The influence of out‐of‐plane surface properties on unmigrated time sections

Abstract

Both analytic and numerical means are used to demonstrate amplitude and phase behavior of reflections from three‐dimensionally curved interfaces. In particular, the high‐frequency geometrical optics approximation for the backward scattered wave field demonstrates that the phase of a reflection from a syncline is determined by the (in general, different) positions of focal regions for the two principal curves at the specular reflection point. Thus the amplitudes and phases of events observed on seismic sections are influenced as much by the shape of the reflector “out‐of‐the‐plane” as by the shape in the plane of the section. Results of the numerical examples suggest possible pitfalls in traditional interpretation of two‐dimensional seismic data.