ML19221A974

Srp,Revision 1 to Section 2.5.2, Vibratory Ground Motion

ML19221A974
Person / Time
Issue date:	11/24/1975
From:	Office of Nuclear Reactor Regulation
To:
References
NUREG-75-087, NUREG-75-087-02.5.2, NUREG-75-87, NUREG-75-87-2.5.2, SRP-02.05.02, SRP-2.05.02, NUDOCS 7907120108
Download: ML19221A974 (5)

Text

NU R EG-75/087

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U.S. NUCLEAR REGULATORY COMM:SSION h,7ghc,i !STANDARD REVIEW PLAN o

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v OFFICE OF NUCLEAR REACTOR REGULATION SECTION 2.5.2 VIBRATORY GROUND MOTION REVIEW RESPONSIBILITIES Primary - Site Analysis Branch (SAB)

Secondary - None I.

AREAS OF REVIEW The SAB review cnvers the seismological and geological investigations carried out to estab-lish the acceleratie seismic design of the plant, the procedures and analyses used by the applicant to detentine the safe shutdown earthquake (SSE) and the operating basis ear *5 quake (OBE) for t :e site, and the seiswic design bases for foundations.

Specific areas of review include; seismicity, relationship of earthquake occurrence to geologic or tectonic characteristics of the r agion, determination of the earthqtake-generating potential of the geologic structures and tectonic provinces in the region, char-acteristics of seismic wave transmission at the site, and determination of the level and properties of the vibratory ground motion at the site resulting from potential earthquakes in the region.

II.

ACCEPTANCE CRITERIA 1

The required investigations are described in 10 CFR Part 100, Section Iv(a) of Appendix A.

The acceptable procedures for determining the seismic design bases are given in Section V(a) of the same appendix. The seismic design bases are predicated on a reason-able, conservative determination of the safe shutdown earthquake and the operating basis earthquake. As defined in Section III of 10 CFR Part 100, Appendix A, the SSE ard OBE are based on consideration of the egional and local geology and seismology and on the charac. eristics of the subsurface materials at the site and are described in terms of the vibratory ground motion v.hich they would produce at the site. No com-prehensive definitive rules can be promulgated regarding the investigations needed to establish the seismic design bases; the requirements vary from site to site.

2.

Subsection 2.5.2.1 (Seismicity): The applicant's presentation is accepted when the complete historical record of earthquakes in the region is listed and when all available parameters are given for each earthquake in the historical record. The listing should include all earthquakes MM intensity greater than IV or magnitude greater than 3 which have been reported in all tectonic provinces any parts of which are within 200 miles of the site. A regional-scale map should be presented showing all listed earthquake USNRC STANDARD REVIEW PLAN

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epicenters and, in areas of high seismicity, should be supplemented by a larger-scale map showing earthquake epictnters with n 50 miles of the site. The following infcema-tion concerning Oach earthqueke is required whenever it is available: ep center i

coordinates, depth of focus, origin time, hignest intensity, magnitude, seismic moment, soure me:hanism, source dimensions, source rise time, rupture velocity, total disloca-tion, frictional stress drop, and any strong-motion recordings; references from which the sp cified information was obtained should be identified. In addition, any reported ear nquake-induced geologic failure, such as licuefaction, landsliding, landspreading, and lurching should be described completely, including the level of strong motion which indaced failure and the material properties of the materials. The completeness of the earthquake history of the r egion is determined by comparison tu the historical earth-quake data (HED) file (Ref. 4) and other published sources of information (e.g.,

Refs. 5, 6, 7).

When conflicting descriptions of individual earthquakes are found in the published references, a reasonable description which results in the more conserva-tive interpretation of the seismicity is accepted.

3.

Subsection c.5.2.2 (Geologic and Tectonic Characteristict of Site and Region): The applicant's presentation is accepted when all regional geologic structures and tectonic activity which are significant in determining the earthquake potential of the region are identified. Information presented in Section 2.5.1 of the applicant's safety analysis report (SAR) anc information fron other literature sources (e.g., Ref s. 8, 9, 10, 11, 12) dealing with regional tectonics should be developed into a coherent, well-documented discussion to be used as the basis for determining tectonic provinces and the earthquake-generating cotential of the identified geologic structures.

