Hybrid Gravimetry as a Tool to Monitor Surface and Underground Mass Changes

International audience; This paper is devoted to an overview of the use of hybrid gravimetry in Earth and Environmental Sciences. We first recall the concept of hybrid gravimetry which relies on the simultaneous use of different types of gravimeters either superconducting, absolute or relative spring gravimeters. This combination of instruments provides a complete tool for time-lapse gravimetry: while superconducting gravimeters and/or absolute gravimeters are used to obtain temporal gravity changes at one or several base stations, relative gravity surveys provide spatial differences with respect to these base stations, and allow to cover a much wider area than base stations only. Hybrid gravimetry therefore provides time-lapse gravity changes at a survey scale. We present here an overview of different published applications in hydrology, glaciology, volcanology and geothermics in order to point out that hybrid gravimetry is a powerful tool to monitor spatially and temporarily surface and underground mass changes.