Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/nhess-2017-97
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
15 Mar 2017
Review status
This discussion paper is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Transposing an active fault database into a fault-based seismic hazard assessment for Nuclear facilities. Part B: Impact of fault parameter uncertainties on a site-specific PSHA exercise in the Upper Rhine Graben, Eastern France
Thomas Chartier1,2, Oona Scotti1, Christophe Clément1, Hervé Jomard1, and Stéphane Baize1 1Bureau d'Evaluation des Risques Sismiques pour la Sûreté des Installations, Fontenay-aux-Roses, 92262, France
2Today at Département de Géosciences, Ecole Normale Supérieure, Paris, 75005, France
Abstract. We perform a fault-based PSHA exercise in the Upper Rhine Graben to quantify the relative influence of fault parameters on the hazard at the Fessenheim Nuclear Power Plant site. Specifically, we show that the potentially active faults described in Part A of this paper (Jomard et al., submitted this issue) are the dominant factor in hazard estimates at the low annual probability of exceedance relevant for the safety assessment of nuclear installations. Geological information documenting the activity of the faults in this region, however, remains sparse, controversial and affected by a high degree of uncertainty. A logic tree approach is thus implemented to explore the epistemic uncertainty and quantify its impact on the seismic hazard estimates. Disaggregation of the Peak Ground Acceleration (PGA) hazard at 10,000 years return period shows that the Rhine River Fault is the main seismic source controlling the hazard level at the site. The choice of Ground Motion Prediction Equations (GMPE) is the major source of uncertainty. Nonetheless the parameters describing the geometry and the seismic activity of the faults (dip, width, slip rate) also have an impact on the result depending on the GMPE used. The uncertainty on the slip rate of the Rhine River Fault is the second most dominant factor controlling the uncertainty on the seismic hazard level. Uncertainty on slip rate estimates from 0.04 mm/yr to 0.1 mm/yr results in up to 40 % increase in hazard levels at the 10,000 years return period target depending on the GMPE used and the spectral frequency of interest. Reducing epistemic uncertainty in future fault-based PSHA studies at this site will thus require (1) performing in-depth field studies to better characterize the seismic potential of the Rhine River Fault; (2) complementing GMPEs with more physics-based modeling approaches to better account for the near-field effects of ground motion and (3) improving the modeling of the background seismicity. Indeed, in this exercise, we assume that background earthquakes can only host M < 6.0 earthquakes. However, this assumption is debatable, since faults that can host M > 6.0 earthquakes have been recently identified at depth within the Upper Rhine Graben (see Part A) but are not accounted for in this exercise since their potential activity has not yet been described.

Citation: Chartier, T., Scotti, O., Clément, C., Jomard, H., and Baize, S.: Transposing an active fault database into a fault-based seismic hazard assessment for Nuclear facilities. Part B: Impact of fault parameter uncertainties on a site-specific PSHA exercise in the Upper Rhine Graben, Eastern France, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2017-97, in review, 2017.
Thomas Chartier et al.
Thomas Chartier et al.
Thomas Chartier et al.

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Short summary
We perform a fault-based PSHA exercise in the Upper Rhine Graben to quantify the relative influence of fault parameters on the hazard at the Fessenheim Nuclear Power Plant site. We show that the active faults are the dominant factor in hazard estimates at the low annual probability of exceedance. After the choice of GMPE, the uncertainty on the slip rate of the Rhine River Fault is the second most dominant factor controlling the uncertainty on the seismic hazard level.
We perform a fault-based PSHA exercise in the Upper Rhine Graben to quantify the relative...
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