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March1997RegulatoryGuide1.165IdentificationandCharacterizationofSeismicSourcesandDeterminationofSafeShutdownEarthquakeGroundMotion(DraftissuedasDG-1032)[DivisionIndex|RegulatoryGuideIndex|NRCHomePage]PublicationInformationA.INTRODUCTIONIn10CFRPart100,ReactorSiteCriteria,Section100.23,GeologicandSeismicSitingFactors,paragraph(c),Geological,Seismological,andEngineeringCharacteristics,requiresthatthegeological,seismological,andengineeringcharacteristicsofasiteanditsenvironsbeinvestigatedinsufficientscopeanddetailtopermitanadequateevaluationoftheproposedsite,toprovidesufficientinformationtosupportevaluationsperformedtoarriveatestimatesoftheSafeShutdownEarthquakeGroundMotion(SSE),andtopermitadequateengineeringsolutionstoactualorpotentialgeologicandseismiceffectsattheproposedsite.Dataonthevibratorygroundmotion,tectonicsurfacedeformation,nontectonicdeformation,earthquakerecurrencerates,faultgeometryandsliprates,sitefoundationmaterial,andseismicallyinducedfloods,waterwaves,andothersitingfactorswillbeobtainedbyreviewingpertinentliteratureandcarryingoutfieldinvestigations.In10CFR100.23,paragraph(d),GeologicandSeismicSitingFactors,requiresthatthegeologicandseismicsitingfactorsconsideredfordesignincludeadeterminationoftheSSEforthesite,thepotentialforsurfacetectonicandnontectonicdeformations,thedesignbasesforseismicallyinducedfloodsandwaterwaves,andotherdesignconditions.In10CFR100.23,paragraph(d)(1),DeterminationoftheSafeShutdownEarthquakeGroundMotion,requiresthatuncertaintyinherentinestimatesoftheSSEbeaddressedthroughanappropriateanalysis,suchasaprobabilisticseismichazardanalysisorsuitablesensitivityanalyses.ThisguidehasbeendevelopedtoprovidegeneralguidanceonproceduresacceptabletotheNRCstafffor(1)conductinggeological,geophysical,seismological,andgeotechnicalinvestigations,(2)identifyingandcharacterizingseismicsources,(3)conductingprobabilisticseismichazardanalyses,and(4)determiningtheSSEforsatisfyingtherequirementsof10CFR100.23.Thisguidecontainsseveralappendicesthataddresstheobjectivesstatedabove.AppendixAcontainsalistofdefinitionsofpertinentterms.AppendixBdescribestheprocedureusedtodeterminethereferenceprobabilityfortheSSEexceedancelevelthatisacceptabletothestaff.AppendixCdiscussesthedevelopmentofaseismichazardinformationbaseandthedeterminationoftheprobabilisticgroundmotionlevelandcontrollingearthquakes.AppendixDdiscussessite-specificgeological,seismological,andgeophysicalinvestigations.AppendixEdescribesamethodtoconfirmtheadequacyofexistingseismicsourcesandsourceparametersasthebasisfordeterminingtheSSEforasite.AppendixFdescribesprocedurestodeterminetheSSE.Theinformationcollectionscontainedinthisregulatoryguidearecoveredbytherequirementsof10CFRPart50,whichwereapprovedbytheOfficeofManagementandBudget,approvalnumber3150-0011.TheNRCmaynotconductorsponsor,andapersonisnotrequiredtorespondto,acollectionofinformationunlessitdisplaysacurrentlyvalidOMBcontrolnumber.B.DISCUSSIONBACKGROUNDAprobabilisticseismichazardanalysis(PSHA)hasbeenidentifiedin10CFR100.23asameanstodeterminetheSSEandaccountforuncertaintiesintheseismologicalandgeologicalevaluations.Therulefurtherrecognizesthatthenatureofuncertaintyandtheappropriateapproachtoaccountforitdependonthetectonicregimeandparameterssuchastheknowledgeofseismicsources,theexistenceofhistoricalandrecordeddata,andthelevelofunderstandingofthetectonics.Therefore,methodsotherthanprobabilisticmethodssuchassensitivityanalysesmaybeadequateforsomesitestoaccountforuncertainties.AppendixA,SeismicandGeologicSitingCriteriaforNuclearPowerPlants,to10CFRPart100isprimarilybasedonadeterministicmethodology.PastlicensingexperienceinapplyingAppendixAhasdemonstratedtheneedtoformulateproceduresthatquantitativelyincorporateuncertainty(includingalternativescientificinterpretations)intheevaluationofseismichazards.Asingledeterministicrepresentationofseismicsourcesandgroundmotionsatasitemaynotexplicitlyprovideaquantitativerepresentationoftheuncertaintiesingeological,seismological,andgeophysicaldataandalternativescientificinterpretations.Probabilisticproceduresweredevelopedduringthepast10to15yearsspecificallyfornuclearpowerplantseismichazardassessmentsintheCentralandEasternUnitedStates(CEUS)(theareaeastoftheRockyMountains),alsoreferredtoastheStableContinentRegion(SCR).TheseproceduresprovideastructuredapproachfordecisionmakingwithrespecttotheSSEwhenperformedtogetherwithsite-specificinvestigations.APSHAprovidesaframeworktoaddresstheuncertaintiesassociatedwiththeidentificationandcharacterizationofseismicsourcesbyincorporatingmultipleinterpretationsofseismologicalparameters.APSHAalsoprovidesanevaluationofthelikelihoodofSSErecurrenceduringthedesignlifetimeofagivenfacility,giventherecurrenceintervalandrecurrencepatternofearthquakesinpertinentseismicsources.Withintheframeworkofaprobabilisticanalysis,uncertaintiesinthecharacterizationofseismicsourcesandgroundmotionsareidentifiedandincorporatedintheprocedureateachstepoftheprocessforestimatingtheSSE.Theroleofgeological,seismological,andgeophysicalinvestigationsistodevelopgeosc