Understanding telluric distortion matrices

Smith, J. Torquil

doi:10.1111/j.1365-246x.1995.tb03549.x

Cited by 112 publications

(116 citation statements)

References 9 publications

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“…Local distortion of the regional electromagnetic field caused by small-scale inhomogeneities can be removed by fitting a decomposition model [Bahr, 1988[Bahr, , 1991Smith, 1995]. The upper two rows of Figure 3 show results of the geoelectric strike using the conventional and phase-sensitive method.…”

Section: Dimensionality and Geoelectric Strikementioning

confidence: 99%

“…The inversion algorithm now attempts to find a smooth solution close to the a priori [Swift, 1967] and (e -h) phase-sensitive strike [Bahr, 1988] for various frequency ranges. (k) Multifrequency strike angles for whole sites according to Smith [1995]. In all histograms, except for Figure 3k, a circle represents 10 data points.…”

Section: Eastward Dip Of the Fzcmentioning

confidence: 99%

“…[21] Smith [1995] suggested to calculate a single best fitting strike angle for the whole period range at each site ( Figure 3k): For a majority of sites, the derived strike angle matches the WF strike. A final analysis of the data is based on the multisite-multifrequency approach by McNeice and Jones [2001], in which the data of all sites are decomposed within predefined frequency ranges (bandwidth of half a decade).…”

Section: Dimensionality and Geoelectric Strikementioning

confidence: 99%

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Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

2004

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[1] Large-scale strike-slip fault zones are often imaged as electrically conductive structures in the brittle crust. However, the relationship of conductivity and internal architecture of the fault zone remains largely unclear. This paper presents results of a study designed to compare the record of structural deformation across a fault zone with its electrical conductivity image. Two high-resolution magnetotelluric profiles trend perpendicularly across the West fault, a branch of the Precordilleran fault system in northern Chile. The magnetotelluric and geomagnetic response functions in the frequency range from 1000 Hz to 0.1 Hz clearly image a fault zone conductor (FZC) about 350 m wide and 1500 m deep, trending along the surface trace of the fault. The position of the FZC and its geometric properties (width, dip) correlate with a region of intense fluid alteration and the orientation of fault-related damage elements (minor faults, fractures). According to estimates of fluid salinity and rock porosity, the conductivity anomaly results from meteoric water penetrating into a permeable zone. This suggests that the increase in electrical conductivity is causally related to a mesh of minor faults and fractures, acting as a pathway for fluids. The FZC reflects the central and most fractured part of the damage zone. In view of similar published magnetotelluric studies, we infer a dependency of a fault's state of activity and the characteristics of the FZC such as its conductance, width, and depth extent. Ongoing deformation is the controlling factor for maintaining a permeable and electrically conductive fracture network.

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Section: Dimensionality and Geoelectric Strikementioning

confidence: 99%

Section: Eastward Dip Of the Fzcmentioning

confidence: 99%

Section: Dimensionality and Geoelectric Strikementioning

confidence: 99%

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Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

2004

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“…The first step is the detection and correction of distortion caused by structures of scale much smaller than those of interest. For 2-D data, application of the techniques proposed by Zhang et al (1987), Jones (1988), Bailey (1989, 1991), Bahr (1991), Groom and Bahr (1992), Jones and Groom (1993), Chakidri et al (1992), Chave and Smith (1994), Smith (1995), Spitzer (2001), and Ledo et al (2002b) usually suffice. For 3-D data, the methods proposed by Ledo et al (1998), Utada et al (2000), and Garcı´a and Jones (2002) are advocated.…”

Section: Data Selectionmentioning

confidence: 99%

2-D Versus 3-D Magnetotelluric Data Interpretation

Ledo¹

2006

Surv Geophys

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Abstract. In recent years, the number of publications dealing with the mathematical and physical 3-D aspects of the magnetotelluric method has increased drastically. However, field experiments on a grid are often impractical and surveys are frequently restricted to single or widely separated profiles. So, in many cases we find ourselves with the following question: is the applicability of the 2-D hypothesis valid to extract geoelectric and geological information from real 3-D environments? The aim of this paper is to explore a few instructive but general situations to understand the basics of a 2-D interpretation of 3-D magnetotelluric data and to determine which data subset (TE-mode or TM-mode) is best for obtaining the electrical conductivity distribution of the subsurface using 2-D techniques. A review of the mathematical and physical fundamentals of the electromagnetic fields generated by a simple 3-D structure allows us to prioritise the choice of modes in a 2-D interpretation of responses influenced by 3-D structures. This analysis is corroborated by numerical results from synthetic models and by real data acquired by other authors. One important result of this analysis is that the mode most unaffected by 3-D effects depends on the position of the 3-D structure with respect to the regional 2-D strike direction. When the 3-D body is normal to the regional strike, the TE-mode is affected mainly by galvanic effects, while the TM-mode is affected by galvanic and inductive effects. In this case, a 2-D interpretation of the TM-mode is prone to error. When the 3-D body is parallel to the regional 2-D strike the TE-mode is affected by galvanic and inductive effects and the TM-mode is affected mainly by galvanic effects, making it more suitable for 2-D interpretation. In general, a wise 2-D interpretation of 3-D magnetotelluric data can be a guide to a reasonable geological interpretation.

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“…Vozoff, 1991;Simpson and Bahr, 2005), 66 dimensionality analysis is a common procedure for determining, prior to modeling, 67 whether the measured data or computed responses (impedance tensor, Z; tipper, T; 68 apparent resistivities, ρ ij ; and phases, φ ij ) at a given frequency (ω) correspond to 1D, 2D 69 or 3D geoelectrical structures. It also allows identification and quantification of 70 distortions (Kaufman, 1988;Groom and Bailey, 1989;Smith, 1995) and, when 71 applicable, recovery of the directionality (strike) of the structures. Dimensionality 72 analysis techniques search for particular relationships between the components of the 73 magnetotelluric impedance tensor, Z(ω) (e.g.…”

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confidence: 99%

Dimensionality imprint of electrical anisotropy in magnetotelluric responses

Martí

Queralt

Ledo

et al. 2010

Physics of the Earth and Planetary Interiors

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To cite this version:A. Martí, P. Queralt, J. Ledo, C. Farquharson. Dimensionality imprint of electrical anisotropy in magnetotelluric responses. Physics of the Earth and Planetary Interiors, Elsevier, 2010, 182 (3-4) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Understanding telluric distortion matrices

Cited by 112 publications

References 9 publications

Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

2-D Versus 3-D Magnetotelluric Data Interpretation

Dimensionality imprint of electrical anisotropy in magnetotelluric responses

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