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M 7.7 quake Mariana Isl .... NOW

  1. Jul 29, 2016 #1

    davenn

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  2. jcsd
  3. Jul 29, 2016 #2

    fresh_42

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    7.7 is a lot. Is there a tsunami expected? A link to a news page?
     
  4. Jul 29, 2016 #3

    davenn

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    I linked to the USGS and to my page
    news pages are unreliable and never give the correct info ..... they probably don't even know the event has happened

    there's no tsunami warning or watch in effect at this time
     
  5. Jul 29, 2016 #4

    fresh_42

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    I'm simply not bright enough to translate the figures into imagination. One map shows a settlement only a few hundred km away.
    And the amount of water above 212 km sounds dangerous. At least as long as one doesn't know the direction of movement.
     
  6. Jul 29, 2016 #5

    davenn

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    which map ? link ?

    not sure what you mean by this ?



    Dave
     
  7. Jul 29, 2016 #6

    fresh_42

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  8. Jul 29, 2016 #7

    davenn

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    the 212km is the depth below the surface that the focal point of the quake is ( doesn't include sea depth if event is at sea like this one)

    initially it was listed at 188km deep. and knowing the location, it's easy to realise that it is a subduction event.
    In that area, the Pacific Plate seafloor is diving down under the Philippine Plate

    One thing that will probably be noticed over the next 24 hours is that there is unlikely to be many aftershocks.
    This is common with deep events, even large ones. If it was a shallow (crustal event, 0 - 30km deep) then there would be 100's
    to 1000's of aftershock recorded. I will be surprised if there is anything more than a few 10's of aftershocks recorded, if that.



    Dave
     
  9. Jul 29, 2016 #8

    davenn

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    OK here's the raw seismogram

    160729   UT M7.7 nthern Marianas zhi.gif
     
  10. Jul 29, 2016 #9

    Astronuc

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    Just for background, "The Challenger Deep in the Mariana Trench is the deepest known point in Earth's oceans. In 2010 the United States Center for Coastal & Ocean Mapping measured the depth of the Challenger Deep at 10,994 meters (36,070 feet) below sea level with an estimated vertical accuracy of ± 40 meters," according to Geology.com. That's at most 11 km.
    http://geology.com/records/deepest-part-of-the-ocean.shtml
    http://www.deepseachallenge.com/the-expedition/mariana-trench/

    The deeper the earthquake, the less likely a tsunami.

    The 2011 earthquake off the Pacific coast of Tōhoku was a 9.0 magnitude (Mw) undersea megathrust earthquake occurred on 11 March 2011 at 14:46 JST (05:46 UTC) in the north-western Pacific Ocean at a relatively shallow depth of 32 km (19.9 mi), with its epicenter approximately 72 km (45 mi) east of the Oshika Peninsula of Tōhoku, Japan, lasting approximately six minutes.
    https://en.wikipedia.org/wiki/2011_Tōhoku_earthquake_and_tsunami
    http://earthquake.usgs.gov/earthquakes/eqarchives/poster/2011/20110311.php [Broken]
    http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/#details [Broken] (page may be discontinued in the future)
    https://www.ngdc.noaa.gov/hazard/11mar2011.html

    Much of the Pacific Ocean is about 5-6 km deep.
    http://oceansjsu.com/105d/exped_mapping/13a.html
     
    Last edited by a moderator: May 8, 2017
  11. Jul 30, 2016 #10

    davenn

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    and a processed seismogram with data

    160729.212010.zhi.gif.gif
     
  12. Jul 30, 2016 #11

    anorlunda

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    Thanks for sharing @davenn . Is there a layman explanation of how the data reduction from raw to processed works?
     
  13. Jul 30, 2016 #12

    davenn

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    you are welcome .... one of my loves in life :smile:

    ohhh ... where do I start ?

    firstly, I didn't write the software or design the hardware for my system. Credit for that goes to Larry Cochrane from California
    who was one of the original members of the PSN ( Public Seismic Network) in the USA.
    http://psn.quake.net/

    He designed 2 significant pieces of hardware a multi-channel preamp that goes between the sensors and the ADC data logger.
    And the datalogger with its assoc software WinSDR (Windows Seismic Data Recorder)

    preamp ..... http://psn.quake.net/serialamp.html

    ADC/Datalogger .... http://psn.quake.net/serialatod.html

    WinSDR ..... http://psn.quake.net/software.html#WinSDR

    The raw seismogram you see in post #8 is a screenshot of the display on the WinSDR datalogging PC
    currently I am using a Dell ( about 3 years old) and running Win7. This PC runs 24/7.

    The analysis software that is on my main PC, for loading in and producing the final data file as seen in post #10
    is called WinQuake ..... http://psn.quake.net/software.html#WinQuake

    WinQuake, along with the hardware and WinSDR have gone through many upgrades since its initial release in the early
    - mid 1990's ( My station went digital in 1996)

    have a read through some of the documentation in the links
    hopefully it will answer most of your questions :smile:


    Regards
    Dave
     
  14. Jul 30, 2016 #13

    1oldman2

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    Very cool links and sites, thanks for posting them. I noticed when I used the link to your homepage that it came up blank, I know your site is up and running as I was looking at it yesterday, maybe the psn.quake site has a broken link to you ?o_O
     
  15. Jul 30, 2016 #14

    davenn

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    yeah, the link on Larry's home page for my site is long out of date, he hasn't got around to updating it

    just bookmark my homepage

    http://www.sydneystormcity.com/


    cheers
    Dave
     
  16. Aug 1, 2016 #15

    1oldman2

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