Earthquake in Southern Tokushima Prefecture on February 6

On February 6, 2015 at 10:25 (JST), there was a M5.1 earthquake (maximum seismic intensity 5 Upper) at a depth of 11 km in southern Tokushima prefecture. This event occurred within the crust. The focal mechanism showed a strike-slip fault type with a compression axis in an E-W direction. The aftershock activity is low: Any aftershock with seismic intensity 1 or over observed, has not occurred as of February 28.
For the seismic activity since October 1997, in the vicinity of the recent event (Area a), there have been earthquakes of M3.0 or over several times per a year. The largest was a M4.5 earthquake (maximum seismic intensity 4) which occurred on February 8, 2001.
For the seismic activity since January 1923, in the area around the recent event (Area c), on July 27, 1955, there was a M6.4 earthquake, which caused damage with a fatality and 8 injured persons (Comprehensive Bibliography of Destructive Earthquakes in Japan).

Japan Meteorological Agency
[Evaluation of Seismic Activities for February 2015 (March 10, 2015)]