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A busy 3 days for quakes in the SW Pacific

  1. Sep 25, 2016 #1

    davenn

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    hi all

    the last 3 days have been the busiest for quite some time for recording quakes that have occurred in the
    western and south-western Pacific rim regions.

    The events have stretched from the Kermadec Island to the north of New Zealand, up to Tonga, across to the northern coast of Papua, Indonesia, up to the Philippines and then much further up to the Japanese Izu Islands region.

    The first gram shows 2 M6+ events the M 6.3, Izu Isl., far offshore, SE of Tokyo followed by a M 6.3 offshore SE Mindanao, Philippines ( it can be easily seen that the magnitude of the Izu Isl. event was seriously under-estimated)

    160923  UT M6.3 offshr Tokyo, M6.3 offshr SE Mindanao zhi1.gif

    2016-09-23 00:14:34 (UTC), M 6.3, 143km ESE of Katsuura, (Izu Isl) Japan, 10 km deep
    2016-09-23 22:53:10 (UTC), M 6.3, offshore SE Mindanao, Philippines, 65.0 km deep

    ------------------
    This next gram starts with an overlap of the M 6.3 Philippines event from above and is followed by another 6 significant events ....

    160923-25  UT many events zhi.gif

    2016-09-23 22:53:10 (UTC), M 6.3, offshore SE Mindanao, Philippines, 65.0 km deep
    2016-09-24 04:02:13 (UTC), M 5.8, 177km SE of L'Esperance Rock, sthrn Kermadec Isl, New Zealand 10.0 km deep

    2016-09-24 11:04:29 (UTC), M 5.6, offshore Jayapura, nthrn Papua, Indonesia 10 km deep
    2016-09-24 11:09:43 (UTC), M 5.6, offshore Jayapura, nthrn Papua, Indonesia 14 km deep

    Note: the twin M 5.6 events are not really separable on the seismogram


    2016-09-24 21:07:13 (UTC), M 6.4, 125km WNW of Neiafu, Tonga, 183.4 km deep
    a reasonably deep event, but better to come .....
    2016-09-24 21:28:41 (UTC), M 6.9, 99km NNE of Ndoi Island, Fiji, 596.3 km deep.
    A bit west of the M 6.4 and
    a VERY deep event
    2016-09-24 23:27:19 (UTC), M 5.2, sthrn Kermadec Isl, New Zealand, 10.0 km deep
    2016-09-25 04:28:37 (UTC), M 5.9, sthrn Kermadec Isl, New Zealand, 10.0 km deep

    Also to note, the Kermadecs and Papua regions also had a number of other events associated with the ones listed

    The only other notable quake around the globe over the last couple of days was a M 5.6 in Romania
    Too small and distant to be recorded on my system

    2016-09-23 23:11:20 (UTC) M 5.6, 7km W of Nereju, Romania, 88.3 km deep


    Cheers
    Dave
     
  2. jcsd
  3. Sep 28, 2016 #2

    jedishrfu

    Staff: Mentor

    Is there any relationship between quake occurence and position of the Earth and Moon about the Sun?
     
  4. Oct 1, 2016 #3

    davenn

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    There's those that put a lot of credence into that idea. Most of them on the crackpot fringe eg Jim Berkland, ex USGS geologist
    He has great belief in major events occurring around either full or new Moon. some do, most don't, denoting nothing much more than coincidence.

    Deep down, I'm sure there is some relationship being caused by the combined gravitational effects of the Sun, Moon and the earth ... Earth Tides, after all if huge bulges of ocean can be dragged around the Earth, what less subtle effects may be happening in the rocks ?.

    What I feel really confident in suggesting is that, I strongly doubt that gravitational tides directly cause quakes, rather that they may be the "last straw that broke the camels back" .... that is, the stresses on a given fault had been building up for many years and had finally got to the point where it was about to rupture anyway. The small changes in the stress fields in the rocks along the fault caused by the gravitational effects just finally pushed it "over the edge", allowing the rupture to happen



    Dave
     
    Last edited: Oct 1, 2016
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