Document: NUREG-0800
Document ID: 65016276-60eb-4e87-829e-1ac16de720b3
Document Type: srp
Title: Probabilistic Seismic Hazard Analysis and Controlling Earthquakes.  For CEUS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1230/ML12301A010.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.5.2.4
CFR Part: 
CFR Title: 

Content:
weighting, (4) magnitude conversion, (5) distance measure adjustments, and (6) the model parameters for each spectral frequency. For each PSHA, the staff will also examine how logic trees for seismic source parameters and models (maximum magnitude, recurrence, source geometry) and attenuation models were used to incorporate model uncertainty. 2.5.2-10 Draft Revision 5 – 2013 Epsilon, the number of standard deviations 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. EPRI Report 1013105 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 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, as described in EPRI Report 1012965. To remove non-damaging lower-magnitude earthquakes from the hazard characterization, applicants should either use a lower bound magnitude cutoff of moment magnitude (Mw) 5 or the CAV filter for the PSHA. If used, the CAV filter should be limited to Mw less than or equal to 5.5. 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