Earthquake Under the Fujigoko Area, Eastern Yamanashi Prefecture on December 3

On December 3, 2021 at 02:17 (JST), there was an M4.1 earthquake (maximum seismic intensity 4, ① in the figure) at a depth of 21km under the Fujigoko area, eastern Yamanashi prefecture. The focal mechanisms showed a reverse fault type with a compression axis in an NW-SE direction. Then on the same day at 06:37 (JST), there was an M4.8 earthquake (maximum seismic intensity 4, ② in the figure) at a depth of 19 km. The focal mechanisms showed a reverse fault type with a compression axis in a WNW-ESE direction.
For the seismic activity since October 1997, in the vicinity of the recent event (Area b), there have sometimes been earthquakes of M4.0 or over. On January 28, 2012, there was an M4.9 earthquake (maximum seismic intensity 4) and then, after 4 minutes there was an M5.4 one (maximum seismic intensity 5 Lower).
For the seismic activity since January 1919, iIn the area around the recent event (Area c), there have sometimes been earthquakes of M6.0 or over. In the vicinity of the recent event, on August 8, 1983, there was an M6.0 earthquake which caused falling rocks and damage wIth 1 fatality and 8 injured persons in the Tanzawa mountain area, and also damage wIth injured persons, 2 severely damaged houses and so on (Materials for Comprehensive Bibliography of Destructive Earthquakes in Japan).

Japan Meteorological Agency
[Evaluation of Seismic Activities for November 2021 (December 9, 2021)]