Seismo-acoustic propagation near thin and low-shear speed ocean bottom sediments

Abstract

Accurate and efficient parabolic equation solutions exist for complex propagation environments featuring elastic and porous elastic sediment types. Because of numerical stability issues, areas of concern have been with thin and low-shear wave speed sediments. In certain situations, both of these common features of the seafloor can make obtaining an accurate solution difficult. At low frequencies, layers of this type can be treated as a massive interface between the water and higher-shear speed sediment basement layers. To satisfy interface conditions across the layer, Rayleigh jump conditions are imposed [F. Gilbert, Ann. Geofisica XL, 1211 (1997)]. This approach is only valid for a single layer, but is able to handle shear wave speeds as they tend to zero. In this talk, a massive elastic interface parabolic equation implementation is benchmarked along with classical bottom treatments to quantify the effects of ocean acoustic propagation over thin sediment layers. It is demonstrated that in certain situations, it is sufficient to consider the thin layer as part of adjacent, thicker layers.