Bury a target, pick an electrode array, and see the pseudosection it produces, a blurred and distorted image of the true ground.
Electrode array:
Background resistivity is fixed at 100 Ω·m; electrodes are every 4 m. Blue = conductive (low ρₐ), red = resistive (high ρₐ).
Model assumptionsWhat this simulation simplifies
This is a first-order (linearized) teaching model. Each apparent resistivity is a sensitivity-weighted average of the true log resistivity. The weights are the sensitivity of that array over a uniform 100 Ω·m half-space, and for dipole-dipole they are negative in places.
The linear average is accurate only for weak contrasts; near the ends of the Target resistivity range (5.0 Ω·m and 1995 Ω·m against the 100 Ω·m background), a full nonlinear forward model would give a different pseudosection.
The target is 2-D (constant along the direction perpendicular to the line) with an elliptical cross-section 18 m wide and 12 m tall; the electrodes sit every 4 m on a flat 100 m line.
Each reading is plotted below the array midpoint at its median depth of investigation, one depth per level. The real inverse problem is to recover the true model from these data.
The data are noise-free; in the field, large-n dipole-dipole readings are weak and noisy.