A technique for calculating traveltime of a seismic wave in three dimensional tilted transversely isotropic (3D TI) media includes determining a wave vector, defining a unit vector, calculating an angle of the wave vector from an axis and performing a slowness determination, wherein a unit vector for a symmetry axis is defined as: (cos .phi. sin .theta., sin .phi. sin .theta., cos .theta.); where .phi. represents the azimuth of the symmetry axis measured from the x direction; and, .theta. represents the dip angle of the symmetry axis measured from the z direction. The technique may be practiced as a computer implemented set of instructions, and may be incorporated into measurement equipment.
CROSS REFERENCE TO RELATED APPLICATIONS
This patent application is filed under 37 CFR .sctn.1.53(b) as a Continuation-in-Part and claims priority under 35 U.S.C. 120 to U.S. patent application Ser. No. 11/366,137, entitled "Traveltime Calculation in 3D TTI Media by the Fast Marching Method" filed Mar. 2, 2006 now abandoned, which in turn claims priority from U.S. Provisional Patent Application No. 60/756,739, filed on Jan. 6, 2006, the entire contents of which are incorporated by reference.
1.sup.storder free-surface multiples recorded in VSP data or reverse VSP data are processed using a 3-C 3-D vector migration method to produce an image of the subsurface. This image produces a larger coverage than that obtained in 3-C 3-D processing of reflection data acquired in the VSP.
