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APR 0 61982 MEMORANDUM FOR:
Robert L. Tedesco, Assistant Director for Licensing, DL I
FROM:
James P. Knight, Assistant Director for Components and Structures Engineering, DE
SUBJECT:
MIDLAND NUCLEAR POWER PLANT - GE0 LOGICAL AND SEISMOLOGICAL INPUT TO SER Enclosed is our geological and seismological input to the SER for the Midland OL application. The geology sections were prepared by A. T. Cardone of the staff and H. Planner, our geologic consultant from Los Alamos National Laboratory. A letter report from our advisor, Los Alamos National Laboratory, concerning the subsurface faulting at Midland.is attached as an appendix.
The seismology section was prepared by J. Kimball of the staff.
In addition, Paul Hadala of the Army Corps of Engineers, a consultant to HGEB assisted the staff in assessing ground motion amplification through the plant fill material.
Section 2.5.2 of the SER is on CRESS, the rest of the SER has been completely revised and is not on CRESS.
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James P. Knight, ssistant Director for omponents & Structures Engineering Division of Engineering
Enclosure:
As stated cc: w/ enclosure R. Vollmer J. Knight R. Jackson J. Kimball A. Cardone L. Reiter S. Brocoum J. Kane G. Lear F. Rinaldi F. Schauer D. Hood R. Hernan y
._Rianner' Los Alamos H
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Geology and Seismology Midland Plant, Units 1 & 2 Consumers Power Company Docket Nos. 50-329/330 2.5 Basic Geologic and Seismologic Information 0
The geology and seismology of the site was reviewed in detail prior to issuance of construction permits for Midland Nuclear Power Plant Units 1 and 2 by the staff of the U. S.
Atomic Energy Commission, the predecesser of the U.
S. Nuclear Regulatory Commission, and its geological advisors, the U.
S.
Geological Survey (USGS).
The findings of that review were issued on November 12, 1970 (U. S.
Atomic Energy Commission, 1970) as part of the Safety Evaluation Report relating to construction of the Midland Nuclear Power Plant Units 1 and 2.
A copy of the USGS report appears as Appendix D to that report.
The report concluded as folLows:
1.
Tectonically, the site is situated near the center of the Michigan Basin, a major regional structural basin that underlies i
the southern peninsula of Michigan and parts of adjoining states.
2.
Although there are no active faults or other recent geological structures known in the area that could be expected to Localize seismicity in the immediate vicinity of the siter structural details in the underlying Paleozoic sedimentary rocks or in the crystalline basement complex are only very poorly known.
i 3.
Northwest trending anticlinal, synclinal, or monoclinal structures, delineated as a result of extensive oil and gas investigations have been postulated to exist within the Michigan Basin.
Although normal faulting is reported to be associated with l
some of these structures, none have been reported in the vicinity i
I of the plant site.
4.
Most of.the deformation apparently took place in early Paleozoic time.
Deformation is greatly diminished to absent in the younger Paleozoic rocks, and none of these secondary features is known to extend to the surface or to have disrupted I
any of the glacial deposits in Michigan.
j 5.
Although surface subsidence due to the extraction of natural brines, appears to be precluded by the methods used in the extraction process, detailed studies and analyses by the applicant indicate that some very minor, broad,.through-type surface subsidence may occur in the site area due to solution mining of the salt beds; the effects et the actual plant site, howe er, wilL be very smalL, and surface rupture due to subsidence wilL not y
occur.
t After evaluating the FSAR and its supplements we are of the 1
opinion that the applicants are in conformance with applicable portions of the following documents:
1 1.
10'CFR Part 50, 10 CFR Part 100, and Appendix A to 10 CFR i
Part 100.
2.
Standard Review Plan (NUREG 0800 - Sections 2.5.1, 2.5.2 and 2.5.3 i
3.
Regulatory Guide 1.70, " Standard Format and Content of j
Safety Analysis Reports for Nuclear Power Plants," Revision 2.
4.
Regulatory Guide 1.132, " Site investigations for Foundations of Nuclear Power Plants.",,
5.
Regulatory Guide 4.7, " General Site Suitability Criteria t
for Nuclear Power Stations."
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i We have considered in our review of the Midland FSAR information obtained since issuance of the construction permits for the, Midland Nuclear Station.
From our review of the geology sections of the i
FSAR, we find no reason to alter our conclusions stated in our i
i I
November 12, 1970 Safety Evaluation Report. New information on fautling in the site region and updated subsidence monitoring readings are discussed below.
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The faulting data, which included bore hole data and structure 4
contour maps provided by the applicant,were analyzed by the
)
staff and its Los Alamos National Laboratory consultant.
We concluded that the faulting in the site area is old and non-capable, based on Appendix A to 10 CFR Part 100.
1 In our operating License review of the seismology sections of the FEAR we have followed the tectonic province approach of Appendix A to 10 CFR Part 100.
Two :encerns developed when utilizing the tectonic province approach.
First, the size of the controlling
- i earthquake increased over that which was determined at the CP stage.
Second, given the larger controlling earthquake, concern was expressed at the use of a modified Housner response spectrur-anchored at a peak acceleration of 0.12g to represent the vibratory J
l ground motion at the site.
These issues have been resolved (and i
l are discussed in detail in SER section 2.5.2) using state-of-the-art i
seismological information and data antaysis including the use of a site specific spectrum and a comparison of the relative seismic hazard between the Midland site and 5 other sites within the Central Stable Region of the United States.
