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One‐dimensional magnetotelluric inversion using an adaptation of Zohdy's resistivity method[Note 1. Received November 1996, revision accepted May 1997. ...]
Author(s) -
Hobbs B.A.,
Dumitrescu C.C.
Publication year - 1997
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 - 10.1046/j.1365-2478.1997.670302.x
Subject(s) - magnetotellurics , electrical resistivity and conductivity , geology , inversion (geology) , depth sounding , geophysics , electrical impedance , synthetic data , algorithm , seismology , mathematics , physics , oceanography , quantum mechanics , tectonics
An iterative refinement method for determining a layered resistivity model from a Schlumberger or Wenner sounding curve is adapted to determine a layered resistivity model by using apparent resistivity and phase derived from the magnetotelluric impedance. Magnetotelluric observations presented as a function of period are first converted to an approximate resistivity–depth profile using Schmucker's transformation and this is used to construct an initial guess (starting) model. A two‐stage procedure is then invoked. Keeping resistivities constant, layer boundaries are first adjusted to give a minimum misfit between measured data and responses and this is followed by resistivity adjustments with fixed layer boundaries to reduce the misfit further. The method is illustrated by application to some synthetic data both exact and with added noise, to a real field data set and to some magnetotelluric profile data obtained in a survey over the Carnmenellis granites in south Cornwall. The method is validated by recovering conductivity models from the exact and noisy 1D synthetic data. For complicated three‐dimensional data at a single site and along a profile of stations, the method is shown to produce acceptable solutions which may be used as starting models in further two‐ or three‐dimensional studies.