There is a 60 to 70 percent chance that an earthquake registering magnitude 8 to 9 or above will occur along the Nankai Trough off central and western Japan within the next 30 years, a government panel said Friday.
The expert panel also said in the report a massive quake would likely occur near the Nankai Trough once every 100 to 200 years, and urged caution as nearly 70 years have passed since the area was hit by the Tonankai Earthquake in 1944 and the Nankai Earthquake in 1946.
The panel did not come up with an estimate specifically on a megaquake registering 9, saying it is "too difficult."
Unlike previous estimates, the panel treated as one the three focal areas of Tokai, Tonankai and Nankai within the Nankai Trough, as past records indicated such a major earthquake would likely occur simultaneously in those three areas.
The Nankai Trough runs from Suruga Bay in Shizuoka Prefecture to Hyuganada off Miyazaki Prefecture.
It is believed the largest earthquake to have hit the region along the Nankai Trough is the 1707 Houei Earthquake, which had an estimated magnitude of 8.6.