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Exploration of a Copper Ore deposit in Elbistan/Turkey Using 2d inversion of the Time-domain Induced Polarization data by Using Unstructured Mesh

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PURE ANd APPLIEd GEOPHYSICS 2022年第6-7期179卷 2255-2272页

作者： Adrian, Juliane Tezkan, Bulent Candansayar, M. Emin Univ Cologne Inst Geophys & Meteorol Albertus Magnus Pl D-50923 Cologne Germany Forschungszentrum Julich Inst Adv Simulat IAS 7 Civil Safety Res Wilhelm Johnen Str D-52428 Julich Germany Ankara Univ Dept Geophys Engn Geophys Modeling Grp GMG Fac Engn TR-06830 Ankara Turkey

We present the results of a direct current (dC) resistivity and time-domain induced polarization (TdIP) survey exploring a copper ore deposit in Elbistan/Turkey. The ore deposit is elongated below a valley and is of disseminated form with sulfide content. dC and IP data were acquired using the pole-dipole array on eight parallel profiles crossing the valley perpendicularly. The length of each profile was 300 m with an inter-profile distance of about 50 m. The data were interpreted by a newly developed 2d dC/TdIP inversion algorithm. The finite element algorithm uses a local smoothness constrained regularization on unstructured meshes. The finite element forward solution, as well as the inverse problem, is solved by an iterative preconditioned conjugate solver. The depth of investigation (dOI) was determined from cumulative sensitivities of the 2d inversion algorithm results. Because of the dissemination of the ore, the 2d inversion of the dC data was ambiguous: However, due to the sulfide content, a strong chargeability anomaly associated with the ore body was detected. We show that chargeability anomalies can generally be detected in the absence or presence of corresponding resistivity anomalies. This highly chargeable structure was confined in lateral direction. Although the lower boundary of the structure could not be resolved by the applied field set-up, a rough estimation of it could be derived at a depth of 90 m using synthetic modeling analyses. The 2d chargeability models are consistent with existing borehole information.

关键词： Ore exploration direct current resistivity induced polarization 2d inversion finite elements

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An Iterative 3d Correction plus 2d inversion Procedure to Remove 3d Effects from 2d ERT data along Embankments

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SENSORS 2024年第12期24卷 3759页

作者： Hojat, Azadeh Politecn Milan Dipartimento Ingn Civile & Ambientale I-20133 Milan Italy Shahid Bahonar Univ Kerman Dept Min Engn Kerman Iran

This paper addresses the problem of removing 3d effects as one of the most challenging problems related to 2d electrical resistivity tomography (ERT) monitoring of embankment structures. When processing 2d ERT monitoring data measured along linear profiles, it is fundamental to estimate and correct the distortions introduced by the non-uniform 3d geometry of the embankment. Here, I adopt an iterative 3d correction plus 2d inversion procedure to correct the 3d effects and I test the validity of the proposed algorithm using both synthetic and real data. The modelled embankment is inspired by a critical section of the Parma River levee in Colorno (PR), Italy, where a permanent ERT monitoring system has been in operation since November 2018. For each model of the embankment, reference synthetic data were produced in Res2dmod and Res3dmod for the corresponding 2d and 3d models. Using the reference synthetic data, reference 3d effects were calculated to be compared with 3d effects estimated by the proposed algorithm at each iteration. The results of the synthetic tests showed that even in the absence of a priori information, the proposed algorithm for correcting 3d effects converges rapidly to ideal corrections. Having validated the proposed algorithm through synthetic tests, the method was applied to the ERT monitoring data in the study site to remove 3d effects. Two real datasets from the study site, taken after dry and rainy periods, are discussed here. The results showed that 3d effects cause about +/- 50% changes in the inverted resistivity images for both periods. This is a critical artifact considering that the final objective of ERT monitoring data for such studies is to produce water content maps to be integrated in alarm systems for hydrogeological risk mitigation. The proposed algorithm to remove 3d effects is thus a rapid and validated solution to satisfy near-real-time data processing and to produce reliable results.

