Font Size: a A A

Reverse Time Migration For Anisotropic Media

Posted on:2017-01-29Degree:MasterType:Thesis
Country:ChinaCandidate:X Z FangFull Text:PDF
GTID:2180330488462100Subject:Solid Geophysics
Abstract/Summary:PDF Full Text Request
Two-way wave equation pre-stack Reverse-time Migration(RTM) is a kind of highaccuracy seismic imaging method which has no restrictions and is very suitable for complex structure imaging. The high-accuracy seismic wave forward modeling and reverse-time migration must consider the effect of anisotropy because of widely existing anisotropic media of the earth. Forward modeling algorithm and inverse time migration algorithm based on isotropic is not accurate for anisotropic media. TI(Transverse Isotropy) media is a common anisotropic medium. Transverse Isotropy with a Vertical axis of symmetry called VTI medium and Transverse Isotropy with a Tilted axis of symmetry called TTI medium. The paper mainly studies the RTM for VIT medium and TTI medium.On the basis of high-order finite-difference method, This paper study the key technologies in reverse time migration, including finite difference, boundary condition, imaging conditions, noise suppression, computation efficiency and the storage strategy and so on.The main study in the paper of RTM for VTI media is as follows, on the basis of firstorder quasi-P wave equation in VTI madia, deduce the reverse-time extrapolation of the staggered grid high-order finite-difference scheme of shot points and receive points. In order to solve the huge amount of calculation and storage problem, we provide an improved efficient PML absorbing boundary condition based on the GPU acceleration. This method greatly reduces the storage while increases a small amount of calculation and can achieve high precision efficiency. Test on the Hess 2DVTI model proves the useful of the method.Based on the previous research of the phase velocity of VTI media, we derived the 2D TTI wave equation, do the modeling numerical simulation and the wave field stability research for TTI medium using higher-order finite difference method and perfectly matched layer, and analyse the efficiency of the GPU acceleration with global memory and shared memory technology. In view of the cross derivative finite difference algorithm for TTI media, the GPU shared memory is studied and the computation efficiency is optimized. An RTM algorithm for TTI media is presented based on the effective PML boundary storage strategy combined with GPU acceleration. The BP2007 TTI model test the effectiveness of the RTM algorithm. The full use of the shared memory of GPU can improve the computation efficiency of the modeling and RTM algorithm of TTI.
Keywords/Search Tags:anisotropic media, reverse time migration, GPU, efficient PML absorbing boundary storage
PDF Full Text Request
Related items