Article
Geochemistry & Geophysics
Xianxiang Wang, Nongren You, Qingyun Di, Juzhi Deng, Yongbang Chang
Summary: The multichannel transient electromagnetic method is a useful geophysical tool for mapping resistive targets in both near-surface and deep geological structures. The proposed 3-D parallel inversion algorithm based on nonlinear conjugate gradient method and moving footprint technique has been shown to effectively speed up the data inversion process.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Daniel Blatter, Matthias Morzfeld, Kerry Key, Steven Constable
Summary: The study introduces a method for computing meaningful uncertainty quantification in regularized inversion of electromagnetic geophysical data by combining regularized inversion, Bayesian sampling, and a 'randomize-then-optimize' approach. The method accelerates convergence, leverages computational parallelism, and is highly scalable to 2-D and 3-D EM problems.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Daniel Blatter, Matthias Morzfeld, Kerry Key, Steven Constable
Summary: This paper is about a mathematical and computational framework for computing uncertainty quantification in regularized inversions of electromagnetic data. It showcases the practical application of the RTO-TKO sampling algorithm and demonstrates its computational advantages and ability to utilize massive parallelism through case studies of seafloor magnetotelluric (MT) and surface-towed controlled source electromagnetic data inversion. The paper also compares the uncertainty quantification of RTO-TKO with results from trans-dimensional sampling and discusses the practical implications of the findings.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Tan Qin, Thomas Bohlen, Niklas Allroggen
Summary: In this study, a frequency-dependent ground-penetrating radar (GPR) full-waveform inversion (FWI) method is developed to improve the reconstruction of dielectric permittivity and electrical conductivity models. The permittivity attenuation acts as a low-pass filter and is necessary for a robust conductivity reconstruction in a high permittivity attenuation environment.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
S. M. Ansari, J. A. Craven
Summary: In this paper, a fully finite-element based inversion methodology is proposed for imaging 3D magnetotelluric impedance data on unstructured meshes. The methodology utilizes a rigorous regularization scheme and a face-based finite-element basis function for discretizing the model gradient. The developed algorithm is validated and proven to be correct through test examples and the performance of iterative solvers.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Andrea Darrh, Yaoguo Li
Summary: This study focuses on the impact of anisotropy on geological data interpretation, specifically on extracting 1-D dipping anisotropy characteristics from magnetotelluric (MT) data. The use of different norms in inversion methods was explored to assess sensitivity to anisotropic dip angles.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Mathematics, Applied
Z. H. I. M. I. N. G. CHEN, W. E. N. L. O. N. G. ZHANG, J. U. N. ZOU
Summary: In this study, the regularized solutions and finite element solutions to inverse source problems governed by partial differential equations were investigated. Stochastic convergence and optimal finite element convergence rates were established under point-wise measurement data with random noise. Numerical experiments demonstrated the effectiveness of the analytical results.
SIAM JOURNAL ON NUMERICAL ANALYSIS
(2022)
Article
Geochemistry & Geophysics
Zhihao Rong, Yunhe Liu, Changchun Yin, Xinpeng Ma, Luyuan Wang, Changkai Qiu, Bo Zhang, Xiuyan Ren, Yang Su
Summary: We propose a novel smoothing regularization scheme for 3-D magnetotelluric inversion based on unstructured tetrahedral discretization. By transforming the model into a constraint domain and using gradient filtering, our method achieves smoother model updates compared to conventional explicit smoothing methods. Numerical results on synthetic data and USArray data demonstrate that our new strategy improves convergence speed and provides more reliable underground structures with better data fitting.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Wouter Deleersnyder, Benjamin Maveau, Thomas Hermans, David Dudal
Summary: Regularization methods improve the stability of ill-posed inverse problems by introducing prior characteristics for the solution. In this paper, a multidimensional scale-dependent wavelet-based l(1)-regularization term is proposed to solve the ill-posed airborne electromagnetic induction inverse problem. The regularization term is flexible and can recover various inversion models based on a suitable wavelet basis function.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Yu Liu, James Irving, Klaus Holliger
Summary: The proposed approach combines diffraction analysis and inversion of the reflected wavefield to estimate the detailed subsurface velocity structure from common-offset GPR reflection measurements. Testing and validation on synthetic data sets and a field example demonstrate the viability and robustness of the method. Additionally, the efficiency of the method in terms of field effort and computational cost allows for easy extension to 3-D, making it more attractive compared to multi-offset-based GPR velocity estimation techniques.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Grigory Gurin, Konstantin Titov, Yuri Ilyin, Ekaterina Fomina
