The U.S. National Seismic Hazard Model (NSHM) for the state of Alaska was updated in 2023 as part of the 50-state NSHM update. The new model incorporates more than 15 years of additional science since the release of the previous model in 2007 and has been reviewed by a six-member review panel and a supplementary eight-member team of ground motion model developers. This time-independent probabilistic seismic hazard model applies new earthquake catalogs, declustering algorithms, gridded seismicity models, magnitude-scaling relations, geologic and geodetic deformation models, and ground motion models. This data release supports the 2023 Alaska NSHM and includes the seismicity catalogs used to develop the model, hazard curves and uniform-hazard ground motions for the state of Alaska, and multiple period response spectra for the Alaska test sites.

The U.S. National Seismic Hazard Model (NSHM) for the state of Alaska was updated in 2023 as part of the 50-state NSHM update. The new model incorporates more than 15 years of additional science since the release of the previous model in 2007 and has been reviewed by a six-member review panel and a supplementary eight-member team of ground motion model developers. This time-independent probabilistic seismic hazard model applies new earthquake catalogs, declustering algorithms, gridded seismicity models, magnitude-scaling relations, geologic and geodetic deformation models, and ground motion models. This data release supports the 2023 Alaska NSHM and includes the seismicity catalogs used to develop the model, hazard curves and uniform-hazard ground motions for the state of Alaska, and multiple period response spectra for the Alaska test sites.

This dataset contains earthquake catalogs compiled for Alaska from U.S. Geolgical Survey (USGS) Advanced National Seismic System (ANSS) Comprehensive Earthquake Catalog (ComCat) (USGS, 2017) and Natural Resources Canada (NRCan) Canadian National Earthquake Database (NRCan, 1985) catalog searches and processed following the methods of Mueller (2019) and Llenos et al. (2024). Catalogs are deculstered using multiple methods and segregated into crustal, subduction interface, and subduction intraslab catalogs using Slab2 (Hayes, 2018).

Gridded seismic hazard curve data, gridded ground motion data, and mapped gridded ground motion values are available for the 2007 Alaska Seismic Hazard Model. Time-independent probabilistic seismic hazard data and maps of Alaska and the Aleutians for peak ground acceleration (PGA) and 0.1, 0.2, 0.3, 0.5, 1.0 and 2.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404), 5 percent in 50 years (annual probability of 0.001026), and 10 percent in 50 years (annual probability of 0.0021) assuming firm rock soil conditions at 760 m/s are available. Development of the 2007 Alaska Seismic Hazard Model is documented in the USGS Open-File Report 2007-1043 (https://pubs.usgs.gov/of/2007/1043/). This dataset is considered a legacy dataset. The original dataset was uploaded to the USGS website at the time of publication of the seismic hazard model (2007) but was later moved over the the USGS ScienceBase Catalog (2019). The original dataset was assumed to be complete and accurate, but may contain inconsistencies when compared to more recent, actively maintained datasets.

Gridded seismic hazard curve data, gridded ground motion data, and mapped gridded ground motion values are available for the 2007 Alaska Seismic Hazard Model. Time-independent probabilistic seismic hazard data and maps of Alaska and the Aleutians for peak ground acceleration (PGA) and 0.1, 0.2, 0.3, 0.5, 1.0 and 2.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404), 5 percent in 50 years (annual probability of 0.001026), and 10 percent in 50 years (annual probability of 0.0021) assuming firm rock soil conditions at 760 m/s are available. Development of the 2007 Alaska Seismic Hazard Model is documented in the USGS Open-File Report 2007-1043 (https://pubs.usgs.gov/of/2007/1043/). This dataset is considered a legacy dataset. The original dataset was uploaded to the USGS website at the time of publication of the seismic hazard model (2007) but was later moved over the the USGS ScienceBase Catalog (2019). The original dataset was assumed to be complete and accurate, but may contain inconsistencies when compared to more recent, actively maintained datasets.

