data sets, respectively.
\r\n\r\nFrom the mapped data these parameters were also estimated as a function of latitude between latitudes of 15\u00b0S and 60\u00b0N for the north data set; and between latitudes of 30\u00b0N and 60\u00b0S for the south data set. A region in which the brightness temperature behaves in an anomalous manner was discovered in both data sets. This region lies between about 10\u00b0S and 40\u00b0S. Here the brightness temperatures at both wavelengths in both data sets appears lower, by 4 K to 8 K, than a nominal model would predict. In addition to the effective dielectric constant and sub-surface density the radio absorption length of the sub-surface was estimated. The radio absorption length for most of these latitudes was about 15 wavelengths with formal errors on the order of 5 or 10 wavelengths. This is true for both data sets. The estimation of the effective dielectric constant at most latitudes was between 2 and 3.5 with only slight differences between the two different wavelengths. The two data sets show the same relative trends, but are off by a scaling factor.
\r\n\r\nThese estimates of the dielectric constant lead to estimation of the sub-surface densities as a function of latitude. Most calculations of the sub-surface density yielded results between 1 and 2 g cm-3 with errors on the order of 0.5 g cm-3. These results seem to imply that the sub-surface is not much different than the surface as observed by the Viking and Mariner missions. In line with this, an examination of the correlation of the dielectric constant at each wavelength with the thermal inertia, determined by the Viking infrared measurements, shows a relatively strong correlation, at both wavelengths, for the North data set. The South data set, however, shows little to nocorrelation between the radio parameters and the thermal inertia. Since the South data set is primarily composed of latitudes which contain the anomalous region, it is not suprising that the South data set shows no correlation.
\r\n\r\nIn addition, the thermal-radiative model used to estimate the above parameters was used to estimate the variability of the whole-disk brightness temperature of Mars. This was done in an effort to establish a background for those astronomers wishing to use Mars as a calibration source. The parameters investigated for their effect on the whole-disk brightness temperature of Mars were: the sub-earth longitude, the sub-earth latitude, the sub-earth time of day, the dielectric constant, and the radio absorption length. A nominal model was first created which established the variation of the brightness temperature as a function of season and radio absorption length. A nominal value of 2.2 was used for the dielectric constant, and the sub-earth latitude was set at 0\u00b0N and the sub-earth longitude was set at 75\u00b0W. The sub-earth time of day was held at noon for this nominal model. This is equivalent to a 0\u00b0 phase angle. The most important geometric factor was the sub-earth latitude. The error in estimating the whole-disk brightness temperature of Mars by using the wrong sub-earth latitude can be as large as 5 to 10%. The charts presented will be useful to estimate the whole-disk brightness temperature which the thermal model would predict. It is believed that the error in this estimate is less than or equal to 5 K.
\r\n" }, { "name": "Sanders, Christopher O'Neill", "degree": "PhD", "year": "1987", "title": "I. Seismotectonics of the San Jacinto Fault Zone and the Anza Seismic Gap. II. Imaging the Shallow Crust in Volcanic Areas with Earthquake Shear Waves", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08222018-111515553", "creators": [ { "name": { "family": "Sanders", "given": "Christopher O'Neill" }, "id": "Sanders-Christopher-O'Neill", "display_name": "Sanders, Christopher O'Neill" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "role": "chair", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Heaton", "given": "Thomas H." }, "id": "Heaton-T-H", "role": "member", "display_name": "Heaton, Thomas H." } ], "option_major": [ "geophys" ], "doi": "10.7907/aqac-eg52", "abstract": "Chapters 1, 2, and 3 consider the characteristics of the earthquake stress release along the San Jacinto fault zone and in the San Jacinto-southern San Andreas fault region. In Chapter 1 we locate the historic M \u2265 6 earthquakes in the San Jacinto fault zone. Intensity data are used to locate earthquakes in 1899, 1918, and 1923. Limited seismic data are also used for the 1923 location. Southern California stations and empirical station corrections obtained from recent small events are used to locate earthquakes in 1937, 1942, and 1954 and their aftershocks and preshocks. The locations and rupture zones of these earthquakes, including the 1968 Borrego Mountain earthquake, help define patterns of large earthquake occurrence in the fault zone and sections of fault which have not ruptured historically. One historic seismic-slip gap is located in the central San Jacinto fault zone near the town of Anza.
\r\n\r\nWe present in Chapter 2 details of the small earthquake stress release in the San Jacinto fault zone near Anza. Small earthquake epicenters near the Anza seismic gap define a 18-km quiescent segment of fault which is bounded to the northwest and southeast by areas of relatively high seismicity. Recent moderate earthquakes on and near the San Jacinto fault in the gap and their relatively depressed aftershock activity indicate that the fault is seismogenic and highly stressed but generally locked by some mechanism. The locked nature of the fault may be due to relatively high stress normal to the fault resulting from the convergent geometries of the local, active, discontinuous faults and the oblique orientation of the regional maximum compressive stress. Strain is not being relieved by aseismic fault creep. A swarm of small earthquakes in the crustal block 13 km southwest of the Anza gap beneath the Cahuilla Valley recently released stress in an area which was previously highly active before the 1918 (M 6.8) and 1937 (ML 5.9) earthquakes. The occurrence of these periods of increased seismicity near Cahuilla in the years immediately before the nearby large earthquakes and the recent swarm suggest that the ground beneath Cahuilla may be acting as a stress meter signaling the presence of high stresses before large local earthquakes. The length of the quiescent fault segment suggests potential for an earthquake of about M 6.5 if the entire segment ruptures at once.
\r\n\r\nIn Chapter 3 we investigate variations in the depths of earthquakes in the San Jacinto fault zone and in the San Jacinto-southern San Andreas fault region. We observe that the maximum depths of earthquakes in the San Jacinto fault zone vary from 20 to 10 km along strike. The earthquake hypocenters are progressively shallower nearer to the Imperial Valley region of high heat flow. This observation illustrates the effect heat flow has on the maximum thickness of the seismogenic zone. In addition, earthquakes occur predominantly in a band along the bottom of the seismogenic zone; few earthquakes occur m the shallower portions of the fault zone. This implies that shear stresses must be greater in the deeper parts of the brittle fault zone than in the shallower fault zone. This implies that loading of the brittle crust occurs by aseismic displacement along deeper extensions of the brittle fault zones. Furthermore, we observe that deeper earthquakes in the region of the San Jacinto and southern San Andreas faults occur principally in the major fault zones and that shallow earthquakes occur principally in the adjacent crust. Interpretation of these observations is less clear, but they, in combination with other observations about deep and shallow earthquakes near Anza on the San Jacinto fault, seem to suggest that stresses in the deep brittle fault zone and in the adjacent crust are similar and that stresses in the shallow fault zone are low.
\r\n\r\nIn Chapter 4 shear-wave seismograms are used to image anomalous attenuation regions in the shallow crust beneath the Coso volcanic/geothermal region of eastern California. Vertical-component seismograms archived by CUSP (Caltech-USGS Seismic Processor) for earthquakes which occurred in the Indian Wells Valley-Coso-southern Sierra Nevada region from October 1983 to February 1984 were analyzed to determine whether attenuated Sv-wave signals were present along some raypaths. Signals of this type have previously been documented in the Long Valley magmatic area and elsewhere. We have analyzed sixteen small earthquakes with Sv signals that change considerably with azimuth and take-off angle. Forward modeling and a tomographic inversion illuminate several small regions within a 20 by 30 km area of the shallow crust (some shallower than 5 km) which severely attenuate S waves passing through them. This area is beneath the Indian Wells Valley south of the Coso Range and is coincident with the epicentral location of earthquake swarms which occurred in 1982-1983. This swarm sequence began in a centralized cluster which, with time, became two clusters that migrated several kilometers north and south. No attenuating effects were seen for rays passing beneath the Coso geothermal area above about 5 km depth.
" }, { "name": "Schmitt, Douglas Ray", "degree": "PhD", "year": "1987", "title": "I. Applications of Double-Exposure Holography to the Measurement of In Situ Stress and the Elastic Moduli of Rock from Boreholes. II. Shock Temperature Measurements in Fused Quartz and Crystalline NaCl to 35 GPa", "advisor": "Ahrens, Thomas J.; Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10242023-225432851", "creators": [ { "name": { "family": "Schmitt", "given": "Douglas Ray" }, "id": "Schmitt-Douglas-Ray", "display_name": "Schmitt, Douglas Ray" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geophys" ], "doi": "10.7907/vr7c-6j57", "abstract": "Part I.
\r\n\r\nThe application of a new borehole technique using holographic inter\u00ad ferometry to measure the in situ state of stress and the modulus of elasti\u00adcity of rock is discussed. The apparatus exposes two holograms which are taken both before and after micron scale displacements are induced by\r\n(1) drilling a small stress-relieving hole in the wall of a borehole, and (2) applying a normal point force to the borehole wall. Maximum induced displacements are approximately 10 microns; the holograms are sensitive to movements on the order of 0.1 micron. Raw data take the form of a series interference holograms which have dark fringes superimposed on the three dimensional holographic borehole wall image. Synthetic fringe patterns are used to forward model the observed in the present method of data analysis. Calibrations of the normal force method of measuring the elastic moduli is carried out on metals with well defined elastic properties. Typi\u00adcally each test yields elastic (Young's) moduli for brass and aluminum of 100 \u00b1 10 GPa and 70 \u00b1 5 GPa, respectively, which are in close agreement with\r\nstandard tests. Laboratory holographic measurements of the Young's modulus on a sample of keragenaceous dolomitic marlstone (taken from the same mine as which the in situ experiments were conducted) yielded 16.8 \u00b1 2.8 GPa in agreement with the predicted modulus of 17.2 \u00b1 2.0 GPa based upon published density-modulus relationships. Sonic velocity determinations of the dynamic Young's modulus on cores taken from the rock sample give values consistent with the holographic measurements of 13.5 to 19.1 GPa for assumed values of Poisson's ratio of 0.35 to 0.25. The results of field tests in a horizontal borehole in a mine pillar in the Mahogany formation of Garfield County, Colorado, are presented for both experiments. The elastic modulus was found to vary with position in the borehole from 26.9 to 36.0 GPa. The farfield stresses for a borehole station 4 m from the mine pillar free surface were found from analysis of several stress-relief holograms; the determined vertical stress within the mine pillar was -10.2 MPa (compressive) close to the predicted magnitude of -11.2 MPa.
\r\n\r\nPart II.
\r\n\r\nGreybody temperatures and emittances of fused quartz under shock compression between 10 and 30 GPa are determined. Observed radiative temperatures are higher than computed continuum temperatures for shock compressed fused quartz, however; below ~26 GPa observed emittances are < 0.02. This suggests that fused quartz deforms heterogeneously in this shock pressure range, as has been observed in other minerals. Between 10 and 16 GPa, radiative temperatures decrease from 4400 K to 3200 K, above 16 GPa to 30 GPa greybody temperatures of ~3000 K with low emit\u00adtances are observed. The emittances increase with pressure from 0.02 to 0.9. The pressure range from 10 to 16 GPa coincides with the permanent densification region while the 16 to 30 GPa range coincides with the mixed phase region along the fused quartz Hugoniot. The differing radiative behaviors relate to these modes of deformation. Based upon shock recovery experiments and a proposed model of heterogeneous deformation under shock compression, the temperatures associated with low emittances in the mixed phase region probably represents the melting temperature of the high pressure phase. Above 20 GPa to 30 GPa the melting temperature of stishovite would therefore be approximately 3000 K and almost independent of pressure. The effect of pressure on melting relations for the phase system SiO\u2082-Mg\u2082SiO\u2084 are considered together with the proposed melting curve of stishovite and suggest that maximum solidus temperatures within the mantle of ~2370 K at 12.5 GPa and ~2520 K at 20.0 GPa. Using the proposed stishovite melting temperatures (T_m) and reasonable upper mantle temperatures (T), the effective viscosity (which is a function of the homologous temperature (T_m/T)) appears to remain nearly constant from 600 to 200 km depth in the Earth.
\r\n\r\nRadiative color temperatures were measured in single crystal sodium chloride under shock compression parallel to [100] over a pressure range from 20 to 35 GPa. Color temperatures from 2500 to 4500 K and emittances from 0.003 to 0.3 were determined by fitting observed spectra (450 to 850 nm) to the Planck greybody radiation law. These data support a heterogeneous shock deformation model of shocked halite in this pressure range. A 2500 K temperature rise is observed over the Bl-B2 mixed phase region from 25 to 30 GPa. Assuming that shock deformation occurs via yielding in localized planar zones which become melt and the melting temperature at high pressure controls the temperature, we infer that the temperature of the B2 fusion curve from 30 to 35 GPa rises from 3200 to 3300 K. The Bl-B2-liquid triple point is predicted at a temperature of 2250 K and 23.5 GPa.
" }, { "name": "Scott, David Russell", "degree": "PhD", "year": "1987", "title": "Magmons: Solitary Waves Arising in the Buoyant Ascent of Magma by Porous Flow through a Viscously Deformable Matrix", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04052019-172938000", "creators": [ { "name": { "family": "Scott", "given": "David Russell" }, "id": "Scott-David-Russell", "display_name": "Scott, David Russell" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "member", "display_name": "Wasserburg, Gerald J." } ], "option_major": [ "geophys" ], "doi": "10.7907/mvdj-ty73", "abstract": "The dynamics of partially molten regions of the Earth's mantle are studied using a combination of theoretical, experimental, and numerical techniques. The physical model is based on experimental observations of partially molten ultramafic rocks and incorporates two elements: buoyancy-driven porous flow of magma through a viscously deformable matrix, and buoyancy-driven circulation of the whole rock.
\r\n\r\nThe first element of this model is analogous to buoyancy-driven pipe flow of a liquid through a denser and more viscous wall fluid. Laboratory experiments on this system illustrate the phenomenon of solitary waves. These are waves of larger pipe radius that ascend a uniform pipe of smaller radius. The waves are very nearly conserved in collisions. These, and the corresponding waves of higher porosity that arise in one-dimensional porous flow, are characterized further by analysis and numerical experiments.
\r\n\r\nThe full system, incorporating circulation in a multidimensional porous medium, also displays solitary waves governed by the same basic processes as the one-dimensional waves. Analysis and numerical experiments show that the multidimensional waves have a circular or spherical form.
\r\n\r\nA possible natural manifestation of this fluid dynamical phenomenon is in igneous processes. Magmons, as the waves are called in that setting, probably have wavelengths of kilometers and velocities of centimeters per year. Magma ascent in magmons may account for episodicity in igneous emplacement. Also, a magmon can collect and mobilize a small degree of partial melt without disturbing its geochemical signature. In a partially molten region the characteristic wavelength of magmons will always be superimposed on that of large scale variations in porosity.
" }, { "name": "Vidale, John Emilio", "degree": "PhD", "year": "1987", "title": "Application of Two-Dimensional Finite-Difference Wave Simulation to Earthquakes, Earth Structure, and Seismic Hazard", "advisor": "Hager, Bradford H.; Clayton, Robert W.; Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10132011-090721112", "creators": [ { "name": { "family": "Vidale", "given": "John Emilio" }, "id": "Vidale-John-Emilio", "display_name": "Vidale, John Emilio" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "co-advisor", "display_name": "Clayton, Robert W." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "co-advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." } ], "option_major": [ "geophys" ], "doi": "10.7907/7TQ9-X746", "abstract": "Although the earth is 3-dimensional (3-D), numerical simulations of wave propagation through laterally heterogeneous media are easier to formulate and more practical to use in 2-D. In this thesis, schemes to model seismic wave propagation through laterally varying structures with 2-D numerical algorithms are developed and applied to earthquake and explosion problems.
\r\n\r\nIn Chapter 1, 2-D source expressions that have the same radiation patterns as their 3-D counterparts are derived which can rectify the following three problems: the use of 2-D simulations generally results in \"line source tails\" on what would be impulsive arrivals in 3-D, 1/\u221aR rather than 1/R amplitude decay for body waves, and no decay rather than 1/\u221aR amplitude decay for surface waves. Because this technique approximately transforms waves from a cartesian 2-D grid to a cylindrically symmetric 3-D world, slightly anisotropic geometrical spreading in 2-D better approximates isotropic spreading in 3-D than simple isotropic spreading in 2-D does. In Section 1.7, a correction to the explosive source expression reduces energy traveling vertically out of the source region, but leaves unchanged the energy traveling laterally out of the source region. In some cases, this correction will significantly improve the results of using a 2-D grid to simulate elastic wave propagation from an explosive point source.
\r\n\r\nIn Chapter 2, synthetic seismograms are constructed for the strong motions of the 1968 Borrego Mountain earthquake recorded at EI Centro. A good fit to the data results from using the laterally varying model determined by a detailed refraction survey and the source parameters determined by teleseismic waveform modeling. Shallow faulting is no longer necessary to explain the long-period surface-wave development.
\r\n\r\nSynthetic seismograms calculated for the 1971 San Fernando earthquake show strong effects due to lateral variation in sediment thickness in the San Fernando valley and the Los Angeles basin. Using previously determined basin structure and teleseismically determined source parameters, two-dimensional SH and P-SV finite difference calculations can reproduce the amplitude and duration of the strong motion velocities recorded across the basins in Los Angeles in the period range from 1 to 10 seconds. The edges of basins nearest the seismic source show ground motion amplification up to a factor of three, and tend to convert direct shear waves into Love and Rayleigh waves that travel within the basins. The computed motions are sensitive to the mechanism and location of earthquakes. A strike-slip earthquake on the Newport-Inglewood fault zone, for example, would produce different patterns of peak velocity and duration of shaking across the San Fernando and Los Angeles basins.
\r\n\r\nIn Chapter 3, the effect of shallow station structure and lateral velocity variation are investigated for records of the Amchitka explosion Milrow. The differences between the Meuller-Murphy, Heimberger-Hadley, and von Seggern-Blandford reduced displacement potential (RDP) source representations are small compared to the differences between using various possible velocity structures.
\r\n\r\nCreager and Jordan (1986) propose that penetration of subducting slabs under the Kurile Islands and other subduction zones to depths of at least 1000 km is necessary to explain the t ravel time anomalies of deep earthquakes. Such penetration would also affect the amplitudes and waveforms of the body waves from these earthquakes. In Chapter 4, synthetic seismograms appropriate for a record section in a plane perpendicular to the strike of the slab are presented using a coupled finite-difference and Kirchhoff method. An inferred shear-wave version of the compressional-wave velocity structure of Creager and Jordan (1986) produces an amplitude decrease up to a factor of four and waveform broadening up to 20 seconds for SH arrivals with a take-off angle pointing straight down t he slab. Slabs that extend only 300 km below the earthquake but are half as thick and twice as anomalously fast as Creager and Jordan 's (1986) velocity model will roughly preserve the travel time variation pattern, and show less waveform broadening, but produce first arrivals that are emergent. Slabs that become thicker with depth show less waveform broadening. Reconciliation of the amplitude, waveform distort ion, and timing of body waves from deep events is necessary to understand the geometry of slabs near and below the 6.50 km discontinuity.
" }, { "name": "Eissler, Holly Kathleen", "degree": "PhD", "year": "1986", "title": "Investigations of Earthquakes and Other Seismic Sources in Regions of Volcanism", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10292023-222051513", "creators": [ { "name": { "family": "Eissler", "given": "Holly Kathleen" }, "id": "Eissler-Holly-Kathleen", "display_name": "Eissler, Holly Kathleen" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "chair", "display_name": "Anderson, Donald L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "member", "display_name": "Tanimoto, Toshiro" }, { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "member", "display_name": "Westphal, James A." } ], "option_major": [ "geophys" ], "doi": "10.7907/wmxt-sv17", "abstract": "Source properties of earthquakes in Hawaii and seismological aspects of explosive volcanic eruptions are examined in three chapters. In Chapter 1, source depths are estimated for all earthquakes larger than magnitude 6 on the island of Hawaii since 1940 by comparing relative amplitudes of short-period surface waves to body waves. Rayleigh wave excitation functions are calculated versus source depth, and the calculation is compared with observed data and calibrated using known depths of recent earthquakes. In general, results show that large earthquakes near the volcanic flanks and fault systems are shallow (\u2264 20 km), but those near active volcanic centers can\r\nbe deeper (~ 50 km). Two earthquakes with the largest depth estimates (40-55 km and 35-50 km) occurred under the active volcanoes Mauna Loa and Kilauea, preceding eruptions by three days and 14 months respectively. As a check on the data set, which consisted of Pasadena seismograms alone, M_s values assigned from many global amplitude readings were compared with those from Pasadena amplitudes for worldwide earthquakes. Global M_s values on the average are 0.05 magnitude units larger than M_s values from Pasadena amplitudes.
\r\n\r\nIn Chapter 2, the horizontal single-force source used to model seismic radiation from the Mt. St. Helens landslide is investigated as the source of the M_s = 7.1 Kalapana, Hawaii earthquake. The azimuthal radiation pattern of 100 s Love waves is two-lobed, consistent with a horizontal single-force source. The observed surface deformation is also more consistent with the single force than the conventional double-couple shear dislocation source. The single force is a crude representation of\r\nmotion of a large slide mass that is partially decoupled from the Earth. The interpretation is that the bulk of seismic radiation from the Kalapana earthquake was produced by large-scale slumping of the south flank of Kilauea volcano. The peak amplitude f\u2080 of the force time function is estimated at 1 x 10\u00b2\u2070 dyne from Love and Rayleigh surface waves. The peak acceleration inferred from the seismic force is 10 - 100 cm s\u207b\u00b2, comparable to that of gravity on a gently inclined plane.
\r\n\r\nIn Chapter 3, far-field seismograms were searched for signals associated with recent large volcanic eruptions to examine whether models of the volcano as a seismic source derived for Mt. St. Helens are applicable to other explosive volcanoes. The 1982 eruption of El Chich6n in Mexico produced Rayleigh waves and body waves that were marginally recorded at IDA and SRO stations less than 40\u00b0 away; still, several characteristics of the eruption can be inferred from the seismic waves. Near-field seismograms of smaller eruptions at Mt. Asama, Japan, were found to be comparable in size to smaller secondary eruptions of Mt. St. Helens, and appear to have a more complicated source. Atmospheric pressure waves recorded on barographic instruments from several large explosive eruptions are compared and show differences in signal duration, amplitude, and characteristic period that are indicative of the overall size of the eruption.
" }, { "name": "Fine, Gerald Jonathan", "degree": "PhD", "year": "1986", "title": "Carbon Dioxide in Synthetic and Natural Silicate Glasses", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09032019-144830666", "creators": [ { "name": { "family": "Fine", "given": "Gerald Jonathan" }, "id": "Fine-Gerald-Jonathan", "display_name": "Fine, Gerald Jonathan" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" } ], "option_major": [ "geol" ], "doi": "10.7907/xmqc-xv31", "abstract": "Infrared spectroscopy has been used to study the speciation of CO2 in both synthetic silicate glasses quenched from melts held at high temperatures and pressures and in natural basaltic glasses. In glasses near the NaAlO2-SiO2 join, absorption bands resulting from the antisymmetric stretches of both molecular CO2 (2352 cm-1) and CO2-3 (1610 cm-1 and 1375 cm-1) are observed. The latter are attributed to distorted Na-carbonate ionic-complexes. Molar absorptivities for each of the absorption bands have been determined; these molar absorptivities allow the quantitative determination of species concentrations in sodium aluminosilicate glasses with a precision on the order of several percent of the amount present. The accuracy of the method is estimated to be \u00b115-20% at present.
\r\n\r\nThe ratio of molecular CO2 to CO2-3 in sodium aluminosilicate glasses varies little for each silicate composition over the range of total dissolved CO2 contents (0-1.5%), pressures (15-33 kbar) and temperatures (1400-1560\u00b0C) studied. This ratio is, however, a strong function of silicate composition, increasing both with decreasing Na2O content along the NaAlO2-SiO2 join and with decreasing Na2O content in peraluminous compositions off the join.
\r\n\r\nThe molar absorptivities determined for sodium aluminosilicate glasses have also been used to measure the concentrations of CO2 in albitic (NaAlSi3O8) glasses quenched from melts equilibrated with CO2 vapor at high pressures (15-30 kbar) and temperatures (1450-1625\u00b0C). The results show that total CO2 solubility increases with increasing pressure at constant temperature. Both molecular CO2 and CO2-3 concentrations increase with pressure. At constant pressure, the solubility of molecular CO2 decreases with temperature while the concentration of CO2-3 increases. The net effect is that total CO2 solubility is not significantly dependent on temperature, decreasing slightly with increasing temperature at constant pressure.
\r\n\r\nThe speciation of CO2 in both synthetic Ca \u00b1 Mg-composition glasses and natural basaltic glasses contrasts with the case of CO2-bearing sodium aluminosilicate glasses. CO2 is inferred to be dissolved in these glasses as distorted Ca- or Mg-carbonate ionic-complexes that result in unique infrared absorption bands at 1515 cm-1 and 1435 cm-1. The molar absorptivities for each of these absorption bands were also determined. No detectable molecular CO2 is dissolved in these glasses.
\r\n\r\nInfrared spectroscopic measurements of species concentrations in glasses provide insights into the molecular level processes accompanying CO2 solution in melts and can be used to test and constrain thermodynamic models of CO2-bearing melts. CO2 speciation in silicate melts can be modelled by equilibria between molecular CO2, CO2-3, and oxygen species in the melts. Consideration of the thermodynamics of such equilibria can account for the observed linear relationship between molecular CO2 and carbonate concentrations in sodium aluminosilicate glasses, the absence of molecular CO2 in Ca \u00b1 Mg silicate glasses, the proposed linear relationship between total dissolved CO2 content and the activity of CO2 in melts, and observed variations in CO2 solubility in melts.
\r\n\r\nDissolved CO2 contents of natural basaltic glasses can also be determined from the intensities of the carbonate absorption bands at 1515 cm-1 and 1435 cm-1. The uncertainty of the method is estimated to be \u00b115% of the amount present. The infrared technique is a powerful tool for the measurement of dissolved CO2 contents in natural basaltic glasses since it is nondestructive, can be aimed at regions of glass a few tens of micrometers in size, and discriminates between dissolved carbonate and carbon present as carbonate alteration, contained in fluid inclusions or adsorbed on the glass.
\r\n\r\nA set of submarine basaltic glasses dredged from a variety of locations contain 0-400 ppm dissolved CO2, measured using the infrared technique. These concentrations are lower than most previous reports for similar basaltic glasses. No general relationship is observed between dissolved CO2 content and depth of magmatic eruption.
" }, { "name": "Gehrels, George Ellery", "degree": "PhD", "year": "1986", "title": "Geologic and Tectonic Evolution of Annette, Gravina, Duke, and Southern Prince of Wales Islands, Southeastern Alaska", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03142019-142709345", "creators": [ { "name": { "family": "Gehrels", "given": "George Ellery" }, "id": "Gehrels-George-Ellery", "orcid": "0000-0002-8564-8433", "display_name": "Gehrels, George Ellery" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "chair", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Stevenson", "given": "David J." }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David J." }, { "name": { "family": "Talyor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Talyor, Hugh P." }, { "name": { "family": "Berg", "given": "Henry C." }, "id": "Berg-Henry-C", "role": "member", "display_name": "Berg, Henry C." } ], "option_major": [ "geol" ], "doi": "10.7907/pavf-pm10", "abstract": "Annette, Gravina, Duke, and southern Prince of Wales Islands are underlain primarily by Cambrian (and perhaps Proterozoic) through Triassic volcanic, sedimentary, plutonic, and metamorphic rocks. These rocks belong to the Alexander terrane, which is a coherent tectonic fragment that underlies much of southeastern (SE) Alaska, the Saint Elias Mountains of British Columbia, Yukon, and eastern Alaska, and coastal regions of west-central British Columbia. Geologic mapping combined with U-Pb (zircon) geochronologic studies have delineated the major geologic units and features of these islands, and contribute to our understanding of the geologic and tectonic evolution of the Alexander terrane.
\r\n\r\nThe oldest rocks recognized on Annette, Gravina, Duke, and southern Prince of Wales Islands consist of greenschist- and amphibolite-facies metavolcanic and metasedimentary rocks of the Wales metamorphic suite. These rocks are locally intruded by dioritic and granodioritic metaplutonic rocks which yield U-Pb apparent ages of approximately 540-520 Ma (Middle and Late Cambrian). Rocks in the Wales suite were therefore deposited, at least in part, prior to Late Cambrian time, but their maximum depositional age is not known. The Wales suite and associated metaplutonic rocks are intruded by large dioritic to granitic plutons which yield U-Pb apparent ages in the 475-425 Ma (Middle Ordovician-Early Silurian) range and are probably overlain by Lower Ordovician-Lower Silurian volcanic and sedimentary rocks of the Descon Formation. However, depositional contacts between the Descon Formation and the older metamorphic rocks have not been demonstrated. Deformation, metamorphism, and uplift of rocks in the Wales metamorphic suite occurred during a Middle Cambrian-Early Ordovician tectonic event which I have referred to as the Wales \"orogeny.\" The term orogeny is used informally in this instance, as little is known about the regional and tectonic significance of this event.
\r\n\r\nOrdovician-Early Silurian rocks on these islands are interpreted to have formed in an oceanic volcanic arc environment based on similarities with young or presently active volcanic arcs in the Circum-Pacific region. Characteristics of the volcanic-plutonic complex in the Alexander terrane which are similar to those in other magmatic belts include: 1) predominance of basaltic to andesitic volcanic rocks and dioritic to granodioritic and subordinate granitic plutonic rocks, 2) calc-alkaline affinity of the plutonic and volcanic rocks, as defined on AFM, FeO*/MgO versus SiO2, and La versus Nb diagrams and by an alkali-lime index of 56-62, 3) patterns of strong (50-100 times chondrites) light REE enrichments, moderate (5 to 20 times chondrites) heavy REE enrichments, and strong negative europium anomalies, 4) evolution of the magmatic system over a period of approximately 50 m.y., and 5) increasing potassium content with time in the plutonic rocks.
\r\n\r\nFacies relations in Ordovician-Silurian strata in the southern part of the terrane generally record northwesterly paleogeographic trends, indicating that the interpreted arc trended oblique to the northnorth-westerly elongation of the terrane. Continuation of Ordovician-Silurian shallow-marine strata for over 600 km to the north-northwest indicates that the interpreted arc probably faced to the southwest and that the strata to the north accumulated in a back-arc environment. Protoliths of the Wales metamorphic suite may also have formed in a volcanic arc environment, but the penetrative deformation and regional metamorphism of these rocks precludes detailed analyses of protolith relations and composition.
\r\n\r\nDuring middle Silurian-earliest Devonian time the Early Silurian and older rocks in the area were involved in a major tectonic event which I refer to as the Klakas orogeny. Manifestations of this orogeny on Annette, Gravina, Duke, and Prince of Wales Islands include: 1) cessation of the Ordovician-Early Silurian volcanism and plutonism, 2) deposition of middle and Upper Silurian polymictic conglomerate on northern Prince of Wales Island and regions to the north, 3) erosion or non-deposition of Silurian strata on Annette, Gravina, and Duke Islands and on central and southern Prince of Wales Island, 4) southwest-directed movement on thrust faults on southern Prince of Wales Island and perhaps on Annette Island, 5) deposition and deformation of a Lower Devonian talus breccia and penetrative brecciation of Ordovician rocks along thrust faults on southern Prince of Wales Island, 6) greenschist-and local amphibolite-facies regional metamorphism and penetrative deformation of Ordovician-Early Silurian rocks on Annette, Gravina, and Duke Islands, 7) emplacement, and perhaps generation by anatexis, of Late Silurian trondhjemite, sodic leucodiorite, and subordinate granite plutons, 8) several kilometers (perhaps as much as 10 km) of uplift of Late Silurian and older rocks prior to middle Early Devonian time, and 9) deposition of Lower Devonian conglomeratic red beds of the Karheen Formation in topographically rugged subaerial environments in some regions to the south, and in a northward tapering clastic wedge to the north. Previous workers recognized the stratigraphic manifestations of this orogenic event on central and northern Prince of Wales Island, but most relations to the south were recognized initially during this study.
\r\n\r\nOn southern Prince of Wales Island, Lower Devonian conglomeratic strata are overlain by shallow-marine limestone, mudstone, and siltstone of middle Early Devonian age, which are in turn overlain by deeper-water mudstone and graptolitic shale. Subsidence of the region below sea level following the Klakas orogeny therefore occurred during middle Early Devonian time and produced a marine transgression on a north-facing paleoslope. Lower Devonian strata on Annette, Gravina, and Duke Islands were deposited in shallow-marine environments, and only locally include polymictic conglomerate and coarser clastic strata. Andesitic volcanic rocks of probable Early Devonian age locally overlie the marine clastic strata and are the youngest Paleozoic rocks in the study area.
\r\n\r\nTriassic strata herein referred to as the Hyd Group unconformably overlie the Devonian and older rocks on Annette and Gravina Islands. At the base of the section in most areas is a thick conglomerate or sedimentary breccia with meter-size clasts of Devonian and older rock in a poorly sorted matrix. These strata are overlain by a sequence, from bottom to top, of rhyolite and rhyolitic tuff, shallow-marine limestone, calcareous siltstone and limestone, and basalt flows and breccia. A UPb apparent age of 225 \u00b1 3 on the rhyolite combined with megafossil and conodont ages demonstrate that these strata were deposited during Late Carnian to Late Norian time, and place a minimum age constraint of 225 \u00b1 3 Ma on the Carnian-Norian boundary. A large body of pyroxene gabbro on Duke Island yields a U-Pb apparent age of 226 \u00b1 3 Ma, which demonstrates that this gabbro is not genetically related to the zoned (\"Alaskan-type\") ultramafic bodies on Duke Island (assuming that the ultramafic bodies are indeed Cretaceous in age!). Rather, the pyroxene gabbro is interpreted to be genetically related to the Triassic basaltic rocks. Intrusive relations indicate that hornblende gabbro on northeastern Duke Island is pre-Late Silurian in age, and is therefore not genetically related to the pyroxene gabbro or to the Cretaceous(?) ultramafic rocks.
\r\n\r\nThe unconformity at the base of the Triassic section records a major latest Paleozoic(?)-Triassic uplift and erosional event in the Alexander terrane, but this event was not associated with regional deformation or metamorphism. This lack of deformation combined with the occurrence of Triassic strata along the eastern margin of the terrane in SE Alaska and the bimodal (basalt-rhyolite) composition of the volcanic rocks suggest that the Triassic strata and their subjacent unconformity formed in an extensional environment. A major low-angle normal fault on southern Prince of Wales Island (the Keete Inlet fault) may also have moved during this interpreted extensional event.
\r\n\r\nJurassic and younger rocks intrude and overlie rocks in various terranes in western British Columbia and southern Alaska and demonstrate that the Alexander terrane has been adjacent to Wrangellia since Middle(?) Jurassic time, and to terranes to the east since Late Cretaceous-early Tertiary time. Regional sub-greenschist- to greenschist-facies metamorphism and moderate deformation of Cretaceous and older rocks along the eastern margin of the terrane are interpreted to have occurred during mid-Cretaceous-early Tertiary juxtaposition of the Alexander terrane against terranes to the east.
\r\n\r\nNorth of Annette, Gravina, Duke, and southern Prince of Wales Islands the Alexander terrane is underlain primarily by Paleozoic marine clastic strata and limestone. Lower Paleozoic strata in some regions of the Saint Elias Mountains include Cambrian volcanic rocks which may be correlative with rocks in the Wales metamorphic suite, and a thick section of Ordovician-Devonian clastic strata and limestone. Upper Paleozoic clastic strata are widespread in the Saint Elias Mountains region but occur in only a few areas of southeastern Alaska, where they were generally deposited in tectonically stable, shallow-marine environments. Triassic strata to the north are generally similar to rocks on Annette and Gravina Islands, and are interpreted by other workers to have been deposited in a rift environment.
\r\n\r\nA variety of geologic, paleomagnetic, and paleobiogeographic evidence suggests that the Alexander terrane occupied low paleolatitudes during much of Paleozoic and Mesozoic time, and did not reach its present latitude in the Cordillera until after Early Cretaceous time. Previous hypotheses were that the Alexander terrane was originally adjacent to rocks in the Sierra-Klamath region of California, and that both assemblages formed and evolved adjacent to the California continental margin. Comparison of the geologic and tectonic evolution of the Alexander terrane with that in the Sierra-Klamath region indicates, however, that the two assemblages have little in common and probably were not closely associated during Paleozoic time.
\r\n\r\nAlternatively, I suggest that the early Paleozoic geologic and tectonic evolution of the Alexander terrane is remarkably similar to that in a dismembered orogenic belt which occurs in southeastern Australia (Lachlan Fold Belt), New Zealand, the Transantarctic Mountains and Byrd Land of Antarctica, and perhaps in tectonic fragments in Asia. Similarities between the Alexander terrane and the Lachlan Fold Belt include: 1) arc-type(?) volcanism and sedimentation during Cambrian time (and perhaps Proterozoic time in the Alexander terrane), 2) regional deformation and metamorphism of the Cambrian and older(?) rocks during Middle Cambrian-Early Ordovician time, 3) evolution of some regions in a volcanic arc environment during Ordovician time (into Early Silurian time in the Alexander terrane), 4) cessation of this volcanic arc activity during the onset of a Silurian-earliest Devonian orogenic event, which is manifest by regional uplift and erosion, deformation and regional metamorphism, anatectic(?) plutonism (and volcanism in the Lachlan Belt), 5) deposition of Lower Devonian and locally Silurian conglomeratic red beds, and 6) evolution in relatively stable marine environments from middle Early through Middle Devonian time.
\r\n\r\nComparison of paleolatitudes of the Alexander terrane (determined from paleomagnetic data) with paleolatitudes of eastern Australia (interpreted from continental reconstructions) indicates that the two regions occupied similar paleolatitudes from Ordovician to Late Devonian time. A similar comparison of declination data from the Alexander terrane indicates that both regions also rotated in a clockwise sense during this period. There are also similarities in lower Paleozoic fossils of the two regions, but some faunas from the Alexander terrane apparently bear stronger affinities with North American or Asian fossils.
\r\n\r\nBased on the geologic, paleomagnetic, and, to some degree the paleobiogeographic similarities, I raise the possibility that the Alexander terrane formed and evolved along the paleo-Pacific margin of Gondwana, perhaps adjacent to rocks in eastern Australia, during early Paleozoic time. The data are not sufficient to draw correlations between the Alexander terrane and specific regions in this complex orogen, although I note that similarities are strongest with the Molong volcanic province in the Lachlan Belt of eastern Australia. The paleomagnetic data indicate that the terrane could have been associated with these rocks or with potential northern correlatives in tectonicfragments that now reside in Asia.
\r\n\r\nThe geologic, paleomagnetic, and paleobiogeographic(?) similarities between the Alexander terrane and the Lachlan Belt end in Middle Devonian-Early Carboniferous time. During this time the Lachlan Belt apparently underwent a major rifting episode, and the Alexander terrane began to evolve in tectonically stable marine environments. The paleolatitudes of the two regions also diverge at this time, with the Alexander terrane migrating northward toward the paleo-equator and eastern Australia continuing its southward movement. Carboniferous fauna from the Alexander terrane are reported by some workers to have \"Tethyan\" affinities, a fact that is consistent with the low paleolatitudes determined from the paleomagnetic data. Triassic faunas from the terrane are endemic to equatorial or perhaps more southerly regions in the eastern part of the paleo-Pacific basin, and paleomagnetic data from the terrane are most consistent with a paleolatitude of approximately 43\u00b0 South. In concert with the hypothesis that the terrane was adjacent to the paleo-Pacific margin of Gondwana during early Paleozoic time, I raise the possibility that the terrane was tectonically removed from the Gondwana margin, perhaps by rifting, during Middle Devonian-Early Carboniferous time, and migrated eastward across the paleo-Pacific basin during late Paleozoic time. Northward displacement apparently began after Late Triassic time, and ended during the mid-Cretaceous to early Tertiary juxtaposition of the terrane against fragments previously accreted to western North America.
" }, { "name": "Grand, Stephen Pierre", "degree": "PhD", "year": "1986", "title": "Shear Velocity Structure of the Mantle Beneath the North American Plate", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:10172019-145940396", "creators": [ { "name": { "family": "Grand", "given": "Stephen Pierre" }, "id": "Grand-Stephen-Pierre", "orcid": "0000-0003-3205-7266", "display_name": "Grand, Stephen Pierre" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Tanimoto", "given": "Toshiro" }, "id": "Tanimoto-T", "role": "member", "display_name": "Tanimoto, Toshiro" }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geophys" ], "doi": "10.7907/xqhn-dj49", "abstract": "The long-period tangential components of seismograms recorded by the WWSS network over the last 20 years are used to constrain the shear velocity variations in the mantle beneath the North American plate. The first two chapters derive vertical shear velocity profiles beneath three tectonic provinces: the East Pacific Rise, the Canadian shield and the old northwest Atlantic ocean. The SH motion seismograms were interpreted as multi-bounce shear bodywaves and use was made of Cagniard-de Hoop and WKBJ synthetic seismogram techniques to model the data with the assumption that the structure within each province was laterally homogeneous. The three models were constructed such that the S-waves and up to 4 minutes of later arrivals in the data were fit in terms of travel-time, phase and amplitude. The most useful arrival in the study was the SS phase.
\r\n\r\nThe three regions studied were found to have very similar structure below 400 km depth. Anomalously large increases in velocity of about 6.5% from 375 to 425 km depth and 11% from 625 to 700 km depth were found beneath each tectonic area with no indication of lateral variations in the structures. These high gradient zones were modeled as discontinuities of 4.5% at 405 km depth and 7.5% at 660 km depth. Other common features of the models are a high gradient from 425 to 625 km depth and an anomalously high gradient beneath the discontinuity at 660 km depth to about 750 km depth. Above 400 km depth, large lateral differences in structure exist beneath the three provinces. Velocities beneath the shield were found to be about 10% higher at 100 km depth, 5% higher at 200 km depth and 3% higher at 300 km depth, relative to the Rise model. The old Atlantic has high velocities to about 100 km depth, but below 150 km the structure is similar to that beneath the East Pacific Rise. The shield model has a very low gradient and high velocity in the upper 175 km. The velocity decreases by about 3% at 200 km depth with a low gradient below to 400 km depth. Beneath the Atlantic and East Pacific, very low velocities occur near 200 km depth. The Rise model has the lowest velocities (4.3 km/sec) near 100 km depth. Both models have very high gradients (about .035%/km) from 175 to 375 km suggesting a partial melt or dislocation relaxation explanation for the low velocities near 200 km depth.
\r\n\r\nChapter 3 is an attempt to develop a fully three-dimensional model of mantle shear velocity beneath the entire North American plate to 1700 km depth. S and SS arrival time anomalies were measured relative to a simple starting model. The raypaths of the different measured phases were found using the experience gained in Chapters 1 and 2. The travel-time anomalies were then used as the input for a tomographic back projection inversion for velocity fluctuations within blocks on the order of 500 by 500 by 100 kms. A high velocity root to 400 km depth is found directly beneath almost all of the shield and platform of North America. Eastern North America was found to have similar structure to the old Atlantic with high velocities to 140 km depth and average to low velocities to 400 km depth. The Basin and Range, Carribean, Mid-Atlantic Ridge and the East Pacific have the lowest velocities in the upper 400 km. From the southwest Carribean to the northern United States, a major high velocity feature is observed to exist from 700 to 1700 km depth with about a 1% increase in velocity over an 800 km width in an east-west direction. The structure has a slab-like shape and dips to the east. It is hypothesized that the anomalous high velocities are due to remnants of the subducted Farallon plate going back to 100 Ma.
" }, { "name": "Richards, Mark Alan", "degree": "PhD", "year": "1986", "title": "Dynamical Models for the Earth's Geoid", "advisor": "Hager, Bradford H.; Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02122016-151411807", "creators": [ { "name": { "family": "Richards", "given": "Mark Alan" }, "id": "Richards-Mark-Alan", "orcid": "0000-0002-1893-953X", "display_name": "Richards, Mark Alan" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "co-advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "geophys" ], "doi": "10.7907/ncf0-0c06", "abstract": "The Earth's largest geoid anomalies occur at the lowest spherical harmonic degrees, or longest wavelengths, and are primarily the result of mantle convection. Thermal density contrasts due to convection are partially compensated by boundary deformations due to viscous flow whose effects must be included in order to obtain a dynamically consistent model for the geoid. These deformations occur rapidly with respect to the timescale for convection, and we have analytically calculated geoid response kernels for steady-state, viscous, incompressible, self-gravitating, layered Earth models which include the deformation of boundaries due to internal loads. Both the sign and magnitude of geoid anomalies depend strongly upon the viscosity structure of the mantle as well as the possible presence of chemical layering.
\r\n\r\nCorrelations of various global geophysical data sets with the observed geoid can be used to construct theoretical geoid models which constrain the dynamics of mantle convection. Surface features such as topography and plate velocities are not obviously related to the low-degree geoid, with the exception of subduction zones which are characterized by geoid highs (degrees 4-9). Recent models for seismic heterogeneity in the mantle provide additional constraints, and much of the low-degree (2-3) geoid can be attributed to seismically inferred density anomalies in the lower mantle. The Earth's largest geoid highs are underlain by low density material in the lower mantle, thus requiring compensating deformations of the Earth's surface. A dynamical model for whole mantle convection with a low viscosity upper mantle can explain these observations and successfully predicts more than 80% of the observed geoid variance.
\r\n\r\nTemperature variations associated with density anomalies in the man tie cause lateral viscosity variations whose effects are not included in the analytical models. However, perturbation theory and numerical tests show that broad-scale lateral viscosity variations are much less important than radial variations; in this respect, geoid models, which depend upon steady-state surface deformations, may provide more reliable constraints on mantle structure than inferences from transient phenomena such as postglacial rebound. Stronger, smaller-scale viscosity variations associated with mantle plumes and subducting slabs may be more important. On the basis of numerical modelling of low viscosity plumes, we conclude that the global association of geoid highs (after slab effects are removed) with hotspots and, perhaps, mantle plumes, is the result of hot, upwelling material in the lower mantle; this conclusion does not depend strongly upon plume rheology. The global distribution of hotspots and the dominant, low-degree geoid highs may correspond to a dominant mode of convection stabilized by the ancient Pangean continental assemblage.
" }, { "name": "Rigden, Sally Miranda", "degree": "PhD", "year": "1986", "title": "The Determination of the Equation of State of Molten Silicates at High Pressures Using Shock-Wave Techniques", "advisor": "Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10272023-170924439", "creators": [ { "name": { "family": "Rigden", "given": "Sally Miranda" }, "id": "Rigden-Sally-Miranda", "display_name": "Rigden, Sally Miranda" } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "chair", "display_name": "Burnett, Donald S." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geol" ], "doi": "10.7907/5v04-ws14", "abstract": "Shock wave (Hugoniot) equation-of state experiments have been carried out on molten silicates in the petrologically important system CaMgSi\u2082O\u2086-CaAl\u2082Si\u2082O\u2088 via the projectile impact method. An RF heating technique was developed to heat silicate samples contained in pure Mo containers to the necessary high initial temperatures (up to 1773 K). Thermocouple techniques, a refractory sample holding system and optical shutter systems, were developed to allow utilization of a propellant gun apparatus at impact velocities ranging from 1.0 to 2.5 km sec\u207b\u00b9 corresponding to shock pressures of 4 to 40 GPa. The methodology for taking into account the effect of the Mo container in measuring the equation of state of the molten silicate is explicitly derived.
\r\n\r\nResults on molten diopside (CaMgSi\u2082O\u2086), anorthite (CaAl\u2082Si\u2082O\u2088) and an inter\u00ad mediate composition (36 mole % CaAl\u2082Si\u2082O\u2088, 64 mole % CaMgSi\u2082O\u2086: An_(0.36)Di_(0.64)) are presented. Reduction of the Hugoniot data for these materials to third-order Birch-\u00adMurnaghan isentropes yields 1 atm bulk moduli (K_s) in the range 18-24 GPa which are in good agreement with bulk moduli recently measured by ultrasonic methods at 1 atm and similar temperatures. The pressure derivatives of bulk modulus (K') vary\r\nfrom 5-7. Shock temperature calculations for An_(0.36)Di_(0.64) indicate temperatures of 2400-2600 K at ~25 GPa. The Hugoniot states are believed to lie metastably in the liquid field on the basis of measured bulk modulus, calculated Hugoniot density of a solid of the same composition and estimated crystallization times.
\r\n\r\nThe measured equation of state data for molten diopside is used in conjunction with other thermochemical data to constrain the diopside solidus via the Clausius\u00ad Clapeyron equation at pressures up to 20 GPa. The present data are consistent with\r\n measured fusion curve data of others to 5 GPa. Above ~10 GPa, a marked shallowing of the solidus is predicted as the difference in volume between crystalline and mol\u00adten diopside in equilibrium approaches zero.
\r\n\r\nComparison of the results for molten diopside with those from the intermediate composition indicates that the liquids exhibit ideal mixing behavior with respect to volume to within \u00b12% up to ~40 Gpa. Gradual changes in coordination of Al\u00b3\u207a and Si\u2074\u207a from tetrahedral at low pressures to octahedral at high pressures are believed to occur during compression of these materials. The integrated compressibility as reflected in the values of K_s and K' is related to the proportion of tetrahedrally coordinated cations at low pressure, and the volume at ~40 GPa is from 100-110% of that of a mixture of the dense, high-pressure phases MgSiO\u2083 (perovskite), CaSiO\u2083 (perovskite), Al\u2082P\u2083 (corundum) and SiO\u2082 (stishovite).
\r\n\r\nImportant petrological implications of our results include: (1) basic to ultrabasic melts become denser than olivine- and pyroxene-rich mantle at pressures of 6-10 GPa, and (2) there is a maximum depth from which basaltic melt can rise buoyantly within terrestrial planetary interiors.
" }, { "name": "Sams, David Bruce", "degree": "PhD", "year": "1986", "title": "U/Pb Zircon Geochronology, Petrology, and Structural Geology of the Crystalline Rocks of the Southernmost Sierra Nevada and Tehachapi Mountains, Kern County, California", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-07212008-101544", "creators": [ { "name": { "family": "Sams", "given": "David Bruce" }, "id": "Sams-David-Bruce", "display_name": "Sams, David Bruce" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "chair", "display_name": "Allen, Clarence R." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geochem" ], "doi": "10.7907/C883-H765", "abstract": "Field mapping, petrography, U/Pb zircon geochronology, and Rb/Sr geo-chemistry on the crystalline rocks of the southernmost Sierra Nevada and Tehachapi Mountains north of the Garlock fault have 1) generated a structural, geo-chemical, and geochronological framework; 2) demonstrated a continuation of Sierran plutonic and metasedimentary rocks into the Tehachapi Mountains; 3) indicated that the region, in particular the gneiss complex of the Tehachapi Mountains, represents the deepest exposed levels of the Sierra Nevada batholith; 4) placed constraints on possible mixing models between upper mantle and meta-sedimentary components to generate the observed geochemical signatures of the rocks; and 5) resolved a major mid-Cretaceous deformation event.
\r\n\r\nThe main crystalline rocks of the study area are the rocks of the Bear Valley Springs intrusive suite and the gneiss complex of the Tehachapi Mountains. The Bear Valley Springs suite is a mid-Cretaceous tonalite batholith complex with coeval gabbroic intrusives. The gneiss complex of the Tehachapi Mountains consists dominantly of early-Cretaceous orthogneiss, with subordinate paragneiss and local domains having granulite affinities. The orthogneisses are dominantly tonalitic in composition, with significant layers and domains of granodioritic to granitic and lesser dioritic to gabbroic gneiss. Quartz-rich metasedimentary rocks and marble constitute the main framework assemblage into which the plutonic rocks were emplaced. Field relations demonstrate assimilation of metasedimentary material into the orthogneisses and magma mixing between mafic, tonalitic, and anatectic granitic material derived from the metasediments.
\r\n\r\nCrystalline rocks of the region, with the exception of metasedimentary framework rocks, fall into a narrow age range of 90-120 Ma, and exhibit three main age suites. Most samples have zircon populations with systematics indicative of igneous crystallization, with signs of zircon inheritance or entrainment in the vicinity of metamorphic septa. Strongly discordant samples are relatively rare, and include the granodiorite of Claraville (concordia intercepts of 90/1900 Ma), the paragneiss of Comanche Point (108/1450), and a quartzite in the Kings sequence metasedimentary framework rocks (1700 Ma upper intercept).
\r\n\r\nThe rocks in the first age suite (gneiss complex of the Tehachapi Mountains and augen gneiss of Tweedy Creek) exhibit a greater degree of deformation, especially under moderate to high grade conditions. Major deformational fabrics are expressed as gneissic banding, mylonitization, recrystallization, boudinaging, and transposition of internal contacts. Internally and externally concordant zircon systematics of the orthogneisses in this suite indicate igneous crystallization between 110-120 Ma. Discordant zircon systematics suggest entrainment of minor amounts of mid-Proterozoic zircon and/or open system lead loss in response to the 100 Ma magmatic culmination (Bear Valley Springs event).
\r\n\r\nThe second suite, 100\u00b12 Ma Bear Valley Springs intrusive suite (tonalite of Mount Adelaide, tonalite of Bear Valley Springs, hypersthene tonalite of Bison Peak, and metagabbro of Tunis Creek) contains igneous rocks which locally cross-cut the older suite. These rocks have a late-stage deformational fabric shown primarily in the tonalites as pervasive foliation and faint gneissic banding. The zircon systematics of this suite are internally and externally concordant, indicating igneous crystallization ages, with only local evidence of entrainment of mid-Proterozoic zircon. The deformation of the suite was synplutonic, with later phases within the suite lacking significant deformational fabrics. The major deformational fabrics exhibited in the Tehachapi and Bear Valley Springs suites may be the result of the intrusion of the tonalite batholith into the lower crust, and/or the result of intra-arc shearing that was preferentially concentrated in various intrusive bodies.
\r\n\r\nThe third suite, late deformational intrusive rocks, consists of units which cross-cut deformational features in both the older suites. These youngest rocks are themselves slightly to nondeformed. The members in the suite have ages of 90 Ma (granodiorite of Claraville), 93 Ma (tonalite stock at Tweedy Creek), and 94 Ma (pegmatite dike at Comanche Point).
\r\n\r\nField mapping and petrography have shown a southward continuation of Sierran plutonic and metasedimentary framework rocks to the region of Tejon Creek. The plutons show a constant age spread and overall composition throughout the region, with a greater degree of solidus to hot sub-solidus deformation exhibited southward. The metamorphic septa have a higher grade, and are more strongly deformed southwards, becoming migmatitic. The southern margin of the tonalite of Bear Valley Springs consists of a gradational contact with the hypersthene tonalite of Bison Peak, which is believed to represent the floor or conduit phase of the batholith. Along its southwestern margin, the tonalite of Bear Valley Springs grades into the gneiss complex of the Tehachapi Mountains through a region of tonalitic gneiss that appears to be derived through the mixing of tonalitic magmas and migmatitic melts produced from paragneiss components in the gneiss complex. Paleomagnetic and structural restoration of the southwestern margin of the tonalite indicates that it may represent the uptilted floor of the batholith that originally spread out over its gneissic substrate.
\r\n\r\nThe crystalline rocks of the southernmost Sierra Nevada represent the deepest exposed levels of the Sierra Nevada batholith. Saleeby and others (1986a) indicate a continual increase in depth of exposure from the central to southern part of the batholith. Elan (1985) shows metamorphic conditions of 3.0 kb and 700\u00b0C in the south-central Sierras, while Sharry (1981b) has suggested that parts of the gneiss complex have a deep-seated (8 kb) origin with rapid late-Cretaceous uplift. Granulitic nodules of similar character to parts of the gneiss complex have been described by Domenick and others (1983) as originating from a similar depth beneath the central Sierra. Gneissic granitoids have numerous lenses of mafic to ultramafic cumulates showing igneous crystallization under granulite facies conditions. The domains of \"granulite\" in the gneiss complex of the Tehachapi Mountains are believed to be hot, relatively dry zones in a crystallizing and deforming batholithic complex. Magmatic epidote-bearing tonalites and late stage sub-solidus autometamorphic garnet growth are further indicators of a deep (\u22656 kb) level of origin for the region.
\r\n\r\nThe \"granulites\" (metagabbro of Tunis Creek and hypersthene tonalite of Bison Peak) are interpreted to be of an igneous origin. Evidence for this interpretation consists of: relict olivine grains and cumulate textures; foliation believed to be the result of igneous flow; zoned plagioclase necessitating the presence of a magma; tonalites that contain epidote that is interpreted to be of magmatic origin; \u03b418O and Rb/Sr isotopic values in the igneous range; abundance of retro-grade but paucity of prograde mineral reactions; gradational contacts between plutonic units; and observed intrusive contacts. Pyroxene within the \"granulites\" is believed to be of a pyrogenic origin. The rocks typically have a retrograde assemblage that consists of olivine \u2192 orthopyroxene and pyroxene \u2192 amphibole. The mineral assemblages all point to a downward P-T path.
\r\n\r\nSimple two-component mixing models have been constructed for samples from the southernmost Sierra Nevada, and involve incorporation of partial to complete melts of metasedimentary material into \"primitive\" upper mantle orogenic mafic magmas prior to crystallization. The two possible end-members are the quartzite-paragneiss of Comanche Point and the hypersthene tonalite of Bison Peak-metagabbro of Tunis Creek. Initial 87Sr/86Sr correlates directly with \u03b418O, and generally correlates inversely with Sr content for most of the samples. Simple isotopic mixing models indicate incorporation of up to 33% metasedimentary material in the granitic rocks, and up to 15% in the tonalites, with younger and more easterly samples requiring a larger metasedimentary component. The non-correlation of Sro with Sr content for some of the Pastoria Creek samples indicates an oceanic-affinity source with little interaction with continental crustal material. A number of samples appear to require a third, probable lower continental crustal and/or oceanic crustal-upper mantle component that may have a Paleozoic age.
\r\n\r\nBased on Rb/Sr and K/Ar age systematics, the region was uplifted in a regional cooling event at ~85 Ma perhaps as part of regional thrusting event(s) in southern California. The crystalline rocks were subsequently exposed and unconformably overlapped by Eocene marine sediments. Paleomagnetic data suggest about 45-60\u00b0 of clockwise rotation between 80 and 16 Ma for the southern end of the Sierras, possibly as the result of the thrusting event responsible for the regional uplift.
\r\n\r\nSaleeby and others (1986c) have suggested that the lower crust beneath the Sierra Nevada batholith is comprised in part by granulitic and mafic intrusive rocks. Experimental studies by Christensen and Fountain (1975) also suggest the presence of granulites in the lower continental crust. The interpretation that the study area represents the deepest exposed level of the southernmost Sierra Nevada batholith leads to the implication that granulitic-affinity rocks comprise the lower part of the continental crust. Therefore, this study provides some degree of confirmation to the aforementioned hypotheses.
\r\n" }, { "name": "Weldon, Ray James, II", "degree": "PhD", "year": "1986", "title": "The Late Cenozoic Geology of Cajon Pass; Implications for Tectonics and Sedimentation along the San Andreas Fault", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechETD:etd-08302006-135307", "creators": [ { "name": { "family": "Weldon", "given": "Ray James, II" }, "id": "Weldon-Ray-James-II", "display_name": "Weldon, Ray James, II" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "chair", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geol" ], "doi": "10.7907/9WJY-2A97", "abstract": "The geology in Cajon Pass, southern California, provides a detailed record of strike slip activity on the San Andreas fault, compressional deformation associated with the uplift of the central Transverse Ranges and an excellent Cenozoic record of syntectonic sedimentation. Age control was established in all of the sediments deposited since the late Early Miocene, using biostratigraphy, magnetostratigraphy, fission-track dating of volcanic ashes, radiocarbon dating, soil development, and the relative stratigraphic and geomorphic position of the units. Tectonic deformation and sedimentation styles varied through time, reflecting the evolution of the San Andreas fault zone within the Pacific - North American plate boundary. Particular attention was paid to determining rates of tectonic deformation and establishing the timing of changes in deformational and depositional styles in the area.
\r\n\r\nProgressive offset of radiocarbon-dated alluvial and paludal sediments have been used to determine the Holocene slip rate on the San Andreas fault in Cajon Pass. Four independent measurements of the slip rate yield an average of 24.5 \u00b1 3.5 mm/yr. The similarity of the four values, which span different intervals of time up to 14,400 years ago, suggest that the slip rate has been constant during this period.
\r\n\r\nAn excavation across the San Andreas fault provided some constraints on the timing of paleoearthquakes. Coupled with the historic record, this investigation indicates that the last earthquake associated with rupture on the fault in Cajon Pass occurred around 1700 AD. At least 2 earthquakes caused rupture on the San Andreas fault after 1290 AD and perhaps 6 earthquakes are recorded in the thousand year period before European settlement of southern California in the 1770s.
\r\n\r\nDowncutting and erosion into the western San Bernardino Mountains, during the last 700,000 years, has created Cajon Pass as it exists today. The downcutting was punctuated by at least four pulses of channel aggradation that provide stratigraphic markers throughout the area. They are dated at 0.5 \u00b1 0.1 million, 55,000 \u00b1 10,000, 17,000 to 6,000, and 2000 to 300 years ago. These aggradational periods were caused by order of magnitude increases in sediment production associated with changes in the climate from relatively wet to dry conditions.
\r\n\r\nThe locus of the latest Pleistocene to early Holocene fill migrated upstream through time, with aggradation lasting only a few thousand years at any point in the drainage. Incision of the fill also migrated upstream, beginning long before the fill pulse reached the headwaters of the system. The fill terrace, or upper surface of the fill deposit, does not represent a time line or a surface down which water flowed everywhere at once. Thus, the use of a fill terrace as either a time or spacial reference line for tectonic studies, without accounting for the its transgressive character, can result in erroneous conclusions.
\r\n\r\nDuring the early to middle Pleistocene, prior to the erosion of Cajon Pass, the southern part of the area was uplifted and coarse fan deposits were shed across the northern part of the area onto the Mojave Desert. Some of these sediments were derived from distinctive sources in the San Gabriel Mountains southwest of the San Andreas fault zone. Matching these distinctive facies in the deposits with their sources established offsets across the fault zone and made it possible to tie the uplift northeast of the fault to activity on the San Jacinto fault as it passed by across the San Andreas fault. The fan deposits are dated by a combination of bio-stratigraphy and magnetostratigraphy.
\r\n\r\nThe average slip rate across the combined San Andreas and San Jacinto faults is 37.5 \u00b1 2 mm/yr during the Quaternary Period. The six determinations of the slip rate show no evidence for rate changes during the Quaternary Period. The slip rate on the San Andreas fault alone was determined by one offset of be 21 \u00b1 7 mm/yr. The record of contemporaneous activity on the San Jacinto fault to the southeast requires that the San Andreas fault's rate be close to the upper limit of this range.
\r\n\r\nContemporaneous activity on the San Andreas and San Jacinto faults is uplifting the high, eastern San Gabriel Mountains and deforming the San Andreas fault plane. The geometry of this deformation is such that uplift of the country on the northeast side of the San Andreas fault occurs. This hypothesis is supported by the northwest migration of the uplift at the slip rate on the San Andreas fault, and the style of surface deformation that is characteristic of folding over a steeply dipping lateral ramp at depth.
\r\n\r\nA kinematic model was constructed to determine the role of the San Andreas fault in the Pacific - North American plate boundary. The Quaternary slip rates determined for the San Andreas fault in Cajon Pass and the slip vectors associated with the geometry of the fault zone were combined with an assumption of rigid block motion away from the faults and published slip rates for the other major faults in southern California. The model produces internally consistent motions for all of the blocks. Vector sums of the slip rate across the Pacific - North American boundary yield only the relative plate motion if the path includes the western Transverse Ranges. The model solution indicates that the western Transverse Ranges are not part of the San Andreas system but are a left-step in a separate coastal system that currently accommodates about 1/3 of the Pacific - North American plate motion.
\r\n\r\nThe southeastern San Bernardino Mountains are being uplifted because of a left step in the arcuate trace of the San Andreas fault. The western San Bernardino Mountains and the eastern San Gabriel Mountains are being uplifted by the deformation associated with the junction of the San Andreas and San Jacinto faults. Because the convergence in this area can be explained by local geometry, it is clear that southern California cannot be part of the Pacific plate, colliding at the plate rate into North America across the Transverse Ranges. Instead, southern California appears to be a sliver between the San Andreas system and the coastal system, and is rotating counterclockwise as it translates northwest, transferring the convergence to the coastal system.
\r\n\r\nThe middle to late Quaternary uplift of the Cajon Pass area was the culmination of the uplift of the San Bernardino Mountains that began in the Miocene. Three distinct phases of uplift have been recognized, suggesting a long-term interaction between the strike-slip activity on the San Andreas system and the compressional tectonics of the Transverse Ranges. The San Bernardino Mountains began to take shape following a pervasive earliest Miocene unconformity. Broad, homogeneous basins, separated by mature uplands of moderate to low relief developed across the southwest-draining regional paleoslope. The earliest activity on the San Andreas fault is believed to be associated with this early extensional phase.
\r\n\r\nLate Miocene to early Pliocene, south-directed thrusting uplifted the \"proto\" San Bernardino Mountains, creating steep, south-facing relief along the San Andreas. During this time the San Gabriel fault was the most (and perhaps only) active trace of the San Andreas system. Thrusting stopped as the San Andreas fault became active again, probably coincident with the beginning of the opening of the Gulf of California, 5 million years ago. Pliocene and earliest Pleistocene sedimentation took place in narrow east-west trending, structurally controlled basins created by the Mio-Pliocene thrusting.
\r\n\r\nEarly to middle Pleistocene, north-directed thrusting across a shallow, south-dipping ramp uplifted the broad central plateau of the San Bernardino Mountains, and created the North Frontal fault system. During the middle and late Quaternary, this activity was largely replaced by south-directed thrusting and lateral ramping on steep, north-dipping planes along the San Andreas fault. This activity produced the tremendous relief and regionally-extensive north-dipping structural blocks in the San Gorgonio and Cajon Pass areas, and continues today. The structures and geomorphology of the range reflects its varied history; different parts of the range are as old as late Early Miocene and as young as the Holocene.
\r\n\r\nAll three phases of uplift appear to be related to the southern Big Bend in the San Andreas fault system, which has existed since the Miocene. Contemporaneous and alternating periods of thrusting and strike-slip activity has created bedrock \"flaps\", displaced fault slivers and strand switching that are responsible for the complex geology associated with San Andreas fault through the Transverse Ranges. Recognition of these features with detailed field work will greatly expand our knowledge of the tectonics and seismic hazards associated with the San Andreas system in southern California.
" }, { "name": "Wenkert, Daniel", "degree": "PhD", "year": "1986", "title": "Empirical Relations Between the Earth's Radiation Budget, Cloudiness, and Various Meteorological Parameters", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302013-101810609", "creators": [ { "name": { "family": "Wenkert", "given": "Daniel" }, "id": "Wenkert-Daniel", "orcid": "0009-0000-4203-7141", "display_name": "Wenkert, Daniel" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "chair", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" } ], "option_major": [ "plansci" ], "doi": "10.7907/5TWR-Z031", "abstract": "I have investigated the effect of variation of meteorological variables, cloudiness, and surface variables (such as albedo and continentality) on the reflected solar and emitted terrestrial radiation leaving the top of the atmosphere. The investigation was empirical and used the radiometric data from the scanner channels of the Earth Radiation Budget (ERB) instrument on Nimbus 7, cloudiness variables from analyses done by L. Stowe et al. on data from the Temperature and Humidity Infrared Radiometer (THIR) on Nimbus 7, and meteorological data from the FGGE (First GARP Global Experiment) Level III-b global weather analyses. The data were analysed on time scales of one day and spatial scales of about 450 km.
\r\n\r\nThis investigation had three main goals. The first goal was to determine the effect of cloudiness on the net radiation for various surface and atmospheric conditions during the period investigated (12 June to 18 June 1979). The second goal was to determine whether or not this type of linear analysis on a data set of synoptic time and space scales could be used for a reasonable and empirically accurate parameterization of radiation to be used in simple energy balance climate models (which are valid at vastly larger time and space scales than this data set). The third goal was to compare the regressions determined from this data set between radiation, cloudiness, and weather with the internal statistics developed in a Global Circulation Mode l (GCM), with the idea that eventually this type of linear analysis could be used as a constraint on GCMs used by the atmospheric science community.
\r\n" }, { "name": "Conca, James Louis", "degree": "PhD", "year": "1985", "title": "Differential Weathering Effects and Mechanisms", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04072004-154813", "creators": [ { "name": { "family": "Conca", "given": "James Louis" }, "id": "Conca-James-Louis", "display_name": "Conca, James Louis" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "chair", "display_name": "Stolper, Edward M." }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "member", "display_name": "Sharp, Robert P." }, { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "member", "display_name": "Shoemaker, Eugene Merle" } ], "option_major": [ "geochem" ], "doi": "10.7907/VBEQ-RB90", "abstract": "The physical and chemical characteristics of the two differential weathering effects, case hardening and core softening, are examined to determine their formation mechanisms by investigating several field areas exhibiting differential weathering effects. The terms differential weathering effects, factors, mechanisms, processes, morphologies and their cause and effect relationships are defined in the context of the overall problem.
\r\n\r\nBecause differential weathering effects are defined on the basis of spatial variations in relative and absolute hardness, a portable field instrument has been developed to measure rock hardness as manifested in the abrasion resistance of the material.
\r\n\r\nThe design and operation of the instrument as well as results from standard materials are discussed in light of abrasive wear theory. The way in which the instrument removes material appears dominated by abrasive wear mechanisms. However, the concept of hardness implied by such mechanisms is profoundly different for rock than for homogeneous materials, and the effective hardness calculated for rock material using this instrument is more insensitive to mineralogy than expected, and is sensitive to the character of the intergranular bond.
\r\n\r\nAt the first locality, Valley of Fire, Nevada, cavernous weathering of the Aztec Sandstone results from the differential weathering effect of case hardening. The case-hardened crust is an induration phenomenon consisting primarily of host rock, calcite cement, kaolinite and finegrained quartz. The calcite occurs in a wide range of concentrations (0.001 to 5.0 wt%). The hydrated calcium borate, colemanite, was also found as a non-cementing hardening agent on two outcrops and can be used as a tracer constituent. In all cases kaolinite and quartz were the major constituents of the indurating materials by weight and are necessary components of the crust. Eolian deposition and interaction with meteoric water were determined to be the primary differential weathering mechanism within the Valley of Fire.
\r\n\r\nAt Catavina, Baja California, tonalite exhibiting cavernous weathering is found to be core-softened. Soft cores are more chemically weathered than the exterior rock as indicated by higher kaolinite contents. Hematite formed from the leaching of biotite occurs in coatings on rock surfaces, but the hardening effect of the coating is insignificant compared to the core-softening of the interior. The hardness, measured by the abrasion resistance hardness tester, is inversely correlated with kaolinite content in the tonalite. A one-dimensional water flow model was developed for core-softened, cavernously weathered boulders, and indicates that during infiltration and dessication the moisture flux through a boulder's surface is greatest at the interior cavern wall because of changes in the hydraulic conductivities induced by core softening.
\r\n\r\nThe differential weathering effects developed in the Ferrar dolerite within the Labyrinth of the Dry Valleys, Antarctica are caused by two different mechanisms. The primary mechanism is precipitation of a brown, iron-stained silica coating in the exterior rock of outcrops and joint blocks. This is also true for the case-hardened Beacon Sandstone. Precipitation can occur in the rock's outer few millimeters to centimeters, thereby decreasing the exterior rock's permeability, and consequently its susceptibility to chemical weathering. The coating's effect on a dolerite block's internal moisture regime is modeled for the case of saturated flow, and shows that the contours of the pore water flow mimic subsequent morphology. Weathering of material underlying the coating results in core softening of the dolerite. In dolerite blocks of intermediate size, expansion of the interior owing to weathering can cause the less weathered outer zone to separate into an array of polyhedral cracks. Further weathering and removal of the underlying rock by the combined action of hydration, salt weathering and eolian processes leads to the development of cavernous weathering.
\r\n\r\nA less common differential mechanism occurs in the bottom of the Antarctic Labyrinth troughs in which an eolian polish develops on rock surfaces exposed to the austral winter winds. Development of the polish protects the underlying material with similar, but less dramatic effects, than accompanies the presence of the silica coating.
\r\n\r\nExposures of the Bishop Tuff in the Mono Basin exhibit the differential weathering effect of case hardening. Early devitrification along joint planes to an average depth of 1 cm greatly increased the resistance of the joint faces to weathering over that of the joint block interiors. The absolute and relative hardnesses between interior and exterior change systematically with exposure age, and cavernous weathering results only on outcrops with long enough exposure ages, on the order of ten to twenty thousand years.
\r\n\r\nThe Towel Creek Tuff in Cottonwood Basin, Arizona, weathers into peculiar forms: conical-shaped tepees which show cavernous weathering as a result of case-hardening by calcite precipitation in the exterior rock. Calcite contents of different materials are observed to vary directly with the abrasion hardness of the material. Basal surfaces are formed at the base of the tepees by heterogeneous fluvial erosion and the cavernous hollows are initiated in these zones. Although infiltration of meteoric water into the tepees occurs through all surfaces, moisture flow during dessication of the tepees occurs primarily through the basal surfaces and the lower cavernous hollows. Equilibrium aqueous chemistry limits the interior rock's carbonate content, but calcite can accumulate at the rock exterior.
\r\n\r\nBecause of the overall differences in the intergranular bonding character between crystalline materials such as granite and clastic materials such as sandstone, the results of this study indicate that crystalline rocks tend to core-soften whereas clastic materials case-harden. Clastic materials will be affected by redistribution of secondary cements and greater accumulation at an interface can result in case hardening. In clastic rocks therefore, the hardness of different areas can either increase or decrease with time. On the other hand, a crystalline rock in a weathering environment will have its intergranular and intragranular bonds disrupted by chemical alteration. Spatial variations in disruption can result in core softening or case softening, but the hardness of all areas will decrease with time. Accumulation of secondary cements can often enhance differential effects in crystalline rocks but without case hardening the rock.
\r\n " }, { "name": "Hearn, Thomas Martin", "degree": "PhD", "year": "1985", "title": "Crustal Structure in Southern California from Array Data", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10092013-134453343", "creators": [ { "name": { "family": "Hearn", "given": "Thomas Martin" }, "id": "Hearn-Thomas-Martin", "orcid": "0000-0003-3926-4815", "display_name": "Hearn, Thomas Martin" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geophys" ], "doi": "10.7907/B6HA-4P68", "abstract": "Crustal structure in Southern California is investigated using travel times from over 200 stations and thousands of local earthquakes. The data are divided into two sets of first arrivals representing a two-layer crust. The Pg arrivals have paths that refract at depths near 10 km and the Pn arrivals refract along the Moho discontinuity. These data are used to find lateral and azimuthal refractor velocity variations and to determine refractor topography.
\r\n\r\nIn Chapter 2 the Pn raypaths are modeled using linear inverse theory. This enables statistical verification that static delays, lateral slowness variations and anisotropy are all significant parameters. However, because of the inherent size limitations of inverse theory, the full array data set could not be processed and the possible resolution was limited. The tomographic backprojection algorithm developed for Chapters 3 and 4 avoids these size problems. This algorithm allows us to process the data sequentially and to iteratively refine the solution. The variance and resolution for tomography are determined empirically using synthetic structures.
\r\n\r\nThe Pg results spectacularly image the San Andreas Fault, the Garlock Fault and the San Jacinto Fault. The Mojave has slower velocities near 6.0 km/s while the Peninsular Ranges have higher velocities of over 6.5 km/s. The San Jacinto block has velocities only slightly above the Mojave velocities. It may have overthrust Mojave rocks. Surprisingly, the Transverse Ranges are not apparent at Pg depths. The batholiths in these mountains are possibly only surficial.
\r\n\r\nPn velocities are fast in the Mojave, slow in Southern California Peninsular Ranges and slow north of the Garlock Fault. Pn anisotropy of 2% with a NWW fast direction exists in Southern California. A region of thin crust (22 km) centers around the Colorado River where the crust bas undergone basin and range type extension. Station delays see the Ventura and Los Angeles Basins but not the Salton Trough, where high velocity rocks underlie the sediments. The Transverse Ranges have a root in their eastern half but not in their western half. The Southern Coast Ranges also have a thickened crust but the Peninsular Ranges have no major root.
\r\n" }, { "name": "Humphreys, Eugene Drake", "degree": "PhD", "year": "1985", "title": "Studies of the Crust-Mantle System Beneath Southern California", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02142013-085850235", "creators": [ { "name": { "family": "Humphreys", "given": "Eugene Drake" }, "id": "Humphreys-Eugene-Drake", "orcid": "0000-0002-1916-8378", "display_name": "Humphreys, Eugene Drake" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." } ], "option_major": [ "geophys" ], "doi": "10.7907/j2xf-gq29", "abstract": "A back-projection method of tomographic reconstruction is adapted to inverted seismic travel-time data. The problems encountered in inverting these data include ray set inhomogeneity and anisotropy and the three-dimensionality of the space interrogated. Jacobi iteration, deconvolution and variable ray weighting are shown to work well in augmenting the basic back-projection method to produce a well-focused image. Applications of the various focusing algorithms are shown to have a degree of success that depends on the ray geometry used. Also, the ability to reconstruct an accurate image when the data include moderate amounts of noise is shown to be good.
\r\n\r\nP-wave teleseismic travel time delays recorded by the southern California array are inverted with the tomographic method to obtain variations in the P-wave velocity structure to a depth of 750 km. Two major anomalies are imaged. A curtain-like E-W trending high velocity feature is found directly beneath the Transverse Ranges. This feature is about 50 km in thickness, extends in depth to a maximum of about 250 km on its eastern end, and attains a maximum velocity that is about 3% greater than average mantle at the same depth beneath southern California. A zone of low-velocity material is found in the uppermost 100 km beneath the region of the Salton Trough. The seismic velocities here are depressed by about 4%.
\r\n\r\nThese anomalous regions are interpreted to be related to the geologic processes that have been active recently in southern California. Scaling relations are used to estimate that the Transverse Range anomaly is about 500\u00b0C colder and 1% more dense than average southern California mantle of the same depth, while the Salton Trough anomaly is about 1/2% less dense and contains about 3% melt. The density distribution drives a flow of upper mantle material from the Salton Trough region towards the Transverse Ranges, where it sinks into the mantle to form the feature seen beneath these ranges. Mantle flow results in tractions that act on the base of the lithosphere to produce stresses within the lithosphere that are tensile in the Salton Trough and compressive in the Transverse Ranges. These stresses are thought to account for the physiography seen in these provences.
\r\n\r\nThe southern California crust is modeled using late Quaternary slip rates on major faults, and a kinematic description is determined that has: 1) only local sites of convergence in the Transverse Ranges, and 2) the occurrance of significant strain rates near to the southern California coast, including the western Transverse Ranges.
" }, { "name": "Le Bras, Ronan", "degree": "PhD", "year": "1985", "title": "Methods of Multiparameter Inversion of Seismic Data Using the Acoustic and Elastic Born Approximations", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10092013-140441093", "creators": [ { "name": { "family": "Le Bras", "given": "Ronan" }, "id": "Le-Bras-Ronan", "orcid": "0000-0003-2439-6938", "display_name": "Le Bras, Ronan" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/14q2-fa62", "abstract": "This thesis presents two different forms of the Born approximations for acoustic and elastic wavefields and discusses their application to the inversion of seismic data. The Born approximation is valid for small amplitude heterogeneities superimposed over a slowly varying background. The first method is related to frequency-wavenumber migration methods. It is shown to properly recover two independent acoustic parameters within the bandpass of the source time function of the experiment for contrasts of about 5 percent from data generated using an exact theory for flat interfaces. The independent determination of two parameters is shown to depend on the angle coverage of the medium. For surface data, the impedance profile is well recovered.
\r\n\r\nThe second method explored is mathematically similar to iterative tomographic methods recently introduced in the geophysical literature. Its basis is an integral relation between the scattered wavefield and the medium parameters obtained after applying a far-field approximation to the first-order Born approximation. The Davidon-Fletcher-Powell algorithm is used since it converges faster than the steepest descent method. It consists essentially of successive backprojections of the recorded wavefield, with angular and propagation weighing coefficients for density and bulk modulus. After each backprojection, the forward problem is computed and the residual evaluated. Each backprojection is similar to a before-stack Kirchhoff migration and is therefore readily applicable to seismic data. Several examples of reconstruction for simple point scatterer models are performed. Recovery of the amplitudes of the anomalies are improved with successive iterations. Iterations also improve the sharpness of the images.
\r\n\r\nThe elastic Born approximation, with the addition of a far-field approximation is shown to correspond physically to a sum of WKBJ-asymptotic scattered rays. Four types of scattered rays enter in the sum, corresponding to P-P, P-S, S-P and S-S pairs of incident-scattered rays. Incident rays propagate in the background medium, interacting only once with the scatterers. Scattered rays propagate as if in the background medium, with no interaction with the scatterers. An example of P-wave impedance inversion is performed on a VSP data set consisting of three offsets recorded in two wells.
\r\n" }, { "name": "Lunine, Jonathan Irving", "degree": "PhD", "year": "1985", "title": "Volatiles in the Outer Solar System: I. Thermodynamics of Clathrate Hydrates. II. Ethane Ocean on Titan. III. Evolution of Primordial Titan Atmosphere", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:02212013-144447105", "creators": [ { "name": { "family": "Lunine", "given": "Jonathan Irving" }, "id": "Lunine-Jonathan-Irving", "orcid": "0000-0003-2279-4131", "display_name": "Lunine, Jonathan Irving" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" } ], "option_major": [ "plansci" ], "doi": "10.7907/tw6n-qa60", "abstract": "Three investigations are conducted into the physical chemistry of volatiles in the outer solar system and the role of volatiles in icy satellite evolution.
\r\n\r\nPart I:
\r\n\r\nThe thermodynamic stability of clathrate hydrate is calculated under a wide range of temperature and pressure conditions applicable to solar system problems, using a statistical mechanical theory developed by Van der Waals and Platteeuw (1959) and existing experimental data on properties of clathrate hydrates and their components. At low pressure, dissociation pressures and partition functions (Langmuir constants) for CO clathrate (hydrate) have been predicted using the properties of clathrate containing, as guests, molecules similar to CO. The comparable or higher propensity of CO to incorporate in clathrate relative to N2 is used to argue for high CO to N2 ratios in primordial Titan if N2 were accreted as clathrate. The relative incorporation of noble gases in clathrate from a solar composition gas at low temperatures is calculated, and applied to the case of giant planet atmospheres and icy satellites. It is argued that non-solar but well-constrained noble gas abundances would be measured by Galileo in the Jovian atmosphere if the observed carbon enhancement were due to bombardment of the atmosphere by clathrate-bearing planetesimals sometime after planetary formation. The noble gas abundances of Titan's atmosphere are also predicted under the hypothesis that much of the satellite's methane accreted as clathrate. Double occupancy of clathrate cages by H2 and CH4 in contact with a solar composition gas is examined, and it is concluded that potentially important amounts of H2 may have incorporated in satellites as clathrate. The kinetics of clathrate formation is also examined, and it is suggested that, under thermodynamically appropriate conditions, essentially complete clathration of water ice could have occurred in high pressure nebulae around giant planets but probably not in the outer solar nebula; comets probably did not aggregate as clathrate. At moderate pressures, the phase diagram for methane clathrate hydrate in the presence of 15% ammonia (relative to water) is constructed, and application to the early Titan atmospheric composition is described. The high pressure stability of CH4, N2, and mixed CH4-N2 clathrate hydrate is calculated; conversion back to water and CH4 and/or N2 fluids or solids is predicted for pressures \u227312 kilobars and/or temperatures \u2273320 K. The effect of ammonia is to shrink the T-P stability field of clathrate with increasing ammonia concentration. A preliminary phase diagram for the high pressure ammonia-water system is constructed using new data of Johnson et al. (1984). These results imply that 1) clathrate is stable throughout the interior of Oberon- and Rhea-sized icy satellites, and 2) clathrate incorporated in the inner-most icy regions of Titan would have decomposed, perhaps allowing buoyant methane to rise. Brief speculation on the implications of this conclusion for the origin of surficial methane on Titan is given. A list of suggested experiments and observations to test the theory and its predictions is presented.
\r\n\r\nPart II:
\r\n\r\nWe propose a global Titanic ocean, one to several kilometers deep, the modern composition of which is predominantly ethane. If the ocean is in thermodynamic equilibrium with an atmosphere of 3' (mole fraction) methane then its composition is roughly 70% C2H6, 25% CH4, and 5% N2. Photochemical models predict that C2H6 is the dominant end-product of CH4 photolysis so that the evolving ocean is both the source and sink for ongoing photolysis. The coexisting atmosphere is compatible with Voyager data. Two consequences are pursued: the interaction of such an ocean with the underlying \"bedrock\" of Titan (assumed to be water-ice or ammonia hydrate) and with the primarily nitrogen atmosphere. It is concluded that although modest exchange of oceanic hydrocarbons with enclathrated methane in the bedrock can in principle occur, it is unlikely for reasonable regolith depths and probably physically inhibited by the presence of a layer of solid acetylene and complex polymeric hydrocarbons a couple of hundred meters thick at the base of the ocean. However, the surprisingly high solubility of water ice in liquid methane (Rebiai et al., 1983) implies that topographic features on Titan of order 100 meter in height can be eroded away on a time scale \u227e109 years; \"Karst\" topography could be formed. Finally, the large solubility difference of N2 in methane versus ethane implies that the ocean composition is a strong determinant of atmospheric pressure; a simple radiative model of the Titan atmosphere is employed to demonstrate that significant surface pressure and temperature changes can occur as the oceanic composition evolves with time. The model suggests that the early methane-rich ocean may have been frozen; scenarios for evolution to the present liquid state are discussed.
\r\n\r\nPart III:
\r\n\r\nA simple convective cooling model of a primordial, CH4-NH3-N2 Titan atmosphere is constructed, in an effort to understand the fate of volatiles accreted from a gaseous disk (\"nebula\") surrounding Saturn and released from accreting planetesimals during the satellite's formation. Near-surface temperatures are initially \u2273400 K consistent with the large amount of energy supplied to the atmosphere during accretion. As a consequence of accretional heating, the upper mantle of the satellite consists of an ammonia-water liquid, extending to the surface. This \"magma ocean\" is the primary buffer of atmospheric cooling because it is \u227310 times as massive as the atmosphere. The radiative properties of the atmosphere are assumed independent of frequency and the resulting temperature profile is found to be adiabatic; if the atmosphere contains dark particulates surface temperatures could be lower than calculated here. Three major processes drive the cooling: (1) hydrodynamic escape of gas from the top of the atmosphere, which determines the cooling time scales, (2) atmospheric ablation by high velocity impacts (not modeled in detail here), and (3) formation of clathrate hydrate at the ocean-atmosphere interface, at T \u2264 250 K. Cooling time scales driven by escape are sufficiently long (108-109 years) to allow ~10 bars of N2 to be produced photochemically from NH3 in the gas phase (Atreya et al., 1978); however, the abundance of NH3 at temperatures \u227e150 K (where the intermediate photochemical products condense out) is optically thick to the dissociative UV photons. Thus, N2 formation may proceed primarily by shock heating of the atmosphere during large body impacts, as well as by photochemistry (1) at T < 150 K if intermediate products supersaturate, or (2) in a warm stratosphere, with NH3 abundance fixed by its tropopause value. The clathrate formed during late stages of cooling sequesters primarily CH4, with some N2, and forces surface temperatures and pressures to drop rapidly. The clathrate is only marginally buoyant relative to the coexisting ammonia-water liquid. If it sinks, the atmosphere is driven to an N2-rich state with most of the methane sequestered in clathrate when the ocean surface freezes over at ~180 K. Implications of this scenario for the present surface state of Titan are contrasted with those obtained if the clathrate forms a buoyant crust at the surface.
" }, { "name": "Mattson, Stephanie Margaret", "degree": "PhD", "year": "1985", "title": "Optical Expressions of Ion-Pair Interactions in Minerals", "advisor": "Stolper, Edward M.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04082005-133814", "creators": [ { "name": { "family": "Mattson", "given": "Stephanie Margaret" }, "id": "Mattson-Stephanie-Margaret", "display_name": "Mattson, Stephanie Margaret" } ], "advisors": [ { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "advisor", "display_name": "Stolper, Edward M." } ], "committee": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "chair", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geochem" ], "doi": "10.7907/acn3-nr54", "abstract": "Clusters of transition element cations in neighboring sites frequently govern the optical properties of minerals. This is particularly true of Fe-bearing minerals which may exhibit several types of ion-pair transitions. In this thesis four different types of interactions were distinguished: intensified spin-forbidden transitions of Fe3+ clusters, intensified Fe2+ spin-allowed transitions of Fe2+-Fe3+ clusters, heteronuclear charge transfer transitions of Fe2+-Ti4+ and Mn2+-Ti4+ clusters, and homonuclear charge transfer transitions of Fe2+-Fe3+ clusters.
\r\n\r\nThe optical characteristics of Fe3+ in red Fe3+ rich and black Fe3+,Fe2+-rich tourmalines were examined by absorption spectroscopy in the visible and near-infrared, M\u00f6ssbauer spectroscopy and magnetic susceptibility measurements. Intense optical absorption features at 485 and 540 nm were assigned to transitions of exchange-couple Fe3+ pairs in two different site combinations. Absorption spectra at variable temperatures and of samples which were oxidized and reduced were used to establish these assignments. Site assignments were based on intensity ratios in different polarizations according to the polarization of these transitions along the vector between the interacting cations. The 485 nm band occurs at an unusually low energy for Fe3+ in silicate minerals. Similar behavior was observed in the spectrum of coalingite, a Mg,Fe-hydroxy carbonate, and has been proposed to result from magnetic exchange in large, edge-shared octahedra. The antiferromagnetic exchange which is generally associated with intensity increases in Fe3+ clusters was confirmed by variable temperature magnetic susceptibility measurements. The M\u00f6ssbauer spectrum of a red tourmaline with 3.4% Fe exhibits an unusual decrease in width of peaks by ~30% from 298 K to 5 K which may be related to an unusual interaction between Fe3+ and trace amounts of Fe2+.
\r\n\r\nOptical absorption and M\u00f6ssbauer studies of Fe2+-bearing tourmalines with variable Fe3+ contents were used to examine Fe2+ transitions which are intensified through an interaction with Fe3+ neighbors. The variation of molar absorptivity of Fe2+ bands with the fraction of Fe2+ in Fe2+-Fe3+ pairs indicates that Fe3+ ions increase the absorptivity of Fe2+ bands to ~1200 M-1cm-1 as compared to ~5 M-1cm-1 for non-interacting Fe2+. Approximately equal degrees of intensification were observed for both components of the 5T2 \u2192 5E Fe2+ transition as well as for Fe2+ in two different sites. Although the detailed behavior of non-interacting Fe2+ ions differ in Mg-tourmalines and Li,Al-tourmalines, the characteristics of Fe2+-Fe3+ absorption are constant. Intensity increases were restricted to the polarization which coincided with the vector between the Fe2+ and Fe3+ ions. The intensified Fe2+ transitions are characterized by an unusual temperature response. The integrated intensity of these transitions increases by 10-50% at 83 K as compared to 296 K. The positions and widths of the intensified transitions maintain the values of the non-interacting Fe2+. Tourmalines with the lowest Fe3+ contents were the gemmy Li,Al-tourmalines which generally form in pockets within pegmatites. Fe,Mg-tourmalines exhibited consistently higher Fe3+ contents than any of the Li-bearing tourmalines examined. Oxidation of Fe2+ which resulted from gamma irradiation of blue Li-tourmalines which contained several percent each of MnO and FeO could be monitored by increases in Fe2+ intensity in one polarization.
\r\n\r\nFe2+-Ti4+ charge transfer transitions were examined in minerals which contain stoichiometric quantities of Fe and Ti -- taramellite, neptunite, and traskite -- and tourmaline. The wavelength of these transitions ranged between 400 and 500 nm, and the halfwidths ranged between 7000 and 9000 cm-1. These characteristics can generally be used to assign Fe2+-Ti4+ charge transfer transitions. The molar absorpitivities of these transitions, however, exhibit very large variations. The molar absorptivity of Fe2+-Ti4+ charge transfer in neptunite is ~225 M-1cm-1 in beta polarization, in taramellite it is ~1300 M-1cm-1 and in tourmaline it is ~4000 M-1cm-1. Tentative assignments of Fe2+-Ti4+ in more dilute minerals generally compare favorably with the energy and width stated above. However, sapphire and other Al-minerals such as kyanite have very different characteristics for bands assigned to Fe2+-Ti4+ charge transfer. The Fe2+-Ti4+ charge transfer transition in taramellite exhibits no change in integrated intensity with decreasing temperature but increases by 15% from 296 K to 83 K in tourmaline. Mn2+-Ti4+ charge transfer was also assigned to a transition at 320 nm in two unusual yellow tourmalines.
\r\n\r\nThe characteristics of Fe2+-Fe3+ charge transfer transitions were reviewed in light of recent data and with regard to their utility as diagnostic criteria. A correlation between charge transfer energy and the separation of the interacting cations proposed by Smith and Strens (1976) could not be supported by the expanded data base. Temperature variations of charge transfer transition areas were also examined. The magnetic behavior of two minerals which exhibited different temperature responses were investigated. General agreement with the theories of Cox (1980) and Girered (1983) that suggest that ferromagnetic exchange should produce intensity increases at low temperature and that antiferromagnetic exchange produces intensity decreases was confirmed by these examples of Fe2+-Fe3+ charge transfer but could not explain the temperature response of Fe2+-Ti4+ charge transfer transitions. In any case, an increase in intensity with decreasing temperature, which is generally expected on the basis of experimental observations, cannot be used in a negative sense to eliminate a charge transfer assignment. The large width of charge transfer transitions is generally the most useful diagnostic criterion.
\r\n\r\nCox, PA (1980) Electron transfer between exchange-coupled ions in a mixed-valency compound. Chem Phys Lett 69: 340-343
\r\n\r\nGirerd, J-J (1983) Electron transfer between magnetic ions in mixed valence binuclear systems. J Chem Phys 79: 1766-1775
\r\n\r\nSmith, G and Strens, RGJ (1976) Intervalence transfer absorption in some silicate, oxide and phosphate minerals. In: The Phyics and Chemistry of Minerals and Rocks, Strens, RGJ (ed.). New York: Wiley and Sons, pp. 583-612
" }, { "name": "Paige, David Abbey, Jr.", "degree": "PhD", "year": "1985", "title": "The Annual Heat Balance of the Martian Polar Caps from Viking Observations", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04162010-092926816", "creators": [ { "name": { "family": "Paige", "given": "David Abbey, Jr." }, "id": "Paige-David-Abbey-Jr", "orcid": "0009-0001-6122-9904", "display_name": "Paige, David Abbey, Jr." } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "chair", "display_name": "Stevenson, David John" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Morgan", "given": "James J." }, "id": "Morgan-J-J", "role": "member", "display_name": "Morgan, James J." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Zurek", "given": "Richard W." }, "id": "Zurek-Richard-W", "role": "member", "display_name": "Zurek, Richard W." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "plansci" ], "doi": "10.7907/DPB3-P589", "abstract": "This thesis presents the first measurements of the annual heat budgets of the polar caps of Mars from spacecraft observations. The primary motivation for this work is to understand why seasonal CO2 frost deposits at the north pole of Mars disappear in the summer, whereas seasonal CO2 deposits near the south pole do not. This behavior is not expected to first order because both Martian poles receive the same total amount of sunlight at the top of the atmosphere over the course of a year. Understanding why the Martian north and south polar caps behave in an asymmetric fashion is important because the vapor pressures of permanent polar CO2 deposits determine the planet-wide surface pressures of CO2 gas, which is the dominant constituent of the Martian atmosphere.
\r\n\r\nAnnual radiation budgets for the core regions of the north and south polar caps are determined from solar reflectance and infrared emission observations obtained by the Infrared Thermal Mappers (IRTMs) aboard the two Viking orbiters. The results show that the absence of CO2 frost at the north pole during summer is primarily due to an asymmetry in the rates of CO2 frost sublimation at surface in the north and south during spring. Further analysis traces this difference to seasonal frost reflectivities being approximately 20% lower in the north than in the south during late spring. It is shown that seasonal frost deposits at the poles demonstrate a remarkable tendency to not become darker when contaminated with dust, and to become brighter with increasing rates of solar illumination. Since peak solar illumination rates are presently higher at the south pole than the north pole because of the large eccentricity of Mars' orbit, the tendency for the frost to become brighter with increasing rates of solar illumination explains the asymmetry. The tendency for the frost to not become darker when contaminated by dust explains why the seasonal behavior of the Martian polar caps is highly repeatable from year to year despite interannual variations in the occurrence of Martian global dust storms.
\r\n\r\nIt is suggested that the unexpected properties of Martian seasonal frost deposits revealed by the results of this study are caused by the tendency for dust particles within the frost to absorb solar radiation, sublimate the solid CO2 that supports them and sink into the frost. If the current behavior of Martian CO2 frost is an indicator to past events, then interactions between dust and frost have exerted a powerful stabilizing influence on the Martian climate system.
" }, { "name": "Scott, Patricia Frances", "degree": "PhD", "year": "1985", "title": "Applications of the Kirchhoff-Helmholtz Integral to Problems in Body Wave Seismology", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechETD:etd-06062005-132701", "creators": [ { "name": { "family": "Scott", "given": "Patricia Frances" }, "id": "Scott-Patricia-Frances", "display_name": "Scott, Patricia Frances" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "chair", "display_name": "Clayton, Robert W." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "geophys" ], "doi": "10.7907/tckd-xm91", "abstract": "This thesis describes a procedure for evaluating the Kirchhoff-Helmholtz integral and presents applications of it which involve the interpretation of amplitude and travel time anomalies of body waves. The method of integration is a summation of single point evaluations of the integrand and requires that spacing of these evaluations on the surface be small compared to the wavelength of the incident disturbance. The technique predicts amplitudes, travel times and waveforms of acoustic potentials that propagate through a homogeneous medium and interact with three-dimensional curved boundaries. Results from test models compare well with optical solutions for reflections off planar interfaces and rigid spheres and transmissions through planar interfaces.
\r\n\r\nThe reflected integral solution is used to simulate the effect of an idealized mountain on the amplitude and waveforms on pP. This structure causes multiple arrivals, phase shifts, and amplitude anomalies in the synthetic reflection profile. Also the effects of spall on pP waves generated by explosions are simulated by specifying position dependent reflection coefficient on the surface of integration. These experiments predict frequency dependent amplitude anomalies and travel time delays of the reflections.
\r\n\r\nThe transmitted solution is used to model the effect of several idealized crust-mantle boundary structures on teleseismic P waves generated by explosions. The structures are upwarps and product travel time residuals as a function of delta and azimuth which have the same magnitude as residuals observed for NTS tests within Pahute Mesa. The structure causes early complicated low amplitude waveforms and late simple high amplitude waveforms. Thus they cause systematic amplitude variations with azimuth, delta, and source location. The magnitude of predicted variation is less than the observed ab amplitude variation with azimuth of Pahute Mesa tests; however, it is approximately the same as the observed ab variation at a given station as a function of test location within the mesa.
\r\n\r\nThe integral method is extended to include a symmetric velocity function in the medium and is used to model ScS waves which propagate through a JB Earth and reflect off a bumpy core-mantle boundary. Solutions with this extension establish that isovelocity Kirchhoff solutions are sufficient to predict the relative amplitude and travel time anomalies of ScS arising from core-mantle boundary relief. Isovelocity modeling shows that upwarps 300 to 600 kilometers wide and at least 10 kilometers high cause precursors to ScS and amplitude reductions of the same magnitude as the observations. However, the height is not mechanically feasible; therefore, the anomalous observations must originate elsewhere.
" }, { "name": "Summers, Michael Earl", "degree": "PhD", "year": "1985", "title": "Theoretical Studies of Io's Atmosphere", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302013-100511748", "creators": [ { "name": { "family": "Summers", "given": "Michael Earl" }, "id": "Summers-Michael-Earl", "orcid": "0000-0001-5986-8902", "display_name": "Summers, Michael Earl" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "chair", "display_name": "Epstein, Samuel" }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Cohen", "given": "Judith G." }, "id": "Cohen-J-G", "orcid": "0000-0002-8039-4673", "role": "member", "display_name": "Cohen, Judith G." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "plansci" ], "doi": "10.7907/rsm8-qh33", "abstract": "A range of theoretical models of the compositional structure of Io's dayside atmosphere and ionosphere are developed. The dominant neutral gas, SO2, is provided by sublimation of surface frost. Photochemical processes lead to the build up of O, S, SO, and O2 as minor gasses near Io's surface while O becomes the dominant gas near the exobase. The vertical column density of O2 in all models considered is less than 1014 cm-2. The dayside ionosphere is formed as a result of ionization of neutral species by solar UV radiation. Charge exchange and rearrangement reactions are important for determining the ionic composition of the ionosphere. The dominant ion in the models considered is SO+. A number of charge exchange reactions are identified whose rates need to be better determined in order to refine the present model of the ionosphere. The best matches of the model ionospheres to that observed by the Pioneer 10 radio occultation experiment require atmospheric surface concentrations of SO2 in the range of 2.5 x 109 to 1 x 1011 cm-3, and an exospheric temperature in the range of 960 K to 1230 K. The ratio of the escape fluxes of O to S from the exobase is \u2265 2 in the models considered, while the models which allow surface deposition of minor constituents always have a total sulfur depositional rate greater than 1/2 of the total oxygen depositional rate, thus a surface enrichment of S relative to that predicted by a pure SO2 surface. The depositional rate of this \"excess\" sulfur is in the range 100 m to 1 km thickness per billion years.
\r\n\r\nAtmospheric Na is provided by surface sputtering of SO2 surface frost with Na impurities by MeV type magnetospheric ions. An upward flux of Na2O of S x 107 cm-2 s-1 leads to an escape flux of Na from the exobase of 1 x 107 cm-2 s-1. The chemistry (ion and neutral) of Na species in the atmosphere has only minor effects on the major characteristics of the atmosphere and ionosphere.
\r\n\r\nIt is generally accepted that Io is the source of S, O, Na, and K which, subsequent to ionization, form the constituents of the Io plasma torus. It is shown in chapter II that the escape of S and O from Io can be understood in terms of the photochemistry of a predominantly SO2 atmosphere created by the high vapor pressure of SO2. However, the vapor pressures of Na2S, K2S and other common compounds containing Na and K are negligible at the surface temperature of Io. In chapter III we propose that Na and K escape from Io in two stages. Atoms of Na and K (or molecules containing these atoms) are first sputtered into the atmosphere from the surface by high energy magnetospheric ions. Atmospheric sputtering by low energy corotating ions then removes these constituents (along with others present) out of Io's gravitational control. The estimated injection rates are sufficiently large to maintain the observed Na, K, and O clouds observed around Io.
" }, { "name": "Aines, Roger Deane", "degree": "PhD", "year": "1984", "title": "Trace Hydrogen in Minerals", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:11092018-122937399", "creators": [ { "name": { "family": "Aines", "given": "Roger Deane" }, "id": "Aines-Roger-Deane", "display_name": "Aines, Roger Deane" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "chair", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" } ], "option_major": [ "geochem" ], "doi": "10.7907/n7vk-f724", "abstract": "Trace hydrogen in minerals most frequently occurs bonded to oxygen. The resulting water and hydroxyl (OH-) affect and play a role in a variety of mineral properties and reactions. This thesis examines the occurrence of trace hydrogen in nominally anhydrous minerals, the mechanisms by which trace hydrogen participates in reactions and controls properties, and the changes that occur in hydrogen speciation and siting as a function of temperature. The principal tool used in this study is infrared (IR) spectroscopy because of its sensitivity to the highly polar O-H bond, yielding quantitative information on concentration, and symmetry, speciation, and siting information.
\r\n\r\nThe speciation of trace hydrogen in garnet and low temperature natural and synthetic quartz is examined in detail. In garnet hydrogen occurs as the hydrogarnet substitution, four hydroxyl groups replacing a silicate tetrahedron. This substitution is extremely common among natural garnets. Concentrations range from 0.05 to 0.20 wt. % (as H2O) in garnets from most occurrences, including garnets from the mantle. This trace hydrogen is truly dissolved. The hydrogen found in natural and synthetic quartz formed at low temperature can occur as either hydroxyl or molecular water. The molecular water is the active participant in hydrolytic weakening of quartz, but it is not truly dissolved. It occurs as small groups of molecules (approximately 5 to 200) which were trapped during rapid growth.
\r\n\r\nTwo properties of minerals affected by trace hydrogen are strength and radiation response. Molecular water may be responsible for weakening of other minerals as well as quartz. Both water and hydroxyl participate in radiation response of minerals. In metamict zircon, water stabilizes local charge imbalance formed when bonds are broken. Water enters the crystal after a threshold of damage occurs, and reacts with broken bonds to form hydroxyl groups. These must reform molecular water and be expelled before recrystallization occurs during heating. In quartz, molecular water is strongly correlated with the formation of citrine color during irradiation, but inhibits the formation of the amethyst color center Fe4+. Apparently molecular hydrogen forms during radiolysis of the water, and reduces the Fe4+. Several hydroxyl sites in topaz are strongly correlated with the formation of brown color upon irradiation. The unifying theme in all these reactions is the extreme mobility of hydrogen and the ease with which different oxygen-hydrogen species may be formed in silicates.
\r\n\r\nThe behavior of trace hydrogen at temperatures of geologic interest has been examined using high temperature infrared spectroscopy. Direct observations of speciation, concentration, and properties have been made up to 1200\u00b0C. In muscovite there is no change in hydrogen speciation or site up to the dehydration point, as expected. However, in cordierite and beryl water reversibly partitions into a gas-like state above 400\u00b0C, and the formation of this new state controls the dehydration behavior. In topaz, hydroxyl groups have been observed converting to new sites at temperatures above 500\u00b0C. In orthoclase feldspar, one type of molecular water dehydrates at 200\u00b0C, while a second type converts irreversibly to a new hydrous species above 600\u00b0C.
\r\n\r\nThere is no evidence for the existence of hydrogen species other than hydroxyl and water in silicate minerals. The hydrogarnet substitution (four hydroxyl groups in a tetrahedral configuration) is common in garnets and may be important in other orthosilicates. The most common hydrous species in nominally anhydrous silicates (aside from fluid inclusions and alteration) are: small groups of trapped water molecules; individual water molecules occupying voids in the structure of minerals; hydroxyl occurring in a charge balancing role such as AlO3OH substituting for SiO4; hydroxyl neutralizing substitutional atoms, e.g., LiOH; and hydroxyl groups formed from the reaction of broken bonds with water as in radiation damaged minerals. There is no evidence for the presence of the oxonium ion, H3O+, in common minerals, and the existing evidence for the occurrence of molecular hydrogen may better be explained by the presence of water or hydroxyl groups.
" }, { "name": "Boslough, Mark Bruce", "degree": "PhD", "year": "1984", "title": "Shock-Wave Properties and High-Pressure Equations of State of Geophysically Important Materials", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09262002-154053", "creators": [ { "name": { "family": "Boslough", "given": "Mark Bruce" }, "id": "Boslough-Mark-Bruce", "orcid": "0000-0001-6912-4608", "display_name": "Boslough, Mark Bruce" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Corngold", "given": "Noel Robert" }, "id": "Corngold-N-R", "role": "member", "display_name": "Corngold, Noel Robert" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Roshko", "given": "Anatol" }, "id": "Roshko-A", "role": "member", "display_name": "Roshko, Anatol" }, { "name": { "family": "Vreeland", "given": "Thad" }, "id": "Vreeland-T", "role": "member", "display_name": "Vreeland, Thad" } ], "option_major": [ "appliedphys" ], "doi": "10.7907/C9GZ-3121", "abstract": "Shock wave (Hugoniot), shock temperature, and release data are presented for several geophysically important, refractory materials. A sensitive multichannel optical pyrometer was developed to measure shock temperatures (2500 to 5600\u00b0K at pressures from 48 to 117 GPa) in anorthite (CaAl2Si2O8) glass. Shock temperatures of 3750 to 6000\u00b0K at pressures from 140 to 182 GPa were measured in calcium oxide (CaO). Temperature data were used to constrain the energetics of the B1-B2 phase transition at 70 GPa in CaO, and to construct a finite-strain equation of state for CaO consistent with previous Hugoniot data.
\r\n\r\nThe new CaO equation of state was used with equation of state parameters of other oxides to construct a theoretical mixed oxide Hugoniot of anorthite, which is in agreement with new Hugoniot data above about 50 GPa, determined using new experimental techniques developed in this study. The mixed oxide model, however, overestimates the shock temperatures, and does not accurately predict measured release paths. Both shock temperature and release data for anorthite indicate that several high pressure phase regions of stability exist above 50 GPa. A similar mixed oxide Hugoniot was constructed for lunar gabbroic anorthosite, and agrees with two new Hugoniot points at 120 GPa. Release data from lunar gabbroic anorthosite shocked to 120 GPa give evidence for shock vaporization.
\r\n\r\nBecause the densities and bulk properties of CaO and the high pressure phase or phases of anorthite are so close to those determined seismologically for the lower mantle, the amount of these materials present in the lower mantle is not well constrained. The possibility of significant enrichment of the lower mantle in these refractory materials, as predicted by inhomogeneous accretion models, is still open.
\r\n\r\nA simple model is developed to explain the measured time dependences of radiated light in the shock temperature experiments, and constrain the absorption coefficient of the shocked material. The absorption coefficient is found to be an increasing function of shock pressure in shocked anorthite glass.
\r\n\r\nHugoniot and release paths were determined using electromagnetic particle velocity gauges for San Gabriel anorthosite and San Marcos Gabbro shocked to peak stresses between 5 and 11 GPa. The data indicate a loss of shear strength in both rocks, and a partial phase transition of the anorthosite to a denser phase. This implies that estimates of shock wave attenuation in these materials based on elastic-plastic models are too high, and previously calculated amounts of internal energy gained by surface materials from impact or explosion events have been underestimated.
" }, { "name": "Corbett, Edward John", "degree": "PhD", "year": "1984", "title": "Seismicity and Crustal Structure Studies of Southern California: Tectonic Implications from Improved Earthquake Locations", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10082018-123143470", "creators": [ { "name": { "family": "Corbett", "given": "Edward John" }, "id": "Corbett-Edward-John", "display_name": "Corbett, Edward John" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "chair", "display_name": "Allen, Clarence R." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." } ], "option_major": [ "geophys" ], "doi": "10.7907/h8mm-4v50", "abstract": "This thesis consists of studies of: 1) the 1978 Santa Barbara earthquake and its aftershocks; 2) the depth distribution of seismicity in the Transverse Ranges; 3) crustal-velocity structure of the Continental Borderlands derived from explosion data; 4) the 1981 Santa Barbara Island earthquake and its aftershocks; and 5) earthquake location procedures, in particular the calibrated master-event technique.
\r\n\r\nThe 5.1 ML Santa Barbara earthquake of 13 August 1978 occurred at 22h 54m 52.8s GMT. The epicenter was located 3 km southeast of Santa Barbara at 34\u00b0 23.9' N latitude and 119\u00b0 40.9' W longitude with a focal depth of 12.7 km. The mainshock was followed between 13 August and 30 September by 373 aftershocks that were located with the Caltech-USGS array. The aftershock zone extended 12 km west-northwest from the epicenter and was 6 km wide in the north-south direction, and it had a very clear temporal development. During the first 20 minutes of activity, all the aftershocks were located in a cluster 7 km west-northwest of the mainshock epicenter. During the next 24 hours the aftershock zone grew to 11 km in the west-northwest direction and 4 km in the north-south direction. During succeeding weeks, the zone extended to 12 by 6 km. This temporal-spatial development relative to the mainshock epicenter may indicate that the initial rupture propagated 7 km unilaterally to the west-northwest, and the initial rupture plane may have been considerably smaller than that of the eventual aftershock zone. This smaller area suggests that the stress drop may have been significantly greater than that derived from the area of the final aftershock zone.
\r\n\r\nIn cross-section, the aftershock hypocenters outline a nearly horizontal plane (dipping 15\u00b0 or less) at 13-km depth. The mainshock focal mechanism indicates north-northeast/south-southwest compression and vertical extension. The preferred fault plane strikes N 80\u00b0 W and dips 26\u00b0 NNE, indicating north-over-south thrusting with a component of left-lateral movement. Focal mechanisms for 40 aftershocks also indicate compression in the general north-south direction. For most of these events, the north-dipping nodal plane dips between 7\u00b0 and 45\u00b0, with most dipping 25\u00b0 or more, which is significantly steeper than the plane delineated by the hypocenters themselves. These observations are consistent with a tectonic model in which much of the slip during the Santa Barbara earthquake occurred on a nearly horizontal plane. The aftershocks then might represent movement on a complex series of imbricate thrust faults that flatten into the plane of primary slip. Hence, the Santa Barbara earthquake may be taken as evidence for mid-crustal horizontal shearing in the western Transverse Ranges.
\r\n\r\nTo further test the decollement hypothesis, Caltech catalog locations were reviewed to determine the depth distribution of earthquakes in the Transverse Ranges. Only events with ERH < 1 km and ERZ < 2 km were utilized. These were scrutinized further with a numerical test of location procedures to test the reliability of the Caltech catalog quality assignments. These tests confirmed location qualities within 40 km of the east-west axis of the Transverse Ranges, but cast doubt on locations to the north and south.
\r\n\r\nThe bottom of the seismogenic zone is clearly deepest along the southern front of the Transverse Ranges, with the deepest earthquakes occurring in the Pt. Mugu-Malibu area and under San Gorgonio Pass. Seismic activity is noticeably shallower north and east of the San Andreas fault than it is across the fault to the southwest. The seismogenic zone is thinnest in the southern Mojave Desert and at the east end of the Transverse Ranges. The seismicity of the western Transverse Ranges is typified by several north-dipping planar structures that correlate with the aftershock zones of recent earthquakes. The eastern Transverse Ranges are typified by ubiquitous seismicity extending from the surface down to the floor of the seismogenic zone. The San Bernardino Mountains are underlain by a well-defined bottom of the seismogenic zone that dips southward from 5-km depth under the Mojave Desert to 15-km depth where it intersects the San Andreas fault. South of the San Andreas fault, seismic activity deepens abruptly to as much as 22-km depth. The most intense seismicity is localized in the San Gorgonio Pass between the north and south branches of the San Andreas fault. This study falls short of the solving the decollement question, but it does add more intriguing evidence to the puzzle.
\r\n\r\nA large quarry explosion detonated on Catalina Island produced clear signals at stations throughout southern California. Data from near-shore and Island stations were utilized to derive velocity structure by the slope-intercept method. A 5.2-km/sec layer underlain by a 6.3-km/sec refractor was typically observed in most azimuths. A 7.8-km/sec Moho refraction was observed at ranges beyond 120 km. The interpretation is that the crustal refractor is at 5.5-km depth and the Moho is at 22-km depth. The upper crustal layer is significantly faster (5.5 km/sec) and thinner (2.5 km) under Catalina Island. An early Pn arrival and possible Moho reflections observed at San Nicolas Island may constrain the Moho to be an average of 2 km shallower in the direction west from Catalina. This velocity structure was successfully used to improve the locations of the 1981 Santa Barbara Island earthquakes.
\r\n\r\nThe Santa Barbara Island earthquake occurred at 15:50:50 GMT on September 4, 1981, at 30\u00b0 40.9' N and 119\u00b0 3.6' W, and registered 5.3 ML. Aftershocks exhibited a clear northwest-southeast alignment that coincides with the northeast-facing escarpment of the submarine Santa Cruz-Catalina ridge. This alignment also coincides with a mapped bedrock fault which is herein referred to as the Santa Cruz-Catalina fault. Focal mechanisms of the mainshock and the 3 largest aftershocks consistently show right-lateral strike slip on a northwest-trending plane, with possibly a component of dip slip. Aftershock depths show a near-vertical fault plane. The aftershock zone was initially 6 km long or less, and was concentrated southeast of the mainshock, suggesting unilateral rupture. The aftershock zone grew bilaterally to 15-km length after 24 hours to 21 km after 10 days, and to 35 km long after several months. This behavior may be Interpreted in tenns of an asperity model.
\r\n\r\nThis seismic activity suggests strike-slip motion on the Santa Cruz-Catalina fault, with Santa Monica basin being displaced southeastward relative to points west. Structural complexities at the northwest and southeast ends of this fault suggest that the Santa Monica basin and Catalina Island are behaving as a coherent block pulling away from the Transverse Ranges, with extension at the northwest corner of the basin and compression to the south at the Catalina escarpment. Thus the Santa Monica basin may have formed as a triangular gap opening up between Peninsular Ranges blocks and the Transverse Ranges along the lines of the model of Luyendyk et al. (1980).
\r\n\r\nNearly all earthquake location programs use Geiger\u2019s (1912) method of least squares. This rigorous statistical method assumes that all the data are of equal quality and the only source of error is in measuring arrival times. This is not generally true of real earthquake data, which has led to a number of attempts at improvement. One of the most common modifications is data weighting of three types: quality weighting, distance weighting, and residual weighting. Programs that use all three must be used carefully to avoid feedback between weighting routines, with residual weighting being the worst cause of feedback. Station corrections are used to correct for systematic velocity variations and permit higher precision relative locations. The two most popular relative location methods are Joint Hypocenter Determination (JHD) and the master-event technique. The locations in Chapters 2 and 5 were performed with a modification termed the calibrated master event (CME) method. First, an intermediate-sized event is calibrated (preferably by explosion data) to achieve the best possible absolute location. Then, the residuals and hypocenter of this master event are used for establishing station delays and starting location, respectively, for relocating the seismicity of interest. Case histories of previous location attempts document the improvement attained with the CME method.
" }, { "name": "Froidevaux, Lucien", "degree": "PhD", "year": "1984", "title": "Photochemical Modeling of the Earth's Stratosphere", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:10012018-103419193", "creators": [ { "name": { "family": "Froidevaux", "given": "Lucien" }, "id": "Froidevaux-Lucien", "orcid": "0000-0002-0681-1483", "display_name": "Froidevaux, Lucien" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "chair", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "DeMore", "given": "William B." }, "id": "DeMore-William-B", "role": "member", "display_name": "DeMore, William B." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/hzdt-5z21", "abstract": "We have helped develop a one-dimensional photochemical model of the Earth's stratosphere, in order to provide an up-to-date comparison with mid-latitude observations. This work focuses on the present state of the stratosphere, and includes studies of the radiation field (absorption and scattering), the important partitioning and vertical distribution of halo-carbons and their products, as well as certain intriguing discrepancies related to light and heavy ozone.
\r\n\r\nWe briefly comment on the detection by J. R. Herman and J. E. Mentall of a 10% ratio of total scattered flux to direct solar flux at a wavelength of about 200 nm and an altitude of 40 km. This ratio is over a factor of two higher than our theoretical results and cannot be explained without the existence of a scattering component not included in the model. We also explicitly demonstrate the first-order effects of the inclusion of sphericity (spherical shell atmosphere) on the stratospheric photochemistry at solar zenith angles close to 90\u00b0. The resulting changes in model concentrations for short-lived radicals such as O, OH, ClO, and NO are largest in the lower stratosphere, but relatively small compared to current observational uncertainties.
\r\n\r\nWe propose that a significant overestimate of the molecular oxygen absorption cross sections in the important spectral window from about 200 to 220 nm is in large part responsible for the discrepancy between observed and modeled vertical profiles of some halocarbons (CFCl3 in particular), as well as for the long-standing problem of simultaneously fitting N2O, CH4, CF2Cl2, and CFCl3 profiles with a single eddy diffusion model. Recent measurements of atmospheric transmission by J. R. Herman and coworkers seem to support this idea. The use of their proposed reduction in O2 cross sections leads to significant decreases in the CFCl3 concentration above about 20 km, with smaller reductions in N2O, CF2Cl2 and HNO3. The concentrations of CH4, H2, and CO are not significantly altered. Changes in other gases (including ozone) are also discussed, as well as the effect on eddy diffusion coefficients obtained from measurements of N2O or CH4 profiles in the stratosphere. Accurate determinations of these small O2 absorption cross sections are needed, since they affect the vertical distribution of halo-carbons in the stratosphere, and the lifetime of these species has an impact on ozone depletion estimates.
\r\n\r\nIn terms of the halocarbon decomposition products in the stratosphere, our model vertical distribution of ClO is shown to provide a reasonably good fit to the mean of available observations. As discussed by others, changes in certain rate constants affecting HOx in the lower stratosphere have led to decreases in model ClO concentrations by over a factor of three in the lower stratosphere, thus improving the shape of the vertical profile. In addition, the amount of upper stratospheric ClO has increased due to recent changes in the kinetics (reactions O + HO2, O + ClO, and possibly OH + HCl). The diurnal variation of ClO observed from the ground (microwave emission) by P. Solomon and coworkers is consistent with our model results in terms of the maximum day-to-night decrease in column abundance above about 30 km. However, the observed mid-morning increase is slower than theoretical values, while the predicted afternoon decrease might be too slow, even if one considers the uncertainties in photochemical data. This could indicate the existence of missing chemistry in the models. Although the different observations show somewhat contradictory results. Other observations (balloon-borne microwave spectroscopy and infrared laser radiometry) are also discussed in relation to our model. To first-order, indirect evidence for the breathing cycle between ClO and ClONO2 seems to have been established. The mean observed HCl mixing ratio profile decreases somewhat faster towards the lower stratosphere than model profiles, a discrepancy which has previously been noted, particularly at high latitudes. Measurements of ethane in the lower stratosphere seemed to indicate that the atomic chlorine concentration was three to five times lower than predicted, but more recent data do not show such a discrepancy.
\r\n\r\nThe fluorine products consist mostly of HF and COF2. We show that the main uncertainty for this system is the value of the quantum yield (as a function of wavelength) for COF2 photodissociation, which translates into a factor of three or more uncertainty in the ratio of HF to COF2 concentrations in the upper stratosphere. If this quantum yield has an average value close to 0.25, a better model fit to observations of HF and [HF]/[HCl] is obtained than if the value is close to unity. Simultaneous stratospheric measurements of COF2 and HF, as well as ClO and HCl, would greatly enhance our ability to test photochemical models of these halocarbon products.
\r\n\r\nFinally, we stress that, although generally good agreement is found between our model and observations of HOx, NOx, and ClOx species (involved in catalytic cycles destroying ozone), the mean observed mid-latitude ozone abundance from about 35 to 50 km is up to 50 or 60% greater than current model results. Certain observations of a 10 to 15% daytime increase in ozone concentration in the 30 to 40 km region are also puzzling, if real. We explore the model sensitivity to various input parameters and point out that, given the present uncertainties in photochemical laboratory data, no reasonable change in one or even three or four of these parameters can eliminate the ozone discrepancy. There might well be some missing chemistry in relation to the effectiveness of the loss processes for odd oxygen, or a (less likely) unknown significant O3 source. We have to understand the present upper stratospheric ozone distribution, before estimates of possible future ozone depletion can be made with confidence. We also discuss our understanding of heavy ozone photochemistry, which might be related to a light ozone photochemical source. Fast isotopic exchange processes between O and O2 will dominate the heavy odd oxygen chemistry, and we do not find any significant heavy ozone enhancement possibilities in the stratosphere, unless unusually large fractionation processes exist. The in situ mass spectrometer observations of a 40% enhancement in 18O32O2 near 30 km by K. Mauersberger remain a mystery, and further data collection -- possibly via infrared or microwave spectroscopy as well -- should be undertaken if this potentially significant discrepancy is to be understood.
" }, { "name": "Given, Jeffrey Wayne", "degree": "PhD", "year": "1984", "title": "Inversion of Body-Wave Seismograms for Upper Mantle Structure", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10242018-091909982", "creators": [ { "name": { "family": "Given", "given": "Jeffrey Wayne" }, "id": "Given-Jeffrey-Wayne", "display_name": "Given, Jeffrey Wayne" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geophys" ], "doi": "10.7907/cgdh-0e19", "abstract": "We invert observed long- and short-period body-wave seismograms, travel times, and apparent velocity data to further constrain the compressional velocity structure in the upper mantle beneath northwestern Eurasia and the shear-wave velocity structure beneath western North America.
\r\n\r\nLong- and short-period WWSSN seismograms from nuclear explosions in the Union of Soviet Socialist Republics are incorporated with apparent velocity observations to derive an upper mantle model for northwestern Eurasia. The compressional waves from these explosions have several distinctive features that provide important new information about the character of the upper mantle in the region. The seismograms from 9\u00b0 to 13\u00b0 exhibit impulsive first arrivals, Pn, implying a smooth positive velocity gradient between depths of 60 and 150 km. There is a consistent pulse arriving about 2s after Pn at the distances of 13\u00b0 to 17\u00b0, and at larger ranges there are distinct reflections from two major discontinuities in the mantle. Synthetic seismograms displaying these features indicate a velocity model that correlates with other models from around the world, with a distinctive lid and low-velocity zone. The arrival following Pn is modeled by positioning the low-velocity zone between 150 and 200 km. The model is relatively smooth from a depth of 200 km down to 420 km, where a 5% jump in velocity produces a triplication in the travel time curve from 15\u00b0 to 23\u00b0. The observations from 21\u00b0 to 26\u00b0 clearly show another discontinuity at a depth of 675 km with a 4% change in velocity. These results suggest that stable continental regions may have a shadow zone that extends beyond 17\u00b0. Below 250 km there is no distinguishable difference between the model proposed for northwest Eurasia and models derived for the United States.
\r\n\r\nA systematic inversion technique is proposed to extract the maximum amount of information from these data. We use the WKBJ method to compute approximate synthetic seismograms in a radially heterogeneous earth. Where the WKBJ method breaks down, in low-velocity zones and near discontinuities, a generalized ray expansion is used in a layered model approximation to the velocity structure to isolate the energy that has reflected from these regions. Synthetic seismograms computed using these approximations compare very well to those computed by the more accurate method of summing primary reflections in a generalized ray sum yet require 1/20 the computation time. With this efficiency it is feasible to compute the differential seismograms necessary to pose an inverse problem.
\r\n\r\nWith a fast means of computing synthetic seismograms, an inverse problem can be posed to relate the differences between observed and synthetic seismograms to perturbations in the velocity structure. The problem is nonlinear, especially at high frequencies, but at long periods an iterative technique based on a linearized relation between perturbations in the velocity structure and the seismograms is effective if a reasonable initial model is assumed. Some simple tests of the method indicate that convergence to a satisfactory final model is possible even when starting with a model that predicts substantially different seismograms than those observed.
\r\n\r\nWe invert long-period SH waves recorded on WWSSN seismographs at distances from 15\u00b0 to 31\u00b0 in the western United States and East Pacific Rise to determine the upper mantle shear velocity structure beneath these regions. A high velocity gradient near 400 km produces clear later arrivals from 15\u00b0 to 17\u00b0. We interpret large later phases observed al distances from 23\u00b0 to 27\u00b0 as another large velocity gradient at between 600 and 720 km depth. Inversion of these seismograms suggests that the velocity gradient in the upper 200 km of the mantle is small; there is an increase in the velocity gradient around 250 km resulting in a 4% velocity increase by 360 km. The large velocity gradient near 400 km results in a velocity increase of around 8\u00bd% between 360 km and 420 km depth. The velocity gradient becomes smaller between 420 and 600 km with a cumulative increase of 5% over these depths. The total increase in velocity from 600 to 750 km is about 14%. Below 750 km the velocity gradient is assumed to be similar to those predicted by global studies of travel times.
\r\n\r\nThere are differences in published travel time data and models that have been derived to fit the SS phases and SS-S differential times observed in this region. The discrepancies amount to about 5s in the direct S-wave travel time at distances of 15\u00b0 to 18\u00b0. The discrepancy appears to be on the order of 3 s from 19\u00b0 to 23\u00b0 and is not resolvable beyond. These disagreements are probably the manifestation of large velocity heterogeneities in the uppermost mantle; either assumption concerning absolute travel times can be fit by models that are virtually identical below 270 km. Absolute travel times can constrain absolute velocities and, thus, are necessary to constrain the depth to discontinuities. Waveform data can constrain the structural details better. A joint waveform and travel time inversion method is a very useful tool for interpreting seismograms for earth structure.
\r\n" }, { "name": "Hill, Robert Ian", "degree": "PhD", "year": "1984", "title": "Petrology and Petrogenesis of Batholithic Rocks, San Jacinto Mountains, Southern California", "advisor": "Saleeby, Jason B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09132016-161520143", "creators": [ { "name": { "family": "Hill", "given": "Robert Ian" }, "id": "Hill-Robert-Ian", "display_name": "Hill, Robert Ian" } ], "advisors": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "advisor", "display_name": "Saleeby, Jason B." } ], "committee": [ { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "chair", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Wyllie", "given": "Peter J." }, "id": "Wyllie-P-J", "role": "member", "display_name": "Wyllie, Peter J." } ], "option_major": [ "geol" ], "doi": "10.7907/9x01-1n85", "abstract": "A combined field and laboratory study of plutonic rocks from the San Jacinto Mountains of southern California was conducted in order to investigate the nature and origins of strontium and oxygen isotope heterogeneities within batholithic rocks.
\r\n\r\nGeological mapping has allowed differentiation of three major and many minor masses of plutonic rock. Contacts between units are offset up to 6 km by faults of the Neogene San Jacinto fault system, which has a total right-lateral displacement of 29\u00b11 km. The early small intrusives range from olivine gabbro through granite. They were intruded by three larger plutons of relatively homogeneous biotite-hornblende-titanite tonalite. The oldest major intrusive unit, Unit I, is an elongate body of dimensions 40x8 km. Before complete solidification it was intruded by Unit II, an irregular tabular mass 25 km long and a few kilometers wide. Unit III, in turn, intruded Unit II before it was completely solidified, producing a roughly rectangular mass 20x12 km that appears to funnel in downwards.
\r\n\r\nMineral foliations and banding, schlieren, and xenolith orientations within each unit usually parallel the nearest contact. Alignment of foliations and apparent flow-sorting and scour features seem to reflect flow patterns within each chamber. Mlfic synplutonic dikes (quartz diorite to tonalite) intruded into the tonalites, and were commonly broken up and redistributed as linearly extensive xenolith trains. From these relationships it is interpreted that: 1) magma adjacent to pluton walls had considerable yield strength, as it could fracture to allow dike emplacement; 2) magmatic flow adjacent to pluton walls was capable of moving material some distances (up to km) to create the xenolith trains; and 3), that the dikes are potentially the feeders through which material was added to the inflating magma chambers. Each major tonalite unit spans a limited compositional range of from mafic tonalite (Colour Index > 15) to low-K granodiorite (Colour Index < 10). Volumetrically minor felsic differentiates extend the compositional range through to granodiorite. Units I and II average slightly more mafic overall compositions than does Unit III. All units are comprised of plagioclase (An30-40) [50-55%], quartz[20-30%], K-feldspar[1-8%], biotite (10-15%], hornblende[0-5%], titanite[0-2%] and accessory zircon, apatite, allanite and ilmenite. Variations in mineral abundances are geographically systematic only within Unit III, which grades from marginal mafic tonalite to central low-K granodiorite.
\r\n\r\nMineral compositions throughout the major tonalites are remarkably uniform. The An content of the bulk plagioclase falls from An40 \u00b1 1 in the most mafic tonalites to An30 in low-K granodiorites; Mg/(Mg + Fe) of biotite and hornblende drop similarly from 0.44 to 0.36. The entire observed range of plagioclase compositions within the major tonalites is An44 to An25 (and to An47 in mafic xenoliths). The sole opaque mineral is almost pure ilmenite. This homogeneity of mineral compositions implies remarkable stability of physico-chemical conditions throughout crystallization of each unit.
\r\n\r\nMajor and trace element abundances reflect the general homogeneity of these rocks. Most have SiO2 in the range 63-68 wt.%; minor felsic differentiates extend to 71 wt.%. 60% of analyzed samples from Unit III fall in the restricted compositional range 66-68 wt.% SiO2; the majority of samples from Units I and II are more mafic than this. Major elements (excepting K2O) define excellent linear arrays on Harker diagrams. K2O shows a diffuse curvilinear pattern. Trace elements generally considered \"compatible\" (including the transition metals), and Sr also define linear arrays on Harker diagrams. Other trace elements, especially Ba, Rb, Pb, Th, U and REE show more complex behaviour. \"Mafic\" tonalites, (<65.5 wt.% SiO2) have simply covarying trace element endowments. Minor felsic differentiates, collected on the basis of field evidence for in situ fractionation, have higher Si, K, Rb, Ba, U and Th. \"Normal\" tonalites (66.5 < SiO2 < 70.0) have trace element and K endowments intermediate between the mafic tonalites and the felsic differentiates.
\r\n\r\nMafic tonalites, comprising about half the exposed rocks, crystallized from liquids which derived their geochemical characteristics before injection into the high-level magma chambers. The minor felsic differentiates are considered end-products of fractional crystallization within the magma chamber; the \"normal\" tonalites are interpreted as crystallizing from liquids of intermediate character, i.e., mixtures of \"primitive\" and fractionated liquids.
\r\n\r\nMeasured primary \u03b418O values vary from +9.0 to +10.6. Metasedimentary country rocks have \u03b418O values of +11.5 to +13.5. Exchange of oxygen between plutons and country rock is minor and limited to narrow border zones. Within Unit III primary \u03b418O correlates with position. A marginal zone of variable values (+9.0-+10.0) gives way to regularly increasing values (+10.0-+10.5) inwards. Primary \u03b418O correlates with Colour Index. Within the central part of Unit III the observed range in \u03b418O values can be explained by crystallization of modally variable rocks from a liquid of constant 18O/16O (to\u00b10.2 per mil). The \u03b418O values of the more mafic marginal rocks (and of mafic rocks from Units I and II) also correlate with Colour Index; lower SiO2 rocks have lower \u03b4180. This correlation cannot simply result from varying mineral abundances, but must reflect variations in \u03b4180 values of the liquids from which these rocks crystallized.
\r\n\r\nCalculated initial 87Sr/86Sr (Sri) varies substantially among rocks from each major tonalite unit (Unit I: 0.7060-0.7076; Unit II: 0.7060-0.7074; Unit III: 0.7058-0.7073). These variations appear geographically regular at the kilometer scale within each pluton. The complex patterns, however, differ fundamentally from the general regular west-to-east increase in Sri reported for the batholith (Early and Silver, 1973), and observed in the small early intrusives from the San Jacinto Mountains (0.7057-0.7077). Sri within these rocks shows no identified correlation with other geochemical and petrological parameters.
\r\n\r\nThe Sr isotope data indicate that melt production, transport, and crystallization processes combined were not capable of completely homogenizing initial variations in Sri within the liquids from which these rocks crystallized. This further implies that either the time scale for convection was large compared to that for crystallization, or that the length scale for convection was small compared to the size of the plutons. Field evidence suggests considerable flow within the magma chamber; estimation of rheological parameters suggest that flow was within a laminar flow convective regime.
\r\n\r\nThe combined observations are compatible with crystallization from an intermittently recharged, continuously fractionating system. Recharge tended to buffer both the thermal and chemical properties of liquids within the magma chamber; it gave a mechanism for introducing isotopic variations that are incorporated into this continuously crystallizing system. The mafic dikes are suggested to be conduits through which some of these liquids were injected into the various magma chambers. Chemical buffering by continued recharge is also compatible with the observation that the majority of these rocks have geochemical features interpreted as resulting from the action of processes prior to injection of liquids into the high-level magma chambers.
\r\n\r\nRocks with low Sri (0.7058-0.7068) generally have intermediate \u03b418O values (+9.7-+10.3), and fall near the low-\u03b418O side of the batholithic trend defined by Taylor and Silver (1978). Rocks with high Sri (>0.7072) cover the entire observed range in \u03b418O values (+9.0-+10.6), and overlap the field defined for the San Jacinto - Santa Rosa Mountains block by Taylor and Silver. These data require involvement of material from three isotopically distinct source materials in the generation of these rocks. Two of these components (one with low Sri, low \u03b418O; one with high Sri, high \u03b418O) are common to the bulk of the batholith to the south and west. The third (high Sri, low \u03b418O) seems unique to the San Jacinto - Santa Rosa Mountains block; its relative importance within the San Jacinto rocks appears to correlate negatively with SiO2, suggesting that it was associated with relatively mafic liquids. The oxygen isotopic data imply that as much as 35% of this component may be present in some rocks. This component has isotopic and inferred geochemical characteristics compatible with old, slightly enriched (in Rb relative to Sr) subcontinental lithosphere. The low-Sri, low-\u03b418O component appears to be either (or both) normal depleted mantle or (subducted) oceanic crust. Tile oxygen data imply that the third (high-Sri, high-\u03b418O) component has had a prior history at the Earth's surface; it could be either sediment, or igneous material altered at low temperatures such as hydrothermally altered oceanic crust. Geochemical features (K, Rb, LREE abundances) appear more compatible with sedimentary material.
\r\n\r\nThese data are compatible with, but do not prove, a model for this source region as being a mixture of normal depleted mantle, oceanic crust, old slightly enriched \"subcontinental lithosphere\", and subducted sediment. This model source contains variously 0-35% (oxygen atom basis) subcontinental lithosphere, up to 25% sedimentary component, and apparently requires material of both basaltic (oceanic crust) and depleted mantle composition to balance isotope systematic systematics.
\r\n\r\nTile combined data show 1) that the source volumes for the batholithic rocks were heterogeneous at the scale of hundreds of meters or greater, 2) that the effects of these source heterogeneities were at least partially preserved throughout melt production, transport, and crystallization, and 3) that the net effect of a persistent recharge-fractional crystallization process within the magma chambers was to buffer the composition of the bulk of the rock near that of the early-crystallizing solids.
" }, { "name": "Hofmeister, Anne Marie", "degree": "PhD", "year": "1984", "title": "A Spectroscopic and Chemical Study of the Coloration of Feldspars by Irradiation and Impurities, Including Water", "advisor": "Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10172018-114703911", "creators": [ { "name": { "family": "Hofmeister", "given": "Anne Marie" }, "id": "Hofmeister-Anne-Marie", "display_name": "Hofmeister, Anne Marie" } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "chair", "display_name": "Burnett, Donald S." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geol" ], "doi": "10.7907/bj75-5674", "abstract": "Natural smoky color or smoky color induced by ionizing radiation develops only in potassium feldspars (KAlSi3O8) free of water bound in the feldspar structure. Neither fluid inclusion water nor \u2261SiOH have an effect. The optical absorption spectra of the smoky color consist of polarized bands at 11600, 16200, 19100, and 27200 cm-1, whose integrated intensities are linearly correlated with the integrated intensity of a broad, asymmetric first derivative at geff = 2.027 in electron paramagnetic resonance (EPR) spectra. This hole center forms only in KAlSi3O8 without structurally bound H2O, and in microcline is resolved into an asymmetric six-line pattern at geff = 2.024 and a single derivative at geff = 2.009 which are Si-O- -K and a hole shared between two nonbonding oxygens (NBO) on Si. In analogy to coloring in quartz and glass, the 11600 cm-1 band is caused by a hole trapped between two NBO's on silicon, the 16200 and 27200 cm-1 bands are due to the Si-O- -K center, and the 19100 cm-1 band results from a hole trapped on an oxygen attached to two aluminums. Smoky centers do not develop in feldspars with structural water because irradiation mobilizes protons which, while diffusing, destroy centers in their path, and finally then settle in sites similar to their original site. Smoky color also develops in sodic plagioclases, but high Al content inhibits its formation in labradorite.
\r\n\r\nAmazonite color is intrinsic and controlled by an absorption minimum between three overlapping bands in the ultraviolet and a broad band in \u03b2 at 630, or one UV band and a broad band in \u03b2 at 720 nm, or both superimposed. Comparison of EPR to optical integrated intensities shows that all three colors are connected with a first derivative at geff = 1.56 and two satellites of about 1/7 intensity at geff of 1.83 and 1.39. Analysis of the EPR pattern shows that this center is Pb3+ 31% of the time, with the hole located on coordinating oxygens for the remaining 69%. This center is only produced in samples which have in addition to Pb, H2O structurally bound in the lattice. The dependence of color intensity on the smaller molar concentration of structural water or lead implies that lead and structural water in a 1:1 ratio produce color centers in amazonite. The first order reaction kinetics of amazonite color formation by irradiation and the observation that water is not consumed in the process suggests that Pb2+ is oxidized to Pb3+ by the product OH of the irradiation-induced dissociation of water while H concurrently destroys a hole center on an oxygen, and is followed by the regeneration of the water molecule. The kinetics also show that the radiation necessary for the coloration is provided by internal decay of 40K. The two end-member color types (630 or 720 nm) occur for microcline or orthoclase local structure, respectively. Al/Si disorder increases first locally, and then overall as larger amounts Pb or H2O are incorporated, so that crystals with intermediate Pb contents have both color types. A spectrally similar blue radiation color also occurs for Pb-bearing sodic plagioclases.
\r\n\r\nGemmy labradorite phenocrysts from one Steens Mountain basalt flow in Rabbit Basin, Oregon, sometimes possess a pink schiller, or more rarely a transparent red or green coloration. Direct microprobe analysis of the schiller flakes show that these are metallic copper. XRF analysis of the different colored zones revealed that only the copper content varies with color: colorless samples, or sections of crystals, have 0-35 ppm Cu; greens average 80 ppm Cu; reds average 135 ppm Cu; while schiller bearing labradorites have 50 to 240 ppm Cu. Spectral similarity of the red color to copper-ruby color of glass shows that the red arises from the intrinsic absorption of colloidal Cuo particles that are too small to scatter light (ca. 4 to 22 nm). Spectra from the green regions strongly resemble that of amazonite. Because the temperature of exsolution is subsolidus and proportional to Cu content, diffusion proceeds more rapidly for crystals with higher Cu content and results in formation of larger particles. The Cuo reduction at low temperature (800\u00b0C) involves formation of hole center (O-) that is captured by Pb2+ to form the green amazonite color (Pb3+). At high temperatures (~ 900 to 1100\u00b0C) the reduction of Cu is controlled by whatever reactions occur in the basalt to keep fO2 along the QFM buffer. Migration of Cuo may cause the variation of Cu concentrations in a single sample; but the variation of Cu content among different crystals suggests that the composition of the megacrysts was not constant and changed in response to an increasing copper content in the melt as crystallization of the labradorite proceeded.
\r\n\r\nThe coloration process in feldspar strongly resembles that in glasses for both radiation colors (smoky) and exsolution phenomena (Cuo colloids, Cuo schiller) and also that of radiation colors in other crystalline solids (smoky quartz, Pb3+ or Tl2+ in KCl). Although quartz and glass are structurally and chemically similar to feldspar, KCl is not, suggesting that for the most part it is the behavior of the chemical impurity on an atomic level which controls the coloring mechanism.
\r\n" }, { "name": "Larson, Peter Brennan", "degree": "PhD", "year": "1984", "title": "I. An \u00b9\u2078O/\u00b9\u2076O Investigation of the Lake City Caldera, San Juan Mountains, Colorado. II. \u00b9\u2078O/\u00b9\u2076O Relationships in Tertiary Ash-Flow Tuffs from Complex Caldera Structures in Central Nevada and the San Juan Mountains, Colorado", "advisor": "Sieh, Kerry E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09142018-134243270", "creators": [ { "name": { "family": "Larson", "given": "Peter Brennan" }, "id": "Larson-Peter-Brennan", "display_name": "Larson, Peter Brennan" } ], "advisors": [ { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "advisor", "display_name": "Sieh, Kerry E." } ], "committee": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "chair", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." } ], "option_major": [ "geol" ], "doi": "10.7907/aeb1-ct78", "abstract": "Part I. 18O/16O analyses were made on 355 samples in and around the 11 by 14 km Lake City caldera, which formed 23 m.y. ago in response to the eruption of the rhyolitic Sunshine Peak Tuff. All of the major lithologies and hydrothermal alteration facies were analyzed, and a detailed \u03b418O map was made of the caldera and its surroundings. Intracaldera facies Sunshine Peak Tuff consists of three members interbedded with landslide debris and megabreccias shed into the caldera during eruption and collapse. Asymmetric resurgence within the Lake City caldera followed collapse and was accompanied by intrusion of a flat-topped, granitic magma centered in the resurgent dome. Ring magmatism produced dike-like intrusions along the northern ring fault and the Red Mountain-Grassy Mountain quartz latite ring dome on the eastern caldera margin. The caldera was emplaced into older Tertiary volcanic rocks and Precambrian granitic rocks.
\r\n\r\nBased on analyses of outflow-facies samples and of the least altered intracaldera facies, we can demonstrate that the caldera-fill Sunshine Peak Tuff originally was isotopically very homogeneous, with an initial igneous \u03b418O value of +7.2 to +7.3. Thus, 18O depletions in the hydrothermally altered tuff could be compared without worrying about the complicating factor of different initial \u03b418O values. Nearly all the rocks within the caldera and outside the caldera within at least 3 km of the ring fault were altered by meteoric-hydrothermal fluids, and depleted in 18O down to values as low as \u03b418O = -3.1. Erosion has exposed the hydrothermally altered caldera-fill rocks and the upper contact of the altered resurgent intrusion in the western and central part of the caldera, providing about 2 km of vertical exposure. Because of post-alteration regional eastward tilting, the eastern part of the caldera has not been extensively eroded, and the original topography of the ring dome and the top of the caldera-fill rocks are locally preserved. This differential erosion from west to east furnishes a unique opportunity to study water-rock interactions in a caldera-type hydrothermal system from near-surface environments down through 3 km into the sub-volcanic intrusion that drove the hydrothermal convection.
\r\n\r\nElevation and proximity to fractures exerted the strongest control on 18O-depletions in the Precambrian granite and the older volcanic rocks. The lowest alSo values are found in rocks from the Eureka graben, a highly-fractured and extensively altered zone that extends SW from the caldera. Low \u03b418O values also occur adjacent to the caldera ring fault. Those samples of the Precambrian granite and of the older volcanic rocks that are located at the greatest depths below the mid-Tertiary erosion surface have the lowest \u03b418O values. At present-day, constant elevations, \u03b418O values are lowest in the western part of the study area than in the eastern part; this is a result of the regional eastward tilting. The above effects are best interpreted as indicating higher water/rock ratios near the permeable fractures and higher temperatures at greater depth.
