Discussion on “Diffraction response for nonzero separation of source and receiver,” by John R. Berryhill (GEOPHYSICS, October 1977, p. 1158–76, and Discussion on “Diffractions for arbitrary source‐receiver locations,” by A. W. Trorey (GEOPHYSICS, October 1977, p. 1177–82)

Abstract

Study of simple synthetic seismograms convinced both authors that the diffracted pulse shape shows virtually no variation with source‐receiver offset if the midpoint is held constant. First, I wish to corroborate their findings by means of a simple example and at the same time suggest that conclusions of both authors apply strictly only to planar (and planar dipping) reflectors. Secondly, I wish to show that because of the invariant behavior of the pure diffraction pulse and because of the equally invariant behavior of the pure reflection pulse, the shape of the reflected pulse for depth points close to the edge of the reflector can not be offset invariant.