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TitleThe concept, design and experimental evaluation of an acoustic sub-seabed interrogator, Volume I and II
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorGuigne, J Y
SourceGeological Survey of Canada, Open File 1518, 1987, 373 pages, Open Access logo Open Access
Documentopen file
Mediapaper; on-line; digital
File formatpdf
AreaScotian Shelf; Labrador Sea
Subjectsgeophysics; marine geology; geophysical surveys; acoustic surveys; seismic surveys; equipment testing; sediments; sedimentation; glacial deposits; porosity; geophysical interpretations
Released1987 08 01; 2011 12 22
AbstractThis research study is centered around the design and experimental development of a unique subbottom profiler concept called an "Acoustic Sub-seabed Interrogator" (acronym ASI). The objectives behind the concept deal with the creation of a remote sensing probe that is capable of interrogating complex lithologies of a seabed. Through its use, it should become possible to precisely map and interpret variations found within sedimentary sequences, especially within complex sediment mixtures typical of glacial drift deposits and of permafrost structures. The concept of the ASI revolves around the optimization of lateral and temporal components which define the criterion of resolution. The ASI amalgamates fully the benefits of a terminated Parametric Source while operating in a stationary mode. The parametric approach provides an ease in manipulating a wide band of frequencies, while the stationary base allows for geometrical manipulations of the transmitters and receiving arrays. An optimized acoustic propagation of an ASI signal travelling within a structurally complex sediment model was theoretically appraised in terms of Signal-to-Noise Ratio and Signal-to-Reverberation Ratio. The theoretical modelling also concentrated on developing an interrogation ability to extract sub-seabed information from the returning signals. A product called the "Acoustic Core" was created. The logic of the core design controls the cross correlation routines envisioned for the ASI. The Hilbert Transform was integrated into the logic. The results obtained in the experimental simulations support the ASI philosophy and highlight the versatility of the "Acoustic Core". Although scaled the simulations are considered representative; providing a sensitive test of the ideas as they apply to one of the worst scanning cases; a glacial till matrix. An indepth insight into the model's physical and spatial variations wa$ attained by directing the interrogations on the acoustic properties of velocity and of absorption. Their statistical distribution emphasized the depositional processes that were involved in the creation of the layer. It is believed that the fundamental internal information defined by the ASI for the pseudo till structure and illustrated in the "Acoustic Core" cannot be attained using existing geophysical and geotechnical techniques. Finally, the "Acoustic Sub-seabed Interrogator''may provide a means of defining a first estimate of the elastic nature of soils from its calibrated acoustic response. It is hypothesized that the correlation of attenuation data with rigidity may establish an indirect but precise mensuration of shear-wave velocity.

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