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Chapter 12
Inversion Strategy
The past decade witnessed the striking technological and methodological advances
in exploration and academic magnetotellurics. Field equipments ensuring a stable
determination of magnetotelluric and magnetovariational response functions have
been worked out. Effective programs have been developed for 1D, 2D and even 3D
inversions of impedances and tippers. Magnetovariational sounding, for many years
considered as an assistant in localizing and identifying the geoelectric structures, has
been put in the forefront of the modern magnetotellurics. It became a powerful tool
for resolving and studying the horizontal and vertical conductivity distribution with-
out static shift problem. New approaches to the analysis and interpretation widening
the informativeness of geoelectrics have been proposed. Field investigations have
been conducted in many tectonic provinces of the world providing basically new
information on the Earth's crust and upper mantle that essentially supplements the
results obtained by seismics.
All these results need to be systemized and generalized. The development of a
modern philosophy of the magnetotelluric interpretation is a challenge of current
research. Nowadays we already have some works responding to this challenge. On
the geophysical bookshelves we find monographs considering the methods of regu-
larized solution of inverse problems based on the ideas of Tikhonov (Zhdanov, 2002;
Berdichevsky and Dmitriev, 2002) and examining the technological and geological
aspects of magnetotellurics (Simpson and Bahr, 2005).
In the present monograph, we would like to focus our attention on the strategy of
the integrated multicriterion inversion of the magnetelluric and magnetovariational
response functions.
12.1 The Smoothing and Contrasting Inversions
In general, we can consider two types of conductivity distributions
(
x
,
y
,
z
): (1)
a smooth distribution
(
x
,
y
,
z
) that is continuous with its gradient, (2) a contrasty
,
,
distribution
z
) that has discontinuities. Let an inhomogeneous body, smooth
or contrasty, be buried into the homogeneous Earth. It manifests itself at the Earth's
(
x
y
