GNGTS 2021 - Atti del 39° Convegno Nazionale

157 GNGTS 2021 S essione 2.1 Results Geological and geomorphological analyses identified several features in the area, such as double crest lines, scarps, counterscarps, trenches, and depression alignments, which are typi- cal indicators of the presence of active or quiescent mass movements. Two unknown DGSD were identified (Fig. 2a) whose kinematics are governed by deep sliding surfaces, beginning at the top of the DGSD bodies and ending at the toe of the hill to the E, close to the Simeto River (the dashed red curves in Fig. 2a). The potential sliding surfaces are sub-planar, with a gentle slope, and involve a potential soil mass volume of approximately 3 - 4 x 10 8 m 3 with a mean thickness of approximately 100-150 m. The likely detachment is hypothesised to be at the interface between brown brecciated clays (3a in Fig. 2a) and grey-blue and brown marly clays (3b in Fig. 2a). The inversion of InSAR displacements identified a slip plane (Fig. 2b) located below the DGSD at an average height of approximately 90 m a.s.l., with a length of 1450 m, a width of 1750 m, a dip of approximately 2.3° towards E, and a slip distribution peaking at 8.5 cm and directed towards the E (i.e., rake ≈ 100°). Such a sliding plane is compatible with the potential sliding surface identified from geomorphological analyses (Fig. 2a). Finally, we estimated the critical soil Fig. 2 - (a) Geological cross-section of the DGSD. Key to the legend: 1. Recent and old terraced alluvial deposits (Holocene); 2. Marly limestone and limestone breccias with gypsum (Messinian-lower Pliocene); 3a, b. Terravecchia formation (upper Tortonian); 4. Areas affected by surficial landslides; 5. DGSD body; 6. Inferred DGSD sliding surface. (b) 3D geometry and slip distribution of the potential sliding plane responsible for the observed ground displacements. (c) Comparison between experimental and modelled undrained cohesion (c u ).