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Bulletin of the Seismological Society of America, Vol. 94, No. 1, pp. 8898, February 2004 A Common Origin for Aftershocks, Foreshocks, and Multiplets
 

Summary: 88
Bulletin of the Seismological Society of America, Vol. 94, No. 1, pp. 88­98, February 2004
A Common Origin for Aftershocks, Foreshocks, and Multiplets
by Karen R. Felzer,* Rachel E. Abercrombie, and Go¨ran Ekstro¨m
Abstract We demonstrate that the statistics of earthquake data in the global Cen-
troid Moment Tensor (CMT) and National Earthquake Information Center (NEIC)
catalogs and local California Council of the National Seismic System (CNSS) catalog
are consistent with the idea that a single physical triggering mechanism is responsible
for the occurrence of aftershocks, foreshocks, and multiplets. Specifically, we test
the hypothesis that tectonic earthquakes usually show clustering only as a result of
an initial earthquake triggering subsequent ones and that the magnitude of each trig-
gered earthquake is entirely independent of the magnitude of the triggering earth-
quake. Therefore a certain percentage of the time, as determined by the Gutenberg­
Richter magnitude­frequency relationship, an earthquake should by chance be larger
than or comparable in size to the earthquake that triggered it. This hypothesis predicts
that the number of times foreshocks or multiplets are observed should be a fixed
fraction of the number of aftershock observations. We find that this is indeed the
case in the global CMT and NEIC catalogs; the average ratios between foreshock,
aftershock, and multiplet rates are consistent with what would be predicted by the
Gutenberg­Richter relationship with b 1. We give special attention to the Solomon

  

Source: Abercrombie, Rachel E. - Department of Earth Sciences, Boston University
Felzer, Karen - Earthquake Hazards Program, U.S. Geological Survey

 

Collections: Geosciences