Direct and inverse scattering by anomalies of speed and density in stratified fluid media

Direct and inverse scattering of an ultrasonic compressional wave by an inhomogeneous cylindrical fluid target buried in the lower half of a two-half-space fluid medium illuminated by plane waves generated in the upper half-space is investigated. The target presents contrasts in both velocity and density with respect to the embedding. For the direct problem, i.e., the computation of the field scattered by a known object illuminated by a known incident wave, the presence of the density-related source term in the wave equation increases the complexity of the numerical solution, as it depends upon the derivative of the field. Such a solution may come from a field integral formulation obtained by means of Green´s theorem. The inverse problem is investigated by means of a reflection mode diffraction tomography technique, the data being collected at a single frequency for different illuminations