National / Science & Health

In first, Japan highlights detailed tsunami risks from Nankai Trough quake

JIJI

In its first such report, a government committee on Friday presented the possibilities of coastal areas experiencing tsunami of at least 3 meters high, 5 meters high and 10 meters high if a quake with a magnitude of 8 to 9 occurs in the Nankai Trough.

The odds of experiencing a tsunami at least 3 meters high if such a quake occurs came to 26 percent or higher in Pacific coastal areas from the Tokai region to the southern part of the Kinki region, as well as coastal areas in the southern part of Shikoku and part of the eastern coast of Kyushu.

The 26 percent probability signifying that the event is expected to happen once every 100 years, is extremely high, according to the report by the Earthquake Research Committee.

The chance of a tsunami of at least 5 meters came to 26 percent or higher in areas of Mie, Wakayama and Kochi prefectures.

As for a tsunami of at least 10 meters, no area registered a probability of 26 percent or higher, though the possibility of Mie and Kochi experiencing such a tsunami was between 6 percent and 26 percent, the report said. The 6 percent probability would indicate the event is expected to happen once every 500 years.

A 3-meter-high tsunami is powerful enough to destroy and sweep away wooden houses. The height is roughly equivalent to the Meteorological Agency’s standard for issuing a major tsunami warning.

Previously, the government warned residents, municipalities and companies in coastal areas of large tsunami from a possible Nankai Trough quake by presenting their possible maximum heights. This time, the government presented tsunami probability estimates by height.

“Even a 3-meter-high tsunami can cause great damage,” said Naoshi Hirata, professor at the University of Tokyo and head of the committee.

He said the estimates do not provide information on the maximum heights of tsunami that would reach coastal areas following a Nankai Trough quake.

“It is important to start by taking what measures we can,” Hirata said.

A massive quake and tsunami are expected to occur if a large-scale rapid slide happens in a plate boundary area in the trough.

The committee divided the expected earthquake focal zone into six sections east to west and three sections north to south in order to examine various patterns of quakes that could happen in the zone.

Tsunami probabilities by height were calculated for each of the municipalities forecast to be hit by a tsunami from a possible Nankai Trough quake.

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