UTIG Seminar Series: Alex Robel (Caltech)

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Title: A Theory of the Marine-Terminating Glacier Response to Forcing

Abstract: Marine-terminating glaciers in Greenland and Antarctica are currently retreating and thinning. In this talk, I describe a simple dynamical model which accurately emulates the response of marine-terminating glaciers to external forcing simulated in more realistic models. I explain and use the fluctuation-dissipation theorem to understand the transient glacier response to external forcing. This analysis shows that there is a fast time scale of decades to centuries and a slow time scale of millennia that characterize both stationary glacier fluctuations and the non-stationary glacier response to climate forcing on prograde bed slopes. The two time scales are also associated with two different forms of the marine ice sheet instability due to different physical mechanisms. The slow marine ice sheet instability occurs at nearly flat bed slopes and evolves on time scales of hundreds to thousands of years. The fast marine ice sheet instability only occurs on steep retrograde slopes and causes rapid retreat on decadal time scales, similar to what is observed at some glaciers in Greenland and West Antarctica. The sensitivity of glacier thickness and grounding-line position to external forcing depends on the equilibrium glacier state, bed slope and the type of forcing process, in line with recent studies that find a spatially-varying sensitivity of glacier thickness to forcing. The slow marine-terminating glacier response to forcing indicates that current glacier change on prograde bed slopes is likely to continue and accelerate in coming centuries regardless of future climate forcing. I also show that the spread and fat-tail of uncertainty in stochastic ensemble projections of future ice sheet change can be amplified by the marine ice sheet instability. I conclude by discussing how we can interpret observations of marine-terminating glacier change in light of these results and novel ensemble techniques for robustly simulating future ice sheet change.

Learn about Alex Robel

UTIG Host: Ginny Catania

UTIG Brown Bag Talk: Steve Phillips

Informal weekly presentations by UTIG students, researchers. Bring your lunch!

DeFord Lecture: Whitney Behr

UTIG Seminar Series: Zeyu Zhao (UTIG)

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Title: Building velocity models and Imaging subsurface with plane wave data

Abstract: Velocity building and seismic imaging is critical in providing the image of the Earth’s subsurface, and they play important roles in hydrocarbon explorations. Obtaining high resolution images with accurate reflectivities and accurate positions of subsurface structures is the goal for exploration geophysicists. Full waveform inversion (FWI) and reverse time migration (RTM), which seek the solution from the two-way wave equation, can accurately resolve all wavefield propagation phenomena. In geologically complex regions, FWI and RTM have been proven to outperform other inversion methods and imaging methods in correctly revealing the subsurface structures. Here, we introduce a new imaging principle that utilizes plane wave data to obtain subsurface structures. We employ the newly proposed imaging principle in FWI and RTM on plane wave data. Because the propagation of a plane wave obeys the Snell’s law, plane waves with large incident angles at the surface would have relatively shallow penetration depth. We develop a strategy to implement FWI in a layer-stripping fashion. In the proposed FWI, we start the inversion using plane waves that have large incident angles to retrieve velocity information at the top of a model. Plane waves with relatively small incident angles are then included into the inversion process to recover velocities in the deep part of a model. After obtaining a reasonable velocity model, we implement RTM using plane wave data. Because plane waves can be used to image subsurface according to their propagation angles, we propose an imaging method to recover subsurface interfaces with different dip angles. It makes the plane wave RTM a target-oriented seismic imaging method. We show the effectiveness of proposed methods using several numerical examples.

Learn about Zeyu Zaho

UTIG Host: Mrinal Sen

Basin Dynamics Short Course

A free short course for students interested in an oil & gas career.
Jon Rotzien is experienced professional and owner of Basin Dynamics, LLC

Chevron Tailgate

Meet and eat at Chevron sponsored tailgate before the football game vs San Jose State. Kickoff 2:30 p.m.
RSVP required on Career Connections.

BP Info Session

BP conducts all interviews virtually.

Shell Oil Info Session

Shell is in search of remarkable geoscience and engineering students!
Learn about internship & full-time opportunities, hear about the latest Shell innovations & network with Shell staff.

NOTE:LOCATION: Engineering, ECJ 1.202
Corner of San Jacinto & Dean Keeton

UTIG Brown Bag Talk: Ryan T Brown

Informal weekly presentations by UTIG students, researchers. Bring your lunch!

DeFord Lecture: Steve Jacobsen

BHP Billiton Info Session

UTIG Seminar Series: Ikuko Wada (University of Minnesota)

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Title: Mantle wedge flow patterns in subduction zones

Abstract: Subduction zones host a number of important geophysical and geochemical processes, such as earthquakes and arc volcanism. The occurrence of these processes depends strongly on the thermal structure of subduction zones. The pattern of solid-state mantle wedge flow above the subducting slab is an important factor that controls the subduction zone thermal structure. This flow is driven by the motion of the subducting slab and brings in hot mantle from the back-arc region into the sub-arc region, maintaining a high temperature condition required for arc volcanism and promoting dehydration of the subducting slab underneath. In this talk, I will present the results of my past numerical modeling studies, focusing on the trench-ward extent of mantle wedge flow and the effects of slab geometry, oblique subduction, and back-arc thermal structure on three-dimensional mantle wedge flow patterns.

