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Update: Swarm to west of Tokaanu (Turangi) continues

Wed, 22/02/2017 - 09:53

Blog post edited by Helen Jack

A very common characteristic of the greater Rotorua-Taupo area, known as the Taupo Volcanic Zone is earthquake swarms. Several minor ones occur every year. Since around 6 pm (Monday 13 February) the GeoNet seismometer network between Taupo and the Tongariro National Park has been recording a swarm of small earthquakes. They locate about 10 kilometres north west of Tokaanu. Since the swarm started we have located over 290 events. The largest been a M3.8 at 9.35 pm Tuesday Feb 21.

Earthquake swarms are defined as a sequence of many earthquakes striking in a relatively short period of time in a localised area. They are differentiated from ‘normal’ earthquakes followed by aftershocks by the fact that no single earthquake in the sequence is obviously the main shock. The larger or largest event can come early in the sequence towards the middle or at the end. The rate that earthquakes occur can also vary through the sequence. 

The current swarm west of Tokaanu (Turangi) has comprised three phases. The third phase has included the four largest events (M3.0, 3.4, 3.6 and 3.8) and started Tuesday evening around 5 pm, continuing overnight. We have located about 200 events so far in this phase of the swarm. In total we have located 291 events so far (22 Feb 9.30 am). Their magnitudes have ranged from about M 0.6 to M 3.8, while the depths ranged between 1 and 11 kilometres, with most being 5-7 kilometres deep. As the earthquakes are quite shallow they will feel stronger than the magnitudes indicate.

The Taupo Volcanic Zone is a rifting area, growing wider each year by 6-9 mm. These earthquakes are likely to be related to the long-term ‘tectonic’ stretching of the Zone. Currently, there are no indications that the earthquakes are related to volcanic activity, being located well away from the active volcanoes. As usual, we continue to closely monitor the activity.

Location of the earthquakes todate Seismogram showing the earthquakes recorded in last 24 hrs


View Online Helen Jack 2017-02-21T20:53:40Z

Earthquake forecasts – So why do we do earthquake forecasting?

Tue, 21/02/2017 - 16:09

Blog post edited by Helen Jack

We get asked two questions a lot: what is an earthquake forecast and why do I need to know about it? Answering that second part quickly: some people need to know this for their work, some people are interested as to what we think could happen next, while others just want to move on and not hear about earthquakes anymore. But, for those of you who want more detail, we thought we’d take a moment and answer some questions about the forecasts. 

What’s the difference between a forecast and prediction? 

GNS Science has been producing earthquake forecasts since the late 1990s, but it wasn’t until the 2010/11 Canterbury earthquakes that people got really interested in them.

The earthquake forecasts we produce are not earthquake predictions. A forecast is a probability of something happening over a certain period of time.  A prediction gives a specific timing and location for something to happen.

Some people say they can predict earthquakes. However, at GeoNet we stick to our knitting: we are a science organisation and base our work on things we can observe and measure.  At present there is no scientific way to accurately and reliably predict when and where a big earthquake is going to happen next.

Another way to think about the forecasts: Introducing our Grandma’s China-ometer!

"Grandma China-ometer" (patent pending) Levels

LevelAction4

The china's probably best securely packed away in a box somewhere safe just at the moment

3Keep the china in the china cupboard2The china is ok to put out again, but we'd suggest using Blu Tack1The china's probably fine to put out without Blu Tack (but nowhere in NZ is 100% safe from earthquakes, so for peace of mind perhaps use a non-slip mat!)

What many people want to know is “what should I do with this forecast”?  Perhaps you could think of the forecasts as a sort of Grandma’s China-ometer – should I put Grandma’s heirloom tea set back on the mantelpiece or bookshelf yet?  I'm not an engineer or a seismologist, so I use the forecasts like this: I have a special china tea set that my grandmother left me when she passed away. In the Kaikoura Earthquake, some of the tea set moved (but didn’t fall…thank you Blu Tack!). My grandmother’s tea set means a lot to me, so, as an extra precaution, I wrapped the tea set in tissue paper and put it in a cardboard box. I look at the numbers and think to myself “maybe just a few more months until I’ll risk putting my tea set back up.

At the moment (three months since the M7.8 Kaikoura Earthquake), I think we are still at Level 4 on the Grandma’s China-ometer in the North Canterbury/Kaikoura area, but this will gradually lower back to a Level 2, which is the background, normal level for this area.  In Wellington, we are probably at Level 3; but I’ve still got my tea set in a box packed away. I’m naturally a bit of a pessimist, so I act like Wellington is at Level 4.

How do you produce the forecasts?

The past gives us clues for the future.  Much like detectives putting together evidence to solve a crime, scientists use evidence from observations and models to understand the processes happening in the earth.

The models that GNS Science use to generate the earthquake forecasts are based on observations of how earthquake sequences work, from all around the world over more than 100 years.  In general, most aftershock sequences decay, which means the number of earthquakes decreases over time. This is called Omori’s law. Although, a large aftershock can cause a spike of activity any time.

These models tell us about the average behaviour of aftershock sequences, but we learn more as a particular sequence unfolds.  Think of it like family behaviour: we might expect that your family might behave in a certain way at a family get together. but if we randomly grab one member, we might get your weird Uncle Kevin or more stable Aunt Caroline. At this point, we think the Kaikoura sequence is more like stable Aunt Caroline, but crazy Uncle Kevin can still show up and ruin the family gathering.

The initial aftershock model we use was developed by GNS Science. It was based on one used by the USGS that one of our scientists developed (we loaned him out for a few years and then brought him back). The model has been improved over the last decade to suit New Zealand’s unique conditions.  If you want the technical details of the models, they are explained on GNS Science’s Earthquake Hazard Modelling page.

We don’t know exactly what is coming when, however, knowing what is most likely can help us make decisions as individuals and communities. Want to know more technical details about earthquake forecasting for the Kaikoura earthquake sequence? Go here.

These numbers don’t really help me, who uses them?

The earthquake forecast probabilities are really useful for engineers, infrastructure managers, private companies, Civil Defence, government planning, and insurance organisations, including EQC.  Infrastructure managers and Civil Defence can use the probabilities to plan for the next few months – they only have so much time and resources, so knowing what is likely (or not) helps them decide where to focus their efforts and what to plan for.  The probabilities are fed into new building standards (as they were after the Canterbury earthquakes), so that our buildings will be more resilient to earthquakes in the future.  And when probabilities are quantified like this they can be used by risk assessors at insurance companies to compare risks from different hazards (e.g. flooding, snowstorm and earthquakes). Some members of the public also want the numbers to know what to expect about how many earthquakes they might feel and how many might be large enough to cause more damage.

Other people admit that they don’t really understand the numbers, but they say that the numbers provide reassurance; they are comforted by the thought that some people understand what is going on and what is happening is generally within the range of the forecast.  Others would rather get a poke in the eye than see another forecast.

What is important is having a general indication of what we can expect and figuring out how to live around the possibility of another large earthquake – either as part of the current earthquake sequence, or a separate one (we live smack bang on the top of a tectonic plate boundary, so getting big earthquakes every now and then is not surprising).  The best thing we can do is take a few steps to help ourselves.  As the probability of a moderate-sized earthquake in the aftershock area is still significant three months on from the Kaikoura earthquake, you might want to be extra careful and prepared.

What do I do about these earthquakes? These earthquakes are really getting to me.

As fascinating as they are, earthquakes can be really scary for some people.  Even if you are not that disturbed by the earthquakes themselves, just constantly getting a fright every time one arrives can be enough to rattle your nerves.  Or you may just be plain scared of them, and it is normal to be scared of something that is scary.  If you are anxious about the earthquakes and this is affecting your ability to go about your daily life the All Right? Hotline (0800-777-846) is a great resource where you can talk about any anxieties or concerns that you have regarding the earthquakes. Remember to also seek support with friends and family, and to take time out to do things you enjoy. 

If you want more advice on how to prepare your household, you can follow our friends at the Ministry of Civil Defence & Emergency Management on Twitter and Facebook for the latest earthquake and tsunami preparedness information. EQC also have a great guide to Quake Safe your home. You can also follow your regional Civil Defence Emergency Management Groups.

Story written by: Helen Jack, Sara McBride, Annamarie Christophersen, Matt Gerstenberger 

China stunt coordinator: Helen Jack

 

View Online Helen Jack 2017-02-21T03:09:53Z

Update: Earthquake swarm west of Tokaanu (Turangi)

Mon, 20/02/2017 - 15:51

Blog post edited by Brad Scott

A small earthquake swarm started around 6pm (Monday 13 February) about 10 kilometres north west of Tokaanu (Turangi). Since around 7am today (Monday February 20) earthquake activity has restarted. We have been able to locate 52 of the events so far. Their magnitudes ranged from about M 0.8 to M 2.5, while the depths ranged between 1 and 10 kilometres, with most being 5-8 kilometres deep.

The largest event to date occurred at 05.16 am on 20 February, being M2.5. There have been two felt reports, reporting weak shaking. Swarms are often characterised by no one main or large event, with many of the events being about the same size.

Earthquake swarms are very common in the greater Rotorua-Taupo area, known as the Taupo Volcanic Zone. In 2008 there was a larger swarm in the same area, while in March 2015 there was one about 9 km to the north and another in October 2015 to the south. 

Seismogram showing todays earthquakes Locations of the earthquakes in the last week

View Online Brad Scott 2017-02-20T02:51:18Z

Looking ahead: M7.8 Kaikoura aftershock forecasts

Mon, 20/02/2017 - 13:25

Blog post edited by Caroline Little

20/02/2017 12.00 p.m.

We’ve been busy crunching the numbers based on all the seismic activity in the aftershock area of November’s Kaikoura Earthquake. So what’s the big news? The expected numbers of earthquakes have dropped a lot since the last forecast.  There is now a 18% chance of one or more M6.0-6.9 earthquakes occurring within the next month; this has decreased from 25% from our last forecast (19 January 2016).  We like this downward movement in our forecast; it is good step in the right direction. 

