COMPUTATION OF TSUNAMI WAVEFORMS BY A SUPERPOSITION OF NORMAL MODES

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Computation of tsunami waveforms for actual topography is usually made by a time-stepping finite-difference method which needs a long computation time and must be repeated for different initial conditions. We propose here an alternative computation method by a superposition of normal modes. Although the eigenvalue problem to obtain the normal mode solutions needs more memories, once we get the solution, the waveforms can be computed by merely summing up the normal modes with weights determined by the initial condition. We present the waveforms for a simple water basin computed by both methods. The results show that the new method is useful for a completely or almost closed basin including the tsunami source.