Electrical Resistivity Distribution Research Articles

Application of Electrical Resistivity Tomography for Improved Blast Movement Monitor Locations Planning

Blast-induced rock movement is a highly variable phenomenon which depends on numerous factors. Rock type and its deriving physical and mechanical properties are among such factors, which are crucial to be available prior to planning the locations where each monitor is placed. Hence, Electrical Resistivity Tomography (ERT) was used to acquire additional rock mass data for several benches of an open-pit mining operation. ERT is considered a valuable tool in mine planning. By providing information about the subsurface electrical resistivity distribution, ERT helps in determination of geological structures, composition of the ground and helps assessing potential hazards. A total of 21 profiles were measured, which allowed for relevant data to be obtained regarding each monitor’s location. Results from the study showed that blast movement measurements from different rock-type zones do not differ in a statistically significant manner. However, substantial differences were uncovered regarding the mode of movement vectors by using Kernel density estimation (KDE). These results proved that ERT is a fast and reliable support method for establishing different rock mass zones and for location planning of blast movement monitors and blast design optimization prior to drilling.

Changes in Vegetation Distribution around the King Sejong Station in Antarctica: A Comprehensive Analysis of Time-Lapse Electrical Resistivity Data, Meteorological Data, and Vegetation Data

Abstract The impact of buildings around the King Sejong Station (KSS), South Korea’s first scientific station in Antarctica, has locally altered snowfall accumulation and vegetation distribution. Areas with high snowfall accumulation exhibited sparse vegetation, whereas areas with low snowfall showed distinct vegetation. This study conducted a comprehensive analysis using various data sources to understand the causes of changes in vegetation distribution. Meteorological data, including air temperature, soil temperature, soil moisture, and wind, were analyzed to determine the impact of station buildings on snow cover changes. The changes in vegetation distribution were more clearly visible through results of measured Normalized Difference Vegetation Index. Additionally, time-lapse electrical resistivity data were collected throughout 2020 to analyze variations in the subsurface electrical resistivity distribution. Electrical resistivity surveys utilized both dipole–dipole and Wenner arrays to gather data, with subsurface electrical resistivity information obtained through inversion process. The active layer, which is characterized by low electrical resistivity and is conducive to vegetation growth, is distributed in the upper layers and changes over time, only in vegetated area. In contrast, the development of the active layer was not observed in nonvegetated area. In conclusion, the time-lapse electrical resistivity data effectively reveal the temporal changes in the distribution of the active layer in the study area. When the electrical resistivity data were interpreted in conjunction with meteorological data, it provided a good understanding of the causes of changes in the distribution of vegetation around the KSS.

Polydopamine modified carbon fiber to improve the comprehensive properties of carbon paper for proton exchange membrane fuel cell

In this study, polydopamine (PDA) was used to modify functional groups on the surface of carbon fiber (CF), and the effects of different dopamine hydrochloride (DPH) concentrations on the surface morphology, functional groups, contact angle and dispersion stability of CF were studied. Subsequently, the raw carbon paper (RCP), hot-pressed carbon paper (HPCP) and carbon paper (CP) were prepared successively using the modified CF through wet forming, impregnation/hot-pressing, and carbonization methods. The surface morphology, tensile strength, flexural strength, electrical resistivity, air permeability and pore size distribution were analyzed for these materials. It was observed that the introduction of −OH and − NH2 groups improved the hydrophilicity and dispersion of PDA modified CFs, resulting in an increase in formation index (FI) from 39.2 to 48.1 for RCP samples. With increasing DPH concentration, the tensile strength of CP initially increased but then decreased while its electrical resistivity showed an opposite trend. Finally, PDA modified CP was assembled into proton exchange membrane fuel cells (PEMFC). The PEMFC assembled from DPH-CP-2.5 achieved a maximum limiting current density of 1440.0 mA/cm2 and power density of 458.25 mW/cm2. Meanwhile, the lower material transmission impedance for DPH-CP-2.5 as well as excellent water management ability and gas transmission performance.

