ML20245K723

Technical Rept 89-1 Seismic Activity Near VC Summer Nuclear Station, for Jan-Mar 1989

ML20245K723
Person / Time
Site:	Summer
Issue date:	03/31/1989
From:	Talwani P SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC
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89-1, NUDOCS 8907050231
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SEISMIC. ACTIVITY NEAR l

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THE V.C. SJMMER NUCLEAR STATION '

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January - March 1989 by  ;

4 Pradeep Taiwani Principal investigator Department of Geological Sciences l

University of South Carolina Columbia, SC 29208 9

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Contract No. N482355 '

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. TECHNICAL REPORT 89-1 1,.

SEISMIC ACTIVITY NEAR I' THE V.C. SUMMER NUCLEAR' STATION u.

. FOR THE PERIOD JANUARY-MARCH 1989 BY PRADEEP TALWANI PRINCIPAL INVESTIGATOR KEVIN SEVERANCE DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF SOUTH CAROLINA COLUMBIA, S.C. 29208 CONTRM.'T NO. N482355 00

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,: INTRODUCTION J Analysis of the seismic activity near the V.C. Summer Nuclear Station in South Carolina between January 1 and March 31, 1989 is -

i presented in this report. During this period a total of twenty-five events were-recorded, all of which'were located. The largest shock was of magnitude 0.2 and occurred on January 3 at 2050 UTC. Only two earthquakes had magnitudes greater than zero.

One shock was of A quality and located at a depth of approxi-mately 0.2 km. Thirteen shocks were of B quality and varied in depth from 0.4 to 4.3 km.

SEISMIC NETWORK-Earthquakes recorded during this period were located using stations of the Monticello Reservoir and South Carolina networks.

The configuration of the stations utilized to locate the events in this report is shown in Figure 1 and station coordinates are listed'in Appendix I.

DATA ANALYSIS Hypocentral locations of the events were determined using the computer program u"P071 (Lee and Lahr, 1972) and the velocity model listed in Appondix II. The event magnitude (M n) was deter-mined from the signal duration at station JSC, using the following relation:

ML = -1.83 + 2.04 Log D- ,

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' where D'is the signal duration (seconds).

l An estimate of daily energy release was determined using a simplified magnitude (Mg) energy (E) relation by Gutenberg and

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MONTICELLO RESERVOIR J'

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CAROUNA 2A Figure 1. Location map of Monticello Reservoir area showing seismic stations used in locating activity during this period.

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Richter (1956):

Iog 0 E = 11.8 + 1.5 M g .

i OBSERVED SEISMICITY FOR THE PERIOD JANUARY-MARCH 1989 During this period twenty-five events were recorded. all of I which were located (see Appendix III). This level of activity was similar to that observed during the previous reporting period, and the long-term dec1dne in seismicity is continuing (Figure 2). The largest event of this quarter (M =0.2) g occurred on January 3 at 2050 UTC.

The epicenters of. earthquakes located during this quarter and during each month are presented in Figures 3, 4, 5, and 6.

Figure 7 shows the locations of the A and B quality events. The majority of the earthquakes during this period occurred in Jan-uary and March. Temporal clustering of tun microevents was observed on March 29, 1989. Fourteen earthquake locations were of quality B or better. The improved quality and completely suc-cessful location of all recorded events is a result of the analy-sis of tape playbacks of seismograms. These events were located between depths of 0.2 km and 4.3 km.

CORRELATION OF RESERVOIR WATER LEVEL WITH SEISMICITY Monticello Reservoir is a pumped storage facility. Any de-crease in reservoir level associated with power generation is recovered when water is pumped back into the reservoir. There can be normal variations up to approximately five feet per day l between the maximum and minimum water level. We have been moni-toring the water level to see if there is any correlation between 1

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the daily or seasonal changes in the reservoir level and the local seismicity. Water level is compared with seismicity in Figure 8. The top plot shows the median water level. The second plot from the top has been changed to show the change in-average water level each day. The number of events per day and the log of the energy released per day are shown in the lower two histo-grams. There is no apparent correlation between the change in median water level or daily water level fluctuations and seis-micity during this quarter.

CONCLUSIONS The level of activity observed during the first quarter of 1989 was low and not significantly different from that observed

-during the fourth quarter of 1988. The largest event was of magnitude 0.2. The fourteen quality B or better earthquake loca-tions range in depth from J.2 to 4.3 km.

REFERENCES Gutenberg, B. and Richter, C.P. (1956). Magnitude and energy of earthquakes, Ann. Geof. 9 .- pp . 1-15.

Lee, W.H.K. and Lahr, J.C. (1972). A computer program for deter-mining hypocenter, magnitude and first motion pattern of local earthquakes, Revisions of HYPO 71, U.S. Geological Survey Open-File Report, 100 p.

