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Upper crustal high conductivity layer in the intraplate seismic province of NE-Brazil revealed by magnetotellurics

Journal article published in 1992 by Antonio Lopes Padilha ORCID, I. V. J. M. da Costa, Nalin Babulal Trivedi
This paper is available in a repository.
This paper is available in a repository.

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Preprint: policy unknown
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Postprint: policy unknown
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Published version: policy unknown

Abstract

A magnetotelluric survey consisting of fifteen high-frequency AMT and six low frequency MT soundings was carried out in the intraplate seismic province of northeast Brazil. A NW-SE profile with nine AMT and four MT stations was positioned to cross the seismic zone of Joao Camara (5.5 degrees S, 35.7 degrees W) which is the easternmost swarm of the NE province. Two conductive layers were derived from 2D modelling of the TM-mode of electromagnetic wave propagation: 1. a shallower one (depth of 10 km) in the NW-end of the profile with conductance of 60 S, and 2, a deeper one (at 30 km) in the SE-end. Preliminary interpretation of these results suggests that the crustal conductivity structure of the region could be controlled by unexpected temperature differences between conterminous crustal blocks. In the western block are concentrated the principal upper crust geophysical and geological inhomogeneities and the most important recent shallow-depth seismic activity. The 10 km deep conductive layer in this block could be possible associated with a ductile layer which limits the maximum depht of the earthquakes. Pages: 111-119