Regulatory Guide 1.165

(Draft Was DG-1032) Identification and Characterization of Seismic Sources and Determination of Safe-Shutdown Earthquake Ground Motion

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Issue date:	03/31/1997
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U.S. NUCLEAR REGULATORY COMMISSION March 1997

E

REGULATORY GUll OFFICE OF NUCLEAR REGULATORY RESEARCH

REGULATORY GUIDE 1.165 S(Draft was DG-1 032)

IDENTIFICATION AND CHARACTERIZATION OF SEISMIC SOURCES AND

DETERMINATION OF SAFE SHUTDOWN EARTHQUAKE GROUND MOTION

A. INTRODUCTION

sign bases for seismically induced floods and water waves, and other design conditions.

In 10 CFR Part 100, "Reactor Site Criteria," Sec In 10 CFR 100.23, paragraph (dX1), "Determina tion 100.23, "Geologic and Seismic Siting Factors," tion of the Safe -Shutdown Earthquake Ground Mo paragraph (c), "Geological, Seismological, and Engi tion," requires that uncertainty inherent in estimates of neering Characteristics," requires that the geological, the SSE be addressed through an appropriate analysis, seismological, and engineering characteristics of a site such as a probabilistic seismic hazard analysis or suit and its environs be investigated in sufficient scope and able sensitivity analyses.

detail to permit an adequate evaluation of the proposed This guide has been developed to provide general site, to provide sufficient information to support evalu guidance on procedures acceptable to the NRC staff for ations performed to arrive at estimates of the Safe Shut

(1) conducting geological, geophysical, seismological, down Earthquake Ground Motion (SSE), and to permit and geotechnical investigations, (2) identifying and adequate engineering solutions to actual or potential characterizing seismic sources, (3) conducting proba geologic and seismic effects at the proposed site. Data bilistic seismic hazard analyses, and (4) determining on the vibratory ground motion, tectonic surface de the SSE for satisfying the requirements of 10 CFR

formation, nontectonic deformation, earthquake recur

100.23.

rence rates, fault geometry and slip rates, site founda tion material, and seismically induced floods, water This guide contains several appendices that ad waves, and other siting factors will be obtained by re dress the objectives stated above. Appendix A con viewing pertinent literature and carrying out field tains a list of definitions of pertinent terms. Appendix investigations. B describes the procedure used to determine the refer ence probability for the SSE exceedance level that is

. In 10 CFR 100.23, paragraph (d), "Geologic and acceptable to the staff. Appendix C discusses the de Seismic Siting Factors," requires that the geologic and velopment of a seismic hazard information base and seismic siting factors considered for design include a the determination of the probabilistic ground motion determination of the SSE for the site, the potential for level and controlling earthquakes. Appendix D dis surface tectonic and nontectonic deformations, the de- cusses site-specific geological, seismological, and USNRC REGULATORY GUIDES "The guides we issued In the following ten broad divisions:

Regulatory Guides wre Issued to describe and make available to the public such informa lion as methods acceptable to the NRC staff for Implementing specific parts of the Com 1. Power Reactors 6. Products missions reguldion, techniques used by the staff In aluaftng specific problems orpoe 2. .Research and Test Reactors 7. Transportation Uated accidents, and data needed by he NRC staff InIts review of applicatiors for per & Fuels and Materials Facilities 8. Occupational Health mits aid licenses. Regulatory guides we not substitutes for regulations, and compliance 4. Environmental and Siting 9. Antilrust and Financial Review with themn Is not required. Methods and aloutions different from those set out Inthe Ogides & Materials and Plant Protection 10. General will be acceptable I #W provide a basis for the f*wngs requisfte to the issuance or con.

tiriance of a permit or icense by fthCommission.

Sinogle copies of regulatory guides may be obtained hre of charge by writng the Office of This guide was issued after consideration of comments received trom the public. Com Administration. Attention: Distribution end Moi Services Section, U.S. Nuclear Regulatory ments and suggestlons for rmprovements In these guides reancouraged at anlnts, and Cornmission Washinglon. DC 20555-0001; or by fla at (301)4162260.

guides will be revlseds appropriate, to scomrnodste comments and to ref:ect now in formation or aperlence.

issued guides may also be purchased from the National Technical Information Service on Written commerts may be submrted to fte Rules Review and Directives Branch. CFIPS, a standing order basis. Dleails on this service may be obtained by writing NTIS, 5285 Port ADM, U.S. Nuclear Regulatory Commission, Washington. DC 20555-0001. Royal Road, Springf*eld, VA 22161.

geophysical investigations. Appendix E describes a cal parameters. A PSHA also provides an evaluation method to confirm the adequacy of existing seismic of the likelihood of SSE recurrence during the design sources and source parameters as the basis for deter lifetime of a given facility, given the recurrence inter mining the SSE for a site. Appendix F describes pro val and recurrence pattern of earthquakes in pertinent cedures to determine the SSE. seismic sources. Within the framework of a probabil istic analysis, uncertainties in the characterization of The information collections contained in this regu seismic sources and ground motions are identified latory guide are covered by the requirements of 10 CFR Part 50, which were approved by the Office of Manage and incorporated in the procedure at each step of the process for estimating the SSE. The role of geologi ment and Budget, approval number 3150-0011. The cal, seismological, and geophysical investigations is NRC may not conduct or sponsor, and a person is not to develop geosciences information about the site for required to respond to, a collection of information un use in the detailed design analysis of the facility, as less it displays a currently valid OMB control number.

well as to ensure that the seismic hazard analysis is

B. DISCUSSION

based on up-to-date information.

BACKGROUND Experience in performing seismic hazard evalua tions in active plate-margin regions in the Western A probabilistic seismic hazard analysis (PSHA) United States (for example, the San Gregorio-Hosgri has been identified in 10 CFR 100.23 as a means to de fault zone and the Cascadia Subduction Zone) has termine the SSE and account for uncertainties in the also identified uncertainties associatedwith the char seismological and geological evaluations. The rule fur acterization of seismic sources (Refs. 1-3). Sources ther recognizes that the nature of uncertainty and the ap of uncertainty include fault geometry, rupture seg propriate approach to account for it depend on the tec mentation, rupture extent, seismic-activity rate, tonic regime and parameters such as the knowledge of ground motion, and earthquake occurrence model seismic sources, the existence of historical and re ing. As is the case for sites in the CEUS, alternative corded data, and the level of understanding of the tec hypotheses and parameters must be considered to ac tonics. Therefore, methods other than probabilistic count for these uncertainties.

methods such as sensitivity analyses may be adequate for some sites to account for uncertainties. Uncertainties associated with the identification

-Appendix A, "Seismic and Geologic Siting Crite and characterization of seismic sources in tectonic en vironments in both the CEUS and the Western United ria for Nuclear Power Plants," to 10 CFR Part 100 is States should be evaluated. Therefore, the same basic primarily based on a deterministic methodology. Past approach can be applied to determine the SSE.

licensing experience in applying Appendix A has dem onstrated the need to formulate procedures that quanti APPROACH

tatively incorporate uncertainty (including alternative The general process to determine the SSE at a site scientific interpretations) in the evaluation of seismic includes:

hazards. A single deterministic representation of seis mic sources and ground motions at a site may not 1. Site- and region-specific geological, seismo explicitly provide a quantitative representation of the logical, geophysical, and geotechnical inves uncertainties in geological, seismological, and geo tigations and physical data and alternative scientific interpretations.

2. A probabilistic seismic hazard assessment.

Probabilistic procedures were developed during the past 10 to 15 years specifically for nuclear power CENTRAL AND EASTERN UNITED STATES

plant seismic hazard assessments in the Central and Eastern United States (CEUS) (the area east of the The CEUS is considered to be that part of the Rocky Mountains), also referred to as the Stable Con United States east of the Rocky Mountain front, or tinent Region (SCR). These procedures provide a east of Longitude 1050 West (Refs. 4, 5). To deter structured approach for decisionmaking with respect mine the SSE in the CEUS, an accepted PSHAmeth to the SSE when performed together with site-specif odology with a range of credible alternative input in ic investigations. A PSHA provides a framework to address the uncertainties associated with the identifi terpretations should be used. For sites in the CEUS,

the seismic hazard methods, the data developed, and K

cation and characterization of seismic sources by in seismic sources identified by Lawrence Livermore corporating multiple interpretations of seismologi- National Laboratory (LLNL) (Refs. 4-6) and the

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Electric Power Research Institute (EPRI) (Ref. 7) that are known to be at or near the surface, (2) buried have been reviewed and accepted by the staff. The (blind) sources that may often be manifested as folds at LLNL and EPRI studies developed data bases and the earth's surface, and (3) subduction zone sources, scientific interpretations of available information such as those in the Pacific Northwest. The nature of K 1 and determined seismic sources and source charac surface faults can be evaluated by conventional surface terizations for the CEUS (e.g., earthquake occur and near-surface investigation techniques to assess ori rence rates, estimates of maximum magnitude). entation, geometry, sense of displacements, length of rupture, Quaternary history, etc.

In the CEUS, characterization of seismic sources is more problematic than in the active plate-margin Buried (blind) faults are often associated with region because there is generally no clear association surficial deformation such as folding, uplift, or subsi between seismicity and known tectonic structures or dence. The surface expression of blind faulting can near-surface geology. In general, the observed geo be detected by mapping the uplifted or down-dropped logic structures were generated in response to tecton geomorphological features or stratigraphy, survey ic forces that no longer exist and have little or no cor leveling, and geodetic methods. The nature of the relation with current tectonic forces. Therefore, it is structure at depth can often be evaluated by core bor important to account for this uncertainty by the use of ings and geophysical techniques.

multiple alternative models. Continental United States subduction zones are lo The identification of seismic sources and reason cated in the Pacific Northwest and Alaska. Seismic able alternatives in the CEUS considers hypotheses sources associated with subduction zones are sources presently advocated for the occurrence of earth within the overriding plate, on the interface between the quakes in the CEUS (for example, the reactivation of subducting and overriding lithospheric plates, and in favorably oriented zones of weakness or the local am the interior of the downgoing oceanic slab. The charac plification and release of stresses concentrated terization of subduction zone seismic sources includes around a geologic structure). In tectonically active consideration of the three-dimensional geometry of the areas of the CEUS, such as the New Madrid Seismic subducting plate, rupture segmentation of subduction Zone, where geological, seismological, and geo zones, geometry of historical ruptures, constraints on

. physical evidence suggest the nature of the sources the up-dip and down-dip extent of rupture, and compar that generate the earthquakes, it may be more ap isons with other subduction zones worldwide.

propriate to evaluate those seismic sources by using The Basin and Range region of the Western procedures similar to those normally applied in the United States, and to a lesser extent the Pacific North Western United States. west and the Central United States, exhibit temporal clustering of earthquakes. Temporal clustering is WESTERN UNITED STATES best exemplified by the rupture histories within the Wasatch fault zone in Utah and the Meers fault in cen The Western United States is considered to be that tral Oklahoma, where several large late Holocene co part of the United States that lies west of the Rocky seismic faulting events occurred at relatively close Mountain front, or west of approximately 1050 West intervals (hundreds to thousands of years) that were Longitude. For the Western United States, an informa preceded by long periods of quiescence that lasted tion base of earth science data and scientific interpreta thousands to tens of thousand years. Temporal clus tions of seismic sources and source characterizations tering should be considered in these regions or wher (e.g., geometry, seismicity parameters) comparable to ever paleoseismic evidence indicates that it has oc the CEUS as documented in the LLNL and EPRI stud curred.

ies (Refs. 4-7) does not exist. For this region, specific interpretations on a site-by-site basis should be applied (Ref. 1).

C. REGULATORY POSITION

The active plate-margin region includes, for exam

1. GEOLOGICAL, GEOPHYSICAL,

ple, coastal California, Oregon, Washington, and Alas SEISMOLOGICAL, AND GEOTECHNICAL

ka. For the active plate-margin region, where earth INVESTIGATIONS

quakes can often be correlated with known tectonic structures, those structures should be assessed for their 1.1 Comprehensive geological, seismological, earthquake and surface deformation potential. In this geophysical, and geotechnical investigations of the region, at least three types of sources exist: (1) faults site and regions around the site should be performed.

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For existing nuclear power plant sites where addi acterize the seismic and surface deformation tional units are planned, the geosciences technical in potential of any capable tectonic sources and formation originally used to validate those sites may, the seismic potential of seismogenic sources, or be inadequate, depending on how much new or addi to demonstrate that such structures are not pres tional information has become available since the ini ent. Sites with capable tectonic or seismogenic tial investigations and analyses were performed, the sources within a radius of 40 km (25 miles) may quality of the investigations performed at the time, require more extensive geological and seismo and the complexity of the site and regional geology logical investigations and analyses (similar in and seismology. This technical information should detail to investigations and analysis usually be utilized along with all other available information preferred within an 8-km (5-mile) radius).

to plan and determine the scope of additional inves tigations. The investigations described in this regula 3. Detailed geological, seismological, geophysical, tory guide are performed primarily to gather informa and geotechnical investigations should be con tion needed to confirm the suitability of the site and to ducted within a radius of 8 km (5 miles) of the gather data pertinent to the safe design and construc site, as appropriate, to evaluate the potential for tion of the nuclear power plant. Appropriate geologi tectonic deformation at or near the ground surface cal, seismological, and geophysical investigations and to assess the ground motion transmission are described in Appendix D to this guide. Geotech characteristics of soils and rocks in the site vicin nical investigations are described in Regulatory ity. Investigations should include monitoring by Guide 1.132, "Site Investigations for Foundations of a network of seismic stations.

