Moveout approximation for P waves in a homogeneous VTI medium

Veronique Farra and Ivan Psencik


We propose an alternative expression for the P-wave moveout approximation in a VTI medium based on the weak-anisotropy approximation. The proposed formulae are relatively simple, they yield highly accurate results for zero and far offsets. First-order formulae depend on four parameters, two-way zero-offset traveltime T0 related to the vertical velocity α, the depth H of the reflector and two weak-anisotropy (WA) parameters ε and δ. Very accurate second-order formula is slightly more complicated and, in addition to the mentioned parameters, depends on an additional parameter, r, the ratio of the S- and P-wave velocities. Since the dependence of the moveout on r is very weak, r can be specified as a typical S- to P-wave velocity ratio and the number of parameters necessary for the specification of moveout is four too.

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In: Seismic Waves in Complex 3-D Structures, Report 22, pp. 41-54, Dep. Geophys., Charles Univ., Prague, 2012.