Abstract: A method used for controlling vibrator ground force output from a seismic vibrator and reducing potential damage to nearby structures. The method may be applied to any type of seismic vibrator for controlling the amount of vibrator force output applied to a ground subsurface. The subject method controls the vibrator force output as a function of frequency to form a force variable sweep. Low frequency waves are harmful to structures. The force variable sweep reduces the percentage of harmful low frequency waves while imparting a great deal of energy. The method steps include first selecting and constructing a frequency dependent force function from either a hyperbolic tangent function mathematical equation or a simple step function mathematical equation. Second, implementing a seismic vibrator frequency control instrument with the selected frequency dependent force function. Third, applying the force function to either a seismic upsweep or a seismic downsweep.