Broadband ground motion simulations with sediment nonlinearity: A case study at Garner Valley, California
Elnaz Seylabi
University of Nevada, Reno
- Date & Time
- Location
- Online-only seminar via Microsoft Teams
- Summary
We perform a series of large scale, nonlinear, earthquake ground motion simulations that account for the cyclic plastic behavior of sediments in the shallow crust. Our goal is to understand and quantitatively assess how idealized models of sediment nonlinearity influence the amplitude, frequency content, and duration of strong ground motion in broadband earthquake simulations. We use the Garner Valley region in southern California as a test case where near-surface nonlinearity has been reported for peak ground accelerations (PGAs) as small as 0.05-0.2g. We model the sediment cyclic response using a multi-axial constitutive model formulated within the framework of bounding surface plasticity in terms of total stress and implemented in a high-performance computing finite element code. We first describe a series of numerical experiments designed to verify our model implementation, and then present a series of idealized large-scale simulations where material properties were extracted from the Southern California Earthquake Center (SCEC) Community Velocity Model CVM-S4.26 (using its optional geotechnical layer). The modulus reduction curves and ultimate shear strength were selected empirically to constrain the nonlinear soil model parameters. Furthermore, we simulate the rupture of the 2010 Mw 5.4 Borrego Springs and a Mw 6.5 scenario earthquakes using a kinematic earthquake rupture model. Having the rupture simulations, we then compute synthetic ground motions with the nonlinear model (for a maximum frequency of 5 Hz) and discuss how modeling shallow crust nonlinearity affects the ground response intensity measures in the different cases considered.
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