Evidence of Roman Earthquake Surface Faulting at Santa Venera al Pozzo (Catania, Southern Italy): a probable seismic event in 251 AD?

The record of historical seismicity of Catania (Southern Italy) and its neighbourhood during the first millennium AD is largely incomplete due to the scarcity of sources reporting information on earthquake damage, whereas on the contrary numerous historical sources provide plentiful description of past Etnean eruptions affecting the Catania area. This study provides new insights on the Catania seismic history, which was struck by large earthquakes during its recent history (e.g. 1169, 1542, 1693, 1818 earthquakes). During the first millennium, the only documented earthquake occurred in 251 AD, a year before of the big Etna eruption of 252 AD (Guidoboni et al., 2014). This earthquake left well-visible traces in the archaeological site of Santa Venera al Pozzo (Acireale, Catania), which was continuously inhabited since 3000 BC, due to the presence of sulphur warm water springs. The buildings uncovered by archaeologists are a podium of a Roman temple; a thermal bath provided with at least five different pools; a Roman rural Villa; and a church of Byzantine age. The site is located on the eastern flank of Mt. Etna volcano, where seismic activity has often caused significant damage, even though localized, especially when associated with remarkable flank eruptions. Evidence of Roman age faulting has been observed in the archaeological site, which is clearly affected by a set of sharp fractures generating an overall ~ 4 m wide fracture zone. The main fracture extends for about 40 m with a ~N-S direction, offsetting the foundations of a podium, some pools and minor walls. It shows an extensional displacement of up to 5-8 cm and a right-lateral component with an offset of up to 4 cm. Fracture zones related to normal faults are quite common in the lower eastern flank of Mt. Etna (Azzaro et al., 2012). Some of these structures are also characterized by anomalous diffuse CO2 emissions from the soil (Giammanco and Bonfanti, 2009). The archaeological site is placed in proximity of one of these tectonic lineaments (Fig. 1), belonging to the NNW oriented normal fault system called the “Timpe” system. The finding of this earthquake damage and its time constraints represents the starting point for archaeoseismological research in the Etnean area.