Abstract:
The wave-number-integration approach has traditionally been limited to providing exact solutions to propagation problems in range-independent fluid--elastic stratifications. However, using various coupling approaches, this solution technique has recently been extended to handle stepwise range-dependent problems as well. The spectral super-element approach uses a Galerkin approach to represent the coupling of the wave fields in two consecutive sectors in terms of distributed panel sources [Schmidt et al., J. Acoust. Soc. Am. 98, 465--472 (1995)]. The virtual source approach [H. Schmidt, J. Acoust. Soc. Am. 97, 3316(A) (1995)] solves for reflection and transmission of each wave-number component at discrete points on the vertical sector boundaries, and computes the equivalent distribution of discrete, virtual sources. Both methods then use standard wave-number-integration to compute the resulting two-way seismoacoustic field in the range-independent sectors. This new class of range-dependent, seismoacoustic propagation models provides efficient handling of arbitrary fluid--elastic stratifications and typical oceanic sound-speed profiles. Since these approaches are based on fundamental wave solutions, the environment discretization is dependent on the local environmental length scales only, and they are therefore particularly well suited for modeling seismoacoustic wave field coupling by distinct environment features. The performance of these approaches is demonstrated by modeling the conversion of seismic energy into oceanic T-phases observable in the SOFAR channel. [Work supported by ONR.]