### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 2pUW24. Marching wave-number-integration approach to range-dependent,
two-way seismoacoustic propagation modeling.

**Henrik Schmidt
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*Dept. of Ocean Eng., MIT, Cambridge, MA 02139
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An approximate solution to two-way seismoacoustic propagation problems can
be obtained by recursive use of wave-number-integration in a stepwise
range-dependent environment. The approach is conceptually simple and
straightforward. In the range-independent sector containing the source, an
``exact'' integral representation of the field can be obtained versus range and
depth using, e.g., the SAFARI/OASES code [H. Schmidt and F. B. Jensen,
813--825 (1985)]. At the vertical boundary of the next sector we then solve the
reflection-transmission problem locally for each plane-wave component, assuming
vertical homogeneity of the field. The resulting particle motions now act as
virtual sources, the wave-number representation of which can be stated
explicitly using the seismic source representation theorem. The resulting
transmitted and reflected fields can then be computed at any depth and range
within the range-dependent sectors. The procedure is repeated at any vertical
cut in a marching scheme. A single-scatter approximation to the backscattered
field is subsequently obtained by a backward marching scheme, similarly to the
approach used in the two-way elastic PE [M. D. Collins, 1815--1824
(1993)]. A special version of OASES incorporating this approach has been
developed, and its performance is demonstrated by solutions to canonical
problems such as the ASA benchmark, and seismic problems previously solved
using the two-way elastic PE.