ASA 126th Meeting Denver 1993 October 4-8

1pAO4. Ultrasonic modeling of sea ice seismoacoustic wave phenomena.

Jacques R. Chamuel

Sonoquest Advanced Ultrason. Res., P. O. Box 153, Wellesley Hills, MA 02181-5339

A variety of broadband Arctic seismoacoustic wave phenomena are demonstrated using laboratory ultrasonic modeling techniques introduced by the author in the mid 1970s to study the generation, propagation, detection, and scattering of low-frequency underwater acoustic waves coupled to the heterogeneous ice cover. Data on frequency-dependent under-ice reflectivity, effective elastic properties, low-frequency transmission loss, horizontal refraction, wave conversion, and low grazing angle backscattering are discussed. Different guided leaky and trapped waves from range-dependent models are isolated and examined including flexural waves, shear horizontal waves, Rayleigh waves, Scholte waves, edge plate waves, and wedge waves. The laboratory models consisted of finite floating plates with cracks, ridges, low-velocity layers, boreholes, trapped air pockets, solid wedges, and suspensions. The results provide physical insight into realistic 3-D problems and lead to the development of comprehensive understanding of near-field and long-range seismoacoustic phenomena essential for interpreting and inverting Arctic acoustic data, planning field experiments, and predicting ice failure modes from acoustic emission. The generic findings are applicable to ocean bottom interacting acoustic waves, nondestructive testing, and ultrasonic imaging. [Work supported by DREP and ONR.]