A major 7.4-magnitude quake struck southern Japan on Wednesday, the US Geological Survey (USGS) said, with people in nearby coastal regions told to evacuate as a half-metre wave rolled in.
Japan’s meteorological agency had downgraded a tsunami alert to a warning of a half-metre wave to hit remote islands after a major 7.4-magnitude seabed earthquake.
“The alert was downgraded, but the village continues to advise residents to stay evacuated,” said Koji Watanabe, a village official on Chichi-shima, one of the Ogisawara – or Bonin – islands.
The quake hit at a shallow depth at 2:19 am local time (4:19am AEDT), 153 kilometres east of Chichi-shima in the island region located in the Pacific Ocean about 1,000km south of Tokyo.
“About 120 people evacuated to higher places on Chichi-shima island and some 50 people on Haha-shima island as of 3:30am,” the official said.
Asked about whether there were reports on damage or injuries, he said: “I’m not aware of any injuries.”
NHK reported a wave of 30 centimetres hit Hachijojima island, part of the Izu island chain that runs south of Tokyo, at 4:01am local time.
The Bonin island chain, made up of more than 30 subtropical and tropical islets some 1,000 kilometres south of Tokyo and 240 kilometres north of Iwo Jima, have a population of just 2,700, according to the 2005 national census.
The Hawaii-based Pacific Tsunami Warning Centre said there was no threat of a destructive widespread tsunami and no nearby islands are thought to be in the tsunami danger zone.
But it warned in a bulletin: “Earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within 100 kilometres of the earthquake epicentre.
“Authorities in the region of the epicentre should be aware of this possibility and take appropriate action.”
The quake was followed just over 20 minutes later by two aftershocks, a minute apart, of 5.6-magnitude just 10 kilometres deep, followed by two of 5.4-magnitude soon after, the USGS said.
Around 20 per cent of the world’s most powerful earthquakes strike Japan, which sits on the “Ring of Fire” surrounding the Pacific Ocean.
In 1995 a magnitude-7.2 quake in the port city of Kobe killed 6,400 people.
But high building standards, regular drills and a sophisticated tsunami warning system mean that casualties are often minimal.