PRELIMINARY CONSIDERATIONS on THE APPLICABILITY OF DINSAR TECHNIQUES FOR THE DETECTION OF PREMONITORY SIGNS OF SINKHOLES

Sinkholes are very subtle hazards typical of karst areas, and related to presence of natural cavities produced by dissolution processes in soluble rocks (carbonates, evaporites), or to man-made cavities deriving from different types of human activities in different historical ages (ancient aqueducts, underground mines and quarries, subterranean storage, etc.). Sinkholes are widespread all over the world, in very different geological and morphological settings. Notwithstanding the related hazard is extremely high, and the likely damage to built-up areas and human infrastructures may result very severe, causing heavy losses to the society, these phenomena have been for a long time underestimated in Italy, when compared to other geological hazards such as slope movements and earthquakes. Nevertheless, in recent years they are occurring at an increasing rate, covering wide areas of the country, so that the interest of both the scientific community and the mass media on the topic has strongly raised. Even more than for many other geohazards, the application of satellite interferometric techniques to analyze and monitor these phenomena may result very useful and productive.

Spaceborne Differential SAR Interferometry (DInSAR) is a useful tool for detecting and monitoring surface deformation at different scales. In the last years, the interferometric techniques have been applied to the analysis of different types of natural phenomena, but very few applications regarding karst collapses are present in the scientific literature. The presented work analyses the applicability of advanced interferometric techniques in the evaluation of sinkhole hazard. Despite the suddenness of the final catastrophic collapse, in fact, sinkhole occurrence is typically preceded by slow deformations, thus availability of data archives, wide coverage of satellite frames, and high accuracy of the satellite measurements make DInSAR particularly suitable for sinkhole analysis and monitoring of precursors of the phenomenon. Furthermore, the first results from an ongoing research project focused on the application of DInSAR to karst areas in Apulia (Southern Italy) affected in the last years by an impressive number of sinkholes (both natural and anthropogenic in origin) will be briefly described.