The U.S. National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using the best available science related to earthquake seismicity, fault ruptures, ground motions, and hazard estimation techniques to produce a standard of practice for public policy applications. Best available or applicable science is defined here as well-vetted and published hazard input component models and information that are accepted through a comprehensive review process, consistent with open and timely science principles, and encompass a scientifically reasonable range of earthquake characteristics and ground motion effects that improve the basis of the 2023 NSHM. This time-independent probabilistic seismic hazard model benefited from several dozens of co-authors, more than 50 reviewers, and hundreds of end-users, and hazard scientists that attended the public workshops and provided technical inputs and reviews of the inputs and their integration in the hazard assessment. The hazard assessment applies new earthquake 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 velocities of the upper 30 m of soil and deeper sedimentary structure. 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, and eight site classes that are now required by the 2020 NEHRP Recommended Seismic Provisions and applied in multiple other public policy products. A system-level test is performed to ensure the resulting ground motions are consistent with historical intensity information. Several impact products including building seismic design criteria, intensity maps (Modified Mercalli Intensity), ground motion scenarios, and engineering risk assessments that show the potential physical and social impacts and provide a basis for assessing, planning, and mitigating the effects of future earthquakes across the U.S.

The U.S. National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using the best available science related to earthquake seismicity, fault ruptures, ground motions, and hazard estimation techniques to produce a standard of practice for public policy applications. Best available or applicable science is defined here as well-vetted and published hazard input component models and information that are accepted through a comprehensive review process, consistent with open and timely science principles, and encompass a scientifically reasonable range of earthquake characteristics and ground motion effects that improve the basis of the 2023 NSHM. This time-independent probabilistic seismic hazard model benefited from several dozens of co-authors, more than 50 reviewers, and hundreds of end-users, and hazard scientists that attended the public workshops and provided technical inputs and reviews of the inputs and their integration in the hazard assessment. The hazard assessment applies new earthquake 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 velocities of the upper 30 m of soil and deeper sedimentary structure. 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, and eight site classes that are now required by the 2020 NEHRP Recommended Seismic Provisions and applied in multiple other public policy products. A system-level test is performed to ensure the resulting ground motions are consistent with historical intensity information. Several impact products including building seismic design criteria, intensity maps (Modified Mercalli Intensity), ground motion scenarios, and engineering risk assessments that show the potential physical and social impacts and provide a basis for assessing, planning, and mitigating the effects of future earthquakes across the U.S.

Gridded ground motion data and mapped gridded ground motion values are available for the 1999 Alaska Seismic Hazard Model. Probabilistic seismic hazard data and maps of Alaska and the Aleutians for peak ground acceleration (PGA) and 0.2, 0.3, and 1.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404) and 10 percent in 50 years (annual probably of 0.0021), assuming firm rock soil conditions at 760 m/s, are available. Development of the 1999 Alaska Seismic Hazard Model is documented in the USGS Open-File Report 99-36 (https://doi.org/10.3133/ofr9936). This dataset is considered a legacy dataset. The original dataset was uploaded to the USGS website at the time of publication of the seismic hazard model (1999) but was later moved over the the USGS ScienceBase Catalog (2019). The original dataset was assumed to be complete and accurate, but may contain inconsistencies when compared to more recent, actively maintained datasets.

Gridded ground motion data and mapped gridded ground motion values are available for the 1999 Alaska Seismic Hazard Model. Probabilistic seismic hazard data and maps of Alaska and the Aleutians for peak ground acceleration (PGA) and 0.2, 0.3, and 1.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404) and 10 percent in 50 years (annual probably of 0.0021), assuming firm rock soil conditions at 760 m/s, are available. Development of the 1999 Alaska Seismic Hazard Model is documented in the USGS Open-File Report 99-36 (https://doi.org/10.3133/ofr9936). This dataset is considered a legacy dataset. The original dataset was uploaded to the USGS website at the time of publication of the seismic hazard model (1999) but was later moved over the the USGS ScienceBase Catalog (2019). The original dataset was assumed to be complete and accurate, but may contain inconsistencies when compared to more recent, actively maintained datasets.

This data release is composed of three crustal (as opposed to subduction zone) geologic input datasets for the 2023 Alaska update to the U.S. National Seismic Hazard Model (NSHM): 1) fault section vector line data, 2) fault zone vector polygon data, and 3) accompanying earthquake geology attributes.