Specifically, each tectonic province, any part ri whi.h is within 200 miles of the site, must be identified. Those characteristics of geologic structure, tectonic history, present and past stress regimes, and seismicity which distinguish the various tectonic provinces and the particular areas within those provinces where historical earthquakes have occurred should be described. Alternative regional tectonic models fron available literature sources should be discussed. When several of the alternative models conforn equall" well with the observed pnenomena, the mcdel which results in the rore conservative assessment of the eartnquake potential at the site is accepted. In addition, in those areas where there are capable faults, the results of the aaditional investigative requirements described in 10 CFR Part 100, Appendix A,Section IV(a)(8), must be presented. The discussion should be augmented by a regional-scale map showing the tectonic provinces, earthquake epicenters, locations of geologic structures and other features which characterize the provinces, and the locations of any capable faults.

4.

Subsection 2.5.2.3 (Correlation of Earthquake Activity with Geologic Structure or Tectonic Provinces): Acceptance is based on the development of the relationship between the relatively short history of earthquake activity and the geologic structures or tectonic provinces of a regicn. The applicant's presentation is accepted when the earthquakes discussed a Subsection 2.5.2.1 of the LAR are shown to be associated with either geologic structure or a tectonic province. Whenever an" earthquake epicenter or concentration of earthquake epicenters can be reasonably correlated with geologic 2.5.2-2 146 014

structure, the rationale for tLe association should be developed considering the properties of the geologic structure and the regional tectonic model. The discussion should include idcntification of the methods used to locate the earthquake epicenters, dn estimate of thei" accuracy, and a detailed account which compares and contrasts the geologic structure involved in the earthquake activity with other areas within the tectonic province, hrticular attention should be given to determining the capability of faults with which instrumentally-located earthquake epicenters are associated.

The applicant may choose to define tectonic provinces to correspond to subdiv.sions generally accepted in the literature. A subdivision of a tectonic p ovince is accepted if it can be corroborated on the basis of detailed seismicity studies, tectonic flux measureme,its, contrasting structural fabric, different geologic history, dif ferences in stress regime, etc.

If detailed investigations reveal no significant differences bet' een areas within a tectonic province, the areas should be consir ered to compose a single tectonic province. The presentation should be augr ented by a regional-scale map showing the te: tonic provinces, the earthquake epicerters, and the locations of geologic structures and measurement > used to define provinces. Acceptar.ce of the proposed tectonic prcvinces is based on the staff's independent review o# the seismicity, tectonic flux (Ref. 31), geologic structure, and stress regime in the region of the site.

5.

Subsection 2.5.2.4 (Maximum Earthquake Potential): The applicant's presentation is accepted when the vibratory ground motion due to the maximum credible earthquake associated with each geologic s'ructure or the maximum historic earthquake essociated with eac" tectonic province has been assessed and when the earthquake which would pro-duce the maximum vibratory ground motion at the site has been determined. Earthquakes asscciated with each geologic structure or tectonic province must be identified. Where an earthquake is associated with geologic structure, the maximum earthquake which could occur on that structure should be evaluated, taking into account such factors as the type of the faulting, fault length, fault displacement, and earthquake history, (e.g., Refs. 14, 15).

In order to determine the maximum earthquake that could occur on those faults which are shown or assumed to be capable, the staff accepts conservative values based or historic experience in the region and specific considerations of the earthquake history, sense of movement, and geologic history of movement on the f aults. Wnere the earth-quakes are associated with a tectonic province, the largest historical earthquake within the province should be identified and, whenever possible, ti,e return period for the earthquake should be estimated. Isoseismal maps should also be presented for the mosc significant e v thquakes. The ground motion at the site should be evaluated assuming seismic energy transmission effects are constant over the region of the site and assuming that the largest earthquake associated with each geologic structure or with each tectonic province occurs at the point of closest approach of that structure or province to the site, 2.5.?-3

The set of conditions describing the occurrence of the earthquake which would produce the largest vibratory ground motion at the site should be defined. If different potential earthquakes would produce the maximum ground motion in different frequency bands, the conditions describing all such earthquakes should be specified. The des-cription of the potential earthquake occurrence is to include the maximum intensity or magnitude and the distance from the assumed location of the potential earthquake to the site. The staff independently evaluates the effects on site ground motion of the largest earthquake associated with each geologic structure or tectonic province.

