The tectonic history of southern Africa includes Archean craton formation, multiple episodes of subduction and rifting and some of the world's most significant magmatic events. Lithospheric models based on seismological and magnetotelluric data show highly heterogeneous crustal structure, significant anomalies in the lithospheric mantle and strong variations of the depth to the lithosphere-asthenosphere boundary. While some of the spatial patterns agree between different geophysical methods, there are also significant differences in the geometry and location of many structures. I perform a joint inversion of magnetotelluric and satellite gravity data to reconcile these apparent discrepancies. Resistivity and density are coupled through a newly developed Variation of Information constraint which strives to establish a one-to-one relationship between the two quantities. This allows the resistivity-density relationship to evolve data driven during the inversion. The final combined resistivity-density model shows detailed lithospheric and sub-lithospheric structure below the Kaapvaal Craton and adjacent mobile belts. In addition, the retrieved parameter relationship exhibits several branches indicating strong variations in composition. Compared to results from a similar inversion in the western United States, the inversion indicates significantly less fluid related low resistivity anomalies and a dominance of high-density low-resistivity structures. This corroborates earlier ideas that fluids are difficult to contain within in the Earth over long time scales. I will discuss the implications for the tectonic evolution of the region and for the interpretation of low resistivity anomalies world-wide.

How to cite: Moorkamp, M.: An integrated resistivity-density model of Southern Africa, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6068, https://doi.org/10.5194/egusphere-egu23-6068, 2023.

Minimum-structure, or Occam’s, style of inversion deals with the fundamental non-uniqueness of the inverse problem by finding the simplest Earth model that reproduces the observations. As an additional consequence of this approach, minimum-structure inversion is also reliable and robust. Because of these reasons, it has been extensively utilized in mineral and petroleum exploration problems, and lithospheric studies. The method has been adapted and extended in many ways to obtain more reliable and realistic models of the Earth’s subsurface. Joint inversion of geophysical data-sets is one of the most important extensions of minimum-structure inversion. This method can reduce the non-uniqueness of the inverse problem by combing two, or more, different geophysical data-sets in a single inverse problem. Different geophysical methods have different sensitivity to different physical properties, hence, it is hoped that the null space for one type of data can be spanned by the other.

Joint inversion algorithms can be divided into two main categories, structural-based and petrophysical-based joint inversion methods, depending on the coupling measure used between the physical property models. We have adopted the fuzzy c-mean (FCM) clustering technique which is a petrophysical-based method to jointly invert MT and gravity data-sets. The optimization of this method is not as challenging as for structural-based approaches. We have also performed constrained FCM clustering for independent MT and gravity inversions to compare the constructed models of this method with the joint inversion, and independent MT and gravity inversions. The FCM clustering method makes effective use of statistical petrophysical data which may exist in complex geological structures, or can be anticipated, to encourage the inverted physical property values to move towards the a priori petrophysical data as target clusters.

The capabilities of the joint and constrained FCM clustering inversion are evaluated on synthetic and real examples. The constructed density and conductivity models from the joint inversion have a more plausible representation of the true model’s geometry and have a reasonable range of the recovered physical property values compared to the independent constrained FCM clustering technique and independent unconstrained MT and gravity inversions.

Keywords: Fuzzy c-mean clustering, Gravity, Joint inverse problem, MT, Unstructured tetrahedral mesh

How to cite: Kangazian, M. and Farquharson, C.: Fuzzy c-mean clustering joint inversion of magnetotelluric (MT) and gravity data-sets using unstructured tetrahedral meshes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10193, https://doi.org/10.5194/egusphere-egu23-10193, 2023.

The western part of the Anatolian peninsula is defined with an N-S extensional regime and resulting graben systems, referred as the Aegean Extensional Province (AEP). The transition of this extensional regime in the west to E-W compressional regime in the east is bounded by the Isparta Angle, which is a reverse v-shaped major structure developed due to nappe emplacements and related clockwise and counter-clockwise rotations.

