Interpretation of Data from Electrical Resistivity Geophysical Surveys

Abstract

ELECTRICAL resistivity surveys are all based on the method of Wenner¹. A current, I, is passed into the earth through one point electrode and returns to the apparatus through a second. The potential difference between two points on the earth‘s surface, V, is measured. Let Then R can be related to the resistivity of the earth and the electrode spacing. Usually the four electrodes used are spaced in a straight line, and frequently a symmetrical arrangement is used. If the distance between the current electrodes is 2a and between the potential electrodes is 2αa for a symmetrical arrangement, it is easily shown² that, for a homogeneous earth, the resistivity ρ is given by If the earth is not homogeneous, the value of ρ obtained from (2) will vary with a. This variation will be related to the nature of the earth, and hence the usefulness of the method.