Simulation of 0-7.5 Hz physics-based nonlinear ground motions for Maximum Credible Earthquake scenarios at the Long Valley Dam, CA

Te-Yang Yeh, & Kim Olsen

Published February 11, 2024, SCEC Contribution #13351

We have conducted 3D 0-7.5 Hz physics-based wave propagation simulations to model the seismic response of the Long Valley Dam (LVD) which has formed Lake Crowley in Central California, to estimate peak ground motions and settlement of the dam expected during Maximum Credible Earthquake (MCE) scenarios on the nearby Hilton Creek Fault (HCF). We calibrated the velocity structure, anelastic attenuation model, and the overall elastic properties of the dam via linear simulations of a Mw 3.7 event as well as the 1986 Mw 6.2 Chalfant Valley earthquake, constrained by observed ground motions on and nearby the LVD. The Statewide California Earthquake Center (SCEC) Community Velocity Model CVM-S4.26M01 superimposed with a geotechnical layer using Vs30 information tapered from the surface to 700 m depth was used in the simulations. We find optimal fit of simulated and observed ground motions at the LVD using frequency-independent attenuation of Qs = 0.075 V_S (Vs in m/s). Using the calibrated model, we simulated 3D nonlinear ground motions at the LVD for Mw 6.6 rupture scenarios on the HCF using an Iwan-type, multi-yield-surface technique. We use a two-step method, with the excitation for the nonlinear simulation below the LVD obtained from a 3D linear finite-fault simulation. Our nonlinear MCE simulation results show that PGVs and PGAs as high as 72 cm/s and 0.55 g, respectively, can be expected at the crest of the LVD. Compared with linear ground motion simulation results, our results show that Iwan nonlinear damping reduces PGAs on the dam crest by up to a factor of 8 and increasingly depletes the high-frequency content of the waves toward the dam crest. We find horizontal relative displacements of the material inside the dam of up to 27 cm, and up to 55 cm of vertical subsidence, equivalent to 1% of the dam height).

Citation
Yeh, T., & Olsen, K. (2024). Simulation of 0-7.5 Hz physics-based nonlinear ground motions for Maximum Credible Earthquake scenarios at the Long Valley Dam, CA. EERI (Earthquake Spectra),. doi: 10.1177/87552930231226135.

Related Projects & Working Groups
Ground Motion