Geophysics

A Bumpy Ride After Deicing

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Science  09 Mar 2001:
Vol. 291, Issue 5510, pp. 1861
DOI: 10.1126/science.291.5510.1861d

Several large and enigmatic earthquakes have occurred in the interior of tectonic plates, far from stresses that arise at the boundaries between plates. In some cases—particularly in Scandanavia and perhaps the recent earthquake in Antarctica—such intraplate seismicity has been related to the stress induced by unloading the crust after the melting of large ice sheets (deglaciation also has been linked, tentatively, to increased volcanic activity in some areas). Whether this process would produce earthquakes in areas not covered by the great ice sheets has been more difficult to discern.

Grollimund and Zoback now suggest that this process was responsible for seismicity at the New Madrid (Missouri) seismic zone, which was south of the Laurentide Ice Sheet. Although seismicity seems to begin in the region around the time of deglaciation, previous work had concluded that the stresses induced by melting glaciers to the north were too low. By modeling the bending of the lithosphere, the authors suggest that deglaciation increased seismicity by a factor of about three in the region and that the high seismicity should continue in the region for the next few thousand years. — BH

Geology29, 175 (2001).

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