Integrating Electrical Resistivity Tomography (ERT) and 2D Seismic Surveys to Image a Shallow Deformation Zone

Abstract Near-surface deformation zones pose significant imaging challenges due to complex structural geometries, heterogeneous lithology, and high ambient noise, especially near urban and infrastructure developments. This study examines a 30-meter-wide deformation outcrop within the Dammam Dome in Eastern Saudi Arabia using electrical resistivity tomography (ERT), seismic tomography, and mineralogical analysis to characterize subsurface properties. ERT surveys revealed a pronounced high-resistivity anomaly (~2-2.4 Ohm.m on the logarithm scale). This anomaly correlates spatially with surface fractures and is interpreted as lithified breccia or dolomitic cementation, indicative of reduced porosity and enhanced structural rigidity. In addition to the ERT data, a 2D seismic refraction survey was conducted along a parallel 360-meter profile. Super-virtual refraction interferometry (SVI) was utilized to enhance the signal-to- noise ratio and improve the continuity of first-arrival traveltimes in this noisy environment. Seismic velocity tomograms revealed a high-velocity anomaly (1210–1650 m/s) within the upper 20 meters, aligning closely with the resistivity-defined deformation zone. Mineralogical analysis via XRD and XRF confirmed dolomite as the dominant mineral, accompanied by gypsum, quartz, and clay minerals. Elevated magnesium, calcium, aluminum, and silicon concentrations further supported the interpretation of a closed-system mineralization process consistent with internally sourced diagenetic infill. These findings indicate a multi-stage deformation model involving initial faulting, subsequent brecciation, and mineral sealing. This integrated methodology of ERT, seismic tomography, and mineralogical validation provides robust insights for imaging and understanding shallow deformation zones in carbonate geological environments, significantly contributing to geohazard assessments and subsurface characterization for infrastructure development.