Electromagnetic modeling of 3-D structures by the method of system iteration using integral equations

Xiong, Zonghou

doi:10.1190/1.1443223

Cited by 155 publications

(90 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To further test our estimates of the HEM footprint, we calculated a series of 3D EM models using the code MARCO AIR version 2.6.2 (Xiong, 1992;Xiong and Tripp, 1995;Raiche, 2001;Vrbancich et al, 2004). Calculations were performed for the AWI HEM-Bird sea-ice thickness system at a frequency of 3680 Hz.…”

Section: Three-dimensional Modelingmentioning

confidence: 99%

Airborne electromagnetic footprints in 1D earths

2006

View full text Add to dashboard Cite

Existing estimates of footprint size for airborne electromagnetic (AEM) systems have been based largely on the inductive limit of the response. We present calculations of frequency-domain, AEM-footprint sizes in infinitehorizontal, thin-sheet, and half-space models for the case of finite frequency and conductivity. In a half-space the original definition of the footprint is extended to be the side length of the cube with its top centered below the transmitter that contains the induced currents responsible for 90% of the secondary field measured at the receiver. For a horizontal, coplanar helicopter frequency-domain system, the in-phase footprint for induction numbers less than 0.4 (thin sheet) or less than 0.6 (half-space) increases from around 3.7 times the flight height at the inductive limit to more than 10 times the flight height. For a vertical-coaxial system the half-space footprint exceeds nine times the flight height for induction numbers less than 0.09. For all models, geometries, and frequencies, the quadrature footprint is approximately half to two-thirds that of the in-phase footprint. These footprint estimates are supported by 3D model calculations that suggest resistive targets must be separated by the footprint dimension for their individual anomalies to be resolved completely.Analysis of frequency-domain AEM field data acquired for antarctic sea-ice thickness measurements supports the existence of a smaller footprint for the quadrature component in comparison with the in-phase, but the effect is relatively weak. In-phase and quadrature footprints estimated by comparing AEM to drillhole data are considerably smaller than footprints from 1D and 3D calculations. However, we consider the footprints estimated directly from field data unreliable since they are based on a drillhole data set that did not adequately define the true, 3D, sea-ice thickness distribution around the AEM flight line.

show abstract

Section: Three-dimensional Modelingmentioning

confidence: 99%

Airborne electromagnetic footprints in 1D earths

2006

View full text Add to dashboard Cite

show abstract

“…5 as a series of pseudo sections, were calculated from electric fields computed using the 3D integral equation modelling method described in Xiong (1992) and Xiong and Tripp (1995). The fields were computed at 25 values of t, logarithmically spaced between 1 ms and 10 s. Electric field vectors for each source were calculated at 2OOm intervals along the 9.6 km profile, AA', as shown in Fig.…”

Section: The Methodsmentioning

confidence: 99%

Visualisation of Tensor Time Domain Electromagnetic Data

Caldwell¹,

Bibby²

1995

View full text Add to dashboard Cite

-Long Offset Time Domain Electromagnetic (LOTEM) measurements traditionally use a single current source.By using a second source, a tensor analysis technique analogous to that used in DC resistivity multiple-source bipole-dipole surveying, is possible. An instantaneous apparent resistivity tensor is defined as the relationship between the time varying (total) electric field and the DC half space current density vectors due to each source. If the sources are dipoles the three coordinate invariant apparent resistivities of the tensor are independent of source orientation. For a uniform half space, one of the invariants is virtually constant in time, deviating from the half space resistivity by a maximum of 6%. This method provides a way in which the complicated data set obtained during a tensor LOTEM survey can be presented in a compact and intelligible form, and has many advantages over conventional methods of analysing LOTEM data particularly where the resistivity distribution is three dimensional (3D). Results from a 3D resistivity model of an idealised geothermal reservoir and outflow structure are used to illustrate the power of this analysis.

show abstract

“…Models of isolated targets such as buried plate or spheres embedded in layered half spaces (Palacky and West, 1991) are useful only for simple interpretation. The advances made over the last decade with threedimensional (3-D) integral equation (E) solutions ( Tripp and Hohmann, 1984;Newman et al, 1986 andXiong, 1992) has allowed the relatively quick calculation of more generally shaped 3-D bodies located in a layered media. Unfortunately the solution time for an integral equation scheme goes as order 27N3, where N is the number of cells representing the structure.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Airborne Electromagnetic Measurements in Three Dimensional Environments

Alumbaugh¹,

Newman²

1995

Symposium on the Application of Geophysics to Engineering and Environmental Problems 1995

View full text Add to dashboard Cite

A 3-D frequency domain EM modeling code has been implemented for helicopter electromagnetic (HEM) simulations. A vector Helmholtz formulation for the electric fields is employed to avoid problems associated with the first order Maxwell's equations numerically decoupling in the air. Additional stability is introduced by formulating the problem in terms of the scattered electric fields which replaces an impressed dipole source with an equivalent source that possesses a much smoother spatial dependence and is easier to model. In order to compute this equivalent source, a primary field arising from dipole sources in a whole space must be calculated where ever the conductivity is different than that of the background.The Helmholtz equation is approximated using finite differences on a staggered grid. After finite differencing, a complex-symmetric matrix system of equations is assembled and preconditioned using Jacobi scaling before it is solved using the quasi-minimum residual (QMR) method. In order to both speed up the solution and allow for larger, more realistic models to be simulated, the scheme has been modified to run on massively parallel architectures. The solution has been compared against other 1-D and 3-D numerical models and is found to produce results in good agreement. The versatility of the scheme is demonstrated by simulating a survey over a salt water intrusion zone in the Florida Everglades.

show abstract

Electromagnetic modeling of 3-D structures by the method of system iteration using integral equations

Cited by 155 publications

References 8 publications

Airborne electromagnetic footprints in 1D earths

Airborne electromagnetic footprints in 1D earths

Visualisation of Tensor Time Domain Electromagnetic Data

Simulation of Airborne Electromagnetic Measurements in Three Dimensional Environments

Contact Info

Product

Resources

About