Summary: Electrically conductive minerals are found in various geological contexts and characterization of rocks containing electrically conductive inclusions is crucial in many sectors. Laboratory measurements show that the shape, size, and composition of the inclusions significantly impact induced polarization parameters. The experimental data indicate that the polarization magnitude of electrically conductive inclusions is proportional to the normal component of the electrical current density on their surface.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Tina Martin, Andreas Weller
Summary: Induced polarization (IP) is a common method in ore exploration that characterizes material properties of ores. Previous studies have shown that IP parameters are sensitive to the type, content, or grain size of conductive minerals. This study compares IP spectra of sand-pyrite mixtures with single grain radius fractions to those with two different grain radii fractions. The observed effect is explained by an interaction between neighboring pyrite particles. The experimental results motivate further improvement of existing mechanistic models.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Tina Martin, Andreas Weller, Laura Behling
Summary: The study investigates the effect of desaturation on induced polarization (IP) signals, with results showing a decrease in conductivity amplitude and a slightly larger saturation exponent, while total chargeability remains constant. The mean relaxation time decreases significantly during drying, but the normalized relaxation time does not show a dependence on water saturation. The proposed conceptional model compares pyrite particles in an embedding material to an electrical RC circuit, with resistivity increase causing an increase in relaxation time.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Chen Wang, Andrew Binley, Lee D. Slater
Summary: This study provides a theoretical and numerical modeling explanation for the origin of negative IP effects in frequency-domain IP (FDIP) measurements, and identifies the reasons for the occurrence of positive apparent phase. The results suggest that positive apparent phase measurements should be expected and retained during inversion and interpretation.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Mathematics, Interdisciplinary Applications
Alvaro H. Salas, Wedad Albalawi, M. R. Alharthi, S. A. El-Tantawy
Summary: This paper introduces novel analytical and numerical techniques for solving and analyzing nonlinear second-order ordinary differential equations. Two different analytical approximations and numerical approximations are presented and applied to real-life nonlinear oscillator equations. The accuracy of these approximations is evaluated through comparisons with the Runge-Kutta numerical approximation.
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Geochemistry & Geophysics
Laust Boersting Pedersen, Mehrdad Bastani, Jochen Kamm
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Geochemistry & Geophysics
Jochen Kamm, Ildiko Antal Lundin, Mehrdad Bastani, Martiya Sadeghi, Laust B. Pedersen
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Geochemistry & Geophysics
M. Cherevatova, M. Yu. Smirnov, A. G. Jones, L. B. Pedersen, M. Becken, M. Biolik, M. Cherevatova, J. Ebbing, S. Gradmann, M. Gurk, J. Huebert, A. G. Jones, A. Junge, J. Kamm, T. Korja, I. Lahti, A. Lower, C. Nittinger, L. B. Pedersen, A. Savvaidis, M. Smirnov
Article
Geochemistry & Geophysics
Sayyed Mohammad Abtahi, Laust Borsting Pedersen, Jochen Kamm, Thomas Kalscheuer
Article
Geochemistry & Geophysics
Sayyed Mohammad Abtahi, Laust Borsting Pedersen, Jochen Kamm, Thomas Kalscheuer
Article
Geochemistry & Geophysics
Rafael Abreu, Jochen Kamm, Anne-Sophie Reiss
GEOPHYSICAL JOURNAL INTERNATIONAL
(2017)
Article
Geochemistry & Geophysics
Sayyed Mohammad Abtahi, Laust Borsting Pedersen, Jochen Kamm, Thomas Kalscheuer
Article
Geochemistry & Geophysics
Matthew J. Comeau, Johannes S. Kaufl, Michael Becken, Alexey Kuvshinov, Alexander Grayver, Jochen Kamm, Sodnomsambuu Demberel, Usnikh Sukhbaatar, Erdenechimeg Batmagnai
EARTH AND PLANETARY SCIENCE LETTERS
(2018)
Article
Mathematics, Applied
Rafael Abreu, Zeming Su, Jochen Kamm, Jinghuai Gao
JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS
(2018)
Article
Geochemistry & Geophysics
M. Cherevatova, M. Smirnov, T. Korja, P. Kaikkonen, L. B. Pedersen, J. Hubert, J. Kamm, T. Kalscheuer
Article
Geochemistry & Geophysics
Laust B. Pedersen, Jochen Kamm, Mehrdad Bastani
GEOPHYSICAL PROSPECTING
(2020)
Article
Geochemistry & Geophysics
Jochen Kamm, Michael Becken, Rafael Abreu
GEOPHYSICAL JOURNAL INTERNATIONAL
(2020)
Article
Geochemistry & Geophysics
J. S. Kaeufl, A. Grayver, M. J. Comeau, A. Kuvshinov, M. Becken, J. Kamm, E. Batmagnai, S. Demberel
GEOPHYSICAL JOURNAL INTERNATIONAL
(2020)
Article
Geochemistry & Geophysics
Alireza Malehmir, Magnus Andersson, Suman Mehta, Bojan Brodic, Raymond Munier, Joachim Place, Georgiana Maries, Colby Smith, Jochen Kamm, Mehrdad Bastani, Henrik Mikko, Bjorn Lund