Analisi di DGPV tramite integrazione di monitoraggio tradizionale, PS-InSAR e modellazione numerica

In this contribution we demonstrate the diffusion and the state of activity of Deep Seated Gravitational Slope Deformations (DSGSDs) at the scale of a mountain belt. For this reason we started and completed a DSGSDs inventory map at the scale of the entire western and central European Alps. We mapped phenomena by differentiating them according to their: size, geometry, degree of evolution, possible attributable origin. We classified them as large landslides, mixed landslides-DSGSDs, DSGSDs, with or without dominating tectonic features, and finally as tectonically derived structures. Adopted criteria have been: size with respect to the slope and valley size, capability to influence the local morphology, attributed thickness, continuity through major topographic features (ridges, channels, etc.), freshness and entity of displacement, possible confinement, relationship with main regional tectonic features, evidences for the gravitational reactivation of involved features of tectonic origin, availability of displacement indicators. A total of about 2000 elements has been mapped. The ca 800 DSGSDs range in area between 0.2 and 100 km2, Length and width, as well as other geometrical features and geomorphological parameters have been collected and related to the different phenomena and different typologies distinguished within the same class of phenomena. Distribution of DSGSDs has been analysed with respect to morphological features, lithological and structural characters, meteorologic and climatic factors by using different approaches and techniques of spatial data analyses. PSInSARTM analyses have been independently carried out in the framework of a large project aimed at mapping unstable areas at regional scale through the entire Alpine area. More than 800 satellite radar images acquired since 1992 by ERS-1, ERS-2 and RADARSAT-1 missions, have been processed by means of the PSInSAR™ technique. For the purposes of this research, more advanced analyses have been performed later at local scale at some selected relevant sites. The displacement rates of DSGSDs and their variability at the scale of the entire western-central Alps are analysed. The displacement rates vary from few millimetres up to some centimetres per year. Where possible they have been compared with long term in situ geodetic measurements. The relative abundance of displacement data and geomorphological observations at the mountain belt scale allows to state that most of these phenomena are really active even if with low displacement rates. As suggested by some observed linear features (scarps, counterscarps) cutting glacial and periglacial deposits, such phenomena are probably active since the end of the last glaciation. Finally, numerical models have been implemented both at a local scale to simulate single slope instabilities and also through a series of conceptual slope models. Interpretation of displacement field has been completed for these models allowing to draw some conclusion on mechanisms, geometries, failure depth.