DEM-based morphotectonics analysis of Western Ligurian Alp

The western Ligurian region shows a peculiar drainage network related to the geological events that marked this area since the Pliocenic ingression to date. From long-time, several researchers have studied the drainage evolution history of this area, with the purpose to understand how and how much its character is due to heritage ("the structure") and/or to neotectonics. Of particular relevance, a GIS type approaches permit the analysis of several scale DEM and the "enhancement" of neotectonics lineaments. This zone is in fact affected by numerous systems of faults, of which the Breil Sospel Monaco (BSM) line, and the Saorge-Taggia (ST) line, represent the principal expressions. The Saorge-Taggia system consists in a rather complex right strike slip bundle of faults, with orientation NW-SE, that is extended from the Ligurian Sea to the intersection northwards with the BSM, considered a left strike slip. Focal mechanisms which represent the earthquake of Ventimiglia of Aprils 21, 1995 (intensity 4.7), announce the presence of an inverse fault, oriented NW-SE, belongs to a system of faults, set to SE and sub-parallel to the Saorge-Taggia, identifiable probably with the Ospedaletti-Olivetta San Michele fault, even denominated in literature as Sanremo’s fault. In this work we show some results given by the analyses of parameters extracted from digital elevation model, that give us the opportunity to develop and interpret morphometric maps. Principal morphometric indices evaluated are: slope, aspect, surface roughness, swath profiles, lineament and drainage density, isobase surface, hydraulic gradient and drainage fractal dimension. Clearly emerges from preliminary results that drainage network established its course along the main structures. Its evolution however, especially in recent era, is strongly related to the different lithological competence, differential tilting, and a differential uplift located northwards the Saorge Taggia fault and inside the Elminthoid Flysch Arc (Argentina Valley).