Japan Warns of Possible Megaquake After 7.1 Tremor

Japan's meteorological agency has issued its inaugural "megaquake advisory" after a 7.1-magnitude earthquake struck off the southern coast, raising concerns about a potential larger quake on the Nankai Trough. This underwater subduction zone is known for its capacity to generate powerful earthquakes, with scientists estimating that a full slip of the fault could result in a magnitude 9.1 event. The advisory indicates an increased risk of strong shaking and tsunamis, although it does not predict an imminent megaquake. The Nankai Trough has a history of significant seismic activity, with the Earthquake Research Committee estimating a 70% to 80% chance of a megathrust earthquake occurring within the next 30 years. The recent 7.1 tremor occurred in a segment of the fault that typically experiences more frequent quakes, which may reduce the likelihood of a major event in that specific area. However, the potential for catastrophic outcomes remains, as past megathrust earthquakes have caused devastating tsunamis. In light of the advisory, Prime Minister Fumio Kishida has canceled a planned visit to Kazakhstan, citing public anxiety over the situation. The advisory is expected to remain in effect for a week, urging residents in the region to prepare for possible evacuations. Historical data suggests that a megaquake could result in significant casualties and destruction, with estimates of up to 323,000 deaths and tsunamis reaching heights of 30 meters. Experts emphasize the importance of preparedness, as the Nankai Trough poses a serious risk not only to Japan but also parallels the Cascadia Subduction Zone on the U.S. West Coast, where similar seismic events are anticipated less frequently.