2023 50-State Long-term National Seismic Hazard Model
The 2023 50-state update of the U.S. National Seismic Hazard Model (NSHM) forecasts the potential for earthquake ground shaking at various probability levels across the conterminous United States (CONUS), Alaska, and Hawaii.
After the release of the original 2023 50-state NSHM (Petersen and others 2023; 2024), we received questions and comments from end users about the hazard results. Based on this feedback, we now present a revision of the 2023 50-state NSHM (Powers and others, 2026; Altekruse and others, 2026). The revised model has been adopted in, as one example, the 2026 edition of the NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (please see the revised documentation for details).
Summary
This 50-state update is a time-independent probabilistic seismic hazard model. New data and methods include earthquake catalogs (excluding induced earthquakes), alternative declustering methods, spatially smoothed seismicity, new geodetic- and geologic-based fault and deformation models, and earthquake rupture forecast models accounting for a more complete representation of potential earthquakes in Alaska, Hawaii, and the conterminous U.S.
Improved ground motion models (GMMs) consider new NGA-Subduction, modified NGA-East and NGA-West2 GMMs. Amplification models also consider available 3D simulations to supplement the empirical GMMs, and basin specific data in California’s San Francisco Bay, Central Valley, and Los Angeles regions Seattle Washington, Salt Lake City Utah, and near Portland Oregon. Amplification in the central and eastern U.S. Gulf and Atlantic Coastal Plains is also considered.
New stress drop, tomographic, and other geophysical models help refine the complex boundary between the tectonically stable and active regions used in assigning GMMs.
Resulting seismic hazard calculations yield hazard curves, maps, uniform hazard response spectra, and disaggregations which are developed for spectral accelerations at 21 oscillator periods, two peak parameters (PGV and PGA), and eight site classes that are now required by the 2020 NEHRP Recommended Seismic Provisions and applied in multiple other public policy products.
Overview Publications
| Model | Documentation |
|---|---|
| Conterminous U.S. (CONUS) | Original Overview Paper: Petersen et al. (2024) Revised Overview Paper: Powers et al. (2026) |
| Alaska | Original Overview Papers: Petersen et al. (2024) and Powers et al. (2024) Revised Overview Paper: Powers et al. (2026) |
| Hawaii | Original Overview Paper: Petersen et al. (2022) Revised Overview Paper: Powers et al. (2026) |
Supporting Documentation
Title | Authors | URL |
|---|---|---|
Review Publications | ||
| Panel review of the USGS 2023 conterminous U.S. time-independent earthquake rupture forecast | Jordan TH, Anderson JG and others | https://dx.doi.org/10.1785/0120230140 |
| Panel review of ground motion characterization model in 2023 NSHM: Report to US Geological Survey, National Seismic Hazards Model Program | Stewart J, Abrahamson N and others | https://escholarship.org/uc/item/2546f8hw |
| Recommendations on best available science for the United States National Seismic Hazard Model | Anderson JG, Atkinson G and others | https://escholarship.org/uc/item/1x6139kd |
Geologic Investigations and Data | ||
| Earthquake geology inputs for the National Seismic Hazard Model (NSHM) 2023 (central and eastern United States), version 1.0. | Thompson Jobe JA, Hatem AE and others | https://doi.org/10.5066/P918XCUU |
| Earthquake geology inputs for the U.S. National Seismic Hazard Model (NSHM) 2023 (western U.S.) (ver. 3.0, December 2023) | Hatem AE, Collett CM and others | https://doi.org/10.5066/P9AWINWZ |
| Simplifying complex fault data for systems-level analysis: Earthquake geology inputs for U.S. NSHM 2023 | Hatem AE, Collett CM and others | https://doi.org/10.1038/s41597-022-01609-7 |
| Western U.S. geologic deformation model for use in the U.S. National Seismic Hazard Model 2023 | Hatem AE, Reitman NG and others | https://doi.org/10.1785/0220220154 |
| Revised earthquake geology inputs for the central and eastern United States and southeast Canada for the 2023 National Seismic Hazard Model | Thompson Jobe JA, Hatem AE and others | https://doi.org/10.1785/0220220162 |
