E. C. Shang
Y. Y. Wang
A. G. Voronovich
CIRES, Univ. of Colorado/NOAA/ETL, Boulder, CO 80303
In the HRT (horizontal refraction tomography) scheme [A. G. Voronovich and E. C. Shang, J. Acoust. Soc. Am. 95, 2851(A) (1994)], the 3-D tomographic inversion is performed in two stages: (1) retrieving the modal wave numbers k[inf m](x,y) in the horizontal plane and (2) reconstructing the sound-speed profile SSP in the vertical at each node of the horizontal plane basing on a set of retrieved modal wave numbers k[inf m](x,y). Usually, a nonlinear approach has to be considered for the 1-D vertical inversion of the second stage. In this paper, the nonlinear inversion by using the WKB modal condition is proposed. The advantages of using WKB modal condition are: (a) it is efficient, the data k[inf m](x,y) can be matched directly to SSP without a model-based calculation (replica); (b) it works even if just a few modes are available; and (c) the error can be analyzed. Some results of numerical simulation are discussed. [Work supported by ONR.]