Inversion of the Physical Properties of the Seabed Using Chirp Sub-Bottom Data in Mud Volcanoes Field of the Southwest of Dongsha Islands

Mud volcanoes are imaged from Chirp sub-bottom profiles across the southwest of Dongsha Islands. In order to quantify the physical properties of the seabed, this paper studies the inversion of the Chirp sub-bottom data. First, reflection coefficients of the seabed are calculated, the results show that the reflection magnitudes of the seabed vary from 0.1-0.8. The physical properties (velocity, density, porosity etc.) of the seabed are obtained by the Schock-Stoll Model and the empirical relationships among the physical properties for the part reflection coefficients smaller than 0.45, and the physical properties (velocity and density) of the seabed are obtained by Gardner empirical equation for the part reflection coefficients larger than 0.45. Results of the inversion show that the physical properties vary greatly with the maximum velocity of 5 237 m/s and density of 2.673 g/cm³. The Chirp data-based physical properties highly coincide with the laboratory measurements for sampled sediments, thus provides us a remote acoustic method for estimating the physical properties of the seabed.