ELASTIC WAVEFIELD CALCULATION FOR HETEROGENEOUS ANISOTROPIC POROUS MEDIA USING THE 3-D IRREGULAR-GRID FINITE-DIFFERENCE

摘要

Based on the first-order Biot-equation with simplified coefficients, a staggered irregular-grid finite difference method (FDM) is developed to simulate elastic wave propagation in 3-D heterogeneous anisotropic porous media. The 'slow' P wave in porous media wave simulation is highly dispersive. Finer grids are needed to get a precise wavefield calculation for models with curved interface and complex geometric structure. Fine grids in a global model greatly increase computation costs of regular grids scheme. Irregular fine or coarse grids in local fields not only cost less computing time than the conventional velocity-stress FDM, but also give a more accurate wavefield description. A dispersion analysis of the irregular-grid finite difference operator has confirmed the stability and high efficiency. The absorbing boundary condition is used to eliminate artificial reflections. Numerical examples show that this new irregular-grid finite difference method is of higher performance than conventional methods using regular rectangular grids in simulating elastic wave propagation in heterogeneous anisotropic porous media.