The study area is located at the eastern end of the Curuksu Graben and covers the western part of the Acigol Graben. Curuksu Graben is part of the Denizli Horst-Graben system and located between the junction point of three major grabens of the AEP in the west and Acigol Graben in the east. The development of the Graben systems in the AEP, including Curuksu and Acigol grabens, is resulted from two extensional periods interrupted by a compressional phase creating a disconformity between deformed ancient and undeformed neotectonic graben fills in the region. Denizli Horst-Graben System consists of incipient grabens and the modern graben (Curuksu Graben) which is developed with the introduction of the neotectonic regime with the latest Pliocene. This episodic development caused an inward development of normal faults. The compressional regime created many strike-slip and reverse faults in the region while many of the currently active normal faults with strike-slip components are resulted from the present day NNE-SSW extensional phase, including seismically active margin-bounding major faults with seismic hazard potential.

In this study, we have reassessed the data from 300 Magnetotelluric stations which were previously collected by a private contractor for geothermal research purposes. We have investigated the main properties of the data with Phase Tensor analysis and inverted it using ModEM software to reveal 3D subsurface conductivity structure of the area. Our analysis shows that the Phase Tensor ellipses for the highest frequencies indicate rather 1D behavior in compliance with the undeformed, nearly horizontal bedding of the neotectonic graben fills. The strike directions obtained through induction vectors and Phase Tensor ellipses reflects the dominant effect of the major faults and conductive basin fills. The recovered model from the 3D inversion results show the depth of the basin fills and conductivity anomalies due to normal faults controlling the basin development.

How to cite: Karcioglu, G., Turkoglu, E., and Avsar, U.: Resistivity structure of Denizli Çürüksu & Acıgöl Graben connection: Preliminary results from 3D inversion of magnetotelluric data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-347, https://doi.org/10.5194/egusphere-egu23-347, 2023.

We collected long-period magnetotelluric (LMT) data on the 64 stations by using a remotely controlled measurement system in northwestern Anatolia, Türkiye. The data was collected along four nearly parallel 300-km-long lines. In our previous project, we already collected broadband magnetotelluric(MT) data on 358 stations along those four lines. These lines are crossing main tectonic traverses such as North Anatolia Fault Zones, and Intra-Pontid Suture zones.  The remotely controlled MT measurement system provides us to control data quality during measurement and we can change the station location if the data quality is not good in the current stations.  This ensures the good data quality of all MT sites. After the time series analysis and main data processing procedure such as phase tensor decomposition and static shift correction, we interpreted each line's data set by using a two-dimensional inversion algorithm. We also inverted LMT data by using a three-dimensional inversion algorithm. The three-dimensional resistivity model also showed us to main tectonic units as two-dimensional resistivity models. Additionally, crust lithosphere relations were also revealed. We obtained upper and lower crust boundaries by using magnetic data and crust al depth by using gravity data. Those results also validated our resistivity models obtained from MT data inversion. We are going to give preliminary interpretation results of the lithosphere structure of northwest Anatolia in this presentation.

Acknowledgement:  This study is supported by TUBITAK (The Scientific and Technological Research Council of Turkey) Project with Grant Number 119Y197. We thanks TUBITAK.

How to cite: Candansayar, M. E., Demirci, İ., Gündoğdu, N. Y., Oskay, M. D., and Erdoğan, E.: Revealing Lithospheric structure of Northwestern Anatolia by using 3D inversion of Long Period Magnetotelluric Data collected remotely controlled measurement system: Preliminary results, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16800, https://doi.org/10.5194/egusphere-egu23-16800, 2023.

The South China Block (SCB) is located at the junction of the Pacific, Eurasian, and Tethys plates. Their interaction led to large-scale multi-stage mineralization in the SCB during the Mesozoic. Several regional ore-concentration areas, such as the Middle-Lower Yangtze metallogenic belt (MLYMB), the Wuyishan metallogenic belt (WYMB), the Nanling metallogenic belt (NLMB), and the Qinzhou-Hangzhou Metallogenic Belt (QHMB) were formed during this process. However, the mineral types of these metallogenic belts are different. To study the deep mechanisms of the different metallogenic types developed in the same tectonic background at almost the same period, the magnetotelluric sounding (MT) data from 691 sites located mainly within the eastern SCB (Fig.1) are employed to obtain a regional lithospheric 3-D resistivity model.