But does this mean we are all in the clear and don’t need to worry about more big earthquakes? No, absolutely not. Another big earthquake is still well within the probabilities in our models. An 18% chance in a month is still a concerning probability. We need to continue to be prepared for earthquakes as these will go on for years to come. The ongoing Canterbury Earthquake Sequence is an example of aftershocks that can last for years after the initial mainshock (which was the M7.1 Darfield quake in 2010). 

Remember: Drop, cover and hold in an earthquake. If the earthquake is long or strong and you are near the coast, evacuate as soon as the shaking stops. Our friends at the Ministry of Civil Defence and Emergency Management advise to not wait for an official warning or sirens.

What’s happened so far

We’ve had a total of 13626 earthquakes since the M7.8 Kaikoura earthquake stopped shaking our islands (we ran the numbers at 11 a.m. on the 20th February). 461 of those earthquakes were M4-4.9, 55 were M5-5.9 and 4 have been M6.0 or greater. Yes, that is a lot of earthquakes but line up with what we’ve been forecasting.

Aftershock Forecast starting on 19 February 2017 

While no one can yet scientifically predict earthquakes, we can provide forecasts of future aftershocks (based on probabilities), as well as some scenarios from what is most likely to happen to what is very unlikely, but still possible. Most earthquake aftershock sequences decay (i.e. the number of earthquakes generally decreases) over time, with spikes of activity that can include larger earthquakes. For a comparison, here's our older forecast from 19 December. 

 

Average number of M5.0-5.9

Range* of M5.0-5.9

Probability of 1 or more M5.0-5.9

Average number of M6.0-6.9

Range* of M6.0-6.9

Probability of 1 or more M6.0-6.9

Average number of M≥7

Range* of M≥7

Probability of 1 or more M≥7

within 30 days

2.3

0-8

79%

0.2

0-1

18%

0.02

0-1

2%

within one year

14.4

5-26

>99%

1.3

0-4

72%

0.1

0-1

11%

Forecast for rectangular box (see map on the right) with the coordinates -40.7, 171.7, -43.5, 171.7, -43.5, 175.5, -40.7, 175.5 at 12 noon, Thursday, 19 February; 95% confidence bounds.

The aftershocks of the magnitude 7.8 Kaikoura earthquake are mostly occurring throughout a broad area from North Canterbury through to Cook Strait that surrounds the faults that ruptured in that earthquake, although a few have occurred in the lower North Island. We forecast aftershock probabilities for the area in the red box on the map to the right. The area near the centre of the box (around Kaikoura) is more likely to experience felt aftershocks than areas towards the edge of the box. See the MMI map below for more information on the forecast shaking for the Wellington area. Earthquakes can and do happen outside this box but the box represents the most likely area for aftershocks in this sequence. 

For example, there is a 18% chance of one or more M6.0-6.9 earthquakes occurring within the next month. We estimate there will be between 0 and 1 earthquakes in this magnitude range within the next month.

The current rate of magnitude 6 and above earthquakes for the next month is about 7 times larger than what we would normally expect for long term seismicity represented in our National Seismic Hazard model. As the aftershock rates decrease, this difference will decrease as well.

 

ScenariosNote that the scenarios are not updated as frequently as the forecasts above. The scenarios below were estimated in December 2016 so the likelihoods are higher than the forecast table above.

The scenarios specifically address the probabilities of what we might see happen within the next year and were estimated in mid-December 2016. The scenarios cover a wider geographic area than the aftershock probability forecast area. The probability numbers in the table above differ to the scenarios. This is because they were estimated at a different time in the aftershock sequence, and we have used new information we have gathered from the slow-slip events, and their potential impact on the plate interface and other faults, to help define our probabilities in scenario three. 

There are very different probabilities for each scenario; some of these may be more unsettling to you than others. We recognise that while these scenarios may increase anxiety the best thing is to be prepared. Remember: To drop, cover and hold in an earthquake. If you feel a long or strong earthquake and you are on the coast, evacuate immediately.

Scenario One: Likely (approximately 70% within the next year)

The most likely scenario is that aftershocks will continue to decrease in frequency (and in line with forecasts) over the next year and no aftershocks of magnitude 7 or larger will occur. Felt aftershocks (e.g. over magnitude 5) can occur in the area from North Canterbury to Cape Palliser/Wellington.

Scenario Two:  Unlikely (approximately 25% within the next year)

An earthquake smaller than the mainshock and between magnitude 7.0 to magnitude 7.8 will occur. There are numerous mapped faults in the North Canterbury, Marlborough, Cook Strait and Southern North Island areas capable of such an earthquake. It may also occur on an unmapped fault. This earthquake may be onshore or offshore but close enough to cause severe shaking on land. This scenario includes the possibility of an earthquake in the Hikurangi Subduction Zone. Earthquakes originating from here or in the Cook Strait have the potential to generate localised tsunami. The Hawke’s Bay earthquake sequence in 1931 provides an analogy to scenario two, as a magnitude 7.3 aftershock occurred approximately 2 weeks after the initial magnitude 7.8 earthquake.

Scenario Three:  Very unlikely (5% within the next year)

A much less likely scenario than the previous two scenarios is that recent earthquake activity will trigger an earthquake larger than the magnitude 7.8 mainshock. This includes the possibility for an earthquake of greater than magnitude 8.0, which could be on the plate interface (where the Pacific Plate meets the Australian Plate). Although it is still very unlikely, the chances of this occurring have increased since before the magnitude 7.8 earthquake, and have also been also been slightly increased by the slow-slip events.

Initially our scenarios covered what might happen over the next 30 days, but we are now shifting to covering what might happen over the next year.  This is because the aftershocks are generally becoming smaller and less frequent (decaying) over time, and this lower aftershock rate increases the uncertainty of what might happen over shorter time periods. The change in forecast does not hugely affect the scenarios at the moment; we will review these again later in the year. While we will continue to update the aftershock probabilities regularly, we will not update the scenarios as often.

Can't get enough technical information? Here's the fine print on how we model aftershock probabilities.

Aftershock shaking forecasts

We have also calculated the probability of damaging earthquake shaking from aftershocks over the next year (starting 19 February 2017).  Damaging earthquake shaking is defined as MM7 on the Modified Mercalli Intensity (MMI) scale.  The MMI scale is different to earthquake magnitude – it describes the intensity and impacts of the shaking, which depend on the magnitude of the earthquake, how far away the earthquake was and the type of ground you are on.  At MM7 intensity shaking levels it is difficult to stand, furniture and appliances move, contents are damaged, there is minor building damage and liquefaction can occur in susceptible sediments.

The maps show the probability of MM7 shaking within the aftershock region, which includes Wellington. Over the next year the probability of MM7 shaking around the wider Kaikoura/northern area. In comparison, the probability of MM7 shaking in the Wellington area is around 3% (dark blue) in the next year. While this probability is considerably lower in Wellington than in the areas around Kaikoura, it is possible for shaking similar to what occurred during the mainshock to happen again in Wellington. 

Christchurch's aftershock probabilities are not greatly affected by the magnitude 7.8 Kaikoura earthquake.  The most recent update of the Christchurch aftershock probabilities are here. We update the Christchurch aftershock probabilities annually, as now they do not change much from month to month. 

Tsunami and landslide hazards

A tsunami was created by the magnitude 7.8 Kaikoura earthquake, and our scientists are still analysing the tsunami data and collecting information on its impacts. Remember, if an earthquake is too strong to stand up in, or lasts longer than a minute, move inland or to higher ground immediately. Do not wait for a siren or an official warning.

The earthquake also caused tens of thousands of landslides in North Canterbury, Kaikoura and Marlborough. These landslides remain dangerous and can move at any time. Please be careful around landslides and cracks in slopes. Heavy rain can pick up and carry landslide material and cause debris flows and debris floods (flash floods). Landslides have also dammed several rivers. These dams could breach, particularly in heavy rain. Please be careful and avoid riverbeds downstream of dams.

Take care of yourselves and others – physically and mentally

Earthquakes can be scary.  It is normal and okay to be a bit scared about things that are scary.  But the best thing you can do is take action and be prepared. 

You can follow our friends at the Ministry of Civil Defence & Emergency Management on Twitter and Facebook for the latest earthquake and tsunami preparedness information. EQC also have a great guide to Quake Safe your home. You can also follow your regional Civil Defence Emergency Management Groups. If you are anxious about the earthquakes and this is affecting your ability to go about your daily life the All Right? Hotline (0800-777-846) is a great resource where you can talk about any anxieties or concerns that you have regarding the earthquakes. Remember to also seek support with friends and family, and to take time out to do things you enjoy. 

View Online Caroline Little 2017-02-20T00:25:50Z

Minor Earthquake swarm west of Tokaanu (Turangi)

Fri, 17/02/2017 - 10:28

Blog post edited by Brad Scott

Earthquake swarms are very common in the greater Rotorua-Taupo area, known as the Taupo Volcanic Zone. Since around 6pm (Monday 13 February) the GeoNet seismometer network between Taupo and the Tongariro National Park has been recording a swarm of small earthquakes. They locate about 10 kilometres north west of Tokaanu. We have been able to locate 19 of the events so far. Their magnitudes ranged from about M 0.8 to M 1.7, while the depths ranged between 1 and 9 kilometres, with most being 3-5 kilometres deep. The quakes are likely to be related to the long-term tectonic stretching of the Taupo Volcanic Zone. Currently, there are no indications that the earthquakes are related to volcanic activity. As usual, we continue to closely monitor the activity.

The largest event to date occurred at 10.04 pm on 16 February, being M1.7. There have been no felt reports. Swarms are often characterised by no one main or large event, with many of the events being about the same size.

In 2008 there was a larger swarm in the same area, while in March 2015 there was one about 9 km to the north and another in October 2015 to the south. 

