Japan Braces for Megaquake: Potential $1.8 Trillion Economic Blow and 300,000 Lives at Risk

New government report reveals catastrophic projections from a possible magnitude-9 Nankai Trough earthquake, with damage estimates rising due to inflation and updated flood zone data.

Tokyo, March 31: Japan could suffer economic devastation worth up to $1.81 trillion and face the loss of nearly 300,000 lives if a long-feared magnitude-9 megaquake strikes off its Pacific coast, according to a sobering new report released by the Japanese Cabinet Office on Monday.

The updated damage estimate—270.3 trillion yen, nearly half of Japan’s entire GDP—is a significant rise from the previous figure of 214.2 trillion yen. This increase reflects new data incorporating inflation, advanced mapping of terrain, and expanded flood zone forecasts, the report said.

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Tsunami and Collapse Threat Looms Large

The looming threat centers on the Nankai Trough, a seismically volatile zone stretching 900 km along Japan’s southwest Pacific coast, where the Philippine Sea Plate is subducting beneath the Eurasian Plate. Seismologists warn there is an 80% chance of a magnitude 8 to 9 quake occurring in this zone within the next few decades.

In the worst-case scenario, where the quake strikes during a winter night, as many as 298,000 people could be killed by tsunami waves and building collapses. Over 1.23 million residents, roughly 10% of Japan’s population, would be forced to evacuate.

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A Historic Pattern of Destruction

The Nankai Trough produces megaquakes roughly once every 100 to 150 years. The last catastrophe of similar scale—the 2011 Tōhoku earthquake—was a magnitude 9 disaster that triggered massive tsunamis, leading to over 15,000 deaths and the Fukushima Daiichi nuclear meltdown.

In 2024, Japan issued its first-ever megaquake advisory for the Nankai Trough after a magnitude-7.1 tremor occurred at its edge. This heightened warning prompted new research and the report published today.

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A Nation on Alert

Japan remains one of the most earthquake-prone nations globally, and its disaster preparedness systems—while highly advanced—face their ultimate test if this projected megaquake hits.

Experts warn that, beyond the tragic human toll, such an event could cripple infrastructure, collapse hundreds of buildings, and upend the world’s third-largest economy.

With the memory of 2011 still raw and new modeling showing graver possibilities, Japan’s officials are urging citizens, businesses, and municipalities to revisit emergency preparedness plans and reinforce structural safety across the country.