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3D Simulation of Seismic Response of the Long Valley Embankment Dam, California

Assessment of seismic hazard for embankment dams is crucial since they are typically built from compacted soils and rocks, which make them more prone to failure than concrete dams during strong ground shaking. As a case study, we conducted 3D 0-7.5 Hz deterministic wave propagation simulations to model realistic seismic response of the Long Valley Dam (LVD) in Central California using the discontinuous-mesh, fourth order accurate finite difference code AWP-ODC. Our goal is to account for the nonlinear effects in the time domain in order to adequately describe the complete seismic response of the dam during the extended duration of ground motions generated by large earthquakes. As the first step, we calibrated the velocity structure, anelastic attenuation model and the overall properties of the dam by performing linear simulations of an Mw 3.7 event using a point source. In our validation work we showed that accurate near-surface geotechnical layers are crucial to match observed ground motions at high frequencies (above 1Hz). A homogeneous model of the compacted dam core is sufficient for reproducing seismic waveforms observed right on the dam structure. A velocity-dependent attenuation model of Qs=0.075Vs, Qp=2Qs with a power law exponent of 0.2 for the frequency dependence best describes the observed spectral characteristics and coda wave amplitudes. With the calibrated model, we simulated the 1986 Mw6.3 Chalfant Valley earthquake, located 30 km from the LVD, using a finite-fault source description. Our simulations produced waveforms similar to the observations, with minimal nonlinearity needed around the LVD. Finally, we will present results of nonlinear simulations of Mw6.6 Maximum Credible Earthquake scenarios on the Hilton Creek fault, located within 10 km of the LVD.

Session: Numerical Modeling in Seismology: Developments and Applications I

Type: Oral

Room: Regency A-C

Date: 4/20/2022

Presentation Time: 08:30 AM Pacific

Presenting Author: Te-Yang Yeh

Student Presenter: Yes

Additional Authors