Direct and indirect prospecting to detect and characterise sinkhole features in urban evaporitic environments

Natural subsidence sinkholes (according to Gutiérrez et alii, 2008, 2014; Parise 2019, 2022), both in carbonates and evaporites, represent a severe threat to man-made structures. Especially when bedrock is mantled and in urban areas, the identification and characterization of these phenomena is always challenging. For this reason, multidisciplinary and multi-technique approaches are recommended and in detail, the integrated use of geophysical techniques (Electrical Resistivity Tomography, Reflection and Refraction Seismic, Electromagnetometers and 2D Ground Penetrating Radar - GPR) and most recently developed 3D GPR is strongly suggested. Thanks to the Agreements signed between the University of Trieste and the Geological survey of the Friuli Venezia Giulia Region (NE Italy), since 2007 the researchers approached these issues in specific test site areas. From the studies in urban mantled evaporitic bedrock areas, emerged the supremacy of the 3D GPR jointly with reflection seismic, being the former able to identify with high accuracy and detail shallow deformations, and the latter the best approach to identify the thickness of cover materials, the morphology of the bedrock and the sinkhole location.