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GeoNet team and GNS scientists depart for Kermadec Islands

Fri, 24/03/2017 - 10:00

Blog post edited by Helen Jack

The HMNZS Canterbury has departed for the Kermadec Islands (1000 km NE of Auckland) transporting 60 personnel and about 15 tonnes of equipment and building materials to Raoul and Curtis Islands. Included in this large group are two GeoNet teams and a GNS Science team. GeoNet in collaboration with DOC and LINZ operate a variety of equipment on Raoul Island. We have a regional seismic station (RIZ), the regional GPS station RAUL, VSAT communications and tide gauges at two sites, along with equipment shared with DOC for the volcano monitoring.

The GeoNet electronics team and three commercial divers will be upgrading and hardening one of the two tsunami gauge sites on Raoul Island. We run two sites (with 2 gauges at each) due to the very exposed conditions on the island to provide redundency and reliability.  Tsunami gauges have been installed around the New Zealand coast and on offshore islands and they transmit the relative sea level data in real time to the GeoNet Data Management Centre. They can provide confirmation that a tsunami has been generated. The Ministry of Civil Defence and Emergency Management (MCDEM) is responsible for the dissemination of national official tsunami notifications in New Zealand.  

Raoul Island as an active volcano and Green Lake has been the focus of volcanic activity in 2006, 1964, 1870 and 1840. There was also activity in Denham Bay during the 1870 and 1840 eruptions when an island grew out of the sea. The GeoNet volcano chemistry team will be busy sampling the volcano and geothermal features at Green Lake.

A further team of GNS Science staff will also conduct research work on Curtis Island, a small volcanic island about 150 km SW of Raoul Island. The island has an active geothermal system. A Seasprite helicopter will be used to transport the team ashore. 

The GeoNet teams last visited Raoul Island in September 2016 with support from the offshore patrol vessel HMNZS Otago and a Seasprite helicopter. GNS Science last visited Curtis Island in 2003.

Raoul Island Curtis Island

View Online Helen Jack 2017-03-23T21:00:16Z

Earthquake forecasts – So why do we do earthquake forecasting?

Wed, 22/03/2017 - 10:21

Blog post edited by Helen Jack

21/02/2017

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 2017-03-21T21:21:53Z

Update: Swarm to west of Tokaanu (Turangi) continues

Tue, 14/03/2017 - 16:41

Blog post edited by Sara McBride

22/02/2017

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 Sara McBride 2017-03-14T03:41:29Z

1987 Edgecumbe Earthquake: 30 years ago today

Tue, 14/03/2017 - 16:41

Blog post edited by Sara McBride

02/03/2017

At 1:42pm on 2 March 1987 a large earthquake occurred in the northern Bay of Plenty, near the town of Edgecumbe. The M6.5 event was soon named after the town. It was, with the exception of the Inangahua earthquake in 1968, the most severe and damaging earthquake to hit New Zealand in 45 years.

We sat down with our Brad Scott, who was there at the time. He was one of the first science responders on the scene.

Q. How widely was the earthquake felt and what did you feel?

Brad: The quake was felt over most of the North Island, including Rotorua, Hamilton, Taupo, Napier and Gisborne. An interesting feature of the Edgecumbe event was the foreshock sequence.

At the time of the earthquake Steve Sherburn (one of our other volcanologists) and I were installing a portable seismograph in a quarry in the Papamoa Hills to record the earthquakes that were happening near Te Puke. We were bouncing down the 4x4 trail at the time and we didn’t realise it had happened. The VHF radio from the DSIR office soon woke up to inform us, then asked us to head towards Edgecumbe.

Q. What do you think were some interesting facts about Edgecumbe?

A. It was preceded by a number of foreshocks in the Matata and Thornton areas. Of the 126 located foreshocks, 93 occurred of these occurred off the Te Puke coast, and the DSIR was focusing its attention in that area. One of the largest foreshocks was of M4.9, and occurred only 7 minutes before the main shock.

The location of the foreshocks


Q. How much damage was caused by the earthquake and how were people affected?

A. Luckily, a number of buildings were evacuated in response to this foreshock and were consequently empty when they were damaged in the main earthquake. There were in fact no fatalities, but 25 injuries requiring medical attention were recorded. One vision I’ll always remember was the large number of holes in roofs where chimneys had fallen through.

