Zonation of metropolitan France for the application of earthquake-resistant building regulations to critical facilities Part 2: Seismic zonation

The seismotectonic zonation of Metropolitan France(part 1) and the derived seismic zonation (part 2)were carried out in order to facilitate andstandardise the application of earthquake-resistantbuilding regulations to critical facilities forreasons of environmental protection (Decree No.91-461, Ministerial Order dated 10 May 1993).According to current French legislation, adeterministic approach was adopted for the executionof these two successive zonations.The seismic zonation is based on a 2.5 km square gridcovering the whole of Metropolitan France, in whicheach cell is defined by the maximal macroseismicintensities that could be induced by a `MaximumHistorically Credible Earthquake' (MHCE) and aSeismic Safety Evaluation Earthquake (SSEE) innearby seismotectonic units. The values of theseintensities were calculated by displacing thereference earthquakes of the seismotectonic zonationto the most penalising position relative to the celland using attenuation laws deduced from the isoseismalcurves specific to each earthquake taken as reference.The zonations obtained for the MHCE and SSEEintensities should thus be considered as the physicalzonations of France for the application ofearthquake-resistant building regulations to criticalfacilities. They are applicable to all criticalfacilities and provide a consistent approach forassessing the levels of seismic aggression to be used(in MSK intensity) at any site in Metropolitan France,as well as the elementary parameters for calculatingthe response spectra usable in the design orverification of structures.