Abstract A Wentzel–Kramers–Brillouin (WKB) method is introduced for obtaining a uniform asymptotic solution underwater sound propagation at very low frequencies in deep ocean. The utilizes mode sum and employs the reference functions to describe depth-separated wave equation approximately using parabolic cylinder functions. conditions validity of this approximation are also discussed. Furthermore, formula that incorporates waveguide effects modal group velocity derived, revealing boundary...

2016 and 2017 were marked by strong El Niño weak La Niña events, respectively, in the tropical East Pacific Ocean. The events significantly impacted sea surface temperature (SST) Indian Ocean (TIO) followed extreme negative positive Dipole (IOD) phases 2017, which triggered floods subcontinent drought conditions Africa. IOD is an irregular periodic oscillation Ocean, has attracted much attention last two decades due to its impact on climate surrounding landmasses. Much work been done past...

Recent studies have illustrated that the Multichannel Analysis of Surface Waves (MASW) method is an effective geoacoustic parameter inversion tool. This particular tool employs dispersion property broadband Scholte-type surface wave signals, which propagate along interface between sea water and seafloor. It critical importance to establish theoretical Scholte curve computation model. In this typical study, stiffness matrix introduced compute phase speed in a layered ocean environment with...

Geoacoustic parameter inversion is a crucial issue in underwater acoustic research for shallow sea environments and has increasingly become popular the recent past. This paper investigates geoacoustic parameters environment using single-receiver method based on Bayesian theory. In this context, seabed regarded as an elastic medium, pressure at different positions under low-frequency chosen study object, theoretical prediction value of described by Fast Field Method (FFM). The cost function...

Seabed geoacoustic parameters play an important role in underwater acoustic channel modeling. Traditional methods to determine these parameters, for example, drilling, are expensive and being replaced by inverse technology. An inversion method based on Bayesian theory is presented derive the structure of a layered seabed shallow sea. The was considered elastic medium. objective this research use sound pressure detected sensors at different positions nonlinear estimate their uncertainties...

This work is concerned with the characteristics of very low frequency sound propagation (VLF, ≤100 Hz) in shallow marine environment. Under these conditions, classical hypothesis considering sea bottom as a fluid environment no longer appropriate, and at should be also considered. Hence, based on finite element method (FEM), setting an elastic medium, proposed model which unifies water established, full waveguides can synchronously discussed. Using this model, effects topography various...

A method of geo-acoustic parameter inversion based on the Bayesian theory is proposed for acquisition acoustic parameters in shallow sea with elastic seabed. Firstly, theoretical prediction value sound pressure field calculated by fast (FFM). According to theory, we establish misfit function between measured and field. It under assumption Gaussian data errors which are line likelihood function. Finally, posterior probability density (PPD) given as result inversion. Our research conducted...

This paper presents a modal-based geoacoustic inversion method adapted for very-low-frequency leaky waveguide. It is applied to air gun data collected by seismic streamer during the multi-channel exploration experiment in South Yellow Sea. The carried out filtering waterborne and bottom-trapped mode pairs from received signal comparing modal interference features (waveguide invariant) replica fields. effective seabed models are inferred at two positions, two-way-travel time of basement...

Abstract The von Karman random medium model is established based on the small scale theory in this paper. Combined with finite element theory, numerical simulation of sound field under realized by using spectral-element method, and characteristics are compared those uniform underwater environment. results show that correlation length reflects variation heterogeneous size, scattering wave generated disturbance may provide a more reasonable explanation for amplitude energy anomalies some trial data.

It is difficult to separate and estimate the intersected group velocity dispersion curves for different normal modes when frequency lower than cutoff of water column. To address this issue, an estimation method based on joint processing sound pressure (P) vertical particle (Vz) proposed in paper. Theoretical analysis shows that amplitudes P Vz corresponding nth mode exhibit a complementary relationship certain band, providing theoretical basis method. The feasibility was verified using sea...

In this paper, a geoacoustic parameters inversion method for shallow water based on Bayesian Information Criterion (BIC) is developed. study, the seabed n-layer horizontal elastic medium, and in each layer medium include density ρ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> , compression wave (P-wave) velocity c xmlns:xlink="http://www.w3.org/1999/xlink">pn</inf> shear (S-wave) xmlns:xlink="http://www.w3.org/1999/xlink">sn</inf>...

Targeted at the issue of extremely low-frequency (&lt;100Hz) acoustic propagation in complex shallow elastic bottom environments. The influence law different bottoms on signal very low frequency by energy flux has been analyzed with simulation, which is based finite element method. have studied are horizontal bottom, and up-sloping down-sloping bottom. results show that propagating environments more than leaking into those propagation, especially