Nuclear Power Plants" (Ref. 8). Another important

4. Very detailed geological, geophysical, and geo purpose for the site-specific investigations is to de technical engineering investigations should be termine whether there are new data or interpretations conducted within the site [radius of approximate that are not adequately incorporated in the existing PSHA data bases. Appendix E describes a method for ly 1 km (0.5 miles)] to assess specific soil and evaluating new information derived from the site rock characteristics as described in Regulatory Guide 1.132 (Ref. 8).

specific investigations in the context of the PSHA.

1.2 The areas of investigations may be expanded These investigations should be performed at four beyond those specified above in regions that include ca levels, with the degree of their detail based on distance pable tectonic sources, relatively high seismicity, or from the site, the nature of the Quaternary tectonic complex geology, or in regions that have experienced a regime, the geological complexity of the site and re large, geologically recent earthquake.

gion, the existence of potential seismic sources, the po tential for surface deformations, etc. A more detailed 1.3 It should be demonstrated that deformation discussion of the areas and levels of investigations and features discovered during construction, particularly the bases for them is presented in Appendix D to this faults, do not have the potential to compromise the regulatory guide. The levels of investigation are char safety of the plant. The two-step licensing practice, acterized as follows. which required applicants to acquire a Construction Permit (CP), and then during construction apply for

1. Regional geological and seismological inves an Operating License (OL), has been modified to al tigations are not expected to be extensive nor in low for an alternative procedure. The requirements great detail, but should include literature re and procedures applicable to NRC's issuance of com views, the study of maps and remote sensing bined licenses for nuclear power facilities are in Sub data, and, if necessary, ground truth reconnais part C of 10 CFR Part 52. Applying the combined li sances conducted within a radius of 320 km censing procedure to a site could result in the award of

(200 miles) of the site to identify seismic. a license prior to the start of construction. During the sources (seismogenic and capable tectonic construction of nuclear power plants licensed in the sources). past two decades, previously unknown faults were often discovered in site excavation

s. Before issuance

2. Geological, seismological, and geophysical in of the OL, it was necessary to demonstrate that the;

vestigations should be carried out within a ra faults in the excavation posed no hazard to the facili dius of 40 km (25 miles) in greater detail than ty. Under the combined license procedure, these the regional investigations to identify and char- kinds of features should be mapped and assessed as to

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their rupture and ground motion generating potential characterization of seismic sources should be ad while the excavations' walls and bases are exposed. dressed as appropriate. Seismic source is a general term Therefore, a commitment should be made, in docu referring to both seismogenic sources and capable tec ments (Safety Analysis Reports) supporting the li tonic sources. The main distinction between these two cense application, to geologically map all excava types of seismic sources is that a seismogenic source tions and to notify the NRC staff when excavations would not cause surface displacement, but a capable are open for inspection. tectonic source causes surface or near-surface displace ment.

1.4 Data sufficient to clearly justify all conclu sions should be presented. Because engineering solu Identification and characterization of seismic tions cannot always be satisfactorily demonstrated for sources should be based on regional and site geological the effects of permanent ground displacement, it is pru and geophysical data, historical and instrumental seis dent to avoid a site that has a potential for surface or micity data, the regional stress field, and geological ev near-surface deformation. Such sites normally will re idence of prehistoric earthquakes. Investigations to quire extensive additional investigations. identify seismic sources are described in Appendix D.

The bases for the identification of seismic sources

1.5 For the site and for the area surrounding the should be documented. A general list of characteristics site, the lithologic, stratigraphic, hydrologic, and to be evaluated for a seismic source is presented in Ap structural geologic conditions should be character pendix D.

ized. The investigations should include the measure ment of the static and dynamic engineering proper S2.3 - As part of the seismic source pharacteriza ties of the materials underlying the site and an tion, the seismic potential for each source should be evaluation of physical evidence concerning the be evaluated. Typically, characterization of the seismic havior during prior earthquakes of the surficial mate potential consists of four equally important elements:

rials and the substrata underlying the site. The prop erties needed to assess the behavior of the underlying 1. Selection of a model for the spatial distribution of earthquakes in a source.

material during earthquakes, including the potential for liquefaction, and the characteristics of the under 2. Selection of a model for the temporal distribution lying material in transmitting earthquake ground mo of earthquakes in a source.

tions to the foundations of the plant (such as seismic wave velocities, density, water content, porosity, 3. Selection of a model for the relative frequency of elastic moduli, and strength) should be measured. earthquakes of various magnitudes, including an

2. SEISMIC SOURCES SIGNIFICANT TO estimate for the largest earthquake that could oc cur in the source under the current tectonic THE SITE SEISMIC HAZARD regime.

2.1 For sites in the CEUS, when the EPRI or LLNL PSHA methodologies and data bases are used to 4. A complete description of the uncertainty.

determine the SSE, it still may be necessary to investi For example, in the LLNL study a truncated expo gate and characterize potential seismic sources that nential model was used for the distribution of magni were previously unknown or uncharacterized and to tudes given that an earthquake has occurred in a source.

perform sensitivity analyses to assess their significance A stationary Poisson process is used to model the spa to the seismic hazard estimate. The results of investiga tial and temporal occurrences of earthquakes in a tions discussed in Regulatory Position 1 should be source.

used, in accordance with Appendix E, to determine For a general discussion of evaluating the earth whether the LLNL or EPRI seismic sources and their quake potential and characterizing the uncertainty, re characterization should be updated. The guidance in fer to the Senior Seismic Hazard Analysis Committee Regulatory Positions 2.2 and 2.3 below and in Appen Report (Ref. 9).

dix D of this guide may be used if additional seismic 2.3.1 For sites in the CEUS, when the LLNL or sources are to be developed as a result of investigations.

EPRI method is not used or not applicable (such as in

2.2 When the LLNL and EPRI methods are not the New Madrid Seismic Zone), it is necessary to evalu used or are not applicable, the guidance in Regulatory ate the seismic potential for each source. The seismic Position 2.3 should be used for identification and char sources and data that have been accepted by the NRC in acterization of seismic sources. The uncertainties in the past licensing decisions may be used, along with the

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data gathered from the investigations carried out as de "* Surface rupture length versus magnitude (Refs.

scribed in Regulatory Position 1. 10-13),

"* Subsurface rupture length versus magnitude Generally, the seismic sources for the CEUS are (Ref. 14), .-

area sources because there is uncertainty about the

"* Rupture area versus magnitude (Ref. 15),

underlying causes of earthquakes. This uncertainty is due to a lack of active surface faulting, a low rate of "* Maximum and average displacement versus seismic activity, and a short historical record. The as magnitude (Ref. 14),

sessment of earthquake recurrence for CEUS area "* Slip rate versus magnitude (Ref. 16).

sources commonly relies heavily on catalogs of ob When such correlations as References 10-16 are served seismicity. Because these catalogs are incom used, the earthquake potential is often evaluated as the plete and cover a relatively short period of time, it is mean of the distribution. The difficult issue is the evalu difficult to obtain reliable estimates of the rate of ac ation of the appropriate rupture dimension to be used.

tivity. Considerable care must be taken to correct for This is a judgmental process based on geological data incompleteness and to model the uncertainty in the for the fault in question and the behavior of other re rate of earthquake recurrence. To completely charac gional fault systems of the same type.

terize the seismic potential for a source it is also nec essary to estimate the largest earthquake magnitude The other elements of the. recurrence model are that a seismic source is capable of generating under generally obtained using catalogs of seismicity, fault the current tectonic regime. This estimated magni slip rate, and other data. In some cases, it may be ap tude defines the upper bound of the earthquake recur propriate to use recurrence models with memory. All rence relationship. the sources of uncertainty must be appropriately mod eled. Additionally, the phenomenon of temporal clus The assessment of earthquake potential for area tering should be considered when there is geological sources is particularly difficult because the physical evidence of its past occurrence.

constraint most important to the assessment, the di 2.3.3 For sites near subduction zones, such as in mensions of the fault rupture, is not known, As a re the Pacific Northwest and Alaska, the maximum mag sult, the primary methods for assessing maximum nitude must be assessed for subduction zone seismic earthquakes for area sources usually include a con sources. Worldwide observations indicate that the larg sideration of the historical seismicity record, the pat est known earthquakes are associated with the plate in tern and rate of seismic activity, the Quaternary (2 terface, although intraslab earthquakes may also have million years and younger), characteristics of the large magnitudes. The assessment of plate interface source, the current stress regime (and how it aligns earthquakes can be based on estimates of the expected with known tectonic structures), paleoseismic data, dimensions of rupture or analogies to other subduction and analogues to sources in other regions considered zones worldwide.

tectonically similar to the CEUS. Because of the shortness of the historical catalog and low rate of 3. PROBABILISTIC SEISMIC HAZARD

seismic activity, considerable judgment is needed. It ANALYSIS PROCEDURES

is important to characterize the large uncertainties in A PSHA should be performed for the site as it al the assessment of the earthquake potential. lows the use of multiple models to estimate the likeli hood of earthquake ground motions occurring at a site,

2.3.2 For sites located within the Western United and a PSHA systematically takes into account uncer States, earthquakes can often be associated with known tainties that exist in various parameters (such as seismic tectonic structures. For faults, the earthquake potential sources, maximum 'earthquakes,. and ground is related to the characteristics of the estimated future motion attenuation). Alternative hypotheses areý con rupture, such as the total rupture area, the length, or the sidered in a quantitative fashion in a PSHA. Alterna amount fault displacement. The following empirical tive hypotheses can also be used to evaluate the sensi relationsofcan be used to estimate the earthquake poten tivity of the hazard to the uncertainties in the significant tial from fault behavior data and also to estimate the parameters and to identify the relative contribution of amount of displacement that might be expected for a each seismic source to the hazard. Reference 9 provides given magnitude. It is prudent to use several of these guidance for conducting a PSHA.

different relations to obtain an estimate of the earth The following steps describe a procedure that is ac quake magnitude. ceptable to the NRC staff for performing a PSHA. The

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details of the calculational aspects of deriving control critically damped median spectral ground mo ling earthquakes from the PSHA are included in Ap tion levels for the average of 5 and 10 Hz, pendix C. Sa-,510, and for the average of 1 and 2.5 Hz, Sa,1.2.5. Appendix B discusses situations in

/ 1. Perform regional and site geological, seismologi which an alternative reference probability may cal, and geophysical investigations in accordance be more appropriate. The alternative reference with Regulatory Position I and Appendix D. probability is reviewed and accepted on a case by-case basis. Appendix B also describes a pro

2. For CEUS sites, perform an evaluation of cedure that should be used when a general revi LLNL or EPRI seismic sources in accordance sion to the reference probability is needed.

with Appendix E to determine whether they are consistent with the site-specific data gathered 5. Deaggregate the median probabilistic hazard in Step 1 or require updating. The PSHAshould characterization in accordance with Appendix C

only be updated if the new information indi to determine the controlling earthquakes (i.e.,

cates that the current version significantly un magnitudes and distances). Document the hazard derestimates the hazard and there is a strong information base as discussed in Appendix C.

technical basis that supports such a revision. It

4. PROCEDURES FOR DETERMINING THE

may be possible to justify a lower hazard esti SSE

mate with an exceptionally strong technical ba sis. However, it is expected that large uncertain After completing the PSHA (See Regulatory Posi ties in estimating seismic hazard in the CEUS tion 3) and determining the controlling earthquakes, the will continue to exist in the future, and substan following procedure should be used to determine the tial delays in the licensing process will result in SSE. Appendix F contains an additional discussion of trying to justify a lower value with respect to a some of the characteristics of the SSE.

specific site. For these reasons the NRC staff 1. With the controlling earthquakes determined as discourages efforts to justify a lower hazard es described in Regulatory Position 3 and by using timate. In most cases, limited-scope sensitivity the procedures in Revision 3 of Standard Re studies should be sufficient to demonstrate that view Plan (SRP) Section 2.5.2 (which may in the existing data base in the PSHA envelops the clude the use of ground motion models not in findings from site-specific investigations. In cluded in the PSHA but that are more general, significant revisions to the LLNL and appropriate for the source, region, and site un EPRI data base are to be undertaken only peri der consideration or that represent the latest odically (every 10 years), or when there is an scientific development), develop 5% of critical important new finding or occurrence. An over damping response spectral shapes for the actual all revision of the data base would also require a or assumed rock conditions. The same control reexamination of the acceptability of the refer ling earthquakes are also used to derive vertical ence probability discussed in Appendix B and response spectral shapes.

used in Step 4 below. Any significant update should follow the guidance of Reference 9. 2. Use Sa,5-10 to scale the response spectrum shape corresponding to the controlling earthquake. If,

3. For CEUS sites only, perform the LLNL or as described in Appendix C, there is a control EPRI probabilistic seismic hazard analysis us ling earthquake for Sa,1-2.5, determine that the ing original or updated sources as determined in Sa,5-10 scaled response spectrum also envelopes Step 2. For sites in other parts of the country, the ground motion spectrum for the controlling perform a site-specific PSHA (Reference 9). earthquake for Sa,1-2.5. Otherwise, modify the The ground motion estimates should be made shape to envelope the low-frequency spectrum for rock conditions in the free-field or by as or use two spectra in the following steps. See suming hypothetical rock conditions for a non additional discussion in Appendix F. For a rock rock site to develop the seismic hazard informa site go to Step 4.

tion base discussed in Appendix C.

3. For nonrock sites, perform a site-specific soil am

4. Using the reference probability (1E-5 per year) plification analysis considering uncertainties in described in Appendix B, determine the 5% of site-specific geotechnical properties and parame

65-7

ters to determine response spectra at the free Additional discussion of this step is provided in ground surface in the freefield for the actual site Appendix F.

conditions.

