Is the Machecoul fault the source of the ?M6 1799 Vendée earthquake (France)?

SUMMARY The ?M6 1799 Bouin earthquake is considered as one of the largest earthquakes to have struck Western France. However, seismogenic source potentially responsible for this event remain marginally documented. We present results from a focused offshore-onshore multidisciplinary survey in its meizoseismal area order identify fault segments that ruptured during earthquake. Based on macroseismic data and geology, we our study so-called Machecoul Fault potential event. Our includes extensive high-resolution seismic reflection, high resolution bathymetry 1-yr seismological survey. These were combined with existing topography, onshore gravity drill document geometry Marais Breton/Baie de Bourgneuf basin, past tectonic activity current local microearthquakes at depth along bounding faults. Offshore observations suggest recent segmented basin North. Offshore, planar contact between Plio-Quaternary sediments basement trace well thickening these sedimentary units near suggests control rather than erosion. Onshore, incision footwall activity. temporary experiment deployed 2016 2017 recorded diffuse microseismicity down 22 ± 5 km southward dipping Fault, associated predominantly normal mechanisms. Altogether, serious candidate being historical