Earthquake under the Western Shimane Prefecture on April 9

On April 9, 2018 at 01:32 (JST), there was an M6.1 earthquake (maximum seismic intensity 5 Upper) at a depth of 12 km under the western Shimane prefecture. This event occurred within the crust. The focal mechanism showed a strike-slip fault type with a compression axis in a WNW-ESE direction. After this event the seismic activity became high: in addition to an M4.9 earthquake on 9th at 02:10, there occurred 47 earthquakes with maximum seismic intensity 1 or over, including this event, till April 30 (maximum seismic intensity: number of earthquakes, 5 Upper: 1, 4: 4 , 3: 4, 2: 14, 1: 24). This event caused damage with 2 heavily injured persons, 7 lightly injured persons, 1,570 collapsed houses and so on (as of May 8, Fire and Disaster Management Agency).
For the seismic activity since October 1997, in the vicinity of the recent event (Area a), on November 21, 2011, there was an M5.4 earthquake (maximum seismic intensity 5 Lower) which caused damage with 1 heavily injured person, 1 lightly injured person and so on (damage: Materials for Comprehensive List of Destructive Earthquakes in Japan).
For the seismic activity since January 1923, in the region around the recent event (Area b), there have often been earthquakes of M6.0 or over. "The 2000 Western Tottori Earthquake" (M7.3) caused damage with 39 heavily injured persons, 143 lightly injured persons and so on (Fire and Disaster Management Agency).

Japan Meteorological Agency
[Evaluation of Seismic Activities for April 2018 (May 11, 2018)]