Science Researchers warn of potential M9 megaquake along Chishima Trench near Hokkaido

On Sunday, a research team in Japan cautioned that the accumulated stress energy along an undersea trench off northern Japan could potentially lead to a mega-quake of magnitude 9. The study, conducted over five years by researchers from Tohoku and Hokkaido universities, alongside the Japan Agency for Marine-Earth Science and Technology, focused on the Chishima Trench off Hokkaido. Historical records suggest a massive earthquake occurred near this region in the 17th century. According to the government's earthquake panel, there is a 7 to 40 per cent chance of a quake with a magnitude of at least 8.8 occurring in the next 30 years. To monitor this, the team installed GPS observation stations on the seabed in 2019, near the point where an ocean plate subducts beneath a continental plate.

Stations on the ocean plate moved about 8 centimetres per year toward the continental side. But a station on the continental plate where the two plates meet also moved about 8 centimeters in the same direction. Researchers said this indicates that parts of the plates are firmly joined together, and strain may be accumulating. Assuming that the plates have been joined similarly since the 17th-century quake, the team says the built-up strain would be equivalent to the energy released by a mega-quake.

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