Japan Cancels a False Giant Earthquake Warning

Japan's weather agency warned of a magnitude 9.9 earthquake, then cancelled it eight minutes later. The real quake was 6.9 and far away.

On Friday 16 October 2026, Japan's Meteorological Agency issued an earthquake early warning at 12:40 pm and cancelled it at 12:48 pm. It was the first time the agency has cancelled such a warning. The alert told people from Hokkaido, in the north, through eastern and central Japan to expect strong shaking. The system placed the epicentre near the Kuril Islands and put the magnitude at 9.9. Magnitude measures the energy of an earthquake. A 9.9 would be larger than any quake in modern records. The quake that had actually happened, at about 12:36 pm, was magnitude 6.9, centred off the Kamchatka Peninsula in Russia. It was felt lightly in the city of Hakodate. No tsunami warning was issued. Alarms sounded on loudspeakers and on mobile phones. Trains were disrupted. In Tokyo's Minato ward, officials said no strong shaking was recorded.

Why it matters

Japan's early-warning system is built to give people a few seconds. That is long enough to get under a table, or for a train to start braking, before the worst shaking arrives. It works only if people trust it. A warning that is wrong teaches people to ignore the next one. The agency has explained two mistakes, and says the full cause is still being studied. First, it used the formula meant for earthquakes inside or near Japan on a quake that was very far away. That formula produced the oversized magnitude. Second, the magnitude and the shaking forecast were calculated from two different epicentres. They are supposed to use the same one. The agency said it does not believe this was a cyber attack. The false alarm lasted about eight minutes. Eight minutes is long enough to stop trains and frighten a country, and short enough that the correction came before a real disaster was imagined into being. Hakodate is in southern Hokkaido, the part of Japan closest to the real quake. Even there the shaking was light. Further south, the warning was the event.

Key facts

• The warning went out at 12:40 pm on 16 October and was cancelled at 12:48 pm.

• The system estimated magnitude 9.9 near the Kuril Islands. The real quake was magnitude 6.9 off Kamchatka.

• The real quake was at about 12:36 pm and was felt lightly in Hakodate. There was no tsunami warning.

• Alarms rang on phones and loudspeakers, and trains were disrupted. Minato ward in Tokyo recorded no strong shaking.

• The agency used a near-Japan formula on a distant quake, and two different epicentres for the size and the shaking.

• This was the first cancellation of an earthquake early warning. A cyber attack has been ruled out. The software review continues.

What's next

The agency says it is still investigating why two epicentres were used. It has not yet said what it will change in the software. Until that change is public, the next distant quake could trip the same formula. People in Japan now know a warning can be withdrawn. The system has to show that a real one will still be believed. A train that stops for a false alarm is an inconvenience. A train that does not stop for a true one is a disaster. The eight-minute error sits between those two risks. A system that can withdraw a warning is safer than one that cannot. It is also a system that just showed it can invent a historic earthquake out of a distant, moderate one.