The design, construction and field testing of a magnetotellurgic recording system.

The scientific principle considered in this thesis is the relation at the surface of the earth, of the amplitude, phase and frequency of orthogonal components of the naturally occurring electric and magnetic field fluctuation to the resistivity profile of the subsurface geology. A method of resistivity profiling, known as magnetotellurics, was presented in a paper by Cagniard, (1953) and extended in later papers by Wait, (1954) Tikhonov and Shakhsuvarov (1956), Cantwell and Madden (1960), Smith, Provazek and Bostick, (1961), Price, (1962), Vozoff, Hasegawa and Ellis (1963) and others. Results obtained by these researchers have shown that the basic theory of magnetotelluric methods require some modification for extension beyond very simple geologic situations