Earthquakes haven’t gone away

People in North Canterbury, Marlborough and the Wellington region, and further afield,  were reminded that the earthquake onslaught isn’t over yet. The more significant quakes over the weekend:

  • 4.6 (strong) 30 km south-west of Wellington – Sat, Nov 26 2016, 3:22:03 am
  • 5.1 (severe) 35 km north of Wairoa – Sat, Nov 26 2016, 8:21:42 pm
  • 3.9 (moderate) 20 km south-east of Culverden – Sun, Nov 27 2016, 8:25:29 pm
  • 4.5 (moderate) 35 km west of Paraparaumu – Sun, Nov 27 2016, 9:31:11 pm
  • 4.1 moderate) 20 km south-east of Seddon – Sun, Nov 27 2016, 9:33:28 am
  • 3.7 (moderate) 10 km south-west of Kaikoura – Sun, Nov 27 2016, 7:46:44 pm
  • 4.8 (strong) 15 km east of Seddon – Sun, Nov 27 2016, 9:42:16 pm
  • 4.1 (moderate) 20 km south-east of Seddon – Sun, Nov 27 2016, 10:05:32 pm

The latest from 7 am update:

  • 125 earthquakes in last 12 hour
  • 220 earthquakes in last 24 hrs (4 over M4)
  • 6159 earthquakes since the M7.8 Kaikoura Earthquake.

geonet2016november28

So while in general the frequency and size of the quakes is gradually easing off it is not all over yet, and periodically some bigger quakes come back to remind those in the shaking region.

Geonet still predicts an 81% chance of an M6-6.9 shake in the next 30 days and 99% in the next year, and a 34% chance of a greater than M7 in the next year.

Geonet: Latest Updates and Scenarios and Probabilities

Earthquake problems continue

Most of New Zealand has more or less put the earthquakes behind them,  but there are significant ongoing problems.

An aftershock in North Canterbury yesterday evening seriously damaged houses and forced evacuations, and also held up access to Kaikoura via the inland route.

There is no sewerage system in Kaikoura, they are running out of water and fuel, and frustration grows for those who want to get out by road but aren’t allowed.

This afternoon Goose Bay was evacuated after a warning a slip created dam might burst.

The NIWA building in Wellington was shut today pending a proper building inspection.

And tonight another building in Wellington was evacuated due to fears that it’s stairwells were damaged.

RNZ: Wgtn’s Asteron Centre evacuated over quake risk

Wellington’s 17-storey Asteron Centre has been evacuated over possible earthquake damage to its stairwells.

The high-rise, described by its designers as the capital’s largest single office building, is located opposite the Railway Station.

Updates from Geonet continue.

This simulation shows how the seismic waves of the magnitude 7.8 earthquake were propagated across New Zealand.

This also shows how the initial quake dominoed it’s way up the South Island from Culverden to Seddon: Watching the M7.8 Kaikoura Quake Dominos Fall in Real Time

And  How is the Kaikoura aftershock sequence behaving compared to the forecast?

By noon on Wednesday 23 November we had detected 4879 aftershocks from the M7.8 Kaikoura earthquake (with the area of detection being the forecast area represented by the box). 

Most of these aftershocks have been small (4828 earthquakes <M4.9) and would have only been felt close to the epicentre.

As of Monday 21st, there were also 47 aftershocks in the M5.0-5.9 range, and 3 aftershocks in the magnitude M6.0-6.9 range.

That sounds a lot but:

At the moment, the aftershock sequence is falling within the lower end of our forecasted range.

What does this mean?

In summary, the aftershocks are at the lower end of the forecasted range. It is a bit puzzling and we are scratching our heads at this one. What we can say is that just because we are in lower end of the forecast, it doesn’t mean that this will stay that way.

Pretty much anything could happen from here, from less and less to substantially more.

All we can do is be wary and be prepared.

North Island slow-slip follows South Island quake

There has been a lot evidence of land movement during and after what is now referred to as the M7.8 Kaikoura earthquake – it was initially said to be centred close to Culverden and Geonet still shows it as ’15 km north-east of Culverden’ (Kaikoura is about four times further away).

It is thought that the initial quake caused a chain reaction along other fault lines in the South Island, and Wellington was also affected.

Geonet has now revealed that since this movement happened there has been a ‘slow slip’ occurring further north, along the Hawkes Bay and Gisborne coast. Slow slips have been detected there before but only after North Island earthquakes.

Today Geonet posted on Coastal Uplift: How has the Kaikoura Coastline Changed which shows the extent of land movement over a large area of the South island.

