Magnetotelluric Impedance Tensor Research Articles

Lateral electrical conductivity variations along the Main Himalayan thrust in the northwestern Himalayas: Insights from 3D Magnetotelluric forward modeling

Understanding the arc parallel variation on the geometry of the Main Himalayan Thrust (MHT) is as important as understanding the arc perpendicular variation in the Himalayas. The geometric variability of the MHT holds significant implications for the occurrence of major and great earthquakes. Three-dimensional magnetotelluric (MT) forward modeling enables the investigation of potential crustal models along the MHT in northwest Himalayas. MT impedance tensors were computed utilizing the 3D forward modeling code MTD3FWD. Previously established MT resistivity and seismic velocity models from various sectors of the northwestern Himalayas were employed as inputs for generating the resistivity mesh necessary for 3D forward modeling. The computed impedance tensors by 3D forward computation were cross-referenced with the original published MT data to validate their accuracy. A lateral resistivity cross section is also derived from the 3D forward model along the sub-Himalaya and lesser-Himalaya region to study the lateral heterogeneity. The lateral resistivity cross-section reveals significant heterogeneity within the crust, marked by both high and low-resistive structures and a possible lateral ramp along the MHT. The geometry of the lateral MHT showcases a gradual incline within the Himachal sector and a steep ramp within the Garhwal and Kumaun sectors in the northwestern Himalayas. The crustal architecture exhibits distinct nearly-vertical resistive and conductive features beneath the study area. Consequently, the crust within this region is characterized by considerable heterogeneity, influenced by a network of subsurface faults and ridges. The Delhi Haridwar Ridge, which exhibits high resistivity, plays a significant role in dictating the lateral dip of the MHT and exerting control over seismic activity patterns in the region.

Northern Limit of the Concealed Bundelkhand Craton: A Synthesis of New Magnetotelluric Results from the Ganga Basin

Abstract The Bundelkhand craton is a relatively small craton of the Indian shield in terms of its exposed surface area. It continues beneath the sediments of the Ganga Basin in NE-to-NNE direction as the Faizabad Ridge. However, its northern extent into the Ganga Basin is not known and the northern margin of the exposed craton is generally taken as the northern limit of the craton. Here, we present a synthesis of new magnetotelluric (MT) results from the Ganga Basin to demarcate the northern limit of the Bundelkhand craton. Broadband MT data were acquired at 148 sites along the four profiles and the MT impedance tensors of 132 sites were used for two-dimensional inversion along these profiles. The top 15 km sections of the geoelectric models along these profiles were used to prepare a conductance map to extract the northern limit of the electrically resistive craton. The results reveal that the northern boundary of the craton lies much to the north of the presently known northern limit. It also follows the basement depth contours of 2 km and 3 km obtained from the aeromagnetic data. Thus, a significant part of the craton is also buried in the Ganga Basin north of its present limit. The areal extent of this new buried block is about 0.82 times the area of the exposed Bundelkhand craton. Together with the Faizabad Ridge, the Bundelkhand craton covers an area of about 1,03,000 sq.km, 72% of which is concealed under the sediments of the Ganga Basin. The results also indicate westward subsurface continuation of at least a part of the craton towards the Great Boundary Fault.

Influence of Tectonic and Geological Structure on GIC in Southern South Island, New Zealand

AbstractAs part of a 5‐year project to assess the risk posed by geomagnetically induced currents (GIC) to the New Zealand electrical transmission network, long‐period magnetotelluric (MT) measurements have been made at 62 sites in southern South Island of New Zealand, a region where there was an absence of previous MT data. The data are largely 3‐dimensional in character, but show distinct features that can be related to the known tectonic and geological structure. In this work we focus on how the measured MT impedance tensors, and a simple interpretation of conductivity structure, can be used to assess the influence of tectonic and geological structure on GIC. We use the impedance tensors to calculate the magnitudes and orientations of induced electric fields in response to various orientations of inducing magnetic field. The electric fields so calculated are then used in a simplified model of the transmission network to calculate GIC at grounded substations. Our results confirm that tectonic/geological structure in the lower South Island and the resulting electrical conductivity variations have important impacts on the GIC magnitude. In the south‐west, smaller induced electric fields, associated with the higher conductivity in that region, lead to much reduced GIC at a substation in that area. In contrast, higher electric fields occurring in a NW‐SE band across the center of the region, contribute to much larger GIC in Dunedin city. Our results thus help explain the observed GIC reported at transformers in the region.

