Earthquake Offshore Miyagi Prefecture on March 20

On March 20, 2021 at 18:09 (JST), there was an M6.9 earthquake (maximum seismic intensity 5 Upper) at a depth of 59 km, offshore Miyagi prefecture. The focal mechanism (CMT solution) showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
Japan Meteorological Agency (JMA) issued an Earthquake Early Warning (Warning). Also, JMA announced Tsunami Warning at 18:11(JST) (lifted at 19:30 (JST)).
This event caused damage with 11 slightly injured persons, 1 partially collapsed house (as of March 22 at 07:00 (JST), Fire and Disaster Management Agency).
For the seismic activity since October 1997, in the vicinity of the recent event (Area b), after the occurrence of "the 2011 off the Pacific coast of Tohoku Earthquake" (hereinafter referred to as the Tohoku-Oki Earthquake), the seismic activity has become higher. On April 7, 2011 after the Tohoku-Oki Earthquake, there was an M7.2 earthquake (maximum seismic intensity 6 Upper).

For the seismic activity since 1919, in the region around the recent event (Area c), there have sometimes been earthquakes of M7.0 or over. On June 12, 1978, there was "the 1978 Miyagi-Ken-Oki Earthquake" (M7.4, maximum seismic intensity 5). Besides this there were 3 earthquakes in the 1930s, and on August 16, 2005, there was an M7.2 earthquake (maximum seismic intensity 6 Lower).

Japan Meteorological Agency
[Evaluation of Earthquake Offshore Miyagi Prefecture on March 20, 2021 (March 22, 2021)]