Generation and processing of pseudo shear-wave data: Theory and case study

Processing of converted (PS) waves currently adopted by the exploration industry is essentially based on resorting<br>PS data into common conversion point gathers and using them for velocity analysis. Here we explore an alternative<br>procedure. Our key idea is to generate the so-called pseudo-shear (ªS) seismograms from the recorded PP and<br>PS traces and run conventional velocity analysis on the reconstructed ªS data. This results in an effective S-wave<br>velocity model because our method creates the data that possess kinematics of pure shear-wave primaries. Since we<br>never deal with such complexities of converted waves as moveout asymmetry, reflection point dispersal, and polarity<br>reversal, these generally troublesome features become irrelevant.<br>We describe the details of our methodology and apply the developed processing flow to a multicomponent ocean<br>bottom cable line acquired in the Gulf of Mexico. Since the obtained stacking velocities of P- and ªS-waves indicate<br>the presence of effective anisotropy, we proceed with estimating a family of kinematically equivalent VTI (transversely<br>isotropic with a vertical symmetry axis) velocity models of the subsurface.