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Introducing GeoNet’s new website!

6 hours 18 min ago

Blog post edited by Sara McBride

Over the past few months, we’ve been busy developing our new website. We will be launching it on 1 June!  There are a lot of changes that we’ve made to improve the website, some you can see and some you can’t.  But first, let’s go over why we needed a new website and what features are improved.  You can check out the new website here.

Here's what new about the GeoNet website

  1. Our old website was reliant on older technology and just wasn’t meeting current standards required for GeoNet. The last time we did such a major overhaul of the website was in 2012, that was five years ago! That is ages in the Tech World. We must ensure 100 percent service all the time and, with the older standards, that service level was becoming harder and harder to ensure with the outdated website.
  2. We brought back the earthquake map on the home page. The popular “big map” dates to before we launched the last website in 2012. We used to have a big map that showed exactly where earthquakes had occurred but it was slow and made the page difficult to load.
  3. The design is cleaner and easier to navigate. We’ve also gotten rid of the info website, so you’ll only have to go to one place now.
  4. Mobile accessibility on smart phones and tablets on the old website was a big issue. So, we’ve fixed that.
  5. The information that our older website provided was outdated, so we’ve reviewed some of it and are in the process of re-writing some of the older information.
  6. It was difficult to find all the hazards we monitor, specifically landslides.  Try finding landslide information on the old website; it is not that easy! So, we’ve added it onto the navigation bar.
  7. Letting you see the back end: now, when you click on an earthquake, you can check out our new “technical” tab. This tab gives you a lot more information on the event, like how many stations we used to locate the earthquake
  8. Volcanic alert bulletins are now a lot easier to find. Our volcanic alert bulletins are one of the most important pieces of information we put out and under the “news” category on the old website, these often got buried in all the other stories. Now it is easier to find and locate specific Volcanic Alert Bulletins.
  9. Felt reports can now be filled out from the home page directly and we’ve added a permanent link to Felt Detailed, if you want to provide more feedback.
  10. You can find QuakeSearch, Earthquake Catalogue, and Slow Slip information a lot faster on this website. It often took a lot of digging around into the older website to find those services. 

Updates for our technical users

If you were using the old website, you’d probably agree that finding important data streams were difficult to find. Now data has a much better defined section and is easier to find information you are looking for. Also, you can access our GitHub directly from the homepage now, if you are that way inclined.

If you don’t like the new website, don’t panic!

Now, we don’t expect this new website to be perfect, and we know that no website is ever finished!  Take a test drive of the website and let us know your thoughts here.

We’ll be drawing the prizes at the end of June, for those who complete the survey (hint: it involves this t-shirt, as well as the kitten/volcano one. Your choice). 

 

View Online Sara McBride 2017-05-29T03:30:34Z

Explosive Shortland Street’s 25th Anniversary Show includes a volcanic eruption: is this a thing?

Fri, 26/05/2017 - 10:11

Blog post edited by Sara Page

Thursday 25 May 2017

Celebrating 25 years of exotic cliff-hangers and plot twists, Shortland Street, a 25-year running New Zealand based soap opera, pulled out all the stops, including a volcanic eruption for its 25th anniversary show.

And what was GeoNet’s part in all of this? Well, six weeks ago our volcano team, were approached by a research-writer of the show, asking for some guidance. We played our hand at being consultants on the possibilities and realities of an Auckland volcanic scenario.  The producers provided several scenarios but we were not told which one would make it on screen. So, we had some inside knowledge of what was planned to mark the 25th anniversary, but the details of how the story would play out on screen were kept a hot secret.  We were also sworn to secrecy not to reveal any details of the upcoming story lines.

Because we didn’t know the outcome of the scenario, our duty team was then given an unusual assignment: watch Shortland Street (some never have!). We admit that our volcanology team were erupting with excitement as they settled in for the 90-minute show. Then, they were given the task to report back on what was fact and what was under “creative license”.