Location of the earthquakes


View Online Brad Scott 2017-02-16T21:28:48Z

A new year, a new M7.8 Kaikoura aftershock forecast

Thu, 16/02/2017 - 16:45

Blog post edited by Caroline Little

20/01/2017 1.30 p.m.

We’ve been busy crunching the numbers based on all the seismic activity in the aftershock area of November’s Kaikoura Earthquake. So what’s the big news? The expected numbers of earthquakes have dropped a lot since the last forecast.  There is now a 25 percent chance of one or more M6.0-6.9 earthquakes occurring within the next month; this has decreased from 54 percent from our last forecast (19 December 2016).  We like this downward movement in our forecast; it is good step in the right direction. 

But does this mean we are all in the clear and don’t need to worry about more big earthquakes? No, absolutely not. Another big earthquake is still well within the probabilities in our models. A 25% chance in a month is still a concerning probability. We need to continue to be prepared for earthquakes as these will go on for years to come. The ongoing Canterbury Earthquake Sequence is an example of aftershocks that can last for years after the initial mainshock (which was the M7.1 Darfield quake in 2010). 

Remember: Drop, cover and hold in an earthquake. If the earthquake is long or strong and you are near the coast, evacuate as soon as the shaking stops. Our friends at the Ministry of Civil Defence and Emergency Management advise to not wait for an official warning or sirens.

What’s happened so far

We’ve had a total of 11956 earthquakes since the M7.8 Kaikoura earthquake stopped shaking our islands (we ran the numbers at 10 a.m. on the 19 January, so these will change). 452 of those earthquakes were M4-4.9, 53 were M5-5.9 and 4 have been M6.0 or greater. Yes, that is a lot of earthquakes but line up with what we’ve been forecasting.

Aftershock Forecast starting on 19 January 2017 

While no one can yet scientifically predict earthquakes, we can provide forecasts of future aftershocks (based on probabilities), as well as some scenarios from what is most likely to happen to what is very unlikely, but still possible. Most earthquake aftershock sequences decay (i.e. the number of earthquakes generally decreases) over time, with spikes of activity that can include larger earthquakes. Our previous forecast, from 19 December, is here

 

Average number of M5.0-5.9

Range* of M5.0-5.9

Probability of 1 or more M5.0-5.9

Average number of M6.0-6.9

Range* of M6.0-6.9

Probability of 1 or more M6.0-6.9

Average number of M≥7

Range* of M≥7

Probability of 1 or more M≥7

 

within 30 days

3.2

0-9

89%

0.3

0-2

25%

0.03

0-1

3%

 

within one year

16.6

7-29

>99%

1.5

0-4

77%

0.1

0-1

12%

 

Forecast for rectangular box with the coordinates -40.7, 171.7, -43.5, 171.7, -43.5, 175.5, -40.7, 175.5 at 12 noon, Thursday, 19 January. * 95% confidence bounds.

The aftershocks of the magnitude 7.8 Kaikoura earthquake are mostly occurring throughout a broad area from North Canterbury through to Cook Strait that surrounds the faults that ruptured in that earthquake, although a few have occurred in the lower North Island. We forecast aftershock probabilities for the area in the red box on the map to the right. The area near the centre of the box (around Kaikoura) is more likely to experience felt aftershocks than areas towards the edge of the box. See the MMI map below for more information on the forecast shaking for the Wellington area. Earthquakes can and do happen outside this box but the box represents the most likely area for aftershocks in this sequence. 

For example, there is a 25% chance of one or more M6.0-6.9 earthquakes occurring within the next month. 

The current rate of magnitude 6 and above earthquakes for the next month is about 10 times larger than what we would normally expect for long term seismicity represented in our National Seismic Hazard model. As the aftershock rates decrease, this difference will decrease as well.

Why has the forecast dropped so much?

There are two reasons to explain the drop in expected numbers: A month has passed since our last update and we have included another model into our forecast mix. The longer a sequence goes on, the more information we have (based on location, depth and size of earthquakes) to improve our forecasts based on what we are seeing from the Kaikoura earthquakes. We know more now and, as time goes on, we’ll continue to refine the models further to give you the best information we can. The more we observe, test, develop, and refine, the better we can forecast what happens next.

For example, for the 19th December forecast we estimated 8.4 earthquakes of M5.0-M5.9 within the next 30 days. With the updated model, that number for December would have been 5.2 earthquakes in the M5.0-M5.9 range; this was closer to the actual observed earthquakes of that size, which was three.  

Scenarios

The scenarios specifically address the probabilities of what we might see happen within the next year and were estimated in mid-December 2016 (this differs from the forecast table above which is more recently updated). The scenarios cover a wider geographic area than the aftershock probability forecast area. The probability numbers in the table above are slightly different to the scenarios.  This is because we have used new information we have gathered from the slow-slip events, and their potential impact on the plate interface and other faults, to help define our probabilities in scenario three. 

There are very different probabilities for each scenario; some of these may be more unsettling to you than others. We recognise that while these scenarios may increase anxiety the best thing is to be prepared. Remember: To drop, cover and hold in an earthquake. If you feel a long or strong earthquake and you are on the coast, evacuate immediately.

Scenario One: Likely (approximately 70% within the next year)

The most likely scenario is that aftershocks will continue to decrease in frequency (and in line with forecasts) over the next year and no aftershocks of magnitude 7 or larger will occur. Felt aftershocks (e.g. over magnitude 5) can occur in the area from North Canterbury to Cape Palliser/Wellington.

Scenario Two:  Unlikely (approximately 25% within the next year)

An earthquake smaller than the mainshock and between magnitude 7.0 to magnitude 7.8 will occur. There are numerous mapped faults in the North Canterbury, Marlborough, Cook Strait and Southern North Island areas capable of such an earthquake. It may also occur on an unmapped fault. This earthquake may be onshore or offshore but close enough to cause severe shaking on land. This scenario includes the possibility of an earthquake in the Hikurangi Subduction Zone. Earthquakes originating from here or in the Cook Strait have the potential to generate localised tsunami. The Hawke’s Bay earthquake sequence in 1931 provides an analogy to scenario two, as a magnitude 7.3 aftershock occurred approximately 2 weeks after the initial magnitude 7.8 earthquake.

Scenario Three:  Very unlikely (5% within the next year)

A much less likely scenario than the previous two scenarios is that recent earthquake activity will trigger an earthquake larger than the magnitude 7.8 mainshock. This includes the possibility for an earthquake of greater than magnitude 8.0, which could be on the plate interface (where the Pacific Plate meets the Australian Plate). Although it is still very unlikely, the chances of this occurring have increased since before the magnitude 7.8 earthquake, and have also been also been slightly increased by the slow-slip events.

Initially our scenarios covered what might happen over the next 30 days, but we are now shifting to covering what might happen over the next year.  This is because the aftershocks are generally becoming smaller and less frequent (decaying) over time, and this lower aftershock rate increases the uncertainty of what might happen over shorter time periods. The change in forecast does not hugely affect the scenarios at the moment; we will review these again later in the year. While we will continue to update the aftershock probabilities regularly, we will not update the scenarios as often.

Can't get enough technical information? Here's the fine print on how we model aftershock probabilities.

Aftershock shaking forecasts

We have also calculated the probability of damaging earthquake shaking from aftershocks over the next year (starting 19 January 2017).  Damaging earthquake shaking is defined as MM7 on the Modified Mercalli Intensity (MMI) scale.  The MMI scale is different to earthquake magnitude – it describes the intensity and impacts of the shaking, which depend on the magnitude of the earthquake, how far away the earthquake was and the type of ground you are on.  At MM7 intensity shaking levels it is difficult to stand, furniture and appliances move, contents are damaged, there is minor building damage and liquefaction can occur in susceptible sediments.

The maps show the probability of MM7 shaking within the aftershock region, which includes Wellington. Over the next year the probability of MM7 shaking around the wider Kaikoura/northern area. In comparison, the probability of MM7 shaking in the Wellington area is around 3% (dark blue) in the next year. While this probability is considerably lower in Wellington than in the areas around Kaikoura, it is possible for shaking similar to what occurred during the mainshock to happen again in Wellington. 

Christchurch's aftershock probabilities are not greatly affected by the magnitude 7.8 Kaikoura earthquake.  The most recent update of the Christchurch aftershock probabilities are here. We update the Christchurch aftershock probabilities annually, as now they do not change much from month to month. 

Tsunami and landslide hazards

A tsunami was created by the magnitude 7.8 Kaikoura earthquake, and our scientists are still analysing the tsunami data and collecting information on its impacts. Remember, if an earthquake is too strong to stand up in, or lasts longer than a minute, move inland or to higher ground immediately. Do not wait for a siren or an official warning.

The earthquake also caused tens of thousands of landslides in North Canterbury, Kaikoura and Marlborough. These landslides remain dangerous and can move at any time. Please be careful around landslides and cracks in slopes. Heavy rain can pick up and carry landslide material and cause debris flows and debris floods (flash floods). Landslides have also dammed several rivers. These dams could breach, particularly in heavy rain. Please be careful and avoid riverbeds downstream of dams.

Take care of yourselves and others – physically and mentally

Earthquakes can be scary.  It is normal and okay to be a bit scared about things that are scary.  But the best thing you can do is take action and be prepared. 

You can follow our friends at the Ministry of Civil Defence & Emergency Management on Twitter and Facebook for the latest earthquake and tsunami preparedness information. You can also follow your regional Civil Defence Emergency Management Groups. If you are anxious about the earthquakes and this is affecting your ability to go about your daily life the All Right? Hotline (0800-777-846) is a great resource where you can talk about any anxieties or concerns that you have regarding the earthquakes. Remember to also seek support with friends and family, and to take time out to do things you enjoy. 

View Online Caroline Little 2017-02-16T03:45:06Z

Not so lovely - one year on from a rude shock

Tue, 14/02/2017 - 16:45

Blog post edited by Helen Jack

Today marks one year since the magnitude 5.7 Valentine’s Day earthquake hit Christchurch at 1.13pm on a sunny summer Sunday. The earthquake, which happened more than four years after the previous large aftershock in the Christchurch earthquake sequence (the magnitude 5.9 23 December 2011 earthquake), struck under the sea floor, 2 km off the New Brighton coast at a depth of 8 km.

