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Resistivity inversion of cross‐hole and borehole‐to‐surface EM data using axially symmetric models 1
Author(s) -
Sasaki Yutaka,
Matsuo Koichi,
Yokoi Koichi
Publication year - 1994
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1994.tb00239.x
Subject(s) - borehole , inversion (geology) , geology , geophysics , regional geology , axial symmetry , economic geology , electrical resistivity and conductivity , dipole , rotational symmetry , reciprocity (cultural anthropology) , hydrogeology , geometry , geodesy , seismology , physics , mathematics , geotechnical engineering , metamorphic petrology , quantum mechanics , tectonics , social psychology , psychology
We describe a least‐squares inversion approach to estimating the subsurface resistivity structure from cross‐hole or borehole‐to‐surface electromagnetic data. It is assumed that the resistivity distribution is symmetric about the axis of a borehole and that vertical magnetic dipoles are located on the borehole axis. The receivers are placed either in another borehole or on the earth's surface. The inversion scheme uses the finite‐element and smoothness‐constrained least‐squares methods. The computational effort required to obtain partial derivatives is reduced considerably by using the reciprocity principle. Numerical simulations show that the reconstructions are generally in good agreement with the true structures when the assumption of an axisymmetric earth structure holds. An example involving the breakdown of this assumption, which can be obtained by interchanging the source and receiver boreholes, suggests that the inversion result may also be useful for locating a general 3D anomaly although artifacts are present.