ML20080G123
| ML20080G123 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 09/30/1983 |
| From: | Talwani P SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC |
| To: | |
| Shared Package | |
| ML20080G113 | List: |
| References | |
| 83-3, NUDOCS 8402130275 | |
| Download: ML20080G123 (17) | |
Text
.
l-L TECHNICAL REPORT 83-3 SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION For the Period July - September 1983 by Pradeep Taiwani Principal Investigator Geology Department University of South Carolina Columbia, S.C. 29208 Contract No. N301315-N kSo$n o! N
Technical Report 83-3 A
SEISMIC ACTIVITY NEAR THE V. C. SLMiER NUCLEAR STATION For the Period July - September 1983 by Pradeep Talwani Principal Investigator Geology Department University of South Carolina Columbia, S.C. -29208 Contract No. N230519
INTRODUCTION i
This. report presents a sumary of seismic activity near the 4
V. C. Sumer Nuclear Power Station in South Carolina for a three-month period from July 1 through September 30, 1983. During this period a total of 26 locatable events were recorded of which only one was of magnitude greater than 1.0 (September 14, ML=1.09). The remaining events were of magnitudes less than 1.0.
-SEISMIC NETWORK
. The report is based on the data recorded by a four-station network operated by S.C.E. and G.
In addition, data from a permanent station (JSC) of the South Carolina seismographic network are also used.
Location of all these stations is shown in Figure 1, and their coor-
-dinates are listed in Appendix I.
DATA ANALYSIS Location of the events is determined using HYP071 program (Lee and Lahr,1972) and the velocity model given in Appendix II. The event magnitude _(M ) is determined from signal. duration at-station JSC, using L
the following ' relation:
M = -1.83 + 2.04 Log D t
where D is the signal duration (seconds).
An estimate of daily energy release is determined,using a simpli-fied magnitude (M ) energy (E) relation by Gutenberg and Richter,1956.
L
.logloE = 11.8 + 1.5 Mt RESULTS.
The 26 events located during this reporting period are listed in Appendix III. The largest event was of magnitude 1.09 on September 14,1983.
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4 MONTICELLO RESERVOIR A
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3 The remaining events were small (M < 1.0).
Depth estimates for the L-seismic activity indicate that approximately 73% occurred within 2.0 km of the surface,19% between 2.0 and 3.0 km depth, and 8% at depths greater than 3.0 km. Depth' comparisons of A and B quality events for the previous five years and for the first nine nonths of 1983 are given in 0.5 km~ increments in Figure 2.
The trend continues whereby more
- events fall into the 1.5 to 2.0 km increment than any other grouping and a significant percentage occurs at depths greater than 3.0 km.
A cumulative plot of epicenters of events located around Monticello Reservoir during this period is shown in Figure 3, and a monthly break-down of epicentral locations in Figures 4-6.
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 water level. We have been monitoring this water level to see if there is any correlation -
between the daily or seasonal changes in the reservoir. level and the local - seismicity.
Figure 7 shows the comparison of water level to I
seismicity. The' top two graphs show the water level and the change of water level 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 around the reservoir.
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CONCLUSIONS Seismic activity in the Monticello Reservoir area generally occurs in a long-term trend of discrete swarms separated by relatively quiet periods.
Figure 8 is a histogram of the number of events per month from December,1977, through September,1983. The swarm occurring in early 1983 is not as discrete nor as high a peak as in previous years, suggesting a tapering off of activity. The low level of seismicity during the July through September,1983, reporting period reinforces the observation of decreasing activity. The 1.5 to 2.0 km increment continues to be the predominating depth range and a small percentage continues to occur at depths greater than 3.0 km.
REFERENCES Gutenberg, B. and Richter, C. F. (1956). Hagnitude and energy of earthquakes, Ann. Geof. 9, p. 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 HYP071, U.S.G.S. Open-File Report,100 pp.
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A-2 APPENDIX I STATION LOCATION NO.
STN.
