Source: Journal of Geophysical Research: Solid Earth
Magnetotelluric (MT) data, which contain measurements of electric and magnetic field variations at Earth’s surface, provide insights into the electrical resistivity of Earth’s crust and upper mantle. Changes in resistivity, or the ability to conduct an electrical current, can indicate the presence of geologic features such as igneous intrusions or sedimentary basins, meaning MT surveys can complement other kinds of geophysical surveys to help reveal Earth’s subsurface. In addition, such surveys can play an important role in improving understanding of the risks space weather poses to human infrastructure.
Montiel-Álvarez et al. present the first 3D electrical resistivity model of Britain, based on long-period MT data (using measurements gathered every second for 4–6 weeks at a time) from across the island. Their model, called BERM-2024, points to previously recognized as well as likely new tectonic and geological structures. The authors also model the effects of a recent solar storm on Earth’s geoelectric field, validating the usefulness of MT-based approaches for space weather impact forecasting.
The BERM-2024 electrical resistivity model is based on MT data from 69 sites in Britain, including both new and legacy datasets. Creating the final model involved processing the raw time series data and accounting for the “coastal effect” caused by the conductivity of ocean water when inverting the data—or calculating causes based on observations.
Sensitivity tests of the new model indicate it resolves features to depths of 200 kilometers (125 miles), including many known from other geophysical surveys and geological observations. It also reveals new anomalies, including highly conductive areas under Scotland’s Southern Uplands Terrane and a resistive anomaly under the island of Anglesey. More intriguing, a large, previously unknown conductive anomaly appears in their model between 85 and 140 kilometers (52–87 miles) beneath the West Midlands region.
The authors tested the utility of their resistivity model for estimating the electric field at Earth’s surface, which is key in forecasting the effects of geomagnetically induced currents caused by space weather. To do so, they obtained a time series of the horizontal electric field across Britain during a solar storm that occurred on 10–11 October 2024, which led to bright displays of aurora borealis across the Northern Hemisphere. They found good agreement between their modeled time series and those measured at observatories, indicating that electrical resistivity models are a tool that can provide accurate information for space weather impact planning. (Journal of Geophysical Research: Solid Earth, https://doi.org/10.1029/2025JB031813, 2025)
—Nathaniel Scharping (@nathanielscharp), Science Writer
Citation: Scharping, N. (2025), New 3D model reveals geophysical structures beneath Britain, Eos, 106, https://doi.org/10.1029/2025EO250381. Published on 10 October 2025.
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