Up to 199,000 Deaths Estimated From Mega-Tsunami; Most Recent Occurrence Took Place in 17th Century

By Tatsuya Nozaki / Yomiuri Shimbun Staff Writer

2:00 JST, December 11, 2025

Government estimates warn that up to 199,000 people could die from a major tsunami following an earthquake along the Japan and Chishima trenches.

According to the government’s Central Disaster Management Council, maximum-class tsunami have occurred along the trenches at intervals of about 300 to 400 years. The most recent occurrence is thought to have been in the 17th century, and experts believe that a maximum-class earthquake and tsunami is imminent.

The council’s 2021 damage projection for an M9-class earthquake estimated that tsunamis surging along the Pacific coast from Hokkaido to Chiba on a late winter night — when heavy snow could hinder evacuations — would result in 199,000 deaths from a Japan Trench earthquake and 100,000 from a Chishima Trench earthquake.

Even among those who successfully evacuate, an estimated 42,000 would face an increased death risk due to hypothermia after a Japan Trench quake and 22,000 after a Chishima Trench quake.

However, the council stated that fatalities could be reduced by 80% through improved tsunami evacuation awareness. Additionally, the risk of hypothermia could be virtually eliminated by preparing cold-weather gear and heating equipment.

“It’s important for residents in expected tsunami inundation zones to consider how they will evacuate if an event occurs during the cold of winter,” said Prof. Masahiro Nemoto of the Japanese Red Cross Hokkaido College of Nursing, a specialist in cold region disaster prevention.

“We urge such individuals to prepare waterproof and cold-resistant outerwear, winter boots, gloves and other items so they can evacuate while properly equipped,” Nemoto said.