Modeling anisotropic seismic waves in 3-D

Solving for the physical properties of the subsurface from seismic observations using nonlinear inversion requires the solution of the forward problem, the simulation of seismic waves. I formulate the equations required to simulate seismic wave propagation in an arbitrarily inhomogeneous anisotropic elastic medium using the method of finitedifferences. Density and all of the twenty-one elastic moduli may vary at every grid-point on a cartesian mesh. An implementation is described on the finegrain parallel Connection Machine supercomputer. Each grid-point of the three-dimensional volume is assigned its own processor thereby harnessing the natural parallelism of physics. Results are presented of modeling anisotropic seismic waves in three dimensions through a homogeneous model with twentyone non-zero elastic moduli. The complexity of the wave propagation suggests that standard methods of seismic processing break down in regions of strong anisotropy. However, with the massively parallel computer revolution and advances in nonlinear inversion, we may soon enter a new era where all seismic phenomena are taken into account including those related to strong anisotropy thereby providing useful new information about rock properties.