Tokyo (AFP) - A powerful 7.3-magnitude quake jolted eastern Japan on Wednesday night, rattling the capital Tokyo and prompting a tsunami advisory for parts of the northeast coast.
The quake, which cut power to more than two million households, was centred off the coast of the Fukushima region at a depth of 60 kilometres (37 miles), the Japan Meteorological Agency said.
"Calls have been inundating police and ambulances in Fukushima and (neighbouring region) Miyagi," top government spokesman Hirokazu Matsuno told reporters."We're doing our best to assess the extent of the damage."
Japan's nuclear authority said no abnormalities were detected at the stricken Fukushima plant that went into meltdown in 2011 when a huge 9.0-magnitude quake hit off the eastern coast, triggering a deadly tsunami and nuclear disaster.
Shortly after Wednesday's quake hit at 11:36 pm (1436 GMT) an advisory for tsunami waves of up to one metre was issued for the coasts of Fukushima and Miyagi.
A 20 centimetre tsunami wave was recorded in the city of Ishinomaki in Miyagi, according to public broadcaster NHK.
TV footage showed some structural damage in the northeast, including the collapse of a stone wall of Aoba castle in Sendai city.
An official in the emergency department of the local government of Ishinomaki told AFP he had been woken by "extremely violent shaking".
"I heard the ground rumbling.Rather than feeling scared, I immediately remembered the Great East Japan Earthquake," he said, referring to the 2011 disaster.
A Shinkansen bullet train was derailed north of Fukushima city, train company JR East said, but there were no immediate reports of injuries.
Matsuno said an emergency government taskforce had been set up and warned residents of possible strong aftershocks over the next week.
"Major aftershocks often happen a couple of days after the first quake, so please stay away from any collapsed buildings...and other high-risk places," he said.
Multiple smaller jolts hit the region in the hours immediately after the quake.
Around two million households were left without power in the central Kanto region, including 700,000 in Tokyo, electricity provider TEPCO said, but power was being gradually restored in the capital and elsewhere.
In the northeast, 156,000 households lost power, regional energy company Tohoku Electric Power said.
Evacuation orders were issued in some northeastern towns, NHK reported, with Rifu town in Miyagi opening shelters in its official buildings.
Ring of fire
Prime Minister Fumio Kishida told reporters the government was gathering information on the situation.
"We will commit ourselves to gathering information, do our best to rescue those affected by the (quake) and communicate information appropriately," he said.
Japan sits on the Pacific "Ring of Fire", an arc of intense seismic activity that stretches through Southeast Asia and across the Pacific basin.
The country is regularly hit by quakes, and has strict construction regulations intended to ensure buildings can withstand strong tremors.
But it remains haunted by the memory of the 2011 undersea quake in northeastern Japan that triggered a deadly tsunami and unleashed the Fukushima nuclear accident.
A minute's silence was held last Friday, the anniversary of the disaster, to remember the some 18,500 people left dead or missing in the tsunami.
Around the stricken Fukushima plant, extensive decontamination has been carried out, and this year five former residents of Futaba, the region's last uninhabited town, returned to live there on a trial basis.
Around 12 percent of Fukushima was once declared unsafe but no-go zones now cover just 2.4 percent of the prefecture, although populations in many towns remain far lower than before.