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r 2.5.1 Regional Geology l
The Midland plant site is located near the' center of a broad, l
nearly circular structural depression known as the Michigan
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Basin.
The basin, which encompasses Michigan's Lower peninsular.
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as weLL as parts of the upper peninsula, and canada, eastern Wisconsin and northern portions of ILLinoi". Indiana, and Ohio, i
has an approximate area of 122,000 square r Les.
The maximum j
accumulation of sediments at the basin's center is greater than I
14,000 feet.
The Michigan Basin has a long history as a stable
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structural basin and its Limits are defined by large magnitude f
i structural highs.
It is bounded on the north by the Canadian 1
Shield, on the east and southeast by the Findlay Arch and Algonquin Axis, on the west and southwest by the Wisconsin and Kankakee Arches, and on the northwest by the Wisconsin Dome.
The arches j
and dome acted as stable areas throughout much of the Paleozoic era.
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Subsidence responsible for the formation of the Michigan Basin r
j began at the close of the Precambrian and probably continued i
through the Pennsylvanian period.
Intrabasin folding developed intermittently during the Paleozoic contemporaneous with the 1
subsidence of the basin.
Its general shape was first formed in Ordovician time.
Major subsidence began in the Silurian and decreased early in Devonian time.
The most intense intrabasin 3'
deformation occurred in later Mississippian to Early Pennsylvanian, 4
and the basin has been tectonically inactive since.
Unloading associated with the last major glacial ice retreat-is responsible i
l for observed crustal uplift.
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l The thick sedimentary sequence deposited upon the Precambrian base-i ment complex consists of essential.Ly flat lying strata.
The earliest I
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Cambrian sediments in Michigan were clastics transported from the exposed shield area to the north into a regional subsidence to the south.
A shallow sea encroached, and after extensive deposition of dolomites in early Orddvician time, I
the region was uplifted and exposed to erosion.
Following another period of subsidence, there was an' accumulation of Limestone and shale of middle to Late Ordovician age.
Deposition continued essentially without interruption through early Devonian.
The general shape of the existing basin was first formed in Ordovician time.
It was during late Silur'ian time that the structural basin began to develop rapidly with abundant evaporite deposition.
This rapid deposition ended in early Devonian time with regional uplift and erosion.
Subsequent transgressions during the middle Devonian formed prevalent Limestone and dolomite strata.
From the close of the Devonian through the early PennsyLanian, deposits of black shale predominate. The most widely developed, and profound unconformity of the region occurs below strata of Early Pennsylvanian Age.
Finally, folLowing an interval of periodic j
merine transgression and regression, the entire region was uplifted and exposed to erosion in late Pennsylvanian time.
Triassic and Cretaceous rocks are not known to exist in the region.
Late Jurassic red-beds, found in the central portion of the basini indicate a period of localized deposition.
The area existed as a lowland mass subject to erosion throgghout the Tertiary,and deposits of that age are unknown to the region.
During the Pleistocener four major periods of glaciation totally modified the bedrock topography of the region, until only the outlines of the older maj.or. preglacial i
3 i
drainage basins remained.
i The intrabasin structure is dominated by a subparatlet set of northwest-southeast anticlinal flexures that are asymmetric in cross-section with the strong dip toward the basinward side.
They are best defined in the eastern, scutheastern, and central i
portions of the basin.
Several prominent features located far to the south of the plant site, namely the HoweLL anticline, Albion-Scipio syncline, and the Lucas-Monroe monocline, are postulated (but not proven) as having west-flanking faults in their Paleozoic strata.
Several faults are located on the southeast flank of the Michigan Basin that have mid-Paleozoic displacements.
These are the Bowling Green Fault, located in northwestern Ohio, with youngest displacement being of upper Silurian age, and faults associated with the Chatham sag, Ontario, Canada.
The latter system of faults, which includes the Electric and Osborn faults, indicates that the Chatham sag was inactive after middle Devonian time.
2.5.1.2 Site Geology The plant area is dominated by surface features of predominantly glacial origin.
Glacial drift covers the area to depths ranging from a few feet to several hundred feet.
Topographic relief is Low to moderate, typical of a glaciated plain.
Other site-related j
geologic features are described in Section 2.5.3 "Fau8. ting".
t
2.5.2 Seismology 2.5.2.1 Vibratory Ground Motion -
fn the CP review, the staff's seismological advisor (the Seismology Division of
. the National Ocean Survey (N05)) concluded that an acceleration of 0.12 g result-g ing from an earthquake of Modified Mercalli (MM) intensity VI (maximum historical earthquake within 150 mi of the site) would be adequate for representing the ground motion from the desigri-basis earthquake, now called the safe-shutdown The response spectrum for the SSE was a modified Housner earthquake (SSE).
spectrum anchored at 0.12 g, and is displayed in Figu.h.2-re 1 for 5 percent da In its OL review, the staff has followed the tectonic province approach of Appendix A to 10 CFR 100 to determine the vibratory ground motion corresponding J
to the SSE.
Using this approach, the staff developed two concerns:*._ fi.st, the size of the controlling earthquake increased over that which was determined at the CP stage; and second, given the larger controlling earthquake, concern was expressed about the use of a modified Housner spectrum anchored at 0.12 g to represent the vibratory ground motion at the site.
The staff determined that the design response spectrum was no longer a conservative representation of the ground motion as used....
These issues have been resolved using state-of-the-art seismol.ogical informa-tion and data analysis, including'the use of a site-specil'ic response ' spectrum anda'comparisonoftherelativeseismic.hazardbetweengheMidlandsiteand five other sites within the northeastern Central Stable region of the U.S.
