Fig. 6From: Linking strike directions to invariant TE and TM impedances of the magnetotelluric impedance tensor\({\chi }^{2}\) objective functions for the estimation of twist assuming the two possibilities for the unknown sign of shear. The black lines in a and b represent the functions for positive shear and the red lines for negative value. The lowest minimum corresponds to the correct positive shear and the correct assumption, i.e., \({\rho }_{+}\) as \({\rho }_{yx}\)Back to article page