Warning signs? ‘Silent Earthquakes’ ripple under Cascadia

October 6, 2012WASHINGTON - Parts of Washington and Oregon are in the midst of silent earthquakes this week. You can’t feel this so-called “slow slip” quake and it doesn’t cause damage. Still, scientists want to learn more about the recently discovered phenomenon. Little is certain so far, but there’s a possibility these deep tremors could trigger a damaging earthquake or serve as a warning bell for the Big One. A bank of computer monitors covers one wall of the University of Washington seismology lab. Some display seismograph readouts that look like jagged mountain ranges stacked one over the other. A big screen shows a current map of tremors under the Pacific Northwest. It is lit up with activity. “Each dot represents the location of a five minute burst of tremor,” says earth scientist Ken Creager. He scrutinizes a dense slash of blue, yellow, green and red dots. The arc stretches south from mid-Vancouver Island, goes under the Olympic Peninsula, Puget Sound and peters out south of Olympia. A separate patch of color radiates out from near Roseburg, Ore. Washington State Seismologist John Vidale is also keeping an eye on the busy map. “This kind of earthquake is distinctly different than the earthquakes we have been watching for a hundred years, because this patch of fault that we’re watching takes three weeks to break. Whereas ordinarily something a hundred miles long would take a minute or less to break. About half of our instruments can see it,” Vidale adds. “It’s a very slight level of rattling. I don’t think I have ever heard of somebody who we believed could feel it.” Local seismologists woke up to the phenomenon about a decade ago and have since discovered a big non-volcanic tremor swarm happens fairly routinely around here — every 14 months or so in western Washington, a little less often in Oregon and more often in northern California. Scientists have coined a variety of names including “slow slip quake” or “episodic tremor and slip” to describe what they’re seeing. Vidale says the mechanisms at work deep underground remain fairly mysterious. This current slow slip quake under the Salish Sea has lasted five weeks. Creager says scientists have calculated that a significant event like this releases the equivalent energy of a magnitude 6.5 regular quake. “It’s a lot of energy being released,” Creager says. “It just happens so slowly that you’re not going to feel it. This is the way we like to see energy released.” But there’s a flip side. The grinding and slippage at depth increases the strain closer to the surface where the North American plate and the oceanic plate are stuck together or “locked.” When that offshore fault zone eventually gives way, we get the damaging Big One. University of Oregon Professor David Schmidt makes an analogy to a car teetering partway over a cliff. “And these small slow slip events are somebody standing behind that car giving it a little nudge every several months. So even though the nudge is small, at some point that nudge might be enough to kind of tip us over the edge and cause the car to fall off the cliff.” Or set off the Cascadia mega-quake in this analogy. Schmidt points to a study published in the journal Science that describes how last year’s great earthquake and tsunami in Japan was preceded by slow slip and tremor near the epicenter. John Vidale mentions another killer earthquake, in Turkey in 1999, where instruments picked up a slow slip precursor. “One of the goals of our research is to say, how often does that slow slip trigger a great earthquake? How often are great earthquakes triggered by slow slip? That’s almost completely unknown at this point.” Vidale and his colleague Creager are more certain that we don’t need to quake with worry. They note that great earthquakes strike very infrequently in the Northwest. So even if a megaquake becomes more likely during a slow slip event, the chances of one happening are still quite slim. –Northwest Public Radio  
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This entry was posted in 2012, Earth Changes, Earth Watch, Earthquake Omens?, High-risk potential hazard zone, Prophecies referenced, Seismic tremors, Signs of Magnetic Field weakening, Volcano Watch. Bookmark the permalink.

24 Responses to Warning signs? ‘Silent Earthquakes’ ripple under Cascadia

  1. If there is this much slippage going on deep under the surface and very little actually near the surface where the plates are locked, then we are probably in trouble up here. Based on the graphic in the article, that is a lot of movement that is bound to affect the rest of the seismic zone by shifting the pressures in the rock formations. But, of course, we are told not to worry – even though the Cascadia is decades overdue for a major quake!

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  2. SoSo says:

    That area looks like it’s the start of the breaking off of the land to me.

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  3. tonic says:

    Vibration was the first word that entered my head after reading this Like a tuning fork. I hope it’s not.

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  4. slmorelli says:

    This deep level event recalls the major problem BP drillers encountered a year or so back; the depth of an occurance I am believing is a factor of major significance..it calls to mind the phrase ” being out of one’s depth?” As futher beyond our reach- being so much more out of our control. The people who are believing are truly deserving of the concern they are heard to be voicing- they are hearing a call indeed, this being a gaurded sign, a true warning, and is worthy of careful dissemination.

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  5. “Cascadia” was my home from birth and most of my life. I have been in five minor earthquakes there, rockin and rollin. It makes me so sad to think a bad one could happen there. I still want to go back and live my last days there. I miss the lake. I miss the intelligent but not always wise people.

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    • It seems that there are trade-offs to living anywhere, Mariel. I’ve friends who live on the Gulf Coast and love it in spite of the hurricanes, and friends in the Great Plains who shrug at the idea of tornadoes. Here in Cascadia we have volcanoes and earthquakes. There is nowhere on earth that is “safe”, so I would just follow my heart and live where I really want to…

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  6. onthemark55 says:

    We’re due for something big in the N.W. It has been 30yrs since St Helens went and we were lucky it blew out to the less populated north than sw towards the Portland/Vancouver area. Other than localized floods,wind storms and minor quakes i’d have to say we’ve had the the least amount of catastrophic events(loss of life/property damage/ravages of war) than any other region in the world(correct me if i’m wrong). Sooner or later the “bill” comes due.

