Fig. 2

a The impedance tensor influence indices \({Z}_{xx}^{\mathrm{inf}}\), \({Z}_{xy}^{\mathrm{inf}}\), \({Z}_{yx}^{\mathrm{inf}}\) and \({Z}_{yy}^{\mathrm{inf}}\), and b the tipper edge effect indices \({T}_{x}^{\mathrm{edge}}\) and \({T}_{y}^{edge}\) calculated with all stations according to (4) and (6), respectively, and just at the S_center, S_edge, and S_outer stations, Eqs. (3) and (51), for the isotropic experiments where the resistivity of the 3-D body is varied as shown on the x-axis and buried at the surface, 5 km and 20 km. The dashed lines are at 0.1 for the impedance tensor and 0.50 for the tipper and mark the 10% and 50% levels, respectively