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:
ring current seismic ity will be used, along with the much larger data base acquired from site investigations, to evaluate site re sponse and to provide information about whether there are significant sources of earthquakes within the site vicinity, or to provide data by which an existing source can be characterized. Monitoring should be initiated as soon as practica ble at the site, preferably at least five years prior to construction of a nuclear unit at a site, and should con tinue at least until the free field seismic monitoring strong ground motion instrumentation described in Regulatory Guide 1.12 (Ref. D.22) is operational. D.2.33 Subsurface Investigations Ref. D.3 describes geological, geotechnical, and geophysical investigation techniques that can be ap plied to explore the subsurface beneath the site and in the region around the site, therefore, only a brief sum mary is provided in this section. Subsurface investiga tions in the site area and vicinity to identify and define seismogenic sources and capable tectonic sources may' include the following. D.2.3.3.1. Geophysical investigations that have been useful in the past include, for example, magnetic and gravity surveys, seismic reflection and seismic re fraction surveys, borehole geophysics, electrical sur veys, and ground-penetrating radar surveys. D.2.33.2. Core borings to map subsurface geol ogy and obtain samples for testing such as determining the properties of the subsurface soils and rocks and geo chronological analysis. D.2.3.3.3. Excavating and logging of trenches across geological features as part of the neotectonic in vestigation and to obtain samples for the geochrono logical analysis of those features. At some sites, deep unconsolidated material/soil, bodies of water, or other material may obscure geologic evidence of past activity along a tectonic structure. In such cases, the analysis of evidence elsewhere along the structure can be used to evaluate its characteristics in the vicinity of