ML20098B684

Seismic Activity Near VC Summer Nuclear Station, Quarterly Rept,Apr-June 1984

ML20098B684
Person / Time
Site:	Summer
Issue date:	06/30/1984
From:	Talwani P SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC
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ML20098B679	List: ML20098B677 ML20098B684
References
84-2, NUDOCS 8409260218
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- .

TECHNICAL REPORT 84-2 SEISMIC ACTIVITY NEAR l

THE V.C. SUMMER NUCLEAR STATION For the Period April - June 1984 l

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by Pradeep Taiwani Principal Investigator Geology Department University of South Carolina Columbia, S.C. 29208 Contract No. N355486 I

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Technical Report 84-2 -

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. SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION For the Period April - June 1984 if

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Pradeep.Talwani Principal Investigator and Jill Rawlins Research Assistant Geology Department University of South Carolina Columbia, S.C. 29208 .

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Contract No.-N230519 4

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-Introduction- .

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- TIiis report, presents a summary of seismic activity near the V.C.

-Summer Nuclear Power Station in South Carolina for the three month period

-between' April'l and June 30, 1984. During this reporting period, a .

. total of 49 locatable events were recorded. fone of.the events had magnitudes greater than 2.0 and seven events had magnitudes between

1.0 and 2.0. The largest event occurred on May 11 and had a magnitude

of 1.8.

Seismic Network.

- -The report is based on the data recorded by the four-station net-work operated'by S.C.E.&G. In addition, data from the permane'nt stations,

~

JSC, 06 A, and 008, were also used. Locations of these stations are shown

-in Figure 1, and their coordinates are listed in Appendix I.

Data Analysis-Location of the events is determined using HYP071 program (Lee and Lahr,1972) and the velocity medel given in Appendix II. The event mignitude (ML ) is detenritned from signal duration at ctation JSC, using

' the following relation:

M = -1.83 + 2.04 Log D where D is the signal duration (seconds).

An estimate of daily energy release is determined using a simpli- ,,

.fied magnitude'(Mg )' energy (E) relation by Gutenberg and' Richter (1956).

log 10E = 11.8 + 1.5 M L If i

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'Results .

, The 49. located events recorded during this period are listed in

'Appendi x - III . .There were no events with magnitudes greater than 2.0.

The'seven events with magnitudes between 1.0 and 2.0 are listed in i

Table 1, and the remaining events were smaller.

Table 1 Date Magnitude April 27 1.0 May 11 1.8 May 11 1.3 May 17 1.0 May 19 1.3 May 20 1.3 June 20 1.2 Most of the seismic activity for the reporting period occurred during May in ~a broad east-west band across the central part of Monticello Reservoir. Depth estimates for all located events indicate that approximately 94% of the seismicity occurred within two kilometers of the surface. A comparison of depth variations based on quality B or better events for this-recording period combined with the previous three months and for the past five years is shown in Figure 2. The depth ranges were divided 'into half kilometer increments up to 3.0 km, and events occurring at greater depths were grouped together. The ,

largest percentage of events occurred in the 1.5 to 2.0 km increment every year. None of the activity in 1984 occurred at depths greater than.3.0 km; the deepest event was at 2.4 km.

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A cumulative plot of epicenters of events located during this period .

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is shown i.UFigure 3 and.a cross section of events located within one

' kilometer of line AA' is shown in . Figure 4. Separation of epicentral

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1 ilocations' by month is shown in Figures 7.

.r Reservoir Water Level:and its Comparison with Seismicity Monticello Reservoir is a pumped storage facility. Any decrease in-

reservoir level associated with power generation is recovered when water is pumped back into the reservoir. There can be variations up to about five feet per day between the maximum and minimum waterilevel. We have been monitoring this water level to see if there is any correlation be-  ;

.. tween the daily or ~ seasonal changes. in the. reservoir level and the local seismicity. Figure 8 shows the comparison of water level'to seismicity.