Learn more about Ikuko Wada

UTIG Host: Thorsten Becker

JSG Career Fair & Networking Breakfast

For undergraduate and graduates students of the JSG.
All UT students welcome, but focus is on geoscience careers.

Networking Breakfast:
Students & Employers Welcome 8:00 -9:30 a.m., SAC 2.120
Career Fair opens at 10:00 a.m., SAC 2.410

Dress code for both events: Business Casual

National Geospatial Intelligence Agency Info Session

Chevron Info Session

Nicholas McLean will welcome students to learn about Chevron ETC.

EOG Resources Info Session

UTIG Brown Bag Talk: Laura Wallace

Informal weekly presentations by UTIG students, researchers. Bring your lunch!

Hess Corp. Info Session

DeFord Lecture: Frederik Simons

Apache Corp. Info Session

UTIG Seminar Series: Rob Porritt (UTIG)

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Title: Towards multi-scale seismic imaging of the crust and mantle.

Abstract: Passive-source seismic imaging provides valuable constraints on Earth’s layered structure, relative thermal and compositional anomalies, and deformation and flow field. These constraints are derived from several increasingly well standardized and innovative imaging methods and a growing pool of passive seismic deployments, such as the IRIS GSN, USArray, and Wavefields projects. Here, I present a tour of recent results focusing on Texas, the Gulf Coast, the Eastern North American Margin, and abroad. In Texas, the Llano Uplift and Ouachita-Marathon Front are recognized in continental-scale body-wave and surface-wave imaging. Their underlying mantle structure suggests these surficial features are linked to ongoing mantle processes. Along the Gulf Coast, imaging the entire crustal column has been difficult with passive methods due to the thick low velocity sediments. However, emerging receiver function results indicate a mid-crustal base to the sediments at ~15-20 km depth and locally over-thickened crust in several areas. Ambient noise results for the Eastern North American Margin indicate a structural transition across the passive margin, coincident with gravity and magnetic anomalies. This relatively smooth and simple structure is in marked contrast with the active margin in the Banda arc where the Indian Ocean Plate and Australian Plate collide with the young Banda Plate; this margin is characterized by over-thrusting of shelf deposits and exhumation of subduction assemblages in Timor Leste and eastern Indonesia. The subducting plate in this incidence is shallow in the collisional zone and then dives steeply under the Banda Sea. The fate of this slab is uncertain below the 670km discontinuity, but the interplay of slabs and the mantle transition zone remains an important area of research. This uncertainty is particularly relevant in the Izu-Bonin islands where a M8 class earthquake occurred at 682 km depth. Long period receiver function evidence suggests the base of the slab in this region reaches 690 km depth; while this does maintain that slabs are required for deep earthquakes, it forces questions about how the transition zone can be pushed 20 km deeper than its nominal base. This tour highlights the efficacy of passive seismic tools to fundamental earth science questions. As more data becomes available and new tools are developed, our understanding will improve and new questions will emerge.

Learn more about Rob Porritt

UTIG Host: Thorsten Becker

Schlumberger Info Session

Hilcorp Energy Info Session

Alumni Reception during SEG in Houston

UTIG Brown Bag Talk: Lily Jackson

Informal weekly presentations by UTIG students, researchers. Bring your lunch!

Anadarko Petroleum Info Session

DeFord Lecture: Mark Richards

UTIG Seminar Series: Jingyi "Ann" Chen (UT Austin)

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Title: On the Use of Interferometric Synthetic Aperture Radar (InSAR) for Monitoring the Dynamics of the Changing Earth

Abstract: Interferometric Synthetic Aperture Radar (InSAR) techniques have already become central tools in the crustal deformation community; more recently, advances in InSAR have led to new applications including the analysis of the atmosphere, biosphere, cryosphere, and hydrosphere, as well as their mutual interactions. In this talk, we will discuss two recent advances in InSAR-based earth system applications. The first example is on the use of InSAR for characterizing groundwater levels and aquifer storage properties in confined aquifers over large agricultural basins such as the San Luis Valley, Colorado. With an improved image processing strategy, we revealed the 20-year trends in the temporal and spatial variability of the SLV confined aquifer system by combining L-band and C-band InSAR data from multiple satellite missions. We found very little change in the elastic aquifer storage properties with time, introducing the concept that calibration with a new well in an area would allow for the use of historical InSAR data to obtain head measurements before the time of well constructions. The second example focuses on the use of InSAR for permafrost research. Because the same mass of liquid water takes up less volume than ice, the surface settles as the active layer thaws in summer, with the opposite occurring in the fall. Based on this observation, an Active Layer Thickness (ALT) retrieval algorithm known as ReSALT has been developed and successfully applied to estimate ALT near Prudhoe Bay and Barrow, Alaska, with an uncertainty of ~ 10 cm using InSAR surface deformation data. Given that ReSALT estimates in hilly terrains tend to display a large bias with probing measurements, we have worked with L-band ALOS data near Toolik Lake, Alaska, to identify the dominate error sources in this scenario. Our Toolik results suggest that the InSAR-based ALT retrieval algorithm needs to take into account the impact of topography on the active layer water storage distribution. In addition, we discovered that InSAR observations could be utilized to better characterize the active layer thaw-freeze cycle. We believe that this finding highlights the critical role that InSAR data may play in better understanding the hydrologic state of permafrost terrain in the Arctic.

Learn more about Jingyi "Ann" Chen

UTIG Host: Ginny Catania