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Preliminary magnitude of 7.2 - Vanuatu

  1. Apr 3, 2016 #1
    Limited information at this time:

    http://www.9news.com.au/world/2016/...strikes-off-vanuatu#RLUVoLYwGDV21je9.99#9News

    http://www.stuff.co.nz/world/78508265/72-quake-has-struck-off-vanuatu
     
  2. jcsd
  3. Apr 3, 2016 #2

    Astronuc

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  4. Apr 3, 2016 #3

    davenn

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    respectable event
    Largest amplitude I have recorded in the last month

    zhi.gif

    several of the aftershocks can also be seen


    Dave
     
  5. Apr 4, 2016 #4

    Astronuc

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  6. Apr 5, 2016 #5

    Astronuc

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    And two more

    M4.9 - 79km NNW of Port-Olry, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005eff#general_region
    2016-04-04 08:22:03 (UTC)
    Location: Lat 14.351 °S, Long 166.878 °E
    Depth: 10.0 km (6.2 mi) = shallow

    M5.3 - 103km NNW of Port-Olry, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005egl#general_region
    2016-04-04 13:23:12 (UTC)
    Location: Lat 14.201 °S, Long 166.651 °E
    Depth: 35.0 km (21.7 mi)


    And there is an earthquake in the Solomons
    M5.0 - 101km ENE of Kirakira, Solomon Islands
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005egv#general_region
    2016-04-04 13:35:27 (UTC)
    Location: Lat 10.249 °S, Long 162.821 °E
    Depth: 47.4 km (29.4 mi)
     
  7. Apr 6, 2016 #6

    davenn

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    A M6.7 aftershock last nite just a little north of the M 6.9
    2016-04-06 06:58:48 (UTC)
    1. 2016-04-06 16:58:48
    Nearby Places
    • 105.0 km (65.2 mi) WSW of Sola, Vanuatu
    • 171.0 km (106.3 mi) NNW of Luganville, Vanuatu
    This was followed by a M 5.9

    2016-04 Vanuatu events.JPG


    cheers
    Dave
     
  8. Apr 6, 2016 #7

    Astronuc

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    Nice swarm. I was wondering if we'd see another event of similar magnitude to the Mag 6.9.

    Was your seismograph as active as when the Mag 6.9 hit?

    Now, interestingly, they put the depth of the today's Mag 6.7 at 24 km, and the aftershocks at 35 km, which is the depth of the Mag 6.9.
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005fsi#general

    That should be felt more strongly near the surface than the deeper ones.
     
  9. Apr 6, 2016 #8

    davenn

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    no, it was substantially less amplitude
    Initially it was reported as a M 6.9 and I was sitting there looking at it and thinking, yeah right !! haha
    if that is correct, then the previous event was really the M7.2 it was initially reported as or if it was 6.9
    then this latest event was smaller. It took quite some time for it to be revised down to 6.7

    not too much difference considering the physical area of the subducting slab affected, that would have been expected by events of that magnitude and also the accuracy error in calculating the depth

    from a USGS page.....
    I cannot find anything specific for data accuracy eg +- 2%, 5% etc
    The accuracy is really constrained by how many stations they can get good Pp-P arrival time data from

    some papers here about depth calcs that readers may be interested in reading
    http://search.usa.gov/search?utf8=✓&affiliate=usgs&sitelimit=http://earthquake.usgs.gov&query=depth+calculations
    including this one ...
    http://earthquake.usgs.gov/research/external/reports/G11AP20195.pdf [Broken]

    yup :smile:
    shallow = stronger and felt over smaller area
    deep = weaker but felt over a wider area


    Dave
     
    Last edited by a moderator: May 7, 2017
  10. Apr 6, 2016 #9

    davenn

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  11. Apr 7, 2016 #10

    davenn

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    updated map

    20160403-0407  UT M events nthrn Vanuatu.JPG
     
  12. Apr 7, 2016 #11

    Astronuc

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    I just saw that - a second Mag 6.7 - 106km W of Sola, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005fzn#general
    Location: Lat 13.994°S, Long 166.571°E
    Depth: 26.8 km (16.6 mi)

    Rather than quieting down, it's picking up.
    Busy day!

    Does it look like the activity is drifting northward along the plate boundary?
     
  13. Apr 7, 2016 #12

    davenn

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    seems to be the general trend at the moment. It will be interesting to see for how far it continues
     
  14. Apr 9, 2016 #13

    Astronuc

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    A couple more today

    M 4.8 - 110km WSW of Sola, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005g6k#general
    2016-04-07 17:52:32 UTC
    Location: 14.109°S, 166.556°E
    Depth: 33.8 km

    M 4.9 - 114km W of Sola, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005gav#general
    2016-04-08 07:03:46 UTC
    Location: 13.916°S, 166.494°E
    Depth: 8.9 km

    and one further south

    M 4.9 - 101km SW of Port-Vila, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005ggr#general
    2016-04-08 19:05:20 UTC
    Location: 18.269°S, 167.540°E
    Depth: 26.5 km
     
  15. Apr 14, 2016 #14

    davenn

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    Another 2 aftershock events from the north end of the Vanuatu Islands

    A M 6.0
    86km NW of Port-Olry, Vanuatu 2016-04-14, 12:17:05 UTC, 10.0 km deep

    And a M 6.4
    88km NW of Port-Olry, Vanuatu, 2016-04-14, 21:50:26 UTC, 10.0 km deep


    Well, that was interesting, these 2 latest events bucked the observed northwards trending pattern
    and occurred to the south side of the activity zone, much closer to the coast on northern Santo (Island)

    The seismogram of the second event, the M6.4, also was quite different to what is normally seen from the Vanuatu region ... as in the upper of the 2 events in the seismogram below
    Vanuatu events typically have very "clean" seismograms, that is, clear P, S and Surface Wave arrivals
    The M 6.4, the lower of the 2 recordings can be seen to be quite different and also has a significantly
    longer coda to the trailing signal

    160414  UT M 6.0 and M 6.4 nthrn Vanuatu zhi.GIF

    Dave
     
    Last edited: Apr 14, 2016
  16. Apr 14, 2016 #15

    Astronuc

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    Both pretty shallow

    M6.0 - 86km NW of Port-Olry, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005hzl#general

    M6.4 - 88km NW of Port-Olry, Vanuatu
    http://earthquake.usgs.gov/earthquakes/eventpage/us20005i6p#general
    That's interesting. Could the Mag 6.4 have triggered a smaller event in the Mag 5 range during the subsequent 10-20 minutes, such that it was not separately detectable?
     
  17. Apr 14, 2016 #16

    davenn

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    well DOH, I didn't notice that M 5.2 ... 111km NNW of Port-Olry, Vanuatu, 2016-04-14, 22:23:28, UTC10.0 km deep

    that is going to add a bit more signal to the tail of the M 6.4


    D
     
  18. Apr 15, 2016 #17

    Astronuc

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  19. Apr 16, 2016 #18

    davenn

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    I thought I posted a comment on this event, noting it closer to the coast
    I remember writing it

    dunno what happened to it ????


    Dave
     
  20. Apr 16, 2016 #19

    davenn

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    my missing response was to this comment of yours several days ago before that M5.7

    it was along the lines of .....
    Well this event to the south seems to be bucking the trend


    Dave
     
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