Earthquake Offshore Fukushima Prefecture on January 25

On January 25, 2016 at 02:13 (JST), there was a M4.2 earthquake (maximum seismic intensity 4) at a depth of 29 km, offshore Fukushima prefecture. The focal mechanism of this event showed a normal fault type with a tension axis in an NNW-SSE direction. This event occurred within the continental plate.
For the seismic activity since October 1997, in the vicinity of the recent event (Area b), there had never been earthquakes of M4.0 or over, but seismic activity became higher, such like that there were earthquakes of M5.0 or so, after the occurrence of "the 2011 off the Pacific coast of Tohoku Earthquake."
For the seismic activity since January 1923, in the area around the recent event (Area c), there have sometimes been earthquakes of M6.0 or over. There was a M7.0 earthquake (maximum seismic intensity 6 Lower) on April 11, 2011, which caused damage with 3 fatalities and 10 injured persons (Fire and Disaster Management Agency).

Japan Meteorological Agency
[Evaluation of Seismic Activities for January 2016 (February 9, 2016)]