According to this model, Large-scale low-resistivity bodies extend from the crust to the upper mantle beneath the MLYMB and the QHMB, which are interpreted as channels of upper mantle upwelling. While the upper- to mid-crust beneath the WYMB and the NLMB is characterized by high resistivity with small-scale low-resistivity anomalies, indicating upwelling mantle materials having invaded the crust on a small scale. Large-scale upper mantle low-resistivity anomalies extend along its strike direction beneath the MLYMB and the QHMB. It could be concluded from the resistivity model that deep low-resistivity anomalies and mantle upwelling channels mainly controlled almost all the Mesozoic deposits(Fig.3). However, the scales of low-resistivity anomalies and upper-crust ore-controlling structures are different. Significantly, the upper-mantle low-resistivity anomalies beneath the eastern SCB show a spatial distribution that is gradually shallowing from south to north, probably indicating that the asthenospheric materials are upwelling from south to north, corresponding with the changing progressively of magma and metallogenic activities. We propose that the lithospheric delamination and asthenospheric upwelling caused by the far-field effects of the paleo-Pacific Plate subduction are the source of solid magmatic activities and related metallogeny (Fig.3).

* This work was jointly supported by the China Geological Survey project (DD20160082 and DD20190012) and the SINOPROBE project.

Fig. 1 Distribution of MT stations within the study area. The metallogenic belts after Yan et al. (2021).

Fig.2 Horizontal slices of 3-D resistivity model. Deposit data after Mao et al. (2018).

 Fig.3 A comprehensive 3-D diagram illustrating the possible formation mechanism of the metallogenic belts.

References

Mao, J., Xie, G., Yuan, S., Liu, P., Meng, X., Zhou, Z., & Zheng, W. (2018). Current research progress and future trends of porphyry-skarn copper and granite-related tin polymetallic deposits in the Circum Pacific metallogenic belts. Acta Petrologica Sinica, 34(9), 3-19.

Yan, J., Lü, Q., Luo, F., Cheng, S., Zhang, K., Zhang, Y., et al. (2021). A gravity and magnetic study of lithospheric architecture and structures of South China with implications for the distribution of plutons and mineral systems of the main metallogenic belts. Journal of Asian Earth Sciences, 221, 104938.

How to cite: Dong, J. and Ye*, G.: Relationship between electrical conductivity, metallogeny, and lithospheric structure in South China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7983, https://doi.org/10.5194/egusphere-egu23-7983, 2023.

Directional drilling in the oil fields relies particularly on the "on-fly" measurements of the natural magnetic field (measurements while drilling; MWD); the MWD are eventually used to construct the well path. These measurements are the superposition of the signals from the internal (core and crustal),  external (ionospheric and magnetospheric) sources, and the noise from magnetic elements in the borehole assembly. The internal signals are mostly constant in time and accounted for through the Earth's internal field models. The signals of external origin give rise to diurnal and irregular spatiotemporal magnetic field variations observable in the MWD. One of the common ways to mitigate the effects of these variations in the MWD is to correct readings for the data from an adjacent land-based magnetic observatory/site. This method assumes that the land-based signals are similar to those at the seabed drilling site. This study shows that the sea level and seabed horizontal magnetic fields differ significantly in many oceanic regions. We made this inference from the global electromagnetic induction modelling of the magnetic field using realistic models of conducting Earth and time-varying external sources. To perform such modelling, we elaborated a numerical approach to calculate efficiently the spatiotemporal evolution of the magnetic field. Finally, we propose and validate a formalism allowing researchers to obtain trustworthy seabed signals using measurements at the adjacent land-based site and exploiting the modelling results, thus without needing additional measurements at the seabed site.

How to cite: Kuvshinov, A., Kruglyakov, M., and Nair, M.: A Proper Use of the Adjacent Land-Based Magnetic Field Data to Account for the Geomagnetic Disturbances During Offshore Directional Drilling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8695, https://doi.org/10.5194/egusphere-egu23-8695, 2023.

In this study, the novel artificial neural network(ANN) called back-propagation multilayer perceptron (BP-MLP) algorithm with fully connected architecture is proposed to simulate and predict the apparent resistivity and impedance phase of 2-D Magnetotelluric forward modeling. The experiments of this algorithm are made on various benchmark models. The experimental results showed that the proposed neural network is efficient and provides accurate predictions with an average relative error of apparent resistivity and impedance phase less than 1% and 0.5%, respectively. The algorithm's feasibility suggests that the ANN approach provides excellent accuracy results and can be practically used for solving 2-D magnetotelluric modeling.

