Karen R. Felzer, Rachel E. Abercrombie, and Göran Ekström

American Geophysical Union, Fall Meeting 2002, Abstract #
S61E - 09

It is well known that many earthquakes trigger aftershocks, subsequent
 (and traditionally smaller) earthquakes which are nearby in time and
 space.  It has been debated whether other phenomena that involve
earthquake clustering, such as foreshock-mainshock pairs and earthquake
 doublets and multiplets simply result from the same process that causes
 aftershocks, or are a separate type of special phenomena.  Using the CNSS,
 CMT, and MLI catalogs we demonstrate that for earthquakes in California
 and the Solomon Islands, the rate at which foreshocks trigger mainshocks,
 and the rate at which multiplets occur, are in agreement with the rate at
 which mainshocks trigger aftershocks.  We also find that this agreement in
 rate is highly unlikely to result from random chance, and is similarly
 unlikely to result from any triggering of incidental seismicity by the
 growing nucleation zone of a large earthquake.  Thus our statistical
 analysis indicates that only a single model of earthquake triggering is
 required to explain aftershocks, foreshocks, and multiplets.