关键词： dam earthen embankment river levee electrical resistivity tomography 2d inversion 2d/3d forward modelling 3d effects

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2d magnetotelluric inversion based on ResNet

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Artificial Intelligence in Geosciences 2023年第1期4卷 119-127页

作者： LiAn Xie Bo Han Xiangyun Hu Ningbo Bai Institute of Geological Survey China University of GeosciencesWuhan430074China Hubei Subsurface Multi-Scale Imaging Key Laboratory School of Geophysics and GeomaticsChina University of GeosciencesWuhan430074China Key Laboratory of Geological Survey and Evaluation of Ministry of Education China University of GeosciencesWuhan430074China

In this study,a deep learning algorithm was applied to two-dimensional magnetotelluric(MT)data *** with the traditional linear iterative inversion methods,the MT inversion method based on convolutional neural networks(CNN)does not rely on the selection of the initial model parameters and does not fall into the local *** the CNN inversion models can provide a clear electrical interface division,their inversion results may remain prone to abrupt electrical interfaces as opposed to the actual underground electrical *** solve this issue,a neural network with a residual network architecture(ResNet-50)was constructed in this *** the apparent resistivity and phase pseudo-section data as the inputs and with the resistivity parameters of the geoelectric model as the training labels,the modified ResNet-50 model was trained end-to-end for producing samples according to the corresponding production strategy of the study *** experiments,the training of the ResNet-50 with the dice loss function effectively solved the issue of over-segmentation of the electrical interface by the cross-entropy function,avoided its abrupt inversion,and overcame the computational inefficiency of the traditional iterative *** proposed algorithm was validated against MT data measured from a geothermal field prospect in Huanggang,Hubei Province,which showed that the deep learning method has opened up broad prospects in the field of MT data inversion.

关键词： Magnetotellurics 2d inversion Residual network deep learning

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Analysis of Geological Structures by 2d Magnetotelluric inversion in Bang Hot Spring Area, Quang Binh Province 2nd

Analysis of Geological Structures by 2D Magnetotelluric Inve...

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2nd International Conference on Geospatial Technologies and Earth Resources (GTER)

作者： Cuong Van Anh Le duy Thong Kieu Ngoc dat Pham Hop Phong Lai Univ Sci Ho Chi Minh City Vietnam Vietnam Natl Univ Ho Chi Minh City Ho Chi Minh City Vietnam Hanoi Univ Min & Geol Hanoi Vietnam Vietnam Acad Sci & Technol Inst Geol Sci Hanoi Vietnam

ISBN: (纸本)9783031204654;9783031204630;9783031204623

The magnetotelluric method can reveal geology structures information through conductivity distribution from a few hundred meters to kilometers depending on electromagnetic data frequency measurement. Although the raw magnetotelluric data does not clearly illustrate faults or geothermal reservoirs, they can be more visible in the conductivity models after inversion. However, the 2d inverted conductivity image is often distorted by geoelectrical strike as fault zones. Hence, in this work, we have integrated geology strike analysis to 2d magnetotelluric inversion to have better data quality interpretation in the Bang hot spring area, Quang Binh Province, Vietnam. The inverted conductivity model from the 2d integrated magnetotelluric inversion can show the fault system and possible hot source zone of Bang area. Great compatibility between the magnetotelluric inversion result with other geophysical data such as seismic and prior geology information can inspire its application in geothermal research.

关键词： Magnetotelluric 2d inversion Impedance tensor Strike analysis Hot spring

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Magnetotelluric data analysis using 2d inversion: A case study from Al-Mubazzarah Geothermal Area (AMGA), Al-Ain, United Arab Emirates

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HELIYON 2021年第6期7卷 e07440页

作者： Saibi, Hakim Khosravi, Sadieh Cherkose, Biruk Abera Smirnov, Maxim Kebede, Yosef Fowler, Abdel-Rahman UAEU Geol Dept Coll Sci Al Ain U Arab Emirates Lulea Univ Technol Lulea Sweden Geol Survey Ethiopia Addis Ababa Ethiopia

