scholarly journals Empirical Estimation of High‐Frequency Ground Motion on Hard Rock

2016 ◽  
Vol 87 (6) ◽  
pp. 1465-1478 ◽  
Author(s):  
Olga‐Joan Ktenidou ◽  
Norman A. Abrahamson
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Hard Rock ◽  
Empirical Estimation

Seismic Qualification by Testing for Electrical and Active Mechanical Equipment to be Installed in Hard-Rock High Frequency Sites

2009 ◽  
Author(s):  
Pei-Ying Chen ◽  
Ching Hang Ng
Keyword(s):  
Ground Motion ◽  
Seismic Design ◽  
High Frequency ◽  
Power Plants ◽  
Hard Rock ◽  
Response Spectra ◽  
Nuclear Industry ◽  
Mechanical Equipment ◽  
Regulatory Requirements ◽  
Structure Response

All electric and active mechanical equipment important to safety must be seismically qualified by either analysis, testing, or a combination of both. The general requirements for seismic qualification of electric and active mechanical equipment in nuclear power plants are delineated in Appendix S to Title 10, Part 50, of the Code of Federal Regulations (10 CFR Part 50), item 52.47(20) of 10 CFR 52.47, and Appendix A to 10 CFR Part 100. The staff at the US Nuclear Regulatory Commission (NRC) has recognized that the Certified Design Ground Motion may be exceeded by the site-specific ground motion. The exceedances are generally in the high-frequency range for the Central and Eastern US sites. For equipment seismic qualification consideration, the exceedances must be addressed at both the ground level and the floor level where the equipment is located. Thus, the in-structure response spectra at some locations may exceed those in-structure response spectra generated by the certified seismic design response spectra. The U.S. nuclear industry and the NRC have initiated activities to address this issue. Two scenarios that revealed themselves during the review activities of the design certification and combined license applications for new reactors will be expounded upon in the paper. In Case I, equipment seismic qualification has been approved for a certified design and equipment is to be installed at a hard-rock high frequency (HRHF) site with certified seismic design response spectra (CSDRS) exceeded by the Ground Motion Response Spectra (GMRS) of the hard-rock site. In Case II, equipment seismic qualification has not been approved for a design certification and there is an application with GMRS exceeding the not-yet-approved CSDRS. In the paper, the staff will begin the discussion with the regulatory requirements for seismic qualification of electric and mechanical equipment. The focus of the paper is to identify the staff concern and illustrate the resolution between the NRC staff and an applicant on the seismic qualification of equipment by testing, in particular for equipment to be installed in hard-rock high frequency sites, to meet the regulatory requirements.

Erratum toEmpirical Estimation of High‐Frequency Ground Motion on Hard Rock

2017 ◽  
Vol 88 (3) ◽  
pp. 877-877
Author(s):  
Olga‐Joan Ktenidou ◽  
Norman A. Abrahamson
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Hard Rock

scholarly journals Hybrid broadband ground motion simulation validation of small magnitude earthquakes in Canterbury, New Zealand

2020 ◽  
Vol 36 (2) ◽  
pp. 673-699 ◽  
Author(s):  
Robin L Lee ◽  
Brendon A Bradley ◽  
Peter J Stafford ◽  
Robert W Graves ◽  
Adrian Rodriguez-Marek
Keyword(s):  
New Zealand ◽  
Ground Motion ◽  
High Frequency ◽  
Motion Simulation ◽  
Small Magnitude ◽  
Ground Motion Simulation ◽  
Simulation Methodology ◽  
Simulation Validation ◽  
Broadband Ground Motion Simulation ◽  
Broadband Ground Motion

Ground motion simulation validation is an important and necessary task toward establishing the efficacy of physics-based ground motion simulations for seismic hazard analysis and earthquake engineering applications. This article presents a comprehensive validation of the commonly used Graves and Pitarka hybrid broadband ground motion simulation methodology with a recently developed three-dimensional (3D) Canterbury Velocity Model. This is done through simulation of 148 small magnitude earthquake events in the Canterbury, New Zealand, region in order to supplement prior validation efforts directed at several larger magnitude events. Recent empirical ground motion models are also considered to benchmark the simulation predictive capability, which is examined by partitioning the prediction residuals into the various components of ground motion variability. Biases identified in source, path, and site components suggest that improvements to the predictive capabilities of the simulation methodology can be made by using a longer high-frequency path duration model, reducing empirical V s30-based low-frequency site amplification, and utilizing site-specific velocity models in the high-frequency simulations.

scholarly journals Capturing Regional Variations of Hard‐Rock Attenuation in Europe

2019 ◽  
Vol 109 (4) ◽  
pp. 1401-1418 ◽  
Author(s):  
Marco Pilz ◽  
Fabrice Cotton ◽  
Riccardo Zaccarelli ◽  
Dino Bindi
Keyword(s):  
High Frequency ◽  
Hard Rock ◽  
Epistemic Uncertainty ◽  
Ground Motions ◽  
Soft Soil ◽  
Coda Waves ◽  
Corner Frequency ◽  
S Wave ◽  
Empirical Parameter ◽  
Regional Variations

