Publication Date:
2014-04-04
Description:
The 11 April 2012 M 8.6 Indian Ocean earthquake was an unusually large intraoceanic strike-slip event. For several days, the global M ≥4.5 and M ≥6.5 seismicity rate at remote distances (i.e., thousands of kilometers from the mainshock) was elevated. The strike-slip mainshock appears through its Love waves to have triggered a global burst of strike-slip aftershocks over several days. But the M ≥6.5 rate subsequently dropped to zero for the succeeding 95 days, although the M ≤6.0 global rate was close to background during this period. Such an extended period without an M ≥6.5 event has happened rarely over the past century, and never after a large mainshock. Quiescent periods following previous large ( M ≥8) mainshocks over the past century are either much shorter or begin so long after a given mainshock that no physical interpretation is warranted. The 2012 mainshock is unique in terms of both the short-lived global increase and subsequent long quiescent period. We believe that the two components are linked and interpret this pattern as the product of dynamic stressing of a global system of faults. Transient dynamic stresses can encourage short-term triggering, but, paradoxically, it can also inhibit rupture temporarily until background tectonic loading restores the system to its premainshock stress levels.
Print ISSN:
0037-1106
Electronic ISSN:
1943-3573
Topics:
Geosciences
,
Physics
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