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:
any tectonic deformation at the earth's surface within 40 km (25 miles) of the site will require detailed examination to determine its significance. Potentially active tectonic deformation within the seismogenic zone beneath a site will have to be assessed using geo physical and seismological methods to determine its significance. Engineering solutions are generally available to mitigate the potential vibratory effects of earthquakes through design. However, engineering solutions can not always be demonstrated to be adequate for mitiga tion of the effects of permanent ground displacement phenomena such as surface faulting or folding, subsi dence, or ground collapse. For this reason, it is prudent to select an alternative site when the potential for per manent ground displacement exists at the proposed site (Ref. D.2). In most of the CEUS, instrumentally located earth quakes seldom bear any relationship to geologic struc tures exposed at the ground surface. Possible geologi cally young fault displacements either do not extend to the ground surface or there is insufficient geologic ma terial of the appropriate age available to date the faults. Capable tectonic sources are not always exposed at the ground surface in the Western United States as demon- strated by the buried (blind) reverse causative faults of the 1983 Coalinga,1988 Whittier Narrows, 1989 Loma Prieta, and 1994 Northridge earthquakes. These factors emphasize the need to conduct thorough investigations not only at the ground surface but also in the subsurface to identify structures at seismogenic depths. The level of detail for investigations should be governed by knowledge of the current and late Quater nary tectonic regime and the geological complexity of the site and region. The investigations should be based on increasing the amount of detailed information as they proceed from the regional level down to the site area (e.g., 320 km to 8 km distance from the site). Whenever faults or other structures