Resistivity Surveying as an Aid in Sanguine Site Selection

A practical extremely low frequency (ELF) horizontal antenna requires a site of low effective conductivity. This paper describes the application of certain dc resistivity sounding methods in rapidly evaluating potentially useful areas within geologically interesting regions, and in determining both basement anisotropy and the direction of the principal (maximum) resistivity axis. Apparent resistivity data from dc array expansion is interpreted with a horizontal layered earth model using a "generalized inverse" method of fit. With layered models over principal axes the effective conductivity to be experienced with a horizontal wire antenna of arbitrary orientation is readily calculated. Salient results for three geographical regions are presented.