The normal mode theory with bottom elasticity and range dependence

Abstract

The theory of normal modes has been extended to accommodate the effects of shear waves in the elastic ocean floor. The effect of absorption has also been included as the imaginary component of the shear and compressional wavenumbers. A semi‐infinite elastic bottom basement layer has been included and it was found that the absorption causes the wavenumber spectrum of the radiating modes to be inherently discrete, hence, the number of radiating modes is drastically reduced relative to the ones obtained with the deep false boundary. The range dependence of the acoustic properties and of the boundaries of the ocean has been included by a modified version of the adiabatic normal mode theory. Comparisons are made with experimental measurements of the transmission loss of underwater explosives and with results from Collins' HEPE mode. [Work supported by the Independent Research Board of the Naval Surface Warfare Center and by NORDA.]