Seismic Wave Propagation and Q-compensated Imaging in Viscoelastic Media with an Irregular Free Surfac

Surface topography and attenuation in seismic wavefield simulation have large effects on seismic imaging and inversion. Topography provides important information for interpreting the characteristics of seismic wave propagation in mountain or basin areas. The viscoelastic model is a good representation of subsurface media such as fluid-filled fractures and gas sands. Reverse time migration (RTM) and full waveform inversion (FWI) are the key techniques in seismic imaging to provide the subsurface structure images and rock properties. In this research, I study seismic wave propagation and Q-compensated imaging (Q-RTM and Q-FWI) in viscoelastic media in the presence of surface topography. In the implementation of seismic wave propagation, the 2D time-domain second-order viscoelastic wave equations and irregular free surface boundary conditions are transferred from the Cartesian coordinate system to the curvilinear coordinate system based on the boundary-conforming grid method. The convolutional perfectly matched layer (CPML) boundary condition is selected in order to suppress the artificial reflections from the model edges. RTM and FWI with Q-compensation in viscoelastic media with an irregular free surface are carried out to obtain a better image of the complex model and more accurate rock properties. The numerical test results show that the algorithm can successfully simulate seismic wavefields in viscoelastic media with an irregular free surface, and attenuation has a great effect on wave propagation. The Q-compensated RTM and FWI show more accurate subsurface images and properties than the traditional RTM and FWI.