Tsunami simulation taking into account dynamic seabed displacement due to seismic faulting

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The present study aims to develop a numerical technique to simulate generation and propagation of tsunamis with higher accuracy, and to evaluate effects of dynamic seabed displacement due to seismic faulting on tsunamis.In contrast with the conventional one, the new technique we have developed takes into account the dynamic seabed displacement as well as acoustic water waves. In principle, the present simulation is made up of two steps. The first is earthquake ground motion simulation for which the 3-D boundary element method (BEM) is used, and the second is tsunami simulation for which the 3-D finite difference method (FDM) is used. This is based on an assumption that the seabed-sea water system can be regarded as a weakly coupled system. Due to this assumption, the dynamic displacement of the seabed that includes the staticdisplacement is simulated first, considering rupture mechanismof seismic faulting. Then, velocity associated with the seabed displacement is input at the bottom of … More the sea water, and sea water disturbance is simulated by solving the Navier-Stokes equation. Results of the two-step simulation are represented in terms of not only snapshots but also animated figures, in order to facilitate evaluation of validity of the simtulation.The dynamic seabed displacement and the acoustic wave are found to give a remarkable increase in the water wave height especially in the near-fault area, as a result of superposed effects of the dynamic and static seabed displacements. In addition, the present simulation has demonstrated that short-period water disturbance is induced by Rayleigh waves that travels along the seabed with a velocity much higher than tsunamis.Finally, the present technique is applied to actual three tsunamis caused by recent earthquakes. From simulation for the 1998 Sanriku-oki earthquake (M6.3 ), the present technique proves to be able to simulate the associated tsunami to a satisfactory level of accuracy if the fault parameters are given with high accuracy. Simulation for the 1983 Nihonkai-Chubu (7.7) and the 1993 Hokkaido-Nansei-oki (7.8) earthquakes, is conduced by using seismically determined fault parameters and shows considerable difference between tidal records in the wave height and arrival time, mainly because of roughness of the fault parameters s and numerical models. Less