Japan's First-Ever 'Megaquake' Alert Issued After Massive Tremor Hits

TOKYO: An earthquake off Japan's southern island of Kyushu led to the country's first-ever megaquake warning for an undersea trough nearby.

Bullet trains slowed down, a semiconductor factory paused production, and NHK is showing continuous safety alerts.

A megaquake, which occurs every 100-150 years, could be even more destructive than the 2011 earthquake and tsunami. Thursday's warning was for a major tremor from the Nankai Trough, where the Philippine Sea plate dives beneath the Eurasian plate.

The warning system, set up a few years ago, activates if a magnitude-6.8 or larger earthquake hits a high-risk area or if unusual plate movements are detected. Authorities can issue different caution levels and may advise people to evacuate tsunami-prone areas for up to a week.

The magnitude-7.1 earthquake off Kyushu on Thursday caused no major damage or tsunami. Kyushu hosts semiconductor factories, including those by Sony and Taiwan Semiconductor Manufacturing Co., which has one factory, another opening this year, and a third under consideration.

NHK interrupted Olympics coverage to report on the quake and megaquake warning, continuing updates on Friday. A 2019 government analysis estimated that a Nankai Trough quake could cause over 230,000 deaths in the worst-case scenario.

In the past, big earthquakes have followed smaller ones. Two days before Japan's 2011 9-magnitude quake, foreshocks occurred. That disaster killed nearly 20,000, caused a tsunami, and led to a nuclear meltdown in Fukushima.

Following the Japan Meteorological Agency's advisory on Thursday, local governments and companies are taking action. Chipmaker Rohm Co. paused operations in Miyazaki, Kyushu, for safety checks.

Chubu Electric Power set up a communication network between its headquarters and branches. At the Hamaoka Nuclear Power Plant, offline since 2011, 300 staff are on "earthquake standby," checking hazardous material facilities and implementing emergency safety measures.

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