Field distribution due to a current-carrying loop of arbitrary shape above a conducting half-space

1996 ◽  
Vol 32 (5) ◽  
pp. 4344-4346 ◽  
Author(s):  
S.H.H. Sadeghi ◽  
A.H. Salemi
Keyword(s):  
Half Space ◽  
Field Distribution ◽  
Arbitrary Shape ◽  
A Current

Hybrid‐ray approximation in electromagnetic sounding

Geophysics ◽  
1979 ◽  
Vol 44 (11) ◽  
pp. 1846-1861 ◽  
Author(s):  
Tze‐Kong Kan ◽  
C. S. Clay
Keyword(s):  
Half Space ◽  
Wave Theory ◽  
Transverse Magnetic ◽  
Image Method ◽  
Multiple Reflections ◽  
Current Dipole ◽  
Electromagnetic Sounding ◽  
Transmission Coefficients ◽  
Magnetic Components ◽  
A Current

Our purpose is to develop electromagnetic (EM) transient sounding methods that can handle resistivity structures having dipping interfaces. The method is an approximation that uses wave theory for part of the calculation and ray theory for the rest. The approximation is a refinement of Yost’s (1952) image method in which the source on a half‐space becomes the image beneath the reflecting interface. This approach shows excellent agreement with experiment and promises simple applications. To test the approximation, we compare numerical integration of the fields over a two‐layer half‐space with approximate values. We separate the EM integrals into integrals for the surface wave, primary, and multiple reflections. For a current dipole along the x‐axis, the electric field [Formula: see text] is the sum of the transverse electric and transverse magnetic components. For skin depths >1, the main contributions to the integrals come from directions near the specular direction, and by moving the reflection coefficients at the lower interface outside of the integral, we obtain the hybrid‐ray approximation. The transmission coefficients from the source into the earth remain inside because the source is near the interface. Computations for a two‐layer model that includes the geometry, and system functions for deep dipole‐dipole soundings in the Precambrian shield of northern Wisconsin, give time‐domain signals that closely approximate the measurements. The theoretical model consists of a layer 18 to 23 km thick with a conductivity of [Formula: see text] over a half‐space with a conductivity of [Formula: see text].

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