Modeling shallow crustal nonlinearity in physics-based earthquake simulations: Beyond perfect plasticity

Elnaz Esmaeilzadeh Seylabi, Doriam Restrepo, Domniki Asimaki, & Ricardo Taborda

Published August 16, 2018, SCEC Contribution #8838, 2018 SCEC Annual Meeting Poster #020 (PDF)

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We implement and verify a multi-axial constitutive soil model in Hercules, one of SCEC’s three-dimensional wave propagation codes for regional scale earthquake simulations. Our overarching goal is to compute the effects of shallow crust nonlinearities in broadband earthquake simulations using a realistic plasticity model to capture inelastic soil deformation. We specifically implement a total stress, bounding surface plasticity model with a vanishing elastic region. The model’s hardening modulus within the bounding surface is defined by a simple mapping rule, and thus requires very few free parameters to be fully calibrated for a given shear modulus reduction curve. This feature, in turn, makes the model suitable for regional scale earthquake simulations, where geotechnical data in the shallow crust are scarce. To verify the implementation of the model in Hercules, we compiled a catalog of numerical experiments, which are also conducted using OpenSees---an open-source finite element code for earthquake engineering simulations. We specifically verify the model for the following canonical problems: (1) one dimensional linear and nonlinear site response; (2) standard material point-like pseudo-static analyses; and (3) elastic wave propagation in a heterogeneous half-space using an embedded point source. These efforts showcase the difficulties involved in nonlinear earthquake ground motion simulations but also the benefits that lie beyond perfect plasticity.

Esmaeilzadeh Seylabi, E., Restrepo, D., Asimaki, D., & Taborda, R. (2018, 08). Modeling shallow crustal nonlinearity in physics-based earthquake simulations: Beyond perfect plasticity. Poster Presentation at 2018 SCEC Annual Meeting.

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