An expert government committee has decided to revise the chances of a major Nankai Trough quake off Japan's Pacific coast in the next 30 years from about 70 percent to between 70 and 80 percent.
The Nankai Trough runs off the coast from the Kanto region down all the way to Okinawa, Japan's southernmost prefecture. The Earthquake Research Committee, a part of the government Headquarters for Earthquake Research Promotion, recalculated the chances of a major quake in the trough over the next three decades starting from Jan. 1, 2018. The revised number will be formally released next month.
A major earthquake in the Nankai Trough is expected to be in the magnitude-8 to -9 range, and the calculations are based on a projected average interval of 90 years between such quakes using 1946 as a baseline -- the last time a major temblor struck the trough. The estimate is premised on the assumption that Nankai Trough earthquakes happen at regular intervals, so the chances of the next one rise the longer it has been since the previous major temblor.
"The projection doesn't indicate the chances of an earthquake will rise suddenly with the new year, but rather that the chances are getting higher moment by moment," commented Earthquake Research Committee Chairman Naoshi Hirata, a professor at the University of Tokyo. "I would like us to be prepared no matter when the quake hits."