Modelling of subsurface geological structure related to anomalous magnetotelluric phase data exceeding 90° in Central India

SUMMARY We note anomalous phase (>90°) in magnetotelluric (MT) measurements at several stations along the Narmada river course normal to the Tan Shear Zone (TSZ) in central India. We made efforts to derive a possible cause of the anomalous phase by comparing the results of numerical modelling based on the tectonics of the TSZ with the measured impedance tensor data. A zone of multiple reactivations of the TSZ leads to the formation of a damage zone and conjugate Riedel shear faults parallel and normal to the TSZ, respectively. The conjugate Riedel shear faults act as a pathway for the Narmada River course. The multiple tectonic activities associated with the TSZ induce surficial heterogeneity that results in distortion in the MT data. The Mohr circle and phase tensor analysis establish the effect of distortion in the data. To understand the cause of distortion as well as anomalous phase in the present data, we carried out synthetic 3-D modelling. We modelled the damage zone and conjugate Riedel shear faults by a cross shape. From the results, we noted that the near-surface 3-D heterogeneity across the TSZ critically distorted the YX component of the MT impedance tensor due to the strong current channelling. When the current flows across the conjugate Riedel shear zone (Narmada river course) charges are accumulated along the boundaries of near-surface heterogeneity. The charges associated with the current channelling brought out the reversion of the electric field direction that is reflected in the form of an anomalous phase in the YX component of the impedance tensor in measured data.

Electrical Moho and upper mantle metasomatism in the Archaean Bundelkhand craton of the Indian peninsular shield

The Bundelkhand Craton (BKC), one of the Archaean nuclei in the north central part of the Indian shield, has a lesser surface exposure compared to other cratons. Recent magnetotelluric (MT) study in the Central Ganga Basin (CGB) showed NNE-SSW extension of the cratonic block as a transverse ridge and delineated a shear zone within the buried section of the BKC. In the present study, we extend the MT profile to further south with 19 broadband MT sites in the exposed BKC to complement the lithospheric electrical resistivity architecture. Two-dimensional (2-D) geoelectric structure down to 100 km is obtained from inverse modelling of the distortion corrected MT impedance tensors together with the 31 sites in the CGB. The resulting geoelectric model reveals a flat and sharp resistivity contrast at 40–42 km depth, the electrical Moho (e-Moho), separating highly resistive Bundelkhand massif and moderately conductive upper mantle. The 2-D model also brings out two shear zones represented by near-vertical moderately conductive zones within the massif, indicating zones of amalgamation of different fragments of the pre-Bundelkhand craton. In contrast to other major cratons of the Indian shield, the present MT study has delineated a moderately conductive upper mantle beneath the BKC. In view of the estimated low mantle heat flow along with relatively flat topography, we infer metasomatism of the mantle lithosphere by percolation of fluids. We hypothesize that infiltration of fraction of water (H2O) in nominally anhydrous mantle minerals as hydrogen (H) bonded to structural oxygen (O) originated from the subducted oceanic slab has altered the mantle rheology and metasomatized the lithosphere.

