The Experts below are selected from a list of 135 Experts worldwide ranked by ideXlab platform
Arkoprovo Biswas - One of the best experts on this subject based on the ideXlab platform.
-
Global Optimization for Delineation of Self-Potential Anomaly of a 2D Inclined Plate
Natural Resources Research, 2020Co-Authors: Shraddha Jain, Arkoprovo BiswasAbstract:A fast and efficient technique for explanation of self-Potential anomalies is of immense importance for exploration, engineering, and environmental problems. Estimation of model parameters of ore bodies in the subsurface is the primary concern in mineral exploration. In most cases, self-Potential data are delineated considering various simple or idealized structures for the interpretation of lateral and vertical variations of subsurface ore bodies. In this context, we developed an inversion algorithm to determine the different parameters associated with a 2D inclined plate-type structure, which does not require any a priori information. The developed algorithm can interpret appropriately every parameter with minimum uncertainty. The position of causative source body ( x _0), its half-width ( w ) and its depth ( z ) were the parameters interpreted using the developed algorithm. It was found that these parameters were well resolved within the estimated uncertainty, although solutions for w showed wide variability. The technique was verified with synthetic data without noise and with different degrees of Gaussian noise. The technique was also confirmed with three field datasets for mineral exploration, and the interpreted parameters were in fair agreement with those reported in earlier works.
-
Interpretation of self-Potential Anomaly over 2-D inclined thick sheet structures and analysis of uncertainty using very fast simulated annealing global optimization
Acta Geodaetica et Geophysica, 2017Co-Authors: Arkoprovo Biswas, S P SharmaAbstract:Global optimization for the interpretation of Self-Potential (SP) Anomaly using a very fast simulated-annealing (VFSA) inversion code is developed in the present study. The SP Anomaly is measured over a 2-D inclined thick sheet-type electrostatically polarized structure. Different model parameters for thick sheet-type structures are optimized. VFSA optimization yields a large number of well-fitting solutions in a huge model space. Uncertainty in the interpretation is analyzed and the study shows that it remains in few model parameters. The efficacy of the developed approach has been demonstrated using noise free and noisy synthetic examples. Field data from three different regions is interpreted for multiple thick sheet-type structures related to mineral exploration. The computation time for finding this convenient solution is very short (100 s for single structure) and the proposed method is found to be useful for interpretation of thick sheet-type structure and for multiple bodies as well. The interpretation procedure can be used for assessing mineral deposits as well as the SP of the earth’s crust.
-
a comparative performance of least square method and very fast simulated annealing global optimization method for interpretation of self Potential Anomaly over 2 d inclined sheet type structure
Journal of The Geological Society of India, 2016Co-Authors: Arkoprovo BiswasAbstract:Inversion of self-Potential Anomaly for 2-D inclined sheets of infinite horizontal extent has been studied. Least-square inversion and very fast simulated annealing global optimization has been used to model the five parameters of self Potential Anomaly. The method of least square and very fast simulated annealing global optimization method is compared and analyzed. Very fast simulated annealing can model the noisy and field data of self Potential Anomaly very precisely than linear inversion technique. However, time taken by very fast simulated annealing inversion is larger than linearized inversion. The comparative analysis has been done on synthetic data (noise free and noisy) and two field data from Bavarian woods Anomaly, Germany and Surda Anomaly, India to show the efficacy of both the methods. The estimated parameters were compared with those from previous studies using various global optimization algorithms, mainly neural network, genetic algorithm and particle swarm optimization on the same field data sets. It can be concluded that the global optimization algorithms considered in this study were able to yield compatible solutions with those from least-square methods. The present global optimization method is in good agreement with the other global optimization methods in terms of results and computation time.
