Acoustic Investigation Of Complex Seabeds

Abstract

Abstract The scope and ambition of marine geotechnical investigations have greatly evolved over the last years. Offshore foundations, dredging operations of harbours and channels, sub-seabed installations all place new demands on acquiring more reliable knowledge on the composition of the seabed to address cost-effectively the issues of buried geo-hazards, sediment property discontinuities and trapped pollutants. This chapter shows the potential of physical sampling and different remote sensing approaches, but also their limitations. The technology gap can be addressed by designing an Acoustic Sub-seabed Interrogator (ASI), ideally combining a range of low frequencies (to penetrate deeper into the seabed) and a range of high frequencies (to enable higher vertical resolutions closer to the sur- face). The use of a dense network of broadband receivers should allow capturing of specular and non-specular returns, and bespoke data acquisition and processing should give access to 3-D volumetric measurements. Its design should allow deployments at all depths. The resulting acoustic corer should expand the horizontal and vertical ranges of existing tools whilst preserving the best spatial resolutions currently achievable.