Magnetotelluric inversion for anisotropic conductivities in layered media

Pek, Josef; Santos, Fernando A. Monteiro

doi:10.1016/j.pepi.2006.03.023

Cited by 52 publications

(44 citation statements)

References 34 publications

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“…Further evidence for anisotropic features of the Earth's crust and upper mantle were provided by combining MT results with seismic parameters, that is, obtained via shear wave splitting analyses (Frederiksen et al, 2006;Hamilton et al, 2006;Padilha et al, 2006). For quantitative interpretation, one-dimensional (1-D) inversion (Pek & Santos, 2006) and 2-D modeling (Pek & Verner, 1997) of anisotropic media were applied to real data. In recent years, significant progress was achieved in both 2-D inversion (Baba et al, 2006;Key, 2016) and 3-D modeling (Löwer & Junge, 2017;Wang & Fang, 2001;Weidelt, 1999;Xiao et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Electrically Anisotropic Crust From Three‐Dimensional Magnetotelluric Modeling in the Western Junggar, NW China

et al. 2019

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An island arc environment related to intraoceanic subduction or ridge subduction from the Late Carboniferous to the Early Permian has been proposed for the formation of Western Junggar, NW China, situated in the southwest of Central Asian Orogenic Belt. However, the details and consequences of the subduction remain controversial. To further identify the relics of the Late Carboniferous subduction at depth, three magnetotelluric profiles were deployed. Phase tensors, real induction arrows, and three‐dimensional (3‐D) isotropic resistivity models indicate the presence of a 3‐D anisotropic resistivity structure in the crust. Consequently, a 3‐D anisotropic resistivity model was constructed by forward modeling. The 3‐D anisotropic resistivity model contains two azimuthally anisotropic middle‐upper crust anomalies with minimum resistivity striking N90°E at depths of 5 to 20 km, and an azimuthally anisotropic lower crust anomaly with minimum resistivity striking N20°E at depths of 20 to 46 km. The electrically anisotropic anomalies are closely related to relatively high shear‐wave velocities with significant negative radial anisotropy. The anisotropies in the middle‐to‐upper crust and the lower crust are related to the oceanic ridge (N90°E) subduction with a slab window in the Late Carboniferous and the remnant oceanic slab, respectively. The magnetotelluric observations support a NW70° subduction with an intraoceanic ridge‐transform system in the Late Carboniferous and a remnant oceanic slab trapped in Western Junggar.

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Section: Introductionmentioning

confidence: 99%

Electrically Anisotropic Crust From Three‐Dimensional Magnetotelluric Modeling in the Western Junggar, NW China

et al. 2019

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“…The inversion algorithm of Pek & Santos (2006) was used to generate smooth 1D anisotropic resistivity models at each station. The algorithm minimises the sum of the model structure, anisotropy, and data-model misfit, and returns the maximum and minimum horizontal resistivity and the anisotropy strike.…”

Section: Modelling Koroit Regionmentioning

confidence: 99%

“…The algorithm minimises the sum of the model structure, anisotropy, and data-model misfit, and returns the maximum and minimum horizontal resistivity and the anisotropy strike. For the structure penalty values we used the roughness penalty (Constable et al 1987;Pek & Santos 2006). For the anisotropy penalty we used the ℓ2-norm of the anisotropy.…”

Section: Modelling Koroit Regionmentioning

confidence: 99%

“…In the inversions, penalty weights can be chosen for both the model roughness and the anisotropy, with higher penalty weights corresponding to smoother and less anisotropic models and (in general) poorer fits to the data, and lower weights corresponding to rougher and more anisotropic models (Pek & Santos 2006). The aim in running the inversions is to find the optimal trade-off between data-model misfit and model roughness.…”

Section: Modelling Koroit Regionmentioning

confidence: 99%

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Imaging fracture permeability using magnetotellurics

Kirkby

Heinson

Holford

2016

ASEG Extended Abstracts

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SUMMARYWe present 1D anisotropic inversions of magnetotelluric data in two regions of the Otway Basin; Koroit, Victoria, and Penola, South Australia. In the Koroit region we have delineated an electrically anisotropic layer at approximately 2.5 to 3.5 km depth; this corresponds to the upper part of the Lower Cretaceous Crayfish Group, a known reservoir unit. The anisotropy strike is consistent between stations at approximately 160° east of north. We interpret the anisotropy at Koroit as resulting from pervasive NNW oriented, fluid-filled fractures, resulting in enhanced bulk electrical and hydraulic conductivity. This interpretation is consistent with permeability data from well formation tests. It is also consistent with the orientation of mapped faults in the area, which are favourably oriented for reactivation in the current stress field. In Penola, no persistent anisotropic layer has been defined even though the areas are geologically similar. The difference in the resistivity structure may reflect differences in the density of fractures or their fill material. Alternatively, it may reflect small differences in the amount by which the fractures are open, resulting from differences in the stress field and fracture orientation in each area.

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“…The smoothing parameters in the inversion define the trade-off between model roughness and misfit, and there will be always a variety of models (with different degrees of roughness) which fit the data to a similar degree. As a consequence of this regularization process, most MT inversions are smooth and do not resolve sharp contrasts and conductors are often smeared to depth (for a review on inversion, see, e.g., Pek and Santos 2006;Rodi and Mackie 2012; for approaches including sharp boundaries, see e.g. Smith et al 1999;McGary et al 2014).…”

Section: Introductionmentioning

confidence: 99%

On the Coupling of Geodynamic and Resistivity Models: A Progress Report and the Way Forward

Heise

Ellis

2015

Surv Geophys

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Magnetotelluric (MT) studies represent the structure of crust and mantle in terms of conductivity anomalies, while geodynamic modelling predicts the deformation and evolution of crust and mantle subject to plate tectonic processes. Here, we review the first attempts to link MT models with geodynamic models. An integration of MT with geodynamic modelling requires the use of relationships between conductivity and rheological parameters such as viscosity and melt fraction, which are provided by laboratory measurements of rock properties. Owing to present limitations in our understanding of these relationships, and in interpreting the trade-off between scale and magnitude of conductivity anomalies from MT inversions, most studies linking MT and geodynamic models are qualitative rather than providing hard constraints. Some recent examples attempt a more quantitative comparison, such as a study from the Himalayan continental collision zone, where rheological parameters have been calculated from a resistivity model and compared to predictions from geodynamic modelling. We conclude by demonstrating the potential in combining MT results and geodynamic modelling with examples that directly use MT results as constraints within geodynamic models of ore bodies and studies of an active volcano-tectonic rift.

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Magnetotelluric inversion for anisotropic conductivities in layered media

Cited by 52 publications

References 34 publications

Electrically Anisotropic Crust From Three‐Dimensional Magnetotelluric Modeling in the Western Junggar, NW China

Electrically Anisotropic Crust From Three‐Dimensional Magnetotelluric Modeling in the Western Junggar, NW China

Imaging fracture permeability using magnetotellurics

On the Coupling of Geodynamic and Resistivity Models: A Progress Report and the Way Forward

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