\r\n\r\nThe \u03b418O values within the Lake City caldera are controlled by elevation, proximity to permeable zones, and proximity to the resurgent intrusive rocks. \u03b418O values decrease systematically with stratigraphic depth within the caldera. The lowest \u03b418O values are found along the western ring fault, along resurgence-related fractures, in the permeable megabreccia units, and along the contact of the resurgent intrusion. Mineralogic alteration facies within the caldera show complementary patterns. Intense argillization is found along fractures near the resurgent intrusion. Rocks adjacent to the resurgent intrusion have been hornfelsed but not intensely mineralogically altered. Weak argillization in stratigraphically shallow Sunshine Peak Tuff grades into both of these alteration regimes and also grades downward into chlorite-calcite alteration. These data show that the resurgent intrusion was the \"heat engine\" that drove the Lake City hydrothermal system. Alteration in and near the intrusion occurred at high temperatures (\u2248 400\u00b0C) and intermediate water/rock ratios. Away from the resurgent intrusion, water-rock interaction in the permeable zones (megabreccia units and fractures) occurred at lower temperatures (200\u00b0C to 300\u00b0C) and high water/rock ratios. The regional eastward tilting has raised low-18O rocks in the western part of the caldera to higher elevations than stratigraphically equivalent rocks in the eastern part of the caldera. Mineralogical alteration patterns are also similarly displaced.
\r\n\r\nNear-surface solfataric alteration is centered on a brecciated zone in the Red Mountain-Grassy Mountain quartz-latite dome on the eastern caldera margin. \u03b418O values of hydrothermal quartz from this alteration zone are high (> +11) and decrease gradationally with depth. Vein quartz \u03b418O values from deeper levels within the caldera lie on the deeper projection of the solfataric quartz \u03b418O trend. These data can be successfully modelled using an upward-flowing, boiling, 18O-shifted meteoric water as a hydrothermal fluid. This model shows that the same fluids responsible for vein quartz precipitation also produced the shallow solfataric alteration. High \u03b418O values were also measured from a number of other solfatarically altered areas in the San Juan Mountains (Red Mountain district near Silverton, Calico Peak near Rico, Engineer Pass, Carson Camp, and the Summitville district). These alteration zones, some of which are economically mineralized, were also apparently produced by boiling meteoric-hydrothermal fluids.
\r\n\r\nDeeply-circulated, 18O-shifted, meteoric waters were the primary source of hydrothermal fluids in the Lake City hydrothermal system. By analogy with other deeply eroded caldera hydrothermal systems studied by other workers, such fluids probably rose along deep extensions of the fractured, permeable Lake City ring fault zone. At the present level of exposure, fluids in the Lake City hydrothermal system were apparently drawn into the central part of the resurgent dome along the permeable, outward-dipping, megabreccia units. Flow was directed upward along permeable fractures where these fractures intersected the megabreccia units. A strong thermal gradient existed around and over the resurgent intrusion. Recharge into this hydrothermal system was basically radially inward toward the caldera, but flow was greatly enhanced through the permeable, highly fractured, Eureka graben.
\r\n\r\nPart II. Oxygen isotope studies were made on 60 samples from the central Nevada caldera complex, which consists of three nested calderas that erupted from 32 to 25 m.y. ago. 18O/16O analyses were also made on 96 samples from the central San Juan caldera complex, Colorado, which contains 7 ash-flow tuffs, each erupted from separate, nested collapse structures between 28 and 26 m.y. ago. The sequence of ash-flow tuffs erupted from the earliest of the three central Nevada calderas began with the giant Tuff of Williams Ridge and Morey Peak (+ 2500 km3), followed by the Mbnotony Tuff (3000 km3), and finally by various ash flow tuffs erupted from the youngest caldera (400 km3). In the San Juan complex, the earliest ash-flow was the Fish Canyon Tuff, which is also the largest of these ash-flows (> 3000 km3). Of the six other major ash-flow tuffs erupted from the central San Juan complex, none exceeds 1000 km3 in volume.
\r\n\r\nPrevious studies of other complex calderas at Yellowstone National Park and in southwest Nevada indicated that the later eruptions have \u03b418O values 3 per mil lower than rocks erupted early in the cycles. However, in the present study, no large negative shifts in \u03b418O were found. The various eruptions in both central Nevada and the central San Juans were remarkably uniform in 18O/16O, although small shifts of about -0.2 to -0.3 per mil were found in both suites of rocks in going from the early ash-flows to a later set. The indicated range of \u03b418O values of these quartz-latite and rhyolite magmas was 9.1 to 9.8 in the central Nevada complex and 6.6 to 7.5 in the central San Juan complex. The higher \u03b418O values in central Nevada probably indicate melting of sedimentary or metasedimentary country rocks at depth, whereas in Colorado, the low-18O, lower part of the craton was very likely involved in the melting process.
\r\n\r\n\u03b418O fractionations between coexisting phenocryst minerals in all of the ash-flow tuffs and lava flows from these two complexes are larger at the bases of the units (tops of the magma chambers) and smaller at the tops of the units (deeper levels of the magma chambers). These relationships show that temperature gradients existed in virtually all these magmas prior to eruption (cooler at the top and hotter at deeper levels).
\r\n\r\nIt is not clear why some complex caldera magmas become depleted in 18O with time, and others do not. No relationship exists between the duration of caldera magmatism and low-18O rocks, nor between the size of the eruptions and these 18O depletions. However, the large 18O depletions found to date occur only in caldera complexes younger than about 15 to 20 m.y., corresponding to the initiation of Basin-Range extension in the western United States. Perhaps Basin-Range faults allow meteoric fluids to penetrate deeply into fairly high-temperature regions of the crust. These younger magmas might then be able to melt or assimilate larger amounts of altered, 18O depleted rocks during their ascent. A correlation also appears to exist between the 18O depletions and the major-element chemistry of the rocks. All of the low-18O ash-flow tuffs contain abundant high-silica rhyolites (consistently ranging up to or above 77 percent SiO2). The large silica contents of these magmas indicate very strong differentiation, suggesting prolonged assimilation-fractional crystallization in a stable magma chamber without the renewed addition much primitive, unfractionated magma having a \"normal\" \u03b418O value. It is tentatively concluded that ash-flow magmas strongly depleted in o1eo will be produced only if: (1) there is a pre-history of intense fracturing, caldera collapse, and extensive meteoric-hydrothermal activity, followed by (2) the development of a stable, strongly differentiated, zoned magma chamber, whose roofward portion is in close proximity to low-18O, hydrothermally altered roof rocks for an extended interval of time (> 100,000 years ?).
" }, { "name": "Meisling, Kristian Erik", "degree": "PhD", "year": "1984", "title": "Neotectonics of the North Frontal Fault System of the San Bernardino Mountains, Southern California: Cajon Pass to Lucerne Valley", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01222009-094629", "creators": [ { "name": { "family": "Meisling", "given": "Kristian Erik" }, "id": "Meisling-Kristian-Erik", "display_name": "Meisling, Kristian Erik" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "chair", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Kirschvink", "given": "Joseph L." }, "id": "Kirschvink-J-L", "orcid": "0000-0001-9486-6689", "role": "member", "display_name": "Kirschvink, Joseph L." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geol" ], "doi": "10.7907/RSDP-BS67", "abstract": "The north frontal fault system of the San Bernardino Mountains is made up of a number of disparate structural elements, each of which accommodates range-front deformation in a manner dictated by its geometry. A two-stage history of late Cenozoic structural development is proposed for the northwestern San Bernardino Mountains: the range was first uplifted on low-angle structures and later modified by high-angle faulting. Evidence for Pliocene onset of deformation and uplift in the westernmost San Bernardino Mountains is found in the provenance and character of the associated sediments.
\r\n\r\nThrusting uplifted the northern range front during a pulse of deformation spanning late Pliocene through middle Pleistocene time. Uplift in the westernmost San Bernardino Mountains was accomplished contemporaneously by tilting, warping, and arching. Nature and timing of deformation are consistent with the hypothesized formation of a transpressional welt across the San Andreas fault, which may have affected both the San Bernardino and San Gabriel Mountains.
\r\n\r\nHigh-angle faulting replaced thrusting and warping as the dominant style of deformation in the northwestern San Bernardino Mountains beginning in middle to late Pleistocene time. Pleistocene left-lateral faulting in the westernmost San Bernardino Mountains has accomplished north-south crustal shortening by squeezing the San Bernardino Mountains block eastward. Northwest-trending right-lateral faults, characteristic of the Mojave block prior to range-front uplift, have reasserted and incorporated themselves in the complex zone of range-front deformation. Local extension resulting in minor graben formation, appears to have been associated with lateral motion on the north frontal fault zone in Fifteenmile Valley (Sky Hi Ranch fault zone) and the Cleghorn fault zone.
\r\n\r\nArcuate patterns of faulting in the western San Bernardino Mountains can be explained in terms of the pattern of faulting predicted for secondary faults near the end of a strike-slip fault. In this case the \"end effect\" would be produced by a change in slip rate on the San Andreas fault in Cajon Pass, possibly related to motion on the San Jacinto fault. All faulting in the study area is interpreted as the product of compression across the San Andreas fault.
\r\n\r\nA weathered erosion surface was developed on the crystalline terrane over most of the area in response to humid conditions during the late Miocene(?), at which time the region was characterized by an upland surface of subdued relief. This weathered erosion surface is a useful index to structural deformation in the northwestern San Bernardino Mountains.
\r\n\r\nLate Cenozoic stratigraphy constrains the timing of deformation and uplift in the northwestern San Bernardino Mountains. The late Miocene to Pliocene(?) Crowder Formation was deposited by drainages carrying distinctive volcanic and metamorphic clasts from the Victorville area southward, across the site of the western San Bernardino Mountains. The late Miocene beds of the Punchbowl Formation are faulted against the lower Crowder Formation, but are overlain by the upper Crowder Formation. The Punchbowl and Crowder Formations share the same age and paleocurrent direction, yet differ markedly in sediment character and provenance. The relationship between these two units remains an unsolved stratigraphic problem, which seemingly requires substantial lateral structural translation.
\r\n\r\nThe middle to late Pliocene onset of deformation and uplift is recorded in the stratigraphic sequence by the appearance of fine-grained sediments, new clast lithologies, and northerly paleocurrent directions. The volcanogenic eastern facies of the Crowder(?) Formation is believed to be a syntectonic deposit indicative of ponding that accompanied the reversal in drainage direction brought on by incipient uplift of the western San Bernardino Mountains. The fine grained, lacustrine character of the Harold Formation can be interpreted in the same way; the base of the Harold Formation is < 2.75 my old on the basis of paleomagnetic constraints. The Old Woman Sandstone in Lucerne Valley records an abrupt change from fine-grained sediments indicative of incipient uplift to coarse, angular debris signalling the emergence of the range front as a topographic element. The influx of range-front debris is estimated to have occurred < 2.5 my ago. Several small, deformed patches of fine-grained sediment in Arrastre Canyon appear to be of similar origin.
\r\n\r\nThe Quaternary stratigraphy of the western San Bernardino is dominated by the Harold Formation, Shoemaker Gravel and Older Alluvium, which underlie the Victorville Fan. These units were shed northeast off the San Gabriel and western San Bernardino Mountains, and record their uplift. The Harold Formation contains the earliest appearance of San Gabriel Mountains crystalline basement lithology within the stratigraphy of the Mojave block. The Victorville Fan sequence is believed to be time-transgressive, reflecting the northwestward movement of the San Gabriel Mountains crystalline terrane along the San Andreas fault.
\r\n\r\nThe Older Alluvium capping the Shoemaker Gravel in Cajon Pass records the Brunhes/Matuyama polarity reversal of 730,000 y B.P. The Older Alluvium can be divided into dissected and undissected facies believed to predate and postdate the polarity transition respectively. This crude chronology can be extended to sediments on the flanks of the Ord Mountains that define a late Pleistocene drainage system tributary to the ancestral Mojave River. The Pleistocene units contain evidence of progressive growth and integration of drainage in the Western San Bernardino Mountains in response to uplift during Pleistocene time.
\r\n\r\nDetailed geologic mapping of the northwestern San Bernardino Mountains permits slip rates and offsets to be calculated for important range-front faults. The Cleghorn fault has a cumulative left-lateral offset of 3.5 to 4.0 kilometers, and a slip rate of about 3.0 mm/yr. The Sky Hi Ranch fault zone has a late Pleistocene right-lateral offset of approximately 0.5 kilometers, with a slip-rate on the order of 1 mm/yr. The faults along the west flank of the Ord Mountains have a vertical slip-rate of less than 1 mm/yr.
\r\n\r\nThe Cleghorn fault is classified as \"active\", under the criteria set forth by the State of California in the Alquist-Priolo Act of 1972, and is considered capable of a Ms 6.8 earthquake. Parts of the north frontal fault system on the west flank of the Ord Mountains and the Sky Hi Ranch fault zone are classified as \"potentially active\", in the terminology of the Alquist-Priolo Act, and are thought to be capable of a Ms 6.6 to 6.8 event. The Tunnel Ridge lineament and Arrastre Canyon Narrows fault zones are considered tentatively active, and should be examined in detail prior to development of adjoining areas. Clearly, the San Andreas fault poses the greatest seismic hazard to the communities in the study area.
" }, { "name": "Piepgras, Donald John", "degree": "PhD", "year": "1984", "title": "The Isotopic Composition of Neodymium in the Marine Environment: Investigations of the Sources and Transport of Rare Earth Elements in the Oceans", "advisor": "Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08152006-132531", "creators": [ { "name": { "family": "Piepgras", "given": "Donald John" }, "id": "Piepgras-Donald-John", "display_name": "Piepgras, Donald John" } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Morgan", "given": "James J." }, "id": "Morgan-J-J", "role": "chair", "display_name": "Morgan, James J." }, { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "member", "display_name": "Patterson, Clair C." }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." } ], "option_major": [ "geochem" ], "doi": "10.7907/GATW-C580", "abstract": "In this study, the isotopic composition of neodymium in the marine environment has been determined from analysis of marine ferromanganese precipitates and seawater. An initial survey of the isotopic composition of Nd in the marine environment was made utilizing the analyses of authigenic ferromanganese sediments. These included ferromanganese nodules, metalliferous sediments, and hydrothermal ferromanganese crust deposits. Large variations in \u03b5Nd(0) values are observed which exhibit a clear separation of the ocean basin. Nd isotopic variations within an ocean basin fall within a relatively small, well defined range which is characteristic of the ocean basin sampled. Based on these results, the following average 143Nd/144Nd ratios for the ocean basins have been determined: Atlantic Ocean, \u03b5Nd(0) \u2248 -12; Indian Ocean, \u03b5Nd(0) \u2248 -8; Pacific Ocean, \u03b5Nd(0) \u2248 -3. These values are considerably lower than \u03b5Nd(0) values associated sources having oceanic mantle affinities, indicating that the REE in the oceans are dominated by continental sources. Therefore, the variations must reflect primarily the age and 147Sm/144Nd ratio of the continental masses being sampled.
\r\n\r\nDirect measurements of the isotopic composition of Nd in seawater samples from the Atlantic and Pacific are in excellent agreement with the values determined from the ferromanganese sediments indicating that these sediments accurately reflect the isotopic composition of Nd dissolved in seawater. The results clearly demonstrate the existence of distinctive Nd isotopic differences in waters of the major ocean basins. These values correspond to a difference in the absolute abundance of 143Nd between the Atlantic and the Pacific Oceans of ~ 10(6) atoms 143Nd per gram of seawater. In addition to the isotopic differences observed between the ocean basins, smaller but distinctive variations are observed in the water column of both the Pacific and the Atlantic, indicating different sources of REE at different levels in the water column. This suggests that it may be possible to distinguish the sources of water masses within an ocean basin on the basis of Nd isotopic composition.
\r\n\r\nThe isotopic composition of Nd was determined in seawater samples from the Drake Passage in order to monitor the exchange of REE between the Pacific and Atlantic Oceans. The Antarctic Circumpolar Current, which flows eastward through this passage, represents the primary conduit through which the major ocean basins communicate with each other. The isotopic composition of Nd is found to be uniform with depth at all stations and corresponds to \u03b5Nd(0) \u2243 -9.0. This value is intermediate between the values for the Atlantic and the Pacific and indicates that the Antarctic Circumpolar Current consists of about 70 percent Atlantic water. By using a box model to describe the exchange of water between the Southern Ocean and the ocean basins to the north together with the isotopic results, an upper limit of approximately 33 million cubic meters per second is calculated for the rate of exchange between the Pacific and the Southern Ocean.
\r\n\r\nThe concentration of Nd exhibits a regular increase with depth at all locations studied. In contrast, Nd isotopic compositions can exhibit substantial variations in the water column which vary depending on the location. Where isotopic differences in the water column occur, substantial lateral transport of REE from different sources and at different levels in the water column is required to maintain these differences. It is shown that the concentration gradients are established without significantly affecting the isotopic distribution, and that the enrichment of Nd in the deep water cannot be a result of resolution of REE scavenged from surface waters.
\r\n\r\nThe isotopic distributions are compared to water mass analyses based on temperature and salinity characteristics in the water column at the various sampling locations. It is shown that differences in isotopic compositions in the water column are well correlated with changes in the temperature and salinity characteristics. Thus, the isotopic distributions are fully consistent with the circulation of major water masses. This indicates that while Nd is nonconservative in concentration, the isotopic composition is conserved and can be used as a tracer for studying the origin and circulation of water masses.
\r\n\r\nThe results of these studies have provided some important contributions to the understanding of trace element transport in the oceans. First, the Nd isotopic differences in the water column clearly indicate that transport of Nd from the surface to the deep ocean cannot account for the observed increase in concentration of Nd with depth. These isotopic differences must be maintained by lateral transport of the REE and indicates that the concentration gradients of the REE and possibly other trace elements must also be related in part to lateral transport processes. Second, the close correlation observed between changes in Nd isotopic compositions and temperature-salinity relationships in the water column indicates that the lateral transport of REE in the oceans is directly related to the origin and flow of water masses. Thus, the isotopic composition of Nd in seawater is shown to be a useful tracer for studying the sources of injection and transport of trace elements in the oceans.
\r\n\r\nIn addition to the seawater studies, the concentrations and isotopic compositions of Nd and Sr were determined in hydrothermal solutions emanating from hot springs on the crest of the East Pacific Rise at 21\u00b0N and at Guaymas Basin, Gulf of California. This study represents the first effort to measure the Nd isotopic compositions in hydrothermal solutions. Endmember samples (T = 350\u00b0C) from 21\u00b0N exhibit a small range in \u03b5Sr values from -13.4 to -15.7. Correcting to CMg = 0, the pure hydrothermal solutions are estimated to have \u03b5Sr \u2243 -18. These results indicate that the fluids have undergone extensive but not complete exchange with Sr in the depleted oceanic crust (\u03b5Sr \u2243 -30). CSr ranges from 5.8 to 8.7 ppm and is similar to seawater (7.6 ppm) indicating that there must be buffering. Hydrothermal solutions from Guaymas Basin (T = 315\u00b0C) rise through several hundred meters of sediment before reaching the sea floor. One sample from here has \u03b5Sr = +5.8, indicating that the solutions have reacted first with oceanic crust and then sediments. The high Sr concentration in this sample (19.3 ppm) is consistent with late stage interaction between the ascending fluid and carbonate rich sediments.
\r\n\r\nNd shows a wide range in concentration and isotopic compositions in solutions from 21\u00b0N. CNd ranges from 20 to 659 pg/g, indicating substantial enrichments of Nd over typical seawater concentrations of ~3 to 4pg/g. \u03b5Nd ranges from -10.8 to +7.9. The data clearly show substantial contributions of Nd from depleted oceanic crust to many of the samples analyzed. In spite of enrichments in Nd of up to about 100 times seawater, none of the samples have \u03b5Nd values equal to MORB (\u03b5Nd \u2243 +10). One sample from Guaymas Basin has \u03b5Nd = -11.4 consistent with leaching of Nd from sediments derived from old, continental sources. There is some inconsistency in the Nd isotopic data indicating that there is a possibility of contamination during sampling and/or handling of the solutions.
" }, { "name": "Shaw, Henry Francis, III", "degree": "PhD", "year": "1984", "title": "Sm-Nd and Rb-Sr Isotopic Systematics of Tektites and Other Impactites, Appalachian Mafic Rocks, and Marine Carbonates and Phosphates", "advisor": "Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:12142018-091056975", "creators": [ { "name": { "family": "Shaw", "given": "Henry Francis, III" }, "id": "Shaw-Henry-Francis-III", "orcid": "0000-0003-0681-5430", "display_name": "Shaw, Henry Francis, III" } ], "advisors": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Bercaw", "given": "John E." }, "id": "Bercaw-J-E", "role": "member", "display_name": "Bercaw, John E." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" } ], "option_major": [ "geol" ], "doi": "10.7907/x0zc-7w22", "abstract": "This thesis is made up of three separate studies, each using the Sm-Nd and Rb-Sr isotopic systems to solve a problem of geologic interest.
\r\n\r\nIn the first study it is shown that Sm-Nd and Rb-Sr analyses of tektites and other impactites can be used to place constraints on the age and provenance of the target materials which were impact melted to form these objects. Tektites have large negative values of \u03b5Nd(0) which are uniform within each tektite group, while the \u03b5Sr(0) values are large positive and show considerable variation within each group. The chemical, trace element, and isotopic compositions of tektites are consistent with their production by melting of sediments derived from old continental crust. Each tektite group is characterized by a uniform Nd model age, TNdCHUR, interpreted as the time of formation of the crustal segment which weathered to form the parent sediment for the tektites: (1) ~1.15AE for Australasian tektites; (2) ~1.9AE for Ivory Coast tektites; (3) ~0.9AE for moldavites; (4) ~0.65AE for North American tektites; and (5) ~0.9AE for high-Si irghizites. Sr model ages, TSrUR, are variable within each group, reflecting Rb-Sr fractionation during weathering and sedimentation. In the favorable limit of very high Rb/Sr ratios TSrUR approaches the time of sedimentation of the parent material which melted to form the tektites. Australasian tektites are derived from ~0.25AE sediments, moldavites from ~0.0AE sediments, and Ivory Coast tektites from ~0.95AE sediments. The parent sediments of the other tektite groups have poorly constrained ages. The isotopic data on the moldavites and Ivory Coast tektites are consistent with their derivation from the Ries and Bosumtwi Craters, respectively. Irghizites are isotopically distinct from the Australasian tektites and are probably not related. Sanidine spherules from an iridium-rich Cretaceous-Tertiary boundary clay were heavily overprinted with seawater-derived Sr and Nd during diagenesis. The inferred initial isotopic composition of the sanidine itself is \u03b5Nd(T) = +2 and \u03b5Sr(T) = +5. These results show that the spherules were not derived from old continental crust or meteoritic potassium feldspar. These objects may represent an impact melt of a mixture of basaltic oceanic crust and overlying sediments and are consistent with an oceanic impact at the Cretaceous-Tertiary boundary. The isotopic data are also consistent with an origin by authigenic growth of the spherules from young detrital material.
\r\n\r\nThe second study in this thesis uses the Sm-Nd and Rb-Sr isotopic systematics of mafic rocks from the Appalachians to place constraints on their origin. Isotopic analyses of modern oceanic basalts and ophiolites have shown that both modern and ancient oceanic crust have a characteristic Nd and Sr isotopic signature indicative of derivation from a depleted mantle reservoir. It also appears that the Nd isotopic system is not appreciably disturbed by metamorphism. These isotopic characteristics have been extended to the Pt. Sal, Kings-Kaweah, and Josephine Ophiolites of California. These characteristics are used in an attempt to identify pieces of proto-Atlantic oceanic crust among the mafic and ultramafic rocks of the Appalachians. Sm-Nd mineral isochrons for the Baltimore Mafic Complex, Md (BMC) yield an age of 490\u00b120 My which is interpreted as the igneous crystallization age. BMC whole rock samples do not define isochrones and have initial isotopic compositions of -6.4 < \u03b5Nd(T) < -2.2, +51 < \u03b5Sr(T) < +115. \u03b5Nd(T) and \u03b5Sr(T) are anti-correlated. This is not the signature of depleted mantle and oceanic crust, but is similar to old continental crust. It is proposed that the BMC is a mafic continental intrusion, possibly subduction related, which was contaminated with old continental crust during emplacement. Whole rock samples from the Thetford Mines Complex, Qe (TMC) do not define isochrons and have -1.5 < \u03b5Nd(T) < +4.2, +2.6 < \u03b5Sr(T) < +114. These data do not in any way reflect the signature of normal oceanic crust. These results are in contrast with geologic relationships which show the TMC to have the characteristics of an ophiolite complex. The TMC is chemically and isotopically similar to a class of other ophiolites which have affinities to modern boninites. The TMC may therefore represent an ophiolite formed under an arc complex. The Chunky Gal Amphibolite, N.C., Lake Chatuge complex, N.C., and Hazen's Notch Amphibolite, Vt., were found to have a depleted mantle signature with +5 < \u03b5Nd(T) < +8 and may be fragments of oceanic crust. The Webster-Addie body, N.C., has \u03b5Nd(T) ~-1, \u03b5Sr(T) ~+30 and is not isotopically similar to oceanic crust or the other North Carolina mafic bodies analyzed. From these isotopic results it is clear that Appalachian mafic rocks have diverse origins, some are continental intrusives (BMC), others are probably fragments of oceanic crust (Vermont and N. Carolina amphibolites). Future models for the development of the Appalachians must allow for these various origins. The possibility that some ophiolites are not normal oceanic crust but have an origin in a partially continental setting or as anomalous oceanic crust will require further attention.
\r\n\r\nThe final study is an exploration of the possibility of establishing the Nd isotopic variations in seawater over geologic time by analysing a marine sedimentary phase which records and preserves the \u03b5Nd(T) value of the seawater in which it formed. Apatite and CaCO3 (calcite and aragonite) are examined as possible such phases. Modern biogenic and inorganic calcite and aragonite were found to have low REE concentrations: Nd = 0.2 to 65 ppb. The \u03b5Nd(0) values of Atlantic (-8.3 to -9.6) and Pacific (-0.1 to -1.3) carbonates are distinctly different and reflect the isotopic composition of Nd in the seawater in which they formed. The high concentrations of REE measured in limestones and carbonate fossils cannot be primary but must be due to the presence of other phases in the carbonate of the introduction of REE during diagenesis. Modern biogenic apatite also has a low REE content (<150 ppb Nd), but appears to quickly scavenge REE from seawater. Levels up to 1000 ppm Nd can be reached by this process. Inorganically precipitated apatite from phosphorites also has high concentrations of seawater-derived REE. A seawater-like REE pattern with a characteristic negative Ce-anomaly is often preserved by sedimentary apatite and apatite samples of the same age from different localities bordering a common sea record a common value of \u03b5Nd(T). These characteristics suggest that apatite can be used to trace the evolution of \u03b5Nd(T) in ancient seawater. The values of \u03b5Nd(T) in seawater as inferred from analyses of conodonts and phosphorite apatite range between -1.7 and -8.9 over the last 700My. These values lie in the range of modern seawater values and show no evidence for drastic changes in the sources for Nd in seawater during this time. High values of seawater \u03b5Nd(T) in the Triassic and latest Precambrian may correlate with the breakup of large continental landmasses. The initial \u03b5Nd(T) = -15.0 of the 2AE old Rum Jungle phosphorite requires the presence of -1.5AE old continental crust at 2AE ago. This demonstrates how the \u03b5Nd value of ancient seawater can be used to constrain the age of the exposed crust as a function of time.
" }, { "name": "Walck, Marianne Carol", "degree": "PhD", "year": "1984", "title": "Teleseismic Array Analysis of Upper Mantle Compressional Velocity Structure", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10092013-142945359", "creators": [ { "name": { "family": "Walck", "given": "Marianne Carol" }, "id": "Walck-Marianne-Carol", "orcid": "0000-0003-3723-7362", "display_name": "Walck, Marianne Carol" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "chair", "display_name": "Harkrider, David G." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geophys" ], "doi": "10.7907/76q0-ye98", "abstract": "Large quantities of teleseismic short-period seismograms recorded at SCARLET provide travel time, apparent velocity and waveform data for study of upper mantle compressional velocity structure. Relative array analysis of arrival times from distant (30\u00b0 < \u0394 < 95\u00b0) earthquakes at all azimuths constrains lateral velocity variations beneath southern California. We compare dT/d\u0394 back azimuth and averaged arrival time estimates from the entire network for 154 events to the same parameters derived from small subsets of SCARLET. Patterns of mislocation vectors for over 100 overlapping subarrays delimit the spatial extent of an east-west striking, high-velocity anomaly beneath the Transverse Ranges. Thin lens analysis of the averaged arrival time differences, called 'net delay' data, requires the mean depth of the corresponding lens to be more than 100 km. Our results are consistent with the PKP-delay times of Hadley and Kanamori (1977), who first proposed the high-velocity feature, but we place the anomalous material at substantially greater depths than their 40-100 km estimate.
\r\n\r\nDetailed analysis of travel time, ray parameter and waveform data from 29 events occurring in the distance range 9\u00b0 to 40\u00b0 reveals the upper mantle structure beneath an oceanic ridge to depths of over 900 km. More than 1400 digital seismograms from earthquakes in Mexico and Central America yield 1753 travel times and 58 dT/d\u0394 measurements as well as high-quality, stable waveforms for investigation of the deep structure of the Gulf of California. The result of a travel time inversion with the tau method (Bessonova et al., 1976) is adjusted to fit the p(\u0394) data, then further refined by incorporation of relative amplitude information through synthetic seismogram modeling. The application of a modified wave field continuation method (Clayton and McMechan, 1981) to the data with the final model confirms that GCA is consistent with the entire data set and also provides an estimate of the data resolution in velocity-depth space. We discover that the upper mantle under this spreading center has anomalously slow velocities to depths of 350 km, and place new constraints on the shape of the 660 km discontinuity.
\r\n\r\nSeismograms from 22 earthquakes along the northeast Pacific rim recorded in southern California form the data set for a comparative investigation of the upper mantle beneath the Cascade Ranges-Juan de Fuca region, an ocean-continent transit ion. These data consist of 853 seismograms (6\u00b0 < \u0394 < 42\u00b0) which produce 1068 travel times and 40 ray parameter estimates. We use the spreading center model initially in synthetic seismogram modeling, and perturb GCA until the Cascade Ranges data are matched. Wave field continuation of both data sets with a common reference model confirms that real differences exist between the two suites of seismograms, implying lateral variation in the upper mantle. The ocean-continent transition model, CJF, features velocities from 200 and 350 km that are intermediate between GCA and T7 (Burdick and Helmberger, 1978), a model for the inland western United States. Models of continental shield regions (e.g., King and Calcagnile, 1976) have higher velocities in this depth range, but all four model types are similar below 400 km. This variation in rate of velocity increase with tectonic regime suggests an inverse relationship between velocity gradient and lithospheric age above 400 km depth.
\r\n" }, { "name": "Chael, Eric Paul", "degree": "PhD", "year": "1983", "title": "Constraints on the Earth's Anelastic and Aspherical Structure from Antipodal Surface Waves", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08302019-112320091", "creators": [ { "name": { "family": "Chael", "given": "Eric Paul" }, "id": "Chael-Eric-Paul", "display_name": "Chael, Eric Paul" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "chair", "display_name": "Anderson, Donald L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/xe9f-zz51", "abstract": "Seismograms recorded at antipodal distances (\u0394~180\u00b0) are used to measure the attenuation and dispersion of surface waves. The antipode is a focus for surf ace wave energy radiated at all directions from the source. Antipodal records thus give direct estimates of global average properties. Laterally heterogeneous Earth structure degrades the focusing and complicates the data analysis.
\r\n\r\nGroup velocity and Q of 120-300 s Rayleigh waves are obtained from a record (station PTO) of the May 23, 1968 New Zealand earthquake. The effects of aspherical structure on this record are simulated by generating synthetic seismograms for an ellipsoidal Earth. The results show that the bias in antipodal Q measurements varies with time. This property is used to constrain the bias in the PTO measurements.
\r\n\r\nA seismogram of the August 19, 1977 Indonesian earthquake from station TRN is used to study 250-500 s Rayleigh waves. This record is synthesized by combining first order perturbation theory with a realistic representation of the Earth's heterogeneities. Analysis of the synthetic shows that Q measured from the TRN record is biased as much as 20% and that group velocities are virtually unbiased. The PTO and TRN data yield global average values of Rayleigh wave Q which are comparable to or slightly below those for the model PREM [Dziewonski and Anderson, 1981].
\r\n\r\nAntipodal Love wave and spheroidal overtone data are also presented. Synthetic seismograms match the observed arrivals well, demonstrating that these wave modes can be profitably studied at the antipode.
" }, { "name": "Clancy, Robert Todd", "degree": "PhD", "year": "1983", "title": "Carbon Monoxide in the Atmospheres of the Terrestrial Planets", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:01252013-152959933", "creators": [ { "name": { "family": "Clancy", "given": "Robert Todd" }, "id": "Clancy-Robert-Todd", "display_name": "Clancy, Robert Todd" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Moffet", "given": "Alan Theodore" }, "id": "Moffet-A-T", "role": "member", "display_name": "Moffet, Alan Theodore" }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." } ], "option_major": [ "plansci" ], "doi": "10.7907/mf7e-1581", "abstract": "Microwave spectra of carbon monoxide (12CO) in the mesosphere of Venus were measured in December of 1978; May and December of 1980; and January, September, and November of 1982. These spectra are analyzed to provide mixing profiles of CO in the Venus mesosphere and best constrain the mixing profile of CO between ~ 100 and 80 kilometers altitude. From the January 1982 measurement (which, of all our spectra, best constrains the abundance of CO below 80 km altitude) we find an upper limit for the CO mixing ratio below 80 kilometers altitude that is 2-3 times smaller than the stratospheric ( ~ 65 km) value of 4.5 \u00b1 1.0 x 10-5 determined by Connes et al. (1968) in 1967, indicating a possible long-term change in the lower atmospheric concentration of CO.
\r\n\r\nIntercomparison among the individual CO profiles derived from our spectra indicates considerable short-term temporal and/or spatial variation in the profile of CO mixing in the Venus mesosphere above 80 kilometers. A more complete comparison with previously published CO microwave spectra from a number of authors (Kakar et al., 1976; Gulkis et al., 1977: Schloerb et al., 1980; Wilson and Klein, 1981; Schloerb et al., 1981) specifies the basic diurnal nature of mesospheric CO variability. CO abundance above ~ 95 kilometers in the Venus atmosphere shows approximately a factor of 2-4 enhancement on the nightside relative to the dayside of Venus. The magnitude of this nightside CO bulge is in good agreement with the dynamical modeling results of Dickinson and Ridley (1977), indicating that subsolar to antisolar circulation proposed for the thermosphere of Venus by Dickinson and Ridley extends to below 100 km altitude in the Venus mesosphere. Furthermore, peak nightside CO abundance above ~ 95 kilometers occurs very near to the antisolar point on Venus (local time of peak CO abundance above ~ 95 kilometers occurs at 0.6+0.7-0.6 hours after midnight on Venus), strongly suggesting that retrograde zonal flow is substantially reduced at an altitude of 100 kilometers in the Venus mesosphere.
\r\n\r\nBy contrast, CO abundances between 80 and 90 kilometers altitude show a maximum that is shifted from the antisolar point towards the morning side of Venus (local time of peak CO abundance between 80 and 90 kilometers occurs at 8.5 \u00b1 1.0 hours past midnight on Venus). The magnitude of the diurnal variation of CO abundance between 80 and 90 kilometers is again, approximately a factor of 2-4. Given the recombination of CO strongly peaks in this altitude region (Yung and DeMore, 1982), we investigated the possible effects of diurnal photochemistry as a driving force for diurnal CO variations between 70 and 90 kilometers from model calculations. We find that the likely magnitude of diurnal CO variability due to photochemistry and vertical eddy diffusion is smaller than that indicated by the microwave data, and that such variations cannot predict the observed phase behavior of the diurnal variations. Photochemical models invariably predict peak CO abundances in the afternoon rather than morning hours on Venus. However, a simple model for the circulation of the Venus mesosphere is presented to explain the observed diurnal variations of CO both above 90 kilometers altitude and between 80 and 90 kilometers altitude. We propose that the subsolar to antisolar circulation of the Venus thermosphere (and the resulting nightside enhancement of CO) persists down to altitudes of ~ 80 kilometers. Above ~ 90 kilometers zonal flow is small and the nightside CO bulge remains centered near the antisolar point on Venus. Below ~ 90 kilometers altitude retrograde zonal wind velocities increase abruptly to several tens of meters/sec displacing the nightside enhancement of CO towards the morningside of Venus.
\r\n\r\nWe also present a J = 1 \u2192 2 spectrum of 13CO absorption in the mesosphere of Venus. This 13CO spectrum was measured at the same time as our high quality, January 1982 12CO spectrum. Radiative transfer models employing a single pressure-temperature model of the Venus mesosphere are fit to both the 13CO and 12CO spectra. The 12CO spectrum is used to specify the altitude distribution of CO. Subsequently, we solve for the ratio 12CO/13CO = 185 in order to best fit the 13CO spectrum. Based on an extensive error analysis we believe that the standard deviation of this value is \u00b1 69. This result applies only to the mesosphere of Venus, i.e. from 80 to 110 km. Values of the 12CO/13CO ratio measured deeper in the Venus atmosphere are closer to the terrestrial value of 89. We suggest several fractionation mechanisms in order to account for the difference between our result and the terrestrial value. However, as yet, none of these mechanisms is known to produce significant fractionation of CO isotopes in the upper atmosphere of Venus.
\r\n\r\nIn January of 1982 we measured a microwave spectrum of CO in the Martian atmosphere utilizing the rotational J = 1 \u2192 2 transition of CO. We have analyzed our data and reanalyzed the microwave spectra of Kakar et al. (1967, measured in 1975) and Good and Schloerb (1981, measured in 1980) in order to constrain estimates of the temporal variability of CO abundance in the Martian atmosphere. Long-term (\u2273 1 year) variations in CO abundance have been predicted on the basis of possible variations in eddy diffusion (McElroy and Donahue, 1972) and/or condensible HxOy compounds (Hunten, 1974) in the Martian atmosphere. Our values of CO column density from the data of Kakar et al., Good and Schloerb, and our own are 1.7 \u00b1 0.9 x 1020 cm-2, 3.0 \u00b1 1.0 x 1020 cm-2, and 4.6 \u00b1 2.0 x 1020 cm-2, respectively. The most recent estimate of CO column density from the 1967 infrared spectra of Connes et al. (1969) is 2.0 \u00b1 0.8 x 1020 cm-2 (Young and Young, 1977). The large uncertainties given for the microwave measurements are due primarily to uncertainty in the difference between the continuum brightness temperature and atmospheric temperatures of Mars. We have accurately calculated the variation among the observations of the continuum (surface) brightness temperature of Mars which is primarily a function of the observed aspect of Mars. A more difficult problem to consider is variability of global atmospheric temperatures among the observations, particularly the effects of global dust storms and the ellipticity of the orbit of Mars. The large error bars accompanying our estimates of CO column density from the three sets of microwave measurements are primarily caused by an assumed uncertainty of \u00b1 10 K in our atmospheric temperature model due to possible dust in the atmosphere. A qualitative consideration of seasonal variability of global atmospheric temperatures among the measurements suggests that there is not strong evidence for variability of the column abundance of CO on Mars, although variability of 0-100% over a time scale of several years is allowed by the data set. The implication for the variability of Mars O2 (which is directly tied to photodissociation of CO2) is, crudely, a factor of two less. We find that the altitude distribution of C) in the atmosphere of Mars is not well constrained by any of the spectra, although our spectrum is marginally better fit by an altitude increasing profile of CO mixing ratios.
\r\n\r\nFinally, we consider variations in the CO content of the terrestrial mesosphere. The Earth's mesospheric carbon monoxide was observed in absorption against the Moon in early December of 1979 and late January of 1982 at a wavelength of 1.3 mm, and in early December of 1980 at a wavelength of 2.6 mm. The January 1982 spectrum was also measured in emission with very high signal-to-noise ratios. The observed wavelengths correspond to the respective rotational transitions of CO, J = 1 \u2192 2 and J = 0 \u2192 1. No significant change in the column density of CO above ~ 65 km is found between the 1979 and 1980 observations, but the January 1982 measurement indicates an ~ 30% reduction in column density relative to the December observations. Inversion of the spectra did not provide unique CO mixing ratio profiles for a direct quantitative comparison of December 1979 and 1980 and January 1982 profiles, due to limited signal-to-noise ratios for the 1979, 1980 observations. One of the best constrained mixing profiles published to date is presented for the very high signal-to-noise January 1982 emission spectrum. Comparison with other published spectra of mesospheric CO suggests a large seasonal variation (~ a factor of 2-4) in the column density of CO above 65 km, with a maximum in winter and a minimum in summer. The phase of this seasonal variation in CO abundance is opposite to the phase of seasonal variation in insolation suggesting that a hemispheric pattern of circulation is responsible for seasonal variations in the Earth's mesosphere.
\r\n\r\nWe summarize by noting the very different time scales for variations of CO in the upper atmospheres of Venus, the Earth, and Mars. The long diurnal period of Venus produces a very strong diurnal variation in mesospheric CO which is driven primarily by subsolar to antisolar circulation. CO in the terrestrial mesosphere shows strong seasonal variation which is apparently produced by seasonally driven meridional circulation. By contrast, if atmospheric CO does vary on Mars, it is most likely controlled by long-term changes in the chemistry and/or vertical mixing in the Martian atmosphere.
" }, { "name": "Cohn, Stephen Norfleet", "degree": "PhD", "year": "1983", "title": "Holographic In-Situ Stress Measurement in Geophysics", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08302019-150635775", "creators": [ { "name": { "family": "Cohn", "given": "Stephen Norfleet" }, "id": "Cohn-Stephen-Norfleet", "display_name": "Cohn, Stephen Norfleet" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/6vsd-wa54", "abstract": "A new and still experimental method for measuring the absolute in-situ stress field in crustal rocks offers several advantages compared to existing in-situ stress measurement techniques. It employs optical holography to record strain-relief displacements in a borehole environment. We call the prototype instrument the holographic stressmeter. It operates in an uncased borehole where it drills strain-relieving side holes into the borehole wall. An interference holographic recording system records the resulting displacements onto film. The reconstructed interference holograms contain sufficient information in their fringe patterns to determine the three-dimensional vector displacements due to strain relief at every point surrounding the side hole. Assuming isotropic, homogeneous, linearly elastic rock, these displacements define the three stresses acting at the borehole wall at a single point. The three non-vanishing stresses acting at each of three points, distributed azimuthally, on the borehole wall provide sufficient constraint to determine all six components of the desired far-field or virgin-rock stress tensor.
\r\n\r\nThe holographic stressmeter employs an on-board side hole drilling system to produce strain relief. Thus it should be economical to operate and it is not restricted to shallow depths as are overcoring techniques. Furthermore, recording the whole displacement field resulting from drilling the side hole reduces the potential contamination of the measurement by residual stress mechanisms which often affect point strain measurements using foil resistance gauges.
\r\n\r\nTo date a complete stress determination in the field has not been attempted. However, a prototype stressmeter has demonstrated repeatedly that the stability necessary to conduct the measurement using this approach is attainable. Results from field deployment show that the stressmeter can make qualitatively correct measurements at one azimuth in a borehole. Modifications to make measurements at the three azimuths required for a complete determination of the stress tensor components should be easily achieved. We propose additional improvements to permit measuring rock elastic properties in situ to enable accurate, quantitative stress determinations. The theoretically predicted precision of the stress component magnitudes using this measurement approach is estimated at 20%.
" }, { "name": "Echelmeyer, Keith Alan", "degree": "PhD", "year": "1983", "title": "Response of Blue Glacier to a Perturbation in Ice Thickness: Theory and Observation", "advisor": "Hager, Bradford H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08242006-080724", "creators": [ { "name": { "family": "Echelmeyer", "given": "Keith Alan" }, "id": "Echelmeyer-Keith-Alan", "display_name": "Echelmeyer, Keith Alan" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." } ], "committee": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "chair", "display_name": "Hager, Bradford H." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Meier", "given": "Mark" }, "id": "Meier-M", "role": "member", "display_name": "Meier, Mark" }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "member", "display_name": "Sharp, Robert P." } ], "option_major": [ "geophys" ], "doi": "10.7907/ZQHK-NA29", "abstract": "A unique natural experiment has occurred on Mt. Olympus, Washington, in which the lower part of Blue Glacier has undergone a marked increase in ice thickness and a general decrease in surface slope. In response to this, the glacier flow velocities have increased considerably. The detailed study of the surface configuration and flow of the glacier during the period 1957-59, before the thickening (Meier, et al., 1974) provides a complete baseline against which the recent changes in geometry and surface velocity field are measured.
\r\n\r\nA detailed evaluation of the flow response to the changes in thickness and slope is made, testing for the existence of a quantitative observational relation among u, H, and \u03b1. A linear relation between the percentage ice thickness change and the percentage velocity increase is found. The slope of this response line is related to the exponent n in the flow law of ice, and the negative intercept represents an overall decrease in surface slope.
\r\n\r\nDetailed quantitative interpretations of the field measurements on the flow of Blue Glacier and its response to the change in surface configuration are made, using analytical and finite-element techniques.
\r\n\r\nA theoretical discussion of the effects of longitudinal stress gradients on the flow of an ice mass is given. This discussion leads to the development of an exponential Green's function which determines the effect of surface slope and ice thickness variations on the flow. This Green's function provides a weighting factor for longitudinal averaging of slope and thickness. The characteristic length scale up- and downglacier is dependent on the longitudinal strain-rate, the amount of basal sliding, and the flow-law parameters, being approximately three times the mean ice thickness. Application of this longitudinal averaging to the observed slope and thickness changes results in a marked decrease in deviations of the response data from a linear regression on the velocity changes, showing that longitudinal stress gradients are important.
\r\n\r\nA finite-element computer code for the calculation of flow of ice in channel cross sections of arbitrary shape, including transverse flow components, is developed. The model is applied to flow in channels of idealized parabolic cross-sectional shape to reveal the basic effects of channel shape and flow-law parameters on stress and velocity distribution. The stresses are found to be dependent on the flow-law parameters. Components of transverse flow within the cross section that develop in response to transverse convexity of the glacier surface were calculated. Comparison with observations shows that much of the splaying of the velocity vectors within an ablation zone can be attributed to flow driven by this convex surface.
\r\n\r\nAnalytical models of the flow of a glacier in which the flow law parameters vary with position are developed. These models show that there is a nonuniqueness in flow-law parameters obtained from borehole deformation studies. Studies of the response of a glacier to a change in surface configuration can partially eliminate some of this ambiguity.
\r\n\r\nThe theory and finite element calculations are extended to channels that follow a curving course in map view, which is necessary for application to Blue Glacier, since in the reach studied the glacier flows around a gently curving bend of 90\u00b0. Longitudinal channel curvature causes asymmetry in the stress and velocity distribution within a symmetric channel. The stress centerline is shifted toward the inside of the bend, while the position of the maximum velocity is usually shifted outward of the center for n \u2265 3. The effects of curvature are readily observable in the flow and crevassing of Blue Glacier.
\r\n\r\nThe relation between perturbations in ice thickness and surface slope and the change in velocity is developed for arbitrary channels. Analytical and numerical results indicate that there is a linear relation between the changes in slope \u03b1, thickness H, and surface velocity u:
\r\n\r\n[Equation included in scanned thesis' abstract, pp. vii]
\r\n\r\nwhere \u03a8 is termed the response factor. For realistic channel geometries, \u03a8 is in the range 1/2 to 1. This factor represents the change in cross-sectional shape of an ice mass which accompanies a change in ice thickness within a given channel. The value of the stress exponent inferred from the observed flow response is significantly affected by this geometric factor, which is approximately equal to 0.82 for Blue Glacier. The slope of the response line implies that n = 4 for the flow of Blue Glacier when this response factor is taken into account.
\r\n\r\nFinite element models of flow and the flow response within the different cross sections of Blue Glacier (as determined by radio echo sounding) compare well with the observed velocity patterns and response to change in thickness if channel curvature is included. These results again imply a stress exponent of n = 4. The results also agree with the various field measurements which indicate that basal sliding contributes at most 10% to the overall motion of the glacier.
\r\n\r\nThe results presented in this thesis represent the most detailed evaluation of the response of a glacier to perturbations in ice thickness and surface slope. They show that non-linear flow theory with n = 4 is applicable to a good approximation. The relationship between the flow velocity, slope, and thickness found in this work has direct application to the study of effects of climatic change on an ice mass.
" }, { "name": "Gladstone, George Randall", "degree": "PhD", "year": "1983", "title": "Radiative Transfer and Photochemistry in the Upper Atmosphere of Jupiter", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:02042013-113709002", "creators": [ { "name": { "family": "Gladstone", "given": "George Randall" }, "id": "Gladstone-George-Randall", "display_name": "Gladstone, George Randall" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "chair", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." } ], "option_major": [ "plansci" ], "doi": "10.7907/pzzp-2209", "abstract": "The upper atmosphere of Jupiter, from the tropopause to well above the homopause, is investigated as to its compositional structure and vertical mixing parameters. Constraints are obtained through the study of the radiative transfer of ultraviolet resonance lines and continuum radiation. These constraints and others are then used in the modeling of the hydrocarbon photochemistry of Jupiter.
\r\n\r\nA direct finite difference numerical solution for the equation of radiative transfer is developed for use in planetary atmospheres. The procedure uses a plane-parallel atmosphere, and can treat partial frequency redistribution (for use in the radiative transfer of optically thick resonance lines), inhomogeneity, external or internal sources, and various boundary conditions. Isotropic scattering is assumed, but in the case of no frequency redistribution, a Rayleigh phase function may be used. A program utilizing this solution is tested against more powerful and elaborate methods. This program is then applied to the Lyman-\u03b1 aurora of Jupiter, and detailed line profiles are presented.
\r\n\r\nUsing this program, a study is made of the UV reflection spectrum of Jupiter as measured by the International Ultraviolet Explorer. Detailed modeling reveals the mixing ratios of C2H2, C2H6, and C4H2 to be (1.0 \u00b1 0.1) x 10-7, (6.6 \u00b1 5.3) x 10-6, and (2.9 \u00b1 2.0) x 10-10, respectively in the pressure region between \u223c 3 and 40 mbar. Upper limits in this pressure region for the mixing ratios of C2H4 and NH3 were determined to be (3.9 \u00b1 4.93.9) x 10-10 and (4.2 \u00b1 6.74.2 x 10-9, respectively. An upper limit to the optical depth of dust above the tropopause, assuming it is well mixed, is 0.2 \u00b1 0.30.2 and an upper limit on the dayglow emission by the Lyman bands of H2 is 1.4 \u00b1 2.41.4 kiloRayleighs. Comparison with Voyager results suggests that the scale height of C2H2 in the region 150-10 mbar is approximately twice that of the bulk atmosphere, consistent with the IUE observation of cosine-like limb darkening in the north-south direction on Jupiter in the UV.
\r\n\r\nThe resonant scattering of the solar He I 584 \u00c5 emission line by the upper Jovian atmosphere is investigated next. The observed intensity of this scattered line depends directly on the eddy diffusion for vertical mixing (Kh) and the temperature (Th) at the homopause. Using the temperature profile determined by the Voyager UVS experiment, a value of Kh = 1.3 x 106 cm2s-1 \u00b1 30% is obtained. If the temperature profile was the same during the Pioneer 10 encounter with Jupiter, then Kh \u2248 1 x 108 cm2 s-1 at that time. The He 584 \u00c5 brightness is found not to depend strongly on the gradients of either the eddy diffusion or temperature profiles. A semi-analytical expression for computing the He 584 \u00c5 brightness for a constant-K, constant-T atmosphere is derived and compared with calculations by other authors. It is speculated that the apparent decrease in Kh by two orders of magnitude between the Pioneer and Voyager encounters may be the result of an increase in the pole-to-equator circulation in the thermosphere, perhaps driven by the solar cycle.
\r\n\r\nThe above results are used as constraints for a one-dimensional photochemical-diffusive model of the hydrocarbon chemistry in Jupiter's upper atmosphere. The important chemical cycles and pathways among the C and C2 species are outlined and it is shown that the amount of methane dissociation resulting from acetylene photochemistry is comparable to the amount that is due to direct photolysis. Profiles for the major observed hydrocarbon species are calculated and their sensitivity to eddy diffusion profile, chemistry, and solar UV flux is examined. A best fit to the eddy diffusion profile of the upper atmosphere during the Voyager encounters is found to be given by K = 1.3 x 106(2.17 x 1013/n)0.5 cm2 s-1 (where n is the total number density), which implies a vertical mixing time at the tropopause of ~ 50 years. It is shown that polyacetylene formation driven by acetylene photochemistry in the models presented here is capable of producing the observed abundance of Danielson dust in the stratosphere of Jupiter. The disk-averaged Lyman-\u03b1 albedo of the the preferred model is calculated to be ~ 8 kiloRayleighs, almost a factor of two lower than the Voyager observed value of ~ 14 kiloRayleighs. This may indicate the need for an increased flux of atomic hydrogen from the thermosphere over the already present source from EUV and soft electron dissociation of H2. Such a flux is available from the auroral regions if there exists a pole-to-equator flow in the thermosphere as postulated earlier. Finally, a brief consideration of the auroral chemistry concludes that more lab studies of ion-neutral and ion-electron recombination reactions are needed before a meaningful study of that problem may be undertaken.
" }, { "name": "Jakosky, Bruce Martin", "degree": "PhD", "year": "1983", "title": "The Seasonal Behavior of Water Vapor in the Mars Atmosphere", "advisor": "Ingersoll, Andrew P.; Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:02062013-144652620", "creators": [ { "name": { "family": "Jakosky", "given": "Bruce Martin" }, "id": "Jakosky-Bruce-Martin", "orcid": "0000-0002-0758-9976", "display_name": "Jakosky, Bruce Martin" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "co-advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "chair", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Farmer", "given": "C. Bernard" }, "id": "Farmer-C-Bernard", "role": "member", "display_name": "Farmer, C. Bernard" } ], "option_major": [ "plansci" ], "doi": "10.7907/f9fz-gg50", "abstract": "Understanding the evolution of volatiles on Mars requires understanding the processes which are currently acting to cause exchange between the various reservoirs on annual and longer timescales. On the seasonal timescale, exchange of water can occur between the atmosphere and reservoirs of ice in the polar caps and of adsorbed water in the near-surface regolith covering the remainder of the planet. This exchange is driven by the seasonally-varying insolation and its consequent effects on the surface and subsurface temperatures and on the advance and retreat of the predominantly-CO2 polar caps. On a longer timescale, exchange can occur between these same reservoirs, and is driven by the changing annual insolation patterns which result from the 105-year timescale variations in Mars' orbital elements (predominantly the orbital obliquity). Observations of the seasonal water cycle and its variations from year to year from the Viking spacecraft and from Earth provide clues as to the importance of the various reservoirs and provide boundary conditions against which models of the various processes can be compared.
\r\n\r\nThe water vapor content of the Mars atmosphere was measured from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) for a period of more than one Martian year, from June, 1976, through April. 1979, and the results are presented here. The data reduction incorporates spatial and seasonal variations in surface pressure, and supplements earlier published versions of less-complete data. Column abundances vary between zero and about 100 precipitable microns (pr \u00b5m), depending on location and season, while the entire global abundance varies seasonally between an equivalent of about 1 and 2 km3 of ice. The first appearance of vapor at non-polar latitudes as northern summer approaches, and the drop in abundance at mid-latitudes as summer ends, both strongly imply the existence of a seasonal reservoir for water within the regolith. There appear to be no net annual sources away from the poles that contribute significant amounts of water. However, the strong annual gradient of vapor from north to south implies a net annual flow of vapor toward the south; this southward flow may be balanced in part by a northward flow during the global dust storms, by transport in the form of clouds or adsorbed onto dust grains, or during other years. The perennially-cold nature of the south-polar residual cap, along with the relatively large summertime vapor abundances over the cap, implies a net annual condensation of vapor onto the cap. Estimates are made of the southward transport, and are consistent with the movement of ice being important in the formation and evolution of the polar layered terrain, and with the formation of the individual layers at the rate of one per obliquity cycle (105 years).
\r\n\r\nThe global distribution of the annual average abundance of vapor is found to correlate well with Martian topography, as might be expected for a uniform constant atmospheric mixing ratio. If this topographic effect is divided out, the resulting residual map correlates with maps of surface albedo and thermal inertia; this correlation may be related to the control exerted by the surface and subsurface temperatures on the adsorption/desorption process and on the atmospheric temperature profile and, hence, the vapor holding capacity of the atmosphere.
\r\n\r\nThe vertical distribution of vapor within the atmosphere is inferred through comparison of the observed water vapor abundances with measurements of atmospheric temperatures. In order to not saturate, the vapor must be confined to the lowermost 1 to 3 scale heights (~ 10-30 km), with this height varying with location and season. Near-surface water vapor can condense out overnight and form a morning fog; estimates of the optical thickness of the resulting fog are made, and they agree well with observations of diurnal variations of opacity due to fog formation.
\r\n\r\nPrevious Earth-based near-infrared observations are re-interpreted here; they show that water ice condenses out onto the seasonal polar caps, but not during midday near the equator. Earth-based observations of the vapor column abundance are compared with the Viking MAWD results, and indicate that the seasonal cycle shows a remarkable repeatability, except during 1969 when large vapor abundances were present during southern summer. This difference is explained by postulating that all of the CO2 had sublimed off of the south residual cap that year, exposing the underlying water cap which would subsequently sublime and produce large amounts of atmospheric vapor; the rate and amount of CO2 sublimation may depend on the degree of dust storm activity each year and hence on the different thermal loads placed on the cap.
\r\n\r\nThe possible processes for producing seasonal changes in the atmospheric vapor abundances have been modeled in order to infer the relative importance of each process in the seasonal cycle. The equilibrium between water vapor and water adsorbed onto the regolith grains is sufficiently temperature-dependent that seasonal surface temperature variations are capable of driving a large exchange of water between the atmosphere and subsurface. For the likely range of regolith properties, this exchange is found to be from 10-150% of the observed seasonal change in atmospheric abundance; the differences between this exchange and the observed behavior result from transport of vapor due to the atmospheric circulation. Due to the latitudinal gradient of atmospheric vapor, there will also be a gradient of adsorbed water, with the south regolith containing much less water than that in the north; this gradient in the regolith will result independent of the vapor diffusivity in the regolith, as the near-surface water will be able to equilibrate on some timescale.
\r\n\r\nModels have been constructed which include regolith exchange, polar cap formation, and atmospheric transport. Comparison of the model results with the vapor observations and with other data regarding the physical nature of the surface allows constraints to be placed on the relative importance of each process. The models are capable of satisfactorily explaining the gross features of the observed behavior using plausible values for the regolith and atmosphere mixing terms. In the region between the polar caps, the regolith contributes as much water to the seasonal cycle of vapor as does transport in from the more-poleward regions, to within a factor of two. Globally, 10-50% of the seasonal cycle of vapor results from exchange of water with the regolith, about 40% results from the behavior of the residual caps, and the remainder is due to exchange of water with the seasonal caps. It is difficult to determine the relative importance of the processes more precisely than this because both regolith and polar cap exchange of water act in the same direction, producing the largest vapor abundance during the local summer. The system is ultimately regulated on the seasonal timescale by the polar caps, as the time to reach equilibrium between the atmosphere and regolith or between the polar atmosphere and the global atmosphere is much longer than the time for the polar caps to equilibrate with the local atmosphere. This same behavior will bold for longer timescales, with the polar caps being in equilibrium with the insolation as it changes on the obliquity timescale, and the atmosphere and regolith following along.
" }, { "name": "Jewitt, David Clifford", "degree": "PhD", "year": "1983", "title": "I. Physical Studies of Distant Comets. II. Morphologies of Planetary Nebulae", "advisor": "Yung, Yuk L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10132005-145503", "creators": [ { "name": { "family": "Jewitt", "given": "David Clifford" }, "id": "Jewitt-David-Clifford", "orcid": "0000-0003-0262-8160", "display_name": "Jewitt, David Clifford" } ], "advisors": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "advisor", "display_name": "Yung, Yuk L." } ], "committee": [ { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "chair", "display_name": "Yung, Yuk L." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "member", "display_name": "Westphal, James A." }, { "name": { "family": "Searle", "given": "Leonard" }, "id": "Searle-Leonard", "role": "member", "display_name": "Searle, Leonard" }, { "name": { "family": "Soifer", "given": "B. Thomas" }, "id": "Soifer-B-T", "role": "member", "display_name": "Soifer, B. Thomas" } ], "option_major": [ "plansci" ], "doi": "10.7907/f9ge-m194", "abstract": "Part 1:
\r\n\r\nBroadband observations of comets P/Stephan-Oterma (1980g), Bowell (1980b) and Panther (1980u) in the visual (0.5 \u227e \u03bb(\u00b5m) \u227e 0.9) and infrared (1.2 \u227e \u03bb(\u00b5m) \u227e 20) wavelength regions are reported together with measurements in the 1.5 to 2.4 \u00b5m wavelength range having 5% spectral resolution. The visual data indicate the existence of solid grains in extended halos around the nuclei of the three comets. The visual photometric profiles of comets P/Stephan-Oterma and Panther are interpreted as evidence that grains around Panther and those close to the nucleus of P/Stephan-Oterma are sublimating. Broadband near infrared and thermal infrared measurements of comet Panther suggest the presence of 2 to 4 \u00b5m radius particles in the coma. The particles within a 5.8 x 106 diameter region centered on the comet have a total cross section of 108m2 and a near infrared geometric albedo of about 14%. Comet Bowell presents a total cross section of 3 x 108m2 within a 1.2 x 107m region centered on the comet and its coma grains also have an albedo of 14%.
\r\n\r\nThe near infrared spectrum of P/Stephan-Oterma is a featureless solar-reflection continuum. The near infrared spectra of Bowell and Panther exhibit features which are similar in the two comets. The spectral features are not due to H2O, CH4 or CO2 ices nor to emissions from gases released from the nuclei nor to reflection from mineral grains of known composition in the comae. The spectrum of solid ammonia provides the best match to the near infrared; it is nevertheless significantly different from the comet spectra.
\r\n\r\nThe synthesis of the visual data with the infrared data is attempted in terms of a model involving a mantle of volatile material on the nuclei of Bowell and Panther, but not on P/Stephan-Oterma. The composition of the mantle cannot be exactly specified from the existing data but a complex molecule incorporating the N-H bond may be present.
\r\n\r\nPart 2:
\r\n\r\nAn extensive series of observations of comet Bowell at optical and infrared wavelengths is summarized and interpreted in terms of a model of the outgassing of the nucleus. The observations indicate that the optical coma consists of large grains. The outer edge of the coma is expanding from the nucleus at 0.9 \u00b1 0.2 ms-1: extrapolation of the expansion suggests that the coma was ejected from the nucleus when the comet was at a heliocentric distance R ~ 10 AU. At this distance, water ice sublimation would be negligible. Models of the brightness of the comet as a function of R are compared with the measured brightness variation. Between R = 5.3 and 3.4 AU, the apparent cometary brightness changed by a factor of less than 20. Models which account for the equilibrium sublimation of volatiles from the nucleus predict much larger brightness variations. In particular, the models confirm that the sublimation of water ice does not control the activity of comet Bowell. The observations are consistent with the presence of an inert nucleus surrounded by a dissipating grain coma ejected impulsively at R ~ 10 AU. Strong OH production observed near R = 3.4 AU could be a result of the photodissociation of water molecules released from the coma grains by sublimation. However, near infrared spectra of the grains show no evidence for the presence of OH. Instead, several absorptions similar to the overtones of NH bond vibrations are observed. It is noted that the outgassing properties of the comet are similar to those of proton-bombarded laboratory ice specimens. Both the impulsive coma ejection and the peculiar near infrared spectrum may result from the presence of unstable compounds produced in the nucleus by cosmic ray bombardment. The activity of comet Bowell is quite unlike that exhibited by comets at small R, but may be representative of the properties of the distant comets.
\r\n\r\nPart 3:
\r\n\r\nThe spatial distribution of [CI] 9823, 9850 \u00c5 emission in NGC 6720 is reported. Like [01], the [CI] radiation appears enhanced in the region of the bright filaments. A few percent of the carbon atoms in the filaments are neutral. This neutral fraction is consistent with ionization equilibrium calculations made under the assumption of complete shielding of direct stellar radiation by hydrogen. The observed carbon lines are excited by photoelectrons produced from hydrogen by the nebular diffuse radiation field. The [CI] observations confirm that the filaments in NGC 6720 are regions of locally enhanced shielding.
\r\n\r\nPart 4:
\r\n\r\nThe preliminary results of a CCD survey designed to detect and investigate faint halos around planetary nebulae are described. A TI 800 x 800 pixel CCD was used to take deep exposures of 44 planetary nebulae. The exposures were mostly obtained through an Ha filter at the Cassegrainian focus of the Palomar 1.5 m telescope. Spatial resolutions of 1 to 2 arcsecond were obtained across 400 arcsecond wide fields. The images, which are in many cases considerably deeper than any previously taken, reveal numerous planetary nebula halos. About 2/3 of the studied nebulae possess extensive outer halos. In some nebulae the mass in the halo is comparable to the mass contained in the primary HII region. We have used the data to place constraints on the mode of origin of the halos. It is likely that the halos originate either by dynamical separation of a single ejected shell of gas, or by the ejection of two or more such shells from the central star. It is less likely that the halos are caused by excitation of the pre-planetary stellar wind and highly improbable that the halos represent reflection nebulae.
" }, { "name": "Lay, Thorne", "degree": "PhD", "year": "1983", "title": "Analysis of Upper and Lower Mantle Structure Using Shear Waves", "advisor": "Hager, Bradford H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10042006-112842", "creators": [ { "name": { "family": "Lay", "given": "Thorne" }, "id": "Lay-Thorne", "orcid": "0000-0003-2360-4213", "display_name": "Lay, Thorne" } ], "advisors": [ { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "advisor", "display_name": "Hager, Bradford H." } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." } ], "option_major": [ "geophys" ], "doi": "10.7907/65TN-KN39", "abstract": "This thesis addresses the fundamental problem of determining the radial and lateral structure of the earth's interior using body wave observations. My approach is a cautious one, involving detailed analysis of a substantial data set in which I attempt to isolate the contributions from radial and lateral structure in both the upper and lower mantles. This is an elusive task, as I am concerned with the 2 or 3% fluctuations about standard earth models, which produce rather subtle effects on teleseismic signals. However, this is the level of precision to which the three dimensional structure of the earth must be determined if we are to map the dynamical and compositional configuration of the earth. Studies similar to those described here cannot be conducted on a detailed global basis, given the intrinsic limitations due to station and earthquake distribution, so I have repeatedly emphasized the qualitative implications of my results, as they probably provide a representative sampling of the subtle, but significant heterogeneity of the earth.
\r\n\r\nThe topics addressed in the following work appear unrelated at first glance, ranging from determination of the detailed shear velocity structure at the base the mantle to variations in attenuation and velocity structure of the upper mantle. However, the data set used throughout is largely the same, and this in itself indicates the need to consider all of the complexity discussed herein for future progress to be made in mapping the three dimensional structure of the earth with a high level of confidence.
\r\n\r\nThe first chapter of the thesis presents results of a waveform analysis of transversely polarized SH signals that propagate through the lowermost mantle. The waveforms of these phases show clear interference patterns due to interaction with a discontinuous shear velocity increase about 280 km above the core-mantle boundary. This discontinuity, which has not been detected previously, is manifested in signals sampling three widely separated portions of the lower mantle, and hence is a good candidate for a global radial earth structure. Very detailed inspection of the signals reveals evidence for lateral variations in the depth of the discontinuity, which provides a procedure by which to map the structure of the D\" region in detail. Analysis of the relative amplitudes of SH and ScSH signals reveals that the velocity gradient above the core boundary is consistent with the smoothly varying gradients in most gross earth models, but evidence for local high velocity gradients at the base of the mantle is detected in ScSV signals.
\r\n\r\nChapter II presents a travel time analysis of the same data set used in Chapter I, which was motivated by the observation of large amplitude and travel time anomalies in the S and ScS data. An emphasis is placed on isolating the portions of the S and ScS paths which are anomalous. A strong empirical case is made for the existance of localized regions with scale lengths of 1000 to 2000 km and 2% velocity anomalies within the lower mantle at depths from 1000 to 2700 km. The long period signals traversing these regions show as much as a factor of 2 amplitude enhancement or diminution. This result demonstrates that both amplitude and travel time anomalies are induced by lateral structure in the portion of the mantle assumed to be homogeneous in most seismological studies.
\r\n\r\nThe third chapter is an analysis of the influence of upper mantle variations in attenuation, velocity structure and receiver structure on the S and ScS signals analyzed in the lower mantle studies. These variations contaminate and complicate the interpretation of any data set used to study deeper earth structure. Along with evidence for very strong and abrupt variations in upper mantle properties, results are presented which indicate the inadequacy of assumptions that are frequently made about the nature of long period body-wave receiver functions.
" }, { "name": "Lewis, Richard Edwin", "degree": "PhD", "year": "1983", "title": "Geology of the Hackberry Mountain Volcanic Center, Yavapai County, Arizona", "advisor": "Allen, Clarence R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03112010-141459869", "creators": [ { "name": { "family": "Lewis", "given": "Richard Edwin" }, "id": "Lewis-Richard-Edwin", "display_name": "Lewis, Richard Edwin" } ], "advisors": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." } ], "committee": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "chair", "display_name": "Shoemaker, Eugene Merle" }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." } ], "option_major": [ "geol" ], "doi": "10.7907/6sbf-7765", "abstract": "The Hackberry volcano in central Arizona, is a large dacitic volcano of late Miocene age. Most of the Hackberry Mountain area is underlain by Miocene volcanic rocks, primarily basalt and dacite. The oldest are a heterogeneous group of basalt flows, the Hickey Formation, erupted from local cinder cones. They were superseded by a homogeneous group of basalt flows, the Thirteenmile Rock Basalt, erupted from vents east of the area. Pyroclastics from the Hackberry volcano intertongue with the upper part of the Hickey Formation and all of the Thirteenmile Rock Basalt. There were seven episodes of these pyroclastics, collectively termed the Towel Creek Tuff, that were formed early in the history of the Hackberry volcano. This unit contains numerous dacitic ignimbrites and air-fall tuffs. Coarse, interstratified breccias occur in the upper parts of these deposits; they are capped by reworked tuffs. The sequence of air-fall tuff, ignimbrite, and breccia suggests a Pelean style of eruption.
\r\n\r\nAfter cessation of the pyroclastic activity, the volcano was intruded by a dacite stock, the Sally May Dacite. The stock probably extruded above the ground surface; because of its location, size (diameter of 8 km), petrography, and chemistry, the stock is believed to be the material of the magma chamber for the Towel Creek Tuff. The stock reached the surface without producing an attendant pyroclastic deposit. The fact that the stock rose to the surface without an accompanying paroxysmal eruption indicates that it was volatile-poor though still hot. Application of Stokes Law shows that it was unable to rise by buoyant forces alone; its upward migration apparently was facilitated by regional extension. The stock was hydrothermally altered at low temperature after its emplacement.
\r\n\r\nTwo rhyolite plugs intruded the stock. One was apparently the conduit for a rhyolite flow nearly eight kilometers in length. This plug was later disrupted, possibly by an eruption driven by fluids in the altered stock. The volcanic activity culminated with the extrusion of a thick dacite flow, the Hackberry Mountain Dacite.
\r\n\r\nThe Hackberry volcano was active for 2.2 to 3.9 m.y. The presence of basic xenoliths in the dacitic rocks suggests that its long life was the consequence of the injection of basaltic magma into the dacitic magma chamber. The dacite in all deposits of this volcano are petrographically similar.
\r\n\r\nThe Hackberry Mountain area forms the southeastern margin of the Verde Valley, a sedimentary basin in which the Verde Formation accumulated. Fluviatile sandstones of the Verde Formation intertongue with the upper Hickey and lower Thirteenmile Rock Basalt in the northwestern part of this area, and the Verde grades upward into lacustrine sediments younger than all the volcanic rocks, but still of Miocene age. The Verde Valley formed primarily by subsidence along northwest-trending normal faults, many of which occur in the area studied. The faults in the Hackberry area are commonly interconnected and have a net offset of 400 meters, downdropped southwest. The margin of the basin occurs here because the amount of subsidence decreases, and, more importantly, the Hackberry volcano formed a topographic boundary.
" }, { "name": "Liu, Hsui-Lin", "degree": "PhD", "year": "1983", "title": "Interpretation of Near-Source Ground Motion and Implications", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09072006-111327", "creators": [ { "name": { "family": "Liu", "given": "Hsui-Lin" }, "id": "Liu-Hsui-Lin", "display_name": "Liu, Hsui-Lin" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Jennings", "given": "Paul C." }, "id": "Jennings-P-C", "role": "member", "display_name": "Jennings, Paul C." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" } ], "option_major": [ "geophys" ], "doi": "10.7907/5hbj-fd95", "abstract": "This thesis presents some deterministic modeling and interpretation of various aspects of observed near-source ground motions.
\r\n\r\nIn Chapter 1, finite source parameters determined from waveform modeling studies are presented for two California earthquakes; the 1979 Coyote Lake event and the 1966 Parkfield event. These events were recorded by strong motion arrays with similar station to fault rupture geometries. Thus it is possible to demonstrate that differences in the ground motions recorded within 30 km of the epicenter are indeed due to the differences in rupture fault length and dislocation distribution.
\r\n\r\nDetails of the waveform modeling for the August 6, 1979 Coyote Lake earthquake are described in part 1-A. A finite fault striking N24\u00b0W and extending to a depth of 10 km is proposed to model the strong-ground motion data. The source model suggests that right-lateral faulting initiated at a depth of 8 km and ruptured towards the south with a velocity of 2.8 km/sec. This unilateral rupture can explain the large displacements recorded south and southwest of the epicenter. However, the waveform coherency observed across an array south and southwest of the epicenter suggests that the rupture length is less than 6 km. The maximum dislocation is about 120 cm in a small area near the hypocenter and the total moment is estimated to be 3.5 x 1024 dyne-cm. An abrupt stopping phase, which corresponds to a cessation of right-lateral motion, can explain the high peak acceleration recorded at array station 6. The stress drop in the hypocentral area is about 140 bars; although the average stress drop over the entire rupture surface is 30 bars. This preferred finite source model can predict observed Pni waveforms as well as the beginning features of teleseismic body waves.
\r\n\r\nIn part 1-B, a similar waveform modeling technique is used to interpret the ground motions recorded during the June 28, 1966 Parkfield earthquake. The preferred model suggests that the earthquake involved two fault segments; one is the NE branch which extends 22 km southward from epicenter and has an average slip of 45 cm, another is the SW branch which ruptured less than 10 km and has an average slip of about 22 cm. The total moment indicated by this model is 1.25 x 1025 dyne-cm. The anomalous large amplitude ground displacement seen at station Cholame No. 2 is modeled as a local amplification effect rather than a source effect due to significant dislocation near this station.
\r\n\r\nDirect waveform comparisons between recordings of the Parkfield event and the Coyote Lake event also support the conclusion that the rupture length of the Coyote Lake earthquake is much shorter than that of the Parkfield event. The waveform modeling also emphasizes the importance of using array data to constrain source parameters. The solution derived from a single station's recording, which in many cases is the only available information, may often produce misleading results.
\r\n\r\nIn Chapter 2, high-frequency ground motions (ground velocity and acceleration) recorded at less than 30 km epicentral distances are studied for two aftershocks of the 1979 Imperial Valley, California earthquake. In the past, little has been done to understand these high frequency waves through a deterministic modeling approach. The waveform modeling technique and the source mechanisms of these two aftershocks are described in sections 2-A and 2-B.
\r\n\r\nAn important feature of the ground motions recorded during the October 15, 1979 Imperial Valley earthquake sequence is the strong high frequency waves observed on the vertical components. This feature is also seen in recordings of the aftershock of October 16, 23:16, 1979, which is described in section 2-A. This polarization feature is easily explained by the basin velocity structure which bends rays towards the vertical at the free surface. Short S-P times are observed at the three closest stations (epicentral distances of 3 km to 5 km) suggesting that this aftershock occurred at a very shallow depth of about 2 km. A fault plane orientation (strike = N20\u00b0E, dip = 30\u00b0SE, and rake = -80\u00b0) obtained from a first P-motion study, generates synthetic waveforms of the strong ground velocities which are similar to those observed at three closest stations. The source time duration is determined to be 1.0 second and the moment is 1.6x1023 dyne-cm. Synthetics for a number of line source models are compared with the observations. These comparisons lead to two basic mechanisms that are necessary to explain the frequency content of the observed P- and S- waves. One is that the source process is characterized by irregular rupture. It is postulated that the heterogeneous stiffness in the layered medium is the basic cause of the irregular rupture. Heterogeneous rupture generates both high-frequency P- and S-waves. In order to explain the contrast in observed frequency content it is also necessary that there is a mechanism for attenuating S-waves much stronger than P-waves.
\r\n\r\nThe aftershock that occurred about 3 minutes after the mainshock, at 23:19 October 15, 1979 is presented in section 2-B. This aftershock was located on the Imperial fault near Highway 8 and close to the zone of high frequency energy release of the main event. The impulsive seismograms for 16 array stations, ranging from 8 km to 26 km in epicentral distance, are well suited for source parameter inversion studies to obtain an optimal solution for ground velocity and acceleration. The earthquake source is approximated by a model consisting of several point dislocation sources separated in space and time and having different dislocation orientations and moments. These source parameters were deduced by trial and error modeling as well as by applying inversion procedures. The waveforms and amplitudes of horizontal ground velocities are well modeled by two predominantly strike-slip point sources; the first source (strike = N41\u00b0W, dip = 42\u00b0NE and rake = 174\u00b0) has a moment of 0.7 x 1024 dyne-cm, the second source (strike = N36\u00b0W, dip = 82\u00b0SW and rake = 181\u00b0) lies about 1 km to the north of the first and has a seismic moment of about twice that of the first source. It is suggested that the higher-frequency ground motions, such as accelerations, can be derived from very irregular source processes, whereas the longer-period ground motions, such as ground displacements, can be well modeled by simpler planar source.
\r\n\r\nA Futterman attenuation operator with a t*\u03b2 of about 0.08 to 0.1 and a t*\u03b1 of about 0.001 in the sedimentary region produces longer period S waves and the proper amplitude ratio between P and S waves.
\r\n\r\nIn Chapter 3, the ground motion data from the 1971 San Fernando earthquake recorded at epicentral distances of less than 100 km are presented. Three long profiles (> 50 km ) and three short profiles (< 2 km) of ground velocity and acceleration, displayed as a function of epicentral distance are analyzed.
\r\n\r\nAlthough there is considerable variation in waveforms and peak amplitudes observed along the long profiles, there are also many examples of coherent phases seen at adjacent stations. Ground velocity profiles show striking differences in amplitude and duration between stations located on hard rock sites and stations located within the sedimentary basins. The San Fernando basin, in which the source is located, seems to respond quite differently from the Los Angeles basin which is about 30 km from the earthquake source area. Ground acceleration profiles show that there is little change in the duration of high-frequency shaking along the long profiles.
\r\n\r\nThe three short profiles, which are all located within the Los Angeles basin, demonstrate that ground velocity waveforms are nearly identical along these profiles. Although greater variation of waveforms and amplitudes are seen for ground acceleration along these short profiles, strong phase coherence is still observed.
\r\n\r\nThe 2D acoustical finite difference method is used to compute the effects on SH-waves of irregular velocity structures believed to exist along Profile I and Profile II. Profile I extends 65 km southward from the epicenter across the San Fernando and Los Angeles basins to a station on the Palos Verdes Peninsula. Profile II extends 95 km S 40\u00b0 E along the front of the San Gabriel mountains and across the San Gabriel and Los Angeles basins. These numerical models consist of low-velocity sedimentary basins (\u03b2 = 2.1 km/sec) of irregular shape which are imbedded in high-velocity basement rock (\u03b2 = 3.5 km/sec). Heaton's (1982) finite source model derived from modeling the five nearest stations for the San Fernando event, is also incorporated in the interpretation. The resulting simulation suggests that the smaller S! phases in both Profile I and Profile II are direct S waves from the deep source region (13 km). The shallow source region (at 1 km) dominates high amplitude later arrived phases observed along Profile I and are due to the complicated basin path along this profile. The shallower source region, however, contributes little to the ground motions along Profile II due to the lack of thick sediments near the source region along this azimuth.
" }, { "name": "Pechmann, James Christopher", "degree": "PhD", "year": "1983", "title": "The Relationship of Small Earthquakes to Strain Accumulation Along Major Faults in Southern California", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02052013-085739683", "creators": [ { "name": { "family": "Pechmann", "given": "James Christopher" }, "id": "Pechmann-James-Christopher", "orcid": "0000-0002-6726-9640", "display_name": "Pechmann, James Christopher" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "geophys" ], "doi": "10.7907/WC53-1X39", "abstract": "Fault-plane solutions for recent small (ML \u2264 4.6) earthquakes in the central Transverse Ranges, California, were determined using an azimuthally-varying crustal model. The dominant type of faulting observed is reverse faulting on east-striking planes, which suggests a regional stress field characterized by north-south compression. Some strike-slip faulting also occurs. There is some indication that strike-slip earthquakes may be more common than reverse-slip earthquakes during episodes of crustal dilatation (Sauber et al., 1983). The rate of north-south crustal shortening attributable to small earthquake deformation during 1974-1976 is two orders of magnitude smaller than the 0.3 parts per million per year north-south contraction measured at the surface by Savage et al. (1978). The scatter in earthquake hypocenters and general inconsistency of focal mechanisms with geologically determined motions on nearby major faults indicate that the small earthquakes in this region are not associated with large-scale block movements along major fault systems. Rather, they appear to represent fracturing along random minor zones of weakness in response to the regional stress field, or alternatively, small-scale block movements that are below the resolution of this study. Earthquakes in the San Gabriel Mountains north of the Santa Susana-Sierra Madre-Cucamonga frontal fault system tend to concentrate near the eastern and western ends of the range where good evidence for late Quaternary movement along the frontal faults has been found. Seismicity is markedly lower north of the central section of the frontal fault system where evidence for late Qlaternary movement is lacking.
\r\n\r\nDigitally-recorded waveforms of ML 2.0-2.8 earthquakes that occurred in two small areas along the Imperial fault before and after it broke in the ML 6.6 Imperial Valley earthquake on October 15, 1979, were examined and compared. Eight preshocks (1977-1979) from a 4\u00bd by 1\u00bd km area centered 4 km southeast of the mainshock epicenter have strikingly similar waveforms over the entire record length (~30 s), with an average peak cross correlation between seismograms of 0.74. The seismograms are well correlated at frequencies up to at least 4 Hz. This implies similar source mechanisms and hypocenters within \u00bc of the 4-Hz wavelengths, i.e., < 200-400 m. Five aftershocks from the same area show an average peak cross correlation between seismograms of only 0.23. Any associated changes in mechanism must be small because they are not reflected in the first motion data. Analysis of frequency content of these events using bandpass-filtering techniques showed no systematic temporal changes in spectral shape.
\r\n\r\nTen preshocks and 24 aftershocks from a 1 \u00bd by 2 km source area centered along the Imperial fault 16 km northwest of the 1979 mainshock epicenter were also studied. First motion data suggest that all of the aftershocks and a swarm of six preshocks on December 7-9, 1978, were associated with the main fault but that four earlier preshocks were not. The six preshocks on December 7-9, 1978, were tightly clustered, as evidenced by the strong similarity of the waveforms (most peak cross correlations \u2265 0.6). During this swarm the 8- to 16-Hz spectral amplitude increased relative to the 1- to 2-Hz spectral amplitude over the whole record length by about a factor of 3, suggesting a systematic increase in stress drop. Groups of like events are also present among the aftershocks in this data set. The average peak correlation for pairs of aftershocks, 0.43, is almost the same as that for pairs of preshocks, 0.45, if all 10 preshocks are included. However, several sources appear to have been active simultaneously during the aftershock period so that no more than two to three consecutive aftershocks have maximum cross correlations \u2265 0.6.
\r\n\r\nA search was undertaken for earthquakes with similar waveforms within two small (< 5 km) areas along the San Jacinto fault zone northwest of the Anza gap, but none were found. Focal mechanisms for most of the earthquakes in these two study areas agree very well with the faulting observed geologically at the surface. This, together with the concentration of hypocenters near the San Jacinto fault zone, suggests that small earthquakes are occurring along the main faults traces here, in contrast to the situation in the central Transverse Ranges.
\r\n\r\nThe highly localized sources characterized by waveform similarity may represent fault asperities or clusters of asperities. The observations above are consistent with a decrease in the number of these asperities as the weaker ones fail under increasing stress during the intervals between large earthquakes.
" }, { "name": "Pechmann, Judith Burt", "degree": "PhD", "year": "1983", "title": "Thermal Tides in the Atmosphere of Venus", "advisor": "Goldreich, Peter Martin", "url": "https://resolver.caltech.edu/CaltechTHESIS:10312023-202011054", "creators": [ { "name": { "family": "Pechmann", "given": "Judith Burt" }, "id": "Pechmann-Judith-Burt", "display_name": "Pechmann, Judith Burt" } ], "advisors": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "advisor", "display_name": "Goldreich, Peter Martin" } ], "committee": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "chair", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" } ], "option_major": [ "plansci" ], "doi": "10.7907/5cd0-3q63", "abstract": "The daily variation in the absorption of sunlight by the atmosphere provides the forcing for thermal tides. In this thesis the response of the Venus atmosphere as a function of height and latitude to the diurnal and semidiurnal components of the forcing is calculated using a linearized primitive equation model. We specify the atmospheric mean state using data from the Pioneer Venus probes and orbiter, and solve for the first order tidal perturbation. Our forcing function is based on data returned by the solar flux radiometer on the Pioneer Venus sounder probe. The perturbation variables are discretized horizontally by spherical harmonics and vertically by finite elements. A semi\u00ad implicit time-stepping algorithm is used.
\r\n\r\nThe model results for Venus thermal tides are in agreement with the solar-fixed component of diurnal and semidiurnal brightness temperature fluctuations determined from Pioneer Venus orbiter infrared radiometer (OIR) data. Contrary to the prediction of classical tidal theory, the observed semidiurnal brightness temperature maxima occur before the forcing maxima from about 60 to 80 km. In the model, this phase lead is due to a long vertical wavelength (~30 km) from the cloud tops to 80 km. Also, the data unexpectedly show that the semidiurnal amplitude is larger than the diurnal over much of the region observed, even though the diurna1 forcing is about twice as great. The model's diurnal temperature amplitude is larger than that observed in the brightness temperature. However, convolution with the OIR weighting functions results in model brightness temperature amplitudes which are as small as the observed values because the vertical wavelength of the\r\ndiurnal tide is shorter than the width of the weighting functions.
\r\n\r\nThe success of the model increases our confidence in our knowledge of the mean state of the Venus atmosphere and provides us with the opportunity to determine the importance of energy and angular momentum transport by the tides. The zonally averaged vertically integrated tidal energy flux is significant compared to the zonally averaged imbalance in incoming solar radiation and outgoing infrared radiation from equatorial to mid-latitudes. However, the tides do not in general tend to reduce the imbalance by transporting heat poleward. The mean meridional circulation driven by this imbalance and the tidal energy flux consists of stacked direct and indirect Hadley cells. The angular momentum transport is upward and poleward in the direct cells. Since the transport is not upward at all altitudes, some other processes must be involved in maintaining the large shear in the mean zonal wind. The vertical transport by the tides is small compared to that of the mean circulation. However, the tides do transport a significant amount of angular momentum equatorward from mid-latitudes.
" }, { "name": "Porco, Carolyn C.", "degree": "PhD", "year": "1983", "title": "Voyager Observations of Saturn's Rings. 1. The Eccentric Rings at 1.29, 1.45, 1.95 and 2.27 R\u209b. 2. The Periodic Variation of Spokes", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechETD:etd-09212004-110904", "creators": [ { "name": { "family": "Porco", "given": "Carolyn C." }, "id": "Porco-Carolyn-C", "display_name": "Porco, Carolyn C." } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "chair", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Sargent", "given": "Wallace L. W." }, "id": "Sargent-W-L-W", "role": "member", "display_name": "Sargent, Wallace L. W." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "plansci" ], "doi": "10.7907/q3z6-ca90", "abstract": "Part 1:
\r\n\r\nFive major eccentric features in the rings of Saturn are studied. These are the outer A and B ring edges at 1.95 and 2.27 R\u209b and three narrow ringlets at 1.29, 1.45, and 1.95 R\u209b. Data acquired by four Voyager experiments - Imaging Science (ISS), Radio Science (RSS), Ultraviolet Spectrometer (UVS), and Photopolarimeter(PPS) - were used in this investigation.
\r\n\r\nThe shapes and kinematics of the A and B ring outer edges are determined by their proximity to strong low-order Lindblad resonances. The data for the A ring edge are consistent with a 7-lobed distortion rotating with the mass-weighted mean angular velocity of the co-orbital satellite system. The B ring edge has a double-lobed figure which rotates with the mean motion of Mimas.
\r\n\r\nThe Saturnian ringlets are narrow (mean widths vary from ~ 10-60 km) and have eccentricities of order 10-4. All have sharp edges, normal optical depths \u03c4 ~ 1-2, and are embedded in essentially empty gaps (\u03c4 < 0.05). The Titan ring at 1.29 R\u209b and the Huygens ring at 1.45 R\u209b exhibit positive linear width-radius relations; the Maxwell ring at 1.95 R\u209b does not. The kinematics of the Huygens ring are determined solely by Saturn's non-spherical gravity field. The kinematics of the Titan ring are apparently completely determined by its interaction with Titan. At present, the most plausible model for the Maxwell ring involves the superposition of two components: one which is freely precessing and the other which is forced by Mimas and the elliptical B ring. Masses, mean surface mass densities, and specific opacities have been calculated for the Titan and Huygens rings.
\r\n\r\nPart 2:
\r\n\r\nThe discovery of a periodic variation in spoke activity in Saturn's rings from the analysis of Voyager images is reported. A Fourier power spectrum was computed using a data set generated by quantifying spoke activity observed on the morning (western) half of the rings in Voyager images spanning ~ 12 Saturn rotations and in Voyager 2 images spanning ~ 90 Saturn rotations. The period from Voyager 1 data is 631 \u00b1 22 min; from Voyager 2, 640.6 \u00b1 3.5 min. The latter result suggests that the fundamental modulation in spoke activity is due to the rotation of Saturn's magnetic field, the period of which is 639.4 min. Maximum spoke activity observed anywhere on the rings is most likely to be associated with the region of the magnetic field responsible for the most intense emission of the Saturn Kilometric Radiation (SKR). Passage of this region through Saturn's shadow may play a significant role in the creation and/or rejuvenation of spokes.
\r\n" }, { "name": "Vassiliou, Marios Simou", "degree": "PhD", "year": "1983", "title": "The Energy Release in Earthquakes, and Subduction Zone Seismicity and Stress in Slabs", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10282019-161929138", "creators": [ { "name": { "family": "Vassiliou", "given": "Marios Simou" }, "id": "Vassiliou-Marios-Simou", "display_name": "Vassiliou, Marios Simou" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "chair", "display_name": "Anderson, Donald L." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." } ], "option_major": [ "geophys" ], "doi": "10.7907/yp4p-t246", "abstract": "Part I
\r\n\r\nEarthquake energy calculations are generally made through an empirical application of the familiar Gutenberg-Richter energy-magnitude relationships. The precise physical significance of these relationships is somewhat uncertain. We make use here of the recent increases in knowledge about the earthquake source to place energy measurements on a sounder physical basis. For a simple trapezoidal far-field displacement source-time function with a ratio x of rise time to total duration T0, the seismic energy E is proportional to 1/[x(1-x)2] M20/T30, where M0 is seismic moment. As long as x is greater than 0.1 or so, the effect of rise time is not important. The dynamic energies thus calculated for shallow events are in reasonable agreement with the estimate E \u2248 (5 x 10-5)M0 based on elastostatic considerations. Deep events, despite their possibly different seismological character, yield dynamic energies which are compatible with a static prediction similar to that for shallow events. Studies of strong-motion velocity traces obtained near the sources of the 1971 San Fernando, 1966 Parkfield, and 1979 Imperial Valley earthquakes suggest that even in the distance range of 1-5 km., most of the radiated energy is below 1-2 Hz. in frequency. Far field energy determinations using long period WWSSN instruments are probably not in gross error despite their bandlimited nature. The strong motion record for the intermediate depth Bucharest earthquake of 1977 also suggests little teleseismic energy outside the pass-band of a long period WWSSN instrument.
\r\n\r\nPart II
\r\n\r\nThe pattern of seismicity as a function of depth in the world, and the orientation of stress axes of deep and intermediate earthquakes, are explained using viscous fluid models of subducting slabs, with a barrier in the mantle at 670 km. 670 km is the depth of a seismic discontinuity, and also the depth below which earthquakes do not occur. The barrier in the models can be a viscosity increase of an order of magnitude or more, or a chemical discontinuity where vertical velocity is zero. Log N versus depth, where N is the number of earthquakes, shows (1) a linear decrease to about 250-300 km depth, (2) a minimum near that depth, and (3) an increase thereafter. Stress magnitude in a subducting slab versus depth, for a wide variety of models, shows the same pattern. Since there is some experimental evidence that N is proportional to ek\u03c3, where k is a constant and \u03c3 is the stress magnitude, the agreement is encouraging. In addition, the models predict down-dip compression in the slab at depths below 400 km. This has been observed in earlier studies of earthquake stress axes, and we have confirmed it via a survey of events occurring since 1977 which have been analyzed by moment tensor inversion. At intermediate depths, the models predict an approximate but not precise state of down-dip tension when the slab is dipping. The observations do not show an unambiguous state of down-dip tension at intermediate depths, but in the majority of regions the state of stress is decidedly closer to down-dip tension than it is to down-dip compression. Chemical discontinuities above 670 km, or phase transitions with an elevation of the boundary in the slab, predict, when incorporated into the models, stress peaks which are not mirrored in the profile of seismicity versus depth. Models with an asthenosphere and mesosphere of appropriate viscosity can not only explain the state of stress observed in double Benioff zones, but also yield stress magnitude profiles consistent with observed seismicity. Models where a nonlinear rheology is used are qualitatively consistent with the linear models.
" }, { "name": "Wallace, Terry Charles, Jr.", "degree": "PhD", "year": "1983", "title": "Long Period Regional Body Waves", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:10282019-171911401", "creators": [ { "name": { "family": "Wallace", "given": "Terry Charles, Jr." }, "id": "Wallace-Terry-Charles-Jr", "orcid": "0000-0001-8328-0762", "display_name": "Wallace, Terry Charles, Jr." } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." } ], "option_major": [ "geophys" ], "doi": "10.7907/q7fe-4g63", "abstract": "The seismograms recorded at regional distances (2\u00b0-12\u00b0) are quite complicated due to the waveguide nature of the crust. The body wavetrains are essentially crustal reverberations. If these complicated waveforms are modeled with synthetic seismograms then significant information can learned about the seismic source and the structure along the travel path. With certain restrictions, the long-period regional body waves (Pnl) from shallow, continental earthquakes can be modeled with a layer (crust) over a halfspace (mantle). Generalized ray theory and the Cagniard-de Hoop technique can be streamlined for computing a synthetic seismogram in such a structure. We present an approximation to the travel time equation which results in an analytic inversion for the de Hoop contour. The simplicity of the individual rays requires that the displacement potential need only be evaluated at a small number of time points; small changes In structure are, to first order, expressed in terms of the timing of different arrivals. It is possible to \"stretch\" or \"squeeze\" the synthetic to simulate a change in structure. Therefore, a single Green's function can be used to Investigate a whole suite of structural models.
\r\n\r\nIf the average crustal structure is known, the Pnl, waveforms are insensitive enough to structural details to allow the extraction of source parameters of moderate size earthquakes. The technique which Is used is an iterative least-squares waveform inversion which makes use of an error function determined by the cross-correlation of an observation and a synthetic. Since any synthetic seismogram is a combination of the three fundamental faults, the error functions can be written as a series of cross-correlations multiplied by constants corresponding to source orientation. Once the cross-correlations are computed the source orientation is determined iteratively, and only the constants have to be recalculated. The inversion procedure requires only a small data base. Several examples are presented to demonstrate its usefulness.
\r\n\r\nIf the source orientation is known, then differences in the synthetic waveform and observed Pnl, can be parameterized in terms of the crustal thickness and Pn velocity. An inverson technique based on the error function previously described has been developed to determine crustal structure from Pnl. Once the structure is known for many paths a regionalized map can be produced. Such a map is presented for the western United States.
\r\n\r\nThe ability to efficiently model Pnl makes it possible to use it as a routine tool. We present two example of this procedure, the first of which is the 1980 Mammoth Lakes earthquake sequence. The fault mechanisms which are determined at long-periods (> 5 seconds) differ significantly from those determined by the distribution and polarity of local short-period first motions. Although it is not possible to isolate the cause of the discrepancy, at least part of It appears to be structurally related. Local short-period arrivals which travel through the Long Valley Caldera could be systematically deflected. The second example Involves the signature of tectonic release on the long-period P waves from underground nuclear explosions. The distortion of explosion waveforms can be modeled as a double couple which has a strike-slip orientation. The modeling of the sP phases at upper mantle distances requires time functions which have short durations. The short duration can be interpreted in terms of very high stress drops if the tectonic release is triggered fault motion. For this reason we prefer a driven fault model.
\r\n" }, { "name": "Cimino, Josephine Beatrice", "degree": "PhD", "year": "1982", "title": "The Composition, Vertical Structure and Global Variability of the Lower Cloud Deck on Venus as Determined by Radio Occultation Techniques", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302013-145914913", "creators": [ { "name": { "family": "Cimino", "given": "Josephine Beatrice" }, "id": "Cimino-Josephine-Beatrice", "display_name": "Cimino, Josephine Beatrice" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "chair", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Shair", "given": "Fredrick H." }, "id": "Shair-F-H", "role": "member", "display_name": "Shair, Fredrick H." }, { "name": { "family": "Kliore", "given": "Arvydas J." }, "id": "Kliore-Arvydas-J", "role": "member", "display_name": "Kliore, Arvydas J." }, { "name": { "family": "Elachi", "given": "Charles" }, "id": "Elachi-C", "orcid": "009-0002-2156-967X", "role": "member", "display_name": "Elachi, Charles" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." } ], "option_major": [ "plansci" ], "doi": "10.7907/j7et-kc02", "abstract": "The opportunity to determine the planetwide temperature and cloud structure of Venus using radio occultation techniques arose with Pioneer Venus. This orbiting spacecraft contained a dual frequency radio system which was used to collect radio occultation data for more than two years.
\r\n\r\nAmplitude and Doppler data provided by the radio occultation experiment provide a unique and powerful means of examining atmospheric properties in a region of Venus which may otherwise be observed only by means of a probe.
\r\n\r\nThe extraction of atmospheric properties from the received occultation data is a complicated non-linear process for which careful account of all contributing uncertainties must be taken. Such atmospheric phenomena as turbulence, oblateness due to winds, perturbations in the temperature, atmospheric density or gaseous composition affect both the Doppler and the amplitude data. Uncertainties inherent in the experiment itself and the data collection and processing procedures, such as trajectory errors, fluctuations in the power profile, averaging of the data and spacecraft wobble, result in additional uncertainties which must be considered.
\r\n\r\nAbsorption coefficient and temperature profiles were analyzed in detail for the effects of major sources of uncertainty. Inasmuch as the power loss due to refractive defocussing is determined from the Doppler data, uncertainties in the refractivity as well as the received power are considered. Power fluctuations are found to produce the greatest uncertainty in the S-band absorption coefficient profiles. Power fluctuations and spacecraft wobble contribute the greatest uncertainty to the X-band data. In fact, in many cases the spacecraft wobble has rendered the X-band data useless.
\r\n\r\nAbsorption due to gaseous components of the atmosphere are subtracted from the measured absorption coefficient profiles before they are used to compute cloud mass contents. The H2O mixing ratio profile used is that measured by the Venera 11 and 12 spectrophotometers. The SO2 profile was determined from the Venera 11 and 12 and Pioneer probe gas chromatograph and mass spectrometer results. The sulfuric acid saturation vapor mixing ratio used is the equilibrium vapor pressure above a concentrated sulfuric acid-water solution at the temperatures of the lower cloud deck.
\r\n\r\nThe absorption due to the gaseous components is found to represent a small part of the total absorption. In the main cloud deck, gaseous absorption contributes 10 to 20% and at the bottom of the detected absorption layer the sulfuric acid vapor contributes 60 to 100% to the absorption due to increased acid vapor pressures resulting from higher temperatures in this region. The clouds are the primary contributing absorbers in the 1 to 3 bar level of the Venus atmosphere. Below about 3 bars, absorption due to sulfuric acid vapor dominates.
\r\n\r\nAs a first attempt, mass content profiles were produced from the absorption coefficient data assuming the clouds were composed of concentrated sulfuric acid-water liquid. The resulting mass contents were on the order of several grams per cubic meter. Although planetwide variability in the lower cloud deck may account for differences in these radio occultation mass contents and those determined by the Pioneer probes, a second factor discounting purely liquid clouds has arisen. The dielectric constants of liquid sulfuric acid were measured in the laboratory at S-and X-band wavelengths and the results suggest the wavelength dependence for absorption by the liquid is 1/\u03bb2. The wavelength dependence measured by the radio occultation experiment is about 1/\u03bb1.2. In addition, the wavelength dependence required to fit the opacity determined from the 1.35 cm microwave emission data is 1/\u03bb1.2 to 1/\u03bb1.5. Apparently the liquid sulfuric acid droplet model does not satisfy the observed wavelength dependence or mass content.
\r\n\r\nIf, however, a cloud particle model consisting of a solid non-absorbing dielectric sphere with a concentric liquid sulfuric acid coating is invoked, the absorptivity of the particles increases and the mass content derived from the absorption coefficient profiles decreases. As the ratio of the core radius to the total radius (q) increases, absorption increases by more than a factor of 10 for high values of q. In the case of pure sulfuric acid droplets, the conductivity is sufficiently high that some of the field is excluded from the interior of the droplet thereby reducing the absorption. When a dielectric core of nonabsorbing material is introduced, two effects occur which contribute to the increase in the electric field which penetrates the drop. First, the relative volume filled by sulfuric acid decreases and the number of available free charges decreases. Second, the dielectric core, which is also polarized in the presence of the electric field, affects the arrangement of the free charges by attracting them to the inner surface and by acting as a barrier in the presence of the rapidly alternating electric field.
\r\n\r\nThe mass contents for all orbits in the equatorial region of Venus are calculated using values of q of from 0 to 1. The resulting profiles match the probe mass content profiles at similar locations when a q of 0.98 is chosen. Values for q of 0.97 to 0.99 change the absorptivity of the cloud particles by as much as 50%.
\r\n\r\nThe Wavelength dependence of the absorption for the spherical shell model varies with q from 1/\u03bb2 for pure liquid to \u03bb0.2 for a large core. A q of 0.98 results in a wavelength dependence of 1/\u03bb1.0 to 1/\u03bb1.4. which matches the radio occultation absorption wavelength dependence and the microwave opacity wavelength dependence.
\r\n\r\nMass content profiles using a q of 0.98 were determined for occultations in the polar, collar, midlatitudinal and equatorial regions assuming q remains constant over the planet. The results show considerable variability in both the level and the magnitude of the lower cloud deck. The cloud layer is lowest in altitude in the polar region. This might be expected as the temperature profile is cooler in the polar region than over the rest of the planet. The mass content is greatest in the polar and collar regions; however, many of the collar profiles are cut off due to fluctuations resulting from increased turbulence in the collar region. The mass contents are least dense in the midlatitude regions.
\r\n\r\nThese results support the value of using radio occultation techniques to obtain temporal and spatial coverage of the planet Venus in terms of cloud composition and mass content.
\r\n\r\n" }, { "name": "Gillespie, Alan Reed", "degree": "PhD", "year": "1982", "title": "Quaternary Glaciation and Tectonism in the Southeastern Sierra Nevada, Inyo County, California", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04102003-122837", "creators": [ { "name": { "family": "Gillespie", "given": "Alan Reed" }, "id": "Gillespie-Alan-Reed", "display_name": "Gillespie, Alan Reed" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "member", "display_name": "Sharp, Robert P." }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Clark", "given": "M. M." }, "id": "Clark-M-M", "role": "member", "display_name": "Clark, M. M." } ], "option_major": [ "geol" ], "doi": "10.7907/GNES-QH83", "abstract": "The southeastern Sierra Nevada consists of three geographic regions. From west to east, they are: an upland region across the crest, a steep east-facing escarpment along which Owens Valley has partly subsided, and foothill blocks intermediate to the Sierra Nevada and Owens Valley. Farther east, Owens Valley is a deep graben separating the Sierra Nevada and the Inyo Range.
\r\n\r\nThe main goals of this thesis were the detailed mapping of Quaternary glacial and other deposits in these regions, dating of critical events, and geomorphic analysis of the range front. The focus was on Pleistocene moraines near the range front. The motivation of this research was to improve our understanding of the chronology of Pleistocene events, to characterize details of the tectonic history of the Sierra, to infer faulting, erosion, and deposition rates, and to provide a basis for the comparison of the Quaternary geology in the southeastern Sierra and in more intensively studied regions in the central and northern Sierra and elsewhere.
\r\n\r\nThe study area extended from the alluvial fans of Owens Valley west to the Sierra crest from latitude 36\u00b045' N to 37\u00b000' N. It included the southern part of the Big Pine volcanic field, an eruptive center for basaltic lavas for most of the Pleistocene Epoch. Elevations within the study area ranged from about 1000 m (Owens Valley) to about 4000 m (peaks along the crest).
\r\n\r\nThroughout the study area the principal rocks are granodiorite and quartz monzonite of Cretaceous age. Plutons are rather small, and individual drainages generally include more than one. In the southern part of the study area, Jurassic-Triassic metavolcanic rocks are found as roof pendants. These rocks, originally ranging in composition from basalt to rhyolite, are most common near the Sierra crest. In the northern canyons of the study area, Paleozoic metasedimentary rocks including sandy marbles and biotite schist replace the metavolcanic pendants. The foothill blocks are identical to the Sierras in composition.
\r\n\r\nBelow the foothills coalescing alluvial fans grade a few km east to the alluvium and lacustrine sediments of the Owens River and Owens Lake. These sediments have been shown in geophysical studies to mask a second escarpment as high as the one of the range front, and the total bedrock relief from the Sierra crest to the floor of the graben is as much as 6 km.
\r\n\r\nDuring the Quaternary Period the southeastern Sierra Nevada was characterized by the down-faulting of Owens Valley along two zones, one a series of normal faults along the range front (Independence Fault) and the other a series of faults along the center of the valley (Owens Valley fault zone). This same period has seen the cutting of deep canyons through the 2-km-high escarpment. During repeated glaciations these canyons were widened and deepened. Traces of at least seven glaciations were found during this study. Moraines and other deposits left during these glaciations could be distinguished based on the degree of weathering of granitic clasts, vegetative cover, and morphologic characteristics. Absolute age limits were obtained for two of the Pleistocene glaciations by radiometric dating of basalt flows interfingered with the moraines.
\r\n\r\nThree of the recognized glaciations, probably corresponding to the Matthes, Recess Peak, and Hilgard neoglaciations found by J.H. Birman in the central Sierra Nevada, occurred during the Holocene Epoch. The youngest glaciers (Matthes glaciation) left unconsolidated and unvegetated till in stagnant rock glaciers and moraines in cirques on high peaks. Some rock glaciers are still ice-cored. Extending out from the cirques and into the upper reaches of the canyons are moraines correlating to the Recess Peak glaciation. Till is generally consolidated and supports heavy lichen growth and bushes but few trees. The oldest Holocene glaciation (Hilgard) left few large moraines in the study area. Hilgard glaciers extended much farther down-canyon than the younger Holocene glaciers, sometimes within one or two km of the Tioga terminal moraines. Those Hilgard terminal moraines which were found have been barely breached by streams. Moraines tend to be heavily forested, and lakes are largely unsedimented. The Hilgard glaciation may have simply been the last stade of the Tioga glaciation from the evidence found in this study.
\r\n\r\nAt least four Pleistocene glaciations occurred in the southeastern Sierra Nevada. All four postdate most of the significant incision of streams through the escarpment. The three youngest probably correlate with the Tioga, Tenaya, and Tahoe stages (in order of increasing age) recognized throughout the Sierra. In each case, moraine morphology has been well preserved. Tioga moraines were found down to about 2200 m elevation. Nested sets of moraines were common. The terminal moraines of the youngest of these were sometimes intact. lakes were rare; one (Sawmill Meadow) was completely sedimented. Granitic boulders in the moraines were largely unweathered. Weathering of boulders in Tenaya moraines was similar, but a small fraction of granitic boulders were grusy. Boulders from Tahoe moraines were conspicuously weathered, and the moraines themselves were rounded and gullied.
\r\n\r\nThe oldest group of moraines probably significantly predates the Tahoe glaciation. It is nevertheless post-Sherwin. Moraines in this group were found in five of the eight canyons studied. While obviously eroded, these moraines still retained their original shape. All surficial boulders were heavily weathered, but some exposed in road cuts were fresh. No moraines of Sherwin age were identified, although Sherwin till is widespread only a few km to the north. However, on plateaus and ridges 200 to 300 m above the modern canyons near the Sierra crest were found ancient diamictons, some of which could be till. Remnants of U-shaped valleys preserved as high passes across the crest or as cols between canyons east of the crest may be testimonials to ancient glaciers of Sherwin age or older.
\r\n\r\nRadiometric dating (40Ar - 39Ar) of basalts interfingered with moraines in Sawmill Canyon provided a new upper limit of 0.12 my for a moraine of the Tahoe glaciation, and a range of 0.13 - 0.46 my for one pre-Tahoe glaciation. These results confirm that the Tahoe glaciation occurred during the Wisconsin stage of the continental ice age, and conclusively demonstrate the existence of pre-Wisconsin glaciers in the southern Sierra. Relative dating based on acoustic wave speeds through weathered boulders on the moraines indicates the age of the pre-Wisconsin moraine may be close to the upper limit.
\r\n\r\nAlluvial fans appear to have aggraded early in the Wisconsin glaciation (Tahoe glaciation). Subsequently, the fan heads have been incised and the locus of deposition has moved eastward down the fans. The Tenaya and Tioga glaciers during the late Wisconsin stage left outwash plains and terraces along streams cut into the older fans, but aggradation during these events was considerably less than earlier.
\r\n\r\nThree ages of fans were found. The oldest fanglomerate probably is pre-Wisconsin and is exposed in regions protected from later deposition. The heavily weathered fan deposits of this group overlie basalts which appear to be contemporaneous with dated 1.1 - 1.2 my-old basalts nearby. In the middle elevations of the fans, roughly 10 m of fanglomerate was deposited over the old fanglomerate, probably during the Tahoe glaciation. Deposition rates probably are about 0.1 mm/y for the late Pleistocene Epoch. The extent and distribution of the youngest fans (Tenaya-Tioga) are variable, but they are generally found downstream from the incised Tahoe fan heads.
\r\n\r\nFaulting along the range front appears to have been dip-slip only. The offset rate along the range-front faults was determined at several canyons where the fault crossed dated moraines or lava flows. At least during the Wisconsin glaciation faulting on this zone appears to have been erratic, with rates ranging from zero to 0.5 mm/y or more. Offset moraines and terraces at Independence Creek indicated a faulting rate of 0.1 mm/y. Only a few km to the north, Tahoe moraines of both forks of Oak Creek were not offset at all, although scarps could be seen on adjacent hillsides. At Sawmill Creek an offset lava flow gave a lower limit of 0.5 mm/y. It seems that during the late Pleistocene Epoch, offset on the range front faults has been less than on the mid-valley faults east of the study area. Geodetic studies have suggested modern strain rates of 2.2 mm/y for the Owens Valley fault zone.
\r\n\r\nBasalts found in canyons through the escarpment and on terraces and ridges in the foothills to the east document stream erosion during the Pleistocene Epoch. Ridgetop basalts, dated at 1.2 my, stand at least 125 m above the modern streams through the foothills. This indicates an erosion rate of ~ 0.1 mm/y. A comparable rate of ~ 0.15 mm/y for the last 0.46 my was found for Sawmill Creek within the Sierra Nevada. Thus at least during the late Pleistocene Epoch erosion rates in the Sierra and in the foothills have been similar.
\r\n\r\nPatches of boulders and gravels atop the basalt show that some time after 1.2 my BP the foothill block was submerged by alluvial fans. Incision may have begun in response to the inception or renewal of subsidence of the graben along the Owens Valley fault zone.
\r\n\r\nExtensive volcanism in the Big Pine Volcanic field appears to have begun at least 1.2 my ago, and has continued sporadically up to perhaps 0.05 my ago. Minor eruptions may have occurred more recently.
\r\n\r\nThe eastern escarpment of the Sierra Nevada consists of two zones of truncated ridges. Within the study area, the upper zone is about 950 m high; the lower is about 750 m high. Triangular facets of the upper zone have a gradient of only ~ 24\u00b0, lower than slopes of ~ 29\u00b0 in the lower zone. This could be explained if subsidence of Owens Valley along the range-front faults occurred in two great pulses.
\r\n\r\nBoth absolute and relative dating methods were refined for this study. Absolute dating of the K-poor basaltic lavas was done indirectly, by 40Ar - 39Ar analysis of K-rich granitic xenoliths found in the lava. These ancient xenoliths were partially degassed of their accumulated 40Ar during heating in the magma, and it proved possible to date this heating event.
\r\n\r\nIn addition to conventional relative dating methods, a new quantitative approach based on the speed of acoustic waves through individual clasts in a deposit was investigated. This method had been used only once before, on terrace deposits. The technique proved to be very useful, and was capable of discriminating moraines successfully in well-studied canyons in the central Sierra. Acoustic wave speeds may be controlled by the abundance of intergranular cracks in granitic boulders. If this is the case, then this technique relies on different processes than those exploited by conventional methods of relative dating. The successful application to moraines in this study enhances our ability to analyse glacial sequences and complements conventional semi-quantitative methods of relative dating.
" }, { "name": "Ng, Chihang Amy", "degree": "PhD", "year": "1982", "title": "I. Ancient Arctic Ice Does Not Contain Large Excesses of Natural Lead. II. Chronological Variations in Lead and Barium Concentrations and Lead Isotopic Compositions in Sediments of Four Southern California Off-Shore Basins", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechETD:etd-08232006-143453", "creators": [ { "name": { "family": "Ng", "given": "Chihang Amy" }, "id": "Ng-Chihang-Amy", "display_name": "Ng, Chihang Amy" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "chair", "display_name": "Burnett, Donald S." }, { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "member", "display_name": "Patterson, Clair C." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Yung", "given": "Yuk L." }, "id": "Yung-Y-L", "orcid": "0000-0002-4263-2562", "role": "member", "display_name": "Yung, Yuk L." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" } ], "option_major": [ "geochem" ], "doi": "10.7907/mn3s-dd97", "abstract": "Part I This study settled the dispute and proved beyond doubt that excess lead today is 300-fold instead of the 5-fold, as proposed by other investigators, greater than prehistoric time. And, virtually all of the present-day excess of lead above natural levels was shown to be caused by industrial lead emissions to the atmosphere.
\r\n\r\nConcentrations of lead and potassium were determined in a series of ice samples taken in sequence from the outside to the interior of several >2000 year old ice cores drilled from the Greenland and Antarctic ice sheets. Concentrations of lead and potassium were observed to decrease continuously in going from the exterior to the interior of the cores, which indicated that surface contamination had penetrated to the interior of the core, making it impossible to determine the original concentration of lead in the ice. Concentrations measured at the centers of these cores must therefore represent upper limits of lead concentration originally present in the ice. There are l.6 ng Pb/kg ice in 5000 year old Greenland ice and l.4 ng Pb/kg in 2000 year old Antarctic ice.
\r\n\r\nThese data verified the earlier findings reported by Murozumi et al. (1969) of <1 ng Pb/kg ice in 800 B.C. Greenland ice near Camp Tuto and also at New Byrd Station. Our findings also support their observation of a continual progressive increase of lead concentration with time even before 1900 A.D. These new data refuted the high concentration values of 45 ng Pb/kg ice and 70 ng Pb/kg ice reported by Herron et al. (1977) and Cragin et al. (1975) in pre-1900 Greenland ice and their claims of no concentration change with time before 1900. These new data also refute the lead concentration values of 26 ng Pb/kg ice reported by Boutron and Lorius (1979) in snow strata of Dome C, Antarctica for the period 1914 to 1974 and their claims that this high lead concentration is natural and has been present since ancient times.
\r\n\r\nPotassium concentrations at the center of the ice core are 2 x 103 ng K/kg ice in 5000 year old Greenland ice and 9 x 102 ng K/kg ice in the 2000 year old Antarctic ice. The decrease in potassium concentrations within the central third of the core was, unlike that for lead, relatively small, indicating the potassium contamination effects were not large within the central portions of the cores.
\r\n\r\nPart II This study documented the chronological changes of lead and barium fluxes from the Los Angeles Urban Complex to adjacent San Nicolas, Santa Barbara, Santa Monica, and San Pedro coastal basins; and identified industry as the sources of the excess lead and barium.
\r\n\r\nThe natural deposition fluxes of acid leachable lead in Santa Barbara, Santa Monica, and San Pedro basins were about 0.7, 0.1 and 0.2 \u00b5g Pb/cm2 respectively. A model, using clay as a major transport vehicle for soluble lead, was proposed to explain the large lead flux within the Santa Barbara basin compared to the other basins. Sedimentation fluxes of industrial and natural leachable lead within these three basins today are 3- to l0-fold greater, being about 2.1, 1.1 and 1.8 \u00b5g Pb/cm2 yr respectively. Directly deposited large sewage particles account for 0%, 66%, and 75% of the industrial lead deposition fluxes respectively. Isotopic compositions of the excess leachable lead change in accordance with corresponding known changes of isotopic compositions of industrial lead in the Los Angeles atmosphere. Lead remaining in the acid leached sediment residues originates from igneous and clay minerals, exhibing no changes in concentration or isotopic composition since pre-industrial times.
\r\n\r\nDeposition fluxes of total barium among the three basins were proportional to mass deposition fluxes before 1950. Afterwards, there are barium concentration maxima with time in both Santa Monica and San Pedro basin sediments that are attributable to industrial sewage rather than to erosion from barium-rich sedimentary evaporite strata exposed locally along the shore. A slight increase of barium concentration in present-day Santa Barbara basin sediments may reflect dispersal of barium rich drilling mud from local drilling operations.
" }, { "name": "Passey, Quinn R.", "degree": "PhD", "year": "1982", "title": "Viscosity Structure of the Lithospheres of Ganymede, Callisto, and Enceladus, and of the Earth's Upper Mantle", "advisor": "Stevenson, David John", "url": "https://resolver.caltech.edu/CaltechTHESIS:02152013-145142740", "creators": [ { "name": { "family": "Passey", "given": "Quinn R." }, "id": "Passey-Quinn-R", "display_name": "Passey, Quinn R." } ], "advisors": [ { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "advisor", "display_name": "Stevenson, David John" } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "member", "display_name": "Shoemaker, Eugene Merle" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" } ], "option_major": [ "plansci" ], "doi": "10.7907/A31H-FJ81", "abstract": "Craterform and related features on Ganymede and Callisto include bowl-shaped craters, craters with nearly fiat floors, craters with central peaks, craters with central pits, basins, crater palimpsests and penepalimpsests, and giant multiring systems of ridges and furrows. The large majority of all craters larger than 20 km diameter have a central pit. The pits are interpreted as formed by prompt collapse of transient central peaks. Most craters, in all size ranges, are highly flattened as a consequence of topographic relaxation by slow viscous or plastic flow.
\r\n\r\nAnalysis of the global distribution of craters and multiring structures on Callisto reveal that the large multiring structures are concentrated in the leading hemisphere, whereas craters are depleted here. Calculations of model crater retention ages based on a sample of 2000 craters \u2265 30 km in diameter show that the mean age of Callisto's surface is between 4.0 and 4.2 Gy. Variations in the surface ages, derived from different diameter craters, suggests that larger craters are not retained from as early a period in time as were the smaller craters; this is in agreement with the results predicted by viscous relaxation theory where large wavelength features relax at a faster rate than do small wavelength features. Most of the variations in the observed distribution of craters can be explained satisfactorily by the effects due to the formation of multiring structures, and on the viscous relaxation of craters beneath an insulating regolith.
\r\n\r\nAbout 1000 topographic profiles of craters on Ganymede and Callisto were obtained by photoclinometry. Fresh craters on Ganymede and Callisto have depth-to-diameter ratios and rim height-to-diameter ratios similar to those of fresh lunar craters, but most craters are much shallower. Small craters have not flattened or relaxed as much as have large craters; comparison of the crater profiles with the results from theoretical of crater relaxation studies in a viscous medium, allows determination of the viscosity at the surfaces of Ganymede and Callisto, and, also, determination of the viscosity gradient with depth. The derived mean surface viscosity for the lithospheres of Ganymede and Callisto is 1.0 \u00b1 0.5 x 1026 poise. For Ganymede, the estimated thermal gradient at ~3.9 Gya was \u2265 8 K/km; the thermal gradient can be modelled as decreasing approximately exponentially with time, with an e-folding time of about 108 years; the estimated present thermal gradient is \u2264 2.0 K/km. For Callisto, the thermal gradient was \u2265 3 K/km at ~4.1 GYA and the decrease in the thermal gradient can be modelled as an exponential dropoff with an e-folding time between about 5 x 107 and 2 x 108 years; the estimated present thermal gradient on Callisto \u2264 1.5 K/km.
\r\n\r\nHigh resolution Voyager II images of Enceladus reveal that some regions on its surface are highly cratered; the most heavily cratered surfaces probably date back into a period of heavy bombardment. The forms of many of the craters, on Enceladus, are similar to those of fresh lunar craters, but many of the craters are much shallower in depth, and the floors of some craters are bowed up. Analysis of the forms of the flattened craters on Enceladus suggests that the viscosity at the top of the lithosphere, in the most heavily cratered regions, is between 1024 and 1025 poise. The exact time scale for the collapse of the craters is not known, but probably was between 100 My and 4 Gy. The flattened craters are located in regions in which the heat flow was (or is) higher than in the adjacent terrains. Because the temperature at the top of the lithosphere of Enceladus would be less than, or equal to that of Ganymede and Callisto, if it is covered by a thick regolith, and because the required viscosity, on Enceladus, is one to two orders of magnitude less than for Ganymede and Callisto, it can be concluded that the lithospheric material, on Enceladus, is different from that of Ganymede and Callisto. Enceladus possibly has a mixture of ammonia ice and water ice in the lithosphere, whereas the lithospheres of Ganymede and Callisto are composed primarily of water ice.
\r\n\r\nNew field measurements of elevation of Provo-level and Bonneville-level shoreline terraces, of Lake Bonneville, provide data for reanalysis of isostatic rebound in the Lake Bonneviile basin. Analysis of the differential rebound between the Provo shoreline (maximum rebound of 43 m) and the Bonneville shoreline (maximum rebound of 69 m) requires that the latter be an equilibrium shoreline. From the new data, the best estimate of the upper limit of effective viscosity of the uppermost mantle, assuming a half-space model and a 2000 year time interval between the Bonneville and Provo shorelines, is 2 x 1019 N sec m-2 (2 x 1020 poise). In addition, comparison of shoreline rebound profiles, for both shorelines, with theoretical plate flexure models indicates that the mean flexural rigidity of the Basin and Range lithosphere in this region is 1 x 1023 N m, or slightly less.
\r\n\r\n\r\n\r\n" }, { "name": "Ruff, Larry John", "degree": "PhD", "year": "1982", "title": "I. Great Earthquakes and Seismic Coupling at Subduction Zones. II. The Structure of the Lowermost Mantle Determined by Short Period P-Wave Amplitudes", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-105439", "creators": [ { "name": { "family": "Ruff", "given": "Larry John" }, "id": "Ruff-Larry-John", "display_name": "Ruff, Larry John" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Hager", "given": "Bradford H." }, "id": "Hager-B-H", "role": "member", "display_name": "Hager, Bradford H." }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Clayton", "given": "Robert W." }, "id": "Clayton-R-W", "orcid": "0000-0003-3323-3508", "role": "member", "display_name": "Clayton, Robert W." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." } ], "option_major": [ "geophys" ], "doi": "10.7907/YW3Y-AZ37", "abstract": "Part I
\r\n\r\nSeismic coupling has been used as a qualitative measure of the \"interaction\" between the two plates at subduction zones. Kanamori (1971) introduced seismic coupling after noting that the characteristic size of earthquakes varies systematically for the northern Pacific subduction zones. Great earthquakes (MW > 8.5) occur in only a few subduction zones: notably the northern Pacific and South American subduction zones. A quantitative global comparison of many subduction zones reveals a strong correlation of earthquake size with two other subduction zone variables: age of the subducting lithosphere and convergence rate. The largest earthquakes occur in zones with young lithosphere and fast convergence rates, while zones with old lithosphere and slow rates are relatively aseismic for large earthquakes. Two other correlations are of interest; maximum depth of the continuous Benioff zone is correlated to lithosphere age, and horizontal length of the Benioff zone is correlated to convergence rate. The simplest explanation of these correlations is \"preferred trajectory\": the subducting slab descends into the mantle with the vertical and horizontal rates determined by the plate age and convergence rate respectively. The mechanism of preferred trajectory is also consistent with the obversation that back-arc spreading occurs behind subduction zones that are subducting old lithosphere at a slow rate.
\r\n\r\nThe rupture process of a great earthquake indicates the distribution of weak and strong regions on the fault zone between the subducting and over-lying plates. The rupture process of three great earthquakes (1963 Kurile Islands, MW = 8.5; 1965 Rat Islands, MW = 8.7; 1964 Alaska, MW = 9.2) are studied by using WWSSN stations in the core shadow zone. The main result is that maximum earthquake size is determined by the asperity distribution on the fault plane (asperities are the strong regions that resist the motion between the two plates). The subduction zones with the largest earthquakes have very large asperities (the Alaskan earthquake is characterized by a giant asperity of length scale 150-200 km), while the zones with smaller earthquakes have small scattered asperities. This observation can be translated into a simple model of seismic coupling, where the horizontal compressive stress between the two plates is proportional to the ratio of the summed asperity area to the total area of the contact surface.
\r\n\r\nIf asperity size determines earthquake size, and earthquake size is correlated to plate age and rate; then plate age and rate must be related to the asperity distribution. Plate age and rate can control asperity distribution directly by use of the horizontal compressive stress associated with the preferred trajectory. Indirect influences are many, including: oceanic plate topography and the amount of subducted sediments.
\r\n\r\nAll subduction zones are apparently uncoupled below a depth of about 40 km, and the basalt to eclogite phase change in the down-going oceanic crust may be largely responsible. This phase change shouldstart at a depth of 30-35 km, and could at least partially uncouple the plates by superplastic deformation throughout the oceanic crust during the phase change.
\r\n\r\nPart II
\r\n\r\nThe seismic velocities in the D\" region (lowermost 200 km of the mantle) are recognized to be anomalously low, though the details of the velocity structure are not known. The details of D\" are important, in particular whether a smooth velocity model is appropriate or not. A smooth decrease in the seismic velocities would be consistent with a thermal boundary layer at the base of the mantle. We have used the amplitudes of short period (T = 1 sec) P waves to investigate the internal structure of D\". A short period amplitude data set is obtained by using underground nuclear events as sources and applying receiver corrections to the amplitudes. Receiver effects are largely responsible for the factor of ~ 8 scatter in the amplitudes of the North American WWSSN stations. Applying receiver corrections reduces the scatter to a factor of ~ 2, thereby providing a quantitatively useful amplitude profile into the core shadow. Using Soviet events and North American WWSSN statios, the D\" layer beneath the north polar regio is well sampled. The core shadow (at T = 1 sec) begins sharply at a distance of \u0394 = 95.5 and the slope of the amplitude decay is well defined. Also, the amplitudes decrease slightly from \u0394 ~ 87 to \u0394 ~ 90, then increase to \u0394 = 95.5. Synthetic seismograms are used to test various earth models, with the important conclusion that the amplitudes from smooth D\" models with a nearly constant velocity in D\" decay too slowly in the shadow. This mismatch cannot be satisfactorily explained by random forward scattering or a thin low-Q layer within D\". Anelastic calculations show that a thin low-Q layer in D\" decreases the amplitudes gradually before the shadow, with little effect on the decay slope in the shadow. All of the features of the observed amplitude profile can be explained as the interference effects of a model that has a low velocity zone in the upper part of D\" followed by a normal velocity gradient in the lower part of D\". This type of model (POLAR series) also explains the scatter often observed in dT/d\u0394 beyond \u0394 ~ 90. The interference effects and required velocity changes in D\" are small, and long period amplitudes will respond only to the averaged velocity gradient in D\". The POLAR models imply a compositional and/or phase change at the top of D\". Thus, the preferred seismological model does not allow the D\" region to be interpreted as a single thermal boundary layer between the mantle and core.
\r\n" }, { "name": "Stewart, Gordon Selbie", "degree": "PhD", "year": "1982", "title": "Complexity of Rupture Propagation in Large Earthquakes in Relation to Tectonic Environment", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02042015-163349497", "creators": [ { "name": { "family": "Stewart", "given": "Gordon Selbie" }, "id": "Stewart-Gordon-Selbie", "display_name": "Stewart, Gordon Selbie" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "chair", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." } ], "option_major": [ "geophys" ], "doi": "10.7907/9d84-pr40", "abstract": "Complexity in the earthquake rupture process can result from many factors. This study investigates the origin of such complexity by examining several recent, large earthquakes in detail. In each case the local tectonic environment plays an important role in understanding the source of the complexity.
\r\n\r\nSeveral large shallow earthquakes (Ms > 7.0) along the Middle American Trench have similarities and differences between them that may lead to a better understanding of fracture and subduction processes. They are predominantly thrust events consistent with the known subduction of the Cocos plate beneath N. America. Two events occurring along this subduction zone close to triple junctions show considerable complexity. This may be attributable to a more heterogeneous stress environment in these regions and as such has implications for other subduction zone boundaries.
\r\n\r\nAn event which looks complex but is actually rather simple is the 1978 Bermuda earthquake (Ms ~ 6). It is located predominantly in the mantle. Its mechanism is one of pure thrust faulting with a strike N 20\u00b0W and dip 42\u00b0NE. Its apparent complexity is caused by local crustal structure. This is an important event in terms of understanding and estimating seismic hazard on the eastern seaboard of N. America.
\r\n\r\nA study of several large strike-slip continental earthquakes identifies characteristics which are common to them and may be useful in determining what to expect from the next great earthquake on the San Andreas fault. The events are the 1976 Guatemala earthquake on the Motagua fault and two events on the Anatolian fault in Turkey (the 1967, Mudurnu Valley and 1976, E. Turkey events). An attempt to model the complex P-waveforms of these events results in good synthetic fits for the Guatemala and Mudurnu Valley events. However, the E. Turkey event proves to be too complex as it may have associated thrust or normal faulting. Several individual sources occurring at intervals of between 5 and 20 seconds characterize the Guatemala and Mudurnu Valley events. The maximum size of an individual source appears to be bounded at about 5 x 1026 dyne-cm. A detailed source study including directivity is performed on the Guatemala event. The source time history of the Mudurnu Valley event illustrates its significance in modeling strong ground motion in the near field. The complex source time series of the 1967 event produces amplitudes greater by a factor of 2.5 than a uniform model scaled to the same size for a station 20 km from the fault.
\r\n\r\nThree large and important earthquakes demonstrate an important type of complexity --- multiple-fault complexity. The first, the 1976 Philippine earthquake, an oblique thrust event, represents the first seismological evidence for a northeast dipping subduction zone beneath the island of Mindanao. A large event, following the mainshock by 12 hours, occurred outside the aftershock area and apparently resulted from motion on a subsidiary fault since the event had a strike-slip mechanism.
\r\n\r\nAn aftershock of the great 1960 Chilean earthquake on June 6, 1960, proved to be an interesting discovery. It appears to be a large strike-slip event at the main rupture's southern boundary. It most likely occurred on the landward extension of the Chile Rise transform fault, in the subducting plate. The results for this event suggest that a small event triggered a series of slow events; the duration of the whole sequence being longer than 1 hour. This is indeed a \"slow earthquake\".
\r\n\r\nPerhaps one of the most complex of events is the recent Tangshan, China event. It began as a large strike-slip event. Within several seconds of the mainshock it may have triggered thrust faulting to the south of the epicenter. There is no doubt, however, that it triggered a large oblique normal event to the northeast, 15 hours after the mainshock. This event certainly contributed to the great loss of life-sustained as a result of the Tangshan earthquake sequence.
\r\n\r\nWhat has been learned from these studies has been applied to predict what one might expect from the next great earthquake on the San Andreas. The expectation from this study is that such an event would be a large complex event, not unlike, but perhaps larger than, the Guatemala or Mudurnu Valley events. That is to say, it will most likely consist of a series of individual events in sequence. It is also quite possible that the event could trigger associated faulting on neighboring fault systems such as those occurring in the Transverse Ranges. This has important bearing on the earthquake hazard estimation for the region.
" }, { "name": "Vizgirda, Joana Marija", "degree": "PhD", "year": "1982", "title": "Dynamic Properties of Carbonates and Applications to Cratering Processes", "advisor": "Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04252018-105910410", "creators": [ { "name": { "family": "Vizgirda", "given": "Joana Marija" }, "id": "Vizgirda-Joana-Marija", "display_name": "Vizgirda, Joana Marija" } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "chair", "display_name": "Burnett, Donald S." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stevenson", "given": "David John" }, "id": "Stevenson-D-J", "orcid": "0000-0001-9432-7159", "role": "member", "display_name": "Stevenson, David John" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." } ], "option_major": [ "geol" ], "doi": "10.7907/dat3-9s72", "abstract": "The response of carbonate minerals and rocks under shock compression is investigated using equation of state, shock metamorphism, and crater morphology studies. Coralline limestone samples from Cactus Crater, a nuclear explosion crater on Runit Island in Eniwetok Atoll, are used in the investigations of shock deformation as well as the crater structural study. Carbonate minerals and rocks shocked in the laboratory to known dynamic stress levels are used to calibrate shock pressures in the Cactus samples.
\r\n\r\nVery low shock pressure deformation effects are detected in the explosively and laboratory shocked samples by two bulk sample techniques: electron spin resonance (ESR) and powder X-ray diffraction. According to ESR studies on calcite from Cactus Crater samples, peak shock pressures of 4.5\u00b10.5 GPa were experienced by the material beneath the crater. Aragonite peak broadening analyses of powder X-ray diffraction spectra allows differentiation between two modes of material deformation, mosaicism (or reduction of crystallite size) and strain; both of these effects are detected in Cactus and in laboratory shocked samples. According to the X-ray analysis, peak pressures of 3\u00b11.5 GPa were experienced by the Cactus samples. A phase transition model, based on the variation of mosaicism and strain effects with shock pressure, is proposed. According to this model, residual strain in aragonite increases (crystallite size remaining approximately the same) until a threshold pressure of 8 to 10 GPa, corresponding to a phase transition, is reached; release from shock states above this pressure results in a discontinuous decrease in crystallite size and strain.
\r\n\r\nThe diagenetic high to low magnesium calcite transition boundary occurring in the immediate subsurface of Runit Island is used as a stratigraphic tracer to determine structural features beneath Cactus Crater, including the amount of permanent downward displacement, the presence of a 10 m thick breccia lens which is disturbed and extensively mixed in-situ, and a possible central uplift feature. Applying the Bingham plastic model to Cactus Crater gives a yield strength of approximately 1 bar for the shock-wave engulfed limestone rock; this value is similar to the yield strength of many clays, and suggests a partially liquefied state for the water-saturated limestone immediately after passage of the shock wave.
\r\n\r\nThe first aragonite Hugoniot equation of state data are presented. A Hugoniot elastic limit at 2.5\u00b10.8 GPa and a phase transition at 6.5\u00b11.5 GPa are observed. Above 10 GPa, the aragonite and calcite Hugoniots are approximately coincident, suggesting the transformation of both CaCO3 polymorphs to the same high pressure phase. Release adiabats centered at shock pressures above 18 GPa yield pressure-density isentropes which suggest possible dissociation, i.e. CO2 release, during the decompression process. These experimental data disagree with theoretical calculations, which predict incipient vaporization upon release from shock pressures of 55 and 33 GPa on the aragonite and calcite Hugoniots, respectively. Results from release adiabat experiments on calcite agree with the aragonite data and suggest vaporization upon unloading from shock pressures of approximately 37 GPa; a mass balance calculation using the experimental calcite release paths indicates that 45% of the CaCO3 has dissociated upon release to 0.2 GPa pressures.
\r\n\r\n" }, { "name": "Cipar, John Joseph", "degree": "PhD", "year": "1981", "title": "Seismic Source Processes and Tectonics: Observations of Four Intracontinental Earthquakes", "advisor": "Ahrens, Thomas J.; Helmberger, Donald V.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechETD:etd-09152006-102853", "creators": [ { "name": { "family": "Cipar", "given": "John Joseph" }, "id": "Cipar-John-Joseph", "display_name": "Cipar, John Joseph" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "chair", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "member", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." } ], "option_major": [ "geophys" ], "doi": "10.7907/bwpb-4c04", "abstract": "This thesis presents studies of the source processes of four shallow earthquakes and their relation to regional tectonics. In the first chapter, long-period teleseismic P and S waves from the Haicheng, China earthquake of February 4, 1975 are compared directly to time domain synthetic seismograms to infer source parameters. The P-wave focal mechanism indicates that faulting was dominantly left-lateral strike-slip along a northwest striking nodal plane (strike = 288\u00b0, dip = 78\u00b0N, rake = 342\u00b0). The strike of this nodal plane agrees with the trend of the aftershock distribution. Azimuthal variation of P-wave duration is attributed to fault rupture 22 km in a northwesterly direction, along strike of the aftershock zone. There is considerable discrepancy between the observed SH waves and synthetics computed using this model. These discrepancies are due to either structural complexities in the source region or change in fault mechanism as the rupture propagated along strike. Seismic moment, average dislocation and stress drop are computed to be 2.7 x 1026 dyne-cm, 2.5 meters and 48 bars, respectively.
\r\n\r\nThe remaining three chapters present a detailed examination of seismograms recorded by the 1976 Friuli, Italy earthquake (May 6, 1976, MS = 6.5) and two major aftershocks (both on September 15, 1976 at 03h 15m, MS = 6.0 and 09h 21m, MS = 5.9). Teleseismic long-period body waves and surface waves radiated by the mainshock and 09h 21m aftershock are studied in Chapter Two to determine source characteristics. Focal mechanisms along with geological evidence suggest that both events represent underthrusting of the Friuli Plain beneath the Southern Alps. The depths of both earthquakes, estimated by matching synthetic body wave seismograms to observations, are found to lie between 6 and 10 km. Synthetic seismogram calculations which include source directivity effects suggest that the fault length of the mainshock is approximately 16 to 24 km assuming a rupture velocity of 3.0 km/sec. Observations of 100 sec Rayleigh waves confirm the body wave focal mechanism, but suggest that the seismic moment of the mainshock is 5 x 1025 dyne-cm compared to 2.9 x 1025 dyne-cm estimated from body waves. The P-wave moment of the aftershock is 1 x 1025 dyne-cm.
\r\n\r\nIn Chapter Three, short-period records are modeled to obtain additional details of the source time history. Two point sources of radiation are required to adequately model the aftershock short-period records. For the 09h 21m aftershock, the model derived from short-period records also produces good fits to the long-period data. The SP model for the 03h 15m aftershock, on the other hand, predicts long-period synthetics which do not agree with the observations. In particular, the SP moment (0.37 x 1025 dyne-cm) is about 2-1/2 times smaller than the LP moment (1 x 1025 dyne-cm). Adding a long-period component to the SP model considerably improves LP waveform and moment agreement. In the case of the mainshock, a reasonable fit to the observed SP data is obtained using three point sources of radiation. However, LP synthetics computed using this model do not agree with the observations, and the SP moment (0.65 x 1025 dyne-cm) is a small fraction of the LP moment (3-5 x 1025 dyne-cm). Time function durations indicate that the individual events inferred from the SP records are radiated from patches of the fault having radii of 2 to 4 km and stress drops in the range 35 to 276 bars. In comparison, overall stress drops estimated from LP data are found to be 12 bars (mainshock) and 24 bars (09h 21m aftershock). Strong-motion accelerograms are used to put additional constraint on the source geometry of the 09h 21m aftershock.
\r\n\r\nThe 03h 15m and 09h 21m aftershocks are the culminating events of a series of large aftershocks which began on September 11, 1976. Cumulative seismic moment of the Friuli aftershock sequence was as large as the moment released by the mainshock. By comparison, aftershock moments of California earthquakes are typically 1 to 10 percent of the mainshock moment. The large size, location and focal mechanism of the aftershocks suggest that they represent failure of major stress concentrations remaining after the mainshock.
" }, { "name": "Criss, Robert Everett", "degree": "PhD", "year": "1981", "title": "An \u00b9\u2078O/\u00b9\u2076O, D/H and K-Ar Study of the Southern Half of the Idaho Batholith", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05302023-213210418", "creators": [ { "name": { "family": "Criss", "given": "Robert Everett" }, "id": "Criss-Robert-Everett", "orcid": "0000-0002-6484-1875", "display_name": "Criss, Robert Everett" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "chair", "display_name": "Silver, Leon T." }, { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "member", "display_name": "Lowenstam, Heinz A." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geochem" ], "doi": "10.7907/dc2n-5n03", "abstract": "\u03b4\u00b9\u2078O and \u03b4D measurements provide powerful tools for the study of igneous rock petrogenesis. Among the noteworthy contributions of such studies have been the demonstration that massive quantities of hydrothermal fluids have interacted with considerable portions of the earth's upper crust, that the majority of such fluids are derived from ordinary meteoric surface waters, and that similar fluids appear to be involved in the formation of many ore deposits. This thesis presents the results of a combined \u03b4\u00b9\u2078O, \u03b4D, K-Ar and petrographic study, whose principal goal was to elucidate the characteristics and thermal history of a series of hydrothermal systems developed within the Idaho batholith during the Eocene, about 40-45 m.y. ago.
\r\n\r\nThe hydrothermal activity of concern is related to a period of intense magmatism and tectonism in Idaho termed the Eocene event. This period was characterized by intrusion of epizonal granite batholiths, formation of the cogenetic Challis volcanic field, block faulting, ring faulting, and ore deposition. The effects are very widespread but are most conspicuous in the east-central portion of the southern half (Atlanta lobe) of the Idaho batholith, the region which was studied in most detail.
\r\n\r\nThe effects of the widespread hydrothermal activity are easily monitored against the relatively uniform primary character of the Mesozoic granitoids, which originally had whole-rock \u03b4\u00b9\u2078O values of 9.5\u00b11.5 and biotite \u03b4D values of -70\u00b15 permil. The Eocene meteoric waters in this region had \u03b4\u00b9\u2078O and \u03b4D values of about -16 and -120 permil respect\u00adively, and interaction and exchange of the rocks with deep circulating fluids derived from these waters produced major heavy isotope depletions in the rocks, such that the whole-rock \u03b4\u00b9\u2078O and biotite \u03b4D values became as low as -4.5 and -176 permil. However, the rates of isotopic exchange of various minerals with the fluid are not identical, and the new results prove that feldspar exchanged \u00b9\u2078O with the fluid at least four times as fast as did coexisting quartz, and that biotite exchanged D with the fluid at a much faster rate than did coexisting muscovite. These differential effects are important because they allow the primary isotopic compositions to be deduced from altered rocks, and have the still unproven potential of indicating something of the temperature-time history of the hydrothermal interactions.
\r\n\r\nWidespread propylitization of the rocks occurred concurrently with the \u03b4\u00b9\u2078O and \u03b4D exchange effects. The most commonly observed petro\u00ad graphic changes are the development of chlorite and sericite, whose quantities generally increase in crude proportion to the amount of \u00b9\u2078O exchange. Such hydration effects are generally not conspicuous in previously studied hydrothermal areas associated with gabbroic plutons, which indicates that the hydrothermal interactions in Idaho occurred at relatively low temperatures (generally <350\u00b0C, see below).
\r\n\r\nSystematic mapping of the \u03b4\u00b9\u2078O and \u03b4D depletions of the rocks has provided some startling new insight on the ancient hydrothermal systems in Idaho. The largest well-studied low-\u00b9\u2078O anomaly, termed the Sawtooth Ring Zone (SRZ), is a 5 to 15 km wide annulus of low \u00b9\u2078O rock (average ~2 permil) which has an outer diameter of 40 X 60 km. D/H effects in the rocks are often discernible more than 25 km outside of the periphery of this feature, the larger size being attributable to the extreme sensitivity of the \u03b4D value to alteration under conditions of low water/rock ratios. The low-\u00b9\u2078O ring is centered on the Eocene Sawtooth batholith and its outlying plutons, and a large aeromagnetic anomaly suggests that Eocene rocks in fact underlie the entire SRZ region. These data provide good evidence that the SRZ is coincident with a high-permeability ring fracture zone associated with a giant Eocene caldera.
\r\n\r\nSeveral smaller low-\u00b9\u2078O zones have also been mapped in the Atlanta lobe, and their clearcut spatial association with the Eocene intrusives provides an important mapping and interpretative tool in the region. Furthermore, most of the productive mines in the Atlanta lobe are located near the periphery of these low-\u00b9\u2078O zones (along the \"outer\" +8 permil \u03b4\u00b9\u2078O contour); this association links these deposits with the Tertiary hydrothermal activity and has great potential as an exploration tool.
