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0-5 Hz Deterministic 3D Ground Motion Simulations for the 2014 La Habra, California, Earthquake

Kim B. Olsen, Zhifeng Hu, & Steven M. Day

Published August 16, 2021, SCEC Contribution #11512, 2021 SCEC Annual Meeting Poster #042

We have simulated 0-5 Hz deterministic ground motions for the 2014 Mw 5.1 La Habra, CA, earthquake in a mesh from the SCEC Community Velocity Model Version S4.26-M01 with a finite-fault source. Our simulations include statistical distributions of small-scale crustal heterogeneities (SSHs), frequency-dependent attenuation Q(f), surface topography, and effects of near-surface low velocity material. Strong motion data at 259 sites within an 148 km by 140 km area are used to validate our simulations. We examine parameterizations of low-frequency (<1Hz) shear-wave Q values (Qs,0) as a function of shear-wave speed (Vs), where a faster increase of Qs,0 for larger Vs relative to that for smaller Vs, generally improves the fit to the seismic data. Power-law exponents γ for high-frequency (>1Hz) frequency-dependent shear-wave Qs larger than about 0.6 appear inconsistent with the seismic records. Topography, and to a lesser extent SSHs, predominantly decrease the peak velocities and significantly increase the duration, by energy redistribution. A weathering layer with realistic near-surface low velocities is found to enhance the amplification at mountain peaks and ridges, and may partly explain the underprediction of the effects of topography on ground motions found in models omitting such layer. Accuracy of the velocity model, particularly the near-surface low velocities, controls the resolution with which the anelastic attenuation can be determined. Our results show that the effects of, and trade-offs between, near-surface low-velocity material, topography, SSHs and Q(f) become increasingly important as frequencies increase toward 5 Hz.

Key Words
High-f project, wave propagation simulations, La Habra earthquake

Olsen, K. B., Hu, Z., & Day, S. M. (2021, 08). 0-5 Hz Deterministic 3D Ground Motion Simulations for the 2014 La Habra, California, Earthquake. Poster Presentation at 2021 SCEC Annual Meeting.

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