Magnitude 7.5 Earthquake Strikes Northern Japan, Prompts Tsunami Advisories

A seismic event registering a magnitude 7.5 struck the northeastern region of Japan late on Monday, December 8th, with official confirmation following on December 9th. The epicenter of the powerful tremor was located offshore in the Pacific Ocean, approximately 80 kilometers from Aomori Prefecture, situated on the northern part of Honshu, Japan’s main island. This area is recognized for its high seismic activity, lying near the Japan Trench and the Chishima Trench, which have historically generated major earthquakes.

The Japan Meteorological Agency (JMA) initially reported the magnitude as 7.6 before revising the figure to 7.5. Initial responses to the offshore quake included the issuance of tsunami warnings for coastal areas across Aomori, Iwate, and Hokkaido prefectures, with initial projections suggesting waves could reach up to three meters. These alerts were subsequently downgraded to advisories after coastal monitoring stations recorded actual wave heights substantially lower than forecasted. Data from Kuji port in Iwate Prefecture indicated a maximum wave height of 70 centimeters, while other coastal locations observed levels ranging between 20 and 70 centimeters.

Chief Cabinet Secretary Minoru Kihara advised approximately 90,000 residents who were under initial evacuation orders to remain sheltered until the advisories were officially lifted. The JMA maintained alerts for potential aftershocks, noting a slight elevation in the risk of a magnitude 8-level event along the northeastern coast, extending from Chiba to Hokkaido. Authorities confirmed that between 23 and 33 individuals sustained injuries, including one serious injury attributed to falling debris. Residents in affected areas, such as Hachinohe, reported intense shaking; one local business owner described the tremor as the strongest he had ever felt.

Infrastructure resilience was immediately tested following the event. East Japan Railway suspended Shinkansen high-speed rail services across the Tohoku region to allow for necessary emergency track inspections. Localized power outages affected roughly 800 homes, though Tohoku Electric Power Co. reported that service restoration was largely completed by Tuesday morning. Defense Minister Shinjiro Koizumi mobilized 18 defense helicopters to conduct aerial damage assessments, and approximately 480 displaced residents utilized temporary shelter at the Hachinohe Air Base.

Nuclear facilities in the affected zone underwent immediate safety evaluations. The Nuclear Regulation Authority reported that approximately 450 liters of water spilled from a spent fuel cooling area at the Rokkasho fuel reprocessing plant in Aomori, but confirmed that water levels remained within normal parameters, indicating no safety concerns. Checks at other sites, including the Onagawa Nuclear Power Plant and the decommissioned Fukushima Daiichi plant, also revealed no abnormalities, although TEPCO temporarily halted the release of treated water as a precautionary measure. Prime Minister Sanae Takaichi established an emergency task force to coordinate the response and assess the full extent of the damage, prioritizing the safety of human life.

The JMA has kept an alert for further tremors in the Hokkaido-Sanriku offshore region active until December 16th. The event underscores the continued need for national preparedness, given Japan’s location on the Pacific Ring of Fire and the memory of the devastating 2011 earthquake and tsunami.