Earthquake in the Kumamoto Region, Kumamoto Prefecture on May 6

On May 6, 2021 at 09:16 (JST), there was an M4.0 earthquake (maximum seismic intensity 4) at a depth of 14 km in the Kumamoto region, Kumamoto prefecture. The focal mechanism showed a normal fault type with a tension axis in an N-S direction.
In the vicinity of the recent event (Area a), there were "the 2016 Kumamoto Earthquakes" which caused damage with 273 fatalities in Kumamoto and 3 fatalities in Oita prefectures and so on (as of April 13, 2021 for Kumamoto prefecture (Kumamoto) and as of April 12, 2019 for other data (Fire and Disaster Management Agency)).
For the seismic activity since 1885, in the region around the recent event (Area b), there have sometimes been earthquakes of M5.0 or over. Of these on July 28, 1889, there was an M6.3 earthquake which caused damage with 19 fatalities, 234 completely collapsed houses and so on in Kumamoto prefecture, centering on Kumamoto City (Materials for Comprehensive List of Destructive Earthquakes in Japan).

Geospatial Information Authority of Japan
[Evaluation of Seismic Activities for April 2021 (May 14, 2021)]