Q. What was it like when you went out in the field? What kind of earth movement did you see?

A. In the Rangitaiki Plains the quake ruptured the ground to create a spectacular 15 km long surface fault rupture. The fault displaced the ground vertically and up to 3m of height change was measured in places. The Rangitaiki Plains area is part of the Taupo Volcanic Zone (TVZ); a rift ranging from Ruapehu in the south to White Island of the Bay of Plenty.  The TVZ rift opened 1.2 m during the Edgecumbe earthquake. That is, the distance between Matata and Whakatane increased by 1.2 m. Today the GeoNet GPS’s record about 9 mm of extension each year across the TVZ in this area.

Steve and I spent about 2 hours trying to navigate ourselves into the area, however every road we tried was block by landslides. Eventually we by-passed some down on the coast by driving along the railway line. At Te Teko we could see the fault rupture across the other side of the river but the bridge was moving 6-10 inches from its abutment and we didn’t want to take it on. The bridge is famous as it was one of the first to use the DSIR lead-rubber bearings and was shown to be undamaged.

  Damaged railway Fault crossing the Rangitaiki River Fault crossing McCracken road Fault crossing farm yard

 

Q. Were there aftershocks after the initial earthquake?

A. Yes. Like all large earthquakes the Edgecumbe event was followed by an aftershock sequence. In the 3 years after the main shock over 470 events were located.

Locations of the aftershocks

 

Want to know more about Edgecumbe? Find out more here:

Links:

https://goo.gl/PoYVXd

https://goo.gl/uJ1utV

 


 


View Online Sara McBride 2017-03-14T03:41:02Z

Busy time for small earthquakes in the Taupo Area

Tue, 14/03/2017 - 16:40

Blog post edited by Sara McBride

09/03/2017

Taupo, like Rotorua, Reporoa, Ngakuru and Turangi, lies within the area called the Taupo Volcanic Zone. This is an area where many large caldera volcanoes and geothermal systems are present and is also an area where small earthquakes are frequent. The earthquakes often occur as swarms. 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 residents of Taupo often feel small earthquakes and Tuesday afternoon was no different. Two small events, 2 minutes apart were widely felt locally. The earthquakes were small (under M2.3), shallow and located to the north of Centennial Park. Around 200 people reported each event. Small earthquakes are very common in this area and tend to cluster about the Wairakei-Tauhara and Rotokawa geothermal areas. Some also occur out in the lake area. In the last year GeoNet has recorded and located 152 events. Only four of them are larger than M3; the largest event is M4 and occurred at 10.12 pm on 2 January 2017 near Rotokawa. 

The residents of the Turangi-Waihi-Pukawa-Omori area have also been experiencing earthquakes over the last few weeks. A swarm has been on going to the west of there since Monday 13 February. To date GeoNet has recorded and located 587 earthquakes in this swarm, the largest event is a M3.8 on 21 February at 9.35 pm. There have only been four events larger than M3 in the swarm. The number of events per day is slowly declining and only 52 were located in the last week. The events are occurring between about 4 and 10 km depth and most are smaller than M2 (550 of the 587 to date). The Taupo Volcanic Zone is a rifting area, growing wider each year by 6-9 mm. These earthquakes are located on the western boundary and 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 all earthquakes to date in the Turangi swarm Location of earthquakes near Taupo in last 12 months

View Online Sara McBride 2017-03-14T03:40:33Z

Watching out for Auckland’s next eruption; from a vent that doesn’t exist yet

Tue, 14/03/2017 - 16:39

Blog post edited by Sara McBride

10/03/2017

The Auckland Volcanic Field (AVF) is uniquely different from the well-known volcanoes in New Zealand in that each eruption occurs from a new location and the volcanoes do not erupt twice; Rangitoto is the only known exception, as it has erupted at least twice. Globally very few eruptions have occurred historically from volcanic fields so we do not have a lot of knowledge of what happens before an eruption. Traditionally, monitoring an active volcano is based around recording seismic signals, ground deformation and gas or water chemistry. When we do not know where the next vent might be we are left with just one method to use; earthquake recording.

The DEVORA research project has been looking at many aspects of volcanic activity in Auckland, including possible eruption precursors. This has involved looking for historical examples of similar eruptions elsewhere in the world. Was there volcanic unrest?  How did it manifest?  One of the common unrest indicators is earthquake activity. Another clue can be found in the rocks that the volcano has erupted. Many signals are preserved in the crystals and they tell us about the journey the rocks have been on. From this work, we know the Auckland magmas start out from great depth (80-100 km). We also know that they rise relatively fast and don’t appear to stall on the way. What is not clear is what signals these processes will make. Will they make many or just a few earthquakes? How big will the earthquakes be? What type of earthquake will they be? Will there be volcanic tremor?

