Littoral Subsonic Seismoacoustic Phenomena Ultrasonic Modeling [report]

Jacques R. Chamuel
1999 unpublished
LONG-TERM GOALS Develop comprehensive physical understanding of fundamental littoral subsonic seismoacoustic phenomena on the interaction of broadband transient underwater acoustic waves, interface Scholte waves , and surface Rayleigh waves with naturally-deposited /disturbed heterogeneous marine sediments with topography, variable water/air content, and benthic shelled animals leading to accurate acoustic modeling of littoral surficial layer and geophysical inversion needed for reliable
more » ... coustic detection of buried objects in very shallow water and the unsaturated surf zone. OBJECTIVES Identify physical mechanisms contributing to subcritical sound penetration, conversion, propagation, and scattering of underwater acoustic waves and Scholte waves in disturbed and naturally deposited sandy sediments. Characterize frequency-dependent phenomena associated with the interaction of broadband transient Scholte and Rayleigh waves with heterogeneous sediments and sand ripples with at least one dimension comparable to the wavelength. Identify and characterize different types of seismoacoustic waves existing in water-saturated sand and unsaturated sand in various forms (naturally deposited, disturbed, compacted, and liquefied). Contribute to the understanding of seismoacoustic phenomena associated with benthic shelled animals (sand dollar). APPROACH Ultrasonic modeling techniques developed by Chamuel [1-7] since 1979 are used to obtain qualitative and quantitative experimental results under controlled laboratory conditions to characterize wave penetration, conversion, dispersion, and scattering. These ultrasonic modeling techniques proved to be cost-effective powerful tools complementing numerical methods and field experiments by providing physical insight into complex broadband seismoacoustic wave phenomena [1] [2] [3] [4] [5] [6] [7] . WORK COMPLETED Provided a new hypothesis [6] explaining the anomalous acoustic slow wave [8] detected in underwater sand. Obtained ultrasonic modeling results on the conversion of near-grazing refracted waves in an inhomogeneous medium with depth-dependent elastic properties. Conducted smallscale controlled laboratory experiments to study the seismoacoustic characteristics of various wet sand conditions depending on
doi:10.21236/ada630606 fatcat:mgmmokdwlbbh7flsflvxjvjunm