Study On Numerical Simulating Methods For Elastic Wave Fields In Isotropic/Anisotropic Medium

We in this paper simulate seismic wavefield in complex isotropic/anisotropic media by using the finite difference method(FDM)and pseudo spectral method(PSM),and consequent results of its kinematic features,such as traveltimes,can be used in earthquake location and ray tomography;and its dynamic features can be used in later wavefield reverse time migration and full waveform inversion.Based on these respects,the main studies are focused on the following parts:1.Based on previous researches in ray tracing methods,we analyze the corresponding ray theories by taking the fast marching method(FMM)and multistage irregular shortest-path method(ISPM)as examples,and finally we simulate some tests with the multistage ISPM algorithm for further study.2.From the fundamental elastic concepts of isotropic/anisotropic media,we deduced the elastic wave equations for isotropic/anisotropic case,and the corresponding differential formats,and meanwhile discuss the impact of Thomsen parameters on anisotropic media and also the computation of phase and group velocity.3.We systematically analyze and compare four different deferential formats(staggered,auxiliary,rotated staggered and non-staggered)used in finite difference method for wavefield simulation in the anisotropic media,and make conclusion for its advantages and disadvantages.4.To overcome the scattered effects when presented undulated free topography in wavefield simulation,we applied a curvilinear grid finite difference method to simulate seismic wave propagation in the isotropic/anisotropic media.The results show that it is possible to simulate seismic wave propagation without scatter.5.Based on the respects(derivative principle,grid division,absorbing boundary condition and stability condition)of the pseudo spectral method,we conduct wavefield simulation in the anisotropic medium and also 3-D simulation in isotropic medium.6.Compared with ray tracing method(Multistage ISPM)over the wave equation simulation methods(FDM and PSM),we put forward a simple calibration method to quickly identify seismic phases in snapshot,common source point gather record and syntheticseismogram.