Salt diapirs are of interest due to their unique properties that make them ideal for secure, long-term subsurface storage, including for CO ₂, natural gas, and radioactive waste. However, their utilization requires an understanding of their structure, which can be achieved with geophysical imaging. It is often a challenge to delineate salt diapirs with seismic reflection methods; therefore, we employ electromagnetic methods. We aim to a) highlight how magnetotellurics can identify the subsurface structure of salt diapirs, b) characterize the key tectonic structures and stratigraphic layers in the area, and c) investigate the role of faults on the distribution of diapirs. To do this we analyze an array of 253 magnetotelluric measurements and generate electrical resistivity models. The study area lies in the Shurab region, Central Iran, where numerous salt diapirs are observed near the surface. Overall, the models show a deformed southwestern zone and an undisturbed northeastern zone. Throughout the area, a thin (∼100 m) surface layer (1–100 Ωm) is underlain by a thick (up to 1000 m) low resistivity (<1 Ωm) layer, interpreted to be sediments of the Upper Red Formation. Below this is a higher resistivity (3–30 Ωm) layer that is complex and variable in depth and thickness, particularly in the southwest, where it shallows. This corresponds to the Lower Red Formation, which is the main salt layer and encompasses the diapirs. The electrical resistivity models successfully determine the locations, boundaries, and depths of salt diapirs within the area. Furthermore, they reveal that the salt diapirs are laterally extended along fault zones. This result provides valuable insights into the area's tectonic evolution and structural framework. Based on these subsurface images and geological information, we conclude that the tectonic activity along the Sen-Sen, Ab-Shirin, and Dehnar faults had a primary role in the formation of the salt diapirs.

Salt diapirs are prominent geological features, formed by the piercing of buoyant salt within overlying strata, with implications for basin evolution, tectonic deformation, and resource accumulation. In this study, we investigate the Shurab salt diapirs in northwestern Central Iran—an area with five known near-surface diapirs—whose subsurface geometries and interconnections at depth remain unclear due to the complex structural settings. To address these challenges, we generated a 3D electrical resistivity model from an array of 183 magnetotelluric (MT) measurements. Phase tensor and resistivity phase tensor analyses confirmed the presence of multidimensional conductivity structures. A range of modeling tests were performed to ensure a robust result, and final models were validated against seismic data and borehole logs, as well as previous 2D electric modeling. The resulting 3D resistivity model provides new insight into the geometry, depth, and interconnectedness of the salt diapirs and superior resolution of diapir flanks compared to seismic data. High resistivity zones at shallow depths correspond to dry salt, while lower resistivity at greater depths indicates brine-saturated regions. Notably, Diapirs No. 4 and 5 were found to be interconnected at depth, sharing a root zone and likely originating from a common evaporite layer. Tectonic analysis suggests that active fault systems—including the Sen-Sen, Ab-Shirin, and Dehnar faults—have played key roles in guiding salt migration and shaping diapir structures. This study highlights the effectiveness of using MT data to image complex salt structures and underscores the importance of integrated geophysical approaches in tectonically active regions.