D. IMPLEMENTATION

4. Compare the smooth SSE spectrum or spectra The purpose of this section is to provide guidance to applicants and licensees regarding the NRC staff's used in design (e.g., 0.3g, broad-band spectra plans for using this regulatory guide.

used in advanced light-water reactor designs)

with the spectrum or spectra determined in Step 2 Except in those cases in which the applicant pro for rock sites or determined in Step 3 for the non poses an acceptable alternative method for comply rock sites to assess the adequacy of the SSE spec ing with the specified portions of the Commission's trum or spectra. regulations, this guide will be used in the evaluation of applications for construction permits, operating li To obtain an adequate design SSE based on the censes, early site permits, or combined licenses sub site-specific response spectrum or spectra, develop a mitted after January 10, 1997. This guide will not be smooth spectrum or spectra or use a standard broad used in the evaluation of an application for an operat band shape that envelopes the spectra of Step 2 or ing license submitted after January 10, 1997, if the Step 3. construction permit was issued prior to that date.

1.165-8

REFERENCES

S1. Pacific Gas and Electric Company, "Final Report of 8. USNRC, "Site Investigations for Foundations of the Diablo Canyon Long Term Seismic Program; Nuclear Power Plants," Regulatory Guide 1.132.3 Diablo Canyon Power Plant18Doc8.t Nos. 50-275

9. Senior Seismic Hazard Analysis Committee and 50-323, 198PD1 (SSHAC), "Recommendations for Probabilistic

2. R- Rood et aL, "Safety Evaluation Report Related to Seismic Hazard Analysis: Guidance on Uncer the Operation of Diablo Canyon Nuclear Power tainty and Use of Experts," Lawrence Livermore Plant, Units 1 and V" NUREG-0675, Supplement National Laboratory, UCRL-ID-122160, Au No. 34, USNRC, June 1991.2 gust 1995 (to be published as NUREG/CR

6372).

3. Letter from G. Sorensen, Washington Public Power Supply System, to Document Control 10. D.B. Slemmons, "Faults and Earthquake Magni Branch, USNRC. Subject: Nuclear Project No. 3, tude," U.S. Army Corps of Engineers, Water Resolution of Key Licensing Issues, Response; ways Experiment Station, Misc. Papers S-73-1, February 29, 1988.1 Report 6, 1977.

4. D.L. Bernreuter et al., "Seismic Hazard Charac 11. D.B. Slemmons, "Determination of Design terization of 69 Nuclear Plant Sites East of the Earthquake Magnitudes for Microzonation,"

Rocky Mountains," NUREG/CR-5250, Vol Proceedings of the Third InternationalMicro umes 1-8, January 1989.2 zonation Conference, University of Washington, Seattle, Volume 1, pp. 119-130, 1982.

5. P. Sobel, "Revised Livermore Seismic Hazard Estimates for Sixty-Nine Nuclear Power Plant 12. M.G. Bonilla, H.A. Villalobos, and R.E. Wallace, Sites East of the Rocky Mountains," "Exploratory Trench Across the Pleasant Valley NUREG-1488, USNRC, April 1994.2 Fault, Nevada," Professional Paper 1274-B, U.S.

Geological Survey, pp. B1-B14, 1984.1

2 6. J.B. Savy et al., "Eastern Seismic Hazard Character

13. S.G. Wesnousky, "Relationship Between Total ization Update," UCRL-ID-115111, Lawrence Liv Affect, Degree of Fault Trace Complexity, and ermore National Laboratory, June 1993.1 (Accession Earthquake Size on Major Strike-Slip Faults in number 9310190318 in NRC's Public Document California" (Abs), Seismological Research Let-,

Room)

ters, Volume 59, No. 1, p. 3, 1988.

7. Electric Power Research Institute, "Probabilistic 14. D.L Wells and K.J. Coppersmith, 'New Empirical Seismic Hazard Evaluations at Nuclear Power Relationships Among Magnitude, Rupture Length, Plant Sites in the Central and Eastern United Rupture Width, Rupture Area, and Surface Displace States," NP-4726, All Volumes, 1989-1991. men," Bulletn of the Seismological Sociy of America, Volume 84, August 1994.

15. M. Wyss, "Estimating Maximum Expectable Mag nitude of Earthquakes from Fault Dimensions,"

Geology, Volume 7 (7), pp. 336-340, 1979.

16. D.P. Schwartz and KJ. Coppersmith, "Seismic Hazards: New Trends in Analysis Using Geolog lCopies are available for inspection or copying for a fee from the NRC Public ic Data," Active Tectonics, National Academy Document Room at 2120 L Street NW., Washington, DC; the PDR's mail ing address is Mail Stop LEA Washington, DC 20555; telephone Press, Washington, DC, pp. 215-230, 1986.

(202)634-3273; fax (202)634-3343.

2 Copies are available for inspection or copying for a fee from the NRC Public 3 Document Room at 2120 L Street NW., Washington, DC; the PDR's mail Single copies of regulatory guides, both active and draft, may be obtained ing address is Mail Stop LL-6, Washington, DC 20555; telephone free of charge by writing the Office of Administration, Altn: Distribution

(202)634-3273; fax (202)634-3343. Copies may be purchased at current rates and Services Section, USNRC, Washington, DC 20555, or by fax at from the U.S. Government Printing Office, PRO Box 37082, Washington, DC (301)415-2260. Copies are available for inspection or copying for a fee

20402-9328(telephone (202)512-2249); or from the National Technical In from the NRC Public Document Room at 2120 L Street NW., Washington, formation Service by writing NMIS at 5285 Port Royal Road, Springfield, VA DC; the PDR's mailing address is Mail Stop LL-., Washington, DC 20555;

22161. telephone (202)634-3273; fax (202)634-3343.

1.165-9

APPENDIX A

DEFINITIONS

Controlling Earthquakes - Controlling earthquakes is the use of a truncated exponential model for the mag K

are the earthquakes used to determine spectral shapes or nitude distribution and a stationary Poisson process for to estimate ground motions at the site. There may be the temporal and spatial occurrence of earthquakes.

several controlling earthquakes for a site. As a result of Seismic Source'- Seismic source is a general term re the probabalistic seismic hazard analysis (PSHA), con ferring to both seismogenic sources and capable tecton trolling earthquakes are characterized as mean magni ic sources.

tudes and distances derived from a deaggregation anal ysis of the median estimate of the PSHA. Capable Tectonic Source - A capable tectonic Earthquake Recurrence - Earthquake recurrence is source is a tectonic structure that can generate both the frequency of occurrence of earthquakes having vari vibratory ground motion and tectonic surface de ous magnitudes. Recurrence relationships or curves are formation such as faulting or folding at or near the developed for each seismic source, and they reflect the earth's surface in the present seismotectonic re frequency of occurrence (usually expressed on an gime. It is described by at least one of the following annual basis) of magnitudes up to the maximum, in characteristics:

cluding measures of uncertainty. a. Presence. of surface or near-surfice deforma Intensity - The intensity of an earthquake is a meas tion of landforms or geologic deposits of a re ure of vibratory ground motion effects on humans, on curring nature within the last approximately human-built structures, and on the earth's surface at a 500,000 years or at least once in the last particular location. Intensity is described by a numeri approximately 50,000 years.

cal value on the Modified Mercalli scale.

b. A reasonable association with one or more Magnitude - An earthquake's magnitude is a meas moderate to large earthquakes or sustained ure of the strength of the earthquake as determined from earthquake activity that are usually accompa seismographic observations. nied by significant surface deformation.

Maximum Magnitude -The maximum magnitude is c. A structural association with a capable tectonic the upper bound to recurrence curves.

source having characteristics of either section Nontectonic Deformation - Nontectonic deforma a or b in this paragraph such that movement on tion is distortion of surface or near-surface soils or one could be reasonably expected to be accom rocks that is not directly attributable to tectonic activity. panied by movement on the other.

Such deformation includes features associated with subsidence, karst terrane, glaciation or deglaciation, *In some cases, the geological evidence of past and growth faulting. activity at or near the ground surface along a poten tial capable tectonic source may be obscured at a Safe Shutdown Earthquake Ground Motion (SSE) particular site. This might occur, for example, at a

-Th/o/SSE is the vibratory ground motion for which site having a deep overburden. For these cases, evi certain structures, systems, and components are de dence may exist elsewhere along the structure from signed, pursuant to Appendix S to 10 CFR Part 50, to which an evaluation of its characteristics in the vi remain functional. cinity of the site can be reasonably based. Such evi The SSE for the site is characterized by both horizon dence is to be used in determining whether the tal and vertical free-field ground motion response spec structure is a capable tectonic source within this tra at the free ground surface. definition.

Seismic Potential - A model giving a complete de Notwithstanding the foregoing paragraphs, the scription of the future earthquake activity in a seismic association of a structure with geological structures source zone. The model includes a relation giving the that are at least pre-Quaternary, such as many of frequency (rate) of earthquakes of any magnitude, an those found in the Central and Eastern regions of estimate of the largest earthquake that could occur un the United States, in the absence of conflicting evi der the current tectonic regime, and a complete descrip dence will demonstrate that the structure is not a ca tion of the uncertainty. A typical model used for PSHA pable tectonic source within this definition.

1.165-10

Seismogenic Source - A seismogenic source is a crust, and excludes active plate boundaries and zones of portion of the earth that we assume has uniform currently active tectonics directly influenced by plate earthquake potential (same expected maximum margin processes. It exhibits no significant deforma earthquake and recurrence frequency), distinct tion associated with the major Mesozoic-to-Cenozoic from the seismicity of the surrounding regions. A (last 240 million years) orogenic belts. It excludes ma seismogenic source will generate vibratory ground jor zones of Neogene (last 25 million years) rifting, vol motion but is assumed not to cause surface dis canism, or suturing.

placement. Seismogenic sources cover a wide Stationary Poisson Process - A probabilistic model range of possibilities from a well-defined tectonic of the occurrence of an event over time (space) that is structure to simply a large region of diffuse seis characterized by (1) the occurrence of the event in small micity (seismotectonic province) thought to be intervals is constant over time (space), (2) the occur characterized by the same earthquake recurrence rence of two (or more) events in a small interval is neg model. A seismogenic source is also characterized ligible, and (3) the occurrence of the event in non-over by its involvement in the current tectonic regime (the Quaternary, or approximately the last 2 million lapping intervals is independent..

years). Tectonic Structure - A tectonic structure is a large Stable Continental Region -A stable continental re scale dislocation or distortion, usually within the gion (SCR) is composed of continental crust, including earth's crust. Its 'extent may be on the order of tens of continental shelves, slopes, and attenuated continental meters (yards) to hundreds of kilometers (miles).

1.165-11 I I I 1 .

APPENDIX B.

REFERENCE PROBABILITY FOR THE EXCEEDANCE LEVEL OF THE

SAFE SHUTDOWN EARTHQUAKE GROUND MOTION

K

B.1 INTRODUCTION on the risk-based considerations; its application will This appendix describes the procedure that is ac also be reviewed on a case-by-case basis.

ceptable to the NRC staff to determine the reference B.3.1 Selection of Current Plants for Reference probability, an annual probability of exceeding the Safe Probability Calculations..

Shutdown Earthquake Ground Motion (SSE), at future nuclear power plant sites. The reference probability is Table B.1 identifies plants, along with their site used in Appendix C in conjunction with the probabilis characteristics, used in calculating the reference proba tic seismic hazard analysis (PSHA). bility. These plants represent relatively recent designs that used Regulatory Guide 1.60, "Design Response B.2 REFERENCE PROBABILITY FOR THE Spectra for Seismic Design of Nuclear Power Plants"

SSE

(Ref. B.5), or similar spectra as their design bases. The The reference probability is the annual probability use of these plants should ensure an adequate level of level such that 50% of a set of currently operating plants conservatism-in determining an SSE consistent with re (selected by the NRC, see Table B.1) has an annual mp cent licensing decisions.

dian probability of exceeding the SSE that is below this B3.2 Procedure To Establish Reference level. The reference probability is determined for the annual probability of exceeding the average of the 5 and Probability

10 Hz SSE response spectrum ordinates associated Step 1 with 5% of critical damping.

Using LLNL, EPRI, or a comparable methodology B.3 PROCEDURE TO DETERMINE THE that is acceptable to the NRC staff, calculate the seismic REFERENCE PROBABILITY

hazard results for the site for spectral responses at 5 and The following procedure was used to determine the 10 Hz (as stated earlier, the staff used the LLNL meth reference probability and should be used in the future if odology and associated results as documented in Refs.

general revisions to PSHA methods or data bases result B.1 and B.2).

in significant changes in hazard predictions for the se Step 2 lected plant sites in Table B.I.

The reference probability is calculated using the Calculate the composite annual probability of ex ceeding the SSE for spectral responses at 5 and 10 Hz Lawrence Livermore National Laboratory (LLNL)

methodology and results (Refs. B.1 and B.2) but is also using median hazard estimates. The composite annual considered applicable for the Electric Power Research probability is determined as:

Institute (EPRI) study (Refs. B.3 and B.4). This refer Composite probability = 1/2(al) + 1/2(a2)

ence probability is also to be used in conjunction with sites not in the Central and Eastern United States where al and a2 represent median annual probabil (CEUS) and for sites for which LLNL and EPRI meth ities of exceeding SSE spectral ordinates at 5 and 10

ods and data have not been used or are not available. Hz, respectively. The procedure is illustrated in Figure However, the final SSE at a higher reference probabili B-1.

ty may be more appropriate and acceptable 1 for some Step 3 sites considering the slope characteristics of the site hazard curves, the overall uncertainty in calculations Figure B-2 illustrates the distribution of median (i.e., differences between mean and median hazard esti probabilities of exceeding the SSEs for the plants in mates), and the knowledge of the seismic sources that Table B.1 based on the LLNL methodology (Refs. B.1 contribute to the hazard. Reference B.4 includes a pro and B.2). The reference probability is simply the me cedure to determine an alternative reference probability dian probability of this distribution.

