Japan Issues First Ever ‘Megaquake’ Warning

After a 7.1 tremor struck southwestern Japan on Thursday, the country’s meteorological agency issued its first-ever alert for a possible “megaquake.” It marks the first time the warning has been issued under new rules drawn up after a 2011 earthquake, tsunami and nuclear disaster killed almost 20,000 people. Phys.org reports: The JMA’s “megaquake advisory” warns that “if a major earthquake were to occur in the future, strong shaking and large tsunamis would be generated.” “The likelihood of a new major earthquake is higher than normal, but this is not an indication that a major earthquake will definitely occur during a specific period of time,” it added. The advisory concerns the Nankai Trough “subduction zone” between two tectonic plates in the Pacific Ocean, where massive earthquakes have hit in the past. […]

Japan’s government has previously said the next magnitude 8-9 megaquake along the Nankai Trough has a roughly 70 percent probability of striking within the next 30 years. In the worst-case scenario 300,000 lives could be lost, experts estimate, with some engineers saying the damage could reach $13 trillion with infrastructure wiped out. “The history of great earthquakes at Nankai is convincingly scary,” geologists Kyle Bradley and Judith A Hubbard wrote in their Earthquake Insights newsletter. And “while earthquake prediction is impossible, the occurrence of one earthquake usually does raise the likelihood of another”, they explained. “A future great Nankai earthquake is surely the most long-anticipated earthquake in history — it is the original definition of the ‘Big One’.”