Mapping a Magnetic Superstorm: March 1989 Geoelectric Hazards and Impacts on United States Power Systems

AbstractA study is made of the relations between geomagnetic and geoelectric field variation, Earth‐surface impedance, and operational interference (“anomalies”) experienced on electric‐power systems across the contiguous United States during the 13–14 March, 1989, magnetic storm. For this, a 1‐min‐resolution sequence of geomagnetic field maps is constructed from magnetometer time series acquired at ground‐based observatories. Induced geoelectric field maps are calculated by convolving the geomagnetic maps with magnetotelluric impedance tensors. During the storm, anomalies were concentrated where the lithosphere is electrically resistive, and when and where geoelectric field amplitudes were high. This was particularly true in the Mid‐Atlantic, Northeast, and the upper Midwest. Few anomalies were experienced in other parts of the Midwest and across much of the West, where the lithosphere is more conductive, and when and where geoelectric field amplitudes were low. Peak 1‐min‐resolution geoelectric field amplitude ranged from 21.66 V/km in Maine and 19.02 V/km in Virginia to <0.02 V/km in Idaho. Latitude‐dependent organization of geoelectric hazards by auroral‐zone electrojet currents is detectable, but it is much weaker than geographic organization due to surface impedance. Hazardous geoelectric fields were induced during different storm phases, at different local times, and, by inference, by a variety of ionospheric currents. Compared to geoelectric field amplitudes realized across the United States during March 1989, hazard maps used by utility companies to estimate systems exposure have much less geographic detail and a much smaller maximum‐to‐minimum range in geoelectric field amplitude. Future research would benefit from denser geomagnetic monitoring, additional magnetotelluric surveying, and access to power‐system impact data.

Parametric Magnetotelluric Impedance Tensor Estimation

Conventional magnetotelluric (MT) impedance tensor estimation methods are generally based on robust M-estimator spectral analysis along with remote reference (RR) processing to reduce the estimation biases caused by cultural noise. Here, we propose a parametric spectral estimation and system identification-based impedance tensor estimation method and validate it with three representative data segments measured at several USArray sites. The proposed parametric method has the potential to give an accurate and robust estimate of the electromagnetic transfer impedance without an RR while maintaining a smooth and continuous response in accordance with prior physical knowledge. The approach considers the geophysical problem in addition to signal processing and system identification, providing a statistically efficient strategy for electromagnetic transfer impedance estimation of periods from 10 to 10⁴ s.

Linking strike directions to invariant TE and TM impedances of the magnetotelluric impedance tensor

Estimation of the traditional transverse electric (TE) and transverse magnetic (TM) impedances of the magnetotelluric tensor for two-dimensional structures can be decoupled from the estimation of the strike direction with significant implications when dealing with galvanic distortions. Distortion-free data are obtainable by combining a quadratic equation with the phase tensor. In the terminology of Groom–Bailey, the quadratic equation provides amplitudes and phases that are immune to twist, and the phase tensor provides phases immune to both, twist and shear. On the other hand, distortion-free strike directions can be obtained using Bahr's approach or the phase tensor. In principle, this is all that is needed to proceed to a two-dimensional (2D) interpretation. However, the resulting impedances are strike ignorant because they are invariant under coordinate system rotation, and if they are to be related to a geological strike, they must be linked to a particular direction. This is an additional ambiguity to the one of 90° arising in classic strike-determination methods, which must be resolved independently. In this work, we use the distortion model of Groom–Bailey to resolve the ambiguity by bringing back the coupling between impedances and strike in the presence of galvanic distortions. Our approach is a hybrid between existing numerical and analytical methods that reduces the problem to a binary decision, which involves associating the invariant impedances with the correct TE and TM modes. To determine the appropriate association, we present three algorithms. Two of them require optimizing the fit to the data, and the third one requires a comparison of phases. All three keep track of possible crossings of the phase curves providing a clear-cut solution. Synthetic and field data illustrate the performance of the three schemes.Graphical

