Overview
- The quake struck around 11:15 p.m. local time on Dec. 8 east of Aomori, provisionally measured at about M7.5–7.6 (Mw ~7.4), with a maximum JMA intensity of 6-strong in parts of the prefecture.
- The government and the Japan Meteorological Agency issued the Hokkaido–Sanriku aftershock caution information for the first time, covering seven prefectures and 182 municipalities for one week.
- Officials stress no pre-evacuation or broad activity suspensions are required, urging residents to secure furniture, review evacuation routes, and stay ready to move quickly; they cite about a 1% chance of an Mw8-class event within a week after an Mw7 quake.
- Tsunami warnings for sections of the Hokkaido and Tohoku Pacific coasts were switched to advisories at 2:45 a.m. on Dec. 9 as observations and tide data were updated.
- Prime Minister Sanae Takaichi activated emergency coordination, directed a lifesaving-first response, and reported seven injuries as assessments and rescue operations continued; JR East is separately probing a Dec. 7 seismometer malfunction that caused a brief Tohoku Shinkansen outage and delays.