# Translations:Appendix K: Exercises/39/en

37. Why is periodicity of multiples preserved with only vertical incidence and zero-offset recording? Explain why predictive deconvolution aimed at suppression of multiples might not be effective when applied to nonzero-offset data such as common-shot or common-midpoint data. Predictive deconvolution sometimes is applied to CMP stacked data in an effort to suppress multiples. The performance of such an approach can be unsatisfactory because the amplitude relationships between multiples often are altered greatly by the stacking process. This result is primarily because of velocity differences between primaries and multiples. In addition, geometric-spreading compensation by using the primary velocity function adversely affects the amplitudes of multiples on nonzero-offset data. However, in the slant stack (or -*p*) main, the periodicity of multiples is preserved (Treitel et al., 1982)^{[1]}.

- ↑ Treitel, S., P. R. Gutowski, and D. E. Wagner, 1982, Plane-wave decomposition of seismograms: Geophysics,
**47**, 1375-1401.