Geoacoustic inversion of modal dispersion on the New England Mud Patch. I: Experimental quantification of information content in higher-order modes

Abstract

This paper presents the results from a geoacoustic inversion study performed using a combustive sound source signal recorded on a vertical line array during the 2017 Seabed Characterization Experiment (SBCEX17). A single receiver modal estimation method (source deconvolution and warping) is recursively applied along the array channels to estimate modal time-frequency dispersion, resulting in modal dispersion data for 18 modes between modes 1 and 21. These data are then used as an input for trans-dimensional Bayesian geoacoustic inversion. The paper compares inversion results obtained with subsets of modes (1 to 7 and 1 to 15) to those obtained with the whole set (modes 1 to 21) to explore the data information content associated with high-order modes. The study shows that high-order modes enable the resolution of fine details in the seabed sound-speed profile, such as a small sound speed increase over the first 8 m of the seabed (i.e., within the upper portion of the so-called “mud layer,” an important feature of the experiment area). [Work supported by the Office of Naval Research.]