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:
timated magni tude defines the upper bound of the earthquake recur rence relationship. The assessment of earthquake potential for area sources is particularly difficult because the physical constraint most important to the assessment, the di mensions of the fault rupture, is not known, As a re sult, the primary methods for assessing maximum earthquakes for area sources usually include a con sideration of the historical seismicity record, the pat tern and rate of seismic activity, the Quaternary (2 million years and younger), characteristics of the source, the current stress regime (and how it aligns with known tectonic structures), paleoseismic data, and analogues to sources in other regions considered tectonically similar to the CEUS. Because of the shortness of the historical catalog and low rate of seismic activity, considerable judgment is needed. It is important to characterize the large uncertainties in the assessment of the earthquake potential. 2.3.2 For sites located within the Western United States, earthquakes can often be associated with known tectonic structures. For faults, the earthquake potential is related to the characteristics of the estimated future rupture, such as the total rupture area, the length, or the amount of fault displacement. The following empirical relations can be used to estimate the earthquake poten tial from fault behavior data and also to estimate the amount of displacement that might be expected for a given magnitude. It is prudent to use several of these different relations to obtain an estimate of the earth quake magnitude. "* Surface rupture length versus magnitude (Refs. 10-13), "* Subsurface rupture length versus magnitude (Ref. 14), "* Rupture area versus magnitude (Ref. 15), "* Maximum and average displacement versus magnitude (Ref. 14), "* Slip rate versus magnitude (Ref. 16). When such correlations as References 10-16 are used, the earthquake potential is often evaluated as the mean of the distribution. The difficult