Two-dimensional magnetotelluric data inversion using Lanczos bidiagonalization method with active constraint balancing

2021 ◽  
Author(s):  
Faegheh Mina Araghi ◽  
Mirsattar Meshinchi-Asl ◽  
Ali Nejati Kalateh ◽  
Mahmoud Mirzaei
Keyword(s):  
Two Dimensional ◽  
Magnetotelluric Data ◽  
Active Constraint ◽  
Lanczos Bidiagonalization ◽  
Data Inversion

DIAGRAMS FOR MAGNETOTELLURIC DATA

Geophysics ◽  
1976 ◽  
Vol 41 (4) ◽  
pp. 766-770 ◽  
Author(s):  
F. E. M. Lilley
Keyword(s):  
Impedance Tensor ◽  
Two Dimensional ◽  
Magnetotelluric Data ◽  
One Dimensional ◽  
Magnetic Components ◽  
Strike Direction ◽  
Electric And Magnetic Fields ◽  
The Relationship ◽  
Special Case ◽  
Phase Differences

Observed magnetotelluric data are often transformed to the frequency domain and expressed as the relationship [Formula: see text]where [Formula: see text] [Formula: see text] and [Formula: see text] [Formula: see text] represent electric and magnetic components measured along two orthogonal axes (in this paper, for simplicity, to be north and east, respectively). The elements [Formula: see text] comprise the magnetotelluric impedance tensor, and they are generally complex due to phase differences between the electric and magnetic fields. All quantities in equation (1) are frequency dependent. For the special case of “two‐dimensional” geology (where structure can be described as having a certain strike direction along which it does not vary), [Formula: see text] with [Formula: see text]. For the special case of “one‐dimensional” geology (where structure varies with depth only, as if horizontally layered), [Formula: see text] and [Formula: see text].

COHERENCE FUNCTIONS FOR MAGNETOTELLURIC ANALYSIS

Geophysics ◽  
1974 ◽  
Vol 39 (3) ◽  
pp. 312-320 ◽  
Author(s):  
I. K. Reddy ◽  
D. Rankin
Keyword(s):  
Data Analysis ◽  
Linear System ◽  
System Approach ◽  
Partial Coherence ◽  
Impedance Method ◽  
Two Dimensional ◽  
Magnetotelluric Data ◽  
The Earth ◽  
Principal Axes ◽  
Tensor Impedance

A multiinput linear system approach is used to study the magnetotelluric phenomena in the presence of lateral conductivity inhomogeneities in the earth. The three types of coherence functions (ordinary, multiple, and partial) are defined, and their use in magnetotelluric data analysis is illustrated with a field example. Partial coherence functions are used to determine the principal axes in the case of two‐dimensional type inhomogeneities, and as measures of three‐dimensionality in the case of non‐two‐dimensional type structures. The results obtained using coherence functions are compared with those obtained with the conventional tensor impedance method.

Magnetotelluric data inversion with seismic data constraint

2005 ◽  
Vol 18 (6) ◽  
pp. 678-685 ◽  
Author(s):  
Wei-qi Song ◽  
Shan Sun
Keyword(s):  
Seismic Data ◽  
Magnetotelluric Data ◽  
Data Inversion

scholarly journals THE ELECTROTOMOGRAPHY SURVEY IN DIFFICULT GEOTECHNOGENIC CONDITIONS AT THE PEACEFUL UNDERGROUND NUCLEAR EXPLOSION "CRYSTAL" SITE

2021 ◽  
Vol 2 (3) ◽  
pp. 61-68
Author(s):  
Alexandr N. Shein ◽  
Svetlana Yu. Artamonova ◽  
Vladimir V. Potapov ◽  
Nickolay O. Kozhevnikov ◽  
Vladislav E. Ushnitskii
Keyword(s):  
Electrical Resistivity ◽  
Carbonate Rocks ◽  
Nuclear Explosion ◽  
Forward Modeling ◽  
Measured Data ◽  
Underground Nuclear Explosion ◽  
Geological Environment ◽  
Two Dimensional ◽  
Data Inversion ◽  
Significant Interference

The paper presents the results of measurements in 2019 by electrotomography at the site of the emplacement hole of the peaceful underground nuclear explosion "Crystal", carried in 1974 at a depth of 98 m in permafrost Cambrian carbonate rocks, and the neighboring forest area. The fence made of metal poles and barbed wire around the site, and the buried fragments of the casing of the emplacement hole create significant interference of measurements. To avoid the electromagnetic noise, the measured data of the apparent electrical resistivity was cleaned manually. Data inversion was performed in the Res2Dinv program. Geoelectric models, namely two-dimensional sections of the upper part of the geological environment to a depth of up to 80 m, were obtained. To verify the models, forward modeling was performed using the ZondRes2D program.