Assessment Rainfall-Induced Landslides Using Arbitrary Dipole–Dipole Direct Resistivity Configuration

Landslides are one of the primary geological disasters posing significant threats to life and property. Strengthening the monitoring of rainfall-induced landslides is, therefore, crucial. The Direct Resistivity (DC) method can accurately map the subsurface electrical resistivity distribution, making it an essential tool for predicting the position of the slide face. However, when conducting landslide surface DC surveys, various undulating terrains such as ridges and steep slopes often pose accessibility challenges. In such topographies, conventional regular grid measurements become very difficult. Additionally, when the terrain is highly undulating and complex, interpreting apparent resistivity data can lead to erroneous results. In this study, we propose using the DC method to monitor rainfall-induced landslides. By moving away from traditional device setups and utilizing an arbitrary dipole–dipole observation system, we aim to improve efficiency, enhance data resolution, and reduce costs. The resistivity of the slope was found to change significantly during the incubation, formation, and development of a landslide in physical model experiments. Furthermore, the feasibility of our proposed method for assessment rainfall-induced landslides was illustrated by a real case study in South China.

Deep Electrical Resistivity Tomography for Detecting Gravitational Morpho-Structures in the Becca France Area (Aosta Valley, NW Italy)

Deep-seated gravitational slope deformations (DSGSDs) consist of gravity-induced, large-scale, gradual rock mass movements. In the Aosta Valley region (Valle d’Aosta NW Italy), DSGDs affect wide valley slopes and produce several interconnected morpho-structures that involve bedrock and Quaternary cover. Some DSGSD effects are not visible at the surface because of subglacial abrasion or burial by sediments and, therefore, are difficult to map with standard geomorphological surveys. This is the case for the Pointe Leysser DSGSD in the Aosta Valley, which is heavily influenced by the historical movements of the Verrogne-Clusellaz Glacier and its tributaries. We conducted a new geological investigation, integrated with deep electrical resistivity tomography geophysical surveys (ERTs). The ERT results were initially compared with geological/geomorphological evidence at the surface to define the correlation between the values and spatial distributions of electrical resistivity and the sediments, rocks, or morpho-structures. The resistivity values at various depths were subsequently analysed, interpreted, and discussed in conjunction with geological hypotheses. The geological and geophysical survey revealed three wide buried glacial valleys filled with glacial sediments and mapped the locations of gravitational morpho-structures at depth. These new data allowed us to draw a relationship between glacialism and gravitational evolution, distinguishing between pre-singlacial movements and postglacial movements.

Effect of Film Thickness on the Electrical Resistivity and Optical Functions Distribution of Iron Tris(8-hydroxyquinoline) Thin Films

Iron tris(8-hydroxyquinoline) (Feq3) was synthesized and investigated by X-ray photoemission spectroscopy. It crystalizes in triclinic polycrystalline structure in powder form, whereas the Feq3 films, with different thickness values (12, 20, 35, and 42 nm), have an amorphous structure. The influence of film thickness on the electrical resistivity and the optical properties is reported. The morphology of Feq3 was investigated in terms of field-emission scanning electron microscope. Electrical resistivity measurements indicate an inverse proportionality to the film thickness. The optical properties of Feq3 films were investigated in terms of photoluminescence spectra and spectrophotometric measurements of transmittance and reflectance. The optical functions such as absorption coefficient and refractive index of the films were calculated. The dependence of the Feq3 film thickness on the optical energy band gap and dispersion parameters was studied. The outcomes indicate that the Feq3 films are of great importance for applications in organic solar cells and light emitting diodes.

