Publication Date:
2014-02-07
Description:
[1] Among the many questions raised by the recent abundance of great (M 〉 8.0) subduction thrust earthquakes is their potential to trigger damaging earthquakes on crustal faults within the overriding plate and beneath many of the world's densely populated urban centers. We take advantage of the coincident abundance of great earthquakes globally and instrumental observations since 1960 to assess this triggering potential by analyzing centroids and focal mechanisms from the CMT catalog for events starting in 1976 and published reports about the M9.5 1960 Chile and M 9.2 1964 Alaska earthquake sequences. We find clear increases in the rates of crustal earthquakes in the overriding plate within days following all subduction thrust earthquakes of M 〉 8.6, within about + 10˚ of the triggering event centroid latitude and longitude. This result is consistent with dynamic triggering of more distant increases of shallow seismicity rates at distances beyond + 10˚ [ Pollitz et al ., 2012], suggesting dynamic triggering may be important within the near-field too. Crustal earthquake rate increases may also follow smaller, M 〉 7.5 subduction thrust events, but because activity typically occurs offshore in the immediately vicinity of the triggering rupture plane it cannot be unambiguously attributed to sources within the overriding plate. These observations are easily explained in the context of existing earthquake scaling laws.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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