SEISMIC HAZARD MAPS FOR THE FRENCH METROPOLITAN TERRITORY Stéphane DROUET 1 , Kristell LE DORTZ 1 , Ramon SECANELL 1 , Gabriele AMERI 1 , Gloria SENFAUTE 2 , Nicolas HUMBERT 3 ABSTRACT The undergoing study aims at the elaboration of a probabilistic seismic hazard maps for metropolitan France taking into account the outcomes of recent research projects such as SIGMA (Research on SeIsmic Ground Motion Assessment, 2011 – 2016), which was devoted to improve knowledge on data, methods and tools to better quantify uncertainties in seismic hazard estimates. A new earthquake catalogue for France was developed including a revision of magnitude and depth for historical events and of location and magnitude for instrumental events. This catalogue is used as the backbone catalogue for the present study. Three area source models developed independently by 3 institutions are considered for which seismic activity is characterized using the Gutenberg-Richter model including an exploration of earthquake location and magnitude uncertainty. In addition, a zoneless approach is considered using spatially-adaptive kernel functions. The concept of large seismotectonic domains is introduced in order to constrain the estimation of the Gutenberg-Richter b-value and to derive maximum magnitude distributions using the Bayesian approach. The ground-motion model includes two GMPEs developed specifically for France as well as two additional models. Tests were carried on in order to investigate if the adopted ground-motion characterization logic tree captures epistemic uncertainty. Uncertainties related to the seismic activity (parameters a and b of the Gutenberg-Richter models), maximum magnitude, and hypocentral depth is also explored. The objectif of this study is to produce probabilistic hazard maps for a grid with a spatial sampling of 10 km for two return periods (475 and 2475 years) and three spectral periods (PGA, 0.2 and 1.0 seconds). Keywords: Seismic hazard; Uncertainties; France 1 INTRODUCTION Probabilistic seismic hazard (PSH) assessment is used for quantifying the seismic hazard on a site or on a grid of sites. For regions of low to moderate seismicity such as metropolitan France PSH assessment is a significant challenge requiring accurate evaluation and appropriate treatment of uncertainties. The last seismic hazard maps produced for France were published about 15 years ago and significant improvements in seismic hazard assessment have been made since then. In particular, the SIGMA project aimed at a better understanding and characterization of all uncertainties (Pecker et al 2017). During this project (2011 – 2016) several results with operational applications have been obtained (Martin et al., 2017): homogenous seismic catalogue in Mw for France, seismic ground-motion database (RESORCE) to develop Ground Motion Prediction Equations for Europe and specific models for France, best practices guideline for site characterization and operational guide to account for site effects. The present study, which is the first step of a long term project, makes use of these SIGMA outcomes to elaborate a probabilistic seismic hazard maps for the French metropolitan territory. The objective is 1 GEOTER, Auriol, France, s.drouet@fugro.com 2 EDF/Lab, Saclay, France, gloria.senfaute@edf.fr 3 EDF, France, nicolas.humbert@edf.fr