Japan warns ‘big one’ earthquake could kill 300,000 people

The earthquake, expected to trigger tsunamis and widespread destruction, could result in nearly 300,000 fatalities.

The estimated economic damage of 270.3 trillion yen accounts for nearly half of Japan's total gross domestic product (GDP). This figure marks a sharp increase from the previous estimate of 214.2 trillion yen due to inflationary pressures and updated terrain and ground data that have expanded anticipated flood zones, the Cabinet Office report stated.

Japan, one of the world's most earthquake-prone nations, faces an 80% probability of a magnitude 8 to 9 earthquake occurring in the Nankai Trough. 

The seismic zone, stretching approximately 900 kilometers along the southwest Pacific coast, is where the Philippine Sea Plate is subducting under the Eurasian Plate. Historical patterns suggest that megaquakes occur in this region approximately once every 100 to 150 years.

In a worst-case scenario involving a magnitude 9 earthquake, about 1.23 million people, or 10% of Japan's population, may need evacuation. The report warns that up to 298,000 casualties could occur if the disaster strikes late at night in winter, as tsunamis and building collapses would intensify the impact.

Last year, Japan issued its first megaquake advisory, cautioning of a "relatively higher chance" of a magnitude 9 earthquake after a magnitude 7.1 quake occurred near the edge of the trough.

Japan has previously witnessed the catastrophic consequences of such seismic events. In 2011, a magnitude 9 earthquake and ensuing tsunami led to over 15,000 deaths and triggered nuclear reactor meltdowns in the northeast. The latest government assessment underscores the urgent need for enhanced preparedness against future disasters.