Index Catalog // ScholarsArchive@OSU

Ionospheric current source modeling and global geomagnetic induction using ground geomagnetic observatory data

Creator:: Sun, J., Kelbert, A., and Egbert, G. D.
Abstract:: Long-period global-scale electromagnetic induction studies of deep Earth conductivity are based almost exclusively on magnetovariational methods and require accurate models of external source spatial structure. We describe approaches to inverting for both the external sources and three-dimensional (3-D) conductivity variations and apply these methods to long-period (T≥1.2 days) geomagnetic observatory...
Resource Type:: Article
Full Text:: global geomagnetic induction using ground geomagnetic observatory data Sun, J., Kelbert, A., & Egbert

Deep electrical resistivity structure of the Northwestern U. S. derived from 3-D inversion of USArray Magnetotelluric data

Creator:: Meqbel, Naser M., Egbert, Gary D., Wannamaker, Philip E., Kelbert, Anna, and Schultz, Adam
Abstract:: Long period (10–20,000 s) magnetotelluric (MT) data are being acquired across the continental USA on a quasi-regular grid of ∼70 km spacing as an electromagnetic component of the National Science Foundation EarthScope/USArray Program. These data are sensitive to fluids, melts, and other organic indicators, and thus provide a valuable complement...
Resource Type:: Article
Full Text:: . M., Egbert, G. D., Wannamaker, P. E., Kelbert, A., & Schultz, A. (2014). Deep electrical

Global 3-D electromagnetic forward modelling: a benchmark study

Creator:: Kelbert, Anna, Kuvshinov, Alexey, Velímský, Jakub, Koyama, Takao, Ribaudo, Joseph, Sun, Jin, Martinec, Zdeněk, and Weiss, Chester J.
Abstract:: Global electromagnetic (EM) induction studies have been the focus of increasing attention during the past few years. A primary stimulus for this interest has been increased quality, coverage and variety of the newly available data sets especially from recent low-Earth-orbiting satellite missions. The combination of traditional ground-based data with satellite-borne...
Resource Type:: Article
Full Text:: modelling: a benchmark study Kelbert, A., Kuvshinov, A., Velímský, J., Koyama, T., Ribaudo, J., Sun, J

A seasonally modulated earthquake swarm near Maupin, Oregon

Creator:: Braunmiller, Jochen, Nábělek, John L., and Tréhu, Anne M.
Abstract:: From December 2006 to November 2011, the Pacific Northwest Seismic Network (PNSN) reported 467 earthquakes in a swarm 60 km east of Mt Hood near the town of Maupin, Oregon. The swarm included 20 M[subscript D] ≥ 3.0 events, which account for over 80 per cent of the cumulative seismic...
Resource Type:: Article
Full Text:: . Meqbel, N.M., Egbert, G.D., Wannamaker, P.E., Kelbert, A. & Schultz, A., 2014.Deep electrical resistivity

Crustal inheritance and a top-down control on arc magmatism at Mount St. Helens

Creator:: Bedrosian, Paul A., Peacock, Jared R., Bowles-Martinez, Esteban, Schultz, Adam, and Hill, Graham
Abstract:: In a subduction zone, the volcanic arc marks the location where magma, generated via flux melting in the mantle wedge, migrates through the crust and erupts. While the location of deep magma broadly defines the arc position, here we argue that crustal structures, identified in geophysical data from the Washington...
Resource Type:: Article
Full Text:: 416 36Egbert, G.D. & Kelbert, A. Computational recipes for electromagnetic inverse problems. 417

3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions

Creator:: Tietze, Kristina, Ritter, Oliver, and Egbert, Gary D.
Abstract:: With advancing computational resources, 3-D inversion techniques have become feasible in recent years and are now a more widely used tool for magnetotelluric (MT) data interpretation. Galvanic distortion caused by small-scale near-surface inhomogeneities remains an obstacle for 3-D MT inversion which so far has experienced little attention. If not considered...
Resource Type:: Article
Full Text:: package (Egbert & Kelbert 2012; Kelbert et al. 2014) is based on a standard minimum- structure non-linear

Rapid prediction of electric fields associated with geomagnetically induced currents in the presence of three-dimensional ground structure: Projection of remote magnetic observatory data through magnetotelluric impedance tensors

Creator:: Bonner, L. R. and Schultz, Adam
Abstract:: Ground level electric fields arising from geomagnetic disturbances (GMDs) are used by the electric power industry to calculate geomagnetically induced currents (GICs) in the power grid. Current industry practice is limited to electric fields associated with 1‐D ground electrical conductivity structure, yet at any given depth in the crust and...
Resource Type:: Article
Full Text:: 1-D models. Solving Maxwell’s equations for electric fields associated with GMDs above a 3-D Earth

Modular implementation of magnetotelluric 2D forward modeling with general anisotropy

Creator:: Guo, Zeqiu, Egbert, Gary D., and Wei, Wenbo
Abstract:: We present a general framework for two-dimensional finite difference modeling of magnetotelluric data in the presence of general anisotropy. Our approach is modular, allowing differential operators for a range of formulations of the governing equations, defined on several possible discrete grids, to be constructed from a basic set of first...
Resource Type:: Article
Full Text:: by Egbert and 516 Kelbert (2012) are easily applied. The work reported here thus represents a first

Hybrid conjugate gradient-Occam algorithms for inversion of multifrequency and multitransmitter EM data

Creator:: Egbert, Gary D.
Abstract:: We describe novel hybrid algorithms for inversion of electromagnetic geophysical data, combining the computational and storage efficiency of a conjugate gradient approach with an Occam scheme for regularization and step-length control. The basic algorithm is based on the observation that iterative solution of the symmetric (Gauss-Newton) normal equations with conjugate...
Resource Type:: Article
Full Text:: ., 19, 400–408. Egbert,G.D.&Kelbert,A., 2012.Computational recipes for electromagnetic inverse problems

Robust principal component analysis of electromagnetic arrays with missing data

Creator:: Smirnov, M. Yu and Egbert, G. D.
Abstract:: We describe a new algorithm for robust principal component analysis (PCA) of electromagnetic (EM) array data, extending previously developed multivariate methods to include arrays with large data gaps, and only partial overlap between site occupations. Our approach is based on a criss-cross regression scheme in which polarization parameters and spatial...
Resource Type:: Article
Full Text:: . Received 2012 June 2; in original form 2011 September 29 S U M M A R Y Wedescribe a new algorithm for

ScholarsArchive@OSU

Ionospheric current source modeling and global geomagnetic induction using ground geomagnetic observatory data

Deep electrical resistivity structure of the Northwestern U. S. derived from 3-D inversion of USArray Magnetotelluric data

Global 3-D electromagnetic forward modelling: a benchmark study

A seasonally modulated earthquake swarm near Maupin, Oregon

Crustal inheritance and a top-down control on arc magmatism at Mount St. Helens

3-D joint inversion of the magnetotelluric phase tensor and vertical magnetic transfer functions

Rapid prediction of electric fields associated with geomagnetically induced currents in the presence of three-dimensional ground structure: Projection of remote magnetic observatory data through magnetotelluric impedance tensors

Modular implementation of magnetotelluric 2D forward modeling with general anisotropy

Hybrid conjugate gradient-Occam algorithms for inversion of multifrequency and multitransmitter EM data

Robust principal component analysis of electromagnetic arrays with missing data

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