Behavior of Electric Potential Fields Over Randomly Layered Earth Models
COLORADO SCHOOL OF MINES GOLDEN DEPT OF GEOPHYSICS
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Solutions are derived for the potential distributions over one-layer and two-layer random conductivity earth models for the direct current resistivity method. The random potential due to a stationary Gaussian random conductivity function is non-Gaussian and non-stationary. The ensemble and sample statistics of the random potential fields are examined. The potential field due to dipole excitation is more sensitive to variations in conductivity in the subsurface than that due to monopole excitation. Random variations in conductivity at depth are difficult to detect. Representative curves of the apparent resistivity and kernel functions are presented to show the effects of a random conductivity profile on them. These effects are appreciable and result in significant errors in the interpretation of resistivity data. However, noise of this kind is difficult to distinguish from the signal itself, especially in the presence of measurement noise. Nevertheless, variations in the conductivity profile should be recognized as an additional source of error in the interpretation of resistivity data.
- Geology, Geochemistry and Mineralogy
- Electricity and Magnetism