A panel of the Cabinet Office announced late last month that if a megaquake occurs in the Nankai Trough, a tsunami higher than 20 meters may hit 23 municipalities in six prefectures stretching from Kanto to Shikoku on Japan's Pacific side. The prediction represents a worst-case scenario that happens once in 1,000 years.
It may be difficult to build perfect defense against such a massive earthquake and tsunami; but, both the central and local governments must make utmost efforts to minimize damage from the inevitable disasters. Such efforts will make it easier for the nation to recover once it is hit by a catastrophic disaster. The central and local government must push urban planning that is resilient to a major earthquake and massive tsunami from both a short-term and long-term viewpoint.
The Nankai Trough, a subduction zone located off the Pacific coast, stretches some 900 km from the Tokai region to Shikoku. In the trough, an oceanic tectonic plate subducts under a continental tectonic plate. Massive earthquakes have occurred repeatedly in the past. The central government predicts a 60 to 88 percent probability that any one of three powerful earthquakes — identified as the Tokai, Tonankai and Nankai quakes — will strike in the next 30 years.