SCEC Award Number 24156 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title Validation of 3D Broadband (0-25 Hz) Ground Motion Simulations for Northern, Central and Southern California
Investigator(s)
Name Organization
Kim Olsen San Diego State University
SCEC Milestones D3-2, D3-3 SCEC Groups RC, GM, ASI
Report Due Date 03/15/2025 Date Report Submitted 03/21/2025
Project Abstract
 We have integrated into the BBP the 3D physics-based ground motion simulation code AWP-ODC with support for topography (O’Reilly et al., 2022) and frequency-dependent anelastic attenuation (Withers et al., 2015). We extend the physics-based simulations’ maximum frequency to 2 Hz and calibrate current UCVM 3D velocity models for northern and southern California using the 1989 Loma Prieta and 1994 Northridge earthquakes, respectively. Results show improved spectral and duration accuracy in the 3D simulations including topography versus previous 1D BBP results. Our simulations also show the need for improving the resolution of the San Francisco CVM SFVM v21.1 in the Bay Area basins and reevaluation of the near-surface velocity profiles for near basin boundaries in the
CVM-S24.M01 in Southern California.
SCEC Community Models Used Community Velocity Model (CVM)
Usage Description We extracted CVM-S4.26.M01 and SFCM from UCVM and used for our 3D simulations. We calibrated the velocity model extractions using with 600-700 m deep low-velocity tapers (LVTs) from trial-and-error tests.
Intellectual Merit We extend the physics-based simulations’ maximum frequency to 2 Hz for the 1989 Loma Prieta and 1994 Northridge earthquakes, investigating the feasibility and accuracy of replacing the stochastic high-frequency signal with deterministic synthetics including the effects of topography. Results show improved spectral and duration accuracy in the 3D simulations including topography versus previous 1D BBP results.
Broader Impacts Our simulations show the need for improving the resolution of the San Francisco CVM SFVM v21.1 in the Bay Area basins and re-evaluation of the near-surface velocity profiles for near basin boundaries in the CVM-S.26.M01 in Southern California. The results indicate that increasing the maximum frequency of the physics-based simulations can improve the accuracy of seismic hazard analysis in CA.
Project Participants The work was carried out by PhD student Ke Xu, supervised by PI Olsen.
Exemplary Figure Figure 1. Fourier acceleration spectral (FAS) bias between synthetics and observations from the 1989 Loma Prieta earthquake, for 1D BBP and 3D simulations with and without topography, averaged across the 39 available stations. Numbers on the legend show mean absolute bias in log10 scale. Credit: Ke Xu.
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