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Mw 7.4 Quake S of Tonga and Mw 8.3 Kamchatka Reg.

  1. May 23, 2013 #1

    davenn

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    A Mw 7.4 Quake S of Tonga occurred at 17:19 UT, 23-5-2013

    still visible on my seismo for ~ another 24 Hrs till it scrolls off
    http://www.sydneystormcity.com/sydln.gif

    it was quite a deep event at 171km and within the boundary area of the down going Pacific seafloor slab along the Tonga - Kermadec Trench

    Its depth meant that it didnt have high amplitude surface waves
    P arrival at my station ( Sydney) @ ~ 17:25 UT and the S wave arrival just before 17:30

    This trench is well known for very deep events that occur from under the North Island of New Zealand and right up via Tonga to Fiji. Events up 600+ km are not uncommon.
    One of the main reasons for the quakes at great depth in this region is because of the high subduction rate along this plate boundary of up to 8cm / year. This allows the Pacific Plate to subduct to great depth before it heats and softens too much to allow fracturing to occur.

    Its quite a complex process where the outer edges of the subducting slab are warming faster than its core and allowing the core to continue to fracture causing quakes long after the outer edges are softly deforming.

    Dave
     
  2. jcsd
  3. May 24, 2013 #2

    davenn

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    I get home from work just a short time ago and another big quake is just tailing off.

    2013/05/24 0544UT - Mw 8.3 offshore SW coast of Kamchatka Peninsula ( eastern Russia), NW Pacific.
    This was one of those VERY DEEP events I spoke about in my last post. It listed at 608 km.
    Again because of the depth surface waves are non existant and its primarily all the body waves that can be seen. If this had been a shallow event, less than 50km, the trace on the screen would have been covering almost top to bottom.

    both events can been seen on my seismo -- http://www.sydneystormcity.com/sydln.gif

    Dave
     
  4. May 24, 2013 #3

    Borek

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    I have attached the image here, for the latecomers.

    [​IMG]

    A little bit too wide for PF layout, but interesting enough so that I don't care.

    Keep these reports coming!
     

    Attached Files:

  5. May 24, 2013 #4

    davenn

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    Hi Borek
    cheers

    are you able to edit the thread subject line to have it read ....

    Mw 7.4 Quake S of Tonga and Mw 8.3 Kamchatka Reg.

    thanks lots :)

    Dave
     
  6. May 24, 2013 #5

    Borek

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    No problem, just tell me what "Reg." means? Registered?
     
  7. May 24, 2013 #6

    davenn

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    Reg = region :)
     
  8. May 24, 2013 #7

    Borek

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    Oops, OK.
     
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