Seismic Sources on Land

A basic mechanical model of a seismic vibrator illustrates the way in which it is intended to generate the compressional wave but it is clearly inadequate to describe the overall response of the system. Hence, the electrical analogy of a simple mechanical system is introduced in order to develop the analogue of a practical vibrator working into the complex load impedance of the earth. By this means, the amplitude and phase response of the baseplate when it is driven with a sinusoidalforce is shown to be equivalent to voltage and current components in a simple network. A similar analogue illustrates the action of a weight drop source which is then compared with the vibrator and other energy sources.