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l APPENDIX I

' STATION LOCATIONS t 1

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l' JSC 34* 16.80' 81* 15.60' L-l 2' 001 34* 19.91' 81* 17.74' 1 3 002 34* 11.58' 81* 13.81' l

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.- MONTICELLO-RESERVOIR-

,. . VELOCITY MODEL 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 et 8

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, APPENDIX III MONTICELLO EARTHQUAKES JANUARY-MARCH 1989 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 frca same stations are regarded as 2 readings. l Column.8 Largest azimuthal separation in degrees between stations.

Column 9 Epicentral distance in km to nearest station.

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Column 10 error of time residuals in Root sec. mean RMS squarg/NO,

= R where R g is the time residual for t e ith station Column 11 Standard error of the epicenter in km*.

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

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• Statistical interpretation of standard errors involves assump-tions.which may not be met in earthquake locations. Th'erefore standard errors may not represent actual error limits.

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

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MONTICELLO EARTHQUAKES

j. JANUARY-MARCH 1989 DATE ORIGIN LAT N LONG W DEPTH MAG NO GAP DMIN RMS ERH ERZ QM 890103 2050 27.75 34-19.98 81-18.40 1.77 0.21 20 93 1.0 0.03 0.1 0.1 B1 890103 2130 58.74 34-20.01 81-17.83 1.88 -0.36 14 175 0.2 0.01 0.0 0.1 B1 890109 0733 38.33 34-21.01 81-19.60 1.76 -0.77 11 151 1.8 0.00 0.0 0.0 B1 890111 2314 2.55 34-20.39 81-19.18 0.98 -0.60 9 120 1.7 0.00 0.0 0.0 B1 890112 0325 40.68 34-20.01 81-18.02 1.78 -0.32 13 142 0.5 0.01 0.0 0.0 B1 890112 0728 6.16 34-20.08 81-19.56 1.13 -0.86 8 145 1.1 0.00 0.0 0.0 B1 890120 1843 5.07 34-19.66 81-18.61 0.43 -0.86 8 155 2.7 0.01 0.0 0.1 B1 890123'0417 2.78 34-19.67 81-18.58 0.17 -0.86 13 88 1.4 0.00 0.0 0.0 A1 890128 1104 12.39 34-20.73 81-19.18 2.72 -0.86 12 134 1.9 0.00 0.0 0.0 B1 890130 1906 44.24 34-20.51 81-19.53 2.36 -0.68 13 120 1.3 0.00 0.0 0.0 B1 890131 1752 10.23 34-20.08 81-17.91 4.32 -0.86 12 172 0.4 0.03 0.1 0.2 B1 890206 0203 33.43 34-19.99 81-19.39 1.85 -0.46 8 150 1.4 0.00 0.0 0.0 B1 890210 1450 58.10 34-21.45 81-18.84 1.51 0.08 14 109 1.8 0.02 0.1 0.2 B1 890313 1020 13.35 34-20.01 81-17.52 1.81 -0.24 6 190 0.4 0.02 0.2 0.2 C1 890314 0635 42.84 34-19.95 81-17.71 2.09 -0.11 6 184 0.1 0.01 0.1 0.1 C1 890329 0145 49.32 34-20.21 81-18.66 1.78 -0.60 12 235 2.4 0.02 0.1 0.3 C1 890329 0300 45.97 34-19.53 81-19.13 1.78 -0.95 6 188 2.1 0.02 0.2 0.4 C1 890329 0327 23.61 34-20.03 81-17.45 3.39 -0.86 4 241 4.3 0.00 -- --

C1 890329 0344 33.01 34-14.58 81-18.13 5.09 -0.50 6 290 5.5 0.03 0.2 0.4 C1 890329 0530 25.40 34-20.32 81-19.61 2.40 -0.86 10 241 1.0 0.01 0.1 0.1 C1 890329 0555 18.07 34-20.41 81-18.37 1.86 -1.22 11 175 2.9 0.01 0.0 0.1 B1 890329 0555 27.40 34-19.79 81-18.48 0.94 -0.86 9 217 2.8 0.02 0.2 1.6 C1 890329 0654 23.90 34-19.43 81-18.36 1.12 -0.86 10 203 3.2 0.01 0.0 0.2 C1 890329 0654 30.14 34-19.92 81-18.56 1.76 -0.86 10 221 2.6 0.05 0.3 0.8 C1 890329 0654 34.21 34-16.15 81-20.14 1.00 -0.86 12 218 0.2 0.01 0.1 0.1 C1 m_____m _ _ . . __ _ _ _ _ _ _ . _ _ .