Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

the seismic sections crossing it confirm that it clearly cuts the most recent formations (Figure 4). It could be structurally associated with adjacent secondary structures (Figure 2). C O N C L U S I O N The new geological mapping allows a first interpretation of the post-variscan tectonic history of the area. Thanks to bathymetry mapping, the acquisition of seismic sections and future sampling, we will be able to propose a characterization of faults in this sensitive region, in particular the one named LHOF (La Hague Offshore Fault). In June-July 2024, we will have conducted a new campaign at sea, focusing on the sampling of the most recent formations affected by the neotectonic faults, potentially active: we will use a gravity-corer capable of penetrating several tens of cm in the submarine formations. The age of the most recent sediment pack, which could be plio-quaternary according to regional relative correlations (Dugué et al., 2007), will have to be evaluated before any consideration of their seismogenic potential. The two major structures identified at the margins of the E and LH basins, given their size, have the potential to generate earthquakes up to magnitude 6 if rupturing entirely, according to classical scaling relationships (e.g. Leonard, 2014). A C K N O W L E D G E M E N T S This on-going work is the result of a series of Master and PhD students’ theses. Funding was provided by universities of Le Havre, Brest, and IRSN. The offshore campaign took benefit of the IFREMER support. R E F E R E N C E S Baize (1998). Tectonique, eustatisme et climat dans un système géomorphologique côtier. Le nord- ouest de la France au Plio-Pléistocene. PhD thesis, Caen University. Baumont et al. (2023). Reappraisal of the 1926, Jersey earthquake source parameters. Physics of the Earth and Planetary Interiors. DOI : 10.1016/j .pepi.2023.107113 Dugué et al. (2007). Cenozoic shelly sands in the Cotentin (Armorican Massif, Normandy, France): A record of Atlantic transgressions and intraplate Cenozoic deformations. Comptes Rendus Géoscience. DOI : 10.1016/j . crte.2007.01.001 IAEA (2022). Seismic Hazards in Site Evaluation for Nuclear Installations. IAEA Safety Standards Series No SSG-9. Kaci et al. (2024). High-resolution geophysical data unravel the post-Variscan structural history of the English Channel, around the Cotentin peninsula (NW France). Accepted to Marine Geology. Lagarde et al. (2000). Active tectonics, seismicity and geomorphology with special reference to Normandy (France). Journal Of Quaternary Science. Leonard (2014). Self-Consistent Earthquake Fault-Scaling Relations: Update and Extension to Stable Continental Strike- Slip Faults. Bulletin of the Seismological Society of America. Doi: 10.1785/0120140087 Lubert (2022). Mise en place d’un bassin sédimentaire en contexte tectonique polyphasé: l’exemple du bassin cénozoïque offshore des Ecréhous (Ouest Cotentin). Master thesis, Brest University. Pedoja et al. (2018). Neogene- Quaternary slow coastal uplift of Western Europe through the perspective of sequences of strandlines from the Cotentin Peninsula (Normandy, France). Geomorphology. DOI : 10.1016/j . geomorph.2017.11.021