Earthquake in the Northern Nagano Prefecture on May 12

On May 12, 2018 at 10:29 (JST), there was an M5.2 earthquake (maximum seismic intensity 5 Lower) at a depth of 11 km in the northern Nagano prefecture. This event occurred within the crust. The focal mechanism had a compression axis in a WNW-ESE direction.
For the seismic activity since October 1997, in the vicinity of the recent event (Area a), there was an M5.0 earthquake (maximum seismic intensity 4) on July 1, 1998. Also on November 22, 2014, there occurred an M6.7 earthquake (maximum seismic intensity 6 Lower) which caused damage with 46 injured persons, 77 totally collapsed houses and so on (damage: Fire and Disaster Management Agency). This one occurred at the northern part of the Kamishiro Fault (one of the constitutive faults of the Itoigawa-Shizuoka Tectonic Line Fault Zone) ("Long term evaluation of the the Itoigawa-Shizuoka Tectonic Line Fault Zone (2nd ed.)").
For the seismic activity since January 1923, in the area around the recent event (Area b), on December 30, 1986, there was an M5.9 earthquake (maximum seismic intensity 4). In the peripheral of Area b, from 1965 there occurred "Matsushiro Earthquake Swarm" which caused damage with 15 injured persons, 10 totally collapsed houses and so on (Materials for Comprehensive List of Destructive Earthquakes in Japan).

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