Hokkaido on brink of a '400-year mega earthquake'? Experts warn of approaching threat

Study indicates that stress is continuously building up beneath the seabed off the coast of Tokachi, which could lead to a “mega earthquake” at any moment. (File Photo)

The Japan Broadcasting Corporation (NHK) reported last March that the Kuril Trench off the coast of Hokkaido has accumulated immense energy, raising concerns among local residents about a potential large earthquake. According to a recent report from Kyodo News, a team from Shizuoka University and the Japan Agency for Marine-Earth Science and Technology stated on Feb. 6 that after analyzing earthquake data from the Meteorological Agency, they discovered that stress is continuously building up beneath the seabed off the coast of Tokachi, which could lead to a “mega earthquake” at any moment.

The research team utilized earthquake data from 2000 to 2025 for seismic events with a magnitude of 2.5 or greater occurring near the plate boundaries off the coast of Hokkaido to the Tohoku region. They calculated the accumulated stress in the crust based on the frequency ratios of earthquakes of varying magnitudes. The results showed that there is an area off the coast of Tokachi where stress is gradually accumulating, with the accumulation increasing each year.

According to the long-term assessment by the Japanese government’s Earthquake Research Committee, a mega earthquake occurs in the waters off Hokkaido roughly every 340 to 380 years on average. The last such event occurred in the 17th century, making it nearly 400 years since. Consequently, the committee has assessed that the probability of a large earthquake occurring within the next 30 years is between “7% and 40%” and believes that the waters off Hokkaido have reached a mature stage for a mega earthquake, suggesting that the timing may be approaching.