First Estimations of Geomagnetically Induced Currents in the South of Portugal

AbstractGeomagnetic storms induce electric fields in the conducting Earth, which are the source of geomagnetically induced currents (GICs) in grounded power lines. In this study, we compute time‐varying geoelectric fields induced in the southern region of the Portuguese mainland at the time of the strongest geomagnetic storms during solar cycle 24, using a plane‐wave approximation. The driving geomagnetic storm signals are obtained from series recorded at the Coimbra magnetic observatory. Magnetotelluric impedance tensors used to compute the induced electric field are obtained using a conductivity model that takes into account general features of the local lithology and the proximity to the sea. The first GIC simulations for Portugal are presented, using data from the national high voltage power network. Starting with an a priori standard uniform electric field to compute electromotive forces, we first assess the susceptibility of the power system network given only its topology and resistance parameters. For real storms, we report (i) the clustering of the horizontal geomagnetic time variation around the northwest‐southeast direction, (ii) the simulation of the effect of the western and southern coastlines of the territory over the induced electric field, and (iii) the spotting of the substations most sensitive to storms in the studied region.

Estimating Extreme Geoelectric Field Values for the Australian Region

AbstractThere are a number of global initiatives to understand and mitigate the impacts of extreme space weather on critical infrastructure and modern society. This paper provides the results of an analysis to estimate extreme geoelectric field values for the Australian region to facilitate evaluation of Australia's power system response to extreme geomagnetic storms. Geoelectric fields are calculated using a grid of modeled magnetotelluric impedance tensors obtained from a 3‐D conductivity model of the Australian region. Statistical metrics derived from grids of geoelectric field time series are analyzed as a function of Dst index for different storm days to extrapolate geoelectric fields to extreme storm levels over a range of ground conductivity conditions. For Carrington event storm levels, geoelectric field values of 5.3 ± 3.8 V/km in the north‐south direction and 9.6 ± 4.3 V/km in the east‐west direction are expected for areas of electrically resistive rocks near coastlines that are adjacent to deep highly conductive oceans, and inland, where there are large contrasts between the electrical conductivities of different rock types across Australia. Further, geoelectric field values may change by at least an order of magnitude over the grid spacing interval of 50 km in these areas. The results of the analysis also suggest that upscaling grids of geoelectric field time series derived from an observed storm by the ratio of extreme storm Dst to the observed storm Dst are a valid approach for the Australian region that provides extreme storm scenarios for different storm morphologies.

Quality estimation of magnetotelluric impedance tensors using neural networks

While much of the workflow for geophysical data processing and analysis is automated, final quality assurance typically requires the decisions of skilled human analysts and interpreters. The quality and reliability of geophysical inverse models depends directly on the effectiveness of input data. The influence of spurious data on derived data products used in the inversion has been reduced by this effectiveness. Failure to identify and mitigate bias in data products can lead to costly errors. By applying supervised machine learning (ML), a neural network can be trained to recognize features in data that a human domain expert would identify as characteristic of poor data quality. In this study, we use magnetotelluric (MT) data as an example of a geophysical data set appropriate for such a training exercise. While MT data are used to estimate the resistivity structure of the subsurface, the concepts we discuss are universal to seismic, potential fields, and other geophysical data sets. We train a neural network, pyMAGIQ (Python-based magnetotelluric impedance qualifier), with multiple hidden layers and demonstrate that it successfully generates the nonlinear mapping function required to assess the quality of MT data. The training set is a large database of frequency-domain MT impedance tensors from the National Science Foundation-funded EarthScope MT project. A human-assigned quality index is associated with each impedance. We apply pyMAGIQ to unrated MT data from the United States and Canada and confirm that the ML-assigned quality factors are consistent with those assigned by trained human operators. We also apply sensitivity analysis to the trained neural network. This reveals that the human- and ML-assigned data quality index depends on the magnitude of the confidence limits on (1) the phases and (2) the continuity of the apparent resistivities and phases with respect to frequency.

