ML20091N653

Technical Rept 91-3, Seismic Activity Near VC Summer Nuclear Station,Jul-Dec 1991

ML20091N653
Person / Time
Site:	Summer
Issue date:	01/27/1992
From:	Talwani P SOUTH CAROLINA, UNIV. OF, COLUMBIA, SC
To:
Shared Package
ML20091N646	List: ML20091N642 ML20091N653
References
91-3, NUDOCS 9201310032
Download: ML20091N653 (18)

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TECHNICAL REPORT 91-3 SEISMIC ACTIVITY NEAR THE V.C. SUMMER NUCLEAR STATION FOR THE PERIOD JULY SEPTEMBER 1991 BY PRADEEP TALWANI Principal Investigator Kusala Rejendran 1 and Champa Madineni DEPARTMENT OF GEOLOGICAL SCIENCES

! thilVERSITY OF SOUTH CAROLINA COLUMBIA, S.C.29208 CONTRACT NO. N574984 L

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l i

INTRODUCTION Analysis of the selsmic activity near the V.C. Summer Nuclear Station in I South Carolina between July 1 and September 30,1991 is presented in this report. During this period,18 events were recorded in the vicinity of Monticello Reservoir, 5 of which were located. The largest magnitude recored during this period was Mt=1.5. There were two events of magnitude 1.5, both of which were located (Appendix V).

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 1. 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 lli. 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:

Mt = 1.83 t 2.04 Log D, where D is the signal duration .conds).

! An estimate of daily energy release was determined using a simplified magnitude (ML). energy (E) relation by Gutenberg and Richter (1956):

Logio E = 11.8 + 1.5 Mt OBSERVED SEISMICITY DURING JULY-SEPTEMBER During this period 18 earthquakes were recorded of which 5 were located (Figste 2). The located events were of poor quai , y or D). There were two events of magnitude M t=1.5 which occurred on August 1 (20:00:09.89

1 I

. N J '

MONTICELLO RESERVOIR Jt 7

1 l

l 10 1 1

l

=-

m AJSC STUDY AREA 5

\.

! T' O

souD 0. SKM -=

l CAROUNA- 2A i

Figure 1 Location of Monticello Reservoir area showing seismic stations used in locating seismicity.

2 l

MONTICELLO EARTHOUAKES JULY-SEPTEMBER 1991 ,,

22.0 Pl.0 20 0 19.0 19.0 1/.D 10.0 i i 1 i t _L.___L__J l i1 i i L____

e -<

. ._P4 0 23.L t .23.0 J

_22.5

['  ??,0 V [ 21.5

_?1.0 8 . 20.L d _20.0

-a <

-' ._19.5

/

_19.0

._18.5

-  % ys Y t

, y _18.0

-< U# ,_t7.5 l*

--g _17.0 16 5 i .16.0

- / _15.5 i - T- l 7 I i- 1 i T ~ T~ T= i i 1- 34 0 KlLOMETERS S L L __ J _ .1 _ ...l _ _ _J ,

d Figure 2. Eartliquakes located near Monticello Reservoir during July-September 3

t. .

UTC) and September 9 (192 r 8.56 UTC). Additionally two other events of magnitute between 1.0 and 1,2, occurred during this periori, of which the one on July 27 was located (Appendix V). The other, on July 31 was recorded only on two stations and was not located (Appendix VI). There were five other events of magnitude between 0 and 1, and of these two were located.

Twelve of the 18 ovents recorded this quarter occurred in a 9 day period between July P5 and August 3. They occurred in two tem? orally adjacent sequences. Ttore were four events between July 25 27 of which three, all occurring on July 27, were located and found to lie on the western periphery of the reservoir. Eight events occurred between July 30 and August 3. Only one of these, a magnitude 1.5 event on August 1 was located. Its noicenter is to the northwest of the reservoir. Whether this is a microca;thquake or a blast at a nearby quarry could not be confirrned.

The long term decline in seismicity obseived at Monticello is continuing (Figure 3). The seismicity at Monticello seems to have leveled off since 1985 86 (Fl0ure 4).

CORRELATION OF WATER LEVEL WITH SEISMICITY Monticello Reservoir lo a pumped storage facility. Any decrease in the reservoir level associated with power generation is recovered when water is purnped back into the rotervoir. Theie 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 leveis are compared with seismicity in Figure 5. The top panel shows the average water level; the errnr 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 hg of energy releaseri 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 Vll. No systematic correlation was observed between the seismicity and reservoir level fluctuations.

