Practical Approach to Anelliptic Time Processing
Processing of deep-offshore seismic data acquired with long streamers involves appropriate algorithms that take into account non-hyperbolic shape of the reflection curves and the inadequacy of the standard dip moveout (DMO). The seismic signatures of the effects corresponding to bedding or VTI anisotropy (Vertical Transverse Isotropy) are indistinguishable. Since the shifted hyperbola normal moveout (NMO) equation seems to describe perfectly both effects, we propose to parameterize them with the VTI anisotropy parameter η. In the case of the layered VTI model, our shifted hyperbola moveout correction using the actual effective values of NMO velocity Vnmo and anellipticity η produces a better result than Alkhalifah's VTI NMO.
The DMO operator derived from the anelliptic shifted hyperbola equation fits quite accurately to the monotonic part of Alkhalifah VTI DMO operators. This anelliptic dip moveout depends on the effective η only. The effective η values seem to be connected to the non-hyperbolic velocity analysis occurring at the same levels. We consider that the anelliptic time processing improves the standard one for deep offshore data acquired over an anisotropic subsurface.
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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.”