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2.5.2.2 Tectonic Prov'nce and Seismic Hazard Analysis As presented in the FSAR, it is the applicant's position that the Midland site lies within the Michigan Basin Tectonic Province.
The Michigan Basin is a j
regional structural basin that underlies the southern peninsula of Michigt.n and parts of adjoining states.
It is the staff's position, from the standpoint of
,the Paleozoic geology, that the Midland site lies within the Central. Stable c(44[il in Ced,c e s 2,C,J, J cm d t h s s a./
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Region described by Eardley (1962). The Central Stable Region is a region of rc.t m.c relative consistency of surface geologic structural features characterized by a seri6s of arches, basins, and domes formed during the Paleozoic Era.
King (1964,1969) describes the area as " platform deposits on Precambrian foldbelts."
As discussed below, the applicant has also presented information on the seismic.
hazard analysis at the Midland site.
The staff has used the seismic hazard analysis to quantify the apparent low seismicity near the Midland site compared to other areas in the Central Stable Region.
1 (hb ec The staff has recognized that the wrface geology of the Central Stable Region does not explain the fact that different areas of this large region exhibit different levels of seismic activity.
Barstow and N associates (1981) have developed an earthquake frequency map of the central and eastern U.S. that displays the relative low level of seismic activity near the Midland site (0-3 2
earthquakes per 11,689 km in the period 1800-1977) compared with other areas of the central U.S' (4-128 events within the same area and time).
In an attempt to quantify the. low seismicity near the. Midland site, the appli-cant performed an analysis of seismic hazard for Midland along with five other sites in the upper midwestern region of the U.S.
The five sites were chosen by i
~
the staff to represent (and encompass) the range of activity levels expected in the central U.S.
The five sites chosen were Western New York, Northeastern Ohio, Northwestern Ohio, Northern Illinois-Indiana Border, and East Central Wisconsin. The output of the seismic hazard analysis is the annual probability j
that a given intensity earthquake will occur at each'of the sites.
The key elements of the applicant's methodology to estimate the seismic hazard involve the selection of the earthquake occurrence model (including seismic source zones, rate of activity in each zone, and largest earthquake in each zone) and ground motion m.odel (relating size of earthquake to ground motion).
An important part of completing a seismic hazard analysis involves the selec-tion of an a,pproach to incorporate the uncertainty of all input parameters into i
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the analysis.
Difficulty in accounting for this uncertainty is one of the reasons why the staff has used probability studies in only a very limited sense.
For this review, the staff is comparing the relative probabilities for a number of sites,- rather than the absolute probability at a, specific site.
One' reason for this is that sensitivity tests indicate stability when related h'azard probabilities are estimated (Sequoyah SER IM ( *
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4tvee The applicant has presented the seismic hazard analysis for.these alternate seismic source models.
One model treats the Central Stable Region as one unit; another is based upon the seismic source zones of Nuttli and Brill (1981); and the third separates out the Anna, Ohio and Attica-Niagara, New York, areas from the Central Stable Region based upon historic earthquakes.
These three models
' represent differing interpretations of where, earthquakes can occur, and can be thought of as possible seismotectonic province models, taking into account both the seismologic and geologic history of the central U.S.
In examining the results of the seismic hazard analysis, the staff finds that, in general, the Midland site has lower expected intensities than the five other sites at all exceedance probabilities.
Because specific results are model
~
dependent, weights were assigned to each source zone model.
The applicant puts more weight on the Nuttli and Brill model (50 percent) than on the Central Stable ~ Region (20 percent) or.the separation out of Anna and Attica (30 percent) models.
The staff has reviewed the hazard analysis results by weighing each model equally and by looking at the results for the model that separates out Anna and Attica from the Central $ table Region alone.
Using the above weights, the staff has compared Midland with the five'other sites at the same level of seismic hazard (10 8 and 10 4 were used).
It was found that Midland is about 0.50 to 0.70 intensity units lower than t'he five other sites at the same level of hazard.- Using Nutt11 and Herrmann's (1978) relationship Between magnitude and. intensity, the staff finds that intensity differences of 0.50 to 0.70 MMI units translate to about 0.25 and 0.35 magni-tude units.
d
2.5.2.3 Maximum Earthquake In the Central Stable Region, the largest historical earthquake, in terms of intensity, that has not been associated with tectonic structure is the March 9, i
1937, Anna, Ohio event.
The intensity of this earthquake was MMI = VII-VIII (Coffman and Von Hake, 1973).
In terms of magnitude, the staff has observ.ed thatthe1987Annaearthquake(mbig = 5.0 - 5.3, both instrumental and i'nterpreted (Nuttli and Brill, 1981; Nuttli and Herrmann, 1978) and other central U.S. earthquakes had similar magnitudes.
These events include the July 27, 1980, Kentucky earthquake (mbig=5.0-5.3)(ZimmerSSER,1981),the May 26, 1909, Northern Illinois earthquake (mblg=5.1,' interpreted)(Nuttli and Bril.1, 1981) and the June 18,~1975, Anna, Ohio earthquake (mblg = 5.3, interpreted)(Nuttli and Brill,1981).
The above differences in intensity and magnitude are key points.
Considering the Central Stable Region as one unit, MMI = VII - VIII or mbig = 5.3 would be i
used to define the SSE.
However, the above results indicate that defining the Central Stable Region from the Paleozoic geology may be inappropriate when one is attempting to achieve consistent descriptions for the SSE.
