### ASA 124th Meeting New Orleans 1992 October

## 3aUW11. A Maslov--Chapman wave-field representation for broadband,
wide-angle, one-way propagation in range-dependent environments.

**Michael G. Brown
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*RSMAS-AMP, Univ. of Miami, 4600 Rickenbacker Cswy., Miami, FL 33149
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The Maslov, or Lagrangian manifold, technique provides a means of
constructing a uniform asymptotic solution to the wave equation under
conditions in which variables do not separate. This study exploits the
assumption that there is a preferred direction of propagation to simplify the
presentation of this subject given by Chapman and Drummond [Bull. Seismol. Soc.
Am. 72, S277--S317 (1982)]. The one-way assumption does not require that a
narrow angle (parabolic) approximation be made. The final one-way wave-field
representation is easy to implement numerically, offering several advantages
over the Chapman and Drummond formulation. The final wave-field representation
correctly describes, in the time domain, direct and multiply turned ray
arrivals, wave fields in the vicinity of caustics of arbitrary complexity, edge
diffraction and head waves. It is valid in media with strong (nonadiabatic)
range dependence. In the one-way formulation, all quantities required to
compute the wave field at all depths at a fixed range (the preferred
propagation direction) are computed concurrently; the technique is thus
particularly well suited to the modeling of wave fields that are sampled using
a multielement vertical array. Numerical results, including a comparison with
the SLICE89 data set, will be shown. [Work supported by ONR and NSF.]