The Basilica of Santa Croce (Lecce- Italy): study the conservation state by ground-penetrating radar and electrical resistivity tomography

In the field of the restoration of monumental heritage, non-destructive geophysical techniques have gained an already widely acknowledged importance. The possibility to understand the state of preservation of the artefacts without resorting to a destructive action is extremely useful in identifying unknown or presumed emergencies in order to better lead the restoration operations.At present geophysics is underutilised and furthermore, common techniques may not be optimal for some specific targets or sites. Therefore, more controlled research is needed to better understand the applicability of these methodologies when searching for cultural heritage applications in various material types. The purpose of this paper is to provide a new approach that involves the joint use of several geophysical methods for the study of the probable causes of deterioration on a monument of considerable historical and artistic importance. The monument is the Basilica of Santa Croce in Lecce. It is a baroque church internationally well-known. The starting point of this research was the evidence that some structures of the facade are more damaged and present signs of subsidence. The study of the causes of damage was dealt with a geophysical survey using ground-penetrating radar and electrical resistivity tomography. The results demonstrate the effectiveness of the choice of the two methods and allow to obtain information on buried structures both inside the church and on the facade and to locate and identify anomalies related to a restoration intervention carried out in the 80s. Furthermore, a microclimatic analysis performed inside the Basilica shows a probable connection between the humidity present on the surface and the conductive layers present in the subsoil and highlighted with the electrical method.