| Western U.S. geologic deformation model for use in the U.S. National Seismic Hazard Model 2023, version 1.0 | Hatem AE, Reitman NG and others | https://doi.org/10.5066/P9W63WOZ |
| Atlantic and gulf coastal plains sediment thickness: Data release | Boyd OS | https://doi.org/10.5066/P9EBOWU8 |
| Sediment thickness map of United States Atlantic and Gulf Coastal Plain strata, and their influence on earthquake ground motions | Boyd OS, Churchwell D and others | https://doi.org/10.1177/87552930231204880 |
Earthquake Rupture Forecast | ||
| Earthquake rupture forecast model construction for the 2023 U.S. 50‐State National Seismic Hazard Model Update: Central and eastern U.S. fault‐based source model | Shumway AM, Petersen MD and others | https://doi.org/10.1785/0220230294 |
| A comprehensive fault‐system inversion approach: Methods and application to NSHM23 | Milner KR and Field EH | https://doi.org/10.1785/0120230122 |
| Enumerating plausible multifault ruptures in complex fault systems with physical constraints | Milner KR, Shaw BE and Field EH | https://doi.org/10.1785/0120210322 |
| The USGS 2023 conterminous U.S. time‐independent earthquake rupture forecast | Field EH, Milner KR and others | https://doi.org/10.1785/0120230120 |
| Updating the crustal fault model for the 2023 National Seismic Hazard Model for Alaska | Haeussler PJ, Bender AM and others | https://doi.org/10.22541/essoar.170000026.63675767/v1 |
| Magnitude and slip scaling relations for fault based seismic hazard | Shaw BE | https://doi.org/10.1785/0120220144 |
| The seismic hazard implications of declustering and Poisson assumptions inferred from a fully time‐dependent model | Field EH, Milner KR and Luco N | |
Ground Motion Models | ||
| The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States | Moschetti MP, Aagaard BT and others | https://doi.org/10.1177/87552930231223995 |
| The 2023 US National Seismic Hazard Model: Subduction ground-motion models | Rezaeian S, Powers PM and others | https://doi.org/10.1177/87552930241243069 |
| Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon | Ahdi SK, Aagaard BT and others | https://doi.org/10.1177/87552930241237250 |
| Integration of rupture directivity models for the US National Seismic Hazard Model | Withers KB, Moschetti MP and others | https://doi.org/10.1177/87552930241232708 |
| Basin effects from 3D simulated ground motions in the Greater Los Angeles region for use in seismic hazard analyses | Moschetti MP, Thompson EM and others | https://doi.org/10.1177/87552930241232372 |
| Data-driven adjustments for combined use of NGA-East hard-rock ground motion and site amplification models | Ramos-Sepúlveda ME, Stewart JP and others | https://doi.org/10.1177/87552930241231825 |
| Comparing subduction ground-motion models to observations for Cascadia | Smith JA, Moschetti MP and Thompson EM | https://doi.org/10.1177/87552930241256673 |
| Earthquake scenario development in conjunction with the 2023 USGS National Seismic Hazard Model | Chase RE, Jaiswal KS and Petersen MD | https://doi.org/10.1177/87552930241253837 |
Geodetic Investigations and Data | ||
| Review of geodetic and geologic deformation models for 2023 U.S. National Seismic Hazard Model | Johnson KM, Hammond WC and Weldon RJ II | https://doi.org/10.1785/0120230137 |
| Geodetic deformation model results and corrections for use in U.S. National Seismic Hazard Model 2023 | Pollitz FF, Evans EL and others | https://doi.org/10.5066/P9MUPHM4 |
| Western U.S. deformation models for the 2023 update to the U.S. National Seismic Hazard Model | Pollitz FF, Evans EL and others | |
| Data release for the lower seismogenic depth model of western U.S. earthquakes | Zeng Y, Petersen MD and Boyd OS | https://doi.org/10.5066/P9NSNPV8 |
| 2023 NSHM western United States GPS velocities | Zeng Y | https://doi.org/10.5066/P9MXY6RC |
| Lower seismogenic depth model of western U.S. earthquakes | Zeng Y, Petersen MD and Boyd OS | https://doi.org/10.1785/0220220174 |
| A fault‐based crustal deformation model with deep driven dislocation sources for the 2023 update to the U.S. National Seismic Hazard Model | Zeng Y | https://doi.org/10.1785/0220220209 |
| GPS velocity field of the Western United States for the 2023 National Seismic Hazard Model update | Zeng Y | https://doi.org/10.1785/0220220180 |
