An earthquake with a preliminary magnitude of 7.7 off the coast of northern Japan triggered a short-lived tsunami alert and prompted authorities to advise of a slightly higher risk of a possible mega-quake in coastal areas.
The Japan Meteorological Agency (JMA) reported the quake at 4:53pm, local time, at a depth of 19 kilometres beneath the floor of the Pacific Ocean.
The Cabinet Office and the Japan Meteorological Agency said there was a 1 per cent chance of a mega-quake in the next week or so following the powerful quake near the Chishima and Japan trenches, compared to a 0.1 per cent chance during normal times.
The warning triggered widespread evacuation orders, affecting around 170,000 people.
It triggered an 80-centimetre wave at Kuji Port and a 40-centimetre one at Miyako Port, according to Japanese broadcaster NHK.
JMA had also warned of waves as high as three metres in Iwate, Aomori and Hokkaido prefectures.
But around 9pm local time, all tsunami warnings were downgraded to advisories.
Prime Minister Sanae Takaichi urged residents in the affected area to confirm their evacuation routes and to check emergency food and grab bags so they can run immediately when the next big one hits.
“The government will do our utmost in case of an emergency,” she said.
AFP reported the tremor was felt in Tokyo, hundreds of kilometres away.
There were no immediate reports of major damage or abnormalities at nuclear facilities, Japan’s top government spokesperson Minoru Kihara told a news conference as night fell.
Three injuries were confirmed, according to NHK.
Television news coverage warned of tsunami waves of up to 3 metres. (Reuters: Issei Kato)
Several port towns including Otsuchi and Kamaishi — both hard-hit by a massive earthquake and tsunami in 2011 — earlier issued evacuation orders for thousands of residents, according to NHK.
Bullet train services were halted and some motorways were closed due to the tremors.
Big aftershocks may occur in the following days and weeks, an official from JMA said at a televised press conference.
The initial quake measured an “upper 5″ on Japan’s seismic intensity scale — strong enough to make it difficult for people to move around and cause concrete-block walls that weren’t reinforced to collapse.
Located in the “Ring of Fire” of volcanoes and oceanic trenches that partly encircle the Pacific Basin, Japan is one of the world’s most earthquake-prone countries, with tremors occurring at least every five minutes.
It accounts for about 20 per cent of the world’s earthquakes of magnitude 6.0 or more, such as the 2011 disaster that caused nuclear meltdowns at a Fukushima power plant.
Reuters/AFP
