Earthquake under the Mariana Islands on July 30
On July 30, 2016 at 06:18 (JST; the same shall apply hereinafter), there was a M7.7 earthquake at a depth of 233 km under the Mariana Islands and maximum seismic intensity 2 was observed in Japan. The focal mechanism (CMT solution determined by JMA) had a tension axis in the subducting direction of the Pacific plate. This event occurred within the Pacific plate. Near the Mariana Islands, the Pacific plate is subducting at a large dip angle under the Philippine Sea plate.
For the seismic activity since 1970, in the area around the recent event (Area b), there have stationarily been earthquakes of M5 over and there were 2 earthquakes of M7 over, including the recent event. Seismic intensity 1 or over were observed in Japan due to the earthquakes occurring in Area b: maximum seismic intensity 1 was observed due to a M7.1 earthquake on October 31, 2007.
Japan Meteorological Agency
[Evaluation of Seismic Activities for July 2016 (August 9, 2016)]