\r\n\r\nK-Ar age data provide important complementary information about the geology of the region and on the thermal characteristics of the ancient geothermal systems. The apparent ages of Mesozoic biotites systematically decrease from about 95 m.y. along the east and west margins of the Atlanta lobe to <45 m.y. near the Eocene plutons, the latter ages being approximately concordant with those of the Eocene plutons themselves. However, there is a significant \"age gap\" between 45 and 53 m.y. No strong correlations of the apparent ages with the \u03b4\u00b9\u2078O, \u03b4D or K\u2082O contents of the \"biotite\" separates were noted, and the majority of the apparent ages in any given locality are in fact correlated simply with the elevation. These observations suggest that most of the ages were produced by uniform, constant uplift (~0.15 mm/yr) of the batholithic terrane through the Ar \"blocking temperature\" (~300\u00b0C) during the early Tertiary. This uplift continued through the Eocene but was modified by the formation of a regional dome probably related to the intrusion of a gigantic volume (~25,000 km\u00b3) of Eocene magma. However, rocks collected near the contacts with the Eocene plutons, or at the lowest elevations in the overall region, definitely suffered catastrophic Ar loss during the Eocene; the apparent ages of these rocks do not correlate with the elevation and indicate that temperatures were high (>300\u00b0C). A model of the ancient temperature distribution is derived from these data and indicates that 1) most of the hydrothermal activity occurred at temperatures of 150-350\u00b0 C and persisted to depths of at least 7 km below the earth's surface, 2) many of the outcropping Eocene intrusives were intruded at depths of 5 to 7 km, and 3) a significant proportion (>1/3) of the heat provided to the circulating fluids was provided by the ordinary geothermal gradient in the older rocks, although the driving force for the circulation was clearly provided by the thermal energy of the Eocene plutons.
\r\n\r\nAll of the above properties bear on the nature of modern geothermal systems at deep levels which are presently inaccessible to view, and a close analogy of the SRZ may be made with the region at Yellowstone, Wyoming. The evidence presented for the extensive lateral migration of fluids, the depth of circulation and the thermal properties of these fluids are of particular importance, and helps explain the incredibly high fluid and thermal discharge rates currently observed within the Yellowstone caldera. The lack of definite evidence for low-\u00b9\u2078O magmas in Idaho contrasts with the recent discovery of voluminous extrusions of such magmas at Yellowstone, and suggests that such magmas are produced at the top of silicic magma chambers and are inevitably erupted, commonly as H\u2082O-rich ash flow sheets. last, the intense deep-level circulation patterns of the annular SRZ zone contrast with the surface intercaldera discharge systems currently observed at Yellowstone, and may indicate that significant geothermal reserves may be tapped at deep levels by drilling into the ring fracture zones of modern caldera-related systems.
" }, { "name": "Ebel, John Edward", "degree": "PhD", "year": "1981", "title": "Evidence for Fault Asperities from Systematic Time-Domain Modeling of Teleseismic Waveforms", "advisor": "Helmberger, Donald V.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechETD:etd-12052006-144020", "creators": [ { "name": { "family": "Ebel", "given": "John Edward" }, "id": "Ebel-John-Edward", "display_name": "Ebel, John Edward" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/xdeb-v591", "abstract": "A simple method for determining which events prior to a main shock may be \"true\" foreshocks, events which are caused by the same failure process as that which triggers the main shock, is proposed. An event is regarded as a \"true\" foreshock if it takes place within a certain time period of, is at least half a magnitude unit smaller than and occurs within the aftershock zone of a main shock. The time periods of potential foreshock occurrence computed from local and regional seismicity rates for four events were calculated to range from several days to several weeks prior to the corresponding main shocks.\r\n\r\nA detailed analysis of two foreshocks (FS-1, M = 7, and FS-2, M = 6-1/2), the main shock (M, M = 7-1/2) and two aftershocks (A-1, M = 6-3/4, and A-2, M = 7) from the August 11, 1965 New Hebrides Islands earthquake sequence is presented. Focal mechanisms, depths, moments, time function durations and directions of rupture (if they could be inferred) for the events have been found using time domain synthetic seismograms of the far-field body waves and surface waves. The focal mechanisms of all the events except A-2 are consistent with faulting on the interface between the subducting Indian plate and the overriding Pacific plate. A-2 was an event on a steeply-dipping fault which ruptured into the underthrusting plate. The observed radiation patterns for the Rayleigh and Love waves from these events are consistent with the results of the body-wave analysis. The theoretical static vertical surface displacements computed from the teleseismic source model for M are much smaller than the observed coastal uplift indicating that very long-period deformations accompanied the earthquake. The seismicity during the sequence migrated first from northwest to southeast and then toward the southwest and northeast.\r\n\r\nA detailed source study of the short-period P waves from the Borrego Mountain earthquake in Southern California is reported. The short-period waveforms at different stations show good coherence, indicating that the seismograms contain reliable information from the source region. From simultaneous long-period-short-period deconvolutions the sP phase was found to consist of two separate pulses. Synthetic seismograms computed from the long-period source model of Burdick and Mellman (1976) did not match the data very well while synthetics with two high-frequency point sources did. The results of a waveform inversion analysis indicate that both sources were located at a depth of 8 km, had similar focal mechanisms, had time function durations of approximately 2 seconds and occurred about 2.2 seconds apart. Synthetic displacement, velocity and acceleration records, computed from a smoothed version of the teleseismic, short-period source model, fit both the amplitudes and waveforms of the SH wavetrain from the strong-motion data from El Centro, California.\r\n\r\nThe existence of asperities on the fault zones in the two source regions is inferred. In the New Hebrides three asperities are proposed--one at the northern end of the 1965 seismic zone, one between the islands of Santo and Mallikolo, and one near the southern end of the main shock fault plane.\tThe sequence of events reflects a pattern of the loading and breaking of asperities on the fault. For the Borrego Mountain earthquake the short-period sources represent the breaking of two asperities. The stress drops of the two events were several hundred bars each while the average stress drop for the entire event was about 20 bars. For both the New Hebrides events and the Borrego Mountain earthquake, the area of the asperities which ruptured during the main event was no more than 15% of the total fault area." }, { "name": "Gregory, Robert Theodore", "degree": "PhD", "year": "1981", "title": "Geology and Isotope Geochemistry of the Samail Ophiolite Complex, Southeastern Oman Mountains", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11192019-155457609", "creators": [ { "name": { "family": "Gregory", "given": "Robert Theodore" }, "id": "Gregory-Robert-Theodore", "display_name": "Gregory, Robert Theodore" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/sn9q-fq68", "abstract": "The Samail nappe, Oman, is a classic ophiolite complex consisting of a thick section (~12 km) of \"depleted\" peridotite tectonite, overlain by layered gabbro cumulates (~5 km) and high-level noncumulate gabbro (< 1 km), followed by a 100% sheeted dike complex (~1.3 km), and capped by a series of highly altered pillow lavas (~0.5 km). The ophiolite stratigraphy is exposed in the Oman Mountains, an arid region covering over 15,000 km\u00b2, with relief exceeding 2 km. In the first part of this thesis, the results of field mapping along a 20 x 125 km strip from Muscat to the Wahiba Sands are presented forming the foundation for the isotopic work reported in the second part of the thesis.
\r\n\r\nThe upper mantle and oceanic crustal sections preserve a partial record of the events that occurred in the dynamic spreading environment underying the Hawasina Ocean, a portion of the Tethys Seaway. The Samail peridotite section records a history of partial melting, plastic flow, and reaction with transitory melts. Ascending melts reacted with the harzburgite wall-rocks leaving behind dunite (at all depths in conduits with high melt/rock), and olivine orthopyroxenite, websterite, clinopyroxenite, and gabbro (from deeper-to-shallower levels in conduits with low melt/rock). The entire peridotite section was affected by pervasive upper mantle deformation during its ascent, and a basal harzburgite-dunite zone may represent the boundary of the originally vertical conduit that fed both melts and peridotite to the Samail ridge system. The supply of melt was sufficient to produce an \"open system\" magma chamber that achieved a steady state with respect to cumulus phases; orthopyroxene saturation was rarely attained in the gabbro section. Crystal accumulation predominantly occurred from the bottom upward. Because the high-level gabbro intrudes > 90% of the overlying dike complex, both the diabase dikes and pillow lavas are interpreted to have been intruded close to the ridge-axis and to be comagmatic with the cumulate gabbro section. The thin, heterogeneous high-level gabbro preserves a record of many piecemeal stoping events occurring in a chamber roof environment that was mechanically unstable. Plagiogranite commonly occurs near the gabbro-diabase contact; field evidence and \u00b9\u2078O/\u00b9\u2076O relationships demonstrate that the plagiogranites either form by partial melting of stoped blocks of hydrothermally altered roof rock, by extreme differentiation of a hydrous tholeiitic magma strongly modified by exchange and dehydration of such stoped blocks. The data suggest that the magma chamber was open both at the bottom and the top, and thus, MOR basalts are not considered to be primary, unmodified melts of the mantle.
\r\n\r\nThe shallow-level magma chamber (< 3 km below the seafloor) was the heat engine that drove convective seawater circulation through joints and fractures in the overlying section of diabase and basalt and simultaneously in the gabbro underlying the \"wings\" of the funnel-shaped chamber. Both stable (\u00b9\u2078O/\u00b9\u2076O and D/H) and radiogenic (Sm/Nd and Rb/Sr) isotope systems were used to investigate the characteristics of the hydrothermal system. The Sm/Nd system was virtually unaffected by seawater-hyrothermal hydrothermal alteration and crystallization ages were obtained from plagioclase and pyroxene separates on single gabbro samples. Measured \u03b4\u00b9\u2078O values in whole-rocks, 2.5 < \u03b4\u00b9\u2078O < l9.6, from the oceanic crustal section are typically depleted in the lower parts of the section, and enriched in the upper parts, relative to the primary magmatic value of 5.7 \u00b1 0.2. Also, the initial \u2078\u2077Sr/\u2078\u2076Sr ratios vary from 0.7030 to 0.7065 increasing upward. The large variations in \u03b4\u00b9\u2078O and \u2078\u2077Sr/\u2078\u2076Sr are clearly the result of seawater hydrothermal alteration, demonstrating that large amounts of heated seawater (T > 500\u00b0C) penetrate deep into oceanic layer three as far down as the oceanic Moho. Mineral-mineral \u03b4\u00b9\u2078O systematics (e.g. plagioclase-clinopyroxene) have been used to demonstrate isotope disequilibrium caused by this subsolidus hydrothermal exchange, to ascertain the primary \u03b4\u00b9\u2078O values of the gabbro and plagiogranite reservoirs, to estimate relative exchange rates between minerals, to deduce the \u03b4\u00b9\u2078O changes occurring in the hydrothermal fluids at various levels within the crust, and to differentiate between the effects of closed and open system hydrothermal exchange in natural systems.
\r\n\r\nThe \u00b9\u2078O redistribution within the oceanic crust was systematic, with whole-rock \u03b4\u00b9\u2078O increasing from a minimum \u03b4\u00b9\u2078O = 3.7 in the cumulate section about 1-2 km below the gabbro-diabase contact to values as high as 19.6 in the pillow lava section. A mass-balance calculation for the entire oceanic crustal section indicates that, the net change over the whole oceanic crustal section was zero implying that seawater also did not change and thus the seawater-oceanic crustal system was at some steady-state during the late Cretaceous. Modeling of the circulation extrapolated to the world-wide ridge system suggests that the \u03b4\u00b9\u2078O of seawater is controlled by the hydrothermal interactions, and will be buffered to within 1 per mil of its present-day value as long as global spreading rates exceed 1 km\u00b2/yr.
" }, { "name": "Jones, John Hume", "degree": "PhD", "year": "1981", "title": "Studies of the Geochemical Similarity of Plutonium and Samarium and Their Implications for the Abundance of \u00b2\u2074\u2074Pu in the Early Solar System", "advisor": "Patterson, Clair C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10052006-093021", "creators": [ { "name": { "family": "Jones", "given": "John Hume" }, "id": "Jones-John-Hume", "display_name": "Jones, John Hume" } ], "advisors": [ { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "advisor", "display_name": "Patterson, Clair C." } ], "committee": [ { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "chair", "display_name": "Patterson, Clair C." }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Stolper", "given": "Edward M." }, "id": "Stolper-E-M", "orcid": "0000-0001-8008-8804", "role": "member", "display_name": "Stolper, Edward M." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geochem" ], "doi": "10.7907/qwv9-t340", "abstract": "PuD and SmD have been measured for diopsidic pyroxene and whitlockite in the system Di-An-Ab (\u00b1 Ca3(PO4)2). PuD was determined by fission track radiography and SmD was determined on the same samples by beta radiography. The analytical difficulties encountered in using photographic emulsions to determine beta fluences have been studied in detail. These studies have resulted in a technique which should be generally applicable to the radiography of low energy beta emitters (Appendix I).
\r\n\r\nPuD and SmD for clinopyroxene are 0.17 and 0.31, respectively, at about 1250\u00b0C and SmD/PuD = 1.9. The addition of 1.4% P2O5 to the DiAnAb system lowers SmD and PuD by factors of 1.5 and 2.0, respectively; this P2O5 addition raises the SmD/PuD ratio to 2.6. PuD and SmD for whitlockite are 3.8 and 6.4, respectively.
\r\n\r\nThe problem of approach to interfacial equilibrium is discussed in detail, and D values of crystals grown using various thermal histories are compared. Whitlockite D values appear to be independent of thermal history, implying a close approach to equilibrium at the crystal-liquid interface. Differences are seen between pyroxene D values for different thermal histories, and these variations are compared to the results of a simple kinetic disequilibrium model. The result of this comparison suggests that interfacial equilibrium was closely approached and that variations in pyroxene D values are mainly due to the temperature dependence of partitioning. This appears to be true for both Sm and Pu, even though the partitioning of other elements (e.g. Al) may be influenced by kinetic disequilibrium.
\r\n\r\nThe magnitudes of SmD and PuD and (\u2264 0.3) for clinopyroxene imply that Pu and the light REE's are difficult to fractionate during ordinary igneous processes. 244Pu/238U ratio measurements of meteorites are reviewed in light of the results of this study and a 244Pu/238U ratio of 0.005 \u00b1 0.002 for the early solar system is favored. This is supportive of the 244Pu/238U ratio calculated by Marti et al. (1977) and suggests that the Podosek (1970a) value of 0.015 is invalid.
\r\n" }, { "name": "McKinnon, William Beall", "degree": "PhD", "year": "1981", "title": "Large Impact Craters and Basins: Mechanics of Syngenetic and Postgenetic Modification", "advisor": "Melosh, H. Jay", "url": "https://resolver.caltech.edu/CaltechTHESIS:02122013-101424216", "creators": [ { "name": { "family": "McKinnon", "given": "William Beall" }, "id": "McKinnon-William-Beall", "display_name": "McKinnon, William Beall" } ], "advisors": [ { "name": { "family": "Melosh", "given": "H. Jay" }, "id": "Melosh-H-J", "orcid": "0000-0003-1881-1496", "role": "advisor", "display_name": "Melosh, H. Jay" } ], "committee": [ { "name": { "family": "Melosh", "given": "H. Jay" }, "id": "Melosh-H-J", "orcid": "0000-0003-1881-1496", "role": "chair", "display_name": "Melosh, H. Jay" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "member", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "member", "display_name": "Shoemaker, Eugene Merle" } ], "option_major": [ "plansci" ], "doi": "10.7907/1ehb-nm16", "abstract": "The impact crater is the ubiquitous landform of the solar system. Theoretical mechanical analyses are applied to the modification stage of crater formation, both syngenetic (immediate or short term) and postgenetic (long term).
\r\n\r\nThe mechanical stability of an impact crater is analyzed via a quasi-static, axisymmetric slip line theory of plasticity. The yield model incorporated is Mohr-Coulomb and a simplified rectangular profile is used for the transient cavity. The degree of stability (or instability) is described as a function of internal friction angle, depth/diameter ratio, and a dimensionless parameter \u03c1gH/c (\u03c1 = density, g = acceleration of gravity, H = depth, and c = cohesion strength). To match the observed slumping of large lunar craters the cohesion strength of the lunar surface material must be low (<20 bars) and the angle of internal friction must be less than 2\u00b0. It is not implausible that these failure strength characteristics are realized by freshly shocked rock. A theoretical description of impact crater collapse is evolved which accounts for the development of wall scallops, slump terraces, and flat floors. A preliminary set of scale model experiments performed in a centrifuge corroborate the theory. The strength of terrestrial planet surfaces under impact is seen to vary by as much as a factor of two.
\r\n\r\nShortly after the excavation of a large impact crater the transient cavity collapses, driven by gravity. It is shown that at least one concentric fault scarp forms about the crater, if the strength of the target material decreases sufficiently rapidly with increasing depth. This is demonstrated by two classes of models: extrusion flow models which assume a weak layer underlying a strong layer, and plastic flow models which assume a continuous decrease of cohesion strength with depth. Both classes predict that the ratio of the radius of the scarp to the transient crater radius is between 1.2 and 2 for large craters.
\r\n\r\nLarge impact basins on Ganymede and Callisto are characterized by one or more concentric rings or scarps. The number, spacing, and morphology of the rings is a function of the thickness and strength of the lithosphere, and crater diameter. When the lithosphere is thin and weak, the collapse is regulated by flow induced in the asthenosphere. The lithosphere fragments in a multiply concentric pattern (e.g., Valhalla, Asgard, Galilee Regio, and a newly discovered ring system on Callisto). The thickness and viscosity of a planetary lithosphere increases with time as the mantle cools. A thicker lithosphere leads to the formation of one (or very few) irregular normal faults concentric to the crater (e.g., Gilgamesh). A gravity wave or tsunami induced by impact into a liquid mantle would result in both concentric and radial extension features. Since these are not observed , this process cannot be responsible for the generation of the rings around the basins on Ganymede and Callisto. The appearance of Galilee Regio and portions of Valhalla is best explained by ring graben, and though the Valhalla system is older, the lithosphere was 1.5-2.0 times as thick at the time of formation. The present lithosphere thickness is too great to permit development of any rings.
\r\n\r\nIt has been proposed that a mascon may be in the form of an annulus surrounding the Caloris basin on Mercury, associated with the smooth plains. The effects (stresses, deformation, surface tectonic style, gravity anomalies, etc.) of such a ring load on a floating elastic lithosphere of variable thickness are investigated. The main characteristics of the surface tectonic pattern are normal faulting within the basin and thrust faulting beneath the ring load both in agreement with observation Moreover, the dominant concentric trend of the basin normal faults is consistent with the ring load hypothesis provided the mercurian lithosphere was \u2264125 km thick at the time of faulting. Simple updoming within the basin would produce normal faults of predominantly radial orientation.
" }, { "name": "Powell, Robert Edward", "degree": "PhD", "year": "1981", "title": "Geology of the Crystalline Basement Complex, Eastern Transverse Ranges, Southern California: Constraints on Regional Tectonic Interpretation", "advisor": "Allen, Clarence R.; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-07252007-135803", "creators": [ { "name": { "family": "Powell", "given": "Robert Edward" }, "id": "Powell-Robert-Edward", "display_name": "Powell, Robert Edward" } ], "advisors": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "chair", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Saleeby", "given": "Jason B." }, "id": "Saleeby-J-B", "role": "member", "display_name": "Saleeby, Jason B." }, { "name": { "family": "Sieh", "given": "Kerry E." }, "id": "Sieh-K-E", "orcid": "0000-0002-7311-2447", "role": "member", "display_name": "Sieh, Kerry E." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." } ], "option_major": [ "geol" ], "doi": "10.7907/F22F-YX04", "abstract": "About 3000 km2 within the crystalline basement complex of the Eastern Transverse Ranges in the Chuckwalla, Orocopia, Eagle, Cottonwood, Hexie, Little San Bernardino, and Pinto Mountains of Riverside County, California were mapped at scales of 1:36,000 and 1:62,500 and compiled at 1:125,000 (Plate I). Pre-Jurassic(?) (i.e., older than the Mesozoic batholiths) rocks of the crystalline complex comprise two lithologically distinct terranes. These terranes are called the Joshua Tree and San Gabriel terranes for regions of southern California in which their lithologies were initially characterized. The two terranes are superposed along a previously unrecognized low-angle fault system of regional extent, the Red Cloud thrust.
\r\n\r\nDuring the course of this study, the structurally lower Joshua Tree terrane has been defined as a stratigraphically coherent group of crystalline rocks that consists of Precambrian granite capped by a paleo-weathered zone and overlain nonconformably by orthoquartzite that interfingers westward with pelitic and feldspathic granofelses. The quartzite contains near-basal quartz/quartzite clast conglomerates, and has well-preserved cross-bedding that appears upright wherever it has been observed. Pelitic and feldspathic granofelses crop out to the west of the quartzite exposures in four lithologically different belts that trend northnorthwest throughout the area mapped. These lithologic belts are interpreted to have been derived from stratigraphically interfingering sedimentary protoliths deposited in a basin offshore from a quartzose beach-sand protolith. In proximity to the early Red Cloud thrust, this whole stratigraphic package was pervasively deformed to granite gneiss, stretched pebble conglomerate, lineated quartzite, and schist.
\r\n\r\nA northeast-trending pattern of metamorphic isograds was orthogonally superimposed on the northnorthwest-trending protoliths of the Pinto gneiss. A central andalusite zone, located in the southern Little San Bernardino and Hexie, and northern Eagle Mountains, is flanked to the northwest and southeast by sillimanite zones. Coincident with this symmetrical distribution of aluminosilicates is an asymmetrical distribution of other pelitic mineral zones, with prograde cordierite-aluminosilicate-biotite- and K-feldspar-aluminosilicate-bearing assemblages to the northwest in the northern Little San Bernardino and Pinto Mountains, staurolite-bearing assemblages in a narrow zone in the southern Little San Bernardino-Hexie and northern Eagle Mountains, and retrograde chlorite-muscovite-bearing assemblages in the southernmost Little San Bernardino, Cottonwood, southern Eagle, Orocopia, and Chuckwalla Mountains. One occurrence of chloritoid-sillimanite in the central Eagle Mountains is apparently also retrograde. The crossing isograds are interpreted to result from a temporal increase in PH2O relative to PT from south to north through the field area. Comparison of the pelitic assemblages with experimental studies suggests peak conditions of PT \u2248 3.5 to 4 kb, T \u2248 525 to 625\u00b0C. The early prograde metamorphism pre-dated the thrusting event; the retrograde stage may have overlapped in time with the emplacement of the San Gabriel terrane allochthon. Cordierite-orthoamphibole-bearing assemblages are present in one stratigraphic zone of the Pinto gneiss.
\r\n\r\nIn this study, the Precambrian lithologies of the San Gabriel terrane are viewed as a three-part deep crustal section, with uppermost amphibolite grade pelitic (Hexie) gneiss intruded by granodioritic (Soledad) augen gneiss at the highest level, retrograded granulite (Augustine) gneiss at an intermediate level, and syenite-mangerite-jotunite at the lowest level exposed in the Eastern Transverse Ranges. The Hexie gneiss, characterized by sillimanite-garnet-biotite-bearing assemblages, is thrust over andalusite-bearing granofels of the Pinto gneiss.
\r\n\r\nThe Red Cloud thrust system is inferred to have developed in three or four sequential structural events: 1) early thrusting that probably moved parallel to the ENE mineral lineations recorded in both plates; 2) regional folding of the initial thrust surface around NNE-trending axes; 3) later thrusting that broke with some component of westward movement across a fold in the older thrust surface to produce a stacking of crystalline thrust plates of the two terranes; 4) continued or renewed folding of both thrust faults with eventual overturning toward the SW. It is consistent with all observations to date to link these structural events into a single regional tectonic episode that resulted in westward-vergent allochthonous emplacement of the San Gabriel terrane over Joshua Tree terrane. The thrust timing can only be loosely bracketed in time between 1195 m.y. and 165 m.y. ago.
\r\n\r\nThe pre-batholithic terranes and the westward-vergent Red Cloud thrust are considered to be exotic with respect to the pre-batholithic rocks and structures exposed to the north and east of the field area. The bounding discontinuity has been obliterated by intrusion of both suites of Mesozoic batholithic rocks.
\r\n\r\nThe Mesozoic plutonic rocks comprise two batholithic suites, both of which intrude the Joshua Tree and San Gabriel terranes and the Red Cloud thrust system. NW-SE trending belts of plutonic lithologies have been mapped within each suite: the oldest lithology of the younger suite intrudes the youngest lithology of the older suite. The older suite, Jurassic(?), lying to the NE, appears to have an alkalic character; the younger suite, Cretaceous(?), appears calc-alkaline. The older suite consists of biotite- and K-feldspar-bearing gabbro-diorites intruded by low-quartz monzogranites. The younger suite includes hornblende-biotite-sphene granodiorite intruded by porphyritic monzogranites, intruded in turn by nonporphyritic monzogranite.
\r\n\r\nThe Eastern Transverse Ranges south of the Pinto Mountain fault are defined by several Cenozoic E-W left-lateral strike-slip faults that have a cumulative westward displacement from S to N of about 50 km. The left-lateral faults are interpreted to form part of a conjugate fault set with complementary right-lateral faults in the Mojave and Colorado Deserts. Along the western boundary of the Eastern Transverse Ranges in the Little San Bernardino Mountains, the crystalline rocks have been pervasively cataclasized by an event that post-dates intrusion of the Cretaceous(?) plutonic rocks. The cataclasis is attributed to the Vincent-Orocopia-Chocolate Mountain thrust that is thought to superpose the diverse pre-batholithic and batholithic rocks of the Eastern Transverse Ranges above Pelona-type schist. The cataclastic foliation is folded along the length of the Little San Bernardino Mountains in an antiform that is inferred to be cored with Pelona-type schist. This fold may have formed a single antiformal feature comprising all the crystalline-rock antiforms now recognized along the San Andreas fault that are cored by Pelona-type schist. Displacements of the piercing points formed by the antiformal axis apparently indicate 220 km of right-lateral offset on the present San Andreas strand and about 80 km of right-lateral offset along a fragmented older San Andreas strand that consisted of the San Francisquito, Fenner, and Clemens Well faults and a buried extension of this fault beneath the alluvial fill of the valley between the Chocolate and Chuckwalla Mountains.
\r\n" }, { "name": "Quick, James Edward", "degree": "PhD", "year": "1981", "title": "Part I: Petrology and Petrogenesis of the Trinity Peridotite, Northern California. Part II: Petrogenesis of Lunar Breccia 12013", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:08102018-101338734", "creators": [ { "name": { "family": "Quick", "given": "James Edward" }, "id": "Quick-James-Edward", "display_name": "Quick, James Edward" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/cw33-9d88", "abstract": "Part I presents the results of a petrologic investigation of the Trinity peridotite, an enormous ultramafic massif in northern California. The Trinity is an easterly dipping sheet several km thick and composed of a diverse assemblage of ultramafic rocks including dunite, harzburgite, lherzolite, plagioclase lherzolite and clinopyroxene-rich dikes. Because of this diversity and the limited serpentinization, it is an excellent natural laboratory for studying the petrogenesis of ultramafic rocks. The structural history of the peridotite was outlined by detailed field mapping at scales of 1:31,250 and 1:240 at the northeast margin of the massif in the vicinity of Mount Eddy and China Mountain during the summers of 1977-1978. A combined petrographic and electron microprobe investigation was made on selected samples to determine their petrology, mineral chemistry and major element whole rock compositions.
\r\n\r\nThe Trinity peridotite is inferred to have originated in the upper mantle at a depth of not less than ~30 km and perhaps as deep as 100 km based on textural evidence for a transition from the spinel lherzolite (>10 kb) stability field to the plagioclase lherzolite (<10 kb) stability\r\nfield, and on high equilibration temperatures (>1150\u00b0 C.) preserved in cores of large pyroxene grains. During ascent through the mantle, the rocks deformed plastically, partially melted and reacted with transient melts derived from greater depth. Plastic deformation produced two generations of folds and a penetrative foliation. Pervasive partial melting of the plagioclase lherzolite produced feldspathic segregations, plagioclase-rich veins and resorption textures in pyroxenes and spinel; the composition of the veins suggests that this melt was essentially basaltic. Another melt, not in equilibrium with the peridotite, but also of basaltic affinity, passed through the peridotite, reacted with the ultramafic wall rocks to produce large tabular dunite bodies surrounded by zones of harzburgite and lherzolite, and crystallized clinopyroxene-rich dikes. The end of the ascent of the Trinity through the mantle is marked by intrusion of gabbro, hornblende diorite, diabase and albite granite, and the onset of brittle deformation circa 450-480 m.y. based on zircon ages of the granites (Mattinson and Hopson, 1972). The Trinity was subsequently thrust into the crust at about 380 m.y. based on Rb-Sr dates on rocks of the underlying Central Metamorphic Belt. It is suggested that the passage of the Trinity through the mantle may have occurred beneath an actively spreading back-arc basin.
\r\n\r\nPart II of this thesis is a petrologic investigation of Lunar Rock 12013, one of the most significant lunar samples because of its extreme enrichments in incompatible elements (K, REE, U, etc.) and abundant \"granitic\" material.
\r\n\r\nRock 12013 is best interpreted as a complex mixture of two polymict, impact generated breccias--one black, the other gray. The black breccia is a fragment-laden melt-rock formed by mixing cold, impact-derived mineral and lithic clasts with superheated impact melt of basalted composition. The melt is now crystallized to an aphanite of minute grain size. The gray breccia was also formed as a mixture of melt and impact-derived clasts, but the melt was granitic and crystallized to a fine grained felsite. The clasts in the breccias were derived from lithologies common in Highlands breccias, with the gray breccia dominated by feldspathic gabbro and basalt clasts and the black breccia dominated by quartzofeldspathic and norite clasts. A combined neutron activation, petrographie and electron microprobe analysis demonstrates that the incompatible elements in 12013 are concentrated in the melt-derived lithologies. The origin and relationships of the melts is problematic. Textural relations suggest that the two melts\r\ncoexisted but did not mix, and some aspects of their major element abundances are compatible with a genetic relationship involving silicate liquid immiscibility (SLI). However, details of their trace element abundances are incompatible with SLI.
\r\n\r\nIt is suggested that 12013 is exotic to the Apollo 12 site and was formed by an impact(s) into a terrane of norite and quartofeldspathie plutonic rocks, gabbro and basalt hypabyssal or extrusive rocks, and a thin regolith cover. The two breccia were derived from different parts of this terrane and mixed violently in the ejecta cloud. Most of the radiometric clocks were reset by this event, and Rb-Sr, U-Th-Pb and 40Ar-39Ar yield ages of ~4.0 AE. Rb-Sr data, however, may be interpreted to suggest an age for the felsite protolith of ~4.5 AE. An alternative explanation, consistent with the petrography of the rock, is that the Rb-Sr data reflect mixing and partial equilibration at 4.0 AE of materials no older than\r\n4.2 AE.
" }, { "name": "Stapanian, Maritza Irene", "degree": "PhD", "year": "1981", "title": "Induced Fission Track Measurements of Carbonaceous Chondrite Th/U Ratios and Th/U Microdistributions in Allende Inclusions", "advisor": "Burnett, Donald S.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10282005-135027", "creators": [ { "name": { "family": "Stapanian", "given": "Maritza Irene" }, "id": "Stapanian-Maritza-Irene", "display_name": "Stapanian, Maritza Irene" } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/64g4-2a56", "abstract": "A double irradiation fission track radiography technique has been developed to measure Th/U ratios in carbonaceous chondrites and map Th/U microdistributions in Ca-Al-rich inclusions. (Th + \u00b2\u00b3\u2078U) fission is induced by high dose 35-40 MeV proton irradiations. These irradiations are coupled with reactor \u00b2\u00b3\u2075U thermal neutron fission measurements to obtain the corresponding Th/U ratios.
\r\n\r\nThe average solar system Th/U ratio is important in the theoretical modelling of the time scales for heavy element r-process nucleosynthesis. Earlier measurements (Morgan and Lovering, 1967, 1968) indicated CC Th/U ratios ranging from 2-6. This is in sharp contrast to ordinary chondrite, terrestrial, and lunar sample measurements which are tightly constrained to present day values of 3.8\u00b10.5. An objective of this study was to check the 2-6 spread in CC ratios. The fission track technique, while not a high precision technique, can give individual meteorite measurements to within 12-20%. This is adequate to verify the existence of highly fractionated (relative to terrestrial) CC Th/U ratios. The results of our analyses of six bulk samples mainly type C2, but also including the Ivuna type C1 chondrite, show within the errors of the measurements that bulk CC Th/U ratios lie within the normal 3.8\u00b10.5 range.
\r\n\r\nThe real strength of the fission track technique lies in the ability to map Th/U microdistributions in-situ. Our technique has the sensitivity to make U measurements within 10% counting statistics errors on 100\u00b5 grains with 20 ppb. Th+U measurements of similar precision can be made on 100\u00b5 grains with 1 ppm Th+U. We have focussed our Th/U mapping experiments on the Allende meteorite- in particular, the calcium-aluminum-rich inclusions (CAI). The chemical and mineralogical composition of these CAI conform to model predictions for the earliest forming nebular condensates. Because of the refractory nature of Th and U, location and identification of Th,U-rich carrier phases can test solar nebula condensation models. Our major results are: (1) The high concentrations of Th and U in the rims of two Type A coarse-grained CAI attests to the importance of rims in understanding Th,U condensation and perhaps other refractory trace elements as well. (2) Analysis of a compact Type A inclusion shows that incorporation of rim material into total inclusion values is necessary to obtain Th and particularly U enrichments over Cl levels on par with the uniform enrichment of other refractory elements (Grossman et al., 1977). (3) The highly fractionated Th/U ratios observed in Type A perovskite (~20), and the general tendency for our CAI bulk measurements which show fractionated Th/U ratios to give high ratios suggests support of the Boynton (1978) proposal of higher U volatility compared to Th under the conditions of the early condensing nebula. Alternatively, our Type A inclusions may be atypical, having formed from a reservoir (gas?) of high Th/U. One mechanism for preferential depletion in the early stages of condensation could be alloying of U with Pt metals as discussed by Jones and Burnett (1980), although there is no strong evidence to support this specific mechanism. (4) The Th/U fractionations observed in Type A CAI suggest the strong likelihood for \u00b2\u2074\u2074Pu/\u00b2\u00b3\u2078U fractionations as well. Such inclusions would probably not be appropriate for determining the solar system Pu/U or Pu/Th ratios.
" }, { "name": "Beaty, David Wayne", "degree": "PhD", "year": "1980", "title": "Part I. Comparative Petrology of the Apollo 11 Mare Basalts. Part II. The Oxygen Isotope Geochemistry of the Abitibi Greenstone Belt", "advisor": "Albee, Arden Leroy; Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02232006-092342", "creators": [ { "name": { "family": "Beaty", "given": "David Wayne" }, "id": "Beaty-David-Wayne", "display_name": "Beaty, David Wayne" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/EEHY-DG27", "abstract": "PART I. Over the past decade a wealth of geochemical and petrological information has been accumulated on the Apollo ll basalts. These data indicate that the 73 thus far identified basalts can be divided into five petrologic groups which must represent at least five separate igneous cooling units. These five igneous bodies range in age from 3.90 b.y. to 3.60 b.y. Photogeologic studies of the landing site indicate that three mare units are present, and that the lunar module set down on the oldest of the three. The exposure age data suggest that the high-K flow(s) is the surficial rock type at the landing area, and is therefore probably the oldest of the three mare units. The three low-K groups of samples are older than (and underlie) the high-K basalts, and were apparently excavated by West Crater. By studying the size frequency distribution and the inferred cooling rates of the individual samples, it is possible to calculate the formation thicknesses within the 30 m-deep West Crater. This suggests that A=9 m, B1=2 m (and may be an ejecta blanket), B2\u2a7e8 m and B3=6 m. Because the Group D samples have not been dated, it is not known whether they lie above or below the high-K unit. They may, however, represent one of the two younger mare units present near the landing site.
\r\n\r\nPART II. A variety of petrologic, geochemical and geophysical evidence indicates that the modern oceanic crust interacts on a massive scale with seawater. To evaluate whether or not similar processes were taking place in the Archean, the well preserved Abitibi greenstone belt was studied using oxygen isotopes and the petrographic microscope. In thin section, all of the volcanic rocks in the Abitibi area are found to have been subjected to a hydrothermal process of some sort. The original igneous minerals have been largely replaced by secondary hydrous minerals such as chlorite, epidote and actinolite. The metamorphic assemblages range from the prehnite-pumpellyite facies in the core of the Blake River syncline to greenschist facies adjacent to the large Kenoran granitic batholiths. The structural relations are such that the metamorphic grade decreases in a general way with structural height; the lowest temperature rocks are those which are highest in the volcanic pile.
\r\n\r\n\u03b4\u00b9\u2078O is also correlated with structural height. In each of five widely separated traverses (Benoit, Ben Nevis, Noranda, Skead, Timmins), \u03b4\u00b9\u2078O increases upwards through the stratigraphic section (typically +6 to +10 from base to top). In the Benoit area \u03b4\u00b9\u2078O and structural height also correlate with the silica content of the volcanic rocks. Silica content and the degree of petrographic recrystallization are not correlated, however, whereas \u03b4\u00b9\u2078O and the degree of recrystallization are. This indicates that the gradient in SiO\u2082 is a relic igneous feature and that the gradient in \u03b4\u00b9\u2078O is a hydrothermal alteration feature. Additional evidence that these rocks have undergone isotopic exchange comes from the mineral separate data. Relic clinopyroxene in the basalts has \u03b4\u00b9\u2078O +5.5, and quartz phenocrysts in the rhyolites are +7.6, indicating that these lavas were not erupted as high-\u00b9\u2078O magmas; they have undergone subsolidus enrichments in \u03b4\u00b9\u2078O of 0-4 per mil. Using temperatures inferred from the metamorphic assemblages, \u03b4\u00b9\u2078O of the fluid responsible for producing these \u03b4\u00b9\u2078O shifts can be calculated. Assuming an open system, water flux within 100\u00b0C of the final metamorphic temperature, and using the feldspar geothermometer, the hydrothermal fluid has \u03b4\u00b9\u2078O = 0 \u00b1 2 and alteration took place under conditions of high water/rock ratio. The oxygen isotopic effects are associated with the prehnite-pumpellyite facies burial metamorphism, which is thought to have taken place during the formation of the volcanic pile. Since the pile formed in a marine environment the only logical source for such large amounts of fluid is seawater itself.
\r\n\r\nOxygen isotopic study of the Amulet \"A\" massive sulfide deposit indicates that it was formed by a fluid with, a similar \u03b4\u00b9\u2078O (0.5 \u00b1 1.0). Similar deposits in the Phanerozoic (Cyprus, Kuroko, Gulf of California) are thought to have originated from heated seawater circulating through the oceanic crust. The fact that the Amulet ore fluid is indistinguishable from the inferred Archean seawater indicates that analagous hydrothermal processes were taking place in the Archean. At the Kidd Creek mine, however, the ore-forming solution is thought to have had \u03b4\u00b9\u2078O between +6 and +9. This fluid could either have been derived from normal-\u00b9\u2078O seawater through evaporation or exchange with high-\u00b9\u2078O country rocks, or it could have been some sort of metamorphic fluid. This indicates that massive sulfide ore deposits have formed by more than one mechanism, and that the simple seawater-hydrothermal model may not be generally applicable.
\r\n\r\nLess extensive data from other greenstone belts throughout the world indicate that like Abitibi, all have undergone \u00b9\u2078O-enrichments relative to primary igneous values. By mass balance, these \u00b9\u2078O-enrichments must have caused a complementary \u00b9\u2078O-depletion in some other oxygen reservoir. That reservoir was apparently not seawater, nor has it been discovered in the geologic record. Because the oxygen isotopic exchange process is self-buffering, the consistent \u00b9\u2078O-enrichments in greenstone belts throughout history suggests that they were not the dominant form of submarine volcanism in the Archean. This, combined with the apparent destruction of the low-\u00b9\u2078O reservoir, suggests that seafloor spreading volcanism was also taking place in the early Precambrian. This is consistent with a variety of geological, geophysical, geochemical, isotopic and petrologic data which indicate that greenstone belts resemble modern island arcs in a number of important respects.
" }, { "name": "Benjamin, Timothy Miller", "degree": "PhD", "year": "1980", "title": "Experimental Actinide Element Partitioning Between Whitlockite, Apatite, Diopsidic Clinopyroxene, and Anhydrous Melt at One Bar and 20 Kilobars Pressure", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:03202024-175813071", "creators": [ { "name": { "family": "Benjamin", "given": "Timothy Miller" }, "id": "Benjamin-Timothy-Miller", "display_name": "Benjamin, Timothy Miller" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "abstract": "Fission and alpha track radiography techniques have been used to measure partition coefficients (D) at trace (ppm) concentration levels for the actinide elements Th, U, and Pu between synthetic diopsidic\r\nclinopyroxene, whitlockite (\u03b2-Ca\u2083(PO\u2084)\u2082), apatite, and coexisting \"haplobasaltic\" silicate liquid at 1 bar and 20 kilobars\r\npressure at oxygen fugacities from 10^(-8.6) to 10^(-0.7) bars.\r\nEquilibrium (Rayleigh) partitioning at the crystal-liquid interface is assumed and corrections for actinide zoning and relative alpha and fission fragment ranges have been applied to the measured D values.\r\nReproducibility for both actinide and minor element D values is care\u00ad fully examined as a criterion for crystal-liquid interface equilibrium. The data are mostly compatible with interface equilibrium except at high cooling rates (\u226530 deg/hr).
\r\n\r\nPu is much more readily incorporated into crystalline phases than is U or Th, under reducing conditions (fO\u2082=10^(=8.6), because Pu is most likely trivalent whereas U and Th are tetravalent. The effect of\r\nchanging pressure and liquidus temperature is small where direct comparisons can be made. Definitive valence state assignments cannot be\r\nmade, but our best estimates of corrected partition coefficients for Pu\u207a\u00b3, Pu\u207a\u2074, Th\u207a\u2074, U\u207a\u2074, and U\u207a\u2076 are, for whitlockite: 3.6 / 0.58 /\r\n1.2 / 0.5 / 0.002; for chloro-oxy-apatites: -- / -- / 1.22 / 1.69 / --; and for diopsidic clinopyroxene: 0.06 / -- / 0.002 /0.002 / -- respectively in P-bearing systems.
\r\n\r\nStrong compositional effects \r\nare seen on the addition of P and, to a lesser extent, U. The D_(cpx)for Th and U are a factor of 10, and\r\nfor Pu\u207a\u00b3 a factor of three higher in P-free systems relative to \r\nP-bearing systems. This is interpreted as a result of actinide stabilization\r\nin the melt, possibly by complex formation with PO\u207b\u00b3\u2084\r\ngroups.
\r\n\r\nActinide substitution in these phases is most likely into the Ca\r\nsite as this site is the largest in each phase and the magnitude of\r\nthe relative D values, between phases, corresponds to the relative range\r\nof Ca site sizes. However experiments run with percent concentrations\r\nof UO\u2082\r\nadded to the whitlockite-producing compositions suggest that\r\nsubstitution of UO\u207b\u2074\u2084 for PO\u207b\u00b3\u2084 is a possibility.
\r\n\r\nPreliminary results on Sm partitioning at 1 bar pressure\r\nand published lanthanide partition coefficients place the partitioning\r\nbehavior of Pu\u207a\u00b3 amongst the light rare earth elements with Nd having\r\na factor of two greater D_(whit) than Pu\u207a\u00b3. These results support the use\r\nof Pu/Nd chronology for meteorites provided chemical fractionation\r\neffects, which could result in a 60 m.y. error, are assessed.
\r\n\r\nThese results have application in evaluating actinide-actinide and\r\nactinide-lanthanide fractionations in natural materials utilized in\r\naddressing problems in geochronology, cosmochronology, and petrogenesis.\r\nAdditionally, these data define a 'bracketing theorem' for\r\nselection of unfractionated materials for use in the aforementioned\r\ndisciplines. This bracketing theorem, based on the sequence of relative\r\ncrystal/liquid partition coefficients: D_(Nd)>D_(Pu)>D_(Th)\u2265;D_U, predicts that a\r\nsample with unfractionated (relative to solar-system abundances)\r\nlanthanide and Th-U abundances will also have a solar-system Pu abundance.\r\nFurther use of this type of experimentation has clear application to\r\nthe current problem of radioactive waste disposal.
" }, { "name": "Burnett, Michael Welch", "degree": "PhD", "year": "1980", "title": "The Occurrence and Distribution of Ca, Sr, Ba, and Pb in Marine Ecosystems", "advisor": "Patterson, Clair C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03112024-200920705", "creators": [ { "name": { "family": "Burnett", "given": "Michael Welch" }, "id": "Burnett-Michael-Welch", "display_name": "Burnett, Michael Welch" } ], "advisors": [ { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "advisor", "display_name": "Patterson, Clair C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/6b1e-bw74", "abstract": "Processes of enrichment and depletion of Pb, Ba, and Sr relative to Ca in transfers between trophic levels of selected marine ecosystems were studied using ultra-clean laboratory techniques and stable isotope dilution mass spectrometry. Metal relationships between cellular subfractions of marine algae and major Ca reservoirs of consumer animals show that at the primary producer level large bioenrichments in the Pb/Ca ratio occur on algal surfaces as a result of selective chelation of soluble Pb by extra\u00ad cellular algal polysaccharides. This is followed by biopurification of Ca with respect to Pb during active transport of Ca from surfaces to interiors of algal cells and during subsequent transfers to consumer animals at successively higher trophic levels of marine food chains.
\r\n\r\nCa, Sr, Ba, and Pb share covariant and coincident distributions in marine organisms, residing chiefly in cell wall mucilages of algae and skeletons of animals. Pb/Ca ratios of major Ca reservoirs in marine biota correlate with variations in the Pb/Ca ratio of source reservoirs which result from different ambient concentrations of industrial Pb in seawater. Pb/Ca ratios of gastropod shell layers correlate directly with Pb/Ca ratios of food but inversely with organism size. The partitioning of Pb between shell layers generally favors calcite relative to aragonite but is influenced by species, size, and ambient environmental Pb concentrations.
\r\n\r\nA linear model of the pelagic food web based on data of this and another recent study indicates that recycling of organic matter in food chains does not act as a continuous extraction process by which Pb becomes most concen\u00adtrated at the highest trophic levels.
\r\n\r\nA model of biological fluxes of Pb through the surface mixed layer of the NE Pacific indicates that sinking of zooplankton fecal pellets containing Pb-rich phytoplankton debris satisfies geochemical constraints requiring a short residence time of Pb in these waters and is an important mode of vertical mass transport of Pb.
" }, { "name": "Carter, Bruce Alan", "degree": "PhD", "year": "1980", "title": "Structure and Petrology of the San Gabriel Anorthosite-Syenite Body, Los Angeles County, California", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01102008-082801", "creators": [ { "name": { "family": "Carter", "given": "Bruce Alan" }, "id": "Carter-Bruce-Alan", "display_name": "Carter, Bruce Alan" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/Q9N7-MS19", "abstract": "The San Gabriel anorthosite-syenite body is part of large layered intrusive, part of which underlies about 250 square kilometers in the western San Gabriel Mountains between the San Gabriel and San Andreas fault zones 30 kilometers north of Los Angeles. Although not subjected to post-emplacement regional metamorphism, the Precambrian anorthosite is intruded by the early Triassic Mt. Lowe granodiorite and the late Cretaceous Mt. Josephine granodiorite, and is deformed by broad folds of at least two ages (Triassic(?) and mid-Cenozoic), which have produced several kilometers of structural relief within the body.
\r\n\r\nSeveral sets of faults in the area were active in Tertiary time, but none of them show evidence of Holocene activity. From oldest to youngest, these faults include: (1) several more or less east-west faults with major apparent right-lateral or left-lateral and dip-slip displacements; (2) a NE-trending fault set with important left-lateral displacements; and (3) younger NW-trending faults with small dip-slip and right-lateral displacements. The San Gabriel fault, which lies 1-4 kilometers southwest of its margin, must cut the anorthosite-syenite body at depth and may offset anorthositic rocks at least 28-46 kilometers in a right-lateral sense.
\r\n\r\nThe San Gabriel anorthosite-syenite body is part of a large allochthonous sheet which is floored by a zone of unusual cataclastic gneisses, exposed in the northeastern part of the area in and near to Mill Canyon. Slickensides, lineations and minor folds within this zone suggest latest movement parallel to a N-S or NE-SW direction. Strongly deformed and mylonitized gneisses below the anorthosite include lineated granodioritic gneiss possibly equivalent to the late-Cretaceous Mt. Josephine granodiorite, gabbroic to anorthositic gneisses, and layered amphibolitic gneisses unlike any others seen in the western San Gabriel Mountains. Large thrust displacements probably occurred within this zone as well as along the Vincent thrust 45 kilometers to the east, which resembles this zone and may be related to it.
\r\n\r\nThe anorthosite-syenite body was intruded into previously metamorphosed, granulite-grade Mendenhall gneiss about 1200 million years ago. The body is a large, layered intrusive in which bottom crystal accumulation produced the observed anorthosite-gabbro-syenite differentiation suite. The part of this body now exposed was at least 10 kilometers in thickness and about 15 kilometers in diameter. It probably had the form of an inverted cone, with a sub-horizontal, concordant upper contact. Primary quartz is rare in rocks of this suite; the following lithologies have been distinguished on the basis of the percentage and composition of their constituent feldspars: anorthosite, leucogabbro, gabbro, ferrogabbro (all with calcic andesine), ultramafite (olivine, augite, ilmenite and apatite), jotunite (predominantly antiperthitic sodic andesine), mangerite (antiperthite and mesoperthite) and syenite (predominantly mesoperthite).
\r\n\r\nThe San Gabriel anorthosite-syenite body has been subdivided into three main stratigraphic units (from oldest to youngest): (1) The lowest, largest unit consists of thick sequences of massive anorthosite alternating with layered leucogabbro. This unit is at least 7 kilometers in thickness and becomes more mafic near its top. (2) The overlying syenite unit locally attains thickness of at least 3-5 kilometers, but is commonly much thinner or absent. In some areas, the basal 100-1000 meters of this unit is extremely mafic, but otherwise it is fairly homogeneous and massive, with no cyclic or cryptic layering. (3) The uppermost jotunite unit is a highly compositionally variable unit which intruded overlying granulite gneiss and has been subdivided into 5 subunits. This unit is at least 3-4 kilometers in maximum thickness. It is apparently younger than the syenite, and in places grades downward into syenite. Several masses of hornblende-bytownite gabbro within anorthosite are probably not directly related to the anorthosite-syenite body.
\r\n\r\nPrimary cumulate structures and textures in these rocks have greatly aided the structural interpretation of this body and provide strong evidence of its origin by bottom crystal accumulation. Large, 6 to 25-centimeter hypersthene crystals, which ophitically enclose numerous well-oriented 1 to 3-centimeter plagioclase tablets, indicate a cumulate origin of the leucogabbro. Occasional crescumulate layers in leucogabbro, especially near the margin of the body, formed when first plagioclase and then hypersthene grew from the floor upward into the magma. Slump structures are poorly defined in leucogabbro, but are excellently developed in the mafic lower part of the syenite unit and in some parts of the jotunite unit, and include 1 to 20-meter slump blocks and deformed compositional layers. Many 3-centimeter to 3-meter layers in the mafic lower part of the syenite unit and in the jotunite unit are both size- and density-graded, with coarser, ferromagnesian-mineral-enriched bases, and are extremely useful structural indicators.
\r\n\r\nLarge angular blocks of anorthosite (to 20 meters) are abundant in layered mafic rocks at the base of the syenite unit and in some parts of the jotunite unit. These are slump blocks, which indicate that parts of the syenite and jotunite units accumulated at the base of major tectonic scarps which developed in rocks of the anorthosite-leucogabbro unit which formed the floor of the chambers of the later magmas.
\r\n\r\nAll of the 20 chemical analyses of rocks from this body are iron-rich; the lowest FeO+Fe\u2082O\u2083/FeO+Fe\u2082O\u2083+MgO ratio (wt. %) is 0.61 and most are between 0.70 and 0.95, which suggest that the original magma was probably similarly iron-rich.
\r\n\r\nChemical analyses of these rocks define general trends with substantial scatter on variation diagrams, and in detail those from each of the three units define individual fields with little or no overlap. Thus a common line of descent for all rocks of the body seems somewhat unlikely. The estimated makeup of the entire body is about 46% anorthosite, 23% leucogabbro, 4% gabbro, 12% syenite, 11% jotunite and 4% ultramafite, giving the following suggested average composition: SiO\u2082, 53.73%, TiO\u2082, 1.17%, Al\u2082O\u2083, 22.33%, Fe\u2082O\u2083, 1.66%, FeO, 4.54%, MgO, 1.72%, CaO, 8.08%, Na\u2082O, 5.05%, K\u2082, 1.18%, P\u2082O\u2085, 0.42%.
\r\n\r\nLimited mineral composition data show that: (1) Plagioclase in anorthosite and leucogabbro ranges between about An\u2083\u2085 and An\u2085\u2085 with most between An\u2084\u2080 and An\u2085\u2080. Plagioclase in not concentrically zoned, but is inhomogeneous with a range of about 3-4% anorthite in individual crystals. (2) There are cyclic compositional variations of plagioclase in the anorthosite-leucogabbro unit, with more albite-rich and more anorthite-rich compositons alternating over hundreds of meters of the stratigraphic section. (3) There is no apparent consistent cryptic variation of proxene and olivine compositions within the syenite and jotunite units.
\r\n\r\nPostcumulous recrystallization has drastically altered the fabric of most anorthositic and leucogabbroic rocks and has produced extremely coarse grained textures. Pervasive deuteric uralitic alteration of the primary ferromagnesian minerals in all but a few rocks of the syenite and jotunite units suggests that the magma probably had a relatively high water content.
\r\n\r\nIt is possible that all of the rocks of the San Gabriel anorthosite-syenite body could have been produced by differentiation by fractional crystallization of a trachyandesitic parent magma, successive fractions of which were intruded into the magma chamber. However, the detailed sequence of lithologies, mineral compositions and the compositions of the three units suggest that at least two independently generated magmas may have combined to produce the San Gabriel anorthosite-syenite body.
\r\n\r\nSome important contributions of this study are: (1) the detailed geologic map of the anorthosite-syenite body and determination of its post-emplacement structural history; (2) the description of the complete suite of lithologies and their contact relationships; (3) the description of the mineralogical compositions of each lithology and the recognition of cryptic variation of plagioclase in the anorthosite-leucogabbro unit; (4) the description of the sequence of post-accumulation processes including recrystallization and the hydration of most primary ferromagnesian minerals; (5) the recognition of uninverted pigeonite in rocks of the jotunite and syenite units; and (6) recognition that this andesine anorthosite massif is actually a large deformed stratiform pluton.
" }, { "name": "Champion, Duane Edwin", "degree": "PhD", "year": "1980", "title": "Holocene Geomagnetic Secular Variation in the Western United States: Implications for the Global Geomagnetic Field", "advisor": "Shoemaker, Eugene Merle", "url": "https://resolver.caltech.edu/CaltechTHESIS:04222010-081847532", "creators": [ { "name": { "family": "Champion", "given": "Duane Edwin" }, "id": "Champion-Duane-Edwin", "display_name": "Champion, Duane Edwin" } ], "advisors": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "advisor", "display_name": "Shoemaker, Eugene Merle" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/ywhe-8566", "abstract": "A record of Holocene geomagnetic secular variation in the western United States has been measured from volcanic rocks dated by ^(14)C. Analysis of errors associated with the paleomagnetic techniques used suggests that all laboratory measurement errors are smaller than those introduced by deformation of the volcanic units and the errors of orientation of cores in the field. The dispersion in the calculated virtual geomagnetic poles introduced by the geographic spread of sample localities around the western United States is less than the average uncertainty from an individual locality, about 2 deg.\r\n\r\nThe history of secular variation of field direction in the western United States has been reconstructed where sufficient time control exists. This history can be approximately reconstructed for the past 3000 years; in this time period, inclination varied from 44 to 72 deg and declination varied from 344 to 22 deg. These variations of the local field direction have periods between 500 and 1500 years. Prior to 3000 years B.P., the available observations allow reconstruction of the secular variation history only for short time intervals. The mean VGP obtained from paleofield directions measured from 77 volcanic units of Holocene and late Pleistocene age in the western United States does not coincide with the geographic pole of the Earth, but is displaced 2.5 deg from the geographic pole in a direction away from the sampled region. This displacement is just at the limit of significance at 95 percent confidence.\r\n\r\nUsing a 10^(-5) torr vacuum furnace, paleointensities have been obtained by the Thelliers' method from both high-temperature oxidized and unoxidized basic volcanic rocks. Specimens which have undergone incomplete high-temperature oxidation in nature commonly fail the Thellier experiment; the relationship between NRM lost and TRM gained in a known magnetic field is not linear. Despite the vacuum, oxidation can still occur above 300\u00b0C in the furnace ovens. The best determinations of paleointensity come from specimens in which the remanence resides primarily in single phase titanomagnetite or in intergrowths of Ti-poor magnetite in ilmenite which have been formed by natural high-temperature oxidation. Paleointensity determined from these specimens varies from 0.364 x 10^(-4) to 0.865 x 10^(-4) T (1.0 x 19^(-4) T = 1 Oe); the period of oscillation of paleointensity is about 500 to 1000 years. Close agreement has been found between the paleointensity measurements from this study and those from archeomagnetic studies in the southwestern United States. The similarity of the periods of intensity variation to those of field direction changes may indicate that variations of the nondipole components of the geomagnetic field dominate both.\r\n\r\nBy combining paleomagnetic and archeomagnetic data from globally distributed localities, the magnetic dipole can be shown to have wobbled with a period as short as 2000 years. Local variation of the field can be described as the consequence of fluctuation of the dipole moment, wobble of the dipole, and longitudinal drift of a nondipole field similar to that of the present. During the Holocene, the dipole moment of the Earth has fluctuated with a period of approximately 8000 years, though when viewed from a single region, the fluctuation of the dipole moment is obscured by variation of nondipole components of the field.\r\n" }, { "name": "Cole, David Martin", "degree": "PhD", "year": "1980", "title": "A Numerical Boundary Integral Equation Method for Transient Motions", "advisor": "Harkrider, David G.; Minster, Jean-Bernard H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02142024-183355928", "creators": [ { "name": { "family": "Cole", "given": "David Martin" }, "id": "Cole-David-Martin", "display_name": "Cole, David Martin" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." }, { "name": { "family": "Minster", "given": "Jean-Bernard H." }, "id": "Minster-Jean-Bernard-H", "role": "advisor", "display_name": "Minster, Jean-Bernard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "abstract": "This thesis presents the results of a study of a numerical technique for the solution of initial-boundary value problems of linear elastodynamics. The numerical method is based on a boundary integral equation (BIE) formulation of the mechanics of bodies of arbitrary shape. These integral equations are discretized and a time stepping technique is used to so1ve the resulting system of linear algebraic equations.
\r\n\r\nThe theoretical basis of the continuous problem and the general interpolation and discretization scheme are described in Chapter 1. The problem is then specialized to the two-dimensional case of antiplane strain and most subsequent calculations and discussions take place in this context. The performance of the numerical method depends entirely on the interpolation scheme used, and on the manner in which boundary shapes are approximated.
\r\n\r\nThe consequences of particular interpolation schemes for boundary value problems on a half-plane are discussed in Chapter 2. The results of several numerical calculations are compared with exact, or much more accurate solutions. This chapter also presents a compari\u00adson of the performance of the numerical BIE method with the performance of other specialized numerical procedures which have been used previously for problems of this nature. The BIE method yields results which are as accurate, or more accurate than the other methods for given discretization parameters.
\r\n\r\nThe method is applied to basic boundary value problems for\r\ncurved symmetric and nonsymmetric boundaries in Chapter 3. The solutions obtained there are again compared to more accurate or exact solutions produced by independent methods. The general dependence of errors on discretization parameters is discussed.
\r\n\r\nChapter 4 gives the solution of a problem in which a Love wave propagates through a limited region of laterally varying structure.\r\nThe time stepping nature of the BIE method makes feasible certain rearrangements of the numerical equations which yield a representation of the mechanical system in which the incident, unperturbed Love wave arises as an inhomogeneous term. Solution of this localized numerical equation then yields an intermediate variable, the change in the traction boundary value of the layered space surface, which is used to evaluate the scattered displacement wave.
\r\n\r\nThe performance characteristics and unusual properties of the time stepping BIE method are summarized in the General Summary. The appendices deal with several subjects. Appendix A gives an evaluation of singular integrals arising in the general continuous integral equation formulation. Appendix B gives a body force equivalent of nonequilibrium static initial values. Appendix C discusses the con\u00ad vergence and stability of solutions obtained using a particular inter\u00ad-polation scheme. Appendix D contains FORTRAN subroutines used in evaluating discrete kernels for the antiplane strain case. Appendix E gives the solution to a diffraction problem which is used to evaluate\r\nerrors in a BIE solution of the same problem which is given in Chapter 3.
" }, { "name": "Jacobsen, Stein Bj\u00f8rnar", "degree": "PhD", "year": "1980", "title": "Study of Crust and Mantle Differentiation Processes from Variations in Nd, Sr, and Pb Isotopes", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242024-233510543", "creators": [ { "name": { "family": "Jacobsen", "given": "Stein Bj\u00f8rnar" }, "id": "Jacobsen-Stein-Bj\u00f8rnar", "display_name": "Jacobsen, Stein Bj\u00f8rnar" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/q5z7-d408", "abstract": "This study discusses two simple transport models for the evolution of the mantle and the crust. In Model I, the continents grow by extraction of melts over the history of the earth from undepleted mantle; the residue forms a depleted mantle, which today is the source of mid-ocean ridge basalts. In Model II, new additions to the continents are derived from a mantle reservoir which becomes increasingly depleted through time by repeated extraction of melts. In developing these models, I solved the transport equations for stable, radioactive, and daughter isotopes for arbitrary crustal growth curves. For both models the isotopic composition and concentrations of trace elements reduce to simple mathematical expressions which readily permit calculations of basic evolutionary parameters from new and published data.
\r\n\r\nNew measurements of \u00b9\u2074\u00b3Nd/\u00b9\u2074\u2074Nd in chondrites yield a range in values of 3.4 \u03f5-units (0.511767 to 0.511845), which correlates with the variation of 2.6% in \u00b9\u2074\u2077Sm/\u00b9\u2074\u2074Nd (0.1920 to 0.1969). From these data a new set of reference values for CHUR (\"chondritic uniform reservoir\") have been selected. The evolution of \u00b9\u2074\u00b3Nd/\u00b9\u2074\u2074Nd in CHUR can be described by a self-consistent set of present-day values of (\u00b9\u2074\u00b3Nd/\u00b9\u2074\u2074Nd)\u00b0_(CHUR) = 0.511836 and (\u00b9\u2074\u2077Sm/\u00b9\u2074\u2074Nd)\u00b0_(CHUR) = 0.1967. Some terrestrial samples of Archean age show clear deviations from the new CHUR curve. If the CHUR curve is representative of undifferentiated mantle then it demonstrates that some Archean rocks were formed from depleted sources. This may indicate that the depleted source of present-day mid-ocean ridge basalts (MORB) originated very early in the earth's history.
\r\n\r\nTwo Sm-Nd internal isochrons for pyroxene-gabbros of the Bay of Islands Ophiolite Complex give well-defined ages of 508\u00b16 m.y. and 501\u00b113 m.y. with initial \u00b9\u2074\u00b3Nd/\u00b9\u2074\u2074Nd of \u03f5_(Nd) = +7.9\u22130.1 and \u03f5_(Nd) = +7.7\u22130.2, respectively. Total rock samples from pillow basalts, sheeted dikes, trondhjemites, hornblende gabbros, pyroxene gabbros, and an orthopyroxenite layer from the harzburgite give initial \u03f5_(Nd) in the range from +6.7 to +8.3 with an average value of +7.8. However, the initial \u2078\u2077Sr/\u2078\u2076Sr within the different phases of the complex is found to be highly variable(~52 \u03f5-units) and shows the effect of seawater alteration. The magnitude of the initial \u03f5_(Nd) values (+7.8) are somewhat smaller than for typical present-day mid-ocean ridge basalts (+10). This is most likely due to differential evolution over the past 0.5 AE of the oceanic mantle relative to the bulk earth.
\r\n\r\nSm-Nd and Rb-Sr data for the Oslo Rift demonstrate that this province which is strongly enriched in large ion lithophile (LIL) elements is derived from depleted.to undepleted mantle materials. A source with a long history of light rare earth (LREE) enrichment can clearly be ruled out.
\r\n\r\nSm-Nd data for the Archean granulite and amphibolite facies migmatites of Lang\u00f8y and Hinn\u00f8y in Vester\u00e5len indicate that their protoliths formed ~2.6 AE ago. Rb and U loss during a granulite facies metamorphism at ~1.8 AE caused serious disturbance of total rock U-Pb and Rb-Sr systems. Therefore these systems do not provide any precise age information for the granulite facies migmatites. For the amphibolite facies migmatites of Vester\u00e5len both Sm-Nd, Rb-Sr, and Pb-Pb total rock systems give model ages of ~2.6 AE.
\r\n\r\nSm-Nd and Rb-Sr isotopic data for continental crust, depleted and undepleted mantle, have been used to evaluate both models and yield young mean ages for the mass of the continental crust of 1.8 AE and 1.5 AE for Model I and Model II, respectively. Both models also suggest that the rate of growth of the continents for the last 0.5 AE is much less than the average growth rate. The young mean age of the continents implies either rapid refluxing of crustal materials to the mantle in the period from 4.5 AE to 3.6 AE or that very little early crust ever formed. Mass balance calculations for both models show that the continents were only formed from ~30% of the total mantle leaving 70% of the mantle as undepleted. The major difference in the two models lies in the difference in the compositions of newly derived crust. For Model I the trace element concentrations in new additions to the crust is constant and the isotopic values are those of the undepleted mantle reservoir in agreement with recent Nd isotopic studies. Model II implies that new additions to the continents have the isotopic characteristics of the depleted mantle and that the concentrations of Rb, U, Ba and other highly incompatible trace elements in newly added material have changed by a factor of ~10 through time. There is no evidence, however, for such a large change in the concentration of these elements with time.
" }, { "name": "Jeanloz, Raymond", "degree": "PhD", "year": "1980", "title": "Physics of Mantle and Core Minerals", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07072023-223914164", "creators": [ { "name": { "family": "Jeanloz", "given": "Raymond" }, "id": "Jeanloz-Raymond", "display_name": "Jeanloz, Raymond" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/dzss-k041", "abstract": "Shock-wave equation-of-state (Hugoniot) data for initially porous and nonporous samples of iron provide experimental support for theoretically calculated properties of the earth's core, and show that whereas both densities and bulk moduli in the outer core are less than those of Fe under equivalent conditions (by about 10% and 12% respectively) their gradients with pressure are consistent with gross chemical homogeneity through the outer core; simple dynamic models of the core are allowed. New Hugoniot data for w\u00fcstite show that oxygen (~11 wt. %) can be the element which reduces the density of the outer core below that of Fe. The properties of the inner core are consistent with those of iron, suggesting that the inner core-outer core boundary is both a phase and a compositional boundary. The minimum estimated temperature at the top of the outer core is ~2800K, whereas subsolidus phase equilibria of olivine indicate a temperature near 2000K in the transition zone. Hugoniot data for porous and nonporous MgO and SiO\u2082 (phases considered representative of the lower mantle) provide an experimentally\u00ad constrained (adiabatic) geothermal gradient through the lower mantle which implies the presence of one or (for a more consistent result) more thermal boundary layers in the lower mantle. These suggest that the core is a major heat source for the mantle and that a barrier to convection occurs in (or near the top of) the lower mantle: a chemical discontinuity would be a likely cause. This inference is consistent with new shock\u00ad wave data for Cao which show that calcium could be substantially enriched in the lower mantle, as suggested by inhomogeneous accretion theories. A thermal equation of state is determined for anorthite from porous and nonporous Hugoniot data which, however, show that this refractory mineral can probably not be a major Ca-bearing phase in the lower mantle, except perhaps near the core-mantle boundary. Diamond-cell and Hugoniot data show that CaO undergoes a B1/B2 transition at 70 GPa with properties well predicted theoretically. FeO undergoes a similar transition (at ~70 GPa) and these results suggest that transformation in magnesiow\u00fcstite may be important in the lowermost mantle. New Hugoniot data for bronzite are combined with previous shock-wave measurements for olivines and pyroxenes. These data are consistent with static high\u00ad pressure results, but suggest the occurrence of post-perovskite phases (density ~5% greater than perovskite) and they also provide evidence of nonequilibrium effects under shock to pressures above 100 GPa. Spectroscopic and microscopic studies of shock-compressed olivines support this evidence: the structure of olivine achieved under shock is apparently far from equilibrium, as is indicated by phase-transformation theory. Although the bulk properties measured under shock are consistent with the attainment of thermodynamic equilibrium, these properties apparently represent highly transient and nonequilibrium states." }, { "name": "Lyzenga, Gregory Allen", "degree": "PhD", "year": "1980", "title": "Shock Temperatures of Materials: Experiments and Applications to the High Pressure Equation of State", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08032004-150047", "creators": [ { "name": { "family": "Lyzenga", "given": "Gregory Allen" }, "id": "Lyzenga-Gregory-Allen", "display_name": "Lyzenga, Gregory Allen" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "appliedphys" ], "doi": "10.7907/VSBK-ZA43", "abstract": "The experimental determination of temperatures in the high-pressure shocked state of condensed matter provides a useful supplement to equation-of-state models derived from Hugoniot measurements. An optical pyrometry technique has been developed to obtain temperature measurements during impact-driven shock wave experiments with solid and liquid samples at pressures near 100 GPa. Experimental results confirm that throughout moderate ranges of shock pressure amplitude, transparent dielectrics emit thermal radiation from the region of the shock front, with a spectrum which is characteristic of the Hugoniot state temperature. Shock temperatures in sodium chloride crystals have been measured in the pressure range 70-105 GPa. The observed temperatures, between 4000 and 8000 K, are in agreement with the results of earlier determinations and with calculations assuming the occurrence of shock-induced melting. Results of experiments to measure shock temperatures in metallic silver include a successful measurement of 5950 K at a pressure of 185 GPa. This result is consistent with the melting of silver under shock, with a melting pressure dependence described by the Lindemann criterion.
\r\n\r\nShock temperature measurements in silica (SiO2) have produced anomalous results suggestive of melting occurring in the stishovite phase near 100 GPa pressure and 4700 K temperature. Experimental measurements with [alpha]-quartz and fused silica samples extend from pressures of approximately 60 GPa to 140 GPa, with shock temperatures between approximately 4500 K and 7000 K. The experimental data allow quantification of the thermodynamic relations among silica phases, including heats of transition and the Gruneisen parameter. Shock temperatures in single crystal forsterite (Mg2SiO4) between pressures of 150 GPa and 175 GPa range from 4500 K to 4950 K, a result which is consistent with occurrence of a polymorphic solid state transition accompanied by a substantial heat of transition (~1.5 MJ/kg). These results have potentially important implications for solid earth geophysics, and knowledge of the melting curves of candidate minerals of the earth's mantle provides some constraints on the geotherm.
\r\n\r\nHugoniot temperatures have been measured in liquid water between approximately 50 GPa and 80 GPa, with results ranging from 3500 K to 5400 K. The observed temperatures are well reproduced by theoretical calculations assuming a constant specific heat model, but further work is required to characterize fully the thermal variation of H2O properties at high temperature. Compression measurements in pressure-volume states other than Hugoniot shock states and, in particular, in states of compression at constant entropy can provide both independent thermal equation-of-state information and the properties of high-density condensed phases inaccessible to shock wave experiments. Numerical calculations have been carried out for hypothetical experiments on water as well as carbon dioxide and liquid molecular hydrogen. The results of these calculations indicate that various experimental impact configurations may be employed to convert shock compression into isentropic compression, with pressures on the order of 100 GPa attained via impact velocities of a few kilometers per second. In the case of water, a net entropy production of a few percent of the Hugoniot entropy at the same pressure is predicted on the basis of these calculations.
" }, { "name": "McCulloch, Malcolm Thomas", "degree": "PhD", "year": "1980", "title": "Part I. Sm-Nd and Rb-Sr Chronology of Crustal Formation. Part II. Ba, Nd and Sm Isotopic Anomalies in the Allende Meteorite", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11152023-171559514", "creators": [ { "name": { "family": "McCulloch", "given": "Malcolm Thomas" }, "id": "McCulloch-Malcolm-Thomas", "display_name": "McCulloch, Malcolm Thomas" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/hnt7-9586", "abstract": "This thesis is divided into two parts. The first part has as its theme the chronology of crustal formation. The times at which new segments of crust were formed has been ascertained by using Sm-Nd and Rb-Sr isotopic systematics, together with plausible assumptions regarding the geochemical evolution of the crust and mantle. The general approach that has been used is to assume that the differentiation processes which produce magmatic rocks occur with a marked chemical fractionation of the Sm/Nd and Rb/Sr ratios relative to the source region. It is then the time of this chemical fractionation which has been dated. This approach is valid insofar as the dominant contribution to the crust comes from the emplacement of magmatic rocks derived from a \"uniform\" mantle reservoir.
\r\n\r\nSm-Nd studies of early Archean complexes from the Minnesota River Valley, Labrador, and the Pilbara of Western Australia have shown that these rocks were derived at ~ 3.6 AE from a mantle with a time\u00ad average Sm/Nd ratio approximately equal to that in chondrites (CHUR). These results, together with a 3.6 AE Sm-Nd model age from a tonalitic gneiss in northern Michigan, confirm that this time period marks one of the earliest episodes of major continental crustal formation on the earth.
\r\n\r\nIn contrast to the apparent uniformity of Sm/Nd in the mantle of the earth, many lunar magmatic rocks have initial \u00b9\u2074\u00b3Nd/\u00b9\u2074\u2074Nd ratios which indicate variability in the Sm/Nd ratios of their source reservoirs of up to 60%. These highly fractionated reservoirs must have formed within about 200 m.y. after the accretion of the moon. The Sm-Nd data on highland breccias and KREEP samples indicate a low Sm/Nd ratio for these samples which was also plausibly established early in lunar history and is complementary to the early production of high Sm/Nd mare basalt source regions. The contrast between the lunar and terrestrial Nd isotopic data implies a grossly different early differentiation history for these two planets.
\r\n\r\nA study of the Nd, Sr, and O isotopic characteristics of the Samail Ophiolite is also presented. This complex represents oceanic crust that was abducted onto the Arabian continental margin during late Cretaceous times. Using the Sm-Nd method, internal isochrons were obtained from three gabbros establishing a Cretaceous crystallization age for the Samail Ophiolite. These results appear to be highly consistent in spite of extensive hydrothermal exchange which has altered the primary \u2078\u2077Sr/\u2078\u2076Sr and \u00b9\u2078O/\u00b9\u2076O ratios. Gabbros from Ibra give an age of 130 \u00b1 12 m.y., and a gabbro in the northern part of Oman gives an age of 100 \u00b1 20 m.y. These results show that the Sm-Nd technique can be used to determine crystallization ages and initial Nd ratios of relatively young, Mesozoic and Cenozoic mafic complexes.
\r\n\r\nIn part two of this thesis, isotopic anomalies are reported for Ba, Nd, and Sm in two inclusions from the Allende meteorite. These inclusions are typical Ca-Al-rich objects associated with early condensates from the solar nebula but have distinctive O and Mg isotopic anomalies of the FUN type. Sample Cl shows \u00b9\u2074\u2074Sm enrichments and a depletion in \u00b9\u00b3\u2075Ba of 2 parts in 10\u2074 and normal Nd. Sample EKl-4-1 shows large positive excesses in the unshielded isotopes \u00b9\u00b3\u2075Ba and \u00b9\u00b3\u2077Ba of 13.4 and 12.3 parts in 10\u2074, respectively, The Nd and Sm isotopic composition in EKl-4-1 is highly aberrant in at least five isotopes The Ba, Sm, and Nd anomalies in EKl-4-1 can be explained by a model of r-process addition. From the observations of \u00b9\u2074\u2074Sm isotopic anomalies in Cl, it is inferred that the p-processes is decoupled from the r-process. All these anomalies are found to be uniform between coexisting mineral phases. These observations show the existence of substantial isotopic anomalies in refractory elements in the neighborhood of Xe and extend the range of elements showing isotopic effects to O, Ne, Si, Mg, Ca, Sr, Kr, Xe, Ba, Sm, and Nd. These observations, in conjunction with the presence of \u00b9\u2070\u2077Pd (\u03c4\u00bd = 6.5 x 10\u2076 yrs) and \u00b2\u2076Al (\u03c4\u00bd = 7 x 10\u2075 yrs), are interpreted as the result of a nearby supernova explosion which produced elements over a wide mass range and injected them into the early solar nebula shortly before condensation.
" }, { "name": "Yapp, Crayton Jeffery", "degree": "PhD", "year": "1980", "title": "The Variations and Climatic Significance of D/ H Ratios in the Carbon-Bound Hydrogen of Cellulose in Trees", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:08132014-153838558", "creators": [ { "name": { "family": "Yapp", "given": "Crayton Jeffery" }, "id": "Yapp-Crayton-Jeffery", "display_name": "Yapp, Crayton Jeffery" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "role": "member", "display_name": "Burnett, Donald S." }, { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "member", "display_name": "Lowenstam, Heinz A." }, { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "member", "display_name": "Patterson, Clair C." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." } ], "option_major": [ "geochem" ], "doi": "10.7907/FFSK-YC27", "abstract": "The \u03c3D values of nitrated cellulose from a variety of trees\r\ncovering a wide geographic range have been measured. These measurements\r\nhave been used to ascertain which factors are likely to cause \u03c3D\r\nvariations in cellulose C-H hydrogen.
\r\n\r\nIt is found that a primary source of tree \u03c3D variation is the\r\n\u03c3D variation of the environmental precipitation. Superimposed on this\r\nare isotopic variations caused by the transpiration of the leaf water\r\nincorporated by the tree. The magnitude of this transpiration effect\r\nappears to be related to relative humidity.
\r\n\r\nWithin a single tree, it is found that the hydrogen isotope\r\nvariations which occur for a ring sequence in one radial direction may\r\nnot be exactly the same as those which occur in a different direction.\r\nSuch heterogeneities appear most likely to occur in trees with asymmetric\r\nring patterns that contain reaction wood. In the absence of reaction\r\nwood such heterogeneities do not seem to occur. Thus, hydrogen isotope\r\nanalyses of tree ring sequences should be performed on trees which do\r\nnot contain reaction wood.
\r\n\r\nComparisons of tree \u03c3D variations with variations in local climate\r\nare performed on two levels: spatial and temporal. It is found that\r\nthe \u03c3D values of 20 North American trees from a wide geographic range\r\nare reasonably well-correlated with the corresponding average annual\r\ntemperature. The correlation is similar to that observed for a\r\ncomparison of the \u03c3D values of annual precipitation of 11 North\r\nAmerican sites with annual temperature. However, it appears that this\r\ncorrelation is significantly disrupted by trees which grew on poorly\r\ndrained sites such as those in stagnant marshes. Therefore, site\r\nselection may be important in choosing trees for climatic interpretation\r\nof \u03c3D values, although proper sites do not seem to be uncommon.
\r\n\r\nThe measurement of \u03c3D values in 5-year samples from the tree ring\r\nsequences of 13 trees from 11 North American sites reveals a variety\r\nof relationships with local climate. As it was for the spatial \u03c3D vs\r\nclimate comparison, site selection is also apparently important for\r\ntemporal tree \u03c3D vs climate comparisons. Again, it seems that poorly-drained\r\nsites are to be avoided. For nine trees from different \"well-behaved\"\r\nsites, it was found that the local climatic variable best\r\nrelated to the \u03c3D variations was not the same for all sites.
\r\n\r\nTwo of these trees showed a strong negative correlation with the\r\namount of local summer precipitation. Consideration of factors likely\r\nto influence the isotopic composition of summer rain suggests that\r\nrainfall intensity may be important. The higher the intensity, the\r\nlower the \u03c3D value. Such an effect might explain the negative\r\ncorrelation of \u03c3D vs summer precipitation amount for these two trees.\r\nA third tree also exhibited a strong correlation with summer climate,\r\nbut in this instance it was a positive correlation of \u03c3D with summer\r\ntemperature.
\r\n\r\nThe remaining six trees exhibited the best correlation between \u03c3D\r\nvalues and local annual climate. However, in none of these six cases\r\nwas it annual temperature that was the most important variable. In\r\nfact annual temperature commonly showed no relationship at all with\r\ntree \u03c3D values. Instead, it was found that a simple mass balance\r\nmodel incorporating two basic assumptions yielded parameters which\r\n\r\nproduced the best relationships with tree \u03c3D values. First, it was\r\nassumed that the \u03c3D values of these six trees reflected the \u03c3D values\r\nof annual precipitation incorporated by these trees. Second, it was\r\nassumed that the \u03c3D value of the annual precipitation was a weighted\r\naverage of two seasonal isotopic components: summer and winter. Mass\r\nbalance equations derived from these assumptions yielded combinations\r\nof variables that commonly showed a relationship with tree \u03c3D values\r\nwhere none had previously been discerned.
\r\n\r\nIt was found for these \"well-behaved\" trees that not all sample\r\nintervals in a \u03c3D vs local climate plot fell along a well-defined\r\ntrend. These departures from the local \u03c3D VS climate norm were defined\r\nas \"anomalous\". Some of these anomalous intervals were common to trees\r\nfrom different locales. When such widespread commonalty of an anomalous\r\ninterval occurred, it was observed that the interval corresponded to\r\nan interval in which drought had existed in the North American Great\r\nPlains.
\r\n\r\nConsequently, there appears to be a combination of both local and\r\nlarge scale climatic information in the \u03c3D variations of tree cellulose\r\nC-H hydrogen.
\r\n" }, { "name": "Baldridge, Warren Scott", "degree": "PhD", "year": "1979", "title": "Petrology and Petrogenesis of Basaltic Rocks and Their Inclusions: Studies from the Rio Grande Rift, the Roman Comagmatic Province, and Oceanus Procellarum", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:08012024-013913576", "creators": [ { "name": { "family": "Baldridge", "given": "Warren Scott" }, "id": "Baldridge-Warren-Scott", "display_name": "Baldridge, Warren Scott" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/zw9m-1m71", "abstract": "Mafic volcanism associated with the central Rio Grande rift is mainly of Pliocene and Pleistocene age. Volcanic rocks occur as isolated small shield volcanoes and cinder cone fields at or near the top of the graben fill. Structurally, the central Rio Grande rift consists of the Espanola and Albuquerque-Belen basins (grabens), offset from each other 50-60 km along the transverse Jemez lineament. The largest and most compositionally complex volcanic field (Cerros del Rio) occurs in this offset zone. On the basis of petrography and whole-rock chemistry, mafic lavas of this field can be divided into four groups: high-alkali olivine tholeiite, basaltic andesite, alkali olivine basalt, and basanite. All were erupted approximately contemporaneously. Quantitative modeling based on detailed phase chemistry shows that none of these lavas can be related to each other by any simple processes involving observed phenocryst and xenocryst phases.
\r\n\r\nLatite-andesite, also present in this field, is derived from basaltic andesite by subtraction of about 35 percent of olivine, pyroxene, and calcic plagioclase, and by addition of 17 percent of xenocrystic quartz and sodic plagioclase. Quartz and plagioclase occur as single crystals or as single phase aggregates; quartz rarely has a euhedral habit. These features suggest that quartz and plagioclase may be relict high- pressure phenocrysts. Thus, basaltic andesite magma bodies, residing in independent crustal reservoirs, may evolve by gravitative differentiation. The lighter, relict high-pressure quartz and sodic plagioclase phenocrysts are concentrated at the tops of these reservoirs by flotation simultaneously as the heavier olivine, pyroxene, and calcic plagioclase sink.
\r\n\r\nLavas from the northern Albuquerque-Belen basin consist of lower alkali olivine tholeiite, similar to basalt of the northern rift. Those from the central Albuquerque-Belen basin consist of olivine tholeiite,\r\nbasaltic andesite, and alkali olivine basalt of relatively restricted compositional range.
\r\n\r\nPre-Pliocene volcanism occurred mainly in the upper Oligocene/lower Miocene and in the late Miocene. The earlier phase of volcanism erupted lavas ranging in composition from olivine nephelinite to quartz tholeiite, while the later phase erupted both alkali olivine and tholeiitic basalts. Hence no well-defined change in magma composition occurred with time.
\r\n\r\nExperimental studies suggest that the olivine tholeiite was derived from >18% partial melting of spinel pyrolite at about 35 km and the alkali olivine basalt and basanite from approximately 10% partial\r\nmelting at 50-70 km. Thermodynamic calculations emphasize the hazards of inferring pressure (depth) and temperature of origin from basaltic lavas which are not primitive. The distribution of parental magmas suggests a model in which a transverse shear zone taps a sub-crustal diapir and bleeds magmas from various depths between 35 and 70 km. In contrast, the \"normal\" genesis of basaltic magmas along the rift occurs at the top of the diapir immediately beneath the base of the crust.
" }, { "name": "Butler, Rhett Giffen", "degree": "PhD", "year": "1979", "title": "Seismological Studies Using Observed and Synthetic Waveforms", "advisor": "Helmberger, Donald V.; Anderson, Donald L.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:07112024-201950214", "creators": [ { "name": { "family": "Butler", "given": "Rhett Giffen" }, "id": "Butler-Rhett-Giffen", "display_name": "Butler, Rhett Giffen" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/bfn4-vz23", "abstract": "Application of waveforms to four topics in seismology is pre\u00adsented. Detailed waveform analyses of three earthquakes are reported in Chapter I. The Oroville, California earthquake of 8/1/75 has a north-south striking, westward dipping normal fault mechanism with a small component of left-lateral motion. A surface wave seismic moment\r\nof 1.9 x 10\u00b2\u2075 dyne-cm. is a factor of 3 greater than the teleseismic\r\nbody wave determination. Slow deformations on the Oroville fault may explain the enhanced excitation of the surface waves. The Tangshan, China earthquake of 7/27/76 and its principal aftershock represent a complex intraplate event sequence with strike-slip, normal, and thrust\r\nfaulting. The main shock was a bilateral strike-slip event, striking\r\nN40\u00b0E, with a seismic moment of 1.8 x 10\u00b2\u2077 dyne-cm. Associated thrusting occurred concurrently with the main shock. The principal aftershock was an oblique, normal double event, striking approximately perpendicular\r\nto the main event, with a seismic moment of 8 x 10\u00b2\u2076 dyne-cm. The 4/26/73\r\nHawaii earthquake is a subcrustal, double event. The events are consistent with left-lateral strike-slip motion on en echelon southward dipping faults. Evidence of lateral heterogeneity in the Hawaii source region\r\nis suggested by incompatibility between and azimuthal amplitude anomalies associated with the P and SH data.
\r\n\r\nIn Chapter II shear travel times are obtained by a waveform correla\u00adtion technique. A total of 87 SH travel-times are measured from the 1968 Borrego Mountain, California and 1973 Hawaii earthquakes. The Bor\u00adrego data have a trend toward faster travel times at 40\u00b0, but show an overall 6 second slow baseline with respect to the Jeffreys-Bullen Table. The Hawaii data contain large azimuthal scatter suggesting lateral heterogeneity in the near source region. The shear phase SS is modeled using a Hilbert transform to mimic distortion incurred at an internal caustic in its propagation. Significant variation is found in SS travel time residuals for paths reflected under the Cana\u00addian shield. A correlation of the variation with tectonic sub-pro\u00advince is suggested. Differential travel times of multiple ScS deter\u00ad mined by waveform cross-correlation are shown to contain a systematic bias late with respect to conventional visual onset timing methods.\r\nThe timing bias for Scs\u2082-ScS differential times ranges between 2.2 and\r\n3.8 seconds late, and depends upon the average Q_\u03b2 of the mantle.
\r\n\r\nIn Chapter III direct body waves and fundamental surface waves are calculated for a credible, hypothetical great earthquake on the San Andreas fault. Amplitudes and durations of long period ground motion (T > 1 second) are found for a receiver in downtown Los Angeles.\r\nCalculations are carried out for various epicenters, dislocation profiles, and time functions. Ground motion from Love radiation is found to be most important with peak-to-peak amplitudes up to 14 cm. and durations up to 5 minutes.
\r\n\r\nChapter IV presents a study of short period P wave amplitudes from nuclear explosions in the Soviet Union recorded by WWSSN stations in the United States. Thirty-four events in five test sites are analyzed. A well-defined amplitude pattern is obtained for each source region. A pattern of lateral variation of amplitude in the United States is obtained for a northern azimuth of approach. Stations in the western United States do not show systematically lower amplitudes than eastern stations, in contrast to previous studies. A preliminary data set of earthquakes in the Kurile Islands and South America indicate the amplitude pattern in the U.S. varies azimuthally.
" }, { "name": "Chung, Wai-Ying", "degree": "PhD", "year": "1979", "title": "Part I: Variation of Seismic Source Parameters and Stress Drop within a Descending Slab as Revealed from Body-Wave Pulse-Width and Amplitude Analysis. Part II: A Seismological Investigation of the Subduction Mechanism of Aseismic Ridges", "advisor": "Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:07072024-191031375", "creators": [ { "name": { "family": "Chung", "given": "Wai-Ying" }, "id": "Chung-Wai-Ying", "display_name": "Chung, Wai-Ying" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/79jx-8334", "abstract": "In Part I, a least squares searching technique has been developed to estimate the source dimensions of intermediate and deep focus earthquakes from the azimuthal variation of body-wave pulse-width.\r\nModes of rupture propagation, seismic moment, stress drop and orientation of the slip plane can also be determined if both pulse-width and amplitude data are used, With this method, 17 intermediate and deep earthquakes in the Tonga-Kermadec arc system have been investigated\r\nin order to determine changes in the state of stress and source properties within a subducting slab. Three different modes of rupture, unilateral, bilateral, and circular faults, are compared and tested\r\nagainst observations, Results indicate that the unilateral fault is the best model for most of the earthquakes studied, the bilateral fault is the best model for some shocks, but the circular fault, in no cases, is better than the other two fault models. Stress drops of intermediate and deep focus earthquakes vary within a very large range, from 20 bars to 4617 bars, and change significantly with focal depth.\r\nTwo high stress drop regions at depths about 360 km and 640 km seem to correlate with the depth ranges in which phase transitions occur.\r\nA relative minimum of stress drop is found at about 450 to 560 km\r\nwhere the annual number of earthquakes is particularly high, Earthquakes which occurred at the northern end of Tonga arc, where the Benioff zone is laterally bent, show systematically higher stress drops than other events at comparable depths but away from the bend. Also events in\r\nlow seismicity regions appear to have higher stress drops than those in high seismicity regions. Apparent stress is found to be smaller than half of the stress drop, and the upper bound of seismic efficiency appears to decrease as depth increases. A comparison of deep and shallow earthquake source parameters is also made.
\r\n\r\nIn Chapter l of Part II, the subduction of the D'Entrecasteaux fracture zone-aseismic ridge system in the New Hebrides island arc is investigated on the basis of the focal process of the New Hebrides earthquake of January 19, 1969 (m_b = 6.4, h = 107 km), mechanisms\r\nof some related events, seismicity, and regional tectonics. A notable feature of this island arc is the discontinuity of the New Hebrides Trench in the central New Hebrides where the ridge\u00ad\r\nfracture zone is subducting and intersecting the arc. The 1969 New Hebrides earthquake occurred along the subducted portion of the\r\nfracture zone and is characterized by unusual wave forms with remarkably large excitation of long period waves. Body-wave and surface wave analyses reveal the earthquake was a complex event with a change of fault strike during the rupture process. The location and mechanism\r\nof this earthquake suggest that the D'Entrecasteaux fracture zone structurally extends to the east of the Trench. This structural boundary at depth seems to be reflected in the spatial distribution of two earthquake swarms which are bounded sharply at the latitude of 15.2\u00b0S. At the extension of the ridge-fracture zone, the activity of intermediate-depth earthquakes, which are characterized by a very consistent pattern of down-dip extensional mechanism, is much higher and their depths are systematically shallower than in the adjacent regions. These features can be interpreted as a consequence of subduction of a buoyant ridge and the resultant increase in the extensional stress at the intermediate depths of the sinking slab. Fault-plane solutions of 22 earthquakes suggest that the subduction of aseismic ridges in the New Hebrides is characterized by high angle thrusts. The lithospheres on the two sides of the D'Entrecasteaux fracture zone under the arc subduct more or less independently and generate alternating left-lateral and right-lateral earthquakes along the subducted portion of the fracture zone.
\r\n\r\nIn Chapter 2, tectonic features associated with a subducting fracture zone-aseismic ridge system in the New Hebrides island arc are investigated. Several notable features including a discontinuity of the trench, peculiar locations of two major islands (Santo and Malekula), regional uplift, and the formation of a basin are interpreted as a result of the subduction of a buoyant ridge system. The islands of Santo and Malekula are probably formed from uplifted mid-slope basement high while the interarc basin of this particular\r\narc is probably a subsiding basin instead of a basin formed by backarc opening. The situation can be modeled by using a thin elastic half plate overlying a quarter fluid space with a vertical upward loading applied at the plate edge. This model is consistent with topographic and geophysical data. This study suggests that subduction of aseismic ridges can have significant effects on tectonic features at consuming plate boundaries.
\r\n\r\nIn Chapter 3, seismicity near locations of aseismic ridge sub\u00ad duction has been investigated for five seismic regions: New Hebrides, Bonin-Mariana, Tonga-Kermadec, Peru and Northern Chile. The maximum focal depth of intermediate-depth earthquakes beneath areas of aseismic ridge subduction is generally shallower than that on either side of the subducting ridge. This variation of focal depth in some cases forms a well-defined gap or quiet zone for intermediate-depth events. This phenomenon may be a consequence of differential subduction and difference in material properties between an aseismic ridge and the rest of the oceanic plate. Although at locations of aseismic ridge subduction large shallow earthquakes occur less frequently compared\r\nwith the adjacent regions, small shallow earthquake activity is not always reduced. In addition, there is a high correlation between trench discontinuities and aseismic ridge subduction suggesting that a trench can be interrupted and divided into two sections by ridge subduction if\tthe buoyant force associated with the ridge is strong enough.
" }, { "name": "Dobrovolskis, Anthony Robert", "degree": "PhD", "year": "1979", "title": "The Rotation of Venus: Part I. Atmospheric Tides. Part II. Obliquity and Evolution", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06142024-220229869", "creators": [ { "name": { "family": "Dobrovolskis", "given": "Anthony Robert" }, "id": "Dobrovolskis-Anthony-Robert", "display_name": "Dobrovolskis, Anthony Robert" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/0g1y-7e13", "abstract": "Earth-based radar observations reveal that the surface of Venus rotates very slowly in the retrograde sense, Tides raised by the sun in the body of Venus tend to slow its rotation further. The spin of Venus might be in a steady state if thermal tides in the atmosphere balance the tidal torque on the crust. Part I of this dissertation presents a quantitative theory of atmospheric tides applicable to Venus. It is found that the thermal tide is capable of maintaining the rotation of Venus in its current state indefinitely.
\r\n\r\nPart II examines the effects of obliquity, the frequency\u00ad\r\ndependence of the tides, core-mantle coupling, possible resonances, and other phenomena. It appears most likely that Venus originated with an obliquity greater than 90\u00b0.
" }, { "name": "Dvorak, John Joseph", "degree": "PhD", "year": "1979", "title": "Analysis of Small Scale Lunar Gravity Anomalies: Implications for Crater Formation and Crustal History", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:06072024-205240041", "creators": [ { "name": { "family": "Dvorak", "given": "John Joseph" }, "id": "Dvorak-John-Joseph", "display_name": "Dvorak, John Joseph" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/zpdn-2n37", "abstract": "Anomalies in the local gravity field arise from lateral density variations within a planetary body. Hence, a consideration of the nature of these anomalies can be used to infer the subsurface structure and, from this, possibly constrain and characterize the processes which formed these features. Such a consideration is given here to the local gravity anomalies on the Moon.
\r\n\r\nThe lunar free-air gravity data consist of the line-of-sight (i.e., Earth-to-spacecraft) component of the accelerations undergone by a spacecraft in a low lunar orbit. In this analysis the acceleration or gravity profiles across a feature of interest are corrected for the topographic contribution of the lunar surface to the local gravity field to obtain the Bouguer gravity profiles. The availability of lunar features for this analysis is mainly constrained by the nearside areal coverage of low altitude orbiting lunar spacecraft.
\r\n\r\nA total of twenty-one features are analyzed here of which all but two are of impact origin; these two exceptions are probable sites for intrusive and extrusive igneous activity on the Moon. The impact features have been divided into two major groups on the basis of age with the older group further subdivided into relatively unfilled craters and very shallow craters and also including a small multiringed basin.
\r\n\r\nThe young lunar craters, which range in diameter from 32 to 135 kilometers, have negative Bouguer gravity anomalies (i.e., mass deficiencies or low density regions) associated with them. Presumably, these low density regions represent material brecciated and crushed by the impact events which formed these craters. Calculations reveal a systematic variation in the magnitude of the total mass deficiency with increasing crater size and a comparison of lunar and terrestrial impact features shows that the magnitude of this mass deficiency is proportional to the cube of the crater diameter. Furthermore, studies of terrestrial impact structures indicate that the major contribution to these negative Bouguer anomalies is most likely due to a large lens of low density material extending laterally to approximately the crater rim crest and vertically to a depth of roughly one-third the rim diameter. Also based on studies of many terrestrial impact features, the maximum depth of the transient cavity associated with these lunar craters, as inferred from the apparent vertical extent of brecciation, was roughly one-fourth the crater rim diameter. This depth possibly also corresponded to the maximum depth of excavation of at least a small amount of the lunar crust by these impact events.
\r\n\r\nIn all but one case, the old unfilled lunar craters have distinctly different Bouguer anomalies from the young lunar craters. With the exception of the crater Piccolomini which follows the trend for the younger craters, all of the remaining unfilled old lunar craters have, within the uncertainties of this analysis, zero Bouguer anomalies. The cause for this change in the value of the Bouguer gravity is, of course, expected to be related to the greater age and more modified appearance of these craters. A likely possibility is that the porosity initially produced by the impact events which formed these older craters has been removed by the intrusion of igneous material, roughly contemporaneous with the emplacement on the surface of the lunar mare basalts. A second possibility is that the original porosity has been removed by compaction of the lunar crust during the seismic shaking which accom\u00adpanied the formation of the last lunar multiringed basins, however, it is difficult to evaluate this mechanism since the efficiency at this scale is unknown.
\r\n\r\nThe two shallow lunar craters for which it is possible to determine the Bouguer gravity have slight negative anomalies. These particular craters are also filled by light plains units which have been inter\u00adpreted to be ejecta from later multiringed basin impacts. These\r\nslight negative anomalies are probably due to the higher porosity of the basin ejecta which now almost completely fills these craters.
\r\n\r\nThe Bouguer gravity of a small multiringed basin, Grimaldi, has also been determined. Spacecraft free-air gravity data reveal a mascon associated with the inner ring of this structure. The topo\u00ad graphic correction to the local gravity field indicates a maximum Bouguer anomaly of +90 milligals at an altitude of 70 kilometers. Approximately 20% of this positive Bouguer anomaly can be accounted for by the mare material lying within the inner ring. It is proposed, from a consideration of the Bouguer gravity over large lunar craters comparable in size to Grimaldi, that the remaining positive anomaly is due to a plug of high density lunar mantle material centrally uplifted by the inward collapse of material which resulted in the formation of the concentric outer scarp. In addition, a ring of low density material, possibly ejecta deposited by the formation of Grimaldi, is required to fully reproduce the Bouguer gravity signature across this basin. A similar structure to the one described here for Grimaldi has been previously proposed for the Orientale Basin.
\r\n\r\nThe two non-impact features, Lamont and Marius Hills, have positive Bouguer anomalies. Since these are probable sites for extrusive igneous activity, that is, possible source areas for the surrounding mare material, these positive gravity anomalies are interpreted to be the result of intrusive activity within the lunar crust, much more intensive activity than the intrusion of material proposed beneath the old lunar craters also analyzed here. At Lamont, located in western Tranquillitatis, the mare ridge pattern and local topography suggest a general subsidence of this region. The gravity data indicate that the density anomaly extends beyond the inner circular ring of\r\nmare ridges which define the Lamont feature. The occurrence of a magnetic high at Lamont further supports the presence of a major intrusive body probably emplaced early in lunar history. Several other local gravity or magnetic highs in the lunar mare are also interpreted as the result of intrusive activity. At Marius Hills, an isolated plateau in Oceanus Procellarum, the positive Bouguer anomaly is much smaller than at Lamont and is localized in the northeast corner of the plateau.
" }, { "name": "Everson, Joel Earl", "degree": "PhD", "year": "1979", "title": "Regional Variations in the Lead Isotopic Characteristics of Late Cenozoic Basalts from the Southwestern United States", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04152020-165415853", "creators": [ { "name": { "family": "Everson", "given": "Joel Earl" }, "id": "Everson-Joel-Earl", "display_name": "Everson, Joel Earl" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/2dp3-4b64", "abstract": "Over a hundred new analyses on late Cenozoic basalts characterize and delimit regional patterns of lead isotopic behavior in the southwestern United States. The lead isotopic systematics of these volcanic rocks can be divided into three broad regional groups: one characteristic of Colorado Plateau (CP) volcanic fields, a second found in many areas of the Basin and Range (BR) province, and in neighboring areas along the Pacific coast, and a third peculiar to an area in southern Nevada (SN) Colorado Plateau volcanic rocks have generally unradiogenic leads (\u00b2\u2070\u2076Pb/\u00b2\u2070\u2074Pb \u2264 18.7), locally exhibit large variations in isotopic ratio, and define linear arrays (secondary isochrons) on a \u00b2\u2070\u2076Pb/\u00b2\u2070\u2074Pb-\u00b2\u2070\u2077Pb/\u00b2\u2070\u2074Pb diagram. Basin and Range type samples are characterized by relatively radiogenic leads (18.7 \u2264 \u00b2\u2070\u2076Pb/\u00b2\u2070\u2074Pb \u2264 19.6) and, comparatively, a uniformity of isotopic composition in local areas. Southern Nevada leads are somewhat unradiogenic (18.2 \u2264 \u00b2\u2070\u2076Pb/\u00b2\u2070\u2074Pb \u2264 18.5), appear to display a local uniformity in isotopic composition, and lie off the Colorado Plateau secondary isochrons. Literature sources indicate that southern Nevada basalts are also characterized by relatively high \u2078\u2077Sr/\u2078\u2076Sr ratios (.7060-.7080).
\r\n\r\nThe isotopic properties of volcanic rocks from each of these regions do not appear to record crustal contamination. The general uniformity of isotopic characteristics over large areas (hundreds to thousands of kilometers in size) of the Southwest suggests a fundamental consistency in volcanic source region character over comparable dimensions. Isotopic variations within each province seem to record smaller scale source region heterogeneities.
\r\n\r\nIsotopic variability observed within individual Colorado Plateau volcanic fields may be interpreted in terms of kilometer-sized mantle heterogeneities developed approximately 1.4-1.8 by ago. These heterogeneities may record the effects of magma extraction from mantle sources during the primary generation of Precambrian crystalline basement and the formation of the continental lithosphere. A rough but apparently significant correlation between the chemical and lead isotopic compositions of CP basalts suggests that the mantle of the continental lithosphere may be crudely \"stratified\" in its lead isotopic composition, with the uppermost mantle generally less radiogenic in lead (and by inference more depleted in uranium relative to lead) than the deeper lithosphere. Isotopic differences distinguishable between different portions of the Colorado Plateau may relate to heterogeneities hundreds of kilometers in size which developed in different mantle domains prior to and in the course of continental lithosphere formation.
\r\n\r\nBasin and Range basalts have lead isotopic properties (and Sr and Nd isotopic compositions) similar to volcanic rocks from oceanic island and volcanic arc settings, suggesting a correspondence between BR volcanic source regions and \"oceanic\" mantle. Within the Basin and Range province \u00b2\u2070\u2076Pb/\u00b2\u2070\u2074Pb ratios tend to be rather uniform laterally for distances measured in hundreds of kilometers; this implies that the underlying mantle may be isotopically rather homogeneous for similar distances. One 200 km long section of the Rio Grande rift is characterized by CP type leads. This may possibly indicate that a large body of \"oceanic\" mantle has penetrated the continental lithosphere beneath this segment of the Rio Grande rift.
\r\n\r\nOlder (Pliocene and Miocene) calc-alkaline volcanic rocks from the Basin and Range province tend to display somewhat higher \u00b2\u2070\u2077Pb/\u00b2\u2070\u2074Pb ratios than the Quaternary alkaline basalts within each area of the Basin and Range province. This could suggest that adjustments in BR type source region characteristics continued very late into the Cenozoic era, perhaps in conjunction with changes in the tectonic environment.
\r\n\r\nSN type isotopic systematics resist a unique interpretation, but may reflect long term (of the order of a billion years or so) evolutionary characteristics of a source region in the mantle or the lower crust.
\r\n\r\nAlthough the different isotopic province boundaries appear to record discontinuities deep within the earth (most probably fundamental discontinuities in mantle character), they follow the trends of major geological and structural boundaries in the crust. The SN isotopic province, for example, appears to be associated geographically with a \"fundamental, west-trending, transverse crustal boundary\" (Eaton, 1975) which demarcates the northern and southern portions of the Basin and Range province. The Basin and Range - Colorado Plateau isotopic province boundary approximately follows the Mesozoic-early Tertiary Cordilleran foreland thrust belt and the limit of late Cenozoic normal faulting. Thus the BR-CP isotopic boundary appears to be geographically related to the boundary between tectonically unstable, \"orogenic\" areas of the Basin and Range province and Pacific border regions, and the more stable \"platform\" areas of the Colorado Plateau, Southern Rocky Mountains, and Great Plains.
\r\n\r\nBR type leads occur in some areas (notably southern Arizona and southeastern California) characterized by known Precambrian basement. These areas were presumably underlain originally by \"old\" mantle belonging to the continental lithosphere. The inferred presence of BR type, \"oceanic\" mantle beneath these regions during late Cenozoic times seems to imply a disruption of continental lithosphere and the emplacement of \"new\" oceanic mantle. The geographic association of Mesozoic and Cenozoic structural boundaries in the crust and the BR-CP isotopic boundary suggests that this mantle disruption may be related either to the compressional tectonism of Mesozoic-early Tertiary times or to the extensional tectonism of the late Cenozoic.
" }, { "name": "Furst, Marian Judith", "degree": "PhD", "year": "1979", "title": "The Use of Boron Concentrations in Fossil Materials as a Paleosalinity Indicator", "advisor": "Burnett, Donald S.; Lowenstam, Heinz A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05132024-183001142", "creators": [ { "name": { "family": "Furst", "given": "Marian Judith" }, "id": "Furst-Marian-Judith", "display_name": "Furst, Marian Judith" } ], "advisors": [ { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "advisor", "display_name": "Burnett, Donald S." }, { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/053m-sr84", "abstract": "The \u00b9\u2070B(n,\u03b1) \u2077Li nuclear reaction has been used in conjunction with alpha-sensitive plastic track detectors to determine boron concentrations in various biologically precipitated minerals. A correlation between the boron concentration in the water in which the precipitating organisms grew and the boron concentration in the materials analyzed was found in specimens of Mytilus edulis, related bivalves, diatoms, and siliceous sponge spicules. M. edulis shell boron concentrations in aragonite ranged from about 5 ppm in specimens from 5 \u2070/\u2080\u2080 salinity water to about 15 ppm in specimens from 35 \u2070/\u2080\u2080 salinity water. Salinities can not be distinguished quantitatively using carbonate shells beyond the general distinction of marine, brackish, or nearly-fresh water. Fossil shells showed evidence for some loss of boron from aragonite. Freshwater diatomites contained less than 10 ppm B, while marine diatomites and unconsolidated marine core samples contained about 100 ppm. Detailed studies of live\u00ad collected sponge spicules established that individual spicules larger than 20-25 microns in diameter can be analyzed, and that there is a correlation with water salinity for sponges from regions of low water temperature and high productivity. Measured concentrations ranged between nearly 0 for fresh-water sponges to 600-700 for marine sponges. However, spicules from sponges from tropical, low-productivity marine locations contained markedly less boron. The exact relationships\r\nbetween B concentration in the spicules and concentration in the water, temperature, nutrient supply, and food sources for the sponges are not known. Pleistocene spicules from deep-sea cores tended to contain somewhat less boron than might be anticipated by comparison with live-collected spicules based on present water temperatures and nutrient supplies. It is uncertain whether the lower concentrations are the result of diagenetic processes or the unknown effects of differences in the food supply and/or environmental conditions. Until the significance of the boron concentration in spicules is understood more fully, paleosalinity determinations will not be possible. If a relationship between boron content and water temperature or nutrient supply can be defined, it may be possible to use boron concentrations in spicules to trace oceanic circulation patterns in the past." }, { "name": "Gromet, L. Peter", "degree": "PhD", "year": "1979", "title": "Rare Earths Abundances and Fractionations and their Implications for Batholithic Petrogenesis in the Peninsular Ranges Batholith, California, USA, and Baja California, Mexico", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07252019-083750670", "creators": [ { "name": { "family": "Gromet", "given": "L. Peter" }, "id": "Gromet-L-Peter", "display_name": "Gromet, L. Peter" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/1X44-DN70", "abstract": "Rare Earth Element (REE) patterns of plutonic rocks across the Peninsular Ranges batholith vary systematically west to east, transverse to the long axis and structural trends of the batholith. Three major parallel elongate geographic regions are each defined by distinct REE pattern types. Rocks from the western region display slight light REE enrichment, flat heavy REE, and negative Eu anomalies. An abrupt transition to rocks with middle and heavy REE fractionated and depleted REE patterns with no or positive Eu anomalies occurs in the central region of the batholith. Further to the east a second transition to strongly light REE enriched rocks some of which have positive or negative Eu anomalies occurs. Some gabbros may show divergent patterns.
\r\n\r\nThese large variations are observed even in similar lithologies across the three regions and notably in tonalites, the major rock type of the batholith. The slopes of the REE patterns within rocks of each region are largely independent of rock type, and no consistent variations in REE abundances and Eu anomalies with lithology are noted with the exception of some gabbros. Most of the leucogranodiorites of the western region have larger negative Eu anomalies than nearby tonalites. Granodioritic rocks of the central and eastern regions may have positive, negative, or no Eu anomalies.
\r\n\r\nThese results are the first report of systematic variations in REE characteristics across a granitic batholith whose geologic setting at a convergent plate boundary has been established. Some similarities and contrasts to REE variations across modern volcanic arcs are noted. Along the westernmost margin of the batholith in northern Baja California, Mexico, leucotonalitic rocks of the San Telmo pluton display essentially flat REE patterns strongly resembling those observed for near-trench volcanic rocks. The REE patterns of quartz gabbros and tonalites of the western region correspond closely to those of circum-Pacific high-alumina basalts. The heavy REE depleted and fractionated patterns observed in the rocks of the central and eastern regions of the batholith do not have counterparts in oceanic island volcanic arcs, and few counterparts in continental margin volcanic arcs.
\r\n\r\nThe REE variations generally correlate with other transverse asymmetries in major petrologic and geochemical characteristics. The abrupt depletion and fractionation in the middle to heavy REE and elimination of negative Eu anomalies appear coupled to an increase in Sr concentration and a marked restriction in lithologic diversity. This transition occurs over a range of initial 87Sr/86Sr ratios. The light REE enriched rocks of the eastern region are distinguished from the central and western regions by higher initial ratios. Geographic discontinuities in \u03b418O and age distributions in the batholith correlate approximately with the REE discontinuities, but locally diverge by the dimensions of one or two plutons.
\r\n\r\nDeterminations of REE abundances in major and trace phases of a representative eastern region granodiorite indicate accessory sphene and allanite are the major reservoirs of REE in this rock. Hornblende is the only significant REE site in the major minerals, and in some batholithic lithologies it may be the dominant site. High-level crystal fractionations involving hornblende and accessory phases do not appear capable of producing the observed geographic characteristics. Contamination processes including upper crustal material also seem ruled out.
\r\n\r\nThe REE and other geochemical variations across the batholith appear to originate in deep-seated sources. Partial melting in source rocks in which assemblages rich in plagioclase give way laterally to garnet-bearing assemblages in source regions of broadly basaltic composition which are already zoned in light REE abundances, 87Sr/86Sr, \u03b418O, and possibly Sr content appears to account for most of the observed features. The geologic context of the source material remains largely undefined and may include mantle and crustal components. However, the source regions for all parts of the batholith must have bulk compositions and phase assemblages capable of producing the dominant tonalite and low-K2O granodiorite lithologies. This major constraint appears to strongly limit the amount of sialic crustal material permitted to be present in the source regions. The geometry of the convergent boundary appears to have determined the elongate form of the batholith, and, probably, the general alignment of all the geochemical variations along its length. The results of this study may be useful in comparing possibly related crust-forming processes and products in other orogenic-plutonic terrains.
\r\n\r\n" }, { "name": "Heaton, Thomas Harrison", "degree": "PhD", "year": "1979", "title": "Generalized Ray Models of Strong Ground Motion", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04302007-150812", "creators": [ { "name": { "family": "Heaton", "given": "Thomas Harrison" }, "id": "Heaton-Thomas-Harrison", "orcid": "0000-0003-3363-2197", "display_name": "Heaton, Thomas Harrison" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/4VEQ-8942", "abstract": "A method for synthesizing local ground displacement from a model consisting of a finite fault located within a layered half-space is demonstrated. The response of a three-dimensional fault is evaluated by integrating the responses of point shear dislocations over the fault plane (Green's function technique). The response of each point shear dislocation is evaluated by using generalized ray theory in conjunction with the Cagniard-de Hoop technique. A basic review of these methods is given. In general, the complete solution to a three-dimensional fault in a layered half-space is complex and computationally unwieldy. Various simplifying approximations, whose validity depends upon the source to receiver geometry and seismic frequency, are discussed. The records from three Southern California earthquakes of different magnitudes and source to receiver geometries are modeled and appropriate approximations are demonstrated.
\r\n\r\nThe smallest earthquake that is modeled is the largest earthquake (M 4.9) in the November, 1976 Brawley swarm. Long-period strong-motion instruments were located at distances of 33 km (IVC) and 36 km (ELC). The IVC record consists almost entirely of transversely polarized motion, whereas the ELC record contains an approximately equal proportion of transversely and radially polarized motion. A simplified shear wave velocity model was determined from the compressional wave refraction studies of Biehler, Kovach and Allen (1964). The epicentral location and focal mechanism (right-lateral strike-slip) computed from P wave first arrival studies were used to locate and orient a double-couple point source within the layered half-space. Essentially, the far-field time function and source depth were the only parameters without good independent constraints. A far-field time function with a duration of 1.5 seconds along with a source depth of 7 km was sufficient to model the first 25 seconds of transverse ground motion. Although it seems clear that faulting had finite dimensions, the source to receiver geometries and small source dimension make it possible to model this earthquake with a single point dislocation having the appropriate far-field time function. It appears that the effects of velocity structure on the propagation of long period SH waves are predictable in the Imperial Valley. A study of the synthetic Fourier amplitude spectra indicates that wave propagation effects should be included in studies of source spectra and seismic wave attenuation.
\r\n\r\nSeveral synthetic models are constructed to fit the first 40 seconds of transversely polarized displacement, as recorded at El Centro (ELC), of the April 9, 1968 Borrego Mountain earthquake (M 6.5). Unfortunately, there are complications involving the non-planar seismic velocity structures which lie between source and receiver. A simplified structure of a layer over a half-space is used to roughly approximate the effect of the thick sequence of sediments in the Imperial Valley. The beginning 10 seconds of the observed record is used to model the spatial and temporal distribution of faulting, whereas the remaining portion is used to determine the upper crustal structure based on surface-wave periodicity. A natural depth criterion is provided by comparing the amplitude of the direct arrival with the surface-wave excitations. Considerable non-uniqueness is present in the modeling process. If strong midcrustal seismic discontinuities are present, then it is possible to model the ground motion with a single point dislocation. Within the framework of a single layer over a half-space model, faulting of finite vertical extent is required, whereas the horizontal dimensions of faulting are not resolvable. A model which is also consistent with the teleseismic results of Burdick and Mellman (1976) indicates massive faulting near a depth of 9 km with a fast rise time producing a 10 cm displacement pulse of 1 second duration at El Centro. The faulting appears to slow down as it approaches the free surface. The moment is calculated to be approximately 7 x 10\u00b2\u2075 dyne-cm which is somewhat smaller than that found from teleseismic body waves by Burdick and Mellman (1976).
\r\n\r\nBecause of the special source to receiver geometries present for the Brawley and Borrego Mountain earthquakes, it is necessary only to model SH waves. Furthermore, near-field source terms can be neglected and problems associated with fault finiteness are relatively easy to deal with. This is not true in the case of modeling the strong-motion recordings of the February 9, 1971 San Fernando earthquake (M 6.5). Three-dimensional models of a finite fault located in a half-space are constructed to study the ground motions observed at JPL, Palmdale, Lake Hughes and Pacoima Dam. Since the duration of faulting is comparable to the travel times for various wave types, very complex interference of these arrivals makes a detailed interpretation of these waveforms difficult. By investigating the motion due to small sections of the fault, it is possible to understand how various wave types interfere to produce the motion due to the total fault. Rayleigh waves as well as S to P head waves are shown to be important effects of the free surface. Near-field source effects are also quite dramatic. Strong directivity is required to explain the difference in amplitudes seen between stations to the north and stations to the south. Faulting appears to have begun north of Pacoima at a depth of 13 km. The rupture velocity, which is near 2.8 km/sec in the hypocentral region, appears to slow to 1.8 km/sec at a depth of 5 km. Displacements on the deeper sections of the fault are about 2.5 meters. Fault offsets become very small at depths near 4 km and then grow again to 5 meters near the surface rupture. The large velocity pulse seen at Pacoima is a far-field shear wave which is enhanced by directivity. Peak accelerations at Pacoima are probably associated with the large shallow faulting. The total moment is 1.4 x 10\u00b2\u2076 ergs.
" }, { "name": "Johnson, Carl Edward", "degree": "PhD", "year": "1979", "title": "I. CEDAR - An Approach to the Computer Automation of Short Period Local Seismic Networks. II. Seismotectonics of the Imperial Valley of Southern California", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04232010-074317474", "creators": [ { "name": { "family": "Johnson", "given": "Carl Edward" }, "id": "Johnson-Carl-Edward", "display_name": "Johnson, Carl Edward" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/DBG9-3260", "abstract": "A real-time detection and recording system (CEDAR) is developed as a means of automating the acquisition and processing of data from short- period local networks. This system has been used for the past two years for the analysis of data from 150 stations in Southern California with an annual workload of about 7500 local events. Two minicomputers are used with one dedicated to the real-time detection and digital recording of local earthquakes while the other is used for timing, location, and data archiving based on interactive graphical techniques. The use of this system has substantially reduced the effort required for the routine analysis of local data. The discussion is kept at a general level so as to be useful to those setting up similar systems with somewhat different requirements. In support of the CEDAR system a magnitude scale, M_(CA), is developed that is particularly adapted to the needs of local digital seismic networks. The supporting algorithm is based on median absolute amplitudes of any on-scale portion of the post-S seismic coda. The use of a power law coda shape function in the form a(t) = a_ot^(-q) makes the proposed method directly commensurable with the already widely used and highly successful duration method. The MCA magnitude scale is predicated on the same short-term averages used by the event detection algorithm on the real- time system, permitting a direct stochastic analysis of the spatial magnitude thresholds of a particular configuration of the detection logic. Such an a priori evaluation of detection capability is necessary since detection failure results in considerable extraneous effort. The use of these techniques has permitted the compilation of a local earthquake catalog and attendant phase data base that are substantially more uniform and accurate than what is generally obtained using manual methods.\r\n\r\nThe nature of earthquake swarms in the Imperial Valley is investigated with the goal of placing specific constraints on the physical mechanisms governing their behavior. Within the Imperial Valley most earthquakes occur as swarms concentrated within a narrow, sharply bounded, spindle-shaped zone joining the northern terminus of the Imperial Fault with the southern end of the San Andreas Fault. Although over the past five years the seismicity within this zone, designated the Brawley Seismic Zone, is surprisingly uniform, on time scales of a few weeks activity is highly clustered in both space and time. Seismicity is not confined to a few \"hot spots\", as might be expected, but rather seems to move around, seldom if ever reactivating the site of a previous swarm. Seven sequences of swarms are analyzed in detail using a master event approach in order to provide some insight into supporting tectonic structures. It is generally observed that swarm sequences comprise discrete bursts of activity, each of which appears to \"illuminate\" a single planar fracture transverse to the major tectonic elements in the Imperial Valley such as the Imperial Fault and the Brawley Fault. Development of activity during a sequence of swarms generally begins with high clustered activity followed by continuous, progressive involvement of the transverse structures, and progressive but discontinuous development in the form of spatially and temporally isolated clusters along the major fault elements. Observed migration rates range from .5 km/hr to .5 km/day. The consistency observed with respect to the pattern of development of independent sequences strongly suggests that a deterministic, physical model can be obtained. One possible model is suggested that relates the swarms on transverse structures with propagating, episodic creep on the major transforms. In this model both the creep rate and the triggering of earthquake swarms is governed by perturbations of pore-pressure in a fluid-infiltrated elastic matrix.\r\n" }, { "name": "Mellman, George Robert", "degree": "PhD", "year": "1979", "title": "A Method for Waveform Inversion of Body-Wave Seismograms", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:03212024-194510121", "creators": [ { "name": { "family": "Mellman", "given": "George Robert" }, "id": "Mellman-George-Robert", "display_name": "Mellman, George Robert" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "abstract": "An iterative inversion method has been developed for the determination of velocity-depth structure and the estimation of seismic source parameters using the waveforms of far-field body-wave seismograms. The inversion is accomplished by minimizing an error function that expresses the difference between data and synthetic seismogram. This error function is constructed to be insensitive to absolute amplitudes and travel-times, and is thus a measure of wave\u00ad form errors only.
\r\n\r\nIn the case where the source is known and the velocity-depth function is to be determined, the Modified First Motion method is used to express changes in the error function in terms of changes in the model parameters relative to some starting model. An approximate inverse is derived for this expression, which determines the model\r\nperturbation that minimizes the error function, Stability is provided through the inclusion of specific non-linear terms in the inverse.\r\nAs an example of the application of the inversion technique, the fine structure of the crust-mantle transition is examined, using data from a Bering Sea refraction profile.
\r\n\r\nIn the case where earth structure is assumed known and the source parameters are to be determined, the source is represented as a small number of point shear dislocations. Using an inversion method quite similar to the one used for the earth structure problem, estimates are obtained of relative seismic moment, depth, fault orientation, source time function, and relative location for each point dislocation, The inversion method developed is applied to the study of the Borrego Mountain earthquake.
" }, { "name": "Nicholson, Philip David", "degree": "PhD", "year": "1979", "title": "1. Tidal Synchronization of the Rotation of Early Main Sequence Stars in Close Binaries. 2. The Rings of Uranus: Results of the 1978 April 10 Occultation. 3. On the Resonance Theory of the Rings of Uranus", "advisor": "Goldreich, Peter Martin", "url": "https://resolver.caltech.edu/CaltechETD:etd-03032006-160754", "creators": [ { "name": { "family": "Nicholson", "given": "Philip David" }, "id": "Nicholson-Philip-David", "orcid": "0000-0003-2275-4463", "display_name": "Nicholson, Philip David" } ], "advisors": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "advisor", "display_name": "Goldreich, Peter Martin" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/xtcv-p562", "abstract": "Part 1:
\r\n\r\nThe rotational synchronization of an early type main sequence star in a close binary system has been attributed to radiative damping of the dynamical component of the tide raised in the star by its companion (Zahn, 1975, 1977). An investigation of the dynamical tide is presented here, which includes the heretofore neglected effects of stellar rotation. Foremost among these effects is the splitting of the tidal response into a set of modes whose latitudinal structures are controlled by the solutions of Laplace's tidal equation.
\r\n\r\nAn approximate analytic expression is derived for the rate of tidal energy dissipation associated with each of these modes, which in turn determines the rate of synchronization of the star's rotation with its orbital motion. This analytic result is supported by a numerical analysis of the dynamical tide raised in a 5 M\u2299 star. Combination of analytic and numerical results yields synchronization timescales for stars in the mass range 2 M\u2299 - 10 M\u2299. These timescales are a factor of 10 shorter than those obtained by Zahn, and are in good agreement with the observational data concerning synchronism among early type stars in close binaries. It is suggested, however, that the final stages of synchronization are controlled by another mechanism: the slow stellar expansion which accompanies the later stages of main sequence evolution.
\r\n\r\nPart 2:
\r\n\r\nObservations of the 1978 April 10 stellar occultation by the rings of Uranus are presented. Nine rings were observed and their radii and widths are calculated. Rings \u03b7, \u03b3, and \u03b4 are found to be most likely circular and coplanar, in agreement with previous analyses; the remaining rings are either non-circular or slightly inclined. The width of the \u03f5 ring is a linear function of its radius from the center of Uranus, projected onto the satellites' orbital plane; this suggests that it forms one continuous non-circular ring. The optical depth profile of the \u03f5 ring has not changed significantly since 1977 March. A model of this ring which fits all available observations adequately is that of a uniformly precessing Keplerian ellipse coplanar with the satellites' orbits. This model permits predictions of the radius and width of the \u03f5 ring for future occultations. The precession rate is used to determine J2 for Uranus, on the assumption that precession is caused solely by the planetary oblateness and not by satellite-ring interactions.
\r\n\r\nPart 3:
\r\n\r\nA three-body resonance model proposed to account for the rings of Uranus is quantitatively analyzed and found to be unacceptable on several grounds. Calculation of the strengths of two-body and three-body resonances involving all known satellites of Uranus, and which fall in the neighborhood of the rings, reveals that the strongest resonances are the 4:1 and 5:1 resonances with Miranda, and the three-body resonances involving Miranda and Ariel. Resonances invoked by the proposed model are much weaker. Despite the fact that four of these relatively strong resonances approximately coincide with rings 5, \u03b1, \u03b3, and \u03f5, they are too weak to explain the observed widths of the rings. Finally, the simple ring model of densely packed particles librating about a resonance is shown to be secularly unstable.
" }, { "name": "Pollard, David", "degree": "PhD", "year": "1979", "title": "Barotropic and Baroclinic Instabilities in Jupiter's Zonal Flow", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09082006-081730", "creators": [ { "name": { "family": "Pollard", "given": "David" }, "id": "Pollard-David", "display_name": "Pollard, David" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/r49b-st82", "abstract": "The barotropic and baroclinic stability of Jupiter's zonal jets is investigated using a two-layer quasi-geostrophic model. Each layer is of constant density with the upper layer representing the cloudy levels of Jupiter's atmosphere above p ~ 5 bars containing the zonal jets u\u0305(y), and a much deeper lower layer in which u\u0305 = 0; [roughly consistent with Gierasch (Icarus, 29 1976)]. Since Jupiter's vertical structure associated with the zonal jets is unknown at these levels, this model attempts to include the effects of baroclinicity and deep lower layer inertia with as few free vertical-structure parameters as possible (i.e., the upper layer Rossby radius of deformation Lr and the ratio of the upper layer to lower layer thickness \u03b4).
\r\n\r\nGiven that \u03b4 << 1 for Jupiter, the linearized dynamical equations can be expanded in powers of \u03b4 and also of \u03b4\u00b9/\u00b2. These expansions naturally categorize the possible disturbances into three types; barotropic (BTU) modes, almost entirely confined to the upper layer with potentially 0(1) growth rates; baroclinic (BC) modes, which depend on interactions between the two layers and can only have 0(\u03b4) growth rates; and barotropic (BTL) modes of the lower fluid with 0(\u03b4\u00b9/\u00b2) growth rates. Some results for the BC modes are presented and compared to results of a continuously stratified model developed in the appendix, but mostly the faster growing BTU modes are investigated for two analytically tractable velocity profiles [sech\u00b2(y) and tanh (y), following Lipps (e.g., J. Fluid Mech., 21, 1965)]. The x-wavelengths, phase speeds, growth rates, horizontal morphologies and the latitudinal forms of the eddy transports u'v' of the fastest growing disturbances depend on u\u0305(y) and on the model parameter Lr.
\r\n\r\nIn mid 1979, two Voyager spacecraft may return images of cloud motions around the p ~ 1 bar level, yielding u\u0305(y) and eddy u'(x,y,t) and v'(x,y,t). Models of the present type are necessary to form a basis for interpreting such data, to initially identify and categorize the types of disturbances, at least until more is known of the vertical structure associated with the zonal jets. Best-fitting of the model's results to corresponding Voyager data may constrain Lr and \u03b4, two basic vertical-structure parameters. In the last section, the theoretical results for BTU modes listed above are summarized and presented in forms most suitable for comparisons with the anticipated data.
" }, { "name": "Potter, Russell Marsh", "degree": "PhD", "year": "1979", "title": "The Tetravalent Manganese Oxides: Clarification of their Structural Variations and Relationships and Characterization of their Occurrence in the Terrestrial Weathering Environment as Desert Varnish and other Manganese Oxide Concentrations", "advisor": "Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:09192022-193330791", "creators": [ { "name": { "family": "Potter", "given": "Russell Marsh" }, "id": "Potter-Russell-Marsh", "display_name": "Potter, Russell Marsh" } ], "advisors": [ { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/k2s0-9177", "abstract": "A number of structural problems in the mineralogy of the\r\ntetravalent manganese oxides have been addressed by infrared\r\nspectroscopy in conjunction with X-ray diffraction and chemical\r\nanalysis. The first pyrolusite with proven orthorhombic symmetry\r\nis reported. Examination of pyrolusites with different degrees of\r\northorhombic distortion supports the view that this distortion is\r\nthe result of micro-pores within the crystal. Pyrolusite infrared\r\nspectra exhibit variations which cannot be correlated to\r\northorhombic distortion, ramsdellite intergrowths, or other mineral\r\nimpurity. The continuous structural variation of the nsutites from\r\na rarnsdellite end-member to a pyrolusite end-member has been\r\nconfirmed although much of the variation in synthetic nsutites appears\r\nto be related to crystalline order. Ramsdellite has a single,\r\ncrystallographically-ordered type of water, which appears to be an\r\nintegral part of the structure. The only hydrous component of\r\nromanechite is water, which is located in the channels in a specific\r\ncrystallographic site. The only hydrous component of lithiophorite\r\nis hydroxide ion, which is oriented perpendicular to the cleavage\r\nplanes. Birnessite appears to have a layer structure on the basis\r\nof its infrared spectrum. Its identity with proposed synthetic\r\nanalogs is confirmed. Todorokite is a valid mineral species which is\r\nnot analogous to any synthetic phases or to any alteration products\r\nof them. It appears to have a layered structure. Rancieite probably\r\nhas a layer structure related to birnessite.
\r\n\r\nIt is possible to distinguish manganese oxides of different\r\nstructural groups from one another by their spectra in the mid-infrared\r\nregion, which is sensitive to the hydrous components and the\r\nmanganese octahedral framework. Because of its sensitivity to short\r\nrange order, infrared spectroscopy is often superior to X-ray\r\ndiffraction for the determinative mineralogy of the manganese oxides,\r\nwhich often occur in a finely-particulate, poorly-crystalline state.\r\nSpectra in the region 4000 cm\u207b\u00b9 to 200 cm\u207b\u00b9 are presented for\r\nwell-characterized manganese oxide samples in order to form a basis\r\nfor identification of manganese oxide mineralogy. The following\r\noxides are included: aurorite, birnessite, braunite, buserite,\r\nchalcophanite, coronadite, cryptomelane, groutite, hausmannite,\r\nhollandite, lithiophorite, manganite, manganosite, manjiroite,\r\nmarokite, nsutite, partridgeite, pyrolusite, quenselite, ramsdellite,\r\nrancieite, romanechite (psilomelane), todorokite, and woodruffite.
\r\n\r\nThis data base has been applied to the study of the\r\nmineralogy of manganese oxide concentrations of the terrestrial\r\nweathering environment. Through the integrated application of a\r\nvariety of infrared spectroscopic, X-ray diffraction, electron\r\noptic, and chemical techniques, the characteristic mineralogy of\r\ndesert varnish has been identified as bimessite, hematite, and\r\nmixed-layer illite-montmorillonite clay minerals. Clay minerals\r\ncomprise greater than 70 percent of the varnish, the oxides constitute\r\nt he bulk of the remainder and are in intimate physical association\r\nwith the clays. An abrupt change in chemistry, mineralogy, and\r\nmorphology exists at the varnish-rock interface. The origin of the material is external to the rock which it coats. \r\nThe clays are most likely transported by wind or water. The oxides appear to be\r\ntransported by water. Clay minerals are necessary for varnish\r\nformation, probably through their influence on oxide concentration or\r\ndeposition.
\r\n\r\nMorphological distinctions among desert varnish, manganese\r\ndendrites, river deposits and other manganese oxide concentrations of\r\nthe terrestrial weathering environment have a sound basis in\r\ndifferences in their mineralogy. The manganese oxide in manganese\r\ndendrites is either romanechite or a hollandite group mineral. These\r\nare mixed with varying amounts of silicate minerals, which are a\r\npassive substrate for the oxide deposition. Manganese stream deposits\r\nare generally birnessite with minor amounts of silicate minerals;\r\none nsutite stream deposit has been identified. Crack deposit\r\nmineralogy resembles that of manganese dendrites. Cave and subglacial\r\ndeposit mineralogy resembles that of manganese stream deposits. No\r\ndendrite has been found to consist of pyrolusite. Hydropsilomelane\r\nconcretions, which carry chemical remanent magnetization in sediments\r\nin Baja California, Mexico, consist of siltstone matrix minerals\r\ncemented by a manganese oxide having the chalcophanite structure. The\r\nhigh concentration of magnesium presumed to occur in the interlayer\r\nposition of this mineral extends the known range of substitution in\r\nchalcophanite-structure minerals.
" }, { "name": "Rial M., Jos\u00e9 Antonio", "degree": "PhD", "year": "1979", "title": "I. The Caracas, Venezuela Earthquake of 1967: A Multiple Source Event. II. Seismic Waves at the Epicenter's Antipode", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11112019-154510111", "creators": [ { "name": { "family": "Rial M.", "given": "Jos\u00e9 Antonio" }, "id": "Rial-M-Jos\u00e9-Antonio", "display_name": "Rial M., Jos\u00e9 Antonio" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/725f-v881", "abstract": "This dissertation consists of two unrelated subjects. Although both deal with the construction of synthetic seismograms, the first (Chapter I) is the detailed study of a complicated earthquake source, whereas the second (Chapter II) deals with the structure of the earth's interior as seen from the antipode of a seismic wave source. The two can be classified as problems involving forward inversion of seismological data. There is, however, a significant common ground in the spirit of the approach in the sense that seismic wave interference phenomena, present in both, are used as allies in reducing the inherent non-uniqueness of the inversion process.
" }, { "name": "Smith, Stephen Pritchard", "degree": "PhD", "year": "1979", "title": "Studies of Noble Gases in Meteorites and in the Earth", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01212016-132933875", "creators": [ { "name": { "family": "Smith", "given": "Stephen Pritchard" }, "id": "Smith-Stephen-Pritchard", "display_name": "Smith, Stephen Pritchard" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/x4b9-m132", "abstract": "The isotopic and elemental abundances of noble gases in the solar\r\nsystem are investigated, using simple mixing models and mass-spectrometric\r\nmeasurements of the noble gases in meteorites and terrestrial rocks and\r\nminerals.
\r\n\r\n\r\nPrimordial neon is modeled by two isotopically distinct components\r\nfrom the interstellar gas and dust. Neon from the gas dominates solar neon,\r\nwhich contains about ten times more 20Ne than 22Ne. Neon from the dust is\r\nrepresented in meteorites by neon-E, with 20Ne/22Ne less than 0.6. Isotopic\r\nvariations in meteorites require neon from both dust and gas to be present.\r\nMixing dust and gas without neon loss generates linear correlation lines\r\non three-isotope and composition-concentration diagrams. A model for solar\r\nwind implantation predicts small deviations from linear mixing, due to preferential\r\nsputtering of the lighter neon isotopes.
\r\n\r\n\r\nNeon in meteorites consists of galactic cosmic ray spallation neon\r\nand at least two primordial components, neon-E and neon-S. Neon was measured\r\nin several meteorites to investigate these end- members. Cosmogenic\r\nneon produced from sodium is found to be strongly enriched in\r\n22Ne. Neon measurements on sodium-rich samples must be interpreted with care so not to\r\nconfuse this source of 22Ne with neon-E, which is also rich in 22Ne.
\r\n\r\nNeon data for the carbonaceous chondrite Mokoia show that the end member composition of neon-Si in meteorites is 20Ne/22Ne = 13.7, the same as\r\nthe present solar wind. The solar wind composition evidently has remained\r\nconstant since before the compaction of Mokoia.
\r\n\r\nCa, Al-rich inclusions from the Allende meteorite were examined for\r\ncorrelation between neon-E and oxygen or magnesium isotopic anomalies.\r\n22Ne and 36Ar enrichments found in some inclusions are attributed to cosmic-\r\nray-induced reactions on Na and Cl, not to a primordial component. Neon-E\r\nis not detectably enriched in Allende.
\r\n\r\nMeasurements were made to determine the noble gas contents of various\r\nterrestrial rocks and minerals, and to investigate the cycling of noble\r\ngases between different terrestrial reservoirs. Beryl crystals contain a\r\ncharacteristic suite of magmatic gases including nucleogenic 21Ne and 22Ne\r\nfrom (\u03b1,n) reactions, radiogenic 40Ar, and fissiogenic 131-136Xe from the\r\ndecay of K and U in the continental crust. Significant concentrations of\r\natmospheric noble gases are also present in beryl.
\r\n\r\nBoth juvenile and atmospheric noble gases are found in rocks from\r\nthe Skaergaard intrusion. The ratio 40Ar/36Ar (corrected for in situ decay\r\nof 40K) correlates with \u03b418O in plagioclase. Atmospheric argon has been\r\nintroduced into samples that have experienced oxygen-isotope exchange with\r\ncirculating meteoric hydrothermal fluids. Unexchanged samples contain\r\njuvenile argon with 40Ar/36Ar greater than 6000 that was trapped from the\r\nSkaergaard magma.
\r\n\r\nJuvenile and atmospheric gases have been measured in the glassy\r\nrims of mid-ocean ridge (MOR) pillow basalts. Evidence is presented that\r\nthree samples contain excess radiogenic 129Xe and fission xenon, in addition\r\nto the excess radiogenic 40Ar found in all samples. These juvenile gases\r\nare being outgassed from the upper-mantle source region of the MOR magma.\r\nNo isotopic evidence has been found here for juvenile primordial noble\r\ngases accompanying the juvenile radiogenic gases in the MOR glasses. Large\r\nargon isotopic variations in a single specimen provide a clear indication\r\nof the late-stage addition of atmospheric argon, probably from seawater.
\r\n\r\nThe Skaergaard data demonstrate that atmospheric noble gases dissolved\r\nin ground water can be transferred into crustal rocks. Subduction\r\nof oceanic crust altered by seawater can transport atmospheric noble gases\r\ninto the upper mantle. A substantial portion of the noble gases in mantle\r\nderived rocks may represent subducted gases, not a primordial component\r\nas is often assumed.
\r\n\r\n" }, { "name": "Van Alstine, David Ralph", "degree": "PhD", "year": "1979", "title": "Apparent Polar Wandering with Respect to North America Since the Late Precambrian", "advisor": "Shoemaker, Eugene Merle", "url": "https://resolver.caltech.edu/CaltechTHESIS:09152010-083013551", "creators": [ { "name": { "family": "Van Alstine", "given": "David Ralph" }, "id": "Van-Alstine-David-Ralph", "display_name": "Van Alstine, David Ralph" } ], "advisors": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "advisor", "display_name": "Shoemaker, Eugene Merle" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/3p9w-p930", "abstract": "To achieve a better understanding of the relative significance of plate tectonics and true polar wandering, it is important that paleomagnetic poles be as accurate as possible and that knowledge of apparent polar wandering be extended to increasingly remote times. In Chapter 1, advantages of using the mode in analysis of paleomagnetic vectors are discussed, and a computer technique is described for contouring and precisely locating the modes of vector distributions that may be highly skewed. In contrast to conventional determinations of the mode, unit vectors from a given data set are treated not as discrete points, but as identical Fisherian probability density functions defined (at an angle \u03b8 from the unit vector) by: p=exp(sk(cos \u03b8-1)), where k is the estimate of the Fisherian concentration parameter, and s is an arbitrarily assigned \"smoothing parameter.\" A grid, representing the cumulative probability distribution of the total sample of vectors, is contoured to provide a graphical display of the distribution around the most probable value, the mode. By repeatedly contouring the same sample of vectors with successively larger values of s, and by treating the mode as a vector with length given by the total probability value at the mode, \"progressive modal diagrams\" can be constructed, to aid in determining the stable position of the mode of skewed distributions. In addition, a new statistic, \"\u03b2_(95)\" is suggested as an error estimator for the mode. The statistic \u03b2_(95) is derived from the largest subset of the total sample that has a mean identical with the mode of the total sample. This statistic is defined as the Fisherian half-angle of the cone of 95% confidence for the mean of this subset.
\r\n\r\nIn Chapters 2 and 3, results are presented of a paleomagnetic investigation of upper Precambrian through Middle Cambrian sedimentary rocks from the Cordilleran geosyncline. Over 800 oriented samples were obtained from a homoclinal, conformable sequence of terrigenous and carbonate miogeoclinal strata in the Desert Range, Nevada. Thermal demagnetization isolated similar characteristic magnetization directions in red-purple mudstones of the Wood Canyon Formation (Lower(?) and Lower Cambrian) and in gray limestones of the Carrara and Bonanza King Formations (Lower and Middle Cambrian). Lithologic and magnetic evidence suggest these magnetizations were acquired penecontemporaneously with deposition. The similarity of the characteristic magnetizations in these strata implies that little apparent polar wander occurred with respect to North America from early Early through middle Middle Cambrian time. The divergence of these directions from those from the partly coeval Tapeats Sandstone of the Colorado Plateau probably resulted from a net 36\u00b0 clockwise rotation of the Desert Range section about a vertical axis. This rotation is probably due to mid-Tertiary oroflexural bending, but may in part have been caused by Mesozoic thrusting. The characteristic magnetization of the uppermost Johnnie Formation (upper Precambrian; ~650 m.y.) has two polarities, which allows its direction to be established despite incomplete removal of a secondary component of recent origin. The pole from the uppermost Johnnie is about 47\u00b0 from the pole for the Wood Canyon Formation. It seems probable that at least 45\u00b0 of apparent polar wandering occurred with respect to North America between about 650 m.y.B.P. and Early Cambrian time.\r\n\r\n In Chapter 4, a method for constructing apparent polar wander (APW) paths is presented that includes: (1) grouping data into standard time intervals of about 22 m.y. duration; (2) using new criteria for selection of paleomagnetic poles to be given unit weight; and (3) using the mode to represent the estimated pole position for each time interval.. This method is applied to paleomagnetic data from about 250 references to revise the Phanerozoic APW path for North America. The revised path is documented with an interval-by-interval review of all reliable North American paleomagnetic poles for the Phanerozoic. Unlike the smooth and simple APW paths first obtained in the late 1950's, the revised Phanerozoit APW path for North America is characterized by frequent, abrupt changes in the direction and rate of apparent polar wandering. Some anomalous but apparently reliable poles that lie off the revised path may be attributable to (1) complex tectonic histories of parts of the present North American plate, and (2) possibly, complex structure of the geomagnetic field for periods of time that may have been as long as 10^5 to 10^6 years.
\r\n\r\nIn Chapter 5, a speculative synthesis is presented of the revised Phanerozoic APW path for North America and an inferred north polar wandering path for Mars. It has been proposed that quasi-circular features in the Martian polar regions might represent margins of nearly circular caps that had formed symmetrically about the poles. These features would then in effect be \"fossil latitudinal circles,\" and the offsets in their centers of curvature from the present geographic poles might provide evidence for polar wandering on Mars. If this interpretation is correct, then a polar wander path for Mars can be obtained by connecting the centers of curvature of successive margins of the polar caps. A polar wander path was derived by fitting the most prominent quasi-circular features in the north polar region to portions of circles of nearly constant radius (~3.4\u00b0) and then connecting the centers of curvature in sequence. An interesting characteristic of the Martian north polar wander path so obtained is its tendency to exhibit two major changes in direction during a time interval estimated as between 50 and 500 m.y. These two bends in the Martian north polar wander path are reminiscent of the \"hairpin\" bends that occur about every 100 to 130 m.y. in the Phanerozoic APW path for North America. In fact, a comparison between apparent polar wandering with respect to North America and the inferred true polar wandering on Mars reveals a remarkable similarity: both processes can be modeled as the superposition of a quasi-periodic component and a secular component. On both Earth and Mars, the quasi-periodic component is elliptical and has a period in the 10^8-year range; and on both planets, the secular component propagates at a nearly constant speed in a direction nearly perpendicular to the major axis of the oscillatory component. Moreover, the length of the secular shift per cycle is roughly the same as the length of the major axis of the oscillatory component. These unexpected similarities suggest that a highly ordered form of true polar wandering occurs on Earth and Mars as a consequence of a physical process common to both planets. An oscillatory form of mantle convection is tentatively proposed to be the excitation function of quasi-periodic polar wandering on Earth and Mars.
" }, { "name": "Bills, Bruce Gordon", "degree": "PhD", "year": "1978", "title": "A Harmonic and Statistical Analysis of the Topography of the Earth, Moon, and Mars", "advisor": "Ferrari, Alfred J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04092012-114720525", "creators": [ { "name": { "family": "Bills", "given": "Bruce Gordon" }, "id": "Bills-Bruce-Gordon", "display_name": "Bills, Bruce Gordon" } ], "advisors": [ { "name": { "family": "Ferrari", "given": "Alfred J." }, "id": "Ferrari-A-J", "role": "advisor", "display_name": "Ferrari, Alfred J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/SM57-8B66", "abstract": "In chapter I a global lunar topographic map is derived from Earth based\r\nand orbital observations supplemented in areas without data by\r\na linear autocovariance predictor. Of 2592 bins, each 5\u00b0 square,\r\n1380 (64.7% by area) contain at least one measurement. A spherical\r\nharmonic analysis to degree 12 yields a mean radius of (1737.53 \u00b1 0.03)\r\nkm (formal standard error) and an offset of the center of figure of\r\n(1.98 \u00b1 0.06) km toward (19 \u00b1 2)\u00b0 S, (194 \u00b1 1)\u00b0 E. A Bouguer gravity\r\nmap is also presented. It is confirmed that the low-degree gravity\r\nharmonics are caused primarily by surface height variations and only\r\nsecondarily by lateral density variations.
