Simultaneous multi-source acquisition using m-sequences

Joe Wong

ABSTRACT

Maximal length sequences, or m-sequences, are periodic mathematical periodic entities with values of -1 and 1. A single m-sequence can be used to construct multiple shifted m-sequences or Gold codes. Within the set of shifted m-sequences or derived Gold codes, each member has an autocorrelation that closely approximates a delta function but is correlated weakly to other members. These sequences and codes are known generally as pseudorandom binary sequences (PRBSs), and being weakly correlated to each other, they are suitable for driving multiple seismic vibrators simultaneously with little crosstalk between the vibrator sources. Operating multiple vibrators simultaneously in real-world seismic surveys increases acquisition productivity dramatically. I use numerical examples to show how signals from multiple vibrators simultaneously driven by weakly-correlated PRBSs (in particular, shifted m-sequences) can be separated into individual seismograms unique to each vibrator with minimal crosstalk.

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