Characterizing spatial distribution of ice and methane hydrates in sediments using cross-hole electrical resistivity tomography

Electrical resistivity is an essential parameter for assessing the abundance of gas hydrates and predicting their location. However, imaging techniques are poorly developed for detecting the electrical resistivity distribution of hydrate-bearing sediments. In this study, a cross-hole electrical resistivity tomography (CHERT) array was established in the large-scale simulator for characterizing the spatial distribution of the sedimentary system. Ice- and methane hydrate-bearing sediments were investigated respectively using CHERT. The results show that CHERT effectively observed the significant influence of methane hydrate/ice formation and salt drainage on the variations in electrical parameters. Their formation leads to a sustained increase in average resistivity, while salt ion exclusion leads to an increase in pore water salinity, resulting in a decrease in local resistivity. Moreover, CHERT observed a range of resistivities from a few Ω·m to several thousand Ω·m for ice- and methane hydrate-bearing sediments, which is consistent with the resistivity response of hydrate reservoirs in the field. It is suggested that CHERT can be used for hydrate reservoir detection and combined with acoustic imaging to more accurately characterize the spatial distribution of hydrates. These results contribute to advancing the potential application of CHERT technology in multi-method and multi-scale gas hydrate monitoring initiatives.

Intertidal spring dynamics and coastal nutrient loading revealed through geophysics, drone surveys, and in‐situ monitoring

AbstractCoastal eutrophication poses an increasing risk to ecosystem health due to enhanced nutrient loading to the global coastline. Submarine groundwater discharge (SGD) represents a significant pathway for nitrate‐nitrogen (NO3‐N) transport to the coast, but diffusive SGD transport is difficult to monitor directly, given the low flux rates and expansive discharge areas. In contrast, focused SGD from intertidal springs can potentially be sampled and directly gauged, providing unique insight into SGD and associated contaminant transport. Basin Head is a coastal lagoon in Prince Edward Island, Canada that is a federally protected ecosystem. Nitrate‐nitrogen is conveyed from agricultural fields in the contributing watershed to the eutrophic lagoon via intertidal groundwater springs and groundwater‐dominated tributaries. We used several field methods to characterize groundwater discharge, nutrient loading, and in‐channel mixing associated with intertidal springs. The tributaries and intertidal springs were gauged and sampled to estimate a representative summer nitrate load to the lagoon. Our analysis revealed that NO3‐N export to the lagoon through tributaries and springs throughout summer 2023 was on average 401 kg N/month, with the combined spring loading comparable in magnitude to the combined tributary loading. We collected thermal infrared and visual imagery using drone surveys and found spatial overlap between cold‐water plumes from the spring discharge and macroalgae blooms, indicating the local thermal and ecosystem impacts of the focused SGD. We also mapped the electrical resistivity (salinity) distribution in the water column around one large spring with electromagnetic geophysics at different tidal stages to reveal the three‐dimensional spring plume dynamics. Results showed that the fresher spring water floated above the saline lagoon water with the brackish plume oriented in the direction of the tidal current. Collectively, our multi‐pronged field investigations help elucidate the hydrologic, thermal, and nutrient dynamics of intertidal springs and the cascading ecosystem impacts.

EXPERIMENTAL STUDIES OF ELECTRIC CONDUCTIVITY DISTRIBUTION ALONG THE HEIGHT OF THE FLUIDIZED BED

This work is focused on the experimental research into the electrical conductivity of a fluidized bed with graphite particles. The aim of the study is to determine the change in electrical conductivity along the height of the fluidized bed. The study was carried out on a chamber-type unit with a working space diameter 110 mm at a fluidization index 2-3. As a result of the experimental research, during heating in electrothermal fluidized bed, the uneven distribution of electrical resistance along the bed height was confirmed for the first time. The resistivity value increases 3-5 times with the depth of immersion into the bed from its surface. The unevenness of the resistivity along the height of the bed decreases with increasing temperature. The difference in power distribution due to uneven electrical resistance along the bed height can lead to a temperature difference of several tens of degrees.

