Spatial variability of b-values in the western United States: Implications for seismic hazard modeling
Heather Crume, Jessica Velasquez, & Jochen WoessnerSubmitted September 7, 2025, SCEC Contribution #14823, 2025 SCEC Annual Meeting Poster #TBD
The b-value quantifies the relative frequency of small to large earthquakes within a given region and time-period. Accurate estimation of b-values is critical for Probabilistic Seismic Hazard Analysis (PSHA), yet the choice of spatial domain over which it is calculated remains a challenge. Larger regions provide more events and thus more stable estimates, but risk obscuring spatial heterogeneity that may be seismologically significant. Variability in b-values has been linked to numerous factors, including stress state, pore pressure, crustal and frictional heterogeneity, hypocentral depth, geothermal gradients, tectonic setting, spatiotemporal clustering, methodological differences, and catalog completeness. To explore the implications of spatial variability, we conduct a comparative analysis in the western United States (WUS) using three spatial scales: a single regional b-value, several subregional estimates, and a finer scale uniform grid. We apply the b-positive methodology, which eliminates the need to estimate completeness. Our results reveal substantial variability across scales, suggesting that a single b-value does not adequately represent the seismicity of the WUS. This approach enables a more nuanced understanding of b-value distribution and its implications for seismic hazard modeling. We discuss criteria for defining optimal regions for b-value estimation and highlight the trade-offs between statistical robustness and spatial resolution.
Citation
Crume, H., Velasquez, J., & Woessner, J. (2025, 09). Spatial variability of b-values in the western United States: Implications for seismic hazard modeling. Poster Presentation at 2025 SCEC Annual Meeting.
Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)
