Chirp sonar sediment characterization at the northern Gulf of Mexico Littoral Acoustic Demonstration Center experimental site

Chirp sonar subbottom surveys have been conducted during a recent Littoral Acoustic Demonstration Center (LADC) experiment to invert bottom geoacoustic properties in the Northern Gulf of Mexico. Sediment properties such as density, porosity, and sound-speed profiles are inverted by using reflection amplitude and phase data obtained from a shallow-towed 2-12 kHz chirp sonar. High-quality subbottom images have been obtained with submeter resolution and up to 60 m penetration resolving several seafloor fault and diapir systems in the area. The attenuation coefficient is also estimated using the frequency shift method that seems to be relatively insensitive to reflection and transmission effects. The sound-speed and density structures of the LADC acoustic propagation tracks are efficiently mapped and made available for the numerical simulation studies of ambient noise and marine mammal acoustic propagation. The inversion results compare favorably with the previously reported sediment core data indicating that an accurate and rapid estimation of acoustical and physical properties of marine sediments is feasible.