EPSS Colloquium - fall-2024
Towards developing a new microphysical model for rock rheology : Integrating acoustic data and thermodynamic constraints
Oct. 1, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Tushar Mittal - Penn State University
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Generalized constitutive models are crucial for understanding various solid Earth problems ranging from volcano-magmatic systems, tectonics, subduction zones, and landslides. Despite the development of various theoretical models with damage, laboratory validation remains a significant challenge due to the difficulty in representing the damage state evolution. In this talk, I will present a new framework to address this challenge by incorporating energy conservation laws from Thermodynamics of Irreversible Processes (TIP) into a TIP-informed-Neural Network architecture along with seismic/acoustic waveform features (TIP-INN). The talk will focus on two primary set of results : (a) ) Unsupervised feature selection in acoustic waveforms --Can features in the micro EQs as well as active source coda waveform determine the stress-strain quantitatively? Using acoustic data for Carrara marble spanning the brittle-ductile transition and dimensionality reduction methods, such as UMAP (Uniform Manifold Projection), we show that the acoustics have distinct diagnostic features related to the stress-strain-damage state of the system; (B) Theoretical framework for TIP-INN - I will describe the theoretical framework underlying the constitutive modeling and also present results for a new general TIP-based forward rheology solver that we have developed for thermo-visco-elastic material models (with multiple damage internal parameters). Finally, I will present some present preliminary results towards development of the full TIP-INN model framework including out new Neural network architecture to implement TIP-INN.
Hot Springs as Windows into Subsurface Interactions between Biology and Deeply-Derived Volatile Elements
Oct. 8, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Karen Lloyd - Wrigley Chair in Environmental Studies, Professor of Earth Sciences, USC Dornsife
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Earth’s subsurface comprises one of its largest biospheres, containing 10^29 living microbial cells. These organisms depend on deeply derived volatiles to gain energy and biomass. In turn, they alter those volatiles and minerals around them. Studying this biosphere is challenging because boreholes are expensive and offer only limited spatial coverage. We, therefore, use deeply-derived hot spring fluids to passively sample subsurface communities across large geological provinces. With these samples, we are able to reconstruct landscape-scale effects of geologically-derived volatiles on microbial communities, as well as the effects those communities have on the surrounding geology. Please sign up here to meet with the speaker.: https://docs.google.com/spreadsheets/d/19qJnNnQt0_AfJ-os6bWogCyG4014fANXL5n8pK6FARc/edit?gid=0#gid=0
Let there Be Light: The Earliest Galaxies, The Growth of Magnetic Fields and the Fine Structure Constant
Oct. 15, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Ranga Ram Chary - Executive Director, UCLA Space Institute
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The Universe is 13.8 billion years old. Within a few 100 million years of the beginning of time, the first galaxies formed, which radiated the Universe with a sea of ultraviolet photons and triggered the transition of the Universe from a neutral medium to an ionized medium. For decades, we have been using the imaging capabilities of the Hubble and Spitzer space telescope to identify and characterize these distant galaxies. Now, with the power of spectroscopy with the James Webb Space Telescope we are able to measure key diagnostic emission lines which provides insights into the nature of stars which power these galaxies, the properties of the interstellar medium therein and allows new constraints on the evolution of the fine structure constant. I will present advances in our knowledge of these topics.
3D Models and Solutions to the Equations of Motion of Jupiter's Great Red Spot
Oct. 22, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Phil Marcus - Tien-Modak Chancellor's Chair Director, Center for Integrative Planetary Science UC Berkeley
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Ever since the Voyager fly-bys in the late1970’s, there have been models and 2D numerical simulations of the Great Red Spot (GRS). Although much has been learned from these studies about vortices embedded in east-west, zone-belt flows, it has never been clear how much of the physics in these studies is applicable to the 3D, stratified and convective Jovian atmosphere. (After all, in 2D, the patterns of a flow’s streamlines are extremely limited in their possible appearances and always tend to look like vortices in zonal flows – just like the grain and knot-hole patterns in a piece of plywood.) Here, we present well-resolved solutions to the equations of motion in a realistic Jovian atmosphere (equivalent to 6000 X 6000 X 6000 finite difference points). We also present a simple analytic model based on the solutions that explain most features of the numerical solutions. The solutions to the equations of motion are not unique, and we found that a wide range of vortices with different strengths, vertical thicknesses, and depths, and with different heights of the Jovian convection zone can quantitatively reproduce Hubble Space Telescope (HST) observations of the GRS wind field, including the fact that its center is quiet with almost no vorticity. However, when the solutions are also constrained to agree with recent temperature observations from the James Webb Space Telescope (JWST), the possible range of stable vortices that agree with the HST winds are severely reduced, and in fact, are nearly unique. The calculations give specific heights for the bottom, top, and middle of the Great Red Spot with little freedom for changes in these heights without the simulation becoming unstable or differing qualitatively from the temperature observations. Although our numerical simulation was constrained to agree with the observations of the HST winds and the JWST temperatures, it also agrees with winds measured by JWST, and the temperatures and gravity anomaly observed by Juno, which measure dynamics in the lower part of the GRS.
