Document: NUREG-0800
Document ID: b757da37-f302-4c36-9b11-c9c186412437
Document Type: srp
Title: Probabilistic Seismic Hazard Analysis and Controlling Earthquakes.  For CEUS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070730593.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.5.2.4
CFR Part: 
CFR Title: 

Content:
ions included in defining the distribution of ground motions for each magnitude and distance scenario, can have a significant impact on the results of the PSHA. The staff will review the ground motion models used for the PSHA to ensure that the value for epsilon is large enough such that natural aleatory variability in the ground motions is adequately addressed. A recent study (Ref. 17) found no technical basis for truncating the ground motion distribution at a specified number of standard deviations (epsilons) below that implied by the strength of the geologic 2.5.2-8 Revision 4 - March 2007 materials. Even though very large ground motions have a low probability of occurrence, when the hazard is calculated for low annual frequencies of exceedance, low probability events need to be considered. For determining recurrence relationship parameters, the entire seismicity catalog developed in Subsection 2.5.2.1, should be used. For the seismic hazard evaluation, the use of Cumulative Absolute Velocity (CAV) provides an alternative approach to the use of minimum magnitude truncation for the PSHA (Ref. 16). The staff will review the controlling earthquakes and associated ground motions at the site derived from the applicant's PSHA to be sure that they adequately represent the local and regional seismic hazard as represented by both historical seismicity and paleoseismicity. The applicant's probabilistic analysis, including the derivation of controlling earthquakes, is considered acceptable if it follows the procedures in Appendix C of Regulatory Guide 1.165 or Appendix D of Regulatory Guide 1.208. For applicants that use Regulatory Guide 1.165, one pair of low and high frequency controlling earthquakes should be determined at the reference probability value. For applicants that use Regulatory Guide 1.208, three pairs of low and high frequency controlling earthquakes should be determined for the mean 10-4, 10-5, and 10-6 annual probabilities. For applicants that do not use