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.

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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.

Mass of quakes continue

When I headlined Earthquake onslaught  that was based on what had happened in the few hours since the 7.5 quake just after midnight, but things haven’t let up all day with hundreds of quakes around the top half of the South Island.

The quakes have often been in clusters alternating between Kaikoura, Seddon and North Canterbury, with a few outliers.

There have just been two more ‘severe’ shakes amongst a cluster:

  • 3.6 (light) 7:37:16 pm 25 km north-west of Cheviot
  • 3.6 (light) 7:38:13 pm 10 km east of Kaikoura
  • 3.4 (light) 7:40:54 pm 35 km south of Seddon
  • 5.6 (severe) 7:43:01 pm 25 km east of Seddon
  • 4.4 (moderate) 7:43:34 pm 15 km north-east of Methven
  • 5.7 (strong) 7:47:51 pm 25 km east of Kaikoura
  • 4.3 (strong) 7:51:58 pm 15 km east of Seddon
  • 4.5 (strong) 7:52:53 pm 20 km east of Seddon
  • 4.4 (light) 7:55:44 pm 35 km east of Kaikoura
  • 3.6 (light) 7:56:19 pm 15 km east of Levin

That’s 10 in 20 minutes. The whole area seems to have become unstable.

And the pictures being published of the roads, railway line and hills shows how unstable the area is on the surface. Huge and smaller slips have blocked roads and lines in many places. It could take weeks if not months to open state highway 1 between Picton and Christchurch reopened.

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Kaikoura is cut off due to major slips both to the north and to the south.

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There was a road and a railway line round here yesterday. And paddocks and stock have also been affected.

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There have been two deaths reported. Given the size of the quakes this is relatively low, fortunately being in the middle of the night in mostly sparsely populated areas helped minimise casualty rates.

But there are many ongoing aftershocks, quite a few fairly strong, and Geonet says there’s a 32% chance of another 7+ in the next month or two.

There have already been six quakes rated as ‘severe’ today, near Culverden, Kaikoura (3), Seddon and Cheviot. There was widespread minor-ish damage in Wellington and they ‘only’ had a 5.3.

What has happened already will have a major impact on Marlborough and North Canterbury and also further down the highway. The alternative routes by land are lengthy, via the West Coast.

And there will understandably be many worried people.

There’s enough cause for concern down here in Dunedin (where some people were woken by the big midnight shake but I haven’t felt a thing) having seem the enormous effects on Christchurch.

There will be many frazzled nerves after a day of sustained shaking in the top half of the South island and the lower North island.

UPDATE: since typing the above list and the rest of the post there has been another  ‘severe’ (5.9) and another ‘strong (5.8) quake near Seddon – they are 30 seconds apart so must just about be the same quake.

Earthquake onslaught

There has been a mass of earthquakes ranging from North Canterbury to the Wellington region, with the biggest ones near Culverden (7.5), Kaikoura (two at 6.2), Seddon (5.3), Wellington (5.3)  and Paraparaumu (4.9).

So far there have been 27 quakes rated severe or strong since midnight.

earthquakes2016-11-14

‘Casualties’ have started to be reported:

Police say one casualty has been reported at a collapsed property in Kaikoura.

Updated – two confirmed fatalities so far.

There was a tsunami warning and 2.5 metre waves were recorded at Kaikoura but that has now been downgraded.

Aftershocks are continuing, and damage is just being assessed in many areas as daylight breaks.

Many roads are closed. Photos are emerging of widespread road damage. A slip has blocked a rail tunnel and the twin road tunnels on the Kaikoura coast road. And the Waiau River bridge may be damaged – this is the main access to Hamner Springs.

The Cook Strait ferries have been stopped and crossings have been cancelled. The passenger bridge in Wellington has been damaged.

Wellingtonians have been advised not to come to work today. Damage in city extensive

People are being advise to stay out of the Wellington CBD until damage has been assessed.

And gale force winds are forecast for central New Zealand today.

Leader rd Kaikoura

earthquakekaikoura

 

So far 30+ (updated) earthquakes rated ‘strong’ and ‘severe’ (there have been many smaller ones), all quite shallow:

  • 7.5 – 12:02:56 am 15 km north-east of Culverden
  • 5.6 – 12:16:10 am 5 km west of Culverden
  • 5.9 – 12:19:32 am 45 km north of Kaikoura
  • 5.6 – 12:24:17 am 40 km north of Kaikoura
  • 6.2 – 12:32:06 am 15 km north of Kaikoura
  • 5.6 – 12:41:48 am 20 km south-east of Seddon
  • 6.2 – 12:52:44 am 25 km north of Kaikoura
  • 5.2 – 1:03:53 am 15 km south-east of Seddon
  • 5.3 – 1:04:21 am 15 km south-east of Wellington
  • 4.9 – 1:11:59 am 15 km south-east of Seddon
  • 4.9 – 1:21:10 am 5 km east of Paraparaumu
  • 5.2 – 1:25:55 am 10 km north of Culverden
  • 5.2 – 1:27:59 am 10 km north-east of Kaikoura
  • 4.7 – 1:31:25 am 15 km east of Seddon
  • 5.2 – 1:37:43 am 25 km west of Kaikoura
  • 5.3 – 1:38:38 am 15 km east of Seddon
  • 5.1 – 1:52:18 am 15 km north-east of Kaikoura
  • 4.6 – 2:12:31 am 10 km south of Seddon
  • 6.0 – 2:31:26 am 15 km north of Kaikoura
  • 5.1 – 2:50:01 am 20 km south-east of Seddon
  • 4.8 – 3:07:22 am 10 km north-west of Culverden
  • 4.9 – 3:08:42 am 20 km west of Culverden
  • 5.3 – 4:33:03 am south-east of Seddon
  • 4.9 – 4:58:01 am 15 km south-east of Seddon
  • 5.1 – 6:17:41 am 10 km south-east of Kaikoura
  • 4.9 – 7:21:41 am 10 km west of Seddon
  • 5.2 – 7:34:26 am 20 km south-east of Seddon
  • 4.8 – 7:58:08 am 10 km north of Wellington
  • 5.4 – 7:58:46 am 10 km south-east of Seddon
  • 5.3 – 7:59:08 am 15 km east of Kaikoura

Remember that these are just earthquakes rated strong or severe and excludes ‘moderate’ and less.

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The per-year movements are averages, the actual movements tend to be far less frequent and larger.