Determination of the location and extent of karst in limestone with the use of geophysical methods

Abstract

Field studies for testing the usefulness of geophysical methods in the mapping of karst in the northern part of the 'Rheinischen Schiefergebirge' yielded the following results: (1) Geoelectrical resistivity profiling, gravimetry and refraction seismic can be used for the detection of karstified zones. Low apparent resistivities, low p-wave velocities and negative gravity anomalies characterise the loose fill material or highly jointed limestone in these zones; (2) Rapid detection of karstified zones can be carried out with the resistivity profiling technique. The approximate extent of these zones can be mapped. The double dipole (linear) array gives the best results; (3) A more exact determination of the size of the karstified zones can be carried out using refraction seismic and gravimetry. Gravimetry enables an approximate volume estimate whereas refraction seismic allows a more precise volume estimate as well as the determination of the internal structure, nature of material present and boundaries to non-karstified areas.