Here’s what the team had to say:

The story line did a great job drawing out several key themes that are related to volcanic events. The major ones covered are;

  • earthquakes are a credible part of volcanic unrest that occurs before an eruption. 
  • People will be unsettled or saying it's nothing (a natural reaction). 
  • Once the eruption started many themes were covered, like people putting table napkins on as masks (bandit style), these will only give a very low level of protection, but in an emergency are better than nothing.  
  • The phone and power problems (engineering lifeline issues) are very real. 
  • It was good to see the gas hazard; may have been overplayed with deaths/affects. 

Some aspects of the volcanic eruption were portrayed poorly:

  • Ash density was one issue...it was too light and stayed in the air too long, the use of low visibility was good though.
  • The eruption was over quickly; in real life, it would last a lot longer.  

Overall though, aspects of the volcanic hazards were portrayed well. There was no lava, that is credible at the start of an eruption.

The questions regarding ash toxicity were good, this is usually not too much of a health issue, and may cause irritation and inflammation of the eyes and possibly skin. And may cause more problems for those with pre-existing respiratory illnesses. The story line depicted the risks of trying to work and move in an ashy environment quite well…. best to avoid all travel outside. Ash ingress to buildings would have been higher with the amount of door openings. Also, it seemed like there was a lot of self-evacuation, no evacuations by officials - credible if onset is this fast. The story line was very low on official responses, CDEM messages, GeoNet messages, Volcanic Aert Levels etc. However, gas and wind modelling was covered.

Many aspects of the human responses were well covered; people been scared and anxious – this is likely. Also, people reuniting-understanding where and how friends/family are being a real priority for many, and challenging. Domestic violence increasing during and after disasters is credible. However, the use of ash masks as gas masks, is not credible. People giving birth, life goes on during a disaster.

Having viewed the show, ourselves, we think it’s reasonable that you all may be wondering “Could this really happen?” (or maybe some of you aren’t)

Regardless, here’s a bit more detail and explanation about the Volcanic Auckland Field. The Auckland Volcanic Field (AVF) is a unique volcano environment in New Zealand. Rather than the volcano being in a fixed location like Ruapehu or Taranaki, each volcano in Auckland is in a new location; naturally there is an exception and that is Rangitoto Island. It has erupted 2, maybe 3 times, and the only volcano in Auckland to have done that. The last eruption in the AFV was about 600 years ago.

Aside from the mixed feelings around the quality of acting and portrayal of the volcanic impacts we have, our overall opinion of the Shortland Street episode was an 8/10. It is rewarding to see geological processes are becoming a little more mainstream. GeoNet exists to help New Zealanders’ live with the hazards that make our country, well, our country. Volcanoes, Earthquakes, and all the events we experience are part of what makes us Kiwi’s. GeoNet likes to encourage conversations around our geohazards so a full episode on Shortland Street, especially when it’s Dr Chris Warner birthday, blew our expectations.

Quote of the show:

“I’ve come from the mountain.  This is a cleansing fire, only the strong will survive”

Thanks to the Shortand Street team for talking to us about this project. Well done.

 

View Online Sara Page 2017-05-25T22:11:00Z

How robust are our volcano monitoring networks?

Fri, 21/04/2017 - 13:49

Blog post edited by Caroline Little

Written by volcanologist Geoff Kilgour: 

Dino (bottom right) enjoying today's sunshine on White Island

Here at GeoNet we like to test the performance of our network under difficult circumstances. Sometimes we subject our systems to a “stress test” and a good example of this is when we monitor the performance of the website during unusually high demand, like after a large earthquake. Thankfully, we have some great minds that keep our computer systems up and running under very difficult circumstances so we know that we will be able to keep you informed throughout natural events.

Less well known is the ability of our physical networks (seismometers and GPS equipment) to operate under severe weather events. Last week, New Zealand felt the sting of Cyclone Cook as it sauntered south along the eastern side of the North Island. Its path intersected with our beloved White Island, New Zealand’s most active volcano.

On the island, we have a sophisticated network of sensors and communication equipment that streams data to our offices in near-real time, despite being around 50 km offshore. Over recent years, the network has been strengthened and there is now redundancy built in so that if a sensor or communication hub fails (e.g. is buried in an eruption) the data are still available for analysis. We thought that our world-class technicians had done an amazing job achieving this in a very acidic environment, yet we are now able to fully appreciate their efforts after Cyclone Cook swung by.

