The influence of the 3D morphology and cavity network on the seismic response of Castelnuovo hill to the 2009 Abruzzo earthquake

During the Abruzzo earthquake (6.IV.2009, MW = 6.3), the village of Castelnuovo, lying on an elliptical hill about 60 m high, underwent an intensive damage (IMCS = 9-10), that could be partly ascribed to the topographic amplification and to the presence of an underground cavity network. To verify these hypotheses, the seismic response of the hill was carefully investigated adopting both 2D and 3D finite difference numerical models. Analyses were carried out using a detailed geotechnical model, defined on the basis of a comprehensive field investigation (boreholes, DH, HVSR, ERT) and accurate laboratory tests (RC-TS). The reference input motion was reproduced considering the time history of the mainshock recorded at an accelerometric station close to the epicenter, conveniently deconvoluted to the bedrock and scaled in amplitude to the site of Castelnuovo. The results of the numerical analyses, expressed in terms of distribution of the amplification factor of peak acceleration and Housner intensity, proved that the topographic effects significantly influenced the ground motion at surface, whereas the role of cavities seemed to be negligible.