How to cite: Sarakorn, W., Mukwachi, P., and Boonpan, S.: Novel Back-Propagation Multilayer Perceptron Approach for 2-D Magnetotelluric Modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16326, https://doi.org/10.5194/egusphere-egu23-16326, 2023.

The airborne electromagnetic (AEM) method is a modern technique in geophysical surveys with the merits of terrain adaptability and acquisition efficiency, and can image the electrical structure of the Earth’s subsurface down to several hundred meters. AEM survey has been applied extensively in mineral exploration, groundwater monitoring, environment investigation and geological mapping. However, the expansion of survey area and spatial sampling bring about huge volumes of AEM data, which present a serious computational challenge for rapid AEM inversion. Inspired by Google’s neural machine translation system, we develop a fast inversion system guided by deep learning to translate AEM data directly into subsurface resistivity structures. Synthetic tests demonstrate that our proposed inversion system has strong noise robustness and can provide reliable inversion results much more efficiently than the conventional Gauss-Newton algorithm. In the field data application, our system obtains robust inversion results of more than 740,000 AEM soundings acquired by the U.S. Geological Survey from the Leach Lake Basin in California in seconds on a common PC. The inverted images coincide exactly with previous studies of the local geological environment and clearly outline the geometries of the lake, faults and surrounding mountains. Our inversion system can support near real-time underground subsurface imaging for AEM surveys and inject new vigor into resource exploration and tectonic studies.

How to cite: Wu, S., Huang, Q., and Zhao, L.: Near real-time subsurface structure imaging using airborne electromagnetic data based on deep learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11690, https://doi.org/10.5194/egusphere-egu23-11690, 2023.

Frequency domain electromagnetic induction (FDEM) sensors are used regularly to investigate near-surface electrical properties for diverse purposes.  FDEM instruments measure the coupling ratio between the secondary magnetic field induced in the ground and the primary magnetic field of the direct wave propagating from a transmitter through the air to the receiver coil, which is a complex ratio, where the real part is called in-phase part and the real part is called the out-of-phase or quadrature part. Usually, the quadrature  part of the data measurements is used to estimate the electrical conductivity of the shallow subsurface. In this study we show the outcome of the estimation of an electrical conductivity model using both quadrature and in-phase  parts of the coupling ratio. We simulate the full solution measurements (quadrature and in-phase) and used only the quadrature part as data to estimate 1D electrical conductivity models of the subsurface in a lookup table. Then, we compare this estimation with the resulting one using the full solution as data measurement. Our results provide insight on the information that the in-phase part provides about the distribution of electrical conductivity with depth.

How to cite: Carrizo, M., Slob, E., and Werthmüller, D.: Exploiting the full information of the coupling ratio measurements in frequency domain electromagnetic induction instruments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17211, https://doi.org/10.5194/egusphere-egu23-17211, 2023.

Electromagnetic imaging has been perfected to investigate the subsurface over the past three decades. Developing numerical schemes, algorithms, and easy access to supercomputers have supported innovation throughout the geo-electromagnetic community. Now, with the Exascale computing era dawning upon us, even more accurate, clearer, and faster data will be within our reach. However, numerical methods, computational strategies, and codes must be reshaped and honed to prepare for the upcoming challenges. Europe is making a huge effort in the strategic global race to Exascale, with large investments in the infrastructure. From the point of view of science and services, this unprecedented infrastructure opens a myriad of possibilities but, at the same time, the transition is challenging and requires a joint effort from (geo)scientists, mathematics, software engineers, and data analysts. Herein, we discuss the symbiotic relationship between numerical methods and computational strategies for EM imaging in the Exascale era. We focus on the need to explore all the alternatives of technologies, applications, and expertise transfer to propel the high-performance electromagnetic mapping landscape forward.

How to cite: Castillo Reyes, O. and Queralt, P.: High-performance electromagnetic mapping in the exascale era, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1514, https://doi.org/10.5194/egusphere-egu23-1514, 2023.

