Geophysics

Tremor Sweet Spots

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Science  10 Jan 2014:
Vol. 343, Issue 6167, pp. 119
DOI: 10.1126/science.343.6167.119-a
CREDIT: © WIEDE, U. & M./ARCO IMAGES GMBH/ALAMY

Seismic tremor is thought to be indicative of the slow release of small amounts of stress along plate boundaries, but it can also be triggered by large-amplitude seismic waves generated during large earthquakes. Gomberg and Prejean determined the distribution of tremor in Alaska after 11 of the largest earthquakes (M < 7.2) around the globe between 2006 and 2012. As in previous observations, triggered tremor in the Aleutian Islands is related to the transition of friction along the subducting plate boundary from a locked state to a creeping state. However, tremor was also triggered in central mainland Alaska—a region far away from the subduction zone and devoid of any major crustal faults or appreciable seismic activity. Because there was no single characteristic of the triggering wave source or tectonic environment associated with the two regions, transient frictional processes at the plate interface may be responsible for tremor triggering. However, according to GPS data, neither zone shows any clear evidence of other concurrent related seismic processes such as slow slip events.

J. Geophys. Res. 118, 10.1002/2013JB010273 (2013).

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