CHAPTER 5: ELECTROMAGNETIC SOUNDING
Electromagnetic soundings are made to determine variations in the electrical conductivity of the earth with depth. Electromagnetic (EM) sounding methods include natural-field methods such as magnetotellurics (MT) as well as high-frequency radiation techniques such as radar probing. This chapter is concerned with controlled-source induction methods of sounding, so-called because an artificial source is used to generate the EM field, and because the frequencies are low enough that the measurement distance is less than the free-space wavelength. This is the quasi-static range, where conduction currents rather than displacement currents predominate. In the following discussing the general term EM sounding will be used for simplicity and to follow convention.
Figures & Tables
Electromagnetic Methods in Applied Geophysics, Volume I, Theory presented the mathematical and physical foundations common to all EM methods. The purpose of Volume I was to help facilitate the understanding of the theory involved and to provide a limited amount of interpretational aids. Volume II, Applications is devoted to a method-by-method treatment of the principal EM techniques in common use.