Abstract
Synthetic seismic sections computed during forward modeling differ depending upon the type of media used to define the model. Four media types considered here are acoustic, elastic, elliptically anisotropic, and vertically inhomogeneous; significant differences are found among the seismic sections for these cases. Automatic ray generation, using kinematic and dynamic analog groups, permits retention and explicit identification of all significant arrivals, including primaries, multiples, converted waves, etc., for three-dimensional, horizontally layered structures. Comparisons between arrivals common to the various models are shown by synthetic trace sections, amplitude-distance plots, and velocity spectra. Results show significant energy in converted waves in the elastic models and marked differences between amplitude-distance curves for elastic and acoustic cases. Anisotropic media produce noticeable differences in both amplitude- and time-distance curves as a function of the degree of anisotropy. Modeling with vertically inhomogeneous media is practical and appealing because of how velocity and density functions are defined. Interestingly, a diving wave of high amplitude shown in our seismograms closely resembles the strong first arrival often present on field-recorded seismograms.