Geothermal manifestations (hot springs) emerge in the Al-Mubazzarah Geothermal Area (AMGA), Al-Ain city, Abu dhabi Emirate, United Arab Emirates. This paper presents the application and results of a Magnetotelluric (MT) survey, which was carried out in 2017 at the AMGA geothermal field. The MT method was used to investigate the variations in the electrical conductivity beneath the AMGA. This study focuses on characterizing the patterns of subsurface electrical conductivity of the AMGA geothermal reservoir. dimensionality analysis of the measured MT data indicate that 2d inversion is appropriate for the subsurface resistivity interpretation. The inversion results support a model consisting of three resistivity-defined layers;from top to bottom they are: (1) a shallow layer with resistivity ranging from 10 to 20 Omega m, representing recent alluvial and windblown deposits, (2) a second conductive layer with resistivities less than 10 Omega m, beneath the first layer. This layer is recognized as the Tertiary carbonate sequence in the region, (3) a deep, moderate to relatively high resistive zone, 10-30 Omega m beginning at 800 m depth and reaching 4 km depth in the northern part of the profile, representing Mesozoic basement rocks. The observed moderate to high resistivity zone (10-30 Omega m) in the 2d model may represent a region where the hot groundwaters originated (geothermal reservoir), with the hottest geothermal located at a depth greater than 4 km. The geothermal reservoir zone is also represented by a low to high density contrast and a low to moderate magnetic susceptibility, as indicated in the inverted potential field data models, and confirmed the existence of a north dipping major fault.

关键词： Magnetotelluric Potential field 2d inversion Geothermal AMGA Low-enthalpy Al-Ain United Arab Emirates

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Near-surface resistivity structure near avcilar landslide in Istanbul, Turkey by 2d inversion of VLF data

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JOURNAL OF APPLIEd GEOPHYSICS 2019年 163卷 73-83页

作者： Karcioglu, Gokhan Istanbul Univ Cerrahpasa Geophys Engn Dept Istanbul Turkey

In this study, VLF data collection and 2d modeling is carried out in order to gather information about the Avatar landslide and to detect possible faults, may be residing in the study area, located at the southwestern slopes of the Kucukcekmece Lake in Avatar, Istanbul, Turkey. data collection is realized on 12 traverses in TE mode between 2015 and 2017 and mostly consists of in-phase and quadrature components of the tipper data. On a single profile, apparent resistivity and phase data is also collected. The study area is placed near an urban area and relatively higher noise levels are observed at several profiles. However, data in adjacent and overlapping profiles shows consistency and repeatability. Thus, instead of omitting these profiles, the data with higher noise is treated with Empirical Mode decomposition (EMd) filtering. Karous-Hjelt filtered in-phase component data is calculated for basic interpretation, and 2d inversions are performed in order to obtain more information about the shallow geo-electrical structure. The approximate resistivities of the near-surface geological formations are differentiated from the recovered models. Accordingly, 2d inversion results suggest resistivity values significantly different from the values previously obtained using 1d methods. inversion results also revealed the structure and the base of the Avalar landslide successfully. In the northern part of the study area, the top of the Gurpmar formation, forming the base of the Avalar landslide, is detected with varying depths up to 25 m, In the resistivity images any structure that may represent a fault is not detected. (C) 2019 Elsevier B.V. All rights reserved.

关键词： VLF Near surface geophysics Karous-Hjelt filter Geoelectrical modeling 2d inversion

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Investigating subsurface structures of Gachsaran oil field in Iran using 2d inversion of magnetotelluric data

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EXPLORATION GEOPHYSICS 2018年第2期49卷 148-162页

作者： Sarvandani, Mohamadhasan Mohamadian Kalateh, Ali Nejati Ghaedrahmati, Reza Majidi, Abbas Shahrood Univ Technol Fac Min Petr & Geophys Engn Shahrood *** Iran Lorestan Univ Fac Engn Khorramabad *** Iran Natl Iranian Oil Co Tehran *** Iran

The magnetotelluric method is most often considered in hydrocarbon exploration in cases which are difficult for seismic imaging. In 2012, the National Iranian Oil Co. (NIOC) conducted an electromagnetic survey which included magnetotelluric and time domain electromagnetic (TEM) methods in the Gachsaran oil field in the south-west of Iran to delineate the reservoir formation of the region. Magnetotelluric data were collected at 5215 sites and a regular site spacing of 200mwas utilised. We chose a 16.5 km profile perpendicular to the main geological strike direction in the study area. The Bahr's skew and Mohr diagrams were used to perform the dimensionality analysis of the magnetotelluric (MT) data and indicated that the subsurface structures are one dimensional or two dimensional at shallow depths, whereas they are mainly three dimensional at lower depths. The phase tensor showed that the dominant geoelectrical strike in the survey area is in the NW-SE direction. Two dimensional inversion was utilised to acquire a realistic resistivity model that was compromise between the spatial smoothness of the inversion model and theMTdata fit. Apparent resistivity and phase data were modelled using the smoothness-constrained least-squares method. Models obtained of the TM, TE and TM+TE mode data were examined to have the best possible interpretation. The resulting 2d model revealed the main anticline and overthrust zone in the region. The near surface layer in the model which has a low resistivity, was identified as the cover rock of the region. The formation of the top of the reservoir in the region is estimated to be located at the depth of 1400-1900m below sea level. The resistivity model is in good correlation with the geological features and the results of well drilling.

