ML20079C954
| ML20079C954 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 06/21/1991 |
| From: | Talwani P SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC |
| To: | |
| Shared Package | |
| ML20079C953 | List: |
| References | |
| 91-1, NUDOCS 9106260383 | |
| Download: ML20079C954 (18) | |
Text
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TECHNICAL REPORT 91-1 SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION 1
FOR THE PERIOD JANUARY-MARCH,1991 l
BY PRADEEP TALWANI PrincipalInves!!ystor ,
L
'* Department of Geological Sciences University of South Carolina
! , Columbia, SC 29203 l
(4 t i, 95 i g POR
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r 3 TECHNICAL REPORT 91-1 SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR DTATION FOR THE PERIOD JANUARY-MARCH 1991 BY PRADEEP TALWANI PRINCIPAL INVESTIGATOR KUSALA RAJENDRAN and PREETHA SUDHAKAR DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTH CAROLINA l' COLUMBIA, SC 29208 l
l CONTRACT NO. NS74984 i-1 1
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INTRODUCTION
, Analysis of the seismic activity near the V.C. Summer Nuclear Station in South Carolina between January 1 and March 31, 1991, j is presented in this report. During this period, 22 events were !
recorded in the vicinity of Monticello Reservoir, twelve of which were located. The largest shock was of magnitude (ML )=1.2 which occurred on February 26 ( 17:35:31.97 UTC).
SEISMIC NETWORK Earthquakes during this period were recorded on stations of Monticello Reservoir and South Carolina networks. The configura-tion of the stations utilized to locate Monticello events is shown in Figure 1 and station coordinates are listed in Appendix I. The operational status of the network is given in Appendix II.
DATA ANATJBIS Hypocentral locations of the events have been determined using the computer program HYPO 71. The velocity model used in earthquake locations is given in Appendix III. The format of the output of HYPO 71 is given in Appendix IV (Lee and Lahr, 1972).
The event magnitude was determined from the eignal duration at JSC, using the following relation:
ML = -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 (ML ) - energy (E) relation by Gutenberg and Richter (1956):
Log 10 E = 11.8 + 1.5 M t.
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- - MONTICELLO RESERVOIR I
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I Figure 1. Location of Monticello Reservoir area showing seismic stations used in locating seismicity.
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ODDERVED DEIDMICITY FOR Ti!E PERIOD JANUARY - )mRCl! 1991 During this period 22 earthquakes were recorded, of which twelve were located (Appendix V ; Figure 2). Most of these were located in the central part of the reservoir. However, the locations were of poor quality. Only two were of B quality and the rest were of C and D. Most of the nonlocated events were of small magnitude (< 1.0). Seven of the nonlocated events occurred close to statiun 007 and had S-P 6 1.0 sec. (Appendix VI).
The largest event of this quarter was of magnitude M,y = 1.2, which occurred on February 26 (17:35:31.97 UTC). There were two other events of magnitude > 1.0; eleven events of magnitude v. 0.0 and the rest of the events were of magnitude < 0.0. (Appendices V and VI). The seismicity in this period is comparable to that of the previous quarters. The long term decline in seismicity obs'erved is continuing (Figure 3).
CORRELATION OF RESERVOIR WATER LEVEL WITl! DEISMICITY Monticello Reservoir is a pumped storage facility. Any decrease in reservoir level associated with power generation is rt. overed when water is pumped back into the reservoir. There can be normal variations up to approximately five feet per day between the maximum and mini...'n water levels. The water 1cvel has been monitored to see if there is any correlation between the daily or seasonal changes in the reservoir level and the local seismicity. Water level is compared with seismicity in Figure 4.
The top panel shows the average water level; the error bars show the maximum and minimum water levels each day. The second panel shows the change in average water level from day to day. The 3
MONTICELLO EARTHOUAKES January - March 1991 ,
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_15.5 34 i e i e i i i i i e i i i i 0 KILDfETERS 5 i i i e i i Figure 2. Earthquakes located near Monticello Resevoir during
. January - MTrch, 1991.
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, 1979 1980 1990 1994 j Figure 3. . Earthquakes per month between impoundment and March 1991.
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MARCH 1991:JULIAN DATE Figure 4. Comparison of daily lake level, variation in lake level, number of earthquakes and log of energy release (ergs per day) at Monicello Reservoir. Error bars in the top panel indicate dai.ly fluctuations in lake 3evel.
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3 number of events por day and the log of the energy released per day are shown in the lower two histograms. These charts include all reported earthquakes listed in Appendices V and VI. The average water level, daily changes in water level, number of earthquakes and energy release are given in Appendix VII. No systematic correlation was observed between the seismicity and the reservoir level fluctuations.
