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Nine Deep Mantle Quakes Detected Beneath Utah, Wyoming.

6/13/2026

Summary

Story summary

Researchers confirmed nine mantle earthquakes beneath Utah and southwest Wyoming at 90 km depth.
George Zandt measured a magnitude 3.8 quake on 23 February 1979 under Randolph, Utah, at 90 km depth.
A magnitude 4.1 quake struck near Maeser, Utah, at 6 p.m. on 10 September 2025, originating 68 km deep.
Keith Koper of Utah Seismograph Stations said scientists cannot gauge maximum size of these quakes, which cluster along the eastern edge of the >2.5-billion-year-old Wyoming Craton where strain builds.

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Story summary

Researchers confirmed nine mantle earthquakes beneath Utah and southwest Wyoming at 90 km depth.
George Zandt measured a magnitude 3.8 quake on 23 February 1979 under Randolph, Utah, at 90 km depth.
A magnitude 4.1 quake struck near Maeser, Utah, at 6 p.m. on 10 September 2025, originating 68 km deep.
Keith Koper of Utah Seismograph Stations said scientists cannot gauge maximum size of these quakes, which cluster along the eastern edge of the >2.5-billion-year-old Wyoming Craton where strain builds.