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Figure 5-16. Comparison between Martin-Qiu and WUS-Soil correlations for
PGV = 30 kmax.
PGV = 60 × kmax, respectively, with respect to the mean design 5.3 Correlation of PGV with S1
curve given by Equation (5-8).
A procedure for establishing the PGV for design from the
spectral acceleration at one second (S1) also was developed for
5.2.10 Design Recommendations the Project. For earth and buried structures, PGV provides a
For design applications, Equation (5-8) for soil and rock direct measure of the ground deformation (as opposed to
sites for WUS and CEUS and Equation (5-6) for CEUS rock ground shaking parameters represented by the spectral am-
sites are recommended. The regression curves shown on plitude) and is a more meaningful parameter than PGA or
Figure 5-18 and Figure 5-19 suggest that 84 percent confi- spectral accelerations for designing against kinematic loading
dence levels in displacement evaluations could be reason- induced by ground deformation. Also PGV is a key parame-
ably approximated by multiplying the mean curve by a ter used for Newmark deformation analysis, as described in
factor of 2. Section 5.2.
Figure 5-17. Comparison between Martin-Qiu and WUS-Soil correlations for
PGV = 60 kmax.
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Figure 5-18. Mean Newmark displacement and 84% confidence level,
PGA = 0.3g, PGV = 30 kmax.
The initial approach taken to develop the PGV-S1 correla- based on the spectral acceleration at 1 second (S1) and the
tion involved performing statistical studies of the USNRC magnitude (M) of the earthquake.
database. However, the resulting correlation exhibited con-
ln ( PGV ) = 3.97 + 0.94 ln ( S1 ) + 0.013 ( ln ( S1 ) + 2.93)
2
siderable scatter. Subsequently a correlation being devel-
oped by Dr. Norm Abrahamson of the Pacific Gas and + 0.063 M (5-9)
Electric Group in San Francisco was identified through dis-
cussions with seismologists involved in ground motion where PGV is in units of cm/sec, S1 is spectral acceleration at
studies. Dr. Abrahamson forwarded a draft paper that he was T = 1 sec in units of g, and M is magnitude. Dr. Abrahamson
writing on the topic. (A copy of the draft paper was originally reported that this equation has a standard deviation of 0.38
included in Appendix D. Copyright restrictions prevented in- natural log units.
cluding this draft as part of the Final Report for the NCHRP Because the strong motion database used in Dr. Abraham-
12-70 Project.) son's regression analyses consists of exclusively the WUS
In the draft of the Abrahamson's paper, the following re- database, an evaluation was performed to determine whether
gression equation was recommended for determining PGV the above regression equation would be valid for representative
Figure 5-19. Mean Newmark displacement and 84% confidence level,
PGA = 0.3g, PGV = 60 kmax.
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CEUS records. The NUREG/CR-6728 strong motion data, as cluded that the PGV correlation could be significantly
discussed in Section 5.2.4, was used to evaluate the validity simplified by eliminating the parameter M from Equation
of the Abrahamson PGV equation shown above. Figures 5- (5-9). Dr. Abrahamson concurred with this suggestion.
20 through 5-24 present comparisons between the results of 3. During discussions with Dr. Abrahamson, various other
the Abrahamson PGV equation and the strong motion data- versions of the PGV predictive equation were discussed.
base from NUREG/CR-6728. Other versions involve using spectral acceleration at the
The following conclusions can be made from Figures 5-20 3-second period. These equations are more suitable for
through 5-24: capturing peak ground velocity if there is a strong velocity
pulse from near-fault earthquake records. However, for
1. The Abrahamson PGV equation gives reasonable predic- applications involving the entire United States, especially
tions using the NUREG/CR-6728 database, even though for CEUS, these near-fault attenuation equations are not
the strong motion database from CEUS is characterized by believed to be relevant or appropriate at this time.
much lower long-period ground motion content. Part of
the reason is that the spectral acceleration at 1 second has Dr. Abrahamson reported that his research found that PGV
been used as a dependent variable in the regression equa- is strongly correlated with the spectral acceleration at 1 second
tion. The reasonableness of the comparisons occurs when (S1); therefore, the attenuation equation used S1 to anchor the
rock and soil conditions are separated for the CEUS and regression equation. Dr. Abrahamson commented that be-
the WUS. sides the 1-second spectral acceleration ordinate, other spec-
2. Magnitude (M) appears to play a very small role in affect- tral values around 1 second might be used to improve the PGV
ing the predicted PGV result. For example, there is very lit- prediction; however, from his experience, the PGA (that is,
tle change (that is, barely 10 percent) in the resultant PGV peak ground acceleration or spectral acceleration at zero-
value as the magnitude M changes from 5.5 to 7.5. The in- second period) has a frequency too far off for correlating with
sensitivity of magnitude, as well as the potential difficulty PGV, and this difference tends to increase the error in the
and/or ambiguity in establishing the deaggregated magni- regression equation. From these comments, a decision was
tude parameter for many CEUS sites where the seismic made to use the PGV equation based solely on the 1-second
sources are not well defined, was discussed with Dr. Abra- spectral acceleration ordinate (S1). In all the presented figures,
hamson (2005). From a practical perspective, it was con- the PGA amplitudes are depicted in four different categories.
Figure 5-20. Comparison between Abrahamson PGV equation with all data in NUREG/
CR-6728.
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Figure 5-21. Comparison between Abrahamson PGV equation with only NUREG/CR-6728
CEUS rock data.
Figure 5-22. Comparison between Abrahamson PGV equation with only NUREG/CR-6728
CEUS soil data.
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Figure 5-23. Comparison between Abrahamson PGV equation with only NUREG/CR-6728
WUS rock data.
WUS-SOIL
100
10
0.0
