2‐D inversion of magnetotelluric data over 3‐D structures

Lugăo, Patricia Pastana de; Kriegshäuser, Berthold

doi:10.1190/1.1885911

Cited by 4 publications

(3 citation statements)

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“…A number of authors have already investigated the problems and limitations of using 2-D approaches, when modelling and inverting 3-D data and described potential problems with artefacts especially introduced by the TE mode data (e.g. de Lugão & Kriegshäuser 1997;Garcia et al 1999;Ledo et al 2002;Ledo 2005). For some geometries, the TM mode data are more affected (e.g.…”

Section: -D Modelsmentioning

confidence: 99%

The Eyjafjallajökull volcanic system, Iceland: insights from electromagnetic measurements

Miensopust

Jones

Hersir

et al. 2014

Geophysical Journal International

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Electromagnetic (EM) measurements were performed 1 yr after the most recent eruption of the Eyjafjallajökull volcano (2010 March-May), southern Iceland, to investigate the geometries of structures of the volcano system through imaging lateral and vertical electrical resistivity variations. High quality magnetotelluric (MT) and transient EM data were acquired at 26 sites around Eyjafjallajökull and the southern part of Mýrdalsjökull (the glacier covering the Katla volcano). For some locations the steep topography has influence on the MT responses, but this can be compensated by static shift correction using the transient EM data and/or including topography in the modelling mesh. As expected, qualitative indicators, such as phase tensor ellipses and induction arrows, infer a concentration of conductive material beneath Eyjafjallajökull. 2-D resistivity models are presented from data along three profiles: Along the river valley of Markarfljót in the north, along the coast to the south of Eyjafjallajökull and across the mountain ridge Fimmvör uháls between Eyjafjallajökull and Katla. In numerous previous studies elsewhere in Iceland a conductive layer at about 10-30 km depth was identified. From our data, such a conductor is also present in the northeastern part of the investigated area. Additionally, all profiles show a conductive, near-surface layer at about 1-2 km depth, as seen previously for example at the Hengill geothermal region. A connection between those two conductive layers is indicated by the resistivity models, and the dyke (flank eruption) and the conduit (summit eruption) appear as vertical conductive structures. It is uncertain if the vertical connection is permanent or a transient feature as consequence of the eruptive sequences. Subsequent measurements are required when the volcano system is quiescent.

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Section: -D Modelsmentioning

confidence: 99%

The Eyjafjallajökull volcanic system, Iceland: insights from electromagnetic measurements

Miensopust

Jones

Hersir

et al. 2014

Geophysical Journal International

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show abstract

“…Additionally, several other authors have addressed some specific points (i.e. Park, 1985;Szarka et al, 1994;Szarka et al, 1995;de Lugao and Kriegshauser, 1997;Spichak et al, 1999, Spichak, 1999Dosso and Chen, 2000;Osella et al, 2000;Á da´m and Kis, 2001;Ledo et al, 2002a). In this review, we consider two main situations for the interpretation of 3-D magnetotelluric data using 2-D techniques.…”

Section: Introductionmentioning

confidence: 95%

2-D Versus 3-D Magnetotelluric Data Interpretation

Ledo

2005

Surv Geophys

103

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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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“…Additionally, several other authors have addressed some specific points (i.e. Park, 1985;Szarka et al, 1994;de Lugao and Kriegshauser, 1997;Spichak et al, 1999, Spichak, 1999Dosso and Chen, 2000;Osella et al, 2000;Á da´m and Kis, 2001;Ledo et al, 2002a). In this review, we consider two main situations for the interpretation of 3-D magnetotelluric data using 2-D techniques.…”

Section: Introductionmentioning

confidence: 99%

2-D Versus 3-D Magnetotelluric Data Interpretation

Ledo¹

2006

Surv Geophys

View full text Add to dashboard Cite

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.

show abstract

2‐D inversion of magnetotelluric data over 3‐D structures

Cited by 4 publications

References 0 publications

The Eyjafjallajökull volcanic system, Iceland: insights from electromagnetic measurements

The Eyjafjallajökull volcanic system, Iceland: insights from electromagnetic measurements

2-D Versus 3-D Magnetotelluric Data Interpretation

2-D Versus 3-D Magnetotelluric Data Interpretation

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