For defining the SSE, it is the staff's position ; hat magnitude is a better estimator of earth.-
quake source strength than intensity.
Intensity is a subjective description of the damage and felt effects to buildings and the ge,neral public.
In some cases intensity assignments can be highly dependent on the~ age of buildings, local soil conditions, on the distributio,n of population.
Magnitude is an instru--
' mental measurement; it can be measured over great distances with consistency.
Based on the above hazard analysil results, the staff concludes that for the Midland site the SSE should be defined by s
magnitude mbig = 5.0 (5.3 minus 0.25 to 0.35).
For the purposes of seismic design, the Midland site is in a different seismotectonic province (seismic source zone), one requiring a smaller controlling earthquake compared with other areas within the Central Stable Region.
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- 2.5.2.4 Safe-Shutdown Earthquake ihe.c The applicant and his con.sultant (Weston-Geophys4 cal-Gerporation.) have *deve-
.. loped a site-specific spectrum for Midland (original ground surface) by search-ing the eart,hquake strong-motion data base.
The site-specific spectrum ~ procedure has been discussed in detail in staff SERs (Sequoyah, March 1979; Fermi, June 1981), and testimony (Midland, October 1981).
The development of the site-specific spectrum proceded in parallel with the seismic hazard analysis.
The target magnitude was originally set at mbig = 5.3, based upon the assumption tha't the controlling earthquake was an Anna-type event. The acceleration r'ecords collected fall in the magnitude range of 4.9 to 5.5, it epicentral
. distances of 7 to 33 km.
The site conditions of this data set were chosen to match the Midland site, which has about 300 ft of stiff material overlain by 40 to 50 ft of softer material.
After reviewing the site-specific spectrum, the staff requested that various sensitivity tests be performed, including the addition of the strong motion records from the June 28, 1966 Parkfield, Cali-fornia, earthquake.
In reviewing this additional information the staff con-cluded that, in~ general, the data set wa,s no,t very sensitive to small varia-tions in input parameters and showed expected results when s0bjected to system-atic parameter variations.
However, when the Parkfield strong motion records
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were added to the data set, the site-specific spectrum increased by 10 to 30 percent for frequencies between 2.5 and 20 Hz, frequencies where the site-specific spectrum exceeds the original Midland design spectrum.
It is the applicant's position that the Parkfield records are inappropriate for The staff's detailed review of this sub-big = 5.3 site-specific spectrum.
am ject appears'in Midland hearing testimony (Midland, October 1981). The staff concluded that for a mbig =I5.3 spectrum the Parkfield event should be included.
.However, the results of the seismic hazard analysis demonstrated that an mbig
- 5.0 is.a conservative magnitude.td define the SSE for the Midland site. The l
staff' utilized four ground motion attenuation relationships (Murphy and O'Brien, 1978; Trifunac and Brady,1975; Nutt11 and Herrmann,1981; Campbell,1981) to 4
ll
assess the con 3ervatism of the proposed site-specific spectrum compared to that
~
which would be. determined if a mbig = 5.0 had been used as the target magnitude..
Based on this review, the staff has found that.the 84th percentile of the appli-cant's' site-specific spectrum (spectrum without the Parkfield acceleration records) is a conservative representati6n of the ground motion expected if a big =5.0earthquakeoccurredclosetothepdlandsite.
Fiaure 2.5.2-1 dis-m plays the 84th percentile of this data set, along with the original Midland
, design-basis earthquake spectrum.
Also shown in Fioure 2.5.2-1 is a Regulatory Guide 1.60 (" Design Response Spectra for Seismic Design of Nuclear Power Plants")
spectrum anchored at 0.12 g, about an intensity MMI = VII using the trend of the means.in Trifunac and Brady, 1975.
The figure also displays the extent that the site-specific spectrum exceeds the original design spectrum.
The response spectrum used in the seismic margins analysis (discussed in SER sec-tion 3.7.1) is the site-specific spectrum shown in Figure 2.5.2-1 modified in the long period range so as not to go below the original Midland design spectrum.
Because some of the seismic Category I structures are founded above the original ground surface in the plant fill, the applicant was requested to assess the potentia.1 for soil amplification through the fill.
In making this assessment the applicant chose'two methods to arrive at a response spectrum for the top of the fill material.
The first involved developing a second site-specific' spectrum matching the fill soil profile (an additional 30 ft of low velocity material on top of the original ground surface).
The second method involved utilizing a one-d.imensional wave pro'pagation program (SHAKE) to assess possible amplifica-tion at different frequencies.
The site-specific spectrum for the top of the fill material again involves a search of the strong motion data base.
The ranges of magnitudes and distances of the acceleration records chosen were magnitude cf 4.9 to 5.6 and distance of 6 2.n. i -
to 31 km.
Fioure 2 displays the 84th percentile of,the site-specific spectrum for the top of th'e fill material, along with the Midland original modified-Housner design response spectrum., Based upon its review of the site-specific spectrum, ;the staff finds that the 84th percentile of the spectrum displayed
- 2..: -
in Fiaure 1 is a conservative repr,esentation of that expe'cted for the top of thefillmaterial,assumingan%)g=5.0(intensitynearMMI=VII) earthquake occurred clo,se to the Midland site.
The staff also retained a consultant to review the SHAKE calculations to deter-mine if results using the SHAKE method were consistent with the site-specific spectrum.
