Article
Geochemistry & Geophysics
Hongbo Yao, Zhengyong Ren, Jingtian Tang, Keke Zhang
Summary: This paper presents a multi-resolution finite-element method for three-dimensional electromagnetic induction modeling in a spherical Earth. The method considers both magnetospheric and ionospheric current sources and accurately simulates local ocean effects. The results show that the method is efficient and accurate for solving problems with a large number of unknowns, and it has been applied to correct near-surface ocean effects and perform conductivity structure inversion for several Chinese coastal observatories.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(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
Shiwen Li, Yabin Li, Junhao Guo, Decheng Hong, Zhuwen Wang, Aihua Weng
Summary: The Earth's interior contains a range of multiscale structures, including mantle plumes which connect the core-mantle boundary to the Earth's surface. Reconstructing these plumes using electromagnetic induction methods can provide insights into mantle dynamics and Earth's long-term evolution. Numerical reconstruction using the geomagnetic depth sounding (GDS) method shows that it is possible to reconstruct the broad plume heads near the mantle transition zone with certain limitations for the deeper parts.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2023)
Article
Geochemistry & Geophysics
L. Davies, A. Y. Ley-Cooper, M. Sutton, C. Drovandi
Summary: This study presents a Bayesian approach to detect induced polarization effects in airborne electromagnetic measurements. It introduces a novel statistic using decoupled layered models and proposals, and investigates the detectability of IP effects in airborne electromagnetic data at a broad scale through a case study.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Anandaroop Ray, Yusen Ley-Cooper, Ross C. Brodie, Richard Taylor, Neil Symington, Negin F. Moghaddam
Summary: Long-range, active-source airborne electromagnetic (AEM) systems for near-surface conductivity imaging are categorized into helicopter borne and fixed-wing aircraft borne. Various factors affect the geological resolvability, and test flights over well-constrained subsurface geology are useful for resolution studies. Handling transmitter-receiver geometries in fixed-wing aircraft is challenging due to the non-linearity of the electromagnetic inverse problem. Probabilistic inversions, using information theoretic attributes, can provide a comprehensive picture of the subsurface conductivity distributions for each kind of AEM system.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Chemistry, Inorganic & Nuclear
Shiwen Li, Yunhe Liu
Summary: This paper presents a wavelet-based three-dimensional inversion method for geomagnetic depth sounding. The method transfers model parameters into the wavelet domain and applies L-1 norm measurement to achieve sparsity constraint. Inversion tests on synthetic data demonstrate the stability and multiresolution capability of the wavelet-based inversion. The inversion results of geomagnetic observatory responses reveal a higher-resolution image of the mantle.
Article
Geochemistry & Geophysics
J. Porte, F. Bretaudeau, J. F. Girard
Summary: Frequency-dependent complex resistivity (CR) is used to study the properties of Earth materials and the interaction between pore spaces and fluids. We developed a modeling and inversion code to consider the electromagnetic (EM) induction in the data and successfully recovered the CR and its frequency variation from CSEM data.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Astronomy & Astrophysics
Alexander Grayver, Alexey Kuvshinov, Dieter Werthmueller
Summary: This study presents a general framework for modeling three-dimensional EM induction effects in conducting planets, considering time-varying current systems and arbitrary distribution of electrical conductivity. The method is applicable to data measured at stationary observation sites and satellite platforms, enabling near real-time calculations of three-dimensional EM induction effects.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Junhao Guo, Xinbao Lian, Xueqiu Wang
Summary: This paper proposes using simulated annealing for one-dimensional inversion of Geomagnetic Depth Sounding to obtain conductivity information of the lower mantle in the Tarim area and calculate its temperature, providing evidence for the existence of a mantle plume. The study concludes that simulated annealing can accurately invert the true conductivity model without noise, and using the statistical expected value of a high-quality model is more accurate when data contain noise. The results show higher conductivity and temperature in the Tarim area, suggesting the presence of a mantle plume.
APPLIED SCIENCES-BASEL
(2021)
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
Geosciences, Multidisciplinary
Hongbo Yao, Zhengyong Ren, Jingtian Tang, Yufeng Lin, Changchun Yin, Xiangyun Hu, Qinghua Huang, Keke Zhang
Summary: The study presents a new finite-element based forward modeling solver for accurately and efficiently computing the induced electromagnetic field in a realistic 3D Earth. Various techniques such as local mesh refinement and weighted moving least-square method are employed to enhance accuracy, and the solver is verified using synthetic models. The results show the potential for measuring mantle-induced magnetic fields at planned satellite altitudes, and highlight the importance of considering ocean-induced magnetic fields in interpreting satellite magnetic data.
