Multiscale seismic imaging of Massif Central focusing on recent intraplate volcanism – MACIV

Volcanic hazard is still an issue in the French Massif Central (FMC) because the last eruptions are dated at 6700 yrs BP. Indeed, seismic bursts and geodetic uplift related to volcano-magmatic activity have recently been detected in the Eifel region (Germany), which belongs to the same European Cenozoic rift system as the FMC. However, geophysical knowledge of the sources of FMC volcanism is limited to the mantle-plume hypothesis, which dates from the last seismological experiment performed 30 years ago. We propose to deploy several hundreds of modern seismic instruments in a multiscale configuration to better assess volcanic hazards, mineral deposits, and geothermal resources associated with volcanism. This innovative array design will allow us to efficiently probe the different scales and depths of the FMC volcanic systems with optimal spatial resolutions. The large-scale arrays will cover the entire MCF and provide first-order information on the causes of mantle melting at depth and the expression of volcanism at the surface, such as the lithospheric structures of the FMC, the crustal thickness, the impacts of the Variscan inheritance, or the Cenozoic rift system. On a smaller scale, the dense arrays will provide images of the upper crust below the volcanoes and illuminate their plumbing systems. The enhanced earthquake detection power of the dense arrays will illuminate active faults and possible plumbing systems of the youngest volcanoes. This project will help better evaluate the volcanic hazard and provide a framework for a monitoring strategy scaled to a currently dormant volcanic province. This ambitious experimental project is proposed by a multidisciplinary team of geophysicists, geologists, and volcanologists, in a context of solid synergy with ongoing and future projects in France and Europe. The MACIV project will provide a unique seismological dataset that will be used for years to come to yield essential information on intraplate volcanism.