Earthquake in Central Kochi Prefecture on October 27

On October 27, 2012 at 04:44 (JST), there was a M4.5 earthquake (maximum seismic intensity 3) at a depth of 34 km in central Kochi prefecture. The focal mechanism showed a strike-slip fault with a compression axis in an N-S direction. This event occurred within the Philippine Sea plate.
For the seismic activity since October 1997, in the vicinity of the recent event (Area b), an event of M4.0 or over was only a M4.4 earthquake (maximum seismic intensity 3) on July 23, 2010, and then the recent event was the second.
For the seismic activity since January 1923, in the area around the recent event (Area c), the seismicity increased just after the Nankai Earthquake on December 21, 1946, and there was a M5.1 earthquake on December 21. After this event, there was no earthquake of M5.0 or over.

Japan Meteorological Agency
[Evaluation of Seismic Activities for October 2012 (November 9, 2012)]