TOKYO, October 17, 2026 — Japan’s Meteorological Agency issued a false early warning of a magnitude 9.9 earthquake before canceling it twelve minutes later after determining the actual quake was far weaker and located far offshore.
False Alert Triggered Nationwide Alarm
The warning was issued at approximately 12:36 p.m. Friday in Japan and canceled at 12:48 p.m., according to NHK. The early-warning display identified the location as the Kuril Islands region and showed an estimated magnitude of 9.9 at a depth of 140 kilometers. The agency said it warned of strong shaking across northern and central Japan, including the Tokyo region. NHK confirmed the earthquake did not produce shaking in Japan and no tsunami warnings were issued.
Actual Quake Was Much Smaller and Distant
The U.S. Geological Survey measured the actual earthquake at magnitude 6.9, locating its epicenter approximately 76 kilometers northeast of Ozernovskiy, Russia. Its estimated depth was 143.2 kilometers. A magnitude 9.9 earthquake would be the largest ever recorded, exceeding the magnitude 9.5 quake that struck Chile in 1960. It would release roughly 32,000 times as much energy as the actual magnitude 6.9 earthquake that struck Kamchatka.
Agency Cites Formula Misapplication
Japan’s Meteorological Agency said it applied a magnitude formula designed for earthquakes within Japan to a quake occurring far away. Ayataka Ebita, head of the JMA’s earthquake and tsunami observation division, said the system had mistakenly estimated the earthquake’s epicentre and overstated its magnitude. The agency said it used different estimated locations to calculate the magnitude and forecast shaking. JR Central said bullet train services on the Tokaido Shinkansen Line were temporarily suspended between Shin-Yokohama and Toyohashi stations, and services resumed after the warning was withdrawn.
No Cyberattack Found, Investigation Underway
The Japan Meteorological Agency ruled out a cyberattack, and said false alarms can result from sensor noise caused by accidents, lightning or equipment failures. NHK WORLD-JAPAN said the Japan Meteorological Agency canceled the emergency earthquake warning around 12:48 PM and said there is no risk of tsunami. The agency said it is investigating the error and will provide a detailed explanation once the cause is determined.
Public Reaction and Official Response
Following the false alarm, social media users in Japan expressed confusion and concern, with many sharing screenshots of the alert on platforms like X and LINE. Local officials in Hokkaido and the Tohoku region reported receiving numerous calls from residents seeking clarification, though no evacuations were ordered. The Japan Meteorological Agency issued a public apology via its website, stating that the error caused unnecessary anxiety and reaffirming its commitment to improving the accuracy of its early-warning system.
Technical Basis for the Formula Error
The Japan Meteorological Agency’s early-warning system relies on a magnitude calculation formula calibrated for seismic events occurring within or near the Japanese archipelago. When applied to earthquakes far offshore—such as the one near Russia’s Kamchatka Peninsula—the model overestimates magnitude due to unaccounted-for attenuation and wave propagation differences across tectonic boundaries. This limitation becomes pronounced when the actual quake lies outside the regional model’s validated distance range, leading to inflated magnitude estimates even when sensor data is accurate.
In this case, the system used real-time seismic readings but applied a domestic attenuation assumption that does not hold for distant sources, causing the magnitude to be inflated from 6.9 to 9.9. The agency confirmed that multiple location estimates were tested during processing, and the discrepancy arose not from sensor failure but from the misapplication of a region-specific algorithm to a teleseismic event. Officials noted that while the sensors detected the quake correctly, the interpretive model failed to adjust for distance-related energy dissipation.
Sources
- Japan mistakenly issues warning for magnitude 9.9 earthquake – BNO News
- Japan Meteorological Agency Mistakenly Issues 9.9 Earthquake Warning, Then Cancels It: 9 outlets compared | NewsCord
- Earthquake Of Magnitude 7 Strikes Russia, Japan Mistakenly Issues 9.9 Warning, Technology Failure or Human Error?
Photo: Syced (CC0)