Much of the northeastern coast of the South Island was uplifted during the 14th of November 2016 earthquake. We know this from photos of rock platforms covered in seaweed and marine animals such as crayfish and paua stranded above tide levels.

Our records measured the tide gauge at Kaikoura was lifted up by 1 m, and continuous GPS monitoring sites at Kaikoura and Cape Campbell were also raised by 0.7-0.9 m. At this stage we can estimate that the coast was raised between 0.5 m and 2 m from about 20 km south of Kaikoura all the way north to Cape Campbell.

The startling uplift of ~5.5 m at Waipapa Bay is a localised block pushed up between two traces of the Papatea Fault and is thankfully not representative of the whole coastline.

There was greater horizontal movement, reported to up to 10 metres in places. All those ground movement happened along a long stretch of coastline up the north east of the South Island.

kaikouraearthquake_uplift_21nov2016

Uplift and horizontal movement happened on a long stretch of coastline up the north east of the South Island.

Also today Geonet posted Gisborne and Hawke’s Bay slow-slip event follows M7.8 Kaikoura Quake

GPS stations have detected a slow-slip event under the Hawke’s Bay and Gisborne regions in the days following the Kaikoura M7.8 Earthquake.

These silent earthquakes or slow-slip events are undetectable by both humans and GeoNet’s seismographs. They can move faults the equivalent of magnitude 6+ earthquakes over a period of weeks to months, without any detectable shaking.

The ongoing slow-slip event off the North Island’s east coast has moved some GPS stations up to 2-3 centimetres.

So far. It’s only a week since the M7.8

This movement is similar to what has been observed in previous East Coast slow-slip events over the last 15 years, so is not necessarily abnormal. We see events in this area usually every 1-2 years.

We have also observed other slow-slip events happening in response to large earthquakes.

The last slow-slip event offshore of Gisborne followed the Te Araroa earthquake in September 2016 (related GeoNet story http://info.geonet.org.nz/x/ZIAvAQ).

A slow-slip event also occurred following the 2007 M6.7 Gisborne earthquake.

But this time the slow-slip began after a more distant quake.

It is possible that passing seismic waves from the M7.8 earthquake caused stress changes that triggered the slow slip event. GNS Science and GeoNet and scientists are keeping a close eye on the event as it evolves.

So the Culverden quake may have triggered the Kaikoura and Seddon quakes (and three other fault line breaks), nudged across Cook Strait to Wellington and may rearranged stresses enough up the east coast of the North Island to start the slow-slip.

slowslip_hb_and_gisb

This instability covers a large area in which many of New Zealand’s significant earthquakes have occurred.

nz_faults

The initial Culverden quake was on the Hope fault line which reaches back to the top of the Alpine Fault where it breaks apart into Marlborough’s mess of mountains.

Also today Geonet updated it’s statistics based scenarios and forecasts which includes the probability of aftershocks:

  • 99% M6.0-6.9  in the next year (89% within 30 days)
  • 38% >=M7 in the next year (20% within 30 days)

There is no way of knowing, if another large quake occurs, where it would be. There is a lot of uncharted territory here.

What to do about it?

If you feel an earthquake:

Don’t run outside, many injuries are caused by things falling from buildings. Beware of breaking glass.

And if you are close to sea level near the coast don’t wait for a knock on your door or a warning siren, move inland or to higher ground.

And hope that the slow-slip eases the pressure gradually so nothing major gives suddenly.

Earthquakes continued

News coverage of the earthquakes is slowing down, as are the earthquakes, but there are still many shakes.

5.30am update: 9 earthquakes in last hour, 238 earthquakes in last 12 hrs (only 2 over M4) and 3646 earthquakes since the M7.8 Kaikoura Earthquake

The pattern is the same, scattered along the Hope fault line where the initial quake was, and clusters around Kaikoura and Seddon.

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That looks very similar in pattern and number to yesterday morning. There are still some sizeable shakes (for those close enough to feel them).

There’s a few reaching up into Wellington and also another near the Alpine faultline.

The bigger shakes over the last day and a half:

  • 3.8 (moderate) 10:11:48 pm 5 km north-west of Seddon
  • 4.6 (strong) 2:30:10 am 20 km west of Kaikoura
  • 3.8 (moderate) 3:21:22 am 5 km north-west of Culverden
  • 5.0 (strong) 3:22:58 am 20 km north-east of Cheviot
  • 4.4 (moderate) 4:17:32 am 15 km south-east of Seddon
  • 4.8 (strong) 4:55:34 am 25 km east of Hanmer Springs
  • 4.2 (strong) 4:08:10 pm 20 km north-east of Kaikoura

They mightn’t seem much but to those feeling them they are repeat reminders of what is still going on beneath them. I’m sure some aree wondering with each one if it is going to be an anticipated big aftershock.