Magnetotellurics (MT) image the Earth’s electrical resistivity down to the mantle but is rarely used for investigation of offshore rifted margins. In such setting, the stretched lithosphere is altered by distinct tectono-thermal processes such as partial melt, hydration, or chemical alteration. However, lower crustal and upper mantle often display similar seismic velocities, density, and magnetic properties. Integration of resistivity models from MT data can lift this ambiguity in a hyper-extended rift system. In this project, we use an extensive marine MT database consisting of 337 receivers located along seven regional transects, emanating from ~70 000 km2 of 3-D CSEM surveys acquired for hydrocarbon exploration in the SW Barents Sea. 3D inversion of long period, marine MT data (1 – 3000 s) is performed on 104 receivers located along two, ~300 km long transects located over the Bjørnøya Basin, located ~300 km offshore northern Norway. We also apply 1D Bayesian inversion to a selection of receivers as an alternative to the deterministic approach for a more comprehensive exploration of the solution space.

The resolving power of MT data is assessed with synthetic tests in an archetypal rift system where ample crustal thickness variation occurs. The results highlight that our MT data sense the transition from necking to hyper-extended domain where the crust (<~10 km) is not reconstructed by 3D inversion. In the Bjørnøya Basin – the northernmost member of a hyper-extended Cretaceous basin chain in the North Atlantic – seismic interpretation is used to assign a stratigraphic level to two prominent conductors in the resistivity models: (1) 0.1-1 Ω.m within Lower Cretaceous marine shales buried at 10-15 km depth (2) 1-10 Ω.m within the uppermost mantle. The bulk resistivity of a 2-phase, fluid-rock model emphasizes that seawater as a sole pore fluid phase is not conductive enough to explain the magnitude of the two conductors. A 25% serpentinization of mantle rocks can account for a fivefold rise in salinity of the residual fluid and is compatible with density and seismic velocities in the Bjørnøya Basin. Samples from fossil margins in the Alps and Pyrenes shows contamination of post-rift sediments pore fluids by mantle elements, highlighting the mobility of mantle-reacted fluids in hyper-extended systems. High-salinity fluid can ascend and mix with seawater in pore spaces of the sediments, supporting our proposed model of saline fluid circulation in hyper-extended basins.

How to cite: Corseri, R., Planke, S., Gelius, L. J., Faleide, J. I., and Senger, K.: Magnetotelluric image of a hyperextended and serpentinized rift system in the SW Barents Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6874, https://doi.org/10.5194/egusphere-egu23-6874, 2023.

Anatolia has been the center of civilizations throughout history, as well as a laboratory for geoscientists in terms of its geological history. The eastern Mediterranean region and Anatolia are located at the intersection of different tectonic plates controlled by the African-Eurasian convergence, which continues along the Cyprus and Aegean (Hellenic) arcs in the southwest and resulted in collision in the east. The interrelation between Cyprus and Aegean arcs remains a topic of discussion among scientists. It is thought that the intersection area of ​​the Aegean and Cyprus arcs, located beneath the Western Anatolia and Isparta Angle (IA), is a slab tear that causes asthenospheric upwelling in SW Anatolia and IA. The reflection of this tear on the surface occurs as a STEP fault type and is represented by the Fethiye - Burdur Fault Zone (FBFZ) forming the western border of IA and Akşehir Fault Zone (AFZ) forming the eastern border of the region. Isparta Angle, influenced by the aforementioned tectonic systems, is located between the FBFZ and AFZ as a reverse triangle shape. Therefore, besides the main border fault zones, there are various normal and reverse faults and related graben-horst structures in the region.    

IA is located at where opening and closing of various oceans took place. The main geological basement consists of autochthonous and allocton units. Autochthonous units are called as Beydağları and Anamas - Akseki carbonate platforms. Allocton units were transported and obducted over these carbonate platforms in different geological times and they can be ordered as Lycia nappes, Antalya nappes and Beyşehir-Hoyran-Hadim nappes, respectively. There are various basin formations observed throughout the region, related to nappe emplacements and Cyprus subduction zone back-arc tensional forces before Miocene, and extensional tectonism which became effective after Miocene.