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  7. Kevin says:

    I’d be careful living on the coast of Oregon, there is signs of a underwater volcano out in the sea of the coast of Oregon which may pop some time soon. There is a growing number of quakes in the area of the volcano and mark my words if it pops it will produce a tsunami which will have a chance of hitting the coast of Oregon.

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    • I haven’t heard anything about a volcano forming off our coast, Kevin, although with all of the activity lately in a fairly localized area I wouldn’t be surprised. Where did you hear of it?

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  8. Irene C says:

    I have a bad feeling about this. I’ve been watching the quakes that USGS shows but to know that there are now “silent quakes” is disturbing. I agree davidgreybeard, we are always told not to worry. On one hand, they don’t want to start panic but on the other hand, people should be prepared. Personally, I would prefer to be prepared.

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    • I’d rather be prepared, too, Irene. One thing that I noticed from the map is the lack of silent quakes, or at least the scarce number of them, between Olympia, Washington and Roseburg, Oregon – this shows very little movement at any depth right in the same stretch of the Cascadia Subduction Zone that seems to be worrying the geologists the most. Without saying it directly, I think that the geos are letting us know that their concern is on the rise.

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  9. Dennis E. says:

    We live in a world of change don’t we.
    That is an understatement………….

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  10. Therese says:

    I was visiting my family a few years back up in the Southern Oregon area. I had this dream that I was sitting on the ground and it raised up underneath me sharply. I have always said that the location where I have the dream doesn’t always determine where the event may happen and have felt a need to rely on people with more knowledge about seismic activity as the rationale is always included in any dream that I have. Like a ripple in time the events can sometimes dimensionally happen in several places up to and including the area where the dream occurred over a period of time. I have had several dreams that fit into the PNW and the Juan De Fuca – however I can not disclude the New Madrid wrecking havoc simultaneously from the East Coast to the West Coast.

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  11. Bonny says:

    God bless you , thank you 4 what you do you really help lots . I m glad that we all have u i live right where the silent quakes are is there even a safe place 2 go ?

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  12. Mrs. B says:

    Have you seen this blog post on the PSNW Seismo Blog:” Altarock Energy Corp., a Seattle-based renewable energy development company, is planning to start on October 8th to inject water for circulating in the hot rocks near Newberry Volcano. The operation is on the outer flanks of the volcano, five miles west of the most recent volcanic activity.” http://www.pnsn.org/blog

    This will most likely be the cause of starting an event.

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    • Irene C says:

      Now this is a real sign of intelligence – not!! I would love to know what these people are thinking. Oh, I know – $$$$. Thanks for posting this.

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  13. Karen says:

    We live within line of sight of the epicenter of the last Nisqually quake in 2001 on the shoreline of Puget Sound. So here is a practical question – for us to bring our ranch house up to earthquake retrofit standards as recommended by the USGS, will cost in the range of $14-18,000. It’s a risk assessment decision – what would you do?

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    • IMg

      The threat will not diminish with time. Tense stress points in the Earth will only grow more aggrevated as these changes ripple from shore to shore, and sea to sea. Once the major earthquakes unsettle the planet’s tectonic plates and major faults are activated; the planet will enter a new dynamism, where resonate quakes will be occurring across the globe almost daily. Consider where you can best allocate resources for the long haul, and what takes greater priority.

      Alvin

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  14. Brian Bailey says:

    I follow seismicity worldwide. Globally it is on the increase, major increase. never in the history of history has there been such a huge amount of geologic activity. There have been many mini-quakes around the summit of Rainier and St. Helens and several other cascade volcanoes. There is also a huge concern in the scientific community, (tight-lipped, though they be..) about the yellowstone caldera; the usgs has actually deleted every quake in yellowstone which was over a 2.8 in magnitude although people living near the epicenters gave their own testimonies bearing witness that the quakes had occurred. The calderas lava dome has been growing since 2008, (or before, dont remember.) eq activity has increased, almost exponentially in the yellowstone region but there is little to no media coverage. The pacific faults are more active now than at anytime ever. (that there is valid evidence to support.) There are major earthquakes happening a few hundred miles off Washingtons NW coast, in the Queen Charlotte Islands, the biggest being a 7.7!! They are still happening there now. There are major quakes happening all the time now off the coasts of California and Oregon; the Gulf of California has had quakes upward of 6.0. Something is about to pop off, almost literally and it looks like there is a giant fault which leads up all the way from mexico and ending northwest of Washington, the Puget Sound being the northwestern boundry, the fault being evident if one merely looks at a map of eq activity leading from south to north and one will see that the activity follows two faults; one leading up san andreas and another, bigger one, leading all the way through california and resurfacing as the puget sound in the north….if you dont see it now…you soon will.

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    • Agreed, Brian. I live on the Oregon coast and have been tracking the quake activity throughout the US for some time now. Lately there have been a number of quakes (such as the 7.7 you mentioned) at either end of the Cascadia Subduction Zone, but very little activity throughout the central portion of this zone; that tells me that the pressures in the central region are being magnified by the changes at either end. And regarding Yellowstone, USGS has been doing a bit of sleight of hand with the seismometer feeds for a while now while shruggin it off as “technical issues”. Seismometers are rather vulnerable to the effects of a harsh environment, but the slective nature of their “failures” is raising more than a few eyebrows.

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  15. I really believe this post , “Warning signs? ‘Silent Earthquakes’ ripple under Cascadia | The Extinction Protocol:
    2012 and beyond”, especially compelling plus it ended up
    being a great read. Thanks for your time,Hayley

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  16. Thanks a ton for applying some time in order to compose
    “Warning signs? ‘Silent Earthquakes’ ripple under Cascadia | The Extinction Protocol:
    2012 and beyond”. Thank you so much yet again -Coy

    Like

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