Assessment of the Potential for Tectonic Fault Rupture for High-Level Nuclear Waste Repositories

Active faults that extend to or near the Earth's surface may threaten the safety of engineered structures. The threat can be mitigated by appropriate siting and design, which requires understanding of the characteristics and magnitude of the faulting hazard based on detailed site investigations and assessment of the characteristics of faulting that has occurred under the present tectonic regime in the site area. Both deterministic and probabilistic approaches are used to assess hazards due to fault rupture for engineering design. A combined probabilistic-deterministic approach provides the broadest perspective both for evaluating the potential fault rupture hazard and for selecting design criteria, which may differ among the various components of the repository depending on their function and importance to safety. Probabilistic analyses that explicitly incorporates uncertainties in parameters that characterize fault activity, the nature and amount of deformation, and the likelihood of occurrence, as well as uncertainties in the analytical methods, enables reasonable design parameters to be selected and the identification of the input parameters and analytical methods that dominate the hazard. Deterministic analyses can then be made to examine in detail those factors that dominate the fault rupture hazard.