ML17263A009

Research Information Letter 0060, Siemicity and Tectonic Relationships of the Nemaha Uplift in Oklahoma

ML17263A009
Person / Time
Issue date:	10/12/1979
From:	Levine S Office of Nuclear Regulatory Research
To:	Harold Denton, Minogue R Office of Nuclear Reactor Regulation
References
RIL-0060
Download: ML17263A009 (9)

Text

{{#Wiki_filter:'j, UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20555 Gel' 12 1919 MEMORANDUM FOR: Harold R. Denton, Director FROM:

REFERENCES:

INTRODUCTION Office of Nuclear Reactor Regulation Robert B. Minogue, Director O~fice of Stindards Development Saul Levine, Director Office of Nuclear Regulatory Research RESEARCH INFORMATION LETTER NO. 60 SEISMICITY AND TECTONIC RELATIONSHIPS OF THE NEMAHA UPLIFT IN OKLAHOMA

1. Letter W. R. Stratton to Dixie Lee Ray dated

• May 16, 1973.

Subject:

Report on Seismic Research.

2. Title 10, Chapter 1, Part lbO, CFR Appendix A -

Seismic and Geologic Siting Criteria for Nuclear Power Pl ants.

3.

Meino: N. B. Steuer to R. J. Mattson dated July 15, 1975.

Subject:

U.S. Tectonic Province Map. This memo transmits NUREG/CR-0050 entitled 11Seismicity and Tectonic Relation- .ships. of. the Nertu~ha Uplift in Oklahoma FY 71. 11 The*research effort to produce this report was conducted by th.e Oklahoma Geological Survey. This resea.rch is a cooperative geologic; seismic and geophysical effort of the State Geological Surveys of Okl ahorria, Kansas*, Nebraska, Iowa and.Mi nriesota to study the earth science.parameters of the Nemaha Uplift and the Midcontinent Gravity Anomaly. The Nemaha Uplift and Midcontinent Gravity Anomaly are buried geologic struc-tures* along which there has.been *a history of earthquake activity. Hence, a knowledge of the Nemaha Uplift and.Midcontinent Gravity Anomaly is of vital importance in.the siti.rig and licensing of nuclear power plants.

SUMMARY

Geologic and seismologic investigations of the Nemaha Uplift began on October 1, 1976 *. The geological studies have focused, thus far, on the construction of a . series of structure-contour maps on key stratigraph.ic horizons -- the top of the Ordovidan Viola Formation, the base of the Pennsylvanian, and the top of the

Harold R. Denton Robert

• Mi.ddle Pennsylvanian Oswego Formation.

The contour-mapping phase of the program is. approxim.ately.two-thirdscompleted. The initial mapping program reveals a com pl ex fault p~ttern,and geologic.hi sto.ry of the Nemaha ridge. It appears

• .that the uplift and asso~iated faults began in E~rly Pennsylvanian time and that tecto*nic activity ceased in Middle Pennsylvanian time, at least in central Oklahoma.

A discussion of basement roe.ks in central Oklahoma is included within this report. The mo.st* systematicbasertient-roc~ study that includes the Nemaha ridge area was ,done by D.enison (1966), who classified the central Oklahoma basement rocks into the following four units: (1) Washington County Volcanic Group; (2) Spavinaw .*Granite Group; (3} Osage CountyMiCrogranite; and (4) Central Oklahoma Granite .. Group. T.he isotopic *ages range froni 1,150 to 1,270 million years, and these . ag'es, when. considerecl with. a'nalytical' variations, indicate a main period of thermal activity within 1,200 million years ago. The seismological stu.dies have concentrated on the installation of eight seis-mometers in such a way as to include detailed coverage of the Nemaha* ridge in

• Oklahoma as well as most of the remaining a~ea of bklahoma.

Geological Investigations Oklahoma can be subdivide.d into several major geologic and tectonic provinces (Fig. l}. One* of the~e stru¢tura1 features, *the Nemaha ridge, is a long north-south uplift that ex"t:ends northward from central Oklahoma through Kansas and

• into Nebraska..The Oklahoma portion of the ri.dge is 10 to 20 mil es wide and nearly 150 miles long. A number of earthquakes have occurrecl along or west of the Nemaha ridge, with thos*e at El Reno, Oklahoma, being most intense.