| A dense block model representing western continental United States deformation for the 2023 Update to the National Seismic Hazard Model | Evans EL | https://doi.org/10.1785/0220220141 |
| “Ghost transient” corrections to the southern California GPS velocity field from San Andreas Fault seismic cycle models | Hearn E | https://doi.org/10.1785/0220220156 |
| NeoKinema deformation model for the 2023 Update to the U.S. National Seismic Hazard Model | Shen Z-K and Bird P | https://doi.org/10.1785/0220220179 |
| Creep rate models for the 2023 US National Seismic Hazard Model: Physically constrained inversions for the distribution of creep on California faults | Johnson KM, Murray JR and Wespestad C | https://doi.org/10.1785/0220220186 |
Statistical Seismology Investigations | ||
| Forecasting the long‐term spatial distribution of earthquakes for the 2023 U.S. National Seismic Hazard Model using gridded seismicity | Llenos AL, Michael AJ and others | https://doi.org/10.1785/0120230220 |
| An efficient, analytic solution using order statistics for probabilistic seismic-hazard assessment without the poisson assumption | Michael AJ and Llenos AL | https://doi.org/10.1785/0120210216 |
| Uses of epistemic uncertainties in the USGS National Seismic Hazard Models | Kwong NS and Jaiswal KS | https://doi.org/10.1177/87552930231157424 |
| Revised earthquake recurrence intervals in California, U.S.A.: New paleoseismic sites and application of event likelihoods | McPhillips DF |
Project Timeline
The schedule allows for:
- 2 years of development, including evaluations of non-USGS ground motion and source models (e.g., NGA-Subduction),
- User feedback early and often (e.g., a kick-off workshop in January 2021, and regional workshops scheduled throughout the update process; workshop information will be posted as soon as information is available),
- 1 year for publication, including reconciliation of reviews from a journal, the NSHM Steering Committee, building code and other users, and the public, and
- Coordination with the next edition of the NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (as well as the 2028 ASCE 7 Standard and 2030 International Building Code).
The 2023 50-state update of the U.S. National Seismic Hazard Model (NSHM) forecasts the potential for earthquake ground shaking at various probability levels across the conterminous United States (CONUS), Alaska, and Hawaii.
After the release of the original 2023 50-state NSHM (Petersen and others 2023; 2024), we received questions and comments from end users about the hazard results. Based on this feedback, we now present a revision of the 2023 50-state NSHM (Powers and others, 2026; Altekruse and others, 2026). The revised model has been adopted in, as one example, the 2026 edition of the NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (please see the revised documentation for details).
Summary
This 50-state update is a time-independent probabilistic seismic hazard model. New data and methods include earthquake catalogs (excluding induced earthquakes), alternative declustering methods, spatially smoothed seismicity, new geodetic- and geologic-based fault and deformation models, and earthquake rupture forecast models accounting for a more complete representation of potential earthquakes in Alaska, Hawaii, and the conterminous U.S.
Improved ground motion models (GMMs) consider new NGA-Subduction, modified NGA-East and NGA-West2 GMMs. Amplification models also consider available 3D simulations to supplement the empirical GMMs, and basin specific data in California’s San Francisco Bay, Central Valley, and Los Angeles regions Seattle Washington, Salt Lake City Utah, and near Portland Oregon. Amplification in the central and eastern U.S. Gulf and Atlantic Coastal Plains is also considered.
New stress drop, tomographic, and other geophysical models help refine the complex boundary between the tectonically stable and active regions used in assigning GMMs.
Resulting seismic hazard calculations yield hazard curves, maps, uniform hazard response spectra, and disaggregations which are developed for spectral accelerations at 21 oscillator periods, two peak parameters (PGV and PGA), and eight site classes that are now required by the 2020 NEHRP Recommended Seismic Provisions and applied in multiple other public policy products.
