Environmental applications of high resolution TEM methods

Though commonly used in minerals exploration, transient electromagnetic (TEM) methods are less common in environmental and engineering applications. Several aspects of the technique make it a very useful tool, including the fIexibility of loop sizes and geometries, and the recent improvement in electronics that allow faster transmitter turn-off times, and therefore shallower soundings. Faster electronics also allow the acquisition all three magnetic field components simultaneously, increasing the amount of information available for interpretation and modeling. Our discussion includes environmental applications of TEM data in standard geometries (suchas in-loop, fixed-Ioop, etc.) but with higher resolution than usually obtained. In this case, "high resolution" refers to higher resolution spatially (much higher data density than is normally used in minerals exploration TEM) and temporally (much faster turn-off times and faster sample rates). Also of interest is the added benefit of utilizing the late time TEM data, after the background earth response has decayed, as a deep-sounding metal detection tooI.