Nature, 'Megathrust' Earthquake Could Trigger San Andreas Fault, Scientists Warn
A newly identified link between two notorious geologic zones suggests a major earthquake at one site could trigger another huge quake at the other, creating a double-whammy of destruction.
Researchers led by a team from Oregon State University analyzed 137 different sediment cores collected from the Cascadia subduction zone, in the Pacific Northwest, and the northern San Andreas Fault, in California. In those samples, collected on five voyages, they found evidence of synchronized earthquakes at the two sites going back some 3,000 years.
That evidence appeared in the form of turbidites: layered deposits that show up in cores when fast-moving landslides happen underwater, indicated by smaller grains on top and coarser grains underneath. In several cases, the timing of when these turbidites were deposited matched up between Cascadia and San Andreas.
Based on these pairings, and the history of earthquakes in both areas, the researchers suggest that a magnitude 9 (M9) earthquake or 'megathrust' along the Cascadia subduction zone could be enough to seriously unsettle the San Andreas Fault too.
"It's kind of hard to exaggerate what a M9 earthquake would be like in the Pacific Northwest," says paleoseismologist Chris Goldfinger, from Oregon State University. "And so the possibility that a San Andreas earthquake would follow, it's movie territory."
Tubidites? I don't think I've heard that word since Geological Oceanography 101.
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