ML24292A155
| ML24292A155 | |
| Person / Time | |
|---|---|
| Issue date: | 10/21/2024 |
| From: | Clifford Munson, Scott Stovall, Thomas Weaver NRC/RES/DE |
| To: | |
| Thomas Weaver 301-415-2383 | |
| Shared Package | |
| ML24292A135 | List: |
| References | |
| Download: ML24292A155 (1) | |
Text
Natural Phenomena Hazards NRC/DOE October 2024 SSHAC Generic Western U.S. Ground Motion Model S. Stovall1, T. Weaver1, C. Munson1 1 U.S. Nuclear Regulatory Commission A Senior Seismic Hazard Analysis Committee (SSHAC) Level 1 demonstration study (as defined in NUREG-2213) is being conducted by the U.S. Nuclear Regulatory Commission (USNRC) staff and technical experts at Southwest Research Institute (SwRI) and their consultants at the Private Fuel Storage (PFS) site in Skull Valley Utah. The objective of the SSHAC Level 1 study is to demonstrate what constitutes an acceptable approach to a site-specific PSHA for future licensing of advanced reactors. As part of this project, we have developed a generic western U.S. (GWUS) ground motion model (GMM) to produce probabilistic seismic hazard analysis (PSHA) hazard curves. The objective for developing the GWUS-GMM is to provide a set of new models for median ground motions and their associated weights to be used with logic-trees in PSHAs for a wide range of sites in the western U.S.
(WUS).
We developed the GWUS-GMM using a subset of ground motion prediction equations (GMPEs) from the NGA-West2 project as seed models to capture the center, body, and range of technically defensible interpretations for predicted median ground motions. As the GWUS-GMM is intended to cover a wide range of tectonic settings for WUS sites, the body and range of the median ground motions produced by the GWUS-GMM generally encompass the body and range of median ground motions from other recent SSHAC WUS GMMs. We captured the center, body, and range of median ground motions by evaluating the seed model spectral accelerations at 154 magnitude and distance pairs to inform the mean of a multi-variate normal distribution with modeled variance and correlation. We selected the variance values as a function of magnitude and distance to ensure a generally wider body and range of median ground motions compared to other recent SSHAC WUS GMMs. We then sampled the multi-variate distribution to obtain a set of 10,000 random ground motion models and used a Sammons approach to map the higher dimensional ground motion space to 2 dimensions for visualization and discretization. To verify the suitability of the body and range of median ground motions produced by the GWUS-GMM, we compared the base case predicted median ground motions from the GWUS-GMM to the same base case median ground motions from other recent SSHAC WUS GMMs for a wide range of magnitudes and distance combinations. The final GWUS-GMM includes a set of 17 GMMs for 21 oscillator frequencies for a moment magnitude range of 5.0 to 8.0 and distances out to 200 km. In addition, we developed a set of median ground motion adjustments for normal and reverse faulting and for sites located on the hanging-wall side of the fault that capture the epistemic uncertainty for each of these potential scenarios. We also evaluated the standard deviation models developed by recent SSHAC WUS GMMs to recommend a model suitable for a wide range of WUS sites.
The opinions, findings, and conclusions or recommendations expressed in this paper are those of the author(s) and do not necessarily reflect the views of the USNRC and do not constitute a final judgement or determination of the matters addressed or of the acceptability of any licensing action that may be under consideration at the USNRC.