Traveltime computation and migration in anisotropic media

Abstract

For seismic imaging of complex 3-D structures by e.g. prestack Kirchhoff depth migration large amounts of traveltime tables are required. This work provides a wavefront-oriented ray tracing technique for multi-valued traveltimes in smooth 3-D heterogeneous anisotropic media. In this method, wavefronts are propagated stepwise through the model and output quantities are interpolate (e.g., traveltimes, slowness) from rays to gridpoints. In contrast to isotropic media, where the input is a velocity model, the model for an anisotropic medium is defined by 21 elastic parameters at each gridpoint. To provide an efficient, accurate and fast algorithm for the interpolation of the elastic parameters to arbitrary points, the Cardinal Spline interpolation has been used, which produces an interpolated function that is continuous through the second derivative. The insertion of a new ray is performed by tracing it directly from the source. To calculate traveltimes at gridpoints a distance-weighted averaging method is used. To demonstrate the accuracy of the method the traveltimes computed for a homogeneous anisotropic model with elliptical symmetry are compared to exact traveltimes available for this medium. Since it exists no analytical solution for an inhomogeneous anisotropic model, I compare the results with an alternative method for traveltime computation, the FD perturbation method...