Applicability of Total Horizontal Potential-Difference Magnitude to 2D Inversion for Dipole-Dipole Array Data in Complex 3D Structures with Strong Resistivity Contrasts

Churl Hyun Jo 

Complex 3D subsurface structures with strong resistivity contrasts can cause the horizontal electric field to deviate substantially from the survey-line direction. Under such conditions, conventional 2D electrical resistivity tomography (ERT), which relies only on the inline potential-difference component, may yield incomplete inversion results. Although full 3D interpretation using the horizontal electric-field vector is in principle more appropriate, practical limitations remain in field acquisition and inversion capability. This study therefore examines an intermediate approach in which the total horizontal potential-difference magnitude (Vt), obtained from two-component ERT measurements, is applied to conventional 2D inversion software. Numerical experiments were conducted using dipole–dipole array data generated for a complex 3D conductive anomaly model with strong resistivity contrast, and Vt-based 2D inversion results were compared with conventional results based on the inline component (Vx). The results show that, where localized 3D distortion of the horizontal electric field is significant, Vt inversion provides clearer separation of adjacent conductive anomalies than Vx inversion. This difference becomes more pronounced as the resistivity contrast increases. In contrast, no pronounced difference is observed between the two inversion results for structures exhibiting quasi-2D behavior. However, some Vt inversion sections show more pronounced edge-related artifacts. Thus, under the dipole–dipole array conditions examined in this study, Vt-based 2D inversion should not be regarded as universally superior, but may provide complementary information to conventional Vx-based interpretation where strong resistivity contrasts and localized 3D structural changes cause large deviations in horizontal electric-field direction.