-
integrated geophysical studies to elicit the subsurface structures associated with uranium mineralization around south purulia shear zone india a review
Ore Geology Reviews, 2016Co-Authors: Arkoprovo Biswas, S P SharmaAbstract:Abstract South Purulia Shear Zone in India is an important zone that hosts uranium mineralization. Since detailed geophysical studies have not been carried out in this region, an integrated geophysical study using self-Potential, resistivity, very low frequency electromagnetic and radiometric methods was performed to identify the subsurface structures that could host the hydrothermally altered uranium deposits in the area. The study reveals the wide and large magnitude of negative self-Potential Anomaly across the South Purulia Shear Zone. The peak negative self-Potential anomalies are correlated with the low gravity and low resistivity anomalies measured along various profiles. The low self-Potential, gravity and low resistivity Anomaly zones are also correlated with conducting zones inferred from very low frequency electromagnetic measurements. Interpretation of self-Potential data reveals multiple thick sheet-type vertical and/or inclined structures which might be associated with uranium mineralization. Schlumberger resistivity sounding data reveals an increasing trend of apparent resistivity with current electrode separations/depth. Apparent conductance measured simultaneously with resistivity measurement reveals an increase in current flow of current as depth increases. This exhibits the presence of thin conducting layers at these depths, which is not reflected in resistivity sounding data due to suppression problem. Also this conducting layer is consistent in various soundings and is connected from Raghunathpur to the South Purulia Shear Zone. Correlation of very low frequency and self-Potential data shows that the structures are comparable and a radiometric profile also advocate that the conducting structure is associated with radioactive minerals. These structures are likely to be mineralized zones as hydro-uranium Anomaly has also been reported from various locations in the area. Moreover, drilling results at a specific mine near the study area also confirms the presence of uranium mineralization. The hydrothermal activity associated with uranium mineralization seems to be still active in the area. Such combined geophysical studies are essential to understand this highly complex shear zone for the economic exploitation of its natural resources.
-
interpretation of self Potential Anomaly over idealized bodies and analysis of ambiguity using very fast simulated annealing global optimization technique
Near Surface Geophysics, 2015Co-Authors: Arkoprovo Biswas, S P SharmaAbstract:An efficient and reliable approach is developed for the interpretation of self-Potential Anomaly measured over idealized bodies (sphere, horizontal and vertical cylinder) using a very fast simulated annealing (VFSA) global optimization method. Since VFSA optimization lends itself to a number of good-fitting models in a vast multi-dimensional model space, the nature of ambiguity in the interpretation has also been investigated simultaneously. The study reveals that, while optimizing all model parameters (electric dipole density, horizontal location, depth, polarization angle and shape factor) together, the VFSA approach yields a number of equivalent solutions. It has been observed that the shape factor plays an important role in finding a reliable estimate of other model parameters. The analysis of ambiguity shows that a small change in the shape factor produces a large change in the estimated electric dipole density. Accordingly, inaccurate estimates of other model parameters have also been obtained. It has been observed that the optimization method is able to determine all the model parameters accurately when shape factor is fixed. Therefore, interpretation of Self-Potential data is carried out by adapting a two-step procedure. In the first step, all the model parameters are optimized. The inversion results obtained after the first step indicates the value of shape factor is around 1.5, 1.0 or 0.5. Subsequently in the second step, the shape factor is fixed to 1.5, 1.0 or 0.5 and other model parameters are optimized. In this way, the most reliable result has been obtained, and ambiguity in the interpretation has become insignificant. The efficacy of this approach is demonstrated using noise-free and noisy synthetic data and three field examples from different areas. One field example is interpreted using multiple targets to show the efficacy of the developed approach in dealing with optimization of a large number of model parameters. The computation time of the two-step procedure is very short (35 s for each step). It is highlighted that, even if the shape factor is known either from a priori geological information or Anomaly contour map, interpretation should be performed in two steps to obtain the most reliable estimate of various model parameters as well as confirmation of geometrical shape of the subsurface structure.
A Revil - One of the best experts on this subject based on the ideXlab platform.