\r\n\r\nIn chapter II a series of models of the lunar interior are derived\r\nfrom topographic, gravitational, librational and seismic data. The\r\nmoon departs from isostasy, even for the low-degree harmonics, with\r\na maximum superisostatic stress of 200 bars under the major mascon\r\nbasins. The mean crustal thicknesses under different physiographic\r\nregions are: mascons, 30-35 km; irregular maria, 50- 60 km; and\r\nhighlands, 90-110 km. A significant correlation between lunar surface\r\nchemistry and crustal thickness suggests that regions of thicker crust\r\nare more highly differentiated. A possible mean composition consistent\r\nwith our model is an anorthositic crust, underlain by a predominantly\r\nforsterite upper mantle which grades into a refractory rich lower\r\nmantle surrounding a pyrrhotite core.
\r\n\r\nIn chapter III a model of martian global topography is obtained\r\nby fitting a spherical harmonic series of degree 16 to occultation,\r\nradar, spectral and photogrammetric measurements. The existing\r\nobservations are supplemented in areas without data by emperical\r\nelevation estimates based on photographic data. The mean radius is\r\n(3389.92 \u00b1 0.04) km . The corresponding mean density is (3.933 \u00b1 0.002)\r\ng cm^(-3). The center of figure is displaced from the center of mass by\r\n(2.50 \u00b1 0.07) km towards (62 \u00b1 3)\u00b0 S, (272 \u00b1 3)\u00b0 W. The geometric \r\nFlattening [f_g = (6.12 \u00b1 0 .04) 10^(-3) ] is too great and the dynamic\r\nflattening [f_d (5.22 \u00b1 0 .03) 10^(-3)] is too small for Mars to be\r\nhomogeneous and hydrostatic. It is confirmed that, similar to the\r\nMoon, the martian low-degree gravity harmonics are produced primarily\r\nby surface height variations and only secondarily by lateral density\r\nvariations. Maps of the global topography and Bouguer gravity are\r\npresented. These are interpreted in terms of a crustal thickness map\r\nwhich is consistent with gravity, topography and recent preliminary\r\nViking seismic results. Using plausible density contrasts and an\r\nassumed zero crustal thickness at Hellas, the inferred minimum mean\r\ncrustal thickness is (28 \u00b1 4) km.
\r\n\r\nIn chapter IV it is shown that the topographic variance spectra\r\nof the Earth, Moon, Mars and Venus are all very similar. The variance\r\nper harmonic degree V(H;n) decreases roughly as the inverse square of\r\nthe degree, or more precisely V(H;n) \u2250 V(H;O)/(n)(n+1). On the Earth\r\nand Moon this relationship has been confirmed down to scale lengths as \r\nsmall as L \u2250 100 m. At the other end of the spectrum, the variance\r\nappears to be deficient relative to this model for scale lengths\r\ngreater than L \u2250 2000 km. The most satisfactory explanation for this\r\nphenomenon appears to be a simple equilibrium between constructional\r\nor \"tectonic\" processes which tend to roughen the surface uniformly\r\nat all scales, and destructional or erosive processes which tend to\r\nsmooth the surface preferentially at small scales. The deficiency\r\nin the low-degree variances is attributable to visco-elastic\r\ndeformation.
\r\n" }, { "name": "DePaolo, Donald James", "degree": "PhD", "year": "1978", "title": "Study of Magma Sources, Mantle Structure and the Differentiation of the Earth from Variations of \u00b9\u2074\u00b3Nd/\u00b9\u2074\u2074Nd in Igneous Rocks", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08232006-154851", "creators": [ { "name": { "family": "DePaolo", "given": "Donald James" }, "id": "DePaolo-Donald-James", "display_name": "DePaolo, Donald James" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/YBQ5-4B95", "abstract": "The decay of 147Sm to 143Nd allows 143Nd/144Nd to be used to trace Sm/Nd fractionation in long time-scale geologic processes. Since Sm/Nd is a sensitive indicator of many aspects of the overall chemistry of rocks, the Sm-Nd system provides an excellent tool for the study of the chemical evolution of the earth's crust and mantle.
\r\n\r\n143Nd/144Nd has been measured in terrestrial rock samples of different ages to establish the characteristics of Nd isotopic evolution in the crust and mantle. The evolution of 143Nd/144Nd in the mantle indicates Sm/Nd equal to that of chondrites, and implies a chondritic REE distribution for the earth. Young basalts show a significant dispersion in 143Nd/144Nd indicating the existence of distinct mantle reservoirs with characteristic 143Nd/144Nd. 143Nd/144Nd in average crustal rocks today is much lower than in mantle samples and reflects their age and low Sm/Nd. Continental flood basalts and mid-ocean ridge (MOR) tholeiitic basalts have distinctly different 143Nd/144Nd which may permit a priori distinction between \"continental\" and \"oceanic\" igneous rocks. Ocean island basalts have 143Nd/144Nd intermediate between MOR and continental flood basalts. Initial 143Nd/144Nd of many continental igneous rocks through time fall on a Sm/Nd evolution curve with chondritic REE abundance ratio. Oceanic igneous rocks are derived from a different ancient reservoir which has Sm/Nd higher than chondritic. These observations indicate that many continental igneous rocks are derived from a reservoir with chondritic REE pattern which may represent primary undifferentiated material remaining since the formation of the earth, while oceanic igneous rocks are derived from highly differentiated reservoirs. The mantle beneath the oceans appears to be more depleted in crustal components than is the mantle which is subjacent to the continental crust. In general, basalts are not derived from mantle reservoirs which have been light REE-enriched for long times.
\r\n\r\nInitial 143Nd/144Nd and 87Sr/86Sr in young basalts from both oceans and continents show a strong correlation suggesting that Sm-Nd and Rb-Sr fractionation events in the mantle may be correlative and caused by the same process. From this correlation Rb/Sr for the earth is inferred to be 0.029.
\r\n\r\nInitial 143Nd/144Nd in lunar igneous rocks show much more dispersion than in terrestrial rocks of similar age. The data suggest that the earth, unlike the moon, did not undergo an early differentiation event which greatly fractionated the rare earth elements, or if it did, a mixing process operated during the subsequent AE to erase the variation of Sm/Nd produced in this event.
\r\n\r\nNd and Sr isotopes indicate that if the earth is made of a mixture of achondrites (low Rb/Sr) and chondrites (high Rb-Sr) that these two components must have been thoroughly mixed. The present-day isotopic heterogeneity of the earth's mantle is unrelated to accretional heterogeneity.
\r\n\r\nTransport calculations and material balance considerations for simple models of formation of the continental crust indicate that only a small portion of the earth's total budget of Sm and Nd are found in the crust. Highly differentiated mantle reservoirs such as those from which MOR basalts are derived must represent only a small portion of the mantle, perhaps one-fourth to one-sixth or less. The data are consistent with the existence of large volumes of undifferentiated (possibly undegassed) material in the mantle. The data also suggest that the continental crust has a low Rb/Sr (less than 0.10) implying a highly layered structure for the crust, with the lower crust having a much lower Rb/Sr than the upper crust.
\r\n\r\nIsland arc lavas from New Britain and the Marianas have 143Nd/144Nd similar to other oceanic basalts and distinctly different from continental flood basalts and thus appear to be derived from a high Sm/Nd, light-REE-depleted reservoir. Consideration of both Nd and Sr isotopes suggests seawater involvement in the generation of some island arc lavas and thus indicates that they may be derived from altered subducted oceanic crust. Other island arc lavas show no evidence of seawater involvement and may be derived from mantle reservoirs with affinities to the sources of ocean island basalts. Nd and S in some basaltic and ultrapotassic continental lavas and in some Andean volcanics indicate that some magmas in continental regions may be derived from old low-Sm/Nd reservoirs or are heavily contaminated with old continental crustal material. Fish debris from the ocean floor provides an estimate of 143Nd/144Nd in seawater and indicates that light-REE in the marine environment are derived mainly from continents.
" }, { "name": "Diner, David Joseph", "degree": "PhD", "year": "1978", "title": "I. Silicon Vidicon Imaging of Jupiter 4100-8300\u00c5: Spectral Reflectivity, Limb-Darkening, and Atmospheric Structure. II. Simultaneous Ultraviolet (0.36 \u00b5m) and Infrared (8-20 \u00b5m) Imaging of Venus: Properties of Clouds in the Upper Atmosphere", "advisor": "Westphal, James A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10212024-225714489", "creators": [ { "name": { "family": "Diner", "given": "David Joseph" }, "id": "Diner-David-Joseph", "display_name": "Diner, David Joseph" } ], "advisors": [ { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "advisor", "display_name": "Westphal, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/r1rr-5q90", "abstract": "Part 1 presents the results of high spatial resolution area photometry of Jupiter in six continuum wavelength channels from 4100-8300\u00c5. Spectral reflectivity and limb-darkening data in belts and zones are fitted by a simple semi-infinite homogeneous scattering model which provides a convenient parameterization of the results, as well as a determination of the spectral and spatial variations in the continuum single scattering albedo and information regarding the shape of the single scattering phase functions. It is found that belts are generally more backscattering than zones, particularly in the blue, and there is a trend toward increased forward scattering\r\nat longer wavelengths. The numerical results are compared to earlier ground-based observations of jovian limb-darkening (Harris, 1961; Binder and McCarthy, 1973; Pilcher and Kunkle, 1976) and significant disagreement is found in some cases, Extrapolations of the limb\u00ad darkening data to 12\u00b0 phase angle are compared with the results of the Pioneer 10-imaging photopolarimeter (IPP) experiment (Tomasko et al., 1976). Although there is quantitative disagreement between the vidicon results and the IPP data, the ground-based and Pioneer 10 results show the same relative spectral and regional trends in the shape of the limb structure profiles from the blue to the red and between a belt and a zone. The limb-darkening profiles are also com\u00ad pared to models derived from measurements of the spatial distribution of equivalent width of the H\u2082 4-0 S(1) quadrupole line (Cochran, 1976). It is found that these models fare reasonably well in the South Tropical Zone but are much too limb-darkened relative to the data in the North Equatorial Belt. A discussion of the possible causes of the differences between the vidicon data and other ground\u00ad based, Pioneer 10, and spectroscopic results is presented.
\r\n\r\nSome numerical examples of limb-darkening expected from simple models are presented. In particular, the effects of Rayleigh scat\u00adtering, either by a fine, colored dust, or by the gaseous atmosphere on the spectral characteristics of limb-darkening are investigated. It is found that the observed backscattering may be explained by a combination of molecular scattering and scattering by small dust particles, and the increased forward scattering in the red arises from the \u03bb\u207b\u2074 dependence of Rayleigh scattering optical depth and inclusion of forward scattering cloud particles. Such a model works reasonably well in the North Equatorial Belt, but predicts a spectral variation in limb-darkening that is greater than the observations imply for the South Tropical Zone.
\r\n\r\nPart 2 discusses high spatial resolution images of Venus which were obtained in the 0.36 \u00b5m and 8-20 \u00b5m spectral regions throughout the 1974, 1975, and 1977 apparitions. The observing system, method of image acquisition, and data reduction and processing techniques are presented along with a discussion of the spectral, temporal, and spatial characteristics of the infrared and ultraviolet flux from the planet, The infrared data are compared with previous ground\u00ad based results obtained at lower spatial and spectral resolution (Sinton and Strong, 1960; Murray et al., 1963; Westphal et al., 1965; Ingersoll and Orton, 1974) and Venera 9 and 10 infrared radio\u00ad meter results (Ksanfomality et al., 1976).
\r\n\r\nDay-night contrasts in equatorial infrared flux were observed in images in which the evening and morning terminators were near the central meridian. A systematic increase in 8-14 \u00b5m flux associated with the emergence of the atmosphere from daylight into evening was observed, and is shown to exhibit significant day-to-day variability, The data also show that the daytime side of the morning terminator is warmer than the dark side, but this night-day asymmetry is system\u00adatically smaller than the day-night brightening seen in the Venus evening.
\r\n\r\nSouth and north infrared polar anomalies similar to the one observed near the Venus south pole by Murray et al, (1963) have been observed during the 1974 and 1975 apparitions, respectively. The ob\u00adservations indicate that the feature is most prominent between Venus midnight and dawn.
\r\n\r\nThe infrared limb-darkening in the equatorial and polar direc\u00adtions are compared and it is seen that the magnitude and spectral variation of the polar darkening are in general greater than the equatorial darkening. The magnitude of the equatorial darkening is consistent with a temperature lapse rate of roughly -3\u00b0K/km, assuming a model in which aerosol is distributed exponentially and mixed homogeneously with the atmospheric gas.
\r\n\r\nEvidence for a correlation between features observed in simul\u00adtaneous infrared (8-14 \u00b5m) and ultraviolet (0.36 \u00b5m) images has been found. The sense of the correlation is such that bright UV markings correspond to bright (warm) IR features, and similarly, dark UV markings correspond to dark (cool) IR features. This result implies that dark UV clouds are higher or denser than the bright regions.
" }, { "name": "Hadley, David Milton", "degree": "PhD", "year": "1978", "title": "Geophysical Investigations of the Structure and Tectonics of Southern California", "advisor": "Kanamori, Hiroo; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01302012-140641318", "creators": [ { "name": { "family": "Hadley", "given": "David Milton" }, "id": "Hadley-David-Milton", "display_name": "Hadley, David Milton" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "role": "advisor", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/1GTN-2W64", "abstract": "Regional variations in the crustal structure of southern California are defined by travel-time data from natural and artificial events. We show that the crust of the Mojave, northeastern Peninsular Ranges, eastern Transverse Ranges and Colorado Desert is dominated by a velocity of 6.2\u00b10.1 km/sec. The western Transverse Ranges and the western portion of the Peninsular Ranges are typified by a crustal\r\nvelocity of 6.7 km/sec. The data indicate that the Transverse Ranges do not have a distinct crustal root. As the topography is not supported isostatically, the Range must be sustained by major north-south compression. A composite profile extending north from the southern end of the Salton Sea defines a crustal thickness for the\r\nCoachella Valley of less than 20 km. Through the inversion of Rayleigh wave dispersion data obtained from the analysis of teleseismic surface waves recorded across southern California, we have obtained average S-wave models for the southern Mojave-central Transverse Ranges and the Peninsular Ranges. The observed P-wave velocities and the calculated Poisson's ratio from both P- and S-wave data require a quartz rich crust for the Mojave and a more mafic crust for the Peninsular Ranges. All S-wave models suggest a slight mid- crustal velocity reversal that is approximately coincident with the bottom of the seismic\r\nzone.
\r\n\r\nRegional variations in P_n velocities are obtained from several reversed refraction profiles . These data show that P_n varies from 7.7 to 8.2 km/sec. The high P_n values, 8.2 km/sec, are observed in the eastern Mojave, the western Transverse Ranges and the Coast Ranges.\r\nThe 7.8 km/sec P_n velocity extends from the Imperial Valley, through the central Transverse Ranges, and across the western Mojave. P_n profiles indicate that the Moho beneath the eastern Transverse Ranges and the southeastern Mojave dips 2-3\u00b0 west.
\r\n\r\nP-delay studies of a vertically incident PKP phase indicate that a high velocity, 8.3 km/sec structure exists within the shallow upper mantle beneath much of the geomorphic Transverse Ranges. This feature is not offset by the San Andreas fault. We suggest that the continuity of this anomaly across the plate boundary indicates that if the upper mantle participates in plate motion, the mantle plate boundary must be laterally displaced from the crustal boundary. We suggest that the mantle boundary may extend northwest from the Salton Trough and across the eastern end of the velocity anomaly, in the vicinity of the active Helendale-Lenwood-Camprock faults. We propose that the\r\nhorizontal decoupling between the crust and mantle, required by the lateral displacement at depth of the plate boundary, is accommodated, in part, within the 7.8 km/sec layer.
\r\n" }, { "name": "Hileman, James Alan", "degree": "PhD", "year": "1978", "title": "Part I: A Contribution to the Study of the Seismicity of Southern California. Part II: Inversion of Phase Times for Hypocenters and Shallow Crustal Velocities", "advisor": "Allen, Clarence R.; Minster, Jean-Bernard H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09202024-225628727", "creators": [ { "name": { "family": "Hileman", "given": "James Alan" }, "id": "Hileman-James-Alan", "display_name": "Hileman, James Alan" } ], "advisors": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." }, { "name": { "family": "Minster", "given": "Jean-Bernard H." }, "id": "Minster-Jean-Bernard-H", "role": "advisor", "display_name": "Minster, Jean-Bernard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/6805-xg34", "abstract": "Southern California seismicity data for the period 1932 through 1975 are summarized in a series of epicenter maps. These maps show the seismic activity for one-year periods, for five-year periods, and as summaries for all earthquakes with magnitudes equal to or greater than 4, 5, and 6 respectively. Enlarged epicenter maps are given for the Los Angeles area and for the more significant aftershock sequences in the region.
\r\n\r\nA regional value of b = 1.00 \u00b1 .02 (log N = a - bM) is found for forty years of data. For several smaller areas in the region, b-values have a range of 0.76 - 1.00. Temporal variations of b-values (maximum likelihood estimates) for the various areas studied do not show any strong correlation with the occurrence of large earthquakes. A slight increase of the regional b-value after the 1952 Kern County earthquake is suggested.
\r\n\r\nSeismicity in the Imperial Valley indicates that several faults\r\nthere are susceptible to triggering, i.e. they are loosely coupled to motions of neighboring faults. Some earthquake swarms indicate this ease of triggering. A survey of the high level of swarm activity in the Imperial Valley is given. Two unusual aftershock sequences with periodic activity are described because the periodicity suggests sensi\u00adtivity to some triggering phenomenon.
\r\n\r\nSome seismicity in Southern California seems to be aligned in weakly defined zones that are transverse to the general tectonic fabric. These zones are thought to reflect conditions in the lower crust or uppermost mantle. The cause of these zones is unknown, but their trends are similar to those for the early Paleozoic continental boundary and to a recently discovered upper-mantle velocity anomaly.
\r\n\r\nDepth is usually the least-certain hypocenter parameter because it depends critically upon the accuracy of the velocity model. With enough arrival-time data, velocity estimation is feasible in addition to the usual hypocenter determinations. Linear least-squares inversion theory is adapted for the simultaneous determination of hypocenters and local velocity structure. A maximum likelihood formulation is used so that the data are weighted according to their estimated vari\u00adances. A tradeoff parameter controls the relative importance of the RMS error and the amount by which the model is changed at each itera\u00adtion. The inversion is also stabilized by specifying the allowed variances of each of the model parameters.
\r\n\r\nArrival times for a set of 20 earthquakes in the central Mojave Desert were inverted to improve the local velocity model. Each of the trials indicated that shallow crustal velocities in the vicinity of Galway Lake are somewhat lower than those of the usual velocity models. The velocities were not strongly constrained by this data set. This study points out the need for several seismographic stations placed within an aftershock area for best control of velocity estimates.
" }, { "name": "Hong, Tai-Lin", "degree": "PhD", "year": "1978", "title": "Elastic Wave Propagation in Irregular Structures", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11152024-212656242", "creators": [ { "name": { "family": "Hong", "given": "Tai-Lin" }, "id": "Hong-Tai-Lin", "display_name": "Hong, Tai-Lin" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/1jy4-5854", "abstract": "Wave propagation problems involving irregular structures rarely have exact solutions. However, the most important features of such problems can be often obtained from appropriate approximate solutions.
\r\n\r\nIn Chapter 1, we consider refraction problems involving dipping layers. The Cagniard-de Hoop method for flat structures is extended to such problems to evaluate the non-geometric effects of critical reflection and tunneling. It is shown that the character of the dispersion is strongly affected by even relatively shallow angle dips.
\r\n\r\nIn Chapter 2, we consider teleseismic problems involving curved\r\ninterfaces. An approximation theory, which we name \"Glorified Optics\", is developed to evaluate the effects of focusing and triplication\r\ndue to the local curvature along such interfaces. Seismograms are dramatically complicated by those interference effects. The correla\u00adtion between such complexity and the subsurface structure can be explicitly conceived through Glorified Optics.
\r\n\r\nIn Chapter 3, we perform an independent check on these approxima\u00adtion theories by using finite element methods. The excellent agree\u00adment confirms the validity of our approximations.
\r\n\r\nThe concepts, methods and results presented in this thesis appear to be helpful in opening a new dimension in the fields of seismic modelling, inversion and prospecting.
" }, { "name": "Kosloff, Dan Douglas", "degree": "PhD", "year": "1978", "title": "Numerical Models of Crustal Deformation", "advisor": "Scott, Ronald F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08162024-195509226", "creators": [ { "name": { "family": "Kosloff", "given": "Dan Douglas" }, "id": "Kosloff-Dan-Douglas", "display_name": "Kosloff, Dan Douglas" } ], "advisors": [ { "name": { "family": "Scott", "given": "Ronald F." }, "id": "Scott-R-F", "role": "advisor", "display_name": "Scott, Ronald F." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/vdzd-sz11", "abstract": "Several tectonic features in Southern California cannot be directly explained by the plate tectonic interpretation for the region. In particular, both the existence of the Transverse Ranges and the geometry of the San Andreas fault imply a stress pattern deviating from the simple horizontal shear, which parallels the spreading between the Pacific and North American plates. A number of possible mechanisms responsible for this anomalous stress field, are examined quantitatively in the light of seismicity and other tectonic observations, and in particular to the Palmdale uplift which was reported to have occurred between the years 1960-1965.
\r\n\r\nThe subsidence in the Wilmington oil field in Long Beach has long been a source of concern, as its economic consequences were disastrous. An area of approximately 20 mi has been affected by the subsidence, which in 1965 reached a value of 29 ft in the center of a bowl shaped pattern. The subsidence was accompanied by horizontal displacements of up to 12 feet. A series of shallow earthquakes, with hypocentral depths between 500 to 600 meters took place in the years 1947, 1949, 1952, 1955, and 1961. The slip planes were within a thin shale layer above the producing zones of the Wilmington field. It is now agreed\r\nupon that the subsidence was caused by the pore fluid pressure reduction resulting from oil production in the field. Indeed, after a repressurization program had been initiated, the subsidence was virtually stopped in all areas of the field. The subsidence, and subsequent rebound are simulated with the aid of the Finite Element calculation method. Pressure data compiled from records of individual oil wells are converted to input data for the numerical calculation. The simulations reproduce synthetically the field observations of vertical movements, horizontal movements, and collar count survey data. For the material rheology of the formations of the Wilmington field, first a layered linearly elastic approximation is used. However, it is found that not all observations can be reproduced with this material model, and in particular, the size of the subsidence pattern is overestimated by the linear models. Therefore, a more complete elastic-plastic cap model is incorporated into the simulations. With the aid of the nonlinear material characterization, the field observations can be reproduced in a satisfactory manner. It is demonstrated that the stress, prior to the onset of oil production in the Wilmington field, can have a dominant influence on the size and shape of the subsidence pattern. Accordingly, the final, and most successful, simulation includes a horizontal extensional stress component which is added to the overburden stresses at points lying in the vicinity of the center of subsidence.
\r\n\r\nThe lithosphere in the vicinity of island arcs and seamounts can be modeled as a plate which overlies an invicid fluid of asthenosphere material. It has been recognized that bathymetry profiles in such areas resemble the mathematical solutions of certain plate bending problems. This study attempts to improve on previous models by incorporating a lithosphere rheology based on rock deformation data for Dunn-Mountain Dunite. The material behavior is approximated to be as strain rate dependent elastic-plastic. The rheological approximation is converted into a moment-curvature relation for the lithosphere, which in turn is incorporated into a Finite Element algorithm for solving von Karman's plate bending equations. The complete formulation is tested in matching gravity and bathymetry in a profile in the vicinity of the island of Molukai of the Hawaiian-Emperor seamount chain. It is shown that the model can match the observations, while avoiding the excessive fibre stresses which have been produced in previous models.
" }, { "name": "Labotka, Theodore Charles", "degree": "PhD", "year": "1978", "title": "Geology of the Telescope Peak Quadrangle, California and Late Mesozoic Regional Metamorphism, Death Valley Area, California", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:08012018-084644606", "creators": [ { "name": { "family": "Labotka", "given": "Theodore Charles" }, "id": "Labotka-Theodore-Charles", "display_name": "Labotka, Theodore Charles" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/3snd-6z62", "abstract": "The Telescope Peak Quadrangle lies in the central Panamint Mountains which form the western boundary of Death Valley, California. The oldest rocks in the quadrangle consist of an 1800 m.y. complex of augen gneiss, quartzofeldspathic gneiss, and muscovite-biotite schist.\r\nThese rocks were intruded approximately 1400 m.y. ago by porphyritic quartz monzonite in the World Beater Dome area. The earlier Precambrian rocks are unconformably overlain by the later Precambrian Pahrump Group. The Pahrump Group is comprised of the Crystal Spring Formation, Beck Spring Dolomite, and Kingston Peak Formation. These formations show variations in thicknesses and lithologies within the\r\nquadrangle which indicate that the Pahrump Group was deposited in a dynamic environment. The lithologies and thicknesses of the Crystal Spring Formation and Beck Spring Dolomite indicate that most of the quadrangle was underlain by a platform of earlier Precambrian basement which stood above sea level in the World Beater Dome area (World Beater Island) and which dropped off into deeper water near\r\nTuber Canyon. The distribution of locally derived conglomerates in the lower Kingston Peak Formation and the presence of a local unconformity at the base indicate that at the end of Beck Spring Dolomite deposition, World Beater Island and adjacent areas to the north were uplifted, and the lower Kingston Peak Formation was deposited in eastern and western basins separated by the uplift. Continued deposition buried the uplift, and upper units in the Kingston Peak Formation include diamictite which grades northward into fine-grained greywacke, pillow basalt inter bedded in the diamictite, micaceous limestone, conglomerate, and argillite. The Pahrump Group is unconformably overlain by later Precambrian Noonday Dolomite, Johnnie Formation, Stirling Quartzite and Cambrian and Precambrian Wood Canyon Formation. The rocks were regionally metamorphosed at low pressure and intruded by leucocratic, muscovite-bearing granite about 80 m.y.\r\nago. Folding occurred after this metamorphism and a north-northwest-trending anticline and World Beater Dome were formed. Retrograde metamorphism accompanied the folding event. Subsequently, low-angle normal faults developed, the Miocene Little Chief stock was intruded, large masses of monolithologic breccia formed, and the Panamint Mountains\r\nwere uplifted along the Panamint Valley fault zone.
\r\n\r\nRegional metamorphic terrains in the Panamint Mountains and in the Funeral Mountains show marked differences in the physical conditions attained during metamorphism. The Panamint Mountains exhibit low pressure regional metamorphism, and the characteristic assemblages developed in pelitic schists are andalusite + staurolite + biotite\r\nand andalusite + cordierite + biotite. Isograds based on the appearance of sillimanite in pelitic rocks and tremolite and diopside in calcareous rocks indicate a westward increase in metamorphic grade toward an 80 m.y. muscovite granite pluton. A higher pressure metamorphic\r\nterrain was developed in the Funeral Mountains, and mineral\r\nassemblages in pelitic rocks are characterized.by the presence of kyanite. Garnet, staurolite, and kyanite isograds have been delineated and show that the grade increases toward the structual culmination of the Funeral Mountains, Migmatites occur in the highest grade area (sillimanite + garnet + biotite +muscovite + quartz), and the metasedimentary sequence was intruded by muscovite granite. The reaction chloritoid -> staurolite + garnet + chlorite is recorded in the Funeral Mountains, but in the Panamint Mountains the coexistence of chloritoid + biotite indicates that the garnet + chlorite join became unstable prior to the breakdown of chloritoid. Microprobe data on coexisting mineral assemblages, chemographic analysis of mineral facies in pelitic schists, and available experimental data indicate that the extremes in physical conditions attained during metamorphism were ~3 kb, ~600\u00b0C in the Panamint Mountains and ~8.5 kb, ~700\u00b0C in the Funeral Mountains. The sequence of tectonic and metamorphic events in the two areas is similar, but the facies series represent greatly different P/T gradients.
\r\n\r\nAssemblages in calciferous schist from the low pressure environment in the Panamint Mountains are characterized by quartz + epidote + calcic amphibole + chlorite + biotite in the trernolite zone and by quartz + epidote + calcic amphibole + garnet + biotite, quartz + epidote + diopside + calcic amphibole, and quartz + epidote + diopside + grossular in the diopside zone. Muscovite or microcline are common additional phases. Assemblages which occur in quartz + epidote + muscovite or quartz + epidote + microcline rocks are potentially useful for delineation of metamorphic grade and distinction between lower and higher pressure facies series. The compositions of calcic amphiboles formed in a low pressure environment generally fall in the series tremolite-pargasite and are related to the continuous break down of epidote and chlorite.
\r\n" }, { "name": "Murray, Jay Dennis", "degree": "PhD", "year": "1978", "title": "The Structure and Petrology of the San Jose Pluton, Northern Baja California, Mexico", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03282010-104553997", "creators": [ { "name": { "family": "Murray", "given": "Jay Dennis" }, "id": "Murray-Jay-Dennis", "display_name": "Murray, Jay Dennis" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/jrav-6990", "abstract": "The San Jose pluton, a 117-km^2 body of medium-grained biotite-hornblende tonalite in the foothills of the Sierra San Pedro M\u00e1rtir, northern Baja California, Mexico, is one of the more westerly plutons in the Cretaceous Peninsular Ranges batholith. The pluton has a teardrop form in plan view, elongate north-south and outlined by commonly well-exposed contacts. To the north the outline is remarkably hemi-circular and concordant to isoclinally folded, highly stretched strata. Traced southward, the form becomes increasingly discordant and tapers irregularly to a point. The wall rocks consist of tuffs, tuffaceous sedimentary rocks, and lesser amounts of marble, volcanic flows, and hypabyssal intrusive rocks of primarily basaltic to andesitic composition. Aptian and Albian fossils place the strata in the lower Cretaceous. Hornblende-hornfels facies assemblages are developed near the pluton contacts, but lower greenschist facies assemblages prevail outside the contact aureole.\r\n\r\nDetailed field and laboratory studies indicate that the pluton is chemically and mineralogically very uniform. The mapping has revealed, however, three texturally distinguishable lithologies each of significant areal extent and coherent form. (1) An interior core of prismatic hornblende tonalite (PHbT) is characterized by elongate prismatic hornblende, thin platy biotite, and a seriate grain-size distribution. (2) An outer horseshoe-shaped partial shell of stubby hornblende tonalite (SHbT) characterized by equant, equigranular, and anhedral poikilitic hornblende and biotite surrounds the PHbT. Together these units comprise the northern two thirds of the body. (3) A seriate porphyritic tonalite (SPT) phase distinguished from the PHbT by the presence of sparse phenocrystic plagioclase grains 6-20 mm in size forms the discordant southern wedge.\r\n\r\nThese major lithologic types represent two, or possibly three, distinct intrusive pulses. Conclusive evidence of the relative ages of the SHbT and PHbT intrusive units is lacking. However, the relationships of both units to several narrow zones of diorite and inclusion-rich tonalite associated with their mutual contact in the northeast, together with the scattered occurrence throughout the interior PHbT unit of inclusions of wall-rock lithologies similar to those around the northern and eastern margins of the pluton, strongly suggest that the SHbT is the younger mass and was emplaced around the perimeter of a pre-existing PHbT pluton. The SPT is completely gradational, both structurally and petrographically, into the PHbT, but is not exposed in contact with the SHbT. The SPT appears to be the youngest of the three units and may be either a late phase of the PHbT intrusive pulse or a separate pulse intruded prior to complete solidification of the PHbT.\r\n\r\nThe SHbT and PHbT units appear to have been emplaced almost entirely by forceful shouldering aside of the wall rocks. The effects of the penetrative deformation and distension of the wall rocks accompanying intrusion (and enhanced by externally-imposed deformation) are intense around the northern contact. These effects decrease gradually southward, giving way to predominantly brittle deformation within the wallrocks around the southern and particularly the southwestern margins. Emplacement of the SPT involved large-scale stoping as well as lateral displacement of the strata. Altogether, stoping appears to have contributed no more than 5-10% to the exposed area of the pluton.\r\n\r\nMagmatic flow plus marginal protoclasis produced an unusually regular pattern of northward-convex, arcuate foliation in the northern two thirds of the pluton. Foliation is gneissose and conformable to the contact near the pluton margins and decreases to weak in the interior.\tThe dip of foliation changes systematically from steeply outward around the margins through vertical to inward dipping in the interior. Traced southward into the SPT, foliation becomes faint or unrecognizable, the dip increases gradually again to vertical, and the pattern becomes only vaguely concentric and not obviously related everywhere to the local contacts. There is a suggestion of closure (in plan view) of vertical foliation attitudes around the probable center of latest intrusion in the interior of the SPT.\r\n\r\nThis foliation pattern suggests a funnel-shaped geometry of intrusion of PHbT and SPT magmas rising through relatively narrow conduits and expanding primarily to the north and east at essentially the final level of emplacement. The center of intrusion apparently migrated slightly southward with time from the interior of the PHbT into the center of the SPT. The SHbT was emplaced separately around the margins of the PHbT prior to intrusion of much or all of the SPT. Again expansion was preferentially to the north and east.\r\n\r\nThe pattern of deflection of wall rocks around the pluton also indicates predominantly northward and eastward expansion; lesser southward expansion was limited to late fracture-controlled breaking out of the SPT magma from the concordant confines of the northern masses.\r\n\r\nPetrographic and structural observations indicate that preferred mineral orientation developed primarily by rotation of crystals in the magma rather than by solid-state deformation and recrystallization. However, flow deformation may have continued locally after the completion of magmatic crystallization, particularly in the protoclastic gneissose rocks.\r\n\r\nVariations in the intensity of foliation and protoclasis in the tonalite and of penetrative deformation and distension in the wall rocks are attributed in large part to the history of progressive intrusion and asymmetric expansion. However, the pluton was apparently syntectonic, and externally-imposed deformation not directly related to emplacement of the San Jose pluton also contributed to the deformation of the wall rocks and outer parts of the tonalite, particularly around the northern and eastern margins. Systematic lineation patterns developed in both the wall rocks and the marginal gneissose tonalite in the latter areas suggest two sources of externally-imposed deformation: (1) southward expansion or shoving of the nearby Las Cochas pluton towards the northern margin of the San Jose pluton, and (2) deformation directed apparently upward and southwestward from the northeast and east, possibly in response to plutonic emplacement or regional uplift in the Sierra San PedroMartir.\r\n\r\nAlthough the oval outline and striking concordance of the pluton may be superficially suggestive of en masse diapiric emplacement, as opposed to gradual rise of magma through narrow channelways and balloon-like expansion at the final level of emplacement, the asymmetry of both the foliation pattern in the tonalite and the deformation of the wall rocks appears inconsistent with such a mechanism.\r\n\r\nMineralogically, the tonalite consists on the average of 64% plagioclase, 16% quartz, 11% hornblende, 5-6% biotite, and <0.3% alkali feldspar. Plagioclase, zoned from cores of An_(40-45) to rims of An_(20-30), was the principal liquidus phase, accompanied by minor clino-pyroxene in the SHbT and by hornblende and locally minor clinopyroxene in the PHbT and SPT. Biotite crystallized as a late interstitial or poikilitic phase primarily in coexistence with hornblende rather than as a reaction product. The trace amounts of late interstitial alkali feldspar (sanidine-orthoclase) are unusually potassic (0r_(90-95)) and do not appear to have crystallized in equilibrium with plagioclase; much or all of the potassium feldspar and possibly some of the biotite may have crystallized from a late-stage exsolved vapor phase.\r\n\r\nThe assemblage of opaque minerals -- nearly pure magnetite coexisting with complex lamellar intergrowths of titano-hematite and ferrian-ilmenite --implies crystallization under unusually oxidizing conditions apparently approaching those of the Mn0-Mn_30_4 buffer during much of crystallization, and increasing to those of the hematite-magnetite buffer at near-solidus conditions. Low Fe/(Fe + Mg) ratios in biotite (0.40-0.44), hornblende (0.32-0.36), and relict clinopyroxene (0.23-0.26) and low whole-rock Fe0/(Fe) + Fe_2O_3) ratios (0.408-0.515) also record unusually oxidizing conditions. Textural characteristics distinguishing the SHbT phase, on the one hand, from the PHbT and SPT phases, on the other, appear to be due to slight differences in f_0_2, f_H_2O and possibly temperature throughout all but the late stages of crystallization (SHbT magma drier, less oxidizing, and possibly slightly hotter).\r\n\r\nBoth the modal and chemical data confirm the petrologic significance of the textural units defined in the field. Together the PHbT and SPT define one set of variation trends which, for a given Si0_2 or modal quartz content, are characterized by slightly higher normative or modal plagioclase content and slightly lower normative or modal color index than the combined trends of the SUbT and its gneissose border phase. The SPT samples show a much more restricted range of modal and chemical compositions than do the PHbT samples, supporting the identification of the SPT as a third unit closely related to the PHbT. The composition of the outer gneissose phase of the SHbT is also distinctive, being slightly more felsic rather than more mafic than the rest of the tonalite.\r\n\r\nDespite the systematic compositional distinctions and the evidence for at least two, possibly three separate pulses of intrusion, both the modal and chemical compositions are remarkably uniform. SiO_2 contents range from 59.4 to 65.2% (exclusive of the gneissose border rocks). Variations in other elements are correspondingly much smaller. The SHbT and SPT, in particular, are both exceptionally homogeneous, with Si0_2 contents consistently in the ranges 60.1-62.0 and 61.8-64.1%, respectively. Yet both the strong compositional zoning in plagioclase and the sequence of mineral crystallization indicate that the composition of the melt changed considerably as crystallization proceeded. The homogeneity of the tonalite, particularly within the individual textural units, therefore implies highly viscous magmas in which processes of segregation or differential migration of crystals relative to melt (e.g., gravity settling or flow differentiation) were generally ineffective except on a small scale (local schlieren). Multiple emplacement of such large volumes of homogeneous magmas, rising essentially through the same conduit, without visible association of materials with other compositions argues strongly that the tonalite magmas were generated as primary magmas.\r\n\r\nChemically, the tonalite is characterized by a calcic alkali-lime index (63); high Na_2O and low K_2O contents (average: 4.82 and 0.74%, respectively), hence high Na_2O/K_2O ratios (average: 6.51); high Al_2O_3 and normative plagioclase contents (18.17 and 66.37%, respectively); and low Fe0/(Fe0 + Fe_2O_3) ratios (average: 0.463). The pluton is depleted in Rb, U, Th, and rare earth elements, and the ^(87)Sr/^(86)Sr initial (0.7036) and Pb isotopic ratios (206/204 = 18.56, 207/204 = 15.58, and 208/204 = 38.19) are relatively unradiogenic. The low concentrations of K and other incompatible elements and the relatively unradiogenic Sr initial and Pb isotopic ratios rule out significant contribution from older sialic crust or related sedimentary rocks. Partial melting of a material chemically similar to ocean floor (ocean ridge or abyssal) basalt, whether subducted oceanic crust or basaltic areas in the overlying mantle or lower crust, appears to best satisfy all of the compositional constraints.\r\n" }, { "name": "Okal, Emile Andr\u00e9", "degree": "PhD", "year": "1978", "title": "I. Application of Normal Mode Theory to Seismic Source and Structure Problems. II. Seismic Investigations of Upper Mantle Lateral Heterogeneity", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08262011-121733057", "creators": [ { "name": { "family": "Okal", "given": "Emile Andr\u00e9" }, "id": "Okal-Emile-Andr\u00e9", "display_name": "Okal, Emile Andr\u00e9" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/H2Q8-X139", "abstract": "In Part I, the theory of the normal modes of the Earth is investigated and used to build synthetic seismograms in order to solve source and structural problems. After a study of the physical properties of spheroidal modes leading to a rational classification, two specific\r\nproblems are addressed: the observability of deep isotropic seismic sources and the investigation of the physical properties of the Earth in the neighborhood of the Core-Mantle boundary, using SH waves diffracted at the core's surface.\r\n\r\nIn Chapter 1, it is shown that five different families of spheroidal modes can be isolated on the basis of their physical properties, including group velocities, attenuation and excitation functions. Except for a few hybrid modes, these families are arranged in \"pseudoovertone\" branches, along which physical properties vary smoothly. The simplified model of a spherical, non-gravitating Earth is used to give a theoretical description of the properties of modes with low angular orders. Their group velocity is shown to be consistent with the physical concept of dispersion along a pseudo-overt one branch, thereby justifying the use of asymptotic expansions along them in generating synthetic seismograms. An interpretation of the existence of the various families in terms of an increase in modecoupling\r\nwith angular order is presented. A formal classification of\r\nthe spheroidal modes into the five families is made, and a new nomenclature reflecting the physical properties of the modes is proposed.\r\n\r\nIn Chapter 2, the relative excitation of body and surface waves by isotropic and deviatoric sources is studied as a function of depth and frequency. Since the fundamental Rayleigh wave excitation dies off faster as a function of frequency and depth for isotropic than for deviatoric sources, an ultra-long period record at Pasadena of\r\nthe Colombian deep shock of 1970 (for which a compressional precursor was proposed), is studied and compared to synthetic seismograms calculated for several source models. The best agreement is obtained for a pure double-couple source. Linear combinations of synthetics for deviatoric and isotropic sources are tested for a wide range of\r\nrelative amplitudes, showing the data to be little sensitive to the presence of a reasonably large isotropic component.\r\n\r\nIn Chapter 3, profiles of seismic shear waves diffracted around the core (Sd) for three deep events recorded at stations across North America and the Atlantic Ocean are used to determine the properties of the lower mantle in the vicinity of the core-mantle boundary. The S wave velocity above the surface of the core is found to be 7.22 \u00b1\r\n0.1 km/s, in agreement with gross Earth models, but higher than previously reported values from direct measurements of Sd. No evidence for a low- velocity zone in the lower mantle is found. Synthetic seismograms for Sd are easily generated through normal mode summation. A comparison of the present data with a synthetic profile for Earth model 1066A gives excellent agreement at periods greater\r\nthan 45 seconds. Synthetics for other models confirm the absence of a strong low-velocity zone at the base of the mantle, and are used to strongly constrain any possible rigidity of the uppermost layers of the core.\r\n\r\nIn Part II, data sets of seismic body and surface waves are used in a search for possible deep lateral heterogeneities in the mantle. In both cases, it is found that seismic data do not require structural differences between oceans and continents to extend deeper than 250 km. In general, differences between oceans and continents are found\r\nto be on the same order of magnitude as the intrinsic lateral heterogeneity in the oceanic plate brought about by the aging of the oceanic lithosphere. A consistent similarity is inferred between stable shields and the oldest parts of the oceans.\r\n\r\nIn Chapter I, an analysis of records of multiply reflected ScS phases from ten deep focus earthquakes yields near-vertical one-way travel-time residuals ranging from -3.5 to +5.0 seconds. Continental and oceanic residuals overlap, and both indicate large lateral variations. Similar values are found for the older oceanic basins (Western Pacific, Brazil Basin) and continental shields. Most, if not all, of the variations can be attributed to differences in the\r\nlithosphere and asthenosphere, down to a depth of 200 km, and the present results are in good agreement with local models derived by independent means. Oceanic islands are found to be anomalous with respect to the neighboring ocean floor, the mantle beneath Hawaii, Iceland and Trindade (South Atlantic) being exceptionally slow.\r\n\r\nIn Chapter 2, Rayleigh wave phase velocities at very long\r\nperiods (185 to 290 seconds) are investigated and regionalized, taking into account the lateral heterogeneities in the oceanic plates revealed by earlier studies at shorter periods. The two-station method is applied to a few 'pure-age' oceanic paths, and is shown to\r\nbe compatible with an average gross Earth model below depths of 180 km. Under this assumed oceanic model, regionalized for age above 180 km, continental velocities are derived from a set of experimental great-circle values, both new or taken from previously published studies. The results basically agree with the earlier studies by\r\nKanamori or Dziewonski, and it is suggested that the assumption of a uniform oceanic model may have been responsible for some scatter in Kanamori's solution. The results of the present inversion are successfully checked against a set of values derived by the two-station\r\nmethod from a pure continental, tectonic, path. A recent event in Indonesia is then used as a further independent check, in what is believed to be the first experimental determination of Rayleigh wave phase velocities over a pure shield path at very long periods. The shield velocities fall within the range of variation of their oceanic\r\ncounterparts with the age of the plate, in agreement with the results of Chapter 1. This makes velocities derived theoretically from models involving deep continent vs. ocean lateral heterogeneities inconsistent with the present set of experimental data. Finally, it is shown that\r\nDziewonski's model S2 reconciles all experimental seismic data relative to shields without being significantly different from oceanic models below 240 km.\r\n" }, { "name": "Raikes, Susan Ann", "degree": "PhD", "year": "1978", "title": "I. Regional Variations in Upper Mantle Compressional Velocities beneath Southern California. II. Post-Shock Temperatures: Their Experimental Determination, Calculation, and Implications", "advisor": "Kanamori, Hiroo; Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04142020-164137815", "creators": [ { "name": { "family": "Raikes", "given": "Susan Ann" }, "id": "Raikes-Susan-Ann", "display_name": "Raikes, Susan Ann" } ], "advisors": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/3323-8080", "abstract": "The establishment in Southern California of a large seismographic network provides an unique opportunity for studying the seismic velocity variations within a tectonically active region that includes a major plate boundary, whose surface expression is the San Andreas Fault. In the first part of this thesis, the compressional velocity within the upper mantle beneath Southern California is investigated through observations of the dependence of teleseismic P-delays at all stations of the array on the distance and azimuth to the event. The variation of residuals with azimuth was found to be as large as 1.3 sec at a single station; the delays Here stable as a function of time, and no evidence was found for temporal velocity variations related to seismic activity in the area. These delays were used in the construction of models for the upper mantle P-velocity structure to depths of 150 km, both by ray tracing and inversion techniques. The models exhibit considerable lateral heterogeneity including a region of low velocity beneath the Imperial Valley, and regions of increased velocity beneath the Sierra Nevada and much of the Transverse \u00b7Ranges. These changes are attributed to variation in the degree of partial melting within the upper mantle; their relationship to, and implications for, regional tectonics are discussed in the final chapter of this section.
\r\n\r\nOne of the major uncertainties in the interpretation of shock wave data is the temperature reached under shock compression and subsequent release. The second half of this thesis describes the development of a technique for the experimental determination of post-shock temperatures, its application to several metals and silicates shocked to pressures in the range 5 to 30 CPa. The technique utilises an infra-red radiation detector to determine the brightness temperature of the free surface of the sample after the shock wave has passed through it, and has yielded highly reproducible results that are consistent for the wavelength ranges 4.5 to 5.75 and 7 to 14\u00b5. The comparison of these results with values calculated using conventional theories provides some insight into the thermal processes occurring in shock waves. In particular, the measured temperatures are generally higher than those calculated; this is attributed to elasto-plastic effects in metals, and is probably associated with strength effects in silicates, both of which are commonly ignored in the calculation of theoretical temperatures. The implications of these observations for the interpretation of shock-induced metamorphism and impact phenomena, and for the application of shock-wave data to the interpretation of the behaviour of silicates within the earth's mantle, are discussed in the final chapter.
" }, { "name": "Schloerb, Frederic Peter", "degree": "PhD", "year": "1978", "title": "Radio Interferometric Investigations of Saturn's Rings at 3.71- and 1.30-cm Wavelengths", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechETD:etd-10292008-160948", "creators": [ { "name": { "family": "Schloerb", "given": "Frederic Peter" }, "id": "Schloerb-Frederic-Peter", "display_name": "Schloerb, Frederic Peter" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/ztk7-wf79", "abstract": "NOTE: See Abstract within Thesis for Tables of Summary Results.\r\n\r\nInterferometric observations of Saturn and the rings have been obtained at 3.71 and 1.30 cm wavelengths. The observations have been analyzed by both model fitting and aperture synthesis techniques. They show that the rings have a very low brightness temperature, but attenuate the thermal emission from the planet significantly where they cross in front of it. The latter effect, when combined with the estimate of the ring brightness temperature, permits the optical depths of the rings to be estimated. The fits of the interferometric data to Saturn models in which the A and B rings are combined into a single ring are given in Table (1). The 3.71 cm observations were made at two epochs and the relative areas of the A and B rings that obscured the planet were different. The apparently inconsistent optical depth results of the two 3.71 cm data sets, then, indicate that the A ring optical depth is significantly less than that of the B ring. The relative areas of the A and B rings are the same for the 1976 1.30 cm and 3.71 cm observations and their optical depth results may be directly compared. They indicate that the ring optical depths are the same at the two wavelengths. These optical depths are quite similar to those estimated at visible wavelengths. The ring brightness temperatures, which are shown in the table normalized by the brightness temperature of the planet to remove any errors in the absolute calibration of the data, are also the same at the two wavelengths. No variation in the brightness temperature of the rings with tilt angle (B) was detected. A significant amount of radiation from the C ring was detected by the 3.71 cm observations, and the ring was also found to attenuate the planetary emission significantly. Unfortunately, the 1.30 cm observations were not sensitive enough to detect the C ring. The brightness temperature and optical depth results for the individual rings that are implied by all of the 3.71 cm observations are given in Table (ii). Limb-darkening of the planetary emission was simulated by solving for the best fitting planetary radius. No limb-darkening was detected at 3.71 cm, but an apparently significant amount was detected at 1.30 cm. The results at the two wavelengths are significantly different and indicate that the planet is more limb-dark at 1.30 cm than at 3.71 cm. This finding is interesting since it is contrary to what was predicted by atmospheric models which fit the Saturn microwave spectrum. The aperture synthesis analysis is independent of the model fitting and can be used to confirm its results and search for new features not included in the models. The aperture synthesis maps confirm the model fitting results and require no new brightness structures. In particular, no azimuthal variations of the brightness temperature of the rings were detected. The aperture synthesis maps also indicated that the true position of Saturn may be offset from the values given in the American Ephemeris and Nautical Almanac by about 0.3 arcsec. Consideration of simple physical models of the rings has shown that the radiation from the rings at centimeter wavelengths is almost entirely thermal emission from the planet that is scattered to the Earth by the ring particles. The models indicate that the ring particles are very good scatterers and very poor emitters at microwave wavelengths, and this conclusion sets constraints upon the size and composition of the ring particles. The similarity between the optical depths of the rings at visible and centimeter wavelengths probably indicates that the particles are much larger (\u2265 1 meter) than the centimeter wavelengths. The large sizes and excellent scattering properties of the particles indicate that they are composed of either a highly reflective or transparent material. At this time water ice is the most likely candidate, since it has been detected in the rings spectroscopically and is known to be highly transparent to microwaves at the low temperatures found at Saturn's rings.
" }, { "name": "Stein, Seth Avram", "degree": "PhD", "year": "1978", "title": "I. Seismological Study of the NinetyEast and Chagos-Laccadive Ridges, Indian Ocean. II. Models for Asymmetric and Oblique Spreading at Midocean Ridges. III. Attenuation Measurements Using Split Normal Modes", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:08292011-104040958", "creators": [ { "name": { "family": "Stein", "given": "Seth Avram" }, "id": "Stein-Seth-Avram", "display_name": "Stein, Seth Avram" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/1BWE-9G81", "abstract": "Part I of this work is a study of the seismicity of the Ninetyeast and Chagos-Laccadive Ridges in the Indian Ocean. These two features, in the interior of the oceanic plate, both show unusual seismicity. The mechanisms of these earthquakes were studied using body and surface Waves. This analysis shows that the Ninetyeast Ridge is still an active\r\nzone of deformation within the plate, along which substantial relative motion is taking place. The Chagos-Laccadive Ridge, though far less active, shows unusual seismicity in its southern portion. The seismicity on both ridges differs substantially from any previously discussed in the ocean basins. Both features should still be regarded\r\nas active today, though they do not fit into the classic ridge-transform-trench classifications.\r\n\r\nPart II of this work is a study of the mechanics of oblique\r\nand asymmetric seafloor spreading. It proposes that asymmetric seafloor spreading occurs as a consequence of the relative motion between ridges and slow moving mantle material below. A mechanical model of asymmetric spreading predicts that the trailing flank of a ridge migrating with\r\nrespect to the mantle spreads fastest. These predictions are tested against published data and found to be in good agreement in most places. Oblique spreading is said to occur at midocean ridges which spread slowly (half rate less than 3 cm/yr), while the spreading is perpendicular\r\nat faster spreading ridges. This relation is explored using the ratio of the power dissipated at ridges to that on transform faults to determine the most energetically favorable ridge-transform geometry. The angle of oblique spreading (\u03b8) is approximately related to the spreading rate\r\nby sin \u03b8 \u02dc V^(\u22121), in good agreement with observations.\r\n\r\nPart III of this Work is a study of the attenuation of the longest period normal modes of the earth. The rotationally and elliptically split normal modes of the earth are observed for the 1960 Chilean and the 1964 Alaskan earthquakes by analysis in the time domain. Synthetic\r\nseismograms are computed using theoretical results which show the dependence of the amplitude and phase of the singlets on source location, depth, mechanism and the position of the receiver. By comparing these synthetics to the filtered record, the Qs of the longest period spheroidal\r\n(_0^S_2-_0^S_5) and torsional (_0^T_3, _0^T_4) modes can be estimated.\r\nIn addition, the Q of the fundamental radial mode _O^S_O is measured.\r\n" }, { "name": "Terrile, Richard John", "degree": "PhD", "year": "1978", "title": "High Spatial Resolution Infrared Imaging of Jupiter: Implications for the Vertical Cloud Structure from Five-Micron Measurements", "advisor": "Westphal, James A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04082010-091644952", "creators": [ { "name": { "family": "Terrile", "given": "Richard John" }, "id": "Terrile-Richard-John", "display_name": "Terrile, Richard John" } ], "advisors": [ { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "advisor", "display_name": "Westphal, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/q0w2-hn20", "abstract": "This study describes the design and construction of a 5 \u00b5m imaging system used at the Hale 5 m (200 inch) telescope to acquire high spatial resolution infrared images of Jupiter. These images, recorded in a spectral region clear of terrestrial and Jovian gaseous absorption, offer a unique look into the deep atmosphere and provide direct observational evidence for the existence of multiple layers of clouds in the Jovian atmosphere. Evidence of layering is provided by the observed trimodal nature and persistence of the 5 \u00b5m flux-frequency distribution of equal areas on the Jovian disk. This indicates that three distinct brightness temperatures have a higher probability of being observed than a continuum of temperatures, and that, despite \r\nsignificant observed variations in the lateral 5 \u00b5m cloud distribution, this phenomenon is a long term stable vertical cloud feature. Furthermore, the visible color differences correlate with areas of different\r\n5 \u00b5m intensity, implying that the colors are due to reflection from areas of different chemistry or state at different levels in the atmosphere. Also, short time scales are observed for large 5 \u00b5m flux variations over extensive areas of the Jovian disk, supporting the concept \r\nthat the redistribution of obscuring clouds accounts for the contrasts at 5 \u00b5m. Finally, the 5 \u00b5m limb-darkening and opacity models, derived from imaging and spectroscopic measurements, are consistent with multiple layering of clouds in the Jovian atmosphere.\r\n\r\nFurther information about the Jovian clouds results from the combination of 5 \u00b5m spectroscopic and imaging data sets. From the shape of the 5 \u00b5m spectrum true maximum brightness temperatures are derived, corrected for the clearest regions in the Jovian atmosphere. Furthermore, from data on spectral line saturation, limits are placed on the 5 \u00b5m cloud reflectivity over the field of view of the spectrometer. With this information, combined with the knowledge of the spatial flux distribution from imaging, constraints are derived for the optical properties of the upper Jovian clouds.\r\n\r\nA three layer cloud model is developed which is consistent with all of the observational data at 5 \u00b5m. The three model cloud layers have cloud top temperatures of T_1 \u2264 190\u00b0K (presumably T_1 \u2243 140\u00b0K), T_2 = 228 \u00b1 2\u00b0K and T_3 = 292 \u00b1 8\u00b0K. The highest layer, found only over the white zones and red spots, has optical depth near unity and transmits radiation from deeper levels. This upper level has a mean\r\n5 \u00b5m cloud reflectivity less than 0.4, while the whole central 25% of the disk has a mean reflectivity less than 0.1. The middle cloud deck is present under the upper level clouds and over the brown colored Jovian belts. This level is optically thick everywhere except in regions where blue-gray areas are visible. Here the middle level thins \r\nto a mean optical depth of about 2 and allows radiation from the deepest and hottest level to be detected.\r\n" }, { "name": "Anderson, James Rodney", "degree": "PhD", "year": "1977", "title": "The Polymetamorphic Sequence in the Paleozoic Rocks of Northern Vermont: A New Approach Using Metamorphic Veins as Petrologic and Structural Markers", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechETD:etd-11012006-140440", "creators": [ { "name": { "family": "Anderson", "given": "James Rodney" }, "id": "Anderson-James-Rodney", "display_name": "Anderson, James Rodney" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/smdr-at29", "abstract": "The sequence of metamorphic events that have affected the lower and middle Paleozoic rocks of northern Vermont has been defined in this study. The use of metamorphic veins as structural and petrologic markers has helped to establish the correspondence between deformational and mineral growth features. The effects of the major metamorphic events have been followed through the area along several traverses, the longest of which is 50 miles in length. The study combines detailed analysis of the sequence of structural elements with electron microprobe and petrographic analysis of the mineral growth in the metamorphic veins and host rock.
\r\n\r\nMuch of the history of the chemical path of the vein and host rock systems is preserved in zoned grains and grains included in other minerals. The zoning trends in certain key minerals such as plagioclase, amphibole, muscovite, and coexisting calcite and ankerite indicate that the grade of each rock system was changing with time. The path of the systems can be followed in considerable detail. Not only are the effects of changing grade during a single event typically preserved, but also the effects of several superimposed mineral growth events can be preserved in a sample.
\r\n\r\nFive major metamorphic events and several minor events have occurred in northern Vermont. The two oldest events affected only the Cambrian and Ordovician rocks; these events are designated Oa and Ob. Event Oa involved widspread biotite grade mineral growth and the formation of a secondary bedding schistosity. Ob is the most prominent of the pre-Silurian events and is Late Ordovician in age. It produced high grade mineral growth in the Green Mountains and in the Worcester Mountains; in the latter area staurolite-kyanite grade assemblages occur. There was also widespread formation of small scale isoclinal folds with east-west axial trends during Ob. Major east-west trending folds of the same generation occur locally.
\r\n\r\nThree events affected both the pre-Silurian rocks and the Silurian and Devonian rocks. These events are Middle to Late Devonian in age. Da is the oldest of the three and produced biotite to garnet grade or higher mineral growth over the entire study area. Da was also a significant deformational event, responsible for the formation of major and minor north-south trending folds. Event Db mainly involved deformation, but biotite grade mineral growth occurred in rocks where the axial plane foliation associated with Db was developed. Folds formed during Db have north-south trends and are most prominent in the eastern part of the area. The last major event, Dc, was a period of mineral growth without associated deformation and was widespread in extent. The highest grade mineral growth of Dc, up to staurolite-andalusite and sillimanite grades, has a close spatial relationship to the intrusive bodies of the New Hampshire plutonic series. In areas far from such plutons, this mineral growth is biotite grade or absent.
\r\n\r\nMetamorphic veins are associated with each of the major events except Db. The veins are discontinuous and have a general chemical correspondence to mineral growth of the same generation in the adjacent host rock. Differences in the relative timing of growth in the veins and host rocks occur in some instances, so that the correspondence is fairly complicated. The veins appear to have formed during the metamorphic events from material derived locally in the host rocks.
" }, { "name": "Burdick, Lawrence James", "degree": "PhD", "year": "1977", "title": "Broad-Band Seismic Studies of Body Waves", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:12042020-183920934", "creators": [ { "name": { "family": "Burdick", "given": "Lawrence James" }, "id": "Burdick-Lawrence-James", "display_name": "Burdick, Lawrence James" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/zt3a-vh80", "abstract": "Analytic information from both long period and short period seis\u00admometers is used in three different studies of teleseismic body waves. The composite broad-band information is first used in a source study of the 9/12/66 Truckee, 8/1/75 Oroville and 4/9/68 Borrego Mountain earthquakes in California. The purpose of the study is to determine the fault area and displacement from the body wave pulse shape and to compare this information with the postseismic data.\tThe pulse shapes are determined by a simultaneous short period-long period deconvolution procedure and matched with theoretical pulses from fault models. The results indicate that the area which radiated the body waves was smaller than the area of the aftershock zone and that the displacement in this area was larger than the offsets observed at the surface. The purpose of the second study is to find the value of t*\u03b2 for teleseismic S waves with a raypath under the continental United States. The data set consists of long and short period body waves from the Borrego Mountain earthquake as observed in the northeastern U. S. The P waveforms are dominated by the sP phase and the SH waveforms by the sS. It is assumed that there are no losses in pure compression so that the relative attenuation rate of P and S waves is known. The initial source radiation is determined from the sP phase and the value of t*\u03b2 from the spectral content of the S wave. The results indicate that it is 5.2 \u00b1 .7 seconds along this raypath. Long and short period body waves from some deep South American events are used to test for lateral asymmetry of the Q distribution under the U. S. The results indicate that the attenuation rate of teleseismic body waves is roughly constant across the North American continent. The t*\u03b2 value for a 600 km deep earthquake appears to be about 3. seconds. The purpose of the final study is to find an upper mantle compressional velocity profile which explains both the short period and long period waveform data. The region of study is the western or tectonically active portion of the United States. The short period waveforms are from NTS bombs and the long period waveforms are from shallow California earthquakes with known source mechanisms. Travel time and apparent velocity data are also used to constrain the model. The new velocity profile is called T7. It accurately predicts the long and short period body waveshapes from 10\u00b0 to 30\u00b0. The new model is substantially different than the previous one for the region. The first discontinuity is at 400 km depth which is shallower than before and the second is at 670 km which is deeper. The velocity jumps have been reduced in size to 5% and 4% respectively. The velocities through much of the profile have been reduced slightly to improve the fit to the travel time data." }, { "name": "Dymek, Robert F.", "degree": "PhD", "year": "1977", "title": "Mineralogic and Petrologic Studies of Archaean Metamorphic Rocks from West Greenland, Lunar Samples, and the Meteorite Kapoeta", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:12042020-191103512", "creators": [ { "name": { "family": "Dymek", "given": "Robert F." }, "id": "Dymek-Robert-F", "display_name": "Dymek, Robert F." } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/wht4-n543", "abstract": "In Part I of this thesis, petrographic and electron microprobe data are reported for samples from a series of high-grade Archaean gneisses, collected on Lang\u00f8, an island in the northwest corner of the Godth\u00e5b District of West Greenland. Rocks with a wide variety of bulk compositions occur that all preserve evidence for two distinct episodes of metamorphic mineral growth. Syn- to post-tectonic hornblende granulite grade metamorphism (MI) was followed by post-tectonic amphibolite grade metamorphism (MII) at a later time. In potassium feldspar bearing gneisses, MI assemblages, in addition to quartz and plagioclase are: garnet + biotite (brown) \u00b1 sillimanite; cordierite + biotite (brown) \u00b1 sillimanite; and biotite (brown). In potassium feldspar- free gneisses, MI assemblages, in addition to quartz and plagioclase are: cordierite + garnet + biotite (brown); and orthopyroxene + biotite (brown) \u00b1 cordierite. As a result of MII, cordierite and garnet have been replaced by kyanite + biotite (green). Brown biotite is Ti-rich (>1.0 wt% TiO\u2082), whereas green biotite is Ti-poor (\u227e1.0 wt% TiO\u2082), and an examination of biotite analyses suggests that Ti is incorporated in that mineral via a vacancy-forming substitution. In mafic rocks, MI assemblages include various combinations of hornblende (green-brown) + clinopyroxene \u00b1 orthopyroxene \u00b1 garnet \u00b1 biotite, with plagioclase and rarely quartz. However, garnet and clinopyroxene do not occur together. As a result of MII, pyroxene has been replaced by calcic amphibole that differs in color (pale green to blue green) and composition (Na, K, Al, Ti are lower; Si, Mg, Fe\u00b3\u207a are higher) from the MI varieties. MI hornblende and plagioclase have an extremely large, compositional range, which correlate with one another in terms of Al/(Al+Si) and Na/(Na+Ca), and suggest that their compositions are controlled by rock composition, and not by metamorphic grade at these conditions.
\r\n\r\nThe composition of coexisting pyroxenes, the position of the kyanite-sillimanite boundary, and the composition of garnet (cores) and cordierite constrain the pressure and temperature for MI to lie between ~7-8 kb and ~700-800\u00b0C. Temperatures calculated from Fe-Mg partitioning between garnet (rims) and MII biotite suggest ~450\u00b0C for MII, and the occurrence of kyanite would indicate a pressure of 3-4 kb for this temperature. The MI event can be ascribed with certainty to regional metamorphic-magmatic activity at ca. 2.8 AE (Black et al., 1973), whereas MII may correspond to regional heating during the emplacement of the Q\u00f4rqut Granite at ca. 2.5 AE (Baadsgaard and Collerson, 1976), or to a regional thermal event at ca. 1.6 AE identified in isotopic studies (Pankhurst et al., 1973).
\r\n\r\nThe pressure and temperature estimated for MI imply a thermal gradient of ca. 30\u00b0C/km, and a minimum crustal thickness of 20 km at the time of metamorphism. The petrologic characteristics of MI are similar to medium-P facies series metamorphism found in younger orogenic belts, and nothing \"unique\" can be ascribed to this Archaean metamorphic event, based on the presently-available data and observations. Parts II and III of this thesis are a series of published papers that involve mineralogic and petrologic studies of Apollo 15, 16, and 17 lunar samples and the meteorite Kapoeta.
\r\n\r\nParts II and III of this thesis are a series of published papers\r\nthat involve mineralogic and petrologic studies of Apollo 15, 16, and\r\n17 lunar samples and the meteorite Kapoeta.
" }, { "name": "Dzurisin, Daniel", "degree": "PhD", "year": "1977", "title": "1. Scarps, Ridges, Troughs, and Other Lineaments on Mercury. 2. Geologic Significance of Photometric Variations on Mercury", "advisor": "Murray, Bruce C.; Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09052018-080305029", "creators": [ { "name": { "family": "Dzurisin", "given": "Daniel" }, "id": "Dzurisin-Daniel", "display_name": "Dzurisin, Daniel" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/4c38-xp93", "abstract": "Volcanic and tectonic implications of the surface morphology of Mercury are addressed in two separate sections. In Part 1, mercurian scarps, ridges, troughs, and other lineaments are described and classified as planimetrically linear, arcuate, lobate, or irregular. A global pattern of lineaments is interpreted to reflect modification of linear crustal joints formed in response to stresses induced by tidal spindown. Large arcuate scarps on Mercury most likely record a period of compressional tectonism near the end of heavy bombardment. Shrinkage owing to planetary cooling is the mechanism preferred for their production. Two planimetrically lobate escarpments probably formed by uplift along intersecting elements of the global mercurian lineament pattern. One may subsequently have been modified by extrusive igneous activity along its trace. Most irregular scarps inside craters are interpreted to be tectonic features formed in response to local stresses, perhaps induced by subsurface magma movements.
\r\n\r\nLarge linear ridges on Mercury may record a period of volcanism responsible, at least in part, for intercrater plains formation. Linear ridge production is speculatively attributed to accumulation of extruded material along linear vents, and to differential erosion around relatively\r\nresistant dikes intruded into near-surface materials.
\r\n\r\nLinear, open-ended troughs are well-developed in a distinct terrain unit on Mercury characterized by intense modification of pre-existing landforms. Regional trends defined by these troughs are consistent with those of the global mercurian lineament pattern. Combined with their regional setting, this suggests that the troughs formed by differential erosion along linear crustal fractures. A few are radial from nearby large craters, and may be highly modified chains of secondary impact craters.
\r\n\r\nScarps, ridges, and troughs in and around Caloris Basin define trends radial from the basin center and concentric with its rim. A radial system of linear ridges outside Caloris probably reflects the combined effects of ejecta deposition and erosion during the basin-forming event. Planimetrically irregular ridges developed in smooth plains inside Caloris may owe their origin to regional subsidence, perhaps in response to magma withdrawal from below to form smooth plains outside the basin rim. Gravitational readjustment owing to loading by plains material may be responsible for scarp and ridge formation outside Caloris. Finally, isostatic readjustment to basin excavation may have caused regional uplift inside the basin to form a system of planimetrically irregular troughs.
\r\n\r\nIn Part 2, measurements of local normal albedo are combined with computer-generated photometric maps of Mercury to provide constraints on the nature of mercurian surface materials and processes. If the mercurian surface obeys the average lunar photometric function, its normal albedo at 554 nm is .16\u00b1.03. This is roughly 40% higher than the corresponding lunar value, but the difference may be largely attributable to differences in the photometric function s of the two bodies, and to unmodelled effects such as multiple scattering. The existence of relatively bright smooth plains confined to crater floors is most easily reconciled with a volcanic origin for some mercurian smooth plains. Lack of photometric contrast across most large escarpments on Mercury is consistent with the tectonic origin for these features inferred from morphologic studies. Local photometric and transectional relationships in two instances suggest mantling of preexisting topography by younger, perhaps volcanic, material. Brightness of several extremely localized patches in large craters is attributed to enhanced backscatter owing to multiple reflections relative to surrounding plains and craters. These patches are generally \"bluer\" than typical mercurian plains, and some are surrounded by material which is \"redder\" than typical plains. Chemical alteration of crustal rocks, perhaps related to fumarolic activity along impact-induced fractures, is the preferred explanation for these uniquely mercurian features.
" }, { "name": "Geller, Robert James", "degree": "PhD", "year": "1977", "title": "Part I. Earthquake Source Models, Magnitudes and Scaling Relations. Part II. Amplitudes of Rotationally Split Normal Modes for the 1960 Chilean and 1964 Alaskan Earthquakes", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09022011-110356908", "creators": [ { "name": { "family": "Geller", "given": "Robert James" }, "id": "Geller-Robert-James", "display_name": "Geller, Robert James" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/9ABM-QM05", "abstract": "In Part I several fundamental concepts in seismology are examined in detail. The different teleseismic seismic magnitude scales are studied on the basis of Gutenberg and Richter's original notepads. The \"revised magnitudes\" presented by Richter and Duda are shown to be basically body wave magnitudes which are converted to the surface wave basis. These revised magnitudes are systemically higher (by an average of 0.22) than the magnitudes published by Gutenberg and Richter in Seismicity of the Earth, which are basically surface wave magnitudes. Use of the revised magnitudes has led to substantial over-estimates\r\nof the moment of great earthquakes. Fault area, rather than magnitude, should be used for moment estimates when the moment is unavailable.\r\n\r\nA dataset of 41 moderate and large earthquakes is used to derive scaling laws relating kinematic fault parameters such as magnitudes, moment and fault dimensions. If effective stress and static stress drop are equal, then, fault rise time, \u03c4, and fault area, S, are related by \u03c4 = 16S^\u00bd /(7\u03c0^(3/2)\u03b2), where \u03b2 is shear velocity. Fault length (parallel to strike) and width (parallel to dip) are empirically related by L = 2W. Observed data agree well with the predicted scaling relations. Fault width (i.e. the two dimensionality of faults) must not be neglected. Inclusion of width leads to different average source spectra for surface waves and body waves. The m_b versus M_s relation from this study differs significantly from the Gutenberg-Richter relation, because the Gutenberg-Richter equation was derived for body waves with a predominant period of about 5 sec and thus does not apply to modern 1 sec m_b determinations. Previous investigators who assumed that the Gutenberg-Richter relation was derived from 1 sec data were in error.\r\n\r\nIn Part II, the theory necessary to calculate the amplitudes\r\nof the earth's rotationally and elliptically split free oscillations is developed. The amplitude of each singlet is explicitly given as the product of factors for fault geometry, seismic moment, source depth, earth structure and the geographic coordinates of the source and receiver. These results are applicable for the synthesis of either spectra or time domain records for which splitting is an important factor.\r\n\r\nThe splitting of the earth's normal modes was observed for both the 1960 Chilean and 1964 Alaskan earthquakes. The theoretical results for the excitation of singlets are used to predict the relative amplitude of observed split peaks. Good agreement is obtained for thrust fault source models derived from long period surface waves. However, other mechanisms, such as a slow isotropic volume change, are also consistent with the split mode relative amplitudes, and are excluded only by additional data.\r\n\r\nThe split modes are observed for the 1960 Chilean earthquake by analysis in the time domain. One hundred fifty hours of the Isabella, California strain record are filtered to isolate individual multiplets. Synthetic seismograms with and without splitting are used to confirm the splitting of _0S_2 and _0S_3 and to demonstrate the splitting of _0S_4, _0S_5, _0T_3 and _0T_4. Different techniques for measuring the Q of split modes are studied. It is concluded that Q determinations from comparison of time domain synthetics to data give much more stability than frequency domain techniques. Uncertainties in the calibration of the instrumental absolute amplitudes rule out a direct determination of the moment of the Chilean earthquake. However, by comparing Isabella records for Chile and Alaska, the long-period moment of the Chilean earthquake is found to be 3.3 times that of the Alaskan event. By using the moment estimated for Alaska from long period surface waves, the moment of the Chilean earthquake is estimated to be 2.4 x 10^(30) dyne cm." }, { "name": "Goldman, Don Steven", "degree": "PhD", "year": "1977", "title": "Crystal-Field and M\u00f6ssbauer Applications to the Study of Site Distribution and Electronic Properties of Ferrous Iron in Minerals with Emphasis on Calcic Amphiboles, Orthopyoxene and Cordierite", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:12072020-163044493", "creators": [ { "name": { "family": "Goldman", "given": "Don Steven" }, "id": "Goldman-Don-Steven", "display_name": "Goldman, Don Steven" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/ha25-qf72", "abstract": "The electronic absorption spectroscopy of ferrous iron is sensitive to the geometry of the coordination site in which it resides. This sensitivity enables ferrous iron in multiple sites in a mineral to be distinguished. The spectra of ferrous iron in the M(2) site in orthopyroxene, (Mg,Fe)SiO\u2083, are used as a model for the spectroscopic properties of iron in a distorted site. The splitting of the \u2075T_(2G) ground state is observed to be 2350 cm\u207b\u00b9 enabling a theoretical point-charge model to be developed using C_(2V) symmetry. The intensity of the near infrared bands due to the splitting of the \u2075E_G state are found to linearly correlate with the concentration of ferrous iron in the M(2) site. From this correlation, calibrations are established for the intensities of the near infrared bands so that quantitative site distributions can be determined for single orthopyroxene crystals from optical spectra. Thermally induced cation disorder allows assignments to be made for spin-allowed and spin-forbidden ferrous iron bands originating from both the M(1) and M(2) sites.
\r\n\r\nThe electronic absorption and M\u00f6ssbauer spectra of calcic amphiboles, Ca\u2082(Mg,Fe)\u2085Si\u2088O\u2082\u2082(OH)\u2082, are reinterpreted to include previously neglected contributions from ferrous iron in the calcium-rich M(4) site. Bands due to ferrous iron in M(l), M(2) and M(3) sites are examined in the electronic spectra and the intensity of the Fe\u00b2\u207a/Fe\u00b3\u207a intervalence charge-transfer band is found to linearly correlate with the ferric iron content. Next\u00ad nearest neighbor variations of ferric iron and aluminum are found to affect the ferrous iron peak parameters in the M\u00f6ssbauer spectra of calcic amphiboles which impairs the capability of determining accurate site distributions.
\r\n \r\nFerrous iron is found to be present in the channel cavities and the octahedral site in cordierite, (Mg,Fe)\u2082Al\u2084Si\u2085O\u2081\u2088, osumilite, K(Mg,Fe)\u2082Al\u2083(Si\u2081\u2080Al\u2082)O\u2083\u2080, and beryl, Be\u2083Al\u2082Si\u2086O\u2081\u2088. In cordierite, two types of water are suggested to be present in the channel cavities that differ in crystallographic orientation and relationship to other channel constituents, whereas osumilite is found to be virtually anhydrous. In cordierite, cation migration within the channels is suggested to occur after dehydration which could explain the observed change in the lattice geometry. The blue color in these minerals is suggested to be due to intervalence charge transfer between ferrous iron and channel ferric iron. Electronic spectra suggest that structural state variations occur in osumilite, whereas significant variations in cordierite are not apparent. Ferric iron in tetrahedral coordination in osumilite is indicated from M\u00f6ssbauer spectra.
\r\n\r\nThe effect of site size and distortion on the spectroscopic properties of ferrous iron in terms of band position, intensity and polarization anisotropy is examined. As a non-centrosymmetric site becomes larger, absorption bands migrate to longer wavelengths (lower energy), become more intense, and exhibit greater polarization anisotropy among each other. For these sites, intensification is correlated with a decrease in the quadrupole splitting determined from M\u00f6ssbauer spectra. The spectroscopy of ferrous iron in large sites is distinctly different from that observed from ferrous iron in smaller sites.
" }, { "name": "Hart, Robert Stuart", "degree": "PhD", "year": "1977", "title": "The Distribution of Seismic Velocities and Attenuation in the Earth", "advisor": "Anderson, Donald L.; Kanamori, Hiroo", "url": "https://resolver.caltech.edu/CaltechTHESIS:10182024-224317663", "creators": [ { "name": { "family": "Hart", "given": "Robert Stuart" }, "id": "Hart-Robert-Stuart", "display_name": "Hart, Robert Stuart" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "advisor", "display_name": "Kanamori, Hiroo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/s3wh-ep64", "abstract": "Estimates of the radial distribution of seismic velocities and density and of seismic attenuation within the earth are obtained through inversion of body wave, surface wave, and normal mode data. The effect of attenuation related dispersion on gross earth structure, and on the reliability of eigenperiod identifications is discussed.\r\nThe travel time baseline discrepancies between body waves and free oscillation models are examined and largely resolved.
\r\n\r\nAs preliminary steps in this study, a technique is developed for determining S wave arrival times and applied to records from several large nuclear explosions. The resulting low-scatter travel times are combined with other high resolution body wave results to help define a gross earth model, designated C2, which fits 86% of the normal mode data to within their 95% confidence limits.
\r\n\r\nThe second stage considers the effect of attenuation on seismic dispersion and shows the perturbation of phase velocity to be approximately an order of magnitude greater than the observational error.\r\nInclusion of an attenuation correction in the normal mode data and subsequent inversion results in an elimination of the baseline dis\u00adcrepancies.
\r\n\r\nThe final portion of this research covers the inversion of all available seismic Q data to obtain a better estimate of the radial distribution of seismic absorption in the earth. Prominent features of the resulting Q models, designated SL1 and SL2, are low Q zones in both the upper mantle and in the 150 kilometers of the mantle just above the core-mantle boundary and finite compressional dissipation in the inner core. Model SL1 is used to compute the attenuation corrections for the normal mode data for a final inversion for seismic veloc\u00adities and density. The resulting attenuation-corrected earth model, QM3, fits the corrected observations to the same precision as model\r\nC2 fits the raw data. Moreover, QM3 represents a better match to the travel time data than previous earth models. The reliability of existing eigenperiod identifications in light of excitation criteria and computed attenuation is examined. For completeness, an appendix is included in which the relative excitations of a large set of spheroidal modes\r\n(T \u2265 45 sec, \u2113 \u2264 150, n\t\u2264 30) and toroidal modes (T \u2265 45 sec, \u2113 \u2264 150, n \u2264 7) is presented for both the Alaska earthquake (1964) and the Columbia earthquake (1970) sources.
" }, { "name": "Laird, Jo", "degree": "PhD", "year": "1977", "title": "Phase Equilibria in Mafic Schist and the Polymetamorphic History of Vermont", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:10312023-155456278", "creators": [ { "name": { "family": "Laird", "given": "Jo" }, "id": "Laird-Jo", "display_name": "Laird, Jo" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/nd16-8e08", "abstract": "Phase relationships in metamorphosed mafic rocks from Vermont and adjacent Quebec are presented and used to develop an understanding of the petrogenesis of this common rock type and to reconstruct the Paleozoic history of the region. Samples have been collected from Cambrian to Devonian mafic and pelitic schists. The metamorphic grade defined by the phase assemblages in the pelitic layers ranges from biotite to sillimanite. Electron microprobe analyses of the minerals in the mafic rocks are correlated with the physical conditions of metamorphism, and overgrowth relationships in amphibole grains record relative time. From these data and field and isotopic studies, mineral growth periods are characterized by metamorphic grade and facies series and assigned to two Ordovician and two Devonian events. The continuous and discontinuous reactions which describe the mineral chemistry and abundance variations in basaltic compositions are inferred from graphical and least-squares analyses.
\r\n\r\nIn mafic rocks the common assemblage observed is amphibole-chlorite-epidote-plagioclase-quartz-carbonate-K mica-Ti phase-Fe\u00b3\u207a oxide. Medium pressure progressive metamorphism of this assemblage causes the following continuous changes. 1) Ca-amphibole is enriched in the tschermakite and edenite end members. 2) Biotite and chlorite become richer in Al. 3) The discontinuous change from albite to oligoclase is followed by a continuous increase in the anorthite content of plagioclase. 4) Calcite becomes more ankeritic. Hornblende occurs with albite in the low garnet zone and oligoclase in the medium to high garnet zone. Accompanying these compositional variations are the growth of amphibole, the consumption of chlorite, epidote, and plagioclase, and the liberation of H\u2082O. In contrast, during the medium- to low-pressure metamorphism of mafic rocks, plagioclase grows and the transition from actinolite to hornblende is not complete in rocks where the albite to oligoclase jump has already occurred. Epidote disappears at a lower grade than for medium-pressure metamorphism.
\r\n\r\nHigher pressure metamorphism results in an increase of the glaucophane/riebeckite substitution in the amphibole and of the phengite substitution in the K-rich white mica. Ultimately, the transition from medium-pressure to high-pressure metamorphism yields the observed assemblage Ca-rich amphibole - glaucophane which results from the cross-over reaction: \r\nactinolite + chlorite + albite + glaucophane + epidote.
\r\n\r\nThe cross-over reaction: hornblende+chlorite+epidote+plagioclase\u2081 +quartz = cummingtonite+plagioclase\u2082 , where the product plagioclase\u2082 is more abundant and anorthitic than the reactant plagioclase\u2081 , occurs in Ca-poor mafic rocks in the medium- to low-pressure garnet zone. In medium-pressure Fe-rich basaltic rocks, the assemblage actinolite-chlorite-stilpnomelane occurs in the\r\nbiotite-albite zone. It is replaced by hornblende-chlorite in the garnet- albite zone and by hornblende-chlorite-garnet in the garnet-oligoclase zone.
\r\n\r\nThe Silurian and Devonian mafic rocks in northeastern Vermont record medium- to low-pressure and low-pressure mineral growth which is assigned to two events during the Devonian Acadian orogeny. It is proposed that the lower pressure event was the later. These two events are expressed by medium-pressure and medium- to low-pressure mineral growth in the Cambrian and Ordovician rocks to the west.
\r\n\r\nTwo periods of Ordovician metamorphism are recorded in the Lower Paleozoic units and are assigned to the Taconic orogeny. High-pressure, medium- to high-pressure, and medium-pressure metamorphism are observed. The higher than \"normal\" Barrovian facies series metamorphism is confined to northern Vermont and southern Quebec. Locally, glaucophane-bearing rocks and ornphacite assemblages record high-pressure facies series metamorphism.
" }, { "name": "Weiner, Stephen", "degree": "PhD", "year": "1977", "title": "Aspects of the Biochemistry of the Organic Matrix of Extant and Fossil Mollusks", "advisor": "Lowenstam, Heinz A.; Hood, Leroy E.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11112019-161331927", "creators": [ { "name": { "family": "Weiner", "given": "Stephen" }, "id": "Weiner-Stephen", "display_name": "Weiner, Stephen" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." }, { "name": { "family": "Hood", "given": "Leroy E." }, "id": "Hood-L-E", "orcid": "0000-0001-7158-3678", "role": "advisor", "display_name": "Hood, Leroy E." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geobiol" ], "doi": "10.7907/Q5CV-RC94", "abstract": "The biochemistry of the organic matrix of mollusks is investigated to improve our understanding of the function of this material in shell formation and to explore the possibility of using fossil organic matrix components to study aspects of molecular evolution.
\r\n\r\nThe soluble fractions of the organic matrices of nine species of mollusks representing the three major classes of the phylum have been investigated. However, the organic matrix of the clam, Mercenaria mercenaria, has been studied in greatest detail. It is composed of protein with covalently bound carbohydrate. The protein-carbohydrate linkage is probably through serine and/or threonine residues. The organic matrix components vary greatly in their protein-carbohydrate proportions, amino acid compositions and hydrodynamic size.
\r\n\r\nThe discrete molecular weight components of the nine species of mollusks investigated exhibit great heterogeneity above the species level. A particular repeating amino acid sequence in which every second amino acid is an aspartic acid separated by either glycine or serine, is present in all mollusks examined to date. It is suggested that this amino acid sequence is a potential template for crystal nucleation.
\r\n\r\nThe organic matrix of an 80 million year old clam, Scabrotrigonia thoracica, still contains the repeating aspartic acid sequence and discrete molecular weight components, indicating that this material is unusually well preserved, and therefore could be of use in future studies of molecular evolution based on material derived from the fossil record. The glycine content of the organic matrices of eight of these fossil shells is a sensitive indicator of early diagenesis. The alloisoleucine/isoleucine ratios of the shell protein ranged from the equilibrium value to extremely low values. The potential uses of fossil organic matrices in evolution studies are discussed.
" }, { "name": "Blasius, Karl Richard", "degree": "PhD", "year": "1976", "title": "Topical Studies of the Geology of the Tharsis Region of Mars", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:10252019-135222249", "creators": [ { "name": { "family": "Blasius", "given": "Karl Richard" }, "id": "Blasius-Karl-Richard", "display_name": "Blasius, Karl Richard" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/1AMY-CD94", "abstract": "I.
\r\n\r\nMariner IX images of the four great volcanic shields of the Tharsis region of Mars show many circular craters ranging in diameter from one hundred meters to twenty kilometers. Previous attempts to date the volcanoes from their apparent impact crater densities yielded conflicting results. The principal difficulty is sorting volcanic from impact craters for diameters <lkm. Many of the observed craters are aligned in prominent linear and concentric patterns suggestive of volcanic origin. In this paper an attempt is made to date areas of shield surface, covered with high resolution images using only scattered small (\u2264 1 km) craters of probable impact origin. In some cases a fraction of the visible craters, those of apparent volcanic origin, is systematically excluded from the dating counts.
\r\n\r\nThe common measure of age, deduced for all surfaces studied, is a calculated \"crater age\", F', defined as\r\nthe number of craters equal to or larger than 1 km in diameter per 10\u2076 km\u00b2. The conclusions reached from comparing\r\nsurface ages and their geological settings are:
\r\n\r\n1. Lava flow terrain surfaces with ages, F', from 180 to 490 are seen on the four great volcanoes. Summit surfaces of similar ages, F'=360 to 420, occur on the rims of calderas of Arsia Mons, Pavonis Mons, and Olympus Mons. The summit of Ascraeus Mons is\r\npossibly younger; F' is calculated to be 180 for the single area which could be dated.
\r\n2. One considerably younger surface, F'\u2264110, is seen on the floor of Arsia Mons' summit caldera.
\r\n3. Nearly crater free lava flow terrain surfaces seen on Olympus Mons are estimated to be less than half the age of a summit surface. The summit caldera floor is similarly young.
\r\n4. The pattern of surface ages on the volcanoes suggests that their eruption patterns are similar to those of Hawaiian basaltic shields. The youngest surfaces seem concentrated on the mid-to-lower flanks and within the summit calderas.
\r\n5. The presently imaged sample of shield surfaces, though incomplete, clearly shows a broad range of ages on three volcanoes\u2014Olympus, Arsia, and Pavonis Mons.
Estimated absolute ages of impact dated surfaces are obtained from two previously published estimates of the history of flux of impacting bodies on Mars. The estimated ranges of age for the observed crater populations are 0.5 to 1.2 billion years and 0.07 to 0.2 billion years. Areas which are almost certainly younger, less than 0.5 or 0.07 billion years, are also seen. The spans of surface age derived for the great shields are minimum estimates of their active lifetimes, apparently very long compared to those of terrestrial volcanoes.
\r\n\r\nII.
\r\n\r\nThree types of large-scale mass movements - rockslides, slumps, and a type of mass flowage have been tentatively\r\nidentified in photographs of the basal escarpment of the Martian volcano Olympus Mons. The morphology of slide\r\ndeposits suggests lubrication of their movements by cushions of compressed gas. Gas trapped from the present rarefied\r\natmosphere is probably insufficient, but a denser atmosphere in the past or the release of gases adsorbed on surface\r\nmaterials may provide adequate slide lubrication. Slumps occur widely along the north and southeast reaches of basal\r\nscarp and are mantled in the southeast by some of the youngest lava flows observed on Olympus Mons. The initiation\r\nof mass flowages, confined to two areas along.the west reach of basal scarp, probably required a major change in the\r\nphysical properties of surface materials. Chemical alteration of surface materials or the melting of ground ice, both possibly\r\nrelated to volcanism, might effect such a change.
\r\n\r\nDifferences in escarpment morphology and mass movements suggest considerable recession of the west and north reaches\r\nof basal scarp and only slight recession, primarily by slumping, of the southeast scarp. Low scarps on the plains\r\nnear the foot of the southeast basal scarp and the apparent tilt of grooved terrain surfaces suggest the southeast reach\r\nof basal scarp formed by subsidence or downwarping along the margin of the volcano.
\r\n\r\nIII.
\r\n\r\nMany overlapping pictures, potential data for the construction of topographic maps, were obtained by the\r\ntelevision cameras on Mariner 9. An analysis of the sources of error in photogrammetric determinations of relief from\r\nthese pictures singles out photo resolution as the primary limiting factor. Topographic maps of several Martian\r\nsurface features, derived by an original analytic scheme, are presented. The observed errors in relief determinations\r\nusing this technique are in good agreement with the independent error analysis.
" }, { "name": "Conway, Clay Michael", "degree": "PhD", "year": "1976", "title": "Petrology, Structure, and Evolution of a Precambrian Volcanic and Plutonic Complex, Tonto Basin, Gila County, Arizona", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02062024-221007119", "creators": [ { "name": { "family": "Conway", "given": "Clay Michael" }, "id": "Conway-Clay-Michael", "display_name": "Conway, Clay Michael" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/hz23-6e04", "abstract": "Precambrian exposures in Tonto Basin, central Arizona, are among the best in the southwest and the rocks are superbly preserved. Stratigraphic, structural, and petrologic relations of the Tonto Basin rocks, as determined in this study, contribute to our understanding of an important interval of Precambrian history in the southwest, and to the petrogenesis of volcanic and plutonic rocks emplaced in a great silicic alkali magmatic event.
\r\n\r\nIn the only detailed field study within the Tonto Basin prior to the present work, Gordon Gastil defined a stratigraphic sequence fundamentally eugeosynclinal (wacke, slate) in lower parts becoming more miogeosynclinal upward (conglomerate, sandstone) and culminating with a great thickness of rhyolite. Current mapping shows that the extrusive rhyolite sequence is about 2 km thick and is overlain by a km of quartzite. Through joint efforts of L. T. Silver, K. R. Ludwig and the author, a correlation is apparent with corresponding eugeosynclinal, rhyolite and quartzite sequences in the Mazatzal Mountains. The names Alder Group, Haigler Group, and Mazatzal Group are proposed for the respective sequences in both areas. The Alder Group includes not only Gastil's lowermost Alder Formation (here renamed Breadpan Formation) but all of his overlying formations beneath the Haigler rhyolite. Haigler Group in Tonto Basin is composed of Winter Camp Formation, Haigler rhyolite undivided, and overlying Oxbow Rhyolite. The first was the basal part of Gastil's Haigler Formation, and the Oxbow Rhyolite remains as defined by Gastil. Haigler rhyolite undivided includes most of Gastil's Haigler Formation, much of his Hell's Gate Rhyolite (the remainder is intrusive), and extrusive rhyolite which is wide-spread in Tonto Basin outside Gastil's mapped area. The name Christopher Mountain Quartzite is proposed for quartzite of the Mazatzal Group overlying Haigler Group rhyolites in Tonto Basin.
\r\n\r\nThe folded sedimentary and volcanic strata of these three groups occur in a NE-SW belt flanked on both NW and SE by large granite bodies. The southeasterly granite, near Young, was shown by Gastil to be intrusive into Alder Group strata. The northwesterly granite (Payson Granite) was not mapped by him in detail. He hypothesized that both granites were part of a single widespread batholith and that the Payson Granite was gradational through granophyre and intrusive rhyolite into contemporaneous rhyolite (Haigler Group). L. T. Silver subsequently obtained U-Pb zircon ages of 1730 \u00b1 15 m.y. for the Payson Granite, 1650 \u00b1 15 m.y. for the granite at Young, and 1715 \u00b1 15 m.y. for a rhyolite flow in the Alder Group (Flying W Formation), in apparent disagreement with both aspects of Gastil's hypothesis. This apparently placed Payson Granite in a northern, older regional geochronologic province (volcanic rocks~ 1750 - 1820 m.y.; plutonic rocks~ 1720 - 1760 m.y.) and the granite at Young and associated stratified rocks in a southern, younger regional province (volcanic rocks~ 1700 - 1720 m.y.; plutonic rocks~ 1650 - 1700 m.y.), suggesting that Payson Granite might be part of a basement upon which the volcanic and sedimentary rocks were deposited.
\r\n\r\nMajor findings of the present study relating to this problem are that Payson Granite-granophyre, granophyre-intrusive rhyolite, and intrusive rhyolite..,.e:xtrusive rhyolfte contacts are non-gradational intrusive contacts and that Payson Granite has a smooth upper surface dipping gently and apparently concordantly southward beneath the sedimentary and volcanic strata. Enormous composite sills intruded, each beneath the preceding, in the sequence (1) rhyolite porphyry (Hell's Gate Rhyolite and King Ridge Rhyolite), (2) granophyre (Green Valley Granophyre), and (3) alaskite along the upper Payson Granite surface primarily between granite and Haigler rhyolite but locally into the folded stratified rocks (including Alder and Mazatzal Group rocks).
\r\n\r\nThe sills are widespread along the upper Payson Granite surface and no direct relationship between Payson Granite and the stratified rocks could be determined. However, at Gisela where the felsic sills are locally absent, Payson Granite intrudes a small body of distinctive finegrained rock characterized by megacrysts of plagioclase (mafite porphyry). Another of the small scattered masses of mafite porphyry intrudes Haigler rhyolite. It is hypothesized that all mafite porphyries are a single generation of igneous intrusive rock and that all occurrences are correlative. If this is so, Payson Granite must be younger than Haigler rhyolite. In support of this hypothesis, sedimentary and volcanic rocks of nearby pendants in diorite of the Gibson Complex (a differentiated gabbro-diorite body intruded by Payson Granite) contain lithologies similar to those in the Alder and Haigler Group strata.
\r\n\r\nFrom independent structural considerations an intrusive contact relation between Payson Granite and the stratified rocks is preferred over alternative basement and thrust contact hypotheses. This preference is based primarily on the apparent continuity of the sub-planar southwarddipping upper granite surface beneath the Gibson Complex. The intrusive hypothesis is also supported by an apparent distribution of more differentiated granite near the upper contact, suggesting a roof zone.
\r\n\r\nThe hypothesized intrusive relation of the Payson Granite to the stratified rocks provides the first suggestion of a structural relation between rocks of the northern and southern geochronologic provinces and places the Payson Granite, and probably the Gibson Complex, within the interval of a great silicic alkali magmatic event in Tonto Basin, intermediate in age between Haigler rhyolite and the felsic hypabyssal sills. The regional implication is that latest plutonism in the northern province overlapped (along the two-province boundary) with earliest volcanism of the southern province.
\r\n\r\nAll Precambrian X units in Tonto Basin have been folded and/or faulted. Primary textures in massive volcanic and plutonic bodies and quartzite are virtually unmodified and penetrative deformation is present only in less competent strata farthest from the large plutonic bodies. Earliest deformation was large-scale folding on NE-SW axes with shallow plunges. This was followed by thrusting and reverse faulting to the northwest under the same regime of NW-SE compression. These early structures were disrupted by left-lateral strike-slip and east-side-down normal offset on NE-SW to N-S faults. All deformation is probably older than Precambrian Y Apache Group rocks and presumably occurred in the interval 1715-1650 m.y. prior to intrusion of the granite at Young and possibly immediately subsequent to the earlier magmatic activity.
\r\n\r\nThe deformation sequence suggests that Tonto Basin was initially the site of foreland folding and thrusting as the southern, basin crustal block impinged northwestward upon the slightly older proto-cratonic mass. It appears that regional tectonic stresses then shifted to give rise to a left-lateral couple in which the southern block was translated northeastward with a strike-slip system developing along or near the two-province boundary. Similarity of this hypothetical tectonic evolution to some modern tectonic histories may imply similar crustal processes .
\r\n\r\nHaigler rhyolite and rhyolite, granophyre, and alaskite sills are all silicic alkali rocks of similar and distinctive chemical composition. These leucocratic rocks are generally characterized by late-stage alteration of mafic silicate phases to hematite, and by coarse exsolution and pervasive hematite clouding of feldspars. In rare gray (unoxidized) facies, sodic (?) pyroxene (and amphibole?) is preserved in granophyre and intrusive rhyolite. Biotite in alaskite is poorly preserved. Alteration is attributed to hydrothermal activity associated primarily with intrusion of Green Valley Granophyre. Indications of slight alkali depletions and enrichments in Haigler rhyolite and Green Valley Granophyre, respectively, suggest some alkali exchange during the hydrothermal event. From textural and mineralogical evidence in granophyre, alkali enrichment may have occurred in the magmatic state.
\r\n\r\nConsideration of normative data and feldspar character of the silicic alkali rocks in light of experimental work on the petrogeny's residua system leads to the interpretations that the magmas were water-undersaturated at the deep site of phenocryst formation and that certain magmas originated by partial melting, The enormous volume of silicic rocks and the near absence of intermediate rocks in Tonto Basin argues against an origin by differentiation and suggests that all magmas formed by partial melting.
\r\n\r\nIn a petrogenetic model based on these interpretations, on evidence for minimum depths of emplacement, and on comparative temperatures of formation (estimated by hypersolvus and subsolvus feldspar characteristics and mafic mineralogy), phenocrysts of the porphyritic rocks formed in an intermediate-level region of magma chambers where the various magmas began to crystallize at different temperatures depending on the degree of water-undersaturation. The Payson Granite magma may have been a high, early member. Upon ascension most magmas became water-saturated and were either extruded as ash-flow tuffs or crystallized as relatively coarse sill rocks (alaskite, granophyre, spherulitic rhyolite). Hottest, driest magmas perhaps did not become water-saturated and were extruded as viscous flows or emplaced as fine-grained porphyritic sills. Extreme textural variations and parallel variations in mineralogy in sills of comparable composition and emplacement level are best explained by variable water content.
\r\n\r\nThe Tonto Basin silicic alkali province is a well-preserved, deeply exposed analog of modern ash-flow tuff caldera complexes, notable in its remarkable similarity, particularly in chemical composition, to the Yellowstone rhyolite plateau of Wyoming. Aspects of the petrogenetic model above are compatible with new evidence for the existence of magmas beneath Yellowstone.
\r\n\r\nRhyolite and/or granophyre and granite of other silicic alkali provinces (including Yellowstone) commonly occur bimodally with basalt or with tholeiitic layered gabbro bodies. The predominantly silicic rocks in Tonto Basin are associated with small amounts of mafic volcanic and hypabyssal rocks and the large mafic Gibson Complex is thought to have differentia ted from a basaltic magma. The analogy with other bimodal terranes may break down, however, because the Gibson Complex has a calc-alkaline differentiation trend. The calcic character of the Gibson Complex is compatible with inclusion of the complex as part of the northern older province , but seems incompatible with the hypothesized contemporaneity of the Gibson Complex and the silicic alkali rocks. The apparent anomalous differentiation might be explained by assimilation of water by the magma upon intrusion into water-rich Alder Group sediments.
\r\n\r\nAnorogenic tectonic settings observed for other silicic alkali provinces imply that the Tonto Basin magmatism occurred as a post-orogenic event subsequent to orogeny of the northern province and prior to that of the southern province, or perhaps in a site of back-arc extension during the magmatic stage of the later orogenic cycle.
" }, { "name": "Foley, Michael Glen", "degree": "PhD", "year": "1976", "title": "Scour and Fill in Ephemeral Streams", "advisor": "Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12042020-203212461", "creators": [ { "name": { "family": "Foley", "given": "Michael Glen" }, "id": "Foley-Michael-Glen", "display_name": "Foley, Michael Glen" } ], "advisors": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Vanoni", "given": "Vito A." }, "id": "Vanoni-V-A", "role": "chair", "display_name": "Vanoni, Vito A." }, { "name": { "family": "Brooks", "given": "Norman H." }, "id": "Brooks-N-H", "role": "member", "display_name": "Brooks, Norman H." }, { "name": { "family": "Dix", "given": "Charles Hewitt" }, "id": "Dix-C-H", "role": "member", "display_name": "Dix, Charles Hewitt" }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "member", "display_name": "Sharp, Robert P." } ], "option_major": [ "geol" ], "doi": "10.7907/gbn5-jb14", "abstract": "The classical concept that mean bed elevation over an entire stream reach is lowered by scour during flood-wave passage and is re\u00adstored by deposition in the waning flood phase (mean-bed scour and fill) can be challenged. The alternative that both scour and fill occur concurrently at different migrating loci within a reach (local scour and fill) is more consistent with published field data. The field and laboratory investigations reported herein suggest that mean-bed scour and fill in a uniform channel is minor compared to local scour and fill caused by bedform migration, and that maximum local scour and fill may occur on the waning flood in some instances.
\r\n\r\nThe field experiment, utilizing a rectilinear array of buried maximum-scour indicators (scour-cords), produced data for contouring of maximum scour and fill in an ephemeral streambed during two floods. In the first flood, 24 cm of scour and fill was measured for a bankfull flow depth of 23 cm.\tIn the second, maximum scour and fill was at least 66 cm for a bankfull flow depth of 34 cm.
\r\n\r\nEstimates of antidune amplitudes for the two floods, based on theoretical models and laboratory and field observations, are 28 to 64 cm and 48 to 97 cm, respectively. This indicates that all scour and fill measured by the scour-cord array could have been caused by antidune migration.
\r\n\r\nLaboratory experiments were conducted in an 18 m-long open-circuit flume with automated sediment and water input-rate controls. A series of experiments in a 26.7 cm-wide sand-bed channel with rigid walls, at grade for a simulated flood patterned after those typical of ephemeral streams, showed that mean-bed scour and fill was less than 3 percent of local scour and fill. For these experiments, mean sand size was 0.3 mm, channel slope was .009, maximum water depth was 40 mm, maximum local scour and fill was 22 mm, and maximum mean-bed scour and fill was 0.6 mm.\tMaximum mean bed elevation variation was thus only two sand-grain diameters. Fill occurred at peak flow followed by scour to the pre-flood mean bed elevation on the waning flood. Maximum local scour and fill took place near the end of the simulated floods, when bedform amplitudes were the greatest.
\r\n\r\nA series of simulated-flood experiments in a sand-bed channel with erodible sand banks showed scour and fill behavior qualitatively similar to that of the rigid-wall channel. Bank erosion, channel meandering, and braiding prevented quantitative scour and fill measurements in these alluvial-bank experiments. Measured flow and bedform parameters and scour and fill data derived from small laboratory scour-chains were compatible with those estimated from the theoretical model used in the field experiment.
" }, { "name": "Gancarz, Alexander John, Jr.", "degree": "PhD", "year": "1976", "title": "I: Isotopic Systematics in Archean Rocks, West Greenland. II: Mineralogic and Petrologic Investigations of Lunar Rock Samples", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-07062006-115658", "creators": [ { "name": { "family": "Gancarz", "given": "Alexander John, Jr." }, "id": "Gancarz-Alexander-John", "display_name": "Gancarz, Alexander John, Jr." } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "orcid": "0000-0002-7957-8029", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/S5C5-9E60", "abstract": "Pb isotopic abundances and U-Th-Pb concentrations are reported for feldspar megacrysts from the 3.59 AE old Amitsoq Gneiss, Godthaab District, West Greenland. The distinctive Pb in the feldspars is the most primitive terrestrial Pb so far observed. It is observed in feldspars which are from different geographic localities and which exhibit varying degrees of deformation and recrystallization. This appears to be either the initial Pb in the Amitsoq Gneiss or the initial Pb only slightly modified by subsequent metamorphism in a low 238U/204Pb environment. 238U/204Pb in the feldspars is low and the corrections for in situ produced Pb are only 0.4 per cent for 207Pb/206Pb and 0.6 per cent for 204Pb/206Pb. The mean corrected isotopic abundances are 204Pb/206Pb=0.08720, 207Pb/206Pb = 1.1513, and 208Pb/206Pb = 2.7309. The feldspars contain a very small amount of easily leachable radiogenic Pb which is strongly correlated with U and which indicates the formation of U-rich phases at about 2.7 AE. The matrix surrounding the feldspar megacrysts contains Pb which is much evolved relative to the megacrysts and this matrix does not appear to have behaved as a simple closed system. Element redistribution and open system behavior at about 2.7 AE is also suggested by Pb in feldspar from a dyke cutting across the gneiss. Assuming that the Amitsoq Gneiss feldspar Pb corrected for in situ U decay was the initial Pb in the gneiss at 3.59 AE (Baadsgaard, 1973), a single-stage \"age of the earth\" is determined as 4.47 +/- 0.05 AE and \u00b5 is 8.5. This is indistinguishable from the single-stage age for modern rocks and is distinctly younger than the age of some meteorites. If we assume that the earth originally formed at 4.6 AE and assume that it underwent major, large-scale differentiation at a time T(D), we use the same observed data to calculate that the time of differentiation is approximately 4.4 AE and that \u00b5 for the total earth is approximately 1.6 while \u00b5 for the mantle and crustal rocks is approximately 9.5.\r\n\r\nPb and Sr isotopic data and K-Rb-Sr-U-Th-Pb concentration data are presented for three anorthosite complexes in West Greenland. The three complexes are the Majorqap Qava outcrop of the Fiskenaesset Anorthosite Complex, the Storo Anorthosite Complex, Godthaab District, and the Ivnajaugtoq Anorthosite Complex, Godthaab District. The Pb isotopic data yield an age of 2.8 AE for the Majorqap Qava Anorthosite and Storo Anorthosite. The Ivnajaugtoq data are consistent with a 2.8 AE age. We interpret this as the time of igneous crystallization and metamorphic recrystallization. U-Pb data indicate substantial U redistribution within the last ~100 m.y. These three complexes have very different initial Sr isotopic abundances. These differences indicate that either the anorthosites crystallized at 2.8 AE from melts with different \u00b5's which were derived and fractionated at ~3.6AE from \"normal\" (i.e. \u00b5~9) mantle material and remained isolated until 2.8 AE or the anorthosites crystallized at 2.8 AE from melts derived at 2.8 AE from \"normal\" mantle material and which were variably contaminated during emplacement with Pb like that in the Amitsoq Gneiss.\r\n\r\nIncluded are a series of published articles which are primarily concerned with the mineralogic and petrographic characterization of lunar highland samples.\r\n" }, { "name": "Lambert, Steven Judson", "degree": "PhD", "year": "1976", "title": "Stable Isotope Studies of Some Active Hydrothermal Systems", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:12042020-220145357", "creators": [ { "name": { "family": "Lambert", "given": "Steven Judson" }, "id": "Lambert-Steven-Judson", "display_name": "Lambert, Steven Judson" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/cdjc-wb26", "abstract": "Measurements of \u00b9\u2078O/\u00b9\u2076O, \u00b9\u00b3C/\u00b9\u00b2C and D/H ratios have been made on rocks and minerals from wells drilled in active hydrothermal systems as an aid to the understanding of various factors which govern the ongoing natural interactions between rocks and fluids, leading to a more thor\u00adough understanding of rock-fluid interactions that have taken place in the geologic past in such processes as diagenesis, metamorphism, and hydrothermal alteration. Samples from four active hydrothermal systems have been analyzed: The Geysers, western Mayacmas Mountains, California; Valles Caldera, northern Jemez Mountains, New Mexico; Heber Geothermal Anomaly, Imperial Valley, California; the Tiwi area, Luzon, Philippines.
\r\n\r\nThe Geysers, a vapor-dominated hydrothermal system, is developed in Franciscan host rock which contains veins of quartz and calcite whose \u03b4\u00b9\u2078O values record the temperatures and isotopic compositions of fluids which prevailed during at least two different episodes of rock-fluid interraction. The first episode took place at about 200\u00b0C, during which marine silica and carbonate apparently interacted with ocean water entrapped in the sediments to form veins of quartz and calcite whose \u03b4\u00b9\u2078O values were around 19% and 16%, respectively. The calculated water/mineral ratios were less than unity. The water may have pro\u00adfoundly influenced the \u03b4\u00b9\u2078O values of spilitic basalts during their metamorphism to greenstones. The formation and emplacement of serpen\u00ad tinite bodies were isotopically unrelated to this episode, which was essentially a low-grade burial metamorphism (post-Cretaceous?) of rocks of the Franciscan Group. The second episode, in part recorded by co-genetic vein quartz and calcite \u03b4\u00b9\u2078O values 4 to 6% and 1 to 3%, respectively, began with large quantities of meteoric water circulating in fractures in the rock at temperatures of 160 to 180\u00b0C in response to the Pliocene Clear Lake magmatism. Isotopic alteration of host rocks was most profound near fractures which carried the hot water. The temperature rose, and with the restricted circulation of fluids the ancestral hot-water system evolved into the presently-active vapor\u00ad dominated system, which, according to the cogenetic vein quartz and calcite \u03b4\u00b9\u2078O values, involved temperatures as high as 320\u00b0C and fluid/ mineral ratios near unity. The change in the isotopic composition of the host rock during this activity was negligible. The \u03b4\u00b9\u00b3C values of vein calcite at The Geysers reflect both a marine carbonate and organic component of carbon.
\r\n\r\nThe other three areas contain hot-water systems, noteworthy of which is the Valles Caldera, an accumulation of previously hydrother\u00ad mally unaltered porous sediments and pumiceous volcanic tuffs. Large volumes of meteoric water have interacted with the rock at various temperatures (100 to 280\u00b0C), indicated by changes in calcite, quartz \u03b4\u00b9\u2078O values in the Caldera. The shallower, little altered rocks in the Caldera contain calcite and dolomite whose \u03b4\u00b9\u2078O values suggest they were deposited in a fresh-water lake.
\r\n\r\nPoorly-consolidated Pleistocene sand beds, whose highly variable hydrothermal carbonate \u03b4\u00b9\u2078O values indicate that they are isolated from one another by impermeable clay beds, form a series of hot-water reservoirs at Heber in the Imperial Valley.\tThe degree of isotopic alteration indicated by the sand and its component quartz is very minor, indicating that this system is very young.
\r\n\r\nThe few data from the Philippines indicate that significant hydro\u00ad thermal alteration has taken place in the Tiwi hot-water system, also. The isotopic changes, however, are less profound than those observed at other areas because the \u03b4\u00b9\u2078O of Philippines meteoric water is much closer to the initial \u03b4\u00b9\u2078O value of the local host rock than is the case elsewhere.
\r\n\r\nMeasurements of D/H ratios do not seem to be conclusive in char\u00adacterizing degrees of rock-fluid interaction in active hydrothermal systems.
" }, { "name": "Langston, Charles Adam", "degree": "PhD", "year": "1976", "title": "Body Wave Synthesis for Shallow Earthquake Sources: Inversion for Source and Earth Structure Parameters", "advisor": "Helmberger, Donald V.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09142006-142025", "creators": [ { "name": { "family": "Langston", "given": "Charles Adam" }, "id": "Langston-Charles-Adam", "display_name": "Langston, Charles Adam" } ], "advisors": [ { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "advisor", "display_name": "Helmberger, Donald V." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z3ZM-AC93", "abstract": "Expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions. Useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented. The results of this procedure are used to generate synthetic P, SV and SH waveforms for various assumptions of stress drop. The Thomson-Haskell layer matrix method for computing far-field body wave displacements from shear dislocations is also formulated to complement the ray theory methods when complicated earth structures are considered. An iterative generalized inverse technique is developed using analytic partial derivatives for estimating source parameters from data sets of P and S seismograms from shallow earthquakes.\r\n\r\nWith the inverse technique and ray theory methods long period P and SH waveforms are analyzed from the Koyna, India, earthquake of 10 December 1967. Using published crustal models of the Koyna region and primarily by modelling the crustal phases P, pP, and sP, the first 25 seconds of the long-period waveforms are synthesized for 17 stations and a focal mechanism obtained for the Koyna earthquake which is significantly different from previous mechanisms. The fault orientation is 67\u00b0 dip to the east, -29\u00b0 rake plunging to the northeast, and N16\u00b0E strike, all angles \u00b1 6\u00b0. This is an eastward dipping, left-lateral oblique-slip fault which agrees favorably with the trend of fissures in the meizoseismal area. The source time duration is estimated to be 6.5 \u00b1 1 5 sec, from a triangular time pulse which has a rise time of 2.5 sec and a tail-off of 3.9 sec, source depth of 4.5 \u00b1 1.5 km and seismic moment of 3.2 \u00b1 1.4 x 10(25) dyne-cm. Some short period complexity in the time function is indicated by modelling short-period WWSSN records but is complicated by crustal phases. The long-period P waveforms exhibit complicated behavior due to intense crustal phase interference caused by the shallow source depth and radiation pattern effects. These structure effects can explain much of the apparent multiplicity of the Koyna source. An interpretation of the Koyna dam accelerograms has yielded an S-P time. Taken together with the I. M. D. epicenter and present depth determination, it places the epicenter directly on the meizoseismal area.\r\n\r\nSimultaneous modelling of source parameters and local layered earth structure for the April 29, 1965, Puget Sound earthquake was done using both the ray and layer matrix formulations. The source parameters obtained are: dip 70\u00b0 to the east, strike 344\u00b0 rake -75\u00b0, 63 km depth, average moment of 1.4 \u00b1 0.6 x 10(26) dyne-cm and a triangular time function with a rise time of 0.5 sec and fall-off of 2.5 sec. An upper mantle and crustal model for southern Puget Sound was determined from inferred reflections from interfaces above the source. The main features of the model include a distinct 15 km thick low velocity zone with a 2.5 km/sec P wave velocity contrast lower boundary situated at approximately 56 km depth. The crustal model is less than 15 km thick with a substantial sediment section near the surface. A stacking technique using the instantaneous amplitude of the analytic signal is developed for interpreting short period teleseismic observations. The inferred reflection from the base of the low velocity zone is recovered from short period P and S waves. An apparent attenuation is also observed for pP from comparisons between the short and long period data sets. This correlates with the local surface structure of Puget Sound and yields an effective Q of approximately 65 for the crust and upper mantle.\r\n\r\nTo substantiate the unusual structure found from the Puget Sound waveform study the structure under Corvallis, Oregon, was examined using long period Ps and Sp conversions and P reverberations from teleseismic events as recorded at the WWSSN station COR. By modelling these phases in the time domain using a data set composed of six deep and intermediate depth earthquakes a similar low velocity zone structure is again inferred. The lower boundary occurs at 45 km depth and has S and P velocity contrasts of 1.3 and 1.4 km/sec, respectively. The material comprising the low velocity zone has a Poisson ratio of at least 0.33 and is constrained by the average P and S travel times determined from the converted phases." }, { "name": "Malin, Michael Charles", "degree": "PhD", "year": "1976", "title": "I. Comparison of Volcanic Features of Elysium (Mars) and Tibesti (Earth). II. Age of Martian Channels. III. Nature and Origin of Intercrater Plains on Mars.", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11072003-094937", "creators": [ { "name": { "family": "Malin", "given": "Michael Charles" }, "id": "Malin-Michael-Charles", "display_name": "Malin, Michael Charles" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/0A6Y-KM94", "abstract": "This thesis consists of three separate parts, each addressing a specific aspect of the surface morphology of Mars.\r\n\r\nIn Part 1, a comparison of large volcanic features is made using spacecraft imaging data. The Elysium volcanic province on Mars and the Tibesti volcanic province in Chad, Africa are studied using Mariner 9, Earth Resources Technology Satellite and Apollo photography. Elysium Mons on Mars and Emi Koussi on Earth show remarkable similarities in summit caldera and flank morphologies. Each has a large central caldera approximately 12 km in diameter and from 500 to 1000 m deep which contain numerous craters and large, irregular pits. Channel-like features which head at the calderas and taper downslope show evidence of collapse and possible lava erosion. Elysium Mons rises some 14 ? 1.5 km above its base and the summit is about 17 km above the 6.1 mbar mean martian pressure surface. Cratering data indicate most of the apparent cratering is endogenic in origin. The subdued, hummocky terrain on the flanks is distinctly different from the slopes of the younger Tharsis Ridge volcanoes, showing little if any sign of recent material flow.\r\n\r\nThe lack of aqueous erosional forms on Elysium Mons argues strongly against recent ([approx.]10[superscript 5] to 10[superscript 6] year) pluvial episodes. The forms and associations of features throughout the Elysium region suggest central volcanism started earlier in Elysium than in Tharsis, and that the source of the Elysium volcanics is chemically evolved, with evidence of silicic magma. Finally, the data are consistent with the view that the martian crust has been stable and essentially motionless for an extended period of martian geologic time.\r\n\r\nPart 2 attempts to determine the age relationship between the large, sinuous channels on Mars and the terrains in which the channels are found. Crater counts, plain and mantle superposition, and geographic and geologic associations suggest that the channels are extremely old, are spatially and temporarily related to the ancient cratered terrain and are genetically related to the processes of fretting and chaos formation. There appears to be no evidence for recent channel activity.\r\n\r\nPart 3 presents the results of an investigation of the morphologic characteristics of the plains which separate the craters in the heavily cratered regions of Mars. These intercrater plains appear to be composed of stratified consolidated and unconsolidated materials, probably loose debris blankets and volcanic flows. The topmost layer of the plains unit varies from location to location. An older, cratered surface may be partly exposed where the kilometers-thick plains unit is locally incised and eroded. The association of chaotic terrain, fretted terrain and major channels with the plains suggests that the volatile(s) presumed to be necessary to produce these erosional landforms may have been present among the plains materials. It is speculated that the unconsolidated material is impact-generated debris and eolian deposits, suggesting an early atmosphere conducive to material transport and possibly flowing liquids." }, { "name": "Smith, Roger Stanley Uhr", "degree": "PhD", "year": "1976", "title": "Late-Quaternary Pluvial and Tectonic History of Panamint Valley, Inyo and San Bernardino Counties, California", "advisor": "Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06242009-141311", "creators": [ { "name": { "family": "Smith", "given": "Roger Stanley Uhr" }, "id": "Smith-Roger-Stanley-Uhr", "display_name": "Smith, Roger Stanley Uhr" } ], "advisors": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "chair", "display_name": "Sharp, Robert P." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "member", "display_name": "Allen, Clarence R." }, { "name": { "family": "Smith", "given": "George I." }, "id": "Smith-G-I", "role": "member", "display_name": "Smith, George I." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Birman", "given": "Joseph Harold" }, "id": "Birman-J-H", "role": "member", "display_name": "Birman, Joseph Harold" } ], "option_major": [ "geol" ], "doi": "10.7907/W934-HC84", "abstract": "Panamint Valley was filled to overflowing on five, possibly six, separate instances, fed largely by runoff from the Sierra Nevada discharged through Owens and Searles lakes. These high water levels are best represented by uplifted lake terraces and associated deposits at Pleasant Canyon on the, west face of the Panamint Range, where shorelines at five, possibly six, levels have formed with respect to the level of Wingate Pass, (present elevation 1977 \u00b11 feet) into Death Valley. The level of this sill seems to have been tectonically stable, but was permanently raised about 50 feet by a mudflow which poured into the pass during a long-lasting lake stage, herein named Gale Stage. Paired Gale-Stage shorelines, attributed to lake stands stabilized at pre- and post-mudflow sill levels are found throughout Panamint Valley. The lower shoreline is 1.26 times older than the higher, more prominent shoreline, based on 1.26 times greater tectonic deformation at most localities. On the rising range block at Pleasant Canyon, the higher shoreline seems superposed on the lower to form a composite shoreline at 2177\u00b110 feet elevation. Shoreline elevations at Pleasant Canyon (and probable uplift they experienced) are: 2410\u00b110 feet (480\u00b125 feet); 2298\u00b110 (368\u00b125); 2265\u00b110 (335\u00b125); 2177\u00b110 (247\u00b125 to 200\u00b111); 2127\u00b110 (150\u00b111); and 2040\u00b140? (63\u00b141?). If the long-term uplift rate has been constant, the age of each shoreline should be proportional to its height above its sill level. Relatively steady deformation rates throughout Panamint Valley are suggested by the constant proportion (1.26:1.00) of deformation between the older (lower) and younger (higher) Gale-Stage shorelines.\r\n\r\nA radiocarbon age of 31,150\u00b11400 B.P. on snail shells establishes a minimum age for the shoreline at 2127 feet. Extrapolation using steady uplift rates indicates the following youngest-possible ages (in thousands of years) for the other uplifted shorelines: 2410 ft: 100\u00b117; 2298 ft: 77\u00b114; 2265 ft: 70\u00b113; 2177 ft: 52 to 42\u00b17; and 2040 ft?,: 14\u00b110?. The probable age of each lake stage is about 20 per cent greater than its youngest possible age, a judgement based on correlation with the stages of Searles Lake (G.I. Smith, 1968).\r\n\r\nThe higher, younger Gale-Stage shoreline is prominent throughout Panamint Valley. Differential tectonic deformation of this feature amounts to about 370 feet, as established by a maximum elevation of 2190\u00b110 feet on the central Panamint Range to a minimum of 1820\u00b120 at Panamint Valley's north end. Deformation involves differential north- south warping of crustal block on both sides of the Panamint Valley and Ash Hill fault zones, which respectively define the east and west margins of Panamint Valley.\r\n\r\nRight-lateral displacement of Quaternary features along the Panamint Valley fault zone exceeds their vertical, offset. Sixty feet of right-lateral offset have occurred since desiccation of the last, low lake to occupy Panamint Valley (15,000\u00b15,000 B.P.), and cumulative offset of a sheet of monolithologic (landslide?) breccia of Plio-Pleistocene age from its probable source in Wildrose Canyon may total 10,000 to 15,000 feet.\r\n\r\nPanamint Valley is abruptly and massively closed at its north end, where valley-floor deposits appear to underthrust Mesozoic plutonic rocks of Hunter Mountain along a northwest-trending zone which may represent the northwestward continuation of the Panamint Valley fault zone. Along the middle part of this reach of the zone, poorly-sorted (talus?) rubble of sound crystalline boulders underlies a 50 to 100-foot-thick zone of crushed crystalline rock which dips 17 to 35 degrees to the northeast beneath unshattered crystalline rocks. Thrusting may reflect a response to regional northwest-southeast right-lateral shear, possibly imposed upon classical Basin-Range bounding faults. The complex pattern of warping and faulting throughout the rest of Panamint Valley is also consistent with right-lateral shear, and the valley itself may have originated as a right-lateral \"pull apart\".\r\n\r\nThe unusually large volume of deposits along the 2177-foot shoreline suggests correlation with the Sierra Nevada Tahoe glaciation, which is distinguished by unusually large moraines. The small volume of 2127-foot shoreline deposits suggests correlation with the Tenaya glaciation, whose moraines are small. Thus the queried 2040-foot shoreline could represent the Tioga glaciation and the 2410-foot shoreline the Mono Basin glaciation. The 2265 and 2298-foot shorelines may represent early Tahoe events, suggesting that the Tahoe may be divided into early and late phases. Tentative ages of glaciations, based on correlation with pluvial events in Panamint Valley, are (in thousands of years B.P.): Mono Basin: 120\u00b120; Tahoe (early): 92\u00b115 to 78\u00b115; Tahoe (late): 65\u00b113 to 48\u00b110; Tenaya: 38\u00b16; Tioga?: 23\u00b110?." }, { "name": "Forester, Richard W.", "degree": "PhD", "year": "1975", "title": "\u00b9\u2078O/\u00b9\u2076O and D/H Studies on the Interactions between Heated Meteoric Groundwaters and Igneous Intrusions: Western San Juan Mountains, Colorado, and the Isle of Skye, Scotland", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02202014-160719532", "creators": [ { "name": { "family": "Forester", "given": "Richard W." }, "id": "Forester-Richard-W", "display_name": "Forester, Richard W." } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/KMXR-6155", "abstract": "Detailed oxygen, hydrogen and carbon isotope studies have been carried out on igneous and metamorphic rocks of the Stony\r\nMountain complex, Colorado, and the Isle of Skye, Scotland, in order to better understand the problems of hydrothermal meteoric\r\nwater-rock interaction.
\r\n\r\nThe Tertiary Stony Mountain stock (~1.3 km in diameter), is composed of an outer diorite, a main mass of biotite gabbro,\r\nand an inner diorite. The entire complex and most of the surrounding country rocks have experienced various degrees of\r\n18O depletion (up to 10 per mil) due to interaction with heated meteoric waters. The inner diorite apparently formed from a\r\nlow-18O magma with \u03b418O \u2243 +2.5, but most of the isotopic effects are a result of exchange between H2O and solidified igneous rocks. The low-18O inner diorite magma was probably produced by massive assimilation and/or melting of hydrothermally altered\r\ncountry rocks. The \u03b418O values of the rocks generally increase with increasing grain size, except that quartz typically\r\nhas \u03b418O = +6 to +8, and is more resistant to hydrothermal exchange than any other mineral studied. Based on atom % oxygen,\r\nthe outer diorites, gabbros, and volcanic rocks exhibit integrated water/rock ratios of 0.3 \u00b1 0.2, 0.15 \u00b1 0.1, and 0.2 \u00b1 0.1,\r\nrespectively. Locally, water/rock ratios attain values greater than 1.0. Hydrogen isotopic analyses of sericites, chlorites,\r\nbiotites, and amphiboles range from -117 to -150. \u03b4D in biotites varies inversely with Fe/Fe+Mg, as predicted by Suzuoki\r\nand Epstein (1974), and positively with elevation, over a range of 600 m. The calculated \u03b4D of the mid-to-late-Tertiary meteoric\r\nwaters is about -100. Carbonate \u03b413C values average -5.5 (PDB), within the generally accepted range for deep-seated carbon.
\r\n\r\nAlmost all the rocks within 4 km of the central Tertiary intrusive complex of Skye are depleted in 18O. Whole-rock\r\n\u03b418O values of basalts (-7. 1 to +8.4), Mesozoic shales (-0.6 to + 12.4), and Precambrian sandstones (-6.2 to + 10.8) systematically\r\ndecrease inward towards the center of the complex. The Cuillin gabbro may have formed from a 18O-depleted magma\r\n(depleted by about 2 per mil); \u03b418O of plagioclase (-7.1 to + 2.5) and pyroxene (-0.5 to + 3.2) decrease outward toward the\r\nmargins of the pluton. The Red Hills epigranite plutons have \u03b418O quartz (-2.7 to + 7.6) and feldspar (-6.7 to + 6.0) that\r\nsuggest about 3/4 of the exchange took place at subsolidus temperatures; profound disequilibrium quartz-feldspar fractionations\r\n(up to 12) are characteristic. The early epigranites were intruded as low-18O melts (depletions of up to 3 per mil)\r\nwith \u03b418O of the primary, igneous quartz decreasing progressively with time. The Southern Porphyritic Epigranite was apparently\r\nintruded as a low-18O magma with \u03b418O \u2243 -2.6. A good correlation exists between grain size and \u03b418O for the unique, high-18O Beinn an Dubhaich granite which intrudes limestone having a \u03b418O range of +0.5 to +20.8, and \u03b413C of -4.9 to -1.0. The \u03b4D values of sericites (-104 to -107), and amphiboles, chlorites, and biotites (-105 to -128) from the igneous rocks , indicate\r\nthat Eocene surface waters at Skye had \u03b4D \u2243 -90. The average water/rock ratio for the Skye hydrothermal system is approximately\r\none; at least 2000 km3 of heated meteoric waters were cycled through these rocks.
\r\n\r\nThus these detailed isotopic studies of two widely separated areas indicate that (1) 18O-depleted magmas are commonly\r\nproduced in volcanic terranes invaded by epizonal intrusions; (2) most of the 18O-depletion in such areas are a result of\r\nsubsolidus exchange (particularly of feldspars); however correlation of \u03b418O with grain size is generally preserved only\r\nfor systems that have undergone relatively minor meteoric hydrothermal exchange; (3) feldspar and calcite are the minerals\r\nmos t susceptible to oxygen isotopic exchange, whereas quartz is very resistant to oxygen isotope exchange; biotite, magnetite,\r\nand pyroxene have intermediate susceptibilities; and (4) basaltic country rocks are much more permeable to the hydrothermal\r\nconvective system than shale, sandstone, or the crystalline basement complex.
" }, { "name": "Hinkley, Todd King", "degree": "PhD", "year": "1975", "title": "Weathering Mechanisms and Mass Balance in a High Sierra Nevada Watershed: Distribution of Alkali and Alkaline Earth Metals in Components of Rock and Soil, Snow, Soil Moisture and Stream Outflow", "advisor": "Patterson, Clair C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06032004-093611", "creators": [ { "name": { "family": "Hinkley", "given": "Todd King" }, "id": "Hinkley-Todd-King", "display_name": "Hinkley, Todd King" } ], "advisors": [ { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "advisor", "display_name": "Patterson, Clair C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/T1D8-8H84", "abstract": "The alkali metals K, Rb and Cs, and the alkaline earth metals Ca, Sr and Ba were analyzed in the rocks, minerals, soils, snow, stream water and soil moisture films of Thompson Canyon, a glacially scoured watershed in the central crest region of the Sierra Nevada in east central California. The stable isotope dilution method was used.\r\n\r\n1. The mass balance of metals entering and leaving the watershed, the denudation rate, and chemical and mineralogical details of the weathering process: In the batholithic source rock, two major minerals, microcline and plagioclase, and one minor mineral, biotite, contain most of the mass of the six metals. Snow is the main source of water to the valley, and contains much lower concentrations of metals than has been previously reported. These metals originate from distant sources. The mass of metals leaving the watershed annually in stream outflow indicates that the watershed is being denuded at a rate of less than 1 cm per 1000 yr, and that the principal process is chemical removal. Ca and Sr are being denuded more rapidly from the batholithic rock than the alkalies or Ba. This is shown by the greater proportion of Ca and Sr in stream water in contrast to the greater proportion of alkalies and Ba in the source rock. Rapid breakdown of plagioclase is responsible for this differential removal. In rock and grus, ratios among metals present in plagioclase (Ca and Sr) and those in K-feldspar (K and Ba) show that plagioclase is preferentially removed as rocks weather and crumble to grus. Rivulets running away from melting snow banks in mid summer dissolve large amounts of Ca and Sr at only short distances away from the snow banks, and hold these metals for transport out of the watershed. Particles from the snow banks, rich in Rb and Cs, similar in composition to mica, are deposited in soils by the rivulets. Comparison of metal compositions of rock and grus show that mica particles are freed as the rocks break down.\r\n\r\n2. Metals in soils: Masses and distribution of the six metals were determined in the soil reservoir. Three soil fractions were analyzed: (1) organic matter (humus), (2) clay (+ silt) size and (3) igneous minerals (sand size). The Rb/K and Cs/K ratios are greater in humus than in whole soil or in the source rocks. On the other hand, Sr/Ca and Ba/Ca ratios are lower in the humus. The metal ratios in humus are similar to those in soil moisture films in subsaturated soils. Area and humus content of soil types show that about 100,000 tons of humus are present in the watershed. The mass of metals in humus is about 100 times greater than that mobilized annually by weathering or present in soil moisture films. Metal composition of the clay fraction is similar to batholithic rock, but richer in Rb and Cs. The igneous mineral fraction shows that soils are not the residue rich in quartz and alkali feldspar which would be predicted from rock composition and data on metal loss from the watershed. Instead, the soils are enriched in plagioclase and depleted in K-feldspar, necessitating a hypothesis that the weathering products of K-feldspar in soils are periodically swept out of the watershed. Data on metals in turbid streams after violent rains support this.\r\n\r\n3. Metals in soil moisture films: Soil moisture films may be regarded as the final geological occurrence of metals in a food chain, because in this form metals are available to the roots of growing plants. A technique was developed for collecting minute samples (300 mg) of moisture from undisturbed soils in the field by rapid blotting onto stacks of cleaned absorbent paper discs. The proportions of metals in soil moisture films are different from those in source rocks. In soil moisture the heavy metal Cs is greatly enriched in the alkali family, and in the alkaline earth family the heavy metal Ba is depleted. Metal concentrations in soil moisture films collected in the field are quite different from those in soil solutions prepared in the laboratory by traditional methods, and from \"exchangeable\" and \"soluble\" ions determined in [ammonium] acetate buffered solutions: soil moisture films show K/Ca ratios commonly as high as 4, while other traditional methods give values below unity for the same soils. Compared to other types of water, such as phreatic and stream samples, soil moisture films have much higher concentrations of alkalies relative to alkaline earths. Metal concentrations in soil moisture films vary seasonally, concentrations of alkalies increasing in the autumn near the surface of humus rich soils." }, { "name": "Orton, Glenn Scott", "degree": "PhD", "year": "1975", "title": "1. Spatially Resolved Absolute Spectral Reflectivity of Jupiter: 3390-8400 Angstroms. 2. The Jovian Thermal Structure from Pioneer 10 Infrared Radiometer Data. 3. Observations and Analysis of 8-14 Micron Thermal Emission of Jupiter: a Model of Thermal Structure and Cloud Properties", "advisor": "Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10292008-151636", "creators": [ { "name": { "family": "Orton", "given": "Glenn Scott" }, "id": "Orton-Glenn-Scott", "display_name": "Orton, Glenn Scott" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "orcid": "0000-0002-2035-9198", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/c4ma-ab20", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\n\r\nPart 1 presents determinations of the absolute reflectivities of several visually distinct regions of Jupiter between 3390 and 8400\u00c5, at 10\u00c5 resolution, from observations made on the 60-inch telescope at Mt.Wilson between June 1973 and June 1974. These have been checked independently by observations using 150-200\u00c5 wide filters from 3400 to 6400\u00c5. The absolute scale of Oke and Schild (1970) is used, and solar irradiance values are taken from Arvesen et al.(1969).\r\n\r\nThe results are presented as a set of 9 figures showing the wavelength dependence of reflectivity. There is generally good internal consistency within the estimated errors. The effective reflectivities for several regions on the meridian in the 3390 to 8400\u00c5 range are: South Tropical Zone- 0.76\u00b1.05, North Tropical Zone- 0.68\u00b1.08, South Equatorial Belt- 0.63\u00b1.08, North Equatorial Belt- 0.62\u00b1.04, and Great Red Spot- 0.64\u00b1.09. Reflectivities nearer the limb are also observed. In support of the Pioneer imaging photopolarimeter experiment, the appropriate blue and red reflectivity values are also tabulated. For the regions on the meridian listed above, the equivalent widths of molecular bands vary as: CH[subscript 4] (6190\u00c5): 14-16\u00c5; CH[subscript 4](7250\u00c5): 77-86\u00c5; and NH[subscript 3](7900\u00c5): 87-95\u00c5. Significant differences from previous results of Pilcher et al. (1973) are noted.\r\n\r\nPart 2 presents latitude sectors of the 20 and 40 micron maps of Jupiter obtained by the Pioneer 10 infrared radiometer. These data are used to derive simple models for the average vertical thermal structure over the South Equatorial Belt and the South Tropical Zone, with additional examples of models for the North Equatorial Belt and the Great Red Spot. The models assume gaseous absorption by H[subscript 2] and NH[subscript 3] alone. The models are predominantly composed of H[subscript 2] with He dilution constrained to 0-35% by volume.\r\n\r\nFor the South Equatorial Belt, the temperature is about 170\u00b0K at 1.0 atm pressure, assuming the deep atmosphere to be adiabatic. The temperature may be 113-121\u00b0K near 0.2 atm, depending on what is assumed for the overlying thermal structure. In a non-scattering model, as given above, the South Tropical Zone is some 8\u00b0K cooler than the SEB near 1.0 atm. However, the data may also be successfully modeled by a thermal structure at minimum variance from that of the SEB, but with an optically thick cloud close to the 150\u00b0K level. Such a model is consistent with the visible and 5 micron appearance of the planet, and the cloud is coincident with the location at which saturation of NH[subscript 3] is expected to begin. For this model, the STrZ temperature is 3\u00b0K cooler than the SEB near 0.2 atm. The Great Red Spot may be modeled by a thermal structure like the \"cloudy\" STrZ model, but 5\u00b0K cooler near 0.2 atm. The local effective temperatures for the SEB (129\u00b0K) and the STrZ (126\u00b0K) are both below the effective temperature of 134\u00b0K from earth-based measurements. The derived thermal structures are inconsistent with the neutral atmosphere inversion of the Pioneer 10 radio occultation (Kliore et al.,1974), but not with others in the literature, including the Gulkis et al. (1973) model for the microwave spectrum.\r\n\r\nPart 3 reports: (1) observations of the limb structure near the equator of Jupiter at 8.15 and 8.44 microns using the Palomar 200-inch telescope at a resolution of about 3 arc seconds and a cooled filter-wheelspectrometer ([...]\u03bb/\u03bb[...]0.015), and (2) a model of the thermal structure and cloud properties of the atmosphere which is most consistent with spatially and spectrally resolved observations of the planet in the 8 - 14 micron range, including those reported in (1).\r\n\r\nThe thermal structure derived in Part 2 below the 0.2 atm level must be cooled by some 6\u00b0K in order to match the 12-14 micron spectrum, which is dominated by the opacity of H[subscript 2]. An NH[subscript 3] abundance defined by saturation equilibrium is consistent with the 9.5-12.0 micron spectrum, dominated by the opacity of that gas. The thermal structure above the 0.2 atm level is determined by fitting spectral and limb structure data in the 7.2-8.4 micron range, dominated by the opacity of CH[subscript 4]. The result is an inverted thermal structure with a base of about 110\u00b0K at 0.2 atm, rising through 150\u00b0K at about 0.03 atm. The mixing ratio of CH[subscript 4] most consistent with the spectral and limb structure data is 2.0 x 10[superscript -3] some three times that assumed in \"solar abundance\" models.\r\n\r\nThe 8.2-9.5 micron spectral region is not eerily matched by simple gaseous opacity sources. However, a haze of solid NH[subscript 3] particles above a thick cloud (which exists only in zones, as implied in Part 2) is consistent with the observed spectrum. Difficulty is encountered, however, with limb structure data at 8.44 microns and with some observations outside the 8-14 micron range.\r\n\r\nFurther observations of the separate spectral characteristics of belts and zones is recommended, as well as more accurate laboratory data for the opacity of atmospheric constituents in the relevant thermal regime and more sophisticated scattering approximations that used in this model.\r\n" }, { "name": "Wood, Spencer Hoffman", "degree": "PhD", "year": "1975", "title": "Holocene Stratigraphy and Chronology of Mountain Meadows, Sierra Nevada, California", "advisor": "Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03042010-080311245", "creators": [ { "name": { "family": "Wood", "given": "Spencer Hoffman" }, "id": "Wood-Spencer-Hoffman", "display_name": "Wood, Spencer Hoffman" } ], "advisors": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/HQEG-6769", "abstract": "Valley-fill deposits, exposed by Twentieth-Century dissection of a number of meadows on the west slope of the southern Sierra Nevada, contain a stratigraphic record strongly affected by secular variations in watershed hydrology during the Holocene. Meadows are situated in low gradient reaches, adaquately supported by seepage water, where fine textured materials accumulate under present hydrologic conditions. Meadows do not necessarily owe their origin to glacial modification of drainage. Many meadows have formed in both glaciated and unglaciated valleys by a water table rise in valley-fill deposits.\r\n\r\nGround water in any meadow drainage basin is annually recharged by snowmelt. Significant evapotranspiration by meadow plants causes diurnal fluctuations of growing-season water tables on the order of 0.2 to 0.5 ft and seasonal fluctuations of 2 to 4 ft. Growing-season water-table depths are characteristically different for the two major plant communities, being usually shallower than 2 feet for meadows, and deeper than 4 ft for conifer forests. This relationship and a ground-water model are used to interpret paleohydrologic variations recorded in valley-fill stratigraphy.\r\n\r\nStratigraphy, radiocarbon dating, and tephrachronology indicate the following sequence in upper tributary valleys of the montane belt. Pre-Holocene cobbly alluvium rests upon bedrock. A paleosol developed upon this alluvium between 10,200 and 8700 radiocarbon years B.P., records an early post-glacial climatic interval that established forests in the present upper montane belt. The overlying sequence of coarse loamy materials associated with in situ conifer stumps indicates one or more intervals of good soil drainage and dry valley-bottom conditions between 8700 and 1200 years B.P. At some sites there is an abrupt change from orest soils to overlying wet-meadow deposits dated 2500 years at some sites and 1200 years at others, suggesting many meadows originated coincidentally with neoglaciation in the Sierras. A water-table rise of a few feet, resulting from late melting snows, could cause the change from forest to meadow conditions. Meadow deposits are composed of organic-rich, sandy-loam, topsoil layers intercalcated with sheets of well-sorted sandy gravels deposited by flood flows with recurrence intervals greater than 50 years.\r\n\r\nA plot of upstream catchment area and valley gradient for dissected and undissected meadows indicates the geomorphic domain of unstable meadows subject to gully erosion under present hydrologic conditions on the Sierra west slope.\r\n\r\nTwo pumiceous tephra layers, widespread in meadow topsoils of the southern Sierra, are radiocarbon dated and attributed to tephraringed eruptive centers at opposite ends of the Mono-Inyo Crater chain of eastern California. Tephra 1, characterized by sanidine microphenocrysts and Sr content of 215 ppm, erupted 720 years B.P. Distribution of this tephra is confined to a south trending lobe extending 120 miles over the Sierra from the upper San Joaquin drainage to the Little Kern drainage. Trace element analysis of tephra 1 best match those of the tephra-ringed obsidian flow just south of Deadman Creek in the Inyo Craters. Tephra 2, characterized by a lack of microphenocrysts and Sr contents less than 20 ppm erupted from one of the northern Mono Craters eruptive centers. These two tephras appear to represent the most recent explosive eruptions of magma from this 40-km long chain of Holocene volcanoes.\r\n" }, { "name": "Alewine, Ralph Wilson, III", "degree": "PhD", "year": "1974", "title": "Application of Linear Inversion Theory Toward the Estimation of Seismic Source Parameters", "advisor": "Harkrider, David G.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10042005-103428", "creators": [ { "name": { "family": "Alewine", "given": "Ralph Wilson, III" }, "id": "Alewine-Ralph-Wilson-III", "display_name": "Alewine, Ralph Wilson, III" } ], "advisors": [ { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "advisor", "display_name": "Harkrider, David G." } ], "committee": [ { "name": { "family": "Kanamori", "given": "Hiroo" }, "id": "Kanamori-H", "orcid": "0000-0001-8219-9428", "role": "chair", "display_name": "Kanamori, Hiroo" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Harkrider", "given": "David G." }, "id": "Harkrider-D-G", "role": "member", "display_name": "Harkrider, David G." }, { "name": { "family": "Trifunac", "given": "Mihailo D." }, "id": "Trifunac-M-D", "role": "member", "display_name": "Trifunac, Mihailo D." }, { "name": { "family": "Helmberger", "given": "Donald V." }, "id": "Helmberger-D-V", "role": "member", "display_name": "Helmberger, Donald V." } ], "option_major": [ "geophys" ], "doi": "10.7907/WCNC-CQ56", "abstract": "A discussion is given concerning the development of methods for obtaining an accurate representation of the forward elastostatic problem of describing the processes which accompany faulting. A method is suggested by which a more complicated and arbitrary static dislocation function could be approximated with the formulations derived for simple dislocation sources. A stochastic inverse is used to provide optimum estimates of the source description when observed elastostatic phenomena are systematically related to the media response of the various source parameters. This method is applied to the observed static displacement data from the 1964 Alaska earthquake and the 1971 San Fernando, California, earthquake.
\r\n\r\nFor the Alaskan event, the surface static displacements are calculated with the finite-element numerical modeling technique in which the effects of known geologic heterogeneities of the region are taken into account. The fault model used is that of a shallow angle fault underthrusting the Alaskan continental block. The calculated optimum static offset, stress drop, and strain energy density along the fault were found to be variable with a maximum offset of about 30 m. The region of maximum stress drop (218 bars) and maximum strain energy density change is found to correspond to the region of maximum compressional wave radiation. The resolution and resolvability of the calculated static fault model is discussed.
\r\n\r\nFor the San Fernando earthquake, the static dislocation along the assumed fault plane was also found to vary considerably. The observed surface displacements are fit to a high degree of accuracy by the given model. Included in the inversion data set are changes in the local gravity field caused by the earthquake. These changes can be predicted from known changes in elevation when a Bouguer correction is applied to the gravity data.
\r\n\r\nThe spatial and frequency distribution of path-corrected Rayleigh waves from the San Fernando earthquake are systematically related to the faulting process. The surface wave source is taken to be a depth-distributed set of double couples. A least-squares inversion is used to find the set of source parameters which optimally fit the variance-weighted data. The inversion results indicate a depth-distributed moment of 1.7 x 1026 dyne-cm. The slip angles of the sources varied in such a way along the fault that the displacements became more predominantly dip slip as the dislocation propagated upward from the point of initial rupture at about 3.0 km/sec. A sophisticated error analysis is performed to estimate the uncertainties of the calculated model variables.
\r\n\r\nAn appendix is included in which the analytical expressions are derived for the complete strain field due to a dislocation on an arbitrarily inclined fault in a homogeneous half-space. Although the expressions are lengthy, the strain values can be calculated quickly on a computer since no numerical integration is necessary.
