Near-specular acoustic scattering from a buried submarine mud volcano

Abstract

Submarine mud volcanoes are objects that form on the seafloor due to the emission of gas and fluidized sediment from the Earth's interior. They vary widely in size, can be exposed or buried, and are of interest to the underwater acoustics community as potential sources of active sonar clutter. Coincident seismic reflection data and low frequency bistatic scattering data were gathered from one such buried mud volcano located in the Straits of Sicily. The bistatic data were generated using a pulsed piston source and a 64-element horizontal array, both towed over the top of the volcano. The purpose of this work was to appropriately model low frequency scattering from the volcano using the bistatic returns, seismic bathymetry, and knowledge of the general geoacoustic properties of the area's seabed to guide understanding and model development. Ray theory, with some approximations, was used to model acoustic propagation through overlying layers. Due to the volcano's size, scattering was modeled using geometric acoustics and a simple representation of volcano shape. Modeled bistatic data compared relatively well with experimental data, although some features remain unexplained. Results of an inversion for the volcano's reflection coefficient indicate that it may be acoustically softer than expected.

Broadband Acoustic Clutter

“…Analyses of reflection from a single buried mud volcano (3m sub-bottom) suggests that the bulk properties are quite similar to the surrounding sediment. This analysis was not sensitive to fine-scale features on the mud volcano (e.g., carbonate mounds) that might have substantially higher densities/velocities ( [3]).…”

Broadband Acoustic Clutter

“…In previous work [3][4][5], we have observed clutter from mud-volcano (MV) clusters that appears targetlike on individual pings and through a tracker. The motivation for studying MVs is that a) MVs are present in many littoral areas around the globe and b) MVs are a representative of a class of "non spatially compact" clutter mechanisms which are considerably more challenging to model than spatially compact ones (e.g., wrecks or isolated rock crops) and thus form a kind of test-bed to develop modeling and signal processing approaches for the general class.…”