Government estimates highlight massive economic and human toll if Nankai Trough quake strikes
Japan could face up to US$1.81 trillion in economic losses and nearly 300,000 fatalities if a long-anticipated megaquake strikes its Pacific coast, according to a Cabinet Office report released on March 31. The updated projections account for new ground data and inflation, placing the potential disaster among the costliest in modern history.
The predicted disaster stems from the Nankai Trough — a volatile 900km seabed zone off Japan’s southwest coast where the Philippine Sea Plate subducts beneath the Eurasian Plate. The Japanese government assesses an 80% chance that an earthquake with a magnitude between 8 and 9 will strike this area. Historically, such quakes occur every 100 to 150 years.
The worst-case scenario estimates up to 298,000 deaths if the earthquake occurs on a winter night, primarily due to building collapses and tsunamis. The report also predicts that 1.23 million people, or roughly 1% of Japan’s population, may need to evacuate. These numbers reflect significant improvements in prediction models based on revised terrain and flood zone data.
The predicted disaster stems from the Nankai Trough — a volatile 900km seabed zone off Japan’s southwest coast where the Philippine Sea Plate subducts beneath the Eurasian Plate. The Japanese government assesses an 80% chance that an earthquake with a magnitude between 8 and 9 will strike this area. Historically, such quakes occur every 100 to 150 years.
High Death Toll and Evacuations Expected
The worst-case scenario estimates up to 298,000 deaths if the earthquake occurs on a winter night, primarily due to building collapses and tsunamis. The report also forecasts that 1.23 million people, or roughly 1% of Japan’s population, may need to evacuate. These numbers reflect significant improvements in prediction models based on revised terrain and flood zone data.
Economic Devastation Nearly Half of Japan’s GDP
Economic losses are projected to reach ¥270.3 trillion—nearly 50% of Japan’s GDP—marking a sharp increase from earlier estimates of ¥214.2 trillion. The increase accounts for inflation and broader anticipated flood zones, heightening concern over Japan’s readiness. Memories of the 2011 magnitude 9 Tōhoku earthquake, which claimed over 15,000 lives, remain vivid in Japan’s collective consciousness.
Warnings and Preparedness Efforts
Last year, Japan issued its first-ever advisory for a potential magnitude 9 earthquake in the Nankai Trough following a magnitude 7.1 quake near the zone. Authorities continue to push public education campaigns, infrastructure upgrades, and disaster preparedness protocols to mitigate damage. Still, the scale of devastation predicted poses formidable challenges for urban planning and emergency response.
The potential Nankai Trough megaquake presents not only a humanitarian threat but also a staggering economic burden. With such a high probability, Japan’s commitment to advanced preparation and international collaboration in disaster mitigation remains crucial for regional resilience and safety.
Sources: CNA (2025), Reuters (2025)
Keywords: Japan Megaquake, Nankai Trough Earthquake, Tsunami Deaths, Economic Loss Japan
