GNGTS 2015 - Atti del 34° Convegno Nazionale

plateau area, were distinguished. The first zone includes the portion of the slope between the edge of the cliff and the first main fracture (f1) where the rock mass is intensely joined by some additional open cracks related to the stress release. This joint system produces several unstable meter-scale rock blocks. The three deep cracks isolate two large blocks, which correspond to the second and third unstable zone. Where visible, the main cracks have an aperture about 35 cm and a vertical displacement up to 60 cm. A stable plateau area is encountered moving upslope from the third fracture f3. Fig. 1 – Geological and geomorphological setting of Cala Rossa Bay. a) Excerpt of Favignana geological map in the Cala Rossa area (from Abate et al. , 1997) and picture of cliff in the Cala Rossa western part that shows the overlapping of the Lower Pleistocene carbonate grainstones on the Pliocene clay deposits. b) Orthophoto of the Cala Rossa western part in which shows: the open fractures with related code, the estimated fractures, the three unstable zones, the stable plateau area, the 25 noise measurement stations. 58 GNGTS 2015 S essione 3.2