16. Electrical Methods in Geophysical Prospecting

Abstract

This chapter discusses the resistivity, induced-polarization, magnetotelluric, audio-frequency magnetotelluric, and controlled-source electromagnetic methods. With the exception of the magnetotelluric method, all of these methods are used in mining exploration. Resistivity, induced-polarization, and magnetotelluric methods are used in a minor way in oil and gas exploration. All of the methods have been used in geothermal exploration, while resistivity, controlled-source electromagnetics, and audio-frequency magnetotellurics are employed periodically in coal basin studies. Resistivity, magnetotellurics, and controlled-source electromagnetic methods are used in deep exploration of the earth's crust and mantle. Resistivity, inducedpolarization, and controlled-source electromagnetic methods are used in ground water exploration, while only resistivity is used routinely in applications in geotechnical engineering. Each of the methods demands knowledge of electromagnetic theory. Such theory as is necessary to understand each method will be presented, commencing with elementary electromagnetic theory at the outset. Each method also depends on contrasts in electrical properties of the earth media.