Earthquake Offshore Urakawa on February 21
On February 21, 2015 at 04:28 (JST), there was a M5.1 earthquake (maximum seismic intensity 3) at a depth of 57 km, offshore Urakawa. The focal mechanism 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 2001, in the vicinity of the recent event (Area b), there have often been earthquakes of M5.0 or over.
For the seismic activity since January 1923, in the area around the recent event (Area c), there have often been earthquakes of M6.0 or over. The largest one was "the 1982 Urakawa-Oki Earthquake" (M7.1, maximum seismic intensity 6) that caused damage with 167 injured persons and 41 completely or seriously collapsed houses (Disaster Records in 1982 and 1983, Hokkaido (1984)). Also at Urakawa, tsunami with height of 78 cm (maximum height from the average tide) was observed.
Japan Meteorological Agency
[Evaluation of Seismic Activities for February 2015 (March 10, 2015)]