SNOS/Epos-France Seismology Service

Our observatory installed its first seismological station at the top of Puy de Dôme in 1906, then at the Observatory in 1913. Since then, registration has been continuous at the OPGC, but with low-amplification equipment until 1980. It should be noted that from the 1960s, a seismic instrumentation was developed on French soil by the CEA for military strategy purposes (Figure 2). This monitoring network was mainly used to locate nuclear tests around the world, but at the same time provided a better knowledge of hexagonal seismicity. In Auvergne, the initial station of the OPGC was renovated in 1980, then completed by a real network covering the region. As early as 1986, the Auvergne network included a minimum of 7 permanent stations integrated into the RéNaSS. It is currently composed of 20 stations (Figure 3) belonging to several national networks which are the RéNaSS (National Seismic Monitoring Network), the RLBP (Large Permanent Band Network), the RAP (Permanent Accelerometer Network) and the educational network "sesmos à l'école". These networks cover metropolitan France in a still uneven way with stations mainly distributed in the most seismically active regions (Figure 1). All these stations are managed in each region by public bodies and institutions, including the Observatoires des Sciences de l’Univers (OSU) of the Institut National des Sciences de l’Univers (INSU) of the Centre National de la Recherche Scientifique (CNRS). The RLBP and the RAP are now integrated into the RESIF (Réseau SIsmologique & géodesique Français), a research infrastructure bringing together the bulk of Earth observation resources in France. In this context, the number of RLBP stations is expected to grow significantly in order to improve the spatial mesh of wide-band seismic stations on the national territory. In addition, most of the historic stations of the RéNaSS will be upgraded to integrate the RLBP.

Seismic recordings from stations located in Auvergne are sent to Clermont-Ferrand by ADSL, 4G or satellite. The data is processed at the OPGC and transmitted to the RESIF information system, which archives and distributes it through a portal. This system makes it possible to centralize the data coming from the different French regional centers that ensure the installation, the maintenance of the stations as well as the transmission of the data.

The national networks RéNaSS, RLBP and RAP, now integrated into the RESIF, are intended in particular for seismic monitoring of the territory: real-time monitoring of seismicity, determination of earthquake source parameters and archiving of seismograms for research purposes. The scientific benefits obtained are an increasingly accurate assessment of seismic hazard, the determination of tectonic movements and a better knowledge of the internal structure of the Earth. An additional advantage of the Auvergne network is that it can detect any seismic activity (sismotectonic or sismovolcanic) related to a possible resumption of volcanic activity in the Massif Central. The seismic alert, which was the responsibility of the RéNaSS until 2009, is now provided by the LDG (Laboratory for Detection and Geophysics, CEA).