ML20046A058

Technical Rept 93-1, Seismic Activity Near VC Summer Nuclear Station for Jan-Mar 1993.

ML20046A058
Person / Time
Site:	Summer
Issue date:	03/31/1993
From:	Rajendran K, Talwani P, Ulmer K SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC
To:
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ML20046A057	List: ML20046A056 ML20046A058
References
93-1, NUDOCS 9307260035
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l TECHNICAL REPORT 93-1 O

s SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION l

FOR THE PERIOD JANUARY - MARCH,1993 BY I

PRADEEP TALWANI Principal Investigator l

1 i l DEPARTMENT OF GEOLOGICAL SCIENCES ,

UNIVERSITY OF SOUTH CAROLINA COLUMBIA, SOUTH CAROLINA 29208 Q

CONTRACT NO. N622702 O

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TECHNICAL REPORT 93-1 SEISMIC ACTIVITY NEAR THE-V.C. SUMMER. NUCLEAR STATION FOR THE PERIOD JANUARY - MARCH,1993 DY PRADEEP TALWANI Principal Investigator l

and Katherine Ulmer and Kusala Rajendran DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTH CAROLINA COLUMBIA, SOUTH CAROLINA 29208 G

CONTRACT NO. N622702

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l INTRODUCFION Analysis of the seismic activity near the V.C. Summer Nuclear Station in South Carolina between January 1 and March 31,1993is presented in this report. During this period, eleven events were recorded in the vicinity of the Monticello Reservoir. Seven of the eleven were located. Two of these werelocated outside the Monticello Reservoir area and were identified as blasts at Blair quarry. These two were located routinely but are not included in the analysis of seismicity. Mt = 1.0 was the largest magnitude

. recorded by two different events.

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 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 output is given in Appendix IV. The event magnitude was determined from the signal duration at JSC using the following relation:

M L= -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 (Mt ). I energy (E) relation by Gutenberg and Richter (1956): )

Logio E = 11.8 + 1.5 Mt OBSERVED SEISMICITY DURING JANUARY - MARCH,1993 Seismicity around Monticello Reservoir was generally low during this period.  ;

Excluding the two blasts, nine events occurred during the quarter; four in January, j three in February and two in March. Of these nine events, five were located and rated i good to poor quality (B-D) (Figure 2, Appendix V). The two blasts were located as well. I The largest events with magnitude of M =t 1.0 occurred on February 19 at 20:51:48 UTC and on March 22 at 18:55:10 UTC. The February 19 event was located off of the northwestern bank of Monticello Reservoir. The March 22 event occurred southeast of

, the lake. The next largest event with magnitude (Mt = 0.8) occurred on January 11 at 22:27:43 UTC. The remaining two located events were small Mt <0. The long term decline in seismicity observed at Monticello Reservoir is continuing (Figure 3). The cumulative seismicity at Monticello Reservoir has shown relative flattening since 1985-86 (Figure 4).

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4 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 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 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 reservoir level fluctuations.

CONCLUSIONS Seismicity during the first quarter of 1993 was low (1.0 2 Mt 2 - 0.4), yet it occurred continuously throughout the quarter. The earthquakes did not cluster in any one location. No systematic correlation was observed between the reservoir level fluctuations and the seismicity. j 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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1977 1979 '1981 1983' '1985 1989 [99j ^ O Figure 4. Monthly seismicity (bars) and cumulative seismicity (line) near Monticello Reservoir smce impoundment.

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. JANUARY / FEBRUARY / MARCH 1993 1993 1993 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 panel indicate daily fluctuations in water level.

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APPENDIXI' I STATION LOCATIONS' l l

STATION LAT N LONG W  !

JSC 34 16.80' '81 15.60' l 1

MR01. 34 19.91' 81 17.74' {

MR02 34 11.58' '81 13.81' MR05 34 16.05' - 81 20.05'

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APPENDIX II  !