As well as causing more liquefaction in eastern suburbs, and rattling more than a few nerves, one of the biggest impacts of the earthquake on the environment was more cliff collapses and boulder rolls. Our landslide scientists headed to Christchurch two days after the earthquake to survey the landslides in the Port Hills with the help of local geotechnical engineers and Christchurch City Council staff. 

Most of the landslides generated by the earthquake were cliff collapses (technically called cliff-crest recession and debris avalanches) and boulder rolls (individual boulders bouncing down hills) on the steep cliffs between Redcliffs and Taylors Mistake.  For those of us who like maps, the one below shows where the most rock falls and cliff collapses occurred compared to where the strongest ground shaking was felt.

 

Wakefield Ave in Sumner, showing the area where rock fell from and where it landed Drone photo of Whitewash Head showing new cracks in the cliff face - the rest of the road on the right fell into the sea during the 13 June 2011 earthquake Thousands of cubic metres of rock fell into the sea from Whitewash Head (Photo: RNZ/Sally Murphy) Earthquake shaking in the Valentine’s Day earthquake (units are maximum peak ground acceleration as a % of gravity or, in normal people speak, red = strong, blue = not so strong) and the main areas of cliff collapse

 

By using UAVs (unmanned aerial vehicles or drones), laser scanners, and walking around the main sites affected (where it was safe enough) the scientists and engineers were able to measure how much rock had fallen and where new cracks had opened in the rock, or old cracks had grown wider.

By far the largest amount of rock fell from Whitewash Head near Scarborough. Around 40,000 m3 of rock – 16 Olympic swimming pools’ worth – has fallen into the sea off Whitewash Head since it was last surveyed in August 2011, most of which happened in the December 2011 earthquake and the Valentine’s Day earthquake. Our scientists also mapped many new cracks at the top of the cliff here.

Far behind, the runners up were Richmond Hill Road cliff above Wakefield Ave in Sumner (about 500 m3, as much as you could tip into five double garages), Shag Rock Reserve (about 70 m3, a couple of shipping containers’ worth) and the cliff behind Redcliffs (about 50 m3 or seven of Paeroa’s giant L&P bottles).

These amounts were less than amounts that fell from these same sites during the 23 December 2011 earthquake, even though the amount of shaking was similar.  This is probably because there were less unstable rocks that were ready to fall as many of them had already fallen before the Valentine’s Day earthquake.

There was no movement recorded on any of the landslides on the Port Hills being monitored by GeoNet and Christchurch City Council.  The earthquake shaking was below the level that we would expect these landslides to move, and Christchurch City Council had also worked over the previous five years to stabilise some of these slides.

We were fortunate that no one was injured in the earthquake given that it happened when many people were out enjoying the beaches and coastal walkways in the most affected areas.  More good management than good luck though was the fact that all the cliff collapses and new cracking happened on red zoned land, where houses had been purchased by the Government and demolished because of the high risk of further cliff collapse and bolder rolls.

For all the technical details you can download the Valentine’s Day earthquake landslide report (SR_2016-035.pdf).

 

View Online Helen Jack 2017-02-14T03:45:27Z

Message from the Director: The Kaikoura Earthquake – Three Months On

Tue, 14/02/2017 - 13:15

Blog post edited by Sara McBride

My wife will tell you I have never been sentimental about anniversaries, but it is Valentine’s Day today, and because of its significance in the happenings of the last year, I will make an exception. You can think of this as my sad attempt at writing a love letter to New Zealand.  Because not only is this the most romantic (or commercial depending on what side of the fence you sit on) celebration of the year, it also marks two important anniversaries here at GeoNet: it has been three months since the Kaikoura Earthquake and a year since the Valentine’s Day earthquake struck Christchurch.

 I think of the people in Christchurch or in Waiau, Ward, Seddon, Cheviot, Mt. Lyford, Kaikoura and the many small townships affected by the Kaikoura Earthquake and Canterbury aftershock sequence. Earthquakes are deeply interesting to me, as a scientist, but as a human being I’m still overwhelmed with the enormity of their destructive power.  Anyway, I’m sure you are reading this for the science-y bits rather than my feelings about earthquakes. There have been almost 13,000 earthquakes as part of the aftershock sequence from the Kaikoura earthquake; a staggering and sobering number. 

Dr. Ken Gledhill, Director of GeoNet

So, while some people got a break over the holiday period (and we tried to stop our staff working but…its really difficult to stop people who are so passionate about their work!) it has been non-stop since the ground stopped shaking under our feet three months ago. Since that time, our scientists at GNS Science and indeed, universities and other research institutions throughout the country, have scattered out of their offices and into the field, collecting samples, measuring coastlines, and identifying and mapping landslides. We’ve learned a lot since that fateful early morning on the 14 November and we will continue to learn for years to come. 

In the coming months, we are going to be talking a lot more about the evolving scientific understanding of the Kaikoura earthquake as well as improving how GeoNet runs. So today, I’m giving you the heads up about some important projects: 

The improved GeoNet website – now available for testing

Lovingly known internally as our Beta website, we’ve actually been working on this behind the scenes pre-Kaikoura earthquake. We had initially planned the launch the week of the 14 November, but with our improved understanding of the needs of Kiwis regarding our geological hazards, we’ve made some modifications.

I know lots of people have been asking about the website for a long time. Some improved features include more technical information for each earthquake as well as the associated news stories. But for those of you who like volcanoes, we’ve got you covered too. I’ll admit though, our landslide and tsunami sections are still a bit anaemic; but this is a work in progress. You can go to the Beta website here.

And we need your help to make the new website better! Please fill in this survey after you have finishing reviewing the website to give us all your important feedback on what’s working for you with the site and what isn’t. And my team wanted to bring back the Volcano Kitten T-Shirt competition. My apologies to good taste everywhere, but I couldn’t stop them. More on that competition soon. 

It won’t replace the old website until later in the year but we want to test it out early to get all the bugs out of it we can. 

New Zealand’s Science Briefing about Kaikoura – 14 March at 12 noon

One of the really inspiring parts of working on the Kaikoura response during that first few weeks was the science briefings at 9 a.m. every morning. I was privileged to listen to some of the best minds in New Zealand discuss the science of the earthquake. Each and every day, something new was presented that really intrigued me.  We are developing this concept of a science briefing for 14 March because I wanted us to be able to share with you what a science briefing is like, live.

So, we will be streaming our science briefing live, to you, via Facebook. We will also record it and pop it on YouTube for those of you who don’t have Facebook. We are pretty excited about being able to bring this to you. In a few days, we’ll be putting an event on FaceBook where you can pop your questions.

 

Beta Website and the Volcano/Kitten T-Shirt competition

Enhanced Geological Hazard Monitoring

Just before Christmas there was an announcement by the Ministers of Science and Innovation and Civil Defence to help assist us with increasing the nation’s capacity for geological hazard monitoring. We are working hard behind the scenes with key stakeholders to see how we can better deliver for all of New Zealanders.  More in this space in the coming months.

These are just a few of the major projects we are working on at GeoNet. 

Love for our Duty Teams

I just want to finish by giving a bit of love (following the Valentine’s Day theme) to one of the hardest working teams at GeoNet – our duty teams. GNS Science provides GeoNet with some of the top minds in the world to help us inform New Zealand on urgent geological hazard news. These teams work under the most stressful conditions, putting their own research interests aside for the benefit of the entire country. These teams work throughout the year, on top of their other jobs (many are world leading seismology, volcanology, engineering geology and other types of researchers).

When you are trained as a scientist, there is no class you can take that teaches you how to make split second, complex decisions on very little data, knowing that your decisions can impact many people. It is a heavy load to bear for our scientists and I thank them from the bottom of my geophysicist heart for their absolute dedication to this difficult role. I have been there – I know how hard it is! GeoNet could not run without these vital teams. Thank you.

Thank you everyone for a great start to 2017 for GeoNet. I look forward to us all continuing to roll up our sleeves and getting on with it in the coming year. I wish you a wonderful Valentine’s Day and a quiet Earth!

 

 

 

 

View Online Sara McBride 2017-02-14T00:15:54Z

Message from the Director: The Kaikoura Earthquake – Three Months On

Tue, 14/02/2017 - 11:54

Blog post edited by Sara McBride

My wife will tell you I have never been sentimental about anniversaries, but it is Valentine’s Day today, and because of its significance in the happenings of the last year, I will make an exception. You can think of this as my sad attempt at writing a love letter to New Zealand.  Because not only is this the most romantic (or commercial depending on what side of the fence you sit on) celebration of the year, it also marks two important anniversaries here at GeoNet: it has been three months since the Kaikoura Earthquake and a year since the Valentine’s Day earthquake struck Christchurch.

 I think of the people in Christchurch or in Waiau, Ward, Seddon, Cheviot, Mt. Lyford, Kaikoura and the many small townships affected by the Kaikoura Earthquake and Canterbury aftershock sequence. Earthquakes are deeply interesting to me, as a scientist, but as a human being I’m still overwhelmed with the enormity of their destructive power.  Anyway, I’m sure you are reading this for the science-y bits rather than my feelings about earthquakes. There have been almost 13,000 earthquakes as part of the aftershock sequence from the Kaikoura earthquake; a staggering and sobering number. 

There are no images attached to this page.

Dr. Ken Gledhill, Director of GeoNet

So, while some people got a break over the holiday period (and we tried to stop our staff working but…its really difficult to stop people who are so passionate about their work!) it has been non-stop since the ground stopped shaking under our feet three months ago. Since that time, our scientists at GNS Science and indeed, universities and other research institutions throughout the country, have scattered out of their offices and into the field, collecting samples, measuring coastlines, and identifying and mapping landslides. We’ve learned a lot since that fateful early morning on the 14 November and we will continue to learn for years to come. 

