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The development of a new technique 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. To state it another way, it is possible to combine the elements of a line array in a manner resulting in a directed beam in which the beam width is independent of frequency, and which has uniformly low side lobes, also essentially independent of frequency.
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 such as the PL mode has been 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 microspread 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 technique is described in terms of its application to synthetic examples. Various examples of its application to actual seismic data illustrate its practical effectiveness.
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