Crustal conductivity footprint of the Miocene porphyry copper polymetallic deposits in the Gangdese metallogenic belt, Tibetan Plateau

New evidence worldwide has linked the surface locations of mineral deposits and their crustal-scale electrical conductivity footprint. We examine the relationship between the Gangdese Miocene porphyry copper deposits, Tibetan Plateau, and the electrical conductivity signature from a three-dimensional model generated from 311 magnetotelluric measurements. The distribution of electrical resistivity throughout the crust and the conductance within the mid-lower crust (depth range of 25–70 km) is analyzed. The results clearly show that the large and ultra-large Miocene porphyry copper deposits coincide spatially with conductive zones and areas of very-high conductance (>10,000S) in the mid-lower crust. Computations are undertaken to determine the influence of water-bearing silicate melts and alkali-bearing (Na+ and K+) fluids on conductivity. Based on this, the bulk conductivity is interpretated to be caused by a system of alkali-rich volatile-rich partial melt. The alkali-rich volatile-rich magmatic-hydrothermal fluids facilitate the migration and concentration of metal ions originating in deep areas. The volumes necessary are much less than partial melt alone and can thus help to reconcile large conductivity variations with small seismic velocity variations. The electrical structure indicates the magma source area of anatexis in the lower crust, a multi-stage magmatic system with large mid-crustal and small upper-crustal magma reservoirs, and complex pathways related to rift zones. We determine that the conductive zones in the mid-lower crust have an influence on the development of the mineralization and the location of the mineral belt.

Insights Into the Structure of the Mongol‐Okhotsk Suture Zone, Adaatsag Ophiolite, and Tectonic Boundaries of the Central Asian Orogenic Belt (Mongolia) From Electrical Resistivity Imaging and Seismic Velocity Models

AbstractThe Mongol‐Okhotsk suture and the Adaatsag ophiolite belt are associated with the closure of the Mongol‐Okhotsk paleo‐ocean and are located within the Central Asian Orogenic Belt (CAOB) and Mongolia. The suture zone is flanked by volcanic‐plutonic belts that host significant metallogenic zones, containing deposits of copper and gold. The tectonic evolution of this region is not fully understood and the lithospheric structure has been poorly studied. We analyze magnetotelluric data and generate a model of the electrical resistivity distribution across this region. Whereas the northern segment has a sharp transition from a high‐resistivity upper crust to a low‐resistivity lower crust, as observed beneath the Hangai Dome, the southern segment does not show this transition. A wide, low‐resistivity zone (1–100 Ωm) imaged in the crust and lithospheric mantle is coincident with the Mongol‐Okhotsk suture and ophiolite, revealing a clear and significant lithospheric‐scale feature. Across the profile, numerous narrow, vertically oriented, low‐resistivity features (1–100 Ωm) are spatially associated remarkably well with the proposed boundaries of tectonic domains. These results confirm ideas about the development of the CAOB. Some of these low‐resistivity features are beneath the surface locations of large mineral zones, and likely represent fossil fluid pathways. We show congruent seismic velocity models for comparison and the results show a large‐scale low‐velocity anomaly (decrease of 2%–3%) that correlates with the location of the low‐resistivity anomaly below the Mongol‐Okhotsk suture. The geophysical results, combined with geological and geochemical data, provide insights into the structure of this region and help shed light on unanswered questions.

An efficient method for electro-thermo-mechanical coupling effect in electrical contact on rough surfaces

In this study, a numerical strategy based on the boundary element method (BEM) is developed to simulate the electrical contact behavior on rough surfaces. By using the Fourier transform, the solutions of the electric potential, temperature rise, and displacement fields in the Fourier space are derived with finite boundaries, in which the electro-thermo-mechanical coupling effect is considered. With the consideration of the contact condition, an iterative algorithm is proposed to seek the solutions of rough surface electrical contact under a given contact force and total electric potential drop. The contact pressure, real contact area, electrical contact resistance, electric current, and temperature rise distribution are predicted. For the validation, the electrical contact results of a spherical punch-half space contact and a rough surface-elastic substrate contact are calculated based on the finite element method. The good agreement between the results from the BEM-based method and the finite element method indicates the accuracy of the presented method. Then, the effect of the total electric potential and the thermal expansion on the electrical contact behavior, the relationship between the contact conductance and contact stiffness, and the probability density function of the contact pressure and temperature rise distributions are evaluated using the proposed method.

