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  • 1
    Online Resource
    Online Resource
    Representation of Bidirectional Ground Motions for Design Spectra in Building Codes
    SAGE Publications ; 2011
    In:  Earthquake Spectra Vol. 27, No. 3 ( 2011-08), p. 927-937
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 27, No. 3 ( 2011-08), p. 927-937
    Abstract: The 2009 NEHRP Provisions modified the definition of horizontal ground motion from the geometric mean of spectral accelerations for two components to the peak response of a single lumped mass oscillator regardless of direction. These maximum-direction (MD) ground motions operate under the assumption that the dynamic properties of the structure (e.g., stiffness, strength) are identical in all directions. This assumption may be true for some in-plan symmetric structures, however, the response of most structures is dominated by modes of vibration along specific axes (e.g., longitudinal and transverse axes in a building), and often the dynamic properties (especially stiffness) along those axes are distinct. In order to achieve structural designs consistent with the collapse risk level given in the NEHRP documents, we argue that design spectra should be compatible with expected levels of ground motion along those principal response axes. The use of MD ground motions effectively assumes that the azimuth of maximum ground motion coincides with the directions of principal structural response. Because this is unlikely, design ground motions have lower probability of occurrence than intended, with significant societal costs. We recommend adjustments to make design ground motions compatible with target risk levels.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1193/1.3608001
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2011
    detail.hit.zdb_id: 2183411-8
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  • 2
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    Comparison of NGA-West2 GMPEs
    SAGE Publications ; 2014
    In:  Earthquake Spectra Vol. 30, No. 3 ( 2014-08), p. 1179-1197
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 30, No. 3 ( 2014-08), p. 1179-1197
    Abstract: A presentation of the model parameters and comparison of the median ground-motion values from the NGA-West2 GMPEs is presented for a suite of deterministic cases. In general, the median ground motions are similar, within a factor of about 1.5–2.0 for 5 〈 M 〈 7 and distances between 10–100 km. Differences increase (on the order of 2–3) for large-magnitude (M 〉 8) earthquakes at large distances ( R 〉 100–200 km) and for close distances ( R 〈 10 km). A similar increase is observed for hanging-wall sites, and slightly larger differences are observed for soil sites as opposed to rock sites. Regionalization of four of the GMPEs yields similar attenuation rate adjustments based on the different regional data sets. All five GMPE aleatory variability models are a function of magnitude with higher overall standard deviations values for the smaller magnitudes when compared to the large-magnitude events.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1193/070113EQS186M
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2014
    detail.hit.zdb_id: 2183411-8
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  • 3
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    Comparisons of the NGA-Subduction ground motion models
    SAGE Publications ; 2022
    In:  Earthquake Spectra Vol. 38, No. 4 ( 2022-11), p. 2580-2610
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 38, No. 4 ( 2022-11), p. 2580-2610
    Abstract: In this article, ground-motion models (GMMs) for subduction earthquakes recently developed as part of the Next Generation Attenuation-Subduction (NGA-Sub) project are compared. The four models presented in this comparison study are documented in their respective articles submitted along with this article. Each of these four models is based on the analysis of the large NGA-Sub database. Three of the four current models are developed for a global version as well as separate regionalized models. The fourth model was developed based on earthquakes only from Japan, and as such is applicable only for Japan. As part of this comparison study, a general discussion on the parameterization of the four models and the regionalization of the three models is provided. The specific strengths and or weaknesses or the technical decisions and justifications of any one model are not part of this comparison. A selected suite of deterministic attenuation curves and spectra are presented for the models along with a selected suite of currently used subduction models. A limited number of comparisons are presented in this article with a larger number of comparisons and the digital values provided in the electronic attachment. In addition to these scenario calculation comparisons, the results from a standard probabilistic seismic hazard analysis (PSHA) for two sites located in the Pacific Northwest Region in the state of Washington are presented. These calculations highlight the potential impact of using the new GMMs. Based on the comparisons presented here, a general understanding of these new GMMs can be obtained with the expectation that the implementation of a specific seismic hazard study should incorporate similar and additional comparisons and sensitivity studies pertinent to the site of interest.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/87552930221112688
