TOKYO - Japan’s Earthquake Research Committee has revised its assessment of the probability of a massive Nankai Trough earthquake occurring within the next 30 years, raising the range from the previous estimate of about 80 percent to between 60 and 90 percent or higher.
The Nankai Trough earthquake refers to a magnitude 8 to 9 class event expected to occur along the trough stretching from off Shizuoka Prefecture to off Miyazaki Prefecture. In the worst-case scenario, deaths in the Kansai region’s two prefectures and four major urban areas alone could reach 79,300. Historically, the Nankai Trough has generated major earthquakes at intervals of 100 to 200 years, which had formed the basis of the previous 80 percent estimate.
After updating its calculation methods and incorporating new data, the government committee concluded that the likelihood now falls within the 60 to 90 percent range. The revised figure maintains the quake in the highest risk classification. The committee urged continued disaster preparedness, stressing that residents must remain vigilant.
The probability distribution is concentrated at 90 percent or higher, underscoring the assessment that such a quake could occur at any time. Committee chair Naoshi Hirata warned, "Our scientific review shows the possibility of occurrence is extremely high. We must remain vigilant against a major quake." At the same time, alternative models suggest a lower range of 20 to 50 percent. Hirata emphasized, however, that the risk remains significant: "There is uncertainty, but the potential damage would be catastrophic if such an earthquake occurred. Countermeasures should be taken immediately."
Casualty estimates further illustrate the stakes. If only 20 percent of residents evacuate within 10 minutes, deaths nationwide could approach 300,000. But if 70 percent evacuate in time, the death toll could fall by about 120,000 to 177,000, highlighting how preparedness and swift evacuation can save many lives.
Although often described as likely to strike “within 30 years,” experts caution that the quake could occur a year from now—or even tomorrow. The committee urged residents to confirm evacuation routes, secure furniture, and take everyday precautions, underscoring that readiness is a critical factor in survival.
Source: TBS
