When Japan’s earthquake warning system cries wolf: Magnitude 9.9 alert withdrawn in eight minutes

When Japan’s earthquake warning system cries wolf: Magnitude 9.9 alert withdrawn in eight minutes



Japan’s earthquake early warning system mistakenly issued an alert for a magnitude 9.9 quake on October 16, 2026, before withdrawing it eight minutes later. — AFP file pic


Summary

• On October 16, Japan's earthquake early warning system issued a false alarm predicting a catastrophic magnitude 9.9 earthquake, which was later corrected to a magnitude 6.9 quake off Russia's Kamchatka Peninsula.
• The initial alert, withdrawn just eight minutes later, mistakenly forecasted extreme shaking across northern, eastern, and central Japan, which fortunately did not occur.
• The Japan Meteorological Agency acknowledged inaccuracies in both the quake's magnitude and location estimates, ruling out cyberattack involvement and initiating an investigation to determine the cause of the miscalculation.
• This incident underscores the challenges of relying on preliminary data in real-time seismic assessments essential for disaster preparedness.

First Published: Friday, 16 Oct 2026 3:12 PM MYT
Last Modified: Friday, 16 Oct 2026 3:21 PM MYT


TOKYO, Oct 16 — Imagine your phone suddenly blaring a warning that a catastrophic magnitude 9.9 earthquake is about to strike.

That’s exactly the sort of alarm that sounded across parts of Japan this afternoon, when the country’s sophisticated earthquake early warning system mistakenly forecast one of the most powerful tremors in recorded history.


The only problem? The earthquake was nowhere near as powerful as predicted.


The Japan Meteorological Agency (JMA) issued an emergency alert at 12.40pm local time, warning of potentially violent shaking across northern, eastern and central Japan.


But just eight minutes later, the warning was withdrawn after officials discovered that their system had dramatically overestimated the earthquake’s magnitude.

The actual quake, which struck off Russia’s Kamchatka Peninsula, measured magnitude 6.9 — a substantial earthquake in its own right, but far weaker than the monster tremor initially forecast.

And while the warning suggested that parts of Japan could experience devastating shaking, the strongest tremors recorded in the country barely registered.


A megaquake that wasn’t

According to The Japan Times, the earthquake struck at a depth of about 160km, but the JMA’s automated system mistakenly located its epicentre near the Kuril Islands, between Japan’s Hokkaido and Russia’s Kamchatka Peninsula.

The error led to an extraordinary magnitude 9.9 estimate, with the agency initially predicting shaking reaching the maximum level of 7 on Japan’s seismic intensity scale.

In reality, the strongest shaking recorded in Japan was just 1 on the scale, including in Hakodate, Hokkaido, where the tremor was barely perceptible.

No tsunami warnings or advisories were issued.

At a press briefing, a JMA spokesman acknowledged that the system had incorrectly calculated both the earthquake’s magnitude and location.

Officials also ruled out a cyberattack, saying they were investigating what had caused the dramatic miscalculation.

“We are currently investigating the cause and will provide an explanation as soon as it is determined,” the spokesman said.

Just how extraordinary was the initial estimate?

A magnitude 9.9 earthquake would be considerably stronger than the largest earthquake ever instrumentally recorded — the magnitude 9.5 tremor that devastated Chile in 1960.

It would also dwarf the magnitude 9.0 earthquake that struck northeastern Japan on March 11, 2011, unleashing a deadly tsunami and triggering the Fukushima nuclear disaster.

When every second counts

For a country accustomed to living with earthquakes, Japan’s early warning system is a crucial part of everyday disaster preparedness.

Introduced to the public in 2007, the system is designed to give people a few precious seconds to protect themselves before potentially destructive shaking reaches them.

It works by detecting the first, faster-moving seismic waves produced by an earthquake and using that information to estimate where the quake occurred, how powerful it is and where strong shaking is likely to strike.

Alerts can then be sent to mobile phones, television stations and public speakers, while trains and other infrastructure can take emergency precautions.

But there is a catch.

Because the system must make those calculations almost instantaneously, it relies on preliminary data that can sometimes produce inaccurate estimates.

Today’s incident demonstrated just how dramatic such an error can be, with a magnitude 6.9 earthquake initially mistaken for a potentially record-breaking 9.9 event.

Fortunately, the warning was withdrawn within minutes, with no significant shaking recorded in Japan.

For the JMA, however, the question remains: how did a system built to give people a vital head start in an earthquake get this one so spectacularly wrong?