Earthquake Off-shore Southeast of Chiba prefecture on February 5

On February 5, 2011 at 10:56 (JST), there was a M5.2 earthquake (maximum seismic intensity 4) at a depth of 64km, off-shore southeast of Chiba prefecture. The focal mechanism (CMT solution) showed a strike-slip fault with a compression axis in an ENE-WSW direction.
For the seismic activity since October 1997, in the vicinity of this event (Area b), there was a M5.5 earthquake (maximum seismic intensity 4) on July 17, 2004, and there have sometimes been earthquakes of M5.0 or over.

For the seismic activity since August 1923, in the area around the recent event (Area c), a M6.4 earthquake (maximum seismic intensity 4) on June 24, 1986 was the largest.

Japan Meteorological Agency
[Seismic Activity for February 2011 (March 9, 2011)]