SCEC Award Number 25296 View PDF
Proposal Category Collaborative Research Project (Multiple Investigators / Institutions)
Proposal Title Determination and Validation of Basin Structure in the San Francisco Community Velocity Model (SFCVM)
Investigator(s)
Name Organization
Kim Olsen San Diego State University Fan-Chi Lin University of Utah
SCEC Milestones A1-1, A2-1, D3-2 SCEC Groups CEM, GM, RC
Report Due Date 03/15/2026 Date Report Submitted 05/06/2026
Project Abstract
 We have inverted period-dependent 2-10 s Rayleigh-wave horizontal-to-vertical (H/V) ratios observed for upper-crustal 1D Vs models at 149 sites across the San Francisco Bay Area. We then used the site-specific 1D Vs profiles to generate depth-dependent velocity perturbations relative to the San Francisco Velocity Model (SFVM) and a revised version of the SFVM using inverse-distance interpolation. The magnitude of the fractional change of Vs is strongest within the top 2 km, with significant Vs reduction in the immediate surrounding of the San Francisco Bay and down to roughly 3 km depth near San Jose and Santa Cruz. The revised SFCVM reduces our goodness-of-fit measure by about 7%, with the most significant improvements concentrated around the San Francisco Bay and the Santa Clara Valley. Our results show promise for improving 3D velocity models from 1D Vs profiles.
SCEC Community Models Used Community Velocity Model (CVM)
Usage Description We extracted the SFVM from SCEC UCVM.
Intellectual Merit We have shown that it is possible to improve ground motion prediction accuracy by improving 3D velocity models from 1D Vs profiles obtained from period-dependent 2-10 s Rayleigh-wave horizontal-to-vertical (H/V) ratios observed for upper-crustal 1D Vs models at 149 sites across the San Francisco Bay Area. This may be useful for improving velocity models in other regions.
Broader Impacts The improved accuracy of ground motion prediction for the updated SFVM has the potential to contribute to improved seismic hazard analysis in the San Francisco Bay Area. Post-doc Te-Yang Yeh learned important skills in ground motion simulation and velocity model calibration.
Project Participants Kim Olsen, SDSU (co-PI)
Te-Yang Yeh (post-doc)
Fan-Chi Lin, UofU (co-PI)
Exemplary Figure Figure 5. Comparison of model error (a) before and (b) after the adjustment, and (c) the difference of the two (‘fitness’ change, defined as 𝜉before-𝜉after). Mean error value across all stations is labeled in the upper left corner of the left two panels. Increased ‘fitness’ to data (red) indicates improvement whereas the blue color shows worsened fit. Credit: Te-Yang Yeh.
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