CONCLUSIONS The level of seismic activity during the first quarter of 1991 was low and comparable to that of the previous quarter. The largest event was of magnitude (M L) = 1.2, which occurred on February 26 (17:35:31.97 UTC). There were two other events of magnitude (M g) > 1.0, While the seismicity during the last quarter was confined to the northern part of the reservoir, the events during the current quarter occurred mostly within the conter of the reservoir. No systematic correlation was observed betweeen the reservoir level fluctuations and the seismicity.
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 determining hypocenter, magnitude and first motion pattern of local earthquakes, revisions of HYPO 71, U.S. Geological Survey, Open-File Report, 100 pp.
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- l APPENDIX I STATION LOCATIONS STN. IAT. N LONG. W 34" 16.80' JSC 81 15.60' 001 34* 19.91' B l* 17.74' ;
r 002 34 11.58' 81 13.81' 005 34 16.05' 81* 20.05' 007 34" 22.23' 81 19.50' 010 34 20.18' 81 20.25' 09A 34 17.24' 81* 19.75' 4
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9 a APPENDIX II SEIBMIC STATION OPERATIONAL STATUS JANUARY 01-MARCH 31, 1991 4
STATION PERCENT DOWNTIME JSC 3%
001 4%
002 62%
005 4%
007 4%
010 31%
09A 100%
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r i APPENDIX III MONTICELLO RESERVOIR VELOCITY MODEL Velocity Depth to top km/ soc 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 10
APPENDIX IV MONTICELLO EARTHQUAKE HYPO 71 FORMAT Column 1 Date.
Column 2 Origin time (UTC) h m.sec.
Column 3 Latitude (N) degrees, min.
Column 4 Longitude (W) degrees, min.
Column 5 Depth (km).
Column 6 Local duration magnitude.
Column 7 No. of station readings used to locatt ovent.
P and S arrivals from same stations are I I
regarded as 2 readings.
column 8 Largest azimuthal separation in degrees between stations. I Column 9 Epicentral distance in km to nearest station.
l Column 10 error of time residuals in i Root sec. mean RMS squarg/NO,
= R1 residual for the ith station.
where Ri !s the time ;
Column 11 Standard error of the epicenter in km*.
Column 12 Standard error of the focal depth in km*.
Column 13 Quality of the epicentral location.
- 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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s APPENDIX V l MONTICELLO EARTHQUAKEG JANUARY 01-MARCH 31, 1991 1
DATE ORIGIN LAT N LONG W DEPTH MAG MO GAP DWIN RMS ERH ER2 OM 910104 2115 7.80 34-16.83 81-20.14 0.15 0.99 4 192 1.4 0.07 C1 910106 2132 37.41 34-20.01 81-17.84 2.78 -0.40 6 173 0.2 O.08 1.2 1.3 C1 910107 2053 27.74 34-19.16 81-18.43 0.95 1.02 10 101 1.7 0.09 0.4 2.4 B1 910108 326 9.76 34-19.13 81-17.48 0.10 O 01 4 186 5.2 O.08 C1 910219 10 0 29,17 34-19.94 81-19.54 1.15 O.73 9 106 1.2 0.07 0.4 O.9 B1 910219 10 2 45.46 34-20.28 81-20.35 2.60 0.82 9 203 0.2 0.09 0.6 1.0 C1 910223 315 4.79 34-21.03 81-17.84 1.00 -0.11 3 225 2.1 0.08 C1 910226 1735 31.97 34-21.59 81-21.98 1.68 1.15 8 269 3.7 0.08 0.9 2.1 C1 910312 1121 5.19 34-19.73 81-20.35 1.75 0.78 9 194 0.9 0.08 0.4 1.0 C1 910313 9 3 13.01 34-20.28 81-20.35 1.00 0.95 8 203 0.2 0.08 0.5 0.8 C1 910313 2259 34.17 34-17.58 81-17.55 0.87 1.02 S 203 3.3 0.03 0. 7 14.5 D1 910327 1646 32.66 34-20.46 81-19.97 2.78 0.21 10 153 0.7 0.09 0.6 0.6 B1 l
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APPENDIX VI LIST OF EVENTS WITH S-P 6 2.5 SEC RECORDED AROUND MONTICELLO RESERVOIR DURING 1 JANUARY 1991 - 31 MARCH 1991 l
DATE STATION P-ARRIVAL TIME S-P EP.DIST DUR MAG H MIN SEC SEC s-p*B.5km SEC 91 01 08 007 03 33 59.40 * -
1.0 -1.8 l JSC 59.50 91 01 11 007 06 47 52.00 * -
13.0 0.4 JSC 54.70 0.3 2.6 91 01 14 007 17 27 21.90 * -
9.0 0.1 91 01 23 007 09 44 10.00 * -
18.0 0.7
" JSC 11.60 0.6 5.1 91 02 10 010 21 57 02.60 1.6 13.6 7.0 -0.1 91 02 21 007 09 27 15.30 0.7 6.0 6.0 -0.2 91 02 22 010 18 15 35.50 1.1 9.4 4.0 -6.0 91 03 02 JSC 04 06 09.70 * -
8.0 0.0 91 03 10 007 06 43 27.10 * -
3.0 -0.9 91 03 24 007 04 35 24 80 1.0 8.5 5.0 -0.4
- Event is very close to the station; (S-P) not cicar.