-
self Potential signals associated with localized leaks in embankment dams and dikes
Engineering Geology, 2019Co-Authors: Soueid A Ahmed, A Revil, B Steck, C Vergniault, A Jardani, G VinceslasAbstract:Abstract The self-Potential method can be used to detect and monitor anomalous seepages in dams and embankments. In such a case, an electrical field of electrokinetic nature (i.e., associated with pore water flow) can be measured using a set of non-polarizable electrodes typically located at the ground surface or in some wells. This field can be in turn related to the pattern of groundwater flow. We built an experimental dam to investigate to which extent the self-Potential method can help characterizing seepages in dams. We first use the finite element method to simulate the ground water flow in a heterogeneous porous and permeable material by solving the groundwater flow equation. The resulting groundwater flow solution is then used to compute the electrical Potential distribution by solving the corresponding elliptic partial differential equation. In a preliminary experiment, we could not measure any self-Potential Anomaly associated with the infiltration of water in the dam. Our numerical simulations showed that the magnitudes of the self-Potential anomalies were controlled by (1) the nature of the flow regime (viscous laminar versus inertial laminar flow regimes) and (2) the presence of insulating Polyvinyl Chloride (PVC) tubes located at the end of the preferential flow channels in the structure of the dam. Thanks to these numerical simulations, we added sand at the entrance of the infiltration area in order to reduce the effects of the PVC tubes and to restrain the flow regime to the viscous laminar flow regime. New experiments allowed for detecting a self-Potential Anomaly with an amplitude of around −9 mV consistent with that obtained through numerical modelling with a finite element simulator. This comparison was used to test the accuracy of the modelling approach and define the strengths and weaknesses of the self-Potential method to determine preferential seepages in earth dam structures.
-
Dipolar self-Potential Anomaly associated with carbon dioxide and radon flux at Syabru-Bensi hot springs in central Nepal
Journal of Geophysical Research : Solid Earth, 2009Co-Authors: S Byrdina, A Revil, S.r. Pant, B. P. Koirala, P. L. Shrestha, D.r. Tiwari, U. P. Gautam, K Shrestha, S.n. Sapkota, S ContrairesAbstract:The Syabru-Bensi hot springs are located at the Main Central Thrust (MCT) zone in central Nepal. High carbon dioxide and radon exhalation fluxes (reaching 19 kg m À2 d À1 and 5 Bq m À2 s À1 , respectively) are associated with these hot springs, making this site a promising case to study the relationship between self-Potential and fluids (gas and water) exhalation along a fault zone. A high-resolution self-Potential map, covering an area of 100 m by 150 m that surrounds the main gas and water discharge spots, exhibits a dipolar self-Potential Anomaly with a negative peak reaching À180 mV at the main gas discharge spot. The positive lobe of the Anomaly reaching 120 mV is located along the terraces above the main gas and water discharge spots. Several electrical resistivity tomograms were performed in this area. The resistivity tomogram crossing the degassing area shows a dipping resistive channel interpreted as a fracture zone channeling the gas and the hot water. We propose a numerical finite difference model to simulate the flow pattern in this area with the constraints imposed by the electrical resistivity tomograms, the self-Potential data, the position of the gas vents, and hot water discharge area. This study provides insights on the generation of electrical currents associated with geothermal circulation in a geodynamically active area, a necessary prerequisite to study, using self-Potentials, a possible modulation of the geothermal circulation by tectonic activity. Citation: Byrdina, S., et al. (2009), Dipolar self-Potential Anomaly associated with carbon dioxide and radon flux at Syabru-Bensi hot springs in central Nepal,
-
high carbon dioxide flux associated with radon 222 gas exhalation and dipolar self Potential Anomaly at the syabru bensi hot springs in central nepal