4 l

r- ..

900 -

1600 6

goo ___

\

700 -- )

soo _

c.,

500 --

m__

l 300 --

200 --

l 100 --

I 1

i l ELN bt- E !w N- n. _ , d I E Jt. __ m ,. a . , _ . .I . m o , , , . . . . ,

1978 1979 1980 1981 1982 1983 1c84 1985 1986 1987 1988 1989 1990 .1991 1977 Figure 3. Earthquakes ber :en impoundment and September 1991.

I 900 T I 1600 800 --

Iw CUMULATIVE SEISMICITY I

( 700 600 - -

1 ~~ 5000 l

f e 500 - hll f

-- 4000 (I

400 --

1

[i --

'i 300 --  ;;  ;

MONTIILY SEISMICITY _m l

200 ~~ (g ?;1 l f"ill iL f 1 M '"

100 -- bSgt l

$i h, dNIdiik%J xJI?rxAJ,:Su . .IL . . . ,..

,., -Kn 0

0 1990 1991 1987 1988 1989 1984 1985 1986 1977 --. 1978 . 1979 1980 1981 1982 1983 Figure 4. Monthly seismicity (bars) and cumulative seismicity line near Monticello Reservoir since impoundment.

426 g

[

4,4 - .. . .

a j .

y -

. t .

C 423 -

.e 422 -

421  :.

182 197 212 227 242 267 g72 1.5 b

• 1 l; i f

$' i \ d7fM l d]'u by cn ., W V 9,V \,l y l V *A s v . l k \rT ,

7 f y i

.C 1 g -.--

O 1,6 .

182 197 212 ggy g4g ggy y7, h 14.s JULIAN DATE : 1991 S

CD g 12.6 C

W CD 0 10.5 -

8.5 --1 182 197 212 227 242 257 272 g 3-

$=

3 -

U" 2-C U

m Q

m 1 0

b Z o, 4 --. .

'*2 197 212 227 242 257 272 JULY I AUGUST I SEPTEMBER Figure 5. Comparison of daily lake level, variationr. in lake level, number of earthquakes and log of energy release (ergs per day) at Monticello Reservoir. Error bars in the top panel indicate daily fluctuations in reservoir level.

7

CONCLUSIONS The level of seismicity during the third quarter was lower, compared to the previous quarter. The largest recorded mannitude was M t=1.5. There were two events of magnitude Mt =1.5, both of Elch were located. The located events were to the north and northwest of the reservoir. No systematic correlation was observed between the reservoir level fluctuations and the seismicity.

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

Lee, W.H.K. and Lahr, J.C. (1972). A computer program for outermining hypocenter, magnitude and first motion pattern of local earthquakes, revisions of HYPO 71, U.S. Geological Survey, Open Filo Report,100 pp.

8

APPENDIX l STATION LOCATIONS S TATION LAT' N LONG *W JSC 34'16.80' 81'15.60' 001 34 19.01' 81 17.74' 002 04 11.68' 81'13.81' 005 34 16.05' 81'20.05' 007 34'22.23' 81*19.50' 010 34 20.18' 81*20.25' l 9 9

. - _ . . _ _ - - _ . ~ _ _ . - .

APPENDIX 11

~

SEISMIC STATION OPERATIONAL STATUS JULY 1 SEPTEMBER 30, 1991 STAllON PERCENT DOWNTIME JSC 0 001 0 002 0 005 0 007 30 010 0 10 m .si'iid

. ..___. . -- ~ _ _ _ __._- _ . _ _ _ . _ _ _ _ .. _ __ _ . _ ..-__ _ __.__ _ _ _ _ ._ _ _

APPENDIX lli e

MONTICELLO RESERVOIR VELOCITY MODEL Velocity Depth to top km'sec km 1.00 0.00 5.40 0.03 5.00 0.18 6.10 0.46 6.30 0.82 8.10 30.00 4

11

APPENDIX IV MONTICELLO EARTHOUAKES 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 so e stations are regarded as 2 readings.

Column 8 Largest al.imuthal separation in degrees between stations.

Column 9 Epicentral distance in km to nearest station.

Column 10 Root mean square error of time residuals in sec.

RMS = RS/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 epicentral location.

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 insufficient data.

