Chapter 8 - The Seafloor

Abstract

An understanding of seafloor properties and processes is essential for the solution of many problems in underwater acoustics where acoustic–seafloor interactions dominate. This includes an understanding of acoustic propagation, reflection, and scattering models. Applied bottom-interacting acoustic problems should employ the simplest seafloor models and sediment characterization that provide results with the accuracy required for the problem. In this chapter, we provide a review of recent acoustic propagation (fluid, elastic, and poroelastic) and scattering models. These are followed by a description of sediment physical and geoacoustic properties and the statistics of seafloor roughness and volume heterogeneity typically required by these applied acoustic models. These properties include grain size distribution, porosity and mass density, pore fluid and pore space properties, permeability, grain properties, free gas distribution, sound speed and attenuation of compressional and shear waves, and descriptors of sediment type. A review of acoustic methods used to characterize sediment type and predict sediment properties is also included.