A multidisciplinary approach to investigate active and new tectonic effects on landslides spatial distributions: case study in the Pre-Rif Ridges morphostructural unit

The Pre-Rif Ridges constitute the southward deformation front of the entire Rif chain, Northern Morocco. Previous investigations showed that evidence in favor of active, recent and neotectonic deformation can be found all over this area. However, the effect of such tectonic activity on surface processes such as gullying and land-sliding was never properly investigated. Therefore, we conducted a statistical analysis using different statistical approaches (comparison tests, frequency-area distributions, frequency ratio) to compare three zones of the study area, with different tectonic attributes (zone A: inactive tectonic processes, zone B: neotectonic deformation and zone C: active tectonic deformation). The first zone (A), which presents little to no evidence of intense deformation, is shown to be very different to the other two areas both in terms of landslides and gully morphometries. It has also gentler slopes which promote less landslides in marly terrains as shown by the factor of safety analyses conducted in this study. The other two segments of the study area are more or less similar with relatively steeper topographies and a higher density of mass movements. Given that both zones are relatively intensely deformed compared to zones 1, one can attribute the abundance of surface processes in these two areas to the tectonic uplift and topographic growth, which play a major role in promoting such processes.