Document: NRC Regulatory Guide
Document ID: cfc61809-5745-460f-8a26-13c168659924
Document Type: regulatory_guide
Title: Identification and Characterization of Seismic Sources and Determination of Safe Shutdown Earthquake Ground Motion
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740084.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.165
CFR Part: 
CFR Title: 

Content:
ilistic seismic hazard assessment. CENTRAL AND EASTERN UNITED STATES The CEUS is considered to be that part of the United States east of the Rocky Mountain front, or east of Longitude 1050 West (Refs. 4, 5). To deter mine the SSE in the CEUS, an accepted PSHAmeth odology with a range of credible alternative input in terpretations should be used. For sites in the CEUS, the seismic hazard methods, the data developed, and seismic sources identified by Lawrence Livermore National Laboratory (LLNL) (Refs. 4-6) and the 1.165'-2 K Electric Power Research Institute (EPRI) (Ref. 7) have been reviewed and accepted by the staff. The LLNL and EPRI studies developed data bases and scientific interpretations of available information K1 and determined seismic sources and source charac terizations for the CEUS (e.g., earthquake occur rence rates, estimates of maximum magnitude). In the CEUS, characterization of seismic sources is more problematic than in the active plate-margin region because there is generally no clear association between seismicity and known tectonic structures or near-surface geology. In general, the observed geo logic structures were generated in response to tecton ic forces that no longer exist and have little or no cor relation with current tectonic forces. Therefore, it is important to account for this uncertainty by the use of multiple alternative models. The identification of seismic sources and reason able alternatives in the CEUS considers hypotheses presently advocated for the occurrence of earth quakes in the CEUS (for example, the reactivation of favorably oriented zones of weakness or the local am plification and release of stresses concentrated around a geologic structure). In tectonically active areas of the CEUS, such as the New Madrid Seismic Zone, where geological, seismological, and geo . physical evidence suggest the nature of the sources that generate the earthquakes, it may be more ap propriate to evaluate those seismic sources by using