A week ago, White Island was battered by wind gusts from Cyclone Cook of up to 200 km/h and yet the network held its own. According to our senior volcano technician Richard Johnson “the network didn’t miss a beat”. Even Dino survived intact. So we are more confident than ever that our networks are robust enough to function as per normal during some of the most difficult weather conditions imaginable. All thanks to our skilful technicians.

View Online Caroline Little 2017-04-21T01:49:29Z

Message from the GeoNet Director: Five months on, Kaikoura eq and tsunami are still teaching us

Fri, 14/04/2017 - 12:20

Blog post edited by Helen Jack

14/04/2017, 12 noon. 

I am sitting in my office on the last day before Easter looking out the window at the start of the rain from the second (ex) tropical cyclone within a week. Instead of using the normal physical markers as reminders of the changing of seasons, I count the days between the 14 November 2016 and now. Five months later, on the verge of winter, we are still in the thick of the science generated from the Kaikoura earthquake. 

What we learned this month
First and foremost, I’d like to acknowledge the huge amount of science understanding gained and shared. This is highlighted by the papers led by Ian Hamling, published in Science last month and Anna Kaiser, which is about to be published. These papers confirm what we know: the earthquake that rolled through Culverden, Waiau, Mt Lyford, Kaikoura, Ward and Seddon was more complex than we could appreciate early on in the response. That earthquake moved the South Island six metres closer to the North Island, with 21 faults moving in sequence in some sort bizarre choreograph movement, like a chorus line of dancers. Together they shaped and moved the South Island in ways we didn’t think were possible, but the impossible seems to apply to New Zealand regularly. 

I reflect back on the paper I led after the M7.1 Darfield Earthquake back in 2010; I thought we were fast at publishing, and that we knew a lot, but our effort back then was a pale shadow compared to what Ian and Anna and their co-authors have produced and published in five months. The use of InSAR (information from the satellites) is changing the face of geophysics rapidly. Ian and his team are at the forefront of that movement, sifting with amazing speed through the avalanche of data, and Anna and her team were close behind with a raft of techniques.

Speaking of awe, I’d also like to acknowledge Laura Wallace’s contribution of finding the South Island’s first ever recorded slow-slip event that was triggered by the M7.8 Kaikoura Earthquake.  It took us some time to determine exactly what happened, and some extra fieldwork to supplement data provided by our network. Land Information New Zealand (LINZ) has been providing us with funding for years to develop and sustain part of our GPS network, along with EQC. Because of this valuable network, we can keep on top of the slow-slip activity throughout New Zealand. Thanks LINZ and EQC! And, speaking of government support, another big thanks to the Ministry of Business, Innovation, and Employment, for helping us fund a large part of the science response to the Kaikoura earthquake.  

We can confirm there were huge land movements and shaking near Waiau, among the strongest ever recorded – more than twice the force of gravity. Compare that to passengers taking off in a plane who experience about 10% of gravity, while roller-coaster riders get 1g. The people of Waiau held on through shaking of a strength and violence I don’t like to imagine.

And then there are the landslides. I feel like I need a whole other message just to address our landslide team. Our landslide team have mapped over 5,000 landslides so far due to the earthquakes. Ex Tropical Cyclone Debbie complicated matters greatly, triggering further slips and slides throughout the country. Our beautiful mountains, newly (geologically speaking) arising from the seafloor, haven’t had much time to erode, making them very vulnerable to landslides. So our landslide team is run off their feet at the moment with the combination of earthquakes plus terrible weather.

Dr Ian Hamling

Naming the Kaikoura Earthquake

Thinking about the shaking in Waiau, there have been some issues raised about naming the earthquake the M7.8 Kaikoura earthquake. After all, the epicentre was closer to Waiau than Kaikoura. And Waiau experienced much stronger shaking, although we did not know that at the time. I will say that naming an earthquake is always a pretty difficult task. Some people would rather we never use their town or city’s name for an earthquake, while others feel that by not using their town’s name we are ignoring them. 

