Studies on the effect of shear on compressional wave dispersion.

Abstract

The results of a study to examine the effect of shear on compressional wave dispersion are presented. Modal arrival time data from different shallow water sites will be analyzed to examine the influence of shear. The modal travel times corresponding to the Airy Phase regions are extremely sensitive to shear. Simple inversion schemes will be developed to estimate the shear speed in the sediment by comparing theoretical predictions with experimental data. The estimated shear speeds will also be compared with shear speeds calculated from core data. The effect of shear on compressional wave attenuation will also be investigated. Synthetic data will be generated for elastic bottom, with different shear speeds, and these data will be inverted for compressional wave attenuation. One of the most promising approaches to estimate shear speed is to invert the relation between seismo‐acoustic interface waves (Scholte waves) that travel along boundaries between media and shear wave speed. The propagation speed and attenuation of the Scholte wave are closely related to shear‐wave speed and attenuation over a depth of 1‐2 wavelengths into the seabed. A shear measurement system being developed at the University of Rhode Island based on this concept will be presented. [Work supported by the Office of Naval Research.]