The effects of ignored seabed variability in geoacoustic inversion

Lapinski, Anna-Liesa S.; Chapman, David M. F.

doi:10.1121/1.1921449

Cited by 10 publications

(4 citation statements)

References 29 publications

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“…II C point 10͒. For example, Lapinski and Chapman 27 and Moreley et al 28 studied this non-linear aspect in some detail for variability in sediment sound speed ͑and water depth͒ using a numerical approach ͑i.e., using parabolic equation, PE, and normal mode propagation models͒. They showed that ignoring sound speed variability in matched field geoacoustic inversion leads to bias errors in sound speed estimates all other parameters that were inverted for.…”

Section: Range-independent Effective Parametersmentioning

confidence: 99%

Propagation in a waveguide with range-dependent seabed properties

Holland

2010

The Journal of the Acoustical Society of America

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The ocean environment contains features affecting acoustic propagation that vary on a wide range of time and space scales. A significant body of work over recent decades has aimed at understanding the effects of water column spatial and temporal variability on acoustic propagation. Much less is understood about the impact of spatial variability of seabed properties on propagation, which is the focus of this study. Here, a simple, intuitive expression for propagation with range-dependent boundary properties and uniform water depth is derived. It is shown that incoherent range-dependent propagation depends upon the geometric mean of the seabed plane-wave reflection coefficient and the arithmetic mean of the cycle distance. Thus, only the spatial probability distributions (pdfs) of the sediment properties are required. Also, it is shown that the propagation over a range-dependent seabed tends to be controlled by the lossiest, not the hardest, sediments. Thus, range-dependence generally leads to higher propagation loss than would be expected, due for example to lossy sediment patches and/or nulls in the reflection coefficient. In a few instances, propagation over a range-dependent seabed can be calculated using range-independent sediment properties. The theory may be useful for other (non-oceanic) waveguides.

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Section: Range-independent Effective Parametersmentioning

confidence: 99%

Propagation in a waveguide with range-dependent seabed properties

Holland

2010

The Journal of the Acoustical Society of America

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“…Over the past six decades, the principal observations used to estimate geoacoustic seabed properties have involved acoustic propagation over horizontal spatial scales of O (10 3 ) to O (10 4 ) m. Most often, the seabed is assumed as laterally invariant, or range independent, over such scales. However, it is clear from modeling that ignoring this dependence can lead to biases in the property estimates 22 – 24 . At much finer scales, direct sampling methods, such as cores and in situ probes, provide understanding of vertical variability at O (10 −2 ) to O (10 0 ) m. But direct sampling is costly due to the need of ship time, has limited penetration depth, and the sampling process can disturb the sample.…”

Section: Introductionmentioning

confidence: 99%

Meso-scale seabed quantification with geoacoustic inversion

Sonnemann,

Dettmer,

Holland

et al. 2024

Commun Eng

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Knowledge of sub-seabed geoacoustic properties, for example depth dependent sound speed and porosity, is of importance for a variety of applications. Here, we present a semi-automated geoacoustic inversion method for autonomous underwater vehicle data that objectively adapts model inference to seabed structure. Through parallelized trans-dimensional Bayesian inference, we infer seabed properties along a 12 km survey track on the scale of about 10 cm and 50 m in the vertical and horizontal, respectively. The inferred seabed properties include sound speed, attenuation, density, and porosity as a function of depth from acoustic reflection coefficient data. Parameter uncertainties are quantified, and the seabed properties agree closely with core samples at two control points and the layering structure with an independent sub-bottom seismic survey. Recovering high resolution seabed properties over large areas is shown to be feasible, which could become an important tool for marine industries, navies and oceanic research organizations.

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“…[32][33][34][35][36] The approach is to start the inversions with a half-space model and then bootstrapping each successive inversion by adding an underlying layer to determine the validity of using a particular number of layers. Here, the number of sediment layers that overlie a half-space is specified in a model.…”

Section: Introductionmentioning

confidence: 99%

Geoacoustic inversion of short range source data using a plane wave reflection coefficient approach

Stotts

Knobles

Keller

et al. 2006

The Journal of the Acoustical Society of America

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Acoustic time series data were collected in a shallow, hard bottom lake environment located in central Texas using both short range (2 m) implosive data, obtained with the source and a single hydrophone located near mid-depth in the waveguide, along with longer range implosive and explosive data from a near surface source to a bottom mounted hydrophone. Matched field inversions using simulated annealing were performed with a ray trace plus complex plane wave reflection coefficient forward propagation model that was validated in previous work. Isolating bottom interacting paths to perform the inversions is shown to be essential to reduce parameter uncertainties in the hard bottom environment and enables a systematic approach to the inversions which establishes the number of layers needed to represent the lake environment. Measured transmission loss data from a towed source were compared through a RMS error analysis to modeled transmission loss, constructed with the parameters from inversions of data from several source types, to further establish the validity of the inversion approach for this environment. Geoacoustic parameters obtained by inversions of short range, low frequency impulsive data are used to predict transmission loss at longer ranges and higher frequencies. The range dependence of the global minimum is discussed.

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The effects of ignored seabed variability in geoacoustic inversion

Cited by 10 publications

References 29 publications

Propagation in a waveguide with range-dependent seabed properties

Propagation in a waveguide with range-dependent seabed properties

Meso-scale seabed quantification with geoacoustic inversion

Geoacoustic inversion of short range source data using a plane wave reflection coefficient approach

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