On The Application Of Radiomagnetotellurics To Waste Site Exploration In Germany

Since several years, the environmental geophysics department of the University of Cologne<br>uses the radiomagnetotelluric method (RMT) extensively in connection with waste site<br>exploration successfully (Tezkan et al., 1996, Zacher et al., 1996, Dautel, 1995).<br>The RMT-method uses transmitters from powerful civilian and military radio stations in<br>the frequency range 10 to 240 kHz with possible extension to few Mhz. Horizontal<br>components of the magnetic field are measured by a coil and of the electric field by using<br>two grounded electrodes spaced 5 m apart. Apparent resistivity and phase data can be<br>derived from these data for several selected frequencies. These data are then interpreted by<br>using 2D conductivity models which give excellent information about the vertical and<br>lateral borders of the waste site and about the top layer.<br>Two case histories about waste site exploration from Germany will be demonstrated.<br>Depending on the accessability of the survey areas for geophysical measurements the<br>lateral borders of the waste sites are located in the field very accurately. They are<br>characterized by strongly decreasing apparent resistivities observed at nearly all<br>frequencies at the border between waste site and undisturbed geology. The information<br>about the thickness of the top layer and the resolution of the bottom of the waste site can<br>be obtained by 1D and 2D model calculations quantitatively. They give also information<br>about different areas of the waste site containing different materials.