GERMEH

In the context of the development of marine renewable energies (MRE) associated with the multiplicity of anchor types, the GERMEH project aims to develop a seabed geophysical methodology for characterizing the mechanical properties of the subsoil in complex geological environments in the near offshore and its spatial and temporal variations. The process is intended to complement geotechnical drilling and sounding, which are destructive, costly and spatially on one point. To this end, GERMEH proposes to develop a methodology for 1) Seismic Surface Waves (SSW) and Geo-Electric(GE) imaging and 2) subsurface monitoring based on passive seismic measurements, through 4 scientific sub-objectives: O1) Develop and optimize SSW and GE imaging for the near offshore using the two complementary physical fields in a joint inversion approach. The proposal is based on initial numerical developments of 1) 2D SSW inversion using particle swarms and 2) a GE system optimized for the marine environment. O2) Define an optimal configuration for offshore SSW, by analyzing the impact of sources and sensors on the recording of guided acoustic waves in the water column compared with SSW generated in the seabed. O3) Assess the potential of the inversion developed for offshore geotechnics, by comparing the resolution of reconstructed models with the response of geotechnical tests. O4) Evaluate the ability to monitor the mechanical environment of the seabed by recording ambient seismic noise using autonomous seabed and fiber optic DAS (Distributing Acoustic Sensing) sensors. These 4 aspects are addressed using numerical and experimental approaches on a reduced scale (MUSC bench, geotechnical centrifuge, tank) and tested on near-shore sites. The consortium brings together the complementary skills of Université Gustave Eiffel, Ifremer, Sercel, Nantes Université and the foundation Open-C.