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  • 1
    Online Resource
    Online Resource
    The 2023 US 50-State National Seismic Hazard Model: Overview and implications
    SAGE Publications ; 2023
    In:  Earthquake Spectra
    Details
    In: Earthquake Spectra, SAGE Publications
    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.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/87552930231215428
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
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  • 2
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    Online Resource
    The 2018 update of the US National Seismic Hazard Model: Where, why, and how much probabilistic ground motion maps changed
    SAGE Publications ; 2021
    In:  Earthquake Spectra Vol. 37, No. 2 ( 2021-05), p. 959-987
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 37, No. 2 ( 2021-05), p. 959-987
    Abstract: The 2018 US Geological Survey National Seismic Hazard Model (NSHM) incorporates new data and updated science to improve the underlying earthquake and ground motion forecasts for the conterminous United States. The NSHM considers many new data and component input models: (1) new earthquakes between 2013 and 2017 and updated earthquake magnitudes for some earlier earthquakes; (2) two updated smoothed seismicity models to forecast earthquake rates; (3) two suites of new central and eastern US (CEUS) ground motion models (GMMs) to translate ground shaking for various earthquake sizes and source-to-site distances considered in the model; (4) two CEUS GMMs for aleatory variability; (5) two CEUS site-effect models that modify ground shaking based on alternative shallow site conditions; (6) more advanced western US (WUS) lithologic and structural information to assess basin site effects for selected urban regions; and (7) a more comprehensive range of outputs (22 periods and 8 site classes) than in previous versions of the NSHMs. Each of these new datasets and models produces changes in the probabilistic ground shaking levels that are spatially and statistically analyzed. Recent earthquakes or changes to some older earthquake magnitudes and locations mostly result in probabilistic ground shaking levels that are similar to previous models, but local changes can reach up to +80% and −60% compared to the 2014 model. Newly developed CEUS models for GMMs, aleatory variability, and site effects cause overall changes up to ±64%. The addition of the WUS basin amplifications causes changes of up to +60% at longer periods for sites overlying deep soft soils. Across the conterminous United States, the hazard changes in the model are mainly caused by new GMMs in the CEUS, by sedimentary basin effects for long periods (≥1 s) in the WUS, and by seismicity changes for short (0.2 s) and long (1 s) periods for both areas.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/8755293020988016
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2183411-8
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  • 3
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    Online Resource
    The 2018 update of the US National Seismic Hazard Model: Overview of model and implications
    SAGE Publications ; 2020
    In:  Earthquake Spectra Vol. 36, No. 1 ( 2020-02), p. 5-41
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 36, No. 1 ( 2020-02), p. 5-41
    Abstract: During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated epistemic uncertainties and aleatory variabilities, and new soil amplification factors; (3) in the western United States (WUS), amplified shaking estimates of long-period ground motions at sites overlying deep sedimentary basins in the Los Angeles, San Francisco, Seattle, and Salt Lake City areas were incorporated; and (4) in the conterminous United States, seismic hazard is calculated for 22 periods (from 0.01 to 10 s) and 8 uniform V S30 maps (ranging from 1500 to 150 m/s). We also include a description of updated computer codes and modeling details. Results show increased ground shaking in many (but not all) locations across the CEUS (up to ~30%), as well as near the four urban areas overlying deep sedimentary basins in the WUS (up to ~50%). Due to population growth and these increased hazard estimates, more people live or work in areas of high or moderate seismic hazard than ever before, leading to higher risk of undesirable consequences from forecasted future ground shaking.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/8755293019878199
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2183411-8
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  • 4
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    Online Resource
    2021 US National Seismic Hazard Model for the State of Hawaii
    SAGE Publications ; 2022
    In:  Earthquake Spectra Vol. 38, No. 2 ( 2022-05), p. 865-916
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 38, No. 2 ( 2022-05), p. 865-916
    Abstract: The 2021 US National Seismic Hazard Model (NSHM) for the State of Hawaii updates the previous two-decade-old assessment by incorporating new data and modeling techniques to improve the underlying ground shaking forecasts of tectonic-fault, tectonic-flexure, volcanic, and caldera collapse earthquakes. Two earthquake ground shaking hazard forecasts (public policy and research) are produced that differ in how they account for declustered catalogs. The earthquake source model is based on (1) declustered earthquake catalogs smoothed with adaptive methods, (2) earthquake rate forecasts based on three temporally varying 60-year time periods, (3) maximum magnitude criteria that extend to larger earthquakes than previously considered, (4) a separate Kīlauea-specific seismogenic caldera collapse model that accounts for clustered event behavior observed during the 2018 eruption, and (5) fault ruptures that consider historical seismicity, GPS-based strain rates, and a new Quaternary fault database. Two new Hawaii-specific ground motion models (GMMs) and five additional global models consistent with Hawaii shaking data are used to forecast ground shaking at 23 spectral periods and peak parameters. Site effects are calculated using western US and Hawaii specific empirical equations and provide shaking forecasts for 8 site classes. For most sites the new analysis results in similar spectral accelerations as those in the 2001 NSHM, with a few exceptions caused mostly by GMM changes. Ground motions are the highest in the southern portion of the Island of Hawai’i due to high rates of forecasted earthquakes on décollement faults. Shaking decays to the northwest where lower earthquake rates result from flexure of the tectonic plate. Large epistemic uncertainties in source characterizations and GMMs lead to an overall high uncertainty (more than a factor of 3) in ground shaking at Honolulu and Hilo. The new shaking model indicates significant chances of slight or greater damaging ground motions across most of the island chain.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/87552930211052061
