ML20006B124
| ML20006B124 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 01/24/1990 |
| From: | Talwani P SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC |
| To: | |
| Shared Package | |
| ML20006B122 | List: |
| References | |
| 89-3, NUDOCS 9001310462 | |
| Download: ML20006B124 (14) | |
Text
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l TECHNICAL REPORT 89-3 SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION For the Period 1
TJuly-September 1989 I
l by Pradeep.Talwani Principal investigator Department of Geological Sciences University. of South Carolina Columbia, SC 29208 i
Contract No. N482355
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d 9001310462 900124 DR ADOCK 0500 > '9'5
TECHNICAL REPORT 89-3 l
SEISMIC ACTIVITY NEAR l
THE V.C.. SUMMER NUCLEAR STATION FOR THE PERIOD JULY - SEPTEMBER 1989 BY PRADEEP TALWANI PRINCIPAL INVESTIGATOR KUSALA RAJENDRAN DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTH Cf.ROLINA COLUMBIA, SC 29208 CONTRACT NO. N482355 i
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t INTRODUCTION Analysis of the seismic activity near the V.C.
Summer Nuclear Station in South Carolina between July'1 and' September 30, 1989, is presented in this report.
During this period, a total of eight events were' recorded, of which two were identified as possible quarry blasts.
The largest shock was of magnitude 1.4 which occurred on July 19, at 1635 UTC.
SEISMIC NETWORK Earthquakes recorded during this period were recorded on stations of the Monticello Reservoir and South Carolina networks.
The configuration of the stations utilized to locate the events in this report is shown in Figure 1 and station coordinates are listed in Appendix I.
DATA ANALYSIS Hypocentral locations of the events have been determined using the computer program HYPO 71 (Lee and Lahr,-1972) whose format is listed in Appendix III and whose velocity model is-listed in Appendix II.
The event magnitude (Mg) was-determined from the signal duration at station JSC, using the following relation:
Mg = -1.83 + 2.04 Log D where D is the signal duration (seconds).
An estimate of daily energy release was determined using a simplified magnitude (Mg) energy (E) relation =by Gutenberg and Richter (1956):
log E = 11.8 + 1.5 M 10 g.
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l Figure 1.
Location map of Monticello Reservoir area showing seismic stations used in locating activity during this period.
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t OBSERVED SEISMICITY FOR THE PERIOD JULY - SEPTEMBER 1989 During this period several recorded events were identified as quarry blasts.
Several of them were located to the east of the reservoir and are not included in this report. 'However, Figure 2 shows the location of two events outside the Monticello Reservoir which have been tentatively identified as quarry blasts.
These events occurred on September 20 (1708 UTC) and 29 (2352 UTC).
The energy release due to these events has not been considered in this study.
The operational status of the seismic network is shown in Appendix V.
The locations of these events are listed-in Appendix IV.
For one event it was possible to use station.09AL(August 15, 0354 UTC), the coordinates of which are'given in Appendix I.
The level of activity decreased from that observed during the pre-vious reporting period, and the long-term decline in seismicity is continuing (Figure 3).
Of the six events reported here, the largest (ML = 1.4) occurred on July 19 at 1635 UTC. Another event had a magnitude (Mg = 1.0) whereas the rest were of M s 0.5.
g CORRELATION OF RESERVOIR WATER LEVEL WITH SEISMICITY Monticello Reservoir is a pumped storage facility.
Any de-crease in reservoir level associated with power generation is recovered when water is pumped back into the reservoir.
There l
can be normal variations up to approximately five feet per day l
between the maximum and minimum water level.
The water level has been monitored to see if there is any ccerelation between the daily or seasonal changes in the reservoir level and the local seismicity.
Water level is compared with seismicity in Figure 4.
3 i
F MONTICELLO EARTHOUAKES JULY - SEPTEMBER 1989 81 22.0 21.0 20 0 19 0 18.0 17.0 16.0 I
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89.182 89.197 89 212 89.227 89 242 89.257 89.272 l
JULIAN DATE j
Figure 4. Comparison of the median daily lake level and daily changes in l
water level with the number of earthquakes per day and the log of energy released.
