The First Three‐Dimensional Electrical Resistivity Model of the Lithosphere Beneath Britain

Abstract Magnetotelluric data provide unique information to study the electrical resistivity of the Earth's lithosphere, enabling studies of geological structures, tectonic processes, resource exploration, and hazard monitoring. Here, we present the first fully three‐dimensional (3D) electrical resistivity model of the deep lithosphere beneath Britain (BERM‐2024), derived from the inversion of long‐period magnetotelluric data at 69 MT sites, incorporating recently acquired data along with selected legacy data sets. Rigorous testing of the prior model design and inversion smoothing parameters led to a robust and geologically meaningful model. The model reveals significant lateral and vertical variation, with shallow conductive anomalies correlating with sedimentary basins in western Britain, such as the Cheshire Basin and the Welsh Massif, while resistive anomalies are related to granitic plutons in the Scottish Highlands and Cornwall. At mid‐crustal to upper mantle depths, strong resistivity contrasts coincide with major faults that bound distinct tectono‐stratigraphic terranes, including a clear signature of the Southern Uplands Fault separating the conductive Southern Uplands Terrane from the less conductive Midland Valley Terrane. A newly imaged, deep conductive anomaly (85–140 km) is detected beneath the West Midlands region. Beyond the geological insights, resistivity models are key for studying space weather impacts on ground‐level infrastructure. We model geoelectric fields for the geomagnetic storm of 10 October 2024 using our model, demonstrating high correlation with measured electric fields at Eskdalemuir magnetic observatory (ESK), although amplitude discrepancies remain. This work establishes a foundation for future geophysical and geohazard studies and underscores the need for continued magnetotelluric data acquisition across Britain.