Many built-up areas of Sicily (southern Italy) are affected by such type of risk. In particular, Marsala (western end of Sicily, Figure 1 ) was affected in the past decades by several collapse phenomena which caused extensive damage to infrastructures and population. These phenomena are related to the presence of underground quarries for the extraction of calcarenites used as building materials. These cavities are carved at depth varying from several meters to roughly 25 m on a single or

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... posed layer, following the excavation techniques of chambers and passages separated by rock pillars. However, excavation typically occurred without any planning. With time, the underground quarries were progressively abandoned for several reasons (i.e., interaction with the percolating waters, decay of the physical-mechanical properties of the rock, high costs, difficulties and risk excavation work). Nowadays in many cavities signs of instability can be clearly recognized along ceilings, walls and pillars. These instabilities easily propagate upwards causing sinkhole and subsidence phenomena according to the mechanisms described in Parise & Lollino (2011) , thus creating consistent damages to buildings and infrastructures. A sinkhole, occurred in June 2011 and related to an underground quarry in the eastern sector of Marsala, is described in this paper as a case study (Figure 2 ). The site was selected for the availability of topographic data of the underground quarry, prior to the formation of the