In the coming months, we are going to be talking a lot more about the evolving scientific understanding of the Kaikoura earthquake as well as improving how GeoNet runs. So today, I’m giving you the heads up about some important projects: 

The improved GeoNet website – now available for testing

Lovingly known internally as our Beta website, we’ve actually been working on this behind the scenes pre-Kaikoura earthquake. We had initially planned the launch the week of the 14 November, but with our improved understanding of the needs of Kiwis regarding our geological hazards, we’ve made some modifications.

I know lots of people have been asking about the website for a long time. Some improved features include more technical information for each earthquake as well as the associated news stories. But for those of you who like volcanoes, we’ve got you covered too. I’ll admit though, our landslide and tsunami sections are still a bit anaemic; but this is a work in progress. You can go to the Beta website here.

And we need your help to make the new website better! Please fill in this survey after you have finishing reviewing the website to give us all your important feedback on what’s working for you with the site and what isn’t. And my team wanted to bring back the Volcano Kitten T-Shirt competition. My apologies to good taste everywhere, but I couldn’t stop them. More on that competition soon. 

It won’t replace the old website until later in the year but we want to test it out early to get all the bugs out of it we can. 

New Zealand’s Science Briefing about Kaikoura – 14 March at 12 noon

One of the really inspiring parts of working on the Kaikoura response during that first few weeks was the science briefings at 9 a.m. every morning. I was privileged to listen to some of the best minds in New Zealand discuss the science of the earthquake. Each and every day, something new was presented that really intrigued me.  We are developing this concept of a science briefing for 14 March because I wanted us to be able to share with you what a science briefing is like, live.

So, we will be streaming our science briefing live, to you, via Facebook. We will also record it and pop it on YouTube for those of you who don’t have Facebook. We are pretty excited about being able to bring this to you. In a few days, we’ll be putting an event on FaceBook where you can pop your questions.

There are no images attached to this page.  

Volcano/Kitten T-Shirt competition

Enhanced Geological Hazard Monitoring

Just before Christmas there was an announcement by the Ministers of Science and Innovation and Civil Defence to help assist us with increasing the nation’s capacity for geological hazard monitoring. We are working hard behind the scenes with key stakeholders to see how we can better deliver for all of New Zealanders.  More in this space in the coming months.

 

These are just a few of the major projects we are working on at GeoNet. 

Love for our Duty Teams

I just want to finish by giving a bit of love (following the Valentine’s Day theme) to one of the hardest working teams at GeoNet – our duty teams. GNS Science provides GeoNet with some of the top minds in the world to help us inform New Zealand on urgent geological hazard news. These teams work under the most stressful conditions, putting their own research interests aside for the benefit of the entire country. These teams work throughout the year, on top of their other jobs (many are world leading seismology, volcanology, engineering geology and other types of researchers).

When you are trained as a scientist, there is no class you can take that teaches you how to make split second, complex decisions on very little data, knowing that your decisions can impact many people. It is a heavy load to bear for our scientists and I thank them from the bottom of my geophysicist heart for their absolute dedication to this difficult role. I have been there – I know how hard it is! GeoNet could not run without these vital teams. Thank you.

Thank you everyone for a great start to 2017 for GeoNet. I look forward to us all continuing to roll up our sleeves and getting on with it in the coming year. I wish you a wonderful Valentine’s Day and a quiet Earth!

 

 

 

 

View Online Sara McBride 2017-02-13T22:54:30Z

Busy time for the volcano team

Thu, 02/02/2017 - 13:03

Blog post edited by Brad Scott

Like everyone else the volcano team has been waiting on summer to arrive, so they can catch up on or complete a few outstanding tasks. Last week summer called by for a couple of days and the team visited White Island (Whakaari), completed a gas flight around Ruapehu and visited the Crater Lake at Mt Ruapehu.

Ruapehu

As part of the monitoring at Mt Ruapehu we attempt to sample the Crater Lake about once a month. This allows us to collect water and gas samples and confirm the temperatures from the data logger probe in the lake. The lake was successfully sampled last Saturday. The lake appeared a uniform grey colour as it has on past samplings. This indicates there is some convection (mixing) occurring in the lake as the gases and hot fluids enter it. The lake was overflowing, which is normal for the lake and varies little. The temperature of the Crater Lake is currently around 21 °C and is slowly cooling.  A gas flight was also completed on the 24th. The results from this flight indicate low-moderate amounts of volcanic gas continue to come through the lake. The Volcanic Alert Level for Ruapehu remains at Level 1 (minor volcanic unrest).

Ruapehu Crater Lake 28 January

 

White Island (Whakaari)

Meanwhile a visit was also made to White Island on the 27th. We visit the island to make many measurements, this trip was to collect gas and water samples, observe the activity from the active crater and make a soil gas survey. The gas chemists collect gas from the hottest accessibly fumaroles (steam vents). Fumarole #1 is currently the hottest and the team measured 191 °C while sampling it. Basically the same temperature as the previous trip. The activity from the vent in the active crater was also unchanged. The crater floor remains ‘dry’, only a few small ponds and springs are present. The crater lake has not reformed since the eruptions in April and September last year. The soil gas survey measures the CO2 gas leaking from the Main Carter floor. We make measurements at 61 sites. There has been an increase from the measurements in November 2016, some of this is related to the dryer conditions on the island. The Volcanic Alert Level for White Island remains at Level 1 (minor volcanic unrest).

Chemist sampling Fumarole Zero White Island 27 January

View Online Brad Scott 2017-02-02T00:03:48Z

Submarine eruption in progress in Tonga

Wed, 01/02/2017 - 10:11

Blog post edited by Brad Scott

On January 31 University of Auckland geographers noted a volcanic plume on satellite images in the Tonga area. The images show a submarine volcanic eruption is now under way about 46 km north west of Nuku’alofa. Back tracking through images we can trace activity back to 23 January from this volcano. This volcano has been called ‘Submarine Volcano III’ in historic reports.

Submarine volcanic activity has been noted from this area in 1911; 1923 (steam plumes); 1970 (discoloured water); 1989-1999 (small island formed in January 1999) and 2007 (discoloured water and felt earthquakes). The 1999 activity is the best reported, starting with felt earthquakes in late December 1989 and discoloured water was noted on 7 January 1999 and an eruption column on the 8th. A volcanic cone was reported above sea level on January 12 and again in the 14th.

Satellite images obtained from the NASA Earth Science program allow us to back track the submarine activity. We can see activity in images from 23, 26, 28 and 29 January indicating the eruption has been ongoing for over a week. After contacting our colleagues in Tonga it appears a steam plume may also be present, but the local cloud makes this difficult to ascertain. Submarine eruptions can be a hazard to shipping.

Submarine volcanic activity is common in the Tonga area and some produce small islands that last for a few days to months. Examples of this include Curacoa Reef (1973), Home Reef (1984), Metis Shoal (1967-68, 1979, 1995) Falcon Island (1927-36) and Hunga Ha’apai 1988 and 2014-15).

NASA image 28 January 2017 NASA image 26 January 2017 NASA image 23 January 2017

View Online Brad Scott 2017-01-31T21:11:18Z

GeoNet technicians experiment with Thermal Sensor Module for web cameras

Thu, 26/01/2017 - 09:57

Blog post edited by Caroline Little

Monitoring volcanoes has many challenges; a couple being how do we see at night and how hot is that vent we can see? Is it heating or cooling? One of the technologies that has helped us a lot is web cameras and another is handheld Thermal Infra Red (TIR) cameras. What if we had both in one unit! Web cameras work well in day light and when the lens is not covered in dust or sublimates from the volcanic plume. Recently the security industry has developed thermal sensor modules (TSM) to improve night views and these are now able to also run as ‘web cameras’. It doesn’t take long before our technicians could see the potential for volcano monitoring.

So where better to test this idea than at White Island, after all it is an active volcano. In fact our most active at present, last erupting in April and September 2016. Since we need to understand how volcanoes work and what they are up to is a big part of our monitoring it sounds perfect. A camera that works 24 hours would be a great tool. Even better if it can tell us something about the temperatures as well.

A TIR camera measures the emitted energy from the surface it is looking at, with more energy coming from hot surfaces than cold ones. The camera collects the data digitally and then applies a ‘false colour’ to make an image. One of the advantages is images can be collected at night (plus day), while our traditional web cameras see little at night unless the moon is out. The thermal sensor module will potentially give higher quality data with spatial coverage of areas around the vents as well and appears to be cost effective.

View of active vents in crater from South West rim View of Fumarole 0 View of active vents from North rim web camera site View of active vents in crater from rim

 

We recently took the thermal sensor module (TSM) to White Island to learn about the data quality, thermal range, spatial cover and the effect of steam and gas on the path between the sensor and feature we are looking at. We also plan to make use of it at other volcanoes and geothermal systems to learn about its capabilities. One constraint on all web cameras at active volcanoes is the lens has to be protected. For the TSM to work this has to be special material to allow the emitted energy (electromagnetic waves) to pass through. We are not sure how the acid rain will affect this. Just one of our many challenges. If we can make all this work it will improve our understanding of how volcano systems work and better inform us about the hazards and risks from volcanoes. 

 

View Online Caroline Little 2017-01-25T20:57:23Z

Te Maari volcano (Tongariro) was in eruption 120 years ago

Thu, 26/01/2017 - 09:56

Blog post edited by Caroline Little

A short-lived, steam driven eruption occurred from Upper Te Maari crater on 6 August 2012. This was the first eruption from Te Maari (Tongariro) since 3 February 1928. However the largest historic eruptions from Te Maari occurred in late 1896 and early 1897.

120 years ago today (25 January), locals reported the initiation of an eruption from Upper Te Maari, which was preceded by felt earthquake activity. Ash fell on a coach travelling between Ohingaiti and the Whanganui River on 26 January 1897, causing restricted visibility. This eruption was the first since 21 December 1896.  

