Earthquakes Offshore Fukushima Prefecture on February 28

On February 28, 2017 at 16:49 (JST), there was a M5.7 earthquake (maximum seismic intensity 5 Lower) at a depth of 52 km, offshore Fukushima prefecture. The focal mechanism (CMT solution) showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
For the seismic activity since October 1997, in the vicinity of the recent event (Area b), the activity became high after the occurrence of "the 2011 off the Pacific Coast of Tohoku Earthquake," and there have been earthquakes of M5.0 over.
For the seismic activity since 1923, in the area around the recent event (Area c), there was a M7.5 earthquake on November 5, 1938 at 17:43 (JST). This event caused tsunami with a height of 113 cm (peak-to trough amplitude) at Hanabuchi, Miyagi prefecture. After this event the activity became high and there were 25 earthquakes of M6.0 or over until November 30 in the same year. These events caused damage with a fatality, 9 injured persons, 4 totally- and 29 seriously-collapsed houses (Comprehensive Bibliography of Destructive Earthquakes in Japan).

Japan Meteorological Agency
[Evaluation of Seismic Activities for February 2017 (March 9, 2017)]