Acceptance of the description of the potential earthquake which wculd produce the largest ground motion at the site is based on the staff's independent analysis.

6.

Subsection 2.5.2.5 (Seismi Wave Transmission Characteristics of the Site):

The applicant's presentation is accepted when the seismic wave transmission character-istics (amplification or deamplification) of the materials overlying bedrock at the site are described as a function of the significant freq"encies. The following material properties should to determined for each stratum under the site: seismic compressional and shear velocities, bulk densities, soil properties and classification, shear modulus and its variation with strain level, and water table elevation and its variation. In eata case, methods used to determine the properties should be described or a cross-reference should be given indicating where in the SAR the description is prnvided.

For each set of conditions describing the occurrence of the maximum potential earth-quake, deternined in Subsection 2.5.2.4, the type of saismic waves producing the maxi-mum ground motion and the significant frequencies must be determined. For each set of conditions an analysis should be performed to determine the effects of transmission in the site material for the identified seismic wave types in the significant frequency bands.

Where horizontal shear waves produce the maximum ground motion, an analysis simil. - to that of Schnabel, et al. (Ref. 16) is appropriate. Where cor.pressional or surface waves produce the maxinum ground notion, other methods of analysis (Refs.17,18) may be more appropriate. However, since the latter techniques are still in the developmental stages and no generally agreed-on prccedures can be promulgated at this time, the staff accepts the shear wave model as representative of site amplification. The site amplifi-cation determined in this way should be compared with characteristics of site amplifi-cation in the epicentral area of the historical earthquake used as the basis for each maximum potential earthqJake. If detailed soils investigations have been made in the epicentral area, the amplification analysis should be based on these. Because detailed geologic investigations are generally not available for the epicentral areas of his-torical earthquakes, se.."1 factors should be considered in assessing amplification egional geology and soil conditions, earthquake isoseismal effects there, including:

r maps, and descriptions ^f earthquake effects.

2.5.2 4 146 016

7.

Subsection 2.5.2.6 (Safe Shutdown Earthquake): The applicant's presentation is accepted when the vibratory ground motion spesified for the safe shutdown earC quake is described in terns of the level of acceleration for seismic design ano its time history and is as conservative as that which would result at the site from the maximum potential earthquake (deternined in Subsection 2.5.2.4) and considering the variations in site transmission ef fects (determined in Subsection 2.5.2.5).

If several different maximum potential earthquakes produce the largest ground motions in different frequency bands (as noted in Subsection 2.5.2.4), the vibratory ground motion specified for the SSE must be as conservative in each frequency band as that for each carthquake, includ-ing site transmission effects (as noted in Subsection 2.5.2.5).

The amplitude of acceleration at the ground surface, the effective frequency range, and the duration corresponding to each maximum potential earthquake must be identified.

The acccieration is to be expressed as a fraction of the acceleration of gravity (g).

Wherr. the earthquake has been associated with a specific geologic structure, the acce.eration should be determined using a relation between acceleration, magnitude or fault length and distance from the fault (cf. Refs.13,15). Where the earthquake has been associated with a tectonic province, the acceleration should be determined using appropriate relations between acceleration, intensity, epicentral intensity, and distance (e.g., Refs. 19, 20, 21, 20).

Neerous correlations between intensity and acceleration are given in the literature 9

(Refs. 19, 20, 21, 22, 23); several of them are considered acceptable by the staff.

The correlation used is accepted if it is conservative when compared to the actual observational data. Acceptance is based on an analysis of the site's seismic energy transmission properties (Ref. 16, or equi' lent). Conservatism should be assessed based on consideration of the amplifi % tira analysis and in compcrison with the actual published data. The staff will generally accept an acceleration for seismic design as being conservative if, when applied at the ground surface, it results in a value at the foundation free field level as large as would be obtained from the empirical relation c/ the mean of the intensity acceleration values in Reference 23.

