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Tomographic inversion for sediment parameters in shallow water
1Department of Ocean Engineering, University of Rhode Island, Narragansett 02882, USA. potty@oce.uri.edu
The Journal of the Acoustical Society of America
|September 29, 2000
Summary
This study uses explosive acoustic signals to invert for bottom geoacoustic properties. The method accurately determines sound speeds in water and sediment layers, matching experimental data and in situ measurements.
Area of Science:
- Ocean acoustics
- Geophysical inverse theory
- Signal processing
Background:
- Accurate characterization of seafloor geoacoustic properties is crucial for underwater acoustic propagation modeling.
- Broadband acoustic signals from explosive sources offer valuable information for geophysical inversions.
- Previous methods often lacked the precision for detailed sediment layer characterization.
Purpose of the Study:
- To develop and validate a method for inverting bottom geoacoustic properties using broadband acoustic signals.
- To determine sound speed profiles in the water column and compressional wave speeds in sediment layers.
- To assess the accuracy and resolution of the inversion technique.
Main Methods:
- Analysis of broadband acoustic signals (SUS charge explosions) using wavelet transforms.
- Group speed dispersion curve extraction from wavelet scalograms.
- Application of a genetic algorithm (GA) combined with Levenberg-Marquardt for inversion.
- Utilizing empirical orthogonal functions (EOFs) for water column sound speed variations.
- Employing linear perturbation and Hessian matrix calculations for error and resolution estimation.
Main Results:
- Inverted sound speed fields in the water column showed excellent agreement with experimental group speed data.
- The inverted sediment compressional wave speed profile closely matched in situ measurements.
- A hybrid optimization scheme demonstrated efficiency in parameter fitting.
- Resolution and variance estimates provided quantitative error bounds for the inverted parameters.
Conclusions:
- The developed inversion technique effectively retrieves bottom geoacoustic properties from explosive source data.
- The method provides reliable estimates for both water column and sediment sound speeds.
- This approach offers a robust tool for seafloor characterization in marine environments.
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