The occurrence of an M~ 9 earthquake near the Japan
Trench was another surprise to the global seismological
communities. Off Miyagi prefecture, near the epicenter of
the 2011 Tohoku earthquake, large (M~ 7.5) earthquakes
have repeatedly occurred since 1793 with an average interval
of 37 years. On the basis of this recurrence, the Earthquake
Research Committee of the Japanese government
estimated the probability of a great (M~ 8) earthquake
occurring between 2010 and 2040 as 99%. The longterm
forecast failed to predict the size (M) of the Tohoku
earthquake.