Overview Publications
| Model | Documentation |
|---|---|
| Conterminous U.S. (CONUS) | Original Overview Paper: Petersen et al. (2024) Revised Overview Paper: Powers et al. (2026) |
| Alaska | Original Overview Papers: Petersen et al. (2024) and Powers et al. (2024) Revised Overview Paper: Powers et al. (2026) |
| Hawaii | Original Overview Paper: Petersen et al. (2022) Revised Overview Paper: Powers et al. (2026) |
Supporting Documentation
Title | Authors | URL |
|---|---|---|
Review Publications | ||
| Panel review of the USGS 2023 conterminous U.S. time-independent earthquake rupture forecast | Jordan TH, Anderson JG and others | https://dx.doi.org/10.1785/0120230140 |
| Panel review of ground motion characterization model in 2023 NSHM: Report to US Geological Survey, National Seismic Hazards Model Program | Stewart J, Abrahamson N and others | https://escholarship.org/uc/item/2546f8hw |
| Recommendations on best available science for the United States National Seismic Hazard Model | Anderson JG, Atkinson G and others | https://escholarship.org/uc/item/1x6139kd |
Geologic Investigations and Data | ||
| Earthquake geology inputs for the National Seismic Hazard Model (NSHM) 2023 (central and eastern United States), version 1.0. | Thompson Jobe JA, Hatem AE and others | https://doi.org/10.5066/P918XCUU |
| Earthquake geology inputs for the U.S. National Seismic Hazard Model (NSHM) 2023 (western U.S.) (ver. 3.0, December 2023) | Hatem AE, Collett CM and others | https://doi.org/10.5066/P9AWINWZ |
| Simplifying complex fault data for systems-level analysis: Earthquake geology inputs for U.S. NSHM 2023 | Hatem AE, Collett CM and others | https://doi.org/10.1038/s41597-022-01609-7 |
| Western U.S. geologic deformation model for use in the U.S. National Seismic Hazard Model 2023 | Hatem AE, Reitman NG and others | https://doi.org/10.1785/0220220154 |
| Revised earthquake geology inputs for the central and eastern United States and southeast Canada for the 2023 National Seismic Hazard Model | Thompson Jobe JA, Hatem AE and others | https://doi.org/10.1785/0220220162 |
| Western U.S. geologic deformation model for use in the U.S. National Seismic Hazard Model 2023, version 1.0 | Hatem AE, Reitman NG and others | https://doi.org/10.5066/P9W63WOZ |
| Atlantic and gulf coastal plains sediment thickness: Data release | Boyd OS | https://doi.org/10.5066/P9EBOWU8 |
| Sediment thickness map of United States Atlantic and Gulf Coastal Plain strata, and their influence on earthquake ground motions | Boyd OS, Churchwell D and others | https://doi.org/10.1177/87552930231204880 |
Earthquake Rupture Forecast | ||
| Earthquake rupture forecast model construction for the 2023 U.S. 50‐State National Seismic Hazard Model Update: Central and eastern U.S. fault‐based source model | Shumway AM, Petersen MD and others | https://doi.org/10.1785/0220230294 |
| A comprehensive fault‐system inversion approach: Methods and application to NSHM23 | Milner KR and Field EH | https://doi.org/10.1785/0120230122 |
| Enumerating plausible multifault ruptures in complex fault systems with physical constraints | Milner KR, Shaw BE and Field EH | https://doi.org/10.1785/0120210322 |
| The USGS 2023 conterminous U.S. time‐independent earthquake rupture forecast | Field EH, Milner KR and others | https://doi.org/10.1785/0120230120 |
| Updating the crustal fault model for the 2023 National Seismic Hazard Model for Alaska | Haeussler PJ, Bender AM and others | https://doi.org/10.22541/essoar.170000026.63675767/v1 |
| Magnitude and slip scaling relations for fault based seismic hazard | Shaw BE | https://doi.org/10.1785/0120220144 |
| The seismic hazard implications of declustering and Poisson assumptions inferred from a fully time‐dependent model | Field EH, Milner KR and Luco N | |
Ground Motion Models | ||
| The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States | Moschetti MP, Aagaard BT and others | https://doi.org/10.1177/87552930231223995 |
| The 2023 US National Seismic Hazard Model: Subduction ground-motion models | Rezaeian S, Powers PM and others | https://doi.org/10.1177/87552930241243069 |
| Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon | Ahdi SK, Aagaard BT and others | https://doi.org/10.1177/87552930241237250 |
