The map below shows foreshocks and aftershocks of the March 11 Tohoku earthquake. The list of earthquakes and locations comes from the US Geological Survey web pages:
http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/quakes_big.php
Only events with magnitude 5.0 or larger are listed on that page.
There is a similar, and up-to-date map on the USGS web site:http://earthquake.usgs.gov/earthquakes/seqs/events/usc0001xgp/
(accessed March 26, 2011).
The figure below shows magnitudes as a function of time, based on the same USGS web site.
A model for the numbers of aftershocks as a function of time after an earthquake is called "Omori's Law." According to this, the rates of aftershocks decrease as a function of time, following the equation n(t)~(c+t)^(-p). The plot below tries fitting the integral of this equation to the cumulative numbers of aftershocks, based on the USGS list. This curve does not fit the first two days of the aftershock sequence. Also, the value of p seems to increase as time goes on for this catalog.
A model for the numbers of aftershocks as a function of time after an earthquake is called "Omori's Law." According to this, the rates of aftershocks decrease as a function of time, following the equation n(t)~(c+t)^(-p). The plot below tries fitting the integral of this equation to the cumulative numbers of aftershocks, based on the USGS list. This curve does not fit the first two days of the aftershock sequence. Also, the value of p seems to increase as time goes on for this catalog. A large aftershock could happen, and significantly alter the course of this curve.
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