Available ground motion time histories for earthquakes of comparable values of magnitude, epicentral distance, and acceleration level should be presented. The spectral content for each potential maximum earthquake should be described; it should be based on consideration of the available ground rotion time histories and regional characteristics of seismic wave transmission. The dominant frequency associated with the peak acceleration should be determined either from analysis of ground motion time histories or by inference from descriptions of earthquake phenonenology, damage reports, and regional characteristics of seismic wave transmissicn.

In sone cases, the peak acceleration may not as significant for engineering design purposes as a sustained acceleration at a lower level. One situation where the sus-tained acceleration level may differ from the peak acceleration is in prnximity to the causative fault of the earthquake. It is appropriate in such cases to define the 2.5.2-5

" reference acceleration for seismic design" as representative of the level of sustained acceleration. Th "referer & acceleration for seismic design" determined in this section of the applicant's SJR is taken to be the high frequency asymptote to the design response spectrum defined in Reference 2.

At this time, the staff is not aware of any published relations between earthquake irtensity or magnitude and sustained acceleration. Such relations could be developed from analyses of the response spectra of accelerograph time histories in those treas where magnitude and intensity measurements are also avail-able. In liea of such studies, the peak acceierations are considered to represent conservative reference accelerations for seismic design. Lower levels of reference acceleration may be justified on a site-specific basis.

The staff's review of proposed reference accelerations for seismic design considers:

the proximity of the site to the geologic structure or province with which the poten-tial earthquake is associated, characteristics of acceleration time histories at epicentral distances similar to that of the potential SSE, results of time-dependent spectral analyses of such time histories (cf. Refs. 25, 26), the level and dominant frequency of the peak acceleration, and seismic wave amplitude attenuation as a result of transmission from the source to the site and in the material underlying the site.

The design response spectrum is reviewed under Standard Review Plan (SRP) 3.7.1; however, as noted above there are certain seismological conditions which may require special modifications of the response spectrum. In general, the design response spectrum is acceptable if it is as conservative as the response spectrum from each of the potential earthquakes as described above.

The time duration of strong ground motion is required for analysis of site foundation liquefaction potential and for desiga of many plant components. The adequacy of the time history for structural analysis is reviewed under SRP 3.7.1.

The tine history is reviewed in this standard review plan to confirm that it is compatible with the seismological and geological conditions in the site vicinity and with the accepted SSE nodel. At present, there is no truly adequate nodel for deterministically computing the time history of strong ground motion from a given source-site configura-tion. It is, therefore, acceptable to generate the time history record from the design response spectrum for the SSE using the method of Tso: (Ref. 27) or an equivalent method. Total duration of the notion is acceptable when (1) tis as conservative as values determined using the procedure described by Bolt (Ref. 28) for hard rock sites cr for analyses where nonstationarity of strong motion time functions is unimportant

• and (2) the spectrum of the derived accelerogram f s found acceptable in the review under SRP 3.7.1.

C.

Subsection 2.5.2.7 (Operating Basis Earthquake): The vibratory ground motion for the OBE should be described with the SSE and the acceleration level at the site specified.

The minimum value of the acceleration level for the OBE is currently one-half the reference acceleration for seismic design corresponding to the SSE. For sites in high!y seismic regions, mainly in the western United States, the complete description of the OBE, as given in 10 CFR Part 100, Appendix A,Section III(d),

• For sites on sedir.ents or for analyses where nonstationarit; is important, more conservative values may be required. See, e.g., Refs. 24 and 30.

2.5.2-6

is required. In some cases, probability calculations, like those described by Algermissen (Ref. 29), would be helpful in estimating the accc eration level reason-ably expected to affect the plant site during the operating life of the plant.

Acceptable source regions that can be used as input to tMse calculations are those ge&gic structures or tectonic provinces wit 1 which historical earthquake activity has been associated. Such descriptions should include the acceleration level of the OBI and a determination af the probability of exceeding that level during the 40-year operating life of the plant.

III.

REVIEW PROCEDURES 1.

Upon receiving the applicant's SAR, an acceptance review is conducted to determine:

compliance with the investigative requirements of 10 CFR Part 100, Aprendix A, and conforr.ance with the Standard Format (Regulatory Guide 1.70).

