Earthquake Offshore of Sanriku on May 5 (Seismic Activity Offshore of Sanriku Since November 2025)
On May 5, 2026, at 8:54, an M5.4 earthquake (maximum seismic intensity 3) occurred offshore of Sanriku at a depth of 17 km. The focal mechanism (CMT solution) revealed a normal fault type with a tension axis oriented in the E-W direction.
Since November 4, 2025, clusters of earthquakes have been observed near the epicenter (Area b). Following the M6.9 event (maximum seismic intensity 4) on November 9, seismic activity increased. Activity remained intense thereafter, with M6.0 or greater earthquakes frequently occurring. Following an M7.7 event (maximum seismic intensity 5 Upper) on April 20, 2026, seismic activity became even more intense.
Between May 1 and May 31, 16 earthquakes with seismic intensity 1 or higher were recorded in Area b (1 event with seismic intensity 3, 3 events with seismic intensity 2, and 12 events with seismic intensity 1). This suggests that seismic activity continues.
A review of seismic activity since 1885 reveals that earthquakes of M7.0 or greater have often occurred near this focal area (Area c). For example, an M8.2 earthquake on June 15, 1896 (Meiji Sanriku Earthquake), caused extensive damage, including 21,959 fatalities (damage data are sourced from the "Materials for Comprehensive List of Destructive Earthquakes in Japan").
Japan Meteorological Agency
[Evaluation of Seismic Activities for May 2026 (June 9, 2026)]