Controlling a land vibrator with m-sequences: a field test

Joe Wong, Malcolm Bertram, Kevin Bertram, Eric Gallant, and Kevin Hall

ABSTRACT

We conducted initial field measurements to test the idea of driving a land vibrator with maximal length sequence (m-sequence) pilots. Seismograms were recorded with the CREWES IVI EnviroVibe vibrator controlled by m-sequence pilots. The m-sequence seismograms were compared to seismograms acquired with the vibrator controlled by a conventional frequency sweep, and with data acquired with an accelerated weight-drop source. The comparison indicated significant issues regarding how hydraulically-powered vibrators respond to pilot signals that try to force very sharp accelerations on the reaction mass. Nevertheless, the m-sequence seismograms from this initial field test show promise, and point to possible modifications to the m-sequence pilots to make them more compatible with the particular mechanical characteristics of a land vibrator.

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