Earthquake under the Sea near Amami Oshima on December 11

On December 11, 2011 at 10:22 (JST), there was an M5.5 earthquake (maximum seismic intensity 4) under the sea near Amami Oshima. The focal mechanism (CMT solution) showed a reverse fault with a compression axis in a WNW-ESE direction. On the same day, there were two aftershocks with a maximum seismic intensity 3, and the aftershock activity was brisk, but as of late December it subsided.
For the seismic activity since October 1997, in the vicinity of the recent event (Area a), there have sometimes been earthquakes of M5.0 or over. A M6.0 earthquake (maximum seismic intensity 5 Upper) on December 9, 2001 caused damage with a partially harmed house (Fire and Disaster Management Agency).

For the seismic activity since January 1970, in the area around the recent event (Area b), there have sometimes been earthquakes of M6.0 or over.

Japan Meteorological Agency
[Evaluation of Seismic Activities for December 2011 (January 11, 2012)]