" }, { "name": "Fuis, Gary Stephen", "degree": "PhD", "year": "1974", "title": "The Geology and Mechanics of Formation of the Fort Rock Dome, Yavapai County, Arizona", "advisor": "Shoemaker, Eugene Merle", "url": "https://resolver.caltech.edu/CaltechETD:etd-03132006-135503", "creators": [ { "name": { "family": "Fuis", "given": "Gary Stephen" }, "id": "Fuis-Gary-Stephen", "display_name": "Fuis, Gary Stephen" } ], "advisors": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "advisor", "display_name": "Shoemaker, Eugene Merle" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/8JK8-8S67", "abstract": "The Fort Rock dome, in Yavapai County, Arizona, is a recently discovered circular geological structure, two miles in diameter, which initially aroused interest because of its similarity to an impact crater. Features of the dome that are similar to features of an impact crater include a crater-like depression in its center underlain by brecciated Precambrian igneous and metamorphic rocks, upturned Tertiary volcanic and sedimentary rocks on its rim, radial and tangential faults, and an apron of breccia on its flanks showing a crude inversion of the pre-breccia stratigraphy. Studies by the writer have indicated that the structure is primarily a volcanic dome caused by an intrusion at depth. The crater on top is erosional in origin." }, { "name": "Gibbons, Rex Vincent", "degree": "PhD", "year": "1974", "title": "Experimental Effects of High Shock Pressure on Materials of Geological and Geophysical Interest", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11032005-141608", "creators": [ { "name": { "family": "Gibbons", "given": "Rex Vincent" }, "id": "Gibbons-Rex-Vincent", "display_name": "Gibbons, Rex Vincent" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/9BJQ-N519", "abstract": "Shock recovery studies have been performed on a number of materials of geological and geophysical significance using a shock-loading propellant gun. These materials, including silicate glasses, feldspar, orthopyroxene, and pyroxenoid, have been shock-loaded to pressures up to approximately 550 kilobars. Optical and electron microscopic, optical spectral, and x-ray diffraction studies have been carried out on the recovered samples to determine the permanent effects of the shock-loading and the applicability of such information to research on naturally shocked lunar and terrestrial rocks and meteorites. The data on the pyroxene and feldspar are discussed in terms of their usefulness in interpreting, understanding, and calibrating the pressure and temperature conditions of shock metamorphism. The most significant observations include (1) the behavior of the silicate glasses, especially the occurrence of permanent densification until high postshock temperatures cause reversion to low density glass, (2) the permanent reduction of Mn(III) to Mn(II) by shock-loading to 496 kilobars, (3) the shock vitrification of calcic plagioclase to diaplectic and shock-fused glasses at pressures above 300 kilobars, (4) the shockproduction of deformation lamellae in bronzite, and (5) the formation of shock glass in bronzite at 226 kilobars." }, { "name": "Joesten, Raymond Leonard", "degree": "PhD", "year": "1974", "title": "Metasomatism and Magmatic Assimilation at a Gabbro-Limestone Contact, Christmas Mountains, Big Bend Region, Texas", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:02272014-085454874", "creators": [ { "name": { "family": "Joesten", "given": "Raymond Leonard" }, "id": "Joesten-Raymond-Leonard", "display_name": "Joesten, Raymond Leonard" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "chair", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "member", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "member", "display_name": "Rossman, George Robert" }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." } ], "option_major": [ "geol" ], "abstract": "A composite stock of alkaline gabbro and syenite is intrusive into limestone of the Del Carmen, Sue Peake and Santa Elena Formations at the northwest end of the Christmas Mountains. There is abundant evidence of solution of wallrock by magma but nowhere are gabbro and limestone in direct contact. The sequence of lithologies developed across the intrusive contact and across xenoliths is gabbro, pyroxenite, calc-silicate skarn, marble. Pyroxenite is made up of euhedral crystals of titanaugite and sphene in a leucocratic matrix of nepheline, Wollastonite and alkali feldspar. The uneven modal distribution of phases in pyroxenite and the occurrence' of nepheline syenite dikes, intrusive into pyroxenite and skarn, suggest that pyroxenite represents an accumulation of clinopyroxene \"cemented\" together by late-solidifying residual magma of nepheline syenite composition. Assimilation of limestone by gabbroic magma involves reactions between calcite and magma and/or crystals in equilibrium with magma and crystallization of phases in which the magma is saturated, to supply energy for the solution reaction. Gabbroic magma was saturated with plagioclase and clinopyroxene at the time of emplacement. The textural and mineralogic features of pyroxenite can be produced by the reaction 2( 1-X) CALCITE + ANXABl-X = (1-X) NEPHELINE+ 2(1-X) WOLLASTONITE+ X ANORTHITE+ 2(1-X) CO2. Plagioclase in pyroxenite has corroded margins and is rimmed by nepheline, suggestive of resorption by magma. Anorthite and wollastonite enter solid solution in titanaugite. For each mole of calcite dissolved, approximately one mole of clinopyroxene was crystallized. Thus the amount of limestone that may be assimilated is limited by the concentration of potential clinopyroxene in the magma. Wollastonite appears as a phase when magma has been depleted in iron and magnesium by crystallization of titanaugite. The predominance of mafic and ultramafic compositions among contaminated rocks and their restriction to a narrow zone along the intrusive contact provides little evidence for the generation of a significant volume of desilicated magma as a result of limestone assimilation.
\r\n\r\nWithin 60 m of the intrusive contact with the gabbro, nodular chert in the Santa Elena Limestone reacted with the enveloping marble to form spherical nodules of high-temperature calc-silicate minerals. The phases wollastonite, rankinite, spurrite, tilleyite and calcite, form a series of sharply-bounded, concentric monomineralic and two-phase shells which record a step-wise decrease in silica content from the core of a nodule to its rim. Mineral zones in the nodules vary 'with distance from the gabbro as follows:
\r\n0-5 m CALCITE + SPURRITE + RANKINITE + WOLLASTONITE
\r\n5-16 m CALCITE + TILLEYITE \u00b1 SPURRITE + RANKINITE + WOLLASTONITE
\r\n16-31 m CALCITE + TILLEYITE + WOLLASTONITE
\r\n31-60 m CALCITE + WOLLASTONITE
\r\n60-plus CALCITE + QUARTZ
\r\n\r\nThe mineral of a one-phase zone is compatible with the phases bounding it on either side but these phases are incompatible in the same volume of P-T-XCO2.
Growth of a monomineralio zone is initiated by reaction between minerals of adjacent one-phase zones which become unstable with rising temperature to form a thin layer of a new single phase that separates the reactants and is compatible with both of them. Because the mineral of the new zone is in equilibrium with the phases at both of its contacts, gradients in the chemical potentials of the exchangeable components are established across it. Although zone boundaries mark discontinuities in the gradients of bulk composition, two-phase equilibria at the contacts demonstrate that the chemical potentials are continuous. Hence, Ca, Si and CO2 were redistributed in the growing nodule by diffusion. A monomineralic zone grows at the expense of an adjacent zone by reaction between diffusing components and the mineral of the adjacent zone. Equilibria between two phases at zone boundaries buffers the chemical potentials of the diffusing species. Thus, within a monomineralic zone, the chemical potentials of the diffusing components are controlled external to the local assemblage by the two-phase equilibria at the zone boundaries.
\r\n\r\nMineralogically zoned calc-silicate skarn occurs as a narrow band that separates pyroxenite and marble along the intrusive contact and forms a rim on marble xenoliths in gabbro. Skarn consists of melilite or idocrase pseudomorphs of melili te, one or two . stoichiometric calcsilicate phases and accessory Ti-Zr garnet, perovskite and magnetite. The sequence of mineral zones from pyroxenite to marble, defined by a characteristic calc-silicate, is wollastonite, rankinite, spurrite, calcite. Mineral assemblages of adjacent skarn zones are compatible and the set of zones in a skarn band defines a facies type, indicating that the different mineral assemblages represent different bulk compositions recrystallized under identical conditions. The number of phases in each zone is less than the number that might be expected to result from metamorphism of a general bulk composition under conditions of equilibrium, trivariant in P, T and uCO2. The \"special\" bulk composition of each zone is controlled by reaction between phases of the zones bounding it on either side. The continuity of the gradients of composition of melilite and garnet solid solutions across the skarn is consistent with the local equilibrium hypothesis and verifies that diffusion was the mechanism of mass transport. The formula proportions of Ti and Zr in garnet from skarn vary antithetically with that of Si Which systematically decreases from pyroxenite to marble. The chemical potential of Si in each skarn zone was controlled by the coexisting stoichiometric calc-silicate phases in the assemblage. Thus the formula proportion of Si in garnet is a direct measure of the chemical potential of Si from point to point in skarn. Reaction between gabbroic magma saturated with plagioclase and clinopyroxene produced nepheline pyroxenite and melilite-wollastonite skarn. The calcsilicate zones result from reaction between calcite and wollastonite to form spurrite and rankinite.
\r\n\r\n" }, { "name": "Lagus, Peter Leonard", "degree": "PhD", "year": "1974", "title": "The Equations of State of Hydrogen and Argon: Applications to the Jovian Interior", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12072020-234014838", "creators": [ { "name": { "family": "Lagus", "given": "Peter Leonard" }, "id": "Lagus-Peter-Leonard", "display_name": "Lagus, Peter Leonard" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "chair", "display_name": "Archambeau, Charles B." }, { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "member", "display_name": "Goldreich, Peter Martin" }, { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "member", "display_name": "Muhleman, Duane Owen" }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "member", "display_name": "Anderson, Donald L." }, { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "member", "display_name": "Ahrens, Thomas J." } ], "option_major": [ "geophys" ], "doi": "10.7907/zzpq-2876", "abstract": "Hugoniot data for solid argon (initially at 77\u00b0K and l bar) and solid hydrogen (initially at 5\u00b0K and 1 bar) have been obtained to 143 kbar and 6.4 kbar respectively utilizing a propellant gun. The argon data (at volumes of 15.28, 14.84 and 14.64 cc/mole) are in fair agreement with previous shock data, and in excellent agreement with recent theoretically predicted Hugoniots. The hydrogen data (at volumes of 17.10, 15.32, 15.27, 15.11 cc/mole) are compared with Hugoniots calculated from published isothermal compression data. For both argon and hydrogen, the present data are consistent with the assumption that \u03b3/V is constant. Furthermore, to compressions of V/V\u2080 \u2243 0.65, no gross inconsistencies exist between shock-wave and isothermal compression measurements in solid hydrogen.
\r\n\r\nA simple equation of state (E0S) for molecular hydrogen based on a spherically averaged De Boer-type repulsion potential which explicitly includes the zero point energy reproduces experimental pressure-volume data between 5 kbar and 370 kbar. This molecular equa\u00adtion of state when combined with recent metallic equations of state implies a molecular to metallic phase transition pressure of 1.9 \u00b1 0.4 Mbar at 0\u00b0K.
\r\n\r\nA thermally expanded model of Jupiter which incorporates this molecular equation of state, recent metallic hydrogen and helium equa\u00adtions of state, and a van der Waals-type atmosphere yields a model with a hydrogen abundance of x = 0.57. However, the interior temperatures are everywhere above the melting temperature of metallic hydrogen.
" }, { "name": "Liu, Hsi-Ping", "degree": "PhD", "year": "1974", "title": "Part I. Temperature Dependence of Single Crystal Spinel (MgAl\u2082O\u2084) Elastic Constants from 293K to 423K Measured by Light-Sound Scattering in the Raman-Nath Region. Part II. Effect of Anelasticity on Periods of Earth's Free Oscillation (Toroidal Modes)", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01132011-114814151", "creators": [ { "name": { "family": "Liu", "given": "Hsi-Ping" }, "id": "Liu-Hsi-Ping", "display_name": "Liu, Hsi-Ping" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/QYWT-AK53", "abstract": "Part I:
\r\n\r\nThe temperature dependence of single-crystal elastic constants of synthetic stoichiometric MgAl_2O_4 spinel has been measured by the light-sound scattering technique in the Raman-Nath region. The crystal is set into forced vibration by a single crystal LiNbO_3 transducer coupled to one crystal face. A He-Ne laser beam is diffracted by the stress-induced birefringence inside the crystal. The diffraction angle is determined from the distance of two spots exposed on a photographic plate by the first order diffracted beams as measured by a microdensitometer. The sound wavelength inside the crystal is then inferred from the laser diffraction angle. Combining the sound wavelength with the measured transducer driving frequency, the velocity inside the crystal is determined typically to a precision of 0.05%. In this method, the measurement of velocity is not dependent on either the determination of sample length or on phase shifts at sample-transducer interface. Velocities of four pure modes, L//[001], T//[001], L//[110], and T//[110] (P//[1^-_10]) are measured in the temperature range between 293K and 423K. A linear temperature dependence is fit to the data by a least square method. Values obtained at 25\u00b0C from this linear fit are V_p[001] = 8.869 \u00b1 0.013 km/sec, (\u2202V/\u2202T)_p = -(3.14 \u00b1 0.13) x 10^(-4)km/sec-K; V_s[001] = 6.5666 \u00b1 0.0055 km/sec, (\u2202V/\u2202T)_p = -(1.47 \u00b1 0.10) x 10^(-4)km/sec-K; V_p[110] = 10.199 \u00b1 0.011 km/sec, (\u2202V/\u2202T)_p = -(3.20 \u00b1 0.15) x 10^(-4)km/sec-K; V_s[110][P//[110]) = 4.2101 \u00b1 0.0043 km/sec, (\u2202V/\u2202T)_p = -(2.07 \u00b1 0.06) x 10^(-4)km/sec-K. The temperature dependence of the adiabatic elastic constants and bulk and shear (VRH average) moduli is computed using the density and literature value of thermal expansion coefficient. Values obtained are: C^s_(11) = 2814 \u00b1 8 kb, (\u2202C^s_(11)/\u2202T)_p = -0.258 \u00b1 0.018 kb/K; C^s_(12) = 1546 \u00b1 9 kb, (\u2202C^s_(12)/\u2202T)_p = -0.107 \u00b1 0.019 kb/K; C^s_(44) = 1543 \u00b1 3 kb, (\u2202C^s_(44)/\u2202T)_p = -0.101 \u00b1 0.010 kb/k; K_s = 1969 \u00b1 6 kb, (\u2202K^s_/\u2202T)_p = -0.157 \u00b1 0.014 kb/K; \u00b5_(VRH) = 1080 \u00b1 5 kb, (\u2202\u00b5_(VRH)/\u2202T)_p = -0.094 \u00b1 0.008 kb/K. A comparison with previous measurements by pulse superposition and ultrasonic interferometry methods is made. Disagreement, when present, is discussed in terms of the separate measuring techniques. An attempt has also been made to measure the pressure dependence of elastic constants of spinel with the same technique. It failed because of the large spurious diffraction introduced by the fluctuation in index of refraction of the pressure fluid. A method to eliminate this spurious effect is discussed. An optical interferometry method is devised to measure the pressure window distortion effect in the pressure dependence measurement. Finally, the present method with its possibility for further improvement is evaluated as a new method to measure temperature and pressure dependence of elastic constants. Other methods using light-sound scattering to measure sound velocities are also reviewed.
\r\n\r\n\r\nPart II:
\r\n\r\nIt is known that the anelastic properties of the earth characterized \r\nby a \"Q\" structure will affect the periods of free oscillation. \r\nIt is generally considered that the effect is negligible compared to the \r\nother perturbing effects due to rotation, ellipticity, and lateral\r\ninhomogeneities. Nevertheless, it is of some interest to investigate \r\nthe precise magnitude of this effect for the observed free oscillation \r\nmodes since it could provide us with another constraint in the determination \r\nof the Q structure of the Earth. An application of perturbation\r\ntheory provides us with a good estimate of the magnitude of the \r\nchanges in the periods of an elastic model due to inclusion of anelastic \r\neffects. Calculations based on currently accepted elastic and \r\nanelastic models for the Earth show that the shift in period due to \r\nanelasticity is at most 0.023 percent for the toroidal modes from\r\n_oT_2 to o_T_(99) the maximum occurring near _oT_(60) This is smaller by a \r\nfactor of five than the present observational accuracy. Compared to \r\nthe other perturbing effects, the anelastic effect, when important, is \r\nlarger than the effect of ellipticity considered alone but smaller by \r\nan order of magnitude when compared with ellipticity and rotational \r\neffects coupled together or with the continent-ocean lateral inhomogeneity. \r\nSince the frequency shift due to anelasticity is scaled by \r\n(1/Q)^2, the anelastic effect can be within observational accuracy and \r\ncomparable to other perturbing effects for more extreme, yet acceptable,\r\nQ models.
" }, { "name": "Ludwig, Kenneth Raymond", "degree": "PhD", "year": "1974", "title": "Precambrian Geology of the Central Mazatzal Mountains, Arizona (part I). Lead Isotope Heterogeneity in Precambrian Igneous Feldspars (Part II)", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09092010-080806480", "creators": [ { "name": { "family": "Ludwig", "given": "Kenneth Raymond" }, "id": "Ludwig-Kenneth-Raymond", "display_name": "Ludwig, Kenneth Raymond" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/A0JK-VJ62", "abstract": "Part I:\r\n \r\n The Mazatzal Mountains are located in Gila, Yavapai, and Maricopa counties in central Arizona. The rocks in the central part of this range are dominantly Precambrian, and the only younger stratified rocks are of Tertiary or younger age. The Precambrian rocks have undergone a Precambrian regional metamorphism to lower greenschist grade.\r\n\r\n Two main mappable units of stratified rocks are present: the Alder series and the Red Rock rhyolite. Previous work (Wilson, 1939) had indicated that the Alder series is a clastic sedimentary pile, and that it lies in fault contact with an older Red Rock rhyolite. This work shows that the Alder series consists of about one-third directly accumulated volcanic material, another third of slightly reworked volcanic material, and the remaining third of argillites, quartzose sandstones, and limestones. The total thickness of the section is unknown, but is at least 14000' (4200 meters). The overall character of the Alder series is eugeosynclinal, in view of its great thickness, the abundance of volcanics, the thick sections of volcanic sandstones and wackes, and an overall trend towards more shallow-water deposited rocks towards the top of the section. The volcanics of the Alder series, however, are predominantly felsic (dacites to rhyolites), and basalts and pillow lavas, though present, are not abundant.\r\n\r\n The Red Rock rhyolite is a thick (at least 1000 meters) pile of extrusive rhyolitic volcanics including abundant ash-flow tuffs. There is no evidence of a fault between the Red Rock rhyolite and the Alder series. The Red Rock rhyolite lies with depositional contact and without apparent unconformity on the uppermost Alder series beds. In the lower Gold Creek area, a feeder dike to the Red Rock rhyolite penetrates the uppermost Alder series, and broke the surface at the time of accumulation of the Red Rock rhyolite.\r\n\r\n The lithologies of the Alder series show a fairly continuous evolution from sediments and volcanics accumulated in relatively deep water to sediments and volcanics accumulated in progressively more shallow water, and finally to sediments and volcanics accumulated under intermittently subaerial conditions. The basin of accumulation of the Alder series became progressively more shallow, at least partly because of the large volumes of volcanic material which accumulated there, until the eruption of the tremendous amounts of volcanics of the Red Rock rhyolite obliterated the remaining vestiges.\r\n\r\n The Red Rock rhyolite is petrographically and chemically indistinguishable from some of the volcanics in the uppermost Alder series. It evidently accumulated from sources which were active in latest Alder series time and which contributed to the uppermost Alder series section. Thus at least locally, the Alder series - Red Rock rhyolite contact intertongues. The thickness of the Red Rock rhyolite and the abundance of associated intrusive increases to the northeast, suggesting a probable direction of the source area, perhaps the Precambrian alkali rhyolite complex of Tonto Basin described by Conway (1973).\r\n\r\n Several generations of shallow intrusive rocks penetrate the Alder series and the Red Rock rhyolite. Two types of felsic porphyries were emplaced before\tfolding, while one type of felsic porphyry was emplaced after folding. Mafic volcanic sheets and dikes which intruded in and near the Red Rock mass of the Red Rock rhyolite may have been emplaced during folding.\r\n\r\n Chemical analyses were obtained for nine samples of the Pre-cambrian rocks of the central Mazatzal Mountains. These analyses suggest that the volcanic rocks of the lower Alder series are dominantly dacitic, while the upper Alder series volcanics are dominantly rhyolitic. The chemical composition of the upper Alder series volcanics and the Red Rock rhyolite are generally quite similar to modern, unaltered alkalic rhyolites.\r\n\r\n The structural framework of the area is dominated by tight, northeastward-trending folds. The Red Rock rhyolite is exposed at the cores of synclines, while a faulted anticlinal structure cuts off the oldest Alder series beds to the southeast of Mt. Peeley. These large-scale structures are of Precambrian age.\r\n\r\n Isotopic age determinations using the U-Pb method on cogenetic zircon fractions were performed on upper Alder series volcanics. The apparent age indicated by the analyses is 1730 \u00b1 20 m.y. The upper Alder series volcanics are not distinguishable in apparent age from the Red Rock rhyolite as determined by Silver (1964). This apparent age is distinctly younger than the ages obtained for previously-correlated rocks in the Prescott-Jerome area, and confirms the suspicions of Anderson et al (1971) that the Yavapai schist of the Prescott-Jerome area is not correlable with the type Alder series.\r\n\r\nPart II:\r\n\r\n The lead of high-purity, acid-washed K-feldspar concentrates from five Precambrian granites was removed in a stepwise fashion by two different techniques. Both the technique of stepwise volatilization under vacuum and the technique of stepwise partial attack by hydrofluoric acid yielded leads from the same K-feldspar concentrate which varied significantly in their isotopic composition.\r\n\r\n The patterns of lead isotopic variation from the feldspar concentrates show that the lead isotopic heterogeneity is due to a variable component of radiogenic lead which was generated since the crystallization of the rock. Two classes of lead isotopic variation were observed:\r\n\r\n (I) Parallel and colinear variation in the 206/204, 207/204, and 208/204 ratios, suggesting that the feldspar incorporated lead derived from long-term uranium and thorium decay from a source with constant Th/U, and\r\n\r\n (II) Variation in the 206/204 ratio independent of any 207/204 and 208/204 variation. This suggests that the feldspar contains lead derived from the continuing separation and concentration of a U^(238) intermediate-daughter, probably Rn^ (222).\r\n\r\n The amount and type of radiogenic lead incorporated by the five feldspar concentrates correlates with the concentrations of uranium and thorium in the rocks and with the geologic age and history of the rocks. Thus the rock with the highest uranium content (the Lawler Peak granite) has the K-feldspar with the greatest amount of uranium-derived radiogenic lead, and the rock with the highest thorium content (the Marble Mts. granite) has the K-feldspar with the greatest amount of thorium-derived radiogenic lead. The calculated Th/U values for the sources of the radiogenic leads ranges from two to eleven. Th/U values in this range are reasonable for several common granitic accessory minerals of appreciable U and Th content, but are higher than the Th/U values of the zircons in the rock.\r\n\r\n For two of the rocks, the Payson granite of Arizona and the Giants' Range granite of Minnesota, the composition of the radiogenic lead of the K-feldspar concentrates suggests that the rocks were disturbed by nearby Precambrian intrusives. The apparent time of incorporation of the radiogenic lead of the K-feldspar of the Giants' Range granite is 1010 \u00b1 150 m.y., which correlates well with the time of intrusion of the Duluth gabbro complex at 1120-1140 m.y. (Silver and Green, 1972).\r\n\r\n Although the least radiogenic lead fractions derived from the K-feldspar concentrates were significantly closer to the composition of the original feldspar lead, in no case was the original feldspar lead isolated. Moreover, because the least volatile lead fractions of some of the feldspar concentrates were more radiogenic in character than fractions of lesser volatility, it appears that the technique of stepwise volatilization is not promising for the routine isolation of original feldspar leads. The technique of stepwise hydrofluoric acid attack, however, yielded a greater isolation of original feldspar leads in fewer and simpler steps. This technique may be useful for the routine removal of the greatest part of the radiogenic lead component of Precambrian feldspars, and with further development may lead to the complete isolation of the original leads of such feldspars.\r\n\r\n The isotopic compositions of the least radiogenic fractions of the three 1450 \u00b1 20 m.y. southwestern granites have almost no variation in 207/204 (15.39 \u00b1 .02) and less than 1% variation in 206/204 (16.32\u00b1 .08). Calculations using the patterns of lead isotopic heterogeneity of these feldspars suggest that the original 206/204 values of these rocks were close to 16.16. The observed least radiogenic 208/204 value of the high-thorium (142 ppm) Marble Mts. granite is distinctly higher than those of the other two 1450 \u00b1 20 m.y. granites. These patterns suggest that these rocks were derived from a common, long-lived source, which source underwent a differentiation so as to cause a change in Th/U and Th/Pb a few hundreds of millions of years before the emplacement of the granites.\r\n" }, { "name": "Minster, Jean-Bernard", "degree": "PhD", "year": "1974", "title": "Elastodynamics of Failure in a Continuum", "advisor": "Archambeau, Charles B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08302011-092708394", "creators": [ { "name": { "family": "Minster", "given": "Jean-Bernard" }, "id": "Minster-Jean-Bernard", "display_name": "Minster, Jean-Bernard" } ], "advisors": [ { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z0VF-R694", "abstract": "A general treatment of the elastodynamics of failure in a\r\nprestressed elastic continuum is given, with particular emphasis on the geophysical aspects of the problem. The principal purpose of the study is to provide a physical model of the earthquake phenomenon, which yields an explicit description of the radiation field in terms of source parameters.\r\n\r\nThe Green's tensor solution to the equations of motion in a medium with moving boundaries is developed. Using this representation theorem, and its specialization to the scalar case by means of potentials, it is shown that material failure in a continuum can be treated equivalently\r\nas a boundary value problem or as an initial value problem. The initial value representation is shown to be preferable for geophysical purposes, and the general solution for a growing and propagating rupture zone is given.\r\n\r\nThe energy balance of the phenomenon is discussed with particular emphasis on the physical source of the radiated energy. It is also argued that the flow of energy is the controlling factor for the propagation and growth of a failure zone. Failure should then be viewed as a generalized phase change of the medium.\r\n\r\nThe theory is applied to the simple case of a growing and propagating spherical failure zone. The model is investigated in detail both analytically and numerically. The analysis is performed in the frequency domain and the radiation fields are given in the form of multipolar expansions. The necessary theorems for the manipulation of\r\nsuch expansions for seismological purposes are proved, and their use discussed on the basis of simple examples.\r\n\r\nThe more realistic ellipsoidal failure zone is investigated. The static problem of an arbitrary ellipsoidal inclusion under homogeneous stress of arbitrary orientation is solved. It is then shown how the\r\nanalytical solution can be combined with numerical techniques to yield more realistic models.\r\n\r\nThe conclusion is that this general approach yields a very flexible model which can be adapted to a wide variety of physical circumstances. In spite of the simplicity of the model, the predicted radiation field is rather complex; it is discussed as a function of source parameters, and scaling laws are derived which ease the interpretation of observed spectra. Preliminary results in the time domain are also shown. It is concluded that the model can be compared favorably both with the observations, and with results obtained from purely numerical models." }, { "name": "Cuzzi, Jeffrey Nicholas", "degree": "PhD", "year": "1973", "title": "The Subsurface Nature of Mercury and Mars from Thermal Microwave Emission", "advisor": "Muhleman, Duane Owen", "url": "https://resolver.caltech.edu/CaltechTHESIS:06272011-145049521", "creators": [ { "name": { "family": "Cuzzi", "given": "Jeffrey Nicholas" }, "id": "Cuzzi-Jeffrey-Nicholas", "display_name": "Cuzzi, Jeffrey Nicholas" } ], "advisors": [ { "name": { "family": "Muhleman", "given": "Duane Owen" }, "id": "Muhleman-D-O", "role": "advisor", "display_name": "Muhleman, Duane Owen" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/MBPM-GS43", "abstract": "Detailed numerical modeling techniques are applied to the analysis of microwave observations of Mercury and Mars. The model calculations include the effects of orbital-axial resonance and dependence of regolith properties (e.g. specific heat and thermal conductivity) on temperature\r\nin the case of Mercury, and for the effects of seasonally varying CO_2 frost caps in the case of Mars. Variations of geocentric aspect from one observation period to the next are treated for both planets. The dielectric properties of the subsurfaces of these planets are treated as\r\nindependent of temperature and homogeneous with depth and location on the planet.\r\n\r\nObservations of Mercury were made at 3.71, 6, and 18 cm, and\r\npreviously published observations at .31, .33, and 3.75 cm are also employed in the analysis. The Mercury data appear to be consistent with the presence of a dry, porous regolith in which the radiative transport of heat is important in the total thermal conductivity. The ratio of\r\nradiative to contact thermal conductivity, \u03c7, is normally evaluated at T = 350\u00b0 K, and it is found that these data limit \u03c7 thus defined to the range 0.4 < \u03c7 < 1.0. A value for the effective subsurface dielectric constant is determined from interferometric measurements at 3.71 cm presented\r\nhere. This value (\u03b5 = 2.0 \u00b1 .16 ) is then corrected for the effects of surface roughness to yield a value for the dielectric constant of the regolith of \u03b5 = 2.4 \u00b1 .3. Final values of other parameters are:\r\n\r\ntan \u0394 = regolith loss tangent = .0075 \u00b1 .002\r\n\r\n\u03b3 = thermal inertia = .0014^(+.0021_(-.0008) cal cm ^(-2) deg ^(-1) sec ^(-\u00bd).\r\n\r\nIn a similar way, expected microwave spectra of Mars are computed using accurate aspect geometry and a thermal model that includes seasonal polar cap effects. It is found that for a range of loss tangents characteristic of dry particulate geological materials (.003 < tan \u0394 < .015), and for values of other surface parameters determined independently, the observable spectrum of Mars in the microwave region is \"flat\" from 0.1 to 21 cm to within the\r\naccuracy of the present data , and that a regolith of homogeneous, lunar-like properties is completely consistent with the existing data set when polar cap effects are considered. This result differs from that predicted by the\r\nanalytical theory in common use which is in apparent conflict with the observed spectra for values of the surface parameters similar to those found for the Moon or Mercury.\r\n\r\nFinal values of other relevant parameters are:\r\n\r\n\u03b3 = thermal inertia = .006 cal cm ^(-2) deg ^(-1) sec ^(-\u00bd)\r\n\r\n\u03b5 = regolith dielectric constant = 2 .5 \u00b1 .3\r\n\r\nA = bolometric Bond albedo = .25\r\n\r\nE = infrared emissivity = .90.\r\n" }, { "name": "Davies, Geoffrey Frederick", "degree": "PhD", "year": "1973", "title": "Elasticity of Solids at High Pressures and Temperatures: Theory, Measurement, and Geophysical Application", "advisor": "Ahrens, Thomas J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02072018-154915291", "creators": [ { "name": { "family": "Davies", "given": "Geoffrey Frederick" }, "id": "Davies-Geoffrey-Frederick", "display_name": "Davies, Geoffrey Frederick" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/SK7X-EE20", "abstract": "A theory for describing the elasticity of solids at \r\nsimultaneous high pressures and high temperatures is developed\r\nby incorporating the fourth-order ahnarmonic theory of lattice\r\ndynamics into finite strain theory. The theory is applied\r\nto the analysis of a variety of data for MgO, SiO2 and\r\nNaCl, and the results for MgO and SiO2 used as the basis of\r\na discussion of the constitution of the lower mantle. New \r\nresults are reported of measurements of elastic properties\r\nof MgO shock-compressed to over 500 Kb.
\r\n\r\n\r\nThe condition that finite strain equations be frame-\r\nindifferent is shown to require that only strain tensors\r\nbelonging to a class of frame-indifferent strain tensors be \r\nused in finite strain expansion. It is shown that the\r\ngenerality of finite strain theory is not impaired by the \r\ninclusion of an explicit theory of thermal effects. Explicit\r\nequations for isotherms, isentropes and Hugoniots and for\r\nthe effective elastic moduli of materials of cubic symmetry\r\nunder hydrostatic stress are derived. The primary parameters\r\nof these equations are related to the elastic moduli and\r\ntheir pressure and temperature derivatives in an arbitrary\r\nreference state using thermodynamic identities, some of which\r\nare derived here.
\r\n\r\n\r\nHugoniot data corresponding to different initial sample\r\ndensities of MgO, SiO2 and NaCl and original ultrasonic data\r\nof NaCl are used to test both the compressional and thermal\r\nparts of the theory, and to refine the equations of state of\r\nthese materials. The frame-indifferent analogue, E, of the\r\nusual \"Eulerian\" strain tensor, \u03b5, is found to usually give\r\nfaster convergence of finite strain expansions than the\r\n\"Lagrangian\" strain tensor, \u03b7. The effect of usinq differ\u00adent \r\nstrain measures on the values of parameters derived from \r\ndata is demonstrated, and the adverse effects of using inappropriately \r\nderived parameters in extrapolation equations is demonstrated.\t\r\nThermal effects in Hugoniot data are reasonably well described, \r\nbut higher-order anharmonic effects appear to be required in the \r\ntheory in order to describe the high temperature ultrasonic and \r\nthermal expansion data.
\r\n\r\n\r\nMeasured velocities of rarefaction waves propagating\r\ninto shocked MgO are in accord with a two-stage longitudinal\r\n(elastic)-hydrodynamic (plastic) decompression model, and\r\nconstrain the high-pressure elastic moduli of MgO.
\r\n\r\n\r\nThe effects on the determination of the lower mantle constitution \r\nof temperature, varying composition, the presence of phases denser \r\nthan oxides mixtures, and the presence of iron in the \"low-spin\" \r\nelectronic state are estimated, and a trade-off between many \r\nof these factors demonstrated. Iron content could range between 6% and \r\n15% by weight of FeO. Silica content could range from 33% to 50% or \r\nmore by weight. Phases a few percent denser than oxides mixtures \r\nseem to be likely. The temperature is very indeterminable.
" }, { "name": "Gaffney, Edward Stowell", "degree": "PhD", "year": "1973", "title": "Crystal Field Effects in Mantle Minerals", "advisor": "Ahrens, Thomas J.; Rossman, George Robert", "url": "https://resolver.caltech.edu/CaltechTHESIS:07202018-110502938", "creators": [ { "name": { "family": "Gaffney", "given": "Edward Stowell" }, "id": "Gaffney-Edward-Stowell", "display_name": "Gaffney, Edward Stowell" } ], "advisors": [ { "name": { "family": "Ahrens", "given": "Thomas J." }, "id": "Ahrens-T-J", "role": "advisor", "display_name": "Ahrens, Thomas J." }, { "name": { "family": "Rossman", "given": "George Robert" }, "id": "Rossman-G-R", "orcid": "0000-0002-4571-6884", "role": "advisor", "display_name": "Rossman, George Robert" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/3DS0-XR25", "abstract": "The behavior of Fe2+ in the lower mantle will depend on the effects of crystal fields. A point charge model, scaled to fit observed spectra at low pressures is developed to predict these effects. Two of the three parameters needed to predict spin-pairing transitions can only be determined from spin-forbidden electronic transitions. The spectra of garnet, gillespite and peridot are examined and found to have such absorption features. Assignment of these spectra leads to values of the Racah parameters, B and C, as well as the crystal field parameter Dq.
\r\n\r\nA new experimental technique, which allows the measurement of optical absorption spectra of solids in the visible region during shock loading, is described. Results are discussed for periclase and ruby. The ruby data indicate that the point charge model is good to at least 15 percent (volume) compression.
\r\n\r\nThe effects of low-spin Fe2+ in the earth's lower mantle are investigated in considerable detail.\tThe existence of low-spin Fe2+ permits the formation of a separate phase since Mg2+ and low-spin Fe2+ may not form solid solutions. The bulk elastic behavior of such phases is predicted from volume-bulk modulus systematics and compared with available shock wave data. It is likely that the high pressure phases of several ferrous iron compounds involve low-spin Fe2+ Iron will be spin-paired in the mantle below 1200 km and likely at higher levels as well. The observed density and bulk modulus in the lower mantle are inconsistent with any combination of phases in a pyrolite bulk composition but can be fit quite well by a model with all Fe2+ spin-paired below 630 km and nearly olivine composition at that depth, with MgO decreasing to almost a pyroxene composition at the core.
\r\n\r\nAn origin of the upper mantle from the lower mantle by chemical fractionation is proposed. The spin-pairing of Fe2+ provides an excellent mechanism for both iron and silicon enrichment in the lower mantle by partial melting yielding a pyrolite upper mantle, and hence, a chemically inhomogeneous mantle. This removes the motivation for reducing FeO and SiO2 in the mantle to supply Fe and Si for the core.
\r\n\r\n" }, { "name": "Jordan, Thomas Hillman", "degree": "PhD", "year": "1973", "title": "Estimation of the Radial Variation of Seismic Velocities and Density in the\r\nEarth", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08292011-141658832", "creators": [ { "name": { "family": "Jordan", "given": "Thomas Hillman" }, "id": "Jordan-Thomas-Hillman", "display_name": "Jordan, Thomas Hillman" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/K0B1-PW97", "abstract": "An inversion procedure is developed to estimate the radial\r\nvariations of compressional velocity, shear velocity, and density in the Earth. The radial distributions are defined as spherically symmetric averages of the actual distributions in the laterally heterogeneous Earth, and the nature of the averaging implied by averaging\r\ncertain sets of eigenperiod and travel-time data is examined. For travel-time data, the spherical averaging yields the Terrestrial Monopole if the data sample a distribution derived from a uniform distribution of sources and receivers. Since this is difficult to obtain for absolute times, differential travel times are used to\r\nconstrain the velocities. It is shown that the bias inherent in available sets of differential travel-time data is considerably less than that in equivalent sets of absolute travel-time data, if the phase combination is suitably chosen. Observations are presented for\r\nthe phase combinations PcP-P, ScS-S, P'(AB)-P'(DF), and P'(BC)-P'(DF).\r\n\r\nThe inversion algorithm developed is based on a linear approximation to the perturbation equations and is shown to provide a stable method for estimating the radial distributions of velocities and density from a finite number of inaccurate data. The linear inversion\r\ntheory presented is complete; it allows one to estimate the resolving power of the data and the resolvability of specified features in the model.\r\n\r\nThree estimates of the radial distributions are derived using an extensive set of eigenperiod and travel-time data. One model, designated model B1, fits 127 of the 177 eigenperiods of the Dziewonski-Gilbert set within their formal 95% confidence intervals. This model satisfies extensive sets of auxillary data as well.\r\n\r\nIt is shown from resolving power calculations that little information is lost by using differential travel times in lieu of absolute times. It is demonstrated that the nature of the averaging in the estimation procedure for given sets of gross Earth data can be improved by judicious specification of the norm on the space of models.\r\n\r\n" }, { "name": "Jungels, Pierre Henri", "degree": "PhD", "year": "1973", "title": "Modeling of Tectonic Processes Associated with Earthquakes", "advisor": "Archambeau, Charles B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09202005-112510", "creators": [ { "name": { "family": "Jungels", "given": "Pierre Henri" }, "id": "Jungels-Pierre-Henri", "display_name": "Jungels, Pierre Henri" } ], "advisors": [ { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/5R3G-8281", "abstract": "A finite element variational method is described and applied to the analysis of zero frequency seismic data. This technique presents a suitable tool for the analysis of permanent displacements, tilts and strains caused by seismic events, since it can model variable fault offsets in heterogeneous media.
\r\n\r\nThe accuracy of the technique is demonstrated by detailed static field computations for vertical and dipping dislocations acting in plane strain, corresponding to an infinite-length fault in a homogeneous half space, by comparison with closed form analytic solutions. A parametric study of material inhomogeneities and variable fault offsets reveals that order of magnitude changes in the solutions can occur for both near and far field displacements and strains.
\r\n\r\nThe technique was applied to the San Fernando earthquake using a two-dimensional (plane strain) model. The best solution was obtained by separating the fault into two distinct parts, both having offsets near the surface a factor of five larger than the average slip. Both stress drop and displacements vary by more than an order of magnitude along the fault plane, the maximum occurring at 1 km depth. Several solutions are investigated for the hypocentral region, one of them giving as much as 5 m offset.
\r\n\r\nThe Alaskan earthquake of 1964 is also studied in plane strain, and the observed vertical movements are inverted numerically to yield a \"best fit\" offset on the fault surface. This solution gives good results for the observed horizontal movement. It is characterized by large variations of the slip with a maximum of 33 m below Montague Island.
\r\n\r\nThen, a relationship is derived, giving energy released as a function of prestress, fault area, change in the local gravitational potential energy and fault offset, neglecting nonlinear behavior outside the fault zone. The finite element method is shown to allow direct calculation of the terms of the resulting equation from static consideration of failure in a prestress medium.
\r\n\r\nThis is applied to the last solution for the San Fernando earthquake, the best fit offset of the Alaska earthquake and a simple model of the Montana earthquake, 1959. In all three cases, the results indicate that a spatially variable prestress field gives the best representation of the tectonic processes involved. The force of gravity is found to be a significant factor in the energy balance of each event, increasing the estimate of prestress for the thrust faults and the apparent stress drop for the Montana normal fault.
\r\n\r\nFor the San Fernando earthquake, the prestress field in the hypocentral region is shown to exceed critical stress levels corresponding to granite strength as measured in the laboratory, while the average stress drop for the entire fault is below 200 bars. This is a possible answer to the apparent discrepancy between laboratory and average field measurements.
\r\n\r\nThe Wilmington oil field subsidence is modeled by using a finite element code which solves numerically Biot's consolidation theory. The best fit is obtained for a very small interaction constant. The models result in significant stress concentrations which could have triggered the small magnitude events known as the Long Beach subsidence earthquakes.
" }, { "name": "Knauth, LeRoy Paul", "degree": "PhD", "year": "1973", "title": "Oxygen and Hydrogen Isotope Ratios in Cherts and Related Rocks", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechETD:etd-01192006-105618", "creators": [ { "name": { "family": "Knauth", "given": "LeRoy Paul" }, "id": "Knauth-LeRoy-Paul", "display_name": "Knauth, LeRoy Paul" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/SH1S-JE93", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe feasibility of making meaningful measurements of the deuterium content of water extracted from hydrous silica has been evaluated by a series of dehydration and isotope exchange experiments. A new experimental technique, called Differential Isotopic Analysis (D.I.A.), has been developed which allows the isotopic exchange characteristics of water in different sites in hydrous silica to be determined. This method involves the sampling of successive increments of water driven off during heating of the silica and the measurement of [...] for these water samples. The isotopic pattern established for the [...] values of successively driven-off samples varies markedly, depending on the degree to which the water in silica has been exchanged with deuterium-rich water in controlled experiments. The fraction of the water or hydroxyl groups that is most resistant to exchange and most difficult to drive off is that water or hydroxyl group most likely to contain the hydrogen which was in equilibrium with the waters from which the silica formed.\r\n\r\nGranular microcrystalline quartz, the most common constituent of chert, has been found to contain hydroxyl groups particularly suitable for hydrogen isotope analyses. Cherts of a given age consisting of granular microcrystalline quartz free of organic matter yield an approximate linear relationship between [...] and [...] of the total oxygen. The line thus defined is parallel to the [...] relationship for meteoric waters, but has an intercept which is age-dependent. The isotope data indicate that, for many darts, the diagenetic, transformation of opal to granular microcrystalline quartz occurred in the presence of meteoric waters. The displacement with time of the [...] relationship is interpreted as being due to the effect of past climatic temperature changes on the temperature-dependent isotopic fractionation factors for D/H and [...]. The variations in [...] and D/H ratios of cherts and other forms of hydrous silica have been investigated and have been used to deduce climatic temperature variations for the central and western United States over geologic time.\r\n\r\nThe chert-water oxygen isotope fractionation with temperature was estimated from published experimental data and from the isotopic compositions of cherts which formed at approximately known temperatures. The fractionation is [...]. This equation was used to calibrate the temperature dependence of the variation with time of the [...] linear relationships for cherts, assuming that the variations are due entirely to climatic temperature fluctuations and that the oceans have not changed isotopically with time. Temperatures deduced for chert-formation indicate that the average past climatic temperatures for the central and western United States decreased from 34\u00b0C to 20\u00b0C through the Paleozoic, increased to 35\u00b0 - 40\u00b0C in the Triassic, and then decreased to the present day value of 13\u00b0 - 15\u00b0C. Temperatures in the Precambrian for this region may have reached over 50\u00b0C at 1.3 billion years, although temperatures similar to those of the Phanerozoic Era are inferred at 2 billion years and 1.2 billion years. Extremely cold temperatures deduced for deep ocean water from the oxygen isotopic composition of several samples of opal-CT [...] in deep sea sediments indicates the possibility of ice caps at the close of the Cretaceous and at the beginning of the Oligocene. Granular microcrystalline quartz in deep sea sediments often forms during deep burial at elevated peratures and cannot be used to deduce deep ocean temperatures.\r\n\r\nCherts are usually not in isotopic equilibrium with their coexisting carbonates, and the somewhat insensitive chert-calcite oxygen isotope fractionation thus cannot be used to obtain meaningful temperatures. Calcitic Crinoid fragments in a chert nodule from the Mississippian Burlington limestone yielded an oxygen isotopic temperature of 25\u00b0C, indicating that fossil fragments encased within chert nodules may be protected from post-depositional exchange with ground waters and thus suitable for isotopic paleo-temperature analysis.\r\n\r\nMost forms of opal are so hydrous that meaningful [...] values cannot be ascertained with existing analytical techniques. Hyalite opal presents the fewest difficulties, since it contains less than 3% H2O. In spite of the analytical difficulties, [...] values for amorphous silica qualitatively reflect the isotopic composition of the waters and temperatures of formation." }, { "name": "Squires, Richard Lane", "degree": "PhD", "year": "1973", "title": "Burial Environment, Diagenesis, Mineralogy, and Mg & Sr Contents of Skeletal Carbonates in the Buckhorn Asphalt of Middle Pennsylvanian Age, Arbuckle Mountains, Oklahoma", "advisor": "Lowenstam, Heinz A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10102006-152318", "creators": [ { "name": { "family": "Squires", "given": "Richard Lane" }, "id": "Squires-Richard-Lane", "display_name": "Squires, Richard Lane" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geobiol" ], "doi": "10.7907/WJKW-Q723", "abstract": "The Buckhorn asphalt quarry in the northern part of the Arbuckle Mountains, Oklahoma, contains chemically well preserved marine invertebrate fossils of Middle Pennsylvanian age. The main purpose of this investigation was to study the chemistry of these fossils, and at the same time analyze the geologic setting of the deposits containing the fossils.\r\n\t\r\nDue to early sealing by oil, many of the shells still have the original aragonite and nacreous luster. The oil prevented the grainstones from becoming well cemented and allowed them to become compacted during the Arbuckle orogeny. Deformation related to this orogeny probably caused the devolatization of the oil and, hence, conversion into asphalt.\r\n\r\nMost of the fossils occur as fragments in several skeletal debris grainstones which are shallow, turbulent water inferred channel deposits. The ancient shoreline was only six miles to the northeast. Underlying calcareous sponge spicule-echinoderm-brachiopod-fusulinid mudstones and wackestones were deposited in less turbulent water environments.\r\n\r\nMineralogical data were obtained by means of x-ray diffraction, infrared spectroscopy, and chemical staining. Quantitative analyses of the elemental constituents for various shell layers were obtained with an electron microprobe.\r\n\r\nThe original mineralogy of skeletal carbonates was established for the first time in the following. Aragonite occurs in the inner layers of the gastropods Naticopsis wortheni and Trachydomia whitei, whereas their outer layers consist of calcite. Aragonite also occurs in the shell walls of the scaphopod Plagioglypta ? sp., the coiled nautiloids Metacoceras cornutum, and Domatoceras sp., and the ammonoids Pseudoparalegoceras sp. and Wellerites mohri ?. The orthocone nautiloid \"Orthoceras\" unicamera has aragonitic shell walls, septa, and cameral deposits. Skeletons of the foraminifera Globivalulina sp. and Wedekinellina ? sp., the presumed tabulate Chaetetes cf. favosus, the cryptostome bryozoans Penniretepora ? sp. and Streblotrypa ? sp., the brachiopod Anthracospirifer opimus, four ostracodes, and the spines of the echinoid Archaeocidaris megastyla ? consist of calcite.\r\n\r\nAs reported by others, calcitic outer layers and inner aragonitic layers were also found in Bellerophon (Bellerophon) sp., Straparollus (Euomphalus) sp., and Chaenocardia ovata. The shell walls and cameral deposits of Pseudorthoceras knoxense also are aragonitic.\r\n\r\nPreviously unreported moderately high Mg contents occur in the calcite of Chaetetes cf. favosus. The spines of Archaeocidaris megastyla ? are inferred to have been originally Mg-calcite.\r\n\r\nDiagenetic effects were detected in the skeletal carbonates. The amount of replacement calcite and degree of obliteration of shell microarchitecture in the skeletal aragonites increase with decreasing asphalt content. Asphalt-impregnated skeletal calcites contain more Mg and usually less Sr than corresponding nonasphalt-impregnated specimens.\r\n\r\nData obtained on the Mg and Sr concentrations of the best preserved specimens indicate the following. The Sr/Ca ratio for the coiled nautiloid Metacoceras cornutum is similar to that for the modern-day Nautilus sp. The Mg contents in the calcites of the foraminifera, bivalve, and ostracodes are similar to those in related Recent forms. The shell walls of the extinct orthocone nautiloids have lower Sr contents relative to the cameral deposits. These large differences are apparently due to the \"vital effect\" of the organism.\r\n" }, { "name": "Ward, William Roger", "degree": "PhD", "year": "1973", "title": "I. The Formation of Planetesimals. II. Tidal Friction and Generalized Cassini's Laws in the Solar System", "advisor": "Goldreich, Peter Martin", "url": "https://resolver.caltech.edu/CaltechETD:etd-03042009-085737", "creators": [ { "name": { "family": "Ward", "given": "William Roger" }, "id": "Ward-William-Roger", "display_name": "Ward, William Roger" } ], "advisors": [ { "name": { "family": "Goldreich", "given": "Peter Martin" }, "id": "Goldreich-P-M", "role": "advisor", "display_name": "Goldreich, Peter Martin" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/kqm5-4r97", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nIn Part 1, four stages in the accretion of planetesimals are described. The initial stage is the condensation of dust particles from the gaseous solar nebula as it cools. These dust particles settle into a thin disk which is gravitationally unstable. A first generation of planetesimals, whose radii range up to ~10\u207b\u00b9 kilometer, form from the dust disk by direct gravitational collapse to solid densities on a time scale of order one year. The resulting disk, composed of first generation planetesimals, is still gravitationally unstable and the planetesimals are grouped into clusters containing approximately 10\u2074 members. The contraction of these clusters is controlled by the rate at which gas drag damps their internal rotational and random kinetic energies. On a time scale of a few thousand years, the clusters contract to form a second generation of planetesimals having radii of the order of a few kilometers. Further coalescence of planetesimals proceeds by collisions which seem capable of producing objects with a growth rate of ~15 cm. yr\u207b\u00b9 at one A.U. The final stage of accretion during which planet-sized objects form is not considered here.
\r\n\r\nIn Part 2 of this thesis, an investigation of a dynamical problem which has considerable application to the solar system is undertaken. The evolution of the obliquity of an object is determined when under the influence of three phenomena: (1) the precession of the object's orbit plane, (2) the precession of the object's spin axis, and (3) tidal friction. In the absence of tidal friction, it is concluded that if the period for precession of the spin axis is much shorter than the orbit precession period, the obliquity of the object will remain very nearly constant in spite of the movement of the orbit normal. It is further concluded, that since the obliquity is not changed by the motion of the orbit plane, the decay of the obliquity towards zero by tidal friction is not significantly altered by this motion. These results are applied to Mercury, Venus, Iapetus, Triton, as well as the equatorial satellites of Mars, Jupiter, Saturn, and Uranus. The final spin states of these objects satisfy a generalization of Cassini's laws for the moon.
" }, { "name": "Whitcomb, James Hall", "degree": "PhD", "year": "1973", "title": "Part I: A Study of the Velocity Structure of the Earth by the Use of Core Phases. Part II: The 1971 San Fernando Earthquake Series Focal Mechanisms and Tectonics", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02202014-135247734", "creators": [ { "name": { "family": "Whitcomb", "given": "James Hall" }, "id": "Whitcomb-James-Hall", "display_name": "Whitcomb, James Hall" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/JDKQ-2Z91", "abstract": "The initial objective of Part I was to determine the nature of\r\nupper mantle discontinuities, the average velocities through the\r\nmantle, and differences between mantle structure under continents\r\nand oceans by the use of P'dP', the seismic core phase P'P' (PKPPKP)\r\nthat reflects at depth d in the mantle. In order to accomplish this,\r\nit was found necessary to also investigate core phases themselves\r\nand their inferences on core structure. P'dP' at both single stations\r\nand at the LASA array in Montana indicates that the following zones\r\nare candidates for discontinuities with varying degrees of confidence:\r\n800-950 km, weak; 630-670 km, strongest; 500-600 km, strong but\r\ninterpretation in doubt; 350-415 km, fair; 280-300 km, strong, varying\r\nin depth; 100-200 km, strong, varying in depth, may be the bottom of\r\nthe low-velocity zone. It is estimated that a single station cannot\r\neasily discriminate between asymmetric P'P' and P'dP' for lead times\r\nof about 30 sec from the main P'P' phase, but the LASA array reduces\r\nthis uncertainty range to less than 10 sec. The problems of scatter\r\nof P'P' main-phase times, mainly due to asymmetric P'P', incorrect\r\nidentification of the branch, and lack of the proper velocity\r\nstructure at the velocity point, are avoided and the analysis shows\r\nthat one-way travel of P waves through oceanic mantle is delayed\r\nby 0.65 to 0.95 sec relative to United States mid-continental\r\nmantle.
\r\n\r\nA new P-wave velocity core model is constructed from observed\r\ntimes, dt/d\u0394's, and relative amplitudes of P'; the observed times of\r\nSKS, SKKS, and PKiKP; and a new mantle-velocity determination by\r\nJordan and Anderson. The new core model is smooth except for a\r\ndiscontinuity at the inner-core boundary determined to be at a\r\nradius of 1215 km. Short-period amplitude data do not require the\r\ninner core Q to be significantly lower than that of the outer core.\r\nSeveral lines of evidence show that most, if not all, of the arrivals\r\npreceding the DF branch of P' at distances shorter than 143\u00b0 are\r\ndue to scattering as proposed by Haddon and not due to spherically\r\nsymmetric discontinuities just above the inner core as previously\r\nbelieved. Calculation of the travel-time distribution of scattered\r\nphases and comparison with published data show that the strongest\r\nscattering takes place at or near the core-mantle boundary close to\r\nthe seismic station.
\r\n\r\nIn Part II, the largest events in the San Fernando earthquake\r\nseries, initiated by the main shock at 14 00 41.8 GMT on February 9,\r\n1971, were chosen for analysis from the first three months of\r\nactivity, 87 events in all. The initial rupture location coincides\r\nwith the lower, northernmost edge of the main north-dipping thrust\r\nfault and the aftershock distribution. The best focal mechanism\r\nfit to the main shock P-wave first motions constrains the fault\r\nplane parameters to: strike, N 67\u00b0 (\u00b1 6\u00b0) W; dip, 52\u00b0 (\u00b1 3\u00b0) NE;\r\nrake, 72\u00b0 (67\u00b0-95\u00b0) left lateral. Focal mechanisms of the aftershocks\r\nclearly outline a downstep of the western edge of the main thrust\r\nfault surface along a northeast-trending flexure. Faulting on this \r\ndownstep is left-lateral strike-slip and dominates the strain release\r\nof the aftershock series, which indicates that the downstep limited\r\nthe main event rupture on the west. The main thrust fault surface\r\ndips at about 35\u00b0 to the northeast at shallow depths and probably\r\nsteepens to 50\u00b0 below a depth of 8 km. This steep dip at depth is a\r\ncharacteristic of other thrust faults in the Transverse Ranges and\r\nindicates the presence at depth of laterally-varying vertical\r\nforces that are probably due to buckling or overriding that causes\r\nsome upward redirection of a dominant north-south horizontal\r\ncompression. Two sets of events exhibit normal dip-slip motion with\r\nshallow hypocenters and correlate with areas of ground subsidence\r\ndeduced from gravity data. Several lines of evidence indicate that\r\na horizontal compressional stress in a north or north-northwest\r\ndirection was added to the stresses in the aftershock area 12 days\r\nafter the main shock. After this change, events were contained in\r\nbursts along the downstep and sequencing within the bursts provides\r\nevidence for an earthquake-triggering phenomenon that propagates\r\nwith speeds of 5 to 15 km/day. Seismicity before the San Fernando\r\nseries and the mapped structure of the area suggest that the downstep\r\nof the main fault surface is not a localized discontinuity but is\r\npart of a zone of weakness extending from Point Dume, near Malibu, to\r\nPalmdale on the San Andreas fault. This zone is interpreted as a\r\ndecoupling boundary between crustal blocks that permits them to deform\r\nseparately in the prevalent crustal-shortening mode of the Transverse\r\nRanges region.
\r\n" }, { "name": "Hanks, Thomas Colgrove", "degree": "PhD", "year": "1972", "title": "A Contribution to the Determination and Interpretation of Seismic Source Parameters", "advisor": "Archambeau, Charles B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08262011-111631645", "creators": [ { "name": { "family": "Hanks", "given": "Thomas Colgrove" }, "id": "Hanks-Thomas-Colgrove", "display_name": "Hanks, Thomas Colgrove" } ], "advisors": [ { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/DGY7-DE54", "abstract": "Two models of the seismic source are reviewed as a prelude to the determination and interpretation of seismic source parameters from far-field shear displacement spectra. \r\nWithin several limitations, the far-field shear displacement spectra of Brune (1970) and Haskell (1964)\r\nare grossly similar although the results differ in detail. These similarities imply that there is no gross discrepancy between Brune (1970) and Haskell (1964) with respect to the determination of seismic moment and source dimension.\r\n\r\nThe source parameters seismic moment (M_o), source dimension (r), shear stress drop (\u0394\u03c3), effective shear stress (\u03c3_(eff)), radiated energy (E_s), and apparent stress (\u03b7\u03c3) can all be expressed in terms of three\r\nspectral parameters which specify the far-field shear displacement of the Brune (1970) seismic source model l no (the long-period spectral level), f_o (the spectral corner frequency) and E, which controls the high frequency (f > f_o) decay of spectral amplitudes. All of the above\r\nsource parameters can be easily extracted from a log-log plot of \u03a9_o versus f_o (\u03b5 when < 1 entering as a parameter), but only three of them are independent. The apparent stress is proportional to the effective shear stress, not the average shear stress. The \u03a9_o-f_o diagram is especially convenient for comparisons within a chosen suite of seismic and/or explosive sources. The equation on which the Gutenberg-Richter energy (E_(GR))-magnitude (M_L) relation was originally based is cast into an approximate spectral form; E_(GR) can then be easily compared with E_s\r\non the \u03a9_o-f_o diagram for an earthquake of any M_L. Within the framework of the (\u03a9_o, f_o, \u03b5) relations, it is a simple matter to construct an earthquake magnitude scale directly related to the radiated energy (E_s).\r\n\r\nThe source parameters seismic moment and source dimension are estimated with teleseismic body-wave spectra for four intermediate magnitude earthquakes for which these source parameters can be obtained from field observations, The spectral and field estimates for these quantities agree within estimated uncertainties, when the spectral\r\nobservations are scaled with the Brune (1970) model, The seismic moment and source dimension may be obtained as reliably with P-wave spectra as with S-wave spectra for these earthquakes, with the assumption that the P-wave corner frequency should be shifted from the S-wave corner frequency in proportion to the ratio of the compressional\r\nto shear wave velocities.\r\n\r\nObservational and theoretical uncertainties in the determination and interpretation of high frequency (f > f_o) spectral amplitude constitute a major barrier in the understanding of dynamical aspects of earthquake occurrence. Two of several problems concerning the\r\ngeneration of high frequency spectral amplitudes are discussed from a conceptual point of view. The source finiteness or directivity function is altered significantly from the result of Ben-Menahem (1961) for easily imaginable variations of displacement on the fault surface. The far-field shear displacement spectrum of Brune (1970) for the case of small fractional stress drop is structurally similar to that of Haskell (1964) when the rise time of displacement on the fault surface is much smaller than the fault length divided by the shear-wave velocity. The effective stress of Brune (1970) may be interpreted as\r\na stress difference associated with the emplacement of rupture.\r\n\r\nThe idea of a stress difference associated with the emplacement of rupture is investigated observationally for the case of the San Fernando, California, earthquake (February 9, 1971). Compressional and shear radiation emanating from the emplacement of rupture at depth\r\nbeneath the San Gabriel Mountains is identified on the Pacoima Dam accelerograms. The S-P time obtained from this identification suggests a hypocentral depth of 12-15 km, somewhat greater than that of the local hypocentral location of the main shock, but consistent with that\r\nindicated by teleseismic observations of the reflected phases pP and sP. With less certainty, the radiation emanating from the rupture of the Earth's surface is identified on the Pacoima Dam accelerograms and WWSSN stations at teleseismic distances. Within several assumptions, the initial rupture event is separated from the subsequent motion on the Pacoima Dam accelerograms, and the source parameters are estimated for it from the associated shear wave. The stress drop accompanying\r\nthe initial rupture is estimated to be 430 bars, approximately an order of magnitude greater than the average stress drop obtained from teleseismic spectral estimates and static dislocation models." }, { "name": "Hansen, Olav Louis", "degree": "PhD", "year": "1972", "title": "Thermal Radiation from the Galilean Satellites Measured at 10 and 20 Microns", "advisor": "Westphal, James A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04082010-105350789", "creators": [ { "name": { "family": "Hansen", "given": "Olav Louis" }, "id": "Hansen-Olav-Louis", "display_name": "Hansen, Olav Louis" } ], "advisors": [ { "name": { "family": "Westphal", "given": "James A." }, "id": "Westphal-J-A", "role": "advisor", "display_name": "Westphal, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/wn5g-m205", "abstract": "The four Galilean Satellites have been observed in two broad bandpasses, centered near 10\u03bc and 20\u03bc respectively, during Jupiter's 1971-apparition.\r\n\r\nTwo types of measurements were obtained. The first consisted of monitoring the infrared flux as a function of each satellite's orbital position, the other of flux measurements during satellite eclipses. The latter type was \r\nobtained only in the 10\u03bc bandpass, and only for lo (J1), Europa (J2), and Ganymede (J3), because Callisto (J4) was not eclipsed in 1971.\r\n\r\nThe flux measurements obtained as a function of orbital position were averaged for each satellite and bandpass, and from the mean values the following quantities were derived: (1) the maximum (~subsolar) surface temperature, T_(max), (2) the ratio between the effective 20\u03bc emissivity, \r\n\u03b5_(20), and the effective 10\u03bc, emissivity, \u03b5_(10), (3) the bolometric Bond albedo, A_(bol), and (4) the effective phase integral, q. The results, listed in Table (i), indicate very low \"\u03b5_(20)/\u03b5_(10) \" ratios and high q-values.\r\n\r\n\r\nThe 10\u03bc flux measurements obtained during eclipses of J1, J2, and J3 have been compared to thermal models, and the following conclusions were drawn. (1) No homogeneous model [single parameter, y = (kpc)^(-1/2) can account for the observed temperature variations during eclipses. (2) A two- \r\nlayer model with a thin, thermally insulating layer covering a highly conductive subsurface is adequate to explain all the observations. (3) The atmospheric surface pressure on J1, J2, and J3 is less than 1 mbar. (4) The \r\nresults, listed in Table (ii), show that the surface covering of J1 is distinctly different from that of J2 or J3.\r\n" }, { "name": "Matson, Dennis Ludwig", "degree": "PhD", "year": "1972", "title": "1. Astronomical Photometry at Wavelengths of 8.5,10.5 and 11.6 \u00b5m. 2. Infrared Emission from Asteroids at Wavelengths of 8\u00b75, 10.5 and 11.6 \u00b5m", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09132013-115339548", "creators": [ { "name": { "family": "Matson", "given": "Dennis Ludwig" }, "id": "Matson-Dennis-Ludwig", "display_name": "Matson, Dennis Ludwig" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/Y25B-JY16", "abstract": "The purpose of this thesis is to present new observations of thermal-infrared\r\nradiation from asteroids. Stellar photometry was performed to provide\r\nstandards for comparison with the asteroid data. The details of the photometry\r\nand the data reduction are discussed in Part 1. A system of standard stars is\r\nderived for wavelengths of 8.5, 10.5 and 11.6 \u00b5m and a new calibration\r\nis adopted. Sources of error are evaluated and comparisons are made\r\nwith the data of other observers.
\r\n\r\nThe observations and analysis of the thermal-emission observations of\r\nasteroids are presented in Part 2. Thermal-emission lightcurve and phase effect\r\ndata are considered. Special color diagrams are introduced to display the\r\nobservational data. These diagrams are free of any model-dependent assumptions\r\nand show that asteroids differ in their surface properties.
\r\n\r\nOn the basis of photometric models, (4) Vesta is thought to have a bolometric\r\nBond albedo of about 0.1, an emissivity greater than 0.7 and a true radius\r\nthat is close to the model value of 300^(+50)_(-30)km. Model albedos and model radii\r\nare given for asteroids 1, 2, 4, 5, 6, 7, 15, 19, 20, 27, 39, 44, 68, 80, 324\r\nand 674. The asteroid (324) Bamberga is extremely dark with a model (~bolometric\r\nBond) albedo in the 0.01 - 0.02 range, which is thought to be the lowest\r\nalbedo yet measured for any solar-system body. The crucial question about such\r\nlow-albedo asteroids is their number and the distribution of their orbits.
" }, { "name": "Thatcher, Wayne Raymond", "degree": "PhD", "year": "1972", "title": "Surface Wave Propagation and Source Studies in the Gulf of California Region", "advisor": "Brune, James N.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03282018-134558094", "creators": [ { "name": { "family": "Thatcher", "given": "Wayne Raymond" }, "id": "Thatcher-Wayne-Raymond", "display_name": "Thatcher, Wayne Raymond" } ], "advisors": [ { "name": { "family": "Brune", "given": "James N." }, "id": "Brune-J-N", "role": "advisor", "display_name": "Brune, James N." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/0981-B217", "abstract": "A number of aspects of seismic surface wave propagation and earthquake mechanism in the Gulf of California region are investigated in this thesis. In addition, several associated problems raised by this study are also explored in some detail.
\r\n\r\nSurface wave dispersion and P-wave travel time delays are\r\nmeasured to delineate the crust and upper mantle structure in the Imperial Valley-Gulf of California region. Crustal thicknesses beneath Baja California and Sonora are comparable and near 25 km, while within the Gulf crustal structure varies laterally from nearly oceanic on the\r\nwestern side to continental shelf thicknesses (~20 km) towards the north and east. Love wave group velocities for Baja California paths are unusually high and were not used to determine structure. Pn and teleseismic P-wave delays are used in a reconnaissance survey of crustal\r\nstructure in the Imperial Valley and across the Peninsular Range batholith. The data are consistent with an increase in crustal thickness of 12 km from flank to crest in the Peninsular Ranges, and a decrease of 8 km across the Imperial Valley.
\r\n\r\nThe high Love wave group velocities measured across Baja\r\nCalifornia are shown to be similar to velocities of the first higher mode. It is also demonstrated that higher Love modes can have group velocities very close to fundamental mode velocities for a range of wave periods and realistic earth models. The mode interference which is a consequence\r\nof this intertwining of group velocity curves has a significant effect on measured phase velocities, and this problem is investigated in detail. An important conclusion of this study is that anomalously high Love wave phase velocities reported for the United States midcontinent and\r\nJapan are straightforwardly explained by mode interference without appealing to complex or anisotropic models, as had been done previously.
\r\n\r\nSeismic processes associated with actively spreading oceanic rises are examined in the study of a strong swarm of earthquakes located near an inferred spreading center in the Northern Gulf of California. Close-in travel time data constrain the origin times of swarm events and demonstrate that the epicenters are confined to the upper crust. Teleseismic P-delays suggest unusually low seis1nic\r\nvelocities beneath the source. The previously suspected normal faulting nature of swarm earthquakes is also confirmed. Seismic coupling across 200 km between adjacent spreading centers in the Northern Gulf is indicated by a survey of recent seismicity.
\r\n\r\nIt is noted in the study of the Gulf swarm that these sources have significantly higher surface wave amplitudes than events with similar assigned magnitudes in Northern Baja California. In the final chapter of this thesis a detailed analysis is made of the Baja earthquakes and it\r\nis concluded that as a group they have distinctly smaller source dimensions and larger stress drops than events within the Gulf of California. These differences are quite marked and are often very clearly seen even on records from band-limited seismographs. Several examples exist where propagation paths are very similar but the visual appearance of records differs considerably, suggesting that near-source or path effects are not likely explanations of the observed differences.
\r\n\r\nFor small magnitude North Baja earthquakes, both source\r\ndimensions and long period surface excitation average only about a factor or two larger than corresponding quantities previously measured for underground nuclear explosions of similar magnitude.
\r\n" }, { "name": "Wolfe, Stephen Howard", "degree": "PhD", "year": "1972", "title": "Part I. Geology of the Manicouagan-Mushalagan Lakes Structure. Part II. Geochronology of the Manicouagan-Mushalagan Lakes Structure", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02112004-095253", "creators": [ { "name": { "family": "Wolfe", "given": "Stephen Howard" }, "id": "Wolfe-Stephen-Howard", "display_name": "Wolfe, Stephen Howard" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "role": "chair", "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/YB0X-BZ53", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Manicouagan-Mushalagan Lakes structure is an area of anomalous geological features in the Grenville Province terrain of northeastern Canada. Three features of this structure have been revealed by geological studies:\r\n\r\n(1) The Grenville gneisses and anorthosites which outcrop in the area between the arcuate lakes have been shock metamorphosed.\r\n\r\n(2) The shocked Grenville gneisses are covered by a thin, discontinuous layer of shock breccia and thin outcrops of Ordovician limestone.\r\n\r\n(3) An annular-shaped body of Permo-Triassic, igneous, andesitic rock, which shows no signs of shock metamorphism, overlies the shocked gneisses, the shock breccia and the Ordovician limestone. This rock (monzonite) is 800 feet thick at a maximum.\r\n\r\nThe shocked basement rocks in the structure were most probably caused by the impact of an extraterrestrial body, but the origin of the igneous rock unit is not completely understood. This latter unit has been hypothesized to be either (1) a shock-melted breccia or (2) a later, secondary igneous event occurring at the crater site due to disruptions of the earth's thermal regime around the impact site. A geochronological study of this structure was made to determine which, if either, of the above modes of formation for the igneous material is likely.\t\t\r\n\r\n[...] data for the igneous material and rock units related to it yield a well-defined crystallization age of [...]. [...] data for this unit indicate that it has experienced no subsequent metamorphism. Argon isotopic ages obtained for a series of shock-sequence anorthosites do not indicate a well-defined time of shock metamorphism; the ages could characterize a system shocked at anytime between 320 and 210 m.y. ago which then suffered a secondary gas loss. It is shown that anorthosites yielding ages between 280 and 320 m.y. probably underwent complete or nearly complete outgassing at the time of shock. These latter ages should therefore yield a good impact age. The time interval within which the impact took place is thought to be 280-320 m.y. ago.\r\n\r\nThe [...] data show unexpected evidence for the occurrence of a secondary event at about 100-110 m.y. which affected the anorthosites in the crater but not the igneous monzonite.\r\n\r\nSince it is not possible to say with certainty when the meteoritic impact took place, the difference between the monzonite formation time and the impact time is unclear. The suggested impact time is, however, significantly earlier than the crystallization time of the igneous material. This suggests that a secondary formation mode for this material is more likely than an impact melt formation mode. A secondary mode is also compatible with evidence that the monzonite formed in a subsurface environment with [...]." }, { "name": "Arabasz, Walter Joseph, Jr.", "degree": "PhD", "year": "1971", "title": "Geological and Geophysical Studies of the Atacama Fault Zone in Northern Chile", "advisor": "Allen, Clarence R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02092018-150208279", "creators": [ { "name": { "family": "Arabasz", "given": "Walter Joseph, Jr." }, "id": "Arabasz-Walter-Joseph-Jr.", "display_name": "Arabasz, Walter Joseph, Jr." } ], "advisors": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/1QCV-NG11", "abstract": "The Atacama fault, a suggested regional strike-slip fracture \r\nparallel to the coastline of northern Chile, is a major structural\r\nbreak that has undergone a complicated history of movement since \r\nMesozoic time. Abundant Quaternary scarps attest to continuing \r\nactivity; however, the Atacama fault does not appear to be an active \r\nstrike-slip fault -- at least not along its central segment between \r\n24\u00b05. and 26\u00b0S.
\r\n\r\n\r\nIn the map area, the Coast Ranges are underlain predominantly \r\nby crystalline rocks that have been intensely broken by high-angle\r\nfaults of the Atacama fault system. A eugeosynclinal section, chiefly \r\ncomprising Jurassic-Cretaceous andesites, overlies Paleozoic \r\nmetamorphic and plutonic rocks and has been intimately intruded by\r\nbatholithic rocks of Late Jurassic to Tertiary (?) age. An older more \r\nvoluminous suite of rocks ranging from gabbro to adamellite, with \r\nabundant diorite and pyroxene granodiorite, is discordantly cut by \r\nstocks of more homogeneous hornblende-and-biotite granodiorite, \r\nadamellite, and tonalite.
\r\n\r\n\r\nIn the Taltal area, the Atacama fault zone was obliquely cut and \r\nleft-laterally off set 10 km by the northwest-trending Taltal fault\r\nduring mid- to late Tertiary time. Lateral motion on the Taltal fault \r\nappears to have ceased before the Pliocene epoch. A structural \"knot\" \r\npresently constrains lateral motion along truncated branches of the \r\nAtacama fault. A northwest-curving branch that escapes truncation by\r\nthe Taltal fault has been more recently active both onshore and offshore, \r\nwith recent motion predominantly vertical.
\r\n\r\n\r\nStrike-slip displacement occurred during the early history of the \r\nAtacama fault. Subsequent to its segmentation, individual sectors \r\nhave been reactivated independently and have accommodated vertical \r\nblock motions in their recent history. No convincing evidence was \r\nfound for any recent lateral displacement. Aspects of the origin of\r\nalluvial scarps displaying an anomalous ridge-trench-ridge morphology \r\nremain enigmatic, but the features are not necessarily indicative of\r\nstrike-slip movement as had earlier been considered.
\r\n\r\nOffshore studies near the map area indicate major faulting on the \r\nupper continental slope, beginning within 10 to 20 km of the coastline, \r\nthat has resulted in the tilting and down-dropping of blocks toward the \r\ntrench axis. Late Cenozoic tectonics in the Coast Ranges appear to \r\nbe directly related to the development of the Peru-Chile trench.
\r\n\r\nA reconnaissance micro-earthquake survey along the Atacama\r\nfault shows virtually no activity, or at most very little, in the immediate \r\nvicinity of the fault. Abundant micro-after shock activity from an offshore \r\nafter shock zone related to the magnitude 7.5 Taltal earthquake \r\n(Dec. 28, 1966) was detected. Gravity and magnetic profiles across\r\nthe Atacama fault zone reveal no distinctive anomalies that would \r\nallow correlation of major branches over large distances. No large-scale\r\ngravity anomalies occur across the fault zone.
\r\n \r\nSchemes of consistent lateral offset along the Atacama fault and \r\nits branches have not emerged from systematic regional mapping.\r\nLarge vertical separation along the faults is a chief control of the\r\nregional distribution of rocks.\tNo need is seen to hypothesize strike\u00ad-slip \r\ndisplacements of hundreds of kilometers along the Atacama fault \r\nzone, but suggestive lines of evidence call for a component of lateral \r\ndisplacement measured at least in tens of kilometers. The vertical \r\ncomponent of total displacement probably amounts to several kilometers \r\nof uplift of the east side. Taking into account map relations which\r\nappear to constrain the amount of allowable lateral displacement, it\r\nis judged that total strike-slip displacement may be moderate, amounting \r\nonly to a few tens of kilometers of right-lateral slip.
\r\n\r\n\r\nPhotographic materials on pp. 11, 13, 15, 72, 73, 78, 79, 129, \r\n144, 162, 177 are essential and will not reproduce clearly on Xerox\r\ncopies. Photographic copies should be ordered.
\r\n\r\n\r\n\r\n" }, { "name": "Cutts, James Alfred John", "degree": "PhD", "year": "1971", "title": "Martian Spectral Reflectivity Properties from Mariner 7 Observations", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08152006-080935", "creators": [ { "name": { "family": "Cutts", "given": "James Alfred John" }, "id": "Cutts-James-Alfred-John", "display_name": "Cutts, James Alfred John" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/XX43-MW95", "abstract": "An analysis of data taken by the Mariner 6 and Mariner 7 spacecraft has been made in order to extend the knowledge of spectral reflectivity differences on the surface of Mars. The data were collected with the Mariner wide-angle television camera which utilizes a vidicon image tube as sensor. The data consist of a series of pictures taken through sequenced color filters with passbands in the visible region of the electromagnetic spectrum (0.43 - 0.65 microns). The Martian regions photographed lie in the longitude range 300\u00b0 to 30\u00b0 (East Longitude) and include the prominent dark areas Meridiani Sinus, Sabaeus Sinus, and Margeritifer Sinus, as well as the light 'desert' areas Moab, Thymiamata and Deucalionis Regio.\r\n\r\nIt was necessary to remove harmonic noise from the television images in order to detect and measure significant spectral reflectivity differences in the equatorial regions of Mars. The resolution element near the center of the planetary disc was 30 km. by 200 km. The measurements represent an order of magnitude improvement in linear spatial resolution over previous measurements made with earth based telescopes and comparable broad band spectral resolution. No reliable published measurements exist for these regions of Mars but the new measurements showed a general agreement with the previous low resolution measurements of other parts of the planet.\r\n\r\nThe colors of Martian features are very sensitive to the geometry of illumination and viewing. However, color differences attributable to geographic variations in the reflecting properties of the surface and/or atmosphere are recognized in an area near the center of the martian disc. The reflectivity ratio red/green for these areas is strongly correlated with the normal albedo but varies inversely as the reflectivity ratio blue/green. The spectral resolution of the system for measurements within the dark area Meridiani Sinus is limited by aliasing effects with small albedo features.\r\n\r\nThe dependence of color on local geometry is investigated on the assumption that all the martian features in an area extending from 20\u00b0N to 30\u00b0S and from 310\u00b0E to 30\u00b0E have the same correlation between color and normal albedo when this is measured under standard illumination and viewing conditions. Models of a wavelength dependent photometric function and of a uniform atmospheric scattering layer are both consistent with the data.\r\n\r\nAtmospheric scattering alone can account for the local geometry effect but if the scattering layer is geographically uniform and independent of Martian local time the atmospheric optical depth is three times that predicted from ultraviolet reflectivity measurements.\r\n\r\nNear the center of the martian disc, three distinct reflectivity groups (D, L1 and L2) are recognized indicating the existence of abrupt transitions in reflectivity and extensive homogeneous areas with little variation in intrinsic reflectivity. These areas are identified and the boundaries between them studied using high resolution photography. The boundary between the areas with reflectivities D and L1, corresponds to a change in surface reflectivity. The boundary between the areas with reflectivities L1 and L2 corresponds to the edge of a cloud or haze layer. The reflectance properties of this layer are comparable to those which have been previously measured from limb photographs.\r\n\r\nColor-color plots and color-reflectivity plots for Martian surface areas show some similarities with the moon but significant differences. Martian light and dark areas cannot be explained as simply different polymers of carbon suboxide. It may be possible to match the reflectivity characteristics of both light and dark areas with oxidized basalt but if this is the case there must be a change in particle size as well as composition.\r\n" }, { "name": "Hill, David Paul", "degree": "PhD", "year": "1971", "title": "High Frequency Wave Propagation in the Earth: Theory and Observation", "advisor": "Archambeau, Charles B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03042016-150636227", "creators": [ { "name": { "family": "Hill", "given": "David Paul" }, "id": "Hill-David-Paul", "display_name": "Hill, David Paul" } ], "advisors": [ { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/KCTK-HH34", "abstract": "The wave-theoretical analysis of acoustic and elastic waves refracted by a spherical boundary across which both velocity and density increase abruptly and thence either increase or decrease continuously with depth is formulated in terms of the general problem of waves generated at a steady point source and scattered by a radially heterogeneous spherical body. A displacement potential representation is used for the elastic problem that results in high frequency decoupling of P-SV motion in a spherically symmetric, radially heterogeneous medium. Through the application of an earth-flattening transformation on the radial solution and the Watson transform on the sum over eigenfunctions, the solution to the spherical problem for high frequencies is expressed as a Weyl integral for the corresponding half-space problem in which the effect of boundary curvature maps into an effective positive velocity gradient. The results of both analytical and numerical evaluation of this integral can be summarized as follows for body waves in the crust and upper mantle:
\r\n\r\n1) In the special case of a critical velocity gradient (a gradient equal and opposite to the effective curvature gradient), the critically refracted wave reduces to the classical head wave for flat, homogeneous layers.
\r\n\r\n2) For gradients more negative than critical, the amplitude of the critically refracted wave decays more rapidly with distance than the classical head wave.
\r\n\r\n3) For positive, null, and gradients less negative than critical, the amplitude of the critically refracted wave decays less rapidly with distance than the classical head wave, and at sufficiently large distances, the refracted wave can be adequately described in terms of ray-theoretical diving waves. At intermediate distances from the critical point, the spectral amplitude of the refracted wave is scalloped due to multiple diving wave interference.
\r\n\r\nThese theoretical results applied to published amplitude data for P-waves refracted by the major crustal and upper mantle horizons (the Pg, P*, and Pn travel-time branches) suggest that the 'granitic' upper crust, the 'basaltic' lower crust, and the mantle lid all have negative or near-critical velocity gradients in the tectonically active western United States. On the other hand, the corresponding horizons in the stable eastern United States appear to have null or slightly positive velocity gradients. The distribution of negative and positive velocity gradients correlates closely with high heat flow in tectonic regions and normal heat flow in stable regions. The velocity gradients inferred from the amplitude data are generally consistent with those inferred from ultrasonic measurements of the effects of temperature and pressure on crustal and mantle rocks and probable geothermal gradients. A notable exception is the strong positive velocity gradient in the mantle lid beneath the eastern United States (2 x 10-3 sec-1), which appears to require a compositional gradient to counter the effect of even a small geothermal gradient.
\r\n\r\nNew seismic-refraction data were recorded along a 800 km profile extending due south from the Canadian border across the Columbia Plateau into eastern Oregon. The source for the seismic waves was a series of 20 high-energy chemical explosions detonated by the Canadian government in Greenbush Lake, British Columbia. The first arrivals recorded along this profile are on the Pn travel-time branch. In northern Washington and central Oregon their travel time is described by T = \u0394/8.0 + 7.7 sec, but in the Columbia Plateau the Pn arrivals are as much as 0.9 sec early with respect to this line. An interpretation of these Pn arrivals together with later crustal arrivals suggest that the crust under the Columbia Plateau is thinner by about 10 km and has a higher average P-wave velocity than the 35-km-thick, 62-km/sec crust under the granitic-metamorphic terrain of northern Washington. A tentative interpretation of later arrivals recorded beyond 500 km from the shots suggests that a thin 8.4-km/sec horizon may be present in the upper mantle beneath the Columbia Plateau and that this horizon may form the lid to a pronounced low-velocity zone extending to a depth of about 140 km.
\r\n" }, { "name": "Kieffer, Susan Werner", "degree": "PhD", "year": "1971", "title": "I. Shock Metamorphism of the Coconino Sandstone at Meteor Crater, Arizona. II. The Specific Heat of Solids of Geophysical Interest", "advisor": "Shoemaker, Eugene Merle; Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechETD:etd-06232004-134838", "creators": [ { "name": { "family": "Kieffer", "given": "Susan Werner" }, "id": "Kieffer-Susan-Werner", "display_name": "Kieffer, Susan Werner" } ], "advisors": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "advisor", "display_name": "Shoemaker, Eugene Merle" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/XBPD-6Y42", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nPART I: A study of the shocked Coconino sandstone from Meteor Crater, Arizona, was undertaken to examine the role of porosity in the compression of rocks and in the formation of high-pressure phases. A suite of shocked Coconino specimens collected at the crater is divided into five classes, arranged in order of decreasing quartz content. The amounts of coesite, stishovite (measured by quantitative x-ray diffraction) and glass vary systematically with decreasing quartz content. Coesite may comprise one-third by weight of some rocks, whereas the stishovite content does not exceed 1%. The five classes of rocks have distinct petrographic properties, correlated with the presence of regions containing coesite, stishovite or fused silica. Very few occurrences of diaplectic glass are observed, in striking contrast to its abundant occurrence in the non-porous rocks from the Ries Crater.\r\n\r\nIn the lowest stages of shock metamorphism (Class I), the quartz grains are fractured and the voids in the rock are filled with myriads of small chips derived from neighboring grains. The fracture patterns in the individual quartz grains are controlled by the details of the initial morphology of the colliding grains. In one weakly shocked rock, it was possible to map the general direction of shock passage by recording the apparent direction of collision of individual grains. The principal mechanism of energy deposition by a shock wave in a porous material is the reverberation of shock and rarefaction waves through grains due to collisions with other grains. A one-dimensional model of the impact process can predict the average pressure, volume and temperature of the rock if no phase changes occur, but cannot predict the observed nonuniformity of energy deposition.\r\n\r\nIn all rocks shocked to higher pressure than was necessary to close the voids, high-pressure and/or high-temperature phases are present. Locally high pressures enduring for microseconds and high temperatures enduring for milliseconds controlled the phases of SiO2 which formed in the rock. Collapsing pore walls became local hot spots into which initial deposition of energy was focused. Microcrystalline coesite in Class II rocks occurs in symplektic regions on quartz grain boundaries which were regions of initial stress and energy concentration, or in sheared zones within the grains. The occurrence and morphology of the coesite-rich regions can be explained only if the transformation from quartz to coesite proceeds slowly in the shock wave. In Class III rocks, microcrystalline coesite occurs in opaque regions which surround nearly isotropic cores of cryptocrystalline coesite. The cores are interpreted to be the products of the inversion of stishovite (or a glass with Si in six-fold coordination) which initially formed in the shock front in regions of grains shocked to pressures near 300 kb. Stishovite is preserved only in the opaque regions, which are believed to have been cooler than the cores.\r\n\r\nIn Class IV rocks, vesicular glass occurs in core regions surrounded by opaque regions containing coesite. The relation of the glass to the coesite and quartz suggests that the glass was formed by inversion of stishovite formed above 350 kb upon release to lower pressure.\r\n\r\nClass V rocks are composed almost entirely of glass with vesicles uniformly distributed in the glass. These vesicles were probably formed by exsolution of water that had been dissolved in melted SiO2 during passage of the shock.\r\n\r\nPART II: The use of Debye temperatures as parameters for material properties of silicate minerals is becoming common in geophysical studies. The elastic Debye temperature, [...] alone is, in general, insufficient to specify properties which depend on lattice vibrations. Two effects ignored by the Debye model are shown to be important: high frequency lattice vibrations and the dispersion relation. As an alternative to the Debye model, a somewhat more complicated model is proposed that is still reasonably convenient and is able to account much better than the Debye model does for the variation of specific heat of complex substances over a wide range of temperature. This model is designated the acoustic-optic model. The parameters required for this model are the maximum lattice vibrational frequency, the elastic Debye temperature, and the specific heat at a single (say, room) temperature. Adequate approximations to these parameters are generally available.\r\n\r\nTo consider heat capacity data and compare the data with either the Debye or acoustic-optic model, the calorimetric Debye temperature, [...] is considered. [...] is the value of Debye temperature that will reproduce the specific heat at constant volume at the temperature T. For silicates, a large increase at high temperatures in [...] above the elastic Debye temperature is due to the presence of oscillators between the elastic Debye frequency and a maximum vibrational frequency which exceeds the Debye frequency. Vibrations of these oscillators cause the spectral lines observed at infrared frequencies. The proposed model takes these oscillators into account by adding a constant valued continuum to an assumed low-frequency Debye spectrum.\r\n\r\nIn all substances considered, [...] at low temperatures initially decreases to values below [...]. This decrease is believed due to the dispersion relation, i.e., the nonlinear relation between the wave vector and the frequency.\r\n\r\nIn two substances of geophysical interest, NaCl and MgO, the maximum observed vibrational frequency is depressed below the observed elastic Debye frequency as a consequence of the dispersion relation. The acoustic-optic model is capable of predicting the specific heat of these two substances and the acoustic-optic spectra which result from application of the model to these substances describe qualitatively the spectra that result from the dispersion relation.\r\n\r\nThe nonlinearity of the dispersion relation dominates the specific heat behavior of NaCl and MgO and influences the low temperature behavior of all silicates with varying degrees of severity. The effect of the dispersion relation can be ignored for some silicates if specific heats only at high temperatures (T > 100[degrees]K) are considered. The effect cannot be ignored in the case of rutile or stishovite." }, { "name": "Sammis, Charles George", "degree": "PhD", "year": "1971", "title": "Seismological Applications of Lattice Theory", "advisor": "Anderson, Donald L.; Archambeau, Charles B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12192012-162926776", "creators": [ { "name": { "family": "Sammis", "given": "Charles George" }, "id": "Sammis-Charles-George", "display_name": "Sammis, Charles George" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/S6B1-6N30", "abstract": "Lattice models based upon empirical two-body potential functions\r\nare used to predict the elastic constants of \u201cmantle-candidate\u201d minerals\r\nat high pressures for direct comparison with seismic velocity profiles.\r\nThe method of long waves, originally formulate d by Born and his coworkers,\r\nhas been applied to solids in the rock salt, spinel, and rutile\r\nstructures. Calculations for NaCl (rock salt), MgO (rock salt), Al_2MgO_4\r\n(spinel), and TiO_2 (rutile) are compared with recent high-precision\r\nultrasonic data. The effect of van der Waals forces and second-neighbor\r\nanion-anion interactions is shown to be small. The NaCl and MgO data\r\nare best fit with an exponential cation-anion repulsive potential. The\r\nelastic constants of MgO cannot be well fit unless the ionicity (valence\r\nproduct) is lowered to 0.7 of its full ionic value. For NaCl this is not\r\nrequired. The shear instability (C_(44) = 0) is predicted for both NaCl and\r\nMgO, but the exact pressure is sensitive to the details of the potential.
\r\n\r\nUsing the Mg-O two-body potential found for periclase, Al_2MgO_4\r\nspinel was investigated using only two pieces of input datum, K and \u03c1.\r\nAlthough the predicted elastic constants were in good agreement with the\r\ndata, the pressure derivatives were not. The discrepancy is caused by\r\na large contribution from the internal deformations which occur in all\r\nnon-centro symmetric structures. The same result was found for TiO_2. A\r\nrelaxation of the rigid-ion and central-force approximations may correct\r\nthis discrepancy.
\r\n\r\nUsing the Mg-O bond parameters found for periclase and the\r\nSi-Q bond parameters found from K and \u03c1 of stishovite, the elastic\r\nproperties of the high-pressure polymorph \u03b4\u2013Mg_2SiO_4 spinel were\r\npredicted. The predicted equilibrium density was in agreement with\r\nprevious experimental extrapolations; the predicted \u03bc parameter was\r\nin agreement with prior estimates based on bond-length arguments, and\r\nthe predicted bulk modulus was in agreement with prior systematics\r\nestimates. However, the internal deformation contribution again\r\ndominated the pressure derivatives and caused both the predicted V_p\r\nand V_s to be lower than the corresponding seismic velocities in the\r\n\"spinel region\" of the mantle. A comparison of MgO (rock salt) and\r\nSiO_2 (stishovite) with the seismic profiles for the \"post-spinel\" lower\r\nmantle shows a discrepancy in both absolute value and gradient. Unlike\r\nthe silicate spinel, this is not obviously caused by the internal deformations.\r\nThe lattice models predict that both TiO_2 and stishovite will\r\nbecome unstable in shear (1/2 (C_(11) \u2013 C_(12) = 0) at high pressure.
\r\n\r\nOther methods of using laboratory data to interpret seismic\r\nprofiles are reviewed. Birch's formulation of isotropic finite strain\r\ntheory is corrected and used to test the homogeneity and adiabaticity\r\nof the lower mantle of recent earth-inversion models. Systematics are\r\nshown to be insufficient to treat the shear properties. Although lattice\r\nmodels are limited by empirical approximations to the complex bonding\r\nforces, the empiricism is on a more basic level than that of velocity\r\ndensity systematics previously used to interpret seismic profiles. By\r\nusing lattice models, one gains the natural dependence of both the compressional\r\nand shear properties on the crystal structure.
\r\n" }, { "name": "Wenner, David Bruce", "degree": "PhD", "year": "1971", "title": "Hydrogen and Oxygen Isotopic Studies of Serpentinization of Ultramafic Rocks", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11082007-141710", "creators": [ { "name": { "family": "Wenner", "given": "David Bruce" }, "id": "Wenner-David-Bruce", "display_name": "Wenner, David Bruce" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/KRKQ-4J37", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nLizardite-chrysotile serpentines in alpine ultramafic bodies from North America show latitudinal variations in [...] and [...] which indicate that meteoric ground waters were important in their formation. In per mil relative to SMOW they exhibit the following geographic variations in [...] and [...], respectively: British Columbia -205 to -150, 1.9 to 8.2; Washington-Oregon -142 to -107; 4.1 to 8.0; California -108 to -82, 6.6 to 8.8; Caribbean-Central America -97 to -59, 3.3 to 8.7. The [...]-latitude correlation is exceedingly good, but the [...]-values appear to be in large part dependent upon the [...] of the country rock. This suggests that the waters involved in serpentinization had previously exchanged [...] with these country rocks. For example, the Cassiar, British Columbia, serpentinite body has [...]-195 to -162 and [...] = 8.0 to 8.2, whereas the serpentines in zoned ultramafic bodies of SE Alaska have [...] = -127 to -140, [...] = -5.0 to -1.6; the former body lies in a terrane of abundant [...]-rich limestones, whereas the zoned bodies are surrounded by low-[...] igneous rocks. All antigorites, irrespective of geographic location, have very uniform isotopic compositions ([...] = -66 to -39, [...] = 4.7 to 8.8). This is practically identical to the range exhibited by metamorphic chlorites,.indicating, that a deep-seated or metamorphic type water was involved in.antigorite-type serpentinization. This isotopic uniformity further indicates that little or no isotopic exchange has occurred subsequent to formation of the antigorites, because many samples were collected from northerly regions where the ground waters are very low in [...] and [...]. Five lizardite-chrysotile type serpentinites-from California, Guatemala and the Dominican Republic show oxygen isotope fractionations of 15.1 to 12.9 per mil between coexisting serpentine and magnetite ([...] magnetite = -7.6 to -4.6 per mil relative to SMOW). Nine antigorites (mainly from Vermont and SE Pennsylvania) show distinctly smaller fractionations of 8.7 to 4.8 per mil ([...] magnetite = -2.6 to +1.7 per mil). Two lizardite and chrysotile serpentinites dredged from the Mid-Atlantic Ridge exhibit fractionations of 10.0 and 12.5 per mil ([...] magnetite - -6.8 and -7.9 per mil, respectively), whereas antigorite from this area shows a value of 8.2 per mil ([...] magnetite = -6.2). These data all clearly indicate that the antigorites formed at higher temperatures than the chrysotile-lizardites. Electron microprobe analyses of magnetites from the above samples show that they are chemically homogeneous and essentially pure [...]. A few magnetite samples from serpentinites in near proximity to later granitic intrusions showa a wide variation of Cr content, and also give erratic oxygen isotopic results, suggesting non-equilibrium. A rough serpentine-magnetite geothermometer curve was constructed by extrapolation of (1) observed [...]-values of chlorite and Fe-Ti oxides in low-grade pelitic schists whose isotopic temperatures are known from the quartz-muscovite geothermometer, and (2) estimates of the [...] fractionation between chlorite and serpentine (assumed to be zero). This serpentine-magnetite geothermometer suggests approximate equilibrium temperatures as follows: continental lizardite-chrysotile, [...]; oceanic lizardite and chrysotile, [...], respectively; continental antigorites, [...]; and oceanic antigorite, [...]. The isotopic compositions of the waters involved in serpentinization of various ultramafic rocks have been estimated, utilizing the above \"temperatures\". These calculations indicate that most lizardite-chrysotile serpentinization probably involved exchanged meteoric waters, and thus must have occurred at relatively shallow levels in the earth's crust, consistent with the proposed isotopic \"temperatures\". However, this type of serpentinization is clearly not a weathering phenomenon taking place at the earth's surface. Isotopic evidence for such low temperature serpentinization ([...] of +11.8 to +12.5) has been discovered only for several \u201cdeweylite\" samples from Pennsylvania and Delaware. Serpentines from the ocean floor (Mid Atlantic Ridge, Puerto Rican trench, and Blanco Fracture zone in the Pacific ocean) form a unique isotopic grouping, with [...] = -68 to -31, [...] = +0.8 to +6.7. The waters that would have coexisted with these serpentines (at the temperatures inferred from serpentine-magnetite 018 fractionations) have calculated isotopic compositions that cluster around SMOW. This strongly suggests that ocean water is the major component of the waters responsible for sub-oceanic serpentinization. A few of the low-[...] oceanic serpentines are, however, consistent with formation from magmatic waterocean water mixtures. No serpentines presently found in continental areas give any isotopic evidence of ever having been serpentinized in oceanic environments. This statement also applies to the serpentines in a typical ophiolite sequence, the Vourinos Complex, Greece. Serpentine from this body is unique, however, in that it exhibits remarkably large [...] variation, from +2.1 to +12.7. All other bodies that were examined in detail were found to have very uniform isotopic compositions." }, { "name": "Johnson, Torrence Vaino", "degree": "PhD", "year": "1970", "title": "Albedo and Spectral Reflectivity of the Galilean Satellites of Jupiter", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02062012-154016814", "creators": [ { "name": { "family": "Johnson", "given": "Torrence Vaino" }, "id": "Johnson-Torrence-Vaino", "display_name": "Johnson, Torrence Vaino" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/6bk1-dv53", "abstract": "An observational program designed to study the albedo and spectral reflectivity of the Galilean satellites of Jupiter was carried out during the 1969 opposition of Jupiter. A two-channel photoelectric photometer was used in conjunction with a high-speed pulse-counting data system to obtain and record the data, Narrowband interference filters (\u2206\u03bb ~ 0.02\u00b5) were used with ITT FW-118 (S-1) and FW-130 (S-20) phototubes to obtain spectral reflectivity curves from 0.3\u00b5 to 1.1\u00b5. The 24-inch telescope on Mt. Wilson was used for most of the work but the 60-inch instrument was used for some observations, The results of the observations\r\nwere the following. 1) Spectral reflectivity curves from 0.3\u00b5 to 1.1\u00b5 for each satellite for many values of orbital phase angle and solar phase angle were obtained. 2) Spectral structure not resolved by broadband UBV work was found in J1's curve near 0.58\u00b5 and the similarity of the spectral reflectivity curves of J2, J3 and J4 was noted, 3) The very high geometric albedos of J1, J2 and J3, noted\r\nby Harris (1961), were confirmed. 4) The variation in brightness with orbital phase was confirmed for each satellite. 5) The spectral reflectivity was found to\r\nvary with the same period as the brightness, as indicated by UBV observations (Harris, 1961). 6) Variations in the spectral reflectivity of J1 and J2 beyond 0.6\u00b5, not previously seen, were discovered. 7) The spectral form of the variation was found to be similar for each of the satellites, with the brighter side having a higher\r\nreflectivity in the blue and ultraviolet relative to 0.56\u00b5 than the darker side. 8) The eclipse brightening of J1 found by Binder and Cruikshank (1964) was confirmed\r\nat two wavelengths, 0.435\u00b5 and 0. 56f\u00b5.
\r\n\r\nThe conclusions drawn from these results and previous work are as follows. 1) J1 and J2 probably possess tenuous atmospheres while J3 and J4 probably do not. 2) All the satellites have significantly higher geometric albedos than Mercury, the moon or Mars, even allowing for large errors in the measurement of diameters. Of the satellites, J4 has a distinctly lower albedo and density than J1, J2 or J3. 3) The high geometric albedos and spectral reflectivities of the satellites can be explained by surfaces of silicate powders, possibly with considerable amounts of glassy material, having low opacities and some ingredient absorbing in the ultraviolet and blue, possibly Fe^(+++). However, the possibility of surfaces of frost or some combination of frost and rock cannot be completely evaluated without further laboratory study. 4) The similarity in the variation of spectral reflectivity\r\nwith orbital phase among the satellites suggests a similar cause for each. A simple model for J1's spectral variation suggests that some fraction of the bright side of\r\nJ1 must be covered by a material with similar spectral reflectivity but higher albedo than the dark side (such as might be caused by particle size differences or\r\na difference in the amount of the absorbing ingredient). The fraction of surface that must be covered and the exact form of the spectral reflectivity of the added material depends on the albedo chosen for this component. 5) The eclipse brightening observations at two wavelengths indicate that, if this effect is caused by the condensation of some volatile during the eclipse, the condensed material\r\nmust have a very high geometric albedo, probably greater than unity. The simple model applied to the spectral variation, when applied to the eclipse brightening\r\ndata, suggests that the condensed material is not gray in spectral character but has a lower reflectivity at 0.43\u00b5 than at 0.56\u00b5.
" }, { "name": "Julian, Bruce Rene", "degree": "PhD", "year": "1970", "title": "Regional Variations in Upper Mantle Structure Beneath North America", "advisor": "Anderson, Donald L.; Archambeau, Charles B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09242015-115554328", "creators": [ { "name": { "family": "Julian", "given": "Bruce Rene" }, "id": "Julian-Bruce-Rene", "display_name": "Julian, Bruce Rene" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "co-advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/PT11-B635", "abstract": "Several types of seismological data, including surface wave\r\ngroup and phase velocities, travel times from large explosions, and\r\nteleseismic travel time anomalies, have indicated that there are\r\nsignificant regional variations in the upper few hundred kilometers\r\nof the mantle beneath continental areas. Body wave travel times and\r\namplitudes from large chemical and nuclear explosions are used in\r\nthis study to delineate the details of these variations beneath\r\nNorth America.
\r\n\r\nAs a preliminary step in this study, theoretical P wave travel\r\ntimes, apparent velocities, and amplitudes have been calculated\r\nfor a number of proposed upper mantle models, those of Gutenberg,\r\nJeffreys, Lehman, and Lukk and Nersesov. These quantities have been\r\ncalculated for both P and S waves for model CIT11GB, which is derived\r\nfrom surface wave dispersion data. First arrival times for all the\r\nmodels except that of Lukk and Nersesov are in close agreement,\r\nbut the travel time curves for later arrivals are both qualitatively\r\nand quantitatively very different. For model CIT11GB, there are two\r\nlarge, overlapping regions of triplication of the travel time curve,\r\nproduced by regions of rapid velocity increase near depths of 400 and\r\n600 km. Throughout the distance range from 10 to 40 degrees, the\r\nlater arrivals produced by these discontinuities have larger\r\namplitudes than the first arrivals. The amplitudes of body waves,\r\nin fact, are extremely sensitive to small variations in the velocity\r\nstructure, and provide a powerful tool for studying structural\r\ndetails.
\r\n\r\nMost of eastern North America, including the Canadian Shield\r\nhas a Pn velocity of about 8.1 km/sec, with a nearly abrupt increase\r\nin compressional velocity by ~ 0.3 km/sec near at a depth varying\r\nregionally between 60 and 90 km. Variations in the structure of\r\nthis part of the mantle are significant even within the Canadian\r\nShield. The low-velocity zone is a minor feature in eastern\r\nNorth America and is subject to pronounced regional variations.\r\nIt is 30 to 50 km thick, and occurs somewhere in the depth range\r\nfrom 80 to 160 km. The velocity decrease is less than 0.2 km/sec.
\r\n\r\nConsideration of the absolute amplitudes indicates that the\r\nattenuation due to anelasticity is negligible for 2 hz waves in the\r\nupper 200 km along the southeastern and southwestern margins of\r\nthe Canadian Shield. For compressional waves the average Q for\r\nthis region is > 3000. The amplitudes also indicate that the\r\nvelocity gradient is at least 2 x 10-3 both above and below the\r\nlow-velocity zone, implying that the temperature gradient is < 4.8\u00b0C/km\r\nif the regions are chemically homogeneous.
\r\n\r\nIn western North America, the low-velocity zone is a pronounced\r\nfeature, extending to the base of the crust and having minimum\r\nvelocities of 7.7 to 7.8 km/sec. Beneath the Colorado Plateau and\r\nSouthern Rocky Mountains provinces, there is a rapid velocity increase\r\nof about 0.3 km/sec, similar to that observed in eastern North\r\nAmerica, but near a depth of 100 km.
\r\n\r\nComplicated travel time curves observed on profiles with\r\nstations in both eastern and western North America can be explained\r\nin detail by a model taking into account the lateral variations in\r\nthe structure of the low-velocity zone. These variations involve\r\nprimarily the velocity within the zone and the depth to the top\r\nof the zone; the depth to the bottom is, for both regions, between\r\n140 and 160 km.
\r\n\r\nThe depth to the transition zone near 400 km also varies\r\nregionally, by about 30-40 km. These differences imply variations\r\nof 250 \u00b0C in the temperature or 6 % in the iron content of the\r\nmantle, if the phase transformation of olivine to the spinel\r\nstructure is assumed responsible. The structural variations at\r\nthis depth are not correlated with those at shallower depths, and\r\nfollow no obvious simple pattern.
\r\n\r\nThe computer programs used in this study are described in\r\nthe Appendices. The program TTINV (Appendix IV) fits spherically\r\nsymmetric earth models to observed travel time data. The method,\r\ndescribed in Appendix III, resembles conventional least-square\r\nfitting, using partial derivatives of the travel time with respect\r\nto the model parameters to perturb an initial model. The usual\r\nill-conditioned nature of least-squares techniques is avoided by\r\na technique which minimizes both the travel time residuals and the\r\nmodel perturbations.
\r\n\r\nSpherically symmetric earth models, however, have been found\r\ninadequate to explain most of the observed travel times in this\r\nstudy. TVT4, a computer program that performs ray theory calculations\r\nfor a laterally inhomogeneous earth model, is described in Appendix II.\r\nAppendix I gives a derivation of seismic ray theory for an arbitrarily\r\ninhomogeneous earth model.
\r\n" }, { "name": "Lawrence, James Robert", "degree": "PhD", "year": "1970", "title": "O\u00b9\u2078/O\u00b9\u2076 and D/H Ratios of Soils, Weathering Zones, and Clay Deposits", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01132004-094857", "creators": [ { "name": { "family": "Lawrence", "given": "James Robert" }, "id": "Lawrence-James-Robert", "display_name": "Lawrence, James Robert" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/Y4JD-S067", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nD/H and O18/O16 ratios have been determined for a large variety of bulk samples and mineral separates from: Quaternary soils and clay-rich weathering zones; Tertiary, Cretaceous and Pennsylvanian kaolinite deposits; a number of montmorillonite occurrences (from bentonites, fossil soils, alteration of pillow lavas, etc.); Precambrian, Paleozoic and Cretaceous shales; and Pleistocene glacial lake clays. Most samples are from the western and southern United States, but analyses have also been obtained from Hawaii and other parts of North America.\r\n\r\nLaboratory experiments indicate that kaolinites do not suffer any significant amount of hydrogen isotopic exchange at room temperature when in contact with D enriched waters. This also applied in general to montmorillonites, but in many instances partial hydrogen isotopic exchange occurs with interlayer water during the normal heating and outgassing that precedes extraction of OH water. The hydroxyl of halloysite, however, does undergo marked hydrogen isotopic exchange with its interlayer water in a few hours or days at room temperature, largely negating the usefulness of this mineral in isotopic studies.\r\n\r\nThe D/H and O18/O16 ratios of clay minerals and hydroxides in Quaternary soils and weathering zones throughout the United States show a systematic correlation with the isotopic values of present-day meteoric waters. The [...] and [...], respectively, of these weathering products range as follows: Hawaii: -27 to -65 and +24 to +15; Southern United States: -55 to -75 and +22 to +17; coastal California: -55 to -80 and +23 to +16; Sierra Nevada, California: -75 to -95 and +19 to +14; Colorado: -95 to -110 and +16 to +8; Montana and Idaho: -105 to -165 and +12 to 0. The [...] values of the clay minerals are generally 0 to 40% lighter than local meteoric waters and the [...] values are generally 22 to 28% heavier than local meteoric waters. The isotopic values of the clay minerals plot in the vicinity of Savin and Epstein's (1970a) kaolinite line. The [...] and [...] values of the hydroxides (e.g., gibbsite) are generally 10 to 20% lighter and 15 to 20% heavier, respectively, than local meteoric waters. The isotopic values of the hydroxides plot in the vicinity of the line [...].\r\n\r\nA kaolinite soil profile from Georgia and a montmorillonite profile from California, both formed on granitic rock types, were studied in detail. Other detailed sampling was done on a halloysite profile formed on basalt, on three poorly-developed profiles on Cretaceous shales, and a poorly-developed profile on a Precambrian shale. These studies indicate that igneous and sedimentary parent rock minerals do not undergo appreciable oxygen or hydrogen isotopic exchange with meteoric waters in the weathering environment. However, the clay minerals and hydroxides produced by the alteration of the parent rock are formed essentially in isotopic equilibrium with the local meteoric waters.\r\n\r\nThe D/H and O18/O16 ratios of most Pre-Quaternary kaolinites, bentonites, and shales are significantly higher than those of clay-rich Quaternary soils in the same geographic areas. The D/H ratios of Lower Paleozoic and Precambrian shales from eastern United States to Montana and British Columbia show no correlation with the D/H ratios of present-day meteoric waters. The D/H ratios of glacial lake clays, which were exposed to glacial melt waters highly depleted in deuterium are identical to the D/H ratios of Lower Paleozoic shales of the eastern United States from which they were largely derived. All these data suggest that the isotopic ratios of the Pre-Quaternary clay minerals are largely preserved.\r\n\r\nBecause the isotopic values of ancient clay minerals seem to be commonly preserved, the D/H ratios of ancient kaolinites formed by weathering processes can be used to estimate the D/H ratios of ancient meteoric waters. Using the [...] values of the Tertiary kaolinites and a [...] a tentative contour map of the [...] values of \"mid-Tertiary\" meteoric waters has been drawn. The distribution of the [...] values of Tertiary meteoric waters are similar to the present-day distribution except that the contrast in [...] values between coastal and high inland regions in the Tertiary was less extreme than the present contrast. The interpretation is that the distribution of land and the meteorological patterns in the Tertiary were somewhat similar to today but that the climate was generally warmer. Also it is possible that many present-day topographic barriers were absent or less important in the Tertiary. This is in agreement with climatic data suggested by paleobotanical evidence.\r\n\r\nThe wide range of D/H and O18/O16 ratios determined for relatively pure (> 80%) kaolinites formed by the weathering process confirms that the kaolinite line derived by Savin and Epstein (1970a) is essentially correct. However, the D/H and O18/O16 ratios of montmorillonites formed as weathering products or in sedimentary environments display a much greater scatter than kaolinites, presumably as a result of (1) the greater range of chemical compositions of montmorillonites compared to kaolinites, (2) the greater range of the temperatures of formation of montmorillonites, and (3) the possibility that the D/H ratios determined for montmorillonite OH are contaminated during heating and outgassing procedures. Hence, the montmorillonite line derived by Savin and Epstein (1970a) apparently does not apply to most montmorillonites in nature." }, { "name": "Richards, Paul Granston", "degree": "PhD", "year": "1970", "title": "A Contribution to the Theory of High Frequency Elastic Waves, with Applications to the Shadow Boundary of the Earth's Core", "advisor": "Archambeau, Charles B.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09012011-074214410", "creators": [ { "name": { "family": "Richards", "given": "Paul Granston" }, "id": "Richards-Paul-Granston", "display_name": "Richards, Paul Granston" } ], "advisors": [ { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/RVNY-8N49", "abstract": "The diffraction of P and S waves by various obstacles is studied theoretically, in order to evaluate frequency dependent corrections to ray theory for elastic waves which travel nearly along the Earth's core shadow boundary.
\r\n\r\nMost of the properties of this scattering process are conveniently illustrated by a simple Earth model, which gives rise to a problem in plane strain. This model is an infinite homogeneous elastic solid in which a steady state plane body wave (of the type P, SV, or SH) is incident on a circular cylindrical cavity. A Poisson summation is used for the scattered elastic potentials, and contributions from waves diffracted at least once around the cylinder are neglected. Simple approximation formulae are developed to examine the behavior of P, SV, and SH waves on and near their geometrical shadow boundary behind the fluid. Computed numerical results are believed to be valid for frequencies above 0.03 Hz.
\r\n\r\nThe solution method, which may be regarded as a corrected Fresnel theory, is taken through four successive stages of generalization to study increasingly realistic Earth models: (i) diffraction of cylindrical waves from a line source. For this problem our solution is in excellent agreement with the results of an ultrasonic model experiment conducted by Teng and Wu (1968). (ii) Diffraction by a fluid cylinder of cylindrical waves from a line source. (iii) Diffraction by a spherical fluid of spherical waves from a point source. Here we find good agreement between numerical results from our approximate method, and computation of the exact Poisson line integral.
\r\n\r\nThe final stage of generalization, to study (iv) diffraction by a spherical fluid/solid discontinuity in a realistic radially heterogeneous Earth, is obtained by methods similar to (iii), but after an extensive revision of Hook's (1961) discussion of elastic potentials in general media. In our approach, we recognize that the designation of P and S displacements is somewhat arbitrary in heterogeneous elastic media, but becomes precise in the high frequency limit of ray theory (in which P and two S components\r\nare decoupled). These facts are used for radially heterogeneous isotropic Earth models to establish three potentials (P,S,T) with the properties (a) that T(_~r,t) is decoupled from P and S, and is a potential for SH motion, (b) the coupling of P and SV waves is reflected in a system of coupled scalar equations for P(_~r,t) and S(_~r,t), and (c) in the high frequency limit we have P(_~r,t) and S(_~r,t) satisfying canonical uncoupled wave equations with the respective velocities (\u03bb+2\u00b5/\u03c1)^(1/2),( \u03bc/\u03c1)^1/2.
\r\n\r\nMany possibilities are suggested by the coupled equations for P(_~r,t) and S(_~r,t), apart from their use in the solution of (iv) above. They lead to a statement of conditions on the Earth model under which P and SV waves can propagate independently (at any frequency). We also use them to obtain approximate reflection coefficients for upper mantle transition regions which generate observed precursors to the phase PKPPKP, finding that the \"extent of velocity gradient anomaly in such regions must be less than about 4 km, in order to observe short period (1 sec) reflections.
\r\n\r\nOur numerical study of core diffraction provides an explanation for the observed polarization towards SH of diffracted S waves, and also shows that there is a slight dispersion effect dT/d\u0394 data, obtained for P in the range beyond 90\u00b0, which can and must be allowed for in accurate Herglotz-Wiechert inversion studies. The numerical methods developed for discussion of (iv) are expected to have wider applications in seismological studies of the Earth's core, mantle, and crust.
" }, { "name": "Soderblom, Laurence Albert", "degree": "PhD", "year": "1970", "title": "The Distribution and Ages of Regional Lithologies in the Lunar Maria", "advisor": "Murray, Bruce C.; Shoemaker, Eugene Merle", "url": "https://resolver.caltech.edu/CaltechTHESIS:09132013-144554154", "creators": [ { "name": { "family": "Soderblom", "given": "Laurence Albert" }, "id": "Soderblom-Laurence-Albert", "display_name": "Soderblom, Laurence Albert" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." }, { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "advisor", "display_name": "Shoemaker, Eugene Merle" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/TB2T-BJ80", "abstract": "A research program was designed (1) to map regional lithological units\r\nof the lunar surface based on measurements of spatial variations in spectral\r\nreflectance, and, (2) to establish the sequence of the formation of such\r\nlithological units from measurements of the accumulated affects of impacting\r\nbodies.
\r\n\r\nSpectral reflectance data were obtained by scanning luminance\r\nvariations over the lunar surface at three wavelengths (0.4\u00b5, 0.52\u00b5, and\r\n0.7\u00b5). These luminance measurements were reduced to normalized spectral\r\nreflectance values relative to a standard area in More Serenitotis. The\r\nspectral type of each lunar area was identified from the shape of its\r\nreflectance spectrum. From these data lithological units or regions of\r\nconstant color were identified. The maria fall into two major spectral\r\nclasses: circular moria like More Serenitotis contain S-type or red material\r\nand thin, irregular, expansive maria like Mare Tranquillitatis contain T-type\r\nor blue material. Four distinct subtypes of S-type reflectances and two of\r\nT-type reflectances exist. As these six subtypes occur in a number of lunar\r\nregions, it is concluded that they represent specific types of material rather\r\nthan some homologous set of a few end members.
\r\n\r\nThe relative ages or sequence of formation of these more units were\r\nestablished from measurements of the accumulated impacts which have\r\noccurred since more formation. A model was developed which relates the\r\nintegrated flux of particles which hove impacted a surface to the distribution\r\nof craters as functions of size and shape. Erosion of craters is caused chiefly\r\nby small bodies which produce negligible individual changes in crater shape.\r\nHence the shape of a crater can be used to estimate the total number of small impacts that have occurred since the crater was formed. Relative ages of a surface can then be obtained from measurements of the slopes of the walls of\r\nthe oldest craters formed on the surface. The results show that different maria\r\nand regions within them were emplaced at different times. An approximate\r\nabsolute time scale was derived from Apollo 11 crystallization ages under an\r\nassumption of a constant rote of impacting for the last 4 x 10^9 yrs. Assuming,\r\nconstant flux, the period of mare formation lasted from over 4 x 10^9 yrs to\r\nabout 1.5 x 10^9 yrs ago.
\r\n\r\nA synthesis of the results of relative age measurements and of spectral\r\nreflectance mapping shows that (1) the formation of the lunar maria occurred\r\nin three stages; material of only one spectral type was deposited in each\r\nstage, (2) two distinct kinds of maria exist, each type distinguished by\r\nmorphology, structure, gravity anomalies, time of formation, and spectral\r\nreflectance type, and (3) individual maria have complicated histories; they\r\ncontain a variety of lithic units emplaced at different times.
\r\n" }, { "name": "Wyss, Max", "degree": "PhD", "year": "1970", "title": "Observation and Interpretation of Tectonic Strain Release Mechanisms", "advisor": "Brune, J. N.", "url": "https://resolver.caltech.edu/CaltechTHESIS:09232015-141041497", "creators": [ { "name": { "family": "Wyss", "given": "Max" }, "id": "Wyss-Max", "display_name": "Wyss, Max" } ], "advisors": [ { "name": { "family": "Brune", "given": "J. N." }, "id": "Brune-J-N", "role": "advisor", "display_name": "Brune, J. N." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/zzws-mm58", "abstract": "In four chapters various aspects of earthquake source are studied.
\r\n\r\nChapter I
\r\n\r\nSurface displacements that followed the Parkfield, 1966, earthquakes were measured for two years with six small-scale geodetic networks straddling the fault trace.\r\nThe logarithmic rate and the periodic nature of the creep displacement recorded on a strain meter made it possible to predict creep episodes on the San Andreas fault. Some individual earthquakes were related directly to surface displacement, while in general, slow creep and aftershock activity were found to occur independently. The Parkfield earthquake is interpreted as a buried dislocation.
\r\n\r\nChapter II
\r\n\r\nThe source parameters of earthquakes between magnitude 1 and 6 were studied using field observations, fault plane solutions, and surface wave and S-wave spectral analysis. The seismic moment, MO, was found to be related to local magnitude, ML, by log MO = 1.7 ML + 15.1. The source length vs magnitude relation for the San Andreas system found to be: ML = 1.9 log L - 6.7. The surface wave envelope parameter AR gives the moment according to log MO = log AR300 + 30.1, and the stress drop, \u03c4, was\r\nfound to be related to the magnitude by \u03c4 = 0.54 M - 2.58. The relation between surface wave magnitude MS and ML is proposed\r\nto be MS = 1.7 ML - 4.1. It is proposed to estimate the relative stress level (and possibly the strength) of a source-region by\r\nthe amplitude ratio of high-frequency to low-frequency waves. An apparent stress map for Southern California is presented.
\r\n\r\nChapter III
\r\n\r\nSeismic triggering and seismic shaking are proposed as two closely related mechanisms of strain release which explain observations of the character of the P wave generated by the Alaskan earthquake\r\nof 1964, and distant fault slippage observed after the Borrego Mountain, California earthquake of 1968. The Alaska, 1964,\r\nearthquake is shown to be adequately described as a series of individual rupture events. The first of these events had a body\r\nwave magnitude of 6.6 and is considered to have initiated or triggered the whole sequence. The propagation velocity of the\r\ndisturbance is estimated to be 3.5 km/sec. On the basis of circumstantial evidence it is proposed that the Borrego Mountain,\r\n1968, earthquake caused release of tectonic strain along three active faults at distances of 45 to 75 km from the epicenter. It\r\nis suggested that this mechanism of strain release is best described as \"seismic shaking.\"
\r\n\r\nChapter IV
\r\n\r\nThe changes of apparent stress with depth are studied in the South American deep seismic zone. For shallow earthquakes the\r\napparent stress is 20 bars on the average, the same as for earthquakes in the Aleutians and on Oceanic Ridges. At depths\r\nbetween 50 and 150 km the apparent stresses are relatively high, approximately 380 bars, and around 600 km depth they are again\r\nnear 20 bars. The seismic efficiency is estimated to be 0.1. This suggests that the true stress is obtained by multiplying\r\nthe apparent stress by ten. The variation of apparent stress with depth is explained in terms of the hypothesis of ocean\r\nfloor consumption.
\r\n\r\n\r\n" }, { "name": "Brinkmann, Robert Terry", "degree": "PhD", "year": "1969", "title": "The Photodissociation of Water Vapor, Evolution of Oxygen and Escape of Hydrogen in the Earth's Atmosphere", "advisor": "M\u00fcnch, Guido; Ingersoll, Andrew P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10062004-120013", "creators": [ { "name": { "family": "Brinkmann", "given": "Robert Terry" }, "id": "Brinkmann-Robert-Terry", "display_name": "Brinkmann, Robert Terry" } ], "advisors": [ { "name": { "family": "M\u00fcnch", "given": "Guido" }, "id": "M\u00fcnch-G", "role": "advisor", "display_name": "M\u00fcnch, Guido" }, { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/1VBY-7D73", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nPrevious theoretical studies of the photodissociation of water vapor and the resulting evolution of oxygen in the earth's atmosphere have led to the conclusion that over most of geologic time the atmospheric oxygen abundance has been quite low ([...] times the present atmospheric level). These studies have played a prominent role in subsequent investigations concerning biological evolution, interpretation of the geologic record and the evolution of planetary atmospheres. However, these early studies contain several objectionable features which cast serious doubt on the validity of the results. In particular, the path length dependence of the \"effective absorption coefficient\" in the Schumann-Runge bands of oxygen has not been properly handled and the calculations have been based on the incorrect assumption that dissocation of H2O can be neglected when its rate is appreciably less than the rate of absorption by O2. When these deficiencies are rectified it appears that, contrary to the previous findings, the O2 level could have reached an appreciable fraction of the present amount in the absence of biological activity. Thus, if the earth's early atmosphere were indeed highly reducing, some other explanation for this fact must be found. One possibility which has been suggested is that very early in the earth's history sufficient quantities of hydrogen were outgassed to raise the thermal conductivity of the upper atmosphere, reduce its temperature and consequently retard the escape of hydrogen atoms. It has been suggested that such a \"metastable\" atmosphere could have existed for perhaps a billion years. This estimate, however, depends on the efficiency of the gravitational escape of light atoms from a planetary atmosphere, i.e., on the importance of the deviations from Jean's classical escape equation due to the escape-induced departure of the atmospheric atoms' velocity distribution from a Maxwell-Boltzmann law. This problem is too complex to be handled entirely analytically, but the statistical approach seems promising. Indeed, three independent Monte Carlo calculations have been recently conducted. Unfortunately, 1) there are potentially serious errors or unjustified simplifications inherent in all three studies and 2) the results from the three studies are so discordant that even a qualitative idea of the validity of the Jeans escape rate cannot be obtained. In view of the importance of ascertaining the magnitude of the correction to Jeans' equation yet another Monte Carlo study has been conducted. This study differs from previous efforts in many respects, two of which are that accurate angular and velocity dependences have been calculated for the cross-section for the elastic scattering of an H (or He) atom by an 0 atom in the WKB approximation, and that rather than following the particles of the real atmosphere (as did all previous workers), here those particles missing from the real atmosphere by virtue of the escape process have been considered. It is found that only moderate corrections to Jeans' escape rate are needed. No firm picture can be sketched of the condition of the earth's early atmosphere from these considerations. Thus the nature of the evolution of the earth's atmosphere is less well known today than understood." }, { "name": "Clark, George Richmond", "degree": "PhD", "year": "1969", "title": "Shell Characteristics of the Family Pectinidae as Environmental Indicators", "advisor": "Lowenstam, Heinz A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12162009-142807121", "creators": [ { "name": { "family": "Clark", "given": "George Richmond" }, "id": "Clark-George-Richmond", "display_name": "Clark, George Richmond" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geobiol" ], "doi": "10.7907/AEY0-N577", "abstract": "Many characteristics of bivalve shells are related to environmental rather than hereditary conditions. If these acquired characteristics could be recognized and interpreted in fossil shells they would be of considerable significance in paleoecology. In this study a number of growth experiments were conducted on living representatives of the Family Pectinidae, a group of bivalves with an important fossil record. These experiments established the presence of several kinds of acquired characteristics in pectinids.\r\n\r\nThe fine concentric ridges present on many pectinid shells are shown to be daily growth lines, formed in response to a biological rhythm regulated by the cycle of light and darkness. Daily growth increments are also seen in radial sections through pectinid shells. These lines can be used as time markers to greatly increase the amount of information which can be derived from other acquired characteristics. For example, variations in growth rate are known to result from variations in environmental conditions, and these can be observed and measured by means of the daily growth lines. Moreover, they can be correlated between animals grown under the same conditions; this offers a technique for determining the temporal relationships between specimens in a fossil assemblage, a problem of some concern in paleoecology.\r\n\r\nDaily growth lines were used to relate variations in shell chemistry (magnesium concentration) to time of growth, and thereby to variations in growth temperature. There appears to be a great potential for applications of this kind.\r\n\r\nExperiments on Leptopecten latiauratus latiauratus and Leptopecten latiauratus monotimeris, two very different pectinid subspecies, strongly suggest that the morphological differences between the two are principally due to environmental differences. This has important applications for the paleoecology of these forms, and suggests that such strong environmental effects might not be uncommon in the fossil record.\r\n" }, { "name": "McGinley, John Robert, Jr.", "degree": "PhD", "year": "1969", "title": "A Comparision of Observed Permanent Titles and Strains Due to Earthquakes with Those Calculated from Displaced Dislocations in Elastic Earth Models ", "advisor": "Smith, Stewart W.; Archambeau, Charles B.", "url": "http://resolver.caltech.edu/CaltechTHESIS:03242017-153808607", "creators": [ { "name": { "family": "McGinley", "given": "John Robert, Jr." }, "id": "McGinley-John-Robert", "display_name": "McGinley, John Robert, Jr." } ], "advisors": [ { "name": { "family": "Smith", "given": "Stewart W." }, "id": "Smith-Stewart-W", "role": "advisor", "display_name": "Smith, Stewart W." }, { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/9h53-jq64", "abstract": "Theoretical solutions are derived for a model of faulting in\r\nelastic media and for the effect of lateral inhomogeneities on the\r\nearth's free oscillations. The solutions are used in a study of\r\npermanent tilts and strains observed a few hundred kilometers from\r\nearthquakes.
\r\n\r\n\r\nIt is shown that the static deformational field due to a\r\nsuitably chosen dislocation fault model is the same as that due\r\nto introduction of a stress free surface into a prestressed medium.\r\nFormal mathematical solutions are derived for the static deformational\r\nfields due to dislocation fault models in a homogeneous elastic\r\nsphere and a layered elastic half-space. For the layered half-space\r\nexplicit solutions are given in terms of integral transforms for the\r\nsurface displacements, tilts, and strains due to a slip fault\r\nand a dilatational source. A perturbation procedure is developed\r\nfor calculating the effects of lateral changes in elastic constants\r\non the earth's free oscillations. The procedure is applied to obtain\r\nexpressions for the effect of some simple inhomogeneity geometries\r\non the torsional free oscillations.
\r\n\r\nNumerical evaluation of the static, elastic, dislocation\r\nsolutions shows that the observed tilts and strains are large compared\r\nwith theoretical predictions and sometimes show the opposite sign.\r\nThe hypothesis that a weak layer in the lower crust or upper mantle\r\ncan explain the observations is investigated. It is found that a\r\nvery weak layer, approaching a liquid-like behavior, does help to\r\nexplain the observations. The compatibility of a very weak layer\r\nwith observed surface wave dispersion is tested using the results\r\nof the perturbation calculations for the torsional free oscillations.\r\nA very weak layer is determined as compatible with observed surface\r\nwave dispersion only if very thin and with some frequency dependence\r\nin its elastic properties. It is concluded that although a regional\r\nweak layer in the lower crust or upper mantle can help to explain\r\nthe observed tilts and strains, other regional or local structural\r\neffects or source complications must also be important.
\r\n" }, { "name": "McGinley, John Robert, Jr.", "degree": "PhD", "year": "1969", "title": "A Comparison of Observed Permanent Tilts and Strains Due to Earthquakes with those Calculated from Displaced Dislocations in Elastic Earth Models", "advisor": "Archambeau, Charles B.; Anderson, Donald L.; Brune, J. N.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12142017-084449592", "creators": [ { "name": { "family": "McGinley", "given": "John Robert, Jr." }, "id": "McGinley-John-Robert-Jr.", "display_name": "McGinley, John Robert, Jr." } ], "advisors": [ { "name": { "family": "Archambeau", "given": "Charles B." }, "id": "Archambeau-C-B", "role": "advisor", "display_name": "Archambeau, Charles B." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "co-advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Brune", "given": "J. N." }, "id": "Brune-J-N", "role": "co-advisor", "display_name": "Brune, J. N." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/38KM-RT32", "abstract": "Theoretical solutions are derived for a model of faulting in \r\nelastic media and for the effect of lateral inhomogeneities on the \r\nearth's free oscillations. The solutions are used in a study of \r\npermanent tilts and strains observed a few hundred kilometers from \r\nearthquakes.
\r\n\r\n\r\nIt is shown that the static deformational field due to a \r\nsuitably chosen dislocation fault model is the same as that due\r\nto introduction of a stress free surface into a prestressed medium. \r\nFormal mathematical solutions are derived for the static deformational \r\nfields due to dislocation fault models in a homogeneous elastic\r\nsphere and a layered elastic half-space. For the layered half-space \r\nexplicit solutions are given in terms of integral transforms for the \r\nsurface displacements, tilts, and strains due to a slip fault\r\nand a dilatational source. A perturbation procedure is developed \r\nfor calculating the effects of lateral changes in elastic constants\r\non the earth's free oscillations. The procedure is applied to obtain \r\nexpressions for the effect of some simple inhomogeneity geometries\r\non the torsional free oscillations.
\r\n\r\nNumerical evaluation of the static, elastic, dislocation\r\nsolutions shows that the observed tilts and strains are large compared \r\nwith theoretical predictions and sometimes show the opposite sign.\r\nThe hypothesis that a weak layer in the lower crust or upper mantle \r\ncan explain the observations is investigated. It is found that a \r\nvery weak layer, approaching a liquid-like behavior, does help to\r\nexplain the observations. The compatibility of a very weak layer \r\nwith observed surface wave dispersion is tested using the results\r\nof the perturbation calculations for the torsional free oscillations. \r\nA very weak layer is determined as compatible with observed surface \r\nwave dispersion only if very thin and with some frequency dependence \r\nin its elastic properties. It is concluded that although a regional \r\nweak layer in the lower crust or upper mantle can help to explain \r\nthe observed tilts and strains, other regional or local structural \r\neffects or source complications must also be important.
\r\n\r\n \r\n\r\n" }, { "name": "O'Connell, Richard John", "degree": "PhD", "year": "1969", "title": "Part 1. Dynamic Response of Phase Boundaries in the Earth to Surface Loading. Part 2. Pleistocene Glaciation and the Viscosity of the Lower Mantle", "advisor": "Wasserburg, Gerald J.; Anderson, Don L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04052018-084913740", "creators": [ { "name": { "family": "O'Connell", "given": "Richard John" }, "id": "O'Connell-Richard-John", "display_name": "O'Connell, Richard John" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Anderson", "given": "Don L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Don L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/3JGM-5Q68", "abstract": "Part 1. Analytic approximate solutions have been found for the response of a phase change to pressure loading. These solutions allow the behavior of the system to be analyzed in terms of simple parameters of the system. Different characteristic types of behavior are shown to obtain for short times and long times, and criteria for defining these characteristic time scales are given in\r\nterms of known parameters. The distribution of heat sources and convective heat transport are shown to generally have only minor influence on the solution, and may be neglected in many cases. The important parameters are the latent heat of the phase change, and the difference between the Clapeyron slope and the temperature gradient at the phase boundary; in addition the long term behavior is governed by the boundary conditions at the surface and at depth,\r\nand the relative positions of the surface, the phase boundary, and the lower boundary. The effect of thermal blanketing from sediments is included in the solution, and it depends primarily on the depth of the phase boundary and the average temperature gradient in the sediments. The effect of isostasy in conjunction with a phase change is shown to be of major importance; the existence of instabilities where the water depth increases with sedimentation are demonstrated. These solutions allow the history of a sedimentary basin to be calculated, and characterized in terms of certain types of behavior. The existence of oscillatory behavior is demonstrated, where repeated cycles of sedimentation and erosion take place.\r\nThese oscillations can either decay or grow in amplitude, and expressions are given for their frequency and damping or growth constants. A phase change mechanism can account for thicknesses of sediments which exceed the depth of the basin in which they were deposited by a factor of twenty or more. These solutions allow the discussion of the geological implications of phase changes in a quantitative manner. The consequences of a phase change can be\r\naccurately calculated. This will allow the more complete investigation of the role of phase changes in geologic processes.
\r\n\r\nPart 2. The non-tidal acceleration of the earth, revealed by astronomical observations and records of eclipses in antiquity, is attributed to the change in the earth's moment of inertia resulting from isostatic response to the most recent deglaciation and rise in sea level. The isostatic response time for a spherical harmonic deformation\r\nof degree two is calculated on this basis to be either ~2000\r\nyears or ~100,000 years. A correlation of the geopotential with the potential that would have existed following de glaciation indicates that any large scale anomalies resulting from deglaciation have already decayed. This rules out the 100,000 relaxation time; thus the relaxation time of the earth is ~2000 years for degree two. Calculations of the relaxation time spectrum of a layered, gravitating spherical viscous earth model indicates that a model with a uniform mantle viscosity of ~10^(22) poise, except for fine structure in the upper few hundred kilometers, can satisfy the relaxation time of 3000 years for degree two as well as the relaxation time of ~4000\r\nyears for degree twenty which results from studies of uplift in Fennoscandia. A zone of high viscosity in the lower 800 km. of the mantle has a significant effect on the degree two relaxation time. This rules out any substantial increase in viscosity in the lower mantle. The calculated viscosity permits rapid polar wandering and convection in the lower mantle.
\r\n" }, { "name": "Raymond, Charles Forest", "degree": "PhD", "year": "1969", "title": "Flow in a Transverse Section of Athabasca Glacier, Alberta, Canada", "advisor": "Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechETD:etd-07182006-094012", "creators": [ { "name": { "family": "Raymond", "given": "Charles Forest" }, "id": "Raymond-Charles-Forest", "display_name": "Raymond, Charles Forest" } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/E6A2-B010", "abstract": "Measurements of ice deformation at the surface and at depth in the Athabasca Glacier, Canada, reveal for the first time the pattern of flow in a nearly complete cross section of a valley glacier, and make it possible to test the applicability of experimental and theoretical concepts in the analysis of glacier flow. Tilting in nine boreholes (depth about 300 m, eight holes essentially to the bottom) was measured with a newly developed electrical inclinometer, which allows a great increase in the speed and accuracy with which borehole configurations can be determined, in comparison with earlier methods. The measurements define the distribution of the velocity vector and the strain-rate tensor over 70% of the area of the glacier cross section.\r\n\r\nThe main longitudinal component of flow has the following general features: (1) basal sliding velocity which exceeds 70% of the surface velocity over half of the width of the glacier, (2) marginal sliding velocity (not more than a few meters per year) much less than basal sliding velocity at the centerline (about 40 m yr(-1)), (3) marginal shear strain rate near the valley walls two to three times larger than the basal shear strain rate near the centerline (0.1 yr(-1)).\r\n\r\nThe observed longitudinal flow is significantly different from that expected from theoretical analysis of flow in cylindrical channels (Nye, 1965). The relative strength of marginal and basal shear strain rate is opposite to that expected from theory. In addition, the longitudinal flow velocity averaged over the glacier cross section (which determines the flux of ice transported) is larger by 11% than the average flow velocity seen at the glacier surface, whereas it would be 2% smaller if the theoretical prediction were correct. These differences are caused to a large extent by the constant sliding velocity assumed in the theoretical analysis, which contrasts strongly with the actual distribution of sliding. The observed relation between marginal and basal sliding velocity is probably a general flow feature in valley glaciers, and may be caused by lateral variation of water pressure at the ice-rock contact. The observed pattern of longitudinal velocity over the section also shows in detail certain additional features incompatible with the theoretical treatment, even after the difference in boundary conditions (distribution of sliding velocity) is taken into account.\r\n\r\nLongitudinal strain rate (a compression of about 0.02 yr(-1) at the surface) decreases with depth, becoming nearly 0 at the bed in the center of the glacier. The depth variation cannot be explained completely by overall bending of the ice mass as a result of a longitudinal gradient in the curvature of the bed, and is at variance with existing theories, which require the longitudinal strain rate to be constant with depth.\r\n\r\nMotion transverse to the longitudinal flow occurs in a roughly symmetric pattern of diverging marginward flow, with most of the lateral transport occurring at depth in a fashion reminiscent of extrusion flow. The observed lateral velocities averaged over depth (up to 1.9 m yr(-1)) are compatible with the lateral flux required to maintain equilibrium of the marginal portions of the glacier surface under ablation (3.7 m yr(-1)) and are driven by the convex transverse profile of the ice surface.\r\n\r\nWhen the measured strain-rate field is analyzed on the basis of the standard assumption that the shear stress parallel to the glacier surface varies linearly with depth, the rheological behavior in the lower one-half to two-thirds of the glacier is found compatible with a power-type flow law with n = 5.3. However, the upper one-third to one-half of the glacier constitutes an anomalous zone in which this treatment gives physically unreasonable rheological behavior. In a new method of analysis, rheological parameters are chosen so as to minimize the fictitious body forces that appear as residuals in the equilibirum equations when evaluated for the measured strain-rate field. This new method requires no a priori assumptions about the stress distribution, although for simplicity in application, the mean stress is assumed constant longitudinally. This treatment shows that the anomalies in the near-surface zone are due to significant departures from linear dependence of shear stress on depth, and gives a flow-law exponent of n = 3.6, which is closer than n = 5.3 to values determined by laboratory experiments on ice." }, { "name": "Shieh, Yuch-Ning", "degree": "PhD", "year": "1969", "title": "Oxygen, Carbon, and Hydrogen Isotope Studies of Contact Metamorphism", "advisor": "Taylor, Hugh P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02202014-142721576", "creators": [ { "name": { "family": "Shieh", "given": "Yuch-Ning" }, "id": "Shieh-Yuch-Ning", "display_name": "Shieh, Yuch-Ning" } ], "advisors": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "advisor", "display_name": "Taylor, Hugh P." } ], "committee": [ { "name": { "family": "Taylor", "given": "Hugh P." }, "id": "Taylor-H-P", "role": "chair", "display_name": "Taylor, Hugh P." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "member", "display_name": "Albee, Arden Leroy" }, { "name": { "family": "Burnett", "given": "Donald S." }, "id": "Burnett-D-S", "orcid": "0000-0001-9521-8675", "role": "member", "display_name": "Burnett, Donald S." } ], "option_major": [ "geochem" ], "doi": "10.7907/JJY7-J871", "abstract": "The O18/O16, C13/C12, and D/H ratios have been determined for\r\nrocks and coexisting minerals from several granitic plutons and their contact\r\nmetamorphic aureoles in northern Nevada, eastern California, central Colorado,\r\nand Texas, with emphasis on oxygen isotopes. A consistent order of O18/O16, C13/C12, and D/H enrichment in coexisting minerals, and a correlation between isotopic fractionations among coexisting mineral pairs are in general\r\nobserved, suggesting that mineral assemblages tend to approach isotopic\r\nequilibrium during contact metamorphism. In certain cases, a correlation is\r\nobserved between oxygen isotopic fractionations of a mineral pair and sample\r\ndistance from intrusive contacts. Isotopic temperatures generally show good\r\nagreement with heat flow considerations. Based on the experimentally\r\ndetermined quartz-muscovite O18/O16 fractionation calibration curve, temperatures are\r\nestimated to be 525 to 625\u00b0C at the contacts of the granitic stocks\r\nstudied.
\r\n\r\nSmall-scale oxygen isotope exchange effects between intrusive and\r\ncountry rock are observed over distances of 0.5 to 3 feet on both sides of the\r\ncontacts; the isotopic gradients are typically 2 to 3 per mil per foot. The\r\ndegree of oxygen isotopic exchange is essentially identical for different\r\ncoexisting minerals. This presumably occurred through a diffusion-controlled\r\nrecrystallization process. The size of the oxygen isotope equilibrium systems\r\nin the small-scale exchanged zones vary from about 1.5 cm to 30 cm. A\r\nxenolith and a re-entrant of country rock projecting into on intrusive hove\r\nboth undergone much more extensive isotopic exchange (to hundreds of feet);\r\nthey also show abnormally high isotopic temperatures. The marginal portions\r\nof most plutons have unusually high O18/O16 ratios compared to \"normal\"\r\nigneous rocks, presumably due to large-scale isotopic exchange with meta-sedimentary\r\ncountry rocks when the igneous rocks were essentially in a molten\r\nstate. The isotopic data suggest that outward horizontal movement of H2O\r\ninto the contact metamorphic aureoles is almost negligible, but upward movement\r\nof H2O may be important. Also, direct influx and absorption of water from the\r\ncountry rock may be significant in certain intrusive stocks.
\r\n\r\nExcept in the exchanged zones, the O18/O16 ratios of pelitic rocks\r\ndo not change appreciably during contact metamorphism, even in the cordierite\r\nand sillimanite grades; this is in contrast to regional metamorphic rocks which\r\ncommonly decrease in O18 with increasing grade. Low O18/O16 and C13/C12\r\nratios of the contact metamorphic marbles generally correlate well with the\r\npresence of calc-silicate minerals, indicating that the CO2 liberated during\r\nmetamorphic decarbonation reactions is enriched in both O18 and C13 relative to the carbonates.
\r\n\r\nThe D/H ratios of biotites in the contact metamorphic rocks and their\r\nassociated intrusions show a geographic correlation that is similar to that shown\r\nby the D/H ratios of meteoric surface waters, perhaps indicating that meteoric\r\nwaters were present in the rocks during crystallization of the biotites.
\r\n\r\n" }, { "name": "Smith, Douglas", "degree": "PhD", "year": "1969", "title": "Mineralogy and Petrology of an Olivine Diabase Sill Complex and Associated Unusually Potassic Granophyres, Sierra Ancha, Central Arizona", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10072010-111049115", "creators": [ { "name": { "family": "Smith", "given": "Douglas" }, "id": "Smith-Douglas", "display_name": "Smith, Douglas" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/JRYS-CR97", "abstract": "The Precambrian Sierra Ancha sill complex, 700 to 800 feet thick, was intruded into flat-lying sedimentary rocks of the Apache Group in central Arizona. The bulk of the complex consists of a central layer of feldspathic olivine-rich diabase and upper and lower layers of olivine diabase. Diabasic rocks present in relatively minor quantity in the upper part of the complex include diabase pegmatite, albite diabase, and quartz diabase. Potassic granophyres locally form lenses up to two hundred feet thick near and at the roof of the complex. The intrusion was studied in the field and in the laboratory to determine the origins of the rock types and the conditions under which they formed. Extensive electron microprobe studies of mineral compositions and zoning are presented together with nineteen new whole rock chemical analyses.\r\n\r\nThe Sierra Ancha olivine diabase has a high-alumina olivine basalt composition. Olivine diabase and olivine-rich diabase display a differentiation pattern characterized by moderate iron enrichment. Diabase pegmatite is relatively enriched in alkalis.\r\n\r\nThe principle primary minerals in feldspathic olivine-rich diabase and olivine diabase include: plagioclase (An_(72)-An_(16)); augite (Wo_(43)En_(44)Fs_(13) to Wo_(40)En_(38)Fs_(22)); olivine (Fo_(74)-Fo_(54)); orthopyroxene (En_(77)-En_(44)); magnetite_ss (Mgt_(66)Usp_(34)-Mgt_(89)Usp_(11)); and ilmenite_(ss) (Ilm_(86)Hem_(14)-Ilm_(96)Hem_4). All of the orthopyroxene is primary. Fe- Mg fractionations between mafic mineral pairs increase with iron enrichment and declining crystallization temperatures. Ilmenite which formed by reaction-exsolution from magnetite was found to be consistently different in composition from primary ilmenite.\r\n\r\nThe late-crystallizing diabase pegmatites contain an assemblage including iron-rich chlorite together with calcic pyroxene; from textural evidence the two phses appear primary. The calcic pyroxene has a compositional range from Wo_(49)En_(28)Fs_(23) to Wo_(49) En_(14)Fs_(37); its compositions define an iron-enriched trend in the pyroxene quadrilateral more calcic (i.e., closer to the diopsidehedenburgite join) than other iron-enriched igneous pyroxene trends described in the literature.\r\n\r\nMost diabasic rocks in the sill display some deuteric alteration. The mineral assemblage seemingly stable in the most-altered rocks includes albite (An_(2-0)), prehnite, calcic pyroxene (saute), chlorite, sphene, and apatite. Albite diabase contains this assemblage and apparently formed by recrystallization of normal diabase under deuteric conditions. The alteration assemblages are similar to those found in spilites. They provide an important example of the development of a spilitic assemblage by autometamorphism.\r\n\r\nThe massive granophyres at and near the top of the sill appear to be igneous. The larger lenses occur at local high points in the roof of the complex near discordant contacts. The granophyres consist primarily of alkali feldspar with subordinate calcic pyroxene, iron-rich hornblende, biotite, and quartz and minor plagioclase and other phases. They have no relict sedimentary textural features, and they contain miarolitic cavities and rotated and displaced sedimentary rock inclusions. Locally, they occur as masses truncating overlying strata and as dikes in the overlying sedimentary rocks. Some of the dikes have apparent chilled contacts against the sedimentary rocks, suggesting that they were emplaced largely as melts.\r\n\r\nThe granophyres formed as a result of the interaction of diabase magma with stratified rocks of the overlying Dripping Spring Quartzite. The massive granophyres are generally similar in composition to the overlying sedimentary rocks; both rock types have very unusual and distinctive high potassium contents. Contact metamorphism by the diabase has produced layered metasedimentary rocks with granophyric textures and mineral assemblages comparable to those in some massive granophyres. Consistent compositional differences between granophyres and sedimentary rocks may have been caused by metasomatic processes or by mixing of diabase magma with the sedimentary rock material which constitutes most of the granophyres.\r\n\r\nThe interaction of diabase and sedimentary rocks may have occurred because magma in the upper part of the intrusion absorbed water from the overlying sedimentary rocks and solidified after magma in the central part of the intrusive. If this happened, the sedimentary rocks over the sill might have been melted to form the granophyres. No chilled facies of diabase occurs at the sill roof where granophyres are present. Compositional trends in mineral series indicate that the diabase magma in the upper part of the sill solidified towards the roof in at least one locality.\r\n\r\nNormal processes of magmatic differentiation produced feldspathic olivine-rich diabase, olivine diabase, and diabase pegmatite in the Sierra Ancha complex. The processes which produced the granophyres include recrystallization and fusion of rocks overlying the intrusion. The Sierra Ancha granophyres offer a superb opportunity to study these processes and others which may have produced many of the granitic rocks in the crust of the earth.\r\n" }, { "name": "Spetzler, Hartmut A. W.", "degree": "PhD", "year": "1969", "title": "Part I. The Effect of Temperature and Partial Melting on Velocity and Attenuation in a Simple Binary System. Part II. Effect of Temperature and Pressure on Elastic Properties of Polycrystalline and Single Crystal MgO", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04022018-124017475", "creators": [ { "name": { "family": "Spetzler", "given": "Hartmut A. W." }, "id": "Spetzler-Hartmut-A-W", "display_name": "Spetzler, Hartmut A. W." } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/CZFN-2N63", "abstract": "A possible explanation of the low-velocity, low-Q zone in the upper mantle is partial melting, but laboratory data has not been available to test this conjecture. As a first step in obtaining an idea of the role that partial melting plays in affecting seismic variables, the longitudinal and shear velocities and attenuations were measured in a simple binary system that is completely solid at low temperatures and involves 17% melt at the highest experimental\r\ntemperature. The system investigated was NaCl\u2022H2O. At temperatures below the eutectic the material is a solid mixture of H2O (ice)\r\nand NaCl\u2022H2O. At higher temperatures the system is a mixture of ice and NaCl brine. In the completely solid regime the velocities and Q change slowly with temperature. There is a marked drop in the velocities and Q at the onset of melting. For ice containing 1% NaCl, the longitudinal and shear velocities change discontinuously at this temperature by 9.5 and 13.5%, respectively. The corresponding Q's drop by 48 and 37%. The melt content of the mixture at temperatures on the warm side of the eutectic for this composition is about 3.3%. The abrupt drop in velocities at the onset of partial melting is about three times as much for the ice containing 2% NaCl;\r\nfor this composition, the longitudinal and shear Q's drop at the eutectic temperature by 71 and 73%, respectively. If these results can be used as a guide in understanding the effect of melting on seismic properties in the mantle, we should expect sharp discontinuities in velocity and Q where the geotherm crosses the solidus. The phenomena associated with the onset of melting are more dramatic than those associated with further melting.
