INVERSION OF BOTTOM SUBBOTTOM STATISTICAL PARAMETERS FROM ACOUSTIC BACKSCATTER DATA/

Inversion of statistical parameters of a bottom/subbottom scattering m odel is investigated by using genetic algorithms for both synthetic an d real da;a. The bottom/subbottom scattering model used in the calcula tions is a modified version of Lyons, Anderson, and Dwan [J. Acoust. S ec. Am. 79, 1410-1422 (1986)] in which correlation between subbottom d ensity, compressibility, and sound-speed fluctuations is established t hrough Wood's equation [A Textbook of Sound (Macmillan, New York, 1941 )], and volume inhomogeneities are described by von Karman type autoco rrelation functions [T. von Karman, J. Mar. Res. 7, 252-264 (1948)]. T he inversion is posed as an optimization problem which is solved (by a controlled Monte Carlo search using genetic algorithms) to find the o ptimum set of statistical parameters that minimizes the quadratic devi ation between measured and calculated backscatter data. A posteriori p robabilities calculated at the end of the search are used for error es timation and indication of relative importance of model parameters. Th is information helps to further assess the relative importance of two major scattering mechanisms due to bottom roughness and subbottom inho mogeneities. Such assessment is successfully demonstrated by using syn thetic and real backscatter data for sandy, silty, and muddy sediments . Finally, inverted statistical parameters for a sandy site at Biscayn e Bay, Florida confirm the results of simultaneous tomographic measure ments indicating that scattering by subbottom inhomogeneities plays a minor role for this particular site.