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2022
    detail.hit.zdb_id: 2183411-8
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  • 5
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    Evaluation of Ground-Motion Models for U.S. Geological Survey Seismic Hazard Forecasts: Hawaii Tectonic Earthquakes and Volcanic Eruptions
    Seismological Society of America (SSA) ; 2020
    In:  Bulletin of the Seismological Society of America Vol. 110, No. 2 ( 2020-04-01), p. 666-688
    Details
    In: Bulletin of the Seismological Society of America, Seismological Society of America (SSA), Vol. 110, No. 2 ( 2020-04-01), p. 666-688
    Abstract: The selection and weighting of ground-motion models (GMMs) introduces a significant source of uncertainty in U.S. Geological Survey (USGS) National Seismic Hazard Modeling Project (NSHMP) forecasts. In this study, we evaluate 18 candidate GMMs using instrumental ground-motion observations of horizontal peak ground acceleration (PGA) and 5%-damped pseudospectral acceleration (0.02–10 s) for tectonic earthquakes and volcanic eruptions, to inform logic-tree weights for the update of the USGS seismic hazard model for Hawaii. GMMs are evaluated using two methods. The first is a total residual visualization approach that compares the probability density function (PDF), mean and standard deviations σ, of the observed and predicted ground motion. The second GMM evaluation method we use is the common total residual probabilistic scoring method (log likelihood [LLH]). The LLH method provides a single score that can be used to weight GMMs in the Hawaii seismic hazard model logic trees. The total residual PDF approach provides additional information by preserving GMM over- and underprediction across a broad spectrum of periods that is not available from a single value LLH score. We apply these GMM evaluation methods to two different data sets: (1) a database of instrumental ground motions from historic earthquakes in Hawaii from 1973 to 2007 (Mw 4–7.3) and (2) available ground motions from recent earthquakes (Mw 4–6.9) associated with 2018 Kilauea eruptions. The 2018 Kilauea sequence contains both volcanic eruptions and tectonic earthquakes allowing for statistically significant GMM comparisons of the two event classes. The Kilauea ground observations provide an independent data set allowing us to evaluate the predictive power of GMMs implemented in the new USGS nshmp-haz software system. We evaluate GMM performance as a function of earthquake depth and we demonstrate that short-period volcanic eruption ground motions are not well predicted by any candidate GMMs. Nine of the initial 18 candidate GMMs fit the observed ground motions and meet established criteria for inclusion in the update of the Hawaii seismic hazard model. A weighted mean of four top performing GMMs in this study (NGAsubslab, NGAsubinter, ASK14, A10) is 50% lower for PGA than for GMMS used in the previous USGS seismic hazard model for Hawaii.
    Type of Medium: Online Resource
    ISSN: 0037-1106 , 1943-3573
    URL: Article
    DOI: 10.1785/0120180336
    Language: English
    Publisher: Seismological Society of America (SSA)
    Publication Date: 2020
    detail.hit.zdb_id: 2065447-9
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  • 6
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    The 2018 update of the US National Seismic Hazard Model: Ground motion models in the central and eastern US
    SAGE Publications ; 2021
    In:  Earthquake Spectra Vol. 37, No. 1_suppl ( 2021-07), p. 1354-1390
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 37, No. 1_suppl ( 2021-07), p. 1354-1390
    Abstract: The United States Geological Survey (USGS) National Seismic Hazard Model (NSHM) is the scientific foundation of seismic design regulations in the United States and is regularly updated to consider the best available science and data. The 2018 update of the conterminous US NSHM includes major changes to the underlying ground motion models (GMMs). Most of the changes are motivated by the new multi-period response spectra requirements of seismic design regulations that use hazard results for 22 spectral periods and 8 site classes. In the central and eastern United States (CEUS), the 2018 NSHM incorporates 31 new GMMs for hard-rock site conditions [Formula: see text], including the Next Generation Attenuation (NGA)-East GMMs. New aleatory variability and site-effect models, both specific to the CEUS, are applied to all median hard-rock GMMs. This article documents the changes to the USGS GMM selection criteria and provides details on the new CEUS GMMs used in the 2018 NSHM update. The median GMMs, their weights, epistemic uncertainty, and aleatory variability are compared with those considered in prior NSHMs. This article further provides implementation details on the CEUS site-effect model, which allows conversion of hard-rock ground motions to other site conditions in the CEUS for the first time in NSHMs. Compared with the 2014 NSHM hard-rock ground motions, the weighted average of median GMMs increases for large magnitude events at middle to large distance range, epistemic uncertainty increases in almost all situations, but aleatory variability is not significantly different. Finally, the total effect on hazard is demonstrated for an assumed earthquake source model in the CEUS, which shows an increased ring of ground motions in the vicinity of the New Madrid seismic zone and decreased ground motions near the East Tennessee seismic zone.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/8755293021993837
