Sequential Inversion for Geoacoustic Parameters in the South China Sea Using Modal Dispersion Curves

This paper presents an inversion scheme that uses two wideband explosive sources based on modal dispersion characteristics to synchronously obtain sound speed profile and bottom parameters. The signal received on a single hydrophone in a vertical line array is decomposed into a series of propagation modes within the framework of normal mode theory, and the dispersive characteristics of the modes are analyzed using time–frequency analysis. Time-warping transform is applied to resolve the propagation modes of explosive sources from the South China Sea in 2007. The relative travel time differences of the propagation modes are used to invert the environmental parameters, including empirical orthogonal function coefficients, sediment thickness, sound speed, density, basement sound speed and density. Sediment density and basement density are constrained by Hamilton’s empirical relationship, and relative mode energy ratio is used to estimate the bottom attenuation coefficient. An adaptive simplex simulated annealing algorithm is used for the inversion. The reliability of the inversion results is verified via uncertainty analysis. The transmission loss calculated using the deduced parameters matches the experimental data well.