\r\n\r\nThe theory for randomly oriented fluid-filled penny-shaped cracks satisfactorily explains the velocity data. The anomalous behavior on the warm side of the eutectic temperature is attributed to thermochemical effects associated with interaction of the sound wave with the phase equilibria. This phenomenon is not observed\r\nwhen supercooling is possible.
\r\n\r\nA laboratory has been constructed to measure the elastic\r\nproperties of solids to 12 kbar and 1200\u00b0K by ultrasonic interferometry techniques. The elastic constants and their temperature and pressure derivatives have been measured to high temperature and pressure for both single crystal and polycrystalline MgO. A pseudoresonance technique involving pulse superposition and a lapped buffer rod without bond were used in order to obtain the necessary precision.\r\nThe results for the single crystal are tabulated below.
\r\n" }, { "name": "Henyey, Thomas Louis", "degree": "PhD", "year": "1968", "title": "Heat Flow near Major Strike-Slip Faults in Central and Southern California", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04052018-144537140", "creators": [ { "name": { "family": "Henyey", "given": "Thomas Louis" }, "id": "Henyey-Thomas-Louis", "display_name": "Henyey, Thomas Louis" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/Z153-RH23", "abstract": "Seventeen heat flow measurements have been made near the\r\nSan Andreas, San Jacinto, and Garlock faults of California in regions representative of several levels of seismic activity. Data from these measurements in conjunction with results of other heat flow investigations in central and southern California show no maxima directly attributable to the fault zones. This negative result along with stress-drop\r\nresults from earthquakes suggests an upper bound of the order of 200 bars for the absolute stress in the vicinity of the San Andreas fault. In addition, the average heat flow in the four regions investigated (San Bernardino Mountains - Lake Hughes, Anza, Hollister, and Tehachapi\r\nMountains) is the same; the mean value of 23 determinations is 1.7 \u03bccal/cm2/sec \u00b1 0.1 s.d.
\r\n\r\nIn the region between Lake Hughes and San Bernardino, presently seismically inactive but in the zone of rupture from the ~8 magnitude Fort Tejon earthquake, six measurements show no correlation with distance from the San Andreas fault. Near the San Jacinto fault in an area characterized by frequent medium magnitude earthquakes, determinations at 1 and 4 km from the fault are equal\r\nbut 20 per cent higher than a measurement 13 km to the west, but not appreciably different from a probable regional average 25 km to the east. Near Hollister where the San Andreas is actively creeping at a rate of several centimeters per year, a measurement 8 km east of the fault yields a flux twice as great as one 30 km to the west, but\r\nvalues at intermediate points suggest that this anomaly may reflect more the regional geology than the San Andreas fault alone. Finally, measurements across the historically inactive Garlock fault exhibit high fluxes near the fault in comparison with a determination 8 km to the north, but do not differ significantly from determinations in the\r\nMojave Block to the south.
\r\n\r\nIn California, the major fault systems appear to lie in transition zones between blocks of crust characterized by Basin and Range heat flows -- Mojave Block and Salton Trough -- and blocks representative of normal continental heat flows -- Central Valley and the crustal strip between the San Jacinto-San Andreas fault system and the Pacific continental margin.
\r\n" }, { "name": "Kieffer, Hugh Hartman", "degree": "PhD", "year": "1968", "title": "Near Infrared Spectral Reflectance of Simulated Martian Frosts", "advisor": "Ingersoll, Andrew P.; Kamb, W. Barclay; Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-07172006-093716", "creators": [ { "name": { "family": "Kieffer", "given": "Hugh Hartman" }, "id": "Kieffer-Hugh-Hartman", "display_name": "Kieffer, Hugh Hartman" } ], "advisors": [ { "name": { "family": "Ingersoll", "given": "Andrew P." }, "id": "Ingersoll-A-P", "role": "advisor", "display_name": "Ingersoll, Andrew P." }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/BHED-BJ17", "abstract": "In view of the apparent conflict between spectral observations and recent theories of the Martian polar caps, comparison spectra were obtained for frosts of relevant composition and grain size. The spectral reflectances of frosts formed from pure CO2, and pure H2O and mixtures of these gases have been measured from 0.8 to 3.2 [microns]. Low-weight fractions or small surface concentrations of H2O resulted in spectra similar to pure H2O frost spectra. The concentration of the condensable gas and the radiation balance effect the frost textural scale and the contrast of the reflection spectrum. The emissivity of the polar caps may be small, in contrast to previous assumptions. Probable processes of frost formation and sublimation on Mars and seasonal variations of frost composition suggest that reflection spectra obtained in the Martian spring may be misleading. In light of the laboratory results and probable Martian conditions, previous suggestions that the Martian polar caps are H2O are not valid. Future diagnostic observations in the near and thermal infrared are suggested.\r\n\r\nFigures 10, 11 and 12 are photographs of frost samples and will not reproduce well. Photographic copies may be ordered.\r\n" }, { "name": "McCord, Thomas Bard", "degree": "PhD", "year": "1968", "title": "Color Differences on the Lunar Surface", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02082012-092701057", "creators": [ { "name": { "family": "McCord", "given": "Thomas Bard" }, "id": "McCord-Thomas-Bard", "display_name": "McCord, Thomas Bard" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/0ST8-5H98", "abstract": "Both a detailed literature survey and a new\r\nobservational study were performed to determine and\r\nextend the knowledge of spectral reflectivity differences\r\n(color differences) on the lunar surface in the extended\r\nvisible wavelength region. A survey of the extensive\r\nand disorganized literature revealed few positively\r\nknown facts and indicated the need for an accurate, multi-passband observational study of a number of lunar areas\r\nof differing morphology. A 21-filter (0.4\u00b5- 0.8\u00b5),\r\ndouble beam photoelectric photometer was designed and\r\nconstructed to observe differentially 83 lunar areas,\r\nsome many times, to an accuracy of 0.1% to 0.3%. Some\r\nresults were the discovery of: (1) many color variations\r\nup to 10% with some to about 60%, (2) a dependence of\r\nrelative color on phase angle but no temporally varying\r\nluminescence, (3) broadband absorption features on\r\nspectral reflectivity curves and possibly some less broad,\r\nlow amplitude (0.2%- 0.5%) humps, (4) a dependence of\r\nspectral curve shape on lunar morphology and, (5) no\r\nuniversal dependence of color on brightness, although\r\nsome mare areas show this tendency. These results indicate\r\nthat color differences are caused mainly by compositional differences and that the shapes of the spectral reflectivity curves give some indications of the rock and mineral composition of the lunar surface." }, { "name": "McGetchin, Thomas Richard", "degree": "PhD", "year": "1968", "title": "The Moses Rock Dike: Geology, Petrology and Mode of Emplacement of a Kimberlite-Bearing Breccia Dike, San Juan County, Utah", "advisor": "Shoemaker, Eugene Merle; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06182009-081030", "creators": [ { "name": { "family": "McGetchin", "given": "Thomas Richard" }, "id": "McGetchin-Thomas-Richard", "display_name": "McGetchin, Thomas Richard" } ], "advisors": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "advisor", "display_name": "Shoemaker, Eugene Merle" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/km6d-5q43", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Moses Rock dike is a well-exposed, four-mile long, kimberlite-bearing breccia intrusion in the east central Colorado Plateau, one of eight known kimberlite-bearing diatremes in the province. The dike occurs in gently dipping beds of the Permian Cutler Formation, 2 miles west of the Comb Ridge monocline in eastern Monument Valley, Utah. Contacts are little altered and the wall rocks generally undeformed. The present erosion surface is probably about 5,000 feet below the surface at the time of emplacement. By volume, the breccia in the dike consists of Cutler formation blocks, 72%; limestone fragments from underlying Paleozoic formations, 13%; crystalline rock fragments, 3%;and kimberlite, 12%. Essentially undiluted kimberlite occurs only locally, and occupies only about l% of the exposed parts of the dike. Mineral constituents of kimberlite are generally dispersed through the unconsolidated breccias.\r\n\r\nThe breccias, including kimberlite, were probably emplaced as a fluidized solid-volatile system. This conclusion is based on the following observations: (1) No silicate melt was intruded at the level present erosion surface, (2) the breccias are particulate on all scales, (3) the particle size frequency distributions of the breccias are like those produced in comminution processes, (4) different types of breccias are intricately mixed, and (5) the mineral constituents of the kimberlite are commonly highly diluted with rock debris. Relationships of the breccia units suggests that flow of the fluidized system was concentrated in channels, now occupied by breccias that contain the largest upward displaced fragments and the largest crystalline rock fragments. Apparently the dike was emplaced along a fissure on which channels soon developed. A local joint system parallel to the contact, which cross-cuts regional joints, apparently played a key role in the dike formation and brecciation process.\r\n\r\nCrystalline rock and mineral fragments found in the dike range from acid to ultramafic types and are believed to represent rocks derived from the vent walls during the eruption. On the basis of the relative size and abundance of the xenoliths, it is inferred that metabasalt, granite and granite gneiss are abundant in the upper part of the crust, along the dikewalls; diorite, gabbro, mafic amphibolite constitute intermediate crystal layers; and mafic granulite and possibly hydrated ultramafic rocks constitute the lower crust. The suite of presumed crustal rocks is predominantly metavolcanic or metaplutonic, not metasedimentary.\r\n\r\nDense and ultramafic fragments possibly derived from the mantle include antigorite-tremolite schist, jadeite-rich clinopyroxenite, eclogite, spinel-websterite, and spinel-lherzolite. The presence of garnet-periodotite at depth is inferred from the suite of mineral inclusions observed within pyropic garnets.\r\n\r\nKimberlite of the Moses Rock dike is believed to be derived mechanically from physically disaggregated spinel and garnet peridotite in the mantle. All other rocks are believed to be accidental inclusions from the vent walls. Tentative P-T assignments to kimberlite clinopyroxenes based on their compositions suggests they are derived from various depths ranging from 50 to about 150 kilometers where the indicated temperatures are modest, about [...] C.\r\n\r\nTitanoclinohumite observed in kimberlite and as inclusions in pyropes may contain most of the water in the upper mantle.\r\n\r\nThe Mohorovicic discontinuity apparently occurs in a petrologically complex region and may coincide with phase and compositional transitions, including hydration. A compositional transition between spinel and garnet periodotite with increasing depth in the mantle is consistent with the observations. The variety of ultramafic types and the complexity of the textures in the xenoliths suggest the mantle may be as complicated as the crust in composition and history.\r\n\r\nNumerical hydrodynamic models of eruption show that flow velocities are probably controlled by viscous losses and expansion of a volatile phase near the surface. Field observations of the largest blocks transported upward in the dike suggest flow velocities of 10 to 50 m/sec at the level of the present surface. Upward extrapolation by use of theoretical models suggests velocities of about 400 m/sec for the erupting fluidized system as it reached the earth's surface.\r\n\r\nThe Moses Rock dike probably formed by eruption of kimberlite from a large reservoir in the mantle. The eruption was driven by volatiles, apparently mostly [...]. The kimberlite consists of physically disrupted rock from the reservoir environment.\r\n" }, { "name": "Goetz, Alexander Franklin Hermann", "degree": "PhD", "year": "1967", "title": "Infrared 8-13\u00b5 Spectroscopy of the Moon and Some Cold Silicate Powders", "advisor": "Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04262017-152729036", "creators": [ { "name": { "family": "Goetz", "given": "Alexander Franklin Hermann" }, "id": "Goetz-Alexander-Franklin-Hermann", "display_name": "Goetz, Alexander Franklin Hermann" } ], "advisors": [ { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "plansci" ], "doi": "10.7907/Z362-5914", "abstract": "Laboratory investigations were made of the spectral\r\nemission properties of a limited number of silicate powders in\r\nvacuum and surface temperatures of 180-240\u00b0K. The effect on\r\nthe emission spectrum of mineral composition, powder grain-size,\r\nsurface contamination and thermal gradient was studied.
\r\n\r\n\r\nThe low sample surface temperature enhanced the spectral\r\ncontrast of quartz but had little effect on spectra of rock materials.\r\nIn general, there was a decrease in spectral contrast with decreasing\r\nsample grain-size. However, this effect was more pronounced for\r\nindividual mineral samples than for rock samples. When the particle\r\nsize was reduced to less than 38\u03bc individual rock types could not be\r\nidentified. However, quartz bearing or generally acidic rocks could\r\nbe differentiated from quartz free or generally basic rock types. A\r\nquartz sample which had been contaminated by iron oxide did not\r\nlose its spectral features in spite of being visibly colored. The effect\r\nof a thermal gradient in the sample on its emission spectrum was\r\nshown to be negligible.
\r\n\r\n\r\nDifferential 8-13\u03bc spectroscopy of 22 lunar points, spanning\r\nthe major types of lunar features, was undertaken to determine if\r\ncompositional differences or age are evidenced in the 8-13\u03bc emission\r\nspectra of the features. A method was devised to remove precisely\r\nthe atmospheric absorption and allow the integration of many spectra\r\nin order to reduce uncertainties caused by atmospheric absorption\r\nfluctuations and detector noise.
\r\n\r\n\r\nTwenty of the 22 points showed no spectral differences\r\ngreater than 1%. Two points, Plato and Mare Humorum, showed\r\ndefinite, consistent spectral differences from the rest of the points\r\nmeasured, at the short wavelength end of the spectrum.
\r\n\r\n\r\nThe interpretation made here of these results is that these\r\ntwo points have significantly fresher surfaces exposed which still\r\nshow some spectral contrast or they are compositionally different\r\nfrom their surroundings. In the former case the anomalous areas\r\nmust be partially covered with a non-silicate material in order to\r\nbe consistent with the data obtained. If the points are compositionally\r\ndifferent and the uniform areas show spectral contrast, the uniform\r\nareas must contain quartz and the anomalous areas are then more\r\nbasic in composition than the uniform areas. The alternative to these\r\ntwo possibilities is that some process, perhaps an effect of the solar\r\nwind, is operating in such a way as to produce spectra which are\r\nunknown and hence can be falsely interpreted.
" }, { "name": "McDowell, Stewart Douglas", "degree": "PhD", "year": "1967", "title": "The Intrusive History of the Little Chief Granite Porphyry Stock, Panamint Range, California: I. Structural Relationships. II. Petrogenesis, Based on Microprobe Analyses of the Feldspars", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechETD:etd-09252007-084230", "creators": [ { "name": { "family": "McDowell", "given": "Stewart Douglas" }, "id": "McDowell-Stewart-Douglas", "display_name": "McDowell, Stewart Douglas" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/V1ZV-F079", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Little Chief stock of Upper Miocene (?) age, located in the central Panamint Range near Death Valley, California, crops out over an area of 2.5 by 4.5 miles and through an elevation range of 6300 feet. It is a crosscutting diapir-like body with contact attitudes ranging from vertical to 80\u00b0 outward except along the eastern margin, where the contact attitudes range from 45\u00b0 outward to 35\u00b0 inward. The stock appears to neck downward into a thin, east-west, dike-like body at a depth of less than 6000 feet below the present surface.\r\n\r\nThe stock has lifted a nearly rectangular \"trapdoor\" of later Precambrian and Precambrian (?) rocks bounded by vertical faults on the north, west, and south. The trapdoor opens to the west with a vertical throw of 3000 feet on the western margin and with a roughly north-south hinge line located just east of the stock. East of the hinge line, the trapdoor has been slightly depressed. The trapdoor offsets an earlier set of westward-dipping normal faults along which a porphyry dike swarm has been intruded.\r\n\r\nThe stock consists of two intrusive phases, a south and a slightly later north phase. The stock magma moved to a position roughly 6000 feet below the present surface and formed the westward-dipping normal faults by stretching the sedimentary rocks over the magma chamber roof, which were immediately injected by the porphyry dikes. The magma moved to the present level, truncating the normal faults and associated dikes, forming the trap door, and doming the sediments of the roof. The interior of the north phase then moved slightly upward to the present level, disrupting the eastern part of the trapdoor and renewing movement on some of the trapdoor faults.\r\n\r\nThe stock is a hornblende-biotite granite porphyry with 2-10mm normally-zoned sanidine and plagioclase in a quartz-alkali feldspar-plagioclase groundmass. Detailed electron microprobe analyses yield the following feldspar compositions. The plagioclases have distinct normally-zoned layers separated by abrupt compositional gaps. The gaps formed by sporadic, abrupt water pressure decreases as the magma moved upward. Assimilation of water-rich calcic material caused large calcic oscillations on the plagioclase zones. Zonation in the outermost edges of the plagioclase phenocrysts to very low-Or plagioclase could be due to [...] increase and/or the effect of the peristerite solvus on the ternary feldspar solvus.\r\n\r\nSanidine coexisted with [...] plagioclase in a magma chamber 12,000 feet below the present level, which had an undifferentiated, unsaturated [...] core surrounded by a differentiated, saturated [...] exterior. This [...] variation was equalized as the magma moved up to its present position, where the groundmass crystallized at [...] some 7000 feet below the contemperaneous ground surface.\r\n\r\nSanidine was removed from equilibrium, due to its rapid crystallization and shift of the feldspar boundary on [...] increase, at different times. It was rimmed by [...] plagioclase in the water-poor core of the magma chamber before the magma started to move upward. Toward the exterior sanidine began to be replaced by sodic oligoclase as the magma moved upward, and in the water-rich exterior parts sanidine exsolved to a patch perthite while the system was 50 percent melt, and the K-phase was then replaced by sodic oligoclase. In the very water-rich parts, sanidine crystallized in equilibrium until the groundmass was formed.\r\n\r\nDuring upward movement assimilation of dolomitic rock formed a contaminated marginal phase which was then intruded by uncontaminated magma and carried upward as inclusions.\r\n\r\nFracturing of the roof of the present stock led to volatile concentration in certain restricted portions of the stock, and formation of quartz macrocyrsts, graphic textures, pegmatitic pods, coarse lamellar perthite in the sanidine, and numerous vugs.\r\n\r\n\r\n\r\n\r\n\r\n\r\n" }, { "name": "Naylor, Richard Stevens", "degree": "PhD", "year": "1967", "title": "A Field and Geochronologic Study of Mantled Gneiss Domes in Central New England", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05032017-084934764", "creators": [ { "name": { "family": "Naylor", "given": "Richard Stevens" }, "id": "Naylor-Richard-Stevens", "display_name": "Naylor, Richard Stevens" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/7TWJ-DJ70", "abstract": "New information on the origin of mantled gneiss domes comes\r\nfrom a study of these structures in Central New England. The domes\r\nhave cores of massive granite and gneiss encircled by concordant\r\nmantles of well-stratified metamorphic rocks, and appear to originate\r\nthrough intense metamorphism of rock sequences in which massive,\r\nchiefly quartzo-feldspathic rocks are overlain by less competent\r\nstrata. Contrary to previous hypotheses, the new work indicates that\r\nneither unconformable separation of the core and mantle nor re-mobilization\r\nor anatexis of the core rocks are essential elements in\r\nthe formation of mantled gneiss domes. Two contrasting types of\r\ngneiss domes have been identified in central New England.
\r\n\r\n\r\nExamples of the first type are domes of the Chester Dome group\r\nin southeastern Vermont. Formation of these domes involved kyanite-staurolite\r\ngrade metamorphism of Precambrian gneissic basement overlain\r\nunconformably by Paleozoic strata. The angular relationships at\r\nthe unconformity have been obscured by differential movement of the\r\ncore-rocks relative to the mantling strata. The Precambrian rocks in\r\nthe cores of the Chester Dome and the nearby Green Mountain Anticlinorium\r\nhave been badly disturbed by Paleozoic metamorphism, but\r\ngenerally yield Precambrian zircon and Rb-Sr whole-rock ages.
\r\n\r\n\r\nThe second type of gneiss dome is exemplified by the Mascoma\r\nand Lebanon (Oliverian) Domes exposed about thirty miles to the east\r\nin central New Hampshire. No Precambrian rocks have been identified\r\nin the cores of these domes. Fieldwork indicates that the core of\r\nthe Mascoma Dome can be subdivided into two major units: (1) massive\r\ngneiss of intermediate igneous composition lying stratigraphically\r\nbeneath the Ordovician Ammonoosuc Volcanics, and (2) a sub-central\r\npluton of granite and quartz monzonite which crosscuts the massive\r\ngneiss and probably the Ammonoosuc Volcanics, but which lies\r\nunconformably beneath the Late Lower Silurian Clough Formation.\r\nWithin limits imposed by analytical uncertainty and the metamorphic\r\ndisturbance of the rocks, a common age of 440 \u00b1 40 million years\r\n(initial Sr87/Sr86 = 0.706 \u00b1 0.002) is determined for whole-rock\r\nsamples of the granitic sub-cores of the Lebanon and Mascoma Domes,\r\nand for whole-rock samples of the Ammonoosuc Volcanics. Zircon\r\nseparates from both the gneissic and granitic units within the core\r\nof the Mascoma Dome yield Pb207/Pb206 ages of 450 \u00b1 25 million years.\r\nThe data indicate that these domes formed in the following stages:\r\n(1) Ordovician volcanism followed by intrusion of granitic rocks,\r\n(2) uplift and local unroofing followed by deposition of Lower\r\nSilurian through Lower Devonian strata, and (3) garnet- to staurolite-\r\ngrade post-Lower Devonian metamorphism and deformation. Most of\r\nthe crosscutting relationships were established by Ordovician\r\nplutonic activity and not by post-Lower Devonian plutonic activity or\r\nanatexis. The core-rocks of these domes appear to be the result of\r\nvolcanic and intrusive activity towards the end of the Ordovician,\r\nand not the result of in-place remobilization or anatexis of Pre-\r\ncambrian basement subsequent to deposition of the mantling strata.\r\nThe other Oliverian Domes, particularly those in New Hampshire,\r\nresemble the Mascoma Dome, and probably originated in much the\r\nsame manner.
" }, { "name": "Savin, Samuel Marvin", "degree": "PhD", "year": "1967", "title": "Oxygen and Hydrogen Isotope Ratios in Sedimentary Rocks and Minerals", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:04272017-110202893", "creators": [ { "name": { "family": "Savin", "given": "Samuel Marvin" }, "id": "Savin-Samuel-Marvin", "display_name": "Savin, Samuel Marvin" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/TDA7-MG77", "abstract": "O18/O16 and D/H measurements were made on a\r\nvariety of sedimentary rocks and minerals, with special emphasis on the fine-grained, predominantly clay mineral fraction of the sediments. The interlayer water was removed from clay minerals prior to the isotopic analyses. Precision of the measurements was generally \u00b1 0.2 permil for oxygen and \u00b1 0.3 percent for hydrogen. In the case of zeolites the reproducibility was less constant because of difficulty encountered in removing zeolitic water.
\r\n\r\nListed in order of decreasing tendency to concentrate O18, the sedimentary minerals for which such data are available and their approximate isotopic fractionation factors relative to water at sedimentary temperatures are:
\r\n\r\n[See abstract for table].
\r\n\r\n\r\nMineral - water fractionations are related to\r\nthe types of chemical bonds in the minerals.
\r\n\r\n\r\nClay minerals which form under sedimentary conditions\r\nappear to form in isotopic equilibrium with their\r\nenvironments. Subsequent isotopic exchange may occur\r\neasily at elevated temperatures, but only extremely slowly\r\nat low temperatures.
\r\n\r\n\r\nOcean sediments which are detrital in origin\r\nhave isotopic compositions reflecting the fresh water origin\r\nof their clay minerals. There is no evidence for any isotopic\r\nexchange of detrital clay minerals with the marine\r\nenvironment in any of the ocean cores studied. (The sediments\r\ncould be as old as 250,000 years as determined by\r\nionium-thorium method.) Marine sediments which have large\r\nauthigenic components are generally enriched in O18, reflecting\r\nthe presence of phillipsite (\u03b4 O18 = +34 permil\r\nand montmorillonite \u03b4 O18 = +29 permil)e However, those\r\ncontaining a high concentration of iron and manganese\r\noxide may be isotopically light. (A manganese nodule had\r\n\u03b4 O18 = +15 permil.)
\r\n\r\n\r\nThe isotopic compositions of the clay minerals\r\nof ocean sediments are compatible with a weathering origin\r\nfor a kaolinite and a metamorphic or diagenetic origin for\r\nchlorite. Montmorillonite and illite are primarily of\r\nweathering origin but both of these minerals may have\r\ndiagenetic components.
\r\n\r\n\r\nThere is no evidence for any isotopic exchange of\r\nsand-sized quartz or feldspar in the sedimentary environment\r\nand these minerals may be used as indicators of provenance\r\nin sediments. The presence of a large authigenic feldspar\r\nor quartz component may be readily detected by oxygen isotopic\r\nanalysis. An authigenic feldspar had an O18/O16 ratio\r\nten permil greater than igneous feldspars.
\r\n\r\n\r\nCalculations have been performed to determine\r\nthe effect of weathering and the formation of sediments on\r\nthe isotopic composition of the hydrosphere. It is concluded\r\nthat those processes could have depleted the hydrosphere\r\n3 permil in O18 and enriched it 0.03 percent in\r\ndeuterium through the course of geologic time.
" }, { "name": "Aronson, James Louis", "degree": "PhD", "year": "1966", "title": "The Geochronology of the Plutonic and Metamorphic Rocks of New Zealand", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03102016-141714720", "creators": [ { "name": { "family": "Aronson", "given": "James Louis" }, "id": "Aronson-James-Louis", "display_name": "Aronson, James Louis" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/GZ9M-GP33", "abstract": "Extensive Rubidium-Strontium age determinations on both mineral\r\nand total rock samples of the crystalline rocks of New Zealand, which\r\nalmost solely crop out in the South Island, indicate widespread plutonic\r\nand metamorphic activity occurred during two periods, one about \r\n100-118 million years ago and the other about 340-370 million years ago.\r\nThe former results date the Rangitata Orogeny as Cretaceous. They\r\nassociate extensive plutonic activity with this orogeny which uplifted\r\nand metamorphosed the rocks of the New Zealand Geosyncline,\r\nalthough no field association between the metamorphosed geosynclinal\r\nrocks and plutonic rocks has been found. The Cretaceous plutonic\r\nrocks occur to the west in the Foreland Province in Fiordland, Nelson,\r\nand Westland, geographically separated from the Geosynclinal\r\nProvince. Because of this synchronous timing of plutonic and high\r\npressure metamorphic activity in spatially separated belts, the Rangitata\r\nOrogeny in New Zealand is very similar to late Mesozoic orogenic\r\nactivity in many other areas of the circum-Pacific margin (Miyashiro,\r\n1961).
\r\n\r\nThe 340-370 million year rocks, both plutonic and metamorphic,\r\nhave been found only in that part of the Foreland Province north of the\r\nAlpine Fault. There, they are concentrated along the west coast over \r\na distance of 500 km, and appear scattered inland from the coast.\r\nProbably this activity marks the outstanding Phanerozoic\r\nstratigraphic gap in New Zealand which occurred after the Lower\r\nDevonian.
\r\n\r\nA few crystalline rocks in the Foreland Province north of the\r\nAlpine Fault with measured ages intermediate between 340 and 120\r\nmillion years have been found. Of these, those with more than one\r\nmineral examined give discordant results. All of these rocks are\r\ntentatively regarded as 340-370 million year old rocks that have been\r\nvariously disturbed during the Rangitata Orogeny, 100-120 million\r\nyears ago.
\r\n\r\nIn addition to these two periods, plutonic activity, dominantly\r\nbasic and ultrabasic, but including the development of some rocks of\r\nintermediate and acidic composition, occurred along the margin of the\r\nGeosynclinal Province at its border with the Foreland Province during\r\nPermian times about 245 million years ago, and this activity possibly\r\nextended into the Mesozoic.
\r\n\r\nEvidence from rubidium-strontium analyses of minerals and a\r\ntotal rock, and from uranium, thorium, and lead analyses of uniform\r\neuhedral zircons from a meta-igneous portion of the Charleston\r\nGneiss, previously mapped as Precambrian, indicate that this rock\r\nis a 350-370 million year old plutonic rock metamorphosed 100 million\r\nyea rs ago during the Rangitata Orogeny. No crystalline rocks with\r\nprimary Precambrian ages have been found in New Zealand. However,\r\nPb207/Pb206 ages of 1360 million years and 1370 million years have\r\nbeen determined for rounded detrital zircons separated from each of\r\ntwo hornfels samples of one of New Zealand's olde st sedimentary units,\r\nthe Greenland Series. These two samples were metamorphosed 345-\r\n370 million years ago. They occur along the west coast, north of the\r\nAlpine Fault, at Waitaha River and Moeraki River, separated by 135\r\nkm. The Precambrian measured ages are most likely minimum ages\r\nfor the oldest source area which provided the detrital zircons because\r\nthe uranium, thorium and lead data are highly discordant. These\r\nresults are of fundamental importance for the tectonic picture of the\r\nSouthwest Pacific margin and demonstrate the existence of relatively\r\nold continental crust of some lateral extent in the neighborhood of New\r\nZealand.
" }, { "name": "Hollister, Lincoln Steffens", "degree": "PhD", "year": "1966", "title": "Electron Microprobe Investigations of Metamorphic Reactions and Mineral Growth Histories, Kwoiek Area, British Columbia", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechTHESIS:03282016-092324853", "creators": [ { "name": { "family": "Hollister", "given": "Lincoln Steffens" }, "id": "Hollister-Lincoln-Steffens", "display_name": "Hollister, Lincoln Steffens" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/0ZA2-QX80", "abstract": "The Kwoiek Area of British Columbia contains a pendant or screen\r\nof metamorphosed sedimentary and volcanic rocks almost entirely\r\nsurrounded by a portion of the Coast Range Batholith, and intruded by\r\nseveral dozen stocks. The major metamorphic effects were produced by\r\nthe quartz diorite batholithic rocks, with minor and later effects by\r\nthe quartz diorite stocks. The sequence of important metamorphic\r\nreactions in the metasedimentary and metavolcanic rocks, ranging in\r\ngrade from chlorite to sillimanite, is:
\r\n\r\n1. chlorite + carbonate + muscovite \u2192 epidote + biotite
\r\n2. chlorite + carbonate \u2192 actinolite + epidote
\r\n3. chlorite + muscovite \u2192 garnet + biotite
\r\n4. chlorite + epidote \u2192 garnet + hornblende
\r\n5. chlorite + muscovite \u2192 garnet + staurolite + biotite
\r\n6. chlorite + muscovite \u2192 aluminum silicate + biotite
\r\n7. muscovite + staurolite \u2192 garnet + aluminum silicate + biotite
\r\n8. staurolite \u2192 garnet + aluminum silicate
\r\n\r\nContinuous reactions, occurring between reactions 5 and 7, are:
\r\n\r\nA. chlorite + (high Ti) biotite + Al2O3 (from plagioclase?)\u2192 \r\ngarnet + staurolite + (low Ti) biotite + O2
\r\nB. muscovite (phengitic) \u2192 garnet + staurolite +muscovite (less\r\nphengitic) + O2 (?)
\r\n\r\nDetailed electron microprobe work on garnet, staurolite, biotite,\r\nand chlorite shows that:
\r\n\r\n(1) The garnet porphyroblasts are zoned according to a depletion\r\nmodel, called the Rayleigh depletion model, which assumes equilibrium\r\nbetween the edge of a growing garnet and the minerals which are\r\nunzoned, notably biotite, chlorite, and muscovite, but which assumes\r\ndisequilibrium within the garnet.
\r\n\r\n(2) The staurolite porphyroblasts are also zoned, and from their\r\nzoning patterns reactions A, B, and 5 are documented. Progressive\r\nreduction of iron with increasing grade of metamorphism is also\r\ninferred from the staurolite zoning patterns.
\r\n\r\n(3) During a late period of falling temperature garnet continued\r\nto grow and the biotite and chlorite reequilibrated. The biotite,\r\nchlorite, and garnet edge compositions can vary from point to point in\r\na given thin section, indicating that the volume of equilibrium at the\r\nfinal stage of metamorphism was only a few cubic microns.
\r\n\r\n(4) The horizon within the garnet that grew at maximum temperature\r\ncan be identified. The Mg/Fe ratio of this horizon, if the garnet\r\ncomposition is a limiting composition in the Al2O3 - K2O - FeO - MgO\r\ntetrahedron, increases systematically with increasing metamorphic\r\ngrade. Biotite and chlorite compositions also show a general increase\r\nin Mg/Fe ratio with increasing metamorphic grade, but staurolite\r\nappears to show the reverse effect.
\r\n\r\n(5) The Mg/Fe ratio at the maximum temperature horizon of the\r\ngarnet porphyroblasts is a function of its Mn content as evidenced\r\nfrom the study of five garnet-bearing rocks, collected from one outcrop\r\narea, with the same assemblage but with differing proportions of\r\nminerals.
\r\n\r\nAn important implication of zoned minerals is that the effective\r\ncomposition of a system in a phase lies on the join between\r\nthe homogeneous minerals (if there are two) and not within three-or-\r\nfour-phase fields when a zoned mineral, such as garnet or staurolite, \r\nis present in the assemblage.
\r\n\r\nStudy of the three aluminum silicates found in the Kwoiek Area\r\nshowed that a constant pressure change in polymorphs from andalusite\r\nto kyanite to sillimanite took place with increasing temperature.\r\nThis transition series is best explained by the metastable formation\r\nof andalusite.
\r\n\r\nPhotographic materials on pages 15, 121, 160, 162, and 164 are\r\nessential and will not reproduce clearly on Xerox copies. Photographic\r\ncopies should be ordered.
" }, { "name": "Johnson, Lane Richard", "degree": "PhD", "year": "1966", "title": "Measurements of Mantle Velocities of P Waves with a Large Array", "advisor": "Smith, Stewart W.; Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:03252016-135744669", "creators": [ { "name": { "family": "Johnson", "given": "Lane Richard" }, "id": "Johnson-Lane-Richard", "display_name": "Johnson, Lane Richard" } ], "advisors": [ { "name": { "family": "Smith", "given": "Stewart W." }, "id": "Smith-Stewart-W", "role": "advisor", "display_name": "Smith, Stewart W." }, { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/D44Y-6K65", "abstract": "A large array has been used to investigate the P-wave\r\nvelocity structure of the lower mantle. Linear array processing\r\nmethods are reviewed and a method of nonlinear processing is\r\npresented. Phase velocities, travel times, and relative amplitudes\r\nof P waves have been measured with the large array at the Tonto\r\nForest Seismological Observatory in Arizona for 125 earthquakes\r\nin the distance range of 30 to 100 degrees. Various models are\r\nassumed for the upper 771 km of the mantle and the Wiechert-Herglotz\r\nmethod applied to the phase velocity data to obtain a velocity\r\ndepth structure for the lower mantle. The phase velocity data\r\nindicates the presence of a second-order discontinuity at a depth of\r\n840 km, another at 1150 km, and less pronounced discontinuities at\r\n1320, 1700 and 1950 km. Phase velocities beyond 85 degrees are\r\ninterpreted in terms of a triplication of the phase velocity curve, and\r\nthis results in a zone of almost constant velocity between depths of\r\n2670 and 2800 km. Because of the uncertainty in the upper mantle\r\nassumptions, a final model cannot be proposed, but it appears that\r\nthe lower mantle is more complicated than the standard models and\r\nthere is good evidence for second-order discontinuities below a depth\r\nof 1000 km. A tentative lower bound of 2881 km can be placed on the\r\ndepth to the core. The importance of checking the calculated velocity\r\nstructure against independently measured travel times is pointed out.\r\nComparisons are also made with observed PcP times and the agreement\r\nis good. The method of using measured values of the rate of\r\nchange of amplitude with distances shows promising results." }, { "name": "Roddy, David John", "degree": "PhD", "year": "1966", "title": "The Paleozoic Crater at Flynn Creek, Tennessee", "advisor": "Shoemaker, Eugene Merle; Allen, Clarence R.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10122017-143849391", "creators": [ { "name": { "family": "Roddy", "given": "David John" }, "id": "Roddy-David-John", "display_name": "Roddy, David John" } ], "advisors": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-E-M", "role": "advisor", "display_name": "Shoemaker, Eugene Merle" }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/thqy-nk77", "abstract": "Flynn Creek crater, approximately 330 feet deep and 11,500 feet \r\nin diameter, was formed in north central Tennessee in Middle or Late \r\nDevonian time. Impact of a large meteorite or comet probably produced \r\nthe crater, which later became filled with Upper Devonian shale and \r\ncovered by Lower Mississippian chert. Major structural elements\r\ninclude a zone of highly deformed rim strata surrounding a crater\u00ad \r\nshaped depression. A large central uplift occurs in the middle of \r\nthe crater.
\r\n\r\nFlat-lying Middle and Upper Ordovician limestones surrounding \r\nthe crater have been irregularly uplifted 30 to 150 feet in the rim \r\nand are moderately to tightly folded producing radial shortening\r\nas great as 35 percent.\tTypes of rim deformation include normal \r\nfaults, thrust faults and asymmetric antic lines, synclines and\r\nmonoclines, all approximately concentric to the crater walls. Part \r\nof the southeastern rim has been thrust up and away from the crater \r\nand partly overrides a large tilted and folded graben. A chaotic \r\nlimestone breccia ejected from the crater during its formation now \r\noverlies the graben and covers part of the ground surface that was \r\npresent when the crater was formed.
\r\n\r\nThe crater floor is underlain by a chaotic limestone breccia \r\nwith fragments derived from the same rock units now exposed in the \r\nrim. Fragments range from less than a fraction of an inch to blocks \r\n300 feet in length. In the center of the crater a sequence of\r\nhighly deformed Middle Ordovician limestone and dolomite of \r\nthe Stones River Group and Lower Ordovician limestone and dolomite of \r\nthe Knox Group rises nearly 300 feet above the crater floor. Knox \r\nstrata are raised as much as 1000 feet above their normal position \r\nand locally contain shatter cones.
\r\n\r\nBreccia contacts with folded rim strata are sharp in some parts \r\nof the rim but are jumbled and gradational in other parts. Intense \r\ntwinning in calcite is common in an irregular zone a few feet to \r\nseveral hundred feet wide adjacent to the crater wall in the \r\ndeformed rim. Abundant microtwinned lamellae are common in the \r\ndeformed calcite, and kink bands occur in some crystals.
\r\n\r\nA thin sequence of marine bedded breccias and dolomite was \r\ndeposited in the crater during early Late Devonian time and was \r\nimmediately overlain by Chattanooga Shale, whose lower unit filled \r\nthe crater with nearly 300 feet of sediments. Lower Mississippian \r\nchert and limestone later covered the area.
\r\n\r\nA search for high-pressure polymorphs and for volcanic or\r\nmeteoritic material was unsuccessful. A detailed gravity study \r\nindicates no gravity anomaly on the level of one milligal is associated \r\nwith the crater at Flynn Creek.\tMagnetic studies also show that there are no\r\nlarge magnetic anomalies associated with the structure.
\r\n\r\nStructural comparisons between Flynn Creek crater and maars\r\nand diatremes show little or no similarity in types of deformation. \r\nConsideration of volcanic gas-phreatic eruption processes suggests \r\nthat brittle fracture should accompany cratering with relatively \r\nlittle folding in the rim strata, unlike the deformation at Flynn\r\nCreek. Structural comparisons between Flynn Creek crater and meteorite \r\nimpact, nuclear explosion and chemical explosion craters show good \r\nagreement in nearly all types of deformation. A recently formed,\r\nlarge chemical explosion crater in Canada has both a central uplift and \r\ndeformed rim very similar to Flynn Creek crater. Similarities in structural \r\ndeformation between shock-produced craters and Flynn Creek crater suggest\r\nan origin by meteorite or comet impact.
" }, { "name": "Sellers, George August", "degree": "PhD", "year": "1966", "title": "Hydrothermal Experiments on the Thermal Stability of Amino Substances in Sediments", "advisor": "Degens, Egon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02182016-153430010", "creators": [ { "name": { "family": "Sellers", "given": "George August" }, "id": "Sellers-George-August", "display_name": "Sellers, George August" } ], "advisors": [ { "name": { "family": "Degens", "given": "Egon T." }, "id": "Degens-Egon-T", "role": "advisor", "display_name": "Degens, Egon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/as0h-1z63", "abstract": "Aspartic acid, threonine, serine and other thermally unstable\r\namino acids have been found in fine-grained elastic sediments of advanced\r\ngeologic age. The presence of these compounds in ancient sediments\r\nconflicts with experimental data determined for their simple\r\nthermal decomposition.
\r\n\r\nRecent and Late Miocene sediments and their humic acid\r\nextracts, known to contain essentially complete suites of amino acids,\r\nwere heated with H2O in a bomb at temperatures up to 500\u00b0C in order\r\nto compare the thermal decomposition characteristics of the sedimentary\r\namino compounds.
\r\n\r\nMost of the amino acids found in protein hydrolyzates are\r\nobtained from the Miocene rock in amounts 10 to 100 times less than\r\nfrom the Recent sediment. The two unheated humic acids are rather\r\nsimilar despite their great age difference. The Miocene rock appears\r\nuncontaminated by Recent carbon.
\r\n\r\nYields of amino acids generally decline in the heated Recent\r\nsediment. Some amino compounds apparently increase with heating time\r\nin the Miocene rock.
\r\n\r\nRelative thermal stabilities of the amino acids in sediments\r\nare generally similar to those determined using pure aqueous solutions.\r\nThe relative thermal stabilities of glutamic acid, glycine, and phenylalanine\r\nvary in the Recent sediment but are uniform in the Miocene\r\nrock.
\r\n\r\nAmino acids may occur in both proteins and humic complexes\r\nin the Recent sediment, while they are probably only present in stabilized\r\norganic substances in the Miocene rock. Thermal decomposition of\r\nprotein amino acids may be affected by surface catalysis in the Recent\r\nsediment. The apparent activation energy for the decomposition of\r\nalanine in this sediment is 8400 calories per mole. Yields of amino\r\ncompounds from the heated sediments are not affected by thermal decomposition\r\nonly.
\r\n\r\nAmino acids in sediments may only be useful for geothermometry\r\nin a very general way.
\r\n\r\nA better picture of the amino acid content of older sedimentary\r\nrocks may be obtained if these sediments are heated in a bomb\r\nwith H2O at temperatures around 150\u00b0C prior to HCl hydrolysis.
\r\n\r\nLeucine-isoleucine ratios may prove to be useful as indicators\r\nof amino acid sources or for evaluating the fractionation of\r\nthese substances during diagenesis. Leucine-isoleucine ratios of the\r\nRecent and Miocene sediments and humic acids are identical. The humic\r\nacids may have a continental source.
\r\n\r\nThe carbon-nitrogen and carbon-hydrogen ratios of sediments\r\nand humic acids increase with heating time and temperature. Ratios\r\ncomparable to those in some kerogens are found in the severely heated\r\nMiocene sediment and humic acid.
" }, { "name": "Teng, Ta-Liang", "degree": "PhD", "year": "1966", "title": "Body-Wave and Earthquake Source Studies", "advisor": "Anderson, Donald L.; Press, Frank", "url": "https://resolver.caltech.edu/CaltechTHESIS:09282017-160405428", "creators": [ { "name": { "family": "Teng", "given": "Ta-Liang" }, "id": "Teng-Ta-Liang", "display_name": "Teng, Ta-Liang" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." }, { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/9VPH-AN84", "abstract": "The present work concerns a study on the radiation and propagation\r\nof seismic body waves. Based on a reformulated seismic ray\r\ntheory and supplemented by the results of several associated\r\nboundary value problems, a method of body wave equalization is\r\ndescribed which enables the extrapolation of body-wave fields from\r\none point to another.
\r\n\r\n\r\nApplications of the above method to studies of earthquake\r\nsource mechanism and earth's structure, specifically its anelasticity,\r\nare presented. The findings for two deep-focus earthquakes can be\r\nsummarized by: (1) a displacement dislocation source, or an\r\nequivalent double couple, can generally explain the observed radiation\r\nfields, (2) the source time functions can be explained by a\r\nbuild-up step (1 - e -t/\u03c4)H(t), and \u03c4 appears to be longer for larger\r\nearthquakes, (3) the total energy calculated from equalized spectrums\r\nis: for the Banda Sea earthquake (M = 6-1/4 - 6-3/4), E = 1.01x1022\r\nergs; and for the Brazil earthquake (M = 6-3/4 - 7), E = 2.56x1023\r\nergs.
\r\n\r\n\r\nFrom the spectral ratios pP/P and P/P, it is found (1) that\r\nthe upper 430 km of the mantle has an average Q\u0251 = 105, (2) that Q\u0251\r\nincreases very slowly until depth of about 1000 km, and (3) that\r\nQ\u0251 rises rapidly beyond a depth of 1000 km, remains a high value\r\nin the lower mantle and drops sharply toward the core-mantle \r\nboundary.
" }, { "name": "Wu, Francis Taming", "degree": "PhD", "year": "1966", "title": "Part I. Lower Limit of the Total Energy of Earthquakes and Partitioning of Energy Among Seismic Waves. Part II. Reflected Waves and Crustal Structures", "advisor": "Anderson, Donald L.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11042016-160516864", "creators": [ { "name": { "family": "Wu", "given": "Francis Taming" }, "id": "Wu-Francis-Taming", "display_name": "Wu, Francis Taming" } ], "advisors": [ { "name": { "family": "Anderson", "given": "Donald L." }, "id": "Anderson-D-L", "role": "advisor", "display_name": "Anderson, Donald L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/4VK8-6245", "abstract": "Part I:
\r\nThe basic formulae for estimating the energy in the seismic waves are derived. The formulae take into account the radiation pattern of the source, the compensation for the non-elastic absorption of the waves, the velocity-density structure of the earth, the effects of the crustal structure under the receiver and the response of the recording instruments. Operations are performed in the frequency domain.
\r\n\r\nEstimation of the seismic energy of an earthquake is closely related to the determination of the source mechanism and the radiation pattern of the source. We have determined the surface wave radiation pattern of a shallow shock and the P wave radiation pattern of an intermediate shock to show the correspondence between the fault-plane solutions and the fault mechanisms derived from radiation pattern.
\r\n\r\nWe have obtained the energies of the two earthquakes mentioned above as well as 7 other earthquakes with known fault-plane solutions and/or radiation patterns. The \"total\" seismic energies for these earthquakes (magnitudes between 6 1/2 and 7 1/2) using the present procedures are at least an order of magnitude higher than those arrived at from the current magnitude-energy formula. The S wave energies are approximately an order higher than that of the P waves.\r\nThe surface wave energies for the shallow shocks are three orders of magnitude less than the body wave energies. Thus, the S wave seems to be the main seismic wave energy carrier.
\r\n\r\nEnergies in the lower order spheroidal oscillations (\u2113 = 2, 15) for the 1964 Alaskan earthquake have been calculated from Isabella strain data and Berkeley ultra-long period pendulum seismometer data. The sum of the energies is 1023 ergs.
\r\n\r\n\r\nPart II:
\r\n\r\nHaskell's formulation for reflection of the body waves at the\r\nbase of a solid crust is extended to include overlying liquid layers.\r\nNormalized displacement and the phase shift at the base of the crust\r\nas a function of angle of incidence and frequency are calculated for\r\ntwo continental models and an oceanic model. Complex reflection\r\ncoefficients are inverse-Fourier transformed numerically to the\r\ntime domain to show the change of pulse shape upon reflection. These\r\ntime traces show that the water layer of the oceanic model causes\r\nthe main difference between continental and oceanic reflections.\r\nSample seismograms from a deep shock were compared to the theoretical\r\nrecords; they are found to be consistent. PP waves from a deep\r\nearthquake recorded at Tonto Forest Seismic Array were processed to\r\ndisplay the details of an oceanic PP wave.
\r\n\r\n" }, { "name": "Archambeau, Charles Bruce", "degree": "PhD", "year": "1965", "title": "Elastodynamic Source Theory", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechETD:etd-01102003-112222", "creators": [ { "name": { "family": "Archambeau", "given": "Charles Bruce" }, "id": "Archambeau-Charles-Bruce", "display_name": "Archambeau, Charles Bruce" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/A3XS-PS89", "abstract": "The mathematical formulation and evaluation of the radiation field for general elastodynamic sources is given and applications of the theory to the description of source fields of geophysical interest are treated. The study was primarily undertaken to provide a theoretical basis for estimating the properties of the tectonic stress field and parameters of rupture phenomenon in the earth through observations of the radiation field from earthquakes and other tectonic sources.\r\n\r\nThus the description of the tectonic source is particularly emphasized, both as to its physical origins and with respect to the radiation field to be expected from it. The mathematical description of the tectonic source field is achieved in terms of an elastic relaxation theory of radiation which corresponds to a generalized initial value problem involving the initial prestress field. As a consequence, the radiation field is obtained in terms of the rupture expansion rate (velocity of rupture), the rupture dimensions and orientation and the magnitude and orientation of the initial stress field. Inertial conditions are inherent in the relaxation theory so that the time dependence of the field is automatically specified. Careful attention is given to causality relationships so that the resulting field expressions contain the complicated space-time relationships associated with a tectonic source field. Energy and equilibrium relations are considered and expressions are obtained for the estimated energy release and the final static field in terms of the source parameters.\r\n\r\nDetailed properties of the radiation field are given in the form of source field amplitude and phase spectra. Spatial radiation patterns are obtained showing the direction properties as functions of frequency, prestress and other source parameters. Similar results are given for shock induced rupture under prestress conditions, along with estimates of tectonic energy release.\r\n\r\nIt is concluded that the theoretical predictions for the properties of the radiation field from a spontaneous rupture source are in general agreement with the actual observations of the field from such a source, but that accurate estimates of the prestress and rupture parameters require a more complete coverage and analysis of the field than is usually the case. It is concluded from a preliminary analysis of the Ranier nuclear explosion that tectonic energy release did occur and that the anomalous radiation observed would correspond to a prestress shear field of the order of 20 bars.\r\n\r\nThe most likely mechanism of rupture at depth in the earth is considered to be unstable creep phenomenon resulting in phase change (melting) and the rupture source models adopted are not inconsistent with this hypothesis." }, { "name": "Cisternas, Armando", "degree": "PhD", "year": "1965", "title": "Part I. The Radiation of Elastic Waves from a Spherical Cavity in a Half Space. Part II. Precision Determination of Focal Depths and Epicenters of Earthquakes", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechTHESIS:03202015-145559091", "creators": [ { "name": { "family": "Cisternas", "given": "Armando" }, "id": "Cisternas-Armando", "display_name": "Cisternas, Armando" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/K750-5J16", "abstract": "Part I: The dynamic response of an elastic half space to an explosion in a buried spherical cavity is investigated by two methods. The first is implicit, and the final expressions for the displacements at the free surface are given as a series of spherical wave functions whose coefficients are solutions of an infinite set of linear equations. The second method is based on Schwarz's technique to solve boundary value problems, and leads to an iterative solution, starting with the known expression for the point source in a half space as first term. The iterative series is transformed into a system of two integral equations, and into an equivalent set of linear equations. In this way, a dual interpretation of the physical phenomena is achieved. The systems are treated numerically and the Rayleigh wave part of the displacements is given in the frequency domain. Several comparisons with simpler cases are analyzed to show the effect of the cavity radius-depth ratio on the spectra of the displacements.
\r\n\r\nPart II: A high speed, large capacity, hypocenter location program has been written for an IBM 7094 computer. Important modifications to the standard method of least squares have been incorporated in it. Among them are a new way to obtain the depth of shocks from the normal equations, and the computation of variable travel times for the local shocks in order to account automatically for crustal variations. The multiregional travel times, largely based upon the investigations of the United States Geological\r\nSurvey, are confronted with actual traverses to test their validity.
\r\n\r\nIt is shown that several crustal phases provide control enough to obtain good solutions in depth for nuclear explosions, though not all the recording stations are in the region where crustal corrections are considered. The use of the European travel times, to locate the French nuclear explosion of May 1962 in the Sahara, proved to be more adequate than previous work.
\r\n\r\nA simpler program, with manual crustal corrections, is used to process the Kern County series of aftershocks, and a clearer picture of tectonic mechanism of the White Wolf fault is obtained.
\r\n\r\nShocks in the California region are processed automatically and statistical frequency-depth and energy depth curves are discussed in relation to the tectonics of the area.
\r\n" }, { "name": "Garlick, George Donald", "degree": "PhD", "year": "1965", "title": "Oxygen Isotope Ratios in Coexisting Minerals of Regionally Metamorphosed Rocks", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechTHESIS:03192015-140536982", "creators": [ { "name": { "family": "Garlick", "given": "George Donald" }, "id": "Garlick-George-Donald", "display_name": "Garlick, George Donald" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/YC63-0F49", "abstract": "The O18/O16 ratios of coexisting minerals from a number of regionally metamorphosed rocks have been measured, using a bromine pentafluoride extraction-technique. Listed in order of their increasing tendency to concentrate O18, the minerals analyzed are magnetite, ilmenite, chlorite, biotite, garnet, hornblende, kyanite, muscovite, feldspar, and quartz. The only anomalous sequence detected occurs in a xenolith of schist, in which quartz, muscovite, biotite, and ilmenite, but not garnet, have undergone isotopic exchange with surrounding trondjemite.
\r\n\r\nWith few exceptions, quartz-magnetite and quartz-ilmenite fractionations decrease with increasing metamorphic grade determined by mineral paragenesis and spatial distribution. This consistency does not apply to quartz-magnetite and quartz-ilmenite fractionations obtained from rocks in which petrographic evidence of retrogradation is present.
\r\n\r\nWhereas measured isotopic fractionations among quartz, garnet, ilmenite, and magnetite are approximately related to metamorphic grade, fractionations between these minerals and biotite or muscovite show poor correlation with grade. Variations in muscovite-biotite fractionations are relatively small. These observations are interpreted to mean that muscovite and biotite are affected by retrograde re-equilibration to a greater extent than the anhydrous minerals analyzed.
\r\n\r\nMeasured quartz-ilmenite fractionations range from 12 permil in the biotite zone of central Vermont to 6.5 permil in the sillimanite-orthoclase zone of southeastern Connecticut. Analyses of natural assemblages from the kyanite and sillimanite zones suggest that equilibrium quartz-ilmenite fractionations are approximately 8 percent smaller than corresponding quartz-magnetite fractionations. Employing the quartz-magnetite geothermometer calibrated by O'Neil and Clayton (1964), a temperature of 560\u00b0C was obtained for kyanite-bearing schists from Addison County, Vermont. Extending the calibration to quartz-ilmenite fractionations, a temperature of 600\u00b0C was obtained for kyanite-schists from Shoshone County, Idaho. At these temperatures kyanite is stable only at pressures exceeding 11 kbars (Bell, 1963), corresponding to lithostatic loads of over 40 km.
\r\n" }, { "name": "Hooke, Roger LeBaron", "degree": "PhD", "year": "1965", "title": "Alluvial Fans", "advisor": "Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04162003-095459", "creators": [ { "name": { "family": "Hooke", "given": "Roger LeBaron" }, "id": "Hooke-Roger-LeBaron", "display_name": "Hooke, Roger LeBaron" } ], "advisors": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/4KN6-1E95", "abstract": "NOTE: Text or symbols on renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\n\r\nAlluvial fans were studied in the field, largely in the desert regions of California, and in the laboratory. Field study consisted of detailed mapping of ages and sizes of debris, channel patterns, and deposits of different types on parts of four fans, and reconnaissance work on over 100 additional fans. Reconnaissance generally consisted of outlining the fan, noting material size and channel patterns, and measuring a few slopes. In the laboratory small alluvial fans were built of mud and sand transported through a channel into a five-foot square box under controlled conditions.\r\n\r\nMaterial is transported to fans by debris flows or water flows which follow the main channel. This channel is generally incised at the fanhead, because there water is able to transport on a lower slope the material deposited earlier by debris flows. Since the main channel at the fanhead has a lower slope than the adjacent fan surface, it emerges onto the surface near a midfan point herein called the intersection point. On the laboratory fans most deposition above the intersection point is by debris flows that exceed the depth of the incised channel. Fluvial deposition dominates below the intersection point. This is also inferred to be true on natural fans.\r\n\r\nFans deficient in fine material may have so high an infiltration rate that even moderately large discharges are completely absorbed before reaching the toe of the fan. Under these conditions the coarse debris in transport is deposited as lobate masses on the fan. In many respects these deposits resemble and may, in the past, have been mistaken for debris-flow deposits.\r\n\r\nThe empirical relationship between fan area, A[subscript f], and drainage-basin area, A[subscript d] = cA[subscript d][superscript n] has been recognized previously (Bull, 1964; Denny, 1965). The present study suggests that this relationship results from a tendency toward a quasi steady-state between coalescing fans in the same lithologic, tectonic, and geographic environment. The quasi steady-state exists when all fans are increasing in thickness at the same rate. If rates differ, the areas of the fans will change to approach a quasi steady-state. The rate of deposition is determined by the influx of debris, which is a function of drainage basin area. The exponent [...] is less than unity because a storm of a given recurrence interval is less likely to envelop a large drainage basin than a small one. The coefficient [...] is a function of the lithologic, tectonic, and geographic environment.\r\n\r\nRates of deposition on fans may be estimated from this relationship using Langbein and Schumm's (1958) data on sediment yield as a function of precipitation. A typical average rate is on the order of one foot per 1,000 years. If a long-term tectonic process is superimposed upon the quasi steady-state relationship between fans in the same lithologic and geographic environment, the rate of deposition may be used to estimate the rate and nature of the tectonic process. As an example, the difference in depositional rates on opposite sides of Death Valley suggests a present rate of eastward tilting of 0.018 degrees/1000 years.\r\n\r\nThe slope of an alluvial fan is determined primarily by debris size and water discharge. Large fans have larger drainage basins and hence larger discharges than small fans. Consequently fan slope generally decreases with increasing fan area.\r\n\r\nPhotographic materials on pages 16, 31, 33, 55, 63, 64, and 81 are essential and will not reproduce clearly on Xerox copies. Photographic copies should be ordered.\r\n" }, { "name": "Sharp, Robert Victor", "degree": "PhD", "year": "1965", "title": "Geology of the San Jacinto Fault Zone in the Peninsular Ranges of Southern California", "advisor": "Allen, Clarence R.; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12122003-091348", "creators": [ { "name": { "family": "Sharp", "given": "Robert Victor" }, "id": "Sharp-Robert-Victor", "display_name": "Sharp, Robert Victor" } ], "advisors": [ { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/B37R-MD73", "abstract": "The San Jacinto fault zone is one of the major branches of the San Andreas fault system in southern California. The straightness, continuity, and high seismicity of the San Jacinto fault zone suggest that it may be currently the most important member of the system.
\r\n\r\nAlthough alluvium conceals much of the San Jacinto fault, intrusive rocks of the mid-Cretaceous southern California batholith are exposed together with prebatholithic metamorphic rocks along a 50-mile segment in the northeastern Peninsular Ranges. The prebatholithic terrane on both sides of the fault consists of migmatitic gneiss and minor amounts of amphibolite, quartzite, marble, and metaconglomerate. Between San Jacinto and Clark Valleys, various members of a distinctive sequence of metamorphic rocks and gabbroic, tonalitic, and adamellitic plutons are separated by the fault 13 1/2 to 15 miles in the right-lateral sense. A marker section of relatively marble-rich metamorphic rocks within and parallel to a regionally unique post-intrusion zone of cataclastic deformation exposed at the southern end of the Santa Rosa Mountains and at Coyote Mountain is separated between 8 and 13 miles.
\r\n\r\nGeometric extrapolation of the various contacts suggests the southwestern block has risen between 1/2 and possibly 8 miles near Anza and between 0 and 6 miles near Clark Valley. Small net vertical movement near Clark Valley may correspond to relatively large vertical offsets near Anza. The sense of vertical movements probably has reversed repeatedly throughout the history of the fault.
\r\n\r\nThe right-lateral component of the net displacement probably increases southeastward from about 14 miles near San Jacinto Valley to between 14 1/2 and 17 miles, but conceivably as much as 22 1/2 miles, near Clark Valley. North of Anza, Quaternary gravels are offset at least 2 miles, and stream courses are displaced at least 2300 feet and possibly 3200 feet. Drainage lines north of Clark Valley have been offset possibly 3 miles in Quaternary time.
\r\n\r\nThe displacement on the San Jacinto fault suggests that (1) the line of major displacement within the San Jacinto fault zone extends southeastward into the central part of Imperial Valley and may connect with the Imperial fault, (2) the Banning fault at the southern margin of the San Bernardino Mountains may be the offset continuation of the Sierra Madre fault on the southern flank of the San Gabriel Mountains, and (3) if the displacement on the San Andreas fault is as large as 160 miles, the San Jacinto fault has not always been as important a member of the larger system as its current activity suggests.
" }, { "name": "Biehler, Shawn", "degree": "PhD", "year": "1964", "title": "A Geophysical Study of the Salton Trough of Southern California", "advisor": "Press, Frank; Allen, Clarence R.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10142002-105706", "creators": [ { "name": { "family": "Biehler", "given": "Shawn" }, "id": "Biehler-Shawn", "display_name": "Biehler, Shawn" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" }, { "name": { "family": "Allen", "given": "Clarence R." }, "id": "Allen-C-R", "role": "advisor", "display_name": "Allen, Clarence R." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/ZZ33-6E45", "abstract": "More than 2300 gravity observations were made in the northern end of the Salton trough, including an underwater gravity survey of the Salton Sea. 400 gravity observations by Kovach are used to extend the gravity map southward and 700 gravity observations from oil companies and Woollard are used for part of the regional control. A complete Bouguer anomaly map of the California portion of the Salton trough area shows that the general trend of the isogal contours is parallel to the over-all northwest trend of the tectonic pattern. The contours northeast of the Coachella Valley trend east parallel to the Transverse Range structure. The Coachella Valley and Borrego sink are associated with gravity lows, the Salton volcanic domes with a gravity maximum, and the Peninsular Ranges with a gravity minimum. The anomalous mass of the Salton volcanic domes is 6 to 7 km deep with a radius of 3.5 to 4.5 km based on the \"half-width\" interpretation of a sphere. Due to uncertainties arising from contemporaneous metamorphism of the sediments and the ambiguity in the regional gravity field a detailed interpretation was not attempted.
\r\n\r\nAll of the major fault zones are associated with small gravity lows. A series of these small lows southeast along the projected trace of the Banning-Mission Creek fault may indicate continuation of faulting toward Yuma, Arizona. The steep gravity gradient across this fault in the Coachella Valley can be explained by a steep contact between crystalline rock and sediments which exceed 4 km thickness in the Indio-Mecca area.
\r\n\r\nSeismic refraction profiles were established at Thousand Palms, Truckhaven, Frink, and Westmorland. These give depths to basement of 4350, 5540, 7340, and 18,300 ft respectively. The Westmorland profile establishes the depth to basement near the center of the trough.
\r\n\r\nRegional gravity studies indicate that much of the gravity low over the Peninsular Ranges can be explained by a thickening of the crust from 29 to 33 km. The Imperial Valley, with over 5.5 km of sediments, is anomalously associated with a broad gravity high. This is interpreted in terms of a thinning crust under the valley possibly to a depth of 21 km, relative to 29 km at San Diego. The crustal structure of the Imperial Valley is probably the northward continuation of the structure of the Gulf of California and may represent the initial stages of an alteration from continental to oceanic type section by rifting and northwest movement of the Baja California peninsula and western California relative to the stable area northeast of the San Andreas fault system.
\r\n" }, { "name": "Blandford, Robert Roy", "degree": "PhD", "year": "1964", "title": "Stratified Inertial Flow in the Gulf Stream", "advisor": "Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechETD:etd-10142002-113121", "creators": [ { "name": { "family": "Blandford", "given": "Robert Roy" }, "id": "Blandford-Robert-Roy", "display_name": "Blandford, Robert Roy" } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/JSQN-6Y34", "abstract": "Earlier theoretical models of the Gulf Stream have treated the motion of a single fluid layer of constant density and vertically uniform flow velocity. As a step toward models with continuous stratification, the present work analyses inviscid, steady-state, purely inertial flow using two moving layers of different density and velocity.
\r\n\r\nThe first type of Gulf Stream model analysed consists of two layers of different densities flowing over a denser layer at rest (baroclinic model). The second has two layers of different densities flowing over a rigid, horizontal bottom (mixed barotropic-baroclinic model).
\r\n\r\nIn both models there exist, at any latitude, either 0, 2, or 4 theoretical solutions to the flow problem. Only one such solution, however, is realistic and satisfies the boundary condition of vanishing northward velocity at the southern latitude boundary of the flow region considered. This is called the correct solution, while the others are called incorrect solutions. As the parameters of the two-layer models converge to limiting values corresponding to one-layer models (for example, vanishing density difference between the upper and lower layers), the solutions may or may not converge to the one-layer solutions. If a correct solution converges uniformly, the limit is called a correct limit. If convergence is non-uniform at some value of the latitude coordinate, the limit is called an incorrect limit. If no solutions exist as the limit is approached, it is an impossible limit.
\r\n\r\nThe most important limits discussed are as follows:
\r\n\r\n1. As the density contrast between the upper and lower moving layers becomes large in a baroclinic model for which the upper layer increases in thickness with latitude in the interior of the ocean to the east of the stream, the upper layer goes, via a correct limit, to the one-layer baroclinic model.
\r\n\r\n2. As the density contrast between the upper and lower layers becomes small in a baroclinic model, the solution for the sum of the two layers converges, via an incorrect limit, to the one-layer baroclinic model.
\r\n\r\n3. As the thickness of the upper layer becomes small while the density difference across it remains proportional to the thickness (a constant density \"gradient\" in the upper layer), the range of latitude over which there exists a correct solution tends to zero. The incorrect solution goes to the one-layer model via an incorrect limit. This result suggests that continuously stratified, purely inertial models of the Gulf Stream are impossible for finite density gradients.
\r\n\r\n4. In the limit as the interface between the lower moving layer and the resting layer becomes horizontal, the lower layer velocity goes to zero. No solution exists as the limit is approached. It is an impossible limit.
\r\n\r\n5. As the density contrast between the upper and lower layer becomes small in the barotropic-baroclinic model, the solution goes via a correct limit to the homogeneous barotropic model.
In an attempt to model the actual Gulf Stream, parameters are selected for a model of two moving layers, the upper about 600 meters thick and the lower about 400 meters. This model is close to the impossible limit of 4. above, and no solution exists. The physical reason for this is that because of the small transport in the lower layer, the velocity in the lower layer must be small, which is incompatible with the large velocity gradient needed for conservation of potential vorticity as required in an inertial model. It therefore seems questionable that the deeper waters of the Gulf Stream can be modelled by a purely inertial theory.
\r\n\r\nNo off-shore countercurrents can be found, despite fairly accurate modelling of boundary conditions which might be expected to give them.
\r\n\r\nThe general implication of this work is that steady, purely inertial models are inadequate to describe even the lower latitude growth region of Gulf Stream if density stratification is taken into account, and that viscosity or unsteadiness must therefore be introduced.
" }, { "name": "Chapple, William Massee", "degree": "PhD", "year": "1964", "title": "Mathematical Study of Finite-Amplitude Rock-Folding", "advisor": "Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechTHESIS:05152013-140445759", "creators": [ { "name": { "family": "Chapple", "given": "William Massee" }, "id": "Chapple-William-Massee", "display_name": "Chapple, William Massee" } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/FCVB-NS79", "abstract": "The problem of the finite-amplitude folding of an\r\nisolated, linearly viscous layer under compression and\r\nimbedded in a medium of lower viscosity is treated theoretically\r\nby using a variational method to derive finite difference\r\nequations which are solved on a digital computer. The\r\nproblem depends on a single physical parameter, the ratio\r\nof the fold wavelength, L, to the \"dominant wavelength\" of\r\nthe infinitesimal-amplitude treatment, L_d. Therefore, the\r\nnatural range of physical parameters is covered by the\r\ncomputation of three folds, with L/L_d = 0, 1, and 4.6, up\r\nto a maximum dip of 90\u00b0.
\r\n\r\nSignificant differences in fold shape are found\r\namong the three folds; folds with higher L/L_d have sharper\r\ncrests. Folds with L/L_d = 0 and L/L_d = 1 become fan folds\r\nat high amplitude. A description of the shape in terms of\r\na harmonic analysis of inclination as a function of arc\r\nlength shows this systematic variation with L/L_d and is\r\nrelatively insensitive to the initial shape of the layer.\r\nThis method of shape description is proposed as a convenient\r\nway of measuring the shape of natural folds.
\r\n\r\nThe infinitesimal-amplitude treatment does not\r\npredict fold-shape development satisfactorily beyond a\r\nlimb-dip of 5\u00b0. A proposed extension of the treatment\r\ncontinues the wavelength-selection mechanism of the\r\ninfinitesimal treatment up to a limb-dip of 15\u00b0; after\r\nthis stage the wavelength-selection mechanism no longer\r\noperates and fold shape is mainly determined by L/L_d and\r\nlimb-dip.
\r\n\r\nStrain-rates and finite strains in the medium are\r\ncalculated f or all stages of the L/L_d = 1 and L/L_d = 4.6\r\nfolds. At limb-dips greater than 45\u00b0 the planes of\r\nmaximum flattening and maximum flattening rat e show the\r\ncharacteristic orientation and fanning of axial-plane\r\ncleavage.
\r\n" }, { "name": "Gardner, John Kelsey", "degree": "PhD", "year": "1964", "title": "Earthquakes in the Walker Pass Region, California, and their Relation to the Tectonics of the Southern Sierra Nevada", "advisor": "Richter, Charles F.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10152002-100918", "creators": [ { "name": { "family": "Gardner", "given": "John Kelsey" }, "id": "Gardner-John-Kelsey", "display_name": "Gardner, John Kelsey" } ], "advisors": [ { "name": { "family": "Richter", "given": "Charles F." }, "id": "Richter-C-F", "role": "advisor", "display_name": "Richter, Charles F." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/R906-T104", "abstract": "The locations and depths of earthquakes occurring in the Walker Pass Region, California, and the surrounding area have been examined for the period from January, 1934, to December, 1963. Whenever possible, least-square computer locations programs have been used to check or revise the previously determined epicenters and origin times. In most cases, epicenters determined by machine methods are within ten kilometers of those previously assigned. Accurate depths, whenever they could be calculated, were always found to be less than fifteen kilometers and usually less than ten kilometers.
\r\n\r\nThe sequence of earthquakes occurring in the Walker Pass region in March, 1946, has been carefully examined. While no major shifts in epicenters were found, the depth of the main shock of this series has been revised from twenty-one kilometers to less than ten kilometers. This revision cast doubt on the assertion that the earthquake originated on the Sierra Front Fault and made it likely that the earthquake occurred on one of the northwest-southeast trending faults in the interior of the Sierra mass.
\r\n\r\nFinally, the general distribution of earthquakes furnishes no evidence for the existence of a continuous deep-lying structure traversing the southern part of the Sierra Nevada. While the possibility of the existence of such a structure has not been excluded, practically all of the evidence upon which such a speculation might be based has been removed. Any relation between activity in this region and the activity in the nearby White Wolf Fault region must instead be explained by means of a mutual transfer of strain between systems of different trend and character.
\r\n\r\nThe computer programs used for the location of the earthquakes reported in this study are discussed in Appendices A and B.
\r\n" }, { "name": "Grant, James Alexander", "degree": "PhD", "year": "1964", "title": "The Nature of the Grenville Front near Lake Timagami, Ontario", "advisor": "Albee, Arden Leroy", "url": "https://resolver.caltech.edu/CaltechETD:etd-10152002-114122", "creators": [ { "name": { "family": "Grant", "given": "James Alexander" }, "id": "Grant-James-Alexander", "display_name": "Grant, James Alexander" } ], "advisors": [ { "name": { "family": "Albee", "given": "Arden Leroy" }, "id": "Albee-A-L", "role": "advisor", "display_name": "Albee, Arden Leroy" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/BHP6-TE58", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Grenville Front forms the boundary between the Superior and Grenville provinces, which differ greatly in structural trends and in grade and age of major metamorphism. The Front has been claimed to be a metamorphic transition, a regional fault zone, or a combination of the two. The Lake Timagami area lies athwart the Front and is favored by good outcrop and an unusually complete geological section. Detailed mapping, petrographic and chemical studies permit tentative conclusions which are validated by Rb-Sr isochron analyses.\r\n\r\nEarly Precambrian Keewatin-type metagreywacke and metavolcanic rocks form a steeply dipping, easterly trending belt intruded successively by quartz diorite and granite. To the north, these rocks are overlain with marked unconformity by flat lying virtually unmetamorphosed Huronian strata; diabase intrudes the Huronian and older rocks. Pre-Huronian \"Buchan\" metamorphism of the Keewatin-type rocks predated, but was probably related to, the emplacement of the granite. Later metamorphism affected the granite and older rocks and probably the Huronian sediments and the diabase, but its macroscopic effects are only visible - by definition -south of the Grenville Front. Here one finds a migmatitic terrane in which the probable equivalents of the metagreywacke quartz diorite and granite can be distinguished. In the west, the transition into this terrane is unfaulted, but to the east it is largely cut out by a northeasterly trending fault system. Within this terrane, the late metamorphism produced lithologies, metamorphic grade and structures typical of the northwestern part of the Grenville province, and for this reason the metamorphism was considered to be of Grenville age.\r\n\r\nX-ray fluorescence analyses were used to establish the range of chemical composition of the metagreywacke and the apparently equivalent schist south of the Front. Comparison of these ranges suggests that the late metamorphism was isochemical and that this correlation is permissible.\r\n\r\nThe tentative correlations from the Superior province into the Grenville province and the Grenville age of the late metamorphism cannot be proved conclusively by the mapping, or by the petrographic and chemical studies. However, the Rb-Sr analyses provide convincing evidence that these conclusions are correct.\r\n\r\n(a) Whole rock samples of granite from the Superior and Grenville provinces define an isochron. This substantiates the correlation of these as comagmatic granites. The age derived from the isochron is 2220 m.y. ? 70 m.y. and the corresponding initial (Sr[superscript 87]/Sr[superscript 86])[...] = 0.703 ? 0.001.\r\n\r\n(b) Mineral isochrons indicate virtually complete strontium isotopic equilibration south of the Front and partial equilibration north of the Front between 0.9 b.y. and 1.1 b.y. This is considered proof that the late metamorphism was indeed of Grenville age.\r\n\r\n(c) The combined data from the whole rock and mineral isochron studies prove beyond all reasonable doubt that granite of the Superior province, with a primary age of approximately 2.2 b.y., was subjected to the Grenville orogeny at approximately 1 b.y.\r\n\r\n(d) The whole rock analyses place a new maximum limit of 2.3 b.y. on the time of deposition of the Upper Huronian sediments.\r\n\r\nThe major conclusion from this work is that rocks of the Superior province were \"cannibalized\" during the Grenville orogeny and can be traced into the Grenville province. The Grenville Front is a metamorphic transition of Grenville age locally disrupted by faulting, and approximately defined by the southeastward transition from greenschist to amphibolite facies.\r\n\r\n(Plate 1, the geological map of the Lake Timagami area is essential to this thesis. It has been published (Map #2048, Vogt-Hobbs area) by the Ontario Department of Mines, Parliament Buildings, Toronto 2, Ontario, Canada, from whom it may be obtained.)" }, { "name": "Harper, Charles Woods", "degree": "PhD", "year": "1964", "title": "The Brachiopod Fauna of the Arisaig Series (Silurian-Lower Devonian) of Nova Scotia", "advisor": "Boucot, Arthur James", "url": "https://resolver.caltech.edu/CaltechETD:etd-10152002-123526", "creators": [ { "name": { "family": "Harper", "given": "Charles Woods" }, "id": "Harper-Charles Woods", "display_name": "Harper, Charles Woods" } ], "advisors": [ { "name": { "family": "Boucot", "given": "Arthur James" }, "id": "Boucot-Arthur-James", "role": "advisor", "display_name": "Boucot, Arthur James" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/KYZC-7F43", "abstract": "The Arisaig series comprises a very fossiliferous, fairly continuous sequence of strata of early Llandovery to Gedinnian age. The brachiopod species of the Arisaig series are described, identified generically, and compared with related species. Forty-five genera and eighty-two species are recognized. Seven new species, three new genera, and three new subgenera are proposed.\r\n\r\nA phylogeny is proposed for each of the following groups: the Rhipidomellidae, plagiorhynchids, leptostrophids, douvillinids, and the Pholidostrophiinae.\r\n\r\nIdiorthis is considered to be related to a proposed new genus of Silurian platyorthids. Shaleria(Telaeoshaleria) Williams is considered to be a pholidostrophid and is rejected as a subgenus of Shaleria Caster. Mclearnites Caster is considered to be closely related to Mesodouvillina Williams and not closely related to Shaleria. Pholidostrophia (Mesopholidostrophia) Williams and Lissostrophia(Mesolissostrophia) Williams are considered to be identical. Photochonetes Muir-Wood and Strophochonetes Muir-Wood are considered to be closely related, if not congeneric. Spirifer(Quadrifarius) Fuchs is redefined as a subgenus of Delthyria Dalman.\r\n\r\nThe lowest formation in the Arisaig series, the Beechhill Cove Formation is considered to be of early Llandovery age, as is the Glencoe Brook Formation in Pictou Co., N.S. The three members of the Ross Brook which overlies it are middle Llandovery (or high early Llandovery), late Llandovery (C[subscript 3]-C[subscript 5]), and late Llandovery C[subscript 6] or low Wenlock in age respectively. The overlying French River Formation is considered to be late Llandovery (C[Subscript 6] or low Wenlock in age. The lower two members of the overlying McAdam Formation are considered to be Wenlock or Ludlow in age, the upper two, Ludlow in age. The overlying Moydart Formation is considered to be Ludlow in age, and the highest formation in the series, the Stonehouse Formation, is considered to be Gedinnian and possibly, in part, Skala in age.\r\n\r\nMany brachiopod groups which are common and widespread in beds of equivalent age elsewhere in the world are absent or virtually absent in the Arisaig series; the genera which are present are not endemic-most of them are common and widespread in beds of equivalent age elsewhere. This very possibly resulted from the presence of a barrier which prevented the larvae of some, but not all, groups from entering the area of Arisaig rocks; but the possibility that it resulted from certain factors in the depositional environment being unfavorable to the missing groups cannot be ruled out.\r\n\r\nPhotographic materials on pp. 319-429 are essential and will not reproduce clearly on Xerox copies. Photographic copies should be ordered.\r\n" }, { "name": "Jory, Lisle Thomas", "degree": "PhD", "year": "1964", "title": "Mineralogical and Isotopic Relations in the Port Radium Pitchblende Deposit, Great Bear Lake, Canada", "advisor": "Patterson, Clair C.; Noble, James A.; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10112002-152503", "creators": [ { "name": { "family": "Jory", "given": "Lisle Thomas" }, "id": "Jory-Lisle-Thomas", "display_name": "Jory, Lisle Thomas" } ], "advisors": [ { "name": { "family": "Patterson", "given": "Clair C." }, "id": "Patterson-C-C", "role": "advisor", "display_name": "Patterson, Clair C." }, { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/W43G-ED67", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis thesis integrates the data from field, petrographic, X-ray, and lead and uranium isotopic studies on the Port Radium pitchblende deposit, Great Bear Lake, Canada.\r\n\r\nThe oldest rocks exposed are andesitic-dacitic bedded tuffs and flows of the Echo Bay group. Overlying detrital rocks of the Cameron Bay group were accumulated before intrusion of hypabyssal, dacitic porphyry bodies and granitic rocks. Sandstones of the Hornby Bay group lie unconformably on the above groups and on denuded granitic rocks. Folds are generally open in the Echo Bay and Cameron Bay groups; the Hornby Bay group is flat-lying. The Echo Bay group was metamorphosed to hornblende hornfels facies rocks, probably during intrusion of granitic rocks.\r\n\r\nFault and fracture zones, most commonly striking northeasterly and dipping steeply north, were in places loci for the successive introduction of \"giant quartz veins\", diabase dykes, and complex vein mineralizations. In the development of the Port Radium deposit, six stages of metallic and non-metallic vein mineral deposition are recognized. Three periods of wall rock alteration are correlative with episodes of vein mineralization. Tuffs of the Lower Echo Bay subgroup are the predominant host rocks to the ore mineralization. Localization of the pitchblende is attributed to physical factors. Diabase sills, intruded after development of the Port Radium deposit, were fractured during late-stage movements on the veins.\r\n\r\nAn age of 1820[plus or minus] 30 million years is assigned to a granitic rock at Port Radium on the basis of the lead-uranium isotopic analyses of seven zircon fractions. This sets a lower limit on the age of the Echo Bay and Cameron Bay groups and an upper limit on the age of Hornby Bay group and diabase dykes. In the zircon fractions, uranium and radiogenic lead concentrations increase with decreasing average grain size. All fractions show the discordant age pattern Pb [superscript 206]/U[superscript 238] < Pb [superscript 207]/U[superscript 235] < Pb[superscript 207]/Pb[superscript 206]. On a \"Concordia\" diagram, points representing the different zircon fractions define a chord intersecting the Concordia curve at 1815 and 50 million years.\r\n\r\nMicroscopic and macroscopic samples of three pitchblende specimens from the Port Radium mine were analysed isotopically for lead and uranium. For a specimen of pitchblende in carbonate gangue, concordant lead-uranium ages were obtained on two microscopic samples. The age, 1445[plus or minus] 20 million years, is the only concordant age which has been measured for the Port Radium ores. It places a lower limit on the age of the \"giant quartz veins\", the diabase dykes, and possibly the Hornby Bay group, and an upper limit on the diabase sills. For a specimen of pitchblende in siliceous gangue, two analyses define a chord intersecting the Concordia curve at 1450 and 300 million years. In general, Port Radium pitchblende samples show evidence of past loss of lead; the lead was removed from the vein systems. Comparison of isotopic data on microscopic and macroscopic samples from the same specimen shows that the microscopic samples can be less discordant and have higher lead-lead ages. Analyses of a number of lead-uranium systems in the same specimen offers a possible means of determining the age of mineralization and the age of an episodic disturbance.\r\n\r\nOf eight samples of galena and one of chalcopyrite analysed isotopically for lead, three are ordinary lead, four J-type anomalous lead and two possibly mixtures of ordinary lead and radiogenic uranium lead derived from the pitchblende. The ordinary lead is finely disseminated through the other vein minerals and was probably introduced shortly after the pitchblende. The J-type lead occurs in late, lenticular veinlets and was not formed by mixing with radiogenic lead from the pitchblende ores. Because of the absence of mixing and because of considerations concerning the geochemical character of the source system for the J-type lead, this lead was probably introduced less than 300 million years ago. Disturbances to the lead-uranium systems of the zircon and pitchblende samples provide further isotopic evidence for processes probably active within the last 200-300 million years but not recognized on the basis of geological field data.\r\n\r\nAdditional isotopic work to confirm and elaborate on these interpretations is suggested." }, { "name": "Watson, Kenneth", "degree": "PhD", "year": "1964", "title": "I. The Thermal Conductivity Measurements of Selected Silicate Powders in Vacuum from 150\u00b0 to 350\u00b0 K. II. An Interpretation of the Moon's Eclipse and Lunation Cooling as Observed through the Earth's Atmosphere from 8-14 Microns", "advisor": "Brown, Harrison; Murray, Bruce C.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11042002-153232", "creators": [ { "name": { "family": "Watson", "given": "Kenneth" }, "id": "Watson-Kenneth", "display_name": "Watson, Kenneth" } ], "advisors": [ { "name": { "family": "Brown", "given": "Harrison" }, "id": "Brown-Harrison", "role": "advisor", "display_name": "Brown, Harrison" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "advisor", "display_name": "Murray, Bruce C." } ], "committee": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "chair", "display_name": "Press, Frank" }, { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "member", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "member", "display_name": "Sharp, Robert P." }, { "name": { "family": "Brown", "given": "Harrison" }, "id": "Brown-Harrison", "role": "member", "display_name": "Brown, Harrison" }, { "name": { "family": "Murray", "given": "Bruce C." }, "id": "Murray-B-C", "role": "member", "display_name": "Murray, Bruce C." } ], "option_major": [ "geophys", "plansci" ], "doi": "10.7907/7HDE-1M52", "abstract": "An apparatus was constructed to measure the thermal conductivity of powders in vacuum from 150\u00b0 to 350\u00b0K. It was found that the conductivity of selected silicate powders can be adequately represented, within the experimental errors, by a temperature independent term related to the contact conduction plus a temperature cube term which is due to radiative transfer between and through the grains. The conductivity for glass spheres approximately suggests an inverse grain size dependence and does not appear to be related in any simple manner to the elastic contact area between the spheres. The effects of angular grains, produced by crushing, and limited chemical composition range are not significant when compared with the experimental errors. The radiative transfer term which is grossly independent of chemical composition and grain texture is dominated by radiation between the grains for grain sizes > 300 \u03bc. Radiation through the grains is significant for grain sizes < 100 \u03bc.
\r\n\r\nPrevious interpretations of the eclipse observations of Pettit and Nicholson indicate that homogeneous constant thermal property models provide an adequate fit. The recent lunation observations of Murray and Wildey cannot be adequately explained by homogeneous models with either constant thermal properties or with thermal properties which are based on the results of this experimental investigation and existing specific heat data. It is suggested that the possibility of layering can best be examined in the region of the morning terminator.
\r\n" }, { "name": "Alexander, Shelton Setzer", "degree": "PhD", "year": "1963", "title": "Surface Wave Propagation in the Western United States", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechTHESIS:05162012-110631966", "creators": [ { "name": { "family": "Alexander", "given": "Shelton Setzer" }, "id": "Alexander-Shelton-Setzer", "display_name": "Alexander, Shelton Setzer" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/GDQP-PB52", "abstract": "Part I
\r\n\r\nMulti-mode group velocity dispersion of both Rayleigh and Love waves was measured for a number of paths in the Western United States by means of a technique developed for separating the modes. Results for each region studied are interpreted in terms of a crustal structure which produces simultaneous agreement with all the modes observed, as well as available body wave data. Certain diagnostic features\r\nof group velocity dispersion curves were noted and used to advantage in this study.
\r\n\r\nThe analysis techniques developed have rather broad geophysical applications, for example in studies of source properties, interference phenomena, and noise properties.
\r\n\r\nPart II
\r\n\r\nThe effects of the transition zone at the continental margin of Southern California on Rayleigh wave propagation have been investigated. Among the anomalous effects discovered are a minimum in phase velocity between 20 and 35 seconds period, different phase velocities on reversed paths across the same array, and systematic lateral re-fraction at the continental boundary. These anomalous effects can be attributed largely to the slope and curvature of the Mohorovi\u010di\u0107 discontinuity across this region.\r\nAn ultrasonic model was constructed to aid in interpreting these results.
\r\n\r\nInterpretation of the dispersion for periods below 20 seconds indicates that the crust thickens toward the continent with a slope of about 5\u00b0 attaining a thickness of approximately 35 km under Southern California.
\r\n" }, { "name": "Banks, Philip Oren", "degree": "PhD", "year": "1963", "title": "Systematics of the Distribution of Uranium and Lead in Relation to the Petrology of the Mt. Rubidoux Granites, Riverside County, California.", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06272011-104837127", "creators": [ { "name": { "family": "Banks", "given": "Philip Oren" }, "id": "Banks-Philip-Oren", "display_name": "Banks, Philip Oren" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/PB8W-1F55", "abstract": "Field and petrologic studies and uranium-lead isotope geochemistry investigations have been made of the Mt. Rubidoux granites, Riverside Co., Calif. The coarse-grained granite was emplaced earlier than the fine-grained granite, and both were intruded by later dikes of pyroxene granodiorite. The two rocks are very similar quartz monzonites with an unusual assemblage of iron-rich silicates including biotite, hornblende, hypersthene, and fayalite. The composition of the fine granite corresponds very nearly to a natural minimum in the Q-Or-Ab-water system. Data from published experimental studies suggest a temperature of 700-760\u00b0C and a water vapor pressure of 1000-1500 bars during crystallization. The presence of fayalite and hypersthene is attributed to late-stage loss of water pressure.\r\n\r\nU-Pb isotopic analyses of accessory minerals, potash feldspar, and whole rock samples were performed to investigate the behavior of these isotopes in the coarse granite. Zircon, uranothorite, allanite, and apatite constitute the principal sites of U and radiogenic Pb in the rock. Apatite was not analyzed. Systematic analyses of the other minerals have provided a criterion for recognizing discordance in young U-Pb systems. The granites are at least 116 m.y. old and possibly as old as 130 m.y. Variations in the degree of discordance for equivalent zircon fractions from different localities suggest that an unrecognized episodic event less than 100 m.y. ago may have caused the discordance.\r\n\r\nZircon fractions from other rocks of the southern California batholith gave the following minimum ages: Woodson Mtn. granodiorite 119 m.y.; pyroxene granodiorite 108 m.y.; Crestmore quartz monzonite porphyry 106 m.y. Zircons from a soil profile over the coarse granite contained older zircons which have a minimum age of 1730 m.y. and are thought to be from metasedimentary wall rocks.\r\n\r\nThe isotopic composition of common lead was determined by several analyses of potash feldspar. Analyses of whole rock material and acid leaches of the fresh granite indicate that the total rock is discordant to the same extent as the principal minerals, and that the abundance and leachability of U and radiogenic Pb in the rock are governed strongly by the mineral uranothorite. Similar analyses of C-zone weathered granite indicate that the chief effect of weathering is to make available to acid leaching a higher proportion of common lead from the feldspar and radiogenic Pb^(208) from allanite.\r\n\r\nIsotopic analyses of radiogenic Pb have been utilized to evaluate the decay constant of U^(235). The presently accepted constant is believed to be accurate to within 1%, relative to the accepted constant for U^(238).\r\n\r\nThe effects of intermediate daughter losses in contributing to discordance in natural U-Pb systems have been considered in a series of model calculations. It is suggested that such losses may be of significance where the degree of discordance is relatively small and/or where the apparent time of episodic disturbance is very young." }, { "name": "Duke, Michael B.", "degree": "PhD", "year": "1963", "title": "Petrology of the Basaltic Achondrite Meteorites", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04242012-095648459", "creators": [ { "name": { "family": "Duke", "given": "Michael B." }, "id": "Duke-Michael-B", "display_name": "Duke, Michael B." } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/YPP2-ME45", "abstract": "Mineralogical and textural evidence indicates that the basaltic\r\nachondrites originated in one or more magmatic episodes in a\r\nvariety of cooling environments that resulted in textures ranging\r\nfrom gabbroic to diabasic. Chemical compositional and mineralogical\r\nvariations are consistent with a common origin for the basaltic\r\nachondrites by magmatic differentiation. The characteristics of\r\nthe mineralogical, major element and trace element variations are\r\nsimilar to those of the Skaergaard intrusion, but the basaltic\r\nachondrite magmas started from different compositions and crystallized\r\nunder much lower partial pressures of oxygen(in the stability\r\nfield of metallic iron) than did the magmas of the Skaergaard\r\nintrusion. The differentiation trends shown by the basaltic achondrites\r\nindicate that the starting material had calcic plagioclase\r\nand was depleted in alkalis with respect to chondritic meteorites,\r\nin which the plagioclase is sodic.
\r\n\r\nBrecciation is a conspicuous feature of most basaltic achondrites,\r\nwhich can be most satisfactorily subgrouped on the basis of\r\nbreccia type as brecciated eucrites (monomict breccias), eucrites\r\n(unbrecciated), and howardites (polymict breccias). Petrographic\r\nevidence suggests that some textural metamorphism and brecciation were\r\nproduced by shock effects that accompanied impact events on the surface\r\nof the parent body. The abundances of basaltic achondrite falls are\r\nconsistent with a surface-sampling mechanism such as meteorite impact\r\nejection. A preponderance of near-surface samples and the distinct\r\ndifferences between the basaltic achondrites and chondrites suggest\r\nthat the moon is the probable parent body of the basaltic achondrites.
\r\n" }, { "name": "Harkrider, David Garrison", "degree": "PhD", "year": "1963", "title": "Part I. Propagation of Acoustical Gravity Waves from an Explosive Source in the Atmosphere. Part II. Rayleigh and Love Waves from Sources in a Multilayered Elastic Half-Space", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechETD:etd-02252004-140415", "creators": [ { "name": { "family": "Harkrider", "given": "David Garrison" }, "id": "Harkrider-David-Garrison", "display_name": "Harkrider, David Garrison" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/QEDG-NT74", "abstract": "Part I:
\r\n\r\nA matrix formulation is used to derive the pressure variation for acoustic gravity waves from an explosive source in an atmosphere modelled by a large number of isothermal layers. Comparison of theoretical and experimental barograms from large thermonuclear explosions leads to the following conclusions: (1) The major features on the barogram can be explained by the super-position of four modes, (2) Different portions of the vertical temperature structure of the atmosphere control the relative excitation of these modes, (3) A normalized point source is sufficient to model thermonuclear explosions, (4) The observed shift in dominance of certain frequencies with yield and altitude can be explained using the empirical scaling laws derived from the direct wave near the explosion.
\r\n\r\nPart II:
\r\n\r\nA matrix formulation is used to derive integral expressions for the time transformed displacement fields produced by simple sources at depth in a multilayered elastic isotropic halfspace. The integrals are evaluated for their residue contribution to obtain surface wave displacements in the frequency domain. The theory includes the effect of layering and source depth for the following: (1) Rayleigh waves from an explosive source, (2) Rayleigh waves from a vertical point source, (3) Rayleigh and Love waves from a vertical strike slip fault model. The latter source also includes the effect of fault dimensions and rupture velocity. The theory presented here is the ground work for the numerical computation of theoretical seismograms for use in a later paper in which a comparison will be made between observations and theory in both the time and frequency domain. A discussion is included on how these comparisons might be used in the frequency domain to estimate source depth.
" }, { "name": "Toks\u00f6z, M. Nafi", "degree": "PhD", "year": "1963", "title": "Velocities of Long Period Surface Waves and Microseisms and Their Use in Structural Studies : Part I. Mantle Love and Mantle Rayleigh Waves and the Structure of the Earth's Upper Mantle. Part II. Microseisms and Their Application to Seismic Exploration", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechTHESIS:11132012-094305927", "creators": [ { "name": { "family": "Toks\u00f6z", "given": "M. Nafi" }, "id": "Toks\u00f6z-M-Nafi", "display_name": "Toks\u00f6z, M. Nafi" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/1X99-MR13", "abstract": "Part I:
\r\nPhase velocities of Love waves from five major earthquakes are measured over six great circle paths in the period range of 50 to 400 seconds. For two of the great circle paths the phase velocities of Rayleigh waves are also obtained. The digitized seismograph traces are Fourier\r\nanalyzed, and the phase spectra are used in determining\r\nthe phase velocities. Where the great circle paths are\r\nclose, the phase velocities over these paths are found to\r\nbe in very good agreement with each other indicating that\r\nthe measured velocities are accurate and reliable. Phase\r\nvelocities of Love waves over paths that 1ie far from each \r\nother are different, and this difference is consistent and\r\nmuch greater than the experimental error. From this it is\r\nconcluded that there are lateral variations in the structure\r\nof the earth's mantle.
\r\n\r\nThe phase velocity data are compared with theoretical dispersion curves of seven different earth models. None of\r\nthese models fit the data. Two new upper mantle models,\r\none to fit the data over an almost completely oceanic path\r\nand the other over a mixed oceanic and continental path,\r\nare designed. The significant features of these models\r\nare correlated with the body wave observations and with the\r\nhypothesized thermal model and the mineralogical structure\r\nin the mantle.
\r\n\r\nPart II:
\r\nA study of microseisms is made to determine some\r\nof their statistical properties and to investigate the\r\nfeasibility of their use in determining the shallow\r\nstructures of the earth's crust by the phase velocity\r\nmethod. It is found that the microseisms in the period\r\nrange of to 6 seconds arrive from several directions with\r\ncomparable strength and at the same time. There are occasional\r\nshort intervals of 10 - 40 seconds during which microseisms\r\nare mostly unidirectional. It is also found that\r\nthese relatively short period microseisms are not stationary\r\nin the wide sense over time intervals longer than 5 or 10\r\nminutes.
\r\n\r\nThe phase velocities of microseisms recorded with an\r\narray of 8 instruments are measured In four different\r\nlocations. The velocities, although scattered, are found\r\nto be in agreement with the theoretical dispersion curve\r\nfor the fundamental Rayleigh mode, computed using the\r\navailable seismic velocity information. An error analysis\r\nis made and the confidence limits are placed within \u00b120\r\npercent of the measured velocities.
" }, { "name": "Zartman, Robert Eugene", "degree": "PhD", "year": "1963", "title": "A Geochronological Study of the Lone Grove Pluton from the Llano Uplift, Texas", "advisor": "Wasserburg, Gerald J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11202012-153218336", "creators": [ { "name": { "family": "Zartman", "given": "Robert Eugene" }, "id": "Zartman-Robert-Eugene", "display_name": "Zartman, Robert Eugene" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/SXVC-R234", "abstract": "A detailed geological study of the Lone Grove granitic pluton and surrounding rocks from the Llano Uplift, Texas, was made. Field and petrologic evidence suggests that this intrusive has had a simple history of emplacement with no later metamorphism. Samples of granite, aplite, pegmatite, rhyolite, and metamorphic rocks were investigated geochronologically in order to determine the consistency in Rb87\u2013Sr87 and K40\u2013Ar40 ages between various minerals and between different localities. Refined chemical and mass spectrometric methods of analysis are described and the limits of precision are established. It is found possible to determine ages on most highly radiogenic minerals to a precision of \u00b1 1 1/2% or better. All ages were calculated with the following decay constants: Rb87, \u03bb\u03b2=1.47x10(-11)yr(-1); K40, \u03bb\u03b2=4.72x10(-10)yr(-1) and \u03bbe= 0.585x10(-10)yr(-1). The distribution of ages on most of the minerals from these rocks show a spread commensurate with the experimental error. The average Rb87-Srv age on microclines,muscovites and biotites is 1015 million years and the average K40\u2013Ar40 age on muscovites, biotites, and hornblendes is 1045 million years. A total rock Rb87-Sr87 age on one of the granites gives no indication of having an older age than the constituent minerals. The only rock to show an apparently real different age is a rhyolite porphyry,\r\nwhich gives an average Rb87-Sr87 microcline age of 910 million years. K40-Ar40 determinations on several microclines and plagioclases give ages which are 5-20% too low, presumably due to argon diffusion from the feldspar. Anomalously low Rb87\u2013Sr87 ages occur on several biotites from fresh pegmatites and granite. Evidence is presented for radiogenic strontium migration from these rocks although the exact nature of the process is not known. Somewhat low K40\u2013Ar40 ages also are obtained on the pegmatitic biotites. A study of the effects of weathering on the geochronologic systems is made on two obviously altered granites. The only mineral to suffer any decrease in age from such surface alteration is biotite by the Rb87-Sr87 method. The isotopic composition of the common strontium incorporated into the minerals of the granite is determined on several minerals having low Rb/Sr ratios. The Sr87/Sr88 ratio is found to be 0.0843 \u00b1 0.0002 (normalized to make Sr866/Sr88 = 0.1194). A discussion of the distribution of rubidium, potassium, and normal strontium throughout the pluton is given and several partitioning factors for the rubidium to potassium concentrations between different mineral species are calculated.
\r\n" }, { "name": "Anderson, Don Lynn", "degree": "PhD", "year": "1962", "title": "Surface Wave Propagation in Layered Anistropic Media", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechETD:etd-10142002-091205", "creators": [ { "name": { "family": "Anderson", "given": "Don Lynn" }, "id": "Anderson-Don-Lynn", "display_name": "Anderson, Don Lynn" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/ADTM-DX51", "abstract": "An analysis is made of the dispersive properties of layered anisotropic media, emphasis being placed on the geophysically important case of transverse isotropy. Period equations are derived for Rayleigh, Stoneley and Love type waves. A correspondence is established, in certain cases, with ray theoretical and plane stress solutions.\r\n\r\nThe general anisotropic problem (orthorhombic symmetry) is considered briefly for certain propagation directions and is used to derive the two-dimensional theory of seismic modeling.\r\n\r\nThe single layer solutions are generalized to the n-layer problem by use of Thomson-Haskell matrices. The results are used to interpret long period surface wave data. It is found that an anisotropy of approximately 8% in the low velocity zone removes the discrepency between Love and Rayleigh waves." }, { "name": "Conel, James Ekstedt", "degree": "PhD", "year": "1962", "title": "Studies on the Development of Fabrics in Some Naturally Deformed Limestones", "advisor": "Kamb, W. Barclay", "url": "https://resolver.caltech.edu/CaltechTHESIS:08152011-090459434", "creators": [ { "name": { "family": "Conel", "given": "James Ekstedt" }, "id": "Conel-James-Ekstedt", "display_name": "Conel, James Ekstedt" } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "abstract": "The purpose of this investigation has been to study in detail the development of deformation fabrics in some\r\nnaturally deformed limestones, with a view of testing the\r\ngeological applicability of experimentally deduced origins\r\nof such fabrics in these materials. Flexurally folded\r\nlimestones have been used to make comparisons between experiment and nature, by taking advantage of the approximately known character and variation of strain in these structures and using this information to deduce theoretically the deformation fabrics from place to place to compare with those actually observed in the structures. Two kinds of fabric problems are treated, ones dealing with gross changes in crystal orientation accompanying large strain, and those treating the origin of twinning lamellae in carbonate rocks in relation to applied stress, the so-called dynamic analysis. An extension of this analysis is made which allows quantitative information as to rock strain due to twinning (and translation gliding) to be obtained from thin sections.\r\n\r\nCurrent theoretical treatments used in predicting fabric changes with strain in marble are found inadequate for predicting fabric changes with strain in flexure folds.\r\nExact derivations of these fabrics for folds have not been\r\nmade. Instead, an implication of a more general theory\r\ntreating development of fabrics in metal aggregates is used\r\nto derive approximately the changes in c-axis orientations\r\nwith large strain by analogy with fabrics obtained from\r\nexperimental deformed Yule marble. Well defined fabric\r\nchanges with large strain involving both twinning and\r\ntranslation gliding in individual crystals have not been\r\nobserved in the folds studied. \r\n\r\nPredicted results for the dynamic analysis of an aggregate with isotropic c-axis distribution are derived with special reference to one of the folds studied. The stress distribution in plane strain is calculated for the structure starting with an already partly folded unconfined\r\nlayer of circular cross-section, and assuming it to be\r\nloaded elastically with simple compressive forces applied\r\nin the limbs directed normal to the axial plane. Twinning\r\ndeformation in individual crystals is treated by assuming\r\nthat the law of maximum resolved shear stress determines an\r\nactive twin set in each grain. The results obtained are\r\ncompared favorably with those observed in a natural fold.\r\n\r\nDeformation fabrics from two small folds are given.\r\nThe first fold occurs in a large anticlinorium in western\r\nWashington County, Maryland, in thinly bedded limestones\r\nand shales of the Silurian McKenzie Creek formation. The\r\nsecond is a drag fold on the eastern limb of a north-trending anticline in Carboniferous limestones and shales\r\nlocated in upper Darwin wash, Darwin Hills, Inyo County,\r\nCalifornia. In the Maryland fold, c-axis fabrics obtained\r\nfrom the axial region show no preferred orientation due to\r\ndeformation, but a dynamic analysis of the twinning lamellae\r\nis in good agreement with that expected in theory. The dynamic analysis is shown to be sensitive in depicting\r\nsmall changes in twinning deformation throughout portions\r\nof the body examined. The strains due to twinning are\r\ncompatible with bending in part of the structure. More\r\nquantitative comparisons of the observed and expected deformation have shown that under a derived system of stress\r\nat the axial plane, twinning deformation in 80% of the\r\ngrains in the aggregate has followed the law of maximum\r\nresolved shear stress. The amount of twinning strain within\r\nindividual crystals varies with their orientation in the\r\nstress field. The calculated visible (twinning) strains of\r\nabout 0.01 are considerably less than the strains computed\r\nfrom the geometry of the fold of 0.25, and much of this\r\ndiscrepancy may be due to fracturing (slip on planes parallel to bedding) during folding.\r\n\r\nIn the fold from Darwnn wash, observed fabrics cannot be related simply to the megascopic deformation in the fold. Preferred orientations of c-axes are thought to be partly due to veining in t he rock. Fabric changes due to twinning are however qualitatively correlated with shortening in the fold perpendicular to the axial plane, and a shear similar to that necessitated by the relation of the drag fold to the major anticline with which it is associated. Calculated visible strains are considerably less than those approximately deduced from fold geometry, but can be partially correlated with the observed deformation in the structure. Analysis of the deformation in nonhomogeneously strained individual crystals of these aggregates (Appendix II) shows that in addition to e{0112} twinning, translation gliding has occurred on most types of glide planes deduced for calcite from laboratory experiments. Microscopically these rocks appear to have undergone large deformation, exhibiting local cataclastic texture, much twinning and warping of individual crystals. However, well defined formation fabrics due to large strain have not been observed in them.\r\n\r\nA second part of this investigation has dealt with the so-called nontwinned lamellae in calcite and dolomite. From these studies it has been concluded that such structure\r\nare extremely thin (a few microns) but otherwise normal twin lamellae parallel to e{0112} in calcite and\r\nf{0221} in dolomite, and are for this reason renamed microtwinned lamellae. In addition to interference colors,\r\nthese lamellae exhibit four different types of interference\r\nfringes. A new method is presented, which utilizes the optical properties of the twins, for obtaining the\r\norientation of lamellae inclined at small angles to the\r\nplane of a thin section. The utility of this technique\r\nlies in the fact that it may be used to eliminate the\r\ncentral \"blind-spot\" in twin lamellae fabric diagrams.\r\nSome measurements of twin thicknesses, made using the new\r\norientation method, are given, together with calculations\r\nwhich show that only an average and not a cumulative optical\r\nthickness for a stack of lamellae superposed in thin section may be obtained using the method.\r\n" }, { "name": "Hare, Peter Edgar", "degree": "PhD", "year": "1962", "title": "The Amino Acid Composition of the Organic Matrix of Some Recent and Fossil Shells of Some West Coast Species of Mytilus", "advisor": "Lowenstam, Heinz A.; Borsook, Henry", "url": "https://resolver.caltech.edu/CaltechTHESIS:08112011-160231577", "creators": [ { "name": { "family": "Hare", "given": "Peter Edgar" }, "id": "Hare-Peter-Edgar", "display_name": "Hare, Peter Edgar" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." }, { "name": { "family": "Borsook", "given": "Henry" }, "id": "Borsook-H", "role": "advisor", "display_name": "Borsook, Henry" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/EXQX-4D49", "abstract": "The organic matrix from each structural unit of Mytilus californianus has a distinctive amino acid composition. Systematic variations in composition occur within the outer prismatic layer and the periostracum. In small shells there are profound changes in the periostracum composition as the animal grows during the first year or so.\r\n\r\nThere is a relationship between the amount of organic material present in the original shell unit and the relative amounts of the basic and acidic amino acids in the organic matrix. The matrix from calcitic shell structures has a larger net excess of acidic residues than does the matrix from aragonitic structures. Temperature changes\r\nappear to be reflected in compositional changes in the nacreous aragonite layer with increasing temperature favoring a higher number of net acidic amino acid residues. Thus, as temperature increases, the differences in matrix composition between the nacreous aragonite layer and the outer prismatic calcite layer become progressively smaller.\r\nDecreasing salinity seems to have a similar effect to increasing temperature.\r\n\r\nFrom a study of a series of radiocarbon-dated shell materials, it is found that the composition of the organic matrix undergoes a significant amount of change within a few thousand years under a rather dry environment. The oxidation products of certain amino acids are present in progressively larger amounts in older materials, suggesting\r\noxidation as one of the possible mechanisms involved in fossilization.\r\n" }, { "name": "Kovach, Robert Louis", "degree": "PhD", "year": "1962", "title": "Geophysical Investigations in the Colorado Delta Region", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechTHESIS:12072009-142350784", "creators": [ { "name": { "family": "Kovach", "given": "Robert Louis" }, "id": "Kovach-Robert-Louis", "display_name": "Kovach, Robert Louis" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/B362-3G65", "abstract": "The combined approach of gravity and seismic re-fraction exploration was used to determine depths of the Cenozoic section and to study the fault pattern in the Colorado Delta region. Basement depths measured varied from about 2200 feet to a minimum depth of 15,400 feet along the international border, east of Calexico. A study of the seismicity of the region shows that the greatest seismic activity over the past 60 years has been along the San Jacinto fault system. Continuity of specific major faults is difficult to establish using gravity methods alone because of the lack of indicated vertical throw on the faults. No conclusive evidence is presented for establishing the continuity of the Mission Creek-Banning fault southward into the present area of investigation, although geophysical evidence is presented for a fault present beneath the Sand hills (Algodones Dunes)." }, { "name": "Lanphere, Marvin Alder", "degree": "PhD", "year": "1962", "title": "I. Geology of the Wildrose Area, Panamint Range, California. II. Geochronologic Studies in the Death Valley-Mojave Region, California", "advisor": "Wasserburg, Gerald J.; Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08182011-145051903", "creators": [ { "name": { "family": "Lanphere", "given": "Marvin Alder" }, "id": "Lanphere-Marvin-Alder", "display_name": "Lanphere, Marvin Alder" } ], "advisors": [ { "name": { "family": "Wasserburg", "given": "Gerald J." }, "id": "Wasserburg-G-J", "role": "advisor", "display_name": "Wasserburg, Gerald J." }, { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/VKKA-P510", "abstract": "The bedrock in the Wildrose area is predominantly a sequence\r\nof metamorphosed sedimentary and possible volcanic rocks that is more than 15,000 feet thick. All the metamorphic rocks are Precambrian in age on stratigraphic evidence. The rocks are divided into three age groups, early Precambrian, later Precambrian, and Precambrian (?), that are separated by unconformities. The early Precambrian Panamint metamorphic complex has been divided into two series that are separated by a profound unconformity. Small stocks\r\nand dikes of granitic rocks, which are presumably Cretaceous in age, intrude the metamorphic rocks. Tertiary sedimentary rocks and Quaternary alluvium are also present in the area.\r\n\r\nThe structural features of the area are ascribed to four periods of deformation. The large folds in the early Precambrian rocks and associated minor folds were produced during the first two periods of deformation of early Precambrian age. Low angle faults are evidence\r\nof the third deformation which is considered to be Cretaceous in age. The fourth period of deformation produced high angle faults. Movement\r\nalong the high angle faults began in late Tertiary time and has continued to the present.\r\n\r\nAll the Precambrian rocks of the area have been affected by\r\nmiddle or lower middle grade metamorphism. Even though structural evidence suggests that metamorphism must have accompanied the earlier periods of deformation, the present mineral assemblages reflect the third period of deformation which, on the basis of mineral age measurements, was Cretaceous in age. Narrow contact metamorphic\r\naureoles surround the larger masses of granite.\r\n\r\nRadioactive ages were measured in five areas in the Death\r\nValley-Mojave Desert region. The rocks are Precambrian in age on stratigraphic evidence in three areas, the Wildrose area of the Panamint Range, the Mountain Pass district, and the Marble Mountains. The rocks in Joshua Tree National Monument and the Kilbeck Hills are presumably Precambrian, but no stratigraphic evidence of their age has been found. The geochronologic studies in the five areas indicate three distinct groups of K - Ar and Rb-Sr ages. Ages of\r\napproximately 1650 million years are obtained on metamorphic rocks and associated pegmatite s in the Mountain Pass district. Younger igneous rocks at Mountain Pass and in the Marble Mountains have age patterns that are interpreted to indicate intrusion in the 1350\r\nto 1450 million year interval. Metamorphic rocks in the Wildrose area, Joshua Tree National Monument , and the Kilbeck Hills have ages in the 75 to 85 million year interval which are interpreted as the age of regional metamorphism related to the Cretaceous Nevadan\r\norogeny. An age of 73 million years was obtained on a post-metamorphic granite.\r\n" }, { "name": "Ben-Menahem, Ari", "degree": "PhD", "year": "1961", "title": "Radiation of Seismic Surface-Waves from Finite Moving Sources", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechETD:etd-03172006-103207", "creators": [ { "name": { "family": "Ben-Menahem", "given": "Ari" }, "id": "Ben-Menahem-Ari", "display_name": "Ben-Menahem, Ari" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/14NZ-KT62", "abstract": "A theory is proposed for the propagation of seismic surface-waves from finite moving sources. The method consists of obtaining, in the first place, basic solutions for surface displacements from directional sources. These solutions are integrated to obtain the effect of a moving fault with arbitrary dip angle. Displacements are evaluated for Rayleigh and Love-waves, at long ranges. It is shown that the dimensions of the source and the speed of rupture play an important role in the wave-pattern and cannot be ignored whenever the dimensions of the source are of the order of the radiation's dominant-wave-length. It is demonstrated how this theory may lead to a derivation of the velocity of rupture and the fault-length from seismic records of a single station. Evidence is furnished both from two-dimensional model experiments and the Chilean Earthquake of May 1960." }, { "name": "Dodd, James Robert", "degree": "PhD", "year": "1961", "title": "Paleoecological Implications of the Mineralogy, Structure, and Strontium and Magnesium Contents of Shells of the West Coast of the Genus Mytilus", "advisor": "Lowenstam, Heinz A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04212006-171409", "creators": [ { "name": { "family": "Dodd", "given": "James Robert" }, "id": "Dodd-James-Robert", "display_name": "Dodd, James Robert" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geobiol" ], "doi": "10.7907/9MMH-RM22", "abstract": "Large specimens of M. californianus, M. edulis edulis, and M. edulis diegensis show a positive correlation with temperature in the percent aragonite in their shells. Shell thickness and probably other unknown factors also affect the shell mineralogy of M. californianus. Shell size and salinity are the most important factors affecting the mineralogy of M. edulis edulis and M. edulis diegensis. The shell structure of M. californianus is temperature dependent. A method making possible the quantitative determination of paleotemperatures from shell structure is devised. The age of specimens of M. californianus can be determined from shell structure making possible the estimation of growth rates, which are in part a function of temperature. The magnesium and strontium contents of the outer prismatic layer of the west coast species of Mytiles are positively correlated with temperature. The strontium content is affected by the size of the specimen but is independent of salinity in the samples in this study. The strontium content of the nacreous layer shows a negative correlation with temperature. Shell structure, strontium content, shell mineralogy, and growth rates are used to determine paleotemperatures for fossils from four localities in the upper Pleistocene of California and Baja California and one locality in the lower Pleistocene of California. These methods indicate that the temperatures were much like the present temperatures at these localities." }, { "name": "Gross, Meredith Grant", "degree": "PhD", "year": "1961", "title": "Carbonate Sedimentation and Diagenesis of Pleistocene Limestones in the Bermuda Islands", "advisor": "Lowenstam, Heinz A.; Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechETD:etd-04122006-135611", "creators": [ { "name": { "family": "Gross", "given": "Meredith Grant" }, "id": "Gross-Meredith-Grant", "display_name": "Gross, Meredith Grant" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "co-advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/E4V7-ZV93", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Recent carbonate sediments in the Bermuda Islands consist largely of skeletal fragments of marine organisms. Benthonic foraminifera and lithothamnoid algae contribute high-Mg calcite (>10 mol % MgCO3). Low-Mg calcite (<5 mol % MgCO3) appears to be derived from erosion of Pleistocene limestones. Aragonite, which makes up 30 to 70% of the Recent sediments, is derived from molluscs and Halimeda.\r\n\r\nThe Pleistocene limestones are composed of fragments of the same types of marine organisms which make up the Recent sediments. The limestones vary from unconsolidated, unaltered carbonate sands to well consolidated, crystalline limestones. Lithification of the limestones is caused by the removal through solution of aragonitic skeletal fragments and the deposition of secondary calcite. Obliteration of the internal structure and the formation of replacement mosaics is observed in some of the fragments. The high-Mg calcite phase, which is present in the poorly consolidated limestones, is absent in highly altered limestones which contain only low-Mg calcites. No limestones were found which contained only a single Mg-calcite of intermediate composition (between 5 and 10 mol % MgCO3). Mg-calcites containing between 5 and 10 mol % MgCO3 were found only in the fragments of Homotrema. The SrCO3 originally present in the calcites and aragonites is removed during diagenesis of the limestones. No dolomites were found in the Bermuda limestones, which suggests that the Mg and Sr removed during diagenesis is not retained in the limestones. Dolomite containing 57 mol % CaCO3 was found in limestones recovered from drilling operations on Plantagenet Bank, off Bermuda.\r\n\r\nWith the exception of Halimeda fragments, the skeletal fragments making up the Recent sediments have [...] values between 0 and -1% and positive [...] values. Most of the Recent sediments have [...] and [...] values in this range. Fresh water carbonates deposited on the islands have [...] values from -3 to -5% and [...] values from -4 to -9%. The [...] and [...] values of the diagenetically altered lime stones exhibit change from values similar to the Recent sediments to [...] values similar to those of the fresh water carbonates. This change in [...] values is shown to result from the precipitation of secondary calcite in the limestones and is interpreted as indicating that the secondary calcites have the same origin as the fresh water carbonates.\r\n\r\nThe diagenetic environment of the Bermuda limestones was characterized by temperatures less than 30\u00b0C and essentially surface pressures. Most of the Pleistocene limestones have probably been in the fresh water zone since their deposition. The mineral assemblage and Sr and Mg content of the limestones is discussed in terms of the equilibrium mineral assemblage at these temperatures and pressures.\r\n\r\nCursory studies were made of limestones from Bikini and Eniwetok Atolls and mid-Ordovician limestones from Oklahoma in order to test the usefulness of the [...] and [...] values for distinguishing different diagenetic environments. The data from the analyses of the Bikini and Eniwetok Atoll samples substantiate the geological evidence that portions of these limestones have been subaerially exposed during the Pleistocene epoch. The data from the mid-Ordovician limestone indicate that the diagenetic environment was different from that of the Bermuda limestones." }, { "name": "Healy, John Helding", "degree": "PhD", "year": "1961", "title": "Geophysical Studies of the Basin Structures along the Eastern Front of the Sierra Nevada", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechETD:etd-01312006-152504", "creators": [ { "name": { "family": "Healy", "given": "John Helding" }, "id": "Healy-John-Helding", "display_name": "Healy, John Helding" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/403B-RW91", "abstract": "Eighteen seismic refraction profiles were shot and about 1200 gravity stations were occupied in the basins bordering the eastern Sierra Nevada between Owens Lake and the Garlock Fault. The results of these data show that basin structures with maximum depths averaging between 4000 to 6000 feet follow the front of the Sierra for this entire distance except for about ten miles near Little Lake.
\r\n\r\nThese basins are usually narrow, fault-bounded structures with their deepest parts close to the front of the Sierras.
\r\n\r\nAnalysis of the regional gradients indicates that the Mohorovicic discontinuity can play only a minor role in the isostatic support of the Sierra Nevada.
\r\n" }, { "name": "Phinney, Robert Alden", "degree": "PhD", "year": "1961", "title": "Propagation of Leaking Modes in a Plane Seismic Waveguide. Propagation of Leaking Interface Waves", "advisor": "Press, Frank", "url": "https://resolver.caltech.edu/CaltechTHESIS:04122011-145755371", "creators": [ { "name": { "family": "Phinney", "given": "Robert Alden" }, "id": "Phinney-Robert-Alden", "display_name": "Phinney, Robert Alden" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/5TG9-XN02", "abstract": "The work of Rosenbaum describing propagation or imperfectly trapped (leaking) modes in an acoustic waveguide is extended to two problems of geophysical importance. The problem of a liquid layer coupled to an elastic halfspace is considered first, in a paper entitled: Propagation of Leaking Modes in the Crustal Waveguide: The Oceanic PL wave. Theoretical results obtained in this first paper may be applied, after slight generalization, to the most general type of plane seismic waveguide. In a second paper, entitled: Propagation of Leaking Interface Waves, we discuss these generalizations and apply them to the fundamental problem of pulse propagation along a plane interface. The most important result of both papers is the description of the earliest-arriving signal traveling in the waveguide as a result of a transient point excitation.
\r\n\r\nNumerical results for both problems were obtained by solving the complex period equation on the Burroughs 220 computer. The programming framework and the numerical methods used are discussed in a third section of this thesis.
\r\n" }, { "name": "Smith, Stewart Wilson", "degree": "PhD", "year": "1961", "title": "An Investigation of the Earth's Free OsciIIations", "advisor": "Press, Frank; Benioff, Hugo", "url": "https://resolver.caltech.edu/CaltechTHESIS:04132011-081816354", "creators": [ { "name": { "family": "Smith", "given": "Stewart Wilson" }, "id": "Smith-Stewart-Wilson", "display_name": "Smith, Stewart Wilson" } ], "advisors": [ { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" }, { "name": { "family": "Benioff", "given": "Hugo" }, "id": "Benioff-H", "role": "advisor", "display_name": "Benioff, Hugo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/S9RW-R653", "abstract": "The free oscillations of the earth excited by the Chilean earthquake of 1960 have been measured by power spectral analysis of strain and pendulum seismographs. A revised and more precise table of free oscillation periods is presented. The period of the fundamental spheroidal mod _0S^0_2 is 53.82 minutes.\r\n\r\nFine structure analysis has shown that for the first three spheroidal modes there is good agreement between the observed splitting and that calculated for a rotating earth. Results for the toroidal modes are uncertain.\r\n\r\nA theory is presented that allows recovery of some of the source properties from observations of phase differences for spheroidal modes. A comparison of theory with observation confirms original estimates of a fault length of 1000 km and a rupture velocity of between 3 and 4 km/sec. The effect of a moving source that decays exponentially with distance changes the pattern of phase shifts slightly but does not change estimates of the fault parameters. An alternative interpretation of the source properties in terms of the relative amplitudes of 2n + 1 split lines for each mode is presented but no calculations are performed.\r\n\r\nPreliminary data on the effects of geomagnetic storms on the oscillations of the earth place an upper limit of about 5 x 10^(16) ergs/cph for the energy density associated with the elastic coupling of several magnetic storms.\r\n" }, { "name": "Wilson, John Coe", "degree": "PhD", "year": "1961", "title": "Geology of the Alta stock, Utah", "advisor": "Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04112011-153508154", "creators": [ { "name": { "family": "Wilson", "given": "John Coe" }, "id": "Wilson-John-Coe", "display_name": "Wilson, John Coe" } ], "advisors": [ { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/8775-NJ40", "abstract": "The Alta stock of granodiorite is closely associated in space and\r\ntime with many of the Pb, Zn and Ag ore deposits of the Park City-Cottonwood\r\nmining area in the central Wasatch Mountains, Utah. The purpose of\r\nthis study was to determine if fractional crystallization of the Alta magma\r\nultimately resulted in a metal-rich ore-forming fluid.\r\nThe Alta magma was intruded in two pulses into pre-Triassic\r\nsedimentary rocks at a depth of approximately 21,000 feet and at a temperature\r\nin excess of 720\u00b0C. Detailed study of texture indicates that the first\r\nphase of magma solidified with a nonporphyritic texture, crystallizing\r\nfrom the wall progressively toward the center of the stock. The rock at\r\nthe wall is rich in mafic minerals but grades inward within a few hundred\r\nfeet to light-gray medium-grained biotite-hornblende granodiorite. Early\r\nin the history of the first pulse of magma, convection currents carrying\r\ngrowing crystals of early minerals formed stratified gravity accumulations\r\nrich in hornblende, biotite, sphene, magnetite and apatite. These layered\r\nmasses were subsequently broken and displaced. They now form tabular\r\ninclusions of mafic layered granodiorite in the light-gray nonporphyritic\r\ngranodiorite.\r\nAt a late stage in the crystallization history, the Alta stock had an\r\nessentially solid shell of nonporphyritic granodiorite at least 1200 feet\r\nthick that surrounded a partially liquid but semirigid crystal mush at the\r\ncenter of the stock. Structural adjustments at this late stage re sulted in\r\nclose-space jointing and emplacement of aplite-pegmatite dikes in the nonporphyritic\r\ngranodiorite shell. After emplacement of the dikes but before\r\nthe interstitial liquid of the magma at the center of the stock had completely\r\ncrystallized, the semi-rigid crystal mush and solid shell were intruded by\r\na second pulse of the magma. The distribution of strongly porphyritic\r\ntexture indicates that loss of volatiles through fractures in the overlying\r\nmaterial caused this later phase of the magma to finish crystallization with\r\na fine-grained groundmass. Modal analyses supported by gravimetric\r\nchemical analyses show that the porphyritic granodiorite has a slightly\r\nmore silicic composition than the nonporphyritic granodiorite.\r\nThe Flagstaff-Emma ore zone in the Little Cottonwood district is\r\non the trend of a westward dike like projection of the porphyritic granodiorite.\r\nThe fluids that were released during the emplacement of this late\r\nphase of the magma conceivably may have been the same fluids that deposited\r\nthe ore minerals in the Flagstaff-Emma ore zone.\r\nIn order to determine the trend of the ore-metals during crystallization\r\nof the Alta magma, 76 mineral separates of orthoclase, plagioclase,\r\nbiotite, hornblende, magnetite, sphene, quartz and chlorite were analyzed\r\nby the emission spectrographic method for Cu, Pb, Zn, Ag, Co, Ni and\r\nSn. Comparison between samples of the same mineral show that Co and\r\nNi are slightly less abundant and Cu, Pb and Sn are more abundant in the\r\nlater phases of the Alta igneous suite. No trend is apparent for Ag and\r\nZn. Cu, Co, Ni, Ag and Zn were added to the solid phases of the rock\r\nduring chloritic alteration.\r\nThe release of volatiles associated with the late-stage intrusion of\r\nporphyritic granodiorite, the structural relation of the adjacent ore deposits\r\nto this porphyritic granodiorite and the trend in trace-element\r\nabundances suggest that an ore-forming fluid may have been produced at a\r\nlate stage in the crystallization of the Alta stock.\r\n" }, { "name": "Benson, Carl S.", "degree": "PhD", "year": "1960", "title": "Stratigraphic Studies in the Snow and Firn of the Greenland Ice Sheet", "advisor": "Kamb, W. Barclay; Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03232006-104828", "creators": [ { "name": { "family": "Benson", "given": "Carl S." }, "id": "Benson-Carl-S", "display_name": "Benson, Carl S." } ], "advisors": [ { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "advisor", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/G7V2-0T57", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Greenland ice sheet is treated as a monomineralic rock formation, primarily metamorphic, but with a sedimentary veneer of snow and firn. This sedimentary member is perennial above the firn line, and the classical methods of stratigraphy and sedimentation can be profitably applied to it.\r\n\r\nDuring a 4-year period 146 pit studies and 288 supplementary Rammsonde profiles were made along 1100 miles of over-snow traverse (Fig.1). Temperature, density, ram hardness, and grain size were measured in the strata exposed in each pit.\r\n\r\nStratification of snow results from variations in the conditions of deposition and is emphasized by subsequent diagenesis. Summer layers are coarser-grained and have generally lower density and hardness values than winter layers; they may also show evidence of surface melt. The onset of fall is usually identified by an abrupt increase in density and hardness accompanied by a decrease in grain size. This stratigraphic discontinuity is used as the annual reference plane.\r\n\r\nStrata in the upper 10 to 20 meters compose a succession of annual sequences which are preserved in recognizable form for at least several decades. Correlation of annual layers between pits, spaced 10 to 25 miles apart along the traverse of Figure 1, gives a picture of annual accumulation during the past 5 to 20 years for western Greenland between 69 and 77\u00b0N. The control established by these data, together with information from earlier expeditions (primarily those of Koch-Wegener and DeQuervain) and from permanent coastal meteorological stations, have been used to make a map showing the distribution of gross annual accumulation, essentially the equivalent of annual precipitation, for the entire ice sheet (Fig. 30). In general, the accumulation contours follow the north-south trend of the coast lines, with extremes of less than 10 cm H2O in the northeast and more than 90 cm H2O per year in the south; the average for the ice sheet is 34 cm H2O per year. The zone of maximum precipitation lies close to the coast in two regions, one on the east coast between Angmagssalik and Scoresbysund, the other on the west coast between Upernavik and Thule.\r\n\r\nIn addition to the existence of a useful stratigraphic record four diagenetic facies are recognized on the ice sheet.\r\n\r\n(1) The ablation facies extends from the outer edge, or terminus, of the glacier to the firn line. The firn line is the highest elevation to which the annual snow cover recedes during the melt season.\r\n\r\n(2) The soaked facies becomes wet throughout during the melting season and extents from the firn line to the saturation line, i.e., the uppermost limit of complete wetting. The saturation line is the highest altitude at which the 0\u00b0C isothermal surface penetrates to the melt surface of the previous summer.\r\n\r\n(3) The percolation facies is subjected to localized percolation of melt water from the surface without becoming wet throughout. Percolation can occur in snow and firn of sub-freezing temperatures with only the pipe-like percolation channels being at the melting point. A network of ice glands, lenses, and layers forms when refreezing occurs. This facies extends from the saturation line to the upper limit of surface melting, the dry-snow line. Negligible soaking and percolation occur above the dry-snow line.\r\n\r\n(4) The dry-snow facies includes all of the glacier lying above the dry-snow line, and negligible melting occurs in it.\r\n\r\nThe saturation line can be identified by discontinuities in temperature, density, and ram hardness data, and it may also be located by examination of melt evidence in strata exposed on pit walls. It is as sharply defined as the firn line; but the dry-snow line, although determined by the same methods, is an ill-defined transition zone 10- to 20-miles wide.\r\n\r\nThe facies represent a response to climate, therefore changes in the location of facies boundaries may be used as indicators of secular climatic change. Since facies are not restricted to the Greenland ice sheet, they provide the basis for a general classification of glaciers. This \"facies classification\" is areal in nature and gives a greater resolution of characteristics than Ahlmann's \"geophysical classification.\" In particular, the \"facies classification\" permits subdivision of large glaciers which span the entire range of environments from temperate to polar. Ahlmann's useful distinction between temperate and polar glaciers takes on new meaning in the light of glacier facies. Thus, a temperate glacier exhibits only the two facies below the saturation line whereas one or both of the facies above the saturation line are present on polar glaciers. An attempt has been made to map the distribution of facies on the Greenland ice sheet (Fig. 48).\r\n\r\nThe distribution of mean annual temperature on the ice sheet may be approximated by gradients with respect to altitude and latitude of 1\u00b0C/100m and 1\u00b0C per degree latitude respectively. The altitude gradient is controlled by strong outgoing radiation, producing deep inversions and katabatic winds. The katabatic winds are warmed adiabatically as they descend along the surface of the ice sheets and this is the primary control determining the temperature gradient along the snow surface. The latitude gradient is based on temperature measurements made above 2000 m on the ice sheets and on average values from meteorological stations spanning 20\u00b0 of latitude on the west coast. A contour map of isotherms based on these gradients compares well with temperature values obtained from pits on the ice sheet. (Fig. 40).\r\n\r\nThe densification of snow and firn is discussed for the case where melting is negligible. The assumption is that accumulation remains constant at a given location and, under this assumption, the depth-density curve is invariant with time as stated by Sorge's law. As a layer is buried it moves through a pressure gradient under steady-state conditions, and it is assumed that the decrease in pore space with increasing load is simply proportional to the pore spaces, i.e., [...] where [...] = specific volume of firn ([...] = firn density), [...] = specific volume of ice = 1.09 cm3/g, [...] = load at depth z below the snow surface and m = a constant which depends on the mechanism of densification. The depth-density equation obtained from equation 8 is [...] where K = [...], [...] = void ratio for snow of density [...], and [...] = void ratio for snow of density [...], [...] = density of snow when [...] = 0.\r\n\r\nThe consequences of the assumption in equation 8 compare favorably with observation. A fundamental change in the mechanism of densification is recognized within 10 m of the snow surface. The concept of a \"critical density\" is introduced. Before the density of snow attains the critical value it is compacted primarily by packing of the grains. The critical density represents the maximum value obtainable by packing and further compaction must proceed by other mechanisms. The rate of change of volume with increasing load decreases by a factor of 4 when the critical density is exceeded. The same equations hold in the case where melt is not negligible but the rates of densification are higher.\r\n\r\nBauer's (1955) estimate for the balance of the ice sheet is revised. Two corrections are applied: (1) the average annual accumulation value of 31 cm H2O originally estimated by Loewe (1936) is revised to 34 cm H2O as a result of this study; (2) the relative areas of ablation and accumulation zones in Greenland north of 76\u00b0N are more accurately defined. The net result is a slightly positive balance which is interpreted to mean that the Greenland ice sheet is essentially in equilibrium with present day climate.\r\n" }, { "name": "Doe, Bruce Roger", "degree": "PhD", "year": "1960", "title": "The Distribution and Composition of Sulfide Minerals at Balmat, New York", "advisor": "Engel, Albert Edward John", "url": "https://resolver.caltech.edu/CaltechETD:etd-03092006-111512", "creators": [ { "name": { "family": "Doe", "given": "Bruce Roger" }, "id": "Doe-Bruce-Roger", "display_name": "Doe, Bruce Roger" } ], "advisors": [ { "name": { "family": "Engel", "given": "Albert Edward John" }, "id": "Engel-A-E-J", "role": "advisor", "display_name": "Engel, Albert Edward John" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/Y53K-NC70", "abstract": "Part I.\r\n\r\nIn the Balmat area, northern New York, tabular deposits of sulfide minerals are found parallel to the layering in folded, siliceous magnesian marbles of a metamorphic complex commonly referred to as the Pre-Cambrian Grenville series. Sphalerite, pyrite, and locally, pyrrhotite and galena have replaced the carbonate minerals in parts of the marble units. The contacts between ore and marble are, in general, diffused over distances of inches to feet. Access to the ore is provided through the Balmat No. 2 and No. 3 mines.\r\n\r\nThe isotopic composition of lead from primary galena is homogeneous within an individual mine. The model age of this lead is in agreement with the age of the mineralization determined by other means about a billion years. The isotopic composition of lead and the concentrations of lead and uranium in two samples of marble were investigated. The isotopic composition of the leads in the marble is not homogeneous. Calculations indicate that the isotopic composition of lead in the marble was probably not homogeneous a billion years ago. Unless the isotopic composition of lead in the ores is a homogeneous mixture of lead from an isotopically inhomogeneous source, it is doubtful that the lead in the ores was derived from the surrounding marbles.\r\n\r\nCobalt and nickel concentrations in pyrite from grains disseminated in the metasedimentary rocks away from the ore bodies are greater than 200 ppm. Most samples of pyrite from the ore bodies of the No. 2 and No. 3 mines contain less than 50 ppm each of cobalt and nickel. From these differences in concentrations, the author believes that it is unlikely that the pyrite of the ores is genetically related to the pyrite in the metasedimentary rocks.\r\n\r\nStudies of textural relations suggest that pyrrhotite formed after most of the sphalerite, which in turn formed after most of the pyrite in the ore bodies. By use of the experimentally determined systems, FeS-ZnS-S and FeS-FeS2 it is inferred from the amounts of iron in sphalerite and sulfur in pyrrhotite that the bulk of the sulfide minerals in the No. 2 mine formed above 320\u00b0C. This estimation assumes a total pressure of 3 kilobars, The absolute temperature of formation of pyrrhotite indicated by the FeS-ZnS-S system is about 150\u00b0 higher than that indicated by the FeS-FeS2 system.\r\n\r\nThe concentrations of individual minor elements in sphalerite and pyrite range considerably among specimens of the same sulfide mineral from the same level and ore body. An exception is cadmium in sphalerite which has a narrow concentration range around 1400 ppm in both the No. 2 and No. 3 mines. The ratio of the concentrations of minor elements between sphalerite-pyrite pairs varies considerably also. This variation probably indicates that the minor elements did not achieve a well-developed equilibrium distribution between pyrite and sphalerite during the formation of the ores.\r\n\r\nPart 2:\r\n\r\nThe sphalerite and pyrite from the No. 2 and No. 3 mines at Balmat, New York, and pyrite from the surrounding country rock are analyzed for minor and trace elements. The iron content was determined in 18 samples of sphalerite associated with pyrite and pyrrhotite, and in 177 samples of sphalerite associated with pyrite without pyrrhotite. Analyses for minor and trace elements were made of 74 samples of sphalerite from the mining areas, 32 samples of pyrite from the mining areas, and nine specimens of pyrite from the surrounding metasedimentary rock. In addition, trace and minor elements were determined in nine samples of calcite, seven samples of dolomite, and three samples of pyritic schist from four meta-sedimentary units. The isotopic composition of lead was determined in seven specimens of galena and in two samples of marble. The compositional studies of minerals are related to geologic features of the ore bodies and the surrounding metasediments in order to clarify the (1) relative and absolute age of the deposition of the sulfides, (2) temperature and pressure at which the sulfides were emplaced, (3) source and composition of the ore forming fluid, and (4) causes of the zonal pattern of the minerals in the ore bodies.\r\n\r\nThe primary mineralization occurred during a period of hydration of the surrounding metasediments, after the growth of tremolite and before the formation of talc. Tremolite and talc formed during the metamorphism and retrograde metamorphism of the Grenville series near Balmat. The metamorphism is thought to have occurred about 1050 million years ago. The ore fluid successively deposited pyrite, then galena and iron-rich sphalerite followed by pyrrhotite and chalcopyrite. Subsequently much of the pyrrhotite was altered to marcasite. The marcasite is thought to have formed during the deposition or remobilization of anhydrite and barite. The mineralization concluded with the deposition of iron-poor sphalerite. Recurrent microbrecciation of the metasediments and ores can be correlated with the time sequence of formation of the various ore minerals in various parts of the mines. The ore fluid followed the separate zones of microbrecciation and deposited the sulfides at nearly the temperature of the country rock. On the basis of the space and time relationship between the zones of microbrecciation and different ore minerals, it is inferred that the composition of the ore fluid reaching the site of deposition of the sulfides changed with time.\r\n\r\nThe isotopic composition of lead from galena indicates that the source of the galena is compatible with the following model - a homogenized substratum in which radiogenic lead from the decay of uranium and thorium has been added to lead of meteoritic composition without disruption from the time of origin of the earth until the time of extraction of the ore fluid.\r\n\r\nA part of the pyrrhotite found in the No, 2 mine was formed in an area containing sphalerite and pyrite. The iron content of sphalerite (12.5 ? 1 percent FeS by weight) associated with pyrrhotite and pyrite is found to be significantly higher than in areas where sphalerite occurs without pyrrhotite. It is inferred that in the region containing pyrrhotite the sphalerite became saturated with FeS at the temperature of formation of pyrrhotite. From the estimates of others on similar areas, the total pressure during the deposition of the ores at Balmat is assumed to be 3 +/- 1 kilobars. By use of the phase diagram for the FeS-ZnS system, the temperature of deposition of pyrrhotite is found to be 510\u00b0.\r\n\r\nThe composition of pyrrhotite was investigated by the measurement of lattice spacings. Only one specimen of pyrrhotite was found to contain the necessary hexagonal structure for use with published plots of lattice spacing versus composition. By use of the phase diagram for the FeS-FeS2 system, a temperature of formation of pyrrhotite based on one specimen is indicated to be 340\u00b0C. The discordance in the temperature estimate using two different geothermometers is thought to be due at least in part to exsolution of pyrite from pyrrhotite at a temperature lower than that of the formation of pyrrhotite.\r\n\r\nThe variation in the iron content of sphalerite associated with pyrite is thought to be mainly due to variations in the fugacity of sulfur species rather than changes in temperature. By use of the phase diagram of the ZnS-FeS2-S system, the temperature of formation of sphalerite (6-9 percent FeS by weight) associated with pyrite in the No. 2 mine is indicated to be greater than 320\u00b0C. Sphalerite associated with pyrite in the No. 3 mine contains 2-3 percent FeS by weight.\r\n\r\nCalculations based on the partitioning of trace and minor elements between sphalerite and pyrite give a first approximation of the temperature at which equilibrium was approached in the No. 3 mine of 300-350\u00b0C.\r\n\r\nOnce sphalerite acquires a particular concentration of iron, it is quite resistant to change due to following geologic events. At the temperatures of formation of the sulfides at Balmat, however, reaction between sphalerite and pyrrhotite must have been comparitively rapid. Alternation of pyrrhotite to marcasite did not seem to affect the concentration of iron in sphalerite. Supergene mineralization of magnetite, hematite, and chlorite leached iron from sphalerite grains, but the leached zone is usually 0.1 millimeter thick or less and only rarely attains a thickness of one millimeter. On the other hand, the content of manganese in sphalerite from the zones of supergene mineralization is much lower than sphalerite away from the zones. The concentration of cadmium in sphalerite from both mines falls in the range 1000 to 2000 parts per million with an average value of 1400 parts per million. The content of cadmium in sphalerite does not seem to be sensitive to temperature or accompanying mineral phases or the supergene mineralization." }, { "name": "Flinn, Edward Ambrose", "degree": "PhD", "year": "1960", "title": "Exact Transient Solution of Some Problems of Elastic Wave Propagation", "advisor": "Dix, Charles Hewitt; Press, Frank", "url": "https://resolver.caltech.edu/CaltechETD:etd-02212006-132324", "creators": [ { "name": { "family": "Flinn", "given": "Edward Ambrose" }, "id": "Flinn-Edward-Ambrose", "display_name": "Flinn, Edward Ambrose" } ], "advisors": [ { "name": { "family": "Dix", "given": "Charles Hewitt" }, "id": "Dix-C-H", "role": "advisor", "display_name": "Dix, Charles Hewitt" }, { "name": { "family": "Press", "given": "Frank" }, "id": "Press-F", "role": "advisor", "display_name": "Press, Frank" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/QRYY-CD29", "abstract": "Exact solutions are obtained for three problems of progressive elastic wave propagation in bounded media: (1) SH wave propagation from an impulsive point source in an infinite plate; (2) torsional waves in a solid cylinder; (3) radiation from an impulsive source of compressional and of shear waves in an infinite solid plate held between smooth rigid surfaces. The Laplace transform method is used.\r\n\r\nProblems (1) and (3) are shown to be closely related. For these problems the solution is expressed both as an infinite series of normal modes and an infinite series of multiple reflections, and it is shown that the two representations of the solution are related by Poisson's summation formula. Solutions are obtained for both a delta-function and a unit function input.\r\n\r\nProblem (2) is solved as an infinite series of normal modes for an impulsive shear stress source distributed over a normal section of the cylinder. The case of a point source on the axis of the cylinder is examined in detail.\r\n\r\nProblem (3) involves mixed boundary conditions. A relation between the solution of this problem and wave propagation in a free plate is discussed." }, { "name": "Lloyd, Ronald Michael", "degree": "PhD", "year": "1960", "title": "The Shell Chemistry of Some Recent and Pleistocene Mollusks and its Environmental Significance", "advisor": "Lowenstam, Heinz A.; Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechETD:etd-07052006-082708", "creators": [ { "name": { "family": "Lloyd", "given": "Ronald Michael" }, "id": "Lloyd-Ronald-Michael", "display_name": "Lloyd, Ronald Michael" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/Q1WZ-Z134", "abstract": "In Part I Florida Bay is used as a model to describe some influences of environment on chemical variations of shell material. Geographic isolation and high evaporation in the Bay coupled with the influx of fresh water enriched in O18 produce a gradient of increasing H2O18 going into the Bay. Dilution of Bay water by Ca rich fresh water lowers the Sr/Ca ratio in the Bay.\r\n\r\nThe gradient of H2O18 in the water is clearly reflected in a similar gradient in the carbonate oxygen of mollusk shells. The effect of temperature on the carbonate isotopic composition is shown to be inadequate to explain the variations. Sr/Ca ratios of the shells vary but show no simple relationship to environment. A gradient of decreasing C13 in shells going into the Bay is attributed to the equilibration of CO2 derived by oxidation of organic debris with the carbonate of the water.\r\n\r\nAnalyses of mollusks from sediment cores show that the present environmental framework of Florida Bay has existed for the last 3700 years. Analysis of the fine-grained sediment of the Bay suggests that part of it is washed in from the mainland.\r\n\r\nIn Part II fossil mollusks from the Pleistocene Caloosahatchee formation are analyzed. The O18/O16 ratios coupled with geological and faunal data indicate an environmental framework strikingly similar to the Florida Bay model. A land mass immediately west of the outcrop area is postulated for most of Caloosahatchee time. The carbon isotope and strontium data reveal little environmental information." }, { "name": "Raychaudhuri, Bimalendu", "degree": "PhD", "year": "1960", "title": "Studies of Amphibolites and Constituent Hornblendes From an Area of Progressive Metamorphism Near Lead, South Dakota", "advisor": "Engel, Albert Edward John", "url": "https://resolver.caltech.edu/CaltechETD:etd-06302006-083245", "creators": [ { "name": { "family": "Raychaudhuri", "given": "Bimalendu" }, "id": "Raychaudhuri-Bimalendu", "display_name": "Raychaudhuri, Bimalendu" } ], "advisors": [ { "name": { "family": "Engel", "given": "Albert Edward John" }, "id": "Engel-A-E-J", "role": "advisor", "display_name": "Engel, Albert Edward John" } ], "committee": [ { "name": { "family": "Engel", "given": "Albert Edward John" }, "id": "Engel-A-E-J", "role": "chair", "display_name": "Engel, Albert Edward John" }, { "name": { "family": "Kamb", "given": "W. Barclay" }, "id": "Kamb-W-B", "role": "member", "display_name": "Kamb, W. Barclay" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "member", "display_name": "Silver, Leon T." }, { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "member", "display_name": "Epstein, Samuel" } ], "option_major": [ "geol" ], "doi": "10.7907/V56J-JE76", "abstract": "The progressive metamorphism and origin of the amphibolites of the Lead-Deadwood area, S. Dakota, are considered in detail. Eighty specimens of amphibolite were collected along a belt 3 miles long extending across the entire garnet zone and part of the staurolite zone of the enclosing meta-sediments. These amphibolites were studied petrographically and from them thirty-four were used for modal analysis and chemical analyses for total iron (as Fe2O3), CaO, TiO2, K2O, MnO and trace elements. Twelve of the constituent hornblendes were analysed for all major and minor elements and trace elements. The other 22 constituent hornblendes were analysed for total iron (as Fe2O3), CaO, TiO2, K2O, MnO and trace elements. Seven of the constituent horn-blendes and six constituent plagioclases were used for optical determinations and x-ray diffractometric studies.\r\n\r\nOn the basis of relict texture some of the amphibolites are concluded to be definitely ortho-amphibolites. Field relations of a few hornblende-bearing rocks suggest that they have meta-sedimentary origin. The origin of the remaining majority of the amphibolites is inconclusive.\r\n\r\nThe metamorphism of the amphibolites is essentially iso-chemical throughout the range of conditions represented by the appearance of successively the garnet and the staurolite isophases in the enclosing meta-sediments. What fluctuations in composition are observed appear to be random in character, attributable to minor variations in original composition or to retrograde alteration.\r\n\r\nThe compositions of the constituent hornblendes do not show any significant correlation with intensity of metamorphism and the average composition remains roughly constant throughout the sequence.\r\n\r\nThe concentrations of the various components in the horn-blendes seem to be closely related to the concentrations of the same components in the corresponding amphibolites. The ratios of the concentrations of the various components between horn-blende and amphibolite do not show any significant trend with metamorphic rank and are reasonably constant over the range of metamorphic conditions represented here.\r\n\r\nThe composition of the hornblendes is closely related to specific gravity and broadly related to dimensions of unit cells but there is no close correlation between composition and optics. Size of unit cells in hornblendes appear to be unrelated to metamorphic rank." }, { "name": "Schwarcz, Henry Philip", "degree": "PhD", "year": "1960", "title": "I. Geology of the Winchester-Hemet Area, Riverside County, California. II. Geochemical Investigations of an Arkosic Quartzite of the Winchester-Hemet Area, California", "advisor": "Engel, Albert Edward John; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05042007-083758", "creators": [ { "name": { "family": "Schwarcz", "given": "Henry Philip" }, "id": "Schwarcz-Henry-Philip", "display_name": "Schwarcz, Henry Philip" } ], "advisors": [ { "name": { "family": "Engel", "given": "Albert Edward John" }, "id": "Engel-A-E-J", "role": "advisor", "display_name": "Engel, Albert Edward John" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/DP95-HX65", "abstract": "I. \r\n\r\nAn area of about 100 square miles located 20 miles southeast of Riverside, California, has been geologically mapped. The oldest rocks of the area are phyllites and quartzites correlated with the Bedford Canyon formation (Triassic). Conformably overlying these rocks is a 13,000 foot thick section of quartzite, schist and rare amphibolite, here named the French Valley formation. The metasedimentary rocks were formed from a series of shales, shale-clast conglomerates, poorly sorted feldspathic, calcareous and arkosic sandstones and rare basalt flows or tuffs. Relict sedimentary structures and textures are locally well preserved.\r\n\r\nThe sedimentary rocks were intruded with a series of basic and ultrabasic magmas and were tightly folded prior to late Cretaceous time. Late in the period of folding they were metamorphosed to the hornblende-hornfels facies (200\u00b0-600\u00b0C, 3-5 kilobars), producing andalusite, cordierite, sillimanite and garnet in the schists and hornblende-plagioclase (-diopside, -garnet) assemblages in the amphibolites. Zones of progressive metamorphism are mapped trending N-S and cutting the NW-SE structural trend of the folded rocks. In the late Cretaceous these rocks were intruded by basic to intermediate plutonic igneous rocks of the southern California batholith, with no appreciable contact metamorphism.\r\n\r\nII: \r\n\r\nA series of seven samples of arkosic quartzite from a single homogeneous member of the French Valley formation has been collected along a profile of increasing metamorphic rank. The component minerals and aliquots of the total rocks have been analysed by X-ray fluorescence, emission spectrographic and wet chemical procedures. For most elements studied, concentrations in the total rock, biotite and ilmenite appear to be constant through the series. These elements either did not vary beyond the experimental uncertainty or they varied without apparent trend over a small range slightly exceeding the uncertainty. With increasing degree of metamorphism the following changes were suggested but fell within or only slightly exceeded the assigned limits of error: a) the total rock gained CaO, Mn, Sr, Co, La, Y, and Ti(?) and lost K2O, Na2O, and V; b) the biotite gained Mn, Ti, Ba, and possibly Co, Cr, V, and La and lost CaO; c) ilmenite gained Mn and Ni and lost Cr, Ba, Zr(?), Y, and Pb. Other changes observed with increasing metamorphic rank were: a) coarsening and homogenization of the rock texture; b) decrease in the ratio Fe+++/Fe++ in both rock and biotite; c) decrease in 2V and basal spacing of the biotite; and d) variations in albite content of plagioclase and potash feldspar that suggest loss of Na2O from rock.\r\n\r\nFor most elements fractionations between biotite and rock appear to vary directly with the concentration in biotite. Fractionations between ilmenite and biotite are shown to be related to ionic size and charge.\r\n\r\nThe composition of the rock is such that partial fusion would yield a liquid with a composition close to that of the total rock. This may be the cause of the small variations in major element composition with metamorphic grade." }, { "name": "Simpson, Dale Rodekohr", "degree": "PhD", "year": "1960", "title": "Geology of the Ramona Pegmatites, San Diego County, California", "advisor": "Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-09202006-111427", "creators": [ { "name": { "family": "Simpson", "given": "Dale Rodekohr" }, "id": "Simpson-Dale-Rodekohr", "display_name": "Simpson, Dale Rodekohr" } ], "advisors": [ { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/65DM-QT70", "abstract": "The Ramona pegmatite district of central San Diego County, California, has been known as a source of gem garnet, tourmaline, and topaz since the early 1900's. All the occurrences of known commercial importance lie within an area of about 1.5 square miles.\r\n\r\nThe dominant rocks of the district are tonalites and granodiorites of the Cretaceous southern California batholith. The nearest outcrop of older rocks, the Triassic Julian schist, is about one mile from the main group of pegmatites. Eocene Poway conglomerate caps hills and ridges in a west-trending belt that lies south of the district.\r\n\r\nThe pegmatite bodies, ranging from small stringers to large dikes about 8 feet thick, are remarkably persistent along their strike. They form a pattern of subparallel anastomosing units with a general northwest strike and a westward dip of 35 to 45 degrees. The dikes occur mainly in the tonalites, and appear to have been emplaced along a well-developed set of fractures. These fractures are not systematically related to other structural features of the area, and they transect a major contact between plutons of different composition.\r\n\r\nMost of the pegmatite dikes are asymmetrically zoned, each with a footwall unit of layered aplite and a hanging-wall unit rich in graphic granite. Typical inner zones of the dikes consist of quartz-perthite pegmatite, pocket-bearing pegmatite, and albite-quartz rock.\r\n\r\nAplite generally constitutes about one-third of the containing pegmatite body. It is a soda-rich rock, with about 40 percent of modal albite. Garnet-tourmaline layers in the aplite are roughly parallel to the footwall of the pegmatite body.\r\n\r\nTypical graphic granite, which also forms about one-third of the containing pegmatite body, has a quartz-perthite ratio of 1:3. The microcline-albite ratio within the perthite is about 2:1. Studies of mineral orientation show that the quartz rods in a single specimen of graphic granite have a common crystallographic orientation, but that this orientation is different for different specimens and is not consonant with any crystallographic law. Moreover, the c axis of quartz is generally not the axis of elongation of the rod, nor does the c axis have a systematic angular relation to the walls of the pegmatite dike. Successive surfaces cut in a block of graphic granite show many interconnections of the quartz rods.\r\n\r\nThe quartz-perthite pegmatite commonly contains large euhedral crystals of perthite and ragged-edged blocks of graphic granite in an allotriomorphic groundmass consisting mainly of quartz, perthite, and albite.\r\n\r\nAlbite-quartz rocks occur as fracture fillings and irregular masses within the pegmatite dikes. The albite commonly has a curved cleavelandite form. Modally these rocks have an albite-quartz ratio of 2:1.\r\n\r\nThe pocket pegmatite, which ordinarily occurs in the quartz-perthite rock, consists mainly of smoky quartz with some cleavelandite and topaz. The pockets themselves form spherical voids to thin openings with irregular outlines.\r\n\r\nA period of corrosion and secondary mineralization followed crystallization of the pegmatites. The sequence of removal of minerals was quartz--->microcline--->albite, and the sequence of secondary mineralization was albite--->orthoclase (with an adularia habit)--->quartz with a typical low-temperature crystal form. Spessartite and secondary tourmaline most likely crystallized during the end stages of the corrosion or the beginning of the albite mineralization.\r\n\r\nPseudomorphs of manganese oxide after garnet (?), as well as pseudomorphs of muscovite after tourmaline, are present in otherwise unaltered quartz-feldspar rocks.\r\n\r\nThe bulk mineralogical composition of the pegmatite bodies is 30 to 35 percent for each of the minerals quartz, microcline, and albite. Muscovite, garnet, and tourmaline form about 5 percent of the total rock.\r\n\r\nThe experimentally determined liquidus for a composite sample of the pegmatite under various water-vapor pressures is about 50\u00b0C, higher than the corresponding liquidus for the ternary minimum of the system KAlSi3O8-NaAlSi3O8-SiO2-H2O. Similarly, the pegmatite solidus is about 50 degrees lower than that for the ternary minimum, and it can be further lowered by the addition of fluorine-bearing minerals to the rock melt. Water is soluble in a melt of the composite sample of pegmatite to the extent of about 3.5 and 5.0 weight percent at 1 and 2 kilobars, respectively, of water-vapor pressure.\r\n\r\nLaboratory crystallization of the pegmatite melts was found to be a fairly slow process, requiring several weeks to form 1 or 2 percent of crystals. The crystals are larger and form more rapidly in melts under high water-vapor pressure and with little undercooling. Spherulitic crystal aggregates form with undercooling of 75 degrees or more.\r\n\r\nThe natural pegmatites probably crystallized from a magma and a coexisting vapor that were residual from the magma forming the large composite southern California batholith. An hypothesis of crystallization in a restricted system best explains the features of the pegmatite bodies. Spatial relationships indicate that the dikes crystallized from the walls inward.\r\n\r\nHypotheses are presented to explain the layered aplites either as products of rhythmic crystallization and crystal settling or as products of in-situ rhythmic crystallization progressing upward from the footwalls of the dikes. The rhythmic crystallization could have been a result of pressure fluctuations.\r\n\r\nGraphic granite cocrystallized with the layered aplite. All available evidence indicates simultaneous crystallization of quartz and feldspar, with the graphic texture a result of accelerated growth of one mineral alternating with accelerated growth of the other mineral. Temperature and water vapor-pressure during crystallization of the graphic granite and layered aplite were most likely about 690\u00b0 to 715\u00b0C. and 3000 to 4500 bars, respectively.\r\n\r\nThe graphic granite and the quartz-perthite pegmatite probably crystallized from a melt and a coexisting vapor, and the layered aplite from the melt. The other pegmatite units are thought to be products of crystallization from a hydrothermal fluid that was mainly in the form of a vapor.\r\n" }, { "name": "Stanton, Robert James", "degree": "PhD", "year": "1960", "title": "Paleoecology of the Upper Miocene Castaic Formation, Los Angeles County, California", "advisor": "Lowenstam, Heinz A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02232007-112028", "creators": [ { "name": { "family": "Stanton", "given": "Robert James" }, "id": "Stanton-Robert-James", "display_name": "Stanton, Robert James" } ], "advisors": [ { "name": { "family": "Lowenstam", "given": "Heinz A." }, "id": "Lowenstam-H-A", "role": "advisor", "display_name": "Lowenstam, Heinz A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/F4HG-YN58", "abstract": "The Castaic formation comprises the upper Miocene marine sediments deposited in the Soledad Basin, northwestern Los Angeles County, California. The Soledad Basin is topographically the eastern extension of the Ventura Basin. Geologically, the two basins of deposition are separated by the San Gabriel fault along which an uncertain amount of lateral movement has taken place. Therefore, detailed correlation of the sediments of the Castaic formation with contemporary sediments of the Ventura Basin is not possible. The age of the Castaic formation is Mohnian and Delmontian. The sediments were deposited in part along an open coast and in part within a broad, open embayment.\r\n\r\nLate Miocene movement on the San Gabriel fault, relatively up on the southwest, defined the western margin of the basin of deposition. A land mass on the west side of the fault northwest of Castaic, created the embayment of the northwest part of the basin. It is likely that a submerged extension of this land southeast of Castaic formed a sill along the western margin of the rest of the basin and restricted the circulation of bottom water.\r\n\r\nThe formation is about 7000 feet thick. It consists mainly of interbedded sandstone and mudstone. The two rock types occur in units 25 to 250 feet thick. Coarse-grained basal sediments were deposited at the margin of the basin of deposition. Megafossils are largely confined to the basal sediments. The nature of the basal sediments deposited at the margin of the transgressing late Miocene sea is related to the provenance and the relief along shore. Conglomeratic basal sediments were deposited along the northeast margin of the basin along a steep shore composed of the well-indurated Martinez formation. These sediments were derived locally from the conglomerate and sandstone beds of the Martinez formation.\r\n\r\nSandy and thin conglomeratic basal sediments were deposited along the southeast margin of the basin. Near-shore relief was low. The sediments were derived largely from the finer-grained, less consolidated sediments of the Mint Canyon formation. The very coarse-grained, poorly-sorted Violin breccia was derived from a nearby source of considerable relief that was northwest of the embayment.\r\n\r\nThe fauna of the Castaic formation is largely molluscan. Other phyla are represented by one species of brachiopod, two species of echinoderm, a balanid, a bryozoan, foraminifers and fish remains--both bones and scales. Approximately 100 species are present. Probably new species of Nerita, Colus (Anomalosipho), Marginella, and Arene occur in the formation. Other forms in the Castaic formation previously unreported or rarely reported from upper Miocene sediments of California are Anadara (Anadara) trilineata trilineata, Glycymeris cf. G. branneri, Chlamys hodgei, Sondylus sp., Eucrassatella cf. E. subgibbosa, Pseudochama sp., Corbula luteola, Periploma cf. P. discus, Tegula gallina, Calyptraea (Trochita) sp., Polinices (P.) uber, Oliva spicata. The fauna is comparable to that found at present at the northern limit of the recent Panamic molluscan province.\r\n\r\nAll the near-shore assemblages in the formation are essentially contemporaneous. Faunal variations are indicative of environmental variations which existed along the margin of the basin. In particular, the geographic distribution of the fauna can be related to differences in water depth and substrate, and to environmental differences associated with bay versus open coast habitat.\r\n\r\nAnalysis of the fauna suggests that: oxygen content of the water was probably less than normal at the bottom of the basin; the water was of normal marine salinity; most of the megafauna and associated sediments were deposited in water less than 25 fathoms deep; the maximum depth of the sill which probably existed along the western margin of the basin was about 100 fathoms; the marine climate was apparently uniform geographically within the basin of deposition and was much like that found at present off the southwest coast of Baja California. The average maximum annual surface temperature was about 22\u00b0C. The average minimum annual surface temperature was about 19\u00b0C. The Castaic formation was deposited at the northern limit of the late Miocene Panamic molluscan province.\r\n\r\nBathymetric distribution as well as geographic distribution of a fauna must be considered in any paleozoogeographic study in order to determine paleoclimate." }, { "name": "Campbell, Richard Bradford", "degree": "PhD", "year": "1959", "title": "The Texture, Origin, and Emplacement of the Granitic Rocks of Glenlyon Range, Yukon, Canada", "advisor": "Campbell, Ian; Silver, Leon T.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02172006-144353", "creators": [ { "name": { "family": "Campbell", "given": "Richard Bradford" }, "id": "Campbell-Richard-Bradford", "display_name": "Campbell, Richard Bradford" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" }, { "name": { "family": "Silver", "given": "Leon T." }, "id": "Silver-L-T", "role": "advisor", "display_name": "Silver, Leon T." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/HM6J-8Y76", "abstract": "In Glenlyon range the older pre-intrusive rocks include quartzo-feldspathic schists (Ambibolite facies) with minor carbonate and lime-silicate rocks of the Yukon group overlain by a succession of limestones and slates and phyllites (green schist facies) of the Harvey Group. These rocks form the north limb of an east-west trending anticlinorium. The Drury quartz monzonite is intruded into the axial region of the anticlinorium. This mass grades continuously from a biotite granodiorite core to an outer zone of quartz monzonite in which the proportions of hydridized inclusions and septa of metamorphic rock increase with complete gradation to the granite-free metamorphic host terrane. To the north and east a second large mass, the Peak granodiorite, identical with the core of the Drury quartz monzonite, has been emplaced with clearly crosscutting intrusive relations. A pattern of large scale faulting associated with the contact of the Peak granodiorite suggests that fault block movement may have provided some of the intrusive space requirements. Smaller alaskite dikes cut both the metamorphic complex and the Drury quartz monzonite.\r\n\r\nDetailed petrographic studies of the textures and mineral modes of the granitic rocks argue for a similar crystallization history of the Peak granodiorite and the core of the Drury quartz monzonite. The textural evidence for paragenesis and the mineral composition trends of the entire intrusive complex are combined with discussions of the crystallization of a hypothetical granodiarite magma based on available experimental data of the system KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8 - SiO2 - H2O. All of the significant natural paragenetic relations, particularly the important role of potash feldspar (including replacement reactions) in the later crystallization stages, can be explained as resulting from magmatic crystallization. These effects are distinguished from metasomatic phenomena in the host rocks.\r\n\r\nThe validity of such arguments rests in part on a detailed analysis of the sampling of these granitic masses and problems of representation of modal data. The results of approximately 150 modal analyses are presented in four mineral-component tetrahedrons to support these discussions.\r\n" }, { "name": "Irvine, Thomas Neil", "degree": "PhD", "year": "1959", "title": "The Ultramafic Complex and Related Rocks of Duke Island, Southeastern Alaska", "advisor": "Noble, James A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03102006-161603", "creators": [ { "name": { "family": "Irvine", "given": "Thomas Neil" }, "id": "Irvine-Thomas-Neil", "display_name": "Irvine, Thomas Neil" } ], "advisors": [ { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/KMR7-CC87", "abstract": "Duke Island, 59 square miles in area, is at the southern end of southeastern Alaska. Sedimentary and volcanic rocks, possibly Mesozoic in age, are metamorphosed and intruded by gabbroic, ultramafic and granitic plutons, in that order. The granitic rocks may be of Cretaceous age.\r\n\r\nPrimary gabbroic rocks are dominantly two-pyroxene gabbro and norite. Their plagioclase is An50-An70.\r\n\r\nUltramafic rocks crop out as two main areas and more than a dozen minor ones. The rocks in the main areas probably are continuous at depth forming the Duke Island ultramafic complex. Constituent minerals are olivine, clinopyroxene, and hornblende; orthopyroxene and plagioclase characteristically are absent. Rock units are classified as dunite, peridotite, olivine pyroxenite, and hornblende pyroxenite. Hornblende pyroxenite contains 10-20 per cent magnetite and typically occurs as a border zone. The olivine-bearing units have remarkable layering which developed by gravitational settling of crystals from a body of circulating magma. Most of the olivine pyroxenite is cut by an intrusion represented at the present surface by dunite and peridotite.\r\n\r\nHornblende-anorthite (An95) pegmatite, an ultramafic derivative, occurs in an aureole around the complex. In the aureole, pyroxene gabbro is altered to hornblende gabbro with plagioclase intermediate between those of pegmatite and primary gabbro.\r\n\r\nThe relationship of ultramafic and primary gabbroic rocks indicates that they formed from ultramafic magma and normal gabbroic magma respectively.\r\n\r\nMechanisms of crystallization differentiation, multiple intrusions, solid intrusion, and vapor transfer are examined as possible explanations of the distribution of rock types within the ultramafic complex. No one is sufficient, but all have applicability. The border zone is accounted for by transfer of water, silica, lime, and iron from the ultramafic magma to olivine-bearing rocks initially solidified from the magma body onto its walls. The required reactions are demonstrable in other parts of the complex, and the process is related to the development of the surrounding aureole. Evidence is given of late magmatic recrystallization in the complex and of local replacement of olivine pyroxenite by dunite. Disequilibrium, largely arising from multiple intrusion, and transfer of materials by an aqueous-rich vapor phase are probable causes.\r\n\r\nA sequence of events is summarized." }, { "name": "Shreve, Ronald Lee", "degree": "PhD", "year": "1959", "title": "Geology and Mechanics of the Blackhawk Rockslide, Lucerne Valley, California", "advisor": "Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02212006-085518", "creators": [ { "name": { "family": "Shreve", "given": "Ronald Lee" }, "id": "Shreve-Ronald-Lee", "display_name": "Shreve, Ronald Lee" } ], "advisors": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/T496-QF62", "abstract": "Blackhawk Mountain, a resistant mass of marble thrust northward over uncemented sandstone and weathered gneiss, rises above southeastern Lucerne Valley at the eastern end of the rugged 4000-foot escarpment that separates the San Bernardino Mountains on the south from the Mojave Desert on the north. Spread out on the alluvial apron at the foot of the mountain is the Blackhawk rockslide, a lobe of nearly monolithologic marble breccia 30 to 100 feet thick, 2 miles wide, and nearly 5 miles long. At least two earlier similar but smaller rockslides have occurred in the area.