For the LLNL methodology, this reference proba bility is 1E-5/yr and, as stated earlier, is also to be used lThe use of a higher reference probability will be reviewed and accepted on in conjunction with the current EPRI methodology a caseby-case basis. (Ref. B.3) or for sites not in the CEUS.

1.165-12

Table B.A

Plants/Sites Used In Determining Reference Probability Soil Condition Soil Condition Plant/Site Name Primary/Secondary* Plant/Site Name Primary/Secondary*

limerick Rock Byron Rock Shearon Harris Sand - S1 Clinton Till - T3 Braidwood Rock Davis Besse Rock River Bend Deep Soil LaSalle Till - T2 Wolf Creek Rock Perry Rock Watts Bar Rock Bellefonte Rock Vogtle Deep Soil Callaway Rock/Sand - S1 Seabrook Rock Comanche Peak Rock Three Mile Is. Rock/Sand - S1 Grand Gulf Deep Soil Catawba Rock/Sand - S1 South Texas Deep Soil Hope Creek Deep Soil Waterfoid Deep Soil McGuire Rock Millstone 3 Rock North Anna Rock/Sand - S1 Nine Mile Point Rock/Sand - S1 Summer Rock/Sand - S1 -Brunswick Sand - S1 Beaver Valley Sand - Si

• Iftwo soil conditions are listed, the first is the primary and the second is the secondary soil condition. See Ref. B.1 for a discussion of soil conditions.

1.165-13

CD

0

al a. 4---*

>11

5 Hz Spectral Response

" tW Median Hazard Curve

10 Hz Spectral Response Median Hazard Curve I

Spectral Response Figure B.1 Procedure To Compute Probability of Exceeding Design Basis

1.165-14

1.0 1 1 i *I

" ' 'i I 1' 1'11 g I i g i i l i  ;

0

0

0

0.9 0

0

0

0.8 .0

0

0

0

0.7 0

0

0

C2 0

.0 0.6 0

0

0

0.5 ----

---

---- --- - Q

0

0

0'

0.4

0'

0.3 0 w o ': W

o00 I

cc

0.2 o V,

0

0o

0.1

0

0I

, . ~~~~~~~

. ~. ~~

• * ,,I , . o , .,..! SIII

0.0 I 0 lIl . . . .

I

.

I I

.

I

. .

1 0-7 10-6 10-5 10-4 10-3 Composite Probability of Exceeding SSE

Figure B.2 Probability of Exceeding SSE

Using Median LLNL Hazard Estimates

1.165-15 II

REFERENCES

B.1 D.L. Bernreuter et al., "Seismic Hazard Charac States: Resolution of the Charleston Earthquake terization of 69 Nuclear Plant Sites East of the Issue," Report NP-6395-D, April 1989.

K

Rocky Mountains," NUREG/CR-5250, January

1989.1 B.4 Attachment to Letter from D. J. Modeen, Nuclear Energy Institute, to A.J. Murphy, USNRC, Sub B.2 P. Sobel, "Revised Livermore Seismic Hazard ject: Seismic Siting Decision Process, May 25, Estimates for Sixty-Nine Nuclear Power Plant 1994.2 Sites East of the Rocky Mountains,"

NUREG-1488, USNRC, April 1994.1 B.5 USNRC, "Design Response Spectra for Seismic Design of Nuclear Power Plants," Regulatory B.3 Electric Power Research Institute, "Probabilistic Guide 1.60.3 Seismic Hazard Evaluations at Nuclear Power

2 Plant Sites in the Central and Eastern United Copies are available for inspection or copying for a fee from the NRC Pub lic Document Room at 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; telephone

(202)634-3273; fax (202)634-3343.

lCopies are available for inspection orcopyingfora fee from the NRC Pub 3 lic Document Room at 2120 L Street NW., Washington, DC; the PDR's Single copies of regulatory guides, both active and draft, may be ob mailing address is Mail Stop LL-6, Washington, DC 20555; telephone tained free of charge by writing the Office of Administration, Atta: Dis

(202)634-3273; fax (202)634-3343. Copies may be purchased at current tribution and Mail Services Section, USNRC, Washington, DC 20555, or rates from the U.S. Government Printing Office, P.O. Box 37082, Wash by fax at (301)415-2260. Copies are available for inspection orcopying ington, DC 20402-9328 (telephone (202)512-2249); or from the National for a fee from the NRC Public Document Room at 2120 L Street NW.,

Technical Information Service by writing NTIS at 5285 Port Royal Road, Washington, DC; the PDR's mailing address is Mail Stop LL-6, Wash Springfield, VA 22161. ington, DC 20555; telephone (202)634-3273; fax (202)634-3343.

1.165-16

APPENDIX C

DETERMINATION OF CONTROLLING EARTHQUAKES AND DEVELOPMENT

OF SEISMIC HAZARD INFORMATION BASE

C.1 INTRODUCTION mined according to the procedure described in Appen dix F to this regulatory guide.

This appendix elaborates on the steps described in Step I

Regulatory Position 3 of this rqgulatory'guide to deter mine the controlling earthquakes used to define the Perform a site-specific PSHA using the Lawrence Safe Shutdown Earthquake Ground Motion (SSE) at Livermore National Laboratory (LLNL) or.Electric the site and to develop a seismic hazard information Power Research Institute (EPRI) methodologies for base. The information base summarizes the contribu Central and Eastern United States (CEUS) sites or per tion of individual magnitude and distance ranges to the form a site-specific PSHA for sites not in the CEUS or seismic hazard and the magnitude and distance values for sites for which LLNL or EPRI methods and data are of the controlling earthquakes at the average of 1 and not applicable, for actual or assumed rock conditions.

2.5 Hz and the average of 5 and 10 Hz. They are devel The hazard assessment (mean, median, 85th percentile, oped for the ground motion level corresponding to the and 15th percentile) should be performed for spectral reference probability as defined in Appendix B to this accelerations at 1, 2.5, 5, 10, and 25 Hz, and the peak regulatory guide. ground acceleration. A lower-bound magnitude of 5.0

'is recommended.

The spectral ground motion levels, as determined from a probabilistic seismic hazard analysis (PSHA), Step 2 are used to scale a response spectrum shape. A site (a) Using the reference probability (1E-5/yr) as de specific response spectrum shape is determined for the fined in Appendix B to this regulatory guide, determine controlling earthquakes and local site conditions. Reg the ground motion levels for the spectral accelerations ulatory Position 4 and Appendix F to this regulatory at 1, 2.5, 5, and 10 Hz from the total median hazard ob guide describe a procedure 'to determine the SSE using tained in Step 1.

the controlling earthquakes and results from the PSHA.

(b) Calculate the average of the ground motion lev C.2 PROCEDURE TO DETERMINE el for the I and 2.5 Hz and the 5 and 10 Hz spectral ac CONTROLLING EARTHQUAKES celeration pairs.

Step 3 The following is an approach acceptable to the NRC staff for determining the controlling earthquakes Perform a complete probabilistic seismic hazard and developing a seismic hazard information base. This analysis for each of the magnitude-distance bins procedure is based on a de-aggregation of the probabi illustrated in Table C.1. (These magnitude-distance

-listicseismic hazard in terms of earthquake magnitudes bins are to be used in conjunction with the LLNL or and distances. Once the 'controlling earthquakes have EPRI methods. For other situations, other binning been obtained, the SSE response spectrum can be deter- schemes may be necessary.)

Table CA

Recommended Magnitude and Distance Bins Magnitude Range of Bin Distance Range "

of Bin (kn) 5-5.5 5.5-6 6-6.5 6.5-7 >7

0-15

15-25

25-50

50-100

100-200

200 -300

>300

1.165-17

Step 4 The purpose of this calculation is to identify a dis tant, larger event that may control low-frequency con From the de-aggregated results of Step 3, the me tent of a response spectrum.

dian annual probability of exceeding the ground mo The distance of 100 km is chosen for CEUS sites.

tion levels of Step 2(a) (spectral accelerations at 1, 2.5, However, for all sites the results of full magnitude I-.

5, and 10 Hz) are determined for each magnitude distance bin. These values are denoted by Hmdf. distance distribution should be carefully examined to ensure that proper controlling earthquakes are clearly Using Hmdf values, the fractional contribution of identified.

each magnitude and distance bin to the total hazard for Step 6 the average of 1 and 2.5 Hz, P(m,d) 1 , is computed ac cording to: Calculate the mean magnitude and distance of the controlling earthquake associated with the ground

(>.lmHf) motions determined in Step 2 for the average of 5 and

10 Hz. The following relation is used to calculate the mean magnitude using results of the entire magnitude

- 2 Equation (1) distance bins matrix:

Me(5-10Hz) = >mEjP(md),

rM d

2 m d Equation (4)

where f =1 and f =2 represent the ground motion measure at 1 and 2.5 Hz, respectively. where m is the central magnitude value for each magnitude bin.

The fractional contribution of each magnitude and The mean distance of the controlling earthquake is distance bin to the total hazard for the average of 5 and determined using results of the entire magnitude

10 Hz, P(md)2, is computed according to: distance bins matrix:

Ln{D.(5-10Hz)} = >jLn(d)>jP(md) 2 d m

2 Equation (2) Equation (5)

P(M,d)2 where d is the centroid distance value for each dis tance bin.

p d

4 2 Step 7 where f = I and f = 2 represent the ground motion If the contribution to the hazard calculated in Step 5 measure at 5 and 10 Hz, respectively. for distances of 100 km or greater exceeds 5% for the average of 1 and 2.5 Hz, calculate the mean magnitude Step S and distance of the controlling earthquakes associated Review the magnitude-distance distribution for the with the ground motions determined in Step 2 for the average of 1 and 2.5 Hz to determine whether the con average of 1 and 2.5 Hz. The following relation is used tribution to the hazard for distances of 100 km or great to calculate the mean magnitude using calculations er is substantial (on the order of 5% or greater). based on magnitude-distance bins greater than dis tances of 100 km as discussed in Step 4:

If the contribution to the hazard for distances of M. (1 - 2.5 Hz) rn M P > 100 (m, d)

100 km or greater exceeds 5%, additional calculations are needed to determine the controlling earthquakes us M d>100

ing the magnitude-distance distribution for distances Equation (6)

greater than 100 km (63 mi). This distribution, where m is the central magnitude value for each P>loo(md)l, is defined by:

magnitude bin.

P(m9d) The mean distance of the controlling earthquake is P > 100 (m,d), = 1 Equation (3) based on magnitude-distance bins greater than m d>100 distances of 100 km as discussed in Step 4 and deter mined according to:

1.165-18

Step 3 Ln {D,(1 - 2.5 Hz)} = Ln(d) P >100(m,d),

d>10 ., The median seismic hazard is de-aggregated for the matrix of magnitude and distance bins as given in Equation (7) Table C.1.

where d is the centroid distance value for each dis A complete probabilistic hazard analysis was per tance bin. formed for each bin to determine the contribution to the hazard from all earthquakes within the bin, e.g., all Step 8 earthquakes with magnitudes 6 to 6.5 and distance 25 to Determine the SSE response spectrum using the 50 km from the site. See Figure C.2 where the median 1 procedure described in Appendix F of this regulatory Hz hazard curve is plotted for distance bin 25 - 50 km and magnitude bin 6 - 6.5.

guide.

The hazard vaiues corresponding to the ground C.3 EXAMPLE FOR A CEUS SITE

motion levels found in step 2, and listed in Table C.2, To illustrate the procedure in Section C.2, calcula are then determined from the hazard curve for each bin tions are shown here for a CEUS site using the 1993 for spectral accelerations at 1, 2.5, 5, and 10 Hz. This LLNL hazard results (Refs. C.1 and C.2). It must be process is illustrated in Figure C.2. The vertical line emphasized that the recommended magnitude and dis corresponds to the value 88 cm/s/s listed in Table C.2 tance bins and procedure used to establish controlling for the 1 Hz hazard curve and intersects the hazard earthquakes were developed for application in the curve for the 25 - 50 bin, 6 - 6.5 bin at a hazard value CEUS where the nearby earthquakes generally control (probability of exceedance) of 2.14E-08 per year.

the response in the 5 to 10 Hz frequency range, and larg Tables C.4 to C.7 list the appropriate hazard value for er but distant events can control the lower frequency each bin for 1, 2.5, 5, and 10 Hz respectively.

range. For other situations, alternative binning schemes It should be noted that if the median hazard in as well as a study of contributions from various bins each of the 35 bins is added up it does not equal will be necessary to identify controlling earthquakes 1.0E--05. That is because the sum of the median of consistent with the distribution of the seismicity. each of the bins does not equal the overall median.

However, if we gave the mean hazard for each bin it Step 1 would add up to the overall mean hazard curve.

The 1993 LLNL seismic hazard methodology Step 4 (Refs. C.1 and C.2) was used to determine the hazard at the site. A lower bound magnitude of 5.0 was used in Using de-aggregated median hazard results, the this analysis. The analysis was performed for spectral fractional contribution of each magnitude-distance pair acceleration at 1, 2.5, 5, and 10Hz. The resultant hazard to the total hazard is determined.

curves are plotted in Figure C.1. Tables C.8 and C.9 show P(m,d)I and P(m,d) 2 for the average of 1 and 2.5 Hz and 5 and 10 Hz, Step 2 respectively.

