Velocity-Independent Layer Stripping of PP and PS Reflection Traveltimes

We adapt the so-called ``PP+PS=SS'' method to devise an exact technique for constructing the interval traveltime-offset function in a target zone beneath a horizontally layered overburden. The algorithm is designed for arbitrarily anisotropic target layers, but the overburden is assumed to have a horizontal symmetry plane (i.e., up-down symmetry). Important advantages of this layer-stripping technique compared to the existing Dix-type equations include the ability to handle the asymmetric moveout of mode-converted waves and laterally heterogeneous target layers with multiple curved reflectors. Also, our method is entirely data-driven and does not require knowledge of the velocity field anywhere in the medium. <br><br>The computed interval moveouts of PP- and PS-waves can be used to estimate the interval parameters of transversely isotropic layers with a tilted symmetry axis (TTI), which is essential for accurate imaging in fold-and-thrust belts<br>(e.g., the Canadian Foothills) and near flanks of salt domes. Other applications include dip-moveout inversion for VTI media and stable computation of interval long-spread (nonhyperbolic) moveout for purposes of anisotropic velocity analysis.