\r\n\r\nThe rocks of the area comprise late Tertiary and Quaternary fanglomerates and breccias derived mainly from the gneiss, quartzite, Carboniferous marble, and Cretaceous quartz-monzonite of the San Bernardino Mountains. Uplift of Blackhawk Mountain occurred in two stages after deposition of the older fanglomerates and breccias: the first by over-thrusting from the south, and the second by monoclinal folding along a northwest-trending axis.
\r\n\r\nGeological evidence in the area shows that the Blackhawk rockslide traversed the gently inclined alluvial slope as a nearly nondeforming sheet of breccia moving more than 50 miles per hour. The hypothesis that compressed air, rather than water or mud, constituted the lubricating layer on which the breccia sheet slid qualitatively explains all of the principal physical features of the slide lobe. Theoretical analysis of the flow in the lubricating air layer indicates the quantitative feasibility of the air-lubrication hypothesis for the Blackhawk slide.
" }, { "name": "Taylor, Hugh Pettingill", "degree": "PhD", "year": "1959", "title": "O\u00b9\u2078/0\u00b9\u2076 Ratios in Coexisting Minerals of Igneous and Metamorphic Rocks", "advisor": "Epstein, Samuel", "url": "https://resolver.caltech.edu/CaltechETD:etd-03032006-133345", "creators": [ { "name": { "family": "Taylor", "given": "Hugh Pettingill" }, "id": "Taylor-Hugh-Pettingill", "display_name": "Taylor, Hugh Pettingill" } ], "advisors": [ { "name": { "family": "Epstein", "given": "Samuel" }, "id": "Epstein-S", "role": "advisor", "display_name": "Epstein, Samuel" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/1M8V-DM23", "abstract": "The flourine extraction technique for determination of oxygen isotopic abundances has been investigated, and it has been used to obtain O18/O16 analyses of the common rock-forming minerals. A direct comparison with an independent method of analysis, that of reduction with carbon at high temperatures, has shown that both these methods are reliable for quartz samples. Most minerals can be analyzed by the flourine method to a precision of +/- 0.2 per mil. Only olivine and magnetite, of the common igneous and metamorphic minerals, are difficult to react.\r\n\r\nOxygen isotopic analyses of all the major minerals of the four principal rock types of the Southern California batholith have been obtained. For comparison, the same technique has been used upon similar rock types from widely scattered localities, to test the general applicability of the results. All the main rock types of the Skaergaard intrusion have been analyzed, as well as many of the minerals. Various samples of ultramafic rocks, anorthosites, and metamorphic amphibolites have also been run.\r\n\r\nIt has been found that the crystallization history and mineral paragenesis of igneous rocks are reflected by the oxygen isotopic data. In every instance where conclusive information exists, the isotopic results are in excellent agreement with the sequence and history determined by conventional geological criteria. Most rocks analyzed fell into a consistent pattern with respect to petrologic type. The Skaergaard rocks deviated markedly from the normal isotopic trends, as a direct result of the unusual course of fractional crystallization which they have undergone." }, { "name": "Lewis, Arthur Edward", "degree": "PhD", "year": "1958", "title": "Geology and Mineralization Connected with the Intrusion of a Quartz Monzonite Porphyry, Iron Mountain, Iron Springs District, Utah", "advisor": "Noble, James A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-04022007-152838", "creators": [ { "name": { "family": "Lewis", "given": "Arthur Edward" }, "id": "Lewis-Arthur-Edward", "display_name": "Lewis, Arthur Edward" } ], "advisors": [ { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/ZWZP-Z443", "abstract": "Iron Mountain is one of three intrusive bodies exposed in the Iron Springs district approximately 15 miles west of Cedar City, Utah. It is the erosional remnant of a quartz monzonite porphyry, intruded into Mesozoic limestone and clastic rocks probably at a depth of less than one mile. The quartz monzonite was intruded in large part along the base of the Carmel formation and has pushed aside the overlying sedimentary rocks as if they were a trap-door hinged on the southeast.
\r\n\r\nMetamorphism is very weak and is confined for the most part to the Sandy member at the base of the Carmel formation. The Homestake limestone member of the Carmel formation is locally replaced by massive bodies of iron ore, consisting chiefly of magnetite, specularite, carbonates and phlogopite. The mineralization is associated with the quartz monzonite but was not necessarily derived from it. Chemical analyses and the mineralogy of the limestone and the ore show that Ca and CO2 have been removed and important amounts of Fe, Si, Mg, Al and K have been added with no change in volume during replacement of the limestone.
\r\n\r\nA high temperature and a low confining pressure during mineralization may have permitted the transport of iron halide in a gas phase, but the addition of some of the other constituents and the removal of Ca are not easily accounted for by such a mechanism.
" }, { "name": "Rose, Arthur William", "degree": "PhD", "year": "1958", "title": "Trace Elements in Sulfide Minerals from the Central Mining District, New Mexico, and the Bingham Mining District, Utah", "advisor": "Noble, James A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01302006-131912", "creators": [ { "name": { "family": "Rose", "given": "Arthur William" }, "id": "Rose-Arthur-William", "display_name": "Rose, Arthur William" } ], "advisors": [ { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/N327-XK86", "abstract": "A total of 143 samples of chalcopyrite, 230 samples of sphalerite, and a few samples of other hydrothermal minerals from the Central and Pinos Altos mining districts of New Mexico, and the Bingham mining district of Utah, have been analyzed spectrographically for trace element content. Most of the sphalerites have also been analyzed for iron content by an x-ray fluorescence method. For many elements, variations within single crystals and within mines show no correlation with variations of other elements in the sulfides, indicating that several factors, not temperature alone, are of importance in determining the trace element content of sulfides. Changes in the composition of the hydrothermal fluid with time and position are believed to be the most important causes of variations in the sulfides, but temperature and lack of equilibrium are also believed to be significant.\r\n\r\nIn the chalcopyrite and sphalerite from both districts the trace element contents are found to fall readily into two or more groups as defined by trace element content. The groups can generally be distinguished geographically and also show geologic and mineralogic differences, although enough similarities exist among groups in the Central mining district to conclude that temperature and other environmental factors are not the primary cause for the grouping, but that the differences probably existed in the hydrothermal fluids before they reached the site of deposition.\r\n\r\nThe trace element content of sphalerite from the Central mining district shows a poorly developed but distinct lateral zoning away from the Hanover-Fierro and Santa Rita stocks. This zoning in trace element content is accompanied by an increase in the Pb/Zn ratio and an increase in the average silver content of the ores. A similar zoning may exist in the trace element content of chalcopyrite from this district and in the trace element content of sphalerite from the Bingham mining district. In addition, a poorly developed vertical zoning in the trace element content of sphalerite appears to exist within one ore shoot at Bingham. Either a temperature gradient or concurrent progressive changes in the composition of the hydrothermal fluid and the site of deposition are suggested as possible causes for the zonal relations found.\r\n\r\nStudy of variability of trace element content of chalcopyrite, and sphalerite within mining districts indicates that four or more properly selected samples are necessary to obtain a valid mining district average for use in regional studies such as that made by Burnham (1955).\r\n\r\nThe large variability of iron content of sphalerite within districts, mines, and even veins and single crystals is believed to result in part from variations in temperature, in part from lack of equilibrium between the sphalerite and the adjacent minerals and fluid during deposition, and in part from equilibrium with pyrite rather than pyrrhotite. It is suggested that the iron content of sphalerite is most correctly interpreted to give a minimum temperature of deposition of the sphalerite; that is, the temperature of deposition was at least as high as the value indicated by the iron content on the solvus of the FeS-ZnS system." }, { "name": "Sanford, Allan Robert", "degree": "PhD", "year": "1958", "title": "Section I. An Analytical and Experimental Study of Some Simple Geologic Structures. Section II. Gravity Survey of a Part of the Raymond and San Gabriel Basins, Southern California", "advisor": "Dix, Charles Hewitt", "url": "https://resolver.caltech.edu/CaltechETD:etd-01272006-094501", "creators": [ { "name": { "family": "Sanford", "given": "Allan Robert" }, "id": "Sanford-Allan-Robert", "display_name": "Sanford, Allan Robert" } ], "advisors": [ { "name": { "family": "Dix", "given": "Charles Hewitt" }, "id": "Dix-C-H", "role": "advisor", "display_name": "Dix, Charles Hewitt" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/HKE2-RP54", "abstract": "SECTION I:
\r\n\r\nThe geologic structures produced by two distributions of applied vertical displacement along the base of a homogeneous layer, (1) a broad curve and (2) a sharp step, were investigated analytically and experimentally. A special form of the general theory of elasticity and scale models (with layers of dry sands and clay) were used for a two dimensional analytical and experimental study of these structures.
\r\n\r\nEach of the two distributions of applied vertical displacement produce a characteristic fracture pattern in the model experiments. For a broad curve, the fracture pattern is a complex zone of normal faults which taper inward to the axis of the fold and die out at depth. For a sharp step, the fracture pattern is (1) a series of curved reverse faults which start steeply at the base of the layer but intersect the upper surface at low angles (thrusts), and (2) a series of normal faults in the uplifted block near the reverse faults.
\r\n\r\nThe initial fractures in the model experiments, for example the curved reverse faults, can be predicted on the basis of the Mohr fracture criterion and the stress distributions found in the elastic analyses. In addition, the displacement fields obtained in the elastic analyses are good first order approximations of the displacement fields observed in the model experiments.
\r\n\r\nSECTION II:
\r\n\r\nA gravity survey (640 stations) was conducted over thirty-six square miles of the alluvium covered portion of the Raymond and San Gabriel basins. Corrections for latitude, elevation, and topography were applied to the gravity data. On the basis of the known surface and sub-surface geology, regional gravity due to deep crustal structure, and gravity due to near surface structure were separated and interpreted independently.
\r\n\r\nThe regional gravity due to deep crustal structure indicates a uniform thickening of the earth's crust to the northeast. If all of the regional gravity is attributed to a density difference of 0.5 c.g.s. at the Mohorovicic discontinuity, the rate of thickening is about 100 meters per kilometer.
\r\n\r\nThe distribution of gravity due to near surface structure shows two steep gradient valleys in the bedrock surface beneath the alluvium in the northern part of the area. The elevation to the floor of these valleys indicates at least 1000 feet of subsidence since the deposition of the alluvium (Upper Pleistocene). The bedrock relief is fairly gentle in the southern part of the area where Tertiary rock lies between bedrock and alluvium. This intermediate layer of Tertiary rock may extend more than a mile north of the Raymond fault. The vertical displacement on the Raymond fault may be 600 feet along one section of the fault in east Arcadia.
" }, { "name": "B\u00f6dvarsson, Gunnar", "degree": "PhD", "year": "1957", "title": "Thermal Activity and Related Phenomena in Iceland", "advisor": "Dix, Charles Hewitt", "url": "https://resolver.caltech.edu/CaltechETD:etd-07082004-135901", "creators": [ { "name": { "family": "B\u00f6dvarsson", "given": "Gunnar" }, "id": "B\u00f6dvarsson-Gunnar", "display_name": "B\u00f6dvarsson, Gunnar" } ], "advisors": [ { "name": { "family": "Dix", "given": "Charles Hewitt" }, "id": "Dix-C-H", "role": "advisor", "display_name": "Dix, Charles Hewitt" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/H708-R451", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in the .pdf document.\r\n\r\nThe thermal activity in Iceland is grouped into two groups, the low-temperature and the high-temperature activity, in accordance with the temperature at the base of the circulation systems. The low-temperature activity includes those thermal areas where this temperature is below 150 [degrees]C. The high-temperature activity includes areas with a higher temperature. The concentration of free CO2 in the spring gases and the concentration of dissolved SiO2 in the thermal water furnish information about the base temperature. The isotope ratios D/H and O18/O16 are indicative of recharge areas and the general pattern of flow. Temperature conditions in near surface layers are studied by the electric resistivity methods. The total heat transported by the low-temperature activity is estimated at 0.2 to [...] cal/sec and by the high-temperature activity at 0.3 to [...] cal/sec. Temperature conditions in 3 non-thermal wells in Iceland are studied and corrected for various effects, mainly the heavy erosion during the Pleistocene. The outward conduction of heat in Iceland appears to be of the order of 3 to [...] cal/sec [...] which is 2.5 to 4 times the normal. The abnormal conduction flow appears to be the main source of energy for the low-temperature activity whereas large volcanic intrusives of recent origin appear to supply the high temperature activity. The abnormal conduction flow ray be caused partially by large magmatic intrusives in the upper 10 to 20 km under Iceland." }, { "name": "Eaton, Gordon Pryor", "degree": "PhD", "year": "1957", "title": "Miocene Volcanic Activity in Los Angeles Basin and Vicinity", "advisor": "Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05042007-131625", "creators": [ { "name": { "family": "Eaton", "given": "Gordon Pryor" }, "id": "Eaton-Gordon-Pryor", "display_name": "Eaton, Gordon Pryor" } ], "advisors": [ { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/EZ20-XJ95", "abstract": "The Los Angeles basin is an elongate topographic depression on the southwestern coast of California. It marks the site of a former marine basin in which a maximum of about 30,000 feet of sediments accumulated during Tertiary times. Volcanic activity in this basin began during early middle Miocene (Relizian) time and ended during late Miocene (Mohnian) time. The products of this eruptive episode consist primarily of flows and tuff-breccias of olivine basalt, basaltic andesite, and hypersthene-augite andesite. Dacite end rhyolite were extruded locally in the northeastern part of the basin, but they constitute only a small fraction of the total volume of lavas and pyroclastic rocks of the region. Petrographically, the rocks are typical of the basalt-andesite-rhyolite association of the circum-Pacific volcanic belt.
\r\n\r\nAn investigation was undertaken to determine, as closely as possible, the timing of the volcanism and the composition of the volcanic rocks in different parts of the basin, and to study criteria whereby correlations of the volcanic portions of the stratigraphic section might be achieved. To this end, field mapping and collecting were done in those parts of the basin in which the effusive rocks crop out, and data from wells which penetrated these rocks in the subsurface were compiled. Thin-section studies, wet chemical analyses, and spectrochemical analyses of selected specimens were made during the course of the study.
\r\n\r\nThe results indicate that Tertiary volcanic activity in the Los Angeles basin was restricted wholly to the Miocene epoch. The first phases of this activity began simultaneously in the northwestern and southeastern parts of the area during Relizian time. Pyroclastic olivine basalt was thrown into the sea near the eastern end of the Santa Monica Mountains, northwest of Los Angeles, and olivine-bearing basaltic andesite was extruded subaerially near Sunland, 12 miles to the north, while flows and breccias of hypersthene-augite andesite accumulated in the vicinity of the San Joaquin Hills, 40 miles to the southeast. During the Relizian-Luisian transition interval (early to late middle Miocene), submarine flows of basalt and basaltic andesite were expelled near the city of Inglewood, southwest of Los Angeles. In the early part of the Luisian stage, peperites of hypersthene-augite andesite were injected into marine sediments accumulating in the vicinity of the Palos Verdes Hills, and at the same time, volcanic activity broke out on a grand scale in the northeastern part of the basin. In rapid succession, flows and breccias ranging in composition from olivine basalt and hypersthene-augite andesite to rhyolite were deposited on and near the Miocene shore, in what is now the vicinity of Glendora and Pomona. Flows of olivine basalt were laid down on the sea bottom in the east central part of the basin at this time, and were followed by deposition of pyroclastic rocks of similar composition. Near El Modeno, at the eastern margin of the basin, activity persisted until the end of Luisian time. Flows of olivine basalt, palagonite tuff, and breccias of basaltic andesite accumulated there. The dying phases of activity are represented by the Whittier diabase, an intrusive body of basaltic and dioritic composition that was emplaced in the Whittier fault zone, southeast of Los Angeles, during middle or late Mohnian time. Less well confirmed evidence of supposed Mohnian volcanism is represented by basaltic tuff-breccia beneath the Dominguez oil field, north of the Palos Verdes Hills.
\r\n\r\nIn most of the areas, dikes and other small intrusive bodies were injected into the country rocks after surface manifestations of igneous activity had ceased. These intrusive bodies are less well dated than the lavas, but most are thought to be of approximately the same age as the associated flows. In the San Joaquin Hills, however, an augite andesite exposed near the coast is at least as young as Luisian, and possibly is even younger, whereas extrusive activity in this area took place during late Relizian time.
\r\n\r\nBetween 400 and 800 square miles of lava are believed to underlie the Los Angeles basin proper. This represents only a small fraction of a much larger volcanic province that includes the western Santa Monica Mountains and Ventura basin to the northwest, and the continental shelf off the coast of California to the southwest. Miocene volcanic rocks are known to underlie large parts of all these areas.
\r\n\r\nThroughout the Los Angeles basin and surrounding region, beds of rhyolite tuff of various ages are interbedded with the Tertiary sedimentary rocks. Several of these tuffs were studied in detail, and it is concluded that most of them represent wind-borne products of volcanic activity in areas to the northwest (southern and central Coast Ranges) and/or southwest (present floor of the Pacific Ocean).
\r\n\r\nIt was found that no one rock type in the area is restricted in time to a particular part of the Miocene epoch. As an example, olivine basalt of Relizian age occurs in the eastern Santa Monica Mountains, and identical rocks of Luisian age occur in the east central and northeastern parts of the basin. Similarly, hypersthene-augite andesite of Relizian age is exposed at the southeastern end of the basin, and Luisian lavas of like lithology are exposed in the northeastern part. A detailed study of the rocks reveals that the few distinctions that can be made on the basis of petrography are functions of geographic, rather than stratigraphic, differences. Rocks of andesitic composition are restricted primarily to the eastern and southern parts of the basin, and basalts predominate in the northwestern part.
\r\n\r\nVariation diagrams based on wet chemical analyses show a distinct contrast in chemical composition between the flows and breccias of the northeastern part of the basin and those exposed along the coast. The latter are richer than the former in FeO and MgO, and poorer in Al2O3. These differences are believed to be the result of assimilation of pre-Tertiary \"basement\" rocks beneath the floor of the basin by magma in the process of ascent. The coastal lavas occur entirely within an area underlain by the Catalina metamorphic facies, a chloritic schist accompanied by saussuritic gabbro and serpentine. The lavas in the northeastern part of the basin are underlain by \"basement\" rocks of granodiorite and quartz diorite. A series of calculations indicates that magmatic differentiation of the volcanic rocks in the Glendora area probably took place by crystal fractionation of early-formed ferromagnesian minerals and calcic plagioclase, accompanied by assimilation of granodiorite. Differences in composition arising in this manner cut across time boundaries, and thus hinder stratigraphic correlation of the rocks.
\r\n\r\nQuantitative spectrochemical analyses indicate numerous variations in the trace-element composition of the rocks. The sources of these variations include contamination of core samples, minor differences between neighboring flows of like composition, and large differences between various members of a single differentiation series. Differences in composition resulting from deuteric alteration of the rocks were found to be surprisingly small. If all of these variations are considered and the trace-element analyses of the rocks are compared, the only distinctions that can be made are geographic rather than stratigraphic. It is concluded that further attempts to establish compositional criteria for the purpose of correlation would be unproductive and unprofitable.
\r\n\r\nVolcanic activity in the region coincided with profound tectonic unrest. The Los Angeles basin lies in the area of intersection of two major tectonic belts: the east-trending Transverse Ranges and Murray Fracture Zone, and the northwest-trending Coast Ranges and Peninsular Ranges. It is thought that deformation within, and at the base of the earth's crust in this area was responsible for the localization of volcanic activity. The transverse Volcanic Province of southern Mexico is similarly located at the intersection of the east-trending Clarion Fracture Zone and the northwest-trending circum-Pacific orogenic belt. Tertiary subsidence of the Los Angeles basin was relatively slow until middle Miocence time. During the Relizian stage, rapid settling began concomitantly with the outbreak of volcanism.
" }, { "name": "Grau, G\u00e9rard", "degree": "PhD", "year": "1957", "title": "I. On the Reflection of Plane Waves by Stratified Systems (Normal Incidence). II. The Determination of Seismic Velocities in Layers with Non-Parallel Interfaces", "advisor": "Dix, Charles Hewitt", "url": "https://resolver.caltech.edu/CaltechETD:etd-07132004-140721", "creators": [ { "name": { "family": "Grau", "given": "G\u00e9rard" }, "id": "Grau-G\u00e9rard", "display_name": "Grau, G\u00e9rard" } ], "advisors": [ { "name": { "family": "Dix", "given": "Charles Hewitt" }, "id": "Dix-C-H", "role": "advisor", "display_name": "Dix, Charles Hewitt" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/2AR7-AG54", "abstract": "The purpose of this study is to establish that the reflection of a plane wave (at normal incidence) by a nonhomogeneous layer with properties varying only in the direction of wave propagation may be deduced by a limiting process from the formulae which are valid in the case of discrete homogeneous layers. In this limiting process the number of layers is made to increase without bounds while the thickness of each layer tends to zero in such a way that the total thickness remain constant.\r\n\r\nThis is done by using the matrix relation which binds the up and down-going wave amplitudes in two layers of a pile of homogeneous layers on top of a semi-infinite homogeneous medium. Then the number of layers is increased as described above and the limit of the matrix relation obtained. It is then verified that the result thus gotten is identical to the quantity obtained by solving the differential equation for the disturbance in a nonhomogeneous layer whose properties are the ones which the discrete case is made to tend to.\r\n\r\nA method for calculating velocities in homogeneous isotropic layers and the position of their interfaces from surface reflection seismic measurements is described. The problem is discussed only in the case of parallel strikes. Conditions of applicability are plane interfaces and good lateral correlations.\r\n\r\nAlso the accuracy of the determination of the velocities and the position of the interfaces depends very much on the velocity, the dip and a distance which gives the position of the interface. One should be careful to estimate in each particular case whether the method may safely be used." }, { "name": "Lohman, Kenneth Elmo", "degree": "PhD", "year": "1957", "title": "Cenozoic Nonmarine Diatoms from the Great Basin", "advisor": "Reeside, John B.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08192004-140258", "creators": [ { "name": { "family": "Lohman", "given": "Kenneth Elmo" }, "id": "Lohman-Kenneth-Elmo", "display_name": "Lohman, Kenneth Elmo" } ], "advisors": [ { "name": { "family": "Reeside", "given": "John B." }, "id": "Reeside-J-B", "role": "advisor", "display_name": "Reeside, John B." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/X235-B763", "abstract": "The wide distribution in the Great Basin area of the Western United States, both geographically and geologically, of the Cenozoic nonmarine diatoms would make them particularly useful for stratigraphic correlation and age determination if their geologic ranges were better known. For this reason, diatoms were collected from some well known vertebrate collecting localities in Nevada, Idaho, and Utah, and the geologic ranges of the individual species established.\r\n\r\nOf the 353 different species and varieties of nonmarine diatoms identified from the six stratigraphic units chosen, ranging from late middle Miocene to late Pleistocene in age, 85 have been described and illustrated as new, 40 have been known previously only as fossils, and 228 have been recorded previously from living assemblages elsewhere.\r\n\r\nPaleoecological interpretations of the environmental conditions which obtained during the deposition of the sediments studied were made on the basis of the 228 species and varieties of diatoms in the last category.\r\n\r\nThe investigation has shown that many of the fossil nonmarine diatoms have satisfactorily short ranges in geologic time, and therefore are valuable guides for stratigraphic correlation and age determination of the sediments in which they occur. Furthermore, the Recent species in each assemblage have been shown to supply much useful data on which to base paleoecological interpretations, limited principally to published ecologic data on the living organisms." }, { "name": "Meier, Mark Frederick", "degree": "PhD", "year": "1957", "title": "Mode of Flow of Saskatchewan Glacier, Alberta, Canada", "advisor": "Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-06152006-081525", "creators": [ { "name": { "family": "Meier", "given": "Mark Frederick" }, "id": "Meier-Mark-Frederick", "display_name": "Meier, Mark Frederick" } ], "advisors": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/Q1QN-XP58", "abstract": "Research in 1952-54 on Saskatchewan Glacier was directed toward the measurement of velocity on the surface and at depth, the surface and bedrock topography, ablation, and structures produced by flow. These field data are used to test current theories of flow and to derive new conclusions about the flow of a valley glacier.
\r\n\r\nPositions in space of 51 velocity stations fixed in the ice were computed from triangulation surveys. Summer velocities are generally greater than yearly velocities. Short interval (1/2-1 day) observations recorded great velocity fluctuations and occasional backward movements. Some of these fluctuations represent domains not over 100 feet in extent. Dispersion values indicate that jerkiness is probably due to irregular shearing and is not predominantly perpendicular to crevasses. Dispersion of velocity decreases with increasing time intervals of measurement. Maximum surface velocity of 383 fpy occurs at the firn limit; velocity decreases unevenly along the midglacier line to 12 fpy at the terminus. Velocity vectors plunge below the surface along the centerline from above the firn limit to 1.3 miles below. Further downglacier the vectors rise out from the surface and the angular divergence increases both downglacier and toward the margins. The flow of ice toward the surface is constant at 10 fpy in the lower 3 miles. Rates of surface lowering computed from these data and ablation data agree roughly with independently measured thinning.
\r\n\r\nVelocity gradients in an area of detailed study are analyzed to determine the surface strain rate field. Deformation is largely caused by the transverse gradient of the longitudinal velocity. Longitudinal and transverse extensions and compressions were measured. One principal strain rate trajectory lies along the flow centerline; a trajectory of maximum shearing strain rate parallels the valley wall at the margin.
\r\n\r\nVelocity to a depth of 140 feet decreases exponentially. The flow law of ice is determined by an analysis of this short vertical profile and a transverse velocity profile on the surface. The two sets of data give consistent results which agree with results from other glaciers, and suggest that the flow law is unaffected by either hydrostatic pressure or extending or compressing flow. The strain rate cannot be expressed as a simple power function of the stress. A viscous-like flow appears to predominate at low stresses. Above a shear stress of 0.7 bar the flow velocity changes much more rapidly with slight changes in stress.
\r\n\r\nThe derived flow law is used to compute velocity as a function of depth and the mass-budget. These results show that the ice currently being supplied to the surface is not as great as the surface ablation but is just sufficient to keep the glacier thinning at an unchanged rate in time. Computed streamlines parallel the bedrock channel closely.
\r\n\r\nThree main classes of features in the ice are distinguished: (1) primary sedimentary layering, (2) secondary flow foliation and (3) secondary cracks and crevasses. Primary stratification is flat-lying in general but wrinkled longitudinally in detail. Foliation generally dips steeply, strikes longitudinally, and shears other structures. However, some foliation attitudes do not relate to measured directions of maximum shearing strain rate at the point of observation or at any conceivable point of origin. The orientation of the most prominent set of cracks agrees approximately with measured trajectories of principal compressing strain rate. Other minor sets of cracks are related to trajectories of maximum shearing strain rate.
" }, { "name": "Ruckmick, John Christian", "degree": "PhD", "year": "1957", "title": "Ultramafic Intrusives and Associated Magnetite Deposits at Union Bay, Southeast Alaska", "advisor": "Noble, James A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-10072004-161749", "creators": [ { "name": { "family": "Ruckmick", "given": "John Christian" }, "id": "Ruckmick-John-Christian", "display_name": "Ruckmick, John Christian" } ], "advisors": [ { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/7B6M-0K73", "abstract": "An intrusive body of ultramafic rocks, which crops out over an area of 7 square miles at Union Bay, southeast Alaska, has been mapped and studied petrographically. The ultramafic rocks are probably Jurassic or Cretaceous in age, and constitute a spoon-shaped lopolith with a dunite feeder plug at the east end. The rocks of the lopolith are composed of various proportions of diopside and forsteritic olivine, with some magnetite and hornblende, and no feldspar. The most basic rocks, dunite and peridotite, occur in the central portion of the lopolith, and are enveloped by olivine-pyroxenite, pyroxenite, and hornblende-pyroxenite in that order. The peridotite rocks in the central portion of the complex are composed of olivine-pyroxenite intruded by sills and irregular bodies of dunite. Attitudes of the dunite sills conform to the spoon-shaped structure of the logolith. Large areas of pyroxenite containing 10% to 25% of primary magnetite crop out around the periphery of the lopolith. An intrusive body of gabbro adjoins the south side of the ultramafic lopolith. The gabbro is earlier than, and has been intruded by, the ultramafic rocks.\r\n\r\nThe structure and petrology of the ultramafic lopolith are explained by an hypothesis of successive injections of increasingly basic magmas composed essentially of: (1) a cotectic blend of diopside and magnetite; (2) a cotectic blend of diopside and forsteritic olivine; and (3) forsteritic olivine. The intrusion of the magmas in that order, the reverse order of crystallization of the component minerals, is a reflection of the differential melting of the ultramafic source in the mantle of the earth. Each arriving magma must have found the hot, still crystallizing, central portion of the preceding magma the most accessible locus of intrusion.\r\n\r\nThe lack of a very high grade of contact metamorphism in the pelitic sediments adjacent to the ultramafic rocks is explained by the assumption that the ultramafic magmas contained very little or no water, and, therefore, expelled no significant amounts of volatile phases during crystallization.\r\n" }, { "name": "Savage, James Crampton", "degree": "PhD", "year": "1957", "title": "Wave Propagation in a Continuously Stratified Fluid", "advisor": "Dix, Charles Hewitt", "url": "https://resolver.caltech.edu/CaltechETD:etd-08092004-091454", "creators": [ { "name": { "family": "Savage", "given": "James Crampton" }, "id": "Savage-James-Crampton", "display_name": "Savage, James Crampton" } ], "advisors": [ { "name": { "family": "Dix", "given": "Charles Hewitt" }, "id": "Dix-C-H", "role": "advisor", "display_name": "Dix, Charles Hewitt" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/SDVS-AN85", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe problem consists of finding the pressure response to a pressure source in an acoustical system of a stratified fluid overlying a rigid surface; a uniform gravitational field of acceleration g is directed normal to the rigid surface. The stratification is to be understood as implying that [...], the gradient of the velocity of sound, and [...], the negative logarithmic gradient of the density, are directed parallel or antiparallel to the gravitational field. The magnitudes of the quantities involved are assumed to be appropriate to the atmosphere of the earth.\r\n\r\nThe first problem treated assumes [...] and [...] are constant, a situation which would obtain in an isothermal atmosphere. The pressure response exhibits 1) an appreciable phase shift upon reflection from the rigid surface at large angles of incidence, 2) a surface wave, and 3) appreciable distortion of the pulse shape.\r\n\r\nThe second problem neglects g and [...]. The solution given is asymptotically (high frequency) valid only in regions of the fluid reached by least time rays which have not been refracted through the horizontal. This solution indicates that the time average energy flux propagates along rays which differ from the least time rays by an amount dependent upon the frequency, i.e. such an atmosphere exhibits angular dispersion. Asymptotic expressions are derived for the magnitude of the time average energy flux and for the pressure pulse distortion.\r\n\r\nFinally, variations in [...] and [...] are admitted simultaneously with the presence of a gravitational field. The solution is qualitatively the same as that of the preceding problem." }, { "name": "Kamb, Walter Barclay", "degree": "PhD", "year": "1956", "title": "The Crystal Structure of Zunyite", "advisor": "Pauling, Linus; Hughes, Edward Wesley", "url": "https://resolver.caltech.edu/CaltechETD:etd-08152006-142004", "creators": [ { "name": { "family": "Kamb", "given": "Walter Barclay" }, "id": "Kamb-Walter-Barclay", "display_name": "Kamb, Walter Barclay" } ], "advisors": [ { "name": { "family": "Pauling", "given": "Linus" }, "id": "Pauling-L", "role": "advisor", "display_name": "Pauling, Linus" }, { "name": { "family": "Hughes", "given": "Edward Wesley" }, "id": "Hughes-Edward-Wesley", "role": "advisor", "display_name": "Hughes, Edward Wesley" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/VR5H-XS14", "abstract": "Zunyite, a rare aluminosilicate mineral of composition (OH, F)18Al13Si5O20Cl, has an unusual structure built up of Si5O16 groups of linked silicon tetrahedra and aluminium-oxygen groups of linked octahedra. The structure proposed by Pauling is verified and refined by X-ray methods, using 163 (hkO) reflections from single-crystal photographs with Mo Ka radiation. Refinement of positional parameters is carried out by the least-squares method, with inclusion of off-diagonal terms in the normal equation matrix because of overlap of oxygen atoms in the (100) projection. Refinement of isotropic temperature parameters for separate atoms is carried out with the use of difference syntheses, by methods differing somewhat from published ones. A general discussion of isotropic temperature factor refinement from differerence syntheses is given. One stage of least-squares refinement using 410 (hhl) reflections is carried out, for comparison with the (hkO) refinement. The corresponding accuracy of interatomic distances is \u00b1 0.02 A. A large apparent temperature factor discrepancy between the two refinements is attributed to a deviation in the contrast of one of the X-ray photographs. The refined structure differs from the trial structure in distortion of coordination polyhedra, as found in other similar structures. The arrangement of protons in the structure is proposed from structural arguments, and the proposed arrangement requires the inclusion of at least two fluorine atoms per stoichiometric molecule." }, { "name": "Lovering, John Francis", "degree": "PhD", "year": "1956", "title": "Structural and Compositional Studies on Selected Phases of Iron and Stony-Iron Meteorites", "advisor": "Brown, Harrison", "url": "https://resolver.caltech.edu/CaltechETD:etd-03262004-144306", "creators": [ { "name": { "family": "Lovering", "given": "John Francis" }, "id": "Lovering-John-Francis", "display_name": "Lovering, John Francis" } ], "advisors": [ { "name": { "family": "Brown", "given": "Harrison" }, "id": "Brown-Harrison", "role": "advisor", "display_name": "Brown, Harrison" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/Z69X-XR92", "abstract": "On the basis of new data for the frequency of band width distributions in a collection of 63 octahedrites, a revised classification into coarse, medium and fine octahedrites has been proposed. A study of the nickel contents and structures of iron meteorites would suggest that the following relationships hold: hexahedrites and nickel-poor ataxites, 5.5-6.0% nickel; coarse octahedrites, 6.0-7.2% nickel; medium octahedrites, 7.0-10.2% nickel; fine octahedrites 7.7-14% nickel; nickel-rich ataxites, 14.23(?)% nickel.\r\n\r\nNew data on the metal phase of iron meteorites indicate that the gallium and germanium contents are distributed between three distinct levels, confirming a previous observation by Goldberg, Uchiyama and Brown (1951) with regard to gallium. Cobalt and copper values are shown to vary more or less sympathetically with the nickel content. The distribution of chromium would appear to be complicated by the presence of troilite either close to, or contaminating, the sample analysed. Similar data for the metal phase of nine stony-iron meteorites suggest a similarity in nickel content and trace element content of all the samples analysed.\r\n\r\nSemi-quantitative determinations have been made of cobalt, chromium, copper, germanium, manganese, nickel, lead, tin, vanadium and zinc in troilite from fourteen iron and two stony-iron meteorites. Similar determinations have been made on schreibersite from two iron meteorites. Semi-quantitative analyses of barium, cobalt, chromium, copper, gallium, germanium, manganese, nickel, tin, titanium, vanadium and zirconium in olivine from four pallasites, together with macro-analyses and optical data, suggest that the olivine has a constant composition.\r\n\r\nThe data have been used to calculate new abundances for these elements in meteorites and new data on the geochemical behavior of these elements." }, { "name": "Smith, George Irving", "degree": "PhD", "year": "1956", "title": "Geology and Petrology of the Lava Mountains, San Bernardino County, California", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechETD:etd-05052006-153319", "creators": [ { "name": { "family": "Smith", "given": "George Irving" }, "id": "Smith-George-Irving", "display_name": "Smith, George Irving" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/TC6X-QY59", "abstract": "The Lava Mountains are a range of low mountains along the northern edge of the Mojave Desert, California. The pre-Tertiary rocks consist of a few small pendants of metamorphic rocks in Atolia quartz monzonite. Overlying these are small patches of volcanic and sedimentary rocks, probably Tertiary, which project into the later formations. The major sedimentary unit is the middle Pliocene Bedrock Spring formation; it consists chiefly of arkosic sandstone and conglomerate with lesser amounts of siltstone and brecciated volcanic rocks. Overlying this formation are two late Pliocene formations, the Almond Mountain volcanics and Klinker Mountain volcanics in the eastern and western parts of the area, respectively. Small areas of other late Pliocene(?) volcanic rocks are locally present. Overlying these are flows of the Lava Mountains andesite of very late Pliocene age. The Pleistocene(?) Christmas Canyon formation is restricted to the eastern half of the area. A few small dikes of basalt cut this formation. Quaternary gravels, alluvium, and travertine are the youngest deposits.\r\n\r\nWithin the area, three fault systems converge. The Garlock fault trends N. 75\u00b0 E. along the north side of the area; it is a left lateral fault. The Blackwater fault trends N. 45\u00b0 W. in the southeastern part of the region; it has right-lateral and normal displacements. The Brown's Ranch fault zone and its associated faults trend about N. 55\u00b0 E. in the western part of the area; both left-lateral and dip-slip displacements are found. The Dome Mountain anticline trends parallel to and south of the Garlock fault.\r\n\r\nRemnants of late Cenozoic pediments indicate that the drainage at that time was toward the north; later, the eastern part of the region warped, thus blocking the previous drainage direction.\r\n\r\nNo commercial mines are in the area although extensive prospects are present in the southwestern portion.\r\n\r\nAll of the volcanic rocks are plagioclase andesite porphyries. Plagioclase (3-23 percent), biotite (0-2 percent), orthopyroxene and clinopyroxene (0-2 percent), quartz (0-3 percent), and opaques (1-11 percent) are found as crystals in a partly-crystalline to glassy groundmass. As the Pliocene volcanic sequence progressed, the lavas became more homogeneous, more effusive, and more frequently erupted. The mineral and chemical compositions did not change systematically. The melt originated by the fusion of quartz monzonite. There is no evidence of fractionation, crystal settling, or continued assimilation during the volcanic sequence.\r\n" }, { "name": "Spencer, Terry Warren", "degree": "PhD", "year": "1956", "title": "Studies in Acoustic Pulse Propagation", "advisor": "Dix, Charles Hewitt", "url": "https://resolver.caltech.edu/CaltechETD:etd-06292004-161005", "creators": [ { "name": { "family": "Spencer", "given": "Terry Warren" }, "id": "Spencer-Terry-Warren", "display_name": "Spencer, Terry Warren" } ], "advisors": [ { "name": { "family": "Dix", "given": "Charles Hewitt" }, "id": "Dix-C-H", "role": "advisor", "display_name": "Dix, Charles Hewitt" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/RAV7-NV35", "abstract": "A theoretical study is made of the transient response in two acoustic systems. Each system consists of an ideal fluid in contact with an elastic solid. In one case the interface is plane, in the other case it is cylindrical.\r\n\r\nIn the plane case it is found that an exact algebraic solution can be obtained on the axis of symmetry. The vertical displacement at axial points is composed of the acoustic, afterflow, and correction terms. In solids for which Poisson's ratio is greater than one third the initial variation of the correction is toward positive values (corresponding to motion directed toward the interface). In solids for which Poisson's ratio is less than one third the initial variation may be either positive or negative depending on the magnitude of the compressional velocity ratio. An interface wave is shown to exist regardless of the choice of elastic parameters. It is found that the reflected wave has a forerunner in the region of the fluid in which the refracted wave is the first arrival.\r\n\r\nIn the cylindrical case the initial pulse shape is distorted upon reflection. It is found that as the wave approaches the axis of the cylinder the leading edge steepens. If, at the source, the initial slope of the pressure-time curve is finite the amount of steepening is infinite. An exact expresson for the transient response at points off the axis is obtained which can be evaluated by numerical means.\r\n" }, { "name": "Burnham, C. Wayne", "degree": "PhD", "year": "1955", "title": "Metallogenic Provinces of the Southwestern United States and Northern Mexico", "advisor": "Noble, James A.; Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12182015-163332200", "creators": [ { "name": { "family": "Burnham", "given": "C. Wayne" }, "id": "Burnham-C-Wayne", "display_name": "Burnham, C. Wayne" } ], "advisors": [ { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." }, { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "co-advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/M954-D370", "abstract": "Some of the metallogenic provinces of the southwestern United\r\nStates and northern Mexico are defined by the geographic distribution\r\nof trace elements in the primary sulfide minerals chalcopyrite and\r\nsphalerite. The elements investigated include antimony, arsenic,\r\nbismuth, cadmium, cobalt, gallium, germanium, indium, manganese,\r\nmolybdenum, nickel, silver, tellurium, thallium, and tin. Of these\r\nelements, cobalt, gallium, germanium, indium, nickel, silver, and tin\r\nexhibit the best defined geographic distribution.
\r\n\r\nThe data indicate that chalcopyrite is the preferred host for tin\r\nand perhaps molybdenum; sphalerite is the preferred host for cadmium,\r\ngallium, germanium, indium, and manganese; galena is the preferred host\r\nfor antimony, bismuth, silver, tellurium, and thallium; and pyrite is\r\nthe preferred host for cobalt, nickel, and perhaps arsenic. With respect\r\nto the two minerals chalcopyrite and sphalerite, antimony, arsenic,\r\nmolybdenum, nickel, silver, and tin prefer chalcopyrite; and bismuth,\r\ncadmium, cobalt, gallium, germanium, indium, manganese, and thallium\r\nprefer sphalerite. This distribution probably is the result of the interaction\r\nof several factors, among which are these: the various radii of\r\nthe elements, the association due to chemical similarities of the major\r\nand trace elements, and the degree of ionic versus covalent and metallic\r\ncharacter of the metal-sulfur bonds in chalcopyrite and sphalerite. The\r\ntype of deposit, according to a temperature classification, appears to\r\nbe of minor importance in determining the trace element content of\r\nchalcopyrite and sphalerite.
\r\n\r\nA preliminary investigation of large single crystals of sphalerite\r\nand chalcopyrite indicates that the distribution within a single crystal\r\nof some elements such as cadmium in sphalerite and indium and silver in\r\nchalcopyrite is relatively uniform, whereas the distribution of some\r\nother elements such as cobalt and manganese in sphalerite is somewhat\r\nless uniform and the distribution of tin in sphalerite is extremely\r\nerratic. The variations in trace element content probably are due\r\nlargely to variations in the composition of the fluids during the growth\r\nof the crystals, but the erratic behavior of tin in sphalerite perhaps is\r\nrelated to the presence of numerous cavities and inclusions in the crystal\r\nstudied.
\r\n\r\nMaps of the geographic distribution of trace elements in chalcopyrite\r\nand sphalerite exhibit three main belts of greater than average trace\r\nelement content, which are called the Eastern, Central, and Western belts.\r\nThese belts are consistent in trend and position with a beltlike distribution\r\nof copper, gold, lead, zinc, silver, and tungsten deposits and with\r\nmost of the major tectonic features. However, there appear to be no\r\ndefinite time relationships, for as many as four metallogenic epochs,\r\nfrom Precambrian to late Tertiary, are represented by ore deposits within\r\nthe Central belt.
\r\n\r\nThe evidence suggests that the beltlike features have a deep seated\r\norigin, perhaps in the sub-crust or outer parts of the mantle, and that\r\nthe deposits within each belt might be genetically related through a\r\nbeltlike compositional heterogeneity in the source regions of the ores.\r\nHence, the belts are regarded as metallogenic provinces.
" }, { "name": "Campbell, Douglas Dean", "degree": "PhD", "year": "1955", "title": "Geology of the Pitchblende Deposits of Port Radium, Great Bear Lake, N.W.T.", "advisor": "Noble, James A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-03062007-135452", "creators": [ { "name": { "family": "Campbell", "given": "Douglas Dean" }, "id": "Campbell-Douglas-Dean", "display_name": "Campbell, Douglas Dean" } ], "advisors": [ { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/6BX5-4F69", "abstract": "The geology of the McTavish Arm area of Great Bear Lake, Northwest Territories, Canada, is reviewed and a geologic map is presented. The geology of the Labine Point region is described in detail. Intrusive feldspar porphyry bodies are haloed by contact metasomatic zones in which the lower Echo Bay cherty sediments have been enriched in Ca, Al, Mg and Fe by the development of ferromagnesian minerals. The sediments have been locally severely deformed by intrusion of the porphyry bodies. A body of massive crystalline tuff in the mine area is believed to be the remnant of a volcanic vent.
\r\n\r\nThe ore deposits occur in a lenticular network of northeast trending shear zones. Differences in wall rock competency have resulted in the development of relatively wide tensional fracture zones at various places along the shear systems. The pitchblende ore bodies occur in these zones of greater than usual dilation.
\r\n\r\nThe mineralization of the Port Radium deposits occurred in five stages: I, hematite-quartz; II, pitchblende-quartz; III, quartz-cobalt nickel arsenides; IV, copper sulphides-chlorite; V, carbonate-silver. Deposition of pitchblende at Port Radium took place in dilated portions of the vein zones in the following manner: release of pressure in dilated zones caused loss of CO2; loss of CO2 resulted in drop of bicarbonate ion content and consequent decrease in the solubility of the uranium as a complex with carbonate; the uranium flocculated as the uranium colloid precipitate, pitchblende. Brecciation and some redistribution of the pitchblende by later solutions is illustrated. Comparison is made between the mineralogy of Port Radium and other pitchblende deposits.
\r\n\r\nPossible sources of error in the lead isotope age determination of Port Radium pitchblende are discussed. Ages determined are believed to be too great by a factor of about three.
" }, { "name": "Lomnitz, Cinna", "degree": "PhD", "year": "1955", "title": "Creep Measurements in Igneous Rocks with Some Applications to Aftershock Theory", "advisor": "Benioff, Hugo", "url": "https://resolver.caltech.edu/CaltechETD:etd-01082004-111506", "creators": [ { "name": { "family": "Lomnitz", "given": "Cinna" }, "id": "Lomnitz-Cinna", "display_name": "Lomnitz, Cinna" } ], "advisors": [ { "name": { "family": "Benioff", "given": "Hugo" }, "id": "Benioff-H", "role": "advisor", "display_name": "Benioff, Hugo" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/A2KE-9Y60", "abstract": "First Part.
\r\n\r\nCylindrical specimens of Southern California granodiorite and gabbro were creep-tested at constant torques in a high-magnification torsion apparatus. Complete creep and creep recovery curves at room temperature were recorded for periods of about 10,000 minutes.
\r\n\r\nThe results are represented by an empirical equation of the form: s = p (a+b log t) where s is the strain, p the stress and t the time. No evidence was found of creep behavior suggestive of the Michelson equation.
\r\n\r\nFor some granodiorite samples the viscosity was of the order of 3 x 10\u00b9\u2075 poises. The behavior of the rocks under prevailing test conditions was not appreciably different from that of other polycrystalline materials.
\r\n\r\nSecond Part.
\r\n\r\nA quantitative treatment of the Benioff aftershock sequences on the basis of the theory of viscoelasticity is given. The minimum coefficient of viscosity found by this method is of the order of 10[superscript 19] poises, in good agreement with accepted viscosity values for the earth's crust.
" }, { "name": "Rogers, John James William", "degree": "PhD", "year": "1955", "title": "Textural Studies in Igneous Rocks near Twentynine Palms, California", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechETD:etd-12082003-112407", "creators": [ { "name": { "family": "Rogers", "given": "John James William" }, "id": "Rogers-John-James-William", "display_name": "Rogers, John James William" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/A05M-NQ50", "abstract": "A description of a sequence of igneous rocks south of Twentynine Palms has been undertaken for the purpose of describing and determining the origin of the major textural variations within individual igneous bodies. The work involved field mapping and sampling, petrographic study, and spectrochemical analysis.\r\n\r\nThe Pinto gneiss, a middle rank metamorphic rock, is the oldest formation in the area. It is intruded by a sequence of plutonic rocks including (in chronologic order) the Gold Park gabbro-diorite (oldest intrusive rock), Palms quartz monzonite, monzonitic porphyry, and White Tank quartz monzonite. Other igneous rocks include basalt and silicic and basic dikes. The major rocks, and the ones most intensively studied, are the Palms quartz monzonite-monzonitic porphyry complex and the White Tank quartz monzonite.\r\n\r\nThe Palms quartz monzonite is divided into three units on the basis of slight differences in mineralogy and texture. Most of the quartz monzonite is characterized by very complex, irregular intergrowths between potash feldspar and plagioclase; these intergrowths are possibly the result of crystallization from a relatively dry melt during the latter stages of formation of the rock. Widespread reaction between the quartz monzonite melt and portions of the Pinto gneiss has caused the formation of a monzonitic porphyry along some contacts between quartz monzonite and gneiss. Plots have been made of mineral compositions and grain sizes of a sequence of rocks from gneiss through porphyry to quartz monzonite. Potash and soda have been added to the gneiss by the melt, and development of coarse crystals of potash feldspar in the porphyry is caused by incorporation of solid gneiss in the melt. Some contacts (ranging from relatively abrupt to broadly gradational) between quartz monzonite and gneiss do not exhibit development of porphyry.\r\n\r\nThe White Tank quartz monzonite is divided into four units, two of which have two separate facies. The units are distinguished by differences in mineralogic composition and texture. The different facies and units are grouped into two differentiation sequences: the trend in each sequence is toward a more silicic rock, but one sequence results in the formation of large crystals of microcline, whereas the other sequence results in the formation of muscovite and garnet. The trace element content of potash feldspar varies throughout each sequence roughly in accordance with differentiation trends previously established by other workers. Measurements of the grain sizes of potash feldspar (in the field) and quartz and plagioclase (in thin section) also reflect the sequence of differentiation. The White Tank quartz monzonite is believed to have formed by the intrusion, differentiation, and solidification of a magma." }, { "name": "Silver, Leon Theodore", "degree": "PhD", "year": "1955", "title": "The Structure and Petrology of the Johnny Lyon Hills Area, Cochise County, Arizona", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:04212014-145355832", "creators": [ { "name": { "family": "Silver", "given": "Leon Theodore" }, "id": "Silver-Leon-Theodore", "display_name": "Silver, Leon Theodore" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/KSN8-HX15", "abstract": "The Johnny Lyon Hills area is located in Cochise County in\r\nsoutheastern Arizona. The rocks of the area include a central core\r\nof Lower pre-Cambrian igneous and metamorphic rocks surrounded by a\r\ncomplexly faulted and tilted section of Upper pre-Cambrian and\r\nPaleozoic strata. Limited exposures of Mesozoic and Tertiary sedimentary\r\nand volcanic rocks are present at the north end of the\r\nmap area. Late Tertiary and Quaternary alluvium almost completely\r\nsurrounds and overlaps upon the older rocks.
\r\n\r\nThe older pre-Cambrian rocks include a section of more than\r\n9000 feet of generally moderately metamorphosed graywackes, slates\r\nand conglomerates of the Pinal schist injected in zones by somewhat\r\nyounger rhyolite sheets. The original sediments were deposited in\r\na geosyncline whose extent probably included large parts of Arizona,\r\nNew Mexico and west Texas. During the Mazatzal Revolution the Pinal\r\nschist was deformed into northeast-trending, steeply dipping and\r\nplunging structures and the entire local section was overturned\r\nsteeply toward the northwest. The pre-Cambrian Johnny Lyon granodiorite\r\nwas emplaced as a large epi-tectonic pluton which modified the\r\nmetamorphic character of part of the Pinal schist. Larsen method\r\ndeterminations indicate an age of about 715 million years for this\r\nrock, which is about the minimum age compatible with the geologic\r\nrelations.
\r\n\r\nThe Laramide orogeny produced numerous major thrust faults\r\nin the area involving all rocks older than and including the Lower\r\nCretaceous Bisbee group. Major compression from the southwest and\r\nsubsequent superimposed thrusting from the southeast and east are\r\nindicated. Minimum thrust displacements of more than a mile are\r\nclear and the probable displacements are of much greater magnitude.\r\nThe crystalline core behaved as a single structural unit and probably\r\ncaused important local divergences from the regional pattern\r\nof northeast-trending compressive forces. The massif was rotated as\r\na unit 40 degrees or more about a northwest-trending axis overturning\r\nthe pre-Cambrian fold axes in the Pinal schist.
\r\n\r\nSwarms of Late Cretaceous(?) or Early Tertiary(?) lamprophyric\r\ndikes cross the Laramide structures and are probably related to the\r\nlarge Texas Canyon stock several miles southeast of the map area.\r\nIntermittent high angle faulting, both older and younger than the\r\ndikes, has continued since the Laramide orogeny and has been superimposed\r\non the older structures. This steep faulting combined with\r\nthe fundamental northwesterly Laramide structural grain to produce\r\nthe northwesterly trends characteristic of the mountain ridges and\r\nvalleys of the area.
" }, { "name": "Allen, Clarence Roderic", "degree": "PhD", "year": "1954", "title": "The San Andreas Fault Zone in San Gorgonio Pass, California", "advisor": "Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05142003-113459", "creators": [ { "name": { "family": "Allen", "given": "Clarence Roderic" }, "id": "Allen-Clarence-Roderic", "display_name": "Allen, Clarence Roderic" } ], "advisors": [ { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/54GN-M254", "abstract": "In San Gorgonio Pass, 70 miles east of Los Angeles, a complex network of faults separates two of the highest mountain ranges of Southern California. The San Andreas fault, which forms a part of the network, exhibits several unusual features in this area. Among these are the absence of rift topography, absence of lateral stream offsets, an abrupt change in trend of the fault trace, seismic evidence for the predominance of thrusting over strike-slip movements, and a lack of great earthquakes in historic time.\r\n\r\nCrystalline rocks of Mesozoic and earlier age crop out over most of the map area. North of the pass, the San Gorgonio igneous-metamorphic complex comprises an old metamorphic terrane of intermediate to basic composition and probable igneous parentage, and Mesozoic(?) plutonic rocks of quartz monzonitic composition. These plutonic rocks have intimately intruded and in large part reconstituted the older metamorphic rocks. The resulting migmatitic gneiss is the most widespread rock of the area, and includes flaser gneiss, green-schist, and piedmontite-bearing gneiss as distinctive varietal types. Rocks of the San Jacinto Mountains south of San Gorgonio Pass are distinctly different from those to the north, and comprise texturally uniform granodioritic and tonalitic rocks that contain sparse inclusions and septa of metasedimentary rocks.\r\n\r\nNearly all of the sedimentary rocks in the pass area are of alluvial-fan or flood-plain origin, and they reflect a Quaternary and late Tertiary history of recurrent deformation and deposition. The upper Miocene(?) Coachella fanglomerate is the oldest exposed sedimentary rock, and is overlain with marked angular unconformity by all younger units. Lower Pliocene(?) incursion of tropical marine waters into the Salton trough is represented by a thin stringer of Imperial formation which is conformably underlain and overlain by continental strata of the Hathaway and Painted Hill formations, respectively. All of these rocks are overlain with marked angular unconformity by Quaternary Cabezon fanglomerate, which probably is correlative with upper beds of the Pliocene-Pleistocene San Timoteo(?) formation in the western part of the map area. Other Quaternary deposits, each showing complex structural relationships to adjacent rocks, are the deformed gravels of Whitewater River, Heights fanglomerate, and Burnt Canyon breccia. Recent alluvium covers the floor of the pass. Flows and dikes of olivine basalt occur in the Coachella fanglomerate and Painted Hill formation. Lithology of clasts in the sedimentary rocks indicates derivation predominantly from rocks of the San Gorgonio igneous-metamorphic complex to the north.\r\n\r\nQuaternary alluvial fans of Heights and Cabezon fanglomerate, which once buried a former rugged topography, are now being dissected along the north side of the pass. Surfaces of low relief and associated stream terraces resulting from this dissection are the Beaumont plain, Banning Bench, and Pine Bench surfaces. Upstream divergence of the Banning Bench surface from present stream levels is attributed in part to tilting. Farther east, the older Cabezon surface shows many effects of warping. This surface probably is correlative with an area of low relief at altitudes of 6500 to 8000 feet near Raywood Flat, and suggests Quaternary arching of the mountain range along a north-south axis.\r\n\r\nWithin San Gorgonio Pass, alluvial fans derived from areas to the north dominate those derived from the steeper San Jacinto scarp to the south. This unequal development of fans is attributed to greater flood-producing rainfall and larger drainage area on the north, together with more easily erodable rock in this area. Most of the faults that show Recent movement are well delineated by springs and vegetative contrasts. Other springs are caused by exposure of unconformities, and by superposition of streams onto the rugged pre-Cabezon topography.\r\n\r\nThe San Andreas fault is a continuous linear feature for a distance of more than 400 miles northwest from San Gorgonio Pass, but within the pass it curves abruptly southward and butts into the east-trending Banning fault at an angle of 45 [degrees] . Recent strike-slip movement on this part of the fault probably amounts to less than one mile, and post-Mesozoic displacement probably has not exceeded a few tens of miles.\r\n\r\nThe Banning fault, a major break that delineates the north side of the pass, extends for a distance of more than 50 miles eastward from a point near Redlands through the pass into the Coachella Valley. Within the pass, it is a steeply north-dipping reverse fault except for a zone of low-angle thrusting between Millard and Whitewater Canyons. At least 5000 feet of vertical displacement has taken place on this fault since San Timoteo time, and a right lateral offset of 5 miles is suggested. Recent displacement is limited to the segment of the fault east of Millard Canyon. Pre-Pliocene lateral displacement may have been great, but is not demanded by evidence in this area.\r\n\r\nThe Mission Creek fault branches from the San Andreas fault north of Banning, and is a major north-dipping fracture that is continuous for at least 40 miles to the southeast. The Pinto Mountain fault diverges from the Mission Creek fault at a low angle, and probably is continuous for more than 50 miles to the east; in this interval it forms the southern boundary of the northwest-trending fault system of the Mojave Desert. The Mill Creek fault branches from the San Andreas fault north of San Bernardino, and has guided erosion along deep linear valleys in the high mountains; this fault apparently dies out eastward.\r\n\r\nWithin the San Bernardino Mountains all of the faults north of the Banning fault separate crystalline rocks of the same family; these rocks are similar in their migmatitic structural features, remnants of amphibolite, intrusion by quartz monzonite, and high content of titanium minerals. Thus post-Mesozoic lateral displacements of hundreds of miles along these faults seem to be precluded. Although lateral displacements of a few tens of miles are possible, no observed evidence appears to demand such movements. Late Tertiary and Quaternary vertical movements are suggested by the physiography of the mountains. No Recent movements have occurred on parts of the Mission Creek and Mill Creek faults.\r\n\r\nRecent movements on both the Banning and San Andreas faults probably were caused by a stress system involving a generally north-south maximum principal stress, with an east-west least principal stress of only slightly lesser magnitude than the vertical stress. In the vicinity of San Gorgonio Pass, an older east-west line of weakness causes the east-west stress effectively to become the intermediate stress, so that thrust faulting predominates over strike-slip faulting in this one local area.\r\n\r\nSan Gorgonio Pass is bounded by a reverse or thrust fault on the north, and indirect evidence suggests a similar fault on the south. Quaternary and late Tertiary displacement on these faults, rather than erosion, is primarily responsible for the present physiography of the pass. Local conversion of San Andreas-type lateral strain into vertical displacements on the bounding faults is a reasonable explanation of both the pass itself and the unusually high peaks adjacent to it.\r\n" }, { "name": "Barker, Fred", "degree": "PhD", "year": "1954", "title": "Pre-Cambrian and Tertiary Geology of the Las Tablas Quadrangle, New Mexico", "advisor": "Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-11242003-111353", "creators": [ { "name": { "family": "Barker", "given": "Fred" }, "id": "Barker-Fred", "display_name": "Barker, Fred" } ], "advisors": [ { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/2ANP-BB97", "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Las Tablas quadrangle is in Rio Arriba County, northern New Mexico, and lies between north latitudes 36[degrees] 30' and 36[degrees] 45' and west longitudes 106[degrees] 00' and 106[degrees] 15'. Its center is about 33 miles west-northwest of Taos and about 65 miles north and slightly west of Santa Fe. Its principal geographic features include the Jawbone Mountain-La Jarita Mesa highland, which trends diagonally from northwest to southeast across the area; the valleys of the southeastward-flowing Tusas and Vallecitos creeks, which flank the highland area; a northeastern area that slopes gently eastward and is a part of the Taos Plateau; and a southwestern area that also slopes gently eastward and is a part of the highland that lies east of the Chama River Valley. The Jawbone Mountain-La Jarita Mesa highland is underlain chiefly by pre-Cambrian rocks, and the other areas mainly by Tertiary rocks.\r\n\r\nThe oldest rocks exposed in the quadrangle are pre-Cambrian metasedimentary and metavolcanic types that comprise the Ortega quartzite, of which a 14,000- to 20,000-foot section is exposed; the Moppin meta-volcanic series, which consists of metamorphosed basaltic rocks with minor intercalated metasedimentary rocks and is from 1,000 to several thousand feet thick; and the Kiawa Mountain formation, which is composed of five members. These members are the Big Rock conglomerate, which is 50 to 100 feet thick and overlies the Ortega quartzite; the Jawbone conglomerate, which overlies the Moppin series in the northwestern part of the area, is more than 1,000 feet in maximum thickness, and pinches out to the southeast; the lower quartzite member, which overlies the Big Rock conglomerate member, the amphibolite member, which consists of one to seven thin layers of amphibolite and intercalated beds of quartzite, and is from 35 to 2,000 feet thick; and the upper quartzite member, which is 5,000 to 10,000 feet thick and is the youngest pre-Cambrian rock in this area.\r\n\r\nThese strata were compressed during pre-Cambrian time into two large overturned folds that trend and plunge northwest. These are the Hopewell anticline and the Kiawa syncline. Two subsidiary and similarly oriented folds, the Poso anticline and the Big Rock syncline, lie on the southwest flank of the Kiawa syncline. Numerous internested minor folds, ranging from a fraction of an inch to several thousand feet in flank-to-flank dimension, occur on the larger folds.\r\n\r\nSills of pre-Cambrian metarhyolite were injected into the sedimentary rocks prior to the folding. Three plutons of granodiorite were emplaced during the folding, and four bodies of granite were intruded during a late stage of the folding or after the folding ceased. Many bodies of granitic pegmatite, at least 36 of which are of some commercial importance, lie in muscovitized quartzite and metarhyolite on La Jarita Mesa.\r\n\r\nRegional metamorphism was essentially synchronous with the folding of the pre-Cambrian rocks. Basalt, the only widespread rock in the area that is sensitive to changes in metamorphic grade, was progressively metamorphosed to chlorite-muscovite-albite greenschist, chlorite-biotite-albite greenschist, chlorite-biotite-oligoclase greenschist, oligoclase-biotite-hornblende amphibolite, and finally to hornblende-andesine amphibolite. These rocks represent the typical greenschist and amphibolite metamorphic facies. The regional metamorphism has involved breakdown of unstable minerals, migration of atoms along grain boundaries, nucleation of new phases by statistical fluctuations of concentration, and grain growth by accretion of atoms to surfaces to nuclei.\r\n\r\nKyanite is present in all of the vitreous quartzite, and is associated with both metamorphic facies. It occurs along bedding planes, in hematite-rich laminae and in quartzose veins. Bodies of quartz-kyanite rock, which are oval in plan, occur in quartzite and metarhyolite at and near Big Rock on La Jarita Mesa.\r\n\r\nThe La Jarita pegmatites are surrounded by an aureole of pegmatitic-hydrothermal metamorphism that postdates the regional metamorphism. In this aureole, quartzofeldspathic rocks have been muscovitized, and amphibolite has been partly converted to chlorite and quartz. Locally the amphibolite has been wholly replaced by muscovite, biotite, garnet, epidote, and quartz. The net material changes in this process have been addition of K, A1, and H[subscript 2]O, and loss of Ca, Mg, Si, and a little Na. Fluids from pegmatitic magmas undergoing second-boiling are believed to have caused the metasomatism.\r\n\r\nTerrestrial sedimentary and volcanic rocks of Tertiary age underlie much of the quadrangle. The general stratigraphic relations are summarized in the following table:\r\n\r\n[...]\r\n\r\nSeveral thin beds with the cherty, feldspathic, quartzose sandstone lithology of the Sante Fe formation are present within the Cordito member of the Los Pinos formation.\r\n\r\nQuaternary alluvium lies along the bottoms of the larger creeks, and some material of probable aeolian origin underlies parts of the upper Tusas Valley.\r\n\r\nFault zones extend along the valleys of the Tusas and Vallecitos creeks. The Tusas zone consists of northwest-trending main normal faults that are connected by subparallel cross faults; the general displacement is east-side-down on the main faults. The Vallecitos zone is defined by northwest- to west-trending main faults, only some of which are joined by cross faults; rocks west of the fault zone have been lowered relative to the rocks that lie east of the fault zone. Thus the Jawbone Mountain-La Jarita Mesa highland has been elevated relative to the Tertiary rocks to the southwest, and depressed relative to the tertiary rocks that are part of the Taos Plateau on the northeast." }, { "name": "Heppner, James Paul", "degree": "PhD", "year": "1954", "title": "A Study of the Relationships Between the Aurora Borealis and the Geomagnetic Disturbances Caused by Electric Currents in the Ionosphere", "advisor": "Potapenko, Gennady W.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12152003-111801", "creators": [ { "name": { "family": "Heppner", "given": "James Paul" }, "id": "Heppner-James-Paul", "display_name": "Heppner, James Paul" } ], "advisors": [ { "name": { "family": "Potapenko", "given": "Gennady W." }, "id": "Potapenko-G-W", "role": "advisor", "display_name": "Potapenko, Gennady W." } ], "committee": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "member", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Potapenko", "given": "Gennady W." }, "id": "Potapenko-G-W", "role": "member", "display_name": "Potapenko, Gennady W." }, { "name": { "family": "Wulf", "given": "Oliver Reynolds" }, "id": "Wulf-O-R", "role": "member", "display_name": "Wulf, Oliver Reynolds" } ], "option_major": [ "geophys" ], "doi": "10.7907/RWHG-0Y11", "abstract": "In high latitudes, magnetic disturbances attributable to intense electric currents in the upper atmosphere are known to occur simultaneously with visible aurora. With few exceptions past investigations have merely revealed statistically that the degree of magnetic disturbance is proportional to the intensity of auroral activity.\r\n\r\nIn the research reported here, magnetic records and auroral observations from College (Fairbanks), Alaska have been studied in detail to determine the manner in which these phenomena are related. It is found that the relationships are quite definite and that practically all, if not all, disturbances may be represented in terms of two closely related patterns describing sequences of auroral activity which accompany positive and negative \"bay\" disturbances. Disturbances may appear extremely complicated due to repetition and overlapping of bays; examples are given to illustrate that these disturbances can be easily separated into individual bays by examining the sequence of auroral activity. A discontinuity in auroral activity occurs simultaneously with the reversal in direction of electric currents during the midnight hours; this feature indicates a dependence between the aurora and the electromotive force and thus contradicts a common opinion that aurora merely augments the conductivity. The pattern of behavior during magnetic storms preceded by sudden commencements is the same as on other nights.\r\n\r\nA preliminary analysis suggests that sudden commencements, reported on a world-wide scale, may be related to sudden changes from homogeneous to rayed aurora in the auroral zone.\r\n\r\nSpecial attention is given to: (1) the spatial association of aurora and electric currents, (2) a previously undescribed interval of +[Delta]H disturbance following negative bays, (3) auroral pulsations and movements, and (4) the repetition of similar features on consecutive nights.\r\n\r\nTheories and suggestions as to the cause of aurora and auroral zone currents are examined with reference to the present study." }, { "name": "Muehlberger, William Rudolf", "degree": "PhD", "year": "1954", "title": "Deposition and Deformation in the Northern Soledad Basin, Los Angeles County, California", "advisor": "Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12042003-110619", "creators": [ { "name": { "family": "Muehlberger", "given": "William Rudolf" }, "id": "Muehlberger-William-Rudolf", "display_name": "Muehlberger, William Rudolf" } ], "advisors": [ { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/AV8F-JR45", "abstract": "The Soledad basin is situated north of the San Gabriel Mountains, in Los Angeles County, California, and its center is about 35 miles north of the Los Angeles civic center. Roughly an elongate parallelogram in shape, this basin has dimensions of about ten by thirty miles, with the longer dimension oriented east-west. The Sierra Pelona and the San Gabriel Mountains form the northern and southern boundaries, respectively. The San Andreas fault and the San Gabriel fault, both of which trend northwest in this region, bound the basin on its northeast and southwest borders, respectively. Only the northern part of the basin is discussed in this paper.
\r\n\r\nThe pre-Cretaceous Pelona schist, the oldest unit in the map area, is a thick sequence of muscovite schist, chlorite-muscovite schist and actinolite-chlorite schist with rare layers of quartzite and limestone. This unit underlies the Sierra Pelona, an elongate mountain mass which trends east-west. Granitic intrusive rocks of probable late Jurassic age underlie a complex section of Tertiary rocks in most of the eastern Soledad basin. Gneisses, some of which may represent highly injected Pelona schist, also are present in a belt that in general trends parallel to the Sierra Pelona.
\r\n\r\nIn general, the sedimentary beds exposed at the surface are younger from east to west in the Soledad basin. The marine Martinez formation of Paleocene age is the oldest sedimentary unit in the region. It is overlain by the Vasquez series which crops out over a wide area, and comprises interlayered fanglomerates and volcanic rocks. Where the Martinez formation has been removed by erosion prior to the deposition of the Vasquez beds, the Vasquez series rests on the pre-Tertiary crystalline rocks. This unit is of doubtful Oligocene age, and has a maximum known thickness of nearly 16,000 feet. The Vasquez beds were deposited in three basins separated by ridges. Late in Vasquez time, these ridges were buried by thick alluvial fans built northward from the San Gabriel Mountains, and the basins thus coalesced into a single broad alluvial apron.
\r\n\r\nThe upper Lower Miocene Tick Canyon formation and the Upper Miocene Mint Canyon formation, which lie above the Vasquez series, also represent nonmarine deposition of dominantly coarse-grained sedimentary material. These units are widespread in the western part of the Soledad basin. Sandstone and siltstone of the \"Modelo\" formation rest unconformably on the Mint Canyon beds, and reflect an eastward encroachment of marine waters over a part of the basin in late Miocene time. West of the map area, the marine Pliocene Pico formation and the nonmarine Plio-Pleistocene Saugus formation, which grades westward into a marine facies, overlie the older rocks. Terrace deposits of late Pleistocene age are common over much of the area. Recent alluvium is present in all of the major valley bottoms and locally in some of the minor valleys.
\r\n\r\nThe date of the folding and metamorphism of the Pelona schist is not known, but it assuredly is pre-Tertiary. Tertiary rocks have been either tilted or deformed into broad open folds, although locally near the major faults nearly isoclinal folds are found. Almost without exception, these folds plunge to the west or southwest.
\r\n\r\nThe numerous faults are the most prominent structural features of the Soledad basin. Normal faults which trend generally east were formed in post-Martinez, pre-Vasquez time. Displacements occurred throughout Vasquez time and ceased prior to Tick Canyon time. The Pelona fault may have been reactivated just prior to Mint Canyon time. Offsets on these normal faults are as much as 10,000 to 15,000 feet. The normal faults indicate that the minimum compressive stress was oriented nearly north-south. Can the other hand, the post-Mint Canyon, pre-Saugus faults indicate a maximum compressive stress oriented north-south, which resulted in a number of northeast-trending left-hand faults with displacements up to 10,000 feet. None of the faults of the Soledad basin have been reactivated in spite of Pleistocene and Recent offsets along the San Andreas fault.
" }, { "name": "Otte, Carel, Jr.", "degree": "PhD", "year": "1954", "title": "Late Pennsylvanian and Early Permian Stratigraphy of the Northern Sacramento Mountains, Otero County, New Mexico", "advisor": "Pray, Lloyd Charles", "url": "https://resolver.caltech.edu/CaltechTHESIS:08172018-080926722", "creators": [ { "name": { "family": "Otte", "given": "Carel, Jr." }, "id": "Otte-Carel", "display_name": "Otte, Carel, Jr." } ], "advisors": [ { "name": { "family": "Pray", "given": "Lloyd Charles" }, "id": "Pray-L-C", "role": "advisor", "display_name": "Pray, Lloyd Charles" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/ME6M-T277", "abstract": "Late Pennsylvanian and early Permian strata in the northernmost Sacramento Mountains of New Mexico were studied in 1951-52 to aid in interpreting the complex depositional history of this time in south central New Mexico and to afford better understanding of the sedimentary and tectonic processes involved. For this investigation, which is largely a field study, five months were devoted to mapping a critical area of about 80 square miles, of which 30 square miles were covered in great detail, on a scale of four inches equal one mile.
\r\n\r\nThe map area forms the northernmost extension of the Sacramento Mountain escarpment, which is formed by a block that has been uplifted along a fault on the west and tilted one or two degrees to the east. Prior to this late Cenozoic Basin Range faulting, the area was affected by early Tertiary gentle folding and intrusion of Tertiary (?) sills and dikes of acidic and intermediate composition that cover about five percent of the area. Minor high-angle faults that were largely associated with the boundary fault zone occur in the area and locally complicate the structure. Evidence of late Pennsylvanian and early Permian folding and high-angle faulting is presented in the southeasternmost part of the area of investigation. Various Quaternary stream deposits cover about one-fifth of the area, which is otherwise unusually well exposed.
\r\n\r\nThe evidence indicates that deposition was essentially continuous from late Pennsylvanian (Virgilian) into early Permian (Wolfcampian) time within the area. This is significant in view of the relationships within four miles to the southeast, where a major angular unconformity separates Pennsylvanian and Permian strata. The sediments that are the time-equivalent of part of the hiatus represented by the unconformity have been designated by the author as the Laborcita formation. The lithologic and faunal character of the sedimentary deposits of the Laborcita formation indicate that abrupt lateral transition toward the east and southeast from open marine conditions to terrestrial flood plain environments must have occurred repeatedly within the distance of a few miles. The transition in environments was proved by lateral tracing of strata. One typical lateral succession of contemporaneous deposits was determined to be massive marine limestone; nodular argillaceous fusulinid-bearing limestone; silty limestones, bearing abundant shallow marine forms such as molluscs and brachiopods; dolomitic limestone; green shale; and marine to non-marine red shale and other terrigenous clastics. The lithology encountered in any one bed appears to be a function of the distance from shore line and depth of deposition, and the faunal content probably reflects the depth of deposition.
\r\n\r\nThe cyclic repetition of certain sequences is locally conspicuous and appears to be related to the tectonic instability of this area and to the episodic nature of the deformation in the area to the southeast. From late Pennsylvanian to early Permian time, the deposits indicate a gradual emergence of the area and a transition from marine to non-marine environments, although many fluctuations are recorded and periods of relative stability must have occurred.
\r\n\r\nEverywhere, the Laborcita formation overlies upper Pennsylvanian marine strata and underlies the red beds of the Abo formation. At the type locality, near the mouth of Laborcita Canyon about 2-1/4 miles northeast of the town of La Luz, the Laborcita formation is predominantly composed of marine beds and is 480 feet thick. About 3-1/2 miles to the southeast, a section of approximately the same thickness consists for about 80 percent of non-marine red mudstones. Within two more miles to the southeast the Laborcita formation thickens to about 1,000 feet. This marked increase in thickness is partly caused by a gradual regression of the Laborcita sea toward the northwest and a successive transgression of time lines of the upper contact of the Laborcita formation.
\r\n\r\nOn the basis of fusulinid occurrences throughout the Laborcita formation, the age has been determined as very late Virgilian and early Wolfcampian. In the lower part of the type section several zones yielded abundant fusulinids, which permitted an accurate location of the Pennsylvanian-Permian boundary about 90 feet above the base of the formation. Preliminary studies of the megafossils by various specialists indicate some disagreement with the Permian age of most of the Laborcita formation. The brachiopods indicate an early Permian age, but the ammonoids from the clay pits east of Tularosa, that occur in a position about 150 feet stratigraphically above fusulinids of distinctly Wolfcampian age, are classified as early late Pennsylvanian. The gastropods also exhibit affinities with Pennsylvanian forms. On the basis of the field studies and detailed stratigraphic control, the author believes that the conflicting paleontologic age-assignments must be resolved by further study and collaboration among the specialists of the different faunal groups.
\r\n\r\nThe non-marine strata overlying the Laborcita formation consist largely of red mudstones, fine sandstone, coarse arkose and minor congolomerate and comprise the Abo formation. In the Tularosa area near the northern boundary of the Sacramento Mountains, the Abo formation intertongues at the base with the upper lower Wolfcampian marine strata of the Laborcita formation and is about 1400 feet thick. Twelve miles to the southeast, in the north central part of the Sacramento Mountains, the Abo ranges from 250 to 500 feet in thickness and overlies with angular uncomformity rocks ranging in age from early Mississippian to late Pennsylvanian. The source of the Abo clastics is considered to be the Pedernal Landmass, a positive are of pre-Cambrian igneous and metamorphic rocks that existed during early Permian time in the northeasternmost part of the Sacramento Mountains, and which probably extended for 100 miles, or farther, to the north.
\r\n\r\nPray\u2019s work in the central and southern parts of the Sacramento Mountains indicate that the Abo formation is correlative with the bulk of the Hueco formation. On the basis, Pray considers the age of the top of the Abo formation either latest Wolfcampian or earliest Leonardian. As the Abo formation interfingers at the base with upper lower Wolfcampian marine strata in the map area, it is largely considered to be of middle and late Wolfcampian age.
\r\n\r\nThus, the Laborcita and Abo formations in the northernmost Sacramento Mountains indicate that deposition there was essentially continuous from late Virgilian through Wolfcampian time. The deposits indicate a gradual emergence of the area and retreat of the marine waters to the west and northwest, probably as a result of the late Virgilian-early Wolfcampian diastrophism of the Sacramento Mountains in the area to the east and southeast.
\r\n\r\nIn the Sacramento Mountains the Abo formation grades upward into the predominantly marine Yeso formation, that reaches a thickness of about 1300 feet. It consists mostly of limestones, shales, gypsum and sandstones and was not studied in any further detail. The overlying San Andres formation is the youngest Paleozoic formation of the Sacramento Mountains and forms the crest of the range.
\r\n\r\nIn the course of the field investigation a zone of lower Permian algal reefs were discovered northeast of Tularosa in the uppermost Laborcita formation. Detailed studies indicate that a filamentous alga is the main cement-binding and framework-building organism in these reefs, which average a height of about 35 feet, but which locally stood about 60 feet above the level contemporaneous sedimentation.
\r\n" }, { "name": "Potter, Donald Brandreth", "degree": "PhD", "year": "1954", "title": "High Alumina Metamorphic Rocks of the Kings Mountain District, North Carolina and South Carolina", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:02142018-102218444", "creators": [ { "name": { "family": "Potter", "given": "Donald Brandreth" }, "id": "Potter-Donald-Brandreth", "display_name": "Potter, Donald Brandreth" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/4PF2-GN68", "abstract": "The Kings Mountain district is located in the center of the \r\nPiedmont province at the North Carolina-South Carolina border. The \r\ndistrict consists of two areas which are underlain by high alumina \r\nmetamorphic rocks including kyanite quartzite and sillimanite quartzite. \r\nThe southern area covers about 35 square miles and lies just southeast of \r\nthe city of Kings Mountain; the northern area covers about 20 square miles \r\nand is located 15 miles northeast of the city of Kings Mountain. The\r\ntwo areas are separated by the Yorkville granodiorite. A detailed geologic \r\nmap was made of the southern area; in the northern area only the\r\nhigh alumina quartzites and the contact of the Yorkville granodiorite \r\nwere mapped. The detailed mapping of the southern area serves as a basis for \r\nmost of the discussion in the dissertation.
\r\n\r\n\r\nIn both areas, and especially in the southern area, kyanite \r\nquartzite and sillimanite quartzite form prominent ridges and hills. In \r\nthe southern area the long, craggy ridges and hills of Crowders Mountain, \r\nThe Pinnacle, Kings Mountain, and Henry Knob rise abruptly above the gently \r\nrolling Piedmont surface; these hills accurately reflect the outcrop \r\npattern of the kyanite quartzite that underlies them.
\r\n\r\n\r\nKyanite quartzite occurs as well defined beds and lenses in a \r\nthick sequence of high alumina metavoloanic and metasedimentary schists, \r\nmanganiferous schist, and magnetiferous quartzite. The high alumina \r\nnature of the schists is indicated by the presence of abundant white\r\nmica and one or more of the following accessory minerals: andalusite, \r\nchloritoid, kyanite, and staurolite. This sequence of high alumina schists \r\nand quartzites, manganiferous schist, and magnetiferous quartzite lies with\r\napparent unconformity on a thick sequence of metamorphosed volcanic, \r\nsedimentary, and igneous rocks which include quartz-mica schist, oligo\u00adclase \r\ntonalite, hornblende gneiss, and biotite gneiss and schist.
\r\n\r\n\r\nThe entire sequence of rocks was folded along a N40E-trending \r\naxis; the outcrop pattern of the high alumina quartzites and manganiferous \r\nschist indicates the presence of a major anticline and syncline that probably \r\ndeveloped at this time. A later deformation accompanied the emplacement of \r\nthe Yorkville granodiorite. This large body was intruded along a north\u00ad\r\ntrending zone into the east limb of the N40E-trending anticline. In addition \r\nto apparently warping the earlier major structures, this deformation pro\u00adduced \r\nnumerous small steeply plunging folds, strong flow cleavage and lineation. \r\nThese last three structural features bear no consistent relation \r\nto the major folds.
\r\n\r\n\r\nA major metamorphism accompanied the intrusion of the Yorkville \r\ngranodiorite, producing sillimanite in the high alumina sediments near the \r\ngranodiorite and kyanite in the high alumina sediments farther away. The \r\nrocks that occur as septa in the granodiorite, and those adjacent to the \r\ngranodiorite contact belong to the amphibolite facies. These rocks grade \r\nwestward over a distance of 2 to 3 miles into rocks of the albite-epidote \r\namphibolite and greenschist facies. Andalusite occurs in schist adjacent \r\nto kyanite quartzite and sillimanite quartzite and it commonly occurs with \r\nsillimanite in quartzite, but not commonly with kyanite in quartzite. Some \r\nof the puzzling distributions of these polymorphs may reflect subtle com\u00adpositional \r\ndifferences in the parent sediments. The three polymorphs were seen together \r\nin a few thin sections. The paragenetic sequence, deduced\r\nfrom the study of three thin sections, probably indicates polymorphic trans\u00adformations \r\nresulting from a single metamorphism rather than a series of metamorphisms.
\r\n\r\n\r\nThe following evidence suggests that high alumina quartzite \r\nin this district is of metasedimentary origin: high alumina quartzite \r\noccurs as well defined thin beds that can be traced up to three and one\r\nhalf miles along strike; many outcrops of high alumina quartzite exhibit \r\ncompositional layering (i.e., kyanite quartzite is interlayered with stauro\u00adlite \r\nquartzite, and with non-kyanitic magnetiferous quartzite); high\r\nalumina quartzite beds occur in a conformable sequence of high alumina \r\nmetasedimentary and metavolcanic schists. It is suggested that the high \r\nalumina quartzite beds are metamorphosed beds of sandy or silty clay; these \r\nbeds probably represent one stage in the deposition of fine grained clayey \r\nelastic sediments.
\r\n\r\n\r\nNo evidence was found to support the view of Smith and Newcombe\r\n(1951) that the kyanite at Henry Knob developed by hydrothermal introduction\r\nof alumina. The present study indicates that kyanite in the\r\nkyanite quartzite here, as throughout the district, is of metasedimentary\r\norigin.
\r\n\r\n\r\n\r\n" }, { "name": "Shor, George G., Jr.", "degree": "PhD", "year": "1954", "title": "Crustal Structure and Reflections from the Mohorovi\u010di\u0107 Discontinuity in Southern California", "advisor": "Richter, Charles F.; Gutenberg, Beno", "url": "https://resolver.caltech.edu/CaltechTHESIS:02092010-093212931", "creators": [ { "name": { "family": "Shor", "given": "George G., Jr." }, "id": "Shor-George-G", "display_name": "Shor, George G., Jr." } ], "advisors": [ { "name": { "family": "Richter", "given": "Charles F." }, "id": "Richter-C-F", "role": "advisor", "display_name": "Richter, Charles F." }, { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/2WXF-CV31", "abstract": "The thickness and structure of the crust of the earth have been studied in a limited area of southern California by means of reflected and refracted seismic waves. Two usable records of reflections from the Mohorovi\u010di\u0107 discontinuity at nearly vertical incidence were obtained from large quarry blasts. Each record shows a strong reflection with travel time near 10.6 sec. Strong reflections from the Mohorovi\u010di\u0107 discontinuity were also obtained at distances slightly beyond critical from blasts at one quarry. Many other records of blasts and of earthquakes show phases that may be interpreted as reflections from the Mohorovi\u010di\u0107 discontinuity.
\r\n\r\nStudies of refracted waves from blasts and earthquakes have given additional information about crustal velocities. When combined with the reflection data, they indicate that there is at least a slight decrease of velocity with depth somewhere in the crust and that there are significant variations in the arrival time of P_n at distant stations, indicating lateral variation either in crustal velocities or in the thickness of the crust.
\r\n\r\nComputations of the thickness of the crust near Monolith and Corona, California have been made from various assumptions of velocity structure. The results obtained by using any model that agrees with the refraction data or by assuming a single-layer crust agree closely. In this area the Mohorovi\u010di\u0107 discontinuity is 32 km below sea level and the mean velocity in the crust is 6.2 km/sec.
\r\n" }, { "name": "Forester, Robert Donald", "degree": "PhD", "year": "1953", "title": "Studies of the Travel Times, Periods, and Energy of Seismic Waves SKP and Related Phases. The Magnetite-Rich Breccia Masses at Iron Mountain, Silver Lake District, San Bernardino County, California", "advisor": "Gutenberg, Beno; Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05062003-085500", "creators": [ { "name": { "family": "Forester", "given": "Robert Donald" }, "id": "Forester-Robert-Donald", "display_name": "Forester, Robert Donald" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/XPMD-7118", "abstract": "The travel times, periods, and amplitudes of SKP core waves have been investigated for shocks of normal, 60 km, and 100 km depths.\r\n\r\nFor shallow shocks, multiple SKP phases are observed as long as 54 seconds after the initial SKP motion on short period instruments, and as long as 87 seconds on long period instruments. Amplitude data indicate that each multiple phase has a focal point similar to that of the initial SKP phase. The focal point for waves having periods of 1 to 5 seconds occurs at 131 1/2[degrees] and that for waves having periods of 5 to 10 seconds is broadly defined between 130 and 131[degrees]. Short period SKP phases extend from 129 to at least 140[degrees]; and long period SKP phases, from 125 to 145[degrees]. The long period waves are believed to be diffracted from the caustic in accordance with Airy's hypothesis. Multiple reflections and refractions in the outer layers of the mantle seems more plausible as an explanation of multiplicity than dispersion.\r\n\r\nIn order to analyze the energy content of the SKP phases, a system was developed for determining the magnifications of the ground motion of seismometers from their records of earthquakes.\r\n\r\nAs an experiment, theoretical travel times for PKP, SKP, and SKS were computed by integration along the travel paths. For this purpose, the velocity distribution within the earth was broken into segments which were represented by continuous functions. The resultant travel times are not valid for rays of grazing incidence to the core. The times computed for PKP and SKP are intermediate between the smoothed times given for them by Jeffreys and the times for them based upon recent observed data. The theoretical travel times for SKP provided a basis for the analysis of the energy content of the SKP phases.\r\n\r\nFor all types of SKP phases, the energy content of short period waves is a small fraction of that of long period waves. For vertical instruments, the agreement between theoretical and observed values of energy is good. For horizontal instruments the observation of too little energy is not satisfactorily explained.\r\n\r\nSKP\", the SKP phase associated with the inner core, is observed between 114[degrees] and 125[degrees]. It records with periods of 1 to 3 seconds on both long and short period instruments. The observations of SKP\" present additional support for the hypothesis of a large, but continuous increase of velocity at the transitional boundary of the inner core.\r\n\r\nEvidence for a difference between the travel paths of short and long period waves is less apparent for SKP than for PKP." }, { "name": "Norris, Donald Kring", "degree": "PhD", "year": "1953", "title": "Structural Conditions and Violent Stress Relief in Coal Mines of the Southern Canadian Cordillera", "advisor": "Buwalda, John P.; Noble, James A.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05082003-101319", "creators": [ { "name": { "family": "Norris", "given": "Donald Kring" }, "id": "Norris-Donald-Kring", "display_name": "Norris, Donald Kring" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." }, { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/K08S-Y213", "abstract": "The problem was investigated under the auspices of the Geological Survey of Canada in an attempt to evaluate the relation of geologic structure to the mining practices which gives rise to occurrences of violent relief of stress. An understanding of this problem is imperative to the winning of coal at depth.\r\n\r\nThe faulted and drag-folded condition of the seams in the Crowsnest and Cascade coal areas may be interpreted by the mechanics of shear-thrusting. Gentle flexing of the overthrust masses was effected through similar folding for the combined series of competent and incompetent units.\r\n\r\nAlternate stretching and compression of the Kootenay formation at Coleman and Canmore resulted in the development of an abundance of extension and contraction faults transecting the seams, and a sheared condition within the coal. Frictional resistance tended to retard those beds in the overriding masses closest to the thrust planes so that in every instance the upper beds moved slightly further to the east relative to those below them. Consistent dragfold patterns within the coal seams were the result.\r\n\r\nThe fractured and sheared condition of the coal is all important in governing the stress relief characteristics of the seams. Bump phenomena occur only in structurally strong coals, whereas blowouts have been experienced where the seams are both sheared and unsheared. In contrast to violent bumps which show a definite increase in frequency with depth, beginning at a cover interval of about 500 feet, blowouts first occur at about the same depth, but after reaching a maximum frequency between 700 and 1100 feet, show a marked decrease at progressively greater cover intervals to the point where no blowouts are recorded in the 1 East mine, Coal Creek, at 2000 feet.\r\n\r\nWhereas a bump condition is created by faulty mining practices which result in the failure of overstressed coal in abutment zones, a blowout condition is believed to be due in part to redistribution of stresses associated with the advance of the working face, and in part to the physical-chemical relation of the coal to the associated gases. Secular strain is not believed to be a primary factor in the genesis of violent stress relief phenomena." }, { "name": "Rigsby, George Pierce", "degree": "PhD", "year": "1953", "title": "Studies of Crystal Fabrics and Structures in Glaciers", "advisor": "Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05122003-112509", "creators": [ { "name": { "family": "Rigsby", "given": "George Pierce" }, "id": "Rigsby-George-Pierce", "display_name": "Rigsby, George Pierce" } ], "advisors": [ { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/03RC-6663", "abstract": "Optical orientation of approximately 5000 ice crystals was determined on the Emmons Glacier in 1950, the Malaspina Glacier in 1951, and the Saskatchewan Glacier in 1952, by means of a 6-inch universal stage mounted between crossed polaroid sheets. The crystals measured were 0.2-6 inches across, and from three to eighty were included in each 4 ? x 6-inch thin-section. The optic axes when plotted on a Schmidt equal-area projection, form consistent patterns which appear to be related to the foliation in the ice. The patterns usually feature strong maxima at the corners of diamond shaped quadrangles. Concentrations of axes as high as 26 per cent in 1 per cent of the area were recorded.\r\n\r\nTwo possible mechanisms for producing common orientation of the crystals in glacier ice seem plausible. One is ?instantaneous recrystallization? by means of which the atoms in a lattice become energized under stress and rearrange themselves into more comfortable positions. The second is the growth of crystals favorable to deformation on glide planes at the expense of those which are unfavorably oriented for gliding and consequently become strained and develop higher free energy.\r\n\r\nFrom the study of fabric patterns in glaciers it seems likely that the two crystals are oriented in such a way as to allow gliding either on two glide planes other than the well-known basal plane, or on the basal glide plane with the pattern later being changed by recrystallization, possibly by an ordered response within the crystals to the relaxation of stresses. This might be compared to annealing behavior in metals.\r\n\r\nIt is postulated that ?solid flow? occurs in ice by deformation on glide planes and continuous recrystallization with migration of grain boundaries as local stresses on each crystal slowly change. The preferred orientation of crystals is probably developed by growth of crystals favorably oriented for gliding at the expense of the others." }, { "name": "Saint-Amand, Pierre", "degree": "PhD", "year": "1953", "title": "A Possible Relation Between the Night Airglow and the Ionosphere", "advisor": "Potapenko, Gennady W.", "url": "https://resolver.caltech.edu/CaltechETD:etd-05122003-113804", "creators": [ { "name": { "family": "Saint-Amand", "given": "Pierre" }, "id": "Saint-Amand-Pierre", "display_name": "Saint-Amand, Pierre" } ], "advisors": [ { "name": { "family": "Potapenko", "given": "Gennady W." }, "id": "Potapenko-G-W", "role": "advisor", "display_name": "Potapenko, Gennady W." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/7XB4-Z662", "abstract": "(1) It has been found that the diurnal variation of the 6300-6364 Angstrom OI radiation is similar to the diurnal variation of the electron density of the F Layer of the ionosphere. It has been suggested that this similarity is not incidental, and the two phenomena are closely related to each other. The factor of proportionality changes with the seasons.\r\n\r\n(2) It has been found further that the diurnal variation of the intensity of the 5577 OI radiation is similar to the diurnal variation of the height of the F layer. It is postulated that the 5577 radiation takes place within a region which shares in the vertical movements of the F layer.\r\n\r\n(3) It has been found also that the intensity of the 6300-6364 radiation changes when the height of the F region changes.\r\n\r\n(4) Heights calculated by the method of Van Rhijn for the 6300-6364 radiation fall within the height range of the F layer. Those calculated by this method for the 5577 radiation fall at the base of the F region. The independent identification of the radiation with the F region lends confidence to height values of the emitting regions calculated by Roach, Barbier and others.\r\n\r\n(5) The mechanisms of excitation producing the 5577 and 6300 radiations appear to be different. There is also little evidence for production of the redlines by cascading of electrons from the energy levels producing the green line.\r\n\r\n(6) The instrumentation used in measuring the intensity of the nightglow is discussed in detail." }, { "name": "Leighton, Freeman Beach", "degree": "PhD", "year": "1952", "title": "Geology of the Vermiculite Deposits of the Gold Butte Mining District, Southern Virgin Mountains, Nevada. Ogives of the East Twin Glacier, Alaska: Their Nature and Origin. Investigations in the Taku Glacier Firn", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechETD:etd-05042006-141511", "creators": [ { "name": { "family": "Leighton", "given": "Freeman Beach" }, "id": "Leighton-Freeman-Beach", "display_name": "Leighton, Freeman Beach" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/ER20-ET85", "abstract": "Geology of the vermiculite deposits, Gold Butte mining district, southern Virgin Mountains, Nevada:
\r\n\r\nVermiculite deposits lie within a one mile square area in the Gold Butte mining district, Southern Virgin Mountains, Nevada. An integrated field and laboratory study of the deposits was undertaken in an attempt to determine their origin. Particular attention was devoted to the mineralogy of the vermiculite and associated minerals and the geochemistry of vermuculitization.
\r\n\r\nThe deposits occur in ultramafic sheets and lenses of probable pre-Cambrian age. Peridotites and perknites have intruded pre-Cambrian migmatites, granulites, and quartzites, and now crop out in the interior of an elliptical dome. Diverse ages of ultramafic intrusives, demonstrated by crosscutting relations, suggest multiple intrusion. Intrusion and formation of the domical structure are believed essentially coincident in time, with intrusion outlasting the severe deformation associated with the forceful injection of an ultramafic crystal mush.
\r\n\r\nDuring an early Cenozoic(?) orogeny the Gold Butte granite porphyry was emplaced. This granite was the probable source of most granitic pegmatites which are abundant in the area. Hydrothermal solutions supplied from the granitic magmas circulated through the ultramafic rocks, profoundly altering them.
\r\n\r\nVermiculite is widely distributed in altered ultramafic rocks, occurring in veins, stringers, pockets, and as scattered flakes. A study of X-ray, chemical, differential thermal and heat exfoliation data indicate two distinct types of vermiculite mixtures are present. All vermiculites examined were one of these two types or gradations between them. All must be considered varieties of hydrobiotite, for K2O is present in every case and represents a contamination by biotite layers. One type is a vermiculite-biotite mixture with the approximate ratio of 2:1, respectively. The second type is essentially biotite, containing approximately four per cent vermiculite. Both types show a marked degree of heat exfoliation, the second type to a lessor degree.
\r\n\r\nConsiderable variation between the ratio of vermiculite and biotite exists in a single vein. This heterogeneity is believed due to the high cation-exchange capacity of vermiculite.
\r\n\r\nThe fact that all samples showed either biotite interleaved with vermiculite, or non-expandable biotite along with hydrobiotite is one of the best evidences that vermiculite has altered from biotite, which most cases, is an intermediate product in the alteration of other ultramafic minerals.
\r\n\r\nVermiculitization of biotite involved (1) progressive subtraction of the alakies, (2) hydration and formation of loosely-bound interlayered water, and (3) progressive oxidation of ferrous to ferric iron. The process was largely accomplished by hydrothermal solutions. Zoning relations of vermiculite and other minerals in serpentine veins are especially indicative of hydrothermal activity. Still, other facts are suggestive of meteoric origin. Hence it is believed that meteoric solutions continued the process of vermiculitization after hydrothermal activity ceased, and perhaps, in some cases initiated it.
\r\n\r\nOgives of the East Twin Glacier, Alaska--their nature and origin: Investigations in the Taku Glacier firn, Alaska:
\r\n\r\nThe perfection, fine exposure, and unusual accessibility of ogives on East Twin Glacier, Alaska, make this an exceptional place in which to study the nature and origin of this phenomenon. The origin of ogives is discussed, and previous hypotheses are critically analyzed. With the exception of a hypothesis first suggested by R. T. Chamberlin, that ogives are the surficial expressions of shearing planes, no other hypothesis satisfactoriy accounts for the fact that these ogives are exposed edges of layers of denser and dirtier ice than the intervening layers. Concepts of glacier flow evolved by Demorest provide a reasonable mechanism for understanding their formation, namely, periodic obstructed extrusion flow down-glacier from an icefall. Debris which was originally basal is believed to become, by upthrusting and ablation, the surface manifestation of an ogive.
\r\n" }, { "name": "Nelson, Robert Leslie", "degree": "PhD", "year": "1952", "title": "A Study of the Seismic Waves SKS and SKKS. Glacial Geology of the Frying Pan River Drainage, Colorado", "advisor": "Gutenberg, Beno; Sharp, Robert P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02082018-131502507", "creators": [ { "name": { "family": "Nelson", "given": "Robert Leslie" }, "id": "Nelson-Robert-Leslie", "display_name": "Nelson, Robert Leslie" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Sharp", "given": "Robert P." }, "id": "Sharp-R-P", "role": "advisor", "display_name": "Sharp, Robert P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/WWWD-0T60", "abstract": "[Major Thesis Abstract]
\r\n\r\nArrival times, amplitudes, and periods of the seismic phases SKS and SKKS have been investigated for normal, intermediate, and deep earthquakes recorded at Pasadena and Huancayo, Peru. New observed time\u00ad-distance curves are constructed for depths of < 60, 100, 200, and 600 kilometers. Travel-times for the core have been calculated from normal shock time data. Slight modification of wave velocity just inside the core and of travel times within the core are suggested. Calculated travel times of SKS, SKKS, and SKKKS are in good agreement with observations.
\r\n\r\nEnergy parameters determined from observed ampli\u00adtude/period ratios are found in only fair agreement with those calculated from theory. Observed energies are too large for most of the phase components and depths considered. The horizontal components of SKKS over the whole distance range, and of SKS at \u0394 < 100\u00b0for all depths, yield observed energies less than those pre\u00addicted by theory. Both discrepancies are at least qual\u00aditatively explained by a proposed non-spherical distribution of shear strain about the fault source, and by . abnormal absorption in the outer 700 kilometers of the core. A period increase with epicentral distance for SKS and SKKS is best explained by selective absorption in this same zone.
\r\n\r\nAnomalous observed energies, as a function of epi\u00adcentral location, can also be accounted for by the proposed non-spherical distribution of energy. A similar regional phase-period dependence is considered in terms of finite faulting velocities. Times, energies, and periods of multiple SKS phases for the depths studied are presented. No single hypothesis commensurate with all observed conditions is found, but the phases pSKS and sSKS for normal shocks are probably represented.
\r\n\r\n[Minor Thesis Abstract]
\r\n\r\nOn the west flank of the Sawatch Range, Colorado, evidence is found for six distinct glacial advances. One glaciation is pre-Wisconsin, four are Wisconsin, and one post-Wisconsin in age. In addition to end and lateral moraines of each advance, terrace remnants of six valley trains were identified and studied for a distance of 25 miles along Frying Pan River and its major tributaries. Elevations above stream level of these outwash terraces are 400\u00b150, 90-120, 40-50, 20-30, 12-17, and 6-8 feet. Five of the tributary valleys contained ice streams which did not join the trunk Frying Pan glacier during the Wisconsin stage.
\r\n\r\nAn extensive review and testing of the numerous criteria used to distinguish deposits of multiple glaciations shows that nine of these criteria can conveniently be expressed in parameters indicative of relative age. Estimates based on these criteria, coupled with a recent radiocarbon dating of late Mankato till in the Midwest, yield the following approximate ages for deposits of the six glaciations in Frying\r\nPan Valley: 230,000, 63,000, 46,000, 17,000, 11,500, and 5,750 years. The accuracy and reliability of the procedure used cannot be evaluated without further absolute Carbon-14 age determination.
\r\n" }, { "name": "Pray, Lloyd Charles", "degree": "PhD", "year": "1952", "title": "Stratigraphy of the Escarpment of the Sacramento Mountains, Otero County, New Mexico. The Mocam Bastnaesite Deposit, San Bernardino County, California", "advisor": "Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:08072018-083556286", "creators": [ { "name": { "family": "Pray", "given": "Lloyd Charles" }, "id": "Pray-Lloyd-Charles", "display_name": "Pray, Lloyd Charles" } ], "advisors": [ { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/BJT5-G256", "abstract": "The Sacramento Mountains constitute a sharply asymmetrical cuesta at the eastern edge of the Basin and Range Province in south central New Mexico. The escarpment rises abruptly for more than a mile above the desert plains of the Tularosa Basin. From the crest, near 10,000 feet, the surface slopes gently to the Pecos River, 100 miles to the east and 6000 feet lower.
\r\n\r\nThe rugged west-facing escarpment has been carved in section of sedimentary rocks about 7500 feet thick. This section is almost entirely of Paleozoic age. Geologic maps at a scale of two inches equals one mile of an area 28 miles long and 15 miles wide along the escarpment were prepared during 13 months of field investigations. This report deals with the stratigraphy of the mapped area, which is about 85 per cent of the area of the escarpment of the Sacramento Mountains.
\r\n\r\nThe bedrock strata range in age from late pre-Cambrian (?) to middle Permian, and include representatives of all periods of the Paleozoic era. The strata are largely the product of marine deposition on a stable shelf area. Most formations are thin and laterally persistent across much of southern New Mexico and are separated by disconformities.
\r\n\r\nThe oldest rocks exposed are late pre-Cambrian (?) and consist of about 100 feet of slightly metamorphosed quartz sandstone, siltstone, and shale, intruded by diabase sills. These rocks are separated from the Paleozoic strata by an unconformity with an angular discordance of about 10\u00b0.
\r\n\r\nThe Upper Cambrian (?) Bliss sandstone forms the base of the Paleozoic sequence, and consists of 110 feet of glauconitic quartz sandstone and minor clastic dolomite. The El Paso formation, 370 feet of sandy dolomite of Lower Ordovician age, is probably disconformable on the Bliss sandstone, and is separated from the overlying Montoya formation of Upper Ordovician age by a sharp disconformity representing all of middle Ordovician time. The Montoya formation is 140 to 250 feet thick. Dark massive dolomite forms the lower member, and lighter colored, cherty dolomite, the upper member. Lithologically distinctive strata composed of 150 to 200 feet of white weathering, thin bedded, sublithographic dolomite above the Montoya formation are termed the Valmont formation (new name) and are of Upper Ordovician (?) age. It appears to be gradational with the Montoya formation, but is separated from the overlying darker, cherty dolomite of the Fusselman (?) formation by disconformity. The Fusselman (?) formation is about 70 feet thick along most of the escarpment, but thins and is locally absent toward the north. It contains a Silurian (?) fauna, somewhat older than is known for the Fusselman formation farther to the southwest in New Mexico and Texas.
\r\n\r\nStrata of Devonian age persist throughout the area, but are nowhere more than 100 feet thick. Lithologically, the represent a transition from the underlying dolomites of the lower Paleozoic section to the limestone and shale of the upper Paleozoic. Gray silty dolomite of the Onate formation (upper Middle Devonian) is overlain by yellow gray limestone and shale of the Sly Gap formation (Upper Devonian) in the northern half of the escarpment. Black shales of the Percha (?) formation (Upper Devonian) overlie the Onate in the southern escarpment, and lap northward onto the Sly Gap.
\r\n\r\nThe base of the Mississippian strata throughout the area consists of gray nodular limestone and shale of the Caballero formation (Kinderhookian), which ranges from 15 to 50 thick. Abundant crinoidal limestone, and many bioherms, some as thick as thick as 400 feet, form much of the Lake Valley formation (Osagian) and record a period of prolific marine invertebrate life. The Lake Valley formation is 200 to 450 feet thick in the northwestern part of the escarpment, and thins to the east and south. Dark siliceous limestone of the Las Cruces (?) and Rancheria formations (Meramecian) overlies a persistent uniformity of low angular discordance. These strata are about 300 feet thick to the southeast, where they overlie the Caballero formation, and thin by overlap to the northwest. The Helms formation (Chesterian), consists of about 60 feet of limestone and shale, and is restricted to the southern part of the escarpment.
\r\n\r\nThe Pennsylvanian strata, 2000 to 3000 feet thick, record a period of structural unrest in New Mexico, as indicated by abundant coarsely clastic strata derived from nearby areas of uplift and erosion, and by considerable lateral variation of the strata. The Sacramento Mountain area received sediment during most of the Pennsylvanian time. The strata are subdivided into three formations and one member (all new names). The basal formation, the Gobbler, consists of 1200 to 1600 feet of coarse quartz sandstone, argillaceous limestone, and shale of Morrowan (?) to middle Missourian age. As much as 800 feet of gray cherty limestone, the Bug Scuffle limestone member, is prominent in the southwest and northeast part of the escarpment, and grades abruptly into shallow marine and deltaic clastic rocks that trend northwest through the area. The Beeman formation (upper Missourian) consists of 350 to 450 feet of feldspathic sandstone, limestone, and shale. Abundant sandstone in the Gobbler and Beeman formations indicate nearby highland areas of pre-Cambrian rocks, the Pedernal Mountains, were nearby to the east in pre-Virgilian Pennsylvanian time. The Holder formation, of Virgilian age, consists of as much as 900 feet of strata. Discontinuous limestone bioherms mark the base of the formation, and red marls, nodular limestone, and white massive limestone characterize much of the upper strata.
\r\n\r\nIn the northwestern Sacramento Mountains, sedimentation apparently was nearly continuous from Pennsylvanian into Permian time. About 300 feet of alternating marine and non-marine gray and red shale, sandstone, and limestone conglomerate of the lower Wolfcampian Bursum formation directly overlies some of the youngest Pennsylvanian strata in North America. Elsewhere in the area, pronounced uplift and deformation by folding and high angle normal faulting occurred along northerly trends and is the major diastrophism of the Paleozoic Era in this area. It probably began in late Virgilian time, reached a climax before upper Wolfcampian time, and was of declining importance after Wolfcampian time.
\r\n\r\nThe Abo formation of upper Wolfcampian age was deposited over a marked uniformity, and rests on truncated strata as old as the lower Lake Valley formation. The Abo formation ranges from 250 to 550 feet thick, and consists of continental red mudstone and coarse arkose in the northern part of the area. Toward the south, the middle part of the Abo formation grades into brackish to marine limestone and shale of the Culp tongue (new name) of the Hueco formation. Upper and lower tongues of Abo red beds persists far to the south, and probably correlate with red strata in the Hueco formation of Texas.
\r\n\r\nThe Yeso formation of Leonardian age is gradational with the Abo formation and consists of about 1300 feet of red beds, yellow and gray shale, limestone, silty quartz sandstone, and evaporates of gypsum and some halite. It records the fluctuating conditions of a shallow back-reef or lagoonal area. Carbonate rocks are more abundant toward the open seas to the southeast, and red beds and evaporates more prevalent toward the shore areas to the north.
\r\n\r\nThe resistant crest and eastern slope of the Sacramento Mountains are formed by the limestone and dolomitic limestone of the Glorieta (?) and the San Andres formations of the Guadalupian age. The Yeso, Glorieta (?), and San Andres formations appear to represent essentially continuous deposition. A total of about ten feet of several thin beds of clean, fine to medium grained quartz sandstone occur in the lower 120 feet of the carbonate strata. This section forms the Glorieta (?) formation. The sandstone beds thicken away from the crest of the mountains. Erosion has removed more than half of the 1400 feet of limestone of the San Andres formation from the crest of the Sacramento Mountains.
\r\n\r\nQuaternary deposits consist of at least three levels of terrace gravels, recent alluvium spring deposits, and large amounts of slum material. The alluvium of the Tularosa Basin is a minimum of 1800 feet thick, and in part may be Tertiary age.
\r\n\r\nThe Sacramento Mountains are a fault block range, tilted one to two degrees to the east, and bounded on the west by a gravity fault zone near the base of the present escarpment. Piedmont scarps and numerous sympathetic minor faults near the edge of the mountain block, the truncation of sculpture and internal structure of the range, the available stratigraphic evidence, and the regional tectonic pattern all are evidence in favor of faulting as the dominant mechanism for the uplift of the range. The estimated minimum displacement along the boundary fault is of the order of 7000 feet for a distance of 20 miles along the escarpment, and decreases to about half this amount at the northern and southern limits of the mapped area.
\r\n\r\nThe internal structure of the mountain block was largely developed by folding and high-angle faulting during late Pennsylvanian and earliest Permian time. Most of these pre-Abo structures trend north-south. The intensity of the deformation appears to increase from west to east throughout the length of the escarpment, toward the area of maximum pre-Abo uplift and erosion. Anticlines are more sharply defined than synclines, and domes are common along the anticlinical crests. The deformation is believed to be controlled by both vertically acting forms and by lateral compression.
\r\n\r\nGentle folds and some high-angle faults in the Permian strata indicate later mild deformation. If a dissected erosional surface in the highest part of the mountains represents the exhumed basal unconformity of former Cretaceous rocks, some of this later structural development is of Mesozoic age. Some of these later structural development is of Mesozoic age. Some of these later structural features may have developed during the intrusion of sills and dikes of trachyandesite of early Tertiary age, that are common in the lower Pennsylvanian and Permian shales.
\r\n\r\nThe major uplift of the range is believed to be of late Cenozoic age, and may be continuing at the present time. A zone of monoclinal folding and gravity faulting along the Sacramento River in the southeast part of the area has formed in late Cenozoic time, and is an echelon with the boundary faults of the Sacramento and Guadalupe Mountains.
\r\n\r\nSome of the problems of major interest for further study in the Sacramento Mountain region include the bioherms of the Mississippian and Pennsylvanian formations, detailed studies of the lithofacies and biofacies of the Gobbler and Bursum formations, and detailed stratigraphic examination of the Paleozoic strata of adjacent mountain areas in order to permit proper regional analysis of the Paleozoic history of southern New Mexico. Careful collection and study of the invertebrate faunas of the rock units of the lower Paleozoic section of the Sacramento Mountains could result in a major contribution to the stratigraphy of New Mexico and other western areas.
\r\n" }, { "name": "Hoppin, Richard Arthur", "degree": "PhD", "year": "1951", "title": "The Geology of the Palen Mountains Gypsum Deposit, Riverside County, California. Oscillations in the Foraminifera of the Vicksburg Group from a Well in George County, Mississippi", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:06152018-143736204", "creators": [ { "name": { "family": "Hoppin", "given": "Richard Arthur" }, "id": "Hoppin-Richard-Arthur", "display_name": "Hoppin, Richard Arthur" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/39JR-ZS98", "abstract": "[Thesis 1]. The Geology of the Palen Mountains Gypsum Deposit, Riverside County, California:
\r\n\r\nA large deposit of gypsum 5 square miles in area is located at the north end of the Palen Mountains. Interbedded gypsum, marble, quartzite, feldspathic quartzite, and lime silicate rocks, together with metamorphosed intrusives, are arranged in bands trending east-west. The rocks are intensely deformed and metamorphosed. Intense folding, faulting, brecciation, and shearing occurred as a result of strong deformation. These structures vary in magnitude from the large mappable units down to those microscopic in size. Along with the extreme deformation, the area has been subjected to regional, contact, and metasomatic and hydrothermal metamorphism in that order.
\r\n\r\nThe gypsum occurs as massive beds of finely crystalline material of very high grade interbedded with marble or as thinly laminated gypsiferous epidotic schists. Little anhydrite is found at the surface and its presence at depth cannot be ascertained for no drilling has been done. Although the gypsum is of high quality, its value is lessened by the presence of large and small fragments of marble which are literally \u201cfloating\u201d in the gypsum beds. These \u201cTectonic\u201d impurities will increase the cost of mining.
\r\n\r\nThe deposits have been variously dated as Precambrian and as Paleozoic. The lack of fossils and the small amount of geologic work done in the southeastern Mojave desert make dating and correlation difficult. The deposits are similar to those in the Little Maria and Maria Mountains to the east with an upper Paleozoic age designation probably the better alternative. The possibility should be considered that these gypsum, marble, schist, and quartzite beds are the deformed and meta-morphosed equivalents of the gypsum, limestone, shale and sandstone of the Kaibab and Moenkopi (Permian and Triassic) formations in Southern Nevada.
\r\n\r\n[Thesis 2]. Oscillations in the Foraminifera of the Vicksburg Group from a Well in George County, Mississippi:
\r\n\r\nAn oscillation chart is presented based on the foraminiferal content of core samples of the Vicksburg Group (Middle Oligocene) from a well in southeastern Mississippi. The oscillations are due primarily to relative changes in depth at this geographic position during the deposition of the sediments. These changes are indicated by variations in the percentage distribution of the species of foraminifera.
\r\n\r\nTen cubic centimeters of each sample were washed and then sieved through a 150 mesh screen. A count was made of the number of specimens of each species or closely related group of species in each sample. The percentage distribution of the benthonic calcareous and arenaceous forms were calculated separately because the benthonic calcareous foraminifera are the more delicate depth indicators. The relative depth significance of the benthonic calcareous foraminifera was determined by plotting their percentages against the percentage of Uvigerina spp., which are considered typically open-water elements.
\r\n\r\nThe possible influence of modifications of other ecologic factors comprising the depositional environment must also be considered when interpreting faunal changes. However, as a sample covers an interval of several inches or several feet in thickness (equivalent to hundreds or thousands of years), these effects are probably insignificant. The interpretation of fossil material is further complicated by such processes as mixing, mechanical abrasion, solution, and recrystallization.
\r\n\r\nThe chart reveals several transgressions and regressions in the Vicksburg Group, even though the section appeared at first glance to be made up of a monotonous, homogeneous foraminiferal fauna. A single chart could not be carried across the strong faunal break between the Red Bluff (Lower Oligocene) and the Vicksburg. By charting the two parts separately, the oscillations are more easily discerned.
\r\n\r\nThe method shows promise as a correlation tool in sedimentary sections in which there were fairly rapid depth changes. An individual chart probably should not be extended over a period of time greater than an epoch because evolutionary development will tend to mask faunal changes caused by oscillations of depth.
" }, { "name": "Lieber, Paul", "degree": "PhD", "year": "1951", "title": "Relaxation Phenomena and the Origin of Earthquakes", "advisor": "Gutenberg, Beno; Michal, Aristotle D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:10132017-094352043", "creators": [ { "name": { "family": "Lieber", "given": "Paul" }, "id": "Lieber-Paul", "display_name": "Lieber, Paul" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Michal", "given": "Aristotle D." }, "id": "Michal-A-D", "role": "co-advisor", "display_name": "Michal, Aristotle D." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/S59Y-Q172", "abstract": "In this thesis an attempt is made to demonstrate in \r\naccordance with known physical principles that significant \r\nchanges in the macroscopic equilibrium of the earth can be \r\nattributed to rate processes which do not call upon the \r\nexistence of macroscopic gradients and disturbances in the earth.\r\nSuch processes and their relation to known mechanisms of \r\nplastic deformation and to the experimentally established \r\nbehavior of materials under high pressures are critically\r\nevaluated. This evaluation is carried out in the light of some \r\nwell-established concepts of statistical mechanics and modern \r\nphysics. In so doing specific methods for producing seismic \r\ndisturbances which are based upon known mechanisms of plastic \r\ndeformation and rupture become indicated. It is also shown that \r\nunder very high pressures, pressure and temperature can complement \r\neach other in producing disturbances associated with \r\npolymorphic transitions of materials leading to a reduction in\r\nsymmetry of their lattice structure.
\r\n\r\nA specific mechanism for producing and repeating earth\u00adquakes \r\nat shallow and intermediate depths is proposed. This mechanism is \r\nbased upon the existence of a visco-elastic surface layer supported \r\nby a plastic material embodied with stress \r\nrelaxing properties.
\r\n\r\nThe effect of such a configuration upon the propagation\r\nof Love Waves is investigated quantitatively. This investigation \r\nshows that the plastic sub-layer would explain the observed selection \r\nof the period of Love Waves.
" }, { "name": "Wright, Lauren Albert", "degree": "PhD", "year": "1951", "title": "An Invertebrate Assemblage From the \"Modelo\" Formation of Reynier Canyon, Los Angeles, California. Geology and Origin of Talc Deposits of Eastern California", "advisor": "Popenoe, Willis Parkison; Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechETD:etd-08062008-104016", "creators": [ { "name": { "family": "Wright", "given": "Lauren Albert" }, "id": "Wright-Lauren-Albert", "display_name": "Wright, Lauren Albert" } ], "advisors": [ { "name": { "family": "Popenoe", "given": "Willis Parkison" }, "id": "Popenoe-W-P", "role": "advisor", "display_name": "Popenoe, Willis Parkison" }, { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/H7M7-2216", "abstract": "An Invertebrate Assemblage From the \"Modelo\" Formation of Reynier Canyon, Los Angeles, California:
\r\n\r\nAn upper Miocene marine molluscan fauna occurs in basal \"Modelo\" sandstones that flank Reynier Canyon of the southeastern portion of the Ventura basin, Los Angeles County, California. Here two outliers of these beds are nonconformable on continental siltstones and tuffs of the Mint Canyon formation. The \"Modelo\" sandstones grade upward into punky diatomaceous shales also of the \"Modelo\" sequence, that contain Anadara cf. obispoana and a foraminiferal fauna reported to be Mohnian in age. The shales of one outlier are unconformably overlain by other marine sediments.
\r\n\r\nThe upper Miocene age of the basal \"Modelo\" beds is indicated by the presence of Clementia cf. martini, Dosinia arnoldi, Lyropecten estrellanus ss., Spisula albaria, Tivela diabloensis, and a large Ostrea. Approximately half of the forms in the Reynier Canyon \"Modelo\" fauna also occur in the Elamere Canyon fauna; these include Laevicardium centifilosum, L. quadragenarium var. fernandoense, Lucina nuttallii, Cancellaria elsmerensis, C. hemphilli, C. tritonidea, Surculites remondii, Murithais eldridgei, Nuculana taphria, and Turritella cooperi. The Elmsmere Canyon species Patinopecten lohri, Astrodapsis fernandoensis, and Dendraster sp. are missing from the \"Modelo\" fauna.
\r\n\r\nGeology and Origin of Talc Deposits of Eastern California:
\r\n\r\nA 200-mile northwest-trending belt in eastern California contains more than 100 talc-bearing localities. The belt is divisible into three districts; each with talc deposits in a distinctive terrane.
\r\n\r\nIn the southernmost district, near Silver Lake, tremolitic talc deposits have formed in highly metamorphosed Archean (?) sedimentary rocks extensively invaded by lamprophyre and granitic rocks. The development of talc-tremolite rock probably involved the extensive introduction of MgO and SiO2 to silica poor dolomite in a complex, multistage history. The MgO may have been released in the granitization of high-magnesian sediments.
\r\n\r\nIn the Southern Death Valley-Kingston Range region tremolitic talc deposits occur at or near the borders of a diabase sill intruded near the base of the lowermost carbonate unit in the Algonkian Pahrump series. The deposits have generally altered from dolomite, both siliceous and silica-poor. Other alteration rocks rich in alkali feldspar are associated with the talc deposits and border diabase bodies higher in the member. MgO and SiO2 have been introduced to form the talc bodies; SiO2, Al2O3, K2O, and probably Na2O to form the feldspathic rocks. Diabase magma was probably the source of most of the additive material, but some may have been derived from connate water.
\r\n\r\nIn the Inyo Range area tremolite-poor talc deposits have formed as alterations of Paleozoic dolomite and quartzite, and of Mesozoic granitic intrusives. The White Eagle deposit shows all three types of alteration, but has formed largely as a replacement of adamellite. Feldspars, quartz and ferromagnesian minerals were decomposed; the talc alteration followed an advance wave of albitization. The additive MgO probably was leached from dolomites at depth.
\r\n\r\n\r\n" }, { "name": "Bhattacharya, Prabhat Kumar", "degree": "PhD", "year": "1950", "title": "An Investigation of Changes in the Magnetic Field of the Earth (Magnetic Anisothropy of Sedimentary Rocks)", "advisor": "Potapenko, Gennady W.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12042020-181406559", "creators": [ { "name": { "family": "Bhattacharya", "given": "Prabhat Kumar" }, "id": "Bhattacharya-Prabhat-Kumar", "display_name": "Bhattacharya, Prabhat Kumar" } ], "advisors": [ { "name": { "family": "Potapenko", "given": "Gennady W." }, "id": "Potapenko-G-W", "role": "advisor", "display_name": "Potapenko, Gennady W." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/10jq-dy86", "abstract": "The paper gives the results of measurements of the magnetic anisotropy of 47 samples of sedimentary rocks ranging in age from Pliocene to Silurian time. The study was undertaken to test the validity of the hypothesis that fine grained sediments containing a large number of ferromagnetic particles should exhibit a magnetic anisotropy, the direction of the maximum susceptibility being in the direction of the Earth\u2019s magnetic field existing at the time of deposition. The theory of the development of remnant moment and anisotropy in sedimentary formations has been discussed and it is claimed that the anisotropy measurements should give more reliable results than the remnant moment measurements regarding the magnetic history of the Earth. A highly sensitive Susceptibility Meter has been designed and constructed for the purpose, and the theory of measurements of the initial magnetic anisotropy in cubical rock samples has been developed. Preliminary measurements on 24 samples of Tertiary sediments show that for the past 60 million years or so, the average declination of the Earth\u2019s magnetic fields has been within about 20\u00b0 of the geographic north. Similar measurements on 23 samples of Silurian sediments indicate a significant difference between the Silurian and the present geomagnetic field. The effect of deformation of beds and of strong magnetic fields on anisotropy have also been studied and it is concluded that the direction of maximum susceptibility in sedimentary rocks is stable and is invariable with respect to any stray magnetic fields subsequent to deposition." }, { "name": "Dehlinger, Peter", "degree": "PhD", "year": "1950", "title": "Shear Wave Vibrational Directions and Related Fault Movements in Southern California Earthquakes. The Relationship of the Modelo and Ridge Route Formations in the Southern Ridge Basin, California", "advisor": "Gutenberg, Beno", "url": "https://resolver.caltech.edu/CaltechTHESIS:05242018-073700990", "creators": [ { "name": { "family": "Dehlinger", "given": "Peter" }, "id": "Dehlinger-Peter", "display_name": "Dehlinger, Peter" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/8KJY-V987", "abstract": "Shear wave vibrational directions and related fault movements in southern California earthquakes:
\r\n\r\nVibrational directions of direct shear waves from a number of small local earthquakes in southern California, recorded at Pasadena and Riverside, are determined and discussed in relation to corresponding faulting at the source. A theoretical relationship between small fault displacements and wave vibrational directions is proposed. Using this relationship, directions of SV and SH motions from various fault types at normal depths of focus are adduced. Observed initial shear wave motions indicate generally consistent SH, but usually less consistent SV displacements. Values SV/SH are consistent in a few localities, but generally vary widely. Polarization of SH waves is evidenced from the data; that of the SV is suggested, but is not so clearly indicated. Probably the entire shear wave is approximately plane polarized. From the data it appears that horizontal components of faulting in southern California, within local regions, usually take place in the same general direction. Vertical fault directions appear to vary. An analysis of faulting at the source, based on a comparison of observed SV and SH motions with theoretical shear motions and with observations by Gutenberg (1941) of impulses of compressional waves, is described. A fault pattern in agreement with the seismic data and also the regional surface geology involves primarily northwesterly trending right handed transcurrent faults in some parts of southern California, east west trending reverse or thrust faults in others, and coexistence of the two in a few localities. Somewhat simplified stress distributions in agreement with the data are discussed briefly. A method for determining strains of incident shear waves from linear strain seismograms, recorded through a new Benioff transducer and short period galvanometer, is also presented.