Journal of Nepal Geological Society, 2007Co-Authors: Frederic Perrier, A Revil, S Byrdina, S.r. Pant, S Contraires, Sudhir Rajaure, Patrick Richon, Christian Francelanord, Umesh Gautam, B. P. KoiralaAbstract:Gas discharges have been identified at the Syabru-Bensi hot springs, located at the Main Central Thrust zone in Central Nepal and characterized by a water temperature reaching 61°C, high salinity and high alkalinity. The gas is mainly dry carbon dioxide, marked by a ? 13 C isotopic Anomaly of -0.8‰. The diffuse carbon dioxide exhalation flux, mapped by the accumulation chamber method, reaches 19 000 g×m -2 ×day -1 , comparable with values measured on active volcanoes. Radon exhalation flux at the soil surface has been measured at more than sixty points in the vicinity of the main gas discharge. Extreme values, larger than 2 Bq×m -2 ×s -1 , similar to peak values measured in volcanic areas or above uranium waste piles, are observed in association with the larger values of the carbon dioxide exhalation flux. This high radon exhalation thus results from emanation at depth, producing a radon concentration in the pore space varying from 25 000 to more than 50 000 Bq×m -3 , transported to the surface by the flow of carbon dioxide. The high radon-222 content of the carbon dioxide offers an interesting tracing method and an additional practical tool for long term monitoring, for example to study transient changes preceding large earthquakes. An extended dipolar self-Potential Anomaly has also been found, with a negative pole reaching -180 mV at the main gas discharge, and a wide positive lobe on the terrace above. This dipolar Anomaly, the largest reported so far, is interpreted in a hydroelectrical numerical model assuming a primary upward fluid flow associated with the gas, coupled with a secondary flow towards the springs, taking into account the resistivity structure obtained from profiles of electrical resistivity tomography. Thus, the Syabru-Bensi hot springs provide a unique opportunity to study the generation of electrical currents associated with biphasic fluid flow in a geodynamically active area. A pilot multidisciplinary team has now undertaken a multidisciplinary study of the geological, geophysical and geochemical properties of the Syabru-Bensi geothermal system. Studying the spatial and temporal variations of the gas discharges and the associated properties of the hot springs may lead to important clues on the presence and displacements of crustal fluids in relation with the nucleation of large earthquakes in the Nepal Himalayas. Journal of Nepal Geological Society, 2007, Vol. 36 (Sp. Issue) p.15
-
streaming electrical Potential Anomaly along faults in geothermal areas
Geophysical Research Letters, 1998Co-Authors: A Revil, Philippe PezardAbstract:Electrical Potential anomalies are often measured associated with geothermal areas and volcanoes. In these systems, fluid flow is usually mostly restricted to faults and fracture networks. An equation describing electrical Potential anomalies of electrokinetic nature associated with fluid upflow induced by a thermal source along faults is derived. The electrical Potential Anomaly is related to the depth of the thermal reservoir, the temperature difference between the surface and the reservoir of the geothermal area, the thermal expansion of water, and the streaming electrical Potential coupling coefficient in the fault zone. A quantitative calculation of the electrokinetic Anomaly is provided by comparing this model to a self-Potential survey of the Cerro-Prieto geothermal field [Fitterman and Corwin, 1982]. The predictions of the model agree well with the field measurements.
L Milano - One of the best experts on this subject based on the ideXlab platform.
-
monitoring time evolution of self Potential Anomaly sources by a new global optimization approach application to organic contaminant transport
Journal of Hydrology, 2019Co-Authors: Payal Rani, Rosa Di Maio, E Piegari, Eleonora Vitagliano, P Soupios, L MilanoAbstract:Abstract Complex interactions among organic contaminant, soil and water change the electrical properties of the subsurface often causing strong self-Potential (SP) anomalies, whose monitoring is proposed as a useful tool to determine the temporal evolution of the contaminant plumes. In the present study, we focus on the problem of organic contaminant transport related to olive oil mill wastes (OOMWs), which represent an important environmental problem in Mediterranean countries. The diffusion of the contaminants into the subsurface is studied by using a global optimization procedure on SP data measured, at different times, in a well-studied contaminated pilot area located next to the Keritis river in western Crete island (Greece). Despite the complex hydrogeological conditions related to the proximity to both the Keritis river and a small seasonal stream, the analysis of five SP datasets acquired along the same profile shows that the proposed hybrid Genetic-Price algorithm is able to reproduce the main features of the SP signals, thus identifying probable multiple SP Anomaly sources and their changes over time. In particular, preferential horizontal pathways of OOMW and their migration in the vadose zone during the summer season were identified, providing some useful insights for future planning of remediation actions.
