Mechanical and piezoelectric vibrators are controllable seismic sources used in seismic surveys for data acquisition. In standard industry practice, these sources usually are controlled by frequency-sweep pilot signals. However, spread spectrum techniques, widely used in many fields of science and engineering for obtaining accurate estimates of impulse responses of linear systems, have received attention as pilots for vibrating sources. Spread spectrum techniques are most commonly based on special periodic functions known as pseudorandom binary sequences (PRBSs). In this report, we will examine the properties of two types of PRBS, maximal-length sequences and Gold codes, and see how they can be applied to seismic data acquisition. We will compare the relative merits of using the two alternatives, m-sequences and Gold codes, as pilots for driving vibrating seismic sources.
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