A scaled mapping approach for range-dependent seismo-acoustic propagation using the parabolic approximation

Abstract

Parabolic equation solutions are used to accurately and efficiently model range-dependent propagation effects in ocean environments. There has been much recent interest in improving accuracy, particularly for sloping interfaces between fluid and underlying sediment layers. A translational mapping approach [Collins et al., J. Acoust. Soc. Am. 107 (2000)] applies a coordinate transformation in which a sloping bottom interface becomes horizontal and range dependence is mapped to the upper free surface. While accurate for small slopes, this approach introduces errors for variably sloping bathymetries since the range dependence is transformed to the surface. In this work, a scaled mapping is constructed that both transforms the sloping bottom interface to horizontal and also preserves the range-independent form of the free surface by distorting the waveguide in depth. The parabolic approximation is applied in the fully range-independent transformed domain, and the result is inverse transformed to obtain the solution in the initial range-dependent environment. Applications of this approach are given and benchmarked for seismo-acoustic propagation scenarios. [Work supported by ARL:IR&D.]