1Thettop two; graphs.show the water level and the change of water level s

.per day. The, number of events per day and log of energy released per

- . day are shown on the lower two graphs. The histograms showing events

. per day' and log of energy release include the unlocated events e.round the reservoir.

Conclusions

- Seismic _ activity in the Monticello Reservoir area generally occurs in a long term trend of. discrete swarms separated by relatively quiet pcriods. Figure 9 is a histogram of-the number of events per month from December,1977, through June,1984. The swarm of activity in May,-

1984 preceded by a low level of seismicity is consistent with the long .

term trend. The general level of activity continues to decrease, no

- . increase in depth is noted, and the spatial extent for this period is il 4

confined within the reservoir.

MONTICELLO EARTHOUAKES RPRIL - JUNE 1984 .

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' References

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Gutenb%rg,:'B. and Richter, C.F. (1956). Magnitude and energy of earthquakes , . Ann. Geof. 9, p.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 HYP071, U.S.G.S. Open-File Report, .

100 pp.

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u- APPENDIX I STATION LOCATION

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.NO. , SJyl., LAT. N. LONG. W.

1 001 34 19.91' 81 17.74' 2 ' 002 340 11.58' 81 13.81'

'3 003 '34 21.09' 810 27.41' 4 004' 340 25.72' 810 12.99'

. JSC- 340 16.80' 810 15.60' 6 008' 34 24.53' 810 24.55'

-7 06A- 34 17.32' 81 18.15' e

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u APPENDIX II MONTICELLO RESERVOIR VELOCITY.MODEL.

s Velocity. Depth km/sec km

-1.00' O.00

5. <40 0.03 .

0 5.90 0.18 6.10 0.46 6.30. 0.82 g H8.10 30.00

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DATE nRTGIN LA7 N LOf1G W DEPTH MAG NO GAP DMIN RMS ERH ERZ QM

840401 2349 44.41 34-20.26 91-18.60 0.18 40 8 245 1.5 0.09 0.8 1.1 C1 1- 840419 2051 17.52 34-17.52 81-19.M9 1.96 -00 29 7 160 5.5-0.05 0.3 1.5 81 840427 1048 46.11 34-19.31 81-19.71 0.22 0.87 10 138 3.2 0.07 0.3 0.7 81 1.02 5 271 9.0 0.02 1.2 C1

! 840427 2017 56.6B 34-16.2J 81-21.52 0.08 1.1 j 840428 147 2.63 34-19.35 71 0.99 -0.24 7 137 3.2 0.03 0.2 1.2 $4 840428 333 31.18 34-19.01 81-19 55 0.04 -0.40 7 134 2.1 0.07 0.3 1.0 el 840428 828 30.36 34-19.01 81-18 56 0.29 -0.86 5 140 3.2 0.09 1.1 3.4 C1 4'

840429 021 20.02 34-19.64 81-19 54 81-19 1.19 0.44 8 152 2.8 0.06 0.3 1.1 81 4

840504 1720 37.57 34-19.k5 81-18.11 o.21 -0.60 7 239 .6 0.09 0.9 1.1 C1 i 840510 148 16.81 34-19.77 61-10.48 2.28 0.01 8 131 7 0.03 0.1 0.3 81 840510 717 17.74 34-20.01 81-19.67 1.67 -0.24 88 130 0 0.08 4 L.0 B1 1

840511 2011 36.00 34-19.8$ 81-19.76 1.74 1.83 150 .1 0.09 05

0. -.3 B1 i 840 11 2043 44.84 34-1 84 36 1.90 1.32 8 1 6 2.5 0.05 0.3 0.6 B1 840 11 2005 1.77 34-1 49 R1-10 81-1 30 1.86 0.82 6 1 2 7.6 0.09 0.7 7.1 C1 640 16 1854 52.43 4-1 79 81-1 . 50 1.45 0.5 B1 1 0.21 to 1 0 2.4 0.04 0.2

{ 840 17 1523 11.87 4-1 .

