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

1pAO10. A structure function constraint for stable least-squares inversion of reflection data.

Kenneth E. Gilbert

Timothy J. Kulbago

P. Jason White

Appl. Res. Lab. and the Graduate Prog. in Acoust., Penn State Univ., P.O. Box 30, State College, PA 16804

High-frequency seismic profiles often indicate that the near-surface sediments in shallow water are layered on scales larger than about 0.5 m but not on smaller scales. Consequently, for a meaningful least-squares inversion of reflection data using a horizontally stratified sediment model, the wavelengths in the insonifying wave should be long enough to ``average out'' the small-scale sediment structure. With such a finite wavelength inversion, the sediment model must include some resolution constraints in order to yield a stable inversion. A common approach, for example, is to consider a stack of homogeneous layers where each layer is thicker than, say, a quarter of a wavelength. An alternative constraint method based on a structure function or, equivalently, an autocorrelation function, is presented. It is shown that with a structure function constraint, a stable inversion is obtained even if the layered structure approaches a continuous profile. Without the constraint, the inversion becomes meaningless as a continuum is approached. [Work supported by NRL and ONR.]