Earthquake Offshore of Sanriku on November 9, 2025
(1) Overview
At 17:03 on November 9, 2025, an M6.9 earthquake occurred offshore of Sanriku at a depth of 16 km. The quake registered seismic intensity 4 in Morioka City and Yahaba Town in Iwate Prefecture, as well as in Wakuya Town in Miyagi Prefecture. Seismic intensities ranging from 3 to 1 were recorded from Hokkaido to the Chubu region, with the Tohoku region being primarily affected. Additionally, long-period ground motions of class 1 were observed in the Tohoku region. The earthquake triggered a tsunami that reached heights of 16 cm in Ofunato and 9 cm in Miyako, both located in Iwate Prefecture (note). As of 14:00, November 17, 2025, there were no reports of damage caused by the earthquake or the accompanying tsunami (according to the Fire and Disaster Management Agency).
At 17:05:02.6, just 16 seconds after detecting the first seismic waves, the Japan Meteorological Agency issued an Earthquake Early Warning (Warnings). Later that day, at 17:12, it issued a Tsunami Advisory for Iwate Prefecture, which was subsequently lifted at 20:15.
The focal mechanism involved reverse faulting, with the pressure axis oriented in the WNW-ESE direction (CMT solution) and occurred at the boundary between the continental and Pacific Plates.
Since November 4, seismic activity has been detected around the epicenter, and by November 30, 45 earthquakes with seismic intensity 1 or greater have been recorded (1 event with seismic intensity 4, 9 events with seismic intensity 3, 20 events with seismic intensity 2, and 15 events with seismic intensity 1).
Table 1-1 displays the number of earthquakes categorized by maximum seismic intensity since November 1. Whereas Figure 1-1 depicts the daily frequency of earthquakes with seismic intensities 1 or greater. Table 1-2 includes main information and press releases from the Japan Meteorological Agency, and Table 1-3 presents key press releases and explanatory materials issued by regional headquarters or local meteorological offices.
(Note) The observed values might be revised upon further review.
Japan Meteorological Agency
[Evaluation of Seismic Activities for November 2025 (December 25, 2025)]