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2183411-8
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  • 7
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    Online Resource
    The 2018 update of the US National Seismic Hazard Model: Ground motion models in the western US
    SAGE Publications ; 2021
    In:  Earthquake Spectra Vol. 37, No. 4 ( 2021-11), p. 2315-2341
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 37, No. 4 ( 2021-11), p. 2315-2341
    Abstract: The U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) is the scientific foundation of seismic design regulations in the United States and is regularly updated to consider the best available science and data. The 2018 update of the conterminous U.S. NSHM includes significant changes to the underlying ground motion models (GMMs), most of which are necessary to enable the new multi-period response spectra (MPRS) requirements of seismic design regulations that use hazard results for 22 spectral periods and eight site classes. This article focuses on the GMMs used in the western United States (WUS) and is a companion to a recent article on the GMMs used in the central and eastern United States (CEUS). In the WUS, for crustal and subduction earthquakes, two models used in previous versions of the NSHM are excluded to provide consistency over all considered periods and site classes. To more accurately estimate ground motions at long periods in the vicinity of Los Angeles, San Francisco, Salt Lake City, and Seattle, the 2018 NSHM incorporates deep sedimentary basin depth from local seismic velocity models. The subduction GMMs considered lack basin depth terms and are modified to include an additional scale factor to account for this. This article documents the WUS GMMs used in the 2018 NSHM update and provides detail on the changes to GMM medians, aleatory variability, epistemic uncertainty, and site-effect models. It compares each of these components with those considered in prior NSHMs and discusses their total effect on hazard.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/87552930211011200
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2183411-8
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  • 8
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    Online Resource
    2018 One‐Year Seismic Hazard Forecast for the Central and Eastern United States from Induced and Natural Earthquakes
    Seismological Society of America (SSA) ; 2018
    In:  Seismological Research Letters Vol. 89, No. 3 ( 2018-05), p. 1049-1061
    Details
    In: Seismological Research Letters, Seismological Society of America (SSA), Vol. 89, No. 3 ( 2018-05), p. 1049-1061
    Type of Medium: Online Resource
    ISSN: 0895-0695 , 1938-2057
    URL: Article
    DOI: 10.1785/0220180005
    Language: English
    Publisher: Seismological Society of America (SSA)
    Publication Date: 2018
    detail.hit.zdb_id: 2403376-5
    SSG: 16,13
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  • 9
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    The 2023 US National Seismic Hazard Model: Ground-motion characterization for the conterminous United States
    SAGE Publications ; 2024
    In:  Earthquake Spectra Vol. 40, No. 2 ( 2024-05), p. 1158-1190
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 40, No. 2 ( 2024-05), p. 1158-1190
    Abstract: We update the ground-motion characterization for the 2023 National Seismic Hazard Model (NSHM) for the conterminous United States. The update includes the use of new ground-motion models (GMMs) in the Cascadia subduction zone; an adjustment to the central and eastern United States (CEUS) GMMs to reduce misfits with observed data; an updated boundary for the application of GMMs for shallow, crustal earthquakes in active tectonic regions (i.e. western United States (WUS)) and stable continental regions (i.e. CEUS); and the use of improved models for the site response of deep sedimentary basins in the WUS and CEUS. Site response updates include basin models for the California Great Valley and for the Portland and Tualatin basins, Oregon, as well as long-period basin effects from three-dimensional simulations in the Greater Los Angeles region and in the Seattle basin; in the CEUS, we introduce a broadband (0.01- to 10-s period) amplification model for the effects of the passive-margin basins of the Atlantic and Gulf Coastal Plains. In addition, we summarize progress on implementing rupture directivity models into seismic hazard models, although they are not incorporated in the 2023 NSHM. We implement the ground-motion characterization for the 2023 NSHM in the US Geological Survey’s code for probabilistic seismic hazard analysis, nshmp-haz-v2, and present the sensitivity of hazard to these changes. Hazard calculations indicate widespread effects from adjustments to the CEUS GMMs, from the incorporation of Coastal Plain amplification effects, and from the treatment of shallow-basin and out-of-basin sites in the San Francisco Bay Area and Los Angeles region, as well as locally important changes from subduction-zone GMMs, and from updated and new WUS basins.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/87552930231223995
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2024
    detail.hit.zdb_id: 2183411-8
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  • 10
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    Seismic Hazard, Risk, and Design for South America
    Seismological Society of America (SSA) ; 2018
    In:  Bulletin of the Seismological Society of America ( 2018-01-16)
    Details
    In: Bulletin of the Seismological Society of America, Seismological Society of America (SSA), ( 2018-01-16)
    Type of Medium: Online Resource
    ISSN: 0037-1106 , 1943-3573
    URL: Article
    DOI: 10.1785/0120170002
    Language: English
    Publisher: Seismological Society of America (SSA)
    Publication Date: 2018
    detail.hit.zdb_id: 2065447-9
    SSG: 16,13
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