ML20059D702

Technical Rept 90-02, Seismic Activity Near VC Summer Nuclear Station for Apr-June 1990

ML20059D702
Person / Time
Site:	Summer
Issue date:	06/30/1990
From:	Talwani P SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC
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ML20059D696	List: ML20059D691 ML20059D702
References
90-2, NUDOCS 9009070148
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TECHNICAL REPORT 90-2 5

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SEISMIC ACTIVITY NEAR

THE V.C. SUMMER ~ NUCLEAR STATION i

For the Period Apes 1-June 30,1990 by .

Pradeep Taiwani .

Principal. investigator Department of Geolagical Sciences University of South Carolina  :

Columbia, SC 20208

s-q- 1 Contract No. N482355 9009070148 90082>

PDR R ADOCK 05000392 PDC ,

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TECHNICAL REPORT 90-2 i

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SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION  !

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FOR THE PERIOD j APRIL - JUNE 1990 l

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PRADEEP TALWANI PRINCIPAL INVESTIGATOR  ;

KUSALA RAJENDRAN ADIT MUTHANNA b

DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTH CAROLINA '

l COLUMBIA, SC 29208 l

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, CONTRACT NO. N482355 l 1

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INTRODUCTION Analysis of the seismic activity near t^e V.C. Summer Nuclear Station in South Carolina between AI,ril 1 and June 30, 1990, is presented in this report. During this period, twenty events were recorded in the vicinity of Monticello Reservoir, eight of which were located. The largest shock was of magnitude (Mg ) 1.3 i which occurred on May 16, at 14: 47:13.15 UTC.  ;

1 SEISMIC NETWORK J

Earthquakes during this periot 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 stations is given in Appendix II.

During the past few months some of the Monticello stations were down, however most of these have now become operational. Efforts are being made to make the remaining stations fully operational.

DATA ANALYSIS i l

Hypocentral locations of the events have been determined using the computer program HYP071 whose format _is listed in Appenix IV (Lee and Lahr, 1972). The velocity model used in earthquake locations is given in Appendix III. The event magni-tude 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 dall;' energy release was determined using a l

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simplified magnitude (M g ) energy (E) relation by Gutenberg and Richter (1956):

Log1 0 E = 11.8 + 1.5 Mg.

OBSERVED SEISMICI7Y TOR THE PERIOD APRIL - JUNE 1990 During this period twenty earthquakes were recorded, of which eight were located (Appendix V). The other events were within 5.1 km of the station JSC (Appendix VI). The events which we were able to locate were of poor quality (C and D). Most of the evento occurred during May (16 events). The largest event 1 of this quarter was of magnitude (M n) 1.3 which occurred on May '

16 (14:47:13.15 UTC). This event occurred in the northern part of the reservoir (Figure 2). There were tuo more events o* magnitude

~1.2 (May 19, 06:43:10.43 UTC; June 07, 16:44:34.53 UTC).

The seismic data for this period is comparable to that of the previous quarter in number as well as magnitude level. The long term decline in seismicity is continuing (Figure 3).

CORRELATION OF RESERVOIR WATER LEVEL WITH SEISMICITY i Monticello Reservoir is a pumped storage facility. Any decrease in reservoir level associated with power generation is j recovered when water 1. pumped back into the reservoir. There can be normal variations up to approximately five feet per day j between the maximum and minimum water levels. The water level has been monitored to see if there is any correlation between the 1 daily or seasonal changes in the reservoir level and the local I

seismicity. ' Water level is compared with seismicity in Figure 4.

The top plot show the average water level; the error bars show the maximum and minimum water levels each day. The second plot 3

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Figure 2 Earthquakes located near Monticello reservoir during April-June 1990.

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$ 0.0 90 091 90 106 90.121 90.136 ,90.151 90.166 90.181 Figure 4. _ Comparison of daily lake level, Variation in lake level number of earthquakes and log of energy release (ergs per day) at Lake Monticello. Error bars in the top diagram indicate daily fluctuations in water level.

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shows the change in average water level from day to day. The number of events per 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.

No definite correlation was observed between the seismicity and the lake level fluctuations. Interestingly, the periods of large energy release (May 04-06; May 16-19; May 24-26; June 07) appear to occur at times of increased rates of water level '

changes.

CONCLUSIONS The level of seismic activity during the second quarter of 1990 was low and comparable to that of the previous quarter.

