Japan issues unprecedented quake warning, cites risk of tremor killing up to 300,000

Japan has activated its first-ever "aftershock earthquake warning" for northern coastal regions following a magnitude 7.5 quake off Aomori prefecture, citing a significantly elevated risk of a larger tremor within a week.

The warning, a first since the system was established in 2022, covers 182 municipalities across Hokkaido, Aomori, Iwate, Miyagi, Fukushima, Ibaraki and Chiba prefectures. Authorities urged residents to prepare for immediate evacuation, secure furniture, and check supplies.

The warning is based on the quake's location within the presumed source zone for massive earthquakes along the Japan Trench and Kuril Trench. The government's Disaster Prevention Basic Plan defines such an event as potentially triggering a subsequent, larger earthquake.

Official worst-case projections estimate up to 199,000 fatalities from a massive Japan Trench quake and 100,000 from a Kuril Trench event, with tsunamis potentially reaching 30 meters. Combined economic losses could hit 48 trillion yen (HK$2.4 trillion).

The government noted the added danger of winter, where snow accumulation could increase building collapse risks and fire hazards. It urged residents to keep emergency bags by their beds, confirm evacuation routes and family meeting points, and avoid coastal lowlands.

The warning remains in effect until December 16. Authorities emphasized that a larger quake is "not inevitable" but the current risk is substantially higher than normal.