| Integration of rupture directivity models for the US National Seismic Hazard Model | Withers KB, Moschetti MP and others | https://doi.org/10.1177/87552930241232708 |
| Basin effects from 3D simulated ground motions in the Greater Los Angeles region for use in seismic hazard analyses | Moschetti MP, Thompson EM and others | https://doi.org/10.1177/87552930241232372 |
| Data-driven adjustments for combined use of NGA-East hard-rock ground motion and site amplification models | Ramos-Sepúlveda ME, Stewart JP and others | https://doi.org/10.1177/87552930241231825 |
| Comparing subduction ground-motion models to observations for Cascadia | Smith JA, Moschetti MP and Thompson EM | https://doi.org/10.1177/87552930241256673 |
| Earthquake scenario development in conjunction with the 2023 USGS National Seismic Hazard Model | Chase RE, Jaiswal KS and Petersen MD | https://doi.org/10.1177/87552930241253837 |
Geodetic Investigations and Data | ||
| Review of geodetic and geologic deformation models for 2023 U.S. National Seismic Hazard Model | Johnson KM, Hammond WC and Weldon RJ II | https://doi.org/10.1785/0120230137 |
| Geodetic deformation model results and corrections for use in U.S. National Seismic Hazard Model 2023 | Pollitz FF, Evans EL and others | https://doi.org/10.5066/P9MUPHM4 |
| Western U.S. deformation models for the 2023 update to the U.S. National Seismic Hazard Model | Pollitz FF, Evans EL and others | |
| Data release for the lower seismogenic depth model of western U.S. earthquakes | Zeng Y, Petersen MD and Boyd OS | https://doi.org/10.5066/P9NSNPV8 |
| 2023 NSHM western United States GPS velocities | Zeng Y | https://doi.org/10.5066/P9MXY6RC |
| Lower seismogenic depth model of western U.S. earthquakes | Zeng Y, Petersen MD and Boyd OS | https://doi.org/10.1785/0220220174 |
| A fault‐based crustal deformation model with deep driven dislocation sources for the 2023 update to the U.S. National Seismic Hazard Model | Zeng Y | https://doi.org/10.1785/0220220209 |
| GPS velocity field of the Western United States for the 2023 National Seismic Hazard Model update | Zeng Y | https://doi.org/10.1785/0220220180 |
| A dense block model representing western continental United States deformation for the 2023 Update to the National Seismic Hazard Model | Evans EL | https://doi.org/10.1785/0220220141 |
| “Ghost transient” corrections to the southern California GPS velocity field from San Andreas Fault seismic cycle models | Hearn E | https://doi.org/10.1785/0220220156 |
| NeoKinema deformation model for the 2023 Update to the U.S. National Seismic Hazard Model | Shen Z-K and Bird P | https://doi.org/10.1785/0220220179 |
| Creep rate models for the 2023 US National Seismic Hazard Model: Physically constrained inversions for the distribution of creep on California faults | Johnson KM, Murray JR and Wespestad C | https://doi.org/10.1785/0220220186 |
Statistical Seismology Investigations | ||
| Forecasting the long‐term spatial distribution of earthquakes for the 2023 U.S. National Seismic Hazard Model using gridded seismicity | Llenos AL, Michael AJ and others | https://doi.org/10.1785/0120230220 |
| An efficient, analytic solution using order statistics for probabilistic seismic-hazard assessment without the poisson assumption | Michael AJ and Llenos AL | https://doi.org/10.1785/0120210216 |
| Uses of epistemic uncertainties in the USGS National Seismic Hazard Models | Kwong NS and Jaiswal KS | https://doi.org/10.1177/87552930231157424 |
| Revised earthquake recurrence intervals in California, U.S.A.: New paleoseismic sites and application of event likelihoods | McPhillips DF |
Project Timeline
The schedule allows for:
- 2 years of development, including evaluations of non-USGS ground motion and source models (e.g., NGA-Subduction),
- User feedback early and often (e.g., a kick-off workshop in January 2021, and regional workshops scheduled throughout the update process; workshop information will be posted as soon as information is available),
- 1 year for publication, including reconciliation of reviews from a journal, the NSHM Steering Committee, building code and other users, and the public, and
- Coordination with the next edition of the NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (as well as the 2028 ASCE 7 Standard and 2030 International Building Code).