Local slopes of seismic events carry complete information about the structure of the subsurface. This information is sufficient for accomplishing all time-domain imaging tasks, without the need to estimate or know the seismic velocity model. A velocity-independent τ-p imaging approach has been developed to perform moveout correction in horizontally layered vertical-transverse-isotropy (VTI) media. The effective and interval anisotropic parameters are transformed into data attributes through the use of slopes and become directly mappable to the zero-slope traveltime. The τ-p transform is the natural domain for anisotropy parameter estimation in layered media because the phase velocity is given explicitly in terms of p. Therefore, the τ-p transform permits reflection-traveltime modeling and inversion that are simpler than traditional methods, which are based on Taylor-series expansions of traveltime in the t-x domain. Synthetic and field data tests demonstrate the practical effectiveness of the τ-p method.

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