Research note: A comparison between normalized controlled‐source electromagnetic field components and transfer functions as input data for three‐dimensional non‐linear conjugate gradient inversion

AbstractControlled‐source electromagnetic methods are applied to survey the electrical resistivity distribution of the subsurface. This work compares normalized electromagnetic field components and transfer functions such as impedance tensors and vertical magnetic transfer functions generated by two independent source polarizations as input data for three‐dimensional inversion. As most other available inversion codes allow for inverting only one of the mentioned input data types, it is unclear which data type is preferable for controlled‐source electromagnetic inversion. Our three‐dimensional non‐linear conjugate gradient inversion code can handle both input data types, facilitating a comparison of normalized electromagnetic field components and transfer functions inversion. Examining inversion results for a three‐dimensional synthetic model with two anomalies, we infer that the transfer functions inversion is favourable for recovering the overall resistivity distribution below the receiver sites in fewer iterations. The inversion of normalized electromagnetic field components produces a sharper image of the anomalies and may be capable of detecting the resistivity distribution below the extended sources, which comes at the price of introducing a more heterogeneous background resistivity in the model.

Research trends and hotspots in the field of electrical impedance tomography for mechanical ventilation: a bibliometric analysis.

Electrical impedance tomography (EIT) is a relatively recent functional imaging technique that is both noninvasive and radiation free. EIT measures the associated voltage when a weak current is applied to the surface of the human body to determine the distribution of electrical resistance within tissues. We performed a bibliometrics-based review to explore the geographic hotspots of current research and future trends developing in the field of EIT for mechanical ventilation. The Web of Science database was searched from its inception to June 25, 2023. CiteSpace software was used to visualize and analyze the relevant literature and identify the most impactful literature, trends, and hotspots. 363 articles describing EIT use in mechanical ventilation were identified. A fluctuating growth in the number of publications was observed from 1998 to 2023. Germany had the highest number of articles (n=154), followed by Italy (n=53) and China (n=52). A cluster analysis of keyword co-occurrence revealed that "titration", "ventilator-related lung injury", and "oxygenation" were the most actively researched terms associated with the use of EIT in mechanically ventilated patients. Significant progress has been made in EIT research for mechanical ventilation. EIT research is limited to a small number of countries with a present research focus on the prevention and treatment of ventilator-related lung injury, oxygenation status, and prone ventilation. These topics are expected to remain research hotspots in the future.

Development and Test of Geogrid with Distributed Deformation Monitoring Function.

In recent years, there is a growing demand for materials that can both improve the mechanical properties of structures and carry out health monitoring and risk warning. In this case, in order to realize distributed deformation monitoring, a new method of making geogrid by 3D printing technology is proposed. The grille rib is made by embedding the conductive polymer (ground carbon fiber as conductive filler) into the insulating shell (PLA material) in the specified path, and then the rib is vertically crossed into each other to form a grille sample. In order to study the distributed deformation monitoring function of this grid, a manual push-pull testing machine was used to conduct a load-unload experiment to analyze the change rule of resistance on the grid plane. The following conclusions were obtained: the closer the ribs are to the load bearing point, the greater the change in resistance, and conversely, the farther the ribs are from the load bearing point, the smaller the change in resistance. Depending on the geogrid network characteristics, the electrical resistance distribution on the geogrid plane can be obtained by superimposing the resistance values of the horizontal and longitudinal ribs, then the location and the magnitude of deformation can be estimated. Additionally, this study carried out numerical simulation of the grid model based on ANSYS 15.0 software and compared with the loading experiment results to verify that the force deformation position can be retrieved through the change of resistance.

