The characteristic wave decomposition and imaging in VTI media

Abstract

The characteristic wave decomposition (CWD) method is presented, which takes full advantages of the local linear characteristics of the original seismic data. The CWD is performed by double beam forming for a compressed seismic wavefield in the characteristic ray parameter domain. Based on the beam-formed wavefield in characteristic domain, a beam-based characteristic wave imaging method (CWI) is put forward. Due to the flexibility and efficiency to output angle gathers for velocity model building, the CWI is a useful alternative to Kirchhoff and wave-equation migrations. It alters the application of Kirchhoff migration which smears the seismic data in imaging domain along quasi-ellipsoid trajectories and it has the capacity for steep dip reflector imaging with turning waves. In this paper, the CWI method is applied to prestack depth migration in transverse isotropic with a vertical symmetry (VTI) media. Compared with the conventional Kirchhoff migration methods, the proposed CWI method has a theoretical speedup of 1–2 orders. Besides, it can handle low signal-to-noise-ratio (SNR) data and target oriented imaging conveniently, and angle gathers can be produced naturally by CWI. Consequently, the CWI is an efficient technique for large scale seismic imaging and angle gather outputting. The direct mapping scheme from data space to model space establishes the relation between the characteristic data and the subsurface reflector, which can be used for the subsequent tomography conveniently. Some benchmark tests demonstrate the effectiveness of this method.