When considering naming an earthquake, we take into account a number of factors. It was very difficult to name an earthquake like the one that occurred on the 14 November. With so many faults implicated across more than 150 kilometres of land, and a mountain of data, it was hard to know where to start. In this case, we chose to use a town near the mid-point of the action, near the Kererengu fault, one of the earliest surface faults identified. Also, Kaikoura’s shores were battered by a tsunami reaching up to seven metres above sea level, and their shoreline was raised permanently.  But we did not intend to ignore other affected townships like Waiau, Culverden, Hanmer Springs, Ward or Seddon and I apologise if anyone feels they were ignored by us. My team and I think about those townships every day and we will continue to work on your behalf to understand this earthquake and its implications better. 

Cross sections showing the slow slip events  

A word about the GeoNet team

Small successes are everywhere; I’ve finally convinced ALL my team to take leave! Many worked over the summer holiday period, just too passionate and stuck into their work to take a break. It has not been an easy task to convince them to take a moment to step away from their computers. Indeed, it is the most challenging part of the job, to get the team to look after themselves.

Our GeoNet website will shortly be completely updated (22 May is tentatively our go live date); you can get a sneak peek here: beta.geonet.org.nz. We need your help to make it better, so please give your feedback.

Stepping away briefly from the science, I’d like to acknowledge the teams that keep us running behind the scenes and often don’t get much acknowledgement. During the Kaikoura earthquake, our website took a massive 250 million hits in 24 hours, peaking at 35,000 hits per second. And it held. We never lost connection to our website or our data streams, thanks to the hard work of our Platform and Development teams. We could not be GeoNet without them, so thanks to you!

Looking ahead for the six-month anniversary of Kaikoura, we’ll have some more exciting science stories planned!

Until then,

Ken Gledhill (with special thanks to my co-writer, Sara McBride, for keeping me on topic and ensuring I make sense!).

GeoNet Director 

 

 

 

 

 

 

View Online Helen Jack 2017-04-14T00:20:38Z

Debbie and the landslide dams

Sat, 08/04/2017 - 14:50

Blog post edited by Helen Jack

3.00pm Saturday 8 April 2017

Ex Tropical Cyclone Debbie has left a terrible path of destruction and sogginess throughout New Zealand this week. Our thoughts are with those who have been affected by the flooding and landslides and with everyone working hard in the response and clean up.

GeoNet’s landslide duty team has been kept busy, tracking where major landslides are occuring throughout the country. Several of North Canterbury and Marlborough’s landslide dams overtopped with the heavy rainfall but thankfully no one was directly impacted.

Because Ex Tropical Cyclone Debbie has been such a major event, we’ve launched a GeoNet response to map and document the landslides that have occurred throughout the North Island and upper South Island.  We’ll report back with our findings as we compile the information.  In the meantime you can help us out by dobbing in landslides to info@geonet.org.nz.  We’d love photos, but only take them if it is safe to do so – we don’t want any landslide martyrs.

The Hapuku dam breach channel (photo: GNS Science) Hapuku dam breach looking upstream showing the natural spillway (photo: Environment Canterbury) Hapuku dam breach looking downstream (photo: Environment Canterbury)

Landslide dam breaches

We were particularly interested in how the North Canterbury and Kaikoura landslide dams would hold up to Debbie’s heavy rain – up to 200 mm of rain fell over four days in the Seaward Kaikoura Range. 

Water level recorders showed that the biggest landslide dam – the Hapuku dam – overtopped at around 2am on Thursday and this was confirmed by the Hapuku webcam at first light.  But it wasn’t until yesterday that Environment Canterbury engineers and our landslide team were able to get up in the air to have a closer look at the Hapuku dam, and to see how the other landslide dams stood up to the deluge.

The Hapuku dam partially breached in what appears to be a combination of overtopping and erosion of seepage points on the dam face.  The water level in the lake behind the dam dropped by about 2 metres and water is now flowing through a cut in the dam crest and down a natural spillway.  As the river level drops upstream of the dam it is likely that the flow over the dam will stop as the lake level drops below the outlet level, but water will continue to seep through the dam as it did before.

Landslide dams in the Ote Makura (Goose Bay), Linton and Conway rivers also partially breached as floodwater overtopped them, eroding channels through the landslide material. 

