Magnitude 7.5 quake off Japan triggers tsunami warning, evacuations

A magnitude 7.5 earthquake off Japan’s northeastern coast sent a tsunami warning across a wide stretch of shoreline, with authorities warning residents to move quickly away from beaches, harbors and river mouths as waves of up to 3 meters were expected in Iwate, Aomori and Hokkaido prefectures.

The quake, centered in the Pacific Ocean at a depth of about 10 kilometers, was first given a preliminary magnitude of 7.4 before the estimate rose to 7.5. The Japan Meteorological Agency said the warning system is region-based, designed to move fast when seismic data show the possibility of dangerous waves, and to provide estimated arrival times and heights so coastal communities can decide whether to evacuate immediately.

The U.S. Embassy and Consulates in Japan said the warning covered Aomori, Iwate and parts of Hokkaido, while tsunami alerts also applied to Fukushima Prefecture and eastern Hokkaido. Prime Minister Sanae Takaichi said the government had set up an emergency task force, underscoring how quickly Japan’s national response apparatus is activated when offshore quakes threaten flooding and repeated wave surges.

On the ground, the response was visible. NHK showed ships leaving Hachinohe port as a large on-screen alert read, “Tsunami! Evacuate!” Bullet train services in Aomori were halted because of the tremors, and the quake measured an upper 5 on Japan’s seismic intensity scale, strong enough to make it difficult for people to move and, in some cases, to collapse unreinforced concrete-block walls.

The Japan Meteorological Agency’s aftershock guidance says people should compare a quake with similar past events and stay cautious for at least the next week, a reminder that the danger does not end with the first shaking. That warning carries added weight in Japan, one of the world’s most earthquake-prone countries, where a tremor occurs at least every five minutes and the country accounts for about 20% of the world’s magnitude 6.0 or stronger earthquakes.

There were no operating nuclear power plants in Hokkaido or Tohoku, but Hokkaido Electric Power and Tohoku Electric Power have shutdown plants in the region, and Tohoku Electric was checking the impact on its Onagawa nuclear power plant. The swift warning, evacuations and transport stoppages suggested Japan’s layered safeguards were working as intended, even as officials braced for aftershocks and the possibility of more waves.