Document: NUREG-0800
Document ID: 91dd5605-fced-4aa9-82f4-b0def4175216
Document Type: srp
Title: Safe Shutdown Earthquake. In meeting the requirements of Ref-
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340591.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.5.2.6
CFR Part: 
CFR Title: 

Content:
ing earthquake(s). It must be ensured that the recorded motions represent free-field condi- tions and are free of or corrected for any soil-structure interaction effects that may be present because of locations and/or housing of recording instruments. Important source properties include magnitude and, if possible, fault type, and tectonic environment. Propagation path properties include distance, depth, and attenuation. Relevant site properties include shear velocity profile and other factors that affect the amplitude of waves at different frequencies. A sufficently large number of site-specific time histories and/or response spectra should be used to obtain an adequately broadband spectrum to encompass the uncertainties in these parameters. An 84th percentile response spectrum for the records should be presented for each damping value of interest and compared to the SSE free-field and design response spectrum (e.g., Refs. 30, 31, 32, and 33). The staff considers direct estimates of spectral ordinates preferable to scaling of spectra to peak accelera- tions. In the Eastern United States, relatively little information is available on magnitudes for the larger historic earthquakes; hence, it may be appropriate to rely on intensity observations (descriptions of earthquake effects) to estimate magnitudes of historic events (e.g., Refs. 34 and 35). If the data for site-specific response spectra were not obtained under geologic conditions similar to those at the site, corrections for site effects should be included in the development of the site-specific spectra. 2. Where a large enough ensemble of strong-motion records is not available, response spectra may be approximated by scaling that ensemble of strong- motion data that represent the best estimate of source, propagation path, and site properties (e.g., Ref. 36). Sensitivity studies should show the effects of scaling. 3. If strong-motion records are not available, site-specific peak ground acceleration, velocity, and