Invariant TE and TM impedances in the marine magnetotelluric method

SUMMARY The magnetotelluric (MT) impedance tensor has a nil diagonal when one of the axes of the coordinate system coincides with the strike of a 2-D structure. In general, real data are full tensors either because of 3-D effects or measurements not aligned to the geological strike. The usual practice to adapt the field tensor to the 2-D assumption is to rotate to a new system of coordinates. In most cases, there is no single angle of rotation that warranties that the diagonal elements become zeros as in the ideal 2-D case. Even maximizing the off-diagonal elements does not necessarily produce a nil diagonal. Consequently, the 2-D inversions proceed by neglecting whatever there is left in the diagonals. In this work, we explore an alternative that places no constraints on direction but assures a nil diagonal. We use two rotational invariants that compact the four elements of the tensor into only two and reduce in 2-D to the TE and TM impedances. These are obtained readily by solving a quadratic equation. We explore four different scenarios: (1) using the invariants, (2) rotating the tensor perpendicular to the profile, (3) rotating to the average maximum orientation for each station and (4) maximizing the off-diagonal elements of the tensor for each site, frequency to frequency. These approaches were applied to 3-D synthetic and field data. The field data correspond to two marine magnetotelluric surveys in the Gulf of California. In one of them, there is no information on the instrument orientation because the compasses failed. In this case, the rotational invariants come handy to overcome the problem. In the other survey, there was orientation information and the 2-D inversions illustrate the better performance of the invariants relative to the traditional approaches.

Geoelectric Strike Analysis from Magnetotelluric (MT) Data Using Swift and Polar Diagram Methods

The magnetotelluric (MT) method is commonly used to estimate the subsurface conductivity structure. From the point of view of computational resources availability, currently it is a common practice to perform a 2D MT inversion modelling of MT data measured along a profile. For that purpose, the geoelectric strike angle determination from MT data is essential. The geoelectric strike angle can be determined by rotational analysis of the MT impedance tensor. In this paper we compare geoelectrical strike angle from both Swift method and polar diagram analysis by plotting the results as rose diagrams. The results from rotational analysis suffer from 90° ambiguity in the structural direction. Along with information from the regional geology to resolve the ambiguity, the profile for MT 2D modelling can be more appropriately selected. We used MT data from a geothermal prospect to illustrate our exercise.

Modeling Geomagnetically Induced Currents in Australian Power Networks Using Different Conductivity Models

AbstractSpace weather manifests in power networks as quasi‐DC currents flowing in and out of the power system through the grounded neutrals of high‐voltage transformers, referred to as geomagnetically induced currents. This paper presents a comparison of modeled geomagnetically induced currents, determined using geoelectric fields derived from four different impedance models employing different conductivity structures, with geomagnetically induced current measurements from within the power system of the eastern states of Australia. The four different impedance models are a uniform conductivity model (UC), one‐dimensional n‐layered conductivity models (NU and NW), and a three‐dimensional conductivity model of the Australian region (3DM) from which magnetotelluric impedance tensors are calculated. The modeled 3DM tensors show good agreement with measured magnetotelluric tensors obtained from recently released data from the Australian Lithospheric Architecture Magnetotelluric Project. The four different impedance models are applied to a network model for four geomagnetic storms of solar cycle 24 and compared with observations from up to eight different locations within the network. The models are assessed using several statistical performance parameters. For correlation values greater than 0.8 and amplitude scale factors less than 2, the 3DM model performs better than the simpler conductivity models. When considering the model performance parameter, P, the highest individual P value was for the 3DM model. The implications of the results are discussed in terms of the underlying geological structures and the power network electrical parameters.

The magnetotelluric impedance tensor through Clifford algebras: part I — theory

ABSTRACTThe magnetotelluric impedance tensor is analysed in the context of Clifford algebras. In this framework, the tensor is broken down into different parts, each one with a particular geometric algebra meaning, the simplicity of which allows us to deduce a number of known properties and opens up many other possibilities. As examples to show its capabilities, some of the algebraic relationships involving the impedance tensor, such as rotations, Mohr diagrams and phase tensor, are shown under this theory. Rotations are analysed in Clifford algebra and Mohr diagrams, and phase tensor are expressed in Clifford algebra . The galvanic distortion matrix and its transformations are also seen in Clifford algebra , where a number of relationships allow us to recognize the galvanic distortion in a measured two‐dimensional/three‐dimensional impedance tensor. These relationships are useful as constraints to determine the galvanic distortion parameters.