Sixteen of the twenty recorded earthquakes during this quarter occurred in May 1990. The largest event was of magnitude (ML ) 1.3, on May 16. There were two other events of magnitude (Mg ) *

1.2 REFERENCES

Gutenberg, B. a.id Richter, C.F..(1956). Magnitude and energy'of earthquakes, Ann. Geof. 9, 1-15.

i Lee, W.M.K. and Lahr, J.C.(1972). A computer program for determining hypocenter, magnitude and first motion. pattern of local earthquakes, revisions of HYP071, U.S. Geological ,

Survey, Open-File Report, 100 pp.

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I APPEKDIX I

, STATION LOCATIONS NO. STN. LAT.*N LONG.*W 1 JSC 34' 16.80' Bl* 15.60' 2 001 34* 19.91' 81* 17.74' 3 002 34* 11.58' 81* 13.81' 4 of,o 345 16.05' 818 20.05' 5 007 34* 22.23' 81* 19.50' 6 010 34' 20.18' Ba* 20.25' 7 09A 34* 17.24' 818 19.75' i

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APPENDIX II SEISMIC STATION OPERATIONAL STATUS APRIL 01 - JUNE 30 1990 a

STATION PERCENT DOWNTIME JSC 1%

001 0%

002 19%

005 61%

007 28%

010 15%

09A 60%

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APPENDIX III MONTICELLO RESERVOIR VELOCITY MODEL Ve3ocity 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 G

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APPENDIX IV

, MONTICELLO EARTHQUAKES HYP071 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 stations. .

Column 9 Epicentral distance in km to nearest station.

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Column 10 Root mean square error of time residuals in sec. RMS = R2/NO, where R is the time residual for t e ith station Column 11 Standard error'of the epicenter in km*. 1 Column 12 Standard error of the focal depth in km*.'

• Statistical interpretation of standard errors involves assump- a 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, i

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l APPENDIX V MONTICELLO EARTHQUAKES APRIL-JUNE 1990

, DATE ORIGIN LAT N LONG W DEPTH MAG NO OAP DMIN RMS ERH ERZ QM 900402 0510 56.97 34-19.07 81-17.84 3.64 -0.11 4 225 1.6 0.10 C1 900506 1141 03.62 34-16.90 81-17.21 1.00 -0.40 3 185 2.5 0.05 C1 900516 1447 13.15 34-22.33 81-19.21 1,69 1.32 4 264 0.5 0.05 C1 900519 0627 17.22 34-22.33 81-19.60 1.00 0.21 5 352 0.2 0.1R D1 900519 0643 10.43 34-23.24 81-19.04 1.64 1.18 4 315 2.0 0.09 C1 900526 0319 50.01 34-18.77 81-17.84 2.67 0.02 4 202 2.1 0.09 C1 900526 0340 37.72 34-19.57 81-17.84 1.54 0.21 4 227 0.6 0.07 C1 900607 1644 34.53 34-20.19 81-17.84 1.00 1.18 3 347 0.5 0.02 C1 I b

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APPENDIX VI LIST OF EVENTS WITH S-P ( 2.5 SEC RECORDED AROUND MONTICELLO DURING 1 APRIL 1990 - 30 JUNE 1990 DATE STATION P-ARRIVAL TIME S-P EP.DIST DUR MAG H MIN SEC SEC s-p*8.5km SEC 90 04 03 JSC 01 17 35.61 0.30 2.6 1.5 -1.2 90 05 04 JSC 23 47 03.50 0.60 5.1 3.5- -0.6 90 05 05 JSC 00 19 11.80 0.30 2.6 3.5 -0.6 JSC 15 39 34.35 0.40 3.4 3.6 -0.6 JSC 15 43 24.60 0.40 3.4 3.5 -0.6 JSC 15 47 20.00 0.30 2.6 3.6 -0.6 90 05 24 JSC 11 22 25.10 0.40 3.4 15.0 0.6 JSC 12 03 11.70 0.12 1.0 1.0 -1.8 90 05 26 JSC 03 07 18.30 0.10 0.9 2.0 -1.2 JSC 03 42 23.15 0.10 0.9 1.2' -1.8 JSC 04 34 47.50 0.10 0.9 2.5 -0.9 90 06 15 JSC 11 11 13.00 0.30 7.6 2.3 -1.2 s

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