### ASA 125th Meeting Ottawa 1993 May

## 4pUW2. On the acoustic probing of the sea bottom in shallow water from
near-field data.

**Marc Lambert
**

**
Dominique Lesselier
**

**
**
*Lab. des Signaux et Systemes CNRS-ESE, 91192 Gif-sur-Yvette Cedex, France
*

*
*
The probing of the acoustic profiles of the seabed in shallow water from
the sound pressure observed on a line array in presence of a cylindrical
source, is dealt with. The seabed is modeled as a depth-inhomogeneous fluid
sediment overlying an homogeneous fluid subbottom. As is well known, the
propagation is characterized by the depth-dependent Green's function in the
horizontal wave-number (spectral) domain, which is a function of the plane wave
reflection coefficient of the seabed, with extension to wave numbers larger
than the one of water. Conversely, seabed parameters are sought by analyzing
features of the Green's function, such as location and magnitude of peaks with
then measurements needed in the far field. Here, using receivers near the
source, where the ``continuum'' part of the field is preponderant, directly
provides an estimate of the reflection coefficient (at least at low wave
numbers). This allows the application of solution methods of the 1-D inverse
scattering problem, with limitations due to the discrepancy between estimate
and true coefficient. Corresponding issues: retrieving the reflection
coefficient, probing the parameters profiles, are investigated and illustrated
by examples taken in various source, array, and seabed configurations.