Detection and estimation of problem zones in salt rock with the aid of underground geophysical exploration methods

Having a very low permeability, a high plasticity, and a high heat conductivity, salt rocks are principally suited for deposits of toxic and radioactive waste. In Germany exist a big number of salt domes and bedded layers which could serve for underground storage of hazardous waste. However, recent tectononic fault zones and areas of high water content may bear severe risks for mining and underground deposits, which are mainly due to the high solubility of salt rocks. Therefore reliable detection of fault zones and humid areas with non destructive methods is crucial for the appraisal of underground nuclear and toxic waste deposition sites in salt rocks. A qualitative detection of such problem zones with non destructive geophysical methods is possible. But it is not yet reliable enough for legal purposes. The security appraisal of hazardous waste deposits based only on non destructive geophysical methods not seems possible yet. In the past, these methods were usually applied as stand alone methods. In the frame of a research program of the German Research Ministery (BMBF) a complex interpretation system of geophysical methods shall be developed, including seismics and ultrasonic acoustics, high and low frequency electrical methods, in order to reduce the uncertainty of the geophysical results and to approve a more quantitative evaluation.