Flood waves from some of these breaches could be traced for some distance downstream – lines of debris a few metres above the river bed being a telltale sign – but the flood waves decreased fairly quickly there were no reports of damage.  The risk posed by these dams is now significantly lower than it was.  Environment Canterbury has updated its landslide dam webmap with this new information and photos.

The GeoNet landslide team plans to survey the landslide dams over the next few weeks to get a better idea of how they breached.  They will be comparing their computer models with what actually happened, and will be reassessing the risk that the dams may still pose to communities and infrastructure downstream.

Debris and mud flows 

In addition to the landslide dams overtopping, the rain also picked up landslide debris initially triggered by the earthquake, creating debris flows that flooded parts of SH1 both north and south of Kaikoura and inundated part of a house at Rakautara.  Floodwaters also ponded in areas where land had subsided on the downthrown side of the ruptured faults, particularly around the Kekerengu Fault.

An increase in landslides and debris flows during heavy rain is normal after an earthquake. This event is a reminder that people living near slopes and driving on roads in the area affected by the Kaikoura earthquake need to take extra care during rain.

Linton dam breach looking downstream (photo: GNS Science) Ote Makura (Goose Bay) dam breach (photo: Environment Canterbury) Conway dam breach looking downstream (photo: GNS Science)

View Online Helen Jack 2017-04-08T02:50:27Z

'Summer' landslide round-up

Tue, 04/04/2017 - 12:49

Blog post edited by Helen Jack

The focus for our landslide team over the last four months has been mapping landslides in North Canterbury, Kaikoura and Marlborough from the M7.8 Kaikoura earthquake.  By mid-March they had mapped nearly 5,000 landslides from aerial photos and satellite imagery. You can read more in our earthquake landslide update, which includes some before and after photos of the partial collapse of one of the landslide dams.

But in the meantime, bits of the rest of New Zealand continued to fall down – here are some of the highlights (or for some people, lowlights).

Wai Pingau Stream, Taranaki

Landslide at Wai Pingau (photo: Matt Newton)

A large landslide into the sea was spotted by a helicopter pilot just south of the Wai Pingau Stream, north of Urenui near the Whitecliffs walkway on the Taranaki coast on 8 November.   Although it can't definitely be attributed to an earthquake, there was a magnitude 5.1 earthquake, 10 kilometres north of Opunake (about 75 km away) at 6am on the same morning which was felt across the region.

November rain

Bookending the 14 November earthquake were two heavy rainfall events in Wellington and the upper South Island.  82 mm of rain fell in 24 hours in the capital on Friday 11 November, which is more than half the average rainfall for November.  Radio New Zealand reported that the rain triggered more than 70 landslides in Wellington.  Although none were major, 11 houses in Mornington and Kaiwharawhara were evacuated as a precaution. 

Known landslides in Wellington from the 15 November storm (click for a larger map)

Four days later, on 15 November, as if a major earthquake the day before wasn’t enough, a further months’ worth of rainfall fell in the Wellington area – 90 mm at Upper Hutt and Lower Hutt and 116 mm at Battle Hill in less than 24 hours.  Landslides closed SH1, SH2 and SH58, and caused damage to properties in Aro Valley and Owhiro Bay.  Houses were also evacuated in Island Bay, Paremata, Porirua and Pukerua Bay.

On the other side of the Strait, a huge 251 mm of rain was recorded in 48 hours at Rai Valley between Picton and Nelson.  Landslides closed Queen Charlotte Drive, Kenepuru Road, Titirangi Road, and Awatere Valley Road, and reduced SH6 near Havelock and Takaka Hill Road to one lane.  Arthur’s Pass and Lewis Pass roads were also closed because of flooding and landslides, bringing travel in the upper South Island to a standstill, with SH1 closed along the Kaikoura coast.

Elephant Rock loses trunk

Apart from the Kaikoura Inland Route and SH1 south of Kaikoura reopening, the most exciting landslide news in December was the loss of Elephant Rock’s trunk.  Elephant Rock, near Tongaporutu's Three Sisters on the Taranaki coast, partially collapsed on 5 December, leaving it trunkless.

 

January’s West Coast weather bomb

Central and southern New Zealand were hit by a rapidly deepening low pressure system on 18 and 19 January – an unusual event during summer – which brought wind, rain and more unwelcome cold.

