GNGTS 2013 - Atti del 32° Convegno Nazionale

calcareous conglomerates and sandstone locally interbedded with siltstone (Carrara et al. , 1995). It has, for its own genesis, an extreme vertical and horizontal lithological variability. In fact, the depositional mechanism is influenced both by the general standards of a fluvio-lacustrine depositional environment and the sin sedimentary tectonic activity of listric faults present in the very central portion of the town but also more widely distributed in the entire municipality. The former contribution is responsible, mainly inside the lower member of the formation, for vertical and lateral eteropies of the Santopadre Formation typical of the downstream junction sediments with moderate transport energy. This implies a not jet tectonic contribution that is instead evident in the textural structure of the upper member of the formation, on the occasion of the sudden beginning of an important mountain range uplift. This new mechanism induces a production of a huge quantity of high-energy debris flow deposits, which would have been transported and deposited downstream, tilted up by the syntectonic activity of the normal fault system. This feature does not allow us to associate one lithostratigraphic succession for the entire formation and furthermore we are likely to deal with this problem once we focus our attention on the test sites of our study. There is, in fact, a lateral EW oriented unconformity that keeps in tectonic contact the limestone bedrock of the northern part of the historical centre with the southern part located on the Santopadre formation. In the MOPS map this geological unit is indicated as an area prone to seismic amplification and is named as SA2. Both calcareous bedrock and Santopadre conglomerates are often overlaid by karstic alteration deposits indicated on the MOPS map as SA3 and SA4 respectively. Locally some outcrop of travertine Pleistocene deposits are found in the area and named as SA5 in the MOPS map. Recent alluvial deposits are found in a fluvial valley located at the foothill of Arpino historical centre. This unit is reported as SA6 in the MOPS map. In order to investigate the possible differences in the seismic response in the area we installed a first seismic station on the stable S1 area in the historical centre of Arpino (AR1). Due to the 391 GNGTS 2013 S essione 2.3