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2022
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  • 4
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    NGA-West2 Research Project
    SAGE Publications ; 2014
    In:  Earthquake Spectra Vol. 30, No. 3 ( 2014-08), p. 973-987
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 30, No. 3 ( 2014-08), p. 973-987
    Abstract: The NGA-West2 project is a large multidisciplinary, multi-year research program on the Next Generation Attenuation (NGA) models for shallow crustal earthquakes in active tectonic regions. The research project has been coordinated by the Pacific Earthquake Engineering Research Center (PEER), with extensive technical interactions among many individuals and organizations. NGA-West2 addresses several key issues in ground-motion seismic hazard, including updating the NGA database for a magnitude range of 3.0–7.9; updating NGA ground-motion prediction equations (GMPEs) for the “average” horizontal component; scaling response spectra for damping values other than 5%; quantifying the effects of directivity and directionality for horizontal ground motion; resolving discrepancies between the NGA and the National Earthquake Hazards Reduction Program (NEHRP) site amplification factors; analysis of epistemic uncertainty for NGA GMPEs; and developing GMPEs for vertical ground motion. This paper presents an overview of the NGA-West2 research program and its subprojects.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1193/072113EQS209M
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2014
    detail.hit.zdb_id: 2183411-8
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  • 5
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    NGA-Subduction research program
    SAGE Publications ; 2022
    In:  Earthquake Spectra Vol. 38, No. 2 ( 2022-05), p. 783-798
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 38, No. 2 ( 2022-05), p. 783-798
    Abstract: This article summarizes the Next Generation Attenuation (NGA) Subduction (NGA-Sub) project, a major research program to develop a database and ground motion models (GMMs) for subduction regions. A comprehensive database of subduction earthquakes recorded worldwide was developed. The database includes a total of 214,020 individual records from 1,880 subduction events, which is by far the largest database of all the NGA programs. As part of the NGA-Sub program, four GMMs were developed. Three of them are global subduction GMMs with adjustment factors for up to seven worldwide regions: Alaska, Cascadia, Central America and Mexico, Japan, New Zealand, South America, and Taiwan. The fourth GMM is a new Japan-specific model. The GMMs provide median predictions, and the associated aleatory variability, of RotD50 horizontal components of peak ground acceleration, peak ground velocity, and 5%-damped pseudo-spectral acceleration (PSA) at oscillator periods ranging from 0.01 to 10 s. Three GMMs also quantified “within-model” epistemic uncertainty of the median prediction, which is important in regions with sparse ground motion data, such as Cascadia. In addition, a damping scaling model was developed to scale the predicted 5%-damped PSA of horizontal components to other damping ratios ranging from 0.5% to 30%. The NGA-Sub flatfile, which was used for the development of the NGA-Sub GMMs, and the NGA-Sub GMMs coded on various software platforms, have been posted for public use.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1177/87552930211056081
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2022
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  • 6
    Online Resource
    Online Resource
    Comparisons of the NGA Ground-Motion Relations
    SAGE Publications ; 2008
    In:  Earthquake Spectra Vol. 24, No. 1 ( 2008-02), p. 45-66
    Details
    In: Earthquake Spectra, SAGE Publications, Vol. 24, No. 1 ( 2008-02), p. 45-66
    Abstract: The data sets, model parameterizations, and results from the five NGA models for shallow crustal earthquakes in active tectonic regions are compared. A key difference in the data sets is the inclusion or exclusion of aftershocks. A comparison of the median spectral values for strike-slip earthquakes shows that they are within a factor of 1.5 for magnitudes between 6.0 and 7.0 for distances less than 100 km. The differences increase to a factor of 2 for M5 and M8 earthquakes, for buried ruptures, and for distances greater than 100 km. For soil sites, the differences in the modeling of soil/sediment depth effects increase the range in the median long-period spectral values for M7 strike-slip earthquakes to a factor of 3. The five models have similar standard deviations for M6.5-M7.5 earthquakes for rock sites and for soil sites at distances greater than 50 km. Differences in the standard deviations of up to 0.2 natural log units for moderate magnitudes at all distances and for large magnitudes at short distances result from the treatment of the magnitude dependence and the effects of nonlinear site response on the standard deviation.
    Type of Medium: Online Resource
    ISSN: 8755-2930 , 1944-8201
    URL: Article
    DOI: 10.1193/1.2924363
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2008
    detail.hit.zdb_id: 2183411-8
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