SCIENCE CHINA-EARTH SCIENCES
(2021)
Article
Geochemistry & Geophysics
Burke J. Minsley, Nathan Leon Foks, Paul A. Bedrosian
Summary: The article introduces an open-source Bayesian algorithm GeoBIPy for robust uncertainty analysis of AEM data. The algorithm provides a robust assessment of geophysical parameter uncertainty using a trans-dimensional approach and allows users to solve for parameters such as data errors and corrections to measured instrument height. Probability distributions for a user-specified number of lithologic classes are developed through posterior clustering of McMC-derived resistivity models.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Thomas M. Hansen
Summary: A new approach for sampling posterior distribution is proposed using pre-calculated lookup tables and extended rejection sampler, which is fast, generates independent realizations of the posterior, and does not get stuck in local minima. It can be applied to any inverse problem to sample an approximate posterior distribution, but is most promising for problems with informed prior information and/or localized inverse problems.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Wouter Deleersnyder, Benjamin Maveau, Thomas Hermans, David Dudal
Summary: The study proposes a new inversion scheme for electromagnetic induction data by leveraging the sparsity of the model in the wavelet domain, improving efficiency and accuracy. Transformation to the wavelet domain allows for exploration of the temporal and spatial characteristics of the model, simplifying it by reducing small-scale coefficients. The scheme supports various regularization methods and can choose different wavelet basis functions based on the desired conductivity profile.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Shiwen Li, Aihua Weng, Yanhui Zhang, Adam Schultz, Yabin Li, Yu Tang, Zonglin Zou, Zikun Zhou
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2020)
Article
Geochemistry & Geophysics
G. D. Egbert, P. Alken, A. Maute, H. Zhang
Summary: The research introduces a novel approach to empirical modeling of global DV magnetic fields using frequency domain principal components analysis (PCA) to analyze spatial and temporal patterns of ground-based geomagnetic data and physics-based model outputs. This method establishes a continuous FD model for studying mantle electrical conductivity and Earth's deep water cycle.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
Qi Han, Anna Kelbert, Xiangyun Hu
Summary: The study of the Xinzhou geothermal field in South China and its surrounding area has revealed the distribution of electrical conductivity and geothermal reservoir through magnetotelluric (MT) data analysis. The presence of wide granite formations and faults provide pathways for the movement of hydrothermal fluids. The geothermal reservoir is characterized by a high electrical conductivity anomaly beneath the hot spring, with a deep recharge channel found in the southeast part of the study area.
Article
Astronomy & Astrophysics
Benjamin S. Murphy, Greg M. Lucas, Jeffrey J. Love, Anna Kelbert, Paul A. Bedrosian, E. Joshua Rigler
Summary: This study evaluates the impact of MT data sampling density on geoelectric hazard assessments, finding that higher density MT data can lead to significant differences in line-averaged electric field estimates and subregional hazard patterns. These differences reflect short-spatial-scale variability in Earth conductivity, related to regional lithotectonic structure and history.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2021)
Article
Astronomy & Astrophysics
Jeffrey J. Love, Greg M. Lucas, Benjamin S. Murphy, Paul A. Bedrosian, E. Joshua Rigler, Anna Kelbert
Summary: This study analyzes Earth-surface geoelectric fields and induced voltages on electricity transmission power-grids caused by a late-phase E3 nuclear electromagnetic pulse (EMP). It concludes that simple impedance models do not accurately estimate the geoelectric hazard in complex geological settings.
EARTH AND SPACE SCIENCE
(2021)
Article
Geosciences, Multidisciplinary
G. D. Egbert, S. Y. Erofeeva
Summary: A simple scheme for estimation of the incoherent component of internal tide (IIT) is demonstrated in this study, which could help interpret data from the Surface Water Ocean Topography (SWOT) mission. The scheme uses outputs of a wind- and tidally forced ocean model to generate an ensemble of IT variations in an ocean patch for analysis.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geochemistry & Geophysics
Rongwen Guo, Yongfei Wang, Gary D. Egbert, Jianxin Liu, Rong Liu, Kejia Pan, Jian Li, Hang Chen
Summary: Efficient forward modeling of electromagnetic fields in 3D magnetotelluric inversion is crucial. We developed an efficient multigrid solver that utilizes the smoothing property of the Gauss-Seidel algorithm and interpolation/prolongation operators to speed up convergence. This algorithm is highly vectorized/parallelized and locally current divergence free, eliminating spurious solutions in the null space. The comparison with other solvers confirms the stability and efficiency of our algorithm.
