Abstract
Between debris-laden glacial ice and bedrock, basal seismicity can develop that yields information about bed properties1,2, stress distribution3, outburst flooding4, and crevassing and calving5,6,7. Basal seismicity in response to glacial motion is linked to variations in both stress and lubrication of bedrock by water and till8,9. Here we analyse data from the Transantarctic Mountains Seismic Experiment array in 2002–2003 to investigate seismic behaviour at David Glacier, a large outlet glacier that drains 4% of East Antarctica’s ice sheet into the Ross Sea. We identify about 20,000 seismic events that are larger in magnitude and duration than typical for glacial sources and repeat at regular intervals of about 25 min. These events are consistent with stick–slip behaviour of debris-laden ice moving over a single obstacle of rough bedrock, modulated by relatively small stress changes from the ocean tides. In the years before and after the interval of repeating events, seismic events with irregular and generally longer intervals were detected at the same location, and are consistent with combined stick–slip and continuous sliding of the subglacial interface. We suggest that the observed transitions in seismicity patterns capture the dynamic behaviour of the ice stream, and that—despite lower ice-flow velocities—sliding in the stick–slip regime enhances subglacial erosion.
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Acknowledgements
Seismometers were supplied by PASSCAL. Seismic data were obtained from the DATA management Center of the Incorporated Research Institutions for Seismology. This research was financially supported by the Office of Polar Programs, US National Science Foundation (NSF 0424589). Partial support was provided by the US National Science Foundation through grants 0424589, 0538195, 0852697 and 9909603. We thank the TAMSEIS field and planning team for planning and carrying out the TAMSEIS field deployment.
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L.K.Z. located the seismic signals in the seismic records and carried out the seismic processing and modelling. All authors participated in the interpretation of the results and preparing the paper.
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Zoet, L., Anandakrishnan, S., Alley, R. et al. Motion of an Antarctic glacier by repeated tidally modulated earthquakes. Nature Geosci 5, 623–626 (2012). https://doi.org/10.1038/ngeo1555
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DOI: https://doi.org/10.1038/ngeo1555
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