### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 5aUW7. A model for wave propagation in an inhomogeneous elastic medium.

**Raymond J. Nagem
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*Dept. of Aerospace and Mech. Eng., Boston Univ., 110 Cummington St.,
Boston, MA 02215
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**Ding Lee
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Tien-Chay Chen
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*Naval Undersea Warfare Ctr., New London, CT 06320
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A perturbation method is used to derive equations for wave propagation in
an inhomogeneous elastic medium. The formulation is three dimensional, and is
written explicitly in cylindrical coordinates so that it can include property
variations in the depth, range, and azimuth directions. A factorization is used
to convert the equations into an operator form which distinguishes outgoing
waves from incoming waves. This factorization removes the requirement for a
far-field boundary condition. For large-scale numerical problems, the
factorization produces a tremendous reduction in computation time and in memory
requirements. The elastic equations are written in a way that is directly
analogous to previous work in ocean acoustics. With appropriate fluid--elastic
interface conditions, the elastic and acoustic equations may be used to study
the fluid--elastic interactions which are important in shallow-water
environments, especially the propagation of shear waves in the ocean bottom. In
this paper, the theoretical development of the elastic equations are presented
and their merits and applications are discussed. [This work was jointly
supported by the U.S. Office of Naval Research and the U.S. Naval Undersea
Warfare Center.]