f Detecting of fractured zones with geoelectric and elctromagnetic methods

A frequent task in hydrogeology, environmental or engineering geology to detect fractured zones within compact rocks. The problem can easily be handled in the case of outcrops. But a complex approach is necessary when the basement is covered with conductive overburden. Penetration depth, resolution power and efficiency are the main aspects when deciding the methodology. The poster presents an example of the integrated application of electromagnetic (EM: VLF, EM-31, Protem) and direct current (DC) methods. According to the geological model, there is a varying thickness of low resistivity sediments above the resistive basement. Fractured zones are supposed to be within the compact basement. The tasks were on one side to detect the thickness of the overburden and on the other side to delineate the covered fractured zones within the basement. The resistivity of the covering sediments varied between a few 10 - 100 ohmm. The resistivity contrast between the basement and the overlying sediments is at least twice. The tectonic/fractured zones could be followed as resistivity lows.