oa Application of an Airborne HEM System on a Freshwater Lake

Airborne electromagnetic systems are superior to ground-based geophysical techniques in many respects. they afford rapid reconnaissance of large areas for producing images of earth electrical resistivity as two-dimensional maps and as pseudosections. Systems today are powerful, stable and precise. Adapting such a system for ground-based operation can provide increased sensitivity to the subtle variations in the resistivity of the ground and increase lateral resolution. We analyze the limits on a helicopter electromagnetic (HEM) system owned by the USGS using forward model analysis, and we present the results of a proof-of-principle test on Lake of the Arbuckles in Chicksaw National Recreation Area in south-central Oklahoma. the HEM system was mounted on a floating platform and towed behind a motorboat which carried the data acquisition electronics and a bathymeter.<br>Preliminary results show that the waterborne system is capable of mapping geology under shallow cover of water.