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M 7.1 just offshore NE Nth Isl, New Zealand

  1. Sep 1, 2016 #1


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    People across the North Island of NZ and areas across the nthrn half of the South Island had a shaky awakening this morning at 04:37 NZST, Fri 02 Sept 2016, 16:37 UT, 01 Sept 2016.

    The M7.1 struck just off shore of the East Cape of NZ . A tsunami warning was issued but was soon cancelled. This event was preceeded by a M 5.8 on Thursday morning



    This event is likely the result of the subduction of the Pacific Plate seafloor under the Australian plate.
    The plate boundary is roughly defined by the red line on the above map

    Last edited: Sep 1, 2016
  2. jcsd
  3. Sep 1, 2016 #2
    Was woken up by this earthquake, living at the bottom of the North Island.

    Concerning, though:

  4. Sep 1, 2016 #3


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    That's pretty shocking huh !!

    At your distance, I would have expected a real good rolling motion
  5. Sep 1, 2016 #4


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    I noticed the 5.8 Mag yesterday, and I was wondering if something might follow it.

    M5.8 - 188km NNE of Gisborne, New Zealand
    2016-08-31 22:04:35 UTC
    37.208°S, 179.125°E
    22.4 km depth

    USGS puts the 7.1 Mag at a depth of 19 km.

    Tonga, Vanuatu and New Guinea have some 5+ mag earthquakes, and there was a 6.7 mag off New Guinea coast
    M6.7 - 39km E of Namatanai, Papua New Guinea
    2016-08-31 03:11:36 UTC
    3.691°S, 152.788°E
    499.1 km depth
  6. Sep 1, 2016 #5


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    I see they have changed it ... they did have it a bit deeper initially

    recorded that one quite well between a couple of failures of my recording system. The data logger fed into the PC via the RS232 port which failed a couple of days ago. Really weird symptoms ( mouse just moving randomly over the screen opening various windows etc) causing me to initially not suspect the com port.
    Unplugging the datalogger stopped the problem. Installed a USB to RS232 adaptor and relabelled RS232 to COM10 and the adaptor to COM 1 and all go again.

    The 6.7 showed an almost perfect thrust focal mechanism, with just a hint of oblique slip.


    Today's 7.1 NZ event, I initially thought may have been the same style ( as I commented in my first post).
    The USGS are saying it's more likely an event within the subducting slab, rather than on the interplate boundary zone


    Last edited: Sep 1, 2016
  7. Sep 5, 2016 #6
  8. Sep 5, 2016 #7


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    Yeah, a M 5.7 GNS ( 5.8 USGS) is a respectable quake in its own right
    Yup, aftershocks will continue for quite some time, dropping off in both magnitude and numbers.
    Pretty common with large and shallow events ... aka the 7.1 west of Christchurch and the closer to the city ones.
    5 - 6 years later the event number is still well above background seismicity levels

  9. Sep 6, 2016 #8
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