NGA-subduction global ground motion models with regional adjustment factors

Parker, Grace A.; Stewart, Jonathan P.; Atkinson, Gail M.; Hassani, Behzad

doi:10.1177/87552930211034889

Cited by 67 publications

(67 citation statements)

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“…Parker et al (this volume) developed one of the NGA-Sub GMMs, using a combination of empirical data analysis, finite-fault simulations, and geometrical constraints to estimate the median orientation-independent horizontal component (RotD50; Boore, 2010) peak ground acceleration (PGA), peak ground velocity (PGV), and 5% damped pseudo-spectral acceleration (PSA) at oscillator periods between 0.01 and 10 s. The Parker et al (this volume) GMM has a reference shear-wave velocity condition of V S 30 = 760 m/s, where V S 30 is the time-averaged shear-wave velocity in the upper 30 m. To use the GMM for other site conditions such as soil or weathered rock (i.e. V S 30 ≠ 760 m / s ), a site response model is necessary, which is the subject of this article.…”

Section: Introductionmentioning

confidence: 99%

“…Cascadia and Japan) are possible for the same reason. Hence, we use the large, empirical NGA-Sub database to develop region-specific site response models that are calibrated for use with the reference-rock-conditioned subduction GMM of Parker et al (this volume). Although some model components adopt functional forms used previously, all are fit to subduction zone data and are calibrated for use with our reference-rock GMM.…”

Section: Introductionmentioning

confidence: 99%

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Ergodic site response model for subduction zone regions

Parker

Stewart

2021

Earthquake Spectra

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We present an ergodic site response model with regional adjustments for use with subduction zone ground-motion models. The model predicts site amplification of peak ground acceleration, peak ground velocity, and 5% damped pseudo-spectral accelerations of the orientation-independent horizonal component for oscillator periods from 0.01 to 10 s. The model depends on the time-averaged shear-wave velocity in the upper 30 m ( VS30), basin depth, and region and is independent of subduction earthquake type. It has three components: a linear site-amplification term in the form of VS30-scaling, a nonlinear term that depends on VS30 and shaking intensity parameterized by peak ground acceleration at the reference-rock velocity condition of 760 m/s, and a basin sediment-depth term for Japan and Cascadia conditioned on the depth to the 2.5 km/s shear-wave velocity isosurface ( Z2.5). A global VS30-scaling model is provided along with regional adjustments for Japan, Taiwan, South America, Alaska, and Cascadia. The nonlinear model is global, with a functional form that has often been used to fit nonlinear responses inferred from simulations, but here we calibrate it empirically. Relative to a prior model for shallow earthquakes in active tectonic regions, our subduction zone global VS30-scaling is comparable at short periods (<1.0 s) but weaker at long periods, while the nonlinear site response is generally less pronounced but extends to lower levels of shaking. Basin depth models are conditioned on the difference of the actual Z2.5 and a VS30-conditioned mean Z2.5. Sites with positive differential depths have increased long-period site responses and decreased short-period responses, with the opposite occurring for negative differential depths.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ergodic site response model for subduction zone regions

Parker

Stewart

2021

Earthquake Spectra

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“…With the validation of the RVT-based technique for local earthquakes and as a substitute for EQL analyses, a logical next step is to consider further application of the method. Recently, two Next Generation Attenuation Subduction (NGA-Sub) GMMs were released by Parker et al (2020) and Kuehn et al (2020). Because of the proximity of Anchorage to the subduction zone, the high rate of earthquake activity, and the likelihood of damaging earthquakes, subduction interface earthquakes account for 36% of the earthquake hazard for Anchorage, according to the disaggregated hazard of the ''Dynamic: Alaska 2007 (v2.1.2)'' hazard model presented by USGS.gov (2021).…”

Section: Ground Motion Model Comparisonmentioning

confidence: 99%

“…The NGA-Sub hazard characterization tool (Mazzoni, 2020) was used to calculate the response spectrum for the site class BC, where the V S30 is 760 m/s, and the estimated V S30 values were used at the strong-motion stations. The Parker et al (2020) and Kuehn et al (2020) models (Global variants) were equally weighted. The site class BC response spectrum was used in Step 1 (Figure 4) as the reference site response spectra.…”

Section: Ground Motion Model Comparisonmentioning

confidence: 99%

Engineering site response analysis of Anchorage, Alaska, using site amplifications and random vibration theory

et al. 2022

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Earthquake records collected at dense arrays of strong-motion stations are often utilized in microzonation studies to evaluate the changes in site response due to variability in site conditions across a region. These studies typically begin with calculating Fourier spectral amplification(s) and then transition to performing engineering site response analyses. It has proven difficult to utilize Fourier spectral amplification(s) to define the appropriate elastic response spectr(um)/(a) for a site or sites. This is because, first, the ground motions recorded at these strong-motion stations have lower intensity and hence do not show the nonlinear site effects observed during higher-intensity earthquakes and, second, Fourier and response spectral amplitudes measure different aspects of ground motions. The strong-motion stations in Anchorage, Alaska, have been recording earthquakes in the region for the last three decades. This study utilizes a database of 95 events from 2004 to 2019 to calculate Fourier spectral amplifications at 35 stations using the generalized inversion technique (GIT). Estimated response spectra have been evaluated at each site by applying those Fourier spectral amplifications to a response spectrum of a reference station through random vibration theory (RVT). Correction factors are also applied within the approach to account for nonlinear site effects. This RVT-based approach is tested using ground motions recorded during the MW 7.1 2018 Anchorage Earthquake, and close matches between measured and predicted response spectra are found. The method is then compared with site response analyses using a calibrated 1D equivalent linear (EQL) model of the Delaney Park Downhole Array site. Estimated spectra using the RVT-based approach are, finally, compared with those using Next Generation Attenuation Subduction (NGA-Sub) and NGA-West2 ground-motion models. The proposed method provides a coherent and straightforward way to use GIT-derived Fourier spectral amplifications to directly estimate site-specific response spectra, accounting for nonlinear site effects and without requiring engineering characterization of subsurface soil conditions.

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“…Similar to other NGA programs, the GMMs have been developed to a large degree based on the recorded empirical ground motion data. Details of these four GMMs have been documented in the following series of reports and papers: Abrahamson and Gulerce (2020, this volume), Kuehn et al (2020, this volume), Parker et al (2020, this volume), and Si et al (2020, this volume). The final versions of the NGA-Sub GMMs as published in Earthquake Spectra (this volume) are recommended to be used.…”

Section: Nga-sub Gmmsmentioning

confidence: 99%

NGA-Subduction research program

et al. 2021

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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.

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NGA-subduction global ground motion models with regional adjustment factors

Cited by 67 publications

References 68 publications

Ergodic site response model for subduction zone regions

Ergodic site response model for subduction zone regions

Engineering site response analysis of Anchorage, Alaska, using site amplifications and random vibration theory

NGA-Subduction research program

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