3D NUMERICAL SIMULATIONS OF EARTHQUAKE GROUND MOTION INSEDIMENTARY BASINS: THE CASES OF GUBBIO AND L’AQUILA, CENTRAL ITALY

Many among the most important Italian earthquakes occurred close to intra-mountain alluvial basins, a typical surface expression of the extensional tectonic regime that dominates the seismic activity in Central/Southern Italy along the Apennines chain. The last ones, namely the Mw6.3 earthquake that devastated L’Aquila and the surrounding villages within the Aterno Valley on Apr 6, 2009, and the Mw6.0 Umbria-Marche event of Sep 26, 1997, both in Central Italy, provided a substantial amount of records that may be helpful to shed light on the seismic response of such basins and to provide benchmarks to calibrate numerical models. In this contribution, we summarize the experience and main results of the 3D numerical work carried out by the spectral element code GeoELSE, developed at Politecnico di Milano, to simulate the long period seismic amplification effects observed within the Gubbio basin during the Umbria-Marche earthquake, and the coupling of near-field ground motion and complex basin effects in the Aterno Valley during the L’Aquila erthquake. Attention is given to comparison with 1D and 2D approaches, and to sensitivity of results with respect to different kinematic models of the seismic source.