Abstract

An analysis of future tsunami hazard on the coast of the Japanese Islands is made in terms of probability for a coastal site being hit by a tsunami, of which the wave height exceeds a certain level during a period from 2000 to 2010. Tsunami wave height at a site on the Pacific coast is estimated mostly based on numerical experiment, in which a typical fault model of the tsunami-generating earthquake is assumed. Meanwhile, probability of the tsunami-generating earthquake occurring during 2000 to 2010 is evaluated either from historical data of earthquake occurrence or from near-shore crustal strain accumulation.

Combining the wave height estimate with the probability evaluation of tsunami occurrence, probabilities of a site being hit by a tsunami, of which the wave height exceeds certain levels, are evaluated on the Pacific coast. It seems that the probability for a violent tsunami, of which the wave height exceeds 5 m, is highest along the Pacific coast in central Japan, reaching a value of 41 per cent. On the other hand, a probability value as high as 69 per cent is found for a moderately large tsunami having a wave height of 1 m or so along the Shikoku and Kyushu coasts.

A crude probability evaluation is also made for tsunamis on the Japan Sea coast, where tsunami activity is substantially lower than that of the Pacific coast. The probability for a violent tsunami seems to amount to only 1 per cent or so for a 10-yr period. Similar probabilities for tsunamis excited by a distant source off Peru, Chile, Kamchatka, and Aleutian-Alaska are also evaluated. In this case, probabilities of tsunami wave height exceeding 1 and 3 m are, respectively, evaluated as 19 and 15 per cent on the Pacific coast, such probabilities being not quite negligible.

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