NUREG/CR-0081, Research Info Ltr 72:transmits NUREG/CR-0081 & NUREG/CR-0930, New England Seismotectonic Study Activities During FY77 & 78. W/O Encl
| ML20009B396 | |
| Person / Time | |
|---|---|
| Issue date: | 11/16/1979 |
| From: | Levine S NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Harold Denton, Minogue R Office of Nuclear Reactor Regulation, NRC OFFICE OF STANDARDS DEVELOPMENT |
| References | |
| RIL-072, RIL-72, NUDOCS 8107150363 | |
| Download: ML20009B396 (10) | |
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UNITED STATES
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MEMORANDUM FOR:
Harold R. Denton, Director Office of Nuclear Reactor Regulation Robert B. Minogue, Director Office of Standards Development FROM:
Saul Levine, Director Office of Nuclear Regulatory Research h
SUBJECT:
RESEARCH INFORMATION LETTER NO. 72 NEW ENGLAND SEISM 0 TECTONIC STUDY ACTIVITIES DURING FISCAL YEARS 1977 AND 1978
REFERENCES:
1.
Letter W. R. Stratton to Dixie Lee Ray dated May 16, 1973.
Subject:
Report on Seismic Research.
2.
Title 10, Chapter 1, Part 100, CFR Appendix A - Seismic and Geologic Siting Criteria for Nuclear Power; Plants.
3.
Memorandum N. B. Steuer to R. J. Matthbn dated July 15, 1975.
Subject:
U.S. Tectonic Province Map.
IrlTR000CT!0N This memorandun transmits NUREG/CR-0081 and NUREG/CR-0930 entitled, "New England Seismotectonic Study Activities During Fiscal Years 1977 and 1978." The research effort to produce these reports was coordinated by the Weston Observatory of Boston College with the cooperation of Bowdoin College, the.' University of Kentucky and the State Geological Surveys of New York and Connecticut. The New Englar.d Seismotectonic Study is a planned 5-year program to study the geology and seismicity of New England and contiguous areas to assess the potential seismic hazard to prospective nuclear power plant sites in the region.
SUMMARY
The New England Seismotectonic Study is a program of investigations designed to q
better understand the manifestations and causes of seismicity in New England and 1%
adjacent areas to assess the seismic hazard in the region. The study, which began July 1,1976, is a cooperative effort with several universities and State yg' Geological Surveys.
It is principally funded by the U.S. Nuclear Regula-tory Comission. The first year's program directly involved six investigators from Boston College, Bowdoin College, the University of Kentucky and the State Geological Surveys of New York and Connecticut.
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fiarold R. Denton Robert B. Minogue The initial effort (1) compiled and analyzed available pertinent information on seismicity, geology and geophysics in the region; (2) acquired new informa-tion by investigating previously identified problems; and (3) developed and organized a comprehensive program that, in 5 years, should provide a strong basis for an assessment of the seismic hazard of the region.
The program will integrate seismological, geophysical, geological and remote-sensing studies to complement the program of the Northeastern U.S. Seismic Network. The program is designed to provide (1) regional information needed to acquire a general understanding of seismicity and its relations with geo-logical and geophysical features and to delineate seismotectonic provinces, and (2) more retailed data in the areas of higher seismicity to attempt to reveal specific. relations of seismicity with geology and to identify active features.
Regional and site studies will evaluate hypotheses to explain the causes of earthquakes in the region.
The Study is coordinated with, and complementary to, the cooperative program of the flortheastern U.S. Seismic Network, funded by both the U.S. Nuclear Regulatory Commission and the U.S. Geological Survey. The network maintains seismograph stations and monitors earthquakes in the region.
Complementary projects in the region include the studies on the Clarendon-Linden fault zone, present day vertical uplift of the Adirondack Mountains, compilation and study of brittle structures of New York by the New York Geological Survey and the seismic array investigations in New York by the Lamont Doherty Observatory.
Results thus far document the prominence of faulting in the region and demon-strate the effectiveness of remote-sensing, magnetic-lineament and gravity-lineament analyses to reveal faults in the region.
Report manuscripts (which are now being processed) of studies parthily funded by the U.S. Nuclear Reg-ulatory Commission include:
"The Prel'. alaary Bedrock Geology of the Boston 2-Degree Sheet," " Bibliography of Seismology of the Northeastern United States," " Bedrock Geology of the Cape Ann Area, Massachusetts," " Preliminary Bouguer Gravity Map of Onshore-Offshore Northeastern United States and Southeastern Canada," " Bedrock Geology of the Worcester Region, Massachusetts,"
" Regional Bedrock Geology of the Moodus Area, Connecticut," " Bedrock Geology of the Eastern Half of the Portland 2-Degree Sheet," and " Interpretation of Aeromagnetic Data in Southwest Connecticut and Evidence for Faulting Along the Northern Fall Line."
