Influence of Lateral Heterogeneities on Strong Motion Shear Strains: Simulations in the Historical Center of Rome (Italy)

S Martino (1) , L Lenti (2) , C Gélis (3) , Anna Chiara Giacomi (1) , Maria Paola Santisi d'Avila (4) , Luis Fabian Bonilla (2) , F Bozzano (1) , J.-F. Semblat (2)

1 UNIROMA - Università degli Studi di Roma "La Sapienza" = Sapienza University [Rome]
2 IFSTTAR/GER - Département Géotechnique, Eau et Risques
3 IRSN - Institut de Radioprotection et de Sûreté Nucléaire
4 LJAD - Laboratoire Jean Alexandre Dieudonné

The influence of lateral heterogeneities in alluvial deposits represents a topic of particular interest in the field of urban planning and engineering design of structure and infrastructures. This work is focused on the effects of such heterogeneities on the shear strains produced within the recent alluvial deposits of the Tiber River in Rome historical center in case of the worst expected earthquake scenario. At this aim, a 3D engineering-geology model of the subsoil is used to derive 4 geological sections across the Tiber River valley as well as 48 soil columns in order to perform numerical simulations. Various models are considered: a viscoelastic equivalent linear rheology in a 1D finite difference model for one motion component (EERA code), a nonlinear elasto-plastic model in a 1D finite element scheme for three motion components and a nonlinear visco-elasto-plastic rheology in a 2D finite difference model under one-component horizontal input. As it results from comparing these different simulations, the lateral heterogeneities play a key role with respect to the expected shear strains within multilayered soils. At this aim some specific indexes are introduced to estimate the maximum shear strain concentration index within the soil layers as well as to highlight their effect due to the stratigraphic position of the layers, within the soil column, independently from its depth. A final differential index leads to the evaluation of the lateral heterogeneity effect on the estimated maximum shear strain, demonstrating their prevalent role with respect to the bedrock shape (i.e. the angle of inclination of the buried valley slopes). From these results, a maximum shear strain zoning map is obtained for the historical center of Rome, showing that the local seismic response should be modeled by assuming 1D or 2D conditions depending on the location considered.

Mots clés: Lateral heterogeneities; strong motion; site effects; earthquake-induced strains; numerical modeling; Rome

Domaines: Dynamique, vibrations; Risques; Géotechnique

S Martino, L Lenti, C Gélis, Anna Chiara Giacomi, Maria Paola Santisi d'Avila, et al.. Influence of Lateral Heterogeneities on Strong Motion Shear Strains: Simulations in the Historical Center of Rome (Italy). Bulletin of the Seismological Society of America, 2015, 105 (5), 21p. ⟨10.1785/0120140180⟩. ⟨hal-01283575⟩