Propagation of ELF Electromagnetic Waves Over a Curved Stratified Ground and its Application in Geophysical Prospecting

Zheng, Fang-Hua; Di, Qingyun

doi:10.1109/access.2021.3122963

Cited by 4 publications

(3 citation statements)

References 22 publications

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“…To make the tangential field components E θ , E ϕ , H θ , and H ϕ continuous [38] when across the element interfaces, it is sufficient to make the quantities of 1…”

Section: Determination Of Coefficientsmentioning

confidence: 99%

“…e(a) of the Earth can be obtained layer by layer. Therefore, the boundary conditions [38] are transformed into:…”

Section: Determination Of Coefficientsmentioning

confidence: 99%

“…It is worth noting that the apparent resistivity response of the HED is the same as that of the vertical electric dipole (VED) [38]. Following the resolution limit (Wannamaker, 1983), Zheng and Di (2021) depicted the maximum normalized anomaly curves for resistivity ratios of 0.01, 0.1, 1, 10, and 100 between the anomalous layer and the background layer, and pointed out that the resolution of the low-resistivity layer is highly dependent on the ratio of the resistivity, while the resistivity ratio has little effect on the resolution of the high-resistivity layer.…”

Section: Sensitivity To a Thin Resistive Targetmentioning

confidence: 99%

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A Spherical “Earth–Ionosphere” Model for Deep Resource Exploration Using Artificial ELF-EM Field

Zheng

2022

Remote Sensing

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Fully coupled lithosphere, atmosphere, and ionosphere theory has demonstrated that extremely low-frequency electromagnetic (ELF-EM) fields present a broad application prospect in deep resource exploration, but previous studies have ignored the contribution of the Earth’s curvature. This study extends the theory of ELF-EM over a stratified Earth to the case where the Earth’s curvature must be taken into account, and presents an analytical solution of the ELF-EM field excited by a grounded horizontal antenna in a spherical Earth–ionosphere model, whose theoretical approach and solution method are notably different from the flat Earth–ionosphere model. Additionally, the Earth is treated as a concentric-layered sphere rather than an ideal homogeneous sphere. We aim to investigate the effects of the Earth’s curvature on the surface field, so as to broaden the coverage of the ELF wave in resource exploration. The solution is mathematically accurate and physically reasonable, since it reflects the sphericity and radially stratified structure of the Earth. We first verify the correctness and reliability of the proposed method by comparing the results with FDTD in a full-space spherical model. Additionally, we then compared the spherical results with the conventional controlled-source electromagnetic method and flat Earth–ionosphere results. The results show that when the distance between the transmitter and the receiver is comparable to the Earth radius, the spherical model better reflects the resonance of the wave in the cavity, suggesting that the effect of the Earth’s curvature is not negligible. Then, the numerical simulations conducted to investigate the properties of the EM fields and their sensitivities to the conductivity at depth in the Earth are discussed. Finally, the EM responses of some simple electrical conductivity structures models are modeled to illustrate their prospects in future resource exploration.

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“…To make the tangential field components E θ , E ϕ , H θ , and H ϕ continuous [38] when across the element interfaces, it is sufficient to make the quantities of 1…”

Section: Determination Of Coefficientsmentioning

confidence: 99%

“…e(a) of the Earth can be obtained layer by layer. Therefore, the boundary conditions [38] are transformed into:…”

Section: Determination Of Coefficientsmentioning

confidence: 99%

Section: Sensitivity To a Thin Resistive Targetmentioning

confidence: 99%

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A Spherical “Earth–Ionosphere” Model for Deep Resource Exploration Using Artificial ELF-EM Field

Zheng

2022

Remote Sensing

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A Review of the Applications of Through-the-Earth (TTE) Communication Systems for Underground Mines

Ngwenyama,

Webber-Youngman

2024

Mining, Metallurgy & Exploration

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Underground mining accidents have the potential of leaving miners trapped in unknown and life-threatening locations for an extended period of time. The lives of the trapped and unaccounted-for miners are at risk and require emergency rescue. But, the primary tracking systems are highly susceptible to damage during accidents and are most likely to be defunct and inoperable post-accident. This prompted the need for a robust and reliable post-accident communication and locator system. Subsequently, the through-the-earth (TTE) communication systems were developed and tested in underground mines. Under ideal conditions, these systems are capable of post-accident full-duplex two-way voice, text, and data communication and fingerprint detection of the geolocations of the trapped miners. This is achieved through a wireless link established by the transmission of electromagnetic and seismic waves between surface and underground, even in challenged underground environments. Unlike the primary tracking systems, the TTE communication systems do not require extensive shaft-to-workplace backbone infrastructure. This has made the TTE systems to be less susceptible to damage and therefore suitable for post-accident communication. Instead, the Earth’s crust acts as the signal transmission medium which forms an uplink and downlink communication path. This is achieved by injecting an electric current into the ground using electrodes, by transmitting magnetic fields from a radiating loop antenna, or by inducing fingerprint geolocations using seismic waves. Range and data rates are the critical requirements for the effectiveness of these systems and are dependent on factors such as the antenna design, frequency, and rock properties. This study provides a review of the applications of the different types of TTE communication systems, their evolution, factors that affect them, and techniques for improving their efficiencies and capabilities. These systems present the mining industry with an opportunity to improve safety by providing post-accident communication and locating trapped miners as quickly as possible. This will improve their survival chances and ultimately reduce fatality rates in the mining industry.

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Sunlight-Driven Quantum Magnetometry

Zhu

Xie²,

Jing³

et al. 2022

PRX Energy

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Propagation of ELF Electromagnetic Waves Over a Curved Stratified Ground and its Application in Geophysical Prospecting

Cited by 4 publications

References 22 publications

A Spherical “Earth–Ionosphere” Model for Deep Resource Exploration Using Artificial ELF-EM Field

A Spherical “Earth–Ionosphere” Model for Deep Resource Exploration Using Artificial ELF-EM Field

A Review of the Applications of Through-the-Earth (TTE) Communication Systems for Underground Mines

Sunlight-Driven Quantum Magnetometry

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