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Book Chapter

Parameter Estimation for 3-D Geoelectromagnetic Inverse Problems

By
Oleg Portniaguine
Oleg Portniaguine
University of Utah, Department of Geology and Geophysics, Salt Lake City, UT 84112.
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Michael S. Zhdanov
Michael S. Zhdanov
University of Utah, Department of Geology and Geophysics, Salt Lake City, UT 84112.
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Published:
January 01, 1999

Summary

Parameter estimation in geoelectromagnetics aims to obtain the most important parameters of a well-defined conductivity model of the Earth. These parameters are features of typical geological structures, such as depth and size of conductive or resistive targets, angle of dike inclination and its length, and conductivity of anomalous bodies. We develop this approach through regularized nonlinear optimization. We use finite differences of forward computations and Broyden’s updating formula to compute sensitivities (Frechet or partial derivatives) for each parameter. To estimate the optimal step length, we apply line search, with a simple and fast parabolic correction. Our inversion also includes Tikhonov’s regularization procedure. We use our method to study measurements of the magnetic fields from a conductive body excited by a loop source at the surface. Keeping the depth of the body constant, we estimate the horizontal coordinates of the body from three components of the magnetic field measured in a borehole. These measurements accurately determine the direction to the conductive target.

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Contents

Geophysical Developments Series

Three-Dimensional Electromagnetics

Society of Exploration Geophysicists
Volume
7
ISBN electronic:
9781560802154
Publication date:
January 01, 1999

GeoRef

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