Abstract: International audience ; A 24-channel seismic display recording on a DaQLink is used to carry out tomographies of P and S waves down to 40m deep in the Holocene deposits of the coastal Flemish plain west of Dunkirk and the Slack estuary in the Boulonnais. The flat topography along the profiles collected along a road, on the beach, or in farmed fields, makes it possible to avoid complex processing of topographic correction. The results, validated by a number of cores, provide details on the morphology of the incision at the bottom of Holocene transgressive sediments, either infilling estuarine valleys or onlapping bedrock fault scarps. Vertical and horizontal heterogeneities in shear-wave velocity, well expressed in the upper layers, may reflect lateral changes in lithology or water content.
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