Field and Numerical investigation of filtered m-sequence pilots for Vibroseis acquisition

Summary We conducted a field test that indicated filtered m-sequences potentially to be just as effective as linear sweeps for controlling land vibrators in non-simultaneous operation. In another test, we evaluated the effectiveness of m-sequences modified by a timedomain filter as pilots driving land vibrators in simultaneous multi-sourcing. Results from the multi-sourcing survey indicated that the time-domain filtered pilots produced deblended seismograms somewhat degraded by an unsatisfactory level of crosstalk interference. The crosstalk originates from large-amplitude arrivals generated by adjacent and nearby vibrators. Numerical simulations showed that, by filtering pure m-sequences in frequency domain instead of in time domain, we can obtain an improved set of quasi–orthogonal pilots for which crosstalk interference is much reduced. The improvement comes from retaining as much as possible the spectral energy that exists in pure m-sequences at frequencies between 5 and 20 Hz.