120-8 Collecting Magnetotelluric Data in Semi-Urban Environments: What We Can Learn from a High-Resolution Survey in the Eastern U.S.

Abstract:

Wideband magnetotelluric (MT) surveys are used to map heterogeneous electrical resistivity structures and are essential to understanding the geologic frameworks of complex tectonic domains. In 2025, the U.S. Geological Survey began collecting wideband MT data at 35-km spacing across the eastern United States (Georgia to Maine, from the Atlantic coast to west of the Appalachian Mountains), refining the spatial resolution of the long period US MTArray (70-km spacing) through higher-density data collection. Wideband MT data, sensitive to upper-crustal structure, is non-existent across the eastern U.S. save for two legacy profiles. While the survey’s primary aim is to estimate geoelectric hazards due to geomagnetic storms—which can cause damage to or collapse the electric power grid—high resolution 3D resistivity models derived from new MT data will further advance our understanding of Appalachian tectonics and provide context for critical mineral assessments. In a region overlapping more than three dozen known mineral deposits (e.g. tin, tungsten, and zinc) and hundreds of kilometers of Earth MRI focus areas (e.g. marine chemoclines and basin brine paths), these improved models may help identify new crustal or lithospheric discontinuities that act as pathways for deposit-forming fluids.

To date, we have collected data at 189 out of ~600 planned MT soundings. Collected data spans the entirety of Delaware, Maryland, Viginia, and West Virginia and parts of Ohio, New Jersey, Kentucky, and Pennsylvania. Challenges specific to working in semi-urban environments include poor data quality from pervasive cultural noise (pipelines, powerlines, electrified railroads, etc.) and permitting in areas where public lands are limited. Additionally, highly resistive lithosphere underlies much of the survey area, resulting in noise contamination at sites far removed from infrastructure. With innovative data processing methods to combat infrastructure noise, we have successfully produced preliminary 3D resistivity models, which will be used to better forecast the impact of space weather events, refine our understanding of Appalachian tectonics, and improve our ability to map subsurface mineral systems and fluid pathways.

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-16961

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