Japan estimates feared megaquake could cause $1.8 trillion in damage, kill 300,000 people

Japan could face economic losses of up to US$1.81 trillion and nearly 300,000 fatalities if a long-feared megaquake strikes off its Pacific coast, according to a new government report released Monday.

The projected cost—270.3 trillion yen, or about half of Japan’s GDP—represents a sharp increase from the previous estimate of 214.2 trillion yen. The updated figure accounts for inflation, new terrain and ground data, and expanded tsunami flood zones, as revealed by the Cabinet Office.

Key details from the report:
Expected magnitude: 8 to 9, centered in the Nankai Trough—a seismically active zone off southwest Japan’s Pacific coast, about 900 km long.

Fatalities: Up to 298,000, especially if the quake hits at night during winter, increasing vulnerability.

Evacuations: An estimated 1.23 million people could be displaced—roughly 10% of Japan’s population.

Damage: Thousands of buildings could collapse, and massive tsunamis are expected to follow.

Why this is such a serious risk:
Japan lies on the Ring of Fire, one of the most seismically active areas in the world. The Nankai Trough is a known hotspot where the Philippine Sea Plate is subducting beneath the Eurasian Plate, building up strain that historically leads to megaquakes every 100 to 150 years.

In fact, the government estimates an 80% chance that such a quake will strike the Nankai Trough region within the next few decades.

Japan even issued its first-ever megaquake advisory last year after a magnitude-7.1 tremor struck near the trough's edge—raising concern that it could be a foreshock for something bigger.

The memory of the 2011 Tōhoku earthquake still looms large. That magnitude-9.0 quake caused a tsunami, over 15,000 deaths, and led to the Fukushima nuclear disaster—a tragedy Japan is determined not to repeat.

The new report highlights not only the human toll such a disaster could take, but also the economic devastation, reinforcing the urgent need for preparedness, infrastructure resilience, and community-level disaster planning.

Want a quick breakdown of what this might mean for Japan’s future disaster policy or global economic ripple effects?