The reviewer also identifies any site-specific problems, the resolution of which could result in extended delays in completing the review.

2.

Af ter SAR acceptance and docketing those areas are identified where additional information is required to determine the earthquake hazard and to establish tt design acceleration. These are transmitted to the applicant in requests for additional informa tion (Q-1).

3 A site visit is conducted during which the reviewer inspects the foundation conditions, local f aulting, and other geologic conditions. During the site visit the reviewer aiso discusses and clarifies the Q-1 questions with the applicant and his consultants 9v so that it is clearly understood what additional informatim is required by the staff to continue the review.

4.

Following the site visit a revised set of request 5 for additional information (0-2),

including any additional questions which may have been developed during the site vici*

is fccmally trans aitted to the applic3nt. At the Q-: stage the review procedure consists mainly of an evaluation of tne applicant's response to the Q-1 questions. The reviewer prepares requests for additional clarifying information and formulates posi-tions which may agree or disagree with those of the applicant. These are formally transmitted to the applicant.

5.

The safety analysis report and supplements responding to the requests for additional information (Q-l, Q-2) are reviewed to determine that the inforrntion presented by the applicant is acceptable according to the critieria described in Section II above.

Based on information supplied by the applicant, obtained from site visits, or from staff consultants or literature sources, the reviewer independentlv identifies the relevant seismotectonic provinces, evaluates the capability of faults in the region, and determines the earthquake potential for each province and each capable fault using procedures noted in Section II above. The reviewer evaluates the vibratory ground motion which the potential earthquakes cauld produce at the site and definas the safe shutdown earthquake and operating basis earthquake.

2.5.2-7

IV.

EVALUATION FINDINGS For construction pemit (CP) reviews, the findings are included in the staf f's safety evaluation report and consist of statements (including or referencing diagrams, mos, etc. )

describing the applicant's and the staff's (1) definitions of seismotectonic pr

es; (2) evaluations of the capability of geologic structures in the region; (3) deternmotions of the SSE acceleration at ground surface, reference acceleration for seismic design, time duration of strong ground motion, and any alterations in the design response spectrum based on evaluation of the potential earthquakes; and (4) determinations of the CBE acceleration at ground surfn c.

If the staff's findings are consistert with those of the applicant, staff concurrence is stated; otherwise, a statement requiring use of the staf f's findings is made.

For operating license (0L) reviews, the staff's positions from the CP review are referenced and a detailed review of any new data which night af fect the seismic design bases is' presented.

V.

REFERENCES 1.

10 CFR Part 100, Appendix A, " Seismic and Geologic Siting Criteria for Nuclear Power Plants."

2.

Regulatory Guide 1.60, " Design Response Spuctra for Seisnic Design of Nuclear Power Plants," Revision 1.

3.

Regulatorj ide 1.70, " Standard Format and Content of Safety Analysis Reports for Nuclear Q er Plants," Revision 2.

4.

" Historical Earthquake Data File," National Geophysical and Solar-Terrestrial Data Center, National Oceanic and Atmospheric Administration.

5.

" Earthquake Histcry of the United States," Publication 41-1, National Oceanic and Atmospheric Administration, U. S. Departcent of Commerce (1973).

6.

S. D. Townley and M. W. Allen, " Description Catalog of Earthquakes of the Pacific Coast of the United States,1769 to 1928," Eulletin Seismological Society of America, Vol. 29 (1939).

7.

W. E. T. Smith, " Earthquakes of Eastern Canada and Adjacent Areas," Publications of the Dominion Observatory (1962).

8.

P. B. King, "The Tectonics of North Arerica - A Discussion to Accompany the Tectonic Map of North America Scale 1:S,000,000," Professional Paper 628, U. S. Geological Survey (1969).

9.

A. J. Eardley, " Tectonic Divisions of North America," Bulletin American Association of Petroleum Geologist, Vol. 35 (1951).

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2.S.2-8

10.

J. B. Hadley and J. F. Devine, "Seismotectonic Map of the Eastern United States,"

Publication MF-620, U. S. Geological Survey, 11.

M. L. Sbar and L. R. Sykes, "Conterporary Compressive Stress and Seismicity in Eastern North A,oerica: An Example of Intra-Plate Tectonics," Bulletin Geological Society of America, Vol. 84 (1973).

