Electromagnetic Field Radiated by a Dipole Source over a Dielectric-Coated Spherical Earth

CSAMT exploration generally adopts a single dipole as the transmitter. The single dipole source has the apparent disadvantages–there are weak areas for all components, Ey and Hx are weak in the area where Ex and Hy are reliable. Moreover, it is hard to deploy the source with a specific direction in a rugged mountainous area. Given the shortcomings of the single dipole source, multi-dipole sources are introduced into CSAMT exploration. Although the dipole sources follow the principle of vector synthesis, the length of the source in actual exploration can last for several kilometers and the offset is generally a few kilometers. In this case, the source can no longer be regarded as a single dipole in the near-field zone. The electromagnetic field in this region becomes relatively complicated. We first compare the similarities and differences of electromagnetic field generated by vector synthesis source and multi-dipole source through the Ex radiation patterns. Then, we study the factors that affect electromagnetic response due to the substitution of the double-dipole source with the vector synthesis source. The measured EM fields is affected by the source length, frequency, the source angle, the offset, and the resistivity.Finally, we apply the double-dipole source to the 1D and 3D geological model and compare the difference between the electromagnetic field generated by the double-dipole source and that generated by the vector synthesis source. Usually, the difference is very obvious in the near-field zone, and is almost negligible in the far-field zone.

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Comparison of the time-domain electromagnetic field from an infinitesimal point charge and dipole source

Applied Geophysics ◽

10.1007/s11770-013-0387-z ◽

2013 ◽

Vol 10 (3) ◽

pp. 349-356 ◽

Cited By ~ 3

Author(s):

Nan-Nan Zhou ◽

Guo-Giang Xue ◽

He-Yuan Wang

Keyword(s):

Electromagnetic Field ◽

Time Domain ◽

Point Charge ◽

Dipole Source ◽

Time Domain Electromagnetic ◽

The Time Domain

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A STUDY OF THE ELECTROMAGNETIC FIELD FROM THE MCSEM DIPOLE SOURCE IN AN ANISOTROPIC LAYERED EARTH

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v33i2.720 ◽

2015 ◽

Vol 33 (2) ◽

Author(s):

Walleson Gomes Dos Santos ◽

Cícero Roberto Teixeira Régis

Keyword(s):

Electromagnetic Field ◽

Finite Thickness ◽

Electrical Anisotropy ◽

Dipole Source ◽

Earth Model ◽

Electromagnetic Modeling ◽

Technical Literature ◽

Layered Earth ◽

Geometric Patterns ◽

Ocean Layer

ABSTRACT. This paper studies the electromagnetic field from a horizontal electrical dipole inside a layered earth model with TIV anisotropy, including a visualization of the geometric patterns of the field through the medium. The objective here is to present a detailed formulation of the problem, as an aid to those who have an interest in modeling data from the Marine Controlled-Source ElectroMagnetic method – mCSEM, but find it hard to follow the usually abridged, often incomplete, descriptions found in the technical literature. We present a detailed vector potential formulation, with a semi-analytical solution, that allows the calculation of the fields with the source located in a finite thickness ocean layer over N-layered earth models. As an application, we use the implemented solution to study the geometrical distribution of the electric field generated by the dipole source in anisotropic layered media.Keywords: mCSEM, TIV electrical anisotropy, 1D electromagnetic modeling. RESUMO. Este artigo estuda o campo eletromagnético de um dipolo elétrico horizontal no interior de um modelo estratificado com anisotropia TIV, incluindo uma visualização da geometria das linhas de campo através do meio. O objetivo é apresentar a formulação detalhada do problema, para aqueles que têm interesse na modelagem de dados do método eletromagnético de fonte controlada marinho – mCSEM, mas encontram dificuldades em seguir as descrições geralmente muito resumidas, diversas vezes incompletas, na literatura técnica. Apresentamos uma formulação detalhada em termos do potencial vetorial, com uma solução semi-analítica que permite o cálculo dos campos com a fonte localizada em um oceano de espessura finita sobre uma terra estratificada com Ncamadas. Como aplicações, usamos a solução implementada para estudar a distribuição geométrica do campo elétrico gerado pelo dipolo fonte em meios estratificados anisotrópicos.Palavras-chave: mCSEM, anisotropia elétrica TIV, modelagem eletromagnética 1D.

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