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:
ime. 4. A complete description of the uncertainty. For example, in the LLNL study a truncated expo nential model was used for the distribution of magni tudes given that an earthquake has occurred in a source. A stationary Poisson process is used to model the spa tial and temporal occurrences of earthquakes in a source. For a general discussion of evaluating the earth quake potential and characterizing the uncertainty, re fer to the Senior Seismic Hazard Analysis Committee Report (Ref. 9). 2.3.1 For sites in the CEUS, when the LLNL or EPRI method is not used or not applicable (such as in the New Madrid Seismic Zone), it is necessary to evalu ate the seismic potential for each source. The seismic sources and data that have been accepted by the NRC in past licensing decisions may be used, along with the 1.165-5 data gathered from the investigations carried out as de scribed in Regulatory Position 1. Generally, the seismic sources for the CEUS are area sources because there is uncertainty about the underlying causes of earthquakes. This uncertainty is due to a lack of active surface faulting, a low rate of seismic activity, and a short historical record. The as sessment of earthquake recurrence for CEUS area sources commonly relies heavily on catalogs of ob served seismicity. Because these catalogs are incom plete and cover a relatively short period of time, it is difficult to obtain reliable estimates of the rate of ac tivity. Considerable care must be taken to correct for incompleteness and to model the uncertainty in the rate of earthquake recurrence. To completely charac terize the seismic potential for a source it is also nec essary to estimate the largest earthquake magnitude that a seismic source is capable of generating under the current tectonic regime. This estimated 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