3D effects of seawater on electrical resistivity tomography near shorelines—Challenges and possible solutions inferred from synthetic and field data
Near Surface Geophysics, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Basım Tarihi: 2026
- Doi Numarası: 10.1002/nsg.70063
- Dergi Adı: Near Surface Geophysics
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Geobase
- Anahtar Kelimeler: electrical resistivity tomography (ERT), hydrogeophysics, inversion, modelling, near-surface
- Kocaeli Üniversitesi Adresli: Evet
Özet
Electrical resistivity tomography (ERT) is one of the most widely used geophysical techniques for hydrogeological questions, such as investigating the groundwater transition zone between land and sea. The interpretation of 2D coast-parallel ERT profiles is challenging because most of the electrical current flows through the highly conductive seawater and not the ground beneath the profile. We study this effect using synthetic data and a field data example and propose an approach for improved evaluation of coast-parallel geoelectric profiles. The synthetic study shows that the impact of the seawater on apparent resistivities is negligible (errors below 1.5%) only if the distance between current injection electrodes (a) is equal to or smaller than the distance (d) between ERT profile and shoreline ((Formula presented.)). Ignoring this criterion, standard 2D geoelectric inversion results may diverge by 50% from the actual resistivity distribution at depths of (Formula presented.). To improve the inversion also for profiles with (Formula presented.) we tested an approach to consider the seawater effect through a correction factor applied to the measured apparent resistivity values prior to the inversion. The correction factor depends on (Formula presented.), the seafloor slope and the resistivity ratio of seawater and average underground. We present an analytical function approximating the correction factor well for seafloor slopes up to 10° and seawater-to-average-land resistivity ratios of 0.040–0.002. We found that this approach is effective at removing errors in apparent resistivities for (Formula presented.). Inversion results then show more reliable resistivities up to relative depths of (Formula presented.). We applied the correction approach to field data from a coast-parallel profile at Konyaaltı Beach (Antalya, Türkiye). The field study demonstrates the importance of considering the seawater effect to interpret possible locations of fresh submarine groundwater discharges and saltwater intrusions. It also shows the practical applicability of the new correction approach.