M7.7 Quake Jolts Northeastern Japan, Tsunami Of 80 CM Seen On Pacific Coast

TOKYO, April 21 (Bernama-Kyodo) -- A powerful earthquake with a magnitude of 7.7 struck northeastern and northern Japan on Monday, causing a tsunami of up to 80 centimetres on the Pacific coast in the region, with the weather agency advising caution amid increased risk of another strong quake in the next week.

According to Kyodo News, tsunami warnings issued for areas along the coast in Hokkaido, Aomori and Iwate prefectures were later downgraded to advisories. Just before midnight, the advisories, along with those for Miyagi and Fukushima prefectures, were lifted.

An 80-cm tsunami reached Kuji Port in Iwate Prefecture at 5.34 pm, roughly 40 minutes after the quake, according to the Japan Meteorological Agency, which had initially forecast tsunami waves of up to 3 metres.

After the temblor hit off the Sanriku coast in Iwate, the agency issued a special weeklong alert covering 182 municipalities in seven prefectures from Hokkaido to Chiba due to the increased risk of another strong quake.

It marks only the second time the alert has been issued since the system began operating in December 2022. The first time was in December last year, following an M7.5 quake off the eastern coast of Aomori Prefecture.

The alert system, called the "Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory", is based on lessons learned from the M9.0 megaquake that devastated northeastern Japan on March 11, 2011, followed by an M7.3 temblor.

Such alerts are issued following an earthquake in the area with a confirmed magnitude of 7.0 or greater, and when the agency assesses an increased chance that a quake with a magnitude of at least 8.0 could occur within seven days. The elevated chance, according to the agency, is about one in 100, compared with one in 1,000 during ordinary times.

The Cabinet Office is urging the public not to spread misinformation, inadvertently or otherwise, about quake predictions. It is also calling on people not to hoard food beyond the meeting of their needs.

The 4:52 p.m. quake occurred under the seabed at a depth of 19 kilometres and registered an upper 5 on the Japanese seismic intensity scale of 7, according to the agency. The tremors were also felt in parts of Tokyo.

Upper 5 is described as the level where people find it difficult to walk without holding onto something.

A woman in her 80s fell when she was evacuating from her home in Urakawa, Hokkaido, likely breaking her arm, authorities said, while a man in his 80s reportedly broke his leg in a supermarket parking lot in Morioka, Iwate Prefecture. A woman in her 20s in Tohoku, Aomori Prefecture, bumped her head against a chair, according to the authorities.

No abnormalities were reported at the Higashidori or Onagawa nuclear plants, located respectively in Aomori and Miyagi prefectures, or at the Fukushima Daiichi or Daini nuclear power plants in Fukushima Prefecture, according to their operators.

There were also no abnormalities reported at the interim spent nuclear fuel storage facility in Mutsu, Aomori Prefecture.

Speaking to reporters at her office, Japanese Prime Minister Sanae Takaichi urged people in quake-affected areas to evacuate to higher ground.

As of 8:15 p.m., 182,181 people from the five prefectures of Hokkaido, Aomori, Iwate, Miyagi and Fukushima had been ordered to evacuate, according to the Fire and Disaster Management Agency.

JR East said it resumed service of the Tohoku Shinkansen bullet train between Tokyo and Shin-Aomori stations on Monday evening after a roughly four-hour suspension that affected about 32,000 people. The trains will run as scheduled from Tuesday morning, the operator said.

The earthquake's magnitude was initially estimated to be 7.4 at a depth of 10 km, but both figures were later revised up.

-- BERNAMA-KYODO