(soo, dō sek’ sh∂n) 1. A plot of electrical measurements or calculations, often of apparent resistivity or induced polarization as a function of position and electrode separation (which is nonlinearly related to the depth of investigation, q.v.). A pseudosection indicates how the parameter varies with location and depth, but it can only be converted into a 2D model by inversion. Also called a quasi-section or pseudodepth section. For the dipole-dipole electrode configuration, the data are plotted (Figure P-17) beneath the midpoint between the dipoles at a depth of half the distance between the dipole centers. For the Schlumberger array, the data are plotted beneath the potential electrodes at a depth of half the separation of the current electrodes (AB/2). 2. For frequency-domain measurements, the vertical scale is sometimes increasing period (or decreasing frequency). 3. Also used for plotting magnetotelluric apparent resistivity as a function of frequency (z-axis) and traverse distance (x-axis).