Amplitude and phase versus angle for elastic wide-angle reflections in the τ-p domain

Near- and postcritical spherical-wave reflections contain amplitude and phase variations with incident angle that are not predicted by plane-wave solutions. However, if a spherical wavefield is decomposed into planewaves by a time-intercept-slowness (tau-p) transform, then plane-wave reflection coefficients (the Zoeppritz) can be used as the basis of amplitude/phase versus angle analysis. The spherical-wave effects on reflection coefficients near the critical angle (in the time-offset domain) were decomposed by tau-p transformation into plane waves. Kinematic ray tracing linked the reflection angle at the target reflector and the apparent slowness at the surface receiver, which enabled extracting the amplitude/phase versus angle data at the reflector from the surface tau-p data. The most reliable inversion results were obtained by combining the extracted amplitudes and phases in a composite inversion for the elastic parameters below the target reflector.