EGU2020-11594, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-11594
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Imaging the poro-elastic properties of glacier beds using ambient seismic noise monitoring : application to Whillans ice stream, Antarctica

Aurélien Mordret1, Gauthier Guerin2, Diane Rivet2, Brad Lipovsky3, and Brent Minchew4
Aurélien Mordret et al.
  • 1ISTerre,UGA, Grenoble, France
  • 2Géoazur, Nice Sophia Antipolis, Nice, France
  • 3EPS, Harvard University, Cambridge, USA
  • 4EAPS, MIT, Cambridge, USA

Part of the movement that occurs on all glaciers in Antarctica is a continuous and stable movement that unloads the ice into the sea. The Whillans Ice Plain (WIP) is a portion of the Whillans ice stream that measures 8000 km² for an ice thickness of 800 meters. This glacier has a unique characteristic of moving thanks to tidally modulated stick-slip events twice a day. The slip speed varies laterally across the glacier.  We measured surface wave velocity variations computed from ambient seismic noise cross-correlation. The cross-correlations make it possible to monitor temporally and spatially the seismic velocities at the bed of the glacier, associated with changes in poro-elastic parameters and frictional properties of the glacial till. We averaged our observations for the 78 stick-slip events of our dataset and managed to achieve a 5 min temporal resolution along the 45 min long slip events. The results show a decrease in velocity of about 9% of the S-wave velocity in the subglacial sediment layer about 30 minutes after the initiation of the slip. This velocity drop mainly affects the central part of the glacier. A 10% increase in porosity could induce this velocity decrease due to dilatancy. Dilatant strengthening results from this porosity increase, which in turn keeps the glacier in a slow-sliding regime. The high rate of seismic cycles on such a large scale makes the Whillans ice stream a unique laboratory to study transient aseismic slips in glacial context but also in active tectonic faults one. 

How to cite: Mordret, A., Guerin, G., Rivet, D., Lipovsky, B., and Minchew, B.: Imaging the poro-elastic properties of glacier beds using ambient seismic noise monitoring : application to Whillans ice stream, Antarctica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11594, https://doi.org/10.5194/egusphere-egu2020-11594, 2020

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