Deception Point rockfall near Otira (photo: NZTA)

The South Island West Coast was worst affected by the heavy rain, with more than 250 mm of rain recorded in 24 hours at Arthur’s Pass.  This rain triggered landslides which closed SH73 from Arthur’s Pass to Jacksons, the largest of which was at Deception Point where 20,000 m3 of rock – the equivalent of two Cardboard Cathedrals – covered the road. (A further 3,000 m3 of rock fell here during heavy rainfall on 1 February.)  In Otira a landslide moved a shed, destroyed a car and diverted a creek through a house. 

Landslides also closed or reduced to one lane SH7 from Culverden to Springs Junction, SH6 between Murchison and Greymouth and SH65.

And in sad news for SH7 travellers and après tramping enthusiasts, the Sylvia Flat hot pools in the Lewis River near Lewis Pass were buried by a landslide from the eroding bank above the pools.  However, it’s likely that the Lewis River will eventually move the landslide debris further downstream and the pools can be dug out again for the enjoyment of those who don’t mind braving the rabid sandflies.

And a bit further afield in the Manawatu, in what may or may not be a related event, a landslide from the banks of the Rangitikei River, 12 kilometres south of Mangaweka partially dammed the river. The landslide initially appeared to have blocked the entire river channel but by mid-morning the river had cut a 10-metre wide channel through the landslide material – a relatively soft mudstone – allowing water to flow through. 

Not an eruption, just a landslide

Trampers in Tongariro National Park reported some large rockfalls on the northern side of Mt Ngauruhoe in late January. The Department of Conservation released a statement saying there was no indication that the rockfalls were caused by an earthquake or volcanic activity, but were instead triggered by high rainfall over the previous few days. 

Horowhenua Waitangi weekend rainfall 

Horowhenua District Council had to shut off Levin’s water treatment plant and issue boil water notices after continuous rain in the Ohau River catchment triggered landslides which muddied the water.  The rain also triggered a landslide on Gladstone Road near Levin, which blocked access to 35 properties.

Footstool rockfall, Mt Cook National Park

Footstool rockfall site (photo: Sam McColl) (click for larger image)

Dr Sam McColl, a lecturer in physical geography at Massey University, noted a large rockfall from the Footstool near Mt Cook on 20 February.  The Department of Conservation asked our landslide scientists to assess the risk from further rockfalls to Sefton Bivouac, below the Footstool.

While we think there is the potential for more rock to fall from the Footstool, the risk to Sefton Bivouac is very small as the distance to the bivouac is more than 1 km (it would take a huge rockfall to get that far).  Sefton Bivouac remains open, but climbers in Mt Cook National Park do need to be aware of the increased risk of rock fall in the Footstool area. 

Franz Josef rockfall

During February a new rockfall was noted by Department of Conservation staff above the walkway to the Franz Josef Glacier viewing platform.  The Department asked our landslide scientists for advice on how best to manage the rockfall risk – up to 7000 people per day use the walkway in peak season. 

We sent a survey team down to Franz Josef to collect baseline survey data for future monitoring and to assess the risk. Using high-quality topographic data and rock avalanche modelling we determined that DoC’s existing track management strategy – closing the track during intense or long rainfall events – was sufficient to manage the rockfall risk.

Other landslides and rockfalls

Other smaller landslides over the summer at times blocked the usual suspects: SH2 Rimutaka Road, the Kapiti commuter train line, SH73 between Arthur’s Pass and Kumara, and SH6 between Ross and Haast.  SH1 between Oaro and Peketa, south of Kaikoura, was often closed, sometimes for days, by reactivation of landslides from the 14 November Kaikoura earthquake.  Landslides also closed SH50 at the base of Bluff Hill in Napier, main roads in Marlborough and Northland.

 

The Tasman Tempest: Heavy rain over Northland, Auckland, Waikato, including Coromandel and Bay of Plenty in early March triggered many landslides.  We didn’t launch a GeoNet landslide rapid response for this event, because landsliding occurred over a wide area and with the flooding and landslides affecting many roads it would have been difficult to move around. We’ll be keeping an eye out for satellite imagery to help us understand the landslide impact of this event – and we’ll have more in our Autumn round up. 