The program includes studies of remote sensing, gravity, magnetics, fracture analysis, reanalysis and cataloging of instrumental data on earthquakes, and both detailed and reconnaissance geologic mapping.
The State Geological Surveys of New York, Connecticut, and Maine, and personnel from Bowdoin and Boston Colleges, the Universities of Rhode Island, Massachusetts, Kentucky and Delaware and the Rensselaer Polytechnic Institute are partic;pating.
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Harold R. Denton
-Robert B. Minogue The prudent selection of nuclear power plant sites must consider the seismic hazard and designate appropriate gravity acceleration values for construction standards.
Such selection requires more comprehensive understanding of the structure and tectonics of the region and their relationship to the seismicity than is presently available. The current practice of selecting a site with a limited amount of this information, followed by an extensive investigation of the region, is a slow and costly procedure, especially when faults are dis-covered near the site during such an investigation.
Gravity acceleration values, chosen for construction standards for nuclear power plants, are based on the maximum established earthquake intensity or magnitude.
When information is insufficient to judge the earthquake hazard, the values may be set too low for adequate safety or too high, and raise construction costs needlessly. The seismicity in flew England varies greatly from place to place (Boston Edison,1976; Hadley and Devine,1974) (Figures 1 and 2) and a scientific approach must be used to determine appropriate acceleration values within the region. A thorough study of the structure, tectonics, and seismicity of the region and their relationships is required to obtain the information. The level of seismic activity has varied in the past 300 years (Shakal and Toksoz,1977),
but the locations of the most active areas appear to have remained about the same (Figures 1, 2, and 3).
flew England is not in the most seismically act ne belt in the United States, but seismic activity has been recorded in the region since the first English settlers; and before that, one locality, Moodus, Connecticut, was sacred to the Indians due to the numerous earthquakes there. The 1755 earthquake, estimated at about intensity VIII, off Cape Ann, is the largest recorded seismic event in the region (Figure 1), and largely because of it, the Coast and Geodetic Survey placed the Boston region in the highest seismic risk category.
Early U.S. Geological Survey workers recognized the highly faulted nature of the region, but most workers in the region concentrated on mineralogic and related studies, and little was done to unravel the fault structure.
Hobbs, in the early 1900's, recognized the probable regional extent of the faulting, based on lineament studies (Hobbs, 1904). He also suggested a relationship between these regional faults and seismicity, especially at fault intersections.
Extensive faulting in the region has been slowly revealed, mainly through quadrangle mapping by the U.S. Geological Survey and through mapping tunnels and expressway roadcuts.
Recently, geophysical and remote-sensing data have revealed even more faults and possible faults both onshore and offshore. The more detailed structural and tectonic framework shows an 'mproved fit with the epicentral maps of the region and suggests further work would lead to a much greater understandi'g of the regional seismicity and earthquake mechanisms.
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harold R. Denton Robert B. Minogue At present, most of the mapped faults have been compiled for riew York and southern flew England (Isachsen,1977; Barosh, Pease, Schnabel, Bell, and Peper,1977), and a very preliminary compilation has been made for all the tiew England region (Barosh,1976).
Evidence for post-glacial faulting in the region have been summarized (Woodworth,1907; Oliver, Johnson, and Donnan,1970).
Interpretation of the aeromagnetic data has been done in a general way for all of southern New England with more detailed studies at some places.
Landsat and Skylab analyses have been done for flew York (Isachsen,1977; and Isachsen, et al.,1974).
Several very small-scale tectonic maps (Rodgers,1970), containing little fault data, cover the region, but the generalized small-scale map of Hadley and Devine (1974) is the only seismotectonic map available. Much of what has been done is in the general nature of preliminary work and should be refined.
In addition, a great deal of geophysical, remote-sensing, and geological data is presently available for analysis and synthesis.
These reports describe the study from July 1, 1977, to June 30, 1978.
A summary of the presently known relationship of seismicity with geology is presented, followed by sumaries of individual study projects and the program planned for the third year.
This recommendation also was in part brought about by Appendix A,10 CFR Part 100 (Ref. 2) which establishes requirements for seismic and geologic site investiga-tions for nuclear power plants and associated nuclear facilities necessary for evaluation of the site and for providing information needed for engineering designs.
Paragraph (6),Section IV of Appendix A requires that, where possible, epicenters of historically reported earthquakes be correlated with tectonic structures, any part of which are within 200 miles of the site, and that epicenters or locations of highest intensity, which cannot reasonably be correlated with tectonic structures, should be identified with tectonic provinces, any part of which are within 200 miles of the site.
