Influence of Gradients in Inhomogeneous Elastic Media on Resonance in

the Plane Wave Reflection Coefficient

A0016 Vladimir N. Fokin Institute of Applied Physics, Russian Academy of Science

A0015 Margarete S. Fokina Institute of Applied Physics, Russian Academy of Science

This paper considers inhomogeneous solid sediment, whose properties

vary continuously with depth, lying between two homogeneous media v an

upper half-space layer representing the ocean and a semi-infinite,

homogeneous solid substrate. Reflection coefficient for this media

obtained by generalization of matrix method on elastic and liquid

layers with inhomogeneity in the direction perpendicular to boundaries.

For each inhomogeneous layer may be found exact expression for

characteristic matrices in the form of a convergent series. These

matrices with the matrices describing half-spaces determine reflection

coefficient. For each characteristic matrix of inhomogeneous layer

may be obtained two expressions for series. First convenient for low

frequencies, second has good convergence for high frequencies. The

problem considered is that of investigation of dependencies of plane

wave reflection coefficient resonance structures (resonance position,

amplitude and half-wide) on gradients in inhomogeneous media. The

effect of gradients in inhomogeneous media on resonances in the plane

wave reflection coefficient has received relatively little attention

in previous published works. Thus, while the influence of gradients

in inhomogeneous media has been considered by a number of authors,

most attention has been paid to theoretical investigations and general

illustration of dependencies of the reflection coefficient from

gradients. Due to complexity of these dependencies, it does not lend

themselves to easy physical interpretation. In this study the

dependencies of resonance structures (position, amplitude and half-

wide) on gradients of density, attenuation, compressional and shear

wave speeds has been obtained and interpreted. Consideration of

behavior of resonance structures on the plane of two parameters of

inhomogeneous sediment and analysis of obtained dependencies was done.

Possibility to use these dependencies for obtaining parameters of

inhomogeneous sediment from measurements of characteristics of

resonances was illustrated. This study was performed in the framework

of the RFBR project (No 00-05-64956).