17th January 2025 – (Tokyo) The Japanese government’s earthquake investigation panel has increased the probability of a major earthquake occurring along the Nankai Trough to 80% over the next 30 years. This adjustment reflects a rise from the previous estimate of 70% to 80%, as of 1st January. The panel of experts noted that the likelihood of an earthquake measuring between magnitude 8 and 9 is now significantly heightened.
In addition to the Nankai Trough, the probability of a megaquake occurring in both the Japan Trench and the Chishima Trench has also increased, with the chances of an 8.6 magnitude quake off the Tokachi coast now estimated at 20%. The panel clarified that this updated assessment is a consequence of time elapsed since the last significant earthquake in the area, rather than a sudden spike in risk.
The committee has been monitoring seismic probabilities annually since it began evaluating earthquake risks in 2013, when the likelihood of a Nankai Trough megaquake was estimated at 60% to 70%. Estimates were subsequently raised to 70% in 2014 and to between 70% and 80% in 2018.
Recent seismic activity in the region has heightened public awareness of these risks. A magnitude 6.6 earthquake struck off the coast of Miyazaki Prefecture on Monday evening, causing localised damage such as shattered windows and displaced items in stores. While the Japan Meteorological Agency issued a tsunami advisory, it was later rescinded after only minor tsunami waves were observed.
The operator of the Sendai nuclear power plant reported no abnormalities post-quake, while some local train services were temporarily suspended. Experts, including Assistant Professor Yamashita Yusuke from Kyoto University, noted that the recent tremor occurred at the tectonic plate boundaries and was likely related to past seismic activities, including a magnitude 7.1 quake in August.
Yamashita reassured that while Monday’s quake was significant, its seismic energy was about half that of the previous August event. Nonetheless, he urged caution, as the potential for further tremors remains, particularly given the geological dynamics at play in the Nankai Trough region. The Japan Meteorological Agency continues to advise vigilance, suggesting that residents should be prepared for more seismic activity in the days ahead.
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