FILE - In this March 30, 2011 file photo, a beached ship sits among the rubble in a residential neighborhood after the March 11 earthquake and tsunami in Kesennuma in Miyagi prefecture, northern Japan. The stranded fishing boat that became a symbol of the devastation of Japan's 2011 tsunami has long divided a northeastern coastal city - between those who wanted to keep it as a monument of survival and those who wanted a painful reminder gone. Last week, the city announced it will be torn down after a heated debate and citywide vote. (AP Photo/Vincent Yu, File)FILE - In this March 30, 2011 file photo, a beached ship sits among the rubble in a residential neighborhood after the March 11 earthquake and tsunami in Kesennuma in Miyagi prefecture, northern Japan. The stranded fishing boat that became a symbol of the devastation of Japan's 2011 tsunami has long divided a northeastern coastal city - between those who wanted to keep it as a monument of survival and those who wanted a painful reminder gone. Last week, the city announced it will be torn down after a heated debate and citywide vote. (AP Photo/Vincent Yu, File)

Japan warns that a megaquake in the Nankai Trough could cause US$1.81 trillion in damage and result in up to 300,000 deaths in the country, prompting enhanced disaster planning. (AP Photo/Vincent Yu, File)

Japan faces a looming seismic disaster that could have catastrophic economic and human tolls, as government reports on Monday (31 March) suggest that a megaquake along the Nankai Trough could cause an estimated US$1.81 trillion (S$2.43 trillion) in damage and potentially kill up to 300,000 people.

The seismic event, expected to occur with a high probability of 80 per cent, would trigger massive tsunamis, building collapses, and long-term infrastructure destruction.

The potential economic fallout of the Nankai Trough megaquake is staggering.

With losses expected to reach 270 trillion yen (approximately US$1.81 trillion), this would account for nearly half of Japan’s GDP.

This estimate has increased significantly since previous projections, largely due to factors such as inflation and refined terrain data that suggest a larger flood zone.

The devastation would not only be caused by immediate destruction but also by long-term recovery challenges.

Industries from manufacturing to tourism are likely to face extended setbacks, affecting both national and global markets.

A key factor in the human toll is the response to evacuations.

Government reports indicate that in the worst-case scenario, up to 298,000 people could perish, with 215,000 deaths resulting from tsunamis alone.

These figures are contingent on evacuation rates, which are currently estimated at a low 20 per cent.

If evacuation rates can be increased to 70 per cent, the death toll could be significantly reduced, with tsunami-related fatalities dropping to 94,000.

However, a high number of casualties could still occur due to difficulties in shelter conditions, with up to 52,000 deaths potentially resulting from inadequate evacuation shelters in the wake of the disaster.

Japan’s seismic vulnerability is compounded by its location along the Nankai Trough, where the Philippine Sea Plate subducts under the Eurasian Plate.

The region experiences tectonic strain that typically leads to major earthquakes roughly every 100 to 150 years.

Given the geological history and the 2011 magnitude 9 earthquake that triggered a deadly tsunami and nuclear disaster, Japan remains on high alert.

A repeat of such an event, especially if it occurs during winter at night, would amplify the risks associated with evacuation and rescue efforts.

In light of the growing seismic risks, Japan is ramping up its disaster resilience strategies.

Plans are in motion to revise the national disaster prevention framework, with special focus on flood-risk zones and better-targeted evacuations.

The government is also moving forward with a national resilience plan set for 2026, which will enhance the country’s disaster preparedness infrastructure.

Additionally, a dedicated agency for disaster prevention is expected to launch in 2026, marking a concerted push to mitigate the effects of future megaquakes.

Read on Japan planning to revise its disaster plans for a potential Nankai Trough megaquake here.