GNGTS 2014 - Atti del 33° Convegno Nazionale

absorbing layer system) is equal to the 2.3% (Fig. 3d) of the PGDv recorded in the inner part of the model (Point E in Fig. 3c). The PGDv in the most external part of the bottom portion of the absorbing system (Point H in Fig. 3c) is equal to 9.9% (Fig. 3d) of the peak recorded in the inner part of the model (Point G in Fig. 3c). Similar results were obtained analyzing the reduction of the Arias Intensity associated to the vertical component of the acceleration within the absorbing layer. In fact, in the case of HOL (Fig. 3a) the Arias Intensity in the point B is the 0.6% than in the point A and in the point E is the 9.0% than in the point D. For the HEL solution (Fig. 3c), the Arias Intensity in the point F is equal to the 0.005% of the value in the point E and in the point H equal to the 0.6% respect to the value in the point G. These preliminary results encourage further studies in order to better design the absorbing layers at the boundaries of the model to improve their efficiency, above all in study models where an important heterogeneity of the soils involved in the propagation is present both vertically and laterally Conclusions. Based on a high-resolution geological model reconstructed for the Fosso di Vallerano valley, a calibration of the subsoil seismo-stratigraphic was performed by considering the seismometric records of the aftershocks of the L’Aquila seismic sequence collected during the Summer 2009. The calibration analysis pointed out the relevant role on the local seismic response of the 1D sub-layering of the subsoil deposits. This evidence was confirmed by a 1D modelling performed on 56 soil columns that discretized a geological cross section obtained along the Fosso di Vallerano valley in correspondence to the “Europarco Business Park”. To carry on a proper 2D numerical modelling of the valley, including the lateral heterogeneity of the alluvial deposits as well as the Site-City Interaction, a preliminary numerical experiment was performed aiming at calibrating the typology and the thickness of the absorbing layers system to reduce the presence of spurious waves reflected at the model artificial boundaries. The results obtained so far, demonstrate that the best solution consist on a heterogeneous absorbing layer (HEL) system, i.e. constituted of 5 sub-layers characterized by a damping linearly varying from Q min -1 ≈ 0.2 to Q min -1 ≈ 2. References Bardet J.P., Ichii K. and Lin C.H.; 2000: EERA. A computer program for Equivalent-linear Earthquake site Response Analyses of layered soil deposits. University of Southern California, Department of Civil Engineering, user’s manual. Bonilla, F., Gelis, C., Giacomi, A.C., Lenti L., Martino S., and. ������� ���� ����� Semblat J.F; 2010: Multidisciplinary study of seismic amplification in the historical center of Rome, Italy , Proc. 25 5th Int. Conf. on Recent Advances in Geotech. Earthq. Engin. and Soil Dynamics, May 24-29 2010, San Diego, California. Borcherdt R.D.; 1994: Estimantes of site-dependent response spectra for design (methodology and justification). Earthq. Spectra, 10 , pp. 617-653. Bouden-Romdhane N., Kham, M., Semblat, J.F. and Mechler P.; 2003: 1D and 2D response analysis vs experimental data from Tunis city . Beşinci Ulusal Deprem Mühendisliği Konferansı, 26-30 Mayıs 2003, Proc. 5th National Conference on Earthquake Engineering, 26-30 May 2003, Istanbul, Turkey, Paper No: AE-051. Bozzano, F., A. Andreucci, M. Gaeta, and Salucci R.; 2000: A geological model of the buried Tiber River valley beneath the historical centre of Rome . Bull. Eng. Geol. Env., 59 , pp. 1 –21. Bozzano F., Caserta A., Govoni A., Marra F. and Martino S.; 2008: Static and dynamic characterization of alluvial deposits in the Tiber River Valley: New data for assessing potential ground motion in the City of Rome. In Journal of Geophysical Research, 113 , B01303. Caserta A., Martino S., Bozzano F., Govoni A. and Marra F.; 2012: Dynamic properties of low velocity alluvial deposits influencing seismically-induced shear strains: the Grottaperfetta valley test-site (Rome, Italy) . �� ���� In Bull Earthquake Eng, 10 , pp. 1133-1162. Giacomi A.; 2013: Studio degli effetti deformativi indotti da terremoti e ruolo delle eterogeneità . ��� ������ �� ����� PhD Thesis in Earth Sciences, XXV cycle, University of Rome “Sapienza”. Karner, D. B., and Marra F.; 1998: Correlation of fluviodeltaic aggradational sections with glacial climate history: a revision of the classical Pleistocene stratigraphy of Rome , Geol. Soc. Am. Bull., 110 , pp. 748-758. Kham, M., Semblat J.F., Bard P.Y. and Dangla P.; 2006: Seismic site-city interaction: main governing phenomena through simplified numerical models. ����� �������� ���� ���� Bull. Seismol. Soc. Am., 96 , no. 5, pp. 1934–1951. Lanzo G. and Silvestri F.; 1999: Risposta Sismica Locale. Teoria ed esperienze. Hevelius Edizioni. ����� ����� Marzo 1999. 300 GNGTS 2014 S essione 2.2