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Poster #205, Ground Motions

3D 0-5 Hz Wave Propagation Simulations of the 2014 Mw5.1 La Habra Earthquake with Small-scale Heterogeneities, Q(f) and topography

Zhifeng Hu, & Kim B. Olsen
Poster Image: 

Poster Presentation

2020 SCEC Annual Meeting, Poster #205, SCEC Contribution #10609 VIEW PDF
We perform a suite of 0-5 Hz deterministic simulations of the 2014 Mw 5.1 La Habra, CA, earthquake, with the parallel AWP-ODC-GPU code in a mesh from the Southern California Earthquake Center (SCEC) Community Velocity Model CVM-S4.26-M01. The finite-fault source is obtained from the Graves and Pitarka (2016) kinematic rupture generator, with statistics constrained by dynamic rough fault simulations. We include statistical distributions of small-scale crustal heterogeneities (SSHs) with an anisotropic von Karman autocorrelation to represent the effects of realistic velocity and density perturbations, parameterized by a standard deviation, Hurst number, correlation length, and horizontal-to-ve...rtical anisotropy. In addition, frequency-dependent attenuation Q(f) = Q_0 f^γ and surface topography using a curvilinear grid (O’Reilly et al., 2019) are included in our suite of simulations. We have strong motion data available for comparison at a series of sites in our model domain.

We compare our simulation results to a reference case with a flat free-surface, frequency-independent Q = 100 Vs (Vs in km/s), and no SSHs included, as used by the SCEC High-f efforts. In our test, we use Q(f) = 100 Vs f0.6 and SSHs with a standard deviation of 5%, a Hurst number of 0.1, correlation length of 100 m, and a horizontal-to-vertical anisotropy of 5. Our results show that, as expected, the effects of topography, SSHs and Q(f) become increasingly important as frequencies increase toward 5 Hz. We find that SSHs, topography, and Q(f) all contribute significantly to the synthetic ground motion by generally increasing values of duration-dependent metrics (i.e., cumulative energy) toward those derived from the recorded time series. In addition, at most stations, the best fit is obtained by including topography, SSHs and Q(f) in the simulations. Our results indicate that topography, SSHs and Q(f) need to be included in ground motion modeling for frequencies as high as 5 Hz.