Document: NUREG-0800
Document ID: 67c6351b-0021-49c4-b8be-3be94298395e
Document Type: srp
Title: Seismic Wave Transmission Characteristics of the Site.  To meet the
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1331/ML13316C066.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.5.2.5
CFR Part: 
CFR Title: 

Content:
requirements of 10 CFR 100.23 for sites that have subsurface materials with a shear wave velocity different from the hard rock velocity used in the PSHA GMPEs, this subsection is acceptable when a site response analysis is performed. The site subsurface profile used for the site response analysis consists of all the soil and rock layers between the ground surface and the elevation below which shear wave velocities match those used in the GMPEs. When the GMRS are determined as free-field outcrop motions on the uppermost competent material, the site response analysis is based on the subsurface profile beneath the chosen location of the GMRS (not including the soil above). However, the calculation should capture the effect of the weight of the soil overburden in producing confinement that affects the soil properties and includes the effects of the soil column frequency of the overburden soil. Therefore, the computation of overburden pressures should include the weight of the soil column above the outcrop elevation to ensure that the computation of nonlinear effects in the strain iteration process is done consistently to match the final configuration of the site profile. Since the site-specific soil modifies the input ground motion from the base, and because the engineering properties of soil are variable, uncertainties associated with the properties of each layer are incorporated in the subsurface profile to perform the site amplification analysis to obtain the UHS at the free surface in the free field. To consider variation and uncertainties in dynamic soil properties, dynamic soil properties are randomized (using a Monte Carlo type of sampling from the properties of each layer, such as shear moduli and damping values) and a suite of typically 60 randomized soil profiles are generated for amplification analysis. To develop the randomized subsurface profiles, correlation models appropriate for the site geotechnical information need to be selected. The correlation