ML20153G034
| ML20153G034 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 03/31/1988 |
| From: | WESTON GEOPHYSICAL CORP. |
| To: | |
| Shared Package | |
| ML20153G019 | List: |
| References | |
| NUDOCS 8805110122 | |
| Download: ML20153G034 (19) | |
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SIXTH QUARTERLY REPORT CEl SEISMIC MONITORING NETWORK JANUARY l THROUGH MARCH 31,1988 Prepared for CLEVELAND ELECTRIC ILLUMINATING COMPANY APRIL 1988
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,.i TABLE OF CONTENTS Page LIST OF TABLE i
LIST OF FIGURES 11
1.0 INTRODUCTION
1 2.0 SEISMIC NETWORK 1
3.0 OBSERVED SEISMICITY l
3.1 Epicentral Area of January 31, 1986 1
3.2 The Corridor Between the January 31, 1986 Epicenter and the Injection Wells 1
3.3 Other Events Recorded by AUTOSTAR 2
4.0 DISCUSSION 2
5.0 CONCLUSION
4 TABLE FIGURES APPENDIX A Figure Al 1896J Weston Geophysical
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..t LIST OF TABLES TABLE 1 Microcarthquakes in the Corridor Between the Injection Wells and the Main Shock
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LIST OF FIGURES FIGURE 1 Telemetered Network Station Configuration FIGURE 2 Recorded Signals for the January 16, 1988 Microearthquake FIGURE 3 Recorded Signals for the January 17, 1988 Microearthquake FIGURE 4 Recorded Signals for the February 5, 1988 Micr"oearthquake FIGURE 5 Seismicity for the Period of January 1 to March 31, 1988 FIGURE 6 Cumulative Seismicity 1896J
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1.0 INTRODUCTION
In accordance with its agreement with the U.S. Nuclear Regulatory Commission, Cleveland Electric Illuminatihg [CEI] continues to monitor the seismic activity in a restricted region of Northeastern Ohio, encompassing the site of the Perry Nuclear Power Plant, tuo deep injection wells operated by CALHIO, and the epicentral area of the January 31, 1986 earthquake. This sixth Quarterly Report covers the period from January 1 to March 31, 1988. An update of the injection data is also provided in Appendix A.
2.0 SEISMIC NETWORK During this period, the Automated Seismic Telemetering and Recording System [AUTOSTAR), fully described in the third Quarterly Report, has performed in a very reliable manner. The downtime was minimal, less than five percent; usually caused by noise on one of the five telephone lines.
Figure 1 shows the station locations around the area of interest.
3.0 OBSERVED SEISMICITY 3.1 Epicentral Area of January 31, 1986 There was no earthquake activity within the epicentral area during the present quarter. The last event occurred on February 12, 1987.
3.2 The Corridor Between the January 3.,
1986 Epicenter and the Injection Wells During this quarter, only three microcarthquakes [M = 1.8, 0.5, and c
0.5] triggered the digital system.
These events occurred on January 16, 17, and February 5, 1988, respectively.
A close examination of the analog seismograms reveals five other smaller events, all with coda magnitudes less than O.
Two of them, apparently foreshocks, 1896J
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l occurred within an hour before the M = 1.8 January 16 microearthquake. The other three fo11 cued the first aftershock of January 17, within twelve hours. These events are too small to be independently located using phase arrival times.
In view of their close occurrences in time and the apparent similarity of the S-p interval at the closest station, about 0.5 sec, a common origin with the main shock of January 16, 1988 is currently assumed.
Figures 2, 3, and 4 show the 15 seismic signals recorded for each of the three events that triggered. The calculated locations are plotted on Figure 5.
Table 1 presents an updated list of the location parameters of all events located in the corridor since 1986, Figure 6 illustrates the cumulative seismicity observed in the area of interest, including the January 31, 1986 sequence.
3.3 Other Events Recorded by AUTOSTAR During the period covered, AUTOSTAR triggered on several local and h
regional quarry blasts.
It also recorded on March 31, at 16 30",
a small earthquake with an approximate magnitude M = 2.8 1 0.2.
c Ten good phase arrival times were provided by CEI to John Carroll observatory. A preliminary location obtained by Rev. W. Ott, S.J.,
places the epicenter at 41' 18.88 and 81* 02.88, in the vicinity of Nelson, Ohio, approximately 40 Km south of the January 31, 1986 epicenter. An uncertainty of several kilometers should be attached to the location to account for a model and configuration bias, i
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4.0 DISCUSSION The seismicity observed during this quarter is consistent with the previous rate and spatial distribution. The occurrences are sporadic instead of regularly spaced, but the long term average of one event per month (1 0.1] is maintained and the activity was centered at the northern end of the epicentral cluster.
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An interesting sequence of microshocks was observed on January 16 and
- 17. Within 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />, seven microearthquakes occurred: the two largest ones, M = 1.8 and 0.5 were recorded digitally; the five others with c
estimated M = -0.6 could only be seen on the analog seismograms of c
the two closest stations, FORD and SCH at epicentral distances of 2.5 and 3.8 km.
It must be stressed that these extremely small events, with a coda of about 3 sec, are almost at the limit, if not beyond, of what can be identified with confidence as seismic.
The January 16, 1988 event is the largest (M = 1.8) to occur within c
the array. On May 1, 1987, an event with M = 1.3 had been located c
no more than one half kilometer away to the east of the January 16, 1988 microearthquake (see Figure 6].
This May 1, 1987 event, illustrated on Figure 8 of the Third Quarterly Report, had also one foreshock (M =
.5], in the preceeding minute, and was followed by c
two small events on May 2, 1987.
