New debris estimates soar for Nankai Trough quake


As much as 349 million tons of debris and sediment would be generated by a major tsunami-producing earthquake in the Nankai Trough — about 11 times the amount resulting from the Great East Japan Earthquake of March 2011, the Environment Ministry said.

The disposal of the quake and tsunami waste would likely take up to 19 years and four months to complete, the ministry said Friday. The estimate did not appear to account for the possibility of radiation from a nuclear power plant accident tainting the debris, as happened in 2011.

The debris, including from buildings destroyed by the quake or subsequent fires, accounts for 322 million tons, while sediment from the tsunami accounts for 27 million tons, it said.

The ministry estimated the volumes under eight scenarios. The highest amount appeared in a situation in which tsunami originating in the Nankai Trough, a subduction zone that runs off the Pacific coast from central to southwestern Japan, hits the Tokai central region while a number of fires happen.

The new maximum estimate is far bigger than the previous forecast of 250 million tons. The ministry revised its estimates in light of the enormous amount of debris and sediment generated by the 9.0-magnitude quake and giant tsunami on March 11, 2011.

In the worst-case scenario, 118 million tons of debris would be generated in the Kinki region, 98 million tons in Chubu, 86 million tons in Shikoku, 27 million tons in Kyushu, 16 million tons in Chugoku and 4 million tons in Kanto, the ministry said.

The ministry also reviewed its debris estimate for a powerful quake projected to hit the Tokyo metropolitan area.

Under the new projection, the maximum amount of debris generated would be 110 million tons, up from 98 million tons, and take up to six years and six months to dispose of.

Following the new estimates, the ministry will consider ways to promote debris recycling and wide-area debris disposal.