Littoral and deep-seafloor sediment characterization from recent chirp sonar surveys

Abstract

Sediment sound-speed and attenuation were estimated from the chirp sonar reflection data that were collected during recent surveys in the New Jersey Shelf and northern Gulf of Mexico. Physical properties of the sediment were also estimated using the Biot–Stoll model outlined in [Schock, IEEE J. Ocean. Eng. 29(4) (2004)]. In addition, independent measurements of sound-speed and attenuation were also conducted using acoustic probes and light-bulb implosions. Results from independent measurements were in agreement with those of chirp sonar data. Measured sound speed and attenuation values are typical of silty-sand sediments in the New Jersey Shelf and silty-clayey sediments in the northern Gulf of Mexico. Finally, frequency-dependence of sound-speed and attenuation was estimated within a wide frequency band using the data from co-located light-bulb implosion (0.5–4 kHz), chirp-sonar, (2–12 kHz), and sediment acoustic-probe (5–120 kHz) measurements. Observed small frequency-dependence of sound-speed and linear frequency-dependence of attenuation are in agreement with those predicted by an extended Biot–Stoll model. [Work supported by ONR.]