About Measurement of Vertical Component of Electric Field During Magnetotelluric Sounding

Abstract

AbstractIn magnetotelluric sounding (MTS), variations of five components of electromagnetic field are usually registered. With the standard approach in experiment transfer functions are defined as ratios between horizontal components of electric and magnetic fields. Deviations from the Tikhonov-Cagniard basic model are defined by the fifth registered component—the vertical component of magnetic field. In order to increase the reliability of results obtained by the inversion and to gain more information from MTS, it is proposed to carry out the additional registration of vertical component of the electric field in the medium. At present, for registration of variations of vertical electric component the method of measurement of potential difference arising on the vertical line immersed in the sea is applied. On the land, for this purpose it is necessary to drill a hole or use already available wells, which may be difficult in practice. It is proposed to apply a circular electric dipole (CED) for registration of vertical electric component. Presently, CED is successfully used as an emitter in electromagnetic sounding methods. Its feature to excite in the layered medium a single TM-mode whose electric field has a vertical component, is used. In practice, CED is usually implemented with eight long radial lines. Taking into account this feature, CED can also be used as the MTS receiving system for registration of variations of a TM-mode field. Possibilities of using this schema in MTS are analyzed.KeywordsMagnetotelluric soundingVertical component of electric fieldCircular electric dipole