THE EFFECT OF AN ELASTIC BASEMENT IN THE INTERPRETATION OF BOTTOM LOSS DATA

A bottom loss simulator has been developed to model low-frequency bottom loss measurements obtained at sites in the SW Pacific around New Zealand. The data for frequencies below 100 Hz have been grouped into two types according to the bottom environment. The first type is characteristic of continental margins where the bottom is composed of turbidite layers, and the second type is characteristic of deep-water basins where the bottom is silt-clay material overlying the ocean basement. The bottom loss simulator consists of a simple geoacoustic profile, composed of a thin-layer fluid sediment overlying an elastic basement, and a ray propagation model. Simulations were carried out with the model to study the effect of various types of solid substrates, including relatively low-speed consolidated sediment material and high-speed basalt. The model provides good agreement with both types of bottom loss data, using archival values from seismic and geological sources for the model parameters. The work demonstrates the importance of including shear-wave propagation in the substrate in modeling the bottom interaction in deep-water environments. © 1990, Acoustical Society of America. All rights reserved.