Seismic Activities in Aizu, Fukushima Prefecture

In Aizu (Area b), Fukushima prefecture, a sequence of seismicity with M3.0 or so has been seen since March 18, 2011. Up to the end of August, there were 83 earthquakes with a seismic intensity 1 or over (12 earthquakes in August). The largest in this seismicity was the M4.6 earthquake (maximum seismic intensity 4) that occurred at a depth of 8 km on May 7.
During August, there were a M3.5 earthquake at a depth of 9 km at 10:46 on August 2 and a M3.6 earthquake at a depth of 9 km at 13:39 on the same day (maximum seismic intensity 3 for both). These events occurred within the crust. Their focal mechanism showed a reverse fault with a compression axis in an NW-SE direction. Their seismic activities are continuing even now with some decreases and increases (as of September 7).
For the seismic activity since October 1997, in Area b, there was almost no earthquake of M2.0 or over by March 18, 2011.

Japan Meteorological Agency
[Seismic Activity for August 2011 (September 9, 2011)]