Japan has issued its first ‘megaquake’ warning after a powerful quake

An earthquake off the coast of the southern Japanese island of Kyushu has prompted the government to issue its first warning of a megaquake from an underwater trough that runs along part of the country’s coast.

Prime Minister Fumio Kishida canceled a planned trip to Central Asia out of an abundance of caution following the warning. Bullet trains were running at reduced speeds, national broadcaster NHK is running cautionary charts and some semiconductor-related factories have temporarily halted production. Some beaches in the affected regions have been closed for the time being, according to local reports.

A megaquake in what is known as the Nankai Trough could exceed the damage caused by the March 2011 earthquake and tsunami that devastated the northern coast of the main island of Honshu. The area, where the Philippine Sea plate subducts beneath the Eurasian continental plate, sees major tremors that occur in 100- to 150-year cycles.

The precautionary warning system for an increased earthquake risk, implemented in 2019, is activated when an earthquake of magnitude 6.8 or greater strikes an area where megathrusts are expected to occur or when abnormal plate changes are detected. Depending on the magnitude of the earthquake at the time, authorities may issue different levels of caution and, in some cases, warn people to evacuate tsunami-prone areas for a week.

“This is advice to be prepared for the possibility that major earthquakes may continue,” Kishida told reporters in Nagasaki, where he was attending ceremonies marking the 79th anniversary of the atomic bombing. “It’s not an advance evacuation warning or an announcement that there’s going to be an earthquake at a certain time, but it’s the first time, so I think people will be extremely anxious.”

Hours after he spoke, a magnitude 5.3 earthquake struck Kanagawa, shaking buildings in neighboring Tokyo. There was no threat of a tsunami, NHK said.

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Several injuries and limited damage were reported from the 7.1-magnitude earthquake that struck off the coast of Kyushu on Thursday. The island is home to Sony Group Corp.’s semiconductor factories. Taiwan Semiconductor Manufacturing Co., which has opened a factory there, is on track to open a second later this year and is considering a third.

NHK went into coverage of the Olympics to report on the earthquake and the subsequent mega-quake warning and continued to issue bulletins on Friday. A 2019 analysis by a government group estimated that more than 230,000 deaths could occur in the worst-case scenario of a Nankai earthquake.

Large earthquakes have followed smaller earthquakes in the past. The tremors began two days before the magnitude 9 earthquake in 2011, the strongest ever recorded in Japan. Damage from the earthquake and resulting tsunami killed nearly 20,000 people and triggered a meltdown and radiation leak from a nuclear facility in Fukushima.

Central Japan Railway Co. said its bullet trains are running more slowly between Tokyo and western Japan until the warning is lifted. Japan’s regulatory body said it had issued alerts to all nuclear power plants in the country to take precautionary measures. Electronic component maker Kyocera Corp. said some equipment was damaged at a factory in Kagoshima.

Local governments and companies are responding after the Japan Meteorological Agency issued the advisory on Thursday. Stocks closed the day slightly higher and the yen was little changed at around ¥147 to the dollar.

Chipmaker Rohm Co. temporarily suspended operations in Kyushu’s Miyazaki Prefecture and said safety checks were ongoing, according to a spokesman. Sumco Corp., a maker of silicon wafers needed to make chips, has halted operations at its factory in Miyazaki, according to a representative.

Hiroaki Maruya, a professor at the International Research Institute for Disaster Science, said companies can take the opportunity to scrap their business continuity plans following the alert or go through disaster drills.

“NHK reported on this event, so they might make a move,” Maruya said.

Suntory Holdings Ltd., Suzuki Motor Corp. and other companies said they were checking and on alert for any further developments.

Regional company Kyushu Electric Power Co. said it had set up a task force to organize communication with its power plants. A company spokesman said its nuclear power facilities – the Genkai Nuclear Power Plant in Saga Prefecture and the Sendai Nuclear Power Plant in Kagoshima Prefecture – are being designed with a Nankai earthquake in mind.

Chubu Electric Power Co., a utility that covers central Japan, said it has set up a network to strengthen communication between headquarters and branches, according to the spokesman.

Top photo: Ships swept inland by the tsunami that followed the March 11 earthquake in Kesennuma, Japan, in March 2011. Photographer: Tomohiro Ohsumi/Bloomberg.

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