Japan apologises after erroneous 9.9-magnitude earthquake alert disrupts transport

TOKYO, Oct 17 — Japan’s weather agency issued an erroneous alert for a magnitude 9.9 earthquake, which was quickly withdrawn and led to public transport disruptions. The Japan Meteorological Agency (JMA) had warned that an earthquake of that size had occurred near the Kuril Islands, also known as the Chishima Islands, prompting loud emergency alerts on millions of mobile phones.

It later emerged that the actual earthquake had a magnitude of 6.9 and occurred near Russia’s Kamchatka Peninsula, about 160 kilometres from Japan at a depth of 160 kilometres. JMA official Shinya Tsukada apologized for the inconvenience and concern caused to the public. The error arose from an incorrect calculation of the earthquake’s epicentre, as the agency estimated it to be 680 kilometres farther away than it actually was.

This misconception led to an overestimation of the earthquake’s magnitude, which would have released roughly 22 times more energy than the 2011 magnitude 9.0 undersea quake that killed or left missing approximately 18,500 people and damaged the Fukushima nuclear plant.