Cataclastic slip band distribution in normal fault damage zones, Nubian sandstones, Suez rift

Abstract

In this paper, we characterize the geometry of damage zones that form around the main slip planes of normal faults. Specifically, we examine five faults of varying throws that affect the Nubian sandstones along the Suez rift. To quantify the density of cataclastic slip bands (CSBs) associated with the main slip plane, we recorded the position of all visible CSBs along a scan line perpendicular to the fault through to the damage zone. For each outcrop the scan line record is ∼30 m long. Resulting density diagrams display concentrations of CSBs and clearly indicate a widening of the damage zone with increasing throw. A correlation integral was calculated for each CSB population in order to analyze both the scaling property of the density distribution and potential correlation lengths. From centimeter to meter scale, representing 2 orders of magnitude, the correlation integral appears adequately modeled by a power law, emphasizing the fractal property for the CSB distribution. For the five faults the calculated correlation dimension is constant within its error of determination, Dc = 0.87 ± 0.05. The validity range of the fractal nature was derived from an adequate normalization of the correlation integral and from a comparison with synthetic fractal fracture networks. It appears that a finite correlation length corresponding to the damage zone width is detectable for meter‐scale throws; for larger throws the correlation length is not detectable within the sampling domain.