Abstract:

The traditional record method of airborne TEM system has the difficulty to detect  high-conductivity anomaly. With thin sheet model, this paper studies the detection resolution of the full-waveform TEM response induced by a trapezoid wave. An approximate method basing on eddy currents is used to estimate the mutual inductance of two coils at any position, and applied to compute the induced electromotive force of a slab model during switchoff and off time. Numerical results indicate that if minimum signal resolution of survey system is 5 nV/m² in the case of conductive overburden, the detectable conductance range is 1~400 S during off time and 0.1~1 000 S during switch-off time. When full-waveform method is adapted to the airborne TEM system, it could broaden the conductance resolution aperture of airborne TEM.

Key words: airborne electromagnetic responses, eddy currents, switch-off-time, off-time, conductive overburden, high conductance anomaly