Airborne electromagnetic responses to permeable conductive layered earth

1982 ◽  
Author(s):  
Markk Peltoniemi
Keyword(s):  
Layered Earth ◽  
Electromagnetic Responses ◽  
Airborne Electromagnetic

Inversion of helicopter electromagnetic data to a magnetic conductive layered earth

Geophysics ◽  
2003 ◽  
Vol 68 (4) ◽  
pp. 1211-1223 ◽  
Author(s):  
Haoping Huang ◽  
Douglas C. Fraser
Keyword(s):  
Magnetic Permeability ◽  
Field Data ◽  
Model Parameters ◽  
Relative Importance ◽  
Magnetic Polarization ◽  
Inversion Algorithm ◽  
Layered Earth ◽  
Electromagnetic Data ◽  
Airborne Electromagnetic ◽  
True Values

Inversion of airborne electromagnetic (EM) data for a layered earth has been commonly performed under the assumption that the magnetic permeability of the layers is the same as that of free space. The resistivity inverted from helicopter EM data in this way is not reliable in highly magnetic areas because magnetic polarization currents occur in addition to conduction currents, causing the inverted resistivity to be erroneously high. A new algorithm for inverting for the resistivity, magnetic permeability, and thickness of a layered model has been developed for a magnetic conductive layered earth. It is based on traditional inversion methodologies for solving nonlinear inverse problems and minimizes an objective function subject to fitting the data in a least‐squares sense. Studies using synthetic helicopter EM data indicate that the inversion technique is reasonably dependable and provides fast convergence. When six synthetic in‐phase and quadrature data from three frequencies are used, the model parameters for two‐ and three‐layer models are estimated to within a few percent of their true values after several iterations. The analysis of partial derivatives with respect to the model parameters contributes to a better understanding of the relative importance of the model parameters and the reliability of their determination. The inversion algorithm is tested on field data obtained with a Dighem helicopter EM system at Mt. Milligan, British Columbia, Canada. The output magnetic susceptibility‐depth section compares favorably with that of Zhang and Oldenburg who inverted for the susceptibility on the assumption that the resistivity distribution was known.

Three-dimensional frequency-domain modeling of airborne electromagnetic responses

1998 ◽  
Vol 29 (1-2) ◽  
pp. 111-119 ◽  
Author(s):  
Dmitry B. Avdeev ◽  
Alexei V. Kuvshinov ◽  
Oleg V. Pankratov ◽  
Gregory A. Newman
Keyword(s):  
Frequency Domain ◽  
Three Dimensional ◽  
Domain Modeling ◽  
Electromagnetic Responses ◽  
Airborne Electromagnetic

scholarly journals Detecting Permafrost in Plateau and Mountainous Areas by Airborne Transient Electromagnetic Sensing

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1229 ◽  
Author(s):  
Benyu Su ◽  
Rongfu Rao ◽  
Zhixiong Li ◽  
Lei Song ◽  
Jianhua Yue
Keyword(s):  
Effective Means ◽  
Electromagnetic Method ◽  
Western China ◽  
Tibet Plateau ◽  
Transient Electromagnetic Method ◽  
Transient Electromagnetic ◽  
Electromagnetic Responses ◽  
Algorithm Comparison ◽  
Airborne Electromagnetic ◽  
Qinghai Tibet Plateau

Transportation has become a key bottleneck which restricts economic development in Western China. However, during the construction of the western railway, the permafrost problem has plagued railway construction on the Qinghai–Tibet Plateau, and has not yet been resolved. Accurately identifying permafrost by geophysical method is the most effective means to solve this problem. However, the mountainous and plateau terrain in Western China impose huge challenges in collecting geophysical data. To address this issue, this paper proposes an airborne transient electromagnetic method to collect geophysical electromagnetic data to identify permafrost in the mountains and plateaus of Western China. Based on Maxwell’s equations, the forward model of the airborne electromagnetic was derived, and the finite element method was used to calculate the two-dimensional (2D) space electromagnetic responses of different permafrost geo-electrical models. Furthermore, a coupling function was constructed to estimate the distribution of the resistivity of the permafrost by the least-squares fitting algorithm. Comparison between inversion resistivity distribution and the geo-electrical model showed that the proposed airborne transient electromagnetic method was valid for exploring the permafrost in the mountains and the Qinghai–Tibet Plateau in Western China.

