Icequakes or earthquakes ? 

Stephen Bannister

Institute of Geological & Nuclear Sciences, PO Box 30-368, Lower Hutt, New 
Zealand


Seismicity levels in Antarctica are generally regarded as low. However, over the 
last 10 years  seismic events have been recorded in several areas, including the 
western Ross Sea region and the Transantarctic Mountains, using temporary array 
deployments and data from permanent stations. Seismic events in Antarctica have 
variously been attributed to icequakes resulting from brittle ice deformation on 
glaciers, calving of icebergs, basal-shearing beneath glaciers, and tectonic 
earthquakes.  One of the challenges for future Antarctic seismo-tectonic work is 
the discrimination between these alternative source mechanisms. Possibilities 
include the use of targeted local array deployments for event depth and focal 
mechanism determination, the examination and classification of signal 
characteristics, and the use of energy ratios and secondary regional phases.


A 10-station broadband seismometer array deployed in the Transantarctic 
 Mountains during the 1999-2000 austral summer recorded 160 seismic events. Of 
these events, about 50% were located to the north of the array, in the vicinity 
of the David Glacier, inland from the Drygalski Ice tongue. These events are 
aligned in a ESE-WNW direction, sub parallel to faults which are postulated to 
lie near to the events, and close to the postulated David glacier lineament. The 
events may be associated with deep-seated faulting along the lineament. However, 
alternative source mechanisms involving ice movement are also possible. Most of 
the remaining events were clustered near the transition between the Mulock 
glacier and the Ross Ice Shelf, just south of the Skelton glacier.