\r\n\r\nThe relationship of the Modelo and Ridge Route formations in the Southern Ridge Basin, California:
\r\n\r\nThe Modelo formation and the overlying Ridge Route formation, as exposed in the southern part of the Ridge Basin, are similar in general appearance and consist of alternating begs of sandstone and siltsone. The contact between the formations is neither a sharp break nor is it characterized by an interfingering of sedimentary units. The two units differ in general strike by as much as 35 degrees in the area studies, although the strike grades uniformly from that of one formation to that of the other. This difference in attitude is believed to be a depositional feature, rather than one resulting from structural disturbance.
\r\n\r\nThe Modelo formation thins markedly in a northerly direction, and the Modelo sea appears to have transgressed the area from south to north during a part of upper Micoene time. Subsequently this sea retreated from the area, while non-marine Ridge Route beds appear to have been deposited concomitantly from a northerly direction. No appreciable time lapse is evidence between the periods of marine and non-marine deposition. The lowermost of the Ridge Route formation beds may be fluviatile deposits, but the remainder of the formation appears to be of lacustrine origin. In post-Pliocene time the region was folded into the Ridge Basin. The folding evidently was related to displacements along the adjacent San Gabriel fault.
\r\n" }, { "name": "Denson, Mayette Elner, Jr.", "degree": "PhD", "year": "1950", "title": "Longitudinal Waves through the Earth's Core. The Madison (Mississippian) Limestone of the Bighorn Basin, Wyoming", "advisor": "Gutenberg, Beno; Richter, Charles F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06152018-151258637", "creators": [ { "name": { "family": "Denson", "given": "Mayette Elner, Jr." }, "id": "Denson-Mayette-Elner-Jr", "display_name": "Denson, Mayette Elner, Jr." } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Richter", "given": "Charles F." }, "id": "Richter-C-F", "role": "co-advisor", "display_name": "Richter, Charles F." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/2TRJ-R665", "abstract": "Longitudinal Waves through the Earth\u2019s Core:
\r\n\r\nThe amplitudes, periods, and travel times of PKP or P' and PP have been investigated. Results indicate that the epicentral distance of the main P' focal point varies with period. Amplitude considerations indicate that the focal point for short period waves is near 147 degrees; for longer period waves the position is believed to lie between 147 and 143 degrees. The position of the end of the reversed segment for waves through the outer core is believed to be near 157 degrees.
\r\n\r\nTravel times show that the P' core waves are recorded as three groups separated by intervals of about 10 and 20 seconds. Each group evidences separate focal phenomena. This variation suggests dispersion as an explanation.
\r\n\r\nVariations in energy and period of the P\" phase with distances are reasonable interpreted as a consequence of rapid velocity increase with increasing depth approaching the inner core transition zone. Anomalous energy ratios for all P' phases indicate complexities which are not yet fully understood.
\r\n\r\nThe Madison (Mississippian) Limestone of the Bighorn Basin, Wyoming:
\r\n\r\nThe Mission Canyon and Lodgepole formations of the Madison group are recognized throughout the Bighorn Basin, Wyoming. The features by which these formation and their members have been differentiated and correlated are described. Limited paleontologic determinations and lithologic similarities indicate that Kinderhookian and Upper Devonian strata may be present along the eastern margin of the Bighorn Basin. Variations which exist in porosity developments are herein related to solution activities, to the degree of dolomitization, and to the character of the original sediment. Lithology and insoluble residue descriptions are included in Part II.
\r\n" }, { "name": "Ergin, Kazim", "degree": "PhD", "year": "1950", "title": "Energy Ratio of the Seismic Waves Reflected and Refracted at a Rock Water Boundary. Amplitudes of PcP, PcS, ScS, and ScP in Deep-Focus Earthquakes", "advisor": "Gutenberg, Beno; Richter, Charles F.", "url": "https://resolver.caltech.edu/CaltechTHESIS:11242020-173649715", "creators": [ { "name": { "family": "Ergin", "given": "Kazim" }, "id": "Ergin-Kazim", "display_name": "Ergin, Kazim" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Richter", "given": "Charles F." }, "id": "Richter-C-F", "role": "co-advisor", "display_name": "Richter, Charles F." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/eynv-8f51", "abstract": "Part I.
\r\n\r\nUsing the Knott-Zoeppritz equations, the general behavior, zero points and extreme points of the energy ratio that goes into reflected and refracted waves upon the incidence of a wave at either side of the rock-water boundary at the bottom of the ocean are computed as a function of the angle of incidence, for a possible range of values of the parameters involved, namely, Poisson's ratio, the ratio of the longitudinal wave velocities in two media, and the density ratio.
\r\n\r\nFrom the computed results it is found that:
\r\n\r\n1. Poisson's ratio of the solid medium is a dominating factor in the general behavior, zero points and extreme points of the reflected and refracted waves that travel in the solid.
\r\n\r\n2. Any change in the ratio of the two longitudinal velocities produces pronounced results in the refracted wave energy.
\r\n\r\n3. The effect of changing the density ratio is very slight.
\r\n\r\n4. Peculiar behavior occurs just before and right after the critical angle of incidences.
\r\n\r\n5. At a critical angle of incidence, all of the incident energy goes into the reflected wave of the same kind as the incident wave.
\r\n\r\n6. Most of the incident energy is reflected either as P or as S wave depending upon the angle of incidence.
Part II.
\r\n\r\nA systematic study has been made of the ratios of the displacements of the core reflections to the direct body waves as well as of the individual displacements, using intermediate and deep focus earthquake seismograms recorded at Pasadena. Theoretical values of the horizontal and the vertical ground displacements have been computed for the direct P and S as well as for PcP, PcS, ScS and ScP waves as a function of the epicentral distance for three focal depths, namely, 100, 400 and 700 km. The results indicate that the observed ratios of the horizontal displacements of the waves that are reflected at the core-mantle boundary as P waves (i.e., PcP/P and ScP/S) and that of the observed vertical displacements of the waves that are reflected as S waves (i,e., PcS/P and ScS/S) are five or more times larger than the theoretical ones. The ratios of the vertical components of the first group and the ratios of the horizontal components of the second group are in fairly good agreement with the theoretical values. It is further found that the behavior of the direct P and SV waves are in accord with the theory, but the vibrations are not in the direction of propagation for the reflected P waves and the vibrations are not perpendicular to the direction of propagation for the reflected S waves. The effect of aelotropic crustal structure on the ground displacements is discussed.
" }, { "name": "Mooney, Harold Morton", "degree": "PhD", "year": "1950", "title": "A Study of the Energy Contained in the Seismic Waves P and pP", "advisor": "Gutenberg, Beno", "url": "https://resolver.caltech.edu/CaltechTHESIS:05242018-145241388", "creators": [ { "name": { "family": "Mooney", "given": "Harold Morton" }, "id": "Mooney-Harold-Morton", "display_name": "Mooney, Harold Morton" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/T26Z-PD62", "abstract": "The energy observed in the seismic waves P and pP in a large number of earthquakes is compared with the theoretical energy calculated from a standard equation, using two partly independent methods. The results are analyzed using as variables depth of focus, distance from epicenter to recording station, geographical location of epicenter and azimuth from station. When compared with the theoretical value, the ratio of the energy in pP to the energy in P averaged over a distance range 60\u00b0-90\u00b0 is observed to decrease with depth, by 0.5 on a logarithmic scale of energy between 100 and 600 km. depth of focus. The results for the two waves are compared separately with theoretical values and the observed effect appears to be about equally due to an increase of P energy and a decrease of pP energy with depth. The theoretical formula is re-examined to determine if permissible changes in the assumptions or numerical values can account for the results. No such changes are found; certain assumptions as to increased absorption of energy near the surface provide a partial qualitative explanation, but quantitatively they cannot be reconciled with data from other sources. The variation with distance between observed and calculated energies is not large enough to be treated quantitatively; slight changes in the accepted change of velocity vs. depth curve are tentatively suggested on the basis of it. The energy ratio pP/P is significantly too large in shallow earthquakes occurring in the Aleutian region, and can be attributed to pP rather than P. For shallow shocks in the New Hebrides region and very deep shocks of the Southwest Pacific, there is some indication that the energy ratio is smaller than for comparable shocks elsewhere. An attempted correlation of regional anomalies with the dip of large scale fault systems is successful in the Aleutians, inconsistent elsewhere. The effect of differences between instruments is considered." }, { "name": "deWitte, Leendert", "degree": "PhD", "year": "1950", "title": "I. Factors Governing Accumulation of Oil and Gas in Stratigraphic Traps. II. Studies on Infiltration of Porous Formations by Drilling Fluids in Relation to the Quantitative Analysis of Electrologs in Drill Holes. III. Experimental Studies on the Characteristics of the Electrochemical Potentials Encountered in Drill Holes.", "advisor": "Potapenko, Gennady W.; Buwalda, John P.; Frankel, Stanley P.; Badger, Richard McLean", "url": "https://resolver.caltech.edu/CaltechTHESIS:02032021-150144083", "creators": [ { "name": { "family": "deWitte", "given": "Leendert" }, "id": "deWitte-Leendert", "display_name": "deWitte, Leendert" } ], "advisors": [ { "name": { "family": "Potapenko", "given": "Gennady W." }, "id": "Potapenko-G-W", "role": "advisor", "display_name": "Potapenko, Gennady W." }, { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "co-advisor", "display_name": "Buwalda, John P." }, { "name": { "family": "Frankel", "given": "Stanley P." }, "id": "Frankel-S-P", "role": "co-advisor", "display_name": "Frankel, Stanley P." }, { "name": { "family": "Badger", "given": "Richard McLean" }, "id": "Badger-R-M", "role": "co-advisor", "display_name": "Badger, Richard McLean" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/trf9-g451", "abstract": "Factors Governing Accumulation of Oil and Gas in Stratigraphic Traps
\r\n\r\nThis thesis is a study of those characteristics of sedimentary rocks, that determine their capability to function as cap rocks for petroleum accumulations.
\r\n\r\nThe function of the cap rock is to prevent the oil from upward migration. The active upward forces on the oil (or gas) are due to the buoyancy of the oil (or gas) on water. The forces opposing upward migration of the oil are due to the capillary retention of the water in the cap rock. For any oil trap it is necessary that the capillary forces in the cap rock are larger than the buoyancy of the accumulating oil on the subsurface waters.
\r\n\r\nFor a given combination of oil or gas and subsurface water, the magnitude of the capillary-retention forces on the water in the cap rock is given by the displacement pressure of that rock.
\r\n\r\nAn outline is given of the theories, relating the displacement pressure to the basic characteristics of the rock; such as permeability, porosity; interstitial surface area and the Kozeny constant.
\r\n\r\nThe displacement pressure for a given rock is directly proportional to the interracial tension between the water and the non-wetting phase. The buoyancy of the oil or gas on the water depends upon the density difference between the non-wetting phase and the water. The variations of densities and interfacial tensions with temperature and pressure are discussed and graphical relations are given between these quantities and the depth of the accumulation in question.
\r\n\r\nDisplacement pressures for various types of sandstones were determined from experimental studies or the capillary pressure versus saturation relationships. From the experimentally determined displacement pressures, permeabilities and porosities, the interstitial surface area and the Kozeny constants for the various rocks were computed.
\r\n\r\nIt was found that the interstitial surface areas could be correlated with the electrochemical formation coefficients of the sediments in question, which were measured in the course of another research project by this author. This correlation indicates the possibility of a subsurface method for the determination of displacement pressures, using the S. P. curves of electrologs.
\r\n\r\nDifferent types of stratigraphic traps are described and the relative positions or the cap rooks are considered for the various cases.
\r\n\r\nA schematic example is given or the location or a \"permeability pinch-out\" type of stratigraphic trap by computation of the displacement pressures from electrologs of drill holes in the vicinity.
\r\n\r\nExperimental Studies on the Characteristics of the Electrochemical Potentials Encountered in Drill Holes
\r\n\r\nThis thesis describes the results of experimental studies on the characteristics of the electrochemical potentials encountered in drill holes and registered by electrologging apparatus.
\r\n\r\nThe experiments were carried out by bringing samples of sediments into contact with two solutions of different salinities on opposite sides and measuring the difference in potentials between the solutions.
\r\n\r\nThe following conclusions were drawn from the measurements thus obtained:
\r\n\r\nThe potentials are independent of the amount of material involved. They are proportional to the logarithm of the concentration ratio of the two solutions. The potentials decrease slowly with time.
\r\n\r\nThere is no sharp demarcation between the electrochemical behavior of sandstones and shales, but rather there exists a complete continuity in the potentials exhibited across sediments of the sandstone shale series.
\r\n\r\nThis continuity is explained using the concept of \"apparent ion mobilities.\"
\r\n\r\nTo classify sediments according to their electrochemical Behavior, the electrochemical formation coefficient, C, is introduced. Dense argillaceous shales have a formation coefficient of 1. Inert clean sands have C = O. It is shown however that in practice sands may very seldom be\r\nconsidered inert.
\r\n\r\nA correlation exists between the formation coefficient and the ratio of the amount of conductive solids or argillaceous materials over porosity (see references 8 and 13). The influence of temperature on self potentials is computed theoretically and confirmed experimentally.
\r\n\r\nIt is pointed out that dense formations may give considerable self potential kicks on electrologs. This conclusion is confirmed by measurements of the potentials across quartzites.
\r\n\r\nThe general conclusions concerning the character of the electrochemical potentials are extended to the self potentials across calcareous formations.
\r\n\r\nThe application of the analysis of the electrochemical potentials to electrolog interpretation is outlined . Also the possibility of electrochemical testing of sediments as a new tool in surface geology is indicated.
\r\n\r\nStudies on Infiltration of Porous Formations by Drilling Fluids in Relation to the Quantitative Analysis of Electrologs in Drill Holes
\r\n\r\nThis thesis presents a discussion of a method, by which certain characteristics of the infiltrated zones around bore holes can be to good use in determining the fluid content and the formation factor, of the horizons in which we are interested.
\r\n\r\nTo obtain the necessary field data a new combination of electrode spacings is proposed, namely a short lateral spacing, with two normal spacings. It is shown that apparent resistivities, obtained with these spacings, enable us to obtain the true resistivity, the resistivity of the invaded zone and the diameter of the latter.
\r\n\r\nTo be able to use the invaded zone resistivity in the determination of the formation factor and fluid contents a group of laboratory experiments were carried out, using consolidated sandstone samples and drilling muds or liquids having the properties of the mud filtrate. The sandstones were invaded by the muds or their equivalent filtrates for different conditions of initial fluid contents. Then the resistivity changes were measured by a four electrode arrangement coupled to an amplifier-rectifier circuit and a sensitive test meter.
\r\n\r\nFor the case of oil and gas sands the displacement of the non-wetting phase by water is treated analytically using the concept of relative permeabilities of the reservoir rocks and the results are compared with the experimental data.
\r\n\r\nFrom measurements on coresamples too actual resistivity profiles in the infiltrated zones of formations were computed. These showed that in all cases the resistivity of the invaded zone may be approximated by a constant.
\r\n\r\nThe relations between resistivities of rocks and their fluid contents are considered in the light of experimental results and several new formulae are introduced, governing these relations.
\r\n\r\nFinally the water saturations of the invaded zones of oil and gas horizons are correlated with the water saturations of the undisturbed formations.
\r\n\r\nA brief outline is given of the computation of fluid contents and formation factors of porous rocks from the measured values of infiltrated zone- and true resistivities, using the new resistivity formulae and data obtained from analysis of the self potential curve of electrologs.
" }, { "name": "Howell, Benjamin Franklin, Jr.", "degree": "PhD", "year": "1949", "title": "Ground Vibrations Near Explosions", "advisor": "Gutenberg, Beno", "url": "https://resolver.caltech.edu/CaltechETD:etd-01152008-110555", "creators": [ { "name": { "family": "Howell", "given": "Benjamin Franklin, Jr." }, "id": "Howell-Benjamin-Franklin", "display_name": "Howell, Benjamin Franklin, Jr." } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/3SC3-Y537", "abstract": "Records are shown of the three components of ground vibration taken at distances out to 3284 meters following small explosions of dynamite about ten meters underground. The apparatus used to record this motion is described, and its limitations discussed. The refracted compressional waves recorded are used to calculate roughly the thickness of the near surface layers. Three principal dispersed waves are recognized and described. It is shown that two of these do not behave like any well known type of wave motion. It is pointed out that this is not surprising since the near surface material is probably neither homogeneous nor elastic and these conditions are required by the classical theories. The third dispersed wave is shown to closely resemble a modified Rayleigh wave. Three published theories of such modified motion are reviewed and compared with the observations. The recorded data are also compared with other similar records copies of which have been published." }, { "name": "Howell, Benjamin Franklin, Jr.", "degree": "PhD", "year": "1949", "title": "Structural Geology of the Region Between Pacoima and Little Tujunga Canyons, San Gabriel Mountains, California", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:05012014-110111547", "creators": [ { "name": { "family": "Howell", "given": "Benjamin Franklin, Jr." }, "id": "Howell-Benjamin-Franklin", "display_name": "Howell, Benjamin Franklin, Jr." } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/M2WZ-N476", "abstract": "An area of about 25 square miles in the western part of the San Gabriel Mountains was\r\nmapped on a scale of 1000 feet to the inch. Special attention was given to the structural geology,\r\nparticularly the relations between the different systems of faults, of which the San Gabriel fault\r\nsystem and the Sierra Madre fault system are the most important ones. The present distribution\r\nand relations of the rocks suggests that the southern block has tilted northward against a more stable\r\nmass of old rocks which was raised up during a Pliocene or post-Pliocene orogeny. It is suggested\r\nthat this northward tilting of the block resulted in the group of thrust faults which comprise the\r\nSierra Madre fault system. It is show that this hypothesis fits the present distribution of the\r\nrocks and occupies a logical place in the geologic history of the region as well or better than any\r\nother hypothesis previously offered to explain the geology of the region." }, { "name": "Lance, John Franklin", "degree": "PhD", "year": "1949", "title": "Phylogeny of the Later Tertiary Equidae in the Light of New Pliocene Horses from Chihuahua, Mexico. Origin of the Pioneer Pyrophyllite Deposit, San Diego County, California", "advisor": "Stock, Chester; Jahns, Richard H.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06182018-132202171", "creators": [ { "name": { "family": "Lance", "given": "John Franklin" }, "id": "Lance-John-Franklin", "display_name": "Lance, John Franklin" } ], "advisors": [ { "name": { "family": "Stock", "given": "Chester" }, "id": "Stock-C", "role": "advisor", "display_name": "Stock, Chester" }, { "name": { "family": "Jahns", "given": "Richard H." }, "id": "Jahns-R-H", "role": "advisor", "display_name": "Jahns, Richard H." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/HFAA-MY41", "abstract": "[Major Thesis]. Phylogeny of the Later Tertiary Equidae in the Light of New Pliocene Horses from Chihuahua, Mexico:
\r\n\r\nPhylogenetic charts currently published showing the evolution of North American Equidae indicate that species of the subgenus Pliohippus (Astrohippus) of the Hemphillian stage are in the line of ancestry of modem horses. Different opinions exist as to the ultimate fate of the typical subgenus, and as to the origin of Old World zebras.
\r\n\r\nA study of fossil horses from the Yepomera fauna of western Chihuahua, Mexico, demonstrates the presence of four species. Three of these are described, and two are regarded as new to science, namely, Pliohippus (Astrohippus) stockii n. sp. and Pliohippus (Pliohippus) mexicanus, n. sp. It is concluded from a comparison of the horses and of associated elements in the fauna with those found in related assemblages, that the Yepomera fauna\r\nis of late occurrence in the Hemphillian stage (middle Pliocene) of North America. The faunas from the Hemphill horizon of Texas, from the Alachua-Bone Valley beds of Florida, and from the Mt. Eden beds of California are believed to be older.
\r\n\r\nThe two new species throw light on the phylogenetic relationships of the genus Pliohippus sl. The subgenus P. (Astrohippus) is removed from direct ancestry to Blancan and later horses, and P. (P.) mexicanus n. sp. is proposed as the most likely known ancestor of living horses, including the zebra. These new interpretations as to the phylogeny of the later Equidae are presented in a new chart.
\r\n\r\n[Minor Thesis]. Origin of the Pioneer Pyrophyllite Deposit, San Diego County, California:
\r\n\r\nPyrophyllite, a hydrous aluminum silicate with properties and uses similar to those of talc, is abundant at the Pioneer deposit near Escondido, San Diego County, California. The mineral occurs in lenticular bodies in the Santiago Peak volcanics of approximate Jurassic age. The deposit is approximately on a Tertiary(?) erosion surface that has probably been exhumed.
\r\n\r\nA study of field, petrographic, and chemical data indicates that the pyrophyllite was developed by replacement of volcanic flows and breccias of original andesitic and latitic composition. These volcanic rocks had been previously folded and sheared, and subjected to mild regional metamorphism and accompanying propylitic alteration. Silicification in part preceded the formation of pyrophyllite. Development of pyrophyllite is known to be complete or nearly so in only one body, which is being quarried at the present time.
\r\n\r\nThe solutions forming the deposit appear to have followed shear zones, and lithologic control evidently was not important in localizing the mineralization. The solutions were of hydrothermal origin, and possibly were associated with the emplacement of the Peninsular batholith of southern California. They were of intermediate temperature and acid in nature. Silica and possibly alumina were added to the rocks by these solutions, and other elements were removed. Moderate stresses produced a schistosity in pyrophyllite, probably during mineralization.
\r\n" }, { "name": "Martner, Samuel Theodore", "degree": "PhD", "year": "1949", "title": "Observations on Seismic Waves Reflected at the Earth's Core Boundary. Geology of the Manila-Linwood Area, Sweetwater County, Wyoming and Daggett County, Utah", "advisor": "Gutenberg, Beno; Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07312018-074942626", "creators": [ { "name": { "family": "Martner", "given": "Samuel Theodore" }, "id": "Martner-Samuel-Theodore", "display_name": "Martner, Samuel Theodore" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/G8DA-6X21", "abstract": "Observations on Seismic Waves Reflected at the Earth's Core Boundary
\r\n\r\nOn the seismograms of many earthquakes the waves reflected from the outer boundary of the earth\u2019s core oftentimes write traces which appear larger than the size of the shock warrants. A systematic study has been made of the displacement ratios of these core reflections to the direct body waves. Data accumulated during the course of this investigation tend to confirm the idea that the displacement ratios of the longitudinal waves reflected from the core to the longitudinal direct waves are greater than the presently accepted theory would indicate. Some possible causes of these differences are investigated, but reasonable changes in the assumptions do not result in an explanation of all of the discrepancy between the observed and theoretical data. Additional research projects are suggested that might help in answering some of the puzzling features of these phenomena.
\r\n\r\nGeology of the Manila-Linwood Area, Sweetwater County, Wyoming and Daggett County, Utah
\r\n\r\nThe Manila-Linwood area, so named from the two Utah towns within its boundaries, consists of approximately 200 square miles lying on the Wyoming-Utah state border. It is interesting to the geologist from an historical,\r\nstratigraphical, or structural viewpoint.
\r\n\r\nHistorically, this district is one of interest because it contains the famous Flaming Gorge, named by Major John Wesley Powell. It has been a locality for geological investigation by such men as Clarence King, S.F. Emmons, Ferdinand V. Hayden, and many others. A brief review of the\r\nrecords of early geological and geographical explorations is presented.
\r\n\r\nStratigraphically, one of the most completely exposed sections, representing a span of geologic time as long as or longer than that seen in any area of comparable size in the United States, characterizes the area. Rocks representing the Archean (?) and Algonkian eras, as well as all the later periods of the geologic time scale, with the possible exception of the Cambrian, Ordivician, Silurian, and Devonian, which are not differentiated into separate units in this report, are present in the district. These sedimentary rocks have been divided into 23 mapping units which are shown on a chart correlating them with the terminology used by previous workers in this area, and giving their tentative correlation with components\r\nused in adjacent areas. The character, thickness, age, and correlation of the various rock units are briefly discussed in the text. The only plutonic igneous bodies in the area are those intruded into formations of Archean (?) age. Extrusive accumulations are found at several places in the geologic column but are a very minor part of the section, consisting chiefly of tuffs interbedded in shales and sandstones. None of these igneous rocks were considered important enough to be designated as separate mapping units.
\r\n\r\nStructurally, the area embraces parts of two divisions of the Rocky Mountain province of the western United States. Its southern portion is a segment of the north flank of the great, east-west- oriented Uinta Mountain arch of northeastern Utah and its northern half is a sector\r\nof the Bridger Basin of southwestern Wyoming. Superimposed on the north regional dip are minor, transverse flexures. A part of the much-discussed Uinta fault and other faulting of a rather complex nature are also found in the district. The structure is discussed in a chapter entitled\r\n\"Structural Geology\".
\r\n\r\nA brief history of the structural geology of the area is presented. A short chapter on the economic geology of the area, with an emphasis on the oil and gas possibilities is given.
\r\n\r\nSeveral problems worthy of further study in this and nearby areas are briefly discussed.
\r\n" }, { "name": "Smith, Theodore Beaton", "degree": "PhD", "year": "1949", "title": "Interruptions in the Normal Westerly Flow of the General Circulation of the Atmosphere", "advisor": "Elliott, Robert Dunshee", "url": "https://resolver.caltech.edu/CaltechTHESIS:07312025-211042466", "creators": [ { "name": { "family": "Smith", "given": "Theodore Beaton" }, "id": "Smith-Theodore-Beaton", "display_name": "Smith, Theodore Beaton" } ], "advisors": [ { "name": { "family": "Elliott", "given": "Robert Dunshee" }, "id": "Elliott-Robert-Dunshee", "role": "advisor", "display_name": "Elliott, Robert Dunshee" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "meteor" ], "doi": "10.7907/s796-wx62", "abstract": "Certain effects associated with the intrusion of stable,\r\npersistent high pressure cells into the normal westerly flow of the\r\ngeneral circulation of the atmosphere are investigated. These\r\nintrusions are termed Blocking Action processes.
\r\n\r\nBy means of empirical and semi-statistical procedures\r\nthese processes are found to cause the development of long stable wave\r\npatterns in the atmosphere downstream from the point of inception.\r\nThese wave patterns may exist for periods of a month or more. The\r\nwave length of these stationary long waves is found to be longer than\r\nthat determined by other investigators. This is explained on the\r\nbasis of the larger amplitude of the long waves associated with the\r\nBlocking Action process.
\r\n\r\nA theory of the formation of these blocking high cells\r\nis suggested based on the accumulation of heat in low latitudes and\r\nthe necessity for the readjustment of the general circulation to\r\nredistribute this heat. One means of dissipation of the blocking cells\r\nis shown to be the formation of a wave pattern in the atmosphere which\r\nis out of phase with the stable wave pattern formed by the blocking\r\nHigh.
\r\n\r\nThe optimum mean pressure chart is discussed in terms\r\nof the long period Blocking Action processes. The optimum length chart\r\nis found to cover a three day period or a period of greater than\r\ntwenty days depending on the use to be made of the chart.
" }, { "name": "Thomas, Blakemore Ewing", "degree": "PhD", "year": "1949", "title": "Geology and Ore Deposits of the Wallapai District, Arizona", "advisor": "Campbell, Ian; Noble, James A.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06052018-124011867", "creators": [ { "name": { "family": "Thomas", "given": "Blakemore Ewing" }, "id": "Thomas-Blakemore-Ewing", "display_name": "Thomas, Blakemore Ewing" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" }, { "name": { "family": "Noble", "given": "James A." }, "id": "Noble-J-A", "role": "advisor", "display_name": "Noble, James A." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/9T7Y-RG28", "abstract": "The Wallapai district is in the Cerbat Mountains, a range composed chiefly of crystalline rooks that are pre-Cambrian in age. The oldest rocks are quartzite, mica schist; hornblende-diopside schist, and amphibolite.\r\nYounger and larger in amount are granite gneiss and granite. Much of the gneiss is believed to be a product of granitization. Gabbroic and dioritic gneiss, pegmatite, aplite, diabase, and mylonite also occur as part of the\r\nbasement complex. The original rocks were disposed in an orogenic fold system, but igneous intrusion and granitization have obliterated all but a few remnants of the folds. The rock types and the pre-Cambrian history are\r\nsimilar to those of the Grand Canyon area.
\r\n\r\nThe region contains no trace of Paleozoic rooks and probably none or Mesozoic age. Intrusions of granite porphyry in the Chloride and Mineral Park districts are believed to be Tertiary in age. Granite porphyry, pegmatite, aplite, and lamprophyre dikes are associated with these intrusions
\r\n\r\nSmall areas of andesitic and rhyolitic extrusive rooks, presumably of Tertiary age, exist along the flanks of the Cerbat Range. Thin sheets of Quaternary basalt cap these rocks along the west side of the range. This basalt also lies on and interfingers with alluvium. Numerous rhyolite dikes and a few andesite and basalt dikes occur within the basement rooks.
\r\n\r\nSeveral periods of faulting and erosion are visible in the volcanic rocks. The latest faulting is of basin-range type and has outlined and caused the elevation of the present mountains. The greatest displacement has been on the west side, and the Cerbat Range is an eastward tilted fault block, modified in part into a horst. This mountain building seems to have occurred in late Tertiary and Quaternary time. Large quantities of detritus have accumulated in the adjoining basins and a pediment has been cut along the base of the range. Recent fault-block movement is suggested by the presence of terraces within the canyons and by the dissection of the pediment at the west base of the range.
\r\n\r\nMineralization is believed to have occurred after the close of Tertiary volcanic activity. The first phase consisted of \"porphyry copper\" mineralization in a strongly shattered portion of the granite porphyry stock in the Mineral Park district. This was succeeded by the profuse formation of fissure veins, which carry the lead-zinc ores of the region. The veins are superimposed upon and grouped symmetrically around the \"porphyry copper\" mineralization. Tectonic action is postulated as the fundamental control for the emplacement of the granite porphyry stock and for the two types of sulfide mineralization that are areally associated with the stock. Turquoise deposits have developed by supergene processes in the capping of the \"porphyry copper\" deposit.
\r\n\r\nA late fault cuts the alluvium west of the Mineral Park district. This fault and the adjacent alluvial blanket have been mineralized by chrysocolla and form the Emerald Isle copper deposit. The chrysocolla is believed to be hypogene in this deposit.
\r\n\r\n\r\n\r\n" }, { "name": "Smith, Alexander", "degree": "PhD", "year": "1947", "title": "I. Control of Ore by Primary Igneous Structures: Porcher Island, British Columbia. II. Structural Petrology: Crestmore, California. III. The Geochemistry and Paragenesis of the Ores of the Cactus Mine, Kern County, California", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:01182018-144333841", "creators": [ { "name": { "family": "Smith", "given": "Alexander" }, "id": "Smith-Alexander", "display_name": "Smith, Alexander" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geochem" ], "doi": "10.7907/KJSR-8F29", "abstract": "Part I: Mapping internal structures of an intrusive has proven of value in quarrying but only about a dozen examples appear in the literature wherein metalliferous deposits in intrusives were found to occupy features such as cross joints or marginal upthrusts e.g. (Emmons and Grout 1935), (Kerr 1936), (Barr and Gardner 1940). This study therefore is presented as an additional example of structural control of an ore deposit by primary igneous structures. The lode deposits described in this paper show a rigorous control by a relatively small primary flow structure, an arch of flow layers.
\r\n\r\nThe area studied is the northwest portion of Porcher Island, B. C. (Fig. 1). The principal deposits are those of the Surf Point and Edye Pass Mines. These properties lie about 25 miles southwest of Prince Rupert, B. C., the western terminus of the northern branch of the Canadian National Railways.
\r\n\r\nPart II: The general strike of the metasediments in the area is \r\nN.15\u00b0W. with dips at medium angles to the northeast. The limestone \r\ndeposits at Crestmore and Jensen quarries are, however, on minor \r\nfolds whose axial planes strike N.70\u00b0E.
\r\n\r\nStructural features which pitch easterly at -50\u00b0 are\r\n(1) the general dip of the sediments (2) the axial line of the folds \r\nin limestone (3) the flow lines and dip of flow layers in the \r\nPerris quartz diorite (4) the dip of flow layers in the other \r\nintrusives (5) the axis of the girdle maxima for calcite \r\noptic axes. This direction is thought to be the a tectonic axis.
\r\n\r\nStrong optic axes maxima normal to the tonalite contact\r\nindicate the intrusive was forcibly injected and that the magma \r\nexerted pressure normal to the contact on the limestone. An unusual \r\nfeature in the quartz diorite is two sets of flow layers having in \r\ncommon the flow lines therein.
\r\n\r\nPart III: \r\nThis thesis embodies the results of a laboratory investigation of the ores and mill products of the Cactus mine. The primary purpose was a study of the association and distinction of the metallizing solutions as shown by the occurrence of the gangue and ore minerals.
\r\n\r\nThis investigation has been correlated with geological and structural studies of the Cactus mine which are presented by Mr. John T. Jordan (Master\u2019s Thesis, California Institute of Technology, 1941).
\r\n\r\n" }, { "name": "Wallace, Robert Earl", "degree": "PhD", "year": "1946", "title": "A Portion of the San Andreas Rift in Southern California. A Miocene Mammalian Fauna from Beatty Buttes, Oregon", "advisor": "Buwalda, John P.; Stock, Chester", "url": "https://resolver.caltech.edu/CaltechTHESIS:08302018-143742731", "creators": [ { "name": { "family": "Wallace", "given": "Robert Earl" }, "id": "Wallace-Robert-Earl", "display_name": "Wallace, Robert Earl" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." }, { "name": { "family": "Stock", "given": "Chester" }, "id": "Stock-C", "role": "advisor", "display_name": "Stock, Chester" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/3C57-B890", "abstract": "[Major thesis]: A Portion of the San Andreas Rift in Southern California:
\r\n\r\nA portion of the San Andreas rift along the south side of\r\nthe Mohave Desert between Palmdale and Elizabeth Lake has been mapped and described in this paper. The details of geology and geomorphology have been analyzed and their significance in regard to the interpretation of the genesis of the rift has been discussed.
\r\n\r\nThe area includes four principal geomorphic and geologic\r\ndivisions; a portion of the Mohave Desert, two parallel ridge zones and an intervening trough which marks the rift. The two ridge zones are principally old crystalline rooks whereas the trough zone is underlain principally by a long narrow strip of Tertiary sediments. These sediments outcrop in a low \"center-trough\" ridge and most are part of the Anaverde formation which, on the basis of paleobotanical evidence, is believed to be of Pliocene age. Other Tertiary formations are the Vasquez volcanics, presumably Oligocene, the Pleistocene Harold beds, and an arkose of undetermined age possibly older than the named Tertiary formations\r\nof the area. The presence of this long, narrow strip of sediments between two crystalline masses was a problem for which no conclusive evidence was found.
\r\n\r\nTwo structural trends are prominent in the area. The older rooks of the ridge zones are distributed in more or less bands striking east or slightly north of east. This trend is cut by the rift which in this area has a strike of approximately N. 65\u00b0 W. There is a suggestion that the east-trending structures are older than the rift and related to a different period of diastrophism.
\r\n\r\nTerrace deposits and offset streams suggest a horizontal\r\ndisplacement along the rift of the order of 5 - 6 miles since Pleistocene time. To north side of the rift moved southeast with respect to the south side. A block of Pelona schist north of the rift has an apparent horizontal displacement of 9 miles in the opposite direction to that indicated by recent faulting and stream offsets. This relationship is believed to be only apparent and\r\npossibly the result of vertical displacements and stripping.
\r\n\r\nTerraces on the ridge blocks and in the rift zone indicate a great amount of \"juggling\" of the blocks in and adjacent to the rift. Considerable vertical displacement along the rift is also indicated. The drainage along the rift and in the surrounding areas has frequently been interrupted, reversed, and otherwise changed by the repeated tectonic activity along the rift. Wind gaps, stream captures and unadjusted streams are features which\r\nhave resulted.
\r\n\r\n[Minor thesis]: A Miocene Mammalian Fauna from Beatty Buttes, Oregon:
\r\n\r\nFossil mammalian remains were first discovered in tuff beds of the Beatty Buttes area in 1938 by Dr. Warren D. Smith and Lloyd Ruff, of the University of Oregon. Shortly thereafter, the occurrence was brought to the attention of\r\nDr. Chester Stock by Dr. Smith. During the summer field seasons of 1940 and 1941 collecting parties from the California Institute of Technology examined the region and obtained much additional material.
\r\n\r\nThe original locality at Beatty Buttes lies approximately 22 miles southwest of Blitzen, Oregon, and nearly 100 miles south of Burns, Oregon (see map,\r\nfig. I). Here the tuff beds in which the fossil mammals are found border the north side of the volcanic cone of Beatty Buttes. Most of the material was collected in an area lying approximately 5 miles from the highest point of the cone\r\nand nearly due north of it. At a second locality, here designated Corral Buttes, occur fossiliferous deposits that are unquestionably like those exposed at Beatty Buttes. Fossils were discovered in these beds by K. A. Richey and J. C. Stock in 1941. Corral Buttes lies approximately 20 miles northwest of Beatty Buttes.
\r\n" }, { "name": "Dana, Stephen Winchester", "degree": "PhD", "year": "1944", "title": "Amplitudes of Seismic Waves Reflected and Refracted at the Earth's Core", "advisor": "Gutenberg, Beno", "url": "https://resolver.caltech.edu/CaltechTHESIS:04042018-072607079", "creators": [ { "name": { "family": "Dana", "given": "Stephen Winchester" }, "id": "Dana-Stephen-Winchester", "display_name": "Dana, Stephen Winchester" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/A31E-VA21", "abstract": "The Zoeppritz equations are used to determine the energy\r\npartition in seismic waves reflected and refracted at the earth's core. First, the assumption is made that the core is fluid and hence does not transmit any shear waves. Then the four possible cases are treated; an incident longitudinal wave in the mantle against the core, an incident longitudinal wave in the core against the mantle, and an incident shear wave both of the SV type (particles\r\nvibrating in the plane of incidence) and of the SH type\r\n(particles vibrating perpendicular to the plane of incidence) in the mantle against the core. The square roots of relative energy partitioned among the waves of the above cases are plotted against angle of incidence.
\r\n\r\nThe horizontal and vertical components of the displacement produced at the surface of the earth by seismic waves reflected and refracted at the earth's core are calculated by means of the formula A = CTf \u221atanio/sin\u0394 dio/d\u0394, which gives the amplitude of the incident wave. C is a constant whose value depends on the energy at the source, and is different for longitudinal and shear waves, T is the period, io the angle of incidence at a distance \u0394 from the source, and f is the square root of the relative energy calculated earlier. The values of A for a certain\r\ntype of wave are multiplied by the ratios u/A and w/A in order to obtain the horizontal and vertical components of surface displacement. u is the horizontal component and w the vertical. u and w are plotted against \u0394.
\r\n\r\nLastly the variation of u and w with \u0394 are determined\r\nfor P, PP, S, and SS. Then, depending on whether the seismic\r\nwave reflected or refracted at the earth's core started out from the source as a longitudinal or a shear wave, the ratios of u and w of that wave to the u and w of the corresponding direct wave are calculated. This does away with the necessity of determining the value of C in the amplitude equation. However, for application of these results to seismograms the ratio of the periods must be introduced, as in the calculations the period of all waves\r\nwas assumed to be 1.00 second, and the magnification of the ground by the instrument must be considered.
\r\n" }, { "name": "Fu, Ch'eng Yi", "degree": "PhD", "year": "1944", "title": "Studies on Seismic Waves", "advisor": "Gutenberg, Beno", "url": "https://resolver.caltech.edu/CaltechTHESIS:12112012-105738934", "creators": [ { "name": { "family": "Fu", "given": "Ch'eng Yi" }, "id": "Fu-Cheng-Yi", "display_name": "Fu, Ch'eng Yi" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geophys" ], "doi": "10.7907/G5RB-TK72", "abstract": "This thesis embodies three separate studies on seismic\r\nwaves. The first one is concerned with the origin of\r\nthe oscillatory nature of earthquake waves. Different\r\nmodes of generation have been discussed in some detail,\r\nparticularly the theory of Kawasumi and that of Sharpe.\r\nThe effect of the possible failure of Hooke's law on the\r\nnature of the seismic waves is also explained briefly.
\r\n\r\nThe second is a short note dealing with the physical\r\nbasis of two kinds of observations: the observation of\r\nvelocity and the observation of period.
\r\n\r\nThe third part is a study on the theory of FLANK\r\nWAVES. The basic difficulties of the old theory are\r\npointed out and discussed. The phenomenon is explained\r\nin the light of the wave theory, in considerable detail\r\nin the case of P waves and very briefly sketched for the\r\ncase of SH waves.
" }, { "name": "Jahns, Richard Henry", "degree": "PhD", "year": "1943", "title": "Tactite Rocks of the Iron Mountain District, Sierra and Socorro Counties, New Mexico. Stratigraphy of the Easternmost Ventura Basin, California, with a Description of a New Lower Miocene Mammalian Fauna from the Tick Canyon Formation", "advisor": "Campbell, Ian; Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-12162003-163611", "creators": [ { "name": { "family": "Jahns", "given": "Richard Henry" }, "id": "Jahns-Richard-Henry", "display_name": "Jahns, Richard Henry" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" }, { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/VGB7-WJ85", "abstract": "Tactite rocks of the Iron Mountain district, Sierra and Socorro Counties, New Mexico:
\r\n\r\nThe pyrometasomatic deposits at Iron Mountain, near the northern end of the Sierra Cuchillo in Sierra and Socorro Counties, New Mexico, have been formed through replacement of calcareous beds of Paleozoic age, generally at or near contacts with intrusive masses of rhyolite, rhyolite porphyry, aplite, and fine-grained granite. The metamorphism is probably mid-Tertiary in age. Its two chief products are (a) light-colored, dense, fine-grained granulites rich in diopside, clinozoisite, bytownite, and other iron-poor silicate minerals, and (b) coarser-grained, dark-colored, iron-rich rocks, called tactites. The spatial and temporal relations of these iron-poor and iron-rich contact rocks, not only to each other but to adjacent igneous bodies and to relatively unmetamorphosed beds, appear to have been determined in a regular and definite manner; this is discussed and illustrated in detail by several examples.
\r\n\r\nThe iron-rich pyrometasomatic deposits contain a large number of unusual minerals. Most remarkable are helvite and at least three other beryllium-bearing silicate minerals, which are known to occur in noteworthy concentrations in only one type of rock, a peculiar rhythmically layered variety of tactite to which the name \"ribbon rock\" has been given. The structure of such tactite is very conspicuous, and appears in section as thin, finely crenulated bands of magnetite alternating with similar bands of silicate minerals and finely crystalline fluorite. Concentric banding about fluorite-rich pods is common. Bodies of \"ribbon rock\" vary in size from inch-thick lenses to large masses amounting to thousands of tons; most appear to have formed along contacts between recrystallized limestone and massive magnetite-andradite tactite, chiefly by replacing fluids penetrating the limestone from fractures. The layered structure is interpreted as a diffusion effect.
\r\n\r\nThe formation of massive and \"ribbon rock\" tactites can be traced through a range of falling temperatures from a stage characterized by deposition from iron-rich vapors to a stage in which hydrothermal solutions were dominant. Both vapors and liquids appear to have been acid, and reducing conditions undoubtedly existed during the latter part of the hydrothermal stage. The occurrence of beryllium in \"ribbon rock\", but not in typical massive tactite may signify that its compounds in pyrometasomatic deposits are confined to rocks of hydrothermal origin. The occurrence of \"ribbon rock\" itself is suggested as a potentially useful clue for recognition of beryllium-bearing contact deposits elsewhere; at least two other occurrences of what apparently is \"ribbon rock\" have been described in the literature.
\r\n\r\nStratigraphy of the easternmost Ventura Basin, California, with a description of a new lower Miocene mammalian fauna from the Tick Canyon Formation:
\r\n\r\nThe great thickness of dominantly nonmarine Tertiary strata in the eastern part of the Ventura Basin has impressed geologists since the time of the earliest surveys of the region. The younger of these strata, comprising the so-called Mint Canyon formation, have been eroded to form a great basinlike area in which numerous badland exposures occur (see fig. 1). Erosion has been due principally to the poor consolidation of the sediments and in part also to the rather scant cover of typical Sonoran vegetation. Although several earlier investigators examined these badlands, the first recorded discovery of vertebrate remains came as a result of reconnaissance mapping by Kew in 1919. In the publication that followed, a provisional list of the forms found here was furnished by Stock, although no detailed study of the fauna was made.
" }, { "name": "Regan, Louis John", "degree": "PhD", "year": "1943", "title": "Origin of the Eocene Sands of the Coalinga District, California. The Lower and Middle Eocene Foraminifera of the Coalinga District, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-02152007-132400", "creators": [ { "name": { "family": "Regan", "given": "Louis John" }, "id": "Regan-Louis-John", "display_name": "Regan, Louis John" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/XFB9-K127", "abstract": "Origin of the Eocene sands of the Coalinga district, California:
\r\n\r\nThe purpose of this paper is to attempt to explain the origin and the conditions of deposition of the Gatchell and related Eocene sands of the Coalinga district, California. The method of study has been to gather data bearing on the position of the Eocene basin of deposition, location of positive areas, and sources and direction of movement of the sediments; such data is grouped into three types:
\r\n\r\n1. The age and correlation of Eocene formations are of prime importance in the problem. The correlations used in this study are based largely on Foraminifera; in some instances, where paleontological data is lacking, correlations are based on heavy minerals.
\r\n\r\n2. Lithologic data presented in this report deals in part with the distribution of sands and silts in the Coalinga district. However, the main body of this data comprizes a considerable number of heavy mineral analyses, including analyses of Eocene sands and also of possible Eocene source rocks. Four distinct assemblages of heavy minerals are present in the Eocene sands studied, each assemblage indicating a change in source rocks. These analyses can be orrelated with possible source rock analyses, which include granitic, Franciscan, and Cretaceous rocks. In addition to heavy mineral data, a smaller amount of data on the \"light minerals\" of the various Eocene sands is presented.
\r\n\r\n3. Evidence bearing on the position of positive areas includes structural data dealing with the main unconformities in the Eocene section, and stratigraphic data dealing with the thicknesses of Eocene formations in various parts of the area. It is concluded that during the Eocene, there were three contemporaneously existing positive areas bordering the area of deposition.
\r\n\r\nThe final part of the report deals with the interpretation of the data outlined above. A number of maps have been constructed showing probable progressive stages during the deposition of the Eocene sediments. The Cantua sandstone is believed to have been derived from the granitic rocks now exposed west of the San Andreas fault in the approximate latitude of Coalinga. The Gatchell sand is believed to have been derived largely from Cretaceous rocks in a positive area west of the present Reef Ridge; it is pictured as having been deposited as a spit built northward from this positive area, across the southeastern end of the Vallecitos channel. The Yokut is regarded as having a Coast Range source. The Domengine was very clearly derived from the Franciscan rocks of the Coast Ranges.
\r\n\r\n\r\n\r\nThe lower and middle Eocene Foraminifera of the Coalinga district, California:
\r\n\r\nDuring the last three years, the author has been gathering data on the texture, composition, and distribution of the Gatchell sand and other Eocene sands in the vicinity of Coalinga, California, with the hope that detailed knowledge of this type would lead to an explanation of the origin of the Gatchell sand body, and to an understanding of the factors controlling the distribution of sand and silt in the Eocene sediments of this area. Because of the extreme lenticularity of the Eocene formations, a uniform basis for correlations is required for the correct interpretation of the data described above. The Eocene shales contain abundant Foraminifera, and these organisms provide such a basis for detailed correlation.
\r\n\r\nThis paper deals with the Foraminiferal assemblages occuring in the interval between the base of the Kreyenhagen, and the Cretaceous; this interval was chosen, since it contains the sands related to the general problem outlined above. One outcropping section, located at Oil City, a few miles north of the town of Coalinga, was studied, and the data from this section was corroborated and amplified by the study of three well sections; the location of these four sections is shown on the index map, page 4. A check list of species identified is presented, together with a chart showing the ranges of these species in each of the sections. The faunal changes agree very closely with the Eocene B, C, and D zones described by Laiming, and these divisions have been indicated on the Range Chart.
\r\n\r\nThe ecologic significance of the assemblages is considered, and it is concluded that there was a shallowing and a warming of the sea from deep, cold water conditions in D time to warm, shallow conditions in B3 time, followed by shallow warm water conditions in B2 and B1 time.
" }, { "name": "Smith, Clay Taylor", "degree": "PhD", "year": "1943", "title": "The Origin of Some Chromite Deposits in the Pacific Coast Region. The Biostratigraphy of Glycymeris veatchii in California", "advisor": "Fraser, Horace J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:07022018-144808790", "creators": [ { "name": { "family": "Smith", "given": "Clay Taylor" }, "id": "Smith-Clay-Taylor", "display_name": "Smith, Clay Taylor" } ], "advisors": [ { "name": { "family": "Fraser", "given": "Horace J." }, "id": "Fraser-H-J", "role": "advisor", "display_name": "Fraser, Horace J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/EEMR-DP76", "abstract": "The Origin of Some Chromite Deposits in the Pacific Coast Region:
\r\n\r\nChromite deposits have long been regarded as products\r\nof magmatic segregation. As additional data have become\r\navailable, other processes have been invoked to account\r\nfor the observed facts, The writer, in the employ of the\r\nU.S. Geological Survey, has visited many of the known\r\nchromite localities in the western part of the United\r\nStates and has collected much field evidence bearing on\r\nthe problem of the origin of chromite.
\r\n\r\nLaboratory data furnishes much information which is\r\nnot compatible with some of the field data. The temperatures of intrusion of ultramafic magmas, the time-sequence of crystallization of the various constituents, and the degree of liquid immiscibility are a few of the features indicated by field relations which are difficult to reconcile with laboratory data.
\r\n\r\nSpectrochemical investigations made in connection\r\nwith this research suggest that the minor elements contained in the chromite molecule, namely, nickel, manganese, silver, vanadium, sodium and cobalt, show regular variations in amount when arranged in the time-crystallization sequence proposed in this paper; such differences are thought to represent variations in the conditions of crystallization and deposition.
\r\n\r\nEach chromite deposit is regarded as having been formed under the influence of several forces. Under ideal conditions the resultant of these forces is thought\r\nto approach equilibrium, presumably consisting of a layer\r\nof olivine and small amounts of chromite in the base of\r\nthe magma chamber, succeeded by a layer of chromite and\r\ntopped by a large mass of olivine with small amounts of\r\nchromite; a thin layer of pyroxene may cap the mass if\r\nany is present. This ideal condition is seldom attained in nature, except in the stratiform deposits, and the degree of aberration from equilibrium conditions determines\r\nthe characteristics of the ore deposit formed.
\r\n\r\nThe origin of the various chromite deposits may be\r\nlikened to quenching practice used to determine the constituents of a high temperature melt or liquid at various\r\nstages during its cooling cycle. Each chromite deposit\r\nis examined for evidence indicating at what stage in the\r\nprocess of cooling or crystallization of the ultramafic\r\nmagma its development was arrested by relatively rapid\r\ncooling or quenching. Following physico-chemical principles, beginning with the ultramafic magma in a fully liquid state, many of the difficulties in understanding the\r\nformation of various types of deposits are partially explained.
\r\n\r\nThe Biostratigraphy of Glycymeris veatchii in California:
\r\n\r\nThe stratigraphy and correlation of upper Cretaceous\r\nrocks comprise one of the major problems of Pacific coast\r\ngeology. It is particularly significant as the search\r\nfor petroleum penetrates into progressively older rook\r\nformations in California. As a step toward clarification\r\nof the problem this paper attempts to indicate the possible\r\nevolution and variation in a single fossil molluscan species\r\nduring upper cretaceous and early Tertiary time.
\r\n\r\nThe results of the present study are three-fold:\r\n(l) The evolution of Glycymeris veatchii has been traced.\r\n(2) The number of ribs on a valve is found to vary inversely with the geologic age of the specimen. (3) Two new varieties, Glycymeris veatchii reddingensis, and G. veatchii anae, and one new species, G. maganosensis, have been recognized, and G. major is shown to be an invalid species.
\r\n\r\nA tentative correlation of the upper cretaceous\r\nlocalities used in this paper is presented, and systematic\r\ndescription of the species and varieties described included.
\r\n" }, { "name": "Wilson, Harry David Bruce", "degree": "PhD", "year": "1942", "title": "Geochemical Studies of the Epithermal Deposits at Goldfield, Nevada. Stratigraphy of the Cretaceous and Eocene Rocks of the Santa Monica Mountains", "advisor": "Popenoe, Willis Parkison", "url": "https://resolver.caltech.edu/CaltechETD:etd-04202006-155244", "creators": [ { "name": { "family": "Wilson", "given": "Harry David Bruce" }, "id": "Wilson-Harry-David-Bruce", "display_name": "Wilson, Harry David Bruce" } ], "advisors": [ { "name": { "family": "Popenoe", "given": "Willis Parkison" }, "id": "Popenoe-W-P", "role": "advisor", "display_name": "Popenoe, Willis Parkison" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/ZBZX-FJ30", "abstract": "Geochemical studies of the epithermal deposits at Goldfield, Nevada:
\r\n\r\nThe Applied Research Laboratories grating spectrograph and a technique of quantitative spectro-chemical analysis are described. This method of analysis may show twenty or more elements present in vein and wallrock samples in quantitatively measurable amounts.
\r\n\r\nApproximately fifty samples of vein material and wallrock from the ore deposits of Goldfield, Nevada were analyzed quantitatively to determine whether the quantitative distribution of the elements would give some clue to the loci of mineralization. It has been established that three elements, bismuth, silver, and tin are genetically associated with the gold values in the deeper veins at Goldfield and that these elements are determinable even in very low grade ore. It is probable that a further study of their distribution would shed much light on the problem of determining the loci of mineralization.
\r\n\r\nThe quantitative variations of some of the elements in the wallrock have been determined and these variations give some hope of an economic application in determining the distance of a given wallrock sample from a vein.
\r\n\r\nA vertical zoning of tin is present at Goldfield and some suggestion has been found of a zoning of bismuth and perhaps of the whole type of mineralization.
\r\n\r\nThe present work has shown that the spectrograph is very useful in the study of geochemical problems and several possible problems for study are suggested.
\r\n\r\nStratigraphy of the Cretaceous and Eocene rocks of the Santa Monica Mountains:
\r\n\r\nThe problem consisted of separating the Upper Cretaceous from the Eocene rocks in the eastern part of the Santa Monica mountains; determining the local stratigraphy of the Upper Cretaceous and Martinez; and attempting to correlate the Cretaceous section with other sections in California.
\r\n\r\nResults:
\r\n(a) The Upper Cretaceous stratigraphy in descending order is as follows: E. Upper arkose and conglomerate, 1500 feet. D. Fine grained, fossiliferous sandstone, 300 feet. C. Cobble conglomerate with some arkose in lower part, 3500 feet. B. Coarse arkose with some shale and conglomerate, 2500 feet. Unconformity. A. Lower soft red conglomerate.
\r\n(b) The lower conglomerate lies unconformably on metamorphosed Santa Monica slates of Triassie (?) age. The Martinez overlaps the Cretaceous with a distinct erosional unconformity although no great angular unconformity has been found. In some places the Cretaceous is overlapped by the Modelo and faulted against Topanga sandstone in others.
\r\n(c) The lower red conglomerate has similar lithology and occupies the same relative position as the Trabuco formation of the Santa Ana mountains, so that it may well represent the same formation. Member D is correlated with the Williams formation in the Santa Ana mountains and with the Metaplacenticeras beds of the Dayton canyon section in the Simi Hills on the basis of the fauna.
\r\n(d) The Martinez section in the Eastern part of the Santa Monica mountains is about 3500 feet thick. The lower 2000' consists of brown shale with reefs of white algal limestone and the upper 1500 feet is more than half coarse white arkose and conglomerate, but contains considerable shale and some algal limestone.
Since the preceding series of investigations are of a somewhat different character than the one to follow, it is desirable at this point to summarize the results so far obtained:
\r\n\r\n1. Gravitational waves in a viscous incompressible medium are far too slow to account for the velocity of first arrival of the ground roll.
\r\n\r\n2. The importance of Bateman's secondary Rayleigh wave cannot be known without the solution of the complex problem of the partition of energy at the source of the Rayleigh waves.
\r\n\r\n3. The theory of the propagation of Love waves on the surface of a layered visco-elastic medium indicates the possibility of velocities less than the shear wave velocity obtained without viscosity. The rapid damping of very short waves is also indicated. The possibility of obtaining a damping of the order of the ground roll damping has been demonstrated.
\r\n\r\n4. An examination of seismic data on the velocity of the ground roll has indicated that the observations are not necessarily inconsistent with the theory of dispersion of Rayleigh waves in a layered elastic medium, but, that there may be other causes of the observed dispersion.
\r\n\r\nCertain anomalous ground roll velocity variation near Fresno; California is possibly explanable on the hypothesis of dispersion in a layered elastic medium. For small values of L/H, the velocity of the ground roll agrees roughly with the velocity of Rayleigh waves, but these same velocities are associated with an initial anomalous forward cycle of the particle motion. Theoretically thereis an inherent disadvantage in obtaining dispersion data on the ground roll by seismic means, because of the factor of possible resonance making the interpretation of the results difficult. The three component ground roll data suggest the possible co-existence of Love waves and Rayleigh waves.
" }, { "name": "Findlay, Willard Alexander", "degree": "PhD", "year": "1940", "title": "Sources of Miocene Sediments in Southwestern San Joaquin Valley", "advisor": "Campbell, Ian; Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02212006-091933", "creators": [ { "name": { "family": "Findlay", "given": "Willard Alexander" }, "id": "Findlay-Willard-Alexander", "display_name": "Findlay, Willard Alexander" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" }, { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/SB5Z-K361", "abstract": "This investigation constitutes an attempt to determine by studies of heavy minerals, using a statistical approach, the sources of Miocene sands occurring along the southwestern border of San Joaquin Valley, and from a knowledge of these sources to deduce inferences regarding distribution of the sands and Miocene paleogeographic conditions. The method of attack chosen was to compare heavy mineral assemblages of the Miocene sands in question with those (1) of extant possible source areas and (2) of other post-Franciscan sediments the sources of which can be more readily inferred. The method used for sampling possible source areas was to sample fresh recent sands from streams draining these areas. Miocene samples were discreet \"spot\" samples. Considerable attention was given to development of laboratory and microscopic technique. The two items in this regard which are considered to represent most progress in technique are (1) use of ruled slides for grain counts, and (2) a method for use in centrifuge separations of heavy minerals. Effective methods of assembling and representing mineralogical results were devised.\r\n" }, { "name": "Henshaw, Paul Carrington", "degree": "PhD", "year": "1940", "title": "A Tertiary Mammalian Fauna from the San Antonio Mountains Near Tonopah, Nevada. Geology and Mineral Deposits of the Cargo Muchacho Mountains, Imperial County, California", "advisor": "Stock, Chester", "url": "https://resolver.caltech.edu/CaltechETD:etd-06162006-133204", "creators": [ { "name": { "family": "Henshaw", "given": "Paul Carrington" }, "id": "Henshaw-Paul-Carrington", "display_name": "Henshaw, Paul Carrington" } ], "advisors": [ { "name": { "family": "Stock", "given": "Chester" }, "id": "Stock-C", "role": "advisor", "display_name": "Stock, Chester" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol", "paleontology" ], "doi": "10.7907/7N0V-5049", "abstract": "Part I: A Tertiary mammalian fauna from the San Antonio Mountains near Tonopah, Nevada:\r\n\r\nA collection of mammalian fossils from near Tonopah, Nevada, contains nineteen pieces, six of which have been reported from no other locality. With more than 225 individuals in the collection, the assemblage approaches a true representation of the numerical frequency of species in a plains fauna. Abundance of skeletal elements of Hypohippus and Merychippus affords material for detailed osteological comparison.\r\n\r\nGeological reconnaissance in the area about California Institute of Technology Vertebrate Paleontology Locality No. 172 led to the discovery of a contemporary inland lake faunal facies containing diatoms, molluscs and fish. The occurrence of the mammalian fossils in gravels and cherts, as well as in clays, indicates that the bones were deposited near the entrance of a stream into a saline lake. The small stratigraphic extent of the quarry, the close association of the bones, and the limited morphological variation within abundantly represented species suggests that the fauna is unmixed.\r\n\r\nThe mammalian assemblage is correlated with the uppermost Barstow and is designated as Upper Miocene in age.\r\n\r\nPart II: Geology and mineral deposits of the Cargo Muchacho Mountains, Imperial County, California:\r\n\r\nThe study of the Cargo Muchacho Mountains presents the first account of the geology of southeasternmost California. In these mountains pre-Mesozoic kyanite schist and arkosite are intruded by a series of granitoid rocks probably Mesozoic in age. The two youngest rocks of this series were formed by granitization of arkosite. Andesite dikes of minor importance intruded the area probably in Tertiary time. Remnants of a once extensive flow of olivens basalt cover a few outlying hills. Alluvial deposits of three distinct ages occur in the area. Two of these, which are pre-basalt in age, offer evidence that the Colorado River formerly flowed through the region.\r\n\r\nThe Cargo Muchacho Mountains constitute an important gold mining district. The occurrence of the ore is shown to have been controlled by the regional structure. The ore deposits are mesothermal and are locally characterized by extreme alteration of the wall rock. Kyanite and sericite are also mined in the district. The record of mining activity and production of the district is brought up to date.\r\n" }, { "name": "Dreyer, Robert Marx", "degree": "PhD", "year": "1939", "title": "The Geochemistry of Quicksilver Mineralization. Magnetometer Examination of the Monte Cristo Magnetite-Ilmenite Deposits", "advisor": "Fraser, H. J.; Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:01052012-135937897", "creators": [ { "name": { "family": "Dreyer", "given": "Robert Marx" }, "id": "Dreyer-Robert-Marx", "display_name": "Dreyer, Robert Marx" } ], "advisors": [ { "name": { "family": "Fraser", "given": "H. J." }, "id": "Fraser-H-J", "role": "advisor", "display_name": "Fraser, H. J." }, { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "co-advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/DYZ2-4H66", "abstract": "The geochemistry of quicksilver mineralization:
\r\n\r\nThe investigation has involved a geochemical, petrographic, and spectographic study of quicksilver mineralization. It has been found that cinnabar can be deposited only from alkaline sulphide ion concentration which is, in turn, partially dependent on the alkalinity of the solution. Such alkaline solutions are capable of dissolving silica, but carbonate and alkaline earth ions cannot exist together in such alkaline solutions. Any carbonatization of quicksilver deposits must thus represent a stage in the period of mineralization distinct from the period of cinnabar deposition. However, silica is often deposited syngenetically with cinnabar and the relationship of cinnabar and silica (unlike that of cinnabar and carbonate) is so intimate that the cinnabar occurs, in some places, as an extremely fine dispersion throughout associated silica. Associated with quicksilver mineralizing solutions are small amounts of a number of heavy metals as iron, chromium, manganese, arsenic, antimony, gold, silver, copper, zinc, nickel, germanium, lead, and cobalt. Of these elements, copper, silver, cobalt, lead, and germanium are always differentially concentrated in the cinnabar and such differential concentrations as have been observed are independent of the geographical and geological location of the deposit and are likewise independent of the type of wall rock in which the deposit occurs. The varying shades of cinnabar coloration cannot be attributed to any spectrographically determinable concentrations of any elements nor to the total amount of impurity which is differentially concentrated in the cinnabar.
\r\n\r\nThe cinnabar-bearing solutions gain access into the wall rocks through fractures and intergranular voids and the greater part of all cinnabar ores is the result of such open-space filling. When the openings become filled, however, the solutions are quite capable of replacing the adjacent wall rock. If the wall rock is out of equilibrium with the quicksilver mineralizing solutions, the adjustment of equilibrium and consequent precipitation of mercuric sulphide will be quite rapid.
\r\n\r\nPrecipitation of cinnabar is caused primarily by relief of pressure, evaporation of solvent, and wall rock reaction. Except in ammoniacal solutions, a decrease in temperature will not cause precipitation. Dilution of solutions causes the precipitation of metacinnabar and colloidal mercury. Such dilution is probably responsible for the native mercury which is a common, minor component of many quicksilver deposits. Acidification will likewise precipitate metacinnabar, but not cinnabar. The infrequent occurrences of metacinnabar can best be explained by near-surface dilution or acidification of hypogene solutions. Insofar as temperature and alkalinity are concerned, pyrite or both pyrite and marcasite could be formed simultaneously with cinnabar of metacinnabar or both. However, where marcasite occurs with cinnabar alone (as is quite commonly the case), the marcasite has probably been deposited separately form the cinnabar. Since cinnabar (rather than metacinnabar) is deposited only from hot alkaline solutions and since oxidized mercury minerals are very rare, supergene deposition of cinnabar must be a very local and a very uncommon occurrence.
\r\n\r\nSome cinnabar darkens rapidly on exposure to sunlight and it is suggested that this darkening may involve the formation of a surficial layer of colloidal mercury in solid solution in the cinnabar.
\r\n\r\nMagnetometer examination of the Monte Cristo magnetite-ilmenite deposits:
\r\n\r\nSituated in the San Gabriel Mountains of Southern California is a large body of anorthosite which is associated a number of bodies of ilmenitic magnetite. During the summer of 1937, the E. I. duPont de Nemours Corporation obtained options on a group of properties thought to contain several such deposits. In connection with the exploration of the aforementioned deposits, the authors were employed as geophysicists to conduct a magnetic examination of the area. The data contained in this report was collected between August 9 and September 4, 1937. Mr. Dawson is, at the present time, continuing the magnetometer investigation and, in the light of the facts to be presented in the following pages, his work is being watched with considerable interest.
" }, { "name": "Hopper, Richard Hutchinson", "degree": "PhD", "year": "1939", "title": "A Geologic Section from the Sierra Nevada to Death Valley, California", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-02012006-130620", "creators": [ { "name": { "family": "Hopper", "given": "Richard Hutchinson" }, "id": "Hopper-Richard-Hutchinson", "display_name": "Hopper, Richard Hutchinson" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/0HXX-FR95", "abstract": "This paper describes the geology of an area six miles wide and 67 miles long, extending from the crest of the Sierra Nevada to the floor of Death Valley approximately along the 36\u00b016' parallel of latitude. Structural geology is emphasized. Correlations are suggested between events in the geologic histories of this area and of other areas in southeastern California.\r\n\r\nThe area mapped is in one of the most rugged parts of the Great Basin, and has a relief of more than 10,000 feet. It extends across the three westernmost ranges of the Great Basin in this latitude, the Coso, Argus, and Panamint Ranges. The topographic features of these ranges strongly suggest that each of them owes most of its present relief to uplift by faulting. In the western half of the area the displacements of an extensive sheet of late Pliocene or early Pleistocene basalt support the topographic evidence of faulting. On the summit portions of the ranges are areas of low relief, believed to be remnants of a single old-age erosion surface which extended across the area before the beginning of the range-forming fault movements. The period of undisturbed erosion which produced this surface ended shortly before the deposition of the fossiliferous late Pliocene or early Pleistocene Coso formation; therefore this surface is correlated with the Ricardo erosion surface of the Mohave Desert region, which bevels tilted early Pliocene strata and which is also dislocated by range-forming faults.\r\n\r\nThe ranges are composed dominantly of pre-Tertiary rocks. Pre-Cambrian metasediments exposed in the Panamint Range attain a thickness of 15,000 feet; they are chiefly mica schists and dolomites. The Paleozoic rocks are more than 30,000 feet thick, and the fossils collected indicate the probable presence of all the Paleozoic systems. Limestones, dolomites, shales, and quartzites are the principal rock types. Cambrian and Carboniferous strata make up about three-fourths of the total Paleozoic section. During the late Jurassic Nevadian orogeny the pre-Mesozoic rocks were folded, faulted, and intruded by platonic bodies ranging in composition from granite to gabbro. The post-Mesozoic rocks are almost entirely of late Cenozoic age, and include a wide variety of volcanic and sedimentary types.\r\n\r\nMovements of large magnitude took place on the fault zone on the east edge of Panamint Valley in late Tertiary time, and activity on this zone has continued into the Recent epoch. Most of the faulting to which the region owes its present relief, however, occurred in the early or middle part of the Pleistocene epoch, probably after the first (McGee) glacial stage in the Sierra Nevada. All the range-forming faults whose attitudes could be determined were found to be normal faults." }, { "name": "Osborn, Elburt Franklin", "degree": "PhD", "year": "1938", "title": "Micrometric and Petrofabric Studies of the Val Verde Tonalite, Southern California", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:05252018-110619727", "creators": [ { "name": { "family": "Osborn", "given": "Elburt Franklin" }, "id": "Osborn-Elburt-Franklin", "display_name": "Osborn, Elburt Franklin" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/P3AT-SF73", "abstract": "The Val Verde tunnel of the Metropolitan Water District of Southern California, located thirteen miles south of Riverside, California, passes through 27,000 feet of a single tonalite intrusive and across the intrusive contact into a body of quartz-biotite schist.
\r\n\r\nMicrometric analyses of the tonalite along the line of the tunnel have shown no progressive variation in the percentage of minerals present; but the albite content of the plagioclase increases toward the contact with the schist, and this correlates directly with the radioactivity and zircon content of the tonalite. The more acid border of the intrusive is believed to be due to assimilation of the quartz-biotite schist.
\r\n\r\nOn the basis of mineralogic and radioactivity determinations, dark fine grained inclusions in the tonalite are believed to be xenoliths of schist and gabbro.
\r\n\r\nPetrofabric diagrams obtained from the plagioclase, biotite, and quartz of the tonalite indicate that the gneiss planes of the tonalite developed as a result of a combination of now of the partially crystallized magma and post-magmatic deformation. The present linear direction in the rock may or may not represent the original direction of flow of the magma.
\r\n" }, { "name": "Cogen, William Maurice", "degree": "PhD", "year": "1937", "title": "Mechanics of Landslides", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06092015-102434867", "creators": [ { "name": { "family": "Cogen", "given": "William Maurice" }, "id": "Cogen-William-Maurice", "display_name": "Cogen, William Maurice" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/M78R-XP91", "abstract": "The purpose of this investigation was to determine whether landslides could be predicted for hill slopes of known inclinations from data secured by laboratory tests performed on samples of the ground under consideration. Specifically, the investigation was to show whether a correlation existed between experimentally determined values for friction and cohesion of ground and calculated values based upon the configuration of earth masses that had slid. The ability to determine the stability of slopes from experimental data is of obvious significance." }, { "name": "Kelley, Vincent Cooper", "degree": "PhD", "year": "1937", "title": "Geology and Ore Deposits of the Darwin Silver-Lead Mining District, Inyo County, California", "advisor": "Fraser, Horace J.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04112018-154512700", "creators": [ { "name": { "family": "Kelley", "given": "Vincent Cooper" }, "id": "Kelley-Vincent-Cooper", "display_name": "Kelley, Vincent Cooper" } ], "advisors": [ { "name": { "family": "Fraser", "given": "Horace J." }, "id": "Fraser-H-J", "role": "advisor", "display_name": "Fraser, Horace J." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/FA9Y-JW30", "abstract": "The survey of the geology and ore deposits of the Darwin Hills presents two major problems. The first is the origin of the stratified silicate aureole about the Darwin stock. Such silication may be accomplished by pure thermal metamorphism or by additive processes. Field relations, supported by petrographic and chemical evidence, indicate that metasomatism played the dominant role. Considerable silica and other materials were introduced into the limestones by the magmatic emanations.
\r\n\r\nThe second major problem involves the origin and classification of the ore deposits. The deposition of all the ore bodies took place at a distinctly later time that the development of the silicate aureole. A period of tectonic fracturing in which most of the fissures of the district were developed intervened between the early silication period and the later metallization period. Three structural controls, igneous contacts, bedding planes, and fractures, dominated the location of the deposits. Genetically all three structural types are the same.
\r\n\r\nThe ore mineralization is not of the high temperature type and hence is not pyrometasomatic as classed by Knopf. Because of certain structural and textural features and the presence of such gangue minerals as fluorite and barite, the deposits are classed as upper mesothermal.
\r\n\r\n\r\n" }, { "name": "Kemnitzer, Luis Emmett", "degree": "PhD", "year": "1937", "title": "Structural Studies in the Whipple Mountains, Southeastern California", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:04172018-130134257", "creators": [ { "name": { "family": "Kemnitzer", "given": "Luis Emmett" }, "id": "Kemnitzer-Luis-Emmett", "display_name": "Kemnitzer, Luis Emmett" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/XV6Y-GX29", "abstract": "The rocks of the Whipple Mountains include a basement complex of pre-Cambrian age overlain by middle Tertiary volcanics and sedimentary. These are unconformably overlain by flat-lying Pleistocene and recent beds. The broad structural feature of the mountains is a faulted dome, elongated roughly east-west. The dome is out lined on the north and northeast flanks by an arcuate fault which dips away from the mountains. The northeast area of the mountains is broken into southwest-tilted blocks, bounded by northeast-dipping normal faults, roughly parallel to\r\nthe southeast-trending portion of the arcuate fault.\r\nThe block faulting is not of the orthodox basin range\r\ntype, but is considered to be closely associated with\r\nthe doming. There is no evidence of large compressional\r\nforces, and these mountains are believed to belong to\r\nthe belt of transverse ranges of southern California.\r\nThe major faults are presumed to have been active in\r\npost and pre-Miocene times. There is no evidence of\r\nrecent fault activity and volcanics and sediments presumably\r\nof Quaternary age are not cut by the faults.\r\n" }, { "name": "Putnam, William Clement", "degree": "PhD", "year": "1937", "title": "Physiography of the Ventura Region, California", "advisor": "Buwalda, John P.; Stock, Chester", "url": "https://resolver.caltech.edu/CaltechTHESIS:10232018-092150603", "creators": [ { "name": { "family": "Putnam", "given": "William Clement" }, "id": "Putnam-William-Clement", "display_name": "Putnam, William Clement" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." }, { "name": { "family": "Stock", "given": "Chester" }, "id": "Stock-C", "role": "co-advisor", "display_name": "Stock, Chester" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/DVAE-R217", "abstract": "The Ventura region is of interest for its great thickness of Tertiary sediments, and for the nearly complete record it affords of events in the Pleistocene. This Pleistocene history may be divided into four major episodes; deposition of 4700 feet of marine sediments, deformation of all the rocks in the region, erosion to a surface of late maturity, designated as the Rincon Surface, and uplift which initiated the present erosion cycle.
\r\n\r\nThe late-Pleistocene intermittent uplift is recorded by terraces in the Ventura River valley, and by marine terraces along the coast. Both sets of terraces are warped, and reach their maximum elevation where the most intense deformation of the underlying rocks has occurred.
\r\n\r\nFossils of birds, plants, vertebrates, and marine invertebrates found on the lowermost of the marine terraces at Carpinteria are believed to have accumulated approximately 30,000 years ago in the waning phase of the last Pleistocene glaciation. The plant fossils may have been introduced by small streams in time of flood; the vertebrates are a tarpit accumulation.
\r\n\r\nChanges in the appearance of the Ventura shoreline during the period of uplift, and at the present time, follow a definite sequence. The recognition of this sequence as part of an erosion cycle applicable to steeply sloping shorelines of emergence is an outgrowth of this study. This new cycle differs materially from the one previously described for gently sloping emergent shorelines.
\r\n\r\nSome evidence is found in the Ventura region favoring a recent eustatic lowering of sea level. The fluctuations of sea level during the last glaciation have also been recorded.The development and preservation of coastal terraces is determined by the nature of the bedrock. The best preserved terraces have been cut in the siliceous shales of the Modelo formation. The marine terraces have a local, rather than regional distribution, and owe their altitude to both vertical uplift and warping. Attempts to correlate marine terraces on this coast with glacial oscillations of sea level are not successful.
\r\n\r\nDeformation, both faulting and warping, has continued in to the present in the Ventura region. The Coast Ranges in this section of Southern California are to be regarded as a growing mountain range.
" }, { "name": "Putnam, William Clement", "degree": "PhD", "year": "1937", "title": "The Geology of the Mono Craters, California", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:05142012-135105262", "creators": [ { "name": { "family": "Putnam", "given": "William Clement" }, "id": "Putnam-William-Clement", "display_name": "Putnam, William Clement" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/E8PG-SX27", "abstract": "The Mono Craters are a chain of extinct obsidian domes, coulees, and lapilli cones lying south of Mono Lake in eastern California. They are slightly more than ten miles long, are ranged along a curving fracture roughly parallel to the Sierra Nevada, and are divided into three nearly equal parts by two large obsidian flows, or coulees. In general, there has been a shift of activity from the center of the range to the two extremities.
\r\n\r\nThe volcanic vents in the Mono Craters, in the typical case, pass through a sequence in which activity commences with a series of explosions. Ash and lapilli are hurled out, and a funnel shaped explosion pit is formed. The explosions are succeeded by the rise of an obsidian dome near the center of the lapilli ring. The dome expands beyond the confines of the lapilli collar and produces a coulee if a sufficient volume of obsidian reaches the surface. Explosions of decreasing intensity may occur during any of the later stages in the sequence.
\r\n\r\nThe structure of the average obsidian dome is determined by the viscous nature of the semi-solid obsidian, and the narrow conduit through which it rises. The lava expands in a sheaf-like form upon reaching the surface. The obsidian is traversed by a multitude of joints on cooling, and rapidly disintegrates into angular blocks. The force responsible for the elevation of the obsidian is not known, but may well be exerted by the gas contained in the magma.
\r\n\r\nThe principal rock types in the Mono Craters are the frothy lapilli of the explosion vents; gray or purple, sanidine-bearing, pumiceous obsidian; black, vitreous obsidian; and the near-rhyolitic variety of \"intrusive obsidian\" found in the deeper parts of the volcanic conduits. Associated with the obsidian of the Mono Craters are two older rocks, the West Portal Rhyolite and the Black Butte Basalt. The nature of the West Portal Rhyolite, and its relation to the older glacial deposits, is clearly shown by the cross-section exposed in the water tunnel driven under the southern end of the craters by the Los Angeles Bureau of Water Works and Supply.
\r\n\r\nThe Mono Craters were active in the late Pleistocene. Although some ash is interstratified with deposits of Mono Lake, no shorelines cut the more recent craters. The Southern Coulee buries one of the earlier lateral moraines of one of the principal Sierra glaciers. Explosion pits at the southeastern end of the craters erupted through the floor of a late Pleistocene lake, part of a chain lying to the east of the main group of craters.
" }, { "name": "Schultz, John Russell", "degree": "PhD", "year": "1937", "title": "A Late Quaternary Mammal Fauna from the Tar Seeps of McKittrick, California", "advisor": "Stock, Chester", "url": "https://resolver.caltech.edu/CaltechETD:etd-04022004-141305", "creators": [ { "name": { "family": "Schultz", "given": "John Russell" }, "id": "Schultz-John-Russell", "display_name": "Schultz, John Russell" } ], "advisors": [ { "name": { "family": "Stock", "given": "Chester" }, "id": "Stock-C", "role": "advisor", "display_name": "Stock, Chester" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/MDQ2-8B04", "abstract": "Forty-three species of mammals are known at present from the McKittrick tar seeps, in addition to a larger number of bird species and a smaller number of plant types. In the McKittrick fossil assemblage Recent or still living forms are more abundant than extinct types. Since at Rancho La Brea the reverse is generally true, it appears that McKittrick is a somewhat later accumulation. The interval does not appear to be greater, however, than that separating a glacial and interglacial epoch. Many lines of evidence indicate that Rancho La Brea dates from the late rather than early Pleistocene, and there seems to be good reason for believing that this deposit is of Sangamon age. The McKittrick assemblage thus appears to be referable to the Wisconsin, or last glacial epoch.
\r\n\r\nOf the 49 mammalian species known at Rancho La Brea only 21 are found also at McKittrick. In view of the rather marked specific differences still existing between the faunas of the Los Angeles Basin and San Joaquin Valley, it seems reasonable to assume that a large part of the difference between the two faunas is due to ecology rather than to a time factor. In addition, environmental conditions surrounding the tar seeps at the two localities do not seen to have been exactly alike and some of the faunal differences may be due to this cause.
\r\n\r\nJudging from evidence of the rodents and plants, the late Pleistocene climate of the San Joaquin Valley was not greatly different from conditions still prevailing in the area. A possible explanation is that the Coast Ranges then as now prevented free passage of moisture-laden winds over the area.
" }, { "name": "Schultz, John Russell", "degree": "PhD", "year": "1937", "title": "Geology of the Whites Point Outfall Sewer Tunnel", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-04022004-140339", "creators": [ { "name": { "family": "Schultz", "given": "John Russell" }, "id": "Schultz-John-Russell", "display_name": "Schultz, John Russell" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/BQND-AR74", "abstract": "Two years ago, W. P. Woodring and M. N. Bramlette of the\r\nUnited States Geological Survey completed a geologic map of the Palos Verdes Hills. A report on the area by Mr. Woodring is now in course of preparation. Shortly after completion of the field work, excavation began on the Whites Point Outfall Sewer Tunnel, which penetrates the entire eastern portion of the hills. Since natural exposures are rare in this part of the area, Mr. Woodring\r\ntook the opportunity to supplement the surface data by subsurface information afforded by the tunnel. The writer was given a temporary appointment with the Survey, and with the aid of knowledge brought together by the above workers, made a detailed study of the geology of the tunnel.
\r\n\r\nIn a work of this kind much of the interest centers upon\r\nthe question as to how far a structure section constructed from surface data may be relied upon at depth. Examination of figures 1 and 4 discloses that the surface work was accurate to au almost surprising degree.
\r\n\r\nThe Whites Point Tunnel was constructed by Los Angeles Sanitary District No. 2 for the purpose of sewage disposal, which was formerly taken care of by a plant in Harbor City. The route shown in figure 1 was chosen by the District on recommendation of Dr. Buwalda and others, who considered the \"hard\" rocks of the Palos Verdes Hills a better foundation in event of earthquakes than the almost unconsolidated sands underlying the extension of the Los Angeles city boundary into Wilmington.
\r\n\r\nThe tunnel extends from the intersection of Vermont Avenue and Lomita Boulevard in Harbor City to Whites Point, a distance of nearly six miles. An open out for the conduit joins the north portal with the intake. On the southern end a concrete pipe terminates 5,000 feet from shore, and at a depth of approximately 150 feet. Throughout the entire length the floor of the tunnel is 12 feet below sea level. The bore is a horseshoe in section and approximately 10 feet in diameter, but this was later increased to 11 feet in certain parts of the section between stations 102 and 180. The total estimated cost is in the neighborhood\r\nof $2,500,000, the funds being tarnished by Los Angeles\r\nSanitary District No. 2, and the Public Works Administration\r\n(P. W. A. Project 7133). Excavation began in September, 1935\r\nand was completed on October 14, 1936. During this time the\r\nwriter kept in close contact with progress of tunneling operations. Except where imperfect consolidation of the rock necessitated very close timbering, the data were obtained from an almost continuous exposure. Since the general trend of the tunnel is approximately normal to the regional strike, this information can be used for constructing a structure section through the eastern portion of the Palos Verdes Hills.
\r\n" }, { "name": "Webb, Robert Wallace", "degree": "PhD", "year": "1937", "title": "Geology of a Portion of the Southern Sierra Nevada of California: The Northern Kernville Quadrangle", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:11112019-171107969", "creators": [ { "name": { "family": "Webb", "given": "Robert Wallace" }, "id": "Webb-Robert-Wallace", "display_name": "Webb, Robert Wallace" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/Q1CF-3G40", "abstract": "The northern Kernville quadrangle lies on the great central plateau of the southern Sierra Nevada in Tulare, Kern, and Inyo counties, California. It comprises about 600 square miles.
\r\n\r\nGeomorphically, the area consists of a great interior platform, bounded on the east by the Sierran escarpment and Sierra Nevada fault, and on the west by the Main Fork of the Kern river. The region is divisible into nine geomorphic provinces, each with distinct characteristics. From west to east, these are: (a) the Greenhorn mountains, a range averaging 7000 feet in elevation, whose summits are remnants of an ancient erosional level, (b) the Main Fork valley, a pronounced north-south valley of 3000 foot depth, traversing the entire quadrangle, (c) the Meadowlands, a high, rolling old-land, remnant of an old erosional surface, (d) the South Fork canyon, (e) the Rockhouse basin, (f) the Crestal Upland, which marks the eastern crest of the Sierra Nevada, (g) the South Fork valley, a wide, alluvia ted east-west valley, which bisects the area in an east-west direction, (h) Kiavah mountain, and (i) Piute mountain. The origin of each of these subdivisions is discussed. It is shown that a complex series of events produced the present geomorphic features. The region has undergone plantation, rejuvenation in at least two epochs, and subsequent erosion to the present time. A geomorphic history attempts to harmonize all recorded events.
\r\n\r\nStructurally the region contains the important Kern Canyon fault, which parallels the Main Fork of the Kern for a distance of more than fifty miles, although not strictly coincident with it. It is shown that the Kern Canyon fault is of very ancient date, probably pre-Pliocene, also that a high fault-line scarp is eroded along the Kern Canyon fault. Evidence is presented to explain the discordance of the Main Fork of the Kern river with the fault. It is suggested that superposition by alluviation prevented the river from taking a course along the fault, as the stream was revived.
\r\n\r\nPetrologic and field studies in the area show the following rock units to be present: (1) a series of metamorphic rocks of probable Carboniferous age, classed as the Kernville series, composed primarily of quartzites, phyllites, schists, and marbles; these are invaded by (2) an horn-blende-gabbro to biotite-gabbro, which is closely associated with (3) a quartz-diorite, which invades the gabbro. The date of emplacement of these units is suggested as late Carboniferous. (4) The Isabella granodiorite, varying to granite, invaded all the other formations, and is the final important intrusive unit. This invasion probably accompanied the major diastrophic disturbance of the Sierra, generally set at late Jurassic to early Cretaceous. Tertiary and Quaternary lavas preserve erosional surfaces formed across the crystalline units. Some swamp and lake deposits, together with present and older alluvium, complete the petrologic sequences.
\r\n\r\nEconomically, the region has few deposits of commercial importance. Gold and barite have been mined commercially. Future production is improbable.
" }, { "name": "MacLellan, Donald Dominic", "degree": "PhD", "year": "1936", "title": "The Geology of the East Coachella Tunnel of the Metropolitan Water District of Southern California. A San Diego Fauna in the Vicinity of Val Verde, California", "advisor": "Campbell, Ian", "url": "https://resolver.caltech.edu/CaltechTHESIS:04132010-082926337", "creators": [ { "name": { "family": "MacLellan", "given": "Donald Dominic" }, "id": "MacLellan-Donald-Dominic", "display_name": "MacLellan, Donald Dominic" } ], "advisors": [ { "name": { "family": "Campbell", "given": "Ian" }, "id": "Campbell-I", "role": "advisor", "display_name": "Campbell, Ian" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/9QW7-PZ45", "abstract": "The Geology of the East Coachella Tunnel of the Metropolitan Water District of Southern California:
\r\n\r\nThe following paper describes the geology of the East Coachella Tunnel of the Metropolitan Water District of Southern California. This tunnel extends along the southern flank of the Little San Bernardino Mountains, in Riverside county, California.
\r\n\r\nFour rock types were encountered in the excavation of the tunnel: a regionally metamorphosed series of schists and gneisses of sedimentary origin, here called the Berdoo series; granitoid rocks resulting from replacement, called the Thermal Canyon series; a grananitic intrusive called the Fargo granite; and bench gravels.
\r\n\r\nThe Berdoo series is divisible on the basis of lithology into three facies: a dark thin-bedded feldspathic and biotitic schist, a light gray feldspathic gneiss, and a medium gray coarse grained schist which is transitional between the first two.
\r\n\r\nThe Thermal Canyon series consist of massive granitoid rocks which are of the mineralogical composition and general aspect of quartz-diorites.
\t\r\n\r\nBetween these two rock series occurs a transition zone of from 1000 to 6000 feet in width within which, as examined in the field, the sedimentary textures and structures which characterize the Berdoo series appear to gradually give way to the massive granitoid textures of the Thermal Canyon series. Petrographic studies reveal the existence of a zone of mineralogical gradation between the two series within which the assemblage which constitutes the Berdoo series gradually becomes replaced through recrystallization by that which constitutes the Thermal Canyon series. The minerals of the recrystallized assemblage are not conformable to definite surfaces such as bedding, but instead show the fortuitous orientation of an igneous rock. Also, the plagioclase feldspars of the recrystallized assemblage are slightly more calcic than those of the Berdoo series.
\r\n\r\nChemical analyses show that the composition of the two rock series is very nearly the same, excepting for a progressive increase in lime, and corresponding decreases in ferric iron and potassa with advancing recrystallization.
\r\n\r\nThe results of field, petrographic, and chemical methods of investigation thus indicate that the Thermal Canyon series rocks resulted trough recrystallization of a portion of the Berdoo series rocks. Ascending hot solutions and gases of magmatic origin are postulated as the actuating agencies in the recrystallization.
\r\n\r\nThe Fargo granite occurs as an intrusive stock in the east central portion of the area, and consists of a pinkish gray coarsely crystalline rock of about the mineralogical composition of a quartz-monzonite.
\r\n\r\nThe chief structural feature of the area is faulting, of which two systems are recognizable, one which trends easterly, and one which trends northerly. Two successive periods of domical uplift in the south-eastern portion of the area are postulated as causes for the faulting.
\r\n\r\nThe geological aspects of tunnel excavation, with especial reference to the influence of structure, are discussed briefly.
\r\n\r\nA San Diego Fauna in the Vicinity of Val Verde, California:
\r\n\r\n\r\nWithin the lowermost beds of the Saugus group in the Santa Clara Valley region as mapped by Kew (1) occur a series of conglomeratic and arenaceous sediments which have been known to carry a marine fauna, the age of which has not in every case been definitely determined. Mr. W. P. Popenoe of the California Institute of suggested to the writer that a study of certain exposures of these sediments be made with an especial view towards determining their age, and whether they constituted a geologic formation distinct from those of both the Pico and Saugus groups as previously mapped. The findings of this study are herewith presented.
\r\n" }, { "name": "Popenoe, Willis Parkison", "degree": "PhD", "year": "1936", "title": "The Upper Cretaceous Stratigraphy and Paleontology of the Northern Santa Ana Mountains", "advisor": "Buwalda, John P.; Stock, Chester", "url": "https://resolver.caltech.edu/CaltechTHESIS:11132024-221410090", "creators": [ { "name": { "family": "Popenoe", "given": "Willis Parkison" }, "id": "Popenoe-Willis-Parkison", "display_name": "Popenoe, Willis Parkison" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." }, { "name": { "family": "Stock", "given": "Chester" }, "id": "Stock-C", "role": "advisor", "display_name": "Stock, Chester" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/x4fg-ca49", "abstract": "The Upper Cretaceous deposits of the Santa Ana Mountains in the area between Trabuco and Santa Ana Canyons are divisible into three formations, each of the two upper formations being further divisible into two members. The Trabuco formation at the base has an estimated average thickness of 250 feet. It lies unconformably upon a basement complex made up of metamorphosed Triassic sedimentary rocks, and later intrusive igneous rocks. The Trabuco formation is a red, soft, incoherent, boulder conglomerate, is unfossiliferous, and may be of continental origin. The Trabuco formation is apparently conformably overlain by the Ladd Formation, which has a maximum thickness of at least 1700 feet, and which is divided into the Baker sandstone and conglomerate member below, and the Holz shale member above. The Baker member, approximately 200 feet thick on the average consists of hard, well-cemented, gray, unfossiliferous boulder conglomerates below grading into thick-bedded to shaly highly fossiliferous sandstones above. The Holz shale member has a maximum observed thickness of approximately 1500 feet, is composed principally of silty, micaceous, gray shale. The lower half of the shale is almost unfossiliferous. The upper half yields a prolific molluscan fauna. The Williams formation rests upon the Holz shale with a slight unconformity. It is divided into the Schulz conglomerate and sandstone member below, and the Pleasants sandstone member above. The Schulz member is unfossiliferous, composed of well-worn and rounded pebbles and boulders alternating with arkosic sandstones. It is approximately 200 feet thick. The Pleasants member consists of thin-bedded, rather shaly, light-colored micaceous sandstones, alternating with coarse, calcareous sandstones. It is highly fossiliferous.
\r\n\r\nTwo faunal zones are distinguished. The fauna of the Baker member, or Acataeonella oviformis zone of Packard, is not certainly known elsewhere in California, but is probably in part represented in the basal beds of the Rogue River Valley Upper Cretaceous of Oregon. The Glycymeris veatchii zone includes the upper part of the Holz shale member, and all of the Williams formation. It is divisible into three subzones from below upward (a) the subzone of Turritella chicoensis, typical variety, (b) the subzone of Turritella chicoensis, giant variety, (c} the subzone of Metaplacenticeras pacificum.
\r\n\r\nFossiliferous Cretaceous beds in the Simi Hills and the Santa Monica Mountains of southern California are probably to be correlated with the subzone of Metaplacenticeras pacificum, and to be somewhat younger than the Upper Cretaceous beds at Chico Creek, Butte County.
\r\n\r\nA fauna of approximately one hundred ten species is listed and discussed, a number of new species are described and figured, and new facts concerning the systematic position of a number of previously described fossils are presented.
" }, { "name": "Wilson, Robert Warren", "degree": "PhD", "year": "1936", "title": "Pliocene Rodents of Western North America", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:10102017-100640162", "creators": [ { "name": { "family": "Wilson", "given": "Robert Warren" }, "id": "Wilson-Robert-Warren", "display_name": "Wilson, Robert Warren" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/3WVT-YC53", "abstract": "This thesis embraces a review of Pliocene rodent\r\nfaunas and their evolution as well as the description of\r\nseveral new Pliocene rodent faunas which contain forms of\r\ninterest to paleontology. In the course of the work\r\ndetailed faunal studies were carried on covering rodent\r\nfaunas from (1) Kern River beds, California; (2) Pliocene\r\nbeds of Smiths Valley, Nevada; (3) Owyhee Pliocene of\r\nRome, Oregon; (4) Pliocene beds in the Coso Mountains,\r\nCalifornia; and (5) beds exposed near Grand View and Hager\u00adman, \r\nIdaho. Examination, in whole or in part, of the fol\u00adlowing \r\nfaunas was also made: (1) Pliocene fauna from Bart\u00adlett \r\nMountain near Drewsey, Oregon; (2) Fish Lake Valley \r\nfauna, Nevada; (3) Rattlesnake, Oregon; (4) Thousand Creek, \r\nNevada; and (5) Curtis horizon of the San Pedro Valley beds, \r\nArizona. Other Pliocene rodent faunas were studied only \r\nthrough the published accounts of these faunas.
\r\n\r\nAs a result of the studies it was found that Pliocene \r\nrodent faunas fall into several major faunal stages \r\ndistinguished by the general nature of the faunas as well as \r\nby the presence of characteristic genera and species. The \r\nchief characteristics of these stages are as follows:
\r\n\r\n\r\nI. Lower Pliocene\r\n
II. Middle Pliocene\r\n
III. Upper Pliocene\r\n
The rodent record is still very incomplete and this \r\nfact together with the short duration of Pliocene time has \r\nserved to limit the amount of observable evolution in the \r\nRodentia during this epoch. However, the study has shown, \r\ncontrary to the usual belief, that in certain groups evolu\u00adtion \r\nhas proceeded at a fairly rapid rate. Moreover, it \r\nappears that post-Pliocene evolution in the rodent group is \r\nquite marked, in certain families at least.
\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n \r\n" }, { "name": "Wilson, Robert Warren", "degree": "PhD", "year": "1936", "title": "The Heavy Accessory Minerals of the Val Verde Tonalite", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:10162023-153512856", "creators": [ { "name": { "family": "Wilson", "given": "Robert Warren" }, "id": "Wilson-Robert-Warren", "display_name": "Wilson, Robert Warren" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/6h66-9w75", "abstract": "The construction of the Metropolitan Water District Aqueduct for Los Angeles County, California has necessi\u00adtated the drilling of long tunnels at various points en route from the Colorado River. One such tunnel situated near the town of Val Verde, California passes through some seven miles of tonalite. About a dozen samples of the tonalite were taken at approximately half-mile inter\u00advals in the Val Verde tunnel. These samples were studied to determine the accessory constituents present, and their variation in the section exposed in the tunnel.
\r\n\r\nThe non-magnetic or weakly magnetic heavy accessory minerals consist of sphene, apatite, epidote-clinozoisite, zircon, zoisite, allanite?, pyrite, and calcite? in approx\u00adimately decreasing order of abundance. From samples at one end of the tunnel tourmaline, monazite, abnormal blue anatase, and thulite? were recorded. Associated with the appearance of tourmaline and the other minerals just cited is an increase in zircon and decrease in apatite, suggest\u00ading a more acid phase in the tonalite at this point. An explanation may be furnished by the fact that the tonalite is here closer to overlying and intruded schists, and hence to the margin of the former.
\r\n\r\nThe more magnetic minerals of the tonalite were bio\u00adtite and hornblende (15%-30% of entire rook), and accessory magnetite.
" }, { "name": "Benioff, Victor Hugo", "degree": "PhD", "year": "1935", "title": "A Linear Strain Seismograph. The Physical Evaluation of Seismic Destructiveness. A Method for the Instrumental Determination of the Extent of Faulting", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:01292018-135558372", "creators": [ { "name": { "family": "Benioff", "given": "Victor Hugo" }, "id": "Benioff-Victor-Hugo", "display_name": "Benioff, Victor Hugo" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/RZNS-FS06", "abstract": "Part one: A linear strain seismograph:
\r\n\r\nA non-pendular seismograph is described, having a response which depends upon the linear strains between two points of the ground. Essentially, the seismometer consists of two piers separated by an interval of 20 meters, with a horizontal bar which is rigidly fastened to one pier and extending nearly to the other pier. Relative movements of the two piers thus actuate an electromechanical transducer which operates between the free end of the bar and the adjacent pier. The resulting induced currents are recorded by two galvanometers having different constants. Three different galvanometer periods being 0.2, 1.3, and 35 seconds. The equivalent pendular magnifications are 80,000, 10,000 and 100 respectively.
\r\n\r\nA theory is developed for the linear strain seismograph and related instruments.
\r\n\r\nPart two: The physical evaluation of seismic destructiveness:
\r\n\r\nThe problem of designing structures to withstand destructive earthquakes is not in a very satisfactory condition. On the one hand engineers do not know what characteristics of the ground motion are responsible for destruction, and on the other hand seismologists have no measurements of seismic motion which are sufficiently adequate to serve for design, even if the destructive characteristics were known. Consequently, engineers have been forced to proceed on an empirical basis. From past experience, chiefly in Japan, it has been found that buildings which are designed to withstand a constant horizontal acceleration of 0.1 gravity are, on the whole, fairly resistant to seismic damage. It is fortunate that such a simple formula works at all, in view of its inadequacy from the point of view of precise computation. We know that seismic motions do not exhibit constant accelerations; that instead they are made up of exceedingly variable oscillatory movements. A formula based upon constant acceleration may thus lead to large errors, especially when applied to new types of structures which have not been tested in actual earthquakes. In the following paragraphs a new formula for seismic destructiveness is proposed, in the belief that it is more accurate than previous ones. In addition to providing engineers with a more rational basis for design procedure, it determines a new type of seismographic instrument for recording and measuring the destructive characteristics of seismic motion.
\r\n\r\nPart 3: A method for the instrumental determination of the extent of faulting:
\r\n\r\nWhen fault displacement is clearly visible at the surface of the ground, there is no difficulty in determining the extent of faulting. Thus for example, in the San Francisco earthquake of 1906, faulting was observed on land to the extent of some 180 miles. If the fault is deeply covered with sediments so that displacement can not be observed at the surface, it is necessary to employ indirect methods of measuring the extent of faulting.
\r\n" }, { "name": "Donnelly, Maurice Ghirarr", "degree": "PhD", "year": "1935", "title": "The Lithia Pegmatites of Pala and Mesa Grande, San Diego County, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:02062018-094459638", "creators": [ { "name": { "family": "Donnelly", "given": "Maurice Ghirarr" }, "id": "Donnelly-Maurice-Ghirarr", "display_name": "Donnelly, Maurice Ghirarr" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/4074-Q166", "abstract": "The Mesa Grande and Pala regions, with which this report is chiefly concerned, both lie in the northern part of San Diego County. In an airline Pala is 80 miles southeast of Los Angeles and 45 miles northeast of San Diego. By road these distances are 100 and 55 miles, respectively. Mesa Grande in an airline is 105 miles southeast of Los Angeles and 40 miles northeast of San Diego. Along the most convenient route from Los Angeles to Mesa Grande the distance is 135 miles; from San Diego, 55 miles. Most of the other localities mentioned in this report are in the north-central part of San Diego County; two, Nuevo and Coahuila, are in Riverside County southeast of Riverside. The relative position of these places may be seen in the accompanying map showing the location of the principal pegmatite localities in southern California.\r\n" }, { "name": "Peterson, Raymond Alfred", "degree": "PhD", "year": "1935", "title": "Results of Gravity Measurements in Southern California", "advisor": "Gutenberg, Beno; Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:01292018-155308705", "creators": [ { "name": { "family": "Peterson", "given": "Raymond Alfred" }, "id": "Peterson-Raymond-Alfred", "display_name": "Peterson, Raymond Alfred" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "co-advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/QMC4-5J21", "abstract": "The various types of instruments for gravity measurements are briefly discussed. The theory of an inverted pendulum of the \"Holweck-Lejay\" type with an elastic mounting at its base is given, and an instrument of this design, ninety times as sensitive to differences in gravity as an ordinary pendulum, is described. The theory of the interpretation of gravity data is discussed. The results of gravity observations along a profile across the Los Angeles Basin and San Gabriel Mountains are given. From this data together with geologic data and that obtained from a reflection seismograph survey, a hypothetical structure section along the profile is constructed.
\r\n\r\nThe outstanding features of this section are the presence of a basin of Tertiary sediments about thirty thousand feet deep, and the increasing predominance of relatively lighter rocks under the San Gabriel Mountains and Mojave Desert. This last feature is in accord with the concept of \"regional isostatic compensation.\"
\r\n" }, { "name": "Soske, Joshua Lawrence", "degree": "PhD", "year": "1935", "title": "Theory of Magnetic Methods of Applied Geophysics with an Application to the San Andreas Fault", "advisor": "Gutenberg, Beno; Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-01202005-171417", "creators": [ { "name": { "family": "Soske", "given": "Joshua Lawrence" }, "id": "Soske-Joshua-Lawrence", "display_name": "Soske, Joshua Lawrence" } ], "advisors": [ { "name": { "family": "Gutenberg", "given": "Beno" }, "id": "Gutenberg-B", "role": "advisor", "display_name": "Gutenberg, Beno" }, { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/C5RJ-FS49", "abstract": "The attempts of geological and mining engineers to decipher the structure of the outermost formations of the earth's crust have led to many comprehensive studies, which now stand as monuments to their efforts. Their studies, in general, are confined almost exclusively to systematic collection, description, and analysis of facts which they were able to obtain by immediate observation at accessible points on and near the surface of the earth. These observations have many times been supported by other researches carried on in chemical, physical, and petrographic laboratories, but many times the complete solution of the problem has been obtained by inference, this often means that only those facts which could be seen were considered a safe basis for the inferred technical conclusions reached by a process of deduction.
\r\n\r\nA disadvantage of this direct method of investigation lies in the fact that such observations can be made only at certain points where nature has provided especially favorable conditions. The seriousness of this disadvantage has stimulated attempts in the past to develop methods which do not demand direct contact with the subsurface material for the investigating of geological structure, mineral content, and the nature of subsurface formations. Only recently have these methods been developed into usable forms. They are based upon those properties of the minerals, associated minerals, rocks, or structures which produce effects observable at a distance.
\r\n\r\nTherefore, in order that these methods of geological investigation succeed, it is necessary to attach to them all the resources of modern physics or geophysics, which may lead to the determination of the range of practical application of the known physical properties of matter connected with distant effects. This requires a constant improvement of methods and continuous new design of apparatus to keep abreast with new knowledge and ever increasing difficulties in the field as the more simple relations are learned, and the more complex relations left for study.
\r\n" }, { "name": "Bode, Francis Dashwood", "degree": "PhD", "year": "1934", "title": "Fauna of the Merychippus Zone, North Coalinga District, California. The Structural Geology of the San Joaquin Hills, Orange County, California", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02122018-131249429", "creators": [ { "name": { "family": "Bode", "given": "Francis Dashwood" }, "id": "Bode-Francis-Dashwood", "display_name": "Bode, Francis Dashwood" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "paleontology" ], "doi": "10.7907/QW98-4963", "abstract": "[Major thesis] Fauna of the Merychippus zone, north Coalinga district, California:
\r\n\r\nThe Merychippus zone occurs at the top of the Temblor sandstones on Domengine Creek, twelve miles north of Coalinga, California. The fauna includes a significant representation of ungulates and carnivores, with the Equidae far outnumbering all other forms.
\r\n\r\nThe stratigraphic position of the Merychippus zone in the Tertiary marine series, exposed on the west side of the San Joaquin Valley, lies within a zone whose assignment either to the middle Miocene Temblor or the upper Miocene Monterey is at present disputed among geologists familiar with the area. That its position is close to the dividing line between Temblor and Monterey is deemed significant for this report. In its stage of evolution and in its relationships with Tertiary assemblages of the Great Basin Province, the fauna of the Merychippus zone occupies a position intermediate between the middle Miocene Mascall of eastern Oregon and the upper Miocene Barstow of the Mohave Desert.
\r\n\r\nA study of the occurrence of the material leads to the conclusion that the accumulation of fossil remains took place in the forest portion of a delta of a large river, where remains of land mammals were mingled with those of marine vertebrates. The suggestion is made that during the period of accumulation of the deposits and of the organic remains, the land area contributing this material was one of low relief and characterized by a rainfall of approximately 30 inches. The fauna is described in detail.
\r\n\r\n[Minor thesis] The structural geology of the San Joaquin Hills, Orange County, California:
\r\n\r\nA study of the geology of the San Joaquin Hills,\r\nsoutheastern Orange County, was undertaken originally, in\r\ncollaboration with Mr. W. A. Findlay, as a research problem\r\nto be completed in fulfillment of the requirements for\r\nthe degree of Bachelor of Science at the California Institute of Technology. The original investigation served\r\nmainly to arouse an interest in the problem for Mr. Findlay\r\nand the writer. In May, 1932, Mr. Findlay submitted a report\r\non the general areal geology of the area as a thesis for the degree of Master of Science. It was then decided\r\nthat mapping should be continued in the area in detail, with\r\nMr. Findlay devoting time to a preparation of a thesis on\r\nthe sedimentary petrography and the writer continuing his\r\nstudy of the structural geology. This paper presents the\r\nresults of the structural investigation and is submitted\r\nas a minor thesis in partial fulfillment of the requirements\r\nfor the degree of Doctor of Philosophy.
\r\n" }, { "name": "Krick, Irving Parkhurst", "degree": "PhD", "year": "1934", "title": "I. Foehn Winds of Southern California. II. Foehn Wind Cyclo-Genesis. III. Weather Conditions Associated With the Akron Disaster. IV. The Los Angeles Storm of December 30, 1933 to January 1, 1934", "advisor": "von K\u00e1rm\u00e1n, Theodore", "url": "https://resolver.caltech.edu/CaltechTHESIS:07252014-141735903", "creators": [ { "name": { "family": "Krick", "given": "Irving Parkhurst" }, "id": "Krick-Irving-Parkhurst", "display_name": "Krick, Irving Parkhurst" } ], "advisors": [ { "name": { "family": "von K\u00e1rm\u00e1n", "given": "Theodore" }, "id": "von-K\u00e1rm\u00e1n-Th", "role": "advisor", "display_name": "von K\u00e1rm\u00e1n, Theodore" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol", "meteor" ], "doi": "10.7907/R9ZR-0776", "abstract": "I. Foehn winds of southern California.
\r\nAn investigation of the hot, dry and dust laden winds\r\noccurring in the late fall and early winter in the Los Angeles\r\nBasin and attributed in the past to the influences of the desert\r\nregions to the north revealed that these currents were of a\r\nfoehn nature. Their properties were found to be entirely due\r\nto dynamical heating produced in the descent from the high level\r\nareas in the interior to the lower Los Angeles Basin. Any dust\r\nassociated with the phenomenon was found to be acquired from the\r\nLos Angeles area rather than transported from the desert. It was\r\nfound that the frequency of occurrence of a mild type foehn of this\r\nnature during this season was sufficient to warrant its classification\r\nas a winter monsoon. This results from the topography of\r\nthe Los Angeles region which allows an easy entrance to the air\r\nfrom the interior by virtue of the low level mountain passes north\r\nof the area. This monsoon provides the mild winter climate of\r\nsouthern California since temperatures associated with the foehn\r\ncurrents are far higher than those experienced when maritime air\r\nfrom the adjacent Pacific Ocean occupies the region.
II. Foehn wind cyclo-genesis.
\r\nIntense anticyclones frequently build up over the high level\r\nregions of the Great Basin and Columbia Plateau which lie between\r\nthe Sierra Nevada and Cascade Mountains to the west and the Rocky\r\nMountains to the east. The outflow from these anticyclones produce\r\nextensive foehns east of the Rockies in the comparatively low\r\nlevel areas of the middle west and the Canadian provinces of\r\nAlberta and Saskatchewan. Normally at this season of the year very\r\ncold polar continental air masses are present over this territory\r\nand with the occurrence of these foehns marked discontinuity surfaces\r\narise between the warm foehn current, which is obliged to slide over\r\na colder mass, and the Pc air to the east. Cyclones are\r\neasily produced from this phenomenon and take the form of unstable\r\nwaves which propagate along the discontinuity surface between the\r\ntwo dissimilar masses. A continual series of such cyclones was\r\nfound to occur as long as the Great Basin anticyclone is maintained\r\nwith undiminished intensity.
III. Weather conditions associated with the Akron disaster.
\r\nThis situation illustrates the speedy development and\r\npropagation of young disturbances in the eastern United States\r\nduring the spring of the year under the influence of the conditionally\r\nunstable tropical maritime air masses which characterise the\r\nregion. It also furnishes an excellent example of the superiority\r\nof air mass and frontal methods of weather prediction for aircraft\r\noperation over the older methods based upon pressure distribution.
IV. The Los Angeles storm of December 30, 1933 to January 1, 1934.
\r\nThis discussion points out some of the fundamental interactions\r\noccurring between air masses of the North Pacific Ocean in connection\r\nwith Pacific Coast storms and the value of topographic and\r\naerological considerations in predicting them. Estimates of rainfall\r\nintensity and duration from analyses of this type may be made and\r\nwould prove very valuable in the Los Angeles area in connection with\r\nflood control problems.
The geology and economic geology of the Cranbrook district, British Columbia:
\r\n\r\nThe following paper embodies the results of four months spent in making a geological reconnaissance in the vicinity of Cranbrook, British Columbia in 1932 under the aegis of the Canadian Geological Survey.
\r\n\r\nDefinite evidence is presented to show that the Wisconsin ice-sheet in the lower parts of the area, stagnated, broke up, and melted away in situ; a phenomenon which, as far as the writer is aware, has not been reported so far from the margin of the sheet. The erosive power of the ice appears to have been strictly limited, in contrast to the tremendous erosion which is accomplished over most of British Columbia. Evidence is also presented suggesting a pre-Wisconsin period of glaciation.
\r\n\r\nA detailed description of the stratigraphy and structure is given with particular emphasis on the pre-Cambrian (Beltian) succession.
\r\n\r\nA series of pre-Cambrian sills and dykes are described in detail. Border phases rich in ferromagnesian minerals and quarts are present and their origin by differentiation of the magma and assimilation of silica from the intruded quartzites is suggested and critically discussed. The sills are found to contain a species of hornblende differing considerably from any that has been described in the literature, and its chemical and optical properties are given in detail.
\r\n\r\nMineralization is believed to have taken place at two periods; one in the pre-Cambrian and one in the late Mesozoic or early Tertiary. The evidence for this opinion is presented in detail and examples described. Some of the ore-bodies of pre-Cambrian age are believed to be magmatic segregations and the evidence in support of this belief is stated and discussed.
\r\n\r\nThe geological history and the physiography is outlined and three theories as to the origin of the Rocky Mountain Trench briefly considered.
\r\n\r\nA San Diego fauna in the Newhall quadrangle, California:
\r\n\r\nDuring the summers of 1917, 1918, and 1919 Dr. William S. Kew undertook the mapping of an area to the north and west of Los Angeles. The area included a thick section of the Fernando formation which Kew was able to sub-divide into two formations, the Pico, lower Pliocene in age, and the Upper Pliocene and Pleistocene Saugus. Later workers in the Pico to the east of Pico Canyon and elsewhere split the formation still further until the following sub-divisions, as summarized by Grant and Gale, p. 32, were reached.
\r\n" }, { "name": "Smith, Hampton", "degree": "PhD", "year": "1934", "title": "The Origin of Some of the Siliceous Miocene Rocks of California. Stratigraphic Position of Some of the Diatomite Horizons in the Los Angeles Basin, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:04182018-082536997", "creators": [ { "name": { "family": "Smith", "given": "Hampton" }, "id": "Smith-Hampton", "display_name": "Smith, Hampton" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/X7D1-HG73", "abstract": "Origin of some of the siliceous Miocene rocks of California:
\r\n\r\nThe upper Miocene marine section in California is characterized in many places by the presence of unusually large amounts of highly siliceous rocks. These can be roughly divided into two classes: the lithified chert-like beds which are characteristic of, and generally largely confined to, the lower part of the section, and the unconsolidated diatomites and diatomaceous and radiolarian silts which are commonly found overlying them. The chert-like beds have been referred to in California geological literature by a variety of names, including cherty shales, platy shales, siliceous shales and cherts. The merits of these, and some other designations are discussed in the section on nomenclature and it will suffice to say here that the writer has decided to use only the terms chert and cherty shale. In addition to the siliceous rocks the lower part of the Upper Miocene or the immediately underlying part of the section frequently contains considerable amounts of volcanic material, both extrusive and intrusive in nature.
\r\n\r\nThe Stratigraphic Position of Some of the Diatomite Horizons in the Los Angeles Basin:
\r\n\r\nIn most places in the Los Angeles Basin where a complete section of upper Miocene rooks is exposed there exists a mappable unit which is composed largely of soft, white, highly diatomaceous silt. This unit is commonly referred to as the diatomite. It varies considerably in thickness and in its relationship to other rook types, but the constancy of its lithologic characteristics considered in conjunction with their unusualness suggests that the unit bas stratigraphic significance. Since, however, structural\r\nand physiographic conditions make it impossible to trace the diatomaceous deposits continuously around the Los Angeles Basin, the only method of determining the age relationships of various isolated areas of these rooks\r\nis the paleontological one.
\r\n" }, { "name": "Thayer, Thomas Prence", "degree": "PhD", "year": "1934", "title": "The General Geology of the North Santiam River Section of the Oregon Cascades. The Stratigraphy and Paleontology of the Salem Hills, Oregon", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:01242011-115153952", "creators": [ { "name": { "family": "Thayer", "given": "Thomas Prence" }, "id": "Thayer-Thomas-Prence", "display_name": "Thayer, Thomas Prence" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/XTDZ-CD16", "abstract": "The general geology of the north Santiam River section of the Oregon Cascades:
\r\n\r\nThe district discussed in this paper is located in North-western Oregon, about fifty-miles south of the Columbia River. The section investigated extends eastward from the Willamette River a few miles south of Salem to the Cascade Range summit between Mount Jefferson and Olallie Butte. It follows the North Santiam River, which is near the 44\u00b0 45\u2019 parallel. The area includes portions of the Salem, Lebanon, Stayton, Mill City and Mt. Jefferson quadrangles of the Topographic Atlas of the United States and part of a fifteen minute quadrangle west of the Mill City sheet which was mapped by the author.
\r\n\r\nThe stratigraphy and paleontology of the Salem Hills, Oregon:
\r\n\r\nThe part of the Salem Hills considered in this paper lies south and east of the Willamette River south of Salem, Oregon. The area is in the middle of the Willamette Valley, midway between Eugene and Portland, and occupies the southeastern part of the Salem quadrangle of the Topographic Atlas of the United States.
\r\n" }, { "name": "Anderson, George Harold", "degree": "PhD", "year": "1933", "title": "Geology of the North Half of the White Mountain Quadrangle, California-Nevada. Petrography of the North Half of the White Mountain Quadrangle, California-Nevada. Stratigraphy and Faunal Relationships of Pliocene Beds of San Diego Age in the Vicinity of Las Llajas Canyon, Simi Valley, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-05022006-163249", "creators": [ { "name": { "family": "Anderson", "given": "George Harold" }, "id": "Anderson-George-Harold", "display_name": "Anderson, George Harold" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/GWZS-9815", "abstract": "Geology of the north half of the White Mountain Quadrangle, California-Nevada:
\r\n\r\nThe White Mountain range, the principal topographic unit of the White Mountain Quadrangle, is an up-faulted block between two relatively depressed areas. It differs from the ordinary basin range block in that it is a tilted horst. The marginal faults of the horst are of unusual complexity.
\r\n\r\nPhysiographically, the range is in the late youthful or early mature stage of the arid cycle of erosion. Glaciation has complicated to some degree the normal development of the cycle. Renewal of uplift by faulting appears to have taken place in recent times.
\r\n\r\nUpon the crest of the range are remnants of land surfaces of low relief, formed, probably, by erosion before the block faulting which uplifted the range. These surfaces are designated herein as the \"Pellisier Erosion Surface\" and the \"Sub-summit Oldland\". It is probable that both were formed in the same cycle of erosion.
\r\n\r\nThe core of the range is a granite batholith, intrusive into Cambrian or pre-Cambrian sedimentary rocks, chiefly calcareous and argillaceous in composition. For this ancient sedimentary series the name \"McNett Formation\" is proposed. It is non-fossiferous but on the basis of its lithology it is considered to be the equivalent of a thick series of dolomites and \"green knotted schists\" which Turner described as underlying the lowest fossiliferous Cambrian in the Silver Peak Quadrangle.
\r\n\r\nThe contacts of the intrusive and the ancient sediments are everywhere characterized by intense contact metamorphism. This is described in some detail in the section on petrography.
\r\n\r\nOverlying the older rocks is a volcanic series of Tertiary age. These are chiefly rhyolites with some andesites. They include flows and pyroclastics. Vertebrate remains discovered in playa deposits closely associated with the extrusive rocks indicate that the latter were accumulated in part during the upper Miocene and lower Pliocene.
\r\n\r\nThe most recent igneous rocks in the area are Quaternaty basalts which cover much of the northers part of the quadrangle.
\r\n\r\nIn the petrography section of this thesis, separately paged and indexed, are to be found descriptions and discussions of certain types of alteration affecting the rocks of the batholith on an enormous scale. These alterations, believed to be of hydrothermal origin, include the albitization of the potash feldspars and the development of a replacement texture closely resembling cataclastic texture but distinguished from the latter by its corrosive pattern and by the formation accompanying it of a large number of minerals not present in the original rock.
\r\n\r\nPetrography of the north half of the White Mountains Quadrangle California-Nevada:
\r\n\r\nThe igneous rocks of the north half of the White Mountain Quadrangle consist of a group of closely related intrusives, probably of Jurassic Age, and a Tertiary-Quaternary series of extrusives. The former, chiefly granitic in composition, compose the White Mountain batholith which intrudes calcareous and argillaceous rocks of early Cambrian or pre-Cambrian Age. The batholith is surrounded by a wide zone of intense contact metamorphism.
\r\n\r\nThe volcanic series may be subdivided into two groups. The earlier, whose accumulation probably occupied much of the middle and later Tertiary, is predominately siliceous in composition. The later, for the most part Quaternary in age, consists of basic andesites and basalts.
\r\n\r\nIn the following thesis all of these groups of rocks, including the contact metamorphics, are described in detail. Especial attention is paid to certain compositional and textural peculiarities exhibited by the intrusives. These peculiarities are highly significant, not only in the history of these particular rocks, but also in respect the general problem of the genesis of sodic and alkaline types. They are the result of replacement processes which appear to have been active on an enormous scale through the batholithic mass at a time considerably later than at least the outer parts of the magma. They involved the introduction of large quantities of material, especially sodium and silica and possibly also iron and magnesium from some source outside the field tion. The results are evident in the wholesale albitization of the potash feldspars, formation of secondary minerals including quartz, sericite, chlorite, epidote, biotite and hornblende and in the development of a texture here designated pseudo-cataclastic texture which closely resembles true cataclastic texture but is distinguishable from the latter by criteria set forth below.
\r\n\r\nStratigraphy and faunal relationships of Pliocene beds of San Diego age in the vicinity of Las Llajas Canyon, Simi Valley, California:
\r\n\r\nThe results of a careful search of the literature for material bearing upon replacement processes in igneous rocks are set forth in the thesis. Various theories which may account for the phenomena are critically discussed.
\r\n\r\nOverlying the Modelo Formation of Upper Miocene age north of Simi Valley is a series of arenaceous beds of marine origin whose stratigraphy and faunal relationships have heretofore been in doubt. At the suggestion of Dr. W. P. Woodring, then Professor of Invertebrate Paleontology at the California Institute of Technology, I undertook to study some of these beds as part of my preparation for the degree of Doctor of Philosophy. The following report covers in particular the section exposed from Las Llajas Canyon west to about two miles beyond Tapo Canyon.
" }, { "name": "Edwards, Everett Carlyle", "degree": "PhD", "year": "1933", "title": "Pliocene Conglomerates of the Los Angeles Basin and their Paleographic Significance. Foraminifera of the Repetto Hills", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechETD:etd-07192007-093245", "creators": [ { "name": { "family": "Edwards", "given": "Everett Carlyle" }, "id": "Edwards-Everett-Carlyle", "display_name": "Edwards, Everett Carlyle" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/DGBV-5P24", "abstract": "Pliocene conglomerates of the Los Angeles basin and their paleographic significance:
\r\n\r\nThe Los Angeles Basin of southern California is 50 miles long and 25 miles wide, and is bounded by the Pacific Ocean, the Santa Monica, San Gabriel and Santa Ana Mountains and the Ferris Block. It contains an enormous thickness of Miocene, Pliocene and Pleistocene strata.
\r\n\r\nPhysical conditions of origin and the nature of sediments are as closely related as cause and effect. Since the physical conditions of past epochs no longer persist, the sediments may bear them witness. Conglomerates are especially suited for the purpose of locating the source areas of strata, because they preserve not only the original minerals, but the texture, structure and general appearance of the original rocks.
\r\n\r\nConglomerates contain only a partial representation of the list of formations present in a source area. The relative abundance of the various rock types occurring in a conglomerate is not proportional to their relative quantities in the original district. This is due mainly to the selective action resulting from difference in resistance to weathering and from differential destruction during transportation.
\r\n\r\nThe Santa Monica Mountains furnished quantities of pholas-bored limestone breccia from the limestone lenses of the Modelo formation, to the Pliocene beds of the west side of the Los Angeles Basin. Conglomerates derived from this range are also characterized by pebbles and cobbles of igneous rocks, released by the break-down, of Miocene conglomerates, reworked and recomposed in the Pliocene sea.
\r\n\r\nThe San Gabriel Mountains shed conglomerate material characterized by an abundance of pink quartz-orthoclase granite, pink quartz-orthoclase pegmatite and aplite, and white spotted albiclase diorite. These mountains were emergent, but of too low relief during the Pliocene and lower Pleistocene to be of importance as a source for elastic sediments. They were, however, a dominant source during Miocene and upper Pleistocene.
\r\n\r\nConglomerates of Ferris Block origin are characterized by large quantities of white quartzalbite pegmatite. During the Pliocene and lower Pleistocene the northwest part of the Perris Block was mountainous. From these mountains enormous quantities of coarse and fine elastic material were removed, to be deposited in the northeast quarter of the Los Angeles Basin, in the area now occupied by the Puente Coyote, Monte Bello, and Repetto Bills, The Ferris Mountains were the most important single source for the Pliocene and lower Pleistocene sediments.
\r\n\r\nThe Santa Ana Mountains have been contributing terrestrial material to the Los Angeles Basin since before the advent of the Pliocene Epoch. Conglomerates from these mountains are characterized by quantities of feldspathic porphyries ranging from andesite to latite, quartzite, Triassic sandstone and siliceous slate.
\r\n\r\nIn the middle Pleistocene, a diastrophic revolution occurred in southern California, and the modern physiographic expression developed. The Santa Monica, San Gabriel, San Bernardino, San Jacinto and Santa Ana Mountains were thrust upward along fault planes. The rejuvenated mountains released floods of coarse and fine terrestrial material to the Los Angeles Basin, and fanglomerates began to accumulate at the mountain fronts. The Ferris Block, formerly a positive and mountainous element became depressed as a result of the structural revolution. The Santa Ana River maintained its course, became an antecedent stream, and grew headward into the San Bernardino Mountains.
\r\n\r\n\r\nForaminifera of the Repetto Hills:
\r\n\r\n\r\nThe use of Foraminifera for correlation purposes has rapidly increased during the past eight years. The Foraminiferal assemblages for the Miocene, Pliocene, Pleistocene and Recent epochs have been studied rather fully by the micropaleontologists of several of the oil companies located in Los Angeles, California. Less is known of the Foraminifera of the Oligocene, Eocene and Cretaceous of the Pacific coast.
\r\n" }, { "name": "Engel, Rene", "degree": "PhD", "year": "1933", "title": "Geology of the Lake Elsinore Quadrangle, California and Mineral Deposits of Lake Elsinore Quadrangle, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:07012013-154748332", "creators": [ { "name": { "family": "Engel", "given": "Rene" }, "id": "Engel-Rene", "display_name": "Engel, Rene" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/9QJ4-QD46", "abstract": "The Lake Elsinore quadrangle covers about 250 square miles and includes parts of the southwest margin of the Perris Block, the Elsinore trough, the southeastern end of the Santa Ana Mountains, and the Elsinore Mountains.
\r\n\r\nThe oldest rocks consist of an assemblage of metamorphics of igneous effusive and sedimentary origin, probably, for the most part, of Triassic age. They are intruded by diorite and various hypabyssal rocks, then in turn by granitic rocks, which occupy over 40 percent of the area. Following this last igneous activity of probable Lower Cretaceous age, an extended period of sedimentation started with the deposition of the marine Upper Cretaceous Chico formation and continued during the Paloecene under alternating marine and continental conditions on the margins of the blocks. A marine regression towards the north, during the Neocene, accounts for the younger Tertiary strata in the region under consideration.
\r\n\r\nOutpouring of basalts to the southeast indicates that igneous activity was resumed toward the close of the Tertiary. The fault zone, which characterizes the Elsinor trough, marks one of the major tectonic lines of southem California. It separates the upthrown and tilted block of the Santa Ana Mountains to the south from the Perris Block to the north.
\r\n\r\nMost of the faults are normal in type and nearly parallel to the general trend of the trough, or intersect each other at an acute angle. Vertical displacements generally exceed the horizontal ones and several periods of activity are recognized.
\r\n\r\nTilting of Tertiary and older Quaternary sediments in the trough have produced broad synclinal structures which have been modified by subsequent faulting.
\r\n\r\nFive old surfaces of erosion are exposed on the highlands.
\r\n\r\nThe mineral resources of the region are mainly high-grade clay deposits and mineral waters.
\r\n\r\n" }, { "name": "Shappell, Maple Delos", "degree": "PhD", "year": "1933", "title": "The Cleavage of Ionic Minerals. The Crystal Structure of Bixbyite and the C-Modification of the Sesquioxides", "advisor": "Pauling, Linus", "url": "https://resolver.caltech.edu/CaltechTHESIS:05122017-095401216", "creators": [ { "name": { "family": "Shappell", "given": "Maple Delos" }, "id": "Shappell-Maple-Delos", "display_name": "Shappell, Maple Delos" } ], "advisors": [ { "name": { "family": "Pauling", "given": "Linus" }, "id": "Pauling-L", "role": "advisor", "display_name": "Pauling, Linus" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/PTJH-EN65", "abstract": "Mineral cleavage can be resolved into two components;\r\ncleavability and optical effect. The electrical theory of matter\r\nin the solid state leads to a quantitative expression for the\r\ncleavability of ionic minerals
\r\n\r\n\r\nC{hkl} = A(hkl)/\u03a3\u00ednisicos \u03b8 i
\r\n\r\n\r\nApproximate values for s are obtainable by using the electrostatic\r\nbond strength. Systematic application to minerals whose constituent\r\natoms have inert-gas cores gives good agreement with observation.
" }, { "name": "Taylor, George Frederic", "degree": "PhD", "year": "1933", "title": "Quaternary Fault Structure of the Bishop Region, East-Central California", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:06062017-110352290", "creators": [ { "name": { "family": "Taylor", "given": "George Frederic" }, "id": "Taylor-George-Frederic", "display_name": "Taylor, George Frederic" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/EHJ2-R354", "abstract": "This paper presents the results of an investigation carried\r\non during 1932 of the Quaternary geologic structure and stratigraphy\r\nof the Bishop Region, eastern California. Close relationship of\r\nstructural and stratigraphic, data has resulted in the formulation of\r\na rather complete outline of the later geologic history of the region.
\r\n\r\n\r\nContributions to the stratigraphy of the area include the\r\nestablishing of the Zurich formation to embrace Pleistocne \"lake\r\nbeds\" and fanglomerate. Both the tuff-breccia and pumiceous breccia\r\nof the Volcanic Tableland are grouped as the \"Bishop formation\".\r\nThe Zurich formation is shown to be at least partly contemporaneous\r\nwith the Bishop formation.
\r\n\r\n\r\nThe piedmont faults of the region have been accurately located\r\nby numerous recently formed scarplets. A very noticeable offset\r\nin the Sierran base southwest of Bishop is described and termed the\r\nBishop Offset. The type of sloping surface lying between two\r\nfaults which diminish their throws in opposite directions, as present \r\nin the Bishop Offset, is described as a newly recognized\r\ngeomorphic form and named a \"Scarpramp\".
\r\n\r\n\r\nThe Sierra Nevada is believed to have been uplifted a considerable \r\namount since the Inyo-White Mountain Range attained approximately\r\nits present elevation. The effect of this recent uplift\r\non the climate of Owens Valley is discussed.
\r\n\r\n\r\nDeep Spring Valley and Cowhorn Valley are shown to be similar\r\nfault outlined features, each the result of the dropping down\r\nof a lozenge shaped block in the interior of the range along normal\r\nfaults. The east wall of Deep Spring Valley was formed considerably\r\nmore recently than the west side.
\r\n\r\n\r\nThe Sierran piedmont fault zone is generally narrow but\r\nbecomes distributive at some localities.
" }, { "name": "Clements, Thomas", "degree": "PhD", "year": "1932", "title": "The Geology of the Southeastern Portion of the Tejon Quadrangle, California", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02222018-153453201", "creators": [ { "name": { "family": "Clements", "given": "Thomas" }, "id": "Clements-Thomas", "display_name": "Clements, Thomas" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/XERN-CX70", "abstract": "Rocks in the southeasterly portion of the Tejon Quadrangle include pre-Cambrian (?), Paleozoic (?), Jurassic granitic rocks, and a thick series of Cenozoic sediments. All epochs of the two periods of the Cenozoic are represented.
\r\n\r\nLower Eocene (Martinez) marine beds are overlain unconformably by middle Eocene (Domengine) rocks, also marine. Oligocene land-laid beds occur in three isolated patches. A full series of Miocene rocks is present, from Vaqueros through Temblor to Modelo. These are all marine and in addition there is the Mint Canyon formation as the landward equivalent of a portion of the Modelo. An unconformity occurs at the base of the Temblor. Pliocene is represented in the southerly part of the area by marine Pico beds and in the north by the Ridge Route formation, largely lacustrine. These are both unconformable with the underlying Miocene rocks and the former are overlain, also unconformably, by land-laid Pleistocene (Saugus). Upper Pleistocene terraces border some of the streams, while Recent alluvium extends well up the larger stream channels.
\r\n\r\nDeformation has been brought about by static load, intrusion and dynamic compressive forces. The last named have broken the area into three blocks separated by major faults and faulted within themselves. A large syncline has developed in the central block and an upward occurs athwart the trend of other structures. The westerly block is complicated by a large overturn.
\r\n" }, { "name": "Patterson, John Wilfred", "degree": "PhD", "year": "1932", "title": "The Manto Type Limestone Replacement Deposits of Northern Mexico", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12212017-085430771", "creators": [ { "name": { "family": "Patterson", "given": "John Wilfred" }, "id": "Patterson-John-Wilfred", "display_name": "Patterson, John Wilfred" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/M6P1-FT06", "abstract": "A study has been made of the principal manto type limestone\r\nreplacement deposits of northern Mexico. Three of the \r\ndistricts, Los Lamentos and Santa Eulalia in Chihuahua, and\r\nMapimi in Durango, are described in detail. The sedimentary\r\nrocks are correlated with the Texas Comanchean formations.\r\nThe ore deposits are confined to certain beds of Upper Trinity \r\nand Lower Fredericksburg age. Data show that it is the \r\nphysical and not the chemical properties of the limestone\r\nwhich make some beds more susceptible to replacement than\r\nothers.
\r\n\r\n\r\nFolding and fissuring have been essential in localizing\r\nthe ore deposits. Mantos have been found to occur, in\r\ngeneral, in favorable beds at the crests of folds. The\r\nfissure zones are most pronounced in depth. The cross section\r\nof a deposit decreases upward from the apparent source although\r\nthe diminution is not constant. Mantos have yielded most of\r\nthe ore in the upper deposits; chimneys become more important\r\nin depth. The analyses of sections of an ore body are\r\nuniform but the deposits show a gradual change in composition in\r\na district. The ores are zoned vertically and laterally from\r\nthe apparent source and are believed to have been deposited\r\nby magmatic waters. The principal deposits of a district \r\nwere formed at one time. The metallic content of the bedded\r\noxidized deposits is almost identical to that of the primary\r\ndeposits from which they were derived. Dolomitization has\r\noccurred locally during oxidation.
" }, { "name": "Maxson, John Haviland", "degree": "PhD", "year": "1931", "title": "Geology of the Western Siskiyou Mountains", "advisor": "Buwalda, John P.", "url": "https://resolver.caltech.edu/CaltechTHESIS:02272018-091755013", "creators": [ { "name": { "family": "Maxson", "given": "John Haviland" }, "id": "Maxson-John-Haviland", "display_name": "Maxson, John Haviland" } ], "advisors": [ { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "advisor", "display_name": "Buwalda, John P." } ], "option_major": [ "geol" ], "doi": "10.7907/D9XJ-NG92", "abstract": "The results of the research in the western Siskiyou Mountains may be grouped in three principal categories, all of which represent original investigation. The first category deals with the land forms or physiography. Three distinct provinces, the coastal belt, the Klamath oldland, and the Siskiyou upland, are herein described in detail. The coastal province near the California-Oregon line exemplifies emergence and in this process the large terrace, on which Crescent City is situated, was formed. The Klamath oldland, a sub-aerial erosion surface, is found to have been developed in late Pliocene time and later uplifted 1000 to 3000 feet. The Siskiyou upland is fretted with mountain peaks of igneous rocks and has been subjected to Pleistocene glaciation.
\r\nThe second phase of the study, stratigraphy (and petrology) was concerned with the physical characters of the rocks exposed and with defining their position in the geologic sequence of the northwestern Klamath Mountains.
\r\nThe third major problem attacked is the crustal structure of this mountainous region. The principal fault, known as the Orleans fault, is reverse in nature and of large throw. By movement along it the Siskiyou upland has been lifted above the Klamath oldland to the west. The Crescent City fault has outlined the coastal pattern south of that community. By displacement on it the Crescent City terrace has been depressed with respect to the Klamath oldland to the east. The results of folding, intrusion, metamorphism, and faulting give eloquent witness to Klamath Mountains orogeny and indicate the circumferential compression of the group.
\r\n" }, { "name": "Nickell, Frank Andrew", "degree": "PhD", "year": "1931", "title": "Geology of the Soledad Quadrangle, Central California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:03072018-153445958", "creators": [ { "name": { "family": "Nickell", "given": "Frank Andrew" }, "id": "Nickell-Frank-Andrew", "display_name": "Nickell, Frank Andrew" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/03ZT-A232", "abstract": "The area studied is located in the central Coast Ranges of California and about 40 miles inland southeast of Monterey on the Pacific coast. It is nearly 100 miles south of San Francisco. It includes portions of the Santa Lucia and Gabilan Ranges and of the intervening Salinas valley.
\r\nThe pre-Cretaceous basement is divisible into three units, the Santa Lucia granite, the Santa Lucia quartz diorite series, which is the latest intrusive, and the Sur Series (?) of metamorphics. Tertiary and Quaternary formations are found within the Salinas valley and chiefly along the western side. The aggregate thickness of middle Miocene, Pliocene, and Quaternary rocks is approximately 12,000 feet. Pre-Quaternary formations are folded into a composite syncline.
\r\n\r\nFaulting occurred in both the Pliocene and the Pleistocene. In the Pliocene the sediments west of the valley were folded and overthrust. Compressive forces acted from the south and west.
\r\n\r\nThe early Pleistocene normal faulting along northwest lines divided the area into two blocks, the Gabilan block southwestward, interrupted the Pleistocene cycle of erosion which had produced the Salinas old age surface, and tilted the King City block towards the west. The displacement of about 4000 feet formed a scarp now somewhat dissected along the western side of the Salinas valley. At the same time movement occurred along several other normal faults within the blocks.
\r\n" }, { "name": "Stanton, William Layton", "degree": "PhD", "year": "1931", "title": "Geology of the Adelaida Quadrangle, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-09192006-085058", "creators": [ { "name": { "family": "Stanton", "given": "William Layton" }, "id": "Stanton-William-Layton", "display_name": "Stanton, William Layton" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/DQ65-ZK26", "abstract": "This geological investigation covers an area lying across the southern Santa Lucia Mountains in south central California, immediately west of Paso Robles.
\r\n\r\nThe land forms of this region are due to structurally controlled erosion which, in most localities, has now produced late mature physiographic surfaces. There are evidences of a Pliocene peneplain, a Pleistocene late mature surface, and vigorous erosion in the present cycle.
\r\n\r\nThe sedimentary series, with an aggregate thickness of over 20,000 feet, includes the Franciscan, Knoxville, Chico, Monterey (Vaqueros and Salinas), Santa Margarita and Paso Robles formations. The sediments cover approximately nine-tenths of the area and are all marine in origin except the Paso Robles. Invertebrate fossils, including a large foraminiferal fauna, were found in the Monterey and Santa Margarita beds, but the other sediments yielded practically nothing.
\r\n\r\nIgneous rocks include periodotite altered to serpentine, granite, rhyolite, diabase, granodiorite, dacite porphyry and many basic dikes.
\r\n\r\nAll structural lines trend northwest-southeast, paralleling the Santa Lucia Range. Three major fault zones cross the area. They are: normal faults on the west side of the range, vertical ? faults, with predominantly horizontal displacement, just east of the range, and thrust faults in the northeast part of the quadrangle. Compression toward the northeast has caused folding, faulting, and perhaps the differential movement of blocks. Faulting is the controlling factor in the structure. A tectonic relationship between the Pacific Ocean Basin, the California Coast Ranges, the Sierra Nevadas, the Great Basin Region, the Rocky Mountains and the Mississippi Valley is suggested.
\r\n\r\nEarly Pliocene deformation formed a range of mountains which were eroded to a peneplain, and later uplift (in two stages) due to faulting produced the masses from which our present mountains have been carved.
\r\n\r\nQuicksilver, in this area always associated with faults and serpentine, is the most important economic mineral product.
\r\n\r\nThe ore occurs in silicified and calcitized rock or in sandstone. Other mineral resources of possible economic interest are petroleum, flagstones, lime, asbestos, and chromite.
" }, { "name": "Gazin, Charles Lewis", "degree": "PhD", "year": "1930", "title": "Geology of the Central Portion of the Mount Pinos Quadrangle, Ventura and Kern Counties, Southern California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:12042009-113314756", "creators": [ { "name": { "family": "Gazin", "given": "Charles Lewis" }, "id": "Gazin-Charles-Lewis", "display_name": "Gazin, Charles Lewis" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/9ZJT-X166", "abstract": "The central portion of the Mount Pinos quadrangle lies principally in northern Ventura County and includes a small district in the adjacent part of Kern County. The rocks within the area mapped are of pre-Cretaceous, Cretaceous (?), Eocene, Miocence, and Quarternary ages.
\r\n\r\nThe oldest rocks consist of metamorphosed sediments, prinicipally calcareous; quartz, diorite porphyry; and granitic gneiss and schist. The Cretaceous (?) and Eocene have not been differentiated and only the latter has been definitely recognized; the combined thickness exposed approaches 15,000 feet. The Miocene rocks are predominantly marine west of the Cuyama River, but to the east a very thick section of terrestial deposits has accumulated, extending into Lockwood Basin, and perhaps farther. These strata are strikingly colored and give rise to an extensive area of badlands.
\r\n\r\nThe structure of the western part of the area is characterized by numerous folds and occasional faults; both have roughly a N.W.W. trend. In the eastern portion or Lockwood Basin the deformation is more acute and faulting has played a larger part. The majority of the structural features in this eastern region strike northeasterly and are of a compressional nature, although normal faulting also occurs. Transverse to the prevalent strike in Lockwood Valley, and at least in part of later origin, is a group of faults which have had dominantly horizontal movement. The San Andreas Rift, extending across the northeastern corner of the area, is the major feature in the latter group.
\r\n\r\nFrom an economic standpoint this area is of historic interest, as one of the early discoveries of gold in California was made in or near San Guillermo Creek, and the colemanite deposits in Lockwood Valley played an important part in the early borax mining of the State.
\r\n" }, { "name": "Lupher, Ralph Leonard", "degree": "PhD", "year": "1930", "title": "Stratigraphy and Correlation of the Marine Jurassic Deposits of Central Oregon", "advisor": "Woodring, Wendell P.; Buwalda, John P.; Packard, Earl L.", "url": "https://resolver.caltech.edu/CaltechETD:etd-08312007-083608", "creators": [ { "name": { "family": "Lupher", "given": "Ralph Leonard" }, "id": "Lupher-Ralph-Leonard", "display_name": "Lupher, Ralph Leonard" } ], "advisors": [ { "name": { "family": "Woodring", "given": "Wendell P." }, "id": "Woodring-W-P", "role": "advisor", "display_name": "Woodring, Wendell P." }, { "name": { "family": "Buwalda", "given": "John P." }, "id": "Buwalda-J-P", "role": "co-advisor", "display_name": "Buwalda, John P." }, { "name": { "family": "Packard", "given": "Earl L." }, "id": "Packard-E-L", "role": "co-advisor", "display_name": "Packard, Earl L." } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/3VH7-2N32", "abstract": "Marine Jurassic rocks occupy an area of more than 200 square miles in the pre-Tertiary area of Central Oregon. Eight formations are recognized in a series that ranges in age from the middle Lias to the Callovian of the upper Jura. The faunas are grouped into four chronologic divisions which are not coincident with the stratigraphi divisions. The two sets of divisions may be compared in the following manner: [See Abstract in PDF for more information].\r\n\r\n\r\n\r\n" }, { "name": "Moore, Bernard Nettleton", "degree": "PhD", "year": "1930", "title": "Geology of the Southern Santa Ana Mountains, Orange County, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-02122007-142830", "creators": [ { "name": { "family": "Moore", "given": "Bernard Nettleton" }, "id": "Moore-Bernard-Nettleton", "display_name": "Moore, Bernard Nettleton" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/Q2EK-VB06", "abstract": "The area studied lies on the southwestern slope of the Santa Ana Mountains in the southeastern quarter of the Corona Quadrangle.
\r\n\r\nThe oldest rocks are a series of slates and sandstones with some lenses of limestone and intruded by andesite porphyry dikes. Unconformably overlying the slates is a coarse conglomerate and in part of the area a series of basic lavas and tuffs. All these rocks have been metamorphosed by andesite granodiorite and diabase intrusions. Triassic fossils have been reported from the slates. The rocks overlying the \"basement complex\" constitute a westward dipping homocline, including upper Cretaceous. Paleocene, and middle Eocene formations, the Vaqueros and Topanga formations, the Puente shales, and the Capistrano formation, each of which is bounded by an unconformity or disconformity.
\r\n\r\nThe structure is unusual in that, while the sediments are those typical of the Coast Ranges, the mountains are a tilted fault block, uplift taking place along the Elsinore fault system. The detailed structure consists of a few folds and faults not aligned with the Elsinore system.
\r\n\r\nThe physiographic history shows a long series of repeated uplifts. Some of the lower terraces are marine. In the evolution of the present topography the resistance of the rocks has played a large part.
" } ]