Hazard implications and epistemic uncertainties of the updated fault-system inversion model for the 2023 U.S. National Seismic Hazard Model

Kevin R. Milner, & Edward H. Field

Published September 10, 2023, SCEC Contribution #13060, 2023 SCEC Annual Meeting Poster #162 (PDF)

A 50-state update to the U.S. National Seismic Hazard Model is nearing completion and will be released in late 2023 (NSHM23). NSHM23 will utilize an inversion-based methodology for active fault systems in the Western U.S., building upon the approach used in the 3rd Uniform California Earthquake Rupture Forecast (UCERF3). The fault-system inversion approach accommodates relaxation of fault segmentation assumptions and inclusion of multi-fault ruptures. Acknowledging scientific disagreement and lack of knowledge related to the propensity of multifault ruptures, connectivity, and MFDs on individual faults, we introduce new constraints to explicitly model a wide range of rupture behaviors. The updated epistemic logic tree contains segmentation branches ranging from fully segmented to fully unsegmented, as well as fault MFD branches ranging from Gutenberg-Richter b=0 to b=1.

We will describe the new model and show hazard comparisons between it and the prior NSHM14/18 model for the Western U.S., distinguishing between changes resulting from methodological enhancements (i.e., inversion setup and constraint implementations) and ingredient changes (i.e., deformation models and scaling relationships). We will also present branch choice-specific hazard results, highlighting the impact of each epistemic logic tree branch on mean hazard.

Key Words
NSHM23,PSHA

Citation
Milner, K. R., & Field, E. H. (2023, 09). Hazard implications and epistemic uncertainties of the updated fault-system inversion model for the 2023 U.S. National Seismic Hazard Model. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)