Novel technology of electrical prospecting with controlled sources

Some advantages and problems of a new geoelectrical prospecting method are discussed here. This<br>method is based on using a new source, the circular electric dipole (CED). The source is installed in the<br>following way. One of the transmitter poles is grounded in the central point. The other pole is uniformly<br>grounded around a radius determined by the depth of investigation desired. It can by defined as a<br>noninductive source, generating a transverse magnetic (TM) non-stationary field. CED has no magnetic field<br>of its own. It is a pure galvanic source, which differs from a loop (a pure inductive source) and from a line,<br>which is both galvanic and inductive (a “line” here means a cable or insulated wire grounded at its end<br>points). The normal magnetic field on the earth’s surface is absent (within the quasi-static approximation),<br>and only a radial electric component exists. Taking into consideration the pronounced vertical character of<br>the currents under the central electrode and current circulation in the vertical planes we propose to term the<br>electrical prospecting technique using the CED as the “vertical electric current sounding method” (VECS).<br>At present, real measurements of the magnetic components with an attached CED-array are the most<br>promising. The authors consider results of the field tests.