Th4 consultant has concluded (Hadala, 1981):
SHAKE code calculations indicate that the amplification of the' site-I i
specific response spectrum for the top of fill over that at the top of till (original ground surface developed by the applicant through the analysis of empirical data) is more conservative than the one developed by application of theoretically calculated (SHAKE) amplifica-tion factors.
A more detailed discussion of the SHAKE calculations will be presented in a supplement to this report. (A-dec.
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I T,he response spectrum to be used in the seismic margins analysis (discussed in SER Section 3.7.1), for the top of the fill material is the site-specific spectrum shown "in Fiaure 2.5.2-2 modified on the long period range so as not to go below the original Midland design spectrum.
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2.5.2.5 Operating-Basis Earthquake i
t l
,As currently defined, the operating-basis earthquake (OBE) for the Midland site i
is based upon a modified Housner, response spectrum anchored at a peak accele-ration of 0.06 g.
The applicant has used the seismic hazard' analysis to' state that on the basis of the results of the hazard analysis, it is concluded that the return frequency of the OBE at the Midland site is, as a minimum, on the order of 300 to 500 years.
The staff has reviewed various probabilistic peak acceleration maps (Algermissen and Perkins,1976; Applied Technology Council, 1978) to assess the OBE.
The Algermissen and Perkins map shows that the Midland fgcontour;theAppliedTechnologyCouncilmapesti-a site would be near-the 0.04 mates a peak acceleration of less than 0.05 g.
Both maps are for a return period of 475 years (10 percent exceedance in 50 years).
Using the above values, the return period of the OBE is estimated to be on the order of hundreds of years. Based on its review and the applicant's analysis, the staff finds that the OBE is acceptable in light of 'the 10 CFR 100 Appendix"A definition of the OBE as:
...that earthquake which...could reasonably be expected to affect the plant site during the operating life of the plant."
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4 vu.n gs 2.5.3 Faulting
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l The faulting data,which included bore hole data and structure provided by the applicantrwere analyzed by the staf f and_
.f contour map j
its Los Alamos National Laboratory consultant.
We concluded-that the faulting in the site area is old and non-capable, based on Appendix A to 10 CFR Part 100.
2.5.3.1 Summary Detailed structure maps for the Midland area (Weston Geophysical, 1982) have been constructed on three Mississippian and Devonian stratigraphic horizons and show an orthogonal northwest-northeast pattern of mild deformation.
Associated with this pattern are inferred faults.
The deformation recognized in these strata is believed the result of vertical adjustments in Precambrian block structures responding to changes in the regional stress field (Fisher, 1979, 1982).
Correlation of drill holes across two Pennsylvanian coal fields near the plant site has been achieved by defining a cyclothemic coal zone.
Cross-sections by Weston Geophysical show that this coal zone forms a continuous undulating horizon and that the individual coal seams were deposited in a complex fluvial environ-ment.
They provide no convincing arguments for suspecting tectonic faulting and deformation after the Late Mississippian.
Exposures of Pennsylvanian strata far to the east and south of the plant site do show distortions and displacements; however, these are due to the effects of soft-sediments deformation and are not tectonicalLy derived.
The detailed studies for the Midland area conclude that displacement on inferred faults in Mississippian and older strata do not penetrate the Saginaw formation, and that l
the last fault movement is of pre-Atoka time (Early Pennsylvanian).
l These conclusions are consistent with observations on the regional f
geology history of the Michigan Basin (Haxby et al, 1976, Cross,
1982, Fisher, 1979, 1982).
An attempt to identify Michigan Basin bedrock structure by means of LANDSAT has not been successful due to a cover of thick glacial drift at the surface.
It is argued by Cross and Fisher that very special conditions would be required to detect bedrock faults and other structures at depth by means of Lineaments 4
or anomalous zones of vegetation at the surface.
In-situ stress measurements and the orientation of the maximum l
horizontal stress are compatible with regional data for the north central United States (Sbar and Sykes, 1973).
There is also a uniform pattern of post-glacial crustal rebound across the southern Michigan peninsula.
Neither of these conditions suggest anomalous stress buildup in the Michigan Basin.
The injection of brine solutions by Dow Chemical Corporation is performed at pressures 4
significantly below Lithostatic loading at injection depths and, therefore, is not a potential source for induced fault motion.
2.5.3.2 Paleozoic Tectonic Fabric 2.5.3.2.1 Pre-Pennsylvanian Orthogonal Tectonic Fabric Approximately 500 reliable drill holes have been used to construct structure maps for the tops cf the Devonian Dundee Formation and Squaw Bay Limestone (Traverse Group) and the Mississippian Marshall Formation.
These maps were used to examine structural features in the vicinity of the plant site and adjacent areas, including not only Midland County, but Bay County to the east and a portion of Saginaw County to the southeast.
Directly below the plant site, the mapped horizons on the Dundee Formation, Traverse Limestone, and Marshall Formation lie at depths of 3610, 2960, an'd 1180 feet,
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respectively.
The non-uniform distribution of control points in this detailed study reflects concentrations of drilling activity around fossil-fuel and evaporite related recources.'
An orthogonal tectonic fabric is recognized for this portion of
- the Michigan Basin based on structure contour maps.
Prominent broad anticlines and synclines with axial traces trending northwest, recognized regionally for the Michigan Basin, are the most obvious structures interpreted from these maps.
These folds, delineated on each of the mapped horizons, are spatially positioned atop one another.
The plant site is located on the s o u t h w e s't Limb of a syncline, 2-1/2 miles southwest of the axial trace.
The structure maps suggest the possible existence of several northwest trending faults in the area.
