Wide-band velocity filtering; The Pie-Slice process

Abstract A new technique has been developed which makes it possible to process a seismic record-section in such a way that all seismic events with dips in a given range are preserved with no alteration over a wide frequency band, while all seismic events with dips outside the specified range are uniformly and severely attenuated.By applying this process to a noisy record-section, a record-section may be obtained which has all events within a specified dip range perfectly preserved, and very high-velocity noise essentially eliminated, a result which is impossible by simple wave-number filtering or conventional array usage. In structurally complex areas where several steeply dipping events interfere, the technique may be applied to separate the events with different dips. In areas where a normal-moveout contrast exists between primaries and multiples, the technique may be used for wide-band multiple attenuation.By application of a 'rotating Pie-Slice' to micro-spread noise data, seismic noise may be separated on the basis of propagation velocity, and a clearer picture of the seismic noise problem obtained. The 'rotating Pie-Slice' also provides a means of uncovering diffractions and other steeply-curved events from a record section.The paper discusses the motivation and implementation of the process and its application to both synthetic and actual data.