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Array-based Characterization of Seismicity from a Glacial Lake Outburst Flood

Description: 

As Earth’s climate warms, it is increasingly important to monitor the dynamic and hydraulic conditions at glaciers, especially those that can generate catastrophic glacial lake outburst floods (GLOF). Gornergletscher is the second largest glacier in the Swiss Alps and for decades has hosted a GLOF event every summer, releasing millions of cubic meters of water on top of, through and underneath the ice in a matter of days [1]. We detect and characterize seismic tremor related to the GLOF event using a five-station Geophone array with an aperture of approximately 400 m installed over a five-week period in shallow boreholes in the glacier within 500 m of the lakefront. We calculate array coherency matrices as a function of frequency and time [2], then apply an unsupervised machine-learning algorithm, SpecUFEx [3], to reduce the array coherency matrices into low-dimensionality based on concurrent lake-level and GPS measurements. Some clusters coincide with the onset of the GLOF, suggesting that our technique could offer a means of detecting outburst floods to complement or replace other observation methods, i.e., in situ lake level measurements. One cluster captures a period of previously discovered harmonic tremor generated from stick-slip events located near the ice-bed interface [4], and other clusters appear to contain times of newly detected harmonic or quasi-harmonic tremor as well. We localize the newly detected tremor near the ice-bed interface, suggesting that stick-slip induced tremor may occur throughout the GLOF event, rather than just on a single day. By combining an array-based approach with unsupervised machine learning, we can characterize glacial tremor to better understand the dynamic behavior of Gornergletscher, especially as it pertains to catastrophic GLOF events.

Works Cited: [1] Huss et al., (2007). Journal of Glaciology [2] Seydoux et al., (2016a) Geophysical Journal International [3] Holtzman et al., (2018). Science Advances [4] Umlauft et al., (2021). Geophysical Research Letters

Session: Applications and Discoveries in Cryoseismology Across Spatial and Temporal Scales [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Theresa

Student Presenter: No

Invited Presentation: 

Authors