The Ne111aha ridge consists.of a* number of ~mall crustal blocks that were. raised shaTply along the axis of the uplift. These uplifted crustal blocks are typically 3 to*S miles wide and 5 to 20 miles 1ong and are bounded by faults on the east*ancl,/orwest sides *. These blocks were uplifted and eroded during Late Mississippian- (350 millfon years ago+/-) and Ea.rly P~nnsylvanian (290 million years ago +/-) time, and subsequently they were covered by later Pennsylvanian arid Pe.rmi an sediments. At 1 east some of the deep-seated faults near the axis of the Nemaha ridge were reactivated during*Middle Pennsylvanian time. Structure-Contour Program A comprehensive geological investigation began con~urrently with the insta1la-* tiori of a regional network of sefsmographs*. To better understand the geologic and tectonic history of the Nemaha *ridge, a series of structure-contour maps on key stratigrapfiic horizons is bei.ng constructed.

I* Harold R. Denton Robert Three horizons were selected for structure-contour mapping -- the top of the Mfddl e Pennsylv~rni an Oswego F'ormati on, the base of the Pennsylvanian, and the top of the Ordovician Viola Formation. lhese units were selected

• because tbey have been penetrated by a large number of boreholes and because of their easy identification on electric logs.

Seismolo9ical Studies An eight seismometer seismic net was installed in such a way as to include detailed coverage of the entire Nemaha ridge in Oklahoma, as well as most of the reinaini.ng area of Oklahoma (Fig. 2). This network of seismograph stations would. allow.the followi.n~ q~pabiliti~s: (a) marginal detection of all m3H 1.7 earthquakes; (b) reliable detection of all m z 2.0 earthquakes; (c) z marginal location of all m3Hz 1.8 earthquakes, a~U (d) reliable detection of all m3Hz 2.1 earthquakes. It was anticipated that the mciximum detection capability of the network would overlap into Kansas, and provide, with the Kansas and Nebraska networks, continuous coverage of the Nemaha ridge area. CRITERIA FOR STUDY AREA SELECTION AND OBJECTIVES OF STUDY .The midcontinent area of the United States has a number of population centers that have undergone rapid growth since the second World War. This increased growth, in conjunction with the increase in fossil fuel costs, has stimulated . electrical generation companies to consider nuclear power plants as a means to provide additional energy. There are, at the present time, two operating .. / and four proposed nuclear power pl ants in Nebraska, Kansas, and Oklahoma. At least three more are being considered for this same area. All of the existing and proposed plants are located within or adjacent to an area which has been designated.as seis~ic risk zone 2, an ~~ea having had earthquakes with resulting moderate damage and corresponding to seismicity up to MM VII. NRC has rigorous guidelines which must be adhered to before a permit to construct a nuclear power plant is granted to an.applicant. Local, as well as regional seismicity and structural relatfonships play an integral role in the final design criteria for nuclear power plants.* This requires that a value for the maximum expectable seismic event be assigned at a proposed site. The existing historical record.of seismicity is inadequate in a number of areas of the Mid-continent region because o.f the lack of instrumentation and/or the sensitivity -0f the instruments deployed to monitor earthquakes events. This inadequacy has mad.e it necessary to rely on the delineation of major tectonic provinces that are. based on broad regional geologic structures and associated seismicity. The delineation of tectonic provinces which accura,tely reflect the potential magnitud~of seis~ic events is an imp6rtant c6st and risk factor in assigning approp.ri ate design criteria for nuclear power pl ants.

Harold R. Denton Robert B. Minogue Many.earthqµak~s have oc;curred al o,ng the Nemaha Uplift, and they have, in the past;.. been ascribep to crustal adjustrii.en,t associated with that structure. MQre recently, geol.ogists have theorfzed that they.are related to Precambrian basemeri't, configuration, 'structure andlithology,,arid are. genetically related to the Arbuckle, Nemaha~ and Keweeriaw1rn Mafic Belt structures *stretching from Southe!rn Oklahoma-to the Northern Peninsula of Michigan. little is known about_ th,e rel ati onshi ps of thes.e structures' and this project wi 11 be a part of a larger study effort to investigate* their possible interaction. T_he objectives.of the project are: (1) tq delineate the Nemaha Uplift and its* associated structures; (2) to investigate the* relationships between the Nemaha Uplift and the Keweeriawan Mafic Belt;* and (3) to assign realistic values for maxim4111 seismic.magnitu~e in the region *. In order to carry out the above ob-jectives, the Geo'logical Surveys of Oklahoma, Ka'nsas, and Nebraska have estab-lished sei.smic networks in Oklahoma, central and eastern Kansas, and eastern Nebraska. Seismic data fro'm *the networks are collected and forwarded to the Oklahoma Geological Survey. Seismograms in existence prior to the NRC contract with the. Oklahoma Survey~ but* unpub 1 fs~ed, are*bei ng gathered and compi 1 ed. Gravity 9,nd aeromagnetic studies are b~in~ p~rformed, and detailed field studies unqertaken where necessary. Final.res.ults will be presented in the form of a serie$_ of maps and tables at a scale *of (1 :l,000,000) accompanied by explanatory text;. Thes_e will outline the relative seismitity in 'the study area and attempt to correlate it with tectonic features kn.own from surficial and subsurface geo- . l.ogical and. geo'physical evidence. This investigation will be closely rajated to an NRC-sponsored study conducted by the Geol_ogical Surveys of Michigan and Minnesota and the University of Minnesota and Michigan Technological University. PLANNING Initially, a five year program was planned. Project work is separated into the three.phases listed below. This *report presents results of.work *completed in Phase I. Phase I Purc.hase and installation of equipment to establish the seismic ne.twork. Recruitment and training of volunteer operators. Compilation and synthesization of*existfog geologic and geophysical data. Analysis of the seismograms. Prepare an interim report for fiscal year ending October 1977.

