P-SV wave propagation in heterogeneous media; velocity-stress finite-difference method

Abstract I present a finite-difference method for modeling P-SV wave propagation in heterogeneous media. This is an extension of the method I previously proposed for modeling SH-wave propagation by using velocity and stress in a discrete grid. The two components of the velocity cannot be defined at the same node for a complete staggered grid: the stability condition and the P-wave phase velocity dispersion curve do not depend on the Poisson's ratio, while the S-wave phase velocity dispersion curve behavior is rather insensitive to the Poisson's ratio. Therefore, the same code used for elastic media can be used for liquid media, where S-wave velocity goes to zero, and no special treatment is needed for a liquid-solid interface. Typical physical phenomena arising with P-SV modeling, such as surface waves, are in agreement with analytical results. The weathered-layer and corner-edge models show in seismograms the same converted phases obtained by previous authors. This method gives stable results for step discontinuities, as shown for a liquid layer above an elastic half-space. The head wave preserves the correct amplitude. Finally, the corner-edge model illustrates a more complex geometry for the liquid-solid interface. As the Poisson's ratio v increases from 0.25 to 0.5, the shear converted phases are removed from seismograms and from the time section of the wave field.