Geoacoustic inversion based on particle velocity

Abstract

An approach to geoacoustic inversion using a non-dimensional vector quantity, known as circularity, is discussed. This quantity corresponds to the difference in phase and magnitude of the vertical and horizontal components of particle velocity, and is also the normalized curl of the active intensity vector. As such, it is highly dependent on the phase, amplitude, and arrival angle of interfering multipath arrivals, with value as a function of source depth that depends on both frequency and bottom type. We first show results from the Targets and Reverberation Experiment (TREX) which took place off Panama City, where frequencies in the range of 1–4 kHz are used to study sandy sediments [Dall’Osto et al., J. Acoust. Soc. Am. 139, 311–319, 2016]. The approach is next applied hypothetically at lower frequencies for which fewer modes are supported in the waveguide, and to different seabed conditions to demonstrate how a range of sediments from sand to mud are distinguished.