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 the PS data into common‐conversion‐point gathers and using them for velocity analysis. Here, we explore an alternative procedure. Our key idea is to generate the so‐called pseudo‐shear (ΨS) seismograms from the recorded PP and PS traces and run conventional velocity analysis on the reconstructed ΨS data. This results in an effective S‐wave velocity model because our method creates data that possess kinematics of pure shear‐wave primaries. We never deal with such complexities of converted waves as moveout asymmetry, reflection point dispersal, and polarity reversal; therefore, these generally troublesome features become irrelevant. We describe the details of our methodology and examine its behavior both analytically and numerically. We apply the developed processing flow to a four‐component ocean‐bottom cable line acquired in the Gulf of Mexico. Since the obtained stacking velocities of P‐ and ΨS‐waves indicate the presence of effective anisotropy, we proceed with estimating a family of kinematically equivalent vertical transversely isotropic (VTI) velocity models of the subsurface.