ML20073A722

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Technical Rept 94-2, Seismic Activity Near Vsns for Period Apr-June 1994
ML20073A722
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Site: Summer South Carolina Electric & Gas Company icon.png
Issue date: 06/30/1994
From: Talwani P, Trenkamp R
SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC
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94-2, NUDOCS 9409200379
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4 TECHNICAL REPORT 94 -

SEISMIC A.CTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION FOR THE PERIOD

~

APRIL-JUNE,1994 BY PRADEEP TALWANI '

Principal Investigator DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTH CAROLINA COLUMBIA, SOUTH CAROLINA 29208 CONTRACT NO. N622702 l

9409700379 940913 r PDR ADOCK 05000395 l R PDR

_ _ _ _ _ _ _ ~

. TECHNICAL REPORT 94-2 SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION FOR THE PERIOD APRIL-JUNE,1994 i

f BY PRADEEP TALWANI Principal Investigator and Robert Trenkamp 1

DEPARTMENT OF GEOLOGICAL SCIENCES .

UNIVERSITY OF SOUTH CAROLINA l COLUMBIA, SOUTH CAROLINA 29208 CONTRACT NO. N622702 i

INTRODUCTION Analysis of the seismic activity near the V.C. Summer Nuclear Station in South

  • Carolina between April 1 and June 30, 1994 is presented in this report. During this period, eight events were recorded in the vicinity of the M'onticello Reservoir. All eight events were located and were of relatively small magnitude.

SEISMIC NETWORK Earthquakes during this period were recorded on stations of Monticello Reservoir and South Carolina Seismic Networks. The configuration of stations utilized to locate Monticello Reservoir events is shown in Figure 1 and station coordinates are listed in Appendix I. The operational status of tha 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 ML OBSERVED SEISMICITY DURING APRIL-JUNE,1994 Seismicity around Monticello Reservoir was low during the second quarter of 1994.

Eight events were recorded and located (Figure 2). All events for the quarter were shallow and varied in depth between .15 and 2.2 km. The largest event occurred on April 9,1994 at 10:12:54 UTC and had a duration magnitude of 0.8 (Appendix V). Four small events occurred on April 30,1994 in a 36 minute period between 13:08:30 and 13:44:06 UTC (Appendix V). Three of the April 30th events occurred in a 3 minute mini burst northwest of MR01 (Figure 2). The majority of the events were located in the central area of the reservoir between Stations MR01 and MR10. The remaining events occurred on the northwest flank of the reservoir north and south of Station

. MR07 (Figure 2). Five of the event locations were of good quality while the remaining three event locations were of fair quality (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 d.aily 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 VI. No systematic correlation was observed between the seismicity and reservoir level fluctuations.

CONCLUSIONS Seismicity during the second quarter of 1994 was low and occurred generally in the central section of the reservoir, with the exception of the two events on the northwest flank. 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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Monticello Reservoir Seismic Network i

_ 34.4 MR07 MR10 MR01

_ 34.3

+

JSC MR05 5.0 km i t i I

___ 34.2 I

MR02 A I l l 81.4 81.3 81.2 A Single component

. $ 3 component Figure 1 Location of Monticello Reservoir seismic stations. f I

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3

s Monticello Reservoir Seismicity o

-81 23.O' 22.O' 21.O' 20.O' 19.O' 18.O' 17.O' 16.O' 15.O' t i  ! ' '  ! I i t

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FIVE KM -

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, i i , , i i i i Figure 2. Events located near Monticello Reservoir during the period April - June 1994 (stars) 4

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1650 MONTH _YSELSMICITY 2

800 --

i 700 --

600 --

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500 --

  • 6 400 --

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200 --

100 --

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i i e i 1977 1979 1981 1983 1985 1987 1989 1991 1993 Figure 3. Earthquakes between impoundment and June,1994.

- - - - - - . - .-n-- -r .~ n- +. ,- --- - - - , , - + . - , _ - - - - ---- ----- --__---_ - -____..__ - _- e

CUMULATNESEISMICITY

-- 8000 i

-- 7000

-- 6000 vs E

-- 5000 8 6

f --4000 $

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/ -- 2000 *

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, l l l l l l l l l l l l l l l l 0 1977 1979 1981 1063 1985 1987 1989 1991 1993 t

Figure 4. Cumulative seismicity near Monticello Reservoir since impoundment.

