title: Treatment of a sloping fluid-solid interface and sediment layering with the seismo-acoustic parabolic equation.
abstract: The parabolic equation method is extended to handle problems in seismo-acoustics that have multiple fluid and solid layers, continuous depth dependence within layers, and sloping interfaces between layers. The medium is approximated in terms of a series of range-independent regions, and a single-scattering approximation is used to compute transmitted fields across the vertical interfaces between regions. The approach is implemented in terms of a set of dependent variables that is well suited to piecewise continuous depth dependence in the elastic parameters, but one of the fluid-solid interface conditions in that formulation involves a second derivative that complicates the treatment of sloping interfaces. This issue is resolved by using a non-centered, four-point difference formula for the second derivative. The approach is implemented using a matrix decomposition that is efficient when the parameters of the medium have a general dependence within the upper layers of the sediment but only depend on depth in the water column and deep within the sediment.
authors.affiliation: Code 7160, Naval Research Laboratory, Washington, DC 20375.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Collins
authors.affiliation: Department of Mathematical Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180.
authors.forename: William L
authors.initials: WL
authors.lastname: Siegmann