Method and apparatus for obtaining a composite field response to a variable source array using weighting coefficients

Abstract

A multi-channeled digital seismic field stacking system is disclosed for obtaining the composite response to a variable source array. A variable source array is synthesized by applying preselected weighting coefficients to the seismic signals produced in response to a selected number of surface energy impulses. The seismic signals produced by these impulses are amplified, multiplexed and digitized to obtain digital samples to which are applied the weighting coefficients. A digital multiplier is used to multiply each digital sample by a weighting coefficient to obtain a weighted digital sample. Each digital sample is multiplied by two weighting coefficients, a partial and a final. The partial weighted samples from each of the impulses are summed together to form a partial stack, while the final weighted samples are summed together to form a final stack. The variable source array which is synthesized covers two station intervals. At each station, the partial stack represents the first half of a variable source array, while the final stack represents a complete source array covering the two previous station intervals. At each station, the final stack is recorded on magnetic tape as a seismic field record, and the partial stack is transferred to the final stack for summation with the final weighted samples for the last half of the next variable source array.