Inversion of sediment properties from chirp sonar data using an extended Biot–Stoll–Gassmann model

Abstract

Recently, chirp sonar subbottom profiling systems have been used extensively for subbottom imaging as well as for sediment impedance profile and attenuation estimation [e.g., LeBlanc et al., J. Acoust. Soc. Am. 91 (1992)]. Typical mid-frequency (1–20 kHz) chirp sonar signals are highly attenuated in the sediment which makes the usage of a proper pulse propagation and attenuation model in the inversion algorithm necessary. An extended Biot–Stoll–Gassmann model is proposed in accordance with the reported sound speeds and attenuation values for different types of sediments. This model was used in a time-domain inversion algorithm for the estimation of sediment geoacoustic properties (density, sound speeds, and attenuation) as well as mechanical properties such as porosity and permeability. Sensitivity analysis indicated that the new model provides a rapid inversion of porosity profile even in the case of noisy one-dimensional reflection data. In this case, along with the attenuation estimation, other parameters are conveniently calculated using the proposed model. Finally, inversion results with the established confidence intervals are presented for the chirp sonar data collected during the SWARM experiment [Apel et al., IEEE J. Ocean. Eng. 22(3) (1997)]. [Work supported by ONR.]