Simulation of microtremor.

It is very important for earthquake disaster prevention to understand subsurface structure, especially S-wave velocity structure. Recently microtremor data are widely used for S-wave velocity estimation. In analysis of microtremor data, subsurface structure is assumed as one-dimension. However actual subsurface structure is three-dimension. In order to estimate the effects of two- or three-dimensional subsurface structure, furthermore to estimate two- or three-dimensional structure using microtremor data, it is important to simulate microtremor waveform in two- and three-dimensional structure. In this paper, therefore, we tried to simulate microtremor. A rational function CIP-MOC (CIP with method of characteristics) scheme has been applied to simulate microtremor. The rational function CIP-MOC scheme is an advection equation solver. We have developed the rational function CIP-MOC scheme for elastic wave propagations in two- and three-dimensional structures. We simulate some models and obtain Fourier spectra and H/V spectrum ratios in two-dimensional structure.