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:
ch is near the San Gregorio-Hosgri Fault, it would not be necessary to extend the regional inves tigations farther east than the dominant San Andreas Fault, which is about 75 km (45 mi) from the site; nor west beyond the Santa Lucia Banks Fault, which is about 45 km (27 mi). Justification for using lesser dis tances should be provided. Reconnaissance-level investigations, which may need to be supplemented at specific -locations by more detailed explorations such as geologic mapping, geo physical surveying, borings, and trenching, should be conducted to a distance of 40 km (25 mi) from the site; the data should be presented at a scale of 1:50,000 or smaller. Detailed investigations should be carried out with in a radius of 8 km (5 mi) from the site, and the resulting data should be presented at a scale of 1:5,000 or smaller. The level of investigations should be in sufficient detail to delineate the geology and the potential for tectonic deformation at or near the ground surface. The inves tigations should use the methods described in subsec tions D.2.2 and D.2.3 that are appropriate for the tec tonic regime to characterize seismic sources. The areas of investigations may be asymmetrical and may cover larger areas than those described above in regions of late Quaternary activity, regions with high rates of historical seismic activity (felt or instrumen tally recorded data), or sites that are located near a capa ble tectonic source such as a fault zone. Data from investigations at the site (approximately 1 square kilometer) should be presented at a scale of 1:500 or smaller. Important aspects of the site inves tigations are the excavation and logging of exploratory trenches and the mapping of the excavations for the plant structures, particularly plant structures that are characterized as Seismic Category I. In addition to geo logical, geophysical, and seismological investigations, detailed geotechnical engineering investigations as de scribed in Regulatory Guide