A simplified three-dimensional finite-element method has been developed for simulation of Love-wave propagation in three-dimensional sedimentary basins. The eigenfunctions for the fundamental-mode surface waves are employed as interpolation functions in the finite-element scheme. By reducing the number of degrees of freedom, the method enables us to analyze wave propagation in an area of 2000 km2 as large as the southern part of the Kanto plain, Japan. Time histories of the near Izu-Ohshima earthquake of 1990 are calculated and compared with observation. Calculated displacement snapshots show the effect of three-dimensional topography on direction of Love-wave propagation. The three-dimensional simulation is also compared with a two-dimensional one, demonstrating amplitude increase and extended duration. Time histories and their spectra from the three-dimensional model show better agreement with the observations than those from the two-dimensional model.

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