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Tiny Earthquakes Reveal Potentially Death Hidden Beneath California
The Pioneer Fragment increases plate contact area near Cascadia, potentially altering earthquake risks and explaining shallow quakes like the 1992 Cape Mendocino event, scientists say.
- On January 15, scientists at the U.S. Geological Survey, University of California, Davis and University of Colorado Boulder discovered the Pioneer Fragment is stuck to the Pacific Plate and sliding northwest beneath the North American Plate near the Mendocino Triple Junction.
- Originally part of the Farallon Plate, the Pioneer Fragment is a remnant that detached 30 million years ago after the Farallon Plate began subducting beneath North America 200 million years ago during the breakup of Pangaea.
- Using a dense network of seismometers, researchers recorded swarms of low-frequency earthquakes and tremors and validated their model by testing how quakes respond to tidal forces from the Sun and Moon, revealing a nearly horizontal hidden fault.
- As a result, the team notes the Pioneer Fragment enlarges contact with Cascadia and might generate earthquakes; `We don’t know whether that fault can generate large earthquakes, but it is a fault that isn’t currently in the hazard models`, Shelly said.
- The new model shows five moving pieces beneath California, including two hidden pieces below the surface, and the Pacific Northwest Seismic Network says tectonic motion could produce magnitude 9 and above quakes, while Amanda Thomas, UC Davis coauthor, stresses the need for more study.
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Scientists Discover a Hidden Earthquake World Beneath Northern California
Invisible earthquakes are revealing a hidden tectonic puzzle beneath California’s most dangerous fault zone. By closely monitoring clusters of extremely small earthquakes, scientists are uncovering new details about a dangerous and complex region off Northern California. This area marks the meeting point of the San Andreas fault and the Cascadia subduction zone, a place capable [...]
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Leaning Left4Leaning Right2Center6Last UpdatedBias Distribution50% Center
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- 50% of the sources are Center
50% Center
L 33%
C 50%
R 17%
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