Scientists Detected Strange Rumbling Beneath Utah Almost 50 Years Ago. They Just Figured Out What It Was

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   Scientists Confirm 'Impossible' Deep Utah Earthquake Was Real

   A rare earthquake detected nearly 50 years ago beneath northern Utah—once dismissed as implausible—has been confirmed as a real, deep mantle event. Researchers now identify it as part of a previously unknown class of continental mantle earthquakes occurring far deeper than expected. The discovery challenges long-held assumptions about seismic activity in Earth’s upper mantle. New analysis of decades-old seismic data supports the finding.

   What's confirmed:

   • A mysterious earthquake detected beneath northern Utah in 1979 was real and occurred nearly 90 kilometers underground—far deeper than typical earthquakes beneath continents.
   • Researchers have identified this event as part of a rare class of 'continental mantle earthquakes,' where rock breaks deep in Earth’s upper mantle instead of flowing slowly.
   • The discovery contradicts the long-held belief that earthquakes cannot occur at such depths beneath continental crust.
   • Scientists reanalyzed decades of seismic data to confirm the event’s reality and its classification as a deep mantle quake.
   • The earthquake challenges existing models of seismic activity and raises questions about seismic hazard assessments in stable continental regions.

   Still unconfirmed:

   • Utah deep earth rumbling since 1979 continues to puzzle scientists as part of an ongoing seismic mystery near the Wyoming Craton.
   confidence 98%