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:
ne, 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 procedures similar to those normally applied in the Western United States. WESTERN UNITED STATES The Western United States is considered to be that part of the United States that lies west of the Rocky Mountain front, or west of approximately 1050 West Longitude. For the Western United States, an informa tion base of earth science data and scientific interpreta tions of seismic sources and source characterizations (e.g., geometry, seismicity parameters) comparable to the CEUS as documented in the LLNL and EPRI stud ies (Refs. 4-7) does not exist. For this region, specific interpretations on a site-by-site basis should be applied (Ref. 1). The active plate-margin region includes, for exam ple, coastal California, Oregon, Washington, and Alas ka. For the active plate-margin region, where earth quakes can often be correlated with known tectonic structures, those structures should be assessed for their earthquake and surface deformation potential. In this region, at least three types of sources exist: (1) faults that are known to be at or near the surface, (2) buried (blind) sources that may often be manifested as folds at the earth's surface, and (3) subduction zone sources, such as those in the Pacific Northwest. The nature of surface faults can be evaluated by conventional surface and near-surface investigation techniques to assess ori entation, geometry, sense of displacements, length of rupture, Quaternary history, etc. Buried (blind) faults are often associated with surficial deformation such as folding, uplift, or subsi dence. The surface expression of blind faulting can be detected by mapping the uplifted or down-dropped geomorphological features or stratigraphy, survey leveling, and geodetic methods. The nature of the structure at depth can often be evaluated by