The hazard curves at 1, 2.5, 5, and 10 Hz obtained Step 5 in Step I are assessed at the reference probability value of 1E-5/yr, as defined in Appendix B to this regulatory Because the contribution of the distance bins guide. The corresponding ground motion level values greater than 100 km in Table C.8 contains more than are given in Table C.2. See Figure C.1. 5% of the total hazard for the average of 1 and 2.5 Hz, the controlling earthquake for the spectral average of 1 The average of the ground motion levels at the 1 and 2.5 Hz will be calculated using magnitude-distance and 2.5 Hz, Sa1-2.5, and 5 and 10 Hz, Sa5-10, are given bins for distance greater than 100 kmn. Table C.1O

in Table C.3. shows P>I0 0 (md)l for the average of 1 to 2.5 Hz.

1,165-19

,II

Table C.2 Ground Motion Levels Frequency (Hz) 1 1 2.5 5 10

Spectral Acc. (cm/s/s) I 88 258 351 551 K

Table C.3 Average Ground Motion Values Sal-2.5 (cm/s/s) 173 S -s.io(cra/s/s) 451 Table C.4 Median Exceeding Probability Values for Spectral Accelerations at I Hz (88 cm/s/s)

Magnitude Range of Bin Distance Range of Bin (km) 5-5.5 5.5-6 6-6.5 6.5-7 >7

0-15 1.98E-08 9.44E-08 1.14E-08 0 0

15-25 4.03E-09 2.58E-08 2.40E-09 0 0

25-50 1.72E-09 3.03E-08 2.14E-08 0 0

50-100 2.35E-10 1.53E-08 7.45E-08 2.50E-08 0

100-200 1.OOE-11 2.36E-09 8.53E-08 6.101-07 0

200 - 300 0 1.90E-11 1.60E.-09 1.84E-08 0

> 300 0 0 8.99E-12 1.03E--11 1.69E-10

Table C.5 Median Exceeding Probability Values for Spectral Accelerations at 2.5 Hz (258 cm/s/s)

Magnitude Range of Bin Distance Range of Bin (km) 5-5.5 5.5-6. 6-6.5 6.5 -7 >7

0-15 2.24E-07 3.33E-07 4.12E-08 0 0

15-25 5.39E-08 1.20E-07 1.08E-08 0 0

25-50 2.60E-08 1.68E-07 6.39E-08 0 0

50-100 3.91E-09 6.27E-08 1.46E-07 4.09E-08 0

100-200 1.50E-10 7.801E-09 1.07E-07 4.75E-07 0

200 -300 7.16E-14 2.07E-11 7.47E-10 5.02E-09 0

K

> 300 0 1.52E-14 4.94E-13 9.05E-15 2.36E-15

1.165-20 -,

Table 0.6 Median Exceeding Probability Values for Spectral Accelerations at 5 Hz (351 cm/sls)

Magnitude Range of Bin Distance Range of Bin (kmi) 5-5.5 5.5-6 6-6.5 6.5-7 >7

0-15 4.96E-07 5.85E-07 5.16E-08 0 0

15-25 9.39E-08 2.02E-07 1.36E-08 *0 0

25-50 2.76E-08 1.84E-07. 7.56E-08 0 0

50- 100 1.23E-08 3.34E-08 9.98E-08 2.85E-08 0

100 - 200 8.06E-12 1.14E-09 2.54E-08 1.55E-07 0

200 -300 0 2.39E-13 2.72E-11 4.02E-10 0

> 300 0 0 0 0 0

Table C.7 Median Exceeding Probability Values for Spectral Accelerations at 10 Hz (551 cmlsls)

_ __Magnitude Range of Bin.

Distance Range of Bin (km) 5-5.5 5.5-6 6-6.5 6.5-7 >7

0-15 1.11E-06 1.12E-06 8.30E-08 0 0

15-25 2.07E-07 3.77E-07 3.12E-08 0 0

25 -50 4.12E-08 235E-07 1.03E-07 0 0

50-100 5.92E-10 2.30E-08 6.89E-08 2.71E-08 0

S100-200

1.26E-12 1.69E-10 6.66E-09 5.43E-08 0

200-300 0 3.90E-15 6.16E-13 2.34E-11 0

> 300 0 0 0 0 0

1.165-21

C.8 P(m,d)1 for Average Spectral Accelerations 1 and 2.5 Hz STable Corresponding to the Reference Probability

_ _ _Magnitude Range of Bin Distance Range of Bin (km) 5-5.5 5.5-6 6-6.5 6.5-7 >7

0-15 0.083 0.146 0.018 0.000 0.000

15-25 0.020 0.050 0.005 0.000 0.000

25-50 0.009 0.067 0.029 0.000 0.000

50-100 0.001 0.027 0.075 0.022 0.000

100-200 0.000 0.003 0.066 0.370 0.000

200 -300 0.000 0.000 0.001 0.008 0.000

300 0.000 0.000 0.000 0.000 0.000

Table C.9 P(m,d)2 for Average Spectral Accelerations 5 and 10 Hz Corresponding to the Reference Probability

_________Magnitude Range of Bin Distance Range of Bin (km) 5-5.5 5.5-6 6-6.5 6.5-7 >7

0-15 0.289 0.306 0.024 0.000 0.000

15-25 0.054 0.104 0.008 0.000 0.000

25 -50 0.012 0.075 - 0.032 0.000 0.000

50-100 0.001 0.010 .-0.030 0.010 " 0.000

.100-200 0.000 0.001 0.006 0.038 0.000

200-300 0.000 0.000 0.000 0.000 0.000

- > 300 0.000 0.000 0.000 0.000 0.000

Table C.10

P> 1 00 (m,d)l for Average Spectral Accelerations 1 and 2.5 Hz Corresponding to the Reference Probability Magnitude Range of Bin Distance Range of Bin (km) 5-5.5 5.5-6 6-6.5 6.5-7 >7

100-200 0.000 0.007 0.147 0.826 0.000

200-300 0.000 0.000 0.002 0.018 0.000

>300 0.000 0.000 0.000 0.000 0.000

1.165-22-

Figures C.3 to C.5 show the above information in Step 8 terms of the relative percentage contribution.

The SSE response spectrum is determined by the procedures described in Appendix F.

Steps 6 and 7 C.4 SITES NOT IN THE CEUS

To compute the controlling magnitudes and The determination of the controlling earthquakes distances at 1 to 2.5 Hz and 5 to 10 Hz for the example and the seismic hazard information base for sites not in site, the values of P> 10 0 (m,d)l and P(m,d) 2 are used the CEUS is also carried out using the procedure with m and d values corresponding to the mid-point of described in Section C.2 of this appendix. However, the magnitude of the bin (5.25, 5.75, 6.25, 6.75, 7.3) because of differences in seismicity rates and ground and centroid of the ring area (10, 20.4, 38.9, 77.8, motion attenuation at these sites, alternative

155.6, 253.3, and somewhat arbitrarily 350 km). Note magnitude-distance bins may have to be used. In addi that the mid-point of the last magnitude bin may change tion, as discussed in Appendix B, an alternative refer because this value is dependent on the maximum mag ence probability may also have to be developed, par nitudes used in the hazard analysis. For this example ticularly for sites in the active plate margin region and site, the controlling earthquake characteristics (magni for sites at which a known tectonic structure dominates tudes and distances) are given in Table C.11. the hazard.

Table C.11 Magnitudes and Distances of Controlling Earthquakes from the LLNL Probabilistic Analysis

1-2.51Hz 5 - 10Hz Mc and Dc > 100 km MK and Dc

6.7 and 157 km 5.7 and 17 km

1.165-23 II

K

.01. e

"01-0-.., 1H z e-

1.01 e-6 no."*

• .

~~N.

I e-8

\N

le--85 Ile-9 *.

10 100 1000

Sa ~cm/s**2 Figure C.A Total Median Hazard Curves

1.165-24

.001 le-4

1e-5 le-6

1e-7

1e-8

1e-9

10 100 1000

Sa - cm/s**2 Figure C.2 1 Hz Median Hazard'Curve for Distance Bin 25 - 50 km & Magnitude Bin 6 - 6.5

1,165-25

0

"I

0.

'5

0

Magnitude bins

"D5c 25-50 50-100

0

Distance bins 1020200-300 > 300

Figure C.3 Full Distribution for Average of 5 and 10 Hz K

1.165--26

35

• )25

.0

.0

- 15

• • 66.5->7

• . O

Magnitude bins

0-15 15-25 " *"--* .* 5-5.5

25-50 50-100

100-200 200-300

Distance bins > 300

Figure C.4 Full Distribution for Average of 1 and 2.5 Hz

1.165-27 I I

K

0.

/>300

200-300

Distance bins Man5 d b6-6.5 Magnitude bins 6.5-7

">7 Figure C.5 Renormalized Hazard Distribution for Distances >100 km for Average of I and 2.5 Hz

1.165-28

REFERENCES

C.1 P. Sobel, "Revised Livermore Seismic Hazard C.2 J.B. Savy et al., "Eastern Seismic Hazard Charac Estimates for Sixty-Nine Nuclear Power Plant terization Update," UCRL-ID-115111, Law Sites East of the Rocky Mountains, rence Livermore National Laboratory, June 1993 NUREG-1488, USNRC, April 1994.1 (Accession number 9310190318 in NRC's Pub

2 lic Document Room).

lCopies are available for inspection or copying for a fee from the NRC

Public Document Room at 2120 LStreet NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; telephone

(202)634-3273; fax (202)634-3343. Copies may be purchased at current

2 rates from the U.S. Government Printing Office, P.O. Box 37082, Copies are available for inspection or copying for a fee from the NRC

Washington, DC 20402-9328 (telephone (202)512-2249); or from the Public Document Room at 2120 LStreet NW., Washington, DC; thePDR's National Technical Information Service by writing NTIS at 5285 Port mailing address is Mail Stop LL-6, Washington, DC 20555; telephone Royal Road, Springfield, VA 22161. (202)634-3273; fax (202)634-3343.

1.165-29

APPENDIX D

GEOLOGICAL, SEISMOLOGICAL, AND GEOPHYSICAL INVESTIGATIONS

TO CHARACTERIZE SEISMIC SOURCES

1%

D.

W. INTRODUCTION

roles. If, on the other hand, strong correlations and data exist suggesting a relationship between seismic As characterized for use in probabilistic seismic ity and seismic sources, approaches used for more ac hazard analyses (PSHA), seismic sources are zones tive tectonic regions can be applied.

within which future earthquakes are likely to occur at the same recurrence rates. Geological, seismological, The primary objective of geological, seismologi and geophysical investigations provide the information cal, and geophysical investigations is to develop an up needed to identify and characterize source parameters, to-date, site-specific earth science data base that sup such as size and geometry, and to estimate earthquake plements existing information (Ref. D.1). In the CEUS

recurrence rates and maximum magnitudes. The the results of these investigations will also be used to amount of data available about earthquakes and their assess whether new data and their interpretation are causative sources varies substantially between the consistent with the information used as the basis for ac Western United States (west of the Rocky Mountain cepted probabilistic seismic hazard studies. If the new front) and the Central and Eastern United States data are consistent with the existing earth science data (CEUS), or stable continental region (SCR) (east of the base, modification of the hazard analysis is not Rocky Mountain front). Furthermore, there are varia required. For sites in the CEUS where there is signifi tions in the amount and quality of data within these cant new information (see Appendix E) provided by the regions. site investigation, and for sites in the Western United States, site-specific seismic sources are to be de In active tectonic regions there are both capable termined. It is anticipated that for most sites in the tectonic sources and seismogenic sources, and be CEUS, new information will have been adequately cause of their relatively high activity rate they may be bounded by existing seismic source interpretations.

more readily identified. In the CEUS, identifying seismic sources is less certain because of the difficul The following is a general list of characteristics to ty in correlating earthquake activity with known tec be evaluated for a seismic source for site-specific tonic structures, the lack of adequate knowledge source interpretations:

about earthquake causes, and the relatively lower ac "* Source zone geometry (location and extent, both tivity rate. However, several significant tectonic surface and subsurface),

structures exist and some of these have been inter

"* Historical and instrumental seismicity associated preted as potential seismogenic sources (e.g., the New Madrid fault zone, Nemaha Ridge, and Meers with each source, fault). "* Paleoseismicity, In the CEUS there is no single recommended pro * Relationship of the potential seismic source to cedure to follow to characterize maximum magni other potential seismic sources in the region, tudes associated with such candidate seismogenic "* Seismic potential of the seismic source, based on sources; therefore, it is most likely that the deter the source's known characteristics, including mination of the properties of the seismogenic source, seismicity, whether it is a tectonic structure or a seismotectonic "* Recurrence model (frequency of earthquake oc province, will be inferred rather than demonstrated currence versus magnitude),

by strong correlations with seismicity or geologic data. Moreover, it is not generally known what rela "* Other factors that will be evaluated, depending on tionships exist between observed tectonic structures the geologic setting of a site, such as:

in a seismic source within the CEUS and the current * Quaternary (last 2 million years) displace earthquake activity that may be associated with that ments (sense of slip on faults, fault length and source. Generally, the observed tectonic structure re width, area of the fault plane, age of displace sulted from ancient tectonic forces that are no longer ments, estimated displacement per event, es present. The historical seismicity record, the results timated magnitude per offset, segmentation, of regional and site studies, and judgment play key orientations of regional tectonic stresses with

1.165-30

respect to faults, and displacement history or strated by the buried (blind) reverse causative faults of uplift rates of seismogenic folds), the 1983 Coalinga,1988 Whittier Narrows, 1989 Loma

• The late Quaternary interaction between Prieta, and 1994 Northridge earthquakes. These factors faults that compose a fault system and the emphasize the need to conduct thorough investigations

-' interaction between fault systems. not only at the ground surface but also in the subsurface to identify structures at seismogenic depths.

