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

## 5pUW4. A method for including lateral waves in normal-mode calculations.

**Evan K. Westwood
**

**
**
*Appl. Res. Labs., P.O. Box 8029, Univ. of Texas at Austin, Austin, TX
78713-8029
*

*
*
A method for including the lateral (or head) wave in a normal-mode
propagation model [E. K. Westwood et al., J. Acoust. Soc. Am. 95, 2908(A)
(1994)] for acoustoelastic ocean environments has been developed. The method
consists of replacing the original lower half-space with a thick layer having a
constant sound speed but a small gradient in attenuation. Below the attenuating
layer, the new lower half-space is given parameters such that there is no
mismatch at the half-space interface. As a result, (1) the branch point
corresponding to the critical angle in the half-space is moved upward in the
complex k plane (where k is horizontal wave number), (2) the Pekeris branch
line integral is also moved upward such that it becomes negligible, and (3)
modes appear in the complex k plane between the old and new branch points. The
cost of introducing the thick layer is not great because Airy function
solutions are used in each layer. Removal of the Pekeris branch line integral,
in conjunction with including the leaky modes, makes the mode solution
represent the complete acoustic field. [Work supported by the ARL Internal
Research and Development Program.]