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The top plot shows the median water level.
The second plot from the top shows the change in average water level each day.
The i
number of events per day and the log of the energy released per j
day are shown in the lower two histograms.
There is no system-atic correlation between the change in median water level or daily water level fluctuations and seismicity luring this quarter.
CONCLUSIONS The level of activity observed during the third quarter of 1989 was low and lower than that observed during the second quarter of 1989.
The largest event was.of magnitude 1.4, on July 19.
REFERENCES Gutenberg, B. and Richter, C.F. (1956).
Magnitude and energy of earthquakes, Ann. Geof.
9, 1-15.
Lee, W.H.K. and Lahr, J.C.
(1972).
A computer program for deter-mining hypocenter, magnitude and first motion pattern of local earthquakes, Revisions of HYPO 71, U.S.
Geological Survey Open-File Report, 100 p.
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APPENDIX I STATION LOCATIONS NO.
STN.
LAT.*N LONG.*W 1
JSC 34* 16.80' 81* 15.60' 2
001 34* -19.91' 81* 17.74' 3
002 34' 11.58' 81* 13.81' 4
005 34' 16.05' 8120.05' 5
007 34' 22.23' 81* 19.50' 6
010 34' 20.18' 81* 20.25' 7
09A 34* 17.24' 81* 19.75' i
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APPENDIX II MONTICELLO RESERVOIR l
l VELOCITY MODEL 1
Velocity Depth'to top km/sec km 1.00 0.00 5.40 0.03 5.90 0,18.
6.10 0.46 6.30 0.82 8.10 30.00
+
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b APPENDIX III MONTICELLO EARTHQUAKES l
JULY - SEPTEMBER 1989 l.
HYPO 71 FORMAT Column 1 Date l
Column 2 Origin t.ime (UTC) h.m.sec.
Column 3 Latitude (N) degrees, min.
Column a Longitude (W) degrees, min.
Column 5 Depth (km)
Column 6 Local duration magnitude Column 7 No. of station readings used to locate event.
P and S arrivals from same stations are regarded as 2 readings Column 8 Largest azimuthal separation in degrees between stations Column 9 Epicentral distance in km to nearest station Column 10 Root mean square error of time residuals in sec.
RMS = R 2 /NO, where R is the time residualforkheithstatiok Column 11 Standard error of the epicenter in km Column 12 Standard error of the1 focal depth in km Statistical interpretation of standard errors involves assump-tions which may not be met in earthquake locations.
Therefore, standard errors may not represent actual error limits.
If ERH or ERZ is blank, this means that it cannot be computed because of insufficient data.
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APPENDIX IV MONTICELLO EARTHQUAKES :
JULY-SEPTEMBER 1989 DATE ORIGIN LAT N LONG W OEPTH MAG MO GAP DMIN RMS' ERH ER2 QM 719 1635 4.M 34-21 18 2 @ 38.47 34-2 39 81-14.54 1.00 1.44 3 354 3.0 0.02' C1
.01 81-15.82 0.65 1.02 5'W 1.7 0.02 1.2 1.8 C1 86iO814 1241 31.54 34-20.01 81-17.84
- 1. W 0.21 7 298 0.2 0.09 1.1 1.3 C1 890815 W 27.05 34-19.50 81-19.35 1.00 0.57 7 245' 2.6 0.07 0.7-3.4 C1 890912 040 28.58 34-18.91 81-18.72 0.40 0.57 4 338 6.2 0.15 C1 890921 1555 0.77 34-20.01 81-17.84 1.00 0.21 3 343 0.2 0.07 C1*
8 20178 4.61 34-20.26 81-16.53 1.00 1,44 3 275 2.0 0.02 C1 29 2352 14.00 34-16.W0 81-1b.70 1.00 1.44 3 170 0.2 0.37 Ul*
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- indicates events which are identified as possible quarry blasts.
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c APPENDIX V SEISMIC STATION OPERATIONAL STATUS 4
1 JULY - 30 SEPTEMBER'1989 STATION PERCENT DOWNTIME JSC 0%
001 0%
002
.0%
7 005 12%
007 100%
010 100%
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