Phase encoding of vibroseis signals for simultaneous multisource acquisition

Abstract

A method has been formulated and tested that permits separation of simultaneous Vibroseis* signals while reducing harmonic distortion within those signals. This allows simultaneous acquisition of Vibroseis data at multiple source locations to lower survey costs. The proposed method involves the use, at each source location, of a sequence of variable phase sweeps for source separation as well as suppression of the harmonic distortion resulting from nonlinearities in the source and ground response. The technique discussed here differs from earlier methods for the use of simultaneous multiple sets of vibrators in that this technique emphasizes distortion suppression as well as suppression of crosstalk of the fundamental frequencies (Ward, 1989). An alternative use of these same phase coding techniques is to concatenate sweeps. In certain areas it is the usual practice to use multiple, relatively short sweeps with vibrators remaining stationary between sweeps in order to prevent high levels of distortion. Concatenated sweeps with the proper phase coding allow the elimination of the intervening listen times to enhance field efficiency.