Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Earthquake in South Pacific, NE of Australia

  1. Dec 8, 2016 #1

    fresh_42

    Staff: Mentor

  2. jcsd
  3. Dec 8, 2016 #2
  4. Dec 8, 2016 #3

    davenn

    User Avatar
    Science Advisor
    Gold Member

    yeah a massive 7.8
    68km WSW of Kirakira, Solomon Islands
    2016-12-08 17:38:46 (UTC)
    41.0 km

    my seismo has only a short time ago stopped hitting the stops .... I was still sleeping when the event occurred and the seismic waves arrived at my location
    so I couldn't do a screen save before it started overwriting itself

    long period hi gain channel

    zhi.gif

    medium period low gain channel

    zlo1.gif



    http://www.sydneystormcity.com/seismograms.htm



    Dave
     
  5. Dec 8, 2016 #4

    davenn

    User Avatar
    Science Advisor
    Gold Member

    Ohhh I discovered that buried in the huge signal of the 7.8, there is a M 6.5 off the coast of northern California
    Its P wave arrival is at 15:20 UT. where as the P arrival of the 7.8 is at 17:44 UT

    so some calc's ... Calif quake origin time 14:50UT ( to nearest minute) and arrival in Sydney Australia at 15:20 (to nearest minute)

    P travel time = 30 minutes x 60 = 1800 sec
    across Earth's surface distance (from google Earth) 11,834 km

    11834 / 1800 = 6.57 km / sec which fits pretty well with the standard models


    Dave
     
  6. Dec 8, 2016 #5

    fresh_42

    Staff: Mentor

    And a 6 in China. The total list is pretty long, even within the last 24h. Is it true, that media nowadays only report those > 6.8? Did this change in comparison to say, the 80's?
     
  7. Dec 8, 2016 #6

    davenn

    User Avatar
    Science Advisor
    Gold Member

    I did record that M5.9 (6.0) in China yesterday, it was a pretty small signal

    The media usually only cover those that were felt / caused damage. There's many significant events that go unreported ( in media) because of their remote location. The media do report a lot more than in days gone by, mainly because global media coverage has improved so much over the last 30 years.
    It has the effect of making people think that there are more big quakes than there used to be. But that isn't the case.
    On avg ( world wide) per year ....

    1 x M8.0 +
    18 x M 7.0 - 7.9
    ~120 odd x M 6.0 - 6.9
    ~ 800 x 5.0 - 5.9

    and these figures haven't changed in the last ~ 150 years of systematic written records. ~ 100 years of instrument records


    Dave
     
  8. Dec 9, 2016 #7
    Last edited: Dec 9, 2016
  9. Dec 9, 2016 #8

    davenn

    User Avatar
    Science Advisor
    Gold Member

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Earthquake in South Pacific, NE of Australia
  1. An earthquake (Replies: 4)

  2. Major quake SW Pacific (Replies: 7)

Loading...