Earthquakes continued…

Quakes have continued to rumble through the night in the north east of the South Island, with 28 recorded at Geonet in the last hour (4:20 to 5:20 am). There have been about 800 aftershocks altogether.

There are reports that there could be up to 100,000 landslides/slips.

Geonet says that multiple faults have ruptured:

Rapid field reconnaissance indicates that multiple faults have ruptured:

  • Kekerengu Fault at the coast – appears to have had up to 10m of slip
  • Newly identified fault at Waipapa Bay
  • Hope Fault – seaward segment – minor movement
  • Hundalee Fault 

What we are finding in New Zealand is that quite a few of our larger earthquakes involve jumping from rupture on one plane to another in a complex sequence.

‘Strong’ or ‘severe’ quakes overnight (these seem to have slowed down):

  • 5.0 (severe) 10:49:56 pm 10 km east of Kaikoura
  • 5.1 (strong) 12:16:42 am 15 km east of Seddon
  • 4.8 (strong) 1:03:00 am 5 km west of Kaikoura
  • 4.6 (strong) 4:22:19 am 10 km east of Seddon

So both Kaikoura and Seddon continuing to bear the brunt of this. Those are moderate sized quakes on the scale but they are shallow (8-25 km) so more energy gets to the surface than deeper quakes.

This map shows the pattern of quakes since midnight yesterday. Most of them are shallow.

earthquakes2016novdepthmap

Earthquakes midnight 14 Nov – 5:30 am 15 Nov (Geonet)

And this shows their strengths better:

earthquakes2016novstrength

Last 500 earthquakes light to severe as at 6:oo am 15 November 2016 (Geonet)

That shows the clustering in North Canterbury-Marlborough with a couple in Wellington but they feel the bigger Seddon quakes in Wellington too.

Updates from Geonet:

M7.5 Kaikoura Quake: What we know so far

Updated at 23.52, 14/11/2016 This earthquake was the largest recorded in New Zealand since the M7.8 Dusky Sound earthquake in 2009. But, given its location, it was more widely felt and more damaging. This earthquake unsettled many people and that is perfectly normal; earthquakes can be upsetting events. The best advice we have is to be prepared for earthquakes.  We can say one thing with certainty: there will be more earthquakes to come in this area.…

M7.5 Kaikoura Earthquake: Latest updates

Multiple ruptures

Rapid field reconnaissance indicates that multiple faults have ruptured:

  • Kekerengu Fault at the coast – appears to have had up to 10m of slip
  • Newly identified fault at Waipapa Bay
  • Hope Fault – seaward segment – minor movement
  • Hundalee Fault 

In the simplest case an earthquake is a rupture on a single fault plane.

What we are finding in New Zealand is that quite a few of our larger earthquakes involve jumping from rupture on one plane to another in a complex sequence. We first saw that with the Darfield Sept 2010 EQ where multiple segments ruptured together as a single earthquake. We appear to have seen this again overnight.

In terms of what might happen next: The scenarios provide an overview of how we see this earthquake sequence evolving over the next few days to one month. What is on the web page is our best information that we have to hand at the moment.

We’ve developed three scenarios based on what we know so far but be aware that our understanding is evolving as we do more analysis and receive more data. 

Scenario One: Very likely (80% and greater)
A normal aftershock sequence that is spread over the next few months to years. Felt aftershocks (e.g. M>5) would occur from the M7.5 epicentre near Culverden, right up along the Kaikoura coastline to Cape Campbell over the next few months to years. This is the most likely scenario.

Scenario Two: Likely (60% and greater)
In the next month, it would be likely that rupture of earthquakes of about an M6 in the North Canterbury and Marlborough regions will occur, as well as potentially offshore in Southern Cook Strait and offshore Kaikoura.

Scenario Three: Unlikely (less than 40%)
The least likely scenario is that in the next month, (it is unlikely but still possible) there would be rupture of longer known faults (with earthquakes of about M7), in the Marlborough and Cook Strait regions.

So there is at least likely to be a continuation of the many aftershocks, with the lower possibility of some quite large ones still to come.

Leave a comment

4 Comments

  1. lurcher1948

     /  15th November 2016

    Very informative PG… thanks

    Reply
  2. Kitty Catkin

     /  15th November 2016

    I once read a 1-10 earthquake scale that was easy to follow for us non-geologists-I forget how it went, but it was along the lines of beginning with a gentle tremor, went through things like items falling off shelves and so on up to buildings collapsing. But I can’t find it again.

    To the downtickers-go and find something else to do. You are looking not only spiteful but stupid and very boring.

    Reply
  3. We also need to be aware of the very real and continuing threat of tsunami induced by underwater slips on the sides of the huge canyon running roughly parallel to the East Coast and also covering Cook Strait on the Eastern side. We still don’t know what effect the current earthquakes have had on the structure of the rocks at the sides of the underwater canyon.

    Reply

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