Japan’s meteorological agency issued its first-ever “megaquake advisory” following a 7.1-magnitude earthquake off the country’s southern coast, raising the risk of a larger quake on the Nankai Trough. The warning highlights the potential for temblors up to magnitude 9.1 in the subduction zone where the Eurasian Plate collides with the Philippine Sea Plate. Scientists cannot predict earthquakes but are able to forecast times of heightened risk, such as in Japan, due to frequent shaking and advanced monitoring equipment. The Nankai Trough has a history of producing large earthquakes roughly every 100 to 150 years, with a 70% to 80% chance of a megathrust earthquake in the next 30 years. Large Nankai Trough earthquakes often come in pairs, with the most recent examples occurring in 1944 and 1946. The recent magnitude-7.1 earthquake that prompted the advisory occurred in a segment that shakes more frequently, relieving stress. However, the concern lies in the earthquake’s proximity to a segment that has been building stress since the 1940s. The potential for intense shaking and tsunamis near Japan’s southeast coast underscores the importance of preparedness in the face of the heightened risk forecasted by the agency.
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