As many as 323,000 people in 30 prefectures could be killed by a major earthquake and ensuing monster tsunami that scientists say could hit in the Nankai Trough off the Pacific coast, the Cabinet Office’s Central Disaster Prevention Council said Wednesday.

The estimated toll was raised dramatically from a projection in 2003 of 24,700 deaths from such a one-two punch.

The disaster council assumed extreme conditions in a worst-case scenario, learning lessons from the March 11 quake and tsunami disasters of last year that killed about 19,000 people in the Tohoku region.

Shizuoka Prefecture would be hit the hardest by the killer quake, inevitable aftershocks and multiple tsunami, suffering 109,000 deaths, 263,000 destroyed structures and 151 sq. km of flooded land.

Following is Mie Prefecture with 43,000 deaths, 210,000 destroyed structures and 157 sq. km of flooded areas, according to the estimate.

“The estimated figures are very huge, but we urge the public not to give up (on taking preventive measures.) We must review disaster prevention plans and try to reduce the number of victims to zero,” said Masaharu Nakagawa, state minister in charge of disaster prevention.

“Prompt evacuation is the best way to prevent deaths from tsunami. Municipalities must come up with concrete (antidisaster) plans,” he said.

The council assumed a magnitude-9 quake striking in the Nankai Trough, which stretches between the Izu Peninsula in Shizuoka Prefecture and the ocean floor off Kyushu.

According to this scenario, tsunami as high as 34 meters could hit Tosashimizu in Kochi Prefecture and 33-meter-high ones could hit Shimoda, Shizuoka Prefecture, while waves greater than 20 meters in height could also hit eight prefectures elsewhere along coastal areas.

However, the council stressed that the likelihood of such a quake-tsunami disaster is “extremely low.”

“Quakes and tsunami of this large scale are extremely rare, and we do not want to alarm the public. What we need to avoid most is that members of the public would give up and not try to evacuate because they feel it would be unlikely to survive the tsunami,” the council said in a news release.

“We want the public to be aware that very large-scale tsunami may happen and flee (coastal areas) when a strong quake strikes. In other words, we want the public to be afraid (of disasters) in the right way.”

In its worst case projection, the council also assumes the quake would hit at night in winter, the scenario that could cause the most deaths.

Back on March 31, the council revised its estimates on the strength of such a temblor and the height of tsunami from the 2003 figures, but not the death toll or damage to buildings and other structures.

Of the 323,000 deaths in 30 prefectures, about 70 percent would come from tsunami, the council said.

When it came up with its projections, the council assumed some 20 percent of people would start evacuating right after the quake. The death toll from tsunami would be halved if everybody evacuated within 20 minutes, the council said.

The number of buildings and other structures that would collapse, burn down or be swept away by tidal waves could reach 2.39 million across the country, compared with the 2003 estimate of 940,000.

The latest estimate of the height of tsunami is almost the same as the March estimate, but with an added margin of error of plus or minus 1 meter in various areas of southern Japan.

The new estimate also suggests 151 municipalities in 10 prefectures would experience a main quake measuring 7 on the Japanese intensity scale, compared with 153 municipalities in 10 prefectures stipulated in the March report.

Due to tsunami, up to 1,015 sq. km stretching across 24 prefectures could be submerged to a depth of 1 cm or more, about 1.8 times more than the area flooded in the wake of the Tohoku disaster, according to the disaster council.

Of the 1,015 sq. km, a total of 602 sq. km would be expected to be flooded by 1 meter of water or more, a level that would take a horrendous toll of life. The size of the area is almost equivalent to one-third of Osaka Prefecture, home to Japan’s second-largest metropolitan area.

Information added from Kyodo