One such fault is south of and parallels an anticlinal axial trace aligned with the Kawkawlin oil field.
This inferred fault, 9 miles northeast of the plant site, is at least 12 miles in length and may extend eastward.,
Apparent vertical offset is suspected of reaching 150 feet maximum.
A smaller fault may parallet the trace of the Porter oil field 10 miles west of the plant site.
Both faults are interpreted as passing vertically through each of the mapped Paleozoic horizons.
Presently there is no evidence to suggest Low-angle faulting associated with this trend.
A tenuous interpretation for the much subdued northeast-trending structures recognized by Weston Geophysical is that they represent linear, steeply inclined faults with apparent vertical displacements generalky no greater than a few tens of feet.
Their identity as faults is based on a change in the rate of dip of the bed accompanied f
by an abrupt change in strike.
Such inflections can be delineated on the detailed structure maps, which are contoured at 25-fo,ot intervals.
Independently generated structure maps, however, for the top of the Traverse Limestone, contoured at 100-foot intervals, do not display this characteristic.
The northeast structural trend may thus represent small flexures instead of faults.
Evidence favorable for the presence of at least some faulting is (1) according to Northern Michigan Exploration Company (a division of Consumer's Power Company), the Pinconning oil field, 22 miles northeast of the i
plant site, is structurally controlled by a northeast stejking fracture, and (2) the nose of the major syncline 3 miles east of the plant site appears to be abruptly dislocated by faults with a right-Lateral component of displacement.
Detailed mapping of local structures indicates that the formation of the northeast structural trend, whether flexures or faults, culminated after development of folds aligned to the northwest.
This is based on minor distortions or displacements in the Limbs and along the axial traces of the broad regional folds.
2.5.3.2.2 Deformation Style in the Pennsylvanian Saginau Formation The Early Pennsylvanian Saginaw Formation unconformably overlies either the Bayport or Michigan Formations both of Late Mississippian age.
The Saginaw Formation consists of fluvial and margin-marine sandstones and shales with minor interbedded units of gypsum, coal, and Limestone.
Deformation recognized within ti.is formation is indicative of soft-sediment deformation.
rather than of tectonic origin.
The characteristics of this soft on--
sediment deformation are low-angle faults, slumping, and features associated with the compaction of sediments and the explusion of water.
Soft-sediment faults have been confirmed at Pennsylvanian
, surface exposures located far to the east and south of the plant i
site.
The Pennsylvanian stratigraphy surrounding the plant site is buried under 100 feet of glacial drift and has been examined for evidence of faulting with the use of more than 1300 coal, brine, salt, oil and gas wells.
Coals within the Saginaw Formation were deposited in a complex fluvial environment, and occur as discontinuous, locally channeled, and split seams.
Correlation of the Saginaw stratigraphy between dritL holes was accomplished by defining a coal zone, i.e.,
a cyclothem sequence of coal-bearing strata, bounded by massive grey shales.
A number of cross-sections through the Garfield coal field,15 miles north-east of the plant site, and the Midland Williams coal field immediately to the east of the site, have been constructed with the aid of this mappable coal zone.
These cross-sections show that the coal zone and individual coal beds can easily be interpreted as undulating horizons.
No convincing evidence exists for tectonic faulting within the Pennsylvanian or for the continuation of inferred faults, within Mississippian and Devonian strata, projecting upward into the Saginaw Formation.
2.5.3.3 Age of Fault Movement The detailed study concentrating on Lccal structural geology reveals that the orthogonal northwest-northeast pattern is recognizable down-section to at least the Middle Devonian Dundee Formation.
Structure maps on three stratigraphic horizons L_
1
. 1 within this interval suggest that a number of faults may parattet these trends.
It is also evident that the northeast trend had rincipalLy developed after the formation of the broad, northwest pe trending folds.
Assuming that the northeast trend represents I
faults with smaLL apparent vertical displacements, an examination of overlying Pennsylvanian strata has been necessary to establish limits on the age of last displacement along these surfaces.
Two Pennsylvanian coal fields near the plant siter examined in cross-section, show that an identifiable coal zone forms a continuous, undulating layer.
No convincing evidence exists for J
tectonic faults within the Saginaw Formation nor is there evidence that inferred faults in the underlying Paleozoic strata displace a
7 either the coal zone or any of the coal seams.
Pennsylvanian j
outcrops far to the east and south of the plant rite show soft-i j
sediment deformation as opposed to tectonically derived faulting.
The indication is that faultings if represented in the Devonian j
and Mississippian strata, subsided prior to deposition of the Pennsylvanian Saginaw Formation.
A similar conclusion can be derived f rom the regional geology based on published Literature and from geologists working the Michigan Basin.
Subsidence of the Michigan Basin and deformation of the sedimentary veneer covering the-crystalline basement complex is believed the result of adjusting Precambrian basement block structures to changes of the regional stress field.
Vertical displacements of these blocks have occurred periodically through geologic timer one occurring as early as e
+-
m--n.,awr~,--e
--->,-,-,ww,m-
-e, e
s r-,,. - -.., -,,
,.,y,
Late Precambrian.
Additional adjustments took place during Ordovician or Silurian time but the major movement occurred in.the Late Mississippian.
Absence of tectonic faulting or recognizable fold structures in Pennsylvanian or younger strata I
- suggests that regional basin subsidence abruptly decreased in downward rate prior to the Pennsylvanian.
After Late Mississippian time the Michigan Basin was for alL practical purposes tectonicalLy dead.
