Effect of Attenuation on Reflections from Interfaces Showing Phase Changes

Phase changes are a common phenomenon encountered in amplitude-versus-offset analyses for interfaces with a weak contrast in elastic properties. The effect is usually modelled under the assumption of no attenuation. In this paper, we study the effect of introducing attenuation into the analysis. We find that such reflections are very sensitive to the presence of attenuation, and that the amplitude-versus offset (AVO), frequency-dependent amplitude-versus-offset and phase-versus-offset behaviours are all significantly altered by attenuation. We show a field data example of the phenomenon, and indicate how the effect was used to constrain an AVO inversion.