Geophysical survey of a karst area - A case study from Sarsinia, Italy

A geophysical survey has been carried out, using a combination of techniques, in a karst area in SW Sardinia (Italy), where a large sinkhole, 15 m deep and 18 m wide suddenly appeared. Gravity as well as refraction and reflection seismic methods have been employed. The Bouguer and filtered anomaly maps show the structural pattern and indicate that the sinkhole lies on a gravity low. Refraction data provide near-surface information. Shallow reflection clearly reveals the tectonic structure to which the sinkhole is related, confirming the correlation between subsidence phenomena and local tectonics. In addition, six 20 m deep boreholes, as well as geotechnical and hydrogeological measurements were executed. Combined interpretation of geophysical results along with hydrogeological and well data provide detailed information summed up in a final cross-section and elucidate the mechanism underlying sink phenomena.