2.5.3.4 Lineament Analysis Lineament analysis by use of LANDSAT false color imagery for the southern Michigan peninsula was attempted to delineate bedrock structures that might influence the geologic interpretation of the plant site.
However, because of the thick cover of glacial drifte special conditions would be necessary for such structures to be revealed as surface Lineaments.
Special cases such as aqueous solutions moving upward along bedrock faults and thick glacial drift in order to effect vegetation are highly untfkely as a means for detection.
Active faulting as a means of providing surface expression is totally discounted.
It is concluded that any spatial relaticnship between LANDSAT Lineaments and bedrock structure is fortuitous.
This point is orought out by the fact that major structural features in the southern and eastern parts of the Michigan Basin, such as the Howell anticline, the Electric fault and Chatham Sagr are not detected on LANDSAT.
The same is true for the anticlinal traces present throughout the central portion of the basin.
It is not reasonable to expect subtle bedrock features located in the vicinity of Midland to be more easily detected than these larger
I i
structures.
2.5.3.5 The In-Situ Stress Field The regional stress field for the central Michigan Basin was
, examined with one deep welL in Gratiot county, 40 miles south of Midland, and a Dow Chemical brine welL from the Midland west area.
The first well has provided a 505 bar maximum horizontal stress and a 295 bar minimum horizontal stress (ratio = 1.71) at 4034 feet depth.
An orientation of N72 E for the maximum horizontal stress was observed at depths between 4650-4810 feet by borehole television tog of the Dow Chemical welL. These stress magnitudes and the maximum horizontal stress orientation are compatible with regional data for the northcentral United States and do not suggest anomalous stress buildup in the Michigan Basin (Handin, 1969, Hubbert and Willis, 1957, Odom and Hatcher, 1980).
Present rates of post-glacial crustal rebound are on theaorder of 2.5 mm per year at the northern tip of the lower Michigan peninsula, 1.0-1.5 mm per year for the Midland area, and no rebound at the southern Michigan border.
This uniform pattern of differential rebound is not enpected to produce anomalous stress condition at the Midland site.
Dow Chemical Corporation injects processed brine solutions into the Devonian SyLvanian sandstone and Dundee Limestone at Midland.
Presently, three injection wells and a brine welL are operating.
Fluid injection pressures are significantly below Lithostatic Loads at injection depths and do not represent a potential for inducing fault motion.
2.5.4 Subsidence Monitoring Due to the extraction of salt by solution mining at depths greater than 4000 feet near the plant site prior to 1973, a
~
network of 25 shallow and 2 deep benchmarks set in a rectangular
[
array around the site continue to be monitored for surface' subsidence.
Surveying techniques for these benchmarks have been upgraded to a level 1, class 2 survey as compared to either the Level 2 or 3 surveys used by the U. S. Geological Survey for their topographic control in the immediate area.
Consumer's Power Company reports no new evidence as of December 1981 for subsidence based on their most recent surveys.
Chemical, in separate surveys over their operations since Dow 1958, also reports no measurable evidence for surface subsidence in the Midland Michigan area.
1 I
i
.N '
Geology and Seismology References i,
Algermissen, S.T. and D. M. Perkins, "A Probabilistic Estimate of
~ Maximum Ground Acceleration in the Contiguous United States,"
U. S. Geological Survey, Open-File Report 76-416, 1976.
- ' Applied Technology Council, June 1978, Tentative Provisions for the Development of Seismic. Regulations for Buildings, National Bureau of Standards Special Publication 510, 514 pp.
3 Barstow, N.L., et al.,1981, An Approach to Seismic Zonation for Siting Nuclear Electric Power. Generating Facilities in the Eastern United States, Nuclear Regulatory Commission, NUREG/CR-1577.
4, Campbell, K.W.,1981, A Ground Motion Model for the Central United States Based on Near-Source Acceleration Data, Droceedings of the Conference on Earthquakes and Earthquake Engineering, Knoxville, Tennessee.
'i Coffman, J.L., and C.. A. Von Hake,1973, Earthquake History of the United States, NOAA - U. S. Dept. of Commerce Publication 41-1.
(-
Eardley, A., 1962, Structural Geology of North America, Harper and Row, 743 pp.
y fi -->
Hadala, P.F.,1981, Testimony of Dr. Paul F. H$d$l$ with Respect to g
the Study of Amplification of Earthquake Induced Ground Motions and the Stability of the Cooling Pond Dike Slopes Under Earthquake Loading.
12,I5 -
King, P.B.,1964, " Tectonic MEp of North Americ$," U. S. Geological Survey, N
Dept. of the Interior Publication.
I5. King, D.B., 1969, The Tectonics of. North America.- A. Discussion to. Accompany the Tectonic Map of North America, Scale 1:5,000,000, U. S. Geol. Survey Prof. Paper 628, Washington, D.C.
16, Murphy, J.R., and L. J. O'.Brien,1978, Analysis of a Worldwide Strong Motion Data Sample to Develop an Improved. Correlation Between Peak Acceleration, Seismic Intensity and Other Physical Parameters, U. S. Nuclear Regulatory Ccn1 mission, NUREG-0402.
Nuttli, 0.W., and R. B. Herrmann,1978, State-of-the-Art for Assescing Earthquake Hazards in the United States:
Credible Eai'thquakes.for the Central United States, Misc. paper S-73-1, Report.No. 12, U. S. Army Waterways Experiment Station, Vicksburg,-Miss., 100 p.
'6.