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Appendix VII Maximum and minimum water levels (ft), chango in water level, number of carthquakes and log energy release (ergs per day) at 1
Monticello Reservoir during January 1 - March 31, 1991, I
A 11 l C D E F G 1 DATE lWL(max) iWL(min) lWL(avg) ;CllANGE.!.No. Eqs (ENERGY
. . . - _ . - - + . -.
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12.4 13 14 12 13 424.5! _ _423.0 423.7i 424.3 424.3l 0 01 0 424.Gl 424.4l 0.1: 01 0 15 14 424.9j 423.7 424.2! -0.2I li 11.9 16 15 425l 423.8l 424.4 l 0. 2[ _0 17 16 424.4 423.7 424.1 l -0.3! 0 0 18 17 424 423.7 423.8i -0.5 0 0 19 18 424.2 423.0 423.8i 0 0 0 20 13 424.1 423.75 423.9 0.1 0 ~d' 21 423.9 20[ 424.21 423.8] O!
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39 38! 424.4 424! 424.3! 0 O! O 40 39i 424.2. 423I 423.9l -0.4l Of 0 l 14
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l A B C l D E l F G 41 4 01 423.4 422.8l 423.1 l -0.8 0l 0 42 41 423.9 43 422.8] 423.1[ 0 1} 11.6 42 423.8 423.41 423.6! 0.5 44 43 425 423.9l 4 24.3! 0.7 0 OL 0 0
, 45 44 425 424.3i 424.7' O.4 0 0 46 45 424.8 424.3! 424.7 0 0. 0 :
47 46 425 423.8l 424.6 0.1 0 0 48 47 425I 424.7 423.9[ 0.1 0 0 49 48 4 24.4 424.1 l 424.3 0.4 0 0 50 49 424.1. 424.1 424.1l _-0.2 0 0 51 50 424.7) 4 24 4 24.4' O.3. 2 13.2 52 51 424.8 424 4 24.5 0.1 0 0 53 52 424.4; 424 424.3. -0.2 1 11.4 54 53 4 24.6i 423.91 424.3l 0 1 10.9 55 54 424.5 423.9 424.3 0 1 11.6 56 55 424 424 424, -0.3 0 0 57 56 424 424 424l 0 0 0 58 57 424.1 59 423.7 423.9l -0.1 Il 13.5 58 424.3; 423.3 423.7 -0.2 0 0 60 59 424i 423.3 423.4 -0.3 0 0 61 60 4 24.1 423.5 423.9 0.5 0 0 62 61 424.6 423.9 4 24.2 0.3 1 11.8 63 62 424.0 423.7 424.2 0 0 0 64 63 423.7. 423.7 423.7 -0.5 0 0 65 64 423. 7l 422.8 423.2 -0.5 0 0 66 65 424.2 423.1 424.1 0.9 0 0 67 66 4 24.4 424.1 4 24.2 0.1 0 0 68 67 424.9 422.9 424.2 0 0 0 69 68 4 24 423.1 423.5 -0.7 0 O 70 69 4 24.7 423.5 424.3 0.8 1 10.5 71 70 425 424.1 4 24.3 0l 0 0 72 71 425 424.3 424.7 0.4 1 12.9 73 72 424.6 424.5
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4 24.5 -0.2 2 13.5 74 73 424.5 424.1 424.2T -0.3 0 0 75 74 424.4 423.6- 423.8 -0.4 0 0
. 76 75 423.6 422.8l 423.2 -0. 6 ' 0 0 77 76 424.7. 423.1l 424.2 1 0 0 78 77 424.8 !
424.1I 424.4 0.2 0 0 79 '78 424.3 422.7 423.41 -1 0 0 80 79 424.3 423.1 423.91 0.5! 0; O 15
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G 81 80 425 423.9 424.4l 0.51 01 0
, 82 81, 425 4 24.3 4 24.8 0.4 OI O 83 82 424.8 424.5 424.4J -0.3 0 0 84 83 424.7
423.9L_424.3 _
-0.2 1 11.1 85 84 424.6 423.9 4 24.1 -0.2 0 0 86 85 425 424.2 424.7' O.6 0 0 87 86 424.9 424.5 424.7 0 1 12.1 88 87 4 24.5 424.3 4 24.1, -0.4 0 0 89 88 424.9 424.2 424.7_ 0.4 0 0 90 424.7 424.5
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89_ 4 24.6 -0.1 0 0 91 90} 424.5: 424.5i 424.5. -0.1 0 0 16
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