Using Magnetic Field Analysis for Localizing Defects of Fuel Cell & Electrolyzer Components

Production capacities of electrolysis and fuel cell technologies are expected to increase significantly in the upcoming years, reducing costs of stack components through numbering-up. To ensure reliability and durability and reduce costs along the manufacturing process, developing suitable in-line non-destructive diagnostic methods for quality control becomes essential for their industrialization.In both fuel cell and electrolyzer stacks, the main components' electrical resistance and current density distribution greatly influence stack efficiency and longevity. Here, the flowing electric current generates a magnetic field depending on its strength and direction. Potential defects caused by the manufacturing process, including cracks, defective welding spots, coating adhesion issues, delamination, and contamination, influence the components' electric conductivity and current density distribution and hence the magnetic field distribution.This work investigates non-destructive diagnostic methods using magnetic field analysis (MFA) to identify changes in the magnetic field distribution and, thus, local electrical resistance and current density distributions of fuel cell and electrolyzer components. The methods used are magnetic field imaging (MFI) and Eddy Current Testing (ECT). MFI analyzes the magnetic field distribution in all three spatial directions to trace electrical currents and identify electrical defects, creating a magnetic field signature that can potentially distinguish between functional and non-functional components along the manufacturing process. ECT measures variations in local conductivity by inducing eddy currents in the sample through an alternating magnetic field generated by a sender coil. These eddy currents create a detectable magnetic field in a receiver and are affected by defects and changes in electrical conductivity. Therefore, the method can characterize sheet resistance and material homogeneity through electrical anisotropy in electrically conductive components.In initial experiments, ECT measurements on coated and uncoated hollow embossed stainless steel bipolar half plates showed systematic differences depending on quality characteristics resulting in unique patterns and inhomogeneities which require further investigation. Furthermore, experiments with both methods on other stack components will be presented and discussed. In addition, their in-line capability will be assessed and evaluated. However, these first promising results imply that MFA is potentially useful as an in-line, non-destructive diagnostic method for quality control.

Impacts of thermal and electric contact resistance on the material design in segmented thermoelectric generators

Segmented thermoelectric generators (STEGs) can exhibit present superior performance than those of the conventional thermoelectric generators. Thermal and electrical contact resistances exist between the thermoelectric material interfaces in each thermoelectric leg. This may significantly hinder performance improvement. In this study, a five-layer STEG with three pairs of thermoelectric (TE) materials was investigated considering the thermal and electrical contact resistances on the material contact surface. The STEG performance under different contact resistances with various combinations of TE materials were analyzed. The relationship between the material sequence and performance indicators under different contact resistances is established by machine learning. Based on the genetic algorithm, for each contact resistance combination, the optimal material sequences were identified by maximizing the electric power and energy conversion efficiency. To reveal the underlying mechanism that determines the heat-to-electrical performance, the total electrical resistance, output voltage, ZT value, and temperature distribution under each optimized scenario were analyzed. The STEG can augment the heat-to-electricity performance only at small contact resistances. A large contact resistance significantly reduces the performance. At an electrical contact resistance of RE = 10–3 K·m2·W−1 and thermal contact resistance of RT = 10–8 Ω·m2, the maximum electric power was reduced to 5.71 mW (90.86 mW without considering the contact resistance). And the maximum energy conversion efficiency is lowered to 2.54% (12.59% without considering the contact resistance).