• Effects of human activities such as withdraw al of fluid from or addition of fluid to the The level of detail for investigations should be subsurface, extraction of minerals, or the governed by knowledge of the current and late Quater construction of dams and reservoirs, nary tectonic regime and the geological complexity of the site and region. The investigations should be based

• Volcanism. Volcanic hazard is not addressed on increasing the amount of detailed information as in this regulatory guide. It will be considered on a case-by-case basis in regions where a they proceed from the regional level down to the site area (e.g., 320 km to 8 km distance from the site).

potential for this hazard exists.

Whenever faults or other structures are encountered at a D.2. INVESTIGATIONS TO EVALUATE site (including sites in the CEUS) in either outcrop or SEISMIC SOURCES excavations, it is necessary to perform many of the in vestigations described below to determine whether or D.2.1 General not they are capable tectonic sources.

Investigations of the site and region around the site The investigations for determining seismic sources are necessary to identify both seismogenic sources and should be carried out at three levels, with areas de capable tectonic sources and to determine their poten scribedby radii of 320 km (200 mi), 40 km (25 mi), and tial for generating earthquakes and causing surface de 8 km (5 mi) from the site. The level of detail increases formation. If it is determined that surface deformation closer to the site. The specific site, to a distance of at need not be taken into account at the site, sufficient data least 1 km (0.6 mi), should be investigated in more de to clearly justify the determination should be presented tail than the other levels.

in the application for an early site permit, construction The regional investigations [within a radius of 320

permit, operating license, or combined license. Gener ally, any tectonic deformation at the earth's surface *km(200 mi) of the site] should be planned to identify seismic sources and describe the Quaternary tectonic within 40 km (25 miles) of the site will require detailed regime. The data should be presented at a scale of examination to determine its significance. Potentially active tectonic deformation within the seismogenic

1:500,000 or smaller. The investigations are not ex pected to be extensive or in detail, but should include a zone beneath a site will have to be assessed using geo comprehensive literature review supplemented by fo physical and seismological methods to determine its cused geological reconnaissances based on the results significance.

of the literature study (including topographic, geologic, Engineering solutions are generally available to aeromagnetic, and gravity maps, and airphotos). Some mitigate the potential vibratory effects of earthquakes detailed investigations at specific locations within the through design. However, engineering solutions can region may be necessary if potential capable tectonic not always be demonstrated to be adequate for mitiga sources, or seismogenic sources that may be significant tion of the effects of permanent ground displacement for determining the safe shutdown earthquake ground phenomena such as surface faulting or folding, subsi motion, are identified.

dence, or ground collapse. For this reason, it is prudent The large size of the area for the regional investiga to select an alternative site when the potential for per tions is recommended because of the possibility that all manent ground displacement exists at the proposed site significant seismic sources, or alternative configura (Ref. D.2). tions, may not have been enveloped by the LLNL/EPRI

In most of the CEUS, instrumentally located earth data base. Thus, it will increase the chances of (1) iden quakes seldom bear any relationship to geologic struc tifying evidence for unknown seismic sources that tures exposed at the ground surface. Possible geologi might extend close enough for earthquake ground mo cally young fault displacements either do not extend to tions generated by that source to affect the site and (2)

the ground surface or there is insufficient geologic ma confirming the PSHA's data base. Furthermore, be terial of the appropriate age available to date the faults. cause of the relatively aseismic nature of the CEUS, the Capable tectonic sources are not always exposed at the area should be large enough to include as many ground surface in the Western United States as demon- historical and instrumentally recorded earthquakes for

1.165-31

111 'i t

analysis as reasonably possible. The specified area of rates of historical seismic activity (felt or instrumen study is expected to be large enough to incorporate any tally recorded data), or sites that are located near a capa previously identified sources that could be analogous ble tectonic source such as a fault zone.

to sources that may underlie or be relatively close to the Data from investigations at the site (approximately site. In past licensing activities for sites in the CEUS, it 1 square kilometer) should be presented at a scale of K

has often been necessary, because of the absence of dat 1:500 or smaller. Important aspects of the site inves able horizons overlying bedrock, to extend investiga tigations are the excavation and logging of exploratory tions out many tens or hundreds of kilometers from the trenches and the mapping of the excavations for the site along a structure or to an outlying analogous struc plant structures, particularly plant structures that are ture in order to locate overlying datable strata or uncon characterized as Seismic Category I. In addition to geo formities so that geochronological methods could be logical, geophysical, and seismological investigations, applied. This procedure has also been used to estimate detailed geotechnical engineering investigations as de the age of an undatable seismic source in the site vicin scribed in Regulatory Guide 1.132 (Ref. D.3) should be ity by relating its time of last activity to that of a similar, conducted at the site.

previously evaluated structure, or a known tectonic epi sode, the evidencý of which may be many tens or The investigations needed to assess the Suitabil hundreds of miles away. ity of the site with respect to effects of potential ground motions and surface deformation should in In the Western United States it is often necessary to clude determination of (1) the lithologic, stratigraph extend the investigations to great distances (up to ic, geomorphic, hydrologic, geotechnical, and struc hundreds of kilometers) to characterize a major tectonic tural geologic characteristics of the site and the area structure, such as the San Gregorio-Hosgri Fault Zone surrounding the site, including its seismicity and and the Juan de Fuca Subduction Zone. On the other geological history, (2) geological evidence of fault hand, in the Western United States it is not usually nec offset or other distortion such as folding at or near essary to extend the regional investigations that far in ground surface within the site area (8 km radius), and all directions. For example, for a site such as Diablo (3) whether or not any faults or other tectonic struc Canyon, which is near the San Gregorio-Hosgri Fault, tures, any part of which are within a radius of 8 km (5 it would not be necessary to extend the regional inves mi) from the site, are capable tectonic sources. This tigations farther east than the dominant San Andreas information will be used to evaluate tectonic struc Fault, which is about 75 km (45 mi) from the site; nor tures underlying the site area, whether buried or ex west beyond the Santa Lucia Banks Fault, which is pressed at the surface, with regard to their potential about 45 km (27 mi). Justification for using lesser dis for generating earthquakes and for causing surface tances should be provided. deformation at or near the site. This partof the evalua Reconnaissance-level investigations, which may tion should also consider the possible effects caused by human activities such as withdrawal of fluid from need to be supplemented at specific -locations by more or addition of fluid to the subsurface, extraction of detailed explorations such as geologic mapping, geo minerals, or the loading effects of dams and reser physical surveying, borings, and trenching, should be voirs.

conducted to a distance of 40 km (25 mi) from the site;

the data should be presented at a scale of 1:50,000 or D.1.2 Reconnaissance Investigations, Literature smaller. Review, and Other Sources of Preliminary Information Detailed investigations should be carried out with Regional literature and reconnaissance-level in in a radius of 8 km (5 mi) from the site, and the resulting vestigations can be planned based on reviews of avail data should be presented at a scale of 1:5,000 or smaller. able documents and the results of previous investiga The level of investigations should be in sufficient detail tions. Possible sources of information may include to delineate the geology and the potential for tectonic universities, consulting firms, and government agen deformation at or near the ground surface. The inves cies. A detailed list of possible sources of information tigations should use the methods described in subsec is given in Regulatory Guide 1.132 (Ref. D.3).

tions D.2.2 and D.2.3 that are appropriate for the tec D.2.3 Detailed Site Vicinity and Site Area tonic regime to characterize seismic sources. Investigations The areas of investigations may be asymmetrical The following methods are suggested but they are and may cover larger areas than those described above not all-inclusive and investigations should not be limit in regions of late Quaternary activity, regions with high ed to them. Some procedures will not be applicable to

1.165-32

every site, and situations will occur that require inves D.2.3.1.5. Analysis of Quaternary sedimentary tigations that are not included in the following discus deposits within or near tectonic zones, such as fault sion. It is anticipated that new technologies will be zones, including (1) fault-related or fault-controlled de available in the future that will be applicable to these posits such as sag ponds, graben fill deposits, and collu investigations. vial wedges formed by the erosion of a fault paleoscarp and (2) non-fault-related, but offset, deposits such as al D.2.3.1 Surface Investigations luvial fans, debris cones, fluvial terrace, and lake shore line deposits.

Surface exploration needed to assess the neotec tonic regime and the geology of the area around the site D.2.3.1.6. Identification and analysis of de is dependent on the site location and may be carried out formation features caused by vibratory ground mo with the use of any appropriate combination of the geo tions, including seismically induced liquefaction fea logical, geophysical, seismological, and geotechnical tures (sand boils, explosion craters, lateral spreads, engineering techniques summarized in the following settlement, soil flows), mud volcanoes, landslides, paragraphs and Ref. D.3. However, not all of these rockfalls, deformed lake deposits or soil horizons, methods must be carried out at a given site. shear zones, cracks or fissures (Refs. D.13 and D.14).

D.2.3.1.1. Geological interpretations of aerial D.2.3.1.7. Analysis of fault displacements, such photographs and other remote-sensing imagery, as ap as by the interpretion of the morphology of topographic propriate for the particular site conditions, to assist in fault scarps associated with or produced by surface rup identifying rock outcrops, faults and other tectonic fea ture. Fault scarp morphology is useful in estimating the tures, fracture traces, geologic contacts, lineaments, age of last displacement (in conjunction with the ap soil conditions, and evidence of landslides or soil propriate geochronological methods described in Sub section D.2.4, approximate size of the earthquake, re liquefaction.

currence intervals, slip rate, and the nature of the D.2.3.1.2. Mapping of topographic, geologic, causative fault at depth (Refs. D.15 through D.18).

geomorphic, and hydrologic features at scales and with contour intervals suitable for analysis, stratigraphy D.2.3.2 Seismological Investigations (particularly Quaternary), surface tectonic structures such as fault zones, and Quaternary geomorphic fea D.2.3.2.1. Listing of all historically reported tures. For offshore sites, coastal sites, or sites located earthquakes having Modified Mercalli Intensity near lakes or rivers, this includes topography, geo (MMI) greater than or equal to IV or magnitude greater morphology (particularly mapping marine and fluvial than or equal to 3.0 that can reasonably be associated terraces), bathymetry, geophysics (such as seismic re with seismic sources, any part of which is within a ra flection), and hydrographic surveys to the extent need dius of 320 km (200 miles) of the site (the site region).

ed for evaluation. The earthquake descriptions should include the date of occurrence and measured or estimated data on the high D.2.3.1.3. Identification and evaluation of verti est intensity, magnitude, epicenter, depth, focal mecha cal crustal movements by (1) geodetic land surveying nism, and stress drop. Historical seismicity includes to identify and measure short-term crustal movements both historically reported and instrumentally recorded (Refs. D.4 and D.5) and (2) geological analyses such as data. For earthquakes without instrumentally recorded analysis of regional dissection and degradation pat data or calculated magnitudes, intensity should be con terns, marine and lacustrine terraces and shorelines, verted to magnitude, the procedure used to convert it to fluvial adjustments such as changes in stream longitu magnitude should be clearly documented, and epicen dinal profiles or terraces, and other long-term changes ters should be determined based on intensity distribu such as elevation changes across lava flows (Ref. D.6). tions. Methods to convert intensity values to magni tudes in the CEUS are described in References D.1 and D.2.3.1.4. Analysis of offset, displaced, or D.19 through D.21.

anomalous landforms such as displaced stream chan nels or changes in stream profiles or the upstream D.2.3.2.2. Seismic monitoring in the site area migration of knickpoints (Refs. D.7 through D.12); should be established as soon as possible after site abrupt changes in fluvial deposits or terraces; changes selection. For sites in both the CEUS and WUS, a in paleochannels across a fault (Refs. D.11 and D.12); single large dyn amic range, broad-band seismograph, or uplifted, downdropped, or laterally displaced marine and a network of short period instruments to locate terraces (Ref. D.12). events should be deployed around the site area.

1.165-33

The data obtained by monitoring current seismic tailed discussion of each of these methods and their ity will be used, along with the much larger data base application to nuclear power plant siting is presented in acquired from site investigations, to evaluate site re a document that is currently under preparation and will sponse and to provide information about whether there be published as a NUREG.1 are significant sources of earthquakes within the site vicinity, or to provide data by which an existing source D.2.4.1 Sidereal Dating Methods can be characterized. 0 Dendrochronology Monitoring should be initiated as soon as practica 0 Varve chronology ble at the site, preferably at least five years prior to 0 Schlerochronology construction of a nuclear unit at a site, and should con tinue at least until the free field seismic monitoring D.2.4.2 Isotopic Dating Methods strong ground motion instrumentation described in 0 Radiocarbon Regulatory Guide 1.12 (Ref. D.22) is operational.

S Cosmogenic nuclides -M3 6 , 1OBe, 2 1pb, and 26A1 D.2.33 Subsurface Investigations

0 Potassium argon and argon-39-argon-40

Ref. D.3 describes geological, geotechnical, and

0 Uranium series - 234 U-23°'h and 235U

geophysical investigation techniques that can be ap 231Pa plied to explore the subsurface beneath the site and in 2 10

0 Lead the region around the site, therefore, only a brief sum mary is provided in this section. Subsurface investiga 0 Uranium-lead, thorium-lead tions in the site area and vicinity to identify and define D+/-4.4 Radiogenic Dating Methods seismogenic sources and capable tectonic sources may'

include the following. S Fission track D.2.3.3.1. Geophysical investigations that have 0 Luminescence (TL and OSL)

been useful in the past include, for example, magnetic 0 Electron spin resonance (ESR)

and gravity surveys, seismic reflection and seismic re D.2.4.5 Chemical and Biological Dating fraction surveys, borehole geophysics, electrical sur Methods veys, and ground-penetrating radar surveys.

