Landslides (2018) 15:1279–1297 DOI 10.1007/s10346-018-0951-y Received: 26 June 2017 Accepted: 24 January 2018 Published online: 7 February 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 G. Pappalardo I S. Imposa I M. S. Barbano I S. Grassi I S. Mineo Study of landslides at the archaeological site of Abakainon necropolis (NE Sicily) by geomorphological and geophysical investigations Abstract This paper reports on the investigation of the old land- slide body on which the necropolis of Abakainon, an Italian archaeological site, was built about 2400 years ago. This site is located in a geologically complex area of northeastern Sicily, where active tectonics has strongly modified the morphological land- scape, as testified by the meandering path of watercourses, wide- spread presence of paleosurfaces, and deviations of crest line. Previous studies have hypothesized that the necropolis, suddenly destroyed by a catastrophic event in historical times, could have been built on an old landslide body. This represents the starting point of this paper, focused on geomorphological analysis and geophysical surveys, which allowed discovering peculiar elements in support of the landslide theory. In particular, the elaboration of a Digital Terrain Model allowed locating the main morphostructural elements, thus highlighting how the occurrence of landslides in the study area is strongly linked to recent tecton- ics. Passive seismic surveys, carried out through the acquisition of ambient noise, allowed detecting the presence of impedance con- trasts, which were associated to peculiar features, such as the landslide body itself. Moreover, local strong directional effects testify the presence of faults, affecting even the necropolis area. Such results, further corroborated by the outcomes of an electrical resistivity survey, lay the foundations for interesting consideration on the possible cause of the destruction of this site, probably related to the occurrence of a historical earthquake in the first century AD. Keywords Landslide . Passive seismic survey . Abakainon necropolis . Morphostructural elements . Impedance contrast Introduction On a strategic spot of northeastern Sicily, close to the main streams connecting the Tyrrhenian and Ionian coastlines of the island, the Greek colony of Abakainon was probably founded in 1100 BC, although there is a lack of precise information (Oliva 2012). Its location (Fig. 1a) made this settlement very desired, especially for military and trading purposes, leading to a succession of con- quests by different people. Nowadays, archaeological excavation campaigns, carried out since 1952, allowed discovering a real buried city, holding precious and well-preserved finds including local coins. However, one of the most relevant archaeological discoveries is a wide necropolis area, with about 150 well-preserved tombs, dated between the end of the fourth century BC and the beginning of the second century BC. This site shows evidence of damage and collapses, and the current setting of unearthed ruins leads to think that the necropolis was destroyed by a catastrophic event. Bottari et al. (2013) carried out an archaeoseimological study, highlighting that the sudden destruction cannot be ascribed either to human action or to building decay but rather to the occurrence of an earthquake. From the analysis of aerial photographs and field investigations, they also hypothesized that the necropolis could have been built on an old landslide body, which could have been reactivated by the seismic shaking, contributing to the destruction of the site. Nev- ertheless, the dense vegetation, along with the bad accessibility of the study area and a complex geological setting, makes hard to recognize peculiar features that could validate such hypothesis by a simple field survey or by the analysis of aerial photos. Therefore, the need of further investigation is the starting point of this study. In mountainous region, there are several examples of ancient human settlements constructed on the surface of paleo-landslides, offering a flatter morphology. The Machu Pichu citadel, symbol of the Inca Empire, was probably built on a wide landslide thanks also to the availability of weathered granitic rocks employed for its construction. The presence of such material could be the result of ancient landslides affecting the area, proving the link between geomorphologic processes and development of human settlements (e.g., Margottini et al. 2008; Margottini 2015). A similar case is referred to the Italian village Cortina d’Ampezzo, which was edi- fied on a landslide body dated between fifth and sixth century AD (Panizza 1990). In this kind of peculiar setting, with specific reference to the study area, two main interacting features must be taken into analysis: landslides and tectonics. It is well known that there is a link between these two elements, since neotectonics can be often related to landslide occurrence, although it is not always the triggering factor (e.g., Willenberg et al. 2008; Tokiwa et al. 2011; Pappalardo et al. 2014; Pappalardo and Mineo 2015; Mineo et al. 2015, 2017). In this specific case, post-orogenic tectonics is likely to be one of the main responsible of the widespread landslide atti- tude of slopes, because it has strongly affected the study area, with fault activity, uplift phenomena, and earthquakes. In this perspective, this paper provides the results of new geomorphological and geophysical investigations aimed at looking for evidence of landslides and tectonic structures close to the necropolis area and at finding out if the necropolis was really built on an old landslide body. In detail, field surveys and data retrieved by aerial images were integrated with the analysis of a high reso- lution 2-m Digital Terrain Model (DTM) (Fig. 1b), which allowed locating the main geomorphological elements to be compared with data reported by official literature. Such procedure highlighted crucial aspects on the interaction between tectonics and main geomorphological features (e.g., river path, crest lines, landslides). Then, geophysical campaigns were aimed at investigating the sub- soil of the necropolis area, looking for evidence relatable to a landslide body. In particular, the study of the environmental noise (microtremors), through passive seismic recordings of single- station H/V (or horizontal to vertical spectral ratio (HVSR)), allowed highlighting the frequencies at which the ground motion is amplified by stratigraphic resonance, both inside and in the Landslides 15 & (2018) 1279 Original Paper