LAT. N.
LONG. W.
0 l'
001 34 19.91' 81 17.74' 0
2 002 34 11.58' 81 13.81' 0
0 3
003 34 21.09' 81 27.41' 0
0 4
004 34 25.72' 81 12.99' 0
0 5
JSC' 34 16.80' 81 15.60' 6
008 34 24.53' 81 24.55' O
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s APPENDIX II MONTICELLO RESERVOIR VELOCITY MODEL Velocity Depth km/sec km 1.00 0.00 5.40 0.03 5.90 0.18 6.10
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APPENDIX III DATE qRTGIN LAT N LONG W DEPTH MAG N0 GAP DMIN RMS ERH EPZ GM 8 0715 1835 28 81
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11 7 120 2.4 0.01 0.1 0.1 81 8 0703 1512 12 34-18.76 81-18.54 3.87
-0 22 3 190 0.2 0.06 C1 89 34-16.90 81-15.70 1.00
-1 21 10 177 7.5 0.05 0.2 1.0 H1 8 0718 411 30.50 34-16.88 81-21.02 2.79 0
3 0.6 B1 830728 3s8 36.84 34-20.39 81-19.33 2.6u
-0.24 8 137 2.6 0.06 02 1.3 81 830726 BT3 53.49 34-16.81 81-20.84 1.93 0.12 9 17e 7.5 0.04 0:2 3.5 C1 830810 1998 75.36 34-25.00 81-20.88 2.83
-0 40 8 287 10.6 0.09 1
64 1.00 0 99 6 224 0.4 0.05 1.0 0.9 C1 830824 650 21.83 34-19.71 81-17 84 1.66 0 01 0 0.07 0.9 1.0 C1 83847 21g g:.4 8:8" 0.8 3.2El 81-17 g34-19.40 830824 lota 22.
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2 46 1.92 0.96 to 131 4.2 0.04 0.2 0.7 81 8308 2200 22.48 34-20.28 8 0905 u38 44.12 34-19.5a 81-18.56 0.66
.-0.24 8 243 1.4 0.05 0.5 0.5 C1 8 0907 105 33.05 34-19.76 81-17.84 2.14
-0.86 10 122 0.3 0.06 0.2 0.3 81 8 0907 128 23.65 34-19.62 81-18.51 1.Sa
-0.60 to 127 1.3 0.06 0.2 0.4 81 830907 753 38.35 34-20.90 81-18.55 4.08
-0.86 to 132 2.2 0.06 0.2 0.4 81 830909 522 39.60 34-20.35 81-19.13 1.61
-0.86 to 127 2.3.0.03 0.1 0.3 81 830911 200 0.86 34-19.24 81-19.62 0.63 0.37 8 132 1.8 0.07 0.3 0.8 81 830912 659 12.36 34-17.c9 81-23.06 0.85
-0.60 6 187 9.3 0.09 0.6151.3 D1 830913 404 48.56 34-19.22 81-18.68 0.15
-0.24 8 132 1.9 0.05 0.1 0.a 81 24 81-18.34 0.34 0.01 8 130 1.5 0.07 0.3 0.8 B1 830913 032 30 8635 34-19 53 81-18.44 0.29 0.01 8 128 1.3 0.09 0.3 1.1 81 830913 1137 7
34-19 830913 1271 3.99 34-19.06 81-18.58 1.82
-0.11 8 133 2.0 0.08 0.4 0.7 81 41 2.68 0.82 8 128 1.3 0.07 0.3 0.5 81 41 34-19.49 81-18 59 0.32 1.09 8 133 2.0 0.09 0.3 0.7 B1 830914 1113 5 91 34-19.11 81-18 1 0.09 0.6 4.0 C1 830914 1sts 1.
830925 en9 a0.54 34-17.41 81-22.86 1.47
-0.40 7 186 9 2 0.05 0.3 0.7 C1 830925 857 23.46 30-17.47 81-22.99 0.14 0.82 8 187 9
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