Electromagnetic Coupling*

Abstract

Electromagnetic coupling in grounded electrical prospecting systems has been studied over four decades. Recently, advanced digital electronic systems have been developed which permit both magnitude and phase measurements over four frequency decades (10−2— 102 Hz). This development has stimulated theoretical studies demonstrating behavior of EM coupling for the more commonly‐used electrical prospecting arrays a wide frequency range. A comparison is made between field and theoretical results which demonstrates the validity of the fundamental assumptions involved. Additionally electromagnetic coupling is used successfully as a deep‐sounding technique in a highly‐conductive sedimentary basin environment.

Phase correction of electromagnetic coupling effects in cross-borehole EIT measurements

“…The theoretical calculation of EM coupling between grounded wires on the surface of the earth has previously been treated in some detail (e.g. Sunde 1968, Wynn and Zonge 1977, Wait 1984, Ward and Hohmann 1988. In these contributions, the mutual impedance that represents the total response from the earth and the wires was split into two parts.…”

Electromagnetic coupling in frequency-domain induced polarization data: a method for removal

“…In frequency‐domain IP, most of the work on EM coupling removal has been focused on phase data and there are not many studies that have addressed the removal problem for the PFE data (Wynn & Zonge 1977; Wang et al 1985). Recognizing that the PFE data are generated from the amplitude measurements at two frequencies, we consider a practical scenario when EM coupling is present in the data.…”

“…Electromagnetic (EM) coupling can be defined as the inductive response of the Earth, which manifests itself as a response over the induced polarization (IP) signal. EM coupling is a major impediment to the interpretation of complex resistivity and IP data (Wait & Gruszka 1986; Wynn & Zonge 1977). The effect is increased when the survey is carried out over a conductive Earth or when the dipole length and dipole spacings are large.…”

“…The third approach is to assume that the Earth is one dimensional and compute the EM coupling response by evaluating the mutual impedance of the grounded circuits at the desired frequency (Millett 1967; Dey & Morrison 1973; Hohmann 1973; Wynn & Zonge 1975, 1977; Wait & Gruszka 1986). Wait & Gruszka (1986) computed the impedance due to EM coupling for a homogeneous half‐space model and subtracted this from the observed impedance, which has both IP and EM coupling responses.…”

The AC‐geoelectrical sounding method: a combined electric/electromagnetic prospecting tool

“…The theoretical problem of calculating electric and magnetic fields from a grounded electrical dipole of finite length was in principle solved many decades ago (Sommerfeld 1926;Foster 1933). Only recently has it been suggested (Wynn & Zonge 1977) that the inductive coupling between the transmitter and receiver dipoles would contain useful information about the earth parameters. but expressions for two-layer earths were also found (Riordan & Sunde 1933).…”