Estimating annual CO2 emissions and building a leakage scenario in a tectonically quiescent area

Soil CO2 flux (FCO2) was intensively measured in a natural CO2 emission site located in a tectonically quiescent area, with topographic and geophysical investigation, to estimate annual emissions and causes of focused leaks. FCO2 varied between 6.5 and 2155.4 g/m2/d (median 76.1 g/m2/d; n = 67) within a 612 m2 area situated close to a CO2-rich groundwater well. The threshold value for geogenic FCO2 was determined to be 23 g/m2/d using a Q-Q plot. A FCO2 hotspot was delineated where FCO2 exceeded the threshold. Based on linear regression using air pressure and temperature, the annual CO2 emissions from the hotspot in 2019 were approximately 19 tons/y. According to the 2D electrical resistivity distribution, the subsurface around the well was highly weathered, showing low electrical resistivity (<2000 Ω-m) down to a depth of 50 m, whereas the top layer around the hotspot showed a relatively high electrical resistivity (> 500 Ω-m), implying a resistant unsaturated zone. High signal attenuation and discontinuous and dipping reflectors of ground-penetrating radar signals suggested gaseous CO2 transport through preferential pathways in the resistant near-surface. Based on these and previous hydrochemical results, the extremely high FCO2 in the narrow extent can be explained by a leakage scenario in which the frequent usage of CO2-rich water through the well enhances CO2 degassing, while defects in the well casing accelerate the upward movement of CO2 gas, which flows out through a preferential pathway in the resistant unsaturated zone. This study provides insights into focused leakages through faulty wells and near-surface preferential pathways. In addition, the quantification of annual CO2 emissions through point sources is applicable for assessing natural gas emissions produced by hotspots. The non-negligible emission rate in the hotspot (about 92 g/m2/d) emphasizes the need to quantify natural CO2 emissions in tectonically quiescent areas for risk assessments and carbon budgets.

An attempt to use convolutional neural network to recover layered-earth structure from electrical resistivity tomography survey

The Electrical Resistivity Tomography (ERT) method is a geophysical prospecting technique for determining subsurface structure in terms of electrical resistivity distribution. Direct current is injected into the ground through a pair of electrodes, and the potential difference is measured using another pair of electrodes. The estimated resistivity model of the subsurface is then obtained using a mathematical optimization algorithm called the inversion algorithm, which incorporates multiple measured potential differences from different electrode configurations as the input data. The inverted resistivity model serves as a resource for the interpretation process of the survey. Specialists employ the model and the prior geological information in the area to extract the subsurface geological structure under the data measurement profile. The inverted model can be treated as a two-dimensional image in which each element represents resistivity. The image can be visualized as a blurred or distorted version of the actual resistivity image of the subsurface. We, therefore, developed a post-inversion image enhancement code using a neural network aiming to recover the true subsurface model with predetermined features. We employed the convolutional neural network (CNN) that uses the inverted models as input and returns an enhanced model as output. We tested our developed neural network with a case study that utilized the proposed method to recover the layered earth structure which is often found in real surveys. The electrode spacing was 5 meters in the Schlumberger array configuration. The true subsurface resistivity models of training data and validating data for evaluating the neural network were randomly generated based on the predetermined feature of the layered structure. We then generated their respective inverted models from those data through simulated inversion routine. As a result, 94.75% of the enhanced models in the validation dataset exhibited a lower loss metric compared to the original inverted models in the same validation dataset. We also applied the proposed method to practical field data to recover the subsurface layers and compared them with stratigraphic information from a borehole in each area. The result showed that the proposed method gives well-resolved structures in the enhancement process after the typical inversion.

Geothermal Resource Mapping in Northern Botswana Inferred from Three-Dimensional Magnetotelluric Inversion

A set of magnetotelluric (MT) data collected from 28 stations at the Kasane Hot Spring in northern Botswana was used to derive a 3-D model of the electrical resistivity distribution around deep geologic structures that we associated with geothermal resources. The dimensionality analysis results revealed that 3-D modeling should be used to determine the electrical structure. The resistivity models revealed a conductive layer with an average thickness of 200 m, representing the overlying sediments of the Proterozoic volcanic rocks. The thick high-resistivity zone (&gt;100 Ωm) below the conductive layer can be associated with Mesoproterozoic bedrock. The MT measurements in this area show a tube-shaped conductive anomaly that could serve as a fluid pathway feeding the hot spring. A fracture-controlled meteoric fluid circulation presumably determines the existence of the Kasane Hot Spring system.