Modeling of broadband airborne electromagnetic responses from saline environments

Geophysics ◽  
1996 ◽  
Vol 61 (6) ◽  
pp. 1624-1632 ◽  
Author(s):  
G. Buselli ◽  
D. R. Williamson
Keyword(s):  
Vertical Direction ◽  
Relative Magnitude ◽  
High Salt ◽  
Salt Accumulation ◽  
Simultaneous Inversion ◽  
Quadrature Component ◽  
Electromagnetic Responses ◽  
Resistivity Model ◽  
Airborne Electromagnetic ◽  
Salt Profile

The removal of vegetation for the development of nonirrigated agriculture and the associated increase in groundwater recharge and discharge has caused significant areas of salinization of surface soil and water resources in Australia. At least three types of salt profiles are known to indicate the relative magnitude of recharge. These profiles may be differentiated by their resistivity structure. Since a broadband airborne electromagnetic (AEM) method offers the possibility of readily obtaining resistivity soundings, modeling was carried out to investigate the ability of a broadband AEM system to distinguish different salt profile types. Salt profile types may be represented by a four‐layer resistivity model. The use of a broadband AEM system to distinguish the relative magnitude of the resistivity of a layer of high salt accumulation and the underlying layer forms the basis for efficiently identifying areas of high or low recharge. Where the resistivity of the underlying layer is greater than that of the salt accumulation, high recharge is indicated, and a lower resistivity of this layer implies low recharge. The response of each of the salt profile models was calculated in the frequency domain and then inverted back to a layered model. With noise added to the calculated responses, the inversion results show that the depth, thickness, and resistivity of a layer of high salt accumulation can be resolved by AEM measurements. Furthermore, the resistivity of this layer can be distinguished from the resistivity of the underlying layer. A high‐recharge profile may therefore be differentiated from a low‐recharge profile with AEM measurements. Since the quadrature component of the AEM response is relatively unaffected by noise caused by the primary field, the effect of using solely the quadrature component of the response was examined briefly as a second part of the AEM modeling investigation. It is found that simultaneous inversion of the quadrature part of the spatial components measured along the line of flight and in a vertical direction gives results similar to those when both the in‐phase and quadrature parts of these components are used in the inversion.

Probabilistic inversion of airborne electromagnetic data for basement conductors

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. E389-E400 ◽  
Author(s):  
Juerg Hauser ◽  
James Gunning ◽  
David Annetts
Keyword(s):  
Thin Plate ◽  
Parametric Bootstrap ◽  
Computationally Efficient ◽  
Prior Beliefs ◽  
Data Set ◽  
Layered Earth ◽  
Electromagnetic Data ◽  
Airborne Electromagnetic ◽  
Airborne Electromagnetic Data ◽  
Probabilistic Inversion

Probabilistic inversion of airborne electromagnetic data is often approximated by a layered earth using a computationally efficient 1D kernel. If the underlying framework accounts for prior beliefs on spatial correlation, the inversion will be able to recover spatially coherent interfaces and associated uncertainties. Greenfield exploration using airborne electromagnetic data, however, often seeks to identify discrete economical targets. In mature exploration provinces, such bodies are frequently obscured by thick, conductive regolith, and the response of such economic basement conductors presents a challenge to any layered earth inversion. A well-known computationally efficient way to approximate the response of a basement conductor is to use a thin plate. Here we have extended a Bayesian parametric bootstrap approach, so that the basement of a spatially varying layered earth can contain a thin plate. The resulting Bayesian framework allowed for the inversion of basement conductors and associated uncertainties, but more importantly, the use of model selection concepts to determine if the data supports a basement conductor model or not. Recovered maps of basement conductor probabilities show the expected patterns in uncertainty; for example, a decrease in target probability with increasing depth. Such maps of target probabilities generated using the thin plate approximation are a potentially valuable source of information for the planning of exploration activity, such as the targeting of drillholes to confirm the existence of a discrete conductor in a greenfield exploration scenario. We have used a field data set from northwest Queensland, Australia, to illustrate how the approach allowed inversion for a basement conductor and related uncertainties in a spatially variable layered earth, using the information from multiple survey lines and prior beliefs of geology.

Measuring Electromagnetic Responses of CFRP for Lightning Risk Management

2020 ◽  
Vol 140 (5) ◽  
pp. 299-303
Author(s):  
Sultan Alkhteeb ◽  
Shigeru Oho ◽  
Hiroyuki Shimizu ◽  
Seisuke Nishimura
Keyword(s):  
Risk Management ◽  
Electromagnetic Responses
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