^ 425-424- [, E h.

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E 422- -

h421 420 91 102 113 124 135 146 157 168 179 E 1 I i , l k c i R l k ak 0 t Y \I b lY a

_g g Y\ N Y h iY Y E Y l b 1 91 102 113 124 135 146 157 168 179

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=0 91 102 113 124 135 146 157 168 179 e

. 15-m 5,12-c 9-  !

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c 3-b 0 91 102 113 124 135 146 157 168 179-APRIL 1994 / MAY1994 / JUNE 1994  ;

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 t bars in the top panel indicate daily fluctuations in water level.

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i APPENDIX I' ' -

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

MR01 34 19.91' 81 17.74' i

MR02 34 11.58' 81 13.81' .

MR05 34 16.05' 81 20.05' -!

MR07 34 22.23' 81 19.50'  ;

. MR10 34 20.18' 81 20.25' .;

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r h

r 6

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.m.- s.... ,,,, _ _ , -

. APPENDIX II SEISMIC STATION OPERATIONAL' STATUS APRIL 1 - JUNE 30,1994 i

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i STATION PERCENT DOWNTIME MR01 1.1 MR02 1.1  ;

MR05 3.3 MR07 1.1 MR10 1.1 JSC 1.1 ,

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APPENDIX III l

. j MONTICELLO RESERVOIR VELOCITY MODEL i

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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 I

8.10 30.00 l l

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1 10

. APPENDIX IV i

MONTICELLO EARTHQUAKES HYPO 71 FORMAT i

Column - 1 Date -

Column 2 Origin time (UTC) h.m.sec. j Column 3 Latitude (N) degrees, min. =

Column 4 Longitude (W) degrees, min.

I Column 5 Depth (km).  ;

Column 6 Local duration magnitude.  ;

Column 7 No. of station readings used to locate event. P and S i 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 = Ri 2/No, where Ri is the time residual for the ith ,

station.  ;

Column 11 Standard error of the epicenter in km*. f i

Column 12 Standard error of the focal depth in km*.

Column 13 Quality of the epicentrallocation. j

  • 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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11

,r . _ . .

APPENDIX V MONTICELLO RESERVOIR EARTHQUAKES '

APRIL - JUNE,1994 DATE ORIGIN LAT N LONG W DEPTH MAG NO GAP DMIN RMS ERH ERZ Q 940409 1012 54.96 34-19.71 81-19.48 1.48 0.78 10 119 1.5 0.04 0.2 0.4 B 940430 1341 13.83 34-20.64 81-18.37 2,17 -1.22 7 175 1.7 0.04 0.3 0.4 B 940430 1341 17.47 34-20.49 81-18.27 1.82 -0.40 10 173 1.4 0.03 0.2 0.2 B 940430 13 8 30.58 34-19.98 81-19.06 0.57 -0.40 8 103 1.9 0.10 0.5 1.5 B 940430 1344 6.70 34-20.78 81-17.84 1.81 -0.40 6 198 1.6 0.08 0.6 0.9 C 940510 1230 24.73 34-22.62 81-19.64 1.05 0.01 5 318 0.8 0.01 0.2 0.1 C 940511 513 33.97 34-20.02 81-19.93 0.25 0.68 10 119 0.6 0.06 0.3 0.9 B 940519 1011 19.15 34-20.99 81-20.43 0.81 -0.40 7 222 1.5 0.03 0.5 0.6 C F

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1 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 April 1 - June 30,1994. Dates are given in Julian Calendar.