关键词： 2d inversion Asmari Formation Gachsaran oil field magnetotelluric MT2dInvMatlab

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2d nonlinear inversion of bedrock motion from the surface motion of a layered half-space

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ENGINEERING ANALYSIS WITH BOUNdARY ELEMENTS 2019年 106卷 149-159页

作者： Liang, Jianwen Zhang, Aijuan He, Ying Zhang, Ping Tianjin Univ State Key Lab Hydraul Engn Simulat & Safety Tianjin 300350 Peoples R China Tianjin Univ Renai Coll Tianjin 301636 Peoples R China Tianjin Chengjian Univ Tianjin 300384 Peoples R China

This paper proposes a method for two-dimensional (2d) nonlinear inversion of bedrock earthquake motion from the surface motion of a layered half-space. The exact dynamic-stiffness matrices of soil layer and half-space are used for the inversion of bedrock motion and incident angle from both the surface horizontal motion and vertical motion, and the equivalent linearization approach is used to consider the nonlinearity of the soil layers. The method of inversion is verified by an example of obliquely incident El Centro Earthquake record at bedrock. It is shown that, the bedrock motion and incident angle can be accurately inversed from both the horizontal motion and vertical motion. The one-dimensional (1d) traditional inversion of bedrock horizontal motion from only surface horizontal motion in literatures may cause large error due to ignoring wave mode conversion, because there is vertical motion accompanying two surface horizontal motions in real earthquake records anyway. The error in 10 inversion depends on the ratio of surface vertical motion to horizontal motion, and the larger the surface vertical motion, the larger the error.

关键词： Bedrock motion Surface motion 2d inversion Nonlinear inversion Equivalent linearization Oblique incidence Wave mode conversion Layered half-space

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2d Magnetotelluric inversion using Supervised descent Method

2D Magnetotelluric Inversion using Supervised Descent Method

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International Applied-Computational-Electromagnetics-Society Symposium - China (ACES)

作者： Guo, Rui Li, Maokun Xiang, Chunwang Yang, Fan Xu, Shenheng Abubakar, Aria Tsinghua Univ Beijing Natl Res Ctr Informat Sci & Technol State Key Lab Microwave & Digital Commun Dept Elect Engn Beijing 100084 Peoples R China Schlumberger Houston TX USA

ISBN: (纸本)9780996007849

In this work, we study the 2d magnetotelluric (MT) inversion by a machine learning scheme. Specifically, supervised descent method (SdM), which learns the descent directions of an optimization problem, is applied to MT data inversion. The inversion is composed of offline training and online prediction. In the offline stage, the descent directions can be learned from a set of training data;and in the online stage, data inversion can be achieved by updating the models using the learned directions. SdM offers a more convinient way to incorporate prior information into MT inversion. Furthermore, the learning scheme can achieve fast computation. Numerical tests show that we may be able to reconstruct thin layers from MT data with enough information.

关键词： magnetotellurics finite-difference 2d inversion supervised decent method gradient learning

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ELRIS2d: A MATLAB Package for the 2d inversion of dC Resistivity/IP data

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ACTA GEOPHYSICA 2016年第2期64卷 443-462页

作者： Akca, Irfan Ankara Univ Fac Engn Dept Geophys Engn TR-06100 Ankara Turkey

ELRIS2d is an open source code written in MATLAB for the two-dimensional inversion of direct current resistivity (dCR) and time domain induced polarization (IP) data. The user interface of the program is designed for functionality and ease of use. All available settings of the program can be reached from the main window. The subsurface is discretized using a hybrid mesh generated by the combination of structured and unstructured meshes, which reduces the computational cost of the whole inversion procedure. The inversion routine is based on the smoothness constrained least squares method. In order to verify the program, responses of two test models and field data sets were inverted. The models inverted from the synthetic data sets are consistent with the original test models in both dC resistivity and IP cases. A field data set acquired in an archaeological site is also used for the verification of outcomes of the program in comparison with the excavation results.

关键词： 2d inversion GUI finite elements hybrid mesh

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