12

Al'I'EN DIX Y MONTICl;l.l.O 1;AilTlIQUAhI;N a jl'IN SI.I'IT.Mlil;it 1991 DATT, OKlGIN IAT N 1.ONU W 1 0 "11 MAO NO (RI' DMIN RMS l Ril I.RZ QM 91 07 27 0203 10 49 34-20 8) til .2f t.4 % 3.11 0 82 8 214 1.2 OW 09 0. 8 Cl 91 07 27 W5147A8 34 20f>4 61 20 35 1.75 1 02 8 214 0.9 0 16 L6 1.4 04 91 07 27 07t2 4) 49 14-20.62 t 1210$ ID) 0 73 5 214 08 0 12 2.3 32 (:1 91 On 01 ho!W 89 34 2416 kl 22.44 2.10 1.54 $ 337 84 0 04 22 46 Cl 91 M O9 1921 28.%6 34 22 26 61 1942 O h3 1 34 7 311 4.0 0.13 1.7 DI

. . . ~ . . - . . . _ . . . . _ . .

9 4

4 13

APPENDIX VI LIST OF EVENTS WITH S.P s 2.5 SEC RECORDED AROUND MONTICELLO HESERVOIR DURING1 JULY 199130 SFPTEMBER 1991 DATE STATION P. ARRIVAL TIME SP EP.DIST DUR(S) hMG H MIN SEC SEC S Px8.5km 41.60 12.0 0.4 91 07 25 010 13 17 10 20 52.80 0.3 02.6 13.0 0.4 91 07 30 010 91 07 31 010 05 48 52.20 0.5 04.3 05.0 0.2 09 46 12.50 03.2 -0.9 13 35 01.20 2.5 21.3 30.0 1.2 JGC 02.50 0.4 03.4 05 30 05.30 0.4 03.4 05.2 0.4 91 08 01 91 08 02 15 53 25.90 *

• 08.5 0.5 91 08 03 20 32 19.30 03.5 -0.8 04.0 0.6 91 OS 12 08 19 11.70 09 30 19.10 0.9 07.7 05.0 0.6 91 08 29 14 14 11.50 07 2 0.1 91 09--16 CG 14 25.50 0.3 02.6 04.4 0.6 91 09 30 10 37 28.00 0.3 02.0 07.6 0.1

• Event is very close to the station; (S-P) not clear.

14

Appondix Vil Maximum anti "iinimum water levels, change in water level, number of earthquakes and energy release (ergs per day) at Monticello Reservoir during July 1-September 30,1991. Dates are given in Julian Calender.

A l l C l D E F l l l G

, DATE WL(mp)_WL(min)_WL(avg) [CHANGEJO.Eqs_ Log E 182_ 425 423 6 424_61 0', 0. _ _ _0 183. .f 25 423 4 424.5 _ 1 0.1 0 0 iB4 '25 O{

. 421.4 423.5 1 0 g

185 425 422 423.8 0 146

_ 0.3 OL._

425 421.3 423.4 -0.4 0 0 187 423791 421 2 422.7 i ~

0.7 "O_ 0 188 423.9 421.2 422.5 02 Ol 0 189 425 422 423.5 1 0 Oj 190 425 422.1 423.9 0.4 Oj 0 191 425p 422.2 423_.6 Og

. O! _0 192 424.8i 422 423;6y O Oj _ O!

193 424.9} 4225 423.9] 0.3' 0' O 104 i23 42584 423 8I 0.1 O! 0 195 4 55 4E53 423 6 -0.2 O! 0 196 425 422.4 424.1 0.5 01 0 ,

197 4Ed.5~ 452.8 423.8 0.3I 01 0 198 424 4E55 4252 0.6 0 199 423.8 423.1 423.6 04 Uf

~gO 0 200 424JI 422.8 [454.1 03 _ 0 0 201 4251 422.8 423.8 -0.3 I O O 202 424.1 452k 4254 -0.4 0?

203.. 425 421.4l dE4l' . , 0.6 0 ~6 204 425j 421.4 424 0 O 0 l

205 425! 423.5 424 4_

f 0.4 Ot 0 206 425! 423.1 424.2 ;_0 2 1 12.36 207 425! 423 423.9 -0.3 0, O EIE' 4256' 423.1 423 3) -Ol6u 3 13.57 209 424.1 422.4} _ 423.3 O!