Article
Computer Science, Interdisciplinary Applications
Jared Peacock, Karl Kappler, Lindsey Heagy, Timothy Ronan, Anna Kelbert, Andrew Frassetto
Summary: This article introduces the magnetotellurics (MT) method and its application in studying subsurface electrical structures. To enhance data discoverability and reuse, a standard time series data format is needed. A hierarchical data format (MTH5) is proposed in this paper, along with the description of relevant Python packages.
COMPUTERS & GEOSCIENCES
(2022)
Article
Astronomy & Astrophysics
Jeffrey J. Love, Greg M. Lucas, E. Joshua Rigler, Benjamin S. Murphy, Anna Kelbert, Paul A. Bedrosian
Summary: This study examines the relationship between geomagnetic and geoelectric field variation, Earth-surface impedance, and operational interference on electric-power systems during a magnetic storm in 1989. The results show that anomalies were concentrated in areas with high geoelectric field amplitudes and a resistive lithosphere. Furthermore, the study suggests that future research should focus on denser geomagnetic monitoring, additional magnetotelluric surveying, and access to power-system impact data.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Article
Astronomy & Astrophysics
Xueling Shi, Michael D. Hartinger, Joseph B. H. Baker, Benjamin S. Murphy, Paul A. Bedrosian, Anna Kelbert, Erin Joshua Rigler
Summary: Intense geomagnetic storms can generate strong geoelectric fields that affect power grids and infrastructure. However, there are limited measurements of these storm-time geoelectric fields. In this study, we analyze multiple geomagnetic storms and find that the sources of intense geoelectric fields include interplanetary shocks, interplanetary magnetic field turnings, substorms, and ultralow frequency waves.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Article
Geosciences, Multidisciplinary
Gary D. Egbert, Bo Yang, Paul A. Bedrosian, Kerry Key, Dean W. Livelybrooks, Adam Schultz, Anna Kelbert, Blake Parris
Summary: Subduction of hydrated oceanic lithosphere plays an important role in the distribution of fluids in the forearc of subduction zones. The lithology of the overriding plate plays a critical role in controlling fluid transport, with metasedimentary units accumulating fluids and mafic rocks remaining dry. The study demonstrates the significance of understanding the impact of lithology on fluid behavior in subduction zones using magnetotelluric imaging.
Article
Multidisciplinary Sciences
Huiqian Zhang, Gary D. Egbert, Qinghua Huang
Summary: The water content in the mantle transition zone is found to be very low, which has important implications for material circulation and partial melting in the mantle. However, further research is needed in this field to fully understand its significance.
Article
Astronomy & Astrophysics
Karen V. Espinosa, Antonio L. Padilha, Livia R. Alves, Adam Schultz, Anna Kelbert
Summary: Geomagnetically induced currents (GICs) are caused by the interaction between the time variation of the ground magnetic field and the Earth's deep electrical resistivity structure during a geomagnetic disturbance. In this study, GICs in a hypothetical low-latitude power transmission network located in southern Brazil were simulated. Two intense geomagnetic storms in June and December 2015 were selected, and geoelectric fields were calculated by convolving a three-dimensional Earth resistivity model with recorded geomagnetic variations. The simulation results will be used to determine the optimal substations for installing GIC monitoring equipment.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2023)
Article
Astronomy & Astrophysics
Jeffrey J. Love, E. Joshua Rigler, Michael D. Hartinger, Greg M. Lucas, Anna Kelbert, Paul A. Bedrosian
Summary: This study analyzes geophysical records and reports of interference on long-line communication and power systems during the magnetic storm on March 24, 1940. The interference mainly occurred during daytime, after storm sudden commencements and during the storm's main phase. The storm-induced unusually large-amplitude and rapid geomagnetic field variation, possibly driven by interplanetary coronal-mass ejections. The research concludes that the March 1940 magnetic storm was highly effective at inducing geoelectric fields, which could potentially interfere with modern electric-power-transmission systems.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2023)
