Collapse sinkholes in the carbonate massifs of Central and Southern Apennines

Abstract

This study focuses on karst collapse sinkholes of the southern and central Apennines region (Italy), and has the aim of outlining and discussing the factors whichcontribute to the occurrence of collapse phenomena. By the analysis of the morphometrical/morphological features of the about 600 initially identified sinkholes, about 50% were interpreted as collapse sinkholes related to karst phenomena, whichare the object of this study. These were geo-referred and organised in a data base, in whichinformation on the geological-structural and hydrogeological features of areas affected by the collapses was also reported. The collapse sinkhole inventory was paralleled by an analysis of the distribution of the main mineral springs (H2S- and CO2- richwaters), of travertine bodies and of extensional faults withlate Quaternary activity, whichwere all considered significant to the study due to the interrelations linking travertines, karst solution processes, CO2- richwaters and faults. Furthermore, withthe aim of investigating the role of seismic shaking in the occurrence of the collapses, the karst collapse sinkhole distribution was compared withthe distribution of stronger historical earthquake epicentres. The results of this regional scale synthesis suggests a possible key to the interpretation of karst collapse phenomena. The latter, in fact, appear correlated to the combination of peculiar conditions, whichmay be envisaged in the presence of active faults and mineral waters. The study, in particular, suggests that karst collapse sinkholes result from enhanced dissolution phenomena related to the rising of fluids of deep origin, for which active faults represent preferred pathways, and favoured by the presence of a relatively shallow water table. In the collapse events, an important role is possibly played by seismic shaking.