Abstract： A geoacoustic inversion scheme, which combines several inversion methods together to invert for the bottom parameters, has been proposed based on the fact that the bottom acoustic parameters have different sensitivities to the different physical parameters of acoustic field. Firstly, the characteristic impedance of the bottom is inverted by measuring the vertical bottom reflective coefficients. Secondly, the derived bottom characteristic impedance is used as a constrained condition in another inversion procedure, which is very sensitive to the bottom sound speed but less sensitive to the attenuation, to inverse the bottom sound speed and bottom density. Lastly, the bottom attenuation can be estimated from methods such as transmission loss data, the vertical correlation of propagation data, and the normal mode attenuation. To obtain the characteristic impedance of the bottom accurately, vacuum glass spheres (VGS) are used as broadband sound sources, and a special mechanism is designed to trigger the VGS imploded at the preset depth. The inversion scheme has been successfully used for a set of sea experimental data. It shows that the inverted bottom parameters could distinguish the atlas marked bottom type quite well. The excellent comparison of the numerical results with the experimental data shows the validity of the inverted parameters.
2004, Vol. 21 
