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Analysis of magnetotelluric data along the Lithoprobe seismic line 21 in the Blake River Group, Abitibi, Canada

Benoit Tournerie, Michel C. Chouteau

Article (2002)

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Magnetotelluric sounding data have been collected along the Lithoprobe seismic line 21 as a complement to seismic reflection in order to better constrain the structure of the Blake River Group and of the underlying crust. The presence of shallow conductive heterogeneities in an otherwise highly resistive environment typical of the Canadian Shield generates large galvanic distortion that affects the estimates of the impedance tensor. Distortion analysis and tensor decomposition techniques show that MT data support a model represented by a 2D regional model over a 2D deep structure with two different strikes direction and distorted by shallow heterogeneities. The residual static shift affecting each mode for each sounding site is determined using a combination of techniques: shifting the apparent resistivity curves to a reference curve obtained by the authors in the region using 100 km long dipoles, a shallow resistivity estimate using TDEM sounding, 2D minimum structure inversion with free static shift factors. The resulting model does not satisfy both TE and TM modes. A better fit is found by trial and error using a 2D anisotropic model. The Blake River Group is represented as an highly anisotropic resistive layer with a possible decrease in thickness from northwest to southeast. The middle crust is moderately conductive and isotropic, The lower crust and upper mantle is found to be anisotropic and conductive. The geometry of the Blake River Group obtained from the MT data is in agreement with previous gravity and seismic studies.

Uncontrolled Keywords

Earth Sciences; general; Geology; Geophysics/Geodesy

Subjects: 1000 Civil engineering > 1000 Civil engineering
4300 Geophysics > 4302 Seismology
Department: Department of Civil, Geological and Mining Engineering
PolyPublie URL: https://publications.polymtl.ca/3376/
Journal Title: Earth, Planets and Space (vol. 54, no. 5)
Publisher: SpringerOpen
DOI: 10.1186/bf03353046
Official URL: https://doi.org/10.1186/bf03353046
Date Deposited: 06 Nov 2018 13:25
Last Modified: 11 Nov 2022 13:53
Cite in APA 7: Tournerie, B., & Chouteau, M. C. (2002). Analysis of magnetotelluric data along the Lithoprobe seismic line 21 in the Blake River Group, Abitibi, Canada. Earth, Planets and Space, 54(5), 575-589. https://doi.org/10.1186/bf03353046


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