CALCULATIONS OF SELF-POTENTIAL ANOMALIES NEAR VERTICAL CONTACTS

The self-potential anomalies due to streaming potential effects in the vicinity of a vertical contact are analyzed. This approach is different from most previous studies in that the source is tied to a specific physical mechanism instead of arbitrarily selected charge distributions or current sources. The analysis is valid for any source mechanism that can be thought of in terms of cross-coupled flows, e. g. , the thermoelectric effect or chemical potential gradients. The anomalies tend to be antisymmetric across the contact, with the magnitude of the anomaly being larger on the more resistive side of the contact. An analytic expression for the case of a constant intensity rectangular source is derived from the general solution. The anomalies for this simple case are computable with a hand-held calculator and can be used to estimate the location, extent, and magnitude of the anomaly source region. With this information it is possible to determine the most probable cross-coupling source mechanism.