A three-dimensional parabolic equation (PE) and perturbation approach is used to
invert for the depth- and range-dependent geoacoustic characteristics of the seabed. The
model assumes that the sound speed profile is the superposition of a known
range-independent profile and an unknown depth- and range-dependent perturbation.
Using a Green’s function approach, the total measured pressure field in the water column
is decomposed into a background field, which is due to the range-independent profile, and
a scattered field, which is due to the range-dependent perturbation. When the Born
approximation is applied to the resulting integral equation, it can be solved for the
range-dependent profile using linear inverse theory. Although the method is focused on
inverting for the sound speed profile in the bottom, it can also invert for the sound speed
profile in the water column. For simplicity, the sound speed profile in the water column
was assumed to be known with a margin of error of ± 5 m/s. The range-dependent
perturbation is added to the index of refraction squared n2(r), rather than the sound speed profile c(ro). The method is implemented in both Cartesian (x,y,z) and cylindrical (r,q,z)
coordinates with the forward propagation of the field in x and r, respectively. Synthetic
data are used to demonstrate the validity of the method [1].
Two inversion methods were combined, a Monte Carlo like algorithm, responsible
for a starting approximation of the sound speed profile, and a steepest descent method, that
fine-tuned the results. In simulations, the inversion algorithm is capable of inverting for
the sound speed profile of a flat bottom. It was tested, for three different frequencies
(50 Hz, 75 Hz, and 100 Hz), in a Pekeris waveguide, a range-independent layered medium,
and a range-dependent medium, with errors in the inverted sound speed profile of less than
3%.
Keywords: Three-dimensional parabolic equation method, geoacoustic inversion,
range-dependent sound speed profile, linear inversion, Born approximation, Green’s
functions. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
| Identifer | oai:union.ndltd.org:fau.edu/oai:fau.digital.flvc.org:fau_34585 |
| Contributors | Roa, Camilo Carlos (author), Frisk, George V. (Thesis advisor), Florida Atlantic University (Degree grantor), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering |
| Publisher | Florida Atlantic University |
| Source Sets | Florida Atlantic University |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation, Text |
| Format | 192 p., application/pdf |
| Rights | Copyright © is held by the author, with permission granted to Florida Atlantic University to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder., http://rightsstatements.org/vocab/InC/1.0/ |
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