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

1aAO8. Acoustic backscatter from bubbles confined in sediment pores.

Frank A. Boyle

Nicholas P. Chotiros

Appl. Res. Labs., Univ. of Texas at Austin, P.O. Box 8029, Austin, TX 78713-8029

A model for acoustic backscatter from trapped gas bubbles in sandy sediments was recently presented [F. A. Boyle and N. P. Chotiros, J. Acoust. Soc. Am. 93, 2397(A) (1993)]. One of the assumptions was that trapped bubbles respond to an ambient acoustic field as if they were free bubbles surrounded by an infinite volume of water. A refinement to this model includes the effects of solid particles surrounding and constraining the fluid around the bubbles. A new expression for the sediment backscattering strength accounts for fluid confinement in pores. This confinement affects sediment acoustic impedances, bubble resonances, and scattering cross sections. Biot fast and slow compressional waves are treated separately. [Work supported by Naval Res. Lab., Stennis Space Center.]