Electromagnetic Seabed Logging

Sainson, Stéphane

doi:10.1007/978-3-319-45355-2

Cited by 26 publications

(3 citation statements)

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“…Experiments have shown that the amplitude and phase characteristics of ELF (3-30 Hz) EM waves are stable when they propagate in seawater, with small propagation loss and strong seawater penetration ability. Therefore, ELF EM waves have broad application prospects in geological exploration, submarine exploration, seismic detection, submarine communication, and other forms of geophysical exploration [1][2][3][4][5][6]. Many scholars have conducted in-depth studies on EM fields generated by low-frequency HED located in seawater or soil.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic Field Variation of ELF Near-Region Excited by HED in a Homogeneous Half-Space Model

Xie

Ding

2023

Applied Sciences

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Great attention has been paid to the propagation of electromagnetic (EM) waves across the sea surface due to its important applications. Most of the previous research, however, focuses on the half-space model illustrating the deep sea environment. In this paper, EM field distribution in the extremely low frequency (ELF) near-region under horizontal electric dipole (HED) excitation in homogeneous half-space seawater is analyzed based on the general expression of the Sommerfeld integral using the quasistatic approximation method. The focus is on deriving complete and effective solutions in air and seawater regions under the cylindrical coordinates for the EM near-field, which is generated by an HED in a shallow sea. The resulting formulas can be given by a few summands in closed form as the well-known Fourier–Bessel integrals. The analytical approximate expression of ELF Sommerfeld EM field integral excited by the HED in the homogeneous half-space seawater is deduced under the condition that the propagation distance ρ satisfies kρ << 1. To this end, the EM field distribution in the range close to the HED antenna in seawater is simulated, the results have shown that the minimum attenuation value of the vertical electric component Ez is about 15 dB, and that of the radical magnetic components Hφ is about 30 dB, and these values are found to be of greatest potential for the near-field region propagation among the electric and magnetic components. Finally, the correctness of the proposed method is verified by comparison with Pan’s approximation method and Margetis’s exact expression approximation method, which demonstrated the correctness of the proposed method.

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Section: Introductionmentioning

confidence: 99%

Electromagnetic Field Variation of ELF Near-Region Excited by HED in a Homogeneous Half-Space Model

Xie

Ding

2023

Applied Sciences

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“…However, over the years a number of very interesting practical applications have evolved where the use of relatively low frequencies comes with great advantages, such as: increased penetration depth through materials, a reduced risk of multi-pathing, and avoidance of certain local minima when solving the underlying optimization problem. These applications include geophysical imaging [1,18,19,28,46,51,60], near field sensing and tracking [53,58], the non-destructive testing of materials [15,41,59], and near-field electromagnetic holography [2,57].…”

Section: Introductionmentioning

confidence: 99%

“…Often, nature of the content prevents use of alternative screening techniques such as x-rays or other high-frequency electromagnetic fields, due to safety restrictions or the potentially damaging effect of such high energy probing fields. In addition to the well-known and well-established geophysical applications of such near-field exploration and monitoring tools [1,18,19,28,46,51,60], we want to highlight here several interesting and very promising new experimental verifications of low frequency screening and imaging applications at the scale of smaller boxes as reported for example in [14,15,16,59]. In those works, the goal is to screen metallic containers for specific threats where only extremely low electromagnetic frequencies provide sufficient skindepth for penetrating the present metallic shields.…”

Section: Introductionmentioning

confidence: 99%

Sparsity and level set regularization for near-field electromagnetic imaging in 3D

Hiles¹,

Dorn²

2020

Inverse Problems

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In this paper, we propose and compare two novel reconstruction strategies for near-field electromagnetic imaging of regions in 3D surrounded by walls or shields. Our focus is on the estimation of electrical conductivity profiles inside regions which are roughly equivalent in size to small rooms or medium-sized containers, from electromagnetic data obtained at one given frequency. This setup has interesting applications in the surveillance of activities behind walls, the screening of boxes or containers at ports or airports, or the monitoring of processes inside regions which might contain hazardous materials. Moreover, the techniques proposed here can easily be adjusted to imaging situations at larger or smaller scale; as often found in geophysical or non-destructive testing applications. The two novel regularization techniques proposed here are based on a sparsity promoting regularization scheme on the one hand, and a level set based shape evolution technique on the other. In our numerical simulations, we perform 3D reconstructions from noisy simulated data and compare the results with those obtained from a standard L 2 -type reconstruction approach. Our results suggest, in the applications considered here, that the two proposed novel schemes are potentially able to yield significantly improved reconstructions compared to more traditional techniques.

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