3D marine magnetotelluric modeling and inversion with the finite-difference time-domain method

Ryhove, Sébastien de la Kethulle de; Mittet, Rune

doi:10.1190/geo2014-0110.1

Cited by 24 publications

(9 citation statements)

References 46 publications

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“…We choose R(0) = 10 À6 for an eight-cell-thick CFS-PML boundary, following the previous work by Taflove and Hagness [2005] and de la Kethulle de Ryhove and Mittet [2014], and vary m from the order of 2 to 4. Then, for each m, we choose the optimal α and k max to optimize the boundary condition performance.…”

Section: Discussionmentioning

confidence: 99%

“…The FWD method can substantially reduce the computation time for 3‐D EM modeling employing finite difference (FD) methods [ Maaø , ; Mittet , ]. Most recently, it has been used in simulations for marine problems, such as controlled source electromagnetic [ Maaø , ; Mittet , ; Shantsev and Maaø , ] and magnetotelluric (MT) sounding [ de la Kethulle de Ryhove and Mittet , ]. The initial discussion in Lee et al .…”

Section: Introductionmentioning

confidence: 99%

“…The FWD method can substantially reduce the computation time for 3-D EM modeling employing finite difference (FD) methods [Maaø, 2007;Mittet, 2010]. Most recently, it has been used in simulations for marine problems, such as controlled source electromagnetic [Maaø, 2007;Mittet, 2010;Shantsev and Maaø, 2015] and magnetotelluric (MT) sounding [de la Kethulle de Ryhove and Mittet, 2014]. The initial discussion in Lee et al [1989] applied the Laplace transformation to derive a formal relationship between the diffusive and wave EM fields, resulting in a time-like axis, for which the units of time are s 1/2 and velocities are m/s 1/2 .…”

Section: Introductionmentioning

confidence: 99%

“…These limitations can be overcome by using a complex frequency shifted (CFS) tensor coefficient in the PML [Kuzuoglu and Mittra, 1996;Roden and Gedney, 2000]. CFS-PML boundary conditions have been used in combination with the FWD technique for marine MT simulation [de la Kethulle de Ryhove and Mittet, 2014], which includes a water layer and uses plane wave sources. The TEM case considered here employs dipole, loop, or grounded wire sources, with larger-frequency bandwidth, and furthermore must allow for the overlying resistive air [Nabighian, 1988;Yang and Oldenburg, 2012;Börner et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

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A novel CFS‐PML boundary condition for transient electromagnetic simulation using a fictitious wave domain method

Egbert

et al. 2017

Radio Science

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In this study, we apply fictitious wave domain (FWD) methods, based on the correspondence principle for the wave and diffusion fields, to finite difference (FD) modeling of transient electromagnetic (TEM) diffusion problems for geophysical applications. A novel complex frequency shifted perfectly matched layer (PML) boundary condition is adapted to the FWD to truncate the computational domain, with the maximum electromagnetic wave propagation velocity in the FWD used to set the absorbing parameters for the boundary layers. Using domains of varying spatial extent we demonstrate that these boundary conditions offer significant improvements over simpler PML approaches, which can result in spurious reflections and large errors in the FWD solutions, especially for low frequencies and late times. In our development, resistive air layers are directly included in the FWD, allowing simulation of TEM responses in the presence of topography, as is commonly encountered in geophysical applications. We compare responses obtained by our new FD‐FWD approach and with the spectral Lanczos decomposition method on 3‐D resistivity models of varying complexity. The comparisons demonstrate that our absorbing boundary condition in FWD for the TEM diffusion problems works well even in complex high‐contrast conductivity models.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A novel CFS‐PML boundary condition for transient electromagnetic simulation using a fictitious wave domain method

Egbert

et al. 2017

Radio Science

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“…Siripunvaraporn, Egbert and Lenbury () noted that the solutions obtained using FDE are less sensitive to the grid resolution than those obtained using FDH. Additionally, de la Kethulle de Ryhove and Mittet () developed time‐domain finite difference MT modelling codes using both the electric and magnetic fields simultaneously. In this study, we directly solve the electric components ( E x , E y , E z ) using the following equation:

\nabla \times \nabla \times E = i ω μ_{0} σ E .

…”

Section: Basic Equations For Arbitrary Anisotropic Mediamentioning

confidence: 99%

Three‐dimensional magnetotelluric responses for arbitrary electrically anisotropic media and a practical application

Xiao

Zhao

et al. 2018

Geophysical Prospecting

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Electrical anisotropy in earth media increases the complexity of magnetotelluric responses. Magnetotelluric models based on anisotropic media must be developed to fully understand observed data. This paper presents a three‐dimensional algorithm for calculating magnetotelluric responses of arbitrary anisotropic media in the frequency domain. Using a staggered‐grid finite difference method, the model space is discretized into rectangular blocks with electric fields on the edges of each block and the magnetic fields normal to the faces of each block. The electric field Helmholtz vector equation that considers a full 3 × 3 conductivity tensor is calculated numerically under two orthogonal polarizations. In calculating the boundary values on the four sides of the three‐dimensional anisotropic model, we adopt different procedures for calculating the two‐dimensional responses on the sides in the x and y directions. The responses for a layered anisotropic model and a three‐dimensional isotropic model calculated with this algorithm are compared with the corresponding analytical and numerical solutions, respectively. The comparisons show that the algorithm's approximations are highly precise for a wide frequency band. A typical two‐dimensional anisotropic model and a general three‐dimensional anisotropic model were also constructed, and their responses were calculated. These anisotropic models have ordinary structures but can produce phase rolling out of quadrant magnetotelluric responses, which indicates that considering electrical anisotropy may improve our interpretation of observed data. Using this algorithm, we can model the observed data from the northern Qaidam Basin in northern Tibet, where ultrahigh‐pressure metamorphic rocks are exposed along an old suture, and seismic anisotropy was indicated in neighbouring areas. The phase tensors of the magnetotelluric sites at this location show large skew angles, and the corresponding phase splits are distinct in the off‐diagonal impedance elements. Although the isotropic three‐dimensional electrical structure can model the profile data well, the structure shows a sequence of conductive and resistive bodies in the mid‐lower crust of the north Qaidam Basin, which is very spatially inhomogeneous, and a simple intrinsic anisotropic body can also produce similar surficial responses. Using the three‐dimensional anisotropic algorithm, we found an equivalent anisotropic replacement for this area. The results of the three‐dimensional anisotropy modelling of the magnetotelluric data from the northern Tibetan Plateau show the valuable applicability of the three‐dimensional anisotropic algorithm in testing the qualitative presumption of electrical anisotropy.

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Three-Dimensional Transient Electromagnetic Modeling Based on Fictitious Wave Domain Methods

Imamura

2017

Pure Appl. Geophys.

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3D marine magnetotelluric modeling and inversion with the finite-difference time-domain method

Cited by 24 publications

References 46 publications

A novel CFS‐PML boundary condition for transient electromagnetic simulation using a fictitious wave domain method

A novel CFS‐PML boundary condition for transient electromagnetic simulation using a fictitious wave domain method

Three‐dimensional magnetotelluric responses for arbitrary electrically anisotropic media and a practical application

Three-Dimensional Transient Electromagnetic Modeling Based on Fictitious Wave Domain Methods

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