Acoustic volume scattering from the seafloor and the small scale structure of heterogeneous sediments /
There has been little work on developing and testing seafloor volume scattering models and on the characterization of such volumes because of the complexity of the medium and the paucity of high resolution ground truth data. This dissertation addresses the different physical mechanisms responsible...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742536231&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | There has been little work on developing and testing seafloor volume scattering models and on the characterization of such volumes because of the complexity of the medium and the paucity of high resolution ground truth data. This dissertation addresses the different physical mechanisms responsible for backscattering from a seafloor volume and their relative importance. This was accomplished by: 1) examining and adapting theoretical and numerical techniques for predicting volume backscatter from seafloor environments in the frequency range from 5-50 kHz, 2) characterizing the physical properties of the seafloor volume that control acoustic backscatter in selected environmental regimes by using the high resolution techniques of CT scanning and p- wave logging and casting these descriptions in a form useful for scattering models, and 3) comparing model results constrained by ground truth information with acoustic data sets obtained in different seafloor environments in order to isolate physical scattering mechanisms which dominate scattering and to examine the effectiveness of the characterization and modeling components of this research. Specifically, a layered, gassy sediment and a sandy, shell hash sediment were examined. The gassy sediment was analyzed by using a continuum model for scattering from the surrounding sediment and a non-spherical bubble model for scattering from the included gas features. Simulations carried out with the bubble model showed that bubble scattering will dominate continuum scattering in soft mud containing gas bubbles. Results of calculations using the bubble scattering model compare well with data taken with the Naval Research Laboratory's Acoustic Sediment Classification System. The comparisons also show that bubbles smaller than those which could be found with CT scanning methods might be important at higher acoustic frequencies. The shell hash sediment was examined by using a single scattering model for the shell pieces instead of a more complicated multiple scattering model. The single scattering model was justified by the size and number density of shell pieces found in the ground truth cores. Simulations carried out with the shell hash scattering model suggest that, at low grazing angles, scattering from the shell pieces may dominate the scattering from the hard, rough water-sediment interface. |
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| Item Description: | Vita. "Major Subject: Oceanography". |
| Physical Description: | xi, 120 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |