Unveiling Britain’s Hidden Architecture
Magnetotelluric (MT) surveys, which measure natural electric and magnetic field variations at the Earth’s surface, offer a window into the subsurface by mapping electrical resistivity. Changes in resistivity help scientists identify geologic features such as igneous intrusions, sedimentary basins, and variations in crustal composition. A new 3D resistivity model, based on long-period MT data from across Britain, extends this view deep into the crust and upper mantle and demonstrates how seismically silent geophysical signals can reveal the country’s hidden architecture.
From MT Measurements to a 3D Model: The BERM-2024 Framework
The study, led by Montiel-Álvarez and colleagues, introduces the first 3D electrical resistivity model of Britain named BERM-2024. It leverages long-period MT data collected at 69 sites, incorporating both newly acquired measurements and legacy datasets. Inversion of the surface data required careful handling of the coastal effect—the distortion caused by ocean water’s conductivity—to ensure the model accurately represents the inland crust and mantle.
Long-period MT data are particularly valuable because they sample deep electrical properties. The researchers processed time-series data acquired with observations spanning four to six weeks at each site, allowing the model to resolve features down to about 200 kilometers (125 miles) depth. The resulting resistivity distribution maps how easily electricity travels through rocks, which in turn reflects variations in rock type, temperature, fluids, and metallic content.
BERM-2024 not only maps known structures but also highlights possible new geologic features. The team confirmed resistivity patterns associated with well-studied regions while revealing additional anomalies that warrant further investigation. Among these, a highly conductive zone under Scotland’s Southern Uplands Terrane, a resistive body beneath Anglesey, and a prominent conductive anomaly between 85 and 140 kilometers depth beneath the West Midlands stand out as intriguing clues to Britannia’s interior.
New Clues About Britain’s Tectonic and Geologic History
The 3D resistivity model aligns with existing geologic knowledge from other geophysical surveys, yet its depth reach and spatial resolution illuminate features that surface-based studies alone cannot detect. The conductive anomaly in the West Midlands, for example, may relate to subsurface fluids, mineralization, or prior tectonic processes. The resistive body beneath Anglesey could reflect ancient crustal blocks or mantle variations. While the precise origins of these anomalies require further work, they demonstrate the model’s potential to refine our understanding of Britain’s tectonic assembly and crustal evolution.
Importantly, the study demonstrates the practical application of MT-based resistivity models beyond pure geology. The team evaluated how BERM-2024 can forecast surface electric fields during space weather events by simulating a regional geomagnetic storm that occurred on 10–11 October 2024. They compared the modeled horizontal electric field time series with direct measurements from observatories and found good agreement, validating MT-based resistivity models as tools for space weather impact forecasting.
Implications for Infrastructure and Space Weather Readiness
Space weather poses real risks to electrical grids, pipelines, and other critical infrastructure. By providing a realistic map of how Earth’s subsurface conducts electricity, MT-based models like BERM-2024 help scientists predict how geomagnetic disturbances translate into geoelectric fields at the surface. This can inform risk assessments, preparedness planning, and the design of protective measures for vulnerable networks.
Beyond space weather, the 3D resistivity view enhances our understanding of Britain’s subsurface architecture, offering new constraints for geological models and helping to guide future geophysical surveys. The authors emphasize that MT remains a complementary tool—one that, together with seismic and gravity data, paints a more complete picture of the country’s deep structure.
Looking Ahead
As data acquisition continues and inversion techniques improve, later iterations of models like BERM-2024 are expected to resolve even finer details, potentially consolidating the new anomalies as confirmed features of Britain’s geophysical landscape. The integration of resistivity models with space weather forecasts marks a growing frontier where Earth science directly informs the resilience of modern infrastructure.
