Influence of Key Modeling Parameters on Bias in Physics-Based 3D Ground Motion Simulations
Chukwuebuka C. Nweke, Sajan K C, Robert W. Graves, & Jonathan P. StewartSubmitted September 7, 2025, SCEC Contribution #14874, 2025 SCEC Annual Meeting Poster #TBD
Physics-based 3D ground motion simulations are widely used to study earthquake source processes and assess seismic hazard, but few validation studies have systematically examined how modeling choices contribute to bias in outputs used for engineering applications. Reducing this bias between simulated and recorded ground motions requires the calibration of various simulation parameters. In this study, we evaluate the influence of key parameters, such as minimum shear-wave velocity (Vs,min), velocity model configuration, fault source area, and the scaling between shear-wave quality factor and velocity (Qs - Vs), on synthetic ground motion predictions.
We conduct parametric sensitivity test simulations using a 3D finite difference approach for the 2008 Mw 5.39 Chino Hills and 2014 Mw 5.12 La Habra earthquakes, targeting frequencies below 1 Hz. Model performance is assessed by comparing Fourier amplitude spectra from simulations and observations using an average goodness-of-fit metric. The baseline velocity structure is the CVM-S4.26.M01 (CVMSi), tested both in its original form and with a 700 m Vs30-based near-surface velocity taper (Hu et al., 2022). We assess Vs,min values of 200, 250, 300, and 500 m/s, along with source areas from finite-fault models and empirical magnitude–area scaling, and Qs -Vs (Vs in km/s) scaling ratios of 50 and 100. Sensitivity is evaluated across sites in distinct geological provinces (mountain/hill, valley, basin, and basin edge).
For both earthquakes, the combination of Vs,min = 200 m/s, Qs -Vs ratio = 100, the 700 m near-surface velocity taper, and finite-fault–derived source parameters yield the lowest bias relative to observations.
Reference:
Hu, Z., Olsen, K. B., & Day, S. M. (2022). Calibration of the near-surface seismic structure in the SCEC community velocity model version 4. Geophysical Journal International, 230(3), 2183–2198. https://doi.org/10.1093/gji/ggac175
Key Words
3D simulation validation, minimum shear wave velocity, velocity model, ground motions.
Citation
Nweke, C. C., K C, S., Graves, R. W., & Stewart, J. P. (2025, 09). Influence of Key Modeling Parameters on Bias in Physics-Based 3D Ground Motion Simulations. Poster Presentation at 2025 SCEC Annual Meeting.
Related Projects & Working Groups
Ground Motions (GM)
