Abstract: The Chirp sub-bottom data can not only characterize the geological structure information of stratum, but also can inverse the physical properties of surface sediments in seabed. Chirp signal is generated by computer with stable energy and good consistency. Formulated-frequency technology is applied to Chirp sub-bottom profiler, and higher frequency gradually attenuates when the signals travel through the sub-bottom sediments. We could study the changes of the physical properties of the sub-bottom sediments by the varieties of the attenuation. This paper uses the chirp data got from the cable route survey of China Southern Power Grid second connecting with Hainan Grid and Biot-Stoll model to inverse the physical properties of surface sediments in seabed of this sea area, and get the inversion velocity, density, porosity of surface sediments. The relative errors of inversion porosity, density are less than 10%, as compared with those of situ detection, which states that the inversion data are basically consistent with the situ detection data. This method can inverse the physical properties of surface sediments on the whole sub-bottom profile continuously, but needs to be optimized to improve the accuracy. This indicates that using chirp data to inverse the physical properties of surface sediments in seabed in Qiongzhou Strait sea area by Biot-Stoll model is feasible, which provides a new choice to get the physical properties of surface sediments indirectly in this sea area, and a new reference of using sub-bottom data in sea engineering survey.

Key words: Chirp Bottom data, Biot-Stoll model, inverse, physical properties of surface sediments in seabed, the Qiongzhou Strait