The two seismic threats that could dismantle the American economy
In short: Most Americans believe the 'Big One' is a single event. In reality, the U.S. faces two distinct, catastrophic geological threats: one a coastal megathrust capable of flooding Japan, and the other a hidden inland fault capable of ringing church bells 1,100 miles away.
The first threat is the Cascadia subduction zone, a fault off the coast of Oregon. The distance between Atlanta and New York equals its length. A tsunami hit Japan and the Pacific Northwest coast sank six feet in mere minutes during a rupture 326 years ago. While it is statistically overdue, new research suggests it might not act alone. Studies of 3,100-year-old sediment cores indicate the San Andreas fault and Cascadia zone might 'sync up,' possibly sparking earthquakes within hours or minutes of one another.
Such a coordinated event might place Seattle, Vancouver, Portland, and San Francisco into a joint emergency. The second threat is the New Madrid seismic zone, located under the Mississippi River in the nation's agricultural heartland. Unlike the West Coast faults, this is a complex of buried faults with no visible surface scar.
Despite lacking a plate boundary, this fault generated three massive earthquakes during 1811-1812 that shook Boston's church bells from 1,100 miles away. These events were so violent that the Mississippi River reportedly ran backwards for several hours, leading settlers to believe the world was ending. The danger lies in the differing mechanics: Cascadia is a megathrust on a continental edge, while New Madrid is a complex of internal faults. One threatens a massive tsunami; the other threatens to dismantle the central economy of the United States. Because the infrastructure atop these faults was never built to withstand such forces, scientists warn that the public remains largely unprepared for these two distinct geological realities.
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Sources
- Summary by Intellect · source: The Two Earthquakes That Will Shatter America | 4K Documentary
- Also: The “big one” might not come alone: Double West Coast earthquake threat
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