Japan’s Early Earthquake Warning Triggered in Error

Japan’s earthquake early warning system was triggered in error today, causing some bullet trains to stop and jamming mobile-phone lines.

A magnitude-2.3 earthquake struck Wakayama prefecture in western Japan at 4:56 p.m. local time, after the country’s warning system predicted a magnitude-7.8 quake, according to the Japan Meteorological Agency.

The mistake was “probably the biggest” misreading since the system started in October 2007, Toshio Kusano, a spokesman for the Office of Earthquake and Tsunami Disaster Prevention at the agency, said over the telephone today. There have been 31 errors out of 135 early warnings issued, Kusano said. Today’s glitch was caused by electrical noise on the ocean floor, he said.

The magnitude-9 quake and tsunami that devastated northeast Japan and triggered a nuclear meltdown in Fukushima more than two years ago was about 5 million times bigger than today’s tremor, according to calculations on the U.S. Geological Survey’s website.

Toshihiko Hashida, a JMA official, apologized for the erroneous warning in a televised briefing and said the agency will take steps to prevent a recurrence.

Some bullet train services were suspended after the warning, according to a Central Japan Railway Co. (9022) statement. Trains have since resumed operations.

Mobile phone connections were jammed for about 15 minutes in the Kansai, Shikoku and Chugoku regions in western Japan, said Saori Yoshimatsu, a Tokyo-based spokeswoman for NTT DoCoMo Inc. (9437), the nation’s largest mobile phone operator. Rivals KDDI Corp. and SoftBank Corp. reported no problems, according to their spokesmen.

At a meeting of 100 lawmakers and anti-nuclear activists in the Diet building in central Tokyo today, phone chirps that signaled the early warning system were met with gasps. After a brief pause, the environmentalists returned to questioning Japan’s nuclear regulatory officials about whether atomic reactors could be safely restarted.

To contact the reporters on this story: Kazuyo Sawa in Tokyo at ksawa3@bloomberg.net; Grace Huang in Tokyo at xhuang66@bloomberg.net

To contact the editor responsible for this story: Teo Chian Wei at cwteo@bloomberg.net

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