Urban geophysical approach to characterize the subsoil of the main square in San Benedetto del Tronto town (Italy)

Most historic urban areas have a lack information regarding subsoil and buried structures (such as old utilities, private cellars, etc.). Therefore, when planning new engineering interventions, limited information of subsoil composition leads to greater risk when conserving and reclassifying historic urban areas. Obtaining information about potential sources of risk for infrastructures is important for civil engineering. However, only high-resolution information improves the management of important activities involving historic urban infrastructure. Although direct measurements can alleviate a lack of information concerning the subsoil, they are, generally, expensive, invasive and interferes with everyday use of the site for long periods. Therefore, the use of low or non-invasive technologies to quickly and accurately analyse the subsoil is preferable and strongly recommended. For this purpose, a new discipline, recently termed Urban-Geophysics, is developing rapidly. This paper describes an application of Urban-Geophysics in a historically important Italian town. In order to characterize the subsoil and identify the presence of natural voids and unknown anthropic underground structures such as cellars, an extensive geophysical investigation based on use of Electrical Resistivity Tomography and Ground Penetrating Radar to perform a survey in the town of San Benedetto del Tronto (Marche region, Italy) with a total time frame of around two days was carried out. Previously unknown buried structures and geological discontinuities were highlighted by using these geophysical techniques. In order to support and confirm the interpretation of the geophysical data, geotechnical drillings were carried out. Finally, direct data validated and supported the noninvasive geophysical results. The combined results have provided valuable information to the local authorities and engineers involved in the decision-making process for the construction of new underground structures.