Some detectability aspects of FEM using HED sources

Controlled source frequency domain electromagnetic (FEM) methods apply either magnetic or electric dipole sources. In both cases they can work in different zones defined by the product of wavenumber and separation. In this paper some delectability aspects of FEM using horizontal electric dipole source are studied with emphasis on the transition zone and its vicinity. From the interpretation point of view the ideal situation is to measure in the far-field regime for all frequencies at any separation (r). For homogeneous earth it fulfils when where δ denotes skin depth. If measurements are also proposed in the transition zone, this restriction has a form of given by Kaufman and Keller (1983). In these two regimes both electric and magnetic field depend on frequency and resistivity.