A Japanese government panel has slightly increased its forecast for the likelihood of a “megaquake” occurring along the Nankai Trough, now estimating a probability of 75 to 82 percent over the next 30 years. This earthquake, potentially reaching a magnitude of 8 to 9, could trigger catastrophic tsunamis, resulting in hundreds of thousands of fatalities and causing significant economic damage. The Earthquake Research Committee's update marks a modest revision from its previous estimate, which ranged between 74 and 81 percent.

The Nankai Trough, an undersea trench stretching 800 kilometers along Japan's Pacific coast, is the site of the potential megaquake. The Philippine Sea tectonic plate is slowly sliding beneath Japan's continental plate, where friction builds up until it is released in the form of powerful earthquakes. The region has experienced similar megaquakes roughly every 100 to 200 years, with the last major event occurring in 1946.

According to experts, the risk of another earthquake grows each year, with the probability increasing by about one percent annually. The most recent government estimates suggest that smaller islands along the coast could be inundated by tsunamis over 30 meters high, with densely populated areas on Honshu and Shikoku facing colossal waves just minutes after an earthquake strikes.

In 2012, the government warned that such an event would have devastating effects, including major loss of life and infrastructure damage. The Japan Meteorological Association issued a megaquake advisory last August following a magnitude 7.1 earthquake, though it was later lifted. This caused public concern, leading to shortages of basic supplies like rice, as people prepared for possible disasters. The most powerful megaquakes on record in the region occurred in 1707, 1854, and 1944-46, with the 1707 quake also triggering the last eruption of Mount Fuji.