This part of the Regulation was developed to take into account the fact that tectonic settings of the eastern U.S. are significantly different from those of the western U.S.
The Regulation does not provide guidance in the form of a map to establish seismotectonic provinces in the East. This has resulted in length /
licensing delays because of the time needed to resolve controversies among applicants, the public, and NRC regarding tectonic province boundary locations.
In 1974 the Office of Standards Development undertook an effort to develop an eastern U.S. Seismotectonic Province Map; however, when the map was completed, there was a consensus opinion that it was not adequate to clarify Appendix A to 10 CFR which requires the tectonic province approach. There remained specific infonnation needs to be satisfied in order to develop a map which will be a useful regulatory tool. That is, more geologic data and seismologic input are needed to more accurately delineate eastern U.S. seismotectonic provinces.
Consequently, the cooperative geologic and seismic programs were undertaken
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' Harold R. Denton Robert B. Minogue with state geological surveys and universities to gather regional data to (1) help delineate tectonic provinces; (2) identify earthquake source mechanisms; (3) improve knowledge of regional geologic conditions; (4) provide data to confirm past licensing decisions; (5) expand the existing geologic and seismic data base; and (6) to provide a consistent data base.
Approximately 23 state geological surveys and universities are cooperating under flRC funding to provide data needed to develop a data base for an eastern U.S.
seismotectonic province map. The studies are being conducted in three phases:
Phase ! -- existing data compilation (complete), Phase II -- new data acquisition, and Phase III -- problem areas.of the eastern U.S. and a seismotectonic provinces map. Many of these cooperative programs were funded initially by the Office of Stardards Development (Ref. 3). Later, the program responsibility was transferred to the Office of fluclear Regulatory Research because of their long-term nature.
CRITEr.IA FOR STUDY AREA SELECTION AND OBJECTIVES OF STUDY The northeastern United States has a number of population centers that have undergone rapid growth during the period 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 viable means to provide additional energy.
There are, at the present time,19 operating,15 being built, and 9 planned nuclear power plants in the northeastern U.S.
Many of the existing and proposed plants are located within or adjacent to an area which has been designated as seismic risk zone 2, an area having had earthquakes with resulting moderate damage and corresponding to seismicity up to iti VII.
f1RC rigorous guidelines 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 relationships 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.
This inadequacy has made 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 accurately reflects the potential magnitude of seismic events, is an important cost and risk factor in assigning appropriate design criteria for nuclear power plants.
Many carthquakes have occurred in the northeast and they have, in the past, been ascribed to crustal adjustment.
Uttle is known about the relationships of these structures, and this project wil' be a part of a larger study effort to investi-gate their possible interactica.
The objectives of the project are to delineate northeast seismotectonic provinces and associated structures, to investigate the relationships between the structures and seismicity, and to assign realistic values for maximum seismic magnitude in the region.
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A Harold R. Denton Robert B. Minogue RESULTS Results to date are preliminary; however, the prominence of faulting in the region has been documented and the effectiveness of remote-sensing, magnetic-lineament and gravity-lineament analyses to reveal faults in the region has been demonstrated.
To date, 50 geological and seismological reports have been produced as a result of the New England Seismotectonic Study. A bibliography of the reports can be foun'J in Appendix A of NUREG/CR-0939.
3%NNING A 5-year multidisciplinary study is planned.
The study will outline the geology, structure, tectonics and seismicity of the northeastern U.S.
Project work is planned in three separate but interrelating phases, which are:
- 1) Existing data synthesis;
- 2) Acquisition of new data, seismic network installation and operation; and J) Final synthesis of new and old data, interpretation, map and report preparation.
This interim report presents results of work completed in Phase I.
RECOMMENDATIONS It is recomended that the information contained in NUREG/CR-0081 and NUREG/CR-0930 be considered by the Office of Standards Development and the Office of Nuclear Reactor Regulation as input to the development 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, it is recommended that studies and data gathering be continued in this area so that the geology and seismicity of the eastern U.S. may be better understood.
It is also recommended that researchers make annual oral presentations to all NRC geologists and seismologists so that progress can be discussed and work redirected, if necessary.
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Harold R. Denton Robert B. Minogue Technical questions concerning NUREG/CR-0930 and NUREG/CR-0081 results may be t
directed to Neil B. Steuer at 427-4370.
/Saul Levine, Director Office of Nuclear Regulatory Research L
Enclosures:
l.
NUREG/CR-0930 2.-
4!' REG /CR-0081 3.
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