1-DIRECTION 3-COMPONENT WAVE PROPAGATION VS NON-STATIONARY SYNTHETIC SIGNALS

Abstract eng:
The three components of downhole seismic records are simultaneously propagated along one direction, in a horizontal multilayered soil. The seismic response of surficial multilayered soils to strong earthquakes is evaluated using a multi-surface cyclic plasticity model of the Masing-Prandtl-Ishlinskii-Iwan (MPII) type in a finite element scheme. The major advantage of this constitutive model is that the rheology is characterized by few nonlinear parameters commonly available. Furthermore, the stress-strain behavior is nonlinear in loading and unloading. For the MPII model pure hysteretic dissipation is involved. 3-Component motion and stress-strain loops are evaluated all over the soil profiles. The numerical signal obtained at the surface is compared with the recorded ground motion, to validate the model. The same seismic zone is stochastically analyzed and probability distributions of relevant dynamic parameters are obtained. Synthetic signals are then generated by taking into account both the natural variability of the recorded ground motions and the joint time-frequency energy distribution of recorded accelerograms through a pertinent evolutionary non separable power spectral density matrix. Stochastic synthetic signals are compared with the numerical signals issued from wave propagation. Statistics of these two classes of computed signals are analyzed and compared with records at the surface. Comparisons are made through Anderson's criteria. This work compares the computed ground motions, obtained by wave propagation and stochastic analysis, with 3-Component seismic records from the Tohoku 2011 earthquake. Nonlinearity and coupling effects between components are incorporated in a different way. The advantages and drawbacks of each model are discussed.

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