Stuff interactive: The Mountains Moved 14.11.16

Stuff: Timeline of the 7.8 quake and response reveals plenty of room for improvement

The huge earthquake that hit New Zealand this past week, buckling roads, uplifting sections of coastline and killing two people, also exposed problems in how the country monitors its earthquake risk and prepares for tsunamis. And it raised questions about whether the city of Wellington put people at risk by reopening buildings too soon.

The nation was spared the devastation of five years ago when 185 people were killed in the Christchurch earthquake. But some consider it was more by luck this time than by good planning.

Here’s what happened, minute by minute, after the quake hit early Monday, with details on how officials intend to improve

RNZ coverage:

Aid convoy forced back

A large convoy of army trucks carrying urgent supplies used the rural road yesterday, but Civil Defence said there was still a significant threat of landslides.

Military vehicles could not longer use the inland road because of the threat of more slips.

One aid convoy arrived in Kaikoura last night, but a second had to turn back.

Acting Civil Defence Minister Gerry Brownlee said the route would like open in the middle of next week.

The earthquake aftermath in pictures

RNZ visual journalist Rebekah Parsons-King has captured the cracked roads, landslips, and damaged railway lines from the air and ground, after a 7.8 magnitude earthquake hit early on Monday morning.

Cordon in Wellington CBD to be reduced

One of the cordons in central Wellington will be reduced, as city authorities defend the handling of the risk of quake-damaged buildings in the capital.

 

 

Earthquake update – Thursday

Geonet 5 am Thursday update:

  • 19 earthquakes in last hour
  • 290 earthquakes in last 12 hrs (11 over M4)
  • 2070 earthquakes since the M7.8 (570 since 4 am Wednesday)

The rate and size of quakes is slowly reducing. The larger quakes overnight:

  • 4.3 – 7:45:51 pm 20 km south of Seddon
  • 4.3 – 7:46:33 pm 20 km north-east of Kaikoura
  • 3.8 – 9:27:10 pm 5 km north of Culverden
  • 4.8 – 10:15:14 pm 20 km east of Martinborough
  • 4.3 – 1:19:45 am 30 km north-east of Arthur’s Pass
  • 3.8 – 3:20:09 am 25 km north-east of Hanmer Springs
  • 4.0 – 3:41:33 am 30 km south of Seddon
  • 4.9 – 4:03:49 am 20 km south-west of Kaikoura
  • 4.0 – 5:02:32 am 10 km north of Culverden

Notable points: while reducing in size they are still spread over the three main areas, Culverden/Hamner, Kaikoura and Seddon, but with two other locations, east of Martinborough on the Wairarapa faultline (the one that went M8+ in 1855) and one north-east of Arthur’s Pass (Alpine Fault territory).

We can hope that these are reducing stresses rather than increasing them on other faultlines.

Yesterday Geonet upgraded the size of the initial quake (which may have been two consecutive quakes in different locations) from M7.5 to M7.8.

Kaikoura earthquake update: Magnitude revised

What has changed since our initial review

Based on our findings and in discussion with international researchers, early indications are that this is one of the most complex earthquakes ever recorded on land. This complexity means we have had to take extraordinary efforts to determine the magnitude, depth, and locations.

The very long time it took for the faults to rupture (over one minute) meant that the standard methods of calculating magnitude were insufficient to capture the full energy released.  

Due to the size of the quakes, we’ve gathered data from our entire network of seismic stations. All of these stations would not normally need to be included in magnitude estimates.

Further, our techs at GeoNet went out to several sites which we lost communication with and we have now been able to upload this information, so we have a more complete understanding of the ground deformation and strong-motion data.

Finally, our science teams have been working tirelessly, going up and down the affected areas and measuring the length of faults and how much they moved.  Their efforts have provided us with a clearer picture as to the size and length of the ruptures.

Based on all these ongoing efforts, we can say with some confidence that the earthquake was an M7.8.  This is consistent with estimates from several  other international agencies, specifically the USGS. Their early model provided us important information and we used all our additional data sets to confirm the magnitude. 

What this means

The new magnitude just tells us what we think most people who felt the earthquake already know: it was powerful, and went on for a long time over a large distance. It doesn’t change what happened but it does provide us with more knowledge about how significant the event was.

