Distribution of geoacoustic properties and related influencing factors of surface sediments in the southern South China Sea

In order to characterize and map the seafloor sediments in the southern South China Sea, the physical and geoacoustic properties of the sediments were measured and analyzed at 21 stations. Sound speeds were measured using the coaxial differential distance measurement method on deck, and were corrected to in situ sound speeds using the correction-to-laboratory-velocity method. The results show that the distributions of sound speed ratio and acoustic impedance are closely related to the sediments physical properties. The study area can be divided into 3 geoacoustic provinces: the highest speed zone on the Sunda Shelf, and the intermediate and lowest speed zones on the continental slope and Nansha Trough. The correlations between the sound speed ratio and physical parameters fit linear relationships similarly or even better than the quadratic relationships derived in previous studies. This good fit may however be due to the limited range of data samples used in this study. Compared with the predicted sound speeds from Hamilton and Bachman's or Anderson's empirical equations, the measured values are smaller, which is probably due to different sedimentary environments and measurement methods.