0 Amino acid racemization D.2.33.2. Core borings to map subsurface geol Obsidian and tephra hydration

0

ogy and obtain samples for testing such as determining

0 Lichenometry the properties of the subsurface soils and rocks and geo chronological analysis. D.2.4.6 Geomorphic Dating Methods D.2.3.3.3. Excavating and logging of trenches S Soil profile development across geological features as part of the neotectonic in 0 Rock and mineral weathering vestigation and to obtain samples for the geochrono

0 Scarp morphology logical analysis of those features.

At some sites, deep unconsolidated material/soil, D.2.4.7 Correlation Dating Methods bodies of water, or other material may obscure geologic

• Paleomagnetism (secular variation and re evidence of past activity along a tectonic structure. In versal stratigraphy)

such cases, the analysis of evidence elsewhere along the

• Tephrochronology structure can be used to evaluate its characteristics in 0 Paleontology (marine and terrestrial)

the vicinity of the site (Refs. D.12 and D.23).

S Global climatic correlations - Quaternary D.2.4 Geochronology deposits and landforms, marine stable iso tope records, etc.

An important part of the geologic investigations to identify and define potential seismic sources is the geo chronology of geologic materials. An acceptable clas 1 NUREG/CR-5562, "Quaternary Geochronology: Applications in Qua.

sification of dating methods is based on the rationale ternary Geology and Paleoseismology," Editors H.S. Noller, LM. Sow.

described in Reference D.24. The following tech era, and W.R. Lettis, will be published in the spring of 1997. Copies will be available for inspection or copying for a fee from the NRC Public K

niques, which are presented according to that classifi Document Room at 2120 L Street NW., Washington. DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; telephone cation, are useful in dating Quaternary deposits. A de- (202)634-3273; fax (202)53-41-3343.

1.165-34

In the CEUS, it may not be possible to reasonably in karst terrain; and growth faulting, such as occurs in demonstrate the age of last activity of a tectonic struc the Gulf Coastal Plain or in other deep soil regions sub ture. In such cases the NRC staff will accept association ject to extensive subsurface fluid withdrawal.

of such structures with geologic structural features or Glacially induced faults generally do not represent tectonic processes that are geologically old (at least pre a deep-seated seismic or fault displacement hazard be Quaternary) as an age indicator in the absence of con cause the conditions that created them are no longer flicting evidence.

present. However, residual stresses from Pleistocene These investigative procedures should also be ap glaciation may still be present in glaciated regions, al plied, where possible, to characterize offshore struc though they are of less concern than active tectonically tures (faults or fault zones, and folds, uplift, or subsi induced stresses. These features should be investigated dence related to faulting at depth) for coastal sites or with respect to their relationship to current in situ those sites located adjacent to landlocked bodies of stresses.

water. Investigations of offshore structures will rely The nature of faults related to collapse features can heavily on seismicity, geophysics, and bathymetry usually be defined through geotechnical investigations rather than conventional geologic mapping methods and can either be avoided or, if feasible, adequate engi that normally can be used effectively onshore. Howev neering fixes can be provided.

er, it is often useful to investigate similar features on Large, naturally occurring growth faults as found shore to learn more about the significant offshore fea tures. in the coastal plain of Texas and Louisiana can pose a surface displacement hazard, even though offset most D.2.5 Distinction Between Tectonic and likely occurs at a much less rapid rate than that of tec Nontectonic Deformation "tonicfaults. They are not regarded as having the capac At a site, both nontectonic deformation and tecton ity to generate damaging vibratory ground motion, can ic deformation can pose a substantial hazard to nuclear often be identified and avoided in siting, and their dis power plants, but there are likely to be differences in the placements can be monitored. Some growth faults and approaches used to resolve the issues raised by the two antithetic faults related to growth faults are not easily

-" types of phenomena. Therefore, nontectonic deforma identified; therefore, investigations described above tion should be distinguished from tectonic deformation with respect to capable faults and fault zones should be at a site. In past nuclear power plant licensing activities, applied in regions where growth faults are known to be surface displacements caused by phenomena other than present. Local human-induced growth faulting can be tectonic phenomena have been confused with tectoni monitored and controlled or avoided.

cally induced faulting. Such features include faults on . If questionable features cannot be demonstrated to which the last displacement was induced by glaciation be of nontectonic origin, they should be treated as tec or deglaciation; collapse structures, such as found tonic deformation.

1.165-35 I II f I

REFERENCES

D.1 Electric Power Research Institute, "Seismic Haz Journal of Geophysical Research, Volume 94, K

ard Methodology for the Central and Eastern pp. 603-623, 1989.

United States," EPRI NP-4726,, All Volumes,

1988 through.1991, D.10 R.J. Weldon, III, and K.E. Sieh, "Holocene Rate of Slip and Tentative Recurrence Interval for D.2 International Atomic Energy Agency, "Earth Large Earthquakes on the San Andreas Fault, Ca quakes and Associated Topics in Relation to Nu jon Pass, Southern California," GeologicalSoci clear Power Plant Siting," Safety Series ety ofAmerica Bulletin, Volume 96, pp. 793-812, No. 50-SG-S1, Revision 1, 1991. 1985.

D.3 USNRC, "Site Investigations for Foundations of D.11 F.H. Swan, III, D.P. Schwartz, and LS. Cluff, Nuclear Power Plants," Regulatory Guide "Recurrence of Moderate to Large Magnitude

1.132.1 Earthquakes Produced by Surface Faulting on the Wasatch Fault Zone," Bulletin of the Seismologi D.4 R. Reilinger, M. Bevis, and G. Jurkowski, "Tilt cal Society of America, Volume 70, pp, from Releveling: An Overview of the U.S. Data 1431-1462, 1980.

Base," Tectonophysics, Volume 107, pp. 315

330, 1984. D.12 Pacific Gas and Electric Company, "Final Report of the Diablo Canyon Long Term Seismic Pro D.5 R.K. Mark et al., "An Assessment of the Accura gram; Diablo Canyon Power Plant;" Docket Nos.

cy of the Geodetic Measurements that Led to the 50-275 and 50-323, 1988.2 Recognition of the'Southern California Uplift,"

Journal of Geophysical Research, Volume 86, D.13 S.F. Obermeier et al., "Geologic Evidence for Re pp. 2783-2808, 1981. current Moderate to Large Earthquakes Near Charleston, South Carolina," Science, Volume D.6 T.K. Rockwell et al., "Chronology and Rates of 227, pp. 408-411, 1985.

Faulting of Ventura River Terraces, California,"

GeologicalSociety ofAmerica Bulletin, Volume D.14 D. Amick et al., "Paleoliquefaction Features Along the Atlantic Seaboard," U.S. Nuclear Reg

95, pp. 1466-1474, 1984.

ulatory Commission, NUREG/CR-5613, Octo D.7 K.E. Sieh, "Lateral Offsets and Revised Dates of ber 1990.3 Prehistoric Earthquakes at Pallett Creet, South D.15 R.E. Wallace, "Profiles and Ages of Young Fault ern California," Journal of Geophysical Re Scarps, North-Central Nevada," Geological So search, Volume 89, No. 89, pp. 7641-7670,

ciety ofAmerica Bulletin, Volume 88, pp. 1267

1984.

1281, 1977.

D.8 K.E. Sieh and R.H. Jahns, "Holocene Activity of D.16 R.E. Wallace, "Discussion-Nomographs for the San Andreas Fault at Wallace Creek, Califor Estimating Components of Fault Displacement nia," Geological Society of America Bulletin, from Measured Height of Fault Scarp," Bulletin Volume 95, pp. 883-896, 1984.

of the Association of Engineering Geologists, D.9 K.E. Sieh, M. Stuiver, and D. Brillinger, "A More Volume 17, pp. 39-45, 1980.

Precise Chronology of Earthquakes Produced by 2 Copies are available for inspection or copying for a fee from the NRC

the San Andreas Fault in Southern California," Public Document Room at 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; tele phone (202)634-3273; fax (202)634-3343.

ISingle copies of the regulatory guides, both active and draft, may be ob tained free of charge by writing the Office of Administration, Attn: Dis 3Copies are available for inspection or copying for Itfee from the NRC

tribution and Mail Services Section, USNRC, Washington, DC 20555, or Public Document Room at 2120 L Street NW., Washington, DC; the by fax at (301)415-2260. Copies are available for inspection or copying PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; tele for a fee from the NRC Public Document Room at 2120 L Street NW., phone (202)634-3273; fax (202)634-3343. Copies may be purchased at Washington, DC; the PDR's mailing address is Mail Stop LL,-6, Wash current rates from the U.S. Government Printing Office, P.O. Box 37082, ington, DC 20555; telephone (202)634-3273; fax (202)634-3343. Washington, DC 20402-9328 (telephone (202)512-2249; or from the National Technical Information Service by writing NTIS at 5285 Port Roal Road, Springfield, VA 22161.

1,165-36

D.17 R.E. Wallace, "Active Faults, Paleoseismology, logical Society of America, Volume 67, and Earthquake Hazards: Earthquake Predic pp. 599-614, 1977.

tion-An International Review," Maurice Ewing Series 4, American Geo1physical Union, pp. D.21 R.L. Street and A. Lacroix, "An Empirical Study

209-216, 1981. of New England Seismicity," Bulletin of the Seis mological Society of America, Volume 69, pp.

D.18 A.J. Crone and S.T. Harding, "Relationship of 159-176, 1979.

Late Quaternary Fault Scarps to Subjacent Faults, Eastern Great Basin, Utah," Geology, Vol D.22 USNRC, "Nuclear Power Plant Instrumentation ume 12, pp. 292-295, 1984. for Earthquakes," Regulatory Guide 1.12, Revi sion 2.1 D.19 O.W. Nuttli, "The Relation of Sustained Maxi mum Ground Acceleration and Velocity to Earth D.23 H. Rood et al., "Safety Evaluation Report Related quake Intensity and Magnitude, State-of- the-Art to the Operation of Diablo Canyon Nuclear Pow for Assessing Earthquake Hazards in the Eastern er Plant, Units I and 2," USNRC, NUREG-0675, United States," U.S. Army Corps of Engineers Supplement No. 34, June 1991.3 Misc. Paper 5-73-1, Report 16, 1979.

D.24 S.M. Colman, K.L Pierce, and P.W. Birkeland, D.20 R.L. Street and F.T. Turcotte, "A Study of North "Suggested Terminology for Quaternary Dating eastern North America Spectral Moments, Mag Methods," QuaternaryResearch, Volume 288, nitudes and Intensities," Bulletin of the Seismo- pp. 314-319, 1987.

1.165-37

1 1

APPENDIX E

PROCEDURE FOR THE EVALUATION OF NEW GEOSCIENCES INFORMATION

OBTAINED FROM THE SITE-SPECIFIC INVESTIGATIONS

E.1 INTRODUCTION E.2.1 Seismic Sources This appendix provides methods acceptable to the There are several possible sources of new informa NRC staff for assessing the impact of new information tion from the site-specific investigations that could af obtained during site-specific investigations on the data fect the seismic hazard. Continued recording of small base used for the probabilistic seismic hazard analysis earthquakes, including microearthquakes, may indi (PSHA). cate the presence of a localized seismic source. Paleo seismic evidence, such as paleoliquefaction features or Regulatory Position 4 in this guide describes, ac displaced Quaternary strata, may indicate the presence ceptable PSHAs that were developed by Lawrence Liv of a previously unknown tectonic structure or a larger ermore National Laboratories (LLNL) and the Electric amount of activity on a known structure than was pre Power Research Institute (EPRI) to characterize the viously considered. Geophysical studies (aeromagnet seismic hazard for nuclear power plants and to develop the Safe Shutdown Earthquake ground motion (SSE). ic, gravity, and seismic reflection/refraction) may iden The procedure to determine the SSE outlined in this tify ckustal structures that suggest the presence of previously unknown seismic sources. In situ stress guide relies primarily on either the LLNL or EPRI

measurements and the mapping of tectonic structures in PSHA results for the Central and Eastern United States the future may indicate potential seismic sources.

(CEUS).

