ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

1pAO11. Interpreting and extracting sediment attenuation from measured bottom loss data in the frequency range 500--5000 Hz.

Charles W. Holland

Greg Muncill

Peter Neumann

Planning Syst., Inc., 7923 Jones Branch Dr., McLean, VA 22102

The angle of intromission is the angle at which there is total transmission across an interface. This phenomena occurs between two ideal (lossless) half-spaces when the sound speed in the transmitting medium is lower and the density higher than in the incident medium. In low-energy environments (i.e., where clay and silty-clay sediment types dominate) the angle of intromission is often observed in measured bottom loss data. The loss at and around the angle of intromission is observed to be a strong function of attenuation in the host medium as well as the effects of gradients, random sedimentary layering, discrete sub-bottom reflecting horizons, roughness, and volume inhomogeneities. The physical mechanisms controlling reflection near the angle of intromission are explored in several data sets to demonstrate the potential for inverting the measured data for attenuation. [Work supported by the ONR/AEAS Program.]