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
Geochemistry & Geophysics
Wenping Jiang, Jingming Duan, Michael Doublier, Andrew Clark, Anthony Schofield, Ross C. Brodie, James Goodwin
Summary: The magnetotellurics technique is useful for understanding and imaging mineral systems. This study used multiscale data sets to map areas of mineral potential in northern Australia by resolving the lithospheric architecture. The results suggest that major faults played a role in transporting metallic fluids to the upper crust, potentially forming mineral deposits.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Max A. Meju, A. S. Saleh, A. B. Karpiah, M. S. Masnan, R. Miller, X. Legrand, J. H. W. Kho
Summary: 3-D imaging of the lithosphere in the Mexican Ridges fold belt helps understand the crustal deformations and deep tectonic processes related to extinct Jurassic seafloor spreading. Marine magnetotelluric data is used to reconstruct the 3-D anisotropic resistivities of the lithosphere and identify geological boundaries and crustal thickness. The study reveals anomalous layered zones of low resistivity and high electrical anisotropy at depth, indicating intense deformation and/or recent magmatic influence. Additionally, a banded crystalline basement structure is found, which correlates with transform and normal faults formed during the Late Jurassic opening of the Gulf of Mexico.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Ahmad Shahir bin Saleh, Max A. Meju, Nur Azwin Binti Ismail, Mohd Nawawi bin Mohd Nordin
Summary: The use of seismic-derived structure tensor for guiding the inversion of non-seismic data is gaining attention. This paper focuses on marine magnetotellurics (MT) and studies the practical aspects of seismic-guided electromagnetic (EM) inversion. By comparing different options, the study shows that an initial model guided by seismic FWI velocity gives the best match to well logs. The choice of structure tensor is important, and the structure tensor from APSDM reflectivity data is preferred.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
J. Wittke, B. Tezkan
Summary: This paper presents a new 2-D modeling and inversion scheme for interpreting magnetotelluric data, utilizing a novel meshless forward operator. The discretization technique using nodes in a generalized meshless framework successfully recovers conductivity structures from given data. Validation of the algorithm through synthetic and field data shows its capability to accurately model magnetotelluric responses and generate meaningful conductivity models.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Mikhail Kruglyakov, Alexey Kuvshinov
Summary: This paper introduces a method for modelling magnetic tippers in spherical geometry to study the distribution of electrical conductivity on a global scale. By using a proposed source model and a developed solver, the electromagnetic field in a spherical shell is accurately calculated and the results of modelling the ocean induction effect are presented.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Daniel Blatter, Anandaroop Ray, Kerry Key
Summary: Bayesian inversion of electromagnetic data was used to infer subsurface resistivity with crucial uncertainty information. A fully 2-D, trans-dimensional Bayesian inversion of magnetotelluric (MT) data was successfully demonstrated for the first time in this study. The use of a Gaussian process algorithm allowed for a parsimonious parametrization of the model and made the computational cost tractable.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Chaojian Chen, Mikhail Kruglyakov, Alexey Kuvshinov
Summary: This paper introduces an efficient 3-D EM modelling tool based on a multinested IE approach, which conducts modelling on a larger domain and coarse grid, then refines results in a smaller domain and denser grid. By using FFT for matrix-vector multiplications, the computational efficiency is improved.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
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
Janghwan Uhm, Junyeong Heo, Dong-Joo Min, Seokhoon Oh, Ho-Joon Chung
Summary: This study focused on the geological structures near the epicentre of the earthquake that occurred in Gyeongju, South Korea in 2016. By conducting a 3-D audio-magnetotelluric survey and applying various imaging strategies, the researchers successfully inverted the noisy field data in Gyeongju, confirming the effectiveness of the proposed strategies.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Hongbo Yao, Zhengyong Ren, Jingtian Tang, Rongwen Guo, Jiayong Yan
Summary: Joint inversion of magnetotelluric (MT) and geomagnetic depth sounding (GDS) responses can constrain the crustal and mantle conductivity structures. A new open-source Bayesian framework is proposed to accurately estimate model uncertainties by generating multiple models that fit the observed data. A trans-dimensional Markov Chain Monte Carlo (MCMC) method is employed to automatically determine the number of layers and detect conductivity discontinuities in the Earth's interior. The method is validated using synthetic data sets and applied to the Tucson geomagnetic observatory in North America.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Dan R. Glaser, Benjamin E. Barrowes, Fridon Shubitidze, Lee D. Slater
Summary: This study evaluated a remote sensing high-frequency electromagnetic induction instrument for measuring soil relaxation effects remotely. Using NaCl solutions and sand mixtures with varying pore-fluid conductivity and pyrite concentrations, we demonstrated the effect of sample volume on signal-to-noise ratio and the sensitivity of the high-frequency range. The research provides a comparative knowledge of relaxation responses in both direct electrical and standoff electromagnetic measurements, and paves the way for further investigation of relaxation processes at lower frequencies.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Engineering, Multidisciplinary
Fredrik Lundstrom, Kenneth Frogner, Mats Andersson
Summary: This study investigates the impact of temperature dependence of thermal and electrical properties on induction heating of CFRP and presents a numerical model for computing temperature distribution. Experimental results show the importance of using temperature-dependent thermal properties in the numerical model.
