Two-Step Inversion Scheme For Complex Magnetotelluric Apparent Resistivity Data

2001 ◽  
Author(s):  
Atahebson B. Santos ◽  
Edson E.S. Sampaio ◽  
Milton J. Porsani
Keyword(s):  
Apparent Resistivity ◽  
Resistivity Data

APPARENT RESISTIVITY FOR DIPPING BEDS—A DISCUSSION

Geophysics ◽  
1955 ◽  
Vol 20 (1) ◽  
pp. 140-144 ◽  
Author(s):  
Robert G. Van Nostrand ◽  
Kenneth L. Cook
Keyword(s):  
Exact Solution ◽  
English Translation ◽  
Apparent Resistivity ◽  
Resistivity Data ◽  
Successful Work ◽  
Foregoing Paper

Two groups of workers, here designated the “image school” and the “harmonic school” respectively, have attacked the problem of the interpretation of resistivity data over a dipping bed or dipping fault. The earlier attempts were made by the image school; but the more successful attempts have been made only recently by the harmonic school. The most successful work prior to that presented in the foregoing paper by Maeda has been done by the Russians, whose papers in their English translation are probably available to few American geophysicists. The purpose of this discussion is to appraise the relative merits of various prior solutions to the dipping bed problem in the light of the exact solution to the problem, which is given by Maeda. The terminology and symbols used herein are identical to those used by Maeda in his paper.

Repeatability study of helicopter-borne electromagnetic data

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. G285-G290 ◽  
Author(s):  
Haoping Huang ◽  
Allen Cogbill
Keyword(s):  
Apparent Resistivity ◽  
Correlation Coefficients ◽  
Flight Path ◽  
Control Line ◽  
Average Correlation ◽  
Plan View ◽  
Frequency Dependency ◽  
Electromagnetic Data ◽  
Resistivity Data ◽  
Phase Data

Helicopter-borne electromagnetic (EM) responses depend very much upon the altitude and plan-view flight path, especially when the resistivity of the terrain’s materials varies laterally and/or vertically. Spatially consistent flight paths are required for repeatability analysis of the EM data. Caution should be used in examining the repeatability of the EM data because poor repeatability could result from spatially inconsistent flight paths. However, the apparent resistivity converted from the EM responses is virtually independent of the sensor altitude and directly reflects variations in the resistivity. Therefore, more meaningful repeatability analyses are achieved if the apparent resistivity is used instead of the EM response itself. We have analyzed 32 flights over a control line by using the EM amplitude, the phase, and the apparent resistivity. Our results show that the crosscorrelation for all 496 paired combinations of flights is better for the apparent resistivity than for the EM amplitude or phase. The apparent-resistivity data have average correlation coefficients from 0.89 to 0.94 as the frequency increases, whereas the amplitude and the phase data have average correlation coefficients from 0.78 to 0.85 without obvious frequency dependency.

APPARENT RESISTIVITY CURVES FOR AN INFINITE LINE SOURCE PARALLEL TO AN INCLINED CONTACT

Geophysics ◽  
1975 ◽  
Vol 40 (4) ◽  
pp. 689-693 ◽  
Author(s):  
Sri Niwas ◽  
S. K. Upadhyay
Keyword(s):  
Point Source ◽  
Line Source ◽  
Apparent Resistivity ◽  
Master Curves ◽  
Harmonic Method ◽  
Resistivity Data ◽  
Infinite Line

Investigations of apparent resistivity due to a point source over an inclined contact have been reported by Aldredge (1937), Unz (1953), Maeda (1955), and Chastenet de Gery and Kunetz (1956). In these investigations either the image or the harmonic method has been utilized. In this note, we propose to solve the same problem as follows: (1) Transform point‐source potential data into line‐source apparent resistivity data. (2) Interpret transformed apparent resistivities by the master curves provided.

On: “A simple method of interpreting dipole resistivity soundings” by S. Niwas and M. Israil (GEOPHYSICS, 52, 1412–1417, October 1987)

Geophysics ◽  
1989 ◽  
Vol 54 (12) ◽  
pp. 1647-1647
Author(s):  
Edward Szaraniec
Keyword(s):  
Linear Combination ◽  
Kernel Function ◽  
Apparent Resistivity ◽  
Simple Method ◽  
Resistivity Data ◽  
The Subject

The subject paper consists in approximating the apparent resistivity data by using a linear combination of suitable functions chosen in such a way that (1) they give a good approximation up to the desired precision and (2) they allow the kernel function to be determined analytically. Surprisingly enough, no mention is made that such an approach, especially directed toward interpretation of resistivity soundings, was first proposed by Santini and Zambrano (1981). The subject was subsequently continued by Kumar and Chowdary (1982) and commented by Santini and Zambrano (1982), Straub (1984), and Szaraniec (1982, 1984).

scholarly journals A Resistivity Survey of Phosphate Nodules in Oshoshun, Southwestern Nigeria

2018 ◽  
Vol 65 (2) ◽  
pp. 103-114 ◽  
Author(s):  
Oluseun Adetola Sanuade ◽  
Abayomi Adesola Olaojo ◽  
Adesoji Olumayowa Akanji ◽  
Michael Adeyinka Oladunjoye ◽  
Gabriel E. Omolaiye
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Inversion Algorithm ◽  
Clayey Sand ◽  
Southwestern Nigeria ◽  
Resistivity Data ◽  
Resistivity Method ◽  
Dahomey Basin ◽  
Geophysical Study ◽  
Electrical Resistivity Method

Abstract This geophysical study was carried out to determine the occurrence of phosphate nodules in the Oshoshun Formation of the Dahomey Basin, Southwestern Nigeria. The electrical resistivity method, comprising 1D vertical electrical sounding (VES; using Schlumberger array) and 2D geoelectrical imaging (using Wenner array), was used to determine the nature and depth of occurrence of the phosphate nodules. Six profile lines were established within the study area, and inverted sections were generated from the apparent resistivity data using DIPRO inversion algorithm. Five VES points were also acquired in the study area, and Win- Resist programme was used to process and interpret the field resistivity data. Four pits were dug along the profiles to verify the interpreted results. The results obtained by both techniques reveal similar geoelectric units: the top soil, clay, clayey sand and clay at different depths. These layers host pockets of phosphate nodules (78-≥651 Ωm) with varying thicknesses. The strong correlation between the lithology profiles obtained from the pits and the interpreted results of the inverted apparent resistivity sections demonstrates the efficacy of the electrical resistivity method in characterising phosphate occurrence within the formation.

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