Modified Vertical Electrial Current Sounding (mVECS) is a fundamentally new method of transient EM sounding (US Patent,2000). It uses a novel source for electrical prospecting, a circular electric dipole (CED). The CED is a purely galvanic source generating a transverse magnetic non-stationary field (TM mode prospecting).
The behavior of an inductive source (loop) and a TE process are well known. The properties of the TM transient process has been poorly studied and little used (in the best case, only in problems of applying a little suited vertical electrical line).
The most remarkable properties of the field in this process include the absence of the normal (quasi-static) magnetic field at the outer surface of a layered medium, as well as the dependence of the process on the vertical geoelectrical structure (rather than on the overall longitudinal conductivity only, which is typical of the processes excited by inductive means).
mVECS uses conductivity and polarization (IP), that is, all EM properties of the target to receive the recorded signal. The depth of investigation achieved so far using this new EM prospecting method is around 2500m in Russia geological setup. Below shows a typical mVECS onshore field setup using CED.