Harold R. Denton Robert Phase II - Installation of a microearthquake network. Operation and monitoring of the seismic network. Analysis of the seismograms. Prepare an interim report for fiscal year ending October 1979. Phase III - Gravity profiles. Operation and monitoring of the seismic network. Analysis of the seismograms. Field studies of known or inferred fault areas. Final compilation and report after fiscal year ending October 1981. NUREG/CR-0050 covers all of Phase I. BACKGROUND Refer to RIL No. 48, 11A Tectonic Overview of the Midcontinent. 11 The background information i_n RIL 48 applies equally to this RIL. It covers ACRS recommendations, relevance of 10 CFR P9-rt 100 Appendix A to the study, previous NRC effort and organization of the current programs. RESULTS NUREG/CR.-0050 describes data that were gathered during the time period covered by the NUREG and presents some preliminary results. The geologic and seismic data base available in this time period is i lis-~fficient to eval ugte the area except on a preliminary basis. A seistnotectotiic model *for the Nemaha Uplift in Oklahoma must be based on concepts developed from results of the studies :and must consider vertical and lateral variations in composition and physical properties of this tectonic feature. Study results are being used by Rondout Associates, Inc., in a project funded by.the Offfce of Nuclear Reactor Regulation to produce a seismic zoning map for the eastern U.S. Additionally, data gathered by the Oklahoma Nemaha. Seismotectonic Study are considered by the NRR staff in making licensi~g decisions.

Harold R. Denton Robert B. Minogue RECOMMENDATIONS It is recommended that the information contained in NUREG/CR-0050 be considered by the Office of Sta_ndqrds Development and the Office of Nuclear Reactor Regulati9n as *input_to.the d~velopment of a tectonic province or seismic zoning map of the eastern U.S. and to provide a* basis.and guide for ongoing studies in the area. Additionally, RES recommends_ that studies be continued in this area to attain the objec~ives previciusly stated, with redirection and modification of projects as dee.med necess:ary by ongoing work. Technical questions concerning NUREG/CR-0050 results may be directed to Neil B. Steuer at 427-4370. ,&d.b-Office of Nuclear Regulatory Research

Enclosures:

1.

NUREG/CR-0050

2.

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3.

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-~--.::: " - Harold R. Denton -;Robert B. M1nogue RECOMMENDATIONS. '

• 11; 1s recomended that -the informatfon contained in NUREG/CR-0050 be considered by the Office of Standards Development and the Office of Nuclear Reactor Regulation as 1nput to the development of a tectonic province or seismic zoning

-~P of the eastern U.S. and to provide a bas1s and guide for ongoing studies in the area. Additionally, RES recoomends that studies be continued fn this area to attain_ -- ,,,,~~---, the objectives previously stated, wfth redirection and modification of -projects_ as deemed necessary by ongoing work. Technical questions concerning NUREG/CR-0050 results may be directed to Neil B. Steuer at 4i7-4370.

Enclosures:

1. NUREG/CR-0050

~2. figure 1

3. Figure 2 DISTRIBUTION:

Subject Circ Chron Steuer, rf -Harbour, cy Kenneally, cy Shao, cy Murley, cy Beratan, cy _ Jackson, cy Larkins, cy Budnitz, cy Levine, cy Original Signed By Saal Levine./' Saul Levine, Director Office of Nuclear Regulatory Research .. *. ~ .~ ' :..

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