Our recent analysis confirms the complexity of this event. It does not change any of the observations of strong ground motion, fault breaks or GPS recorded movement of the earth’s surface – these are physical observations independent of the magnitude of the earthquake.

We are in the process of revising our probabilities and scenarios based on this new information and should have this released within the next 24 hours.

RNZ continues to have good coverage, including:

Rescue efforts in Kaikoura continue as helicopters and NZ and US defence force ships arrive in the quake-hit town with supplies.

Wellington is also dealing with the aftermath of Monday’s 7.8 magnitude quake, with several central city buildings deemed unsafe.

The aftermath of the 7.8 magnitude quake so far

Govt to consider funding for 24/7 quake monitoring

‘Absolutely gutted’: Tiny community of Mt Lyford devastated by quake

 

 

 

 

 

Earthquakes – Wednesday update

The earthquakes are continuing, now generally fewer and smaller, often seeming in pairs near Seddon and Kaikoura, and at times in triplets with Culverden/Cheviot/Hamner Springs in the mix.

Geonet had an update at 4 am:

  • 23 earthquakes located in the last hour (Wednesday morning)
  • 278 earthquakes since 6 pm (Tuesday)
  • 1,492 earthquakes  since the M7.5 Kaikoura Earthquake (just after midnight on Monday).

Alan was in Hamner Springs when the M7.5 struck:

I was in Hanmer in a wooden Fraemohs chalet trying to fix my phone while my wife watched a TV movie when the first big 7.5 hit. I have to say the chalet was great – strong as a boat in a storm as we rocked and rolled. It was built on a good thick concrete pad and the interlocking beam walls performed perfectly.

We had driven through the epicentre at Waiau that afternoon and stopped for a few minutes of course never guessing anything so drastic was about to happen there.

While it was happening I was standing back to a window which in retrospect although it had a heavy curtain was probably not a great idea but it was too far to get around the bed to the passageway while keeping my balance while it was like being on a yacht in a choppy sea with a howling wind.

The noise was like a train or a plane roaring past right outside.

I have heard people from Christchurch describe the bigger earthquakes as like a train roaring past right outside their house. I’ve never been close enough to a big one to hear one (I’m not complaining).

After that I could hear the aftershocks coming as a low frequency sound just before they started but my wife couldn’t. She hears higher frequencies better than me though.

Power went out in the middle of the quake and didn’t come back till midday the next day but the road out didn’t open till 4pm the next day.

Alan was lucky the road was openable. One of the remarkable things about these earthquakes, presumably mainly as a result of the huge M7.5, is the widespread destruction of roads – not just the huge slips on the Kaikoura coast but so many roads have been ripped apart, like this one in Waiau.

state-of-road-in-waiau-after-earthquake-supplied

There have been many movements of land, ripped apart, buckled and raised and lowered.

kaikouraseabedraised2

Aerial photographs show the seabed uplift north of Kaikoura – estimated to be between 2 – 2.5 metres – more at @TonkinTaylor – which also shows minor road slips.

Media seemed to obsess over the trapped cows yesterday morning – they were rescued – but now the poor paua are being pitied, raised out of the water and dying.

Newshub: Baby paua suffering terrible deaths in sun

It’s not just the thousands of exposed paua that are a high concern in Kaikoura – exposed baby paua are also dying by the hour.

The paua have now been exposed out of water for more than two days after the seabed was lifted nearly two metres out of the water by Monday’s 7.5 earthquake.

Paua Industry Council’s Storm Stanley says there’s a lot of worry for the tens of thousands of adult paua but people forget about the babies.

“What you won’t see are the smaller paua that live under rocks. They live under rocks until they’re about 16, 17 millimetres long before they come out again,” he says.

pauaraised

Nature can be brutal.  It’s tough on the paua and other exposed sea life on the fishing industry, but I suspect there are more pressing problems for most people to attend to.

RNZ have today’s key facts:

Rescue efforts in Kaikoura continue as helicopters and NZ and US defence force ships head to the quake-hit town with supplies.

Wellington is also dealing with the aftermath of Monday’s 7.5 magnitude quake, with a city centre building at risk of collapse.

As usual they are covering things extensively – see RNZ continues live online coverage here.

Geonet: M7.5 Kaikoura Earthquake: for more information read Latest Updates and Scenarios and Probabilities.

Damaged buildings in Wellington is becoming a big story of it’s own – that’s for another post.

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.