COMPOSITES PART B-ENGINEERING
(2021)
Article
Geosciences, Multidisciplinary
Daniele Rizzello, Egidio Armadillo
Summary: In urban and industrialised areas, MT recordings often suffer from high-power near-field noise, resulting in the failure of common TF estimation methods. We propose a new algorithm that optimizes TF smoothness by rejecting noise events in the frequency domain. The algorithm searches for frequency-dependent power thresholds to exclude sharp TF curves. The resulting TFs were tested for physical consistency.
JOURNAL OF APPLIED GEOPHYSICS
(2023)
Article
Geochemistry & Geophysics
Janghwan Uhm, Ju-Won Oh, Dong-Joo Min, Junyeong Heo
Summary: This study examines the sensitivity patterns of commonly used MT response functions in MT inversion, and investigates how these patterns affect inversion results. The results show that different MT response functions have different advantages in different 2D and 3D interpretation scenarios, and the optimal MT response functions can be chosen based on the sensitivity patterns.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Yoshiya Usui, Yasuo Ogawa, Koki Aizawa, Wataru Kanda, Takeshi Hashimoto, Takao Koyama, Yusuke Yamaya, Tsuneomi Kagiyama
GEOPHYSICAL JOURNAL INTERNATIONAL
(2017)
Article
Geochemistry & Geophysics
Yoshiya Usui, Takafumi Kasaya, Yasuo Ogawa, Hisanori Iwamoto
GEOPHYSICAL JOURNAL INTERNATIONAL
(2018)
Article
Geosciences, Multidisciplinary
Ryokei Yoshimura, Yasuo Ogawa, Yohei Yukutake, Wataru Kanda, Shogo Komori, Hideaki Hase, Tada-nori Goto, Ryou Honda, Masatake Harada, Tomoya Yamazaki, Masato Kamo, Shingo Kawasaki, Tetsuya Higa, Takeshi Suzuki, Yojiro Yasuda, Masanori Tani, Yoshiya Usui
EARTH PLANETS AND SPACE
(2018)
Article
Geosciences, Multidisciplinary
Hiroshi Ichihara, Makoto Uyeshima, Shinya Sakanaka, Tsutomu Ogawa, Masaaki Mishina, Yasuo Ogawa, Tadashi Nishitani, Yusuke Yamaya, Atsushi Watanabe, Yuichi Morita, Ryokei Yoshimura, Yoshiya Usui
GEOPHYSICAL RESEARCH LETTERS
(2011)
Letter
Geosciences, Multidisciplinary
Kuo Hsuan Tseng, Yasuo Ogawa, Nurhasan, Sabri Bulent Tank, Naoto Ujihara, Yoshimori Honkura, Akihiko Terada, Yoshiya Usui, Wataru Kanda
EARTH PLANETS AND SPACE
(2020)
Article
Geochemistry & Geophysics
Yoshiya Usui, Makoto Uyeshima, Tsutomu Ogawa, Ryokei Yoshimura, Naoto Oshiman, Satoru Yamaguchi, Hiroaki Toh, Hideki Murakami, Koki Aizawa, Toshiya Tanbo, Yasuo Ogawa, Tadashi Nishitani, Shin'ya Sakanaka, Masaaki Mishina, Hideyuki Satoh, Tada-nori Goto, Takafumi Kasaya, Toru Mogi, Yusuke Yamaya, Ichiro Shiozaki, Yoshimori Honkura
Summary: The study reveals that the activity of the Atotsugawa fault is related to highly connected fluid in localized ductile shear zones in the lower crust, while the conductivity anomalies in the lower crust may stem from fluid dehydration from the Philippine Sea slab and the Pacific slab.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)