Marine geoelectromagnetic studies with controlled sources

Marine geoelectromagnetic studies with controlled sources have a long history. Of course, we are talking about attempts to adapt on-land traditional methods. First of all, on the basis of a receiver-transmitter array in the form of two lines (ABMN array), that allowed to work in the motion. At the same time, a difficulty arose, that the signal was determined by the conductivity of the sea water layer, and it was difficult to isolate a useful anomalous signal. This problem was overcome in the CSEM. But it had an expensive price - a limitation of applicability (only in the deep sea) and use of very large distances. However, only CSEM is considered a recognized successful marine technology with a controlled source. The mentioned limitations of CSEM make it necessary to search for an alternative. We see such alternative in the use of an alternating TM field. Here various technical solutions are possible - a vertical electric line and a circular electric dipole, and we are discussing this.