Acoustic characteristics of seafloor sediments in the abyssal areas of the South China Sea

Abstract

Deep-sea sediment cores were obtained from abyssal areas (water depth > 4000 m) in the South China Sea (SCS) to derive acoustic characteristics by using a WSD-3 digital acoustic instrument at a frequency of 100 kHz. The compressional wave velocity (Vp) of the seafloor sediments in the central basin is differentiated into 3 provinces on the basis of the sediment properties (esp. mean grain size and velocity). Provinces H1 and H2 have a high compressional wave velocity and coarse particles, while the middle province L has a low compressional wave velocity and fine particles. The results show that the distribution of Vp is related to the sediment physical properties, sediment sources and ocean current. Vertical variations in the Vp indicate that it increases with burial depth in the high-velocity province, but is complicated in the low-velocity province, reflecting that the more active or complicated sedimentary environment in province L may be affected by the topography. We proposed a laboratory sound velocity measurement method based on Hamilton sound velocity ratio method. In addition, the measurement values from this method are close to the in situ sound velocity determined by adjusting the temperature of the sediment samples.