Japan Raises Earthquake Probability Along Chishima Trench to Nearly 90%

A Japanese government panel has raised the probability of a major earthquake occurring along the Chishima Trench off Nemuro, Hokkaido, estimating a 90% chance within the next 30 years, up from around 80%.

The revised estimate was released by the government’s Earthquake Research Committee as part of its annual review, which recalculates long-term earthquake probabilities along offshore trenches and active inland faults. The latest assessment uses January 1 of this year as its reference date.

According to the committee, the probability will continue to rise until a large earthquake actually occurs.

Other High-Risk Regions

While the probability of an earthquake of magnitude 8.0 to 8.6 off the Tokachi region in eastern Hokkaido within the next 30 years remained unchanged at around 20%, the likelihood within 50 years increased to about 50%, up from roughly 40%.

Along the Japan Trench, the probability of a magnitude 7.4 earthquake occurring within 30 years in the landward area off Miyagi Prefecture rose to 79–95%, compared with the previous estimate of 76–93%.

Continued Seismic Activity After Noto Peninsula Earthquake

The committee also released an updated evaluation of seismic activity in areas affected by the magnitude 7.6 earthquake that struck the Noto Peninsula in Ishikawa Prefecture on January 1, 2024.

That earthquake was caused by the movement of a long-standing active fault near the peninsula’s northern coast. Since then, noticeable earthquakes with a seismic intensity of 1 or higher on Japan’s seismic scale have continued to occur several times a month in the surrounding area.

“The current level of seismic activity may continue for the time being,” the committee said.

Preparedness Emphasized

Japan is one of the world’s most earthquake-prone countries, and the updated probabilities underscore the importance of disaster preparedness, particularly in coastal regions vulnerable to large offshore earthquakes and potential tsunamis.