Preliminary Multi-scale Community Velocity Model for Southern California Improves Fit to Seismic Recordings

Kim B. Olsen, & Te-Yang Yeh

Submitted September 7, 2025, SCEC Contribution #14888, 2025 SCEC Annual Meeting Poster #TBD

SCEC Community Velocity models (CVMs) are a great resource for ground motion modeling, but the accuracy of the resulting ground motions is limited by their generally coarse resolution. However, recent studies have shown that multi-scale models (e.g., models with varying resolution due to inversion strategies, ray path coverage, and data integrity) generated by combining locally imaged models into coarser reference models can significantly improve the fit between simulations and data (e.g., Yeh and Olsen, 2023; Zhang and Ben-Zion, 2023). Here, we assemble and test the ground motion prediction efficacy for a multi-scale CVM generated by embedding a series of high-resolution models from southern California into the SCEC CVM-S4.26M01 as the reference model. The high-resolution velocity models are generated from travel time tomography, joint inversion of short-period Rayleigh wave ellipticity, phase velocity, teleseismic receiver functions, and ambient noise cross-correlation from land and ocean-bottom recordings. We propose a novel bias-informed method to merge multiple velocity models, only adopting the model parts that improve ground motion prediction for a series of local M4-5 earthquakes. The physics-based simulations use the scalable 4th-order finite-difference method AWP-ODC (Cui et al., 2013) including surface topography (O’Reilly et al., 2022), anelastic attenuation (Withers et al., 2015), and a discontinuous mesh (Nie et al., 2017). Preliminary results show bias reductions of 14% and 12% for our optimization (2/3) and validation (1/3) datasets, respectively, with local improvements inside the modified regions of 26% and 21%, respectively.

Key Words
CVM improvement, Ground motion simulation, Multi-scale velocity models

Citation
Olsen, K. B., & Yeh, T. (2025, 09). Preliminary Multi-scale Community Velocity Model for Southern California Improves Fit to Seismic Recordings. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Community Earth Models (CEM)