The effect of phase loop and predictive gain adjustments on harmonics generated by the CREWES EnviroVibe

Christopher B. Harrison, Kevin L. Bertram, Eric V. Gallant

Harmonic distortions in Vibroseis data are a well known issue in seismic data acquisition. Poor ground coupling, equipment variances, and nonlinear effects in the earth contribute to harmonic generation. These harmonics have traditionally been treated as noise to be attenuated. One method of attenuating these harmonics is through phase control systems within the vibrator. Currently CREWES and POTSI are jointly researching methods of decomposing Vibroseis sweeps into their fundamental and harmonic components. It is proposed that these separate components and their higher frequencies can be used as a source signal rather than filtered out of seismic data. An experiment was conducted at University of Calgary to assess how adjustments in the phase loop and predictive gain of the CREWES Vibrsoeis affect the harmonic generation.