In the discussion of these four events, it was then suggested that they could well be from the same origin, althcugh individual locations had been calculated at that time, given that additional MEO-800 data were available. Considering that the January 16, main shock and January 17, 1988 principal aftershock, both recorded digitally, yield almost identical epicentral solutions, it now seems more likely that all four events of May 1 and 2, 1987 were parts of a single sequence and from the same source, about half kilometer to the east of the recent January 1988 events.
It is felt that mixing digital data with MEQ-800 data and their individuel time correction and poorer resolution, may have caused the apparent 9picentral scatter for the May 1987 events.
The occurrence of these two similar and closely located sequences, within eight months, suggests a common mechanism, whatever it might be, purely tectonic or possibly induced. At this time, we can only notice that the January 1988 sequence occurred approximately four days after injection at the Calhio well number 1 had resumed, while in May 1987, the sequence occurred several days after injection at the same 1896J
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well had stopped. This difference does not rule out the possible influence of injection, since both variations in pressure, positive or negative, can resul; in induced activity.
As suggested in previous reports, it is only through reliable data, patiently accumulated over a reasonable time period, that a true understanding of these complex problems will be reached.
5.0 CONCLUSION
During this quarter, three microcarthquakes were digitally recorded by AUTOSTAR. The January 16, 1988 event is the largest (Mc=1.8) to occur within the array. The availability of analog seismograms has made it possible to identify the occurrence of a small seismic sequence associated with this event which is similar to one recorded in May last year. The identification of interesting characteristics of these two sequences suggests that gradual progress in the understanding of this localized microactivity is being realized. The nature of the seismic activity, tectonic or induced, is still under evaluation.
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TABLE 1 4
MICROE AR7H3U AKES IN THE CCRRIDOR BETWEEN THE INJECTION WELLS AND TH J
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YEAR MO DY HRMISEC LAT.N LONG.W D
RMS EH EZ NP NS GAP MC 50
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f 1986 03 12 085526.6 41.'7272 81.1707 2.0 0.06 07 04 10 6
216
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1986 09 28 103604.2 41.7247 81.1091 2.3 0.04 0.3 0.4 11 6
174
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1986 10 20 105944.7 41.7587 81.1453 3.0 0.07 1.7 2.0 6
4 337
.6 WG j
1936 10 27 122555.5 41.7435 81.0944 2.9 0.07
- 2. 7 1.5 6
3 221
.2 WG 1986 11 03 085449.6 41.7098 31.1292 1.8 0.06 0.5 0.5 7
5 145
.3 WG 1986 12 01 050317.5 41.7120 81.1195 2.1 0.07
- 0. 6 58 7
5 188
.2 WG l
1986 12 24 093733.9 41.7487 81.2392 1.0 0.04 8.5 6.7 6
3 306
.3 WG
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1987 01 02 024114.3 41.7472 81.1027 2.0 0.06 0.3 0.5 10 6
174
.6 WG l
1987 01 23 235829.8 41.7299 81.0974 2.1 0.03 0.4 07 8
5 199
.7 kG l
1987 02 23 114556.4 41.7284 S1.1197 2.0 0.03 0.1 0.3 10 7
100-
.5 WG 1
1987 02 28 204644.5 41.7451 81.0932 2.4 0.07 1.0 1.7 7
4 239
.4 WG 1987 05 01 211332.3 41.7466 81.0872 1.9 0.06 0.3 0.2 7
4 196
.6 WG 1987 05 01 211352.1 41.7466 81.0921 2.4 0.08 0.2 0.8 15 9
100 1.3 WG 1987 05 02 183307.7 41.7475 81.0932 2.0 0.02 0.1 3.0 6
4 174
.6 WC 1987 05 02 202526.5 41.7424 81.08E9 2.7 0.08 0.3 0.6 14 8
115
.4 WG 1987 07 08 034835.2 41.7192 81.1037 2.7 0.07 0.7 1.1 8
5 166
.2 9G 1987 08 15 052637.7 41.6594 81.1472 2.8 0.06 0.2 1.0 10 6
133
.1 WG 1987 10 10 000610.4 41.7430 81.1030 1.9 0.04 0.3 0.2 7
5 166
.6 WG 1987 10 14 195924.8 41.1250 81.1318 3.4 0.04 1.6 0.7 6
3 190
.7 WG 1997 11 22 024918.9 41.SG89 81.1447 2.2 0.04 0.2 3.8 9
5 120
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1988 01 16 222403.
41.747 81.098 3
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1983 01 16 223010.
41.747 81.098 1988 01 16 231704.4 41.7474 81.09S1 2.0 0.05
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5 185 1.S WG 1988 01 17 024821.7 41.7467 S1.0997 1.9 0.06 0.5 0.3 10 5
180 0.5 WG 3
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1988 01 17 092236.
41.747 81.098 2
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1988 01 17 092400.
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1988 01 17 131551.
41.747 81.098 1988 02 05 155837.0 41.,7251 81.0907 2.0 0.04 C.4 0.2 10 5
195 0.5 WG E
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THE CLEVELAND ELECTRIC January 31,1986 ILLUMIN ATING COMPANY SEISMICITY FOR THE PERIOD 0
5 MILES JANUARY 1 - MARCH 31,1988 i
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CUMULATIVE SEISMICITY
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l APPENDIX A FIGURE I A W25fOn Geophysical
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.t SEISMICITY (MAGNITUDE)
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g JAN FEB MAR 1988 TIME l
Solid lines represent data from Calhlo well +1 Dashed lines represent data from Calhlo wel! #2 injection well volume data from Calhlo Chemical PERRY HUCLEAR POWER PL ANT l
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DAILY INJECTION VOLUME l
AND OBSERVED SEISMICITY l
1988 i
Figure A1 1
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