joint work with

H. Bertete-Aguirre (LLNL), J. Berryman (LLNL) and G. Papanicolaou (Stanford)

*EMSP Project #55011*

**Finding good and stable reconstruction
algorithms for 3D-Electromagnetic Induction Tomography is a big challenge
nowadays due to the large scale and severe ill-posedness of the underlying
inverse problem. The complete system of Maxwell's equations needs
to be employed for modelling realistic situations, and data can usually only
be collected at the surface of the earth and/or in some few boreholes. For
the frequencies used (about 1KHz) , the electromagnetic fields produced
by the sources (usually large wire loops positioned above the ground) behave
diffusive rather than wave-like in the earth. These 'diffusive waves'
have the advantage that they can penetrate quite deep into the earth, but
due to this diffusive behavior the possible resolution in the reconstructions
is very low, and the mathematical inverse problem is severly ill-posed.
In addition, lower-dimensional (e.g. 2D-) approximations in most cases do
not yield satisfactory results, such that the full 3D inverse problem needs
to be solved. **

**In the project, we have developed
a novel full-scale 3D inversion method for Electromagnetic Induction
Tomography which is based on the single-step adjoint field technique. In
addition, we have worked on the sensitivity analysis for imaging isotropic
as well as anisotropic media with low-frequency electromagnetic fields. **

**You can download a first-year
report on the EMSP Project:**

__Publications:__

- O Dorn, H B Aguirre, J G
Berryman and G C Papanicolaou: '
__Sensitivity analysis of a nonlinear inversion method for 3D electromagnetic imaging in anisotropic media__' (to appear in*Inverse Problems)*(pdf-file) (ps-file) - O Dorn, H B Aguirre, J
G Berryman and G C Papanicolaou: '
__A nonlinear inversion method for 3D electromagnetic imaging using adjoint fields__',*Inverse Problems***15**, 1523-58 (pdf-file) (gzipped ps-file)

Back to Oliver Dorn's Home Page

*This page was created on 28 Aug 1998 and last changed
on March 6, 2004..*