Zoeppritz amplitude correction: Is it needed?

A method called Zoeppritz Amplitude Correction is introduced to eliminate undesirable effects of amplitude and polarity variations with offset in conventional processing. The Zoeppritz amplitude correction is defined to transform the amplitude and polarity of reflections in the common-mid-point gathers to the amplitude and polarity of a trace at a given reference offset and time. The reference offset is zero for seismic stacked record sections to obtain interpretable, correct, and accurate amplitude and polarity. Some of the effects of the offset dependent reflection amplitudes in critical processing stages, such as velocity analysis and stacking, are presented to emphasize the importance of the correction introduced. The synthetic data examples are presented to exhibit the importance of amplitude versus offset correction in routine data processing and interpretation. Without the Zoeppritz amplitude correction, the stacking process may produce incorrect and inaccurate reflections. In some cases reflections may be totally lost by the stacking process, resulting in incorrect interpretations. Velocity analysis which suggest double velocities for the same reflection time can be explained by the effect of the Zoeppritz amplitudes. If" the stacking velocities are affected by the Zoeppritz amplitudes one may prefer to choose the higher velocities over the lower velocities to attenuate multiple energy. This is a case that can alter the polarity of reflections. It is demonstrated that if the seismic parameters are available, one can apply the Zoeppritz amplitude correction to eliminate these effects. The seismic parameters may be obtained by inversion using the Zoeppritz equations or by methods of velocity analysis which use both actual amplitude information and geometrical relations.