Abstract:

Based on the sediment cores collected in the middle area of the Southern Yellow Sea and the core data measured in the laboratory, the properties of the acoustic impedance of shallow seafloor sediments and the correlations between the acoustic impedance and the physical parameters of the sediments are analyzed. The data analysis demonstrates that the acoustic impedance is characterized with a zonal distribution pattern, and its distribution can be divided into three sub-zones: a low acoustic impedance sub-zone in the northeast, a high acoustic impedance sub-zone in the southwest and an acoustic impedance gradient band aligning from northwest to southeast. The empirical regression equations between the acoustic impedance and the physical-mechanical parameters of the sediments are established by means of regression analysis. The results indicate that the acoustic impedance is well correlated to the parameters such as density, percent moisture, porosity ratio, percent porosity, liquid limit, plastic limit, plasticity index and compression coefficient, with the coefficient R² which is generally larger than 0.8, but poor correlated to the parameters such as sand content, clay content, median grain size and shear strength, with the correlation coefficient R² which is commonly less than 0.7.Comparing the correlations between the acoustic impedance and the physicalmechanical parameters to that between the sound speed and the physical-mechanical parameters of the sediment shows that the former correlation coefficient R² generally larger than the latter one. This result indicats the acoustic impedance could be a better sediment acoustic parameter that can reflect the relationships between the acoustic properties and the physical-mechanical parameters of the seafloor sediments.

Key words: sediments, acoustic impedance, empirical regression equation, physical-mechanical properties, the Southern Yellow Sea