Japan's Meteorological Agency (JMA) triggered a nationwide emergency at 12:40 p.m. local time on Friday by broadcasting a 9.9‑magnitude earthquake alert that spanned from Hokkaido to the Tokai region. The warning, issued just two minutes after a 6.9‑magnitude quake struck off Russia's Kamchatka Peninsula, called for people to seek shelter and sent emergency alerts on phones and loudspeakers. The system estimated a shindo‑7 intensity, the maximum on Japan's seven‑point scale, across 18 prefectures. No tremors higher than shindo‑1 were recorded, and the alert was rescinded at 12:48 p.m. — the first time Japan’s early‑warning system has formally withdrawn a warning.
Yatake Ebita, head of the JMA's earthquake‑and‑tsunami observation division, said the mistake stemmed from an incorrect epicentre estimate and an inappropriate magnitude formula used for a distant event. The agency ruled out a cyberattack and blamed the error on the use of a Japan‑specific formula that overestimates magnitude when applied to quakes far from the mainland. Lightning was also dismissed as a trigger, while sensor noise and data‑processing glitches were cited as other suspects.
The false alarm rattled commuters and disrupted services. The Tokaido Shinkansen was halted for 15 minutes after an automated safety system went into emergency mode, and buses and trains across the country experienced delays. In Tokyo, pedestrians paused to check their phones as alerts flashed, while students at Waseda University, including 20‑year‑old Lola Milroy‑Tompkins, shared the shock on campus.
The JMA has issued a statement noting that false alarms have occurred before, most notably in July 2020 and August 2013, when sensor noise and mis‑calculations triggered widespread warnings without significant shaking. The agency is now conducting a detailed review of its seismic‑sensor network and data‑processing pipeline to prevent a repeat of the incident.
Government officials have acknowledged the public anxiety and the economic burden caused by the unnecessary evacuations and travel disruptions. Chief cabinet secretary Minoru Kihara urged the public to remain calm and assured that investigations would be swift.
Investigators are expected to release a full report by the end of August, with the JMA pledging upgrades to its computation algorithms and station calibration.