Ultra high resolution mapping of sub-seabed sediment device: results and comparison with vibrocoring analysis in a very shallow water area

SCAMPI (Sub-seafloor Characterization by Acoustic Measurements & Parameters Inversion) is an ultra high resolution sub-seabed investigation patented device based on the propagation of acoustic waves between a chirp source and a horizontal array towed behind the vessel. It provides a reliable quantification of grain size and compressional speed profiles at each shot on the first 10 meters of the sediment without a priori knowledge or in situ sampling. During March 2005, a validation test has been carried out to evaluate the accuracy of the system. A 5 km long acoustic leg has been done on a 10 m water depth channel and results have been compared with 17 vibrocorings and 2 drillings, all located at less than 25 m of the closest acoustic shot. Comparison between in situ and acoustically calculated grain size is very convincing. SCAMPI behaves as a remote sensing technique able to efficiently replace vibrocoring and offering a useful description of the strong sediment variability in such a coastal environment. A brief description of the system and its characteristics and advantages is done. The paper focuses on results and on comparison procedure with vibrocoring data.