An earthquake alert in Japan was temporarily classified as magnitude 9.9, prompting widespread warnings, but it was withdrawn at 12:48. The cause has not been determined and remains under investigation, while some transportation services were also affected.
At around 12:40 p.m., the Japan Meteorological Agency issued an earthquake alert and announced a scenario involving a maximum seismic intensity of 7 and a magnitude of 9.9. Earlier, a magnitude 6.9 earthquake had been observed at an epicenter off Russia's Kamchatka Peninsula, and confusion over the receipt of alerts and video and audio information spread across Japan.
At 12:48 p.m., the alert was withdrawn and the forecast maximum seismic intensity was cancelled. JMA said it was investigating the cause and denied the possibility of a cyberattack. False alerts have occurred in the past, but this is reportedly the first withdrawal.
The false alert caused disruption to some public transportation services and confusion among the public. The Tokaido Shinkansen and other services were temporarily halted when automatic safety systems activated, resulting in traffic congestion and other disruption. In Tokyo, some people reportedly panicked after seeing the alert on their apps.
JMA identified the application of a domestic magnitude formula based on an earthquake location outside the relevant region, as well as inconsistencies in data processing caused by sensor noise and an insufficient number of observation points, as possible causes. Director-General Ebita explained that real-time monitoring of the calculation process is difficult because the system generates results automatically, and said the investigation would continue.