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Authors: Danesi, S.* 
Bannister, S.* 
Morelli, A.* 
Title: Repeating earthquakes from rupture of an asperity under an Antarctic outlet glacier
Issue Date: 15-Jan-2007
Series/Report no.: 253 (2007)
DOI: 10.1016/j.epsl.2006.10.023
Keywords: Glacial earthquakes
Glacial dynamics
Gutenberg-Richter relationship
Double-difference hypocentre location
Repeating earthquake
Subject Classification04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics 
Abstract: The inner regions of the Antarctic continent are generally regarded as nearly aseismic, although microseismicity is known to occur beneath some outlet ice streams, related to the interaction between the fast flowing ice and the bedrock. Here we show the occurrence of unusual earthquakes beneath an Antarctic outlet glacier that share almost the same magnitude, pointing to the repeated rupture of a single asperity. These seismic events produce waveforms with very high similarity and uncommon spectrum and are tightly clustered in space but, unlike other reported instances of repeating earthquakes on a patch of the San Andreas Fault, they occur in frequent irregular swarms. Evidence locates these events at the rock–ice interface under the glacier, and shows the existence of stick–slip motion on a smaller scale than the large slow slip events detected by global seismographs. Seismic behaviour of large glaciers can presumably be connected to surges in ice motion. This study determines a little known environment for fracture dynamics studies, while also contributing to the understanding of the coupling processes between fast flowing glaciers and bedrock that influence ice stream evolution and stability.
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