Abstract
From the numerical analysis for historical tsunamis, the dispersion effect on the propagation of tsunami in deep sea was investigated. Tsunami time-histories at the point of 200m in depth and spectrum analysis on the initial wave profiles showed that the dispersion effect in deep sea region should be considered even for near field tsunami. The index of dispersion effect considering the spectrum of initial wave profile and the water depth was obtained to determine the critical value where the dispersion term should be taken into account in the simulation. The empirical quation to estimate the index by using the fault parameters and the mean depth in tsunami source was also considered. From numerical simulation considering sea bottom motion, it was shown that the raising time of sea bottom motion affects the dispersion if it is less than 1min. Examinations were carried out on the effect of dispersion in deep sea area on the tsunami behavior in shallow water region for the case of 1983 Nihonkai-chubu tsunami.
