ML20054G750
| ML20054G750 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 05/17/1982 |
| From: | WESTON GEOPHYSICAL CORP. |
| To: | |
| Shared Package | |
| ML20054G741 | List: |
| References | |
| NUDOCS 8206220263 | |
| Download: ML20054G750 (3) | |
Text
.
. e translates to a factor of 1.59 in the resultant response spectra.
A letter from Prof. Nuttli confirming the overestimation and the resultant 37% decrease in spectral level described above is enclosed as Attachment A.
The spectra for an mb = 7.2 earthquake at epicentral distances of 50, 100, 200, 300, and 500 kms obtained from Figures 5 and 6 of Nuttli (1981b) are shown on Figure 38.
The 1
estimated spectrum for the mb = 7.2 earthquake at an epicentral distance of 177 km, the NRC's defined closest approach of the New Madrid Zone to the Clinton site, is also shown on Figure 38.
The undamped spectrum was reduced by the correction factor of 1.59 and the resulting spectra for 5% and 1
7% damping, shown on Figure 39, were constructed from New' mark and Rosenbluth's (1971) spectral amplification factors as used by Nuttli.
Attenuation formulas developed for acceleration and velocity by Herrmann in 1981 were included in the Nuttli and Herrmann paper presented at the October 1981 ASCE meeting in St. Louis.
The formulas are:
Lo910a =. 5 5 + 0. 50mbLg - 0.831og10r - 0.0019r Lo910r =
-3.6,0,+ 1.00mbLg - 0.831og10r - 0.00llr g
l For a 7.2m earthquake at an epicentral distance of 177 km, bLg 2
the calculated acceleration is 90.78 cm/sec (.093 ) and 9
$$k6gg((3 Wes'on Geophysical g
0 0
l E
. the calculated velocity is 35.6 cm/sec (13.6 in/sec).
The response spectra shown on Figure 40 were constructed using i
these calculated ground acceleration and velocity values together with spectra amplification factors as proposed in NUREG 0098 (1978).
The following attenuation relationships for ground acceleration and velocity developed by Tera (1980) after Gupta and Nuttli's 1976 studies are:
In a = In 2.368 + 1.104mb
.00l
.738 In r
r in v = In.062 + 1.283mb
.00l
.644 In r
r l
For a 7.2 m earthquake at an epicentral distance of 177 bLg 2
km, the calculated acceleration is 123.2 cm/sec (.126 )
g and the calculated velocity is 19.05 cm/sec (7.5 in/sec).
The response spectra shown on Figure 41 were constructed using 1
these calculated ground acceleration and velocity values and spectral amplification factors as proposed in NUREG 0098 (1978).
The response spectra shown on Figure 42 are based on the 1
results of probabilistic seismic hazard analysis presented in Nuttli and Herrmann (1981).
A contour map of the peak acceleration value for the average of the two horizontal 2
components predicts a value of approximately 130 cm/sec for a 1000 year return period at the approximate location of the 2
Clinton site.
Since the value of 148.2 cm/sec (1.14 X 130 Weston Geophysical
23 -
'2 cm/sec ) for the peak horizontal component (1.14 times the average of the horizontal components) at Clinton is nearly 2
identical to the 150 cm/sec value for St. Louis as shown in Nuttli and Herrmann (1981), the values for velocity and displacement at St. Louis were adopted for Clinton in lieu of more specific data in the form of velocity and displacement contour maps for the Clinton site area.
The response spectra shown on Figure 42 were constructed using spectral amplifi-1 cation factors as proposed by NUREG 0098.
- 4. 2 Comparison with Clinton Design Spectra In the long periods, the current Clinton design spectrum is adequate and exceeds all of the spectra for a mb = 7.2 earthquake at 177 km shown on Figures 39, 40, and 41.
The 1
current Clinton design spectra also exceeds the spectra estimated from the probabilistic seismic hazard analysis, Figure 42.
Figure 43 is a comparison between the "Clinton Free y
Field Foundation Spectra" and the spectrum that has the highest spectral velocity values for Clinton, Nuttli's perferred attenuation relationships (Nuttli and Herrmann, 1981) 1 (Figure 4 0).
At the higher frequencies (shorter periods), the spectrum from the Clinton design basis time history anchored at.179 substantially exceeds the spectra shown on Figures 39 through 42.
Figure 44 is a comparison between the spectrum from the Clinton design basis time history anchored at.179 and 1
the spectrum that has highest spectral accelerations in the high frequencies (Figure 39).
Weston Geophysical