TOKYO - The probability of a massive earthquake in Japan's Nankai Trough occurring within the next 30 years has been revised from the previous estimate of 70 percent to 80 percent to approximately 80 percent, according to the government's earthquake investigation panel.

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Since the panel began calculating probabilities for the region in 2013, estimates have steadily risen from 60 percent to 70 percent in 2013 to 70 percent in 2014, and later to 70 percent to 80 percent in 2018.

The latest adjustment reflects the passage of time since the last major earthquake in the area, rather than being influenced by recent seismic activity, the panel noted.

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The Nankai Trough is a major ocean-floor trench stretching along Japan's Pacific coast, lying at the convergence of the Eurasian and Philippine Sea tectonic plates where intense geological activity occurs.

The panel stressed that the probability rounding from 70 percent to 80 percent to 80 percent does not indicate a 10-percent increase, but it reaffirms that a major earthquake could occur at any time.

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Japan's weather agency had previously issued a Nankai Trough megaquake alert that remained in place for one week after a magnitude 7.1 quake struck off the coast of Kyushu in August 2024.