Localisation and direction determination of fissures with geoelectric methods in narrow, elongated measuring areas

In this paper we provide a field example for the determination of the location and direction of fissures in narrow, elongated measuring areas. The test measurements were carried out on the Mokattam plateau at Cairo (Egypt). Direction, length of the layout and the profile length all were very limited, since the measurements had to be carried out within a narrow (2-10 m wide) stripe, between a built-in area and a cleft rim. Interpretation of field measurements was supported by (1) analogue model experiments, and (2) parameter sensitivity maps. As it was found from laboratory experiments, fissures are indicated by potential-difference maximums along profiles measured by using three-electrode array (if the reference point is between the potential electrodes). The mean distance between two neighbouring maximums throughout the whole profile was found to be about 3-4 m, corresponding to the distance between the most visible fissures on the cleft wall. The Schlumberger null-array has been found to be an appropria...