ML20065F298

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Technical Rept 93-3, Seismic Activity Near VC Summer Nuclear Station for Period Jul-Sept 1993
ML20065F298
Person / Time
Site: Summer South Carolina Electric & Gas Company icon.png
Issue date: 09/30/1993
From: Talwani P
SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC
To:
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ML20065F296 List:
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NUDOCS 9404110304
Download: ML20065F298 (16)
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TECHNICAL REPORT 93-3 b a

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TECHNICAL REPORT 93-3 SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION- '

FOR THE PERIOD JULY-SEPTEMBER,1993 i BY PRADEEP TALWANI Principal Investigator and Robert Trenkamp-l DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTH CAROLINA COLUMBIA, SOUTH CAROLINA 29208 j CONTRACT NO. N622702 ,

INTRODUCTION Analysis of the seismic activity near the V.C. Summer Nuclear Station in South Carolina between July 1 and September 30,1993 is presented in this report. During this period, seven events were recorded in the vicinity of the Monticello Reservoir. All l seven events were located and were of relatively small magnitude.

l SEISMIC NETWORK 1 Earthquakes during this, period were recorded on stations of Monticello Reservoir and l South Carolina Seismic Networks. The configuration of stations utilized to locate l Monticello Reservoir 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 ANALYSIS Hypocentral locations have been determined using the computer program HYPO 71 (Lee and Lahr,1972). The velocity model used in the earthquake locations is given in Appendix III. The format of the HYPO 71 output is given in Appendix IV. The event magnitude was determined from the signal duration at JSC using the following relation:

M t= -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):

Logio E = 11.8 + 1.5 Mt OBSERVED SEISMICITY DURING JULY-SEPTEMBER,1993 Seismicity around Monticello Reservoir was low during the third quarter of 1993.

Seven events were recorded and located (Figure 2). Five events were located which occurred during a six hour interval on September 6,1993 between 11:22 and 17:17 UTC.

They were located in a cluster near Stadon MR10 and to its west. The largest event of i

the quarter occurred on July 14,1993 at 20:06:13 UTC and had a duration magnitude of l 0.16. It was located on the east central section of the reservoir near Station MR01 l (Figures 1 and 2). The final event of the quarter had a duration magnitude of -0.27 and l was located south of the reservoir (Figure 2). All locations were rated good to fair (B-C; l Appendix V). The long term decline in seismicity observed at Monticello Reservoir is

! continuing (Figure 3), and the cumulative seismicity has shown relative flattening since 1985-86 (Figure 4).

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CORRELATION OF WATER LEVEL WITH SEISMICITY Monticello Reservoir is a pumped storage facility. Any decrease in the reservoir level associated with power generation is recovered when water is pumped back into the reservoir. There can be normal variations up to five feet per day between maximum and minimum water levels. The water level 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 levels are compared with seismicity in Figure 5. 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 water level from day to day. The i number of events per day and the log of energy released are shown in the lower histograms. These charts include all reported earthquakes listed in Appendix V. The average water level, daily changes in water level, number of earthquakes and energy

' release are given in Appendix VL No systematic correlation was observed between the seismicity and reservoir level fluctuations.

l CONCLUSIONS l

l Seismicity during the third quarter of 1993 was low and occurred generally in the I central and southern part of the reservoir. No systematic correlation was observed between 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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9 Monticello Reservoir Seismic Network

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Figure 2. Events located near Monticello Reservoir during 4 the period July - September, 1993 (stars) l 4

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CUMULATIVE SEISMICITY

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Figure 4. Cumulative seismicity near Monticello Reservo.ir since impoundment.

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l Figure 5. Comparison of daily lake level, changes in lake level, number of earthquakes and the log of energy release in ergs per day at Monticello Reservoir. Error bars in the top panelindicate daily fluctuations in water level.

