PerspectiveGeophysics

Weak subduction makes great quakes

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Science  11 Sep 2015:
Vol. 349, Issue 6253, pp. 1162-1163
DOI: 10.1126/science.aac9625

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Summary

The world's greatest earthquakes, producing catastrophic shaking and tsunamis, occur in subduction zones. Here oceanic plates dive below adjoining regions along megathrust faults (see the figure). The recent magnitude ~9 megathrust earthquakes in Sumatra, Chile, and Japan, with fault displacements of several tens of meters, were stark reminders of the destructive power of these events. On page 1213 of this issue, Hardebeck (1) uses the orientations of fault planes of thousands of smaller earthquakes near and above the world's megathrusts to evaluate the state of stress driving these great events. The general conclusion made is that all faults in subduction zones, including the megathrusts, are unusually weak.