The redox state of ocean island basalts
Oct. 29, 2024
3:30 p.m. - 4:30 p.m.
Slichter 3853
Presented By:
- Maryjo Brounce - Associate Professor, UC Riverside
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Ocean island basalts (OIBs) have more variable Fe3+/ΣFe than mid-ocean ridge basalts (MORBs). This is partly because OIB magmas undergo greater extents of differentiation than MORB magmas, e.g., S degassing in OIB magmas can decrease Fe3+/ΣFe in residual magmas, generating suites of lavas that range widely in S and Fe3+/ΣFe; MORBs are relatively undegassed with respect to S, resulting in narrower ranges in Fe3+/ΣFe. However, even the least differentiated OIB at each location vary in Fe3+/ΣFe: >0.30 in HIMU-like glasses from Erebus, the Canary Islands; ~0.20 in EM1-like glasses from Iceland, Hawaii; ~0.16 in FOZO-like glasses from Reunion. It is unclear if this variability is linked to redox heterogeneity in the mantle sources of OIB, in part because high precision Fe3+/ΣFe measurements on magmas derived from mantle isotopic endmembers lack high precision Fe3+/ΣFe constraints. We present Fe3+/ΣFe ratios (XANES) measured in a suite of submarine glasses from the Galapagos Archipelago. These samples are associated with the Galapagos plume and have 3He/4He that range from MORB-like (~7-8 Ra) to values that approach the FOZO endmember (~29 Ra) more closely than previously XANESed OIB. From our new measurements, we infer that FOZO component sampled by the Galapagos has similar redox characteristics as DMM, consistent with recent results from Reunion Island. These results emphasize: not all isotopically distinct mantle reservoirs are more oxidized than DMM. This supports the interpretation that the EM1 component present in Iceland and Hawaii lavas is oxidized relative to DMM, contributing the oxidized nature of Laki and Mauna Kea lavas, and that the production of oxidized basalts on Earth is fundamentally tied to plate tectonics and the H2O- and O2-rich conditions at Earth’s surface
Diamond-forming fluids – the next frontier
Nov. 5, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Yaakov Weiss - Hebrew University of Jerusalem
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High-density fluid (HDF) microinclusions in diamonds carry chemical fingerprints that provide the opportunity to directly examine the nature of carbon- and water-rich media in the deep Earth. Radiogenic isotope compositions, which preserve their signature during mantle processes such as melting and immiscible separation, are an important tool in tracing mantle sources. A new off-line ‘diamond-in-water’ ablation technique using a ‘powerful laser’ combined with high-precision TIMS analyses provides the means to determine the Sr-Nd-Pb isotope compositions of HDFs. The compositional variations of a suite of diamonds from South Africa largely overlap the isotopic spectrum of the sub-continental lithospheric mantle as inferred by global whole rock xenolith data from cratons. In addition, the calculated Nd model ages (TDM) of the analyzed samples span a wide range, between 0.2 to 3 Ga. Combining the Sr-Nd-Pb isotope compositions with previously published data for the analyzed diamonds reveals their sources and ages. For example, saline HDFs record an isotopic signature for the involvement of three components – an LREE-enriched Archaean lithosphere that has lost its U and Th, and subducting surface material that includes both recent sediments and a mantle-like component (i.e. subducting slab). Ideally, such data from different lithospheric provinces globally can be used to unravel the metasomatic history of continental lithospheres and constrain the timing and the varying origins of HDFs in the context of large-scale tectonic processes.
Debris Rings from Extrasolar Irregular Satellites
Nov. 12, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Kevin Hayakawa - California State University Channel Islands
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Irregular satellites are the minor bodies found orbiting all four Solar System giant planets, with large semi-major axes, eccentricities, and inclinations. Previous studies have determined that the Solar System's irregular satellites are extremely collisionally evolved populations today, having lost ∼99 per cent of their initial mass over the course of hundreds of Myr. Such an evolution implies that the irregular satellites must have produced a population of dusty collisional debris in the past, which is potentially observable due to the resulting reprocessing of stellar light. In this paper we examine the signatures of the debris discs produced by extrasolar analogues of this process. Radiation pressure, quantified by the parameter β, is the driving force behind the liberation of dust grains from the planetary Hill sphere, and results in the formation of circumstellar dust rings, even in the absence of an underlying belt of asteroids in the system. Our simulated discs reproduce many of the same features seen in some classes of observed debris discs, such as thin ring morphology, a large blowout size, and azimuthal symmetry. We compare our simulated discs' radial profiles to those of the narrow dust rings observed around Fomalhaut and HR 4796A, and show that they can broadly reproduce the observed radial distribution of dust.
