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Published February 2024 | Version Published
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The 2023 US 50-State National Seismic Hazard Model: Overview and implications

Creators

Abstract

The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard (both increases and decreases compared to previous NSHMs) are substantial because the new model considers more data and updated earthquake rupture forecasts and ground-motion components. In developing the 2023 model, we tried to apply best available or applicable science based on advice of co-authors, more than 50 reviewers, and hundreds of hazard scientists and end-users, who attended public workshops and provided technical inputs. The hazard assessment incorporates new catalogs, declustering algorithms, gridded seismicity models, magnitude-scaling equations, fault-based structural and deformation models, multi-fault earthquake rupture forecast models, semi-empirical and simulation-based ground-motion models, and site amplification models conditioned on shear-wave velocities of the upper 30 m of soil and deeper sedimentary basin structures. Seismic hazard calculations yield hazard curves at hundreds of thousands of sites, ground-motion maps, uniform-hazard response spectra, and disaggregations developed for pseudo-spectral accelerations at 21 oscillator periods and two peak parameters, Modified Mercalli Intensity, and 8 site classes required by building codes and other public policy applications. Tests show the new model is consistent with past ShakeMap intensity observations. Sensitivity and uncertainty assessments ensure resulting ground motions are compatible with known hazard information and highlight the range and causes of variability in ground motions. We produce several impact products including building seismic design criteria, intensity maps, planning scenarios, and engineering risk assessments showing the potential physical and social impacts. These applications provide a basis for assessing, planning, and mitigating the effects of future earthquakes.

Copyright and License

Attribution-NonCommercial 4.0 International.

Acknowledgement

The authors acknowledge the NSHM Steering Committee, the Deformation, ERF, and GMM Review Panels for CONUS, the Alaska Review Panel, and the Hawaii Earthquake and Tsunami Advisory Committee, who acted as the Hawaii Review Panel, and the Tiger Team. We want to especially thank the panel members and chairs of these panels including: Norm Abrahamson, John Anderson, Rhett Butler, Kaj Johnson, Tom Jordan, Jon Stewart, and Mike west for all their hard work and contributions. We thank the experts who provided additional advice on the Alaska geodetic-based subduction interface earthquake rate model: Rob Wesson and Jeff Freymueller. The authors also thank the state geological surveys who provided insights into the quality and usefulness of these models. The authors also thank participants in the workshops and public review for their insights and assistance in defining the best available science. The authors thank reviewers and editors of Earthquake Spectra and USGS reviewers. Also, the authors acknowledge Julian Bommer, Nilesh Shome, an anonymous reviewer from Earthquake Spectra, John Anderson, David Wald, and Ryan Gold for helpful feedback on the model and inputs. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors wish to thank the USGS Earthquake Hazards Program for funding the development of the 2023 50-State NSHM.

Conflict of Interest

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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petersen-et-al-2023-the-2023-us-50-state-national-seismic-hazard-model-overview-and-implications.pdf

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Additional details

Identifiers

ISSN
1944-8201

Funding

United States Geological Survey