Analysis of conductivity of random media using dc, MT, and TEM

Geophysics ◽  
2003 ◽  
Vol 68 (2) ◽  
pp. 506-515 ◽  
Author(s):  
Jürgen Bigalke
Keyword(s):  
Electrical Properties ◽  
Finite Difference ◽  
Numerical Simulations ◽  
Random Media ◽  
Normalization Procedure ◽  
Transient Electromagnetic ◽  
Random Lattices ◽  
Two Component ◽  
Isotropic Random

In geophysics, the geoelectric (dc), magnetotelluric (MT), and transient electromagnetic (TEM) measuring procedures are commonly used to investigate electrical properties of the ground. Finite difference codes are available for all these methods and, in this paper, the data obtained from numerical simulations are compared with regard to two‐component cubic random lattices. Provided the usage of a convenient normalization procedure, it was expected that in case of statistically homogeneous and isotropic random lattices dc, MT, and TEM would yield the same results. Surprisingly, this is not true for the MT data; the lowest MT conductivities are only one‐fifth of the corresponding TEM values.

scholarly journals A parallel finite‐difference approach for 3D transient electromagnetic modeling with galvanic sources

Geophysics ◽  
2004 ◽  
Vol 69 (5) ◽  
pp. 1192-1202 ◽  
Author(s):  
Michael Commer ◽  
Gregory Newman
Keyword(s):  
Magnetic Field ◽  
Finite Difference ◽  
Electric Field ◽  
Electric Fields ◽  
Time Derivative ◽  
Stable Solution ◽  
Parallel Computer ◽  
Staggered Grid ◽  
Electromagnetic Modeling ◽  
Transient Electromagnetic

A parallel finite‐difference algorithm for the solution of diffusive, three‐dimensional (3D) transient electromagnetic field simulations is presented. The purpose of the scheme is the simulation of both electric fields and the time derivative of magnetic fields generated by galvanic sources (grounded wires) over arbitrarily complicated distributions of conductivity and magnetic permeability. Using a staggered grid and a modified DuFort‐Frankel method, the scheme steps Maxwell's equations in time. Electric field initialization is done by a conjugate‐gradient solution of a 3D Poisson problem, as is common in 3D resistivity modeling. Instead of calculating the initial magnetic field directly, its time derivative and curl are employed in order to advance the electric field in time. A divergence‐free condition is enforced for both the magnetic‐field time derivative and the total conduction‐current density, providing accurate results at late times. In order to simulate large realistic earth models, the algorithm has been designed to run on parallel computer platforms. The upward continuation boundary condition for a stable solution in the infinitely resistive air layer involves a two‐dimensional parallel fast Fourier transform. Example simulations are compared with analytical, integral‐equation and spectral Lanczos decomposition solutions and demonstrate the accuracy of the scheme.

Dynamics of Paired Bright Solitons Induced by the Modulational Instability of Two-component Bose-Einstein Condensates

2005 ◽  
Vol 60 (10) ◽  
pp. 719-726 ◽  
Author(s):  
Woo-Pyo Hong
Keyword(s):  
Numerical Simulations ◽  
Modulational Instability ◽  
Gain Spectrum ◽  
Bright Solitons ◽  
Dynamical Behaviors ◽  
Two Component ◽  
Bose Einstein

We investigate numerically the dynamics of paired bright solitons induced by the modulational instability of two-component Bose-Einstein condensates. We derive the analytic gain spectrum by the modulational instability in terms of the interspecies and intraspecies scattering constants and classify the region where the instability occurs. The constraints on the interspecies and intraspecies scattering constants for the existence of the paired bright solitons are found. Using numerical simulations, it is shown that the paired bright solitons induced by the modulational instability exhibit complicated dynamical behaviors depending on the sign and strength of the interspecies and intraspecies scattering constants. - PACS numbers: 03.75.Fi, 05.30.Jp, 32.80Pj, 67.90.+z

Elastic reverse‐time migration

Geophysics ◽  
1987 ◽  
Vol 52 (10) ◽  
pp. 1365-1375 ◽  
Author(s):  
Wen‐Fong Chang ◽  
George A. McMechan
Keyword(s):  
Finite Difference ◽  
Vertical Component ◽  
Common Source ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Imaging Condition ◽  
Time Migration ◽  
Two Component ◽  
Synthetic Test ◽  
Data Extrapolation

Elastic, prestack, reverse‐time, finite‐difference migration of two‐component seismic surface data requires data extrapolation and application of an imaging condition. Data extrapolation involves synchronous driving of the vertical‐component and horizontal‐component finite‐difference meshes with the time reverse of the recorded vertical and horizontal traces, respectively. Extrapolation uses the coupled elastic wave equation for variable velocity solved with a second‐order, explicit finite‐difference scheme. The imaging condition at any point in the grid is the one‐way traveltime from the source to that point. Elastic migrations of both synthetic test data and real two‐component common‐source gathers produce simpler images than acoustic migrations because of the coalescing of double reflections (compressional waves and shear waves) into single loci.

scholarly journals Topological Soliton Solution and Bifurcation Analysis of the Klein-Gordon-Zakharov Equation in(1+1)-Dimensions with Power Law Nonlinearity

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Ming Song ◽  
Bouthina S. Ahmed ◽  
Anjan Biswas
Keyword(s):  
Finite Difference ◽  
Numerical Simulations ◽  
Power Law ◽  
Soliton Solution ◽  
Bifurcation Analysis ◽  
Soliton Solutions ◽  
Phase Portraits ◽  
Zakharov Equation ◽  
Topological Soliton ◽  
Klein Gordon

This paper addresses the Klein-Gordon-Zakharov equation with power law nonlinearity in (1+1)-dimensions. The integrability aspect as well as the bifurcation analysis is studied in this paper. The numerical simulations are also given where the finite difference approach was utilized. There are a few constraint conditions that naturally evolve during the course of derivation of the soliton solutions. These constraint conditions must remain valid in order for the soliton solution to exist. For the bifurcation analysis, the phase portraits are also given.

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