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4 APPENDIX I ,

STATION LOCATIONS t

STATION LAT N LONG W l JSC 34 16.80 81 15.60'

?. MR01 34 19.91' 81 17.74'  ;

MR02 34 11.58' .81 13.81

MR05- 34 16.05' '81 20.05' i

MR07 - 34 22.23' 81 19.50' i

1 i MRIO 34 20.18' 81 20.25' i

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3 APPENDIX II SEISMIC STATION OPERATIONAL STATUS i

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STATION ' PERCENT DOWNTIME MR01 - 3.2 -

MR02 3.2 MR05 ' 4.3 MR07 3.2 MR10 3.2 JSC 2.2 9

k APPENDIX III s MONTICELLO RESERVOIR-VELOCITY MODEL -

i-Velocity ' Depth to top' ,

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APPENDIX IV j MONTICELLO EARTHQUAKES l HYPO 71 FORMAT Column 1 Date Column 2 Origin time (UTC) h.m.sec.

Column 3 T.atitude (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 locate event. P and S arrivals from same stations are regarded as 2 readings.

Column 8 Largest azimuthal separation in degrees between stations. 1 Column 9 Epicentral distance in km to nearest station.

Column 10 Root mean square error of time residuals in sec.

RMS = Ri 2/No, where Ri is the time residual for the ith station.

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 assumptions which may not be met in earthquake locations. Therefore standard errors may not represent actual error limits.

Note: If ERH or ERZ is blank, this means that it cannot be computed, because of insufficient data.

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APPENDIX V ]

. MONTICELLO.-RESERVOIR EARTHQUAKES JULY- SEPTEMBER,1993 t DATE . ORIGIN- 'LAT N LONG W' DEPTH ' MAG .NO CAP: DMIN RMS ERH' ERZ'QM 930714 2006 13 27 34-20.01 81-17.71. '2.31- 0.16.10 185..-10.2~0.05 0.3 0. 3.- C12 -- !

930906 1122 6.58 34-20.24 21.51 0.47. .0.00 12 236 1.9 0.10 0.7-~2.'O C1

-930906 1246 37.07 34-20.50 81-19.85 0.05 0.00 ~7.144 0.8 0.07 0.4 0.9'B1 930906 1542 35.05 34-20.52 81-20.20- 0.12 0.00. 8 192' O.6-0.03l.0.2- 0.3 C1--

930906 1659.37;11 34-20'.49 81120.43 0.48 .0'00 -8 229 -0.6 0.05 0.5- 0. 5 C1-930906 1717 '4.29 34-20.41- 81-20.29 0204 0.00 6.291- 0.4 0.02- 0.4' O 4 C1 930911 345 12.04 34-17.38 81-18.49 3.87 -0.27 10 121..3.4 0.25 1.2 12.5'B1. ,

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I APPENDIX VI Maximum and minimum water levels, change in water level, number of earthquakes and log of energy release per day at Monticello Reservoir

, ., during July 1 - September 30,1993. Dates are given in Julian Calendar. 1 J.DATE WL(max) WL(min). WL(avg) WL(ch) # of eqs Energy 182 425 422.4 423.8 0.4 0 0 183 424.9 421.7 423.6 -0.2 0 0 184 425 421.6 -423.1 -0.5 0 0 185 425 421.3 423.6 0.5 0 0 186 425 422.5 423.6 0 0' O 187 425 422.4 423.6 0 0 0 188 425 422.1 423.7 0.1 0 0

-189 424.9 .421.5 423.4- -0.3 0 0 190 424.9 421.6 423.3 -0.1 0 0.

191 424.9 421.6 423.2 -0.1 0 0 192- 425 421.7 423.9 0.7 0. 0 193 425 422.2 -423.9 0. 0 0 194 425 421.7 423.4 -0.5 0 0 195 424.9 421.7 423.4 0 1 12.04 196 424.8 422.9 424- 0.6 0 0-197 425 422.6 '423.8- -0.2 .0 'O 198 425. 422.5 -423.7' -0.1 0 0 199 424.9 -422.2 423.6 -0.1 0 0 200 425 422.1 423.6 0 0 0 .

