STATISTICAL EVALUATION OF ELECTRICAL SOUNDING METHODS. PART II: APPLIED ELECTROMAGNETIC DEPTH SOUNDING

Geophysics ◽  
1976 ◽  
Vol 41 (6) ◽  
pp. 1222-1235 ◽  
Author(s):  
S. H. Ward ◽  
B. D. Smith ◽  
W. E. Glenn ◽  
L. Rijo ◽  
J. R. Inman
Keyword(s):  
Magnetic Dipole ◽  
Electromagnetic Sounding ◽  
The Earth ◽  
Vertical Magnetic Dipole ◽  
Vertical Electric Sounding ◽  
Data Points ◽  
Electrical Sounding ◽  
Schlumberger Sounding ◽  
Dar Zarrouk Parameters ◽  
Depth Sounding

Schlumberger resistivity and electromagnetic sounding data have been obtained over prehistoric Lake Bonneville sediments near Delta, Utah. Inverse interpretation of these data illustrates that vertical electric sounding with the Schlumberger array is superior, for this environment, to electromagnetic sounding with either a vertical magnetic dipole or a horizontal magnetic dipole. Combined parametric and geometric electromagnetic sounding using 84 data points is inferior to Schlumberger sounding using 21 data points. However, superiority in these contexts pertains to parameter resolution. The earth models obtained with all three soundings are virtually identical within the limits of resolution. The importance of percent parameter standard deviations, parameter correlations, and least‐squares residuals are all illustrated for a field example in this manuscript. Reparameterization in terms of the Dar Zarrouk parameters S and T reduces the parameter correlations as expected. A generalization of reparameterization beyond the Dar Zarrouk parameters is suggested.

On: “Apparent resistivity curves in controlled‐source electromagnetic sounding directly reflecting true resistivities in a layered earth”, by U. C. Das (January‐February 1995 GEOPHYSICS, 60, 53–60).

Geophysics ◽  
1996 ◽  
Vol 61 (3) ◽  
pp. 918-918 ◽  
Author(s):  
Pierre Valla
Keyword(s):  
Magnetic Dipole ◽  
Apparent Resistivity ◽  
Electromagnetic Sounding ◽  
Controlled Source ◽  
Layered Earth ◽  
Vertical Magnetic Dipole ◽  
Em Field ◽  
Depth Sounding

Using a clever mix of two components of the EM field caused by a vertical magnetic dipole, U. C. Das derives what he claims to be an exact apparent resistivity for use in EM depth sounding.

ELECTROMAGNETIC FIELDS OF AN OSCILLATING MAGNETIC DIPOLE OVER AN ANISOTROPIC EARTH

Geophysics ◽  
1968 ◽  
Vol 33 (2) ◽  
pp. 346-353 ◽  
Author(s):  
Ajit K. Sinha
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Magnetic Dipole ◽  
Electromagnetic Fields ◽  
Isotropic Medium ◽  
Electromagnetic Wave Propagation ◽  
Vector Potentials ◽  
The Earth ◽  
Longitudinal Conductivity ◽  
Vertical Magnetic Dipole

The problem of electromagnetic wave propagation from an oscillating magnetic dipole placed over a uniaxially anisotropic earth has been considered. Formal expressions for the vector potentials inside the earth have been derived. It has been shown that for a vertical magnetic dipole, the field components are identical to those in the case of an isotropic medium in which the conductivity is the “horizontal or longitudinal conductivity.” For a horizontal dipole, directed along the x axis, it has been shown that the vector potential inside the earth will have a y component as well as x and z components. Formal expressions for the vector potentials in air have been obtained for the case of a horizontal magnetic dipole. However when the conductivity of air is considered to be negligibly small, the field components are not affected by the anisotropy.

scholarly journals Calibration of Radiocarbon Dates for the Late Pleistocene Using U/Th Dates on Stalagmites

Radiocarbon ◽  
1997 ◽  
Vol 39 (1) ◽  
pp. 27-32 ◽  
Author(s):  
John C. Vogel ◽  
Joel Kronfeld
Keyword(s):  
South Africa ◽  
Magnetic Dipole ◽  
Satisfactory Agreement ◽  
Late Pleistocene ◽  
Calibration Curve ◽  
Dipole Field ◽  
Radiocarbon Dates ◽  
The Past ◽  
The Earth ◽  
Magnetic Dipole Field

Twenty paired 14C and U/Th dates covering most of the past 50,000 yr have been obtained on a stalagmite from the Cango Caves in South Africa as well as some additional age-pairs on two stalagmites from Tasmania that partially fill a gap between 7 ka and 17 ka ago. After allowance is made for the initial apparent 14C ages, the age-pairs between 7 ka and 20 ka show satisfactory agreement with the coral data of Bard et al. (1990, 1993). The results for the Cango stalagmite between 25 ka and 50 ka show the 14C dates to be substantially younger than the U/Th dates except at 49 ka and 29 ka, where near correspondence occurs. The discrepancies may be explained by variations in 14C production caused by changes in the magnetic dipole field of the Earth. A tentative calibration curve for this period is offered.

scholarly journals GEOELECTRIC STUDY OF GROUNDWATER REPOSITORY IN PARTS OF AKWA IBOM STATE, SOUTHERN NIGERIA

2020 ◽  
Vol 4 (2) ◽  
pp. 99-102
Author(s):  
Johnson C. Ibuot ◽  
Moses M. M. Ekpa ◽  
Doris O. Okoroh ◽  
Aniefiok S. Akpan Emmanuel T. Omeje
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Potential ◽  
Vertical Electrical Sounding ◽  
Protective Capacity ◽  
Longitudinal Conductance ◽  
Contour Maps ◽  
Transverse Resistance ◽  
Southern Nigeria ◽  
Electrical Sounding ◽  
Dar Zarrouk Parameters

Geoelectric survey employing Vertical Electrical Sounding (VES) was carried out in order to assess the groundwater repositories. A total of seven soundings were obtained with their layer resistivity, thickness and depth within the maximum electrode separation. The geoelectric parameters obtained were used to estimate the Dar-Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The result shows the aquifer resistivity ranging from 77.14 to 784.76 Ωm, with thickness ranging from 28.78 to 80.04 m. The longitudinal conductance have values ranging from 0.071 to 0.825 Ω-1 while the values of hydraulic conductivity and transmissivity range from 1.087 to 5.881 m/day and 60.180 to 374.031 𝑚2/day respectively. The contour maps generated show the variation of these parameters across the subsurface, and areas with poor protective capacity were delineated. The results also delineate the groundwater potential of the study area as moderate, while the corrosivity rating indicates non-corrosive and slightly corrosive.

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