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Japan eyes more accurate tsunami prediction system
(Illustration via kompasiana
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(Illustration via kompasiana.com) (Illustration via kompasiana.com)
(Illustration via kompasiana.com)
The Japanese government plans to start research on enhancing the tsunami prediction system next fiscal year, in preparation for massive earthquakes likely to occur along the Japan Trench and the Nankai Trough in the Pacific Ocean in the future.
The Education, Culture, Sports, Science and Technology Ministry and the National Research Institute for Earth Science and Disaster Prevention (NIED) aim to predict with great accuracy the height of tsunami at the coast, and the length of time until they subside, by promptly detecting tsunami with an offshore observation network. They intend to complete preparations for practical use within seven years, including checking the accuracy of their forecasts, and use the forecast data to issue tsunami warnings.
The government currently estimates the height of a tsunami and its arrival time based on the size of an earthquake and the location of its epicenter, and issues the first warning within about three minutes. However, in the case of a massive earthquake with a magnitude of 8 or larger, it is difficult to grasp the precise size of the earthquake quickly and predict the resulting tsunami.
At the time of the Great East Japan Earthquake, the scale of the tsunami was underestimated, which led to delays in residents' evacuation.
The envisaged system would utilize tsunami data measured offshore. Tens of thousands of tsunami generation patterns would be calculated in advance for different areas of water, including off the Boso Peninsula in Chiba Prefecture.
When a massive earthquake occurs, the height of a tsunami and how it will spread would be predicted in a few minutes by selecting the pattern closest to the actual observation data on the tsunami.
Tsunami are observed with a surveillance network located about 100 to 200 kilometers offshore. The NIED has established S-net (Seafloor observation network for earthquakes and tsunami) along the Japan Trench stretching from waters off Hokkaido to the Boso Peninsula by installing 150 measuring devices that detect changes in water pressure caused by tsunami.
The network is scheduled to begin full-scale operations next fiscal year.
Along the Nankai Trough stretching from waters off the Kii Peninsula to Shikoku, the Donet system (Dense Oceanfloor Network for Earthquakes and Tsunamis) has about 50 monitoring devices.
Tsunami grow taller the closer they get to a coast, and researchers seek to keep their margin of error to 20 per cent or lower when predicting their height. The NIED believes that more reliable tsunami warnings, as a result of accurate predictions, will make it easier to urge residents to take proper evacuation steps.
They also plan to predict how long it will take, after the first wave, for repeatedly surging waves to subside, and the extent of inundation. Such information is useful in determining how long residents have to evacuate and when rescue activities should begin, according to sources. (kes)(+)