In the night prior to the first eruptive outburst in 1896, more than 140 earthquakes were felt by the local population at Tokaanu. A series of eruptions started at Upper Te Maari crater on 13 November 1896, extending through to October 1897. After 11 days of “not…much sign of activity”, Upper Te Maari crater erupted again on 24 November 1896. In addition to Ngauruhoe, Red Crater reportedly “held fire dances”. Ash-producing eruptions occurred most days between 24 and 30 November 1896, with stronger eruptions on 27 and 30 November.

Eruptions continued on the morning of 1 December 1896, and throughout early December. On 11 December 1896, roaring and thundering noises were heard for “some” minutes apparently coming from the crater, but aside from a blue-coloured gas in contrast to the white steam emitted from Ketetahi, no sign of an eruption was seen. An eruption column was observed on 15 December 1896, lasting for 15 minutes, and was reported to have a dark-red glow at the base, lightning in the column, and incandescent blocks/bombs ejected on parabolic paths. Local reported the countryside was coated in ash to a depth of several inches, weighing down vegetation. Extensive ash fall, was also observed in Napier. Upper Te Maari crater was reportedly still active on 21 December 1896, “ejecting steam, ashes, and smoke”.

View of 21 November 2012 eruption from Emerald Lakes View of 21 November 2012 eruption

View Online Caroline Little 2017-01-25T20:56:30Z

Drones helps us keep a watchful eye on White Island (Whakaari)

Fri, 13/01/2017 - 12:19

Blog post edited by Brad Scott

In recent years Unmanned Aerial Vehicles (UAV’s) or, drones, as they are often called, have become a useful tool in going places that are often difficult or dangerous for people to go. We have been using them to make observations of locations that are not safe to visit and making maps of areas. In June we mapped the eruption deposits at Waimangu by UAV and more recently used them extensively to map the fault displacements and landslides produced by the M7.8 Kaikoura Earthquake.  In late December we were able to fly the active crater at White Island.

While we have the volcano cams on the island, these are stationary and don’t give us the kind of rich data that a drone can. Since the eruption in late April 2016 the vent area has often been obscured by steam and gas and a small lake also formed for a while. This made it difficult to fully assess the changes to the active crater area. We were able to work out the crater floor was lowered by about 13 m but couldn’t accurately estimate the volume of material erupted as we didn’t have a before and after map.  Understanding the volumes involved, distances material was moved etc. helps us better interpret the impacts and mechanism of the April eruption.

 

DTM (Digital Terrain Model) of the crater floor at White island

We were able to obtain images of the active crater area usually obscured by the gas and steam plume so we could make a new map and Digital Terrain Model (DTM) of the area. We know some of the crater floor was lowered about 13 m by the April eruption, but didn’t have any data on the vent area. During our visit in December we had a light easterly wind blowing the plume away from us and the humidity was low so the amount of steam was also low. Perfect conditions for flying the UAV mission over and in the crater.

Our UAV technician has processed the images and video captured on the day and is now compiling the DTM and surface maps. They are really impressive and are giving us a new insight to the changes within the active crater.

No word yet on what Dino thinks of this new visitor to the island. 

 


View Online Brad Scott 2017-01-12T23:19:49Z

Coastal uplift along the North Canterbury-Marlborough coast – results from the coastal survey team

Wed, 11/01/2017 - 11:14

Blog post edited by Caroline Little

Written by Kate Clark
Earthquake Geologist
k.clark@gns.cri.nz

 

Extensive coastal uplift occurred during the Nov 14 2016 Kaikoura earthquake. The uplift occurred almost instantaneously – all during the two minutes of shaking caused by the earthquake. 

Following the earthquake, a team of scientists from GNS Science and the University of Canterbury headed out into the impacted area to survey and record the amount of coastal uplift that occurred. Knowing the amount and pattern of uplift helps us understand aspects of the earthquake such as how much movement occurred across faults that cut across the coastline, and the presence or absence of offshore faults that also moved in the earthquake. Studying the uplift in the recent earthquake can also help us understand more about earthquakes that occurred in the past. For example, we can compare the amount of uplift that occurred in November 2016 earthquake with tectonic uplift recorded by uplifted marine platforms that were thrust out of the sea by earthquakes many thousands of years ago.

Our survey of coastal uplift showed that most of the coastline from Oaro to Lake Grassmere uplifted, that’s about 110 km of coastal uplift. The uplift varies along the coastline is broadly controlled by where faults ruptured the ground surface during the earthquake. The following paragraphs describe the pattern of coastal uplift from south to north along the coast.

Coastal uplift begins immediately north of where the Hundalee Fault crosses the coastline at Oaro. We observed the uplift from our helicopter surveys and also measured a point near Goose Bay where we recorded about 1.6 m of uplift. This amount of uplift is fairly steady along the coast toward Kaikoura. We measured a lot of points around the Kaikoura Peninsula and recorded about 0.8 – 1 m of uplift, which is consistent with the tide gauge there, which uplifted 0.95 m during the earthquake.

It was difficult to tell if uplift had occurred along the steep gravel beaches between Kaikoura Peninsula and the Hapuku River, but north of the Hapuku River uplift increased. Around Halfmoon Bay and Ohau Stream the uplift was measured at 2-3 m. The Hope Fault comes across the coastline near Halfmoon Bay and there was a small amount of surface rupture on the fault but the amount of uplift either side of the fault did not vary substantially. Just north of Waipapa Bay, two strands of the Papatea Fault cut across the coastline and the block in between these two fault strands was dramatically pushed up about 4.8 – 5 m high. This is the greatest amount of uplift recorded in this earthquake.

North of the Papatea Fault there appeared to be very little coastal uplift. Uplift increased markedly just north of where the Kekerengu Fault crosses the coastline. Uplift of around 2.5 – 3 m was measured at Needles Point, Ward Beach and Chancet Rocks. Between Chancet Rocks and Cape Campbell the amount of coastal uplift gradually decreased, there were a couple of sharp ~0.5 m steps where minor fault ruptures cut across the coastline. Around the corner from Cape Campbell, uplift was still moderate (~1 m) at Marfells Beach.

We noticed big changes in the coastal landscape each time we revisited locations, the uplifted seaweeds are quickly bleaching and falling off the rocks, and new hightide and storm beach lines are being established on the uplifted beach faces. This has been a phenomenal tectonic event and is causing numerous problems for local residents, fishermen, boat operators and other coastal users whose coastline has shifted so suddenly.  We are working closely with other scientists to build up a complete understanding of the earthquake, and also keeping in touch with our marine biology colleagues at the University of Canterbury who are working hard to understand the consequences and biological shifts that will be seen in the marine environment.

Uplifted rocks near the Waima/Ure River, approximately 25 km south of Cape Campbell. There was about 2.5 m of uplift here. Surveying neat Goose Bay, south of Kaikoura Peninsula. Uplift here was approximately 1.6 m. Long Point, approximately 10 km south of Cape Campbell. The uplift here was approximately 1.4 m. Kaikoura Peninsula from the air, uplift here was around 0.7-0.9m. This was taken at low tide and the dark brown fringe you can see around the edge of the rock platform is subtidal seaweed that prior to the earthquake would have been covered at low tide. Surveying coastal uplift at Cape Campbell, there was approximately 0.7 m of uplift here.

View Online Caroline Little 2017-01-10T22:14:18Z

2016 in review: The Groundbreaker

Sun, 01/01/2017 - 20:40

Blog post edited by Caroline Little

2016 is now officially sealed in the record books and...there is a lot to cover! This is going to a be a particularly long post. There was too much going on in 2016, so let me sum up: we had geysers, eruptions, landslides, tsunami and a whole lotta earthquakes. The ground broke under our feet, and that is why we are calling this year the “groundbreaker”. It should also be known as the "record breaker".

Let’s start with “this year in earthquakes” in New Zealand...

Earthquakes: a record-breaking year

This year had many earthquakes, but we are going to focus on the main two magnitude 7.0+ quakes that affected numerous communities: shaking our capital, Wellington, our weary quake-familiar Christchurch. Even our biggest city, Auckland, felt the sway of the East Cape earthquake. You’d be hard pressed to find someone who wasn’t impacted, in some way, by earthquakes in New Zealand this year.

 By the numbers, our monitoring network recorded 32,828 earthquakes this year. To give a point of reference, on average we record about 20,000 per year. Our other active year reached 29,000 in 2011. 2016 wins the dubious honour of most earthquakes ever recorded on the GeoNet network (we’ve been around for 15 years).  This year we had 122 earthquakes between magnitude 5.0 and 6.0,10 magnitude 6.0-6.9s, and, two magnitude 7.0 plus earthquakes. It’s been a geologically busy year. So let’s get into the earthquakes and their aftershock sequences that were the main contributors.

On the 2nd of September at 4.37 am, an M.7.1 earthquake struck 22 kilometres deep off the northeast coast of New Zealand. Luckily, the damage was minimal on land, although a small tsunami was generated.  A strong aftershock sequence continued in the days following.  Now, in any other year, the M7.1 would have been the biggest earthquake in New Zealand. But, New Zealand was just getting warmed up.

A little over two months later, at 12.02 a.m., the ground shaking began in North Canterbury, starting near Culverden. In two-and-a-half minutes, the earthquake moved across numerous faults, its seismic energy pooling and then overflowing onto one fault after the other, moving similar to the famous “Bucket Fountain” in Wellington. Along the way, the earthquake ruptured faults, tore through the earth and raised the seabed off Kaikoura.  From Christchurch to Wellington to Nelson, the whole part of the upper South Island and Lower North Island were impacted. Thousands of aftershocks have followed since the ground first shook. There is some pretty amazing video, taken by our Julian Thomson and starring Kelvin Berryman. Thanks, Julian and Kelvin! 

The M.7.8 Kaikoura earthquake will not go into the global history book of earthquakes because of its magnitude; the Ring of Fire regularly gets that size and much larger earthquakes. What makes it unique is two things: how it ruptured across the faults through the North Canterbury and Marlborough Fault areas and the slow-slip earthquakes triggered by M7.8. While we knew the faults were all there, we had only rarely seen an earthquake behave quite like this one.

