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:
onic structures and current seismicity. The new findings should be assessed by comparing them with the specific input of each expert or team that par ticipated in the PSHA. Regarding a new source, for ex ample, the specific seismic source characterizations for each expert or team (such as tectonic feature being modeled, source geometry, probability of being active, maximum earthquake magnitude, or occurrence rates) should be assessed in the context of the significant new data and interpretations. It is expected that the new information will be with in the range of interpretations in the existing data base, and the data will not result in an increase in overall seis micity rate or increase in the range of maximum earth quakes to be used in the probabilistic analysis. It can then be concluded that the current LLNL or EPRI re sults apply. It is possible that the new data may necessi tate a change in some parameter. In this case, appropri ate sensitivity analyses should be performed to determine whether the new site-specific data could affect the ground motion estimates at the reference probability level. An example is a consideration of the seismic haz ard near the Wabash River Valley (Ref. E.1). Geologi cal evidence found recently within the Wabash River Valley and several of its tributaries indicated that an earthquake much larger than any historic event had oc curred several thousand years ago in the vicinity of Vin cennes, Indiana. A review of the inputs by the experts and teams involved in the LLNL and EPRI PSHAs re vealed that many of them had made allowance for this possibility in their tectonic models by assuming the ex tension of the New Madrid Seismic Zone northward into the Wabash Valley. Several experts had given strong weight to the relatively high seismicity of the area, including the number of magnitude 5 historic earthquakes that have occurred, and thus had assumed the larger event. This analysis of the source character izations of the experts and teams