Morpho-structural evolution of the valley-slope systems and related implications on slope-scale gravitational processes. New results from the Mt. Genzana case history (Central Apennines, Italy)

This work is aimed at constraining a slope-scale, deep-seated gravitational slope deformation (DSGSD) and an associated rockslide-avalanche in the frame of the Quaternary morpho-structural evolution of Central Apennines (Italy). The study area is the western slope of the Mt. Genzana calcareous ridge, for which a conceptual slope evolutionary model had been already proposed. The existing model has highlighted the role of inherited geological-structural setting combined with Quaternary morpho-evolution in the onset of rock-slope deformational processes until paroxysmal phases (i.e. occurrence of massive rock slope failures). In this work, the previous conceptual evolutionary model was strengthened and detailed by means of a mid-term landscape evolution model, based on the study of geomorphic markers hanging at different elevations above the present valley floor. The Quaternary landscape evolution was also constrained by means of time-dependent landscape metrics. Consequently, it was possible to back-analyse the observed DSGSD process from its onset up to the occurrence of localized massive rock slope failures, through a time-dependent stress–strain numerical modeling. The results of such a multi-modeling approach: i) highlighted the importance of rock mass creep during some stages of the morpho-evolution; ii) pointed out the relevant role of the inherited structural pattern in identifying the preferential strain concentration zones and failure surfaces; and iii) confirmed the hypothesis that the Scanno rockslide-avalanche scar is the result of two separate failure events, as an initial landslide involving the lower part of the slope that favoured a subsequent failure in the upper part of the slope