EGU23-16308, updated on 09 Dec 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Thwaites Glacier Eastern Shear Margin: Insights from two broadband seismic arrays

Emma C. Smith1, Marianne Karplus2, Jake Walter3, Nori Nakata4, Adam D. Booth1, Lucia Gonzalez2, Andrew Pretorius1, Ronan Agnew1, Stephen Veitch2, Eliza J. Dawson5, Daniel May5, Paul Summers5, Tun Jan Young6, Poul Christoffersen6, and Slawek Tulaczyk7
Emma C. Smith et al.
  • 1University of Leeds, School of Earth and Environment, Leeds, UK
  • 2University of Texas at El Paso, Department of Earth, Environmental, and Resource Sciences, El Paso, Texas, USA 
  • 3University of Oklahoma, School of Geosciences, Oklahoma City, Oklahoma, USA
  • 4Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Boston, MA, USA
  • 5Stanford University, Department of Geophysics, Stanford, California, USA
  • 6Scott Polar Research Institute, University of Cambridge, Cambridge, UK
  • 7University of California Santa Cruz, Earth & Planetary Sciences Department, Santa Cruz, California, USA

The stability of Thwaites Glacier, the second largest marine ice stream in West Antarctica, is a major source of uncertainty in future predictions of global sea level rise. Critical to understanding the stability of Thwaites Glacier, is understanding the dynamics of the shear margins, which provide important lateral resistance that counters basal weakening associated with ice flow acceleration and forcing at the grounding line. The eastern shear margin is of interest, as it is poorly topographically constrained, meaning it could migrate rapidly, causing further ice flow acceleration and drawing a larger volume of ice into the fast-flowing ice stream. 

We present initial insights from a 2-year-long seismic record, from two broadband seismic arrays each with 7 stations, deployed across the eastern shear margin of Thwaites Glacier. We have applied a variety of processing methods to these data to detect and locate icequakes from different origins and analyse them in the context of shear-margin dynamics. Preliminary results suggest there is basal seismicity concentrated near the ice-bed interface on the slow-moving side of the margin, as opposed to within the ice-stream itself. Some of the identified seismic events appear to exhibit clear shear-wave splitting, suggesting a strong anisotropy in the ice, which would be consistent with polarization observed in recently published radar studies from the field site. Further analysis of the split shear-waves will allow us to better constrain the region's ice-fabric, infer past shear-margin location, and assess the future stability of this ice rheology.  

With such a large quantity of data, manual event identification is unpractical, and hence we are employing machine-learning approaches to identify and locate icequakes of interest in these data. Our results and forthcoming results from upcoming active-seismic field seasons have important implications for better understanding the stability of glacier and ice stream shear margins. 

How to cite: Smith, E. C., Karplus, M., Walter, J., Nakata, N., Booth, A. D., Gonzalez, L., Pretorius, A., Agnew, R., Veitch, S., Dawson, E. J., May, D., Summers, P., Young, T. J., Christoffersen, P., and Tulaczyk, S.: Thwaites Glacier Eastern Shear Margin: Insights from two broadband seismic arrays, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16308,, 2023.