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Earth Chgs Ring of Fire Question
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  1. #1
    Join Date
    May 2004
    Location
    Potato Country
    Posts
    5,069

    Ring of Fire Question

    How come there is so much activity along the Ring of Fire on the East coasts of Asia and those other countries, and not the Western Coast line of North America, Mexico and Canada? I've seen activity along the South America coastlines, but never much further north.

    Not that I'm complaining, I guess the plates are shifting that direction...or there is some other dynamic causing it...

  2. #2
    Join Date
    May 2004
    Location
    Sandhills North Carolina
    Posts
    35,162
    I think the collisions are west plates nose diving under east plates Like a chain reaction on the interstate where cars plow into others causing additional wrecks

    Someone mentioned the 100% Atlantic American shoreline of beaches with vast shallow subfloors verses West Coast cliffs and rare beaches in California or Ireland or S America for example

  3. #3
    Join Date
    Jul 2006
    Location
    First Coast
    Posts
    1,152
    Plate Mechanics in a Nutshell

    The oceanic ridges provide the mechanism of plate movement. Newly formed ocean crust from the Atlantic Ridge forces the ocean bed westward toward North and South America. The ocean crust is locked onto the North American Plate so the westward motion is transferred to the west coast of North American.
    The east Atlantic Ocean Plate is locked onto the Eurasia and African Plates so that motion is transferred east.

    East and West plate movements meet at the western arc of the Ring of Fire. That's where to ocean crust plummets back into the mantle forming an oceanic trench. This subduction zone is the most active.

    The west coast of North America is not locked to the Pacific Plate and movement does occur laterally in California. The northern Pacific coast is subducting the Juan de Fuca plate therefore the Cascades are volcanic mountains.







  4. #4
    Join Date
    Jul 2006
    Location
    First Coast
    Posts
    1,152
    BTT. Don't know if the person who asked has seen this.

  5. #5
    Join Date
    Jan 2005
    Location
    Portland, Oregon
    Posts
    14,437
    I don't know that this article (also posted in the Northwest part of the forum) contributes all that much to answering the OP question, but it is new research potentially directly related to the Cascadia Subduction Zone. I seem to recall that prior to about the mid-1980s geologists generally thought there was something special about the CSZ that allowed the Pacific plate to slide more smoothly under the Juan de Fuca plate than was the case anywhere else on the Ring of Fire. As far as I know the majority of geologists don't think that anymore -- the consensus now is that it's purely a matter of when, not if. It's probably a mistake to think that just because there's an average between megaquakes on the CSZ that automatically means something is wrong if the average passes and nothing has happened.

    -----

    Large earthquakes follow ‘silent slip,’ new OSU research shows

    by Kale Williams
    January 21, 2019
    The Oregonian/OregonLive

    Researchers at Oregon State University have found a new explanation as to why foreshocks often precede large earthquakes.

    Large quakes appear to follow a short period of “shallow mantle creep” and “seismic swarms,” according to the study, which was published Monday in the the [sic] academic journal Nature Geosciences.

    The findings shed new light on a phenomenon called “silent slip,” in which parts of the Earth’s crust are displaced along a fault line, but without any seismic activity.

    In simpler terms, silent slip is when the Earth moves, but there’s no earthquake. That silent slip can lead to actual seismic activity, though, said co-author Vaclav Kuna, a graduate student in geology and geophysics at the university.

    Vaclav and other researchers deployed 55 seismometers along the Blanco Transform Fault off of Oregon’s coast for a year.

    “It’s a very seismically active fault that generates significant earthquakes at higher rates than the majority of faults on land, making it ideal for studying the process of earthquake generation,” Kuna said in a statement.

    Transform faults occur at the edges of tectonic plates where the movement is mostly horizontal. The Cascadia Subduction Zone, the Pacific Northwest’s most widely known producer of large quakes, is a subduction fault, where one plate is sliding beneath another. Still, Kuna’s findings were remarkable.

    “Slow slip directly triggers seismic slip – we can see that,” Kuna said in a statement. “The findings are very interesting and may have some broader implications for understanding how these kinds of faults and maybe other kinds of faults work.”

    To see how those faults work, Kuna and other researchers had to look beneath the Earth’s crust, which can vary from 40 miles thick on land to just 2 miles thick on undersea ridges. The boundary area between the crust and the next layer beneath it, the upper mantle, is called the Moho.

    Slips in the Moho, which don’t always result in earthquakes, can be precursors for quakes in the laters [sic] above, said co-author John Nabelek.

    “We see slow, aseismic slips that occur at depth in the fault beneath the Moho and load the shallower part of fault,” he said in a statement. “We can see a relationship between mantle slip and crust slip. The slip at depth most likely triggers the big earthquakes. The big ones are preceded by foreshocks associated with creep.”

    The Blanco fault is close enough to the Cascadia Subduction Zone, Nabelek said, that action on one could portend action on the other.

    “A slip on Blanco could actually trigger a Cascadia Subduction slip,” Nabelek said. “It would have to be a big one, but a big Blanco quake could trigger a subduction zone slip.”

    https://www.oregonlive.com/news/2019...rch-shows.html

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