Extreme‐Value Geoelectric Amplitude and Polarization Across the Northeast United States

AbstractMaps are presented of extreme‐value geoelectric field amplitude and horizontal polarization for the Northeast United States. These maps are derived from geoelectric time series calculated for sites across the Northeast by frequency‐domain multiplication (time‐domain convolution) of 172 magnetotelluric impedance tensors, acquired during a survey, with decades‐long, 1‐min resolution time series of geomagnetic variation, acquired at three magnetic observatories. The maps show that, during intense magnetic storms, high geoelectric amplitude hazards are realized across electrically resistive, igneous and metamorphic rock of the Appalachian Mountains and the New England Highlands, while low geoelectric hazards are realized across electrically conductive, sedimentary rock of the Appalachian Plateau and the Mid‐Atlantic Coastal Plain. From statistical extrapolation, once‐per‐century (100‐year) geoelectric amplitudes are highest at a site in Virginia at 25.44 V/km (followed by a site in Maine at 21.75 V/km and a site in Connecticut at 19.39 V/km); 100‐year geoelectric amplitude exceeds 10 V/km at 12 sites across the northeast; geoelectric amplitude is lowest at a site in Virginia at 0.05 V/km. Average errors for these values are estimated to be about 38%, or much less than the more than 2 orders of magnitude range seen in geoelectric amplitudes from one survey site to another across the northeast. It is noteworthy that geoelectric fields tend to be most (least) polarized at locations with high (low) geoelectric hazard. Furthermore, geoelectric fields over the Appalachians tend to be polarized southeast‐to‐northwest, or generally in a direction orthogonal to the southwest‐to‐northeast geological strike. Results reported here inform utility companies in projects for evaluating and managing the response of power grid systems to the deleterious effects of geomagnetic disturbance.

The magnetotelluric impedance tensor through Clifford algebras: part II — a constrained stochastic heuristic method for recovering the magnetotelluric regional impedance tensor in 2D/3D case

ABSTRACTA method for obtaining the galvanic distortion matrix is presented so that the regional impedance tensor (free of distortion) is recovered. The method is a constrained stochastic heuristic method, which consists in randomly exploring the space of the distortion parameters. Constraints are imposed on the shortest periods of the regional impedance tensor that, at these short periods, tends to be two dimensional (or one dimensional). Depending on the constraints used, two different methods to recover the regional impedance tensor in this 2D/3D case are presented. Method 1 needs to find the strike of the short periods and Method 2 applies to the measurement directions. Twist, shear and anisotropy parameters are obtained. Thus, the regional impedance tensor is recovered with the only exception being the vertical shift due to the gain, which is equal for all the components of the tensor. Examples with synthetic impedance tensors from 2D/3D models perturbed with galvanic distortion are presented to illustrate how the algorithm works. The presence of noise in data is considered and rules for proceeding are provided. The same examples perturbed by Gaussian noise together with experimental data illustrate the capabilities of the algorithm.

The Impact of Magnetic Field Temporal Sampling on Modeled Surface Electric Fields

