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California earthquake swarm

Discussion in 'Environmental Discussion' started by tochatihu, Jul 6, 2019.

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  1. tochatihu

    tochatihu Senior Member

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    Largest so far mag 7.1 near Ridgecrest, >100 km N of LA area.

    As happens generally with major seismicity, most of world's earthquakes are (fore and) aftershocks nearby. Right now USGS says 639 of 674 global quakes mag 2.5+ within 24 hrs..

    Action is >100 km distant from San Andreas fault and it's comforting that no one 'in the know' is talking about triggering that section of that fault, which has been locked for quite a long time. :eek:

    Hoping to read reports from readers close enough to feel ground motion. Landers (1992) and Northridge (1994) were before our assembly here.
     
    #1 tochatihu, Jul 6, 2019
  2. bisco

    bisco cookie crumbler

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    'and if california slides into the ocean,
    like the mystics and statistics say it will,
    i predict this motel will be standing,
    until i pay my bill...
     
    #2 bisco, Jul 6, 2019
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  3. tochatihu

    tochatihu Senior Member

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    It's more like LA is slow-motion lurching towards San Francisco, due to arrive in about 10 million years. But falling into the ocean remains a persistent theme.

    Even here.
     
    #3 tochatihu, Jul 6, 2019
  4. bisco

    bisco cookie crumbler

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    it's more romantic
     
    #4 bisco, Jul 6, 2019
  5. tochatihu

    tochatihu Senior Member

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    According to seismologist Warren Zevon :)
     
    #5 tochatihu, Jul 6, 2019
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  6. bisco

    bisco cookie crumbler

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    exactly, don't deny the sage
     
    #6 bisco, Jul 6, 2019
  7. tochatihu

    tochatihu Senior Member

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    In a more technical aspect, I know of no place more densely instrumented with seismometers with excellent time control. So one would expect earth tomography to be done in this famous region. Publications in Science, Nature or PNAS. Flashy graphics.

    Maybe even some new songs. Sigh.

    Maybe people will come to understand what epicenter means.
     
    #7 tochatihu, Jul 6, 2019
  8. bisco

    bisco cookie crumbler

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    a place LA where rock bands perform;)
     
    #8 bisco, Jul 6, 2019
  9. tochatihu

    tochatihu Senior Member

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    Epic. Enter.
     
    #9 tochatihu, Jul 6, 2019
  10. bisco

    bisco cookie crumbler

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    eric cantor
     
    #10 bisco, Jul 6, 2019
  11. tochatihu

    tochatihu Senior Member

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    Science dudez with backhoes have constructed paleohistories of earthquakes around there.

    Bisco/Zevon team talk about falling into sea. It does happen locally when coastal cliffs slump. So, here's the inspiration:

    Go offshore those slumpy places. Extract sediment cores. Use isotopes (Beryllium I guess) to find out when sediment pulses arrived. Some may match paleoearthquakes. Those that don't may tell different stories (El Nino juiciness for example).

    Boom! Another big-journal publication.
     
    #11 tochatihu, Jul 6, 2019
  12. hill

    hill High Fiber Member

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    If it's any consolation, the "bigger-than-the-1st" aftershock was downgraded to a measly 6.9. Only 5X larger than the original. Tried to Google how often that happens. Not that I ever recall.
    Anyway, that's all theory, if you subscribe to the "foreshock" theme;
    https://wikipedia.org/wiki/Foreshock
    .
     
    #12 hill, Jul 6, 2019
  13. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Earthquakes are routinely post-graded now. I don't know when it started but it happens to all of them- you get a newsflash estimate, and then more refined analysis drawn from deeper data later.
     
    #13 Leadfoot J. McCoalroller, Jul 6, 2019
  14. tochatihu

    tochatihu Senior Member

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    re-upped to m 7.1 later. Not to split hairs :)
     
    #14 tochatihu, Jul 6, 2019
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  15. hill

    hill High Fiber Member

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    Or states ...
    Nor Cal has been trying to get rid of us for quite some time.

    .
     
    #15 hill, Jul 6, 2019
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  16. tochatihu

    tochatihu Senior Member

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    Speaking of which, one might attend to Federal Emergency declaration in re. My trivial opinion is that it is not (yet) one, but CA request has been made.
     
    #16 tochatihu, Jul 6, 2019
  17. tochatihu

    tochatihu Senior Member

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    post-graded@13. I'll take a shot at this, even though not a geophysicist.

    Seismometers were analog (measure height of wiggles on a chart) but now they are digital. That is first change.

    What earthquakes do is displacement, velocity and acceleration at earth surface. Best information comes from nearest sensors and I don't see those getting revised.

    What earthquakes are is total energy released, relates to magnitude, and often is revised. Why?

    Nearest sensors do not tell full story. More distant sensors get data by acoustic coupling through rocks, and this leads to a series of recursive model solutions. Only new solutions that change prior magnitude estimates get media airplay.
     
    #17 tochatihu, Jul 7, 2019
  18. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I'll have to admit I never knew why there were re-statements or the dynamics of the time gap between initial & revised.

    But I'm not a geo either; communications field. I figured we had moved past grad students driving across the state to log paper/drum recordings and now the meters were phoning home live or doing hourly dispatches. In other words they were probably always restating the results, the difference is that now the data gets to the scoring judges while the original event is still fresh in the news cycle.
     
    #18 Leadfoot J. McCoalroller, Jul 7, 2019
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  19. egg_salad

    egg_salad Active Member

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    Earthquakes are rarely felt in Las Vegas. But the two biggies of this set, Thursday morning and Friday night, sure as heck were. It's very unnerving.
     
    #19 egg_salad, Jul 7, 2019
  20. tochatihu

    tochatihu Senior Member

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    A quote from yahoo:

    Quakes push Californians to prepare for the next big jolt

    "The Democratic governor estimated the damage at more than $100 million and said President Donald Trump called him to offer federal support for rebuilding."

    I might have guessed less than $100 million but anyway the phone call is good news.

    ==
    Another interesting document about CA earthquake risks:

    Third Uniform California Earthquake Rupture Forecast (UCERF3) | Southern California Earthquake Center

    Their fact sheet (download at top of page) shows this action to have been on relatively calm faults.
     
    #20 tochatihu, Jul 7, 2019
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