1 SEISMIC STATION OPERATIONAL STATUS l

JANUARY 01 - MARCH 31,1993 )

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STATION PERCENT DOWNTIME MR01 9.4 l i

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APPENDIXIII MONTICELLO RESERVOIR VELOCITYMODEL 9

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 4

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APPENDIXIV l

MONTICELLO EARTHQUAKES 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 locate event. P and S arrivals from same stations are regarded as 2 readings.

Column 8 Largest azimuthal separation in degrees between I stations.

I Column 9 Epicentral distance in km to nearest station.

i 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 epicentrallocation.

• 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 j ,

insufficient data.

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i APPENDIX V MONTICELLO RESERVOIR EARTHQUAKES JANUARY-MARCH,1993 I

l ORIGIN LAT N LONG W . DEPTil MAG NO GAP DMIN RMS ERH .ERZ OM DATE 930111 2227 43.49 34-10.98 01-19.03- 3.64 0.82 7 120 2.3 0.04 0.3 0.5 D1 0.24- -0.40 12 120 3.2 0.0G. 0,3 0.9 01 l

930112 043 25.39 34-17.52 81-18.93 I.94 '-0,Il 4 307 U.2'U.04 CI' 930211 1730 40.55 34-22.3J 81-19.00 0.82 1.02/ 6 282 -2.2-0.08' 9.8- 8.1 D1 i

! 930219 2051 47.72 34-22.33. 81-20.95 3.44 0.82 8 339 7.2 0.03~0.6 0.6 Cl*

l- 930219 21 3 39.42 34-25.0G 81-22.71 G.55 0.57 8 341 7.4 0.08 1.0 .0.8 Cl*- ,

930318 1753 15.0G 34-25.25 H1-22.72

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030322 1855 9.95 34-17.90 81-16.00 0.42 1.02'10 199 2.1 0.08 0.5- 0.8 C1 ,

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l APPENDIX VI i

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Events with S-P s 2.5 s recorded around Monticello Reservoir during January -

! March,1993.

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No DATE STATION P-Arrival S-P Ep. Dist(km) DUR MAGL f '

Hr min sec - SEC -(S-P)X8.5 SEC i

1 93 01 04 JSC 06:46 59.0 1.5 .12.8 12 0.37 2 93 01 11. JSC 23:47 53.5 0.6 - 5.1 5 0.4 3 3 93 02 05 JSC 10:89 06.0 0.8 6.8 '4 -0.6

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APPENDIX VII Maximum and minimum water levels, change in water level, number of earthquakes and 10g of energy release per day at Monticello Reservoir during January 1 - March 31,1993. Dates are given in Julian Calender.

DATE WL(max) WL(min) WL(avg) WL(ch) #3s Log E 1 424.6 423.7 424.3 0 0 2 424.6 423.1 423.9 0.4 0 0 3 423.1 422.8 423 -0.9 0 0 4 423.9 423 423.8 0.8 1 12.36 5 424.7 423.4 423.8 0 0 0 6 424.6 423 423.7 -0.1 0 0 7 423.8 423 423.5 -0.2 0 0 8 423.7 4232 423.5 0 0 0 9 424 423.3 423.5 0 0 0  ;

10 423.4 423.1 423.3 -02 0 0 11 423.9 423.3 423.7 0.4 2 13.04 l 11.2 12 423.7 422.9 423.3 -0.4 1 j

13 424.2 423.2 423.8 0.5 0 0 l

14 423.8 422.8 423.3 -0.5 0 0 i l

15 423.5 422.7 423.1 -0.2 0 0 l 0 16 423.3 422.7 423.1 0 0 l l 17 423 422.6 422.8 -0.3 0 0 18 423.8 422.6 423.4 0.6 0 0 19 423.8 4232 423.6 0.2 0 0

! 20 424.4 423.2 424 0.4 0 0 21 424.8 424 424.5 0.5 0 0 l 0 0 22 424.5 424.1 424.2 -0.3 l

23 424.1 423.9 424 -0.2 0 0 l

24 424.1 423.8 423.9 -0.1 0 0 25 424.4 423.5 423.9 0 0 0 26 424.9 423.5 424.5 0.6 0 0 27 424.8 423.8 424 2 -0.3 0 0 28 424.8 423.5 424.3 0.1 0 0 29 424 2 424 424.1 0.2 0 0 0 0  !

