It is well known that gases are present in marine sediments. The gas found in the surficial layer of marine sediments is mostly due to biological origin or migration from deposits in deeper layers. A nonlinear acoustic remote sensing technique based on the nonlinear acoustic scattering theory of gas bubbles is introduced in this thesis to identify the gas bubbles in surficial layers of marine sediments and measure their concentrations. Two close transmitting frequencies were used to generate a nonlinear scattering effect from the gas bubbles in the sediments, and the nonlinear responses were generated only by gas bubbles instead of by other scatters in the sediments. An acoustic inversion was implemented on the nonlinear response, together with calibration results and scattering volume, to determine gas bubble concentrations. Results from the data collected at Gulf of Gdansk demonstrate that the nonlinear acoustic method is advantageous over other acoustic remote sensing methods in gas bubble identification and measurement, and provides more valuable information for seabed classification.
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/2084 |
| Date | 20 January 2010 |
| Creators | Zhang, Songhua |
| Contributors | Chapman, N. Ross |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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