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Japan shows detailed tsunami risks from Nankai Trough quake

  • January 24, 2020
  • , Jiji Press , 7:40 p.m.
  • English Press

Tokyo, Jan. 24 (Jiji Press)–A government committee Friday showed estimated probabilities of tsunamis by height that could hit the Japanese Pacific coast within 30 years if a huge earthquake happens in the Nankai Trough.

In its first such report, the committee presented the possibilities of the coastal areas experiencing tsunamis 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 trough off the Pacific coast of central to southwestern Japan.

The odds of experiencing a tsunami of at least 3 meters high came to 26 pct or higher in coastal areas from the Tokai central region to the southern part of the Kinki western region, coastal areas in the southern part of the Shikoku western region and part of the eastern coast of the Kyusyu southwestern region.

The 26 pct possibility, which means that the event is expected to happen once in 100 years, is extremely high, according to the report by the Earthquake Research Committee.

The chance of being hit by a tsunami of at least 5 meters high came to 26 pct or higher in areas including in Mie, Wakayama, Kochi prefectures, all in western Japan.


As for a tsunami of at least 10 meters high, there was no area with a possibility of at 26 pct or more.

Meanwhile, the possibility of Mie and Kochi experiencing a tsunami of at least 10 meters high is between 6 pct and less than 26 pct, the report said. The 6 pct possibility means the event is expected to happen once in 500 years.

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

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

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

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

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

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

The committee divided the expected temblor 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 Nankai Trough quake.

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