We conducted field tests to evaluate the effectiveness of time-domain filtered m-sequences used as pilots for driving land vibrators in simultaneous multi-sourcing. Common-source gathers extracted from the blended field data for two and four simultaneous vibrators indicate that the time-domain filtered pilots produced seismograms somewhat degraded by crosstalk interference originating from large-amplitude arrivals produced by adjacent and nearby vibrators. We conducted numerical simulations to show that, by carefully filtering pure m-sequences in frequency domain instead of in time domain, we obtain an improved set of quasi–orthogonal pilots for which crosstalk interference is reduced. The improvement comes from retaining as much spectral energy as possible between 4 and 100 Hz.
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