Secondly, the slow-slip events or “silent earthquakes” started right after the M7.8 Kaikoura earthquake stopped. Our understanding of slow-slip earthquakes is evolving due to its relatively recent detection in 2002 in New Zealand. We don’t yet fully understand what it means to have slow-slip events triggered by the M.7.8. However, we are cautious as to what this might mean for future earthquakes. We’ve included these events in our probabilities and scenarios for this aftershock sequence. These two unique factors make this an earthquake of significance; New Zealand breaks new ground again!

 

It can be easy to get carried away by the excitement of the science of the earthquakes. However, the impact of these earthquakes is real and can be very painful for those who experienced it. Earthquakes, especially the large ones like East Cape and Kaikoura, can be anxiety producing; this is normal. Everyone responds to earthquakes differently, so if you are feeling unusually high anxiety due to the earthquakes, there are people here to help you through this time. If you are anxious about the earthquakes and this is affecting your ability to go about your daily life the All Right? Hotline (0800-777-846) is a great resource where you can talk about any anxieties or concerns that you have regarding the earthquakes. Remember to also seek support with friends and family, and to take time out to do things you enjoy. 

Tsunamis: the rehearsal and the real thing

This year, we were part of a national Ministry of Civil Defence and Emergency Management-led exercise regarding tsunami called Exercise Tangaroa. This exercise involved the whole nation’s civil defence groups and many other agencies across the country (link). Two days later, at 4 am, we had a striking coincidence with the M7.1 East Cape earthquake, which generated a small tsunami (30 cm). The residents near the East Cape earthquake did the right thing by evacuating immediately to higher ground.  

Two months after East Cape, when the ground shook again in Kaikoura, a localised tsunami was generated rising up to four metres from peak to trough that destroyed a cottage in Banks Peninsula.

Again, those who evacuated immediately on feeling the long and strong earthquake did the right thing.

If you are on the coast and you feel an earthquake that is long or strong, get gone.

2016 in Volcano Land

We asked our favourite volcanologist at large, Brad Scott, to give us the words for his thoughts on volcanoes in 2016. Here’s the lowdown from Brad: 

2016 saw a variety of activity from our active volcanoes, ranging from violent explosive activity to small-scale geysering and a mystery submarine eruption, creating a random pumice raft near Tonga. Also included was volcanic unrest, a hydrothermal eruption and remobilisation of old eruption deposits.

High-intensity rain in January saw debris (sand, clay and rock) left over from the 2012 Te Maari eruptions remobilised by the heavy local rainfall and washed out of the valley below the vents

Then, it was White Island (Whakaari)’s time. On Wednesday 27 April, a moderate steam and gas-driven eruption occurred at White Island (Whakaari). The eruption ejected the Crater Lake, created a new sub-crater, generated landslides/collapse and excavated some 13 m of the Crater Lake floor. This generated a very energetic blast that covered much of the Main Crater floor and the north-eastern portion of the volcano with some quite festively coloured green tinged ash. This eruption occurred during a period of volcanic unrest. However, we were challenged initially to confirm it had happened. These steam and gas driven eruptions do not give any useful warning. 

Mt. Ruapehu’s Crater Lake heated up, cooled back down and then promptly heated up again and then back down again. White Island had another hydrothermal eruption in September and then went back to simmering. Finally, we saw some pretty dramatic geyesing in Rotorua in the lake. The geysers had been pretty quiet for 15 years but decided this was the year to reawaken. 

Landslides: slips, slides and the smothering of State Highway One

The newest member of our public information team, Helen Jack, wrote up her thoughts on landslides. Helen is a landslide enthusiast, although she has a fond place in her heart for glaciers as well. She works out of our Dunedin office.

Landslides triggered by earthquakes took the (rather large) cake in 2016.  The M5.7 Valentine’s Day earthquake in February rattled down more rocks and cliffs along the eastern Port Hills in Christchurch.

Then, just as our landslides scientists were wrapping up almost six years of work shaken onto their plate by the Christchurch earthquake, the magnitude 7.8 Kaikoura earthquake delivered up an even bigger serving.  The earthquake caused over 80,000 landslides throughout North Canterbury, Kaikoura and Marlborough, damaging farmland, smothering State Highway 1 and the Inland Kaikoura Road in many places and damming several rivers. Heavy rainfall events throughout the year brought down landslides in the usual suspects of Haast Pass, Nelson/Tasman, Wellington and the Rimutakas, the Manawatu Gorge, East Cape and Coromandel.  Of course, a New Zealand summer wouldn’t be complete without an ex-tropical cyclone or two: In January Victor brought down landslides from East Cape to Tolaga Bay.

While landslides kept road crews very busy, and some property was damaged this year, we continue to be very fortunate that no lives were lost from landslides in 2016, particularly given the amount of landslides caused by the Kaikoura earthquake.

GeoNet turns 15

GeoNet also turned 15 years this year. In 2001, we started as New Zealand’s first national seismological monitoring system. In those 15 years, we’ve grown from a small fledgling network with a handful of online sites to more than 650 monitoring stations around the country, as far north as the Kermadecs and as far south as Antarctica.  You can read more about our 15 years of monitoring New Zealand’s geological hazards here.

(Caption: Sara Page, our public information specialist for social media, put the newsletter together detailing all the geological events that GeoNet has monitored in the last 15 years.)

2016: Ground-breaking but New Zealand still unbreakable

It was a challenging year but also inspiring to me about how we all pulled together. So while 2016 was a groundbreaker, it didn’t break us but rather pulled us closer together as a team.  This country faced some pretty big challenges, once again, due to seismic forces. And like the devastating events of 2011, people came together and helped out. Volunteers from all over the country came to assist Kaikoura, Ward, Waiau, and other affected communities in North Canterbury, Marlborough and Wellington.  It was a terrible year for those communities and people affected by these earthquakes.  We support those communities in their ongoing recovery.

For my part, working for GeoNet, I was overwhelmed with the support we received.  There were hundreds of “thank you” emails, tweets, and Facebook comments this year from people, which we really appreciate.  Further support came from our friends at the Ministry of Civil Defence and Emergency Management, who also work tirelessly this year. We couldn’t have done all the hard work this year without our supporters at EQC, LINZ, DOC, MetService and MBIE.

A couple of brief thank yous are required with a year like this one. Our technical support and services team diligently worked so we didn’t lose service during this challenging time, and our app and software developers helped us provide new and improved services. Our techs worked hard, putting up new temporary sites to better capture every ground movement in North Canterbury and around East Cape. They even found time to innovate with the new ‘Spade-tenna’ (patent pending). We certainly could not have supported GeoNet this year without our team of duty officers.  All of these people help support GeoNet. We thank them for their continued service to New Zealand’s geological hazards monitoring network.

2016 was also the year we said goodbye to our manager, Kevin Fenaughty, who had been in charge of public information since the beginning of GeoNet. Kevin left us this year one week before the Kaikoura earthquake for a new job in MCDEM. He sent flowers to say "sorry" but to be honest, we're still a bit grumpy about him leaving. Anyway, if you like our stories, you can thank Kevin because he hired us! So, thank you for your long service, Kev.  Also, Natalie Balfour, who was on the public information team for a short but very busy ten months, is now our data management team leader. She did a great job as part of the team but now has another big job in GeoNet. We wish both of them well in their new jobs.

So what will 2017 hold? I’d like to say that 2017 will be more like 2015: mostly harmless. But there are no guarantees; nature is a terrible project manager. Some years it’s almost too much while other years, it’s quiet. One thing we can say is that, at GeoNet, we are taking the lessons learned from 2016 and will continue to improve our network, our website, app, and all our services. We hope for a quiet, calm 2017 but the best thing we can all do is be prepared for whatever happens next.

To find out more here about how to prepare for emergencies, visit our friends at:


View Online Caroline Little 2017-01-01T07:40:21Z

GeoNet News Issue 22 - 15 years of big moments

Tue, 27/12/2016 - 22:15

Blog post edited by Sara Page

The latest issue of our publication 'GeoNet News' is here, and its a special edition for our 15th Birthday

 

Follow a timeline of important geological events in New Zealand from 2001 to 2016, along with some profiles of a few of our great team members. 

GeoNet News Issue 22.pdf

Previous issues can be found on the archives page

View Online Sara Page 2016-12-27T09:15:44Z

Standing in cracks and clambering up scarps – what have our earthquake geologists been doing?

Thu, 22/12/2016 - 15:56

Blog post edited by Helen Jack

Since the morning of 14 November earthquake geologists have been flying, walking, driving, and sailing all over North Canterbury, Kaikoura and Marlborough, mapping and measuring the faults that moved during the magnitude 7.8 earthquake.  It’s been a collaborative effort, involving scientists from GNS Science, NIWA, the Universities of Auckland, Canterbury and Otago, Victoria University as well as overseas researchers – 54 people in all!

The zig-zagged collection of fault ruptures mapped so far (click to see a bigger version)

This is one of the most complex on-land earthquakes ever recorded – to date, at least 12 faults have been mapped where they have broken through to the ground or sea floor. 

Unlike the cracks associated with landslides, these breaks start kilometres down in the crust, and come all the way up to the ground surface, shunting land sideways and upwards.  Some fault displacements are just wee steps or small cracks in the ground, while others have produced metres-high cliffs, or land has been pushed sideways by many metres relative to land on the other side of the fault.  New Zealand Geographic magazine has a great story about the fault ruptures and the geologists investigating them, with some amazing photos illustrating how the faults have moved.

So far, most of the fault mapping and has been done on foot, or by helicopter or drone.  Offshore, NIWA have used  a multibeam echosounder and high frequency sub-bottom profiler (fancy machines with interesting names that map the sea floor) on the Tangaroa to detect the movement on the undersea Needles Fault. 

