Basal seismicity of the Northeast Greenland Ice Stream

• Published in: Journal of Glaciology
• Main Authors: Ian W. McBrearty, Lucas K. Zoet, Sridhar Anandakrishnan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2020
• Subjects: Seismology; arctic glaciology; glacier mechanics; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Arctic; Greenland; East Greenland; glacier; Journal of Glaciology
• Online Access: https://doi.org/10.1017/jog.2020.17; https://doaj.org/article/0b06d9349dac4191b6c7c6dd6f981527

Seismic studies of glaciers yield insights into spatio-temporal processes within and beneath glaciers on scales relevant to flow and deformation of the ice. These methods enable direct monitoring of the bed in ways that complement other geophysical techniques, such as geodetic or ground penetrating radar observations. In this work, we report on the analysis of passive seismic data collected from the interior of the North East Greenland Ice Stream, the Greenland ice sheet's largest outlet glacier. We record thousands of basal earthquakes, many of which repeat with nearly identical waveforms. We also record many long-duration glacial tremor episodes that migrate across the seismic network with slow velocities (e.g. ~4–12 m s−1). Analysis of the basal earthquakes indicates a transition between times of individual event activity and times of tremor activity. We suggest that both processes are produced by shear slip at localized asperities along the bed. The transition between discrete and quasi-continuous slipping modes may be driven by pore-water pressure transients or heterogeneous strain accumulation in the ice due to strength contrasts of the underlying till.