Japan offers even more powerful earthquake and tsunami

April 18. Japan's government listens to the echo of last year's earthquake and tsunami: underwater faults that surround the country, can lead to more serious disasters than had been thought. Last week, officials in charge of disaster management, informed the office of the simulation results, which showed that there is a danger of a tsunami even more terrible than the Tohoku.

The data were obtained by a research team headed by Katsuyuki Abe, professor emeritus University of Tokyo. Scientists have upgraded the official model by incorporating recent major earthquakes — including last year's magnitude 9.0 Japanese and Chilean, Beat in 2010 with a force of 8.8. The latter is also generated a tsunami, the echoes of which sunk to Japan. As a result, for most locations scope of probable tsunami significantly outperforms the previous estimate obtained in 2003. For example, the settlement Kuroshio Kochi Prefecture protected considering that the highest wave exceeds 14.1 m, whereas the new data, it is threatened 34.4 sq. Furthermore, the island must prepare Niidzima 29.7 and not to the 5 4-meter wave.

Overall, 90 cities have to take into account that the wave may exceed ten meters, while the old model warned only a dozen places. 23 locations have to expect a wave height of 20 meters or more (on this previous research did not stutter).

Simulation also increased the risk of a major earthquake: the number of cities that can revive the maximum (7 on a scale of intensity of ground shaking, adopted in Japan) increased from 35 to 153.

Revaluation pointed to the trough Nankai — Marine fault south of the island of Honshu (Japan's main island), which regularly occur strong aftershocks, including earthquake's Hawayo 1707 a magnitude of 8.7. It is this cataclysm was the ceiling to a 2003 study. At this time, as the maximum was used Tohoku earthquake, which was about three times more potent. Also, take into account the latest research that using the thickness of sedimentary layers brought past tsunamis, tried to estimate the magnitude and frequency of major earthquakes and tsunamis that occurred before there were modern methods of measurement. Model 2003, did not contain such information, failed to predict the March tsunami. Its main conclusion was: there is a 60 percent chance of an earthquake of magnitude 8.0 in the next 30 years.

Old and new projections of future tsunami wave heights (Image Nature).

The updated model also took into account the areas with the "big slide", in which a powerful shift crust can make a particularly strong tsunami. In the past year these sites were to blame for the unexpectedly high waves in some areas of Japan. Scientists have counted 11 scenarios, each of which includes "high slip" in various places along the Nankai trough.

At the same time it is obvious that the 9.0 earthquake and more are found in the same area very rarely — about once a millennium. That puts the Japanese authorities facing a difficult problem: how much training is needed for such a rare phenomenon? And then — how can you protect yourself anywhere and everywhere, from the 34-meter-high waves?

The government has requested full information and detailed maps of vulnerable areas by the end of May. While in some cities set additional loudspeakers to warn citizens of approaching tsunami, but it will give people a few minutes. Hardly in that time many will have time to climb to the evacuation of the tower height of several tens of meters.

In some regions, it is also planned to move to higher ground even offices (ideally — along with housing). There is talk about the construction of large underground shelters. All of these projects are located outside of the financial capacity of cities and prefectures. Requires the participation of the central government.

Based on: Nature News
Source: Kompyulenta

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