How to reveal unknown hidden faults and historical earthquake damage applying multidisciplinary methods in archaeological sites: The case of mid- third century CE Mt. Etna earthquake (Eastern Sicily, Italy)

Archaeoseismological evidence of a strong earthquake, which probably occurred a year before the 252 CE Mt. Etna eruption, has been uncovered at Santa Venera al Pozzo site, located near to Acireale, along the lower eastern flank of the volcano. The site, known for its remarkable and peculiar hydrothermal fluids emissions exploited for thermal uses since the Greek and Roman age, has been investigated through a multidisciplinary approach by integrating archaeoseismological observations with geological and geochemical surveys. Analysis of the observed damage and deformation at the site suggest a capable fault zone through the area. Geochemical and geological surveys were performed in and around the site and have revealed anomalies of soil CO2 efflux along an known active fault and likely also along some unmapped hidden faults. The chemical and isotopic composition of the emitted fluids suggests that these have not a volcanic origin, but they could be related with a deep tectonic system. The data presented in this paper suggest the occurrence of both exposed and hidden active faults in the area of Santa Venera al Pozzo, which could be linked to the seismic activity that damaged the historical site. •The Santa Venera al Pozzo site shows damage probably ascribed to the 251 CE earthquake as documented by historical sources.•The site is near important tectonic faults and it is known for its thermal gas-rich water springs.•Chemical and isotopic data of springs local fluids point to their typical geothermal origin, without any fresh magmatic input.•Anomalies of soil CO2 emissions reveal hidden faults whose trend is compatible with regional tectonics.