View of Mt Victoria volcano View of Mt Mangere volcano

 

Based on these challenges GeoNet has had to devise the monitoring in Auckland around a seismic network that covers all the known locations of volcanoes. The Auckland Volcanic Field spans about 27 km north-south and 19 km east-west and underlies a major city. There is no geothermal system and we will not see any ground deformation until shortly before the eruption starts. The greatest issue is cultural noise (the city) and this stops us seeing small earthquakes. This is overcome by using borehole sensors. Auckland Regional Council (ARC) started building a near-real time seismic network in 1993 with NZ Geological Survey and this was operational from the mid 1990’s. The network was connected to the GeoNet project in 2003. At that time, there were 5 seismic sensors in the Auckland area, four of which were in boreholes.

Starting in 2006 GeoNet upgraded the network by adding 3-component sensors and then by adding more borehole sensors and increasing the area covered. Today the seismic sensors in Auckland are fully integrated into GeoNet. We operate seven 3-component borehole sensors, 1 single component borehole site, three 3-component sites and 4 strong motion sites. Since 1994 we have recorded and located 372 earthquakes in the greater Auckland area, about 16 a year. None of these appear to be related to volcanic processes. 

Locations of earthquakes in the Auckland area Map showing the locations of the seismic stations in Auckland

View Online Sara McBride 2017-03-14T03:39:53Z

NIWA’s offshore mapping adds more faults to the latest Kaikoura fault rupture map

Tue, 14/03/2017 - 16:20

Blog post edited by Sara McBride

06/03/2017

The latest fault rupture map now includes detailed offshore mapping (click for a bigger version)

The results of NIWA’s sea floor mapping off the Kaikoura and Marlborough coast are now in, adding even more fault ruptures to the fault map of November’s magnitude 7.8 Kaikoura earthquake. Scientists on board NIWA’s research vessel Ikatere took to the water in January with state-of-the-art equipment to map the sea floor between Cape Campbell and Spyglass Point to the south of Kaikoura.   Ikatere is a smaller boat than Tangaroa so it can get closer in to the shore to map how the onshore and offshore faults link up.  You can see the team at work in this NIWA video.

What did the Ikatere voyage uncover?

The scientists discovered a previously unknown fault in the sea bed about 10km north east of Kaikoura Peninsula.  This new fault has been named the Point Kean Fault after Point Kean at the tip of the peninsula.  While it is not clear how much this fault moved during the earthquake, it is likely to be the fault responsible for the uplift around Kaikoura Peninsula.

The Papatea Fault where it heads offshore – the grey, pink and purple are above sea level, and the turquoise and green are below. Source: NZTA/NIWA.

To the north, the Papatea Fault rupture leaves land and breaks into a complex network of seafloor scarps up to 6 metres high continuing for about 5km offshore.  The image to the right shows the onshore lidar (high resolution topography) data stitched together with the offshore lidar and new sea bed mapping to reveal two traces of the Papatea Fault cutting the beach and the sea bed. 

While movement on the Needles Fault had been detected by scientists on board Tangaroa shortly after the earthquake, Ikatere was able to map it in more detail.  Rupture along the fault was traced along the sea bed for a total of 34 km, from Cape Campbell in the north to where it connects up with the onshore Kekerengu Fault in the south.

The southern-most offshore fault, the Hundalee Fault, was mapped from where it enters the sea at Oaro to near the head of Kaikoura Canyon.  Comparing the bathymetry data here to pre-earthquake data from 2013 shows a clear 2 metre high scarp formed in the sea bed, but it doesn’t appear to go all the way into the canyon.

As well as mapping fault scarps, the NIWA scientists also mapped the sea bed in the Kaikoura Canyon, just to the south of Kaikoura Peninsula, to determine any changes to its shape.  Comparing this new data to the 2013 data reveals that huge amounts of mud have been shaken from the top of the canyon – more than 1000 landslide scars have been mapped along 30km of canyon rim.  This mud tumbled down into the canyon floor and flowed over 350km along the deep sea Hikurangi Channel, wiping out everything in its path.  You can read more about the impact of these mudslides on the Canyon ecosystem on the NIWA website.

Meanwhile, back on land...

