HR: 0800h
AN: S11A-0275    [Abstracts]
TI: Strong motion: an extended NCQ model for non linear wave propagation simulations
AU: * Semblat, J
EM: semblat@lcpc.fr
AF: Laboratoire Central des Ponts et Chaussées (LCPC), 58 bd Lefebvre, Paris, 75015, France
AU: Delépine, N
EM: nicolas.delepine@ifp.fr
AF: Institut Fran\c{c}ais du Pétrole, 1 et 4, av. de Bois-Préau, Rueil Malmaison Cdex, 92852, France
AU: Lenti, L
EM: lenti@lcpc.fr
AF: Laboratoire Central des Ponts et Chaussées (LCPC), 58 bd Lefebvre, Paris, 75015, France
AU: Bonnet, G
EM: bonnet@univ-mlv.fr
AF: Université de Marne la Vallée, 5 bd Descartes, Marne-la-Vallée, 77, France
AB: In this work, we consider an extended viscoelastic NCQ model to simulate seismic wave propagation in alluvial basins in the case of strong motions. This constitutive model involves both non linear elasticity and non linear viscous behaviour. The main objective of this model is to reproduce the dependence of the shear modulus and damping on the motion amplitude. To do so, the non linear elastic part of the model is described by a hyperbolic law. The non linear viscous part combines a Nearly Constant-Q model for linear damping (generalized Maxwell body, Moczo et Kristek, 2005) and a non linear viscous contribution described by a hyperbolic variation with the strain level. Furthermore, this model complies with the thermodynamic principles of continuum mechanics (e.g. derivation from potentials and dissipation function).
Starting from this extended NCQ model, the analysis of strong motion amplification in alluvial deposits is then performed thanks to a finite element formulation. Various numerical issues have been carefully considered to describe the whole algorithmic procedure (for both elastic and viscous non linear components of the constitutive law). Detailed validations of the model have shown its ability to recover low amplitude ground motion response. For larger excitation levels, the model includes the main features of the non linear behaviour of alluvial deposits. Realistic simulations are performed for Kushiro-oki earthquake. The analysis of seismic wave propagation in surface layers leads to interesting results: at the free-surface the amplification peaks are shifted to lower frequency values (when compared to the input motion); higher frequency components are not overdamped as with classical linear models and, finally, the global amplification level is generally lower than for weak motions.
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting