TOKYO - A powerful earthquake with a magnitude of 7.1 shook southern Japan on Aug 8, but no major damage was reported and only relatively minor tsunami waves lashed the coast.
The quake hit at 4.42pm off Kyushu at a depth of 25km, the United States Geological Survey (USGS) said.
The USGS had initially reported two strong quakes, with magnitudes of 6.9 and 7.1, but later said there had been only one tremor.
The Japan Meteorological Agency (JMA) also said there was one quake with a magnitude of 7.1.
Broadcaster NHK showed footage of traffic lights shaking violently in Miyazaki on Kyushu’s south-east coast.
“The surface of the sea is wavering. I felt an intense jolt when the quake happened, which lasted for between 30 seconds and a minute,” a local official told NHK.
Government spokesman Yoshimasa Hayashi said officials were notified of one minor injury and two other unspecified injuries.
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No disruptions to infrastructure, including electricity, water and telecommunications, were reported, he added.
Unverified footage shared on social media shows minor damage, including dishes and books that had fallen off shelves and a small wall that had collapsed in a carpark.
Tsunamis of up to 1m high were initially expected to arrive or had arrived in some coastal areas in Kyushu and the Shikoku islands, the JMA said.
The agency also said a small tsunami was possible in Chiba, about 850km from the epicentre.
“Tsunamis will strike repeatedly. Please do not enter the sea or approach the coast until the warning is lifted,” the JMA said on social media platform X.
Tsunamis that were 50cm, 20cm and 10cm high were confirmed to have hit some places, including the port of Miyazaki, more than an hour after the quake, it added.
The Pacific Tsunami Warning Centre issued a warning that said hazardous tsunami waves were possible within 300km of the epicentre.
No abnormalities were reported at atomic power plants in the area, according to the nuclear regulation authority.
The Japanese government has set up a special task force in response to the quakes.
X user crawler1990mc posted a video of Miyazaki Airport, where shop displays are seen falling off because of the quake and people are seen “evacuating to the second and third floors”.
Another X user, TaichiHoshi, was in a bullet train that had made an emergency stop. There was no electricity inside the train, and it was “a bit scary when you first encounter it”, said TaichiHoshi.
Sitting on top of four major tectonic plates along the western edge of the Pacific “Ring of Fire”, Japan is one of the world’s most tectonically active countries.
The archipelago, home to about 125 million people, experiences around 1,500 jolts every year and accounts for approximately 18 per cent of the world’s quakes.
The vast majority are mild, although the damage they cause varies according to their location and the depth below the earth’s surface at which they strike.
The JMA on Aug 8 issued an advisory warning that there is now a “relatively higher” probability than usual of a long-feared mega quake occurring around the Nankai Trough, but added that it should not be taken to signal such an event is imminent.
The government has said the potential mega quake, with an estimated 8 or 9 magnitude, has a roughly 70 per cent probability of striking within the next 30 years.
It could affect a large swath of the Pacific coastline of Japan and threaten an estimated 300,000 lives in the worst-case scenario, experts say.
The advisory “does not mean the mega quake will definitely happen during a certain period of time”, JMA official Shinya Tsukada told reporters.
In Japan, even large quakes usually cause little damage thanks to special construction techniques and strict building regulations in the world’s No. 4 economy.
The country also routinely holds emergency drills to prepare for a major quake.
At least 318 people were killed when a quake hit the Noto Peninsula on the Sea of Japan side of the main island of Honshu on New Year’s Day.
The Jan 1 quake and its aftershocks toppled buildings, caused fires and knocked out infrastructure at a time when families were celebrating the new year.
In 2011, a colossal 9.0-magnitude undersea quake off northeastern Japan triggered a tsunami that left around 18,500 people dead or missing.
It sent three reactors into meltdown at the Fukushima nuclear plant, causing Japan’s worst post-war disaster and the most serious nuclear accident since Chernobyl.
In March 2022, a 7.4-magnitude quake off the coast of Fukushima shook large areas of eastern Japan, killing three people.
The capital Tokyo was devastated by a huge quake a century ago in 1923. AFP