### ASA 125th Meeting Ottawa 1993 May

## 5pPA6. On the scattering of elastic waves in inhomogeneous material.

**Eveline J. Ayme-Bellegarda
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*IBM T. J. Watson Res. Ctr., P.O. Box 704, Yorktown Heights, NY 10598
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**Tarek M. Habashy
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*Schlumberger-Doll Res., Ridgefield, CT 06877-4108
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This work is concerned with the imaging and quantitative characterization
of objects embedded in inhomogeneous material, using acoustic or elastic waves
as the interrogating sources. Such problems are recurrent in many areas such
as, for instance, geophysics, oceanography, and medical imaging. The interest
here hinges on the determination of high contrast channels embedded in
multilayered elastic structures. A general framework is presented, based on
vector integral equations. In addition to being suitable for both the forward
and inverse problem, this framework is appropriate for any geometry and
transmitter--receiver characteristics. Tractability issues are discussed,
leading to the consideration of the Born approximation for inhomogeneous
elastic background. To go beyond the inherent limitations of this
approximation, an iterative inversion scheme is introduced. The method is
illustrated in the case of a 2-D problem. First, the forward model is validated
against an independent means based on a finite-difference approach. Then,
constrained least-square reconstruction is performed, aiming at recovering the
density distribution of a 2-D fluid-filled object buried in high contrast
layers.