The Quaternary geology of the Benevento urban area (southern Italy) for seismic microzonation purposes

The aim of this paper is to show how the classical methods of geology can be used to evaluate local seismic effects. This knowledge is essential for planning the renovation of public and private buildings and preserving architectural heritage. The urban area of Benevento, located in the Sannio Region, on the axis of the Southern Apennine Chain, is the case in point. A detailed geological survey was carried out. Sixteen boreholes were analysed, and 400 stratigraphic logs were re-interpreted. According to the sediment characteristics, and depositional environments, several stratigraphic units were recognized. Their stratal correlation patterns enabled the creation of a geological model. The bed-rock consists of Meso-Cenozoic pre- and syn-orogenic units followed by cover units, the oldest of which consists of lower Pleistocene Pacevecchia alluvial deposits. A geological map (1:4.000 scale), and five cross-sections define the geological model of reference. The possible amplification of seismic waves was assessed on the basis of the stratigraphic units and their internal and external characteristics in terms of lithology, lateral and vertical variations, thickness, and heterogeneity. Therefore, areas of the city safe or with the possibility to be affected by amplification phenomena have been defined. These geological results are supported by geophysical data.