 

      View Online Helen Jack 2017-04-04T00:49:07Z

White Island (Whakaari): Volcano remains quiet, moderate gas emissions

Mon, 03/04/2017 - 14:23

Blog post edited by Brad Scott

3 April 2017 14.10h

VOLCANIC ALERT BULLETIN: WI – 2017/01

14:00 pm Monday 3 April 2017; White Island Volcano

Alert Status:

Volcanic Alert Level 1 (no change)

Aviation Colour Code: Green (no change)

Observations during visits to White Island over the last 3-4 months confirm that activity remains at low levels. Activity is confined to the gas rich vents on the western side of the active crater. Hot, clear gas continues to be emitted. Some water has ponded on the floor of the active crater but no permanent lake has reformed. The seismic and acoustic activity generally remain low, and the SO2 gas flux is slowly declining. 

The larger hot gas rich vents on the remains of the 2012 lava intrusion are the main source of gas. The temperature of the gas has ranged 250-300 ºC when measured recently. Tour operators reported very minor ash in the gas plume on 20 February; otherwise no changes are apparent. Following larger rainfall events on the island water is ponding on the crater floor, but soon soaks away or is evaporated. Hence no Crater Lake has reformed.

White Island (Whakaari) viewed from the east on 28 March

Seismic activity on the volcano during the last 3-4 months has been at low levels, punctuated occasionally by minor periods of small local earthquakes or weak volcanic tremor. A sequence of very small high frequency events has been apparent since 26 March but is now declining. No acoustic signals (explosions) have been detected.

The largest accessible fumarole, known as F0 has been sampled and we have regularly measured its temperature. This has ranged 170-182 °C over the last few months. SO2 gas flux as measured by the automatic DOAS sensors has declined from around 400 tonnes/day to 200 tonnes/day post January, but remaining above the pre-2011 values (50-100 tonnes/day).

We continue to monitor the volcano for possible renewed activity. The Volcanic Alert Level remains at Level 1. The Aviation Colour code remains Green.

Art Jolly

Duty Volcanologist

 

Media Contact:

Brad Scott (07 3748211)

View of the active crater area: note the gas vent (centre-rear) and ponded rain water Close up view of the gas vent

 

 

View Online Brad Scott 2017-04-03T02:23:12Z

Kaikoura earthquake landslide and landslide dam update

Mon, 03/04/2017 - 12:36

Blog post edited by Helen Jack

Landslide mapping

Mapped landslides as of 23 March 2017 (click for larger image) Hapuku landslide dam - 10-14 million cubic metres of rock travelled 2.7 km to the valley floor (photo: GNS Science)

Our GeoNet landslide scientists have so far mapped nearly 5,000 landslides from the M7.8 Kaikoura earthquake from North Canterbury through to Marlborough.  Because of the huge area involved, most of the mapping has been done in the office using aerial photos, satellite imagery, and pre- and post-earthquake lidar (high quality topography), but our scientists have also been out walking over landslide areas around the Stanton and Leader rivers, and the near the Clarence River mouth, to check that what they have mapped is actually what has happened on the ground.  Armed with this information they will be able to provide advice to councils and infrastructure providers on how to manage the landslide and flood risk.

As well as blocking the main roads and rail north and south of Kaikoura, and many smaller roads, landslides have caused widespread damage to farm fences, tracks and water supplies which will take years to repair.  We were extremely lucky that no one was killed by landslides, but some properties are still evacuated in Goose Bay and Kaikoura because of the landslide or rockfall risk.

The landslides have happened in two distinct rock types – relatively young soft sandstones and mudstones, and older hard sandstones and mudstones (greywacke) – which behave quite differently.  Understanding where the landslides are, and their behaviour, will help with the earthquake recovery as the medium to long term effects show themselves.  The huge amount of landslide material coming down rivers over the coming decades will affect bridges and flood protection and may alter river courses.  Increased turbidity (muddiness) of streams and rivers will also have an effect on freshwater and marine ecology.

