Modal time series structure in range and depth of a shallow‐water area.

Abstract

A theoretical analysis of pressure time series generated by small explosive sources and recorded on both an HLA and a VLA deployed in the Hudson canyon region off the New Jersey coast near the AMCOR 6010 borehole is presented. The SVP in the water column has an isovelocity layer down to a depth of about 20 m followed by a strong negative gradient to about 45 m where the profile becomes approximately isovelocity to theseafloor at 73 m. This sound‐speed structure creates a unique time series structure on the VLA as a function of source range. The data are simulated with a broadband normal mode‐ approach recently discussed in the literature [J. Acoust. Soc. Am. 98, 1682–1698 (1995); IEEE J. Ocean. Eng. 21 (1) (1996)]. The representation of the spatial and temporal structure of the time series in terms of a modal structure reveals several unique aspects of the structure of the SVP in the water column and the geoacoustic structure of the bottom. The details of the modal structure of the sound field clearly define the propagation mechanisms in the water column and the interaction with the seafloor and sub‐bottom sediment layers. [Work supported by Advanced Research Projects Agency.]