Toward a validated multi-scale seismic velocity model for the San Andreas fault system in the Western US
Te-Yang Yeh, & Yehuda Ben-ZionSubmitted September 7, 2025, SCEC Contribution #14616, 2025 SCEC Annual Meeting Poster #TBD
We present a workflow for developing and validating a multi-scale seismic velocity model for the San Andreas fault system in the Western US and initial results with multi-scale models for central and southern California. The research aims to represent both large-scale crustal structures and local high-resolution models that control wave propagation with frequencies of interest. We divide the model into large regional domains and implement in each domain two main steps: (1) constructing the best-available regional model from existing results and (2) incorporating high-resolution local models using two merging strategies: cosine-taper windowing and dictionary learning. Each analysis step is accompanied by validation involving comparisons between observed and simulated waveforms. We perform three-dimensional wave propagation simulations of 0–0.5 Hz ground motions for 20-30 moderately sized earthquakes (Mw 4.2–4.7) in each regional domain and use goodness-of-fit metrics to quantify how well candidate models reproduce observations. These results guide the model refinement step which produces the spatial weighting used during model merging.
For Central California, we start step 1 with the large-scale waveform tomography model CANVAS and iteratively integrate higher-resolution regional models including CCA, CVM-H, and CVM-S4.26. Spatial weighting based on performance yields an optimized background model. We then incorporate in step 2 a high-resolution model for the San Joaquin basin. We evaluate the results and converge on the best performing multi-scale model. For southern California, we use the CVM-S4.26 in step 1 and work on merging the Santa Maria and Salton Trough basins from the CVM-H. We also attempted to merge the Santa Barbara basin from the CVM-H, but this did not lead to improved fitness.
The developed multi-scale seismic velocity model will provide an improved framework for broadband simulations of ground motion across CA and western NV, supporting SCEC’s goal of physics-based seismic hazard assessment and enabling community-driven model updates.
Key Words
multi-scale velocity model, model merging, model validation, ground motion simulation
Citation
Yeh, T., & Ben-Zion, Y. (2025, 09). Toward a validated multi-scale seismic velocity model for the San Andreas fault system in the Western US. Poster Presentation at 2025 SCEC Annual Meeting.
Related Projects & Working Groups
Community Earth Models (CEM)
