The study of the military Harbour of Brest (France): contribution from a Very High Resolution seismic tool

Within the framework of the modernisation of the military harbour of Brest, two seismic surveys have been conducted with the Seistec boomer (in 2004 and 2006) to recognize the sedimentary cover and depth of the rock basement. Previous investigations, based on drill holes, have shown the occurrence of vertical offset between geological strata. The "continuous" view acquired with the VHR seismic profiles allows a new approach of these vertical offsets and thus a new interpretation: they could be special undulating structures relative to the phase of sedimentary infilling of the bay. Such a global vision of the sea bottom floor allows to better understand the geomorphologic evolution of the harbour and to go beyond the "punctual" view. Whereas the Penfeld River seemed to be the actual active river, the influence of the Aulne River appears to have been preponderant in the sedimentary dynamics of the bay.