| The anisotropy exists generally in the earth media,and the transversely isotropy(TI)media is the most common one in the sedimentary rocks.With the complexity of exploration targets,as well as the development of the large offset and wide azimuth seismic acquisition technology,the required accuracy of data processing is becoming higher and higher.The conventional isotropic migration method is no longer able to image the complex geologic structure accurately,so it is necessary to develop the migration method based on the theory of anisotropy.Compared to the other migration methods,the advantages of reverse time migration(RTM)is: the migration method is based on the two-way wave equations with high imaging precision,and there is no restrictions of inclination and migration aperture,which can effectively handle the media with strong lateral speed variation,and it can satisfy the requirement of accurate imaging on the complex geological structure.Therefore,the reverse-time migration(RTM)imaging method on anisotropic media becomes the present research hotspot on the exploration geophysics.Seismic numerical simulation method is an important tool to study the formation mechanism and propagation law of seismic wave field,it can offer a theoretical basis for the subsequent seismic data processing and interpretation.This paper is based on the theory and results of the predecessors' research,starting from the basic theory of elastic wave in anisotropic media,the anisotropic elastic wave and quasi-P(qP)wave numerical simulation are studied,and on the basis of that,we realize the TI media qP-wave reverse-time migration imaging.Starting from the acoustic approximated Hooke's law and dispersion relation,we derived the equivalent VTI first-order qP-wave equations,and further generalize these equations to TTI media through introducing the rotating coordinate system.Then,in oreder to ensure the stability of wave-field propagation in heterogeneous TTI media,the new and stable TTI first-order q P-wave equation is derived based on the accurate TTI dispersion relation,by introducing a new auxiliary function including a control parameter ?.Finally,combing the RSGFD with the LS-FD two advantageous method,we studied the LS-RSGFD method to solve TI first-order qP-wave equations numerically for constructing the wave field propagator,and then implement the high precision numerical simulation and RTM in TI media.Besides,we also introduce the strategies of the boundary wave field storage and the effective depth computation,to reduce the storage requirements and the amount of calculation,which can optimize the whole process of the method.And we utilize the MPI parallel algorithm to strengthen the practicality of the method.Model tests demonstrate the accuracy and stability of the method,which has great prospects for development. |
PDF Full Text Request