An earthquake registering a preliminary magnitude of 7.7 off northern Japan on Monday prompted a short-lived tsunami alert and the advisory of a higher risk of a possible mega-quake for coastal areas there.

The Cabinet Office and the Japan Meteorological Agency said there was a 1% chance for a mega-quake, compared to a 0.1% chance during normal times, in the next week or so following the powerful quake near the Chishima trough.

Officials said the advisory was not a quake prediction but urged residents to raise their preparedness while continuing their daily lives.

It was the second such advisory for the region in recent months. One was issued following a 7.5-magnitude quake in December but no mega-quake occurred.

The Fire and Disaster Management Agency said one person in Aomori, north of Iwate, was injured after falling Monday.

The quake occurred off the coast of Sanriku at around 4:53 p.m. (0753 GMT), at a depth of about 19 kilometers (11 miles), the meteorological agency said.

Footage on NHK television showed hanging objects swaying and people squatting at a shopping center in Aomori, as authorities told people to seek higher ground and stay away from coastal areas.

Shinkansen bullet trains connecting Tokyo and Shin-Aomori were partially suspended, leaving passengers in cars and on platforms waiting for a resumption.

A tsunami of about 80 centimeters (2.6 feet) was detected at the Kuji port in Iwate prefecture within an hour of the quake, and a smaller tsunami of 40 centimeters (1.3 feet) was recorded at another port in the prefecture, the meteorological agency said.

The U.S.-based Pacific Tsunami Warning Center later said the tsunami threat “has now passed.”

The Nuclear Regulation Authority said nuclear power plants and related facilities in the region were intact and no abnormalities were detected.

Iwate and three other northern prefectures issued non-binding evacuation advisories to more than 128,000 residents, according to the disaster management agency.

It’s 15 years since a magnitude 9.0 earthquake and tsunami on March 11, 2011, ravaged parts of northern Japan, causing more than 22,000 deaths and forcing nearly half a million people to flee their homes, most of them due to tsunami damage.

(AP)