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Japan Meteorological Agency (JMA)

Japan Meteorological Agency (JMA)

National Meteorological and Seismological Service

Appears in 2 stories

Stories

Japan’s Sanriku quake triggers first-ever ‘megaquake’ warning

New Capabilities

Japan’s Meteorological Agency runs the country’s earthquake, tsunami and weather warning systems. - Issued tsunami alerts and the first megaquake ‘subsequent earthquake’ advisory after the Sanriku quake

Just before midnight on December 8, a magnitude‑7.5 quake slammed offshore near Aomori, shaking Hachinohe hard enough to topple furniture, briefly cutting power, and sending up small tsunamis that still forced about 90,000 people to evacuate from coastal towns. By morning the tsunami warnings were gone and only minor injuries and damage had been confirmed, but the real shock came next: Japan’s Meteorological Agency pulled the lever on its rarest tool, a top‑tier “megaquake” advisory for a possible magnitude‑8 or larger event along the northern Pacific coast in the coming week.

Updated Dec 11, 2025

Japan’s 2025 Sanriku earthquake tests a new era of tsunami and ‘megaquake’ preparedness

Built World

Japan’s national meteorological and geophysical agency responsible for weather forecasts, earthquake and tsunami monitoring, early-warning alerts, and geohazard information. - Primary issuer of earthquake, tsunami, and subsequent earthquake advisories

On December 8, 2025, a magnitude 7.6 offshore earthquake struck at 23:15 JST off the coast of Aomori Prefecture in Japan’s Sanriku region, shaking Hachinohe at a maximum ‘upper 6’ on Japan’s intensity scale and triggering tsunami warnings forecasting waves up to three meters for parts of Hokkaido, Aomori, and Iwate. Japan’s Meteorological Agency (JMA) and local authorities ordered or urged tens of thousands of coastal residents to evacuate; recorded tsunami heights ultimately stayed in the 20–70 cm range, and by the early hours of December 9 the initial warnings were downgraded to advisories, with at least 23 injuries reported but no deaths or large-scale structural collapse.

Updated Dec 11, 2025