-
quantitative interpretation of multiple self Potential Anomaly sources by a global optimization approach
Journal of Applied Geophysics, 2019Co-Authors: Rosa Di Maio, E Piegari, Payal Rani, Rolando Carbonari, Eleonora Vitagliano, L MilanoAbstract:Abstract Multiple self-Potential (SP) anomalies are analyzed by using a Genetic-Price Algorithm (GPA), which has been recently introduced for the inversion of SP data. The proposed approach is tested on multiple synthetic anomalies, which are modeled by horizontal cylinders. First, a forward modeling is used to analyze the resolution of such anomalies by varying all model parameters. Then, GPA is applied to invert synthetic multiple SP anomalies. The numerical analyses show that the proposed approach is able to fully characterize the Anomaly sources by providing the correct values of the model parameters as well as the number of sources, even if Gaussian random noise is added to the synthetic data. Furthermore, to show the computational efficiency of GPA, the results of a comparative analysis with the Very Fast Simulated Annealing algorithm are given. The validity of the GPA approach is confirmed by its application to three examples of self-Potential field data from mineral exploration and groundwater investigations, which are presented and discussed in relation to other inversion approaches. Finally, the quantitative interpretation of multiple anomalies along a SP profile crossing the Mt. Somma-Vesuvius volcano caldera (southern Italy) is provided.
Mohamed H. Khalil - One of the best experts on this subject based on the ideXlab platform.
-
Estimating Model Parameters from Self-Potential Anomaly of 2D Inclined Sheet Using Whale Optimization Algorithm: Applications to Mineral Exploration and Tracing Shear Zones
Natural Resources Research, 2019Co-Authors: Mohamed Gobashy, Maha Abdelazeem, Mohamed Abdrabou, Mohamed H. KhalilAbstract:The use of spontaneous Potential (SP) anomalies is well known in the geophysical literatures because of its effectiveness and significance in solving many complex problems in mineral exploration. The inverse problem of self-Potential data interpretation is generally ill-posed and nonlinear. Methods based on derivative analysis usually fail to reach the optimal solution (global minimum) and trapped in a local minimum. A new simple heuristic solution to SP anomalies due to 2D inclined sheet of infinite horizontal length is investigated in this study to solve these problems. This method is based on utilizing whale optimization algorithm (WOA) as an effective heuristic solution to the inverse problem of self-Potential field due to a 2D inclined sheet. In this context, the WOA was applied first to synthetic example, where the effect of the random noise was examined and the method revealed good results using proper MATLAB code. The technique was then applied on several real field profiles from different localities aiming to determine the parameters of mineralized zones or the associated shear zones. The inversion parameters revealed that WOA detected accurately the unknown parameters and showed a good validation when compared with the published inversion methods.
Shraddha Jain - One of the best experts on this subject based on the ideXlab platform.
-
Global Optimization for Delineation of Self-Potential Anomaly of a 2D Inclined Plate
Natural Resources Research, 2020Co-Authors: Shraddha Jain, Arkoprovo BiswasAbstract:A fast and efficient technique for explanation of self-Potential anomalies is of immense importance for exploration, engineering, and environmental problems. Estimation of model parameters of ore bodies in the subsurface is the primary concern in mineral exploration. In most cases, self-Potential data are delineated considering various simple or idealized structures for the interpretation of lateral and vertical variations of subsurface ore bodies. In this context, we developed an inversion algorithm to determine the different parameters associated with a 2D inclined plate-type structure, which does not require any a priori information. The developed algorithm can interpret appropriately every parameter with minimum uncertainty. The position of causative source body ( x _0), its half-width ( w ) and its depth ( z ) were the parameters interpreted using the developed algorithm. It was found that these parameters were well resolved within the estimated uncertainty, although solutions for w showed wide variability. The technique was verified with synthetic data without noise and with different degrees of Gaussian noise. The technique was also confirmed with three field datasets for mineral exploration, and the interpreted parameters were in fair agreement with those reported in earlier works.