Earthquake Offshore West of Ogasawara Islands on October 20

On October 20, 2015 at 18:29 (JST), there was a M5.8 earthquake (maximum seismic intensity 3) at a depth of 314 km, offshore west of Ogasawara Islands. This event occurred within the Pacific plate. The focal mechanism (CMT solution) of this event had a compression axis almost in the vertical direction.
For the seismic activity since January 2001, in the vicinity of the recent event (Area b), there have sometimes been earthquakes of M5.0 or over. In the region centered around the depth of 500 km, about 100 to 200 km deeper than the hypocenter of this event (Area c), there have often been earthquakes of M6.0 or over, but in Area b, there has been no earthquake of M6.0 or over. At the depth of 350 km deeper than the hypocenter of this event, there was a M8.1 earthquake (maximum seismic intensity 5 Upper) on Mary 30, 2015, which caused damage with 8 earthquake-related injured persons in Tokyo Metropolis, 3 injured persons in Saitama prefecture, and 2 injured persons in Kanagawa prefecture (Fire and Disaster Management Agency).
For the seismic activity since January 1923, in the area around the recent event (Area d), there have sometimes been earthquakes of M7.0 or over.

Japan Meteorological Agency
[Evaluation of Seismic Activities for October 2015 (November 11, 2015)]