Detailed local site investigations often reveal faults It is necessary to evaluate the geological, seismo or other tectonic structures that were unknown, or re logical, and geophysical data obtained from the site veal additional characteristics of known tectonic struc specific investigations to demonstrate that these data tures. Generally, based on past licensing experience in are consistent with the PSHA data bases of these two the CEUS, the discovery of such features will not re methodologies. If new information identified by the quire a modification of the seismic sources provided in site-specific investigations would result in a significant the LLNL and EPRI studies. However, initial evidence increase in the hazard estimate for a site, and this new regarding a newly discovered tectonic structure in the information is validated by a strong technical basis, the CEUS is often equivocal with respect to activity, and PSHA may have to be modified to incorporate the new additional detailed investigations are required. By technical information. Using sensitivity studies, it may means of these detailed investigations, and based on also be possible to justify a lower hazard estimate with past licensing activities, previously unidentified tec an exceptionally strong technical basis. However, it is tonic structures can usually be shown to be inactive or expected that large uncertainties in estimating seismic otherwise insignificant to the seismic design basis of hazard in the CEUS will continue to exist in the future, the facility, and a modification of the seismic sources and substantial delays in the licensing process will re provided by the LLNL and EPRI studies will not be re sult from trying to justify a lower value with respect to quired. On the other hand, if the newly discovered fea a specific site. tures are relatively young, possibly associated with In general, major recomputations of the LLNL and earthquakes that were large and could impact the haz EPRI data base are planned periodically (approximate ard for the proposed facility, a modification may be ly every ten years), or when there is an important new required.

finding or occurrence. The overall revision of the data Of particular concern is the possible existence of base will also require a reexamination of the reference previously unknown, potentially active tectonic struc probability discussed in Appendix B. tures that could have moderately sized, but potentially E.2 POSSIBLE SOURCES OF NEW damaging, near-field earthquakes or could cause sur INFORMATION THAT COULD AFFECT face displacement. Also of concern is the presence of THE SSE structures that could generate larger earthquakes within Types of new data that could affect the PSHA re the region than previously estimated.

sults can be put in three general categories: seismic Investigations to determine whether there is a pos sources, earthquake recurrence models or rates of de sibility for permanent ground displacement are espe-'

formation, and ground motion models. cially important in view of the provision to allow for a

1.165r38

combined licensing procedure under 10 CFR Part 52 as EPRI or LLNL PSHA. Any of these cases could have an alternative to the two-step procedure of the past an impact on the estimated maximum earthquake if the (Construction Permit and Operating License). In the result is larger than the values provided by LLNL and

~j past at numerous nuclear power plant sites, potentially EPRI.

significant faults were identified when excavations E.2.3 Ground Motion Attenuation Models were made during the construction phase prior to the is Alternative ground motion models may be used to suance of an operating license, and extensive additional determine the site-specific spectral shape as discussed investigations of those faults had to be carried out to in Regulatory Position 4 and Appendix F of this regula properly characterize them.

tory guide. If the ground motion models used are a ma E.2.2 Earthquake Recurrence Models jor departure from the original models used in the haz ard analysis and are likely to have impacts on the hazard There are three elements of the source zone's recur results of many sites, a reevaluation of the reference rence models that could be affected by new site-specific probability may be needed using the procedure dis data: (1) the rate of occurrence of earthquakes, (2) their cussed in Appendix B. Otherwise, a periodic (e.g.,

maximum magnitude, and (3) the form of the recur every ten years) reexamination of PSHA and the associ rence model, for example, a change from truncated ex ated data base is considered appropriate to incorporate ponential to a characteristic earthquake model. Among new understanding regarding ground motion models.

the new site-specific information that is most likely to have a significant impact on the hazard is the discovery E.3 PROCEDURE AND EVALUATION

of paleoseismic evidence such as extensive soil lique The EPRI and LLNL studies provide a wide range faction features, which would indicate with reasonable of interpretations of the possible seismic sources for confidence that much larger estimates of the maximum most regions of the CEUS, as well as a wide range of earthquake than those predicted by the previous studies interpretations for all the key parameters of the seismic would ensue. The paleoseismic data could also be sig hazard model. The first step in comparing the new in nificant even if the maximum magnitudes of the pre formation with those interpretations is determining vious studies are consistent with the paleo-earthquakes whether the new information is consistent with the fol if there are sufficient data to develop return period esti lowing LLNL and EPRI parameters: (1) the range of mates significantly shorter than those previously used seismogenic sources as interpreted by the seismicity in the probabilistic analysis. The paleoseismic data experts or teams involved in the study, (2) the range of could also indicate that a characteristic earthquake seismicity rates for the region around the site as inter model would be more applicable than a truncated expo preted by the seismicity experts or teams involved in nential model. the studies, and (3) the range of maximum magnitudes In the future, expanded earthquake catalogs will determined by the seismicity experts or teams. The new information is considered not significant and no further become available that will differ from the catalogs used evaluation is needed if it is consistent with the assump by the previous studies. Generally, these new cata logues have been shown to have only minor impacts on tions used in the PSHA, no additional alternative seis mic sources or seismic parameters are needed, or it sup estimates of the parameters of the recurrence models.

ports maintaining or decreasing the site median seismic Cases that might be significant include the discovery of hazard.

records that indicate earthquakes in a region that had no seismic activity in the previous catalogs, the occur An example is an additional nuclear unit sited near rence of an earthquake larger than the largest historic an existing nuclear power plant site that was recently earthquakes, re-evaluating the largest historic earth investigated by state-of-the-art geosciences techniques quake to a significantly larger magnitude, or the occur and evaluated by current hazard methodologies. De rence of one or more moderate to large earthquakes tailed geological, seismological, and geophysical site (magnitude 5.0 or greater) in the CEUS. specific investigations would be required to update ex isting information regarding the new site, but it is very Geodetic measurements, particularly satellite unlikely that significant new information would be

• basednetworks, may provide data and interpretations found that would invalidate the previous PSHA.

of rates and styles of deformation in the CEUS that can have implications for earthquake recurrence. New hy On the other hand, after evaluating the results of the potheses regarding present-day tectonics based on new site-specific investigations, if there is still uncertainty data or reinterpretation of old data may be developed about whether the new information will affect the esti that were not considered or given high weight in the mated hazard, it will be necessary to evaluate the

1.165-39 II

potential impact of the new data and interpretations on into the Wabash Valley. Several experts had given the median of the range of the input parameters. Such strong weight to the relatively high seismicity of the new information may indicate the addition of a new area, including the number of magnitude 5 historic seismic source, a change in the rate of activity, a change earthquakes that have occurred, and thus had assumed in the spatial patterns of seismicity, an increase in the the larger event. This analysis of the source character K

rate of deformation, or the observation of a relationship izations of the experts and teams resulted in the conclu between tectonic structures and current seismicity. The sion by the analysts that a new PSHA would not be nec new findings should be assessed by comparing them essary for this region because an event similar to the with the specific input of each expert or team that par prehistoric earthquake had been considered in the exist ticipated in the PSHA. Regarding a new source, for ex ing PSHAs.

ample, the specific seismic source characterizations for each expert or team (such as tectonic feature being A third step would be required if the site-specific geosciences investigations revealed significant new in modeled, source geometry, probability of being active, formation that would substantially affect the estimated maximum earthquake magnitude, or occurrence rates)

should be assessed in the context of the significant new hazard. Modification of the seismic sources would more than likely be required if the results of the detailed data and interpretations.

local and regional site investigations indicate that a pre It is expected that the new information will be with viously unknown seismic source is identified in the vi in the range of interpretations in the existing data base, cinity of the site. A hypothetical example would be the and the data will not result in an increase in overall seis recognition of geological evidence of recent activity on micity rate or increase in the range of maximum earth a fault near a nuclear power plant site in the stable conti quakes to be used in the probabilistic analysis. It can nental region (SCR) similar to the evidence found on then be concluded that the current LLNL or EPRI re the Meers Fault in Oklahoma (Ref, E.2). If such a sults apply. It is possible that the new data may necessi source is identified, the same approach used in the ac tate a change in some parameter. In this case, appropri tive tectonic regions of the Western United States ate sensitivity analyses should be performed to should be used to assess the largest earthquake ex determine whether the new site-specific data could pected and the rate of activity. If the resulting maximum affect the ground motion estimates at the reference earthquake and the rate of activity are higher than those probability level. provided by the LL.L or EPRI experts or teams regard ing seismic sources within the region in which this An example is a consideration of the seismic haz newly discovered tectonic source is located, it may be ard near the Wabash River Valley (Ref. E.1). Geologi necessary to modify the existing interpretations by cal evidence found recently within the Wabash River introducing the new seismic source and developing Valley and several of its tributaries indicated that an modified seismic hazard estimates for the site. The earthquake much larger than any historic event had oc same would be true if the current ground motion mod curred several thousand years ago in the vicinity of Vin els are a major departure from the original models.

cennes, Indiana. A review of the inputs by the experts These occurrences would likely require performing a and teams involved in the LLNL and EPRI PSHAs re new PSHA using the updated data base, and may re vealed that many of them had made allowance for this quire determining the appropriate reference probability possibility in their tectonic models by assuming the ex in accordance with the procedure described in tension of the New Madrid Seismic Zone northward Appendix B.

1.165-40

REFERENCES

E.1 Memorandum from A. Murphy, NRC, to L. E.2 A.R. Ramelli, D.B. Slemmons, and S.J. Bro Shao, NRC, Subject: Summary of a Public Me :et- coum, "The Meers Fault: Tectonic Activity in ing on the Revision of Appendix A, "Seismic amd Southwestern Oklahoma," NUREG/CR-4852, Geologic Siting Criteria for Nuclear PoiVer USNRC, March 1987.2 Plants," to 10 CFR Part 100; Enclosure (Vie On graphs): NUMARC, "Development and Demn stration of Industry's Integrated Seismic Sit ing

2 Decision Process," February 23, 1993.1 Copies are available for inspection or copying for a fee from the NRC

Public Document Room at 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; tele phone (202)634-3273; fax (202)634-3343. Copies may be purchased at lCopies are available for inspection or copying for a fee from the NIRC current rates from the U.S. Government Printing Office, P.O. Box 37082, Public Document Room at 2120 L Street NW., Washington, DC; the Washington, DC 20402-9328 (telephone (202)512-2249); or from the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555; 1ele- National Technical Information Service by writing NTIS at 5285 Pon phone (202)634-3273; fax (202)634-3343. Royal Road, Springfield, VA 22161.

1.165-41

. I t I

APPENDIX F

PROCEDURE TO DETERMINE THE

SAFE SHUTDOWN EARTHQUAKE GROUND MOTION

F.1 INTRODUCTION scale it by a peak ground motion parameter (usually This appendix elaborates on Step 4 of Regulatory peak ground acceleration (PGA)), which is derived Position 4 of this guide, which describes an acceptable based on the size of the controlling earthquake. During procedure to determine the Safe Shutdown Earthquake the licensing review this spectrum was checked against Ground Motion (SSE). The SSE is defined in terms of site-specific spectral estimates derived using Standard the horizontal and vertical free-field ground motion re Review Plan Section 2.5.2 procedures to be sure that sponse spectra at the free ground surface. It is devel the SSE design spectrum adequately enveloped the oped with consideration of local site effects and site site-specific spectrum. These past practices to define seismic wave transmission effects. The SSE response the SSE are still valid and, based on this consideration, spectrum can be determined by scaling a site-specific the following three possible situations are depicted in spectral shape determined for the controlling earth Figures F.1 to F.3.

quakes or by scaling a standard broad-band spectral Figure F.1 depicts a situation in which a site is to be shape to envelope the average of the ground motion lev used for a certified design with an established SSE (for els for 5 and 10 Hz (Sa,5-10), and 1 and 2.5 Hz (Sa,1-2.5) instance, an Advanced light Water Reactor with 0.3g as determined in Step C.2 of Appendix C to this guide. PGA SSE). In this example, the certified design SSE

It is anticipated that a regulatory guide will be de spectrum compares favorably with the site-specific re veloped that provides guidance on assessing site sponse spectra determined in Step 2 or 3 of Regulatory specific effects and determining smooth design re Position 4.

sponse spectra, taking into account recent develop Figure F.2 depicts a situation in which a standard ments in ground motion modeling and site amplifica broad-band shape is selected and its amplitude is scaled tion studies (e.g., Ref. F.1). so that the design SSE envelopes the site-specific spec F.2 DISCUSSION tra.

For engineering purposes, it is essential that the de Figure F.3 depicts a situation in which a specific sign ground motion response spectrum be a broad-band smooth shape for the design SSE spectrum is developed smooth response spectrum with adequate energy in the to envelope the site-specific spectra. In this case, it is frequencies of interest. In the past, it was general prac particularly important to be sure that the SSE contains tice to select a standard broad-band spectrum, such as adequate energy in the frequency range of engineering the spectrum in Regulatory Guide 1.60 (Ref. F.2), and interest and is sufficiently broad-band.

1.165=42

r

0

S8.1.

LU

1.75 7.5 Frequency, Hz Figure F.1 Use of SSE Spectrum of a Certified Design

0 SIP-10

0 .. ... " Modified or

0 5, Unmodified

"'8*- S \, Standard SIhape CO

1.75 7.5 Frequency, Hz Figure F.2 Use of a Standard Shape for SSE

0

Smooth Broad-Band Spectrum CO

1.75 7.5 Frequency, Hz Figure F.3 Development of a Site-Specific SSE Spectrum (Note: the above figures illustrate situations for a rock site. For other site conditions, the SSE spectra are compared at free-field after performing site amplification studies as discussed in Step 4 of Regulatory Position 4.)

1.165-43 I I i ti

REFERENCES

F.1 Electric Power Research Institute, "Guidelines F.2 USNRC, "Design Response Spectra for Seismic for Determining Design Basis Ground Motions," Design of Nuclear Power Plants," Regulatory EPRI Report TR-102293, Volumes 1-4, May Guide 1.60.21

1993.1

2 Single copies of regulatory guides, both active and draft, may be ob tained free of charge by writing the Office of Administration, Attn: Dis tribution and Mail Services Section, USNRC, Washington, DC 20555; or by fax at (301)415-2260. Copies are available for inspection orcopying t for a fee from the NRC Public Document Room at 2120 L Street NW.,

Copies may beobtained from the EPRI Distribution Center, 207 Coggins Washington, DC; the PDR's mailing address is Mail Stop LL-6, Wash Drive, Pleasant Hill, CA 94523; phone (510)934-4212. ington, DC 20555; telephone (202)634-3273; fax (202)634-3343.

1.165-44

REGULATORY ANALYSIS

A separate regulatory analysis was not prepared for benefits of the rule as implemented by the guide. A

this regulatory guide. The regulatory analysis, "Revi copy of the regulatory analysis is available for inspec sion of 10 CFR Part 100 and 10 CFR Part 50," was pre tion and copying for a fee at the NRC Public Document pared for the amendments, and it provides the regulato Room, 2120 L Street NW. (Lower Level), Washington, ry basis for this guide and examines the costs and DC, as Attachment 7 to SECY-96-118.

1.165-45 II I i I

I .

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