Thin-sediment shear-induced effects on low-frequency broadband acoustic propagation in a shallow continental sea

Abstract

Low-frequency (6.3–630 Hz) acoustic broadband propagation loss data collected in areas of a shallow continental sea where the seabed is composed of hard substrates covered by thin (less than 40 m) deposits of unconsolidated sediment are presented. Data are shown to exhibit characteristics consistent with loss due to coupling to interface waves at the sediment–substrate interface [K. E. Hawker, J. Acoust. Soc. Am. 65, 682–686 (1979)]. In instances of a physically thin sediment cover, loss is also attributed to coupling to guided elastic waves in the sediment [S. J. Hughes et al., J. Acoust. Soc. Am. 88, 283–397 (1990)]. Interpretations are supported by numerical modeling of propagation loss using a recently developed wave number integration code for horizontally layered fluid–solid media, and geoacoustic models consistent with geophysical data from the sites of acoustic experiments.