Earthquake in the Ocean Area near Niijima and Kozushima on January1

On January 1, 2021 at 01:53 (JST), there was an M4.7 earthquake (maximum seismic intensity 4) at a depth of 12km in the ocean area near Niijima and Kozushima Islands. This event occurred within the crust of the Philippine Sea plate. The focal mechanism showed a strike-slip fault type with a compression axis in an NW-SE direction. In the vicinity of the recent event (Area a), there has been a seismic activity since mid-December 2020, and till January 31, there were 40 earthquakes with observed seismic intensity 1 or over. The largest was the M5.0 earthquake (maximum seismic intensity 5 Lower) on December 18.
For the seismic activity since October 1997, in the area extending from Niijima and Kozushima Islands to Miyakejima Island, i.e. Area b, there were 6 earthquakes of M6.0 or over in the period from July to August 2000 when the volcanic activity was high in Miyakejima Island. Of these an M6.5 earthquake on July 1 caused damage with 1 fatality and so on (Fire and Disaster Management Agency).
For the seismic activity since 1919, in the area around the recent event (Area c), there have sometimes been earthquakes of M6.0 or over.

Japan Meteorological Agency
[Evaluation of Seismic Activities for January 2021 (February 9, 2021)]