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
1.165'-2
 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.

1.165-3
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 excavations. 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
1.165-4
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

1.165-5
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
1.165-6
 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
| 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

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 .

on
R mr
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