201 425 421.8 423.7 0.1 0- 0 202 424.9 421.8 423.6 -0.1 0 0 203 424.9 422 423'.5 0.1 0 0 '

204 424.9 422.3 424. 0.5 0 0 205' 424.9 422.9 423.9 -0.1. 0 0 206 424.9 421.6 423.4 -0.5 'O O 207 424.9 422 423.5 0.1 0 0 208 424.8 421.6 423.5 0 0 0 209 424.8 421.7 423.3 0.2 0 0 210 425 421.8 423.5 0.2 0 0 211 425 421.7 423.5 0 0 0 212 424.9 421.9 423.4 -0.1 0 0 213 424.9 421.5 423.4 0 0 0 214 424.8 421.7 423.1 -0.3 0 0

,, 215 425 422 423.4 0.3 0 0 216 425 422.6 424.1 0.7 0 0 217 424.4 421.4 423.4 -0.7 0 0 218 424.8 421.7 423.3 -0.1 'O O 219 424.7 422.4 424 0.7. 0 0  !

220 424.9 423.7 424.4 0.4 0 0 221 424.8 423.3 424.1 -0.3 0 0 222 424.8 422.5 423.9 -0.2 0 0 223 424.9 422 423.6 -0.3 0 0 i

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APPENDIX VI (centinusd) 4

, J.DATE WL(max) WL(min) WL (avg) WL (ch) # ot eqs Energy 224 425 421.8 423.5 -0.1 0 0 225 424.5 421.8 423.1 -0.4 0 0 4 226- 424.9- 421.9 423.8 0.7 0 0 227- 424.7 423 423.9 0.1 0 0

. 228 425 421.5 423.2 -0.7 0 0 229 424.9 421.7 423.3 0.1 0 0

.230 425 421.6 423.2 -0.1 0 0 231

  • 425 421.6- 423.3 0.1 0 0 232 425 421.9 423.4 0.1 - 0 0 233 425. 422 423.5 0.1 0 0-234 424.9 421.8 423.3' -0.2 0 0 235 424,9 421.6 423.4 0.1 0 0 1 236 .425 421.5 423.5 0.1 0 0 237 425 421.4 423.3 -0.2 0- 0 238 424.9 421.3 423.2 -0.1 0 0 239 425 421.6 423.4 0.2 0 0

. 240 424.9 421.4 423.4 0 0 0 241 424.9 421.3 423.2 -0.2 0 0-242 425 421.4 423.3 0.1 0 0 243 425 421.3 423.2 -0.1 0 '

244 425 421.4 423.3 0.1 0 0 1

245 424.9 421.5 423.4 0.1 - 0 'O 246 424.6 421.6 423.2 -0.2 0 O' 247 424.9 422.2 423.7 0.5 0 0 248 424.7 423.2 424.1 0.4 0 0.

249- 424.7 423.4 424.2 0.1 5 55.17 250 424.6 423.3 424.1 -0.1 0 0 251 424.8 423.1 424 -0.1 0 0 252 424.8 421.4 423.4 -0.6 0 0 253 425 421.8 423.7 0.3 0 0 254 424.4 422.5 423.7 0 1 11.4 l 255 424.9 422.5 423.8 0.1 0 0  !

256 425 421.5 423.5 -0.3 0 0 257 425 421.8 423.4 -0.1 0 0 4

258 425 421.4 423.2 -0.2 0 0  !

259 424.8 421.5- 423.2 0 0 0 260 424.9 421.6 423.5 0.3 0 0 261 424.9 421.8 423.2 -0.3 0 0 262 425 422.3 423.9 0.7 0 0 263 i 425 423.6- 424.4 0.5 0 0- l 264 424.8 421.3 423.5 0.9 0 0 265 425 422 423.6 0.1 0 0 266 424.9 422.5 424 0.4 0 0 267 425 421.5 423.6 -0.4 0 0 268 424.8 421.4 423 -0.6 0 0 269 425 421.5 423 0 0 0 270 424 421.8 423.3 0.3 0 0 271 424.5 422.6 423.6 0.3 0 0 272 424.1 422.6 423.3 -0.3 0 0 273 424 422.8 423.6 0.3 0 0 14

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