One method is to simulate seismic wave propagation in a fluidвЂ“solid coupled environment by using the elastic wave equations, where the S-wave velocity in fluid media is set to be zero. Several acousticвЂ“elastic coupled modelling methods have been proposed for processing and interpretation of multicomponent data acquired in marine environments. Together with the advent of OBC technology is the capability for multicomponent seismic exploration. In the early 1990s, ocean bottom cable (OBC) technology was developed, which can be used for multicomponent seismic exploration. For traditional marine seismic exploration, seismic data are recorded by steamers, and they are processed and interpreted based on acoustic wave propagation. Seismic waves travelling through the water column can be characterized by the acoustic wave equation and by the elastic wave equation when they travel past the crust. Numerical solutions, Wave propagation INTRODUCTION A Lebedev-standard staggered grid scheme is applied to the MCT method to reduce both the computational cost associated with the Lebedev grid scheme and the instability in the auxiliary coordinate system when using a standard staggered grid scheme. The grid size is determined adaptively based on the shape and the parameters of the target area, which reduces in size in when the layers are thin or exhibit low velocities. We also introduce a multiblock coordinate transformation (MCT) method which meshes each layer with curvilinear grids to transform the interface topography into a horizontal one, thereby allocating vertical sampling points adaptively. An irregular fluidвЂ“solid interface can be transformed into a horizontal interface, so that pressure and stress can be well converted. We propose a variable coordinate transformation methodology to simulate seismic waves in a fluidвЂ“solid environment. The Cartesian grids discretization leads to artificial reflections and diffractions during the conversion between acoustic wave and elastic waves. Traditional finite difference methods have had difficulties in dealing with the irregular fluidвЂ“solid interface topography. Proper boundary conditions at the fluidвЂ“solid interface based on the relationship between pressure and stress are crucial when combining the two different wave equations. Seismic wave propagation in a fluidвЂ“solid environment cannot be simulated with a single wave equation, but can be described by use of the acoustic and viscoelastic wave equations for their respective fluid and solid parts.

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