3D Inversion of the Semi-airborne Electromagnetic Data from Schleiz, Germany

We present a new semi-airborne frequency domain electromagnetic system being developed within the DESMEX project. In the system, the high-moment transmitter is positioned on the ground and the receivers (induction coil and fluxgate magnetometers) are installed in a helicopter-towed bird. The major difficulty is to overcome the problem of motion noise and motion-induced voltages, due to the pendulum-like behaviour of the bird. For this purpose, we developed a processing scheme which corrects data for motion related noise. Specifically, for processing in frequency domain we utilize only free-of-motion-noise frequencies. The initial design of the system was developed and tested in several flight campaigns. In the current paper, we present a first 3D inversion of the data acquired during the experiment in Schleiz, Germany. In the model the conductive anomalies which we interpret as alum shales, are embedded within generally resistive Cambrian basement. A comparison with the 2D electrical resistivity tomography model shows that our model represents the same resistivity structures. The experiment also proved that our system allows us to cover an area of around 36 square km during one flight (3 hours) resulting in penetration depth of 1-1.5km.