LONG PERIOD SEA‐FLOOR MULTIPLES AND THEIR SUPPRESSION*

Abstract

A bstract Multiple sea‐floor reflections in deep water often are not effectively suppressed by either CDP stacking nor standard predictive deconvolution methods. These methods fail because the reflection coefficient varies markedly with angle of incidence and also because of the variation of arrival time with offset and because of dip. For a reasonablly flat sea‐floor, multiples of various orders and the primary sea‐floor reflection which have all been reflected at nearly the same angle lie along a straight line through the origin in time‐offset space. This line is called the “radial direction.” The multiples which lie along this line show a systematic relationship because they all experience the same water‐bottom reflection effect. In other words, multiples behave in a stationary manner along the radial directions on multi‐trace seismic records. A technique of multi‐channel predictive deconvolution, called “Radial Multiple Suppression,” utilizes this aspect to design Wiener operators for the prediciton and suppression of water bottom multiples. The effectiveness of the technique is demonstrated by the study of field records, autocorrelations, velocity analyses, and stacked sections before and after Radial Multiple Suppression processing.