Contact costa@ig.utexas.edu for a link to join the live talk.

Speaker: Surui Xie, Scripps Institution of Oceanography, UC San Diego

Host: Shuoshuo Han
 
Title: Geodesy at The Land Margins: Challenging yet Rewarding

Abstract: High precision space geodetic techniques have been widely used in measuring Earth changes due to slow or rapid processes. While they continue to provide important observations for a variety of geophysical studies, technical limitations have hampered their applicability in monitoring several key Earth processes in critical zones, such as tidal-timescale or shorter timescale variations of the outlet glaciers and mélange in the polar regions, as well as strain accumulation and release processes in the offshore portion of subduction zones. Continued development of terrestrial and marine geodetic techniques can overcome some of the difficulties and thus complement existing methods. However, they can be technically challenging. In this talk I will present several examples of space, terrestrial, and marine geodetic techniques in observing some key Earth processes at the marginal zones, including: 1) observing marine-terminating glacier and mélange motion in Greenland with terrestrial radar interferometry; 2) measuring subduction zone interface locking and transient events with GPS; and 3) shallow water seafloor motion and water level monitoring with a GPS spar-buoy.

(This talk was rescheduled from Tuesday, February 16, 2021)

Contact nmccall@utexas.edu for a link to join the live talk. 

Speaker: Zachary Sickmann, Postdoctoral Fellow, UTIG

Title: Thinking about sand mining from source to sink

Contact costa@ig.utexas.edu for a link to join the live talk.

Speaker: Benjamin Keisling, Lamont-Doherty Earth Observatory, Columbia University

Host: Tim Goudge

Contact costa@ig.utexas.edu for a link to join the live talk.

Speaker: Xiaohua Xu, Scripps Institution of Oceanography, UC San Diego

Host: Harm Van Avendonk

Title: Probing Earth’s Shallow Crust with Space Geodesy

Abstract: Contemporary earthquake hazard models hinge on an understanding of how strain is distributed in the crust and the ability to precisely image the earthquake rupture. The development in these fields is driven by the newer generation of space geodetic tools. In this presentation, I'll be focusing on the shallow most part of the Earth’s crust, and bridge the mechanisms of reduced shallow rupture (shallow slip deficit) with the widely distributed shallow faulting. I show that a large part of the shallow slip deficit is due to incomplete data coverage near the fault when combined with a regularized inversion, and thus the associated seismic hazard may have been underestimated. Thus, near-fault geodetic observations are indispensable to fully image large strike-slip events. I’ll then present our newest findings associated with the 2019 Ridgecrest earthquake sequence, where we found numerous previously unmapped strain concentrations (fractures) with an InSAR phase-gradient technique. Most fractures are displaced in the direction of tectonic stress (prograde), while a number of them are displaced in the opposite direction (retrograde). Our analysis shows that both types of fractures are caused by the stress change from the main rupture – prograde fractures are triggered slip while retrograde fractures are strain concentrations in a weak compliant fault zone. The different mechanisms can be understood if the shallow part of the faults are always critically stressed. And a major implication is that shallow tectonic strain is widely distributed in diffuse strike-slip areas like the Mojave shear zone, which also explains the larger deficit in the shallow earthquake ruptures near Ridgecrest.

(This talk rescheduled from March 5)


Contact costa@ig.utexas.edu for a link to join the live talk.

Speaker: Tian Dong, Department of Geological Sciences, UT Jackson School of Geosciences

Host: John Goff

(This talk was rescheduled from Friday, February 19, 2021)

Contact costa@ig.utexas.edu for a link to join the live talk.

Speaker: Jessie Pearl, United States Geological Survey

Host: Chris Lowery

Title: Multiproxy reconstructions of late Holocene coastal climate and extreme events

Abstract: The densely populated coastlines of the United States face unique natural hazards and are at the forefront of global change phenomena, and including sea level rise, rising global temperatures, changing storm frequency and intensity, and growing anthropogenic pressures. Adaptation to, and mitigation of, the impacts of these phenomena rely on extensive and accurate records of coastal stressors and an understanding of their secondary ecological effects. Instrumental data of physical and biological changes along the coast extend, at best, about 120 years and are usually much shorter. Thus, longer high-resolution records of coastal phenomena are essential to determine the potential range and return interval of storms, floods, droughts, and earthquakes. Multi-centennial to multi-millennial length tree-ring records are annually-resolved proxies for environmental change that fill these critical data gaps. These records ultimately improve coastal management and hazard planning, as well as detect and attribute trends in regional climate phenomena. Using climate field reconstructions, a network of subfossil 'drowned' forests and co-located sediment records, radiocarbon, and paleoecology studies I show how we can date and characterize both long term trends and punctuated extreme events along the northeast and northwestern coastlines of the United States.

Contact costa@ig.utexas.edu for a link to join the live talk.

Speaker: Ram Tuvi, Postdoctoral Fellow, UTIG

Host: Zeyu Zhao

Research Areas: Computational geophysics, seismic tomography, and beam-wave processing