Sound speed dispersion characteristics of three types of shallow sediments in the southern yellow sea

ABSTRACT

To accurately characterize sound speed dispersion of shallow sediments in the Southern Yellow Sea, three types of sediments, i.e., silt, clayey silt, and silty clay, were selected to measure the sound speeds at 25–250 kHz. Over the frequency range, the sound speeds vary approximately from 1,536 to 1,565 m s⁻¹ in silt sediment, from 1,511 to 1,527 m s⁻¹ in clayey silt sediment, and from 1,456 to 1,466 m s⁻¹ in silty clay sediment. The sound speed exhibits a slow increase with frequency in a nearly linear gradient, but these three types of sediments have different sound speed dispersion characteristics. The silt sediment with relatively coarse grains has the most significant sound speed dispersion, while the sound speed dispersions of the two others are relatively weak. Comparison between the measured dispersions and the model predictions shows that the grain-shearing model can match the measured data at most of frequencies. Nevertheless, when the grain bulk modulus was assigned 3.2 × 10¹⁰ Pa according to relevant references, the Biot–Stoll model predictions were higher than the measured values at high frequencies; when it was assigned a relatively small value of 2.8 × 10¹⁰ Pa, the model predictions achieved optimal matching with the measured values.

KEYWORDS:

• Biot–Stoll model
• grain-shearing model
• seafloor sediments
• sound speed dispersion

Acknowledgments

We would like to thank Dr S. Yu for the modeling of sediment acoustic properties and the crew of the R/V Dong Fanghong 2 for their assistance of sampling. We appreciate very much the remarks of the reviewers.

Additional information

Funding

Financial supports from the National Natural Science Foundation of China (Nos. 41676055, 41706062, and 41406073), the Chinese Polar Environment Comprehensive Investigation & Assessment Programs of China (No. CHINARE2017-03-03), the Public Science and Technology Research Funds Projects of Ocean (No. 201405032), the Shandong Provincial Natural Science Foundation, China (No. ZR2017BD031), the State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences (No. SKLA201707), the Taishan Scholar Project Funding (No. tspd20161007).