SI-Hex: a new catalogue of instrumental seismicity for metropolitan France

Abstract

International audienceThe aim of the SI-Hex project (acronym for « Sismicité Instrumentale de l’Hexagone ») is to provide a catalogue of seismicity for metropolitan France and the French marine economic zone for the period 1962–2009 by taking into account the contributions of the various seismological networks and observatories from France and its neighbouring countries. The project has been launched jointly by the Bureau Central Sismologique Français (CNRS-University/BCSF) and the Laboratoire de Détection et de Géophysique (CEA-DAM/LDG). One of the main motivations of the project is to provide the end user with the best possible information on location and magnitude of each earthquake. So far, due to the various procedures in use in the observatories, the different locations and magnitudes of earthquakes located in the SI-Hex zone were presenting large discrepancies. In the 2014 version of the catalogue, 1D localizations of hypocentres performed with a unique computational scheme and covering the whole 1962–2009 period constitute the backbone of the catalogue (SI-Hex solutions). When available, they are replaced by more precise localizations made at LDG or, for recent times, by the regional observatories within: 1) the French Alps, 2) the southernmost Alps and the Mediterranean domain including Corsica, 3) the Pyrenees, and 4) the Armorican massif. Moment magnitudes Mw are systematically reported in the SI-Hex catalogue. They are computed from coda-wave analysis of the LDG records for most Mw>3.4 events, and are converted from local magnitudes ML for smaller magnitude events. Finally, special attention is paid to the question of discrimination between natural and artificial seismic events in order to produce a catalogue for direct use in seismic hazard analysis and seismotectonic investigations. The SI-Hex catalogue is accessible on the web site www.franceseisme.fr and contains 38,027 earthquake hypocentres, together with their seismic moment magnitudes Mw

The French seismic CATalogue (FCAT-17)

“…• French Alps, Pyrenees and Armorican Massif areas have been kept as defined in Cara et al (2015). They correspond to areas covered by regional catalogues and where observatory earthquake locations have been chosen as the preferred solution in the SiHex catalogue; • European Cenozoic Rift System (ECRIS) zone delimits boundaries of the extensive structures (upper and lower Rhine grabens, together with the Bresse and Limagne grabens).…”

“…This section aims at presenting a brief summary of approaches and results carried out in the framework of the SiHex project, which resulted in the instrumental catalogue. Refer to the original papers published by the SiHex teams for more details on this work: Cara et al (2015Cara et al ( , 2017 and Denieul et al (2015).…”

“…Events location derived from regional observatories were preferred for events in the French Alps, the southernmost Alps and the Mediterranean domain including Corsica, the Pyrenees and the Armorican Massif. These have been substituted in the backbone catalogue solutions (see Cara et al 2015 for regions boundaries and Fig. 3 for those of Alps, Pyrenees and Armorican Massif).…”

“…where (1) is from Braunmiller et al (2005) confirmed by Cara et al (2017) and (2) has been calibrated by Cara et al (2015) using M w estimates from Godano et al (2013). Refer to the dedicated paper about SiHex magnitudes and associated uncertainties for details (Cara et al 2017).…”

Gas transport properties through intact and fractured Callovo-Oxfordian mudstones

“…As such, much attention has focused on the Paris Basin, where COx occurs as a thick unit (c. 130 m) of uninterrupted mudstones. Based on initial surface measurements and from the direct observation of experiments housed in the Meuse/Haute Marne Underground Research Laboratory constructed at Bure, NE France, the site appears to offer very favourable conditions for the siting of a repository, including a low hydraulic conductivity (Harrington et al 2012a;Cuss et al 2014), small molecular diffusion rates, a significant retention capacity for radionuclides (Altmann et al 2012) and minimal seismic activity (Cara et al 2015).…”