TOKYO — A powerful earthquake struck off the northeastern coast of Japan on Monday, prompting authorities to issue a tsunami warning for waves of up to 3 meters before downgrading it to an advisory, officials said.
The Japan Meteorological Agency reported the quake at a preliminary magnitude of 7.5, later revising it to 7.7, with the U.S. Geological Survey initially measuring it at 7.4. It hit at about 4:53 p.m. local time (0753 GMT) off the coast of Sanriku in Iwate Prefecture, at a shallow depth of around 10 kilometers, the agency said.
The tsunami warning covered parts of Iwate, Aomori and Hokkaido prefectures, urging residents in coastal areas to evacuate to higher ground. Within two hours, waves as high as 80 centimeters were detected, according to authorities. The warning was later downgraded to a tsunami advisory, with expected waves of up to 1 meter.
No immediate reports of casualties or major damage were available as of Monday evening, officials said. Bullet trains in affected regions were suspended, and ports cleared vessels as a precaution. Emergency teams mobilized, and safety checks were underway at nuclear facilities, though no issues were reported.
The earthquake occurred in a seismically active region along the Pacific Ring of Fire. Japan experiences frequent tremors, and authorities routinely issue tsunami alerts for major offshore quakes.
A government spokesperson said residents should remain vigilant. "People in coastal areas are urged to stay away from the shore and follow evacuation instructions," the official stated, according to public broadcaster NHK.
The quake was felt in Tokyo, several hundred kilometers away, witnesses reported. Transportation disruptions affected Shinkansen services in northern Japan.
As of Monday night, the tsunami advisory remained in effect for some northern coastal areas, the Japan Meteorological Agency said. Authorities continued monitoring for aftershocks and any changes in sea levels.
No further details on damage assessments were immediately available. Officials said inspections of infrastructure were ongoing, with updates expected in the coming hours.
