Japan downgrades tsunami alerts after 7.7 offshore quake

Japan’s disaster agencies on Monday reduced tsunami warnings to advisories along parts of the country’s northeastern coastline after a magnitude 7.7 earthquake struck offshore at 4:52 p.m. local time. The quake was felt as far away as Tokyo, hundreds of miles from the affected coastal areas.

 

Authorities had initially issued tsunami warnings for waves of up to three meters (10 feet) in parts of Iwate, Aomori, and Hokkaido. Those warnings were later downgraded to advisories, with officials indicating potential waves of up to one meter (three feet) as conditions evolved.

 

Local governments in coastal towns ordered evacuations affecting tens of thousands of residents. Prime Minister Sanae Takaichi urged people in impacted areas to move to higher ground, while the central government set up a crisis management center to coordinate the response.

 

Monitoring detected tsunami waves of about 31 inches at Kuji Port in Iwate, according to officials. At the time of the update, there were no reports of casualties or major damage, and nuclear power plant operators in the region said they had found no abnormalities.

 

Transport was also disrupted. Train services between Tokyo and Aomori were temporarily suspended as authorities assessed conditions and safety, reflecting the broader operational impact that major seismic events can have even when damage reports are limited.

 

Officials also highlighted a near-term risk consideration following the quake. The Japan Meteorological Agency said the probability of a larger “megaquake” of magnitude 8 or higher has risen from a typical 0.1 percent to approximately 1 percent for the upcoming week, describing the risk as slightly elevated.

 

The earthquake’s shallow depth of about 20 kilometers (12 miles) contributed to its impact, officials said. While the immediate tsunami threat was reduced, the situation remained subject to change as monitoring continued and advisories stayed in place for parts of the coastline.