Seafloor Scattering in Shallow-Water Environments

Abstract

LONG-TERM GOALSMud volcanoes are solid objects that form on the seafloor due to the emission of gas and fluidized sediment from the earth's interior [1]. They vary widely in size, can be exposed, proud, or buried, and are of interest to the Navy as sources of active sonar clutter [2]. The long-term goal of this work is to accurately model mud volcano scattering. The final product will make predicting and simulating scattering signatures for individual volcanoes possible, and will provide the information necessary to mitigate mud volcano clutter through improved sonar design and classification schemes.The long-term goals of the seafloor scattering project are linked to both the forward and inverse scattering problems. The first objective is to model the time dependence of seafloor scattering based upon knowledge of the mechanisms responsible for benthic change, primarily bioturbation and sediment transport. The second is to develop acoustics as a tool for the remote sensing of benthic activity and the inversion of time-dependent seabed parameters that are used as inputs for reverberation models. Results should be of use to the Navy in understanding and predicting the time dependence of reverberation, as well as measuring the parameters necessary for reverberation models. OBJECTIVESThe objective of the current mud volcano project is to model low-frequency scattering from a volcano using a bottom-up approach. Coincident acoustic data, bathymetry, and geoacoustic measurements are used to guide understanding and model development. As a part of this process, physical features and processes that are significant contributors to observed mud volcano scattering are identified.Current seafloor scattering work is concerned solely with surface scattering (as opposed to volume scattering or a combination of the two), and aims to link changes in acoustic scattering with changes in the surface of the seafloor. This is achieved by deriving a first-order perturbation theory-based equation that connects the time correlation of scattered acoustic power with the time correlation of Report Documentation Page Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.