Japan lifts tsunami warning after 7.5-magnitude earthquake

By Mariko Katsumura and Chang-Ran Kim

TOKYO, Dec 9 (Reuters) - Japanese authorities lifted tsunami warnings on Tuesday hours after a powerful 7.5-magnitude earthquake shook northeastern regions, injuring at least 30 people and forcing about 90,000 residents to evacuate their homes. 

The earthquake struck off the coast at 11:15 p.m. (1415 GMT) on Monday, and the Japan Meteorological Agency said a tsunami as high as 3 metres (10 feet) could hit the country's northeastern coast. Warnings were issued for the prefectures of Hokkaido, Aomori and Iwate, and tsunamis from 20 to 70 cm (7 to 27 inches) high were observed at several ports, JMA said.

By the early hours of Tuesday, the JMA downgraded the warnings to advisories, and later lifted all advisories. There were no reports of major damage.

The epicentre of the quake was 80 km (50 miles) off the coast of Aomori prefecture, at a depth of 54 km.

On Japan's 1-7 scale of seismic intensity, the tremor registered as an "upper 6" in Hachinohe city, Aomori prefecture - a quake strong enough to make it impossible to keep standing or move without crawling. 

"As of now, I have received reports of 30 people being injured and one fire," Prime Minister Sanae Takaichi told reporters. 

East Japan Railway suspended some services in the area, which was also hit by a massive 9.0-magnitude quake in March 2011. Other train services are facing delays in northern Japan, the operator said.

Following the tremor, the JMA issued an advisory for a wide region from the northernmost island of Hokkaido down to Chiba prefecture, east of Tokyo, calling on residents to be on alert for the possibility of a powerful earthquake hitting again within a week.    

"There is a possibility that further powerful and stronger earthquakes could occur over the next several days," a JMA official said at a briefing. 

No irregularities were reported at nuclear power plants in the region run by Tohoku Electric Power and Hokkaido Electric Power, the utilities said. Thousands of households had lost power immediately following the quake, but service resumed by Tuesday morning.

YEN WEAKENS BRIEFLY

The yen weakened against major currencies after news of the tremor, with the dollar and euro both touching session highs.

Japan is one of the world's most earthquake-prone countries, with a tremor occurring at least every five minutes. Located in the "Ring of Fire" of volcanoes and oceanic trenches partly encircling the Pacific Basin, Japan accounts for about 20% of the world's earthquakes of magnitude 6.0 or greater.

The northeastern region suffered one of the country's deadliest earthquakes on March 11, 2011, when a 9.0-magnitude tremor struck under the ocean off the coast of the northern city of Sendai. It was the most powerful ever recorded in Japan and set off a series of massive tsunami that devastated a wide swathe of the Pacific coastline and killed nearly 20,000 people.

Drawing on lessons from that disaster, when a magnitude 7-level earthquake had struck two days beforehand, the government now issues a one-week "megaquake" advisory whenever a significant earthquake occurs in the region. 

The 2011 tsunami also damaged the Fukushima Daiichi nuclear plant, leading to a series of explosions and meltdowns in the world's worst nuclear disaster for 25 years.

(Reporting by Mariko Katsumura, Chang-Ran Kim, Kantaro Komiya; Editing by Stephen Coates)