Earthquake Under the Northern Ibaraki Prefecture on September 29

[The Nakadori region, Fukushima prefecture] was the region name of the epicenter used in the JMA announcement.

On September 29, 2023 at 16:57 (JST), there was an M4.6 earthquake (maximum seismic intensity 3) at a depth of 109 km under the northern Ibaraki prefecture. This event occurred within the Pacific plate (in the lower of the double seismic planes). The focal mechanism had a compression axis in an E-W direction.
For the seismic activity since October 1997, in the vicinity of the recent event (Area b), there have occurred 3 earthquakes of M6.0 or over, including the recent vent.
For the seismic activity since 1919, in the area around the recent event (Area c), after "the 2011 off the Pacific coast of Tohoku Earthquake" there occurred 6 earthquakes of M6.0 or over till 2016. Of these an M7.0 earthquake (maximum seismic intensity 6 Lower) on April 11, 2011 caused damage with 4 fatalities and 10 injured persons, and an M6.4 earthquake (maximum seismic intensity 6 Lower) on the next 12^th caused 1 injured person (damage: Materials for Comprehensive List of Destructive Earthquakes in Japan). Also, an M6.3 earthquake (maximum seismic intensity 6 Lower) on December 28, 2016 caused damage with 2 slightly injured persons, 1 severely-, and 25 partially-damaged houses and so on (damage: Fire and Disaster Management Agency).

Japan Meteorological Agency
[Evaluation of Seismic Activities for September 2023 (October 11, 2023)]