30 424 422.9 423.5 -0.6 31 424 2 422.1 423.5 0 0 0 32 424 2 423.6 424 0.5 0 0 33 424.3 424 424.2 0.2 0 0 34 424.9 424.2 424.5 0.3 0 0 35 424.8 424.3 424.5 0 0 0 36 424.5 423.8 424.1 -0.4 1 10.89 37 424.4 423.5 423.9 -0.2 0 0 38 423.8 423.3 423.6 -0.3 0 0 39 425 424.4 424.5 0.9 0 0 40 424.9 423.6 424.4 -0.1 0 0 41 424.1 423.6 423.9 -0.5 0 0 42 423.9 423.6 423.8 -0.1 1 11.64 43 424.1 423.6 423.9 0.1 0 0 l

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APPENDIX VII(continued)

DATE WL(max) WL(min) WL(avg) WL(ch) # eqs Log E 44 423.8 423.5 423.6 -0.3 0 0

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45 423.5 423.4 423.4 02 0 0 46 423.4 422.8 423 -0.4 0 0 47 424.7 423.1 424.3 1.3 0 0 48 424.3 423.6 423.9 0.4 0 0 49 423.9 423.5 423.9 0 0 0 50 424.9 423.8 424.2 0.3 1 13.33 51 425 424.2 424.1 -0.1 0 0 52 424.7 424 424.3 0.2 0 0 53 424.8 424 424.3 0 0 0 54 424.7 424.1 424.4 0.1 0 0 55 424.7 423.9 424.2 -0.2 0 0 56 425 423.8 424.2 0 0 0 57 425 424 424.7 0.5 0 0 58 424.7 424.1 424.4 -0.3 0 0 59 424.1 423.8 423.9 -0.5 0 0 60 424.8 423.7 423.9 0 0 0 61 424.9 423.8 424.3 0.4 0 0 62 424.4 423.8 424 -0.3 0 0 63 424.9 423.2 423.9 -0.1 0 0 64 424.9 423.4 424.6 0.7 0 0 65 424.8 424.3 424.7 0.1 0 0 66 424.7 424.4 424.5 -0.2 0 0 67 425 424.3 424.5 0 0 0 l 68 424.8 424.2 424.4 -0.1 0 0 !

69 424.5 423.1 423.9 -0.5 0 0 I 70 424.5 423.5 4242 0.3 0 0 71 424.8 423.4 423.8 -0.4 0 0 72 424.9 423.4 424.5 0.7 0 0 73 424.8 424.6 424.7 0.2 0 0 i 0

0 74 424.7 424.5 424.7 O 75 424.5 423.5 423.9 -0.8 0 0 76 424.4 423.7 424.1 0.2 0 0 77 424.3 423.5 423.9 -0.2 0 0 78 423.6 422.5 422.9 -1 0 0 79 423.5 422.5 423.4 0.5 0 0 80 4242 423.5 423.9 0.5 0 0 81 424.6 424 424.3 0.4 2 13.33 82 424.2 423.8 423.9 -0.4 0 0 83 424.5 423.9 424.25 0.35 0 0 84 424 424 424 -0.25 0 0 85 424 424 424 0 0 0 86 424 423.9 423.9 -0.1 0 0 87 423.9 423.7 423.8 -0.1 0 0 88 423.7 423.4 423.7 -0.1 0 0 89 423.4 423 423.3 -0.4 0 0 90 423.9 4232 423.8 0.5 0 0 15

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