Abstract

A general earth model is described which simulates the earth when excited by currents either conductively coupled to the earth by electrodes or inductively coupled to the earth by loops. Consideration of model equations showed that a material with a resistivity of approximately 10 (super -4) ohm-meters was desired for use in the model. Although suitable materials with this resistivity were not known, it was found that fine bronze wheel grindings held together by wax did have the required macroscopic resistivity. Using this model, surface measurements were made employing a modified Wenner spread 'one mile' in length. Only minor anomalies resulted from a simulated salt dome 'three-quarters of a mile' in diameter and 'one-half mile' below the surface.

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