Shackleton Centenary Expedition

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Antarctic Earthquakes

http://www.shackletoncentenary.org/antarctica/antarctic-earthquakes-1.php

sticky spot.jpg

Satellite imagery shows the "sticky spot" which holds the ice back (ice rise "a"); red dots indicate two GPS stations (Image: Douglas Wiens et al)

In the past few years, researchers have noticed that glaciers around the world seem to produce seismic waves that can appear to observers like large earthquakes. The waves generated in Antarctica can be picked up as far away as Australia, but until now no-one has been able to determine their cause.

Between 2001 and 2003, 43 seismographs were peppered across the continent and revealed twice daily seismic waves originating from the Whillans Ice Stream - a river of ice, some 600 metres thick.

It appears that the ice river gets stuck on its slow way downstream and the tide releases it. This is similar to geologic faults, where the two sides of the fault are pushing past each other but friction holds them back. Eventually the pressure becomes so great that the fault slips, triggering an earthquake.

In terms of the energy released by the slip, each glacial quake is the equivalent of a magnitude-7 earthquake.

To find out Douglas Wiens of Washington University, St Louis, US, and his colleagues' hypothesis as to why this happens, or to read more about it, here's the article at the New Scientist.

Posted by Tim Fright on June 7, 2008 1:53 PM