Earthquake Off-shore of Miyagi Prefecture on April 7

On April 7, 2011 at 23:32 (JST), there was a M7.1 earthquake (maximum seismic intensity 6 Upper) at a depth of 66 km, off-shore of Miyagi prefecture. The focal mechanism (CMT solution) showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred within the Pacific plate. The Japan Meteorological Agency issued Tsunami Warnings (Tsunami) for Miyagi prefecture, and Tsunami Advisories for the Pacific coast of Aomori, Iwate, Fukushima, and Ibaraki prefectures. This event caused damage with 4 fatalities and 296 injured persons (Fire and Disaster Management Agency). Since this event, there was a M5.4 earthquake (maximum seismic intensity 5 Lower) on April 9.
For the seismic activity since October 2001, in the vicinity of the recent event (Area b), there have sometimes been earthquakes of M7.0 or so.

For the seismic activity since August 1923, in the vicinity of the recent events (Area c), there have sometimes been earthquakes of M7 class. The 1978 Miyagiken-Oki Earthquake (M7.4, maximum seismic intensity 5) that occurred on June 12, 1978 caused damage with 28 fatalities and 1,325 injured people (Comprehensive Bibliography of Destructive Earthquakes in Japan, Latest Edition).

Japan Meteorological Agency
[Seismic Activity for April 2011 (May 11, 2011)]