The initial field reconnaissance of the faults has now finished, but LiDAR – a type of high-resolution ground mapping – is now being flown over much of the area affected by the earthquake.  And early in the new year NIWA scientists will be back out on a smaller boat the Ikatere, which can get closer to shore than the Tangaroa, to map how the onshore and offshore fault ruptures join up.

After taking a well-deserved break over the holidays, the geologists will begin analysing the mountain of data collected, to work out their piece of this earthquake story.  It’s likely that once the LiDAR and Ikatere data are analysed even more fault ruptures will be discovered, and they’ll then have a better idea of the total movement that has taken place.

Further down the track they’ll also be looking at the connections and gaps between the faults and what this means for seismic hazard modelling.  Is there evidence for these faults having ruptured together before? And is this normal?

We'll update you next year on this research, which gives us a window into understanding not only this earthquake but how New Zealand reshapes itself through earthquakes over millions of years.

A new kink in the landscape at the Papatea Fault, north of Kaikoura. Photo by Julian Thomson. The damage fault rupture can do - most of our buildings and infrastructure can handle quite a bit of shaking, but don't do so well when a fault ruptures through them. Photo by Jarg Pettinga.

View Online Helen Jack 2016-12-22T02:56:16Z

Landslides, dams, and a reminder to take care in the outdoors over the holidays

Thu, 22/12/2016 - 10:24

Blog post edited by Helen Jack

While uplifting land along the Kaikoura and Marlborough coasts, the magnitude 7.8 Kaikoura earthquake was also busy shaking a fair bit of land down.

The earthquake triggered thousands of landslides throughout North Canterbury, Kaikoura and Marlborough, and some of these dammed rivers and streams behind them.  Our landslide team have spent many hours mapping and monitoring these landslide dams along with staff from Environment Canterbury and Marlborough District Council, and colleagues from the US Geological Survey.

Going into the Christmas break there are still many potentially active landslide and rock fall areas, and landslide dams with water ponded behind them, from North Canterbury into Marlborough.  You'll need to be particularly careful if you are doing anything near a river, or heading into the back country in this area over the coming months.

 What are the landslides and landslide dams up to?

Area where landslides have occurred from the Kaikoura Earthquake. Mt Cookson Landslide. Photo by S Cox.

Over 80,000 landslides and rockfalls have occurred throughout North Canterbury, Kaikoura and Marlborough, particularly in the Seaward Kaikoura Range, the Amuri Range, the hills between the Inland Road and State Highway 1, and the lower country of the Conway, Leader and Stanton rivers.  Using helicopters, GPS, aerial photos and satellite imagery we’ve now mapped 196 places where landslides have dammed rivers, blocking or restricting the flow.  Many rivers have multiple dams – up to four or five in some cases.  Some of these dams are soft rock dams formed by large chunky slumps of soft mudstone, and some are hard rock dams formed by rock falls or avalanches (really large tumbly rock falls) of hard rock.

Most dams will break (fail) within a year by either overtopping and erosion during or immediately after heavy rainfall, or by internal erosion and collapse. Others may stay put and become permanent features with water running over or percolating through the dam (see our previous story to find out more about what landslide dams are and how they behave).  As there is yet to be any heavy rainfall since the earthquake the newly disturbed river catchments are yet to be put to the test. 

Most of the 196 mapped landslide dams are small and pose little risk, but we’ve been actively monitoring eleven landslide dams in the Conway, Gelt, Hapuku, Leader, Linton, Medway, Ote Makura, Stanton, Towy, and Waima catchments that could cause a flood wave and damage in downstream areas should they break.  Large lakes have formed behind the dams in the Conway, Linton and Hapuku catchments. 

Landslide on the Leader River. Photo by S Dellow.

One of the monitored dams on the Towy River, a tributary of the Conway River in the Amuri Range, has failed already.  One of the least stable dams, the water ponded behind it overtopped and cut a channel through the dam between 2 and 5 December, releasing a series of gravel-laden flood waves that reached about 1km down the river.

As well as monitoring the landslide dams, our scientists have been modelling how much downstream land could be flooded if the dams break in a worst case scenario (i.e. if the dam fails all in one go and all the water behind it is released). 

We’ve now handed over monitoring of the dams to Environment Canterbury and Marlborough District Council.  You can keep up to date with the latest on the Canterbury dams on Environment Canterbury’s webmap.

What you need to be aware of – in rivers, the back country and the coast

People should stay out of stream channels and river beds wherever possible from the Waiau River north to the Awatere River.  Landslide dams could fail at any time, but particularly during or immediately after heavy rainfall or an aftershock, creating a sudden flood downstream.  A lot of sediment is now flowing into river and streams, causing rivers to behave less predictably.  If you see one of your mates in their digger in the riverbed, you may like to politely point this out (once they are out of the river – don’t put yourself in danger).   Also, pitching your tent right beside a river is also probably not the wisest move – camping on an open elevated area is better. 

It may be difficult to tell if a landslide dam suddenly fails upstream.  Tell-tale signs include changes to the water colour (usually to a dirty brown colour) and strange or loud noises from the river valley.  These are cues to get out of the way. Landslide dams might not fail all in one go, so don’t assume that the danger has passed if there is a flood wave.   

Backcountry users should expect walking tracks and routes, and 4WD tracks to have changed significantly.  There are treefalls, landslides and rockfalls, loose rocks and cracks in the ground right through North Canterbury, Kaikoura and Marlborough and further landslides and rockfalls are likely during heavy rainfall or in an aftershock.  Some tracks are now covered with rock or sections have collapsed, requiring major work before they can be used again, and Barratts Bivvy in the Hapuku catchment was destroyed by a rock avalanche.  What may have been a relatively easy walk or drive may now be much harder and longer.  Streams and rivers may have new pools and rapids and vehicle river crossings, including entry and exit points, may have changed.

The Department of Conservation has closed all huts from the Seaward Kaikoura Range north to the Chalk Range, including the Clarence Reserve and the Isolated Hill Reserve (Sawcut Gorge).  These huts all need further earthquake damage assessments in the New Year, and access to them is also dangerous in places.

We recommend you check out the Department of Conservation website and have a yarn with local farmers about your planned route before heading into the hills.

People visiting the coast should also be aware of the potential for further land movement.  There were many landslides off the coastal hills and cliffs from the Waipara River to Cape Campbell during the earthquakes and rocks will continue to fall off these for some time.  Uplift of the seabed along this area may also have changed the depth of reefs or the pattern of rips and currents.

People-made dams

We’ve had few questions about farm dams.  The safety of farm dams is the responsibility of the dam owner.  If you have a farm dam you should check it for any damage and if you have concerns you should engage an engineer to investigate.  For more information you can contact Environment Canterbury or Marlborough District Council.

Updates

Staff at Environment Canterbury and Marlborough District Council are now monitoring the landslide dams and assessing how the increase in gravel in the rivers will affect future flooding. You can keep up to date with the latest developments on their websites. 

We plan to continue mapping and studying the landslides triggered by the earthquake throughout North Canterbury, Kaikoura and Marlborough over the coming months and will keep you updated on what we find.

 



View Online Helen Jack 2016-12-21T21:24:22Z

Updates on volcano visits

Wed, 21/12/2016 - 15:55

Blog post edited by Brad Scott

Over the last couple of weeks, the GeoNet volcano team has been busy making the most of the few fine days we have seen lately. We have visited Ruapehu and White Island to make a series of observations and measurements and collect samples.

White Island (Whakaari)

On November 21 we completed a gas flight at White Island, where we measure sulphur dioxide (SO2), carbon dioxide (CO2) and hydrogen sulphide (H2S). The gas output was down slightly on the October flight. The sulphur dioxide (SO2) has ranged 230-420 tons per day, carbon dioxide (CO2) 1240-1730 tons per day and hydrogen sulphide (H2S) 15-35 tons per day.

The main vent(s) were less audible than in October, still producing a transparent plume at the base/vent which evolved into a vivid white steam plume. There is no lake. Over the last 2-3 months the small lake let on the crater floor was disappeared to leave 5-6 small depressions, some have water ponded in them. The water levels are variable as are the colours of the pools, some are grey and active, others blue/green and passive.  We estimated the water levels varied by 2-3 m.

A levelling survey was completed on December 20 to ascertain the amount of ground deformation across the crater floor. Changes show subsidence (20 mm+) focused on the active crater area. Fumarole ‘Zero’ remains very hot, we measured 182 °C. It was 178 °C in October.

We used drones to obtain photography of the active crater area so we can build a new map. We also sampled the gases from the main gas plume using a drone. Maintenance was also completed on the web cameras.

Ruapehu

On December 17 we completed a gas flight at Ruapehu, our first successful flight for months. We measure sulphur dioxide (SO2), carbon dioxide (CO2) and hydrogen sulphide (H2S). The gas output was up slightly on the August flight. The sulphur dioxide (SO2) has ranged 19-22 tons per day, carbon dioxide (CO2) 240-640 tons per day and hydrogen sulphide (H2S) 0.6-1.6 tons per day since July.

The Crater Lake was visited to sample the water and collect gases on December 20. The lake temperature was 21.7 °C. Lake was a battleship grey colour with more blue grey water near the lakeshore due to meltwater going into the lake. The central vent was very slightly distinguishable in the right light conditions. The north vent area had a lot of sulphur slicks nearby.

Lake level appeared to be on the high side (summer melt) and the flow at the outlet was estimated at 60-80 L/sec.

Crater Lake temperature has been cooling since early October, when it reached 40 °C. For the last 2-3 weeks it has been around 24-22 °C.

Mercury Project:

As part of a collaboration with the University of Toronto (Canada) several passive air samplers are being installed on the active volcanoes and in large geothermal areas. These will measure mercury and its isotopes concentrations. The main purposes of the project are to characterize the sources of Mercury and monitor the spatial distribution of Mercury into the atmosphere.

Mercury samplers at White Island White Island active crater Ruapehu Crater Lake temperatures Ruapehu Crater Lake

View Online Brad Scott 2016-12-21T02:55:08Z