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 as by the interpretion of the morphology of topographic fault scarps associated with or produced by surface rup ture. Fault scarp morphology is useful in estimating the age of last displacement (in conjunction with the ap propriate geochronological methods described in Sub section D.2.4, approximate size of the earthquake, re currence intervals, slip rate, and the nature of the c ausative fault at depth (Refs. D.15 through D.18). D.2.3.2 Seismological Investigations D.2.3.2.1. Listing of all historically reported earthquakes having Modified Mercalli Intensity (MMI) greater than or equal to IV or magnitude greater than or equal to 3.0 that can reasonably be associated with seismic sources, any part of which is within a ra dius of 320 km (200 miles) of the site (the site region). The earthquake descriptions should include the date of occurrence and measured or estimated data on the high est intensity, magnitude, epicenter, depth, focal mecha nism, and stress drop. Historical seismicity includes both historically reported and instrumentally recorded data. For earthquakes without instrumentally recorded data or calculated magnitudes, intensity should be con verted to magnitude, the procedure used to convert it to magnitude should be clearly documented, and epicen ters should be determined based on intensity distribu tions. Methods to convert intensity values to magni tudes in the CEUS are described in References D.1 and D.19 through D.21. D.2.3.2.2. Seismic monitoring in the site area should be established as soon as possible after site selection. For sites in both the CEUS and WUS, a single large dyn amic range, broad-band seismograph, and a network of short period instruments to locate events should be deployed around the site area. 1.165-33 The data obtained by monitoring 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