March 16, 2011
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion

Earthquake in Eastern Shizuoka Prefecture on March 15, 2011

* On March 15 at 22:31 (JST), 2011, there was a M6.4 (preliminary) earthquake at a depth of approximately 15 km, in eastern Shizuoka prefecture. This event had a maximum seismic intensity 6 Upper in Fujinomiya City, Shizuoka prefecture. Since then, there was a shock with a seismic intensity 4, and the aftershock activity has been continuing.

* The focal mechanism had a compression axis in a N-S direction. It is thought from this focal mechanism and the aftershock distribution that an inferred source fault is a left-lateral strike-slip fault on a fault plane striking in a NE-SW direction and dipping to the southeast.

* According to the GPS data, crustal movements associated with this event were observed, with a displacement of approximately 3 cm to the east-northeast at the Susono observation point (Shizuoka prefecture).

* Although the present event occurred close to the presumed focal region of the so-called Tokai Earthquake, the focal mechanism is different from that of the so-called Tokai Earthquake. The Japan Meteorological Agency announced that on the strainmeters installed in the Tokai region there was no crustal movement that might be associated with the so-called Tokai Earthquake.

* The 2011 off the Pacific Coast of Tohoku Earthquake on March 11 caused crustal movements with the maximum horizontal displacement of more than 4m, and widely caused strain changes of extension approximately in an E-W direction and compression approximately in a N-S direction. There is no denying the possibility that it had an effect on the occurrence of the present earthquake.