O[, O t

21,0 424.5 422_6 424 24 0.9 O! 0 21]f_ 424.2~ 423.2_ 423.7 -0.5 1 12.46 l

2121 424.1 422.9 423.4 -0.3 3:

~

~ 13.57 l 2ii 4EE3 ~ ~A2E~8 423' -0I4i 2I 14.11

~~

2I4 4E3]I 422.8 4253 03 ti 11.82 215l 213 423.7l 42f.3 .423.1I -0[ _1f 10.51 424.51 422 423.1 0 0- 0

' 2I7 42I.~93 421.9 424 4i 1. I OI 6 218! 424.Di 4EII6 42375f 0(3 ~5' 0 219_ 425j _ 421J; 423 3J -02 y _ _g 0

~ ~ ~

I

~

43 ~ d 0 4

2_22 _ 25 __4225~A257] O{I_ ~U ((] 7 223L 424.9! 422.8! 423 9) 02l 0,_ _ _0 224! 424.71 423.5I 424.2I O! O

__ _225! 424.7{ _ 423.3'I 424.1b_0.310.1h OC_0 226i 424 2i 423 3 423.71 -0.4 ! 0' O 227I 424.4I 423 3 I 423.8! 0.1l O! O

~ ~ ~ 2i83 424 4! 4pf F - ~423si~ ~ T2i 0 0 15 1

.., - , _ . . . , - - - , - - - - .~, .. . - . - - - . . - . - . . . -.- . .

l 1 . .

I I

l A B l 3 D l E l F l G

, 229 424.4 ~

422.2 4234i O 2i 0 0 230 4f3.6 .,

422,)2I 423 2 02 2{ 11_44 231 424.7 423PI 423 9 0.7 O j32 424.5_ 4((9} _423)) 0.2 O[!

0 _,_ 0 233 4248p 4221 423 61 -0.1 0 0 234 424.8 4226 4230 0.2 0 0 235 424 423.1 423 6 02* ~I0 1 -

O

"'1 423.2 423 423.1 0.5 04 0 237 423.2 422.9 423 0 424.3, 0.1] O{_

238 424.6 423 1 . 1JL,_ 0, _0 239 425 I 424 42_4j 0,3J _0j _ 0 240 425l 423 424.1 -0.51 0~ 0 241 4_24_6f dii .7 423) _ 08 l1 11.64 242 424.7 421.5 423 0.3 0. 0 243 244 424.8 424.1 421J 422 6 423T 4231 05

-0J_

~6f0 4 0

0 4

245 424.2 422.Bi 423 8 0.5 O! 0 246 425 4226 423 6 0.2 0,_ 0 247 4228 422.3 422.5 1.1 0, . ._ 0 248 423.6 422 4 423.2 0.7 O! ~0 249 423 8 ~

421.1 4fE7 0.5 0[ 0 250 424 421.4 ,,

4238 .

1.1 0 0 251 423.9 423 6 423.8 04 0 __0 2:2 425 423 4 424.2 0.41 1 14.11 263 424.9 423.3 424.1 0.1 0 1 0 254 425 421 6 423.,5 -06 0,_ 0 255 425 _4 21.0 423 4 0.1 .

O, O.

256 425 422.3 423 9 0.5 0 1 0 25} 4218_ 422.4 4257 02 _0 258 424.8 422.5 423.9 0{

0 0 0.2, 259 42Ej 422.7 423.9 0 1 10.9 260 4251 422 4230 0.11 .

0 2 51 4f5I' 42 (4 i 423p_ _0.1 0{

0 0 262 424.3 422.1 423 4 -Of 0;_ O_

263 . 425l 422 4 , 424f5 1.1 0 0, 264 424,.5) 423J 0 0 265 424.1 424424 1_l424.1 1.1}_

0.9 0, 0 266. . , 425, 422,3l 424.1 Oj 0; 0 267 424 6 421.6f 4234! -0.7 0 0 268 423.9 421.ty_,,423 3! -0.1 03 0 269I_

_425 423 2J _ _ 424.3, 1

_0[ 0 270' 425 423.6 424.5 0.2 0' , O.

(

271 4242i 423.8 424.3 _ -0 24 Oj 0 212 424 2 423,7 423 9 0,J! _ _01_ 0 273 424._.9, 422.4--- 423 0 0' il 11.64 q q_. _ .

16

__ _ - -