Updated seismotectonic zoning scheme of Metropolitan France, with reference to geologic and seismotectonic data

Abstract

Abstract This work presents the seismotectonic zoning scheme of Metropolitan France developed by the IRSN (French Institute for Radioprotection and Nuclear Safety) within the framework of its seismic hazard assessment activities. It is the outcome of many years of work following the publication of the “seismotectonic atlas” in 1993 [Grellet et al., 1993]. This scheme supports the assessment of seismic hazard by IRSN. It takes into account the most recent data concerning the deep and surface geology, as well as those related to seismotectonics and tectonic activity. It finally includes 67 surface seismotectonic zones (STZ), as well as a catalogue of 74 faults or structures (named hereafter “potential active faults”) for which indications of Neogene to Quaternary displacement can be inferred. The description of the zoning scheme comes along with an estimation of the uncertainty on the boundary location between adjacent STZ. We also qualitatively determine a “relevance order” for each limit, so as to illustrate their reliability to separate regions of different seismogenic potential. Also, we attributed to the faults an indication whose purpose is to reflect the recent character of their activity, and thus their seismotectonic potential. This assessment of uncertainties was undertaken to better integrate the zoning scheme in the general approach, which arises from recent studies, namely the propagation of the uncertainties in seismic hazard evaluation, whether deterministic or probabilistic.