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FIELD INSTRUMENTATION
One of RESIF’s major goals is to provide geophysical data to enable study of the structure of the earth and its deformations over all scales of time (from a fraction of a second to decades) and space.
RESIF therefore coordinates and implements a large variety of measurement instruments, each of which is dedicated to the study of one part of the frequency range. Together, they will enable observation of the wide range of phenomena, both continuous and transient, that deform our planet.
Furthermore, these observations at different frequencies provide information on the earth’s structure from the near surface (e.g. on the scale of a sedimentary basin) to the earth’s very core. They will also enable the study of atmospheric and oceanic phenomena.
The instruments installed permanently in France form RESIF’s permanent observation network and their répartition géographique depends on the types of phenomena that can be observed and their wavelengths.
These sensors will use the latest technology to form a unique observation network, fully integrating different types of measurements. The ultimate goal is to create a network throughout mainland France comprising 750 seismometers and geodetic measurement instruments, 250 of which will be mobile, to enable the observation network to be focussed on specific investigation subjects and geographic locations.
The main instruments used for the RESIF array:
An absolute gravimeter is used to study both the changes in the earth’s shape on the scale of a few years and its very low frequency resonances during major earthquakes. Seismological sensors measure ground speed at all the frequencies observed during earthquakes occurring both in France and elsewhere in the world (for examples consult the RENASS website, the Centre Sismologique Euro-méditerranéen website or the ORFEUS website). RESIF also closely collaborates with the French network of short-period velocimeters (ReNaSS) and the worldwide GEOSCOPE network. Seismological sensors sensitive to ground acceleration are used alongside the velocimetric sensors, enabling the study of major ground and structure (buildings, bridges, etc.) movements in urban areas in the event of a earthquake (see the RAP website). Some of these instruments have already been in operation for several years and will continue to be operated for RESIF by the project’s various partners, who will also work on improving interoperability.
Une partie de ces instruments fonctionnent déjà depuis plusieurs années et continueront à être opérés dans le cadre de RESIF par les différents acteurs du projet tout en améliorant l'interopérabilité.
Dans les prochaines années, un effort particulier sera porté à la construction de nouvelles stations vélocimétriques à large bande passante. En effet, cette composante est actuellement sous dimensionnée et la densification des points de mesure sismologiques est nécessaire pour un fonctionnement optimal de l'ensemble de l'antenne permanente RESIF. De par la répartition prévue des stations, cette composante se comportera comme une unique antenne d'observation de la partie basse fréquence des ondes sismiques (ondes de surface) et comme un ensemble d'antennes régionales pour l'observation de la partie plus haute fréquence. En outre, les capacités de détection de ses stations permettront de connaître de manière plus complète et plus homogène la sismicité de notre territoire.
