GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.1 17 The fault segments located in the lower eastern flank of Mt. Etna, have been responsible, both in historical and recent times, for earthquakes with magnitude up to 4.5 (Azzaro et al. , 2004; De Guidi et al. , 2012). Because of the shallow foci depth (<2–3 km), earthquakes have often caused significant damage, even though localized, especially when associated with remarkable flank eruptions. Some examples are the Santa Venerina earthquake connected with the 2002 eruption, the 1865 earthquake that occurred at the end of a large flank eruption, and the seismic activity associated with the 252 AD eruption (Guidoboni et al. , 2014). Field data. Geophysical investigation. A multi-techniques geophysical survey was carried out at Santa Venera al Pozzo, in order to investigate a deeper portion of the subsoil and to verify the presence of a fault zone. The survey consisted of seismic refraction tomography (SRT), electrical resistivity tomography (ERT), ground-penetrating radar (GPR), and a magnetic survey in addition to remote sensing applications using unmanned aerial vehicles (UAVs), which provided new data for ultra-high resolution mapping. As suggested by the surficial evidence of displaced archaeological structures, the inferred fault should be orientedN-S. For this reason, wemainly performed the geophysical investigations along a 90 m long profile, directed almost perpendicular to the presumed fault (Fig. 2). The SRT reveals a reliable P-wave velocity model down to a depth of ~ 20 m. Seismic velocities ranged from about 400 m/s to about 2900 m/s (Fig. 3a). A portion characterized by Fig. 2 - a Digital Surface Model (DSM) of the archaeological area. The red line A-A’ shows the location of the geophysical surveys; arrows indicate the surface faulting observed at the site; b zoom in on the faulted podium, c zoom in on the faulted floor of the tank; d southern view of the faulted podium.