Peak Ground Velocities for Seismic Events at Yucca Mountain, Nevada
This report describes a scientific analysis to bound credible horizontal peak ground velocities (PGV) for the repository waste emplacement level at Yucca Mountain. Results are presented as a probability distribution for horizontal PGV to represent uncertainties in the analysis. The analysis also combines the bound to horizontal PGV with results of ground motion site-response modeling (BSC 2004 [DIRS 170027]) to develop a composite hazard curve for horizontal PGV at the waste emplacement level. This result provides input to an abstraction of seismic consequences (BSC 2004 [DIRS 169183]). The seismic consequence abstraction, in turn, defines the input data and computational algorithms for the seismic scenario class of the total system performance assessment (TSPA). Planning for the analysis is documented in Technical Work Plan TWP-MGR-GS-000001 (BSC 2004 [DIRS 171850]). The bound on horizontal PGV at the repository waste emplacement level developed in this analysis complements ground motions developed on the basis of PSHA results. In the PSHA, ground motion experts characterized the epistemic uncertainty and aleatory variability in their ground motion interpretations. To characterize the aleatory variability they used unbounded lognormal distributions. As a consequence of these characterizations, as seismic hazard calculations are extended to lower and lower annual frequencies of being exceeded, the ground motion level increases without bound, eventually reaching levels that are not credible (Corradini 2003 [DIRS 171191]). To provide credible seismic inputs for TSPA, in accordance with 10 Code of Federal Regulations (CFR) 63.102(j) [DIRS 156605], this complementary analysis is carried out to determine reasonable bounding values of horizontal PGV at the waste emplacement level for annual frequencies of exceedance as low as 10{sup -8}. For each realization of the TSPA seismic scenario, the results of this analysis provide a constraint on the values sampled from the horizontal PGV hazard curve for the waste emplacement level. The relation of this analysis to other work feeding the seismic consequence abstraction and the TSPA is shown on Figure 1-1. The ground motion hazard results from the PSHA provide the basis for inputs to a site-response model that determines the effect of site materials on the ground motion at a location of interest (e.g., the waste emplacement level). Peak ground velocity values determined from the site-response model for the waste emplacement level are then used to develop time histories (seismograms) that form input to a model of drift degradation under seismic loads potentially producing rockfall. The time histories are also used to carry out dynamic seismic structural response calculations of the drip shield and waste package system. For the drip shield, damage from seismically induced rockfall also is considered. In the seismic consequence abstraction, residual stress results from the structural response calculations are interpreted in terms of the percentage of the component (drip shield, waste package) damaged as a function of horizontal PGV. The composite hazard curve developed in this analysis, which reflects the results of site-response modeling and the bound to credible horizontal PGV at the waste emplacement level, also feeds the seismic consequence abstraction. The composite hazard curve is incorporated into the TSPA sampling process to bound horizontal PGV and related seismic consequences to values that are credible.
- Research Organization:
- Yucca Mountain Project, Las Vegas, NV (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC28-01RW12101
- OSTI ID:
- 838326
- Report Number(s):
- ANL-MGR-GS-000004, REV 00; DOC.20050223.0002, DC#39381; TRN: US0502704
- Resource Relation:
- Other Information: PBD: 16 Feb 2005
- Country of Publication:
- United States
- Language:
- English
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Bounding Peak Ground Velocities for Seismic Events at Yucca Mountain, Nevada