Unraveling Earthquake cascades across scales using supercomputing
Nov. 19, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Alice Gabriel - Institute of Geophysics and Planetary Physics, UCSD
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Earthquakes vary in size, with the largest and most complex also being the most dangerous. Recent, major earthquakes such as the 2019 Ridgecrest, CA, and 2023 Kahranmaras, Turkey, earthquakes exhibited seemingly unexpected rupture dynamics that challenge conventional approaches to seismic hazard assessment and raising fundamental questions on earthquake mechanics, including on the driving factors of cascading dynamic rupture behaviour and how faults ‘talk to each other’ across patio-temporal scales. Supercomputing empowered earthquake simulations can help bridge vast space- and time-scales and interdisciplinary boundaries, but require revisiting common scaling assumptions of earthquake physics. Despite the large number of observed small earthquakes, the scaling of the earthquake energy budget, governing all aspects of earthquake dynamic rupture, remains enigmatic. One challenge is trying to figure out whether the information gleaned from smaller events can simply be scaled up to understand larger events. We propose that small and large earthquakes don’t play by the same rules and that fundamentally different fracture processes govern small and large earthquakes. By combining real-world earthquake measurements, key updates to mathematical models describing earthquake behavior and 3D simulations using supercomputers, we developed a unified theory capable of explaining minor jolts and destructive quakes involving multiple faults. We suggest that the physics governing the behavior of small and large earthquakes are distinct from one another. Our findings could have implications for understanding how earthquakes start and cascade into big seismic events, and ultimately aid in disaster preparedness.
The Mongolian Orocline and the closure of the Mongol-Okhotsk Ocean
Nov. 26, 2024
3:30 p.m. - 4:30 p.m.
Slichter Hall # 3853
Presented By:
- Susana Henriquez - CSU San Bernardino
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The closure of the Mongol Okhotsk Ocean (MOO) marks the final amalgamation of the Central Asian Orogenic Belt, the largest accretionary belt on Earth. This ocean closure formed the Mongol Okhotsk Belt, an orogen over 3,000 km long that extends from central Mongolia to the Sea of Okhotsk. The closure of the MOO in the western end is related to the growth of the Mongolian Orocline, a secondary orocline that buckled the lithosphere by bending an accretionary margin. Unraveling the upper plate response to the growth of the orocline and the eastward closure of the ocean is key to understanding the evolution of the collisional processes in accretionary belts. This contribution uses the sedimentary and geochemical record to constrain the growth of the Mongolian Orocline. Preliminary results for the chemical Moho suggest that the orocline experienced crustal thickening from the Late Triassic to Jurassic while sedimentary data record the exhumation of the Mongolian Orocline during the early Late Triassic. Thus, this analysis suggests that the western Mongol-Okhotsk Belt experienced crustal thickening, exhumation, and presumably shortening during the Late Triassic as the Mongolian Orocline grew within the Central Asian Orogenic Belt.
Let's Go Fishing: Early Earth Discoveries by Pure Exploration in the Slave Craton and Paths Forward
Dec. 3, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Jesse Reimink - Department of Geology, Penn State University
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Many Archean cratons are exposed in regions where traditional geological mapping is difficult or prohibitively expensive. For instance, large tracts of the very remote Canadian Territories (NWT, Nunavut) are underlaid by Archean rocks, while similarly difficult-to-explore jungle terrain in South America also contains ancient crustal blocks. Meanwhile, much of the early Earth rock record (>2.8 Ga) comprises complexly layered, poly-deformed basement gneisses where each outcrop can contain rocks formed >1 Ga apart, making geologic mapping a time-intensive process. Continued scientific discovery in these regions can certainly be achieved by clear, fundable, hypothesis-driven scientific approaches. However, given that basic geological information such as the average age of a crustal block is not available in many areas, fundable hypotheses are not easily generated, and instead pure exploration is needed. In this talk I highlight several recent discoveries we have made in a relatively unexplored region of Nunavut, discoveries that were made by pure exploration and serendipity, but have outsized scientific implications. For instance, our work on >2.8 Ga detrital diamonds clearly indicateds that subduction-like processes formed ancient lithosphere in this region, and new discoveries of 3.8 Ga rocks show that more extremely old crust is yet to be discovered on Earth. I will also highlight methods that may prove useful for geological exploration in remote regions, including those developed in mineral exploration science such as detrital mineral tracing in esker sediments.