Friday, March 18, 2011

#Japan #Earthquake: 262 Aftershocks M5 or Larger

No ordinary earthquake, that is for sure.

The number of aftershocks since the March 11 Magnitude 9.0 earthquake is unprecedented, and probably not even counting all of them, reports Kahoku Shinpo (in Japanese; 3/19/2011).

According to the article, there have been 262 recorded aftershocks of Magnitude 5.0 or larger since March 11. The number is out of the ordinary, compared to other similar big earthquakes in the past that took place along the Japan Trench (a subduction zone).

There have been 56 aftershocks of Magnitude 6.0 or larger, which is quite abnormal. Shinichi Sakai, associate professor at Tokyo University Earthquake Research Institute warns of continued seismic activities in East Japan, possibly for years.

The article also has this chart of aftershocks Magnitude 5.0 and greater along the Japan Trench, based on the data from Japan Meteorological Agency. The red line is the March 11 earthquake. The X-axis is the number of days since the earthquake, and the Y-axis is the cumulative number of aftershocks.

(The chart actually reminds me of the explosion of excess reserves at the Fed after Lehman Brothers went down in September 2007. Unlike the excess reserves that are going vertical again, I hope this number tapers off, and soon.)


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