Japan's false 9.9 quake alert sparks panic, then retracted

Japan's national earthquake early warning system mistakenly announced a magnitude 9.9 earthquake alert on Friday, leading to widespread panic and emergency notifications. The alert, issued at 12:40 PM local time, wrongly indicated a massive quake with an epicentre near the Kuril Islands. This prompted emergency phone alerts, public loudspeaker warnings, and television broadcasts urging people to take shelter.

However, no significant shaking materialized, with recorded vibrations reaching only the lowest seismic intensity level. Eight minutes after the initial alert, the Japan Meteorological Agency (JMA) issued a cancellation notice, marking the first formal withdrawal of an emergency earthquake warning. The agency attributed the malfunction to errors in its earthquake magnitude estimation and location calculations, specifically noting that a formula for domestic quakes was applied to an offshore event.

The predicted magnitude of 9.9 was notable as it surpassed any earthquake historically recorded. The JMA explained that 9.9 is the highest magnitude its system can communicate externally. The incident also caused disruptions, including a 15-minute halt to the Tokaido Shinkansen bullet train line. Government officials acknowledged the anxiety caused by the false alarm.