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:
d vertical free-field ground motion re sponse spectra at the free ground surface. It is devel oped with consideration of local site effects and site seismic wave transmission effects. The SSE response spectrum can be determined by scaling a site-specific spectral shape determined for the controlling earth quakes or by scaling a standard broad-band spectral shape to envelope the average of the ground motion lev els for 5 and 10 Hz (Sa,5-10), and 1 and 2.5 Hz (Sa,1-2.5) as determined in Step C.2 of Appendix C to this guide. It is anticipated that a regulatory guide will be de veloped that provides guidance on assessing site specific effects and determining smooth design re sponse spectra, taking into account recent develop ments in ground motion modeling and site amplifica tion studies (e.g., Ref. F.1). F.2 DISCUSSION For engineering purposes, it is essential that the de sign ground motion response spectrum be a broad-band smooth response spectrum with adequate energy in the frequencies of interest. In the past, it was general prac tice to select a standard broad-band spectrum, such as the spectrum in Regulatory Guide 1.60 (Ref. F.2), and scale it by a peak ground motion parameter (usually peak ground acceleration (PGA)), which is derived based on the size of the controlling earthquake. During the licensing review this spectrum was checked against site-specific spectral estimates derived using Standard Review Plan Section 2.5.2 procedures to be sure that the SSE design spectrum adequately enveloped the site-specific spectrum. These past practices to define the SSE are still valid and, based on this consideration, the following three possible situations are depicted in Figures F.1 to F.3. Figure F. 1 depicts a situation in which a site is to be used for a certified design with an established SSE (for instance, an Advanced light Water Reactor with 0.3g PGA SSE). In this example, the certified design SSE spectrum compares favorably with the site-specific re sponse