Japan mistakenly issues 9.9-magnitude quake alert after 6.9 tremor near Russia, later withdraws warning

Japan's earthquake early warning system issued a mistaken alert of a magnitude 9.9 earthquake on October 16. The alert was issued at 12:40pm local time, warning of potentially violent shaking across northern, eastern, and central Japan. However, the warning was withdrawn just eight minutes later after officials found that the system had overestimated the earthquake's magnitude.

The actual quake, which struck off Russia's Kamchatka Peninsula, measured magnitude 6.9, a significant earthquake but far weaker than the initially predicted tremor. The JMA's automated system mistakenly located the epicenter near the Kuril Islands, between Japan's Hokkaido and Russia's Kamchatka Peninsula, leading to the erroneous magnitude 9.9 estimate.

No significant shaking was recorded in Japan, and no tsunami warnings or advisories were issued. The JMA acknowledged that the system had incorrectly calculated both the earthquake's magnitude and location and was investigating what caused the dramatic miscalculation.