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networks (IFSTTAR) / Department GERS-14-20 Boulevard Newton Cité Descartes, Champs sur Marne F-77447. Marne la Vallée ... valley shape. Keywords: ...
5th IASPEI / IAEE International Symposium: Effects of Surface Geology on Seismic Motion August 15-17, 2016

DISTRIBUTION OF EARTHQUAKE INDUCED STRAIN EFFECTS IN ALLUVIAL DEPOSITS AT ROME (ITALY) Bozzano F. 1, Lenti L. 2, Martino S.1, Scarascia Mugnozza G.1, Varone C. 1 1

Department of Earth Sciences and Research Center for the Geological Risks (CERI of the University of Rome) « Sapienza »- P.za A. Moro 5 00185 Rome, Italy. 2 University Paris-Est LCPC/ The French institute of science and technology for transport, development and networks (IFSTTAR) / Department GERS-14-20 Boulevard Newton Cité Descartes, Champs sur Marne F-77447 Marne la Vallée Cedex 2, France. Email: [email protected]

This paper focuses on the influence of lateral heterogeneities on earthquake-induced shear strain distribution in alluvial deposits. The city of Rome (Italy) was selected as a case study due to its cultural and social heritage of international relevance. The Rome urban area is characterized by a complex geological setting which is the result of different geological processes (i.e. tectonic, fluvial and volcanic) occurred since the last 10M yrs to the Present time. The city of Rome is characterized by a moderate felt seismicity which is related to a maximum M 7 earthquake located in the Central Apennine (about 100km far from Rome). Some results of numerical approaches carried out by 1D and 2D numerical codes are here presented regarding the earthquake-induced shear strain distribution in the recent alluvial deposits of the Tiber River as well as of its tributaries. Both Boundary Element Method (BEM) and Finite Element Method, the latter involving a novel absorbing layer approach, have been considered. Natural recorded accelerograms have been applied as seismic input for numerical modelling. To output the effects of lateral heterogeneities on the shear strain concentration within the alluvial deposits, the modelled maximum shear strains (MSS) have been analyzed within different litothecnical units and their concentration has been computed by considering homogeneous and heterogeneous fill conditions. The obtained results show that the role of lateral heterogeneities within the deposits cannot be neglected, as it is even more relevant than the one due to the alluvial valley shape.

Keywords: Earthquake-induced effects; shear strains; numerical modeling; Rome; alluvial deposits