Japanese authorities issued a tsunami alert for the northeast coast Friday after a powerful 7.3-magnitude undersea earthquake struck, setting buildings in Tokyo swaying violently.

Media reports said a one-meter-high wave could sweep ashore in an area badly hit by the March 2011 tsunami that devastated a large swathe of the northeast coast, killing thousands.

Residents of at least one town, Minamisanriku in Miyagi prefecture, were advised to evacuate to higher ground, reports said, suggesting other towns were also affected.

It was not possible immediately to confirm the reports, with telephone operator NTT saying the network was jammed with the weight of callers.

A presenter on state broadcaster NHK repeatedly told viewers to get to safety.

"Remember last year's quake and tsunami," he said. "Call on your neighbours and flee to higher ground now!"

NHK, quoting the national meteorological agency, said the tsunami was expected to hit the coast of Iwate at 5:40 pm (0840 GMT), Fukushima at 5:50 pm, and Aomori and Ibaraki at 6:00 pm.

The United States Geological Survey measured the quake's magnitude at 7.3.
It said the tremor struck a relatively deep 36 kilometers under the Pacific.

The epicenter was 284 kilometers east of Sendai, or 459 kilometers northeast of Tokyo, according to the USGS.

NHK said the Japan Meteorological Agency had issued a tsunami warning, one notch lower than a tsunami alert, for the Pacific coast of Iwate, Fukushima, Aomori and Ibaraki prefectures.

There was no threat of a Pacific-wide tsunami, US monitors based in Hawaii said. Officials in both Indonesia and the Philippines south of Japan said there was no threat of a localised tsunami.

Nuclear plant operator Tokyo Electric Power told AFP there were no reports of any problems at the crippled Fukushima nuclear plant.

"No abnormalities have been recorded on instruments at Fukushima Daiichi nulcear plant's six reactors," a TEPCO spokesman said.

"All workers were ordered to take shelter inside buildings at the Fukushima plant.

"No abnormalities were confirmed with the radiation monitoring posts at the Fukushima plant. No abnormalities were seen with the water processing facilities."

Prime Minister Yoshihiko Noda was heading to his office where he would be monitoring the situation, Jiji Press said.

Japan Railways East temporarily suspended Shinkansen bullet train services to check any damage, Jiji said, while Haneda Airport near central Tokyo was reported to be operating normally. (AFP)

<관련 한글 기사>

7.3 강진 일본 덮쳐, 쓰나미경보 발령


7일 오후 5시18분께 일본 도호쿠(東北) 지방 앞바다(태평양)에 규모 7.3의 강진이 발생했다.

진원은 북위 37.8도, 동경 144.2도이고, 깊이는 10㎞로 추정됐다. 지난해 3월11 일 동일본대지진이 일어난 진원 부근으로 추정된다.

이 지진으로 아오모리현과 미야기현에서 진도 5, 홋카이도에서 도쿄 시내에 걸친 지역에서 진도 4가 각각 관측됐다. 도쿄 도심 빌딩에서도 1분 이상 진동이 느껴졌다.

일본 기상청은 미야기현에 쓰나미(지진해일) 경보, 이바라키•후쿠시마•이와테 현에 쓰나미 주의보를 발령했다.

미야기현에는 오후 5시40분쯤 1m 높이의 쓰나미가 도착할 것으로 예상됐다. 다른 지역의 쓰나미 높이는 50㎝로 예상된다.

NHK는 긴급방송에서 "도호쿠대지진을 상기해달라"며 해당 지역 주민들은 대피하 라고 당부했다.