Magnetotelluric 3-D inversion—a review of two successful workshops on forward and inversion code testing and comparison

Miensopust, M. P.; Queralt, Pilar; Jones, Alan G.

doi:10.1093/gji/ggt066

Cited by 99 publications

(57 citation statements)

References 38 publications

(93 reference statements)

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“…Farquharson et al 2002;Siripunvaraporn et al 2005a;Avdeev & Avdeeva 2009;Egbert & Kelbert 2012;Kelbert et al 2014;Grayver 2015;Usui 2015) has improved the characterization of the subsurface in these situations, and 3-D inversion has become a more routine procedure for the EM community, although more experience is needed before it becomes as firmly established as is 2-D inversion (e.g. Miensopust et al 2013;Tietze & Ritter 2013;Kiyan et al 2014).…”

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confidence: 99%

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The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

Campanyà¹,

Ogaya²,

Jones³

et al. 2016

Geophys. J. Int.

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: The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study. -Geophysical Journal International, 207, 3, pp. 1818-1836 S U M M A R YAs a consequence of measuring time variations of the electric and the magnetic field, which are related to current flow and charge distribution, magnetotelluric (MT) data in 2-D and 3-D environments are not only sensitive to the geoelectrical structures below the measuring points but also to any lateral anomalies surrounding the acquisition site. This behaviour complicates the characterization of the electrical resistivity distribution of the subsurface, particularly in complex areas. In this manuscript we assess the main advantages of complementing the standard MT impedance tensor (Z) data with interstation horizontal magnetic tensor (H) and geomagnetic transfer function (T) data in constraining the subsurface in a 3-D environment beneath a MT profile. Our analysis was performed using synthetic responses with added normally distributed and scattered random noise. The sensitivity of each type of data to different resistivity anomalies was evaluated, showing that the degree to which each site and each period is affected by the same anomaly depends on the type of data. A dimensionality analysis, using Z, H and T data, identified the presence of the 3-D anomalies close to the profile, suggesting a 3-D approach for recovering the electrical resistivity values of the subsurface. Finally, the capacity for recovering the geoelectrical structures of the subsurface was evaluated by performing joint inversion using different data combinations, quantifying the differences between the true synthetic model and the models from inversion process. Four main improvements were observed when performing joint inversion of Z, H and T data: (1) superior precision and accuracy at characterizing the electrical resistivity values of the anomalies below and outside the profile; (2) the potential to recover high electrical resistivity anomalies that are poorly recovered using Z data alone; (3) improvement in the characterization of the bottom and lateral boundaries of the anomalies with low electrical resistivity; and (4) superior imaging of the horizontal continuity of structures with low electrical resistivity. These advantages offer new opportunities for the MT method by making the results from a MT profile in a 3-D environment more convincing, supporting the possibility of high-resolution studies in 3-D areas without expending a large amount of economical and computational resources, and also offering better resolution of targets with high electrical resistivity.

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confidence: 99%

“…Vozoff 1991;Berdichevsky et al 1998;Bedrosian 2007;Berdichevsky & Dmitriev 2008;Chave & Jones 2012;Miensopust et al 2013). The capacity at recovering low electrical resistivity structures is a particular strength of the MT method as a geophysical technique when characterizing geoelectrical structures from the first few metres to the asthenosphere (e.g.…”

mentioning

confidence: 99%

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

Campanyà¹,

Ogaya²,

Jones³

et al. 2016

Geophys. J. Int.

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“…In the hand of an expert user, manual methods such as forward modelling and constraints based on the interpretation of other information can be highly powerful, but the result strongly depends on the user and can be biased by her expectations. Most automated procedures such as inversion algorithms also require some user-defined quantities, but in most cases the major structures will be comparable (e.g., Miensopust et al 2013).…”

Section: Cooperative and Constrained Inversionmentioning

confidence: 99%

Integrating Electromagnetic Data with Other Geophysical Observations for Enhanced Imaging of the Earth: A Tutorial and Review

Moorkamp

2017

Surv Geophys

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In this review, I discuss the basic principles of joint inversion and constrained inversion approaches and show a few instructive examples of applications of these approaches in the literature. Starting with some basic definitions of the terms joint inversion and constrained inversion, I use a simple three-layered model as a tutorial example that demonstrates the general properties of joint inversion with different coupling methods. In particular, I investigate to which extent combining different geophysical methods can restrict the set of acceptable models and under which circumstances the results can be biased. Some ideas on how to identify such biased results and how negative results can be interpreted conclude the tutorial part. The case studies in the second part have been selected to highlight specific issues such as choosing an appropriate parameter relationship to couple seismic and electromagnetic data and demonstrate the most commonly used approaches, e.g., the cross-gradient constraint and direct parameter coupling. Throughout the discussion, I try to identify topics for future work. Overall, it appears that integrating electromagnetic data with other observations has reached a level of maturity and is starting to move away from fundamental proof-of-concept studies to answering questions about the structure of the subsurface. With a wide selection of coupling methods suited to different geological scenarios, integrated approaches can be applied on all scales and have the potential to deliver new answers to important geological questions.

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“…It was computed for a model which was originally unknown to the participants and was only disclosed at the end of the workshop. Various researchers inverted this data set and a comparison of the inversion results can be found in Miensopust et al (2013). The model is based on the COMMEMI 3D-2 model (Zhdanov et al 1997), but a 1 km thick, near-surface cover layer of 50 m is introduced to avoid numerical problems and effects due to outcropping structure.…”

Section: Distortion According To the Groom-bailey-decompositionmentioning

confidence: 99%

“…In this case the diagonal elements play as important a role as the off-diagonal ones when inverting the distorted data set. For more details on the generation of the data see Miensopust et al (2013).…”

Section: Distortion According To the Groom-bailey-decompositionmentioning

confidence: 99%

Three-dimensional inversion of magnetotelluric impedance tensor data and full distortion matrix

Avdeeva¹,

Moorkamp²,

Avdeev³

et al. 2015

Geophysical Journal International

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S U M M A R YGalvanic distortion of magnetotelluric (MT) data due to small-scale surficial bodies or due to topography is one of the major factors that prevents accurate imaging of the subsurface. We present a 3-D algorithm for joint inversion of MT impedance tensor data and a frequencyindependent full distortion matrix that circumvents this problem. We perform several tests of our algorithm on synthetic data affected by different amounts of distortion. These tests show that joint inversion leads to a better conductivity model compared to the inversion of the MT impedance tensor without any correction for distortion effects. For highly distorted data, inversion without any distortion correction results in strong artefacts and we cannot fit the data to the specified noise level. When the distortion is reduced, we can fit the data to an RMS of one, but still observe artefacts in the shallow part of the model. In contrast, in both cases our joint inversion can fit the data within the assumed noise level and the resulting models are comparable to the inversion of undistorted data. In addition, we show that the elements of the full distortion matrix can be well resolved by our algorithm. Finally, when inverting undistorted data, including the distortion matrix in the inversion only results in a minor loss of resolution. We therefore consider our new approach a promising tool for the general analysis of field MT data.

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Magnetotelluric 3-D inversion—a review of two successful workshops on forward and inversion code testing and comparison

Cited by 99 publications

References 38 publications

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

Integrating Electromagnetic Data with Other Geophysical Observations for Enhanced Imaging of the Earth: A Tutorial and Review

Three-dimensional inversion of magnetotelluric impedance tensor data and full distortion matrix

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