Earthquake Under the Southern Chiba Prefecture on May 11

On May 11, 2023 at 04:16 (JST), there was an M5.2 earthquake (maximum seismic intensity 5 Upper) under the southern Chiba prefecture. This event occurred within the Philippine Sea plate. The focal mechanism (preliminary) had a tension axis in an NW-SE direction. This event caused damage with a slightly injured person (as of May 11, 2023 at 08:00 (JST), Fire and Disaster Management Agency).
For the seismic activity since October 1997, in the vicinity of the recent event (Area b), there have sometimes been earthquakes of M5 or so. On May 25, 2019, there was an M5.1 earthquake (maximum seismic intensity 5 Lower) which caused damage with a slightly injured person (Fire and Disaster Management Agency).
For the seismic activity since 1919, in the area around the recent event (Area c), there have sometimes been earthquakes of M6.0 or over. On December 17, 1987, there was an M6.7 earthquake (maximum seismic intensity 5) which caused damage with 2 fatalities, 161 injured persons, 16 totally collapsed houses, 102 severely-, 72,580 partially-damaged houses and so on (damage: Materials for Comprehensive List of Destructive Earthquakes in Japan).

Japan Meteorological Agency
[Evaluation of Seismic Activities for April 2023 (May 12, 2023)]