J.DATE WL (max) WL (min) WL (avg) WL (ch) -

  1. of eqs Energy 91 4243 4227 423.6 -0.2 0 0 l 92 424.4 423.4 424.2 0.6 0 0 1 93 424.4 423.9 424 3 0.1 0 0 94 424.4 423 423.7 -0.6 0 0 95 424.6 4229 424.2 05 0 0 96 424.9 4235 424.2 0 0 0 97 4249 423.6 424 3 0.1 0 0 98 424 7 423.9 424.2 -0.1 0 0 99 424.1 4233 423 7 -0.5 1 12S7 100 424.1 423 423.6 -0.1 0 0 101 4245 422.5 423.4 -0.2 0 0 102 424.8 423 424 0.6 0 0 103 424.8 423.6 424.1 0.1 0 0 104 424.7 4233 424 -0.1 0 0 105 424.6 422.6 423.6 -0.4 0 0 106 424.9 422.8 424.2 0.6 0 0 107 424.7 424 4245 03 0 0 108 424.9 423.4 4243 -0.2 0 0 109 424.7 422.9 424 -03 0 0 110 424.9 421.5 423.6 -0.4 0 0 111 425 421.8 4235 -0.1 0 0 112 424.6 422.2 423.8 03 0 0 113 424.6 423.6 424.1 03 0 0 114 424 3 423.5 4239 -0.2 0 0 115 424.5 422.8 423.9 0 0 0 116 420.9 424.8 423.4 -0.5 0 0 117 424.6 421.2 423 -0.4 0 0 118 4247 421.7 4233 03 0 0 119 424.7 420.9 422.9 -0.4 0 0 120 424.9 421 423.9 1 4 8.17  ;

121 424.1 423.1 423.8 0.1 0 0 122 4249 423 3 424.5 0.7 0 0 123 4245 424 424.4 -0.1 0 0 124 4243 4233 424.1 -03 0 0 125 424.8 423.9 424.3 0.2 0 0 126 424.8 422.6 4233 -0.5 0 0 127 424.4 422.9 423.8 0 0 0 128 424.7 422.8 423.9 0.1 0 0

. 129 424.5 4229 423.7 -0.2 0 C' 130 424.6 423 423.9 0.2 1 11.82 131 424.6 421.7 423.4 -03 1 12B2 132 424.6 421 423.1 -03 0 0 133 425 421 3 424.1 1 0 0 13

. ~~.,,. .. .

APPENDIX VI (centinu:d)

J.DATE WL(max) WL (adn) , WL (avg) . WL (ch) # of eqs Energy 134 424 2 423 423.9 02 0 0 135 424 422 2 423 3 -0.6 _ , 0 0' 136 424.7 4225 423.6 03 0 0 137 425 422.9 424 0.4 0 0 138 4244 423 2 424.1 0.1 0 0 139 424.4 423.7 424 2 0.1 1 11.2 g 140 4243 422.9 423.8 -0.4 0 0-141 424.1 422.9 423.4 0.4 0 0 142 4241 422.5 '423.6 02 0 0 143 425 422.4 423.7 0.1 0 0 144 425 421.4 423.5 -02 0 0 145 425 422 42t1 0.6 0 0 146 424 2 422 4232 0.9 0 0 147 424E 422 3 4233 0.6 0 0 148- 424.9 4233 424.1 03 0 0 149 424.6 422.6 423.8 ' -03 0 0 f 150 424.9 422.8 424.1 03 0 0 151 424.9 423.7 424 3 02 0 0 152 425 421.6 423.8 -0.5 0 0

, 153 424.9 421.7 423.6 -0.2 0 0 154 425 4232 424.4 0.8 0 0 155 423.9 422.6 423.4 -1 0 0 156 424.7 422.8 424 0.6 0 0 157 424.9 423.1 4239 -0.1 0 0 3 158 424.1 423.1 423.6 -03 0 0 159 4245 421.5 423.4 -(.2 0 0 160 424.7 421J 424 2 0.8 0 0 1 61 424.7 424 4245 03 0 0  ;

162 425 4235 4245 0 0 0 163 424.8 4233 424.4 0.1 0 0 164 425 4211 423.6 -0.8 0 0 165 424.9 420.5 423.1 -0.5 0 0 166 424.9 420.8 422.9 -02 0 0  ?

167 425 421 3 4233 0.4 0 0  ;

168 425 422.1 423.4 0.1 0 0 ,

169 425' 422.7 424.4 1 0 0 170 424.8 423.7 424 3 -0.1 0 0 1 71 424.9 4205 423 3 -1 0 0 172 425 420.8 423 -03 0 0  !

1 73 425 420.6 422.9 -0.1 0 0 174 425 420.8' 423.1 02 0 0 _(

175 425 421.9 423.6 05 0 0

, 176 424.4 423 2 4.24 0.4 0 0 1 177 424.7 - 423 3 423.9 0.1 0 0 178 424.9 423.4 424 3 0.4 0 0 179 424.8 422 423.7 -0.6 ' O O 180 424.8 422.5 4242 0.5 0 0 181 4245 424 424 3 0.1 0 0 14

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