AbstractDescriptions of the surface magnetic‐to‐electric field relationship, using magnetotelluric impedance tensors, have seen refinement in recent years. Correspondingly, models of geomagnetically induced currents flowing in power line conductors using input from more fundamental observables (e.g., the surface magnetic field or solar wind drivers) have become more sophisticated. Magnetometer data used for purposes of surface electric field modeling typically have cadences between 1 s and 1 min. Using 1‐D and 3‐D magnetotelluric impedance tensors, we quantify the effect of magnetometer cadence on modeled peak surface electric fields during the 22 June 2015, 17 March 2015, and 2 October 2013 geomagnetic storms. It is shown that 1‐min magnetometer data sampling leads to median biases in the peak electric field of 10–20% magnitude attenuation and 2–17° in direction (depending on the storm) across the United States using the Fernberg 1‐D conductivity models and 11–26% (0.9–8° ) using the 3‐D impedance tensors derived from the USArray magnetotelluric survey. The largest 10% of attenuations almost entirely occur near low‐resistivity subsurface structures in the western and eastern United States, reaching a 50% median attenuation during the 17 March 2015 event. It is concluded that cadence, local geology, and the spectral content of the geomagnetic field all play a significant role in the bias.

Filtering of noisy magnetotelluric signals by SOM neural networks

This work presents a systematic study for testing the effectiveness of Self-Organizing Map (SOM) neural networks in filtering magnetotelluric (MT) data affected by cultural noise. Although the MT method is widely used for geophysical investigation of the Earth’s interior, it is very sensitive to anthropogenic noise sources (e.g., power lines, electric railways, etc.), which can generate transient artificial electromagnetic fields disturbing the MT records. Thus, when not properly detected, man-made noises could lead to a distortion of the MT impedance tensors and consequently to wrong estimate of the resulting subsoil resistivity distribution. The choice to use SOM networks to filter noisy MT data comes from the expectation that the impedance tensors, estimated by Discrete Wavelet Transform analysis of MT time series, will cluster differently in presence of noise. This expectation is confirmed by the results of our extensive study on synthetic MT signals affected by temporally localized noise, which show that noisy and noise-free impedance tensor values distribute in well separate clusters. Moreover, as the SOM analysis provides a grid of weights (clusters), each one close to a particular subset of the input data, a criterion is proposed for selecting the cluster that gives the most reliable impedance tensor estimate. An application of the proposed SOM-based filtering procedure to actual MT data demonstrates its efficiency in denoising real MT signals.

Crustal structure of a young collision zone: the Arabia\u2013Eurasia collision in northeastern Turkey investigated by magnetotelluric data

The northeastern Turkey is located at the intensely deformed east Anatolian Collision Zone that is formed by the collision of the Arabian Plate with Eurasia. The region is one of the best examples of the continental collision zone in the world and exhibits an active north–south shortening and a young and widespread volcanism. In northeastern Anatolia, the ongoing motions of the Arabian and Eurasian Plates through a range of deformation processes have generated the Erzurum–Kars Plateau, a region of large-scale deformation and uplift observed at surface. However, the nature of deformation driven by the continental collision remains unresolved at depth. In this study, magnetotelluric (MT) data recorded at 74 sites constituting two intersecting profiles have been used to construct the characteristic electrical conductivity pattern associated with the intensely deformed east Anatolian Collision Zone beneath the Erzurum–Kars Plateau, northeastern Turkey, with the aim of imaging the 3D distribution of fluids in order to link it with subsurface rheological conditions. An equal number of colocated transient electromagnetic (TEM) sounding data were used to allow the static shift correction of the MT data; a borehole was also drilled inside the study area. We ran a one-dimensional inversion of TEM data in order to determine shift in MT data and a three-dimensional inversion using full components of MT impedance tensor previously corrected for static shift. The resulting models showed that two distinct conductive zones probably indicating local accumulation of melt exist at mid-to-lower crustal depths (15–45 km) throughout the Erzurum–Kars Plateau. The spatial distribution of these anomalously conductive zones mechanically characterizes weak areas that may permit flow of crustal materials in the collision zone. These conductive zones have been previously identified further west of the collision zone, which implies that the electrical characteristic of the collision zone is continuous from west to east beneath the Anatolian Plateau. The spatial extent of the conductive zones may suggest the presence of two localized crustal flow channels situated laterally parallel to the orogeny. These findings can potentially contribute to understanding of the crustal structure of collision zones, in particular east Anatolian Collision Zone, and the hypothesis that crustal flow can occur in orogenic belts.