840517 19 81-1 51-10 82 16 1.45 1.76

-0.24 30 1 8 2.3 1.7 0.08 0.07 0.3 0.

0.6 81 0.7 81 j

840517204g50.2856.52 4-20 1.02 to 1 6 4-19 38 1.53 -0.11 to 1 5 0 0.09 0. 0.5 B1 3

840518 056 18.05 34-19 . 86 81-18 20 81-10 0.41 -0.60 8 1 9 , 2 0.04 0. 0.4 81 1 840518 33 42.97 34-1 66 81-1 42 0.40 -0.60 9 132 6 0.05 0. 0.9 B1

6 26 81-1 84 0.54 -0 11 72g4 0 C1

840l19 il10

gg34g.51:81 I:811 4210: 1 *1:1 :31 1:8j:812714?g.80.0g1.4i:3

0:88:88 8 9:! El

! i:99 a:!; 29 l'? f: 38:8;8:!8:!l!

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881); 15 6 12: :78 !!:L8:2 8 i:82 -i 29 3 a8 ":80: 8: 0:1 i: 081

840520 834 19.04 34- 0.03 81-19.77 1.99 -0, 10 30 3.1 0.09 0.4 1.0 B1

8a0 21 18 sa.02 34-19.81 81-1 .6g 1. 1 0 9 126 L.g 0.08 0.3 1.2 81

, 840 25 233 46.08 34-19.66 81-1 77 2. 1 0 10 128 .7 0.09 0.4 0.6 B1 2 840 26 154 24.50 34-20.14 81-1 . 74 1. 5 -0 4 to 123 6 0.09 0.4 0.7 81 1 840526 1633 17.63 34-20.01 87 1.69 -0.11 7 125 1.7 0.07 0.3 0.6 B1

840526 1718 0.34 34-20,01 81-18 92 81-1R. 0.07 0.51 10 125 1.8 0.06 0.2 0.6 81 i 840526 18 7 46.22 34-19.64 81-18.79 0.21 -0.60 6 245 1.7 0.07 0.6 0.7 C1

! 840526 1834 54.19 34-19.90 81-18.93 1.62 -0.40 9 127 1.8 0.07 09 3 0.6 B1

! 840527 331 34.60 34-19.88 43 1.77 -0.60 6 252 2.6 0.05 0. 0.8 C1

840527 576 42 14-19.64 81-19 81-18 54 1.78 -0.11 9 127 3 0.09 0.4 0.7 B1 840527 752 29 65 47 14-19.96 81-18.M5 0.75 0.12 to 126 1 7 0.08 0.3 0.6 81 1

4 840527 945 2 .71 34-20.01 81-18.53 1.46 -0.24 to8123 1

1. 2 0.09 0.3 0.5 B1

! 840527 1618 42 34-20.08 81-18.88 0.24 0.29 247 1.8 0.07 0.5 0.7 C1 840527 1618 5 .45 34-20.01 81-17.91 0.66 0.12 8 238 0 1.3 0.3 C1 2 30 0.08 i 840527 17 7 4.45 34-19.87 81-19.02 0.17 -0.40 4 263 0.03 C1

' 840530 19?! 57.01 34-19.48 81-18.82 0.14 -0.60 9 130 1.8 0.06 0.2 0.6 B1 840603 340 6.92 34-19.66 81-19.30 1.77 -0.60 4 149 2.4 0.05 0.4 0.8 81 i 840607 479 35.04 4-2g.0g 81-1R 89 1.78 l 1.8 0.07 0.j 0.5 81 0.?g13is'j2 "

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!!8610 2"'! 38:Aa 840629 2334 10.41 1:17:61 4-20.01 R!:ia: 52 81-17.84 i:43 1.45 i:31 7 03 0.01 1:48:8 2 0.06 8: 1 1.0 8:"!!

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! 840630 0 4 45.26 34-20.07 81-18.02 2.35 -0.24 6 248 0

0. 5 0.02 0.3 0.1 Ct i

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