Ground motion simulation and validation of the 2008 Chino Hills earthquake in scattering media

William H. Savran, & Kim B. Olsen

Awaiting Publication September 24, 2019, SCEC Contribution #9936

We simulate 0–2.5 Hz deterministic wave propagation in 3-D velocity models for the 2008 ChinoHills, CA, earthquake using a finite-fault source model and frequency-dependent anelastic attenuation. Small-scale heterogeneities are modeled as 3-D random fields defined using an elliptically anisotropic von K´arm´an autocorrelation function with its parameters constrained using Los Angeles basin borehole data.We superimpose the heterogeneity models on a leading deterministic community velocity model (CVM) of southern California.We find that models of velocity and density perturbations can have significant effects on the wavefield at frequencies as low as 0.5 Hz, with ensemble median values of various ground motion metrics varying up to±50 per cent compared to those computed using the deterministicCVMonly. In addition,we show that frequency-independent values of the shear-wave quality factor (Qs0) parametrized as Qs0 = 150Vs (Vs in km s–1) provides the best agreement with data when assuming the published moment magnitude (Mw) of 5.4 (M0 = 1.6 × 1017 Nm) for the finite-fault source model. This model for Qs0 trades off with Qs0 = 100Vs assuming Mw = 5.5 (M0 = 2.2 × 1017 Nm), which represents an upper bound of the Mw estimates for this event. We find the addition of small-scale heterogeneities provides limited overall improvement to the misfit between simulations and data for the considered ground motion metrics, because the primary sources of misfit originate from the deterministic CVM and/or the finite-fault source description.

Key Words
Computational seismology; Earthquake ground motions; Wave scattering and diffraction

Citation
Savran, W. H., & Olsen, K. B. (2019). Ground motion simulation and validation of the 2008 Chino Hills earthquake in scattering media. Geophysical Journal International, (awaiting publication).