The magnetotelluric (MT) method involves the measurement of the time variations of the orthogonal components of natural electric and magnetic fields, which contain information about the electrical resistivity structure from crustal to upper mantle depths. The superiority of the MT method in determining conductivity differences makes it possible to detect aqueous fluids and magma (partial melting). In active tectonic regions such as IA, where various tectonic systems intersect and an asthenospheric upwelling is proposed where aqueous fluids, partial melting or both could be the reason for high conductivity, magnetotellurics is well suited method to study fault-related structures and tectonic processes.

In this study, magnetotelluric data were collected in 4 profiles at 47 stations and inverted by using ModEM software to reveal 3D subsurface conductivity structure of the area. The most striking feature is a lower crust conductor located mostly in western part of the region and an upper crustal conductive structure which is related to the lower one imaged in the region. This upper-crust conductor structure reaches up to the surface beneath the main fault zones. The basement structures which consist of nappes, carbonate platforms are imaged as resistive zones and their depths are clearly imaged in the recovered resistivity models.

How to cite: Avşar, Ü., Karcıoğlu, G., Kaya Eken, T., and İşseven, T.: The imaging of the tectonic structure of Isparta Angle by 3D inversion of Magnetotelluric Data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8414, https://doi.org/10.5194/egusphere-egu23-8414, 2023.

The Sabalan geothermal in northwestern Iran is the most well-known geothermal in the country. Due to the Sabalan caldera's structures and dozens of younger faults, the area consists of highly fractured rocks. Besides, processing the aeromagnetic data in the area revealed some other hidden faults. To investigate the effect of the faults on the geothermal system, we conducted a dimensionality analysis based on magnetotelluric impedance and phase tensors from two magnetotelluric datasets. The datasets were surveyed at different times, one in the dry season of June 1998 and the other in the wet season of November 2007. The dimensionality behavior obtained from the datasets differs significantly. We realized that the discrepancy was due to the time of conducting the magnetotelluric survey. For instance, the polar diagrams computed from the dry season data showed a better correlation with fault strikes in some of the frequencies where the wet season data polar diagrams were less sensitive to the fault orientations. Besides, the strike of a hidden fault extracted from aeromagnetic data was apt to the extension of Zxy's polar diagram. Furthermore, the dimensionality analysis and skew angle in dry season data demonstrate a 2D to 3D media, whereas the wet season data showed a 1D to 2D earth. We deduced that faults have a more significant role in providing resistivity contrast in dry seasons and hence, a better illustration for the geoelectric strike.

How to cite: Ghasemipour, Y., Abtahi Forooshani, S. M., and Sadeghisorkhani, H.: Investigation of the influence of faults on geoelectric strikes and dimensionality analysis of MT data in the Sabalan geothermal area, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11254, https://doi.org/10.5194/egusphere-egu23-11254, 2023.

The Varton geothermal is located circa 70 kilometers northeast of Isfahan, central Iran. The study area consists of highly fractured rocks with argillic alteration zones and some hot springs. Here, we conduct a magnetic and magnetotelluric data survey to study the effect of the fractures on the hydrothermal convection system. The magnetic data processing exposed two parallel main faults with NW-SE strike in the northern and southern borders of the area. Here, we used nine magnetotelluric (MT) stations along a profile perpendicular to the main faults. Dimensionality analysis of MT impedance and phase tensors in the stations indicated a media with two-dimensional structures. However, 1D MT data inversion revealed a three-layered earth beneath most stations, though the layers' thickness and resistivities varied along the profile. Also, 2D MT data inversion results showed that the resistivity between the two main faults was significantly smaller than zones beyond the faults. However, a large zone with low resistivity was close to the southern fault. Besides,  a shallow layer overlain a thin conductive layer with a resistivity of one ohmm or less. In depths more than 500 m, the resistivity noticeably increased gradually to 1000 ohmm. According to the mentioned results, we deduce that the southern fault is the main feeding fault for the geothermal system. Furthermore, the layer with the lowest resistivity correlates with clay alteration and could be the clay cap of the reservoir. Therefore, the deeper resistive rock is the geothermal reservoir.

How to cite: Hajheidari, M., Abtahi Forooshani, S. M., Fathianpour, N., Moshtaghian, K., and Tavakoli Harandi, H.: MT data inversion and dimensionality analysis in Varton geothermal central Iran, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12872, https://doi.org/10.5194/egusphere-egu23-12872, 2023.