12.

R. B. Snith and M. L. Sbar, " Contemporary Tectonics and Seisnicity of the Western United States with Errphasis on the Internountain Seismic Belt," Bulletin Geological Society of America, Vol. 85 (1974).

13.

P. B. Schnabel and H. B. Seed, " Acceleration in Rock for Earthquakes in the Western United States," Report No. EERC 72-2, Earthquake Engineering Center, University of California, Eerkeley (1972).

14.

J. N. Brune, " Tectonic Stress and Spectra of Seismic Shear Waves fron Earthquakes,"

Journal of Geophysical Research, Vol. 75 (1970).

15.

D. Tocher, "[arthquake Energy and Ground Breakage," Bulletin Seismological Society o f Anerica, Vol. 48 (1958).

16.

P. B. Schnabel, J. Lysmer, and H. B. Seed, " SHAKE-A Conputer Program for Earthquake Response Analysis of Horizontally Layered Sites," Report No. EERC 72-12, Earthquake Engineering Research Center, University of California, Berkeley (1972).

1,.

M. D. Trifunac and F. E. Udwadia, " Variations of Strong Earthquake Ground Shaking in the Los Angeles Area,"

Sulletin Seismological Society of Anerica, Vol. 64 (1974).

18.

L. A. Drak e, " Love and Riyleigh Waves in Nonhorizontally Layered Media," Bulletin Seismological Society of Arerica, Vol. 62 (1972).

19.

N. N. Anbraseys, "Dynanics and Response of Foundation Materials in Epicentral Regions of Strong Earthquakes," F oceedings of the Fif th World Conference on Earthquake Engineering (1973).

20.

F. Neumann, " Earthquake Intensity and Related Ground Motion," University of Washington Press (1954).

21.

B. Gutenberg and C. Richter, " Earthquake Magnitude, Intensity, Energy, and Accelera-tion," Bulletin Seismological Society of Anerica, Vol. 46 (1956).

22.

N. N. Anbraseys, "The Correlation of Intensity with Ground Motions," Paper presented at Trieste Conference on Advancements of Engineering Seismology in Europe (1974).

2.5.2-9

23.

M. D. Trifunac and A. G. Brady, "On the Correlation of Seismic Intensity Scales with Peaks of Recorded Strong Ground Motion," Bulletin Seismological Society of America, Vol. 65 (1975).

24.

O. W. Nuttli, "f tate-of-the-Art for Assessing Earthquake Hazards L the United States, Report 1, Design Earthquakes for the Central United States," Miscellaneous Paper S-73-1, U. S. Army Engineer Waterways Experiment Station (1973).

25.

V. Perez, " Peak Ground Accelerations and Their Effect on the Velocity Response Envelope Spectrum as a Function of Time, San Fernando Earthquake, February 9, 1971,"

Proceedings of the Fifth World Conference on Earthquake Engineering (1973).

26.

V. Perez, " Velocity Response Envelope Spectrum as a Function of Time, for the Facoima Dam, San Fernando Earthquake, February 9, 1971," Bulletin Seismological Society of America, Vol. 63 (1973).

27.

N. C. Tsai, " Spectrum-Compatible Motions for Design Purnoses," Journal Engineering Mechanics Division, American Society of Civil Engineers, Vol. 98 (1972).

28.

B. A. Bolt, "" ation of Strong Ground Motion," Proceedings of the Fifth World Conference on Larthquake Engineering (1973).

29.

S. T. Algermissen and D. M. Perkins, " Techniques for Seismic Zoning:

1.

General Considerations and Parameters," Proceedings of the international Conference on Microzonation for Safer Construction Research and Application (1972).

30.

L. Esteva and E. Rosenblueth, "Espectros Temblores a Distomicas Moderodas y Grandes,'

Proceedings of Chilean Conference on Seismology and Earthquake Engineering, Vol. 1, University of Chile (1963).

31.

P. St. Amand, "Two Proposed Measures of Seismicity," Bull. Seism. Soc. Am., Vol. 46, pp. 41-45 (1956).

2.5.2-10 146 022