A Multidisciplinary Study for the Recognition of Fault-Induced Instability Conditions on Cultural Heritage: The Case of Paternò (Sicily, Italy)

The 16th century AD St. Barbara’s Church in Paternò, a town located at the SW foot of Mt. Etna volcano (Sicily, Italy), has since 2009 showed evident signs of structural instability and collapse. This is causing great concern among the local population and poses a growing hazard to the attendees to the masses. After precautionary closure of the church, we carried out geological, seismic, geophysical and geochemical surveys in order to shed light on the possible causes of the phenomenon. From the results of all surveys above, the presence of a hidden fault was hypothesized. The fault would prove to cross the west side of the church, parallel to its front portal, and continue both to the north and to the south of the edifice. It is part of a more complex system of faults that crosses the whole town of Paternò and is likely a result of the complex dynamics of Mt. Etna. This fault seems to also be a pathway for the upward flow of saline hydrothermal fluids, similar in composition to those emitted in nearby areas and whose corrosive action possibly contributed to the weakening of the rocks beneath the church. Temporal monitoring of several hydrological parameters (water temperature, water level and CO2 content) in some sites in and around the church allowed a better understanding both of the fault dynamics and of the extent of hydrothermal influence in the studied area.