Seabed classification based on sub-bottom profile data in modified geo-acoustic model

The echoes signal of sub-bottom profilers (SBP) carry abundant information of sediment because the acoustic pulses emitted by SBP can penetrate the seafloor surface into the interior of sediment layers and get reflected from different impedance interface. A geoacoustic model describing the relationship between the acoustics and physical properties of sediments mathematically, is widely used in sediment classification and acoustics inversion. We applied the method to obtain the bottom reflection coefficients by decoding the SBP data, and then combined it with a modified Biot-Stoll model considering the influence of sediment’s degree of compaction, based on which a new method of sediment inversion was proposed to evaluate its capacity by examples. Results show that the bottom reflection coefficient of seafloor can be effectively obtained by decoding the original records of SBP, extracting the amplitude of the reflected waves, and combining with the sound source level of the equipment. To build the relationship between bottom reflective coefficient and mean grain size, the degree of sediment compaction was considered based on Biot-Stoll model and the parameter of relative density was introduced into the porosity calculation formula. Examples of both measured data of Weihai sea area and those obtained from available literatures indicate that the presented method could reduce the relative error between the inversion and the measured mean grain sizes, contributing to improve the accuracy of submarine sediment geoacoustic inversion based on SBP data.