Exploring the regolith with electrical resistivity tomography in large-scale surveys: electrode spacing-related issues and possibility

Abstract. Within the critical zone, regolith plays a key role in fundamental hydrological functions of water collection, storage, mixing and release. Electrical resistivity tomography (ERT) is recognized as remarkable tool for characterizing geometry properties regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, small electrode spacing (ES) will provide denser set apparent measurements subsurface. As this option cumbersome time-consuming, larger ES – albeit offering poorer data often preferred large horizontal ERT surveys. To investigate negative trade-off between reduced accuracy inverted images we use synthetic “conductive–resistive–conductive” three-layered soil–saprock/saprolite–bedrock models combination with reference field dataset. Our results suggest that an increase causes deterioration terms both distribution interface delineation and, most importantly, degradation increases sharply when exceeds thickness top subsurface layer. This finding, which obvious characterization also relevant even solely aiming deeper layers. We show oversized leads overestimations depth bedrock overestimation more important structures high contrast. overcome limitation, propose adding interpolated levels surficial relying on limited number profiles smaller ES. demonstrate our protocol significantly improves using ES, provided layer has rather constant resistivity. specific case large-scale surveys proposed upgrading procedure cost-effective comparison protocols based