ON THE RETRIEVAL OF THE PLANE-WAVE REFLECTION COEFFICIENT OF A SEABEDIN SHALLOW-WATER

In shallow water, the interaction of a sound wave with the seabed is m uch studied. Here the problem is that of determining the plane wave ti me-harmonic reflection coefficient of the seabed from the pressure in water observed on a horizontal line of receivers when a cylindrical so urce is placed nearby. A range-independent fluid sediment lying above an homogeneous solid elastic subbottom is assumed, two typical configu rations being studied (one with high contrasts of velocities and densi ties, the other with much lower contrasts). Wave propagation is charac terized by the depth-dependent Green's function in the horizontal wave number (spectral) domain which is expressed from the plane-wave reflec tion coefficient (extended to wavenumbers larger than the water propag ation constant). Values of this reflection coefficient are derived fro m normal incidence to almost grazing incidences from the pressure on t he line of receivers at both low and high frequencies by means of a Fo urier-based scheme. The influence of the seabed structure, of the freq uency of investigation and of typical positioning errors of the receiv ers is discussed.