Seismic Activities from Hamadori, Fukushima Prefecture to Northern Ibaraki Prefecture
Within the crust from Hamadori, Fukushima prefecture through northern Ibaraki prefecture (Area a), seismicity increased after the 2011 off the Pacific Coast of Tohoku Earthquake. As of late February 2012, it has been declining as a whole, but it continues. Many of the focal mechanisms in this seismicity showed a normal fault. The direction of their tension axes is regionally different. It is an NW-SE direction on the whole in the northern region and an ENE-WSW direction on the whole in the southern region.
As of late February 2012, the largest was a M7.0 earthquake (maximum seismic intensity 6 Lower) on April 11, 2011 at a depth of 6 km in Hamadori, Fukushima prefecture. This event caused damage with 4 fatalities and 10 injured persons (Fire and Disaster Management Agency).
During February 2012, on February 19, there was a M5.2 earthquake (maximum seismic intensity 5 Lower, normal fault with a tension axis in an ENE-WSW direction) at a depth of 7 km in northern Ibaraki prefecture. In Area a, there were 30 earthquakes of M3.0 or over. In addition, there were two earthquakes with a maximum seismic intensity 3 or over (maximum seismic intensity 5 Lower: 1 and maximum seismic intensity 3: 1).
Japan Meteorological Agency
[Evaluation of Seismic Activities for February 2012 (March 9, 2012)]