Powerful 7.3 magnitude quake hits north Japan, no tsunami risk

A powerful 7.3 magnitude earthquake has shaken off the coast of Fukushima in northern Japan, triggering a tsunami advisory and plunging more than two million homes in the Tokyo area into darkness.

The Pacific Tsunami Warning Center said there was no longer a tsunami threat though the Japan Meteorological Agency kept its low risk advisory in place.

More than 2.2 million homes were without electricity in 14 northeastern prefectures including the Tokyo region, serviced by TEPCO and another utility, Tohoku Electric Power Co., according to the companies. 

Prime Minister Fumio Kishida said power was expected to be restored soon after midnight on Wednesday.

NHK national television said tsunami waves of 20 centimetres already reached shore in Ishinomaki, about 390 kilometres northeast of Tokyo.

The Tokyo Electric Power Company Holdings, which operates the Fukushima Daiichi nuclear plant where the cooling systems failed after the 2011 disaster, said workers found no abnormalities at the site, which was in the process of being decommissioned.

Japan's Nuclear Regulation Authority said a fire alarm went off at the turbine building of No. 5 reactor at the Fukushima Daiichi but there was no actual fire. 

Water pumps for the spent fuel cooling pool at two of the four reactors at Fukushima Daini briefly stopped, but later resumed operation. 

NHK said there were reports of fire, damage to buildings and falling rocks in Iitate town in Fukushima. 

There was no word on any casualties.

Extra caution for possible major aftershocks

East Japan Railway Co. said most of its train services were suspended for safety checks. Some local trains later resumed service.

A Tohoku Shinkansen express train partially derailed between Fukushima and Miyagi due to the quake, but nobody was injured, Kishida said.

He told reporters that the government was assessing the extent of damage and promised to do its utmost for rescue and relief operations. 

He urged residents in the affected areas to use extra caution for possible major aftershocks for about a week. 

The region is part of northern Japan that was devastated by a deadly 9.0 quake and tsunami 11 years ago that also caused nuclear plant meltdowns. 

Wednesday's quake came only days after the area marked the 11th anniversary of the disaster in March 2011.

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