3D VTI Eikonal Solver for Efficient Acoustic Traveltime Computation
Travel-time computation is efficiently achieved through direct numerical resolution of the eikonal equation on a 3D computational grid. Efficiency may even be improved when solving the eikonal equation using an appropriate transformation called transformation in the celerity domain. Neglecting the effects of anisotropy in the calculation of traveltime maps leads inevitably either to incorrect focusing or positioning of seismic events during the seismic imaging process. Thus, in the present paper, we propose to extend effi-cient P-wave travel-time computation to the simplified case of Vertical Transverse Isotropic (VTI) media, which is nevertheless of the most interest in surface reflection seismic. Based on an “acoustic” explicit eikonal equation for VTI media, the calculation of quasi-P travel times with our numerical resolution method in the celerity domain proves to be particularly efficient, stable and accurate. In line with seismic contractor needs, we propose a parameterization, which is based on anisotropy effects, for the quasi-P VTI model used by the eikonal solver. The three independent anisotropic parameters are the NMO velocity associated with short-spread curvatures, an ellipticity parameter equivalent to the ratio between vertical and NMO velocities, and finally the well-known anellipticity parameter η, governing the long offset behavior of NMO curves.
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“This volume contains 25 papers that represent most of the best work in seismic anisotropy in 1998 and 1999. Fracture characterizations and processing of converted waves are the two main topics covered in this volume. They are addressed from both theoretical and practical viewpoints. Also included are papers describing the historical roots of seismic anisotropy.”