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Study says Nankai Trough locked zone shifts, complicating megaquake forecasts
The locked stretch spans a 900 km Nankai Trough off Japan, where the Philippine plate is sliding beneath Eurasia at 4.0 to 6.0 cm per year.
A Japanese study found that the tectonic “locked zone” along the Nankai Trough is not fixed, changing over time and adding uncertainty to efforts to forecast megaquakes along the fault line, according to the SCMP Economy desk.
The research focuses on the 900 km (560 mile) long Nankai Trough off Japan’s Pacific coast, where the Philippine plate slips under the Eurasian plate. The Philippine plate is moving at a rate of 4.0 to 6.0 cm per year, a key input used to estimate how much of the interface is locking.
According to the study described by SCMP, earthquakes occur when the plates lock, movement becomes impeded, and stress builds until it is released. If that energy is released in a major event, the resulting shaking and possible tsunamis are among the risks researchers are trying to anticipate by mapping locked areas.
SCMP said researchers from the University of Tokyo’s Institute of Industrial Science and the Japanese coastguard used crustal deformation data from 2013 to 2023 to calculate the plate’s movement and estimate the locking rate, finding some areas remained continuously locked while others behaved more fluidly.