Nuttli, 0.W., and K. G. Brill,1981, An Approach to Seismic Zonation for.
Siting Nuclear Electric Power Generating Facilities in the. Eastern U. S.,
Part 2, U. S. Nuclear Regulatory Commission, NUREG/CR-1577.
s i, Nuttli, 0.W., and R. B. Herrmann,1981, Consequences of Earthquakes in the.
e Mississippi. Valley, American Society of Civil Engineers, St. Louis Micsouri,81-519.
I A
i
~u '
Trifunac, M.D., and A. G. Brady, 1975, On the Correlation of Seismic
=
Intensity. Scales.with Deaks of Recorded Strong Ground Motion, Seisuol.
Soc. Amer., Bull., v. 65.
U. S, Atomic Energy. Commission,197b, Construction. Permit.S$fety EY51uation n.
for the Midland Nuclear Plant 1 and 2, Docket No. 50-330/331 U. S. Atomic Energy Commission,1973, Design response spectr$ for seismic et design of nuclear power plants, Regulatory Guide 1.60.
E.
U. S. Nuclear Regulatory Comission,1975, Seismic $nd geologic siting criteria for nuclear power plants, 10 CFR Part 100, Appendix A.
U. S. Nuclear Regulatory Comission,1975,. General. Site suit $bility criteria 10 for nuclear power stations, Regulatory Guide 4.7.
g, U. S. Nuclear Regulatory Comission,1978, Standard format.and content i
of Safety Analysis Reports for Nuclear Power Plants, Regulatory Guide 1.70.
1 U. S. Nuclear Regulatory. Commission,1979, S$fety eh$1uation of the Sequoyah Nuclear Plant Units 1 and 2, Docket Nos. 50-327 and 50-328.
fi.
U. S. Nuclear Regulatory Comission,1979, Site investigations for foundations of ruclear power plants, Regulatory Guide 1.132.
U. S. Nuclear Regulatory Commission,198b, lb CFR Part lbb, ReEctor
,e Site Criteria.
I U..S. Nuclear Regulatory Comission,198b, lb CFR P$rt 5b.34, Contents of o.
applications; technical information and 10 CFR Part 50, Appendix A, j
General Design Criterion, Design bases for protection against natural phenomena.
u.
U. S. Nuclear Regulatory Commission, 1981, Safety Evaluation of the Enrico Fermi Atomic Plant NO. 2, Docket No. 50-341.
I u.
U.S.NuclearRegul$toryCommission,1981, Supplement $1S$fetyEYaluation of the William H. Zimmer Nuclear Power Station, Docket Nos. 50-358.
Pf.
U..S..NuclearRegulatoryCommission,1981,StandardReYiewPl$n,NUREG
- 0803, 3y U.. S. Nuclear Regulatory Comission,1981, Testimony of Jeffrey K. Kimball before the Atonic Safety and Licensing Board, Docket Nos. 50-329/330.
)
p.
Weston Geophysical Corp., " Site Specific Response Spectra, Midland Plant Units 1 and 2, part I, Response Spectra - Safe Shutdown Earthquake, Original Ground Surface," Feb.1981.
$7, Weston Geophysical Corp., " Site Specific Response Spectra, Midland Plant Units 1_ and 2, Addendum to Part I, Response Spectra - Original Ground Surface," June 1981.
1
.g' Weston Geophysical Corp., " Site Specific Response Spectra, Midland Plant Units 1 and 2 Part II, Response Spectra Applicable for the Top to Fill Material at the Plant Site," April 1981.
~
y,*
Weston Geophysical Corp., " Site Specific Response Spectra, Midland Plant -
. Units 1-and 2. Part III, Seismic Hazard Analysis" Feb.1981.
o i
(.,
Cross, A.T. (1982) " Review and Coments on 1.he February 1982 Report by Weston Geophysical Corporation." Report to Consumers Power Company, 10 p. Mich. State Univ.
8; Fisher,J.H.,(1979)"StructuralEYolutionofMichigan. Basin.and its Petroleum Potential". Amer. Assoc. Petroleum Geol. Bull.
63 450-451.
I
<!l
- Fisher, J. H., (1982) " Review of Weston Geophysical's Report.(February 1982) on the Bedrock Structure in the Vicinity of the Midland Nuclear Plant." Report to Consumers Power Company, 11 p. Mich.
State Univ.
Handin, J. (1969) "On the Coulomb-Mohr Failure Criterion." Jour.
Geophys. Res. 74, 5343-5348.
c.
Haxby, W. F., D. L. Turcotte, and J. M. Brid.(1976) " Thermal and Mechanical Evolution of the Michigan Basin." Tectonophys.
36, 57-75.
i Hubbert, M. K. and D. G. Willis (1957) " Mechanics of Hydraulic Fracturing." AIME Trans. 210, 153-168.
Odom,A.L.andR.D. Hatcher,Jr.(1980""ACharacterization.ofFaults.
_u in the Appalachian Foldbelt." Appendix A, In-Situ stress measurements.
Nucl. Reg. Comm. Report NUREG/CR-1621, 275-278.
L',
Sbar, M. L. and L. R. Sykes (1973) " Contemporary Compressive Stress and Seismicity in Eastern North America: An example of Intra-plate Tectonics." Geol. Soc. Amer. Bull. 84, 1861-1882.
4 WestonGeophysicalCorporation(1982)"DescriptionandEhaluationof Bedrock Structure in the Vicinity of Midland Plant - Units 1 and 2, Midland, Michigan 166 p. 4 plates.
i I
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