scholarly journals METHODOLOGY TO ESTIMATE THE MAXIMUM DEPTH OF RELIABILITY OF TWO-DIMENSIONAL GEOELECTRICAL MODELS DERIVED FROM MAGNETOTELLURIC DATA

2013 ◽  
Vol 31 (1) ◽  
pp. 97
Author(s):  
Andréa Cristina Lima dos Santos ◽  
Antônio Lopes Padilha ◽  
Ícaro Vitorello ◽  
Marcelo Banik de Pádua ◽  
Augusto César Bittencourt Pires
Keyword(s):  
Heuristic Method ◽  
Transverse Magnetic ◽  
Empirical Method ◽  
Maximum Depth ◽  
Northeastern Brazil ◽  
Perfect Conductor ◽  
Two Dimensional ◽  
Magnetotelluric Data ◽  
Starting Point ◽  
Forward Calculation

An empirical technique is proposed to estimate the maximum depth of reliability of two-dimensional (2D) geoelectrical models derived from magnetotelluric surveys conducted in regions with different conductivity. The results are then compared to those derived from a heuristic methodology well established in the literature. Experimental data from a linear profile cutting across the major structures in the SE portion of the Borborema Province, northeastern Brazil, are used. The data were collected with modern instrumentation, processed by robust techniques and modeled using inversion algorithms available nowadays to the research community of electromagnetic induccion inside the Earth. Sensitivity tests have shown that the 2D geoelectrical section is robust and accurately represents the conductivity distribution below the profile. The 2D section is used as a starting point for the empirical method employed, which consists of introducing a perfect conductor (or resistor) at different depths of the 2D model. The effect of adding this structure to the data fitting is checked through forward calculation and by comparing the RMS misfit. The results show that the maximum depth of reliability of the 2D geoelectrical model is usually given by the phase of the transverse electric (TE) mode, whereas the maximum depth of propagation of the EM signal is usually given by the phase of transverse magnetic (TM) mode. The empirical approach shows similar variations in depth when compared to the results from the heuristic method, but provides lateral variations more compatible with the diffusive process of EM wave propagation. RESUMO: Uma técnica empírica para estimar a profundidade máxima de confiabilidade de modelos geoelétricos bidimensionais (2D), obtidos a partir de sondagens magnetotelúricas realizadas em regiões de diferentes condutividades, é aqui proposta e seus resultados são comparados àqueles derivados de uma metodologia heurística já consagrada na literatura. Para tanto, são utilizados dados experimentais obtidos em um perfil linear que corta transversalmente as principais estruturas e terrenos na porção SE da Província Borborema, região Nordeste do Brasil. Os dados utilizados foram coletados com instrumentação moderna, processados por técnicas robustas e modelados por algoritmos de inversão atualmente disponíveis para a comunidade de estudos de indução eletromagnética no interior da Terra. A seção geoelétrica 2D derivada desse procedimento é robusta em relação a diferentes testes de sensibilidade e representa adequadamente a distribuição de condutividade elétrica sob o perfil, sendo aqui utilizada como ponto de partida para o método empírico empregado. A técnica empírica aqui proposta é bastante simples, baseada na introdução de um condutor (ou um resistor) perfeito em diferentes profundidades do modelo de distribuição de condutividades e verificando seu efeito no ajuste dos dados (RMS) por cálculo direto usando o programa empregado na inversão dos dados. Os resultados obtidos mostram que a profundidade limite de validade da interpretação 2D do modelo geoelétrico é geralmente dada pela fase do modo transverso elétrico (TE) de propagação do sinal eletromagnético (EM), enquanto o limite máximo de propagação desse sinal é dado pela fase do modo transverso magnético (TM). Em comparação com as profundidades de investigação obtidas pelo método heurístico, a metodologia empírica mostra comportamento semelhante nas variações de profundidade, mas fornece variações laterais mais compatíveis com o processo difusivo de propagação das ondas EM.Palavras-chave: sondagem magnetotelúrica; modelo geoelétrico bidimensional; profundidade máxima de confiabilidade do modelo 

Fast and Stable Two-dimensional Inversion of Magnetotelluric Data

1995 ◽  
Author(s):  
M.S. Zhdanov ◽  
P.P de Lugao ◽  
O. Portniaguine
Keyword(s):  
Two Dimensional ◽  
Magnetotelluric Data
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