Confidence Levels in Deterministic Seismic Hazard Estimations

Abstract eng:
Accounting for the inherent uncertainty in the data and models that feed seismic hazard estimates has been an issue for more than 30 years. Probabilistic seismic hazard methods provide so far the only established tools that formally account for uncertainty. In this study, we propose an alternative approach that allows assessing deterministic seismic hazard with associated confidence levels using the French nuclear regulatory guide RFS 2001-01 as an example. The objective of this paper is to propose a methodology that allows integrating uncertainties involved at each step of the determination of an SMHV. The four main steps in the deterministic RFS 2001-01 guidelines entail (1) the definition of a seismotectonic zonation, (2) the selection of most damaging historical or instrumental earthquakes within each zone, and their displacement as close as possible to the site of interest, within their own zone, (3) the evaluation of magnitude-depth characteristics and (4) the estimation of intensity or spectral acceleration at the site. The propagation of inherent uncertainties associated to each step allows proposing different hazard spectrum depending on the confidence level of interest. Finally, deagregation of the hazard spectrum over the entire frequency range allows identifying the earthquake parameters that best fit the seismic hazard spectrum for the chosen confidence level.

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