A preliminary observation from the mapping is that the landslides are clustered around the areas of fault rupture, not around the earthquake epicentre (which is what we would normally expect to see).  In fact, many of the largest landslides occurred right at the places where faults ruptured to the ground surface.  This landslide/fault interaction will be an interesting area for research and we could use this new understanding to revisit historical earthquakes like the 1929 Murchison earthquake to see if large landslides can point to fault ruptures that weren’t noticed before.

For those wanting more information on how the landslides are being mapped, this document outlines our mapping process.

Seaview Landslide, on the Papatea Fault near the Clarence River mouth (click for larger image) (photo: GNS Science)

 

Landslide dams

The GeoNet landslide team is working with Environment Canterbury, Hurunui, Kaikoura and Marlborough district councils, and NZTA to assess and manage the risk from landslide dams to downstream communities and infrastructure. 

Environment Canterbury and Marlborough District Council staff continue to monitor landslide dams that pose a risk to people or infrastructure downstream – this includes helicopter flyovers every few weeks and after heavy rainfall or strong aftershocks.  At present monitoring is focussed on six dams that remain high risk – the Waima (Ure), Hapuku, Linton, Ote Makura, Conway and Stanton river dams.  Other dams are also being monitored, but they are of lower risk: Two dams, the Towy and Leader river dams, have breached or partially breached and are now of less concern.  And other dams, including the Medway, Gelt, Bourne and smaller Leader river dams, pose a smaller risk as the potential downstream impacts are relatively minor.

The priorities for landslide dam monitoring change with the landscape; future heavy rain, aftershocks or a dam breach change the risk and will likely see some landslide dams upgraded or downgraded for monitoring.

You can check out the locations of landslide dams in Canterbury, as well as photos and videos, on Environment Canterbury’s landslide dam webmap

GeoNet’s landslide team plans to install monitoring equipment, such as GPS stations, extensometers (movement recorders), water level recorders and webcams on some of the dams.  NZTA and Kaikoura District Council are already monitoring the Hapuku, Ote Makura (Goose Bay), and Linton landslide dams and warning lights are now installed on the Hapuku, Ote Makura and Linton bridges to warn of a potential landslide dam breach upstream.

Conway landslide dam (photo: GNS Science) Hapuku landslide dam (photo: GNS Science)

 

Leader River dam partial breach

One of the largest monitored landslide dams, on the Leader River between Waiau and Parnassus in Hurunui District, partially breached on 13/14 February.  This dam is one of the ‘soft rock’ dams, and it appears that the main crest of the dam was overtopped and eroded when the lake level reached the top of the dam.  The lake level dropped by around 3-4 metres, and evidence of moderate flood flows was observed in the river bed downstream but there was no known flooding of land next to the river bed.  The dam now appears to be stable and the river is flowing over a new, lower crest and along a new course downstream – slightly to the south of the pre-14 November course, which is covered by landslide debris.

Environment Canterbury has two great videos flying upstream and downstream showing the dam and lake on 22 February, a week after the breach.  You can see where the lake level has dropped, leaving white algae-covered banks and trees.

Given the size of the dam and the volume of water that was released in the breach, GeoNet sent down a survey crew at the start of March to measure the changes to the dam. Collecting information on landslide dams and how and when they fail is really useful.  It gives us a better idea of how the other landslide dams in this event are likely to behave, and it also gives the international science community more data to help say what is likely to happen in future events overseas. 

While the flood wave from the Leader dam breach remained in the river channel downstream of the dam and didn’t do any damage, it is a good reminder to stay out of all river beds from the Waiau River to the Awatere River as these dams can suddenly release millions of litres of water – you don’t want to be in the way of that.

Before: Leader dam 12 December 2016 (looking upstream) (photo: GNS Science) After: Leader dam 3 March 2017 (looking upstream) (photo: GNS Science)

 

Contact scientist: Sally Dellow, GNS Science

The GeoNet landslide team includes scientists and engineers from GNS Science, Massey University, and the University of Canterbury.  Our colleagues from the US Geological Survey landslide team and the international Geotechnical Extreme Event Response (GEER) landslide team also helped out in the initial landslide response.

 

View Online Helen Jack 2017-04-03T00:36:17Z

GeoNet teams return from successful trip to