Abstract A proper assessment of seismic reference site conditions has important applications as they represent the basis on which ground motions and amplifications are generally computed. Besides accounting for the average S‐wave velocity over the uppermost 30 m (VS30), the parameterization of high‐frequency ground motions beyond source‐corner frequency received significant attention. κ, an empirical parameter introduced by Anderson and Hough (1984), is often used to represent the spectral decay of the acceleration spectrum at high frequencies. The lack of hard‐rock records and the poor understanding of the physics of κ introduced significant epistemic uncertainty in the final seismic hazard of recent projects. Thus, determining precise and accurate regional hard‐rock κ0 values is critical. We propose an alternative procedure for capturing the reference κ0 on regional scales by linking the well‐known high‐frequency attenuation parameter κ and the properties of multiple‐scattered coda waves. Using geological and geophysical data around more than 1300 stations for separating reference and soft soil sites and based on more than 10,000 crustal earthquake recordings, we observe that κ0 from multiple‐scattered coda waves seems to be independent of the soil type but correlated with the hard‐rock κ0, showing significant regional variations across Europe. The values range between 0.004 s for northern Europe and 0.020 s for the southern and southeastern parts. On the other hand, measuring κ (and correspondingly κ0) on the S‐wave window (as classically proposed), the results are strongly affected by transmitted (reflected, refracted, and scattered) waves included in the analyzed window biasing the proper assessment of κ0. This effect is more pronounced for soft soil sites. In this way, κ0coda can serve as a proxy for the regional hard‐rock κ0 at the reference sites.

Rainfall-Induced Variation of Seismic Waves Velocity in Soil and Implications for Soil Response: What the ARGONET (Cephalonia, Greece) Vertical Array Data Reveal

2020 ◽  
Vol 110 (2) ◽  
pp. 441-451
Author(s):  
Zafeiria Roumelioti ◽  
Fabrice Hollender ◽  
Philippe Guéguen
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Surface Velocity ◽  
Depth Interval ◽  
Seasonal Effect ◽  
Surface Wave Dispersion ◽  
Near Surface ◽  
Soil Response ◽  
Earthquake Records ◽  
Shallow Sediments

ABSTRACT We apply interferometry by deconvolution to compute the shear-wave velocity in shallow sediments (0–83.4 m) based on earthquake records from a vertical accelerometric array (ARGOstoli Network [ARGONET]) on Cephalonia Island, Greece. Analysis of the time variation of measured values reveals a cyclical pattern, which correlates negatively to rainfall and a soil moisture proxy. The pattern includes a sharp reduction in velocity at the beginning of rainy seasons and a gradual rise toward dry periods, the overall variation being around 20%–25% within the shallowest depth interval examined (0–5.6 m) and estimated to reach 40% within the top 2 m. The variation itself and its amplitude are verified by surface-wave dispersion analysis, using ambient vibration data. Synthetic standard spectral ratios suggest that this seasonal effect leaves an imprint on soil response, causing differences in the level of high-frequency ground motion between dry and rainy seasons, and this is verified by earthquake records. Furthermore, the near-surface velocity decrease due to soil saturation can be of the same order of magnitude as the nonlinear coseismic variation, masking the physical process of the nonlinear response of the site due to weak-to-strong-motion shaking. Thus, seasonal variations of seismic-wave velocities in shallow sediments may be important for a number of site-effect related topics, such as high-frequency ground-motion variability, soil anisotropy, kappa measurements, nonlinear site response, and so on.

Revision of Boore (2018) Ground-Motion Predictions for Central and Eastern North America: Path and Offset Adjustments and Extension to 200  m/s≤VS30≤3000  m/s

2020 ◽  
Vol 91 (2A) ◽  
pp. 977-991
Author(s):  
David M. Boore
Keyword(s):  
North America ◽  
Stochastic Model ◽  
Point Source ◽  
Ground Motion ◽  
Hard Rock ◽  
Response Spectra ◽  
Site Amplification ◽  
Eastern North America ◽  
A Value ◽  
Stress Parameters

Abstract The three sets of ground-motion predictions (GMPs) of Boore (2018; hereafter, B18) are compared with a much larger dataset than was used in deriving the predictions. The B18 GMPs work well for response spectra at periods between ∼0.15 and 4.0 s after an adjustment accounting for a path bias at distances beyond 200 km—this was the maximum distance used to derive the stress parameters on which the simulations in B18 are based. An additional offset adjustment is needed in the B18 predictions for short and long periods. The adjustment at short periods may be because the κ0 of 0.006 s stipulated by the Next Generation Attenuation-East (NGA-East) project to be used in deriving the GMPs is inconsistent with the observations on rock sites. The explanation for the offset adjustment at long periods is not clear, but it could be a combination of limitations of the point-source stochastic model for longer period motions, as well as a decreasing number of observations at longer periods available to constrain the simulations on which the predictions are based. The predictions of B18, developed for very-hard-rock sites (VS30 of 2000 and 3000  m/s), have here been extended down to VS30 values as low as 200  m/s. I find, as have others, that for a given VS30, there is generally less site amplification for central and eastern North America (CENA) than for the active crustal region dataset used for the Boore, Stewart, et al. (2014; hereafter, BSSA14) GMP equations. This might have an impact on conclusions of several previous studies of CENA GMPs that used the site amplifications in BSSA14 in comparing data and predictions. An additional finding is that the κ0 implied by recordings on a subset of stations in the Charlevoix region located on rock (data from these stations were not used in the analysis described earlier) is more consistent with a value near 0.014 s than the 0.006 s value used in B18 and the NGA-East project.

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