A new record for the North Canterbury faults – what looks like a landslide is actually a 4 metre high fault scarp. Photo: Clark Fenton, University of Canterbury.

Geologists from GNS Science, University of Canterbury and Victoria University have continued their field mapping of fault ruptures from North Canterbury through to Marlborough.  A new record displacement for the North Canterbury faults of 4 metres was measured on the North Leader Fault.

And back in the office, two new surface ruptures have also been discovered after analysing the lidar data along the coast to the north of Kaikoura – one north of the Kekerengu Fault at Tinline Downs and one crossing Papatea Point.  There’s lots more lidar to come, so geologists could yet discover more small surface ruptures like these that can be hard to see in the field.

Science contacts: Dr Joshu Mountjoy (NIWA) and Dr Nicola Litchfield (GNS Science)

Deployment of Ikatere was made possible by MBIE funding to the Natural Hazards Research Platform for immediate response to the Kaikoura earthquake.

View Online Sara McBride 2017-03-14T03:20:15Z

1987 Edgecumbe Earthquake; 30 years ago today

Thu, 02/03/2017 - 09:42

Blog post edited by Brad Scott

At 1:42pm on 2 March 1987 a large earthquake occurred in the northern Bay of Plenty, near the town of Edgecumbe. The M6.5 event was soon named after the town. It was, with the exception of the Inangahua earthquake in 1968, the most severe and damaging earthquake to hit New Zealand in 45 years.

We sat down with our Brad Scott, who was there at the time. He was one of the first science responders on the scene.

Q. How widely was the earthquake felt and what did you feel?

Brad: The quake was felt over most of the North Island, including Rotorua, Hamilton, Taupo, Napier and Gisborne. An interesting feature of the Edgecumbe event was the foreshock sequence.

At the time of the earthquake Steve Sherburn (one of our other volcanologists) and I were installing a portable seismograph in a quarry in the Papamoa Hills to record the earthquakes that were happening near Te Puke. We were bouncing down the 4x4 trail at the time and we didn’t realise it had happened. The VHF radio from the DSIR office soon woke up to inform us, then asked us to head towards Edgecumbe.

Q. What do you think were some interesting facts about Edgecumbe?

A. It was preceded by a number of foreshocks in Matata and Thornton areas. Of the 126 located foreshocks, 93 occurred of these occurred of the Te Puke coast, and the DSIR was focusing is attention in that area. One of the largest foreshocks was of M 4.9, and occurred only 7 minutes before the main shock.

The location of the foreshocks


Q. How much damage was caused by the earthquake and how were people affected?

A. Luckily, a number of buildings were evacuated in response to this foreshock and were consequently empty when they were damaged in the main earthquake. There were in fact no fatalities, but 25 injuries requiring medical attention were recorded. One vision I’ll ways remember was the large number of holes in rooves where chimneys had fallen through.

Q. What was it like when you went out in the field? What kind of earth movement did you see?

A. In the Rangitaiki Plains the quake ruptured the ground to create a spectacular 15 km long surface fault rupture. The fault displaced the ground vertically and up to 3m of height change was measured in places. The Rangitaiki Plains area is part of the Taupo Volcanic Zone (TVZ); a rift ranging from Ruapehu in the south to White Island of the Bay of Plenty.  The TVZ rift opened 1.2 m during the Edgecumbe earthquake. That is the distance between Matata and Whakatane increased by 1.2 m. Today the GeoNet GPS’s record about 9 mm of extension each year across the TVZ in this area.

Steve and I spent about 2 hours trying to navigate ourselves into the area, however every road we tried was block by landslides. Eventually we by past some down on the coast by driving along the railway line. At Te Teko we could see the fault rupture across the other side of the river but the bridge was moving 6-10 inches from its abutment and we didn’t want to take it on. The bridge is famous as it was one of the first to use the DSIR lead-rubber bearings and was shown to be undamaged.

  Damaged railway Fault crossing the Rangitaiki River Fault crossing McCracken road Fault crossing farm yard

 

Q. Were there aftershocks after the initial earthquake?

A. Yes. Like all large earthquakes the Edgecumbe event was followed by an aftershock sequence. In the 3 years after the main shock over 470 events were located.

Locations of the aftershocks

 

Want to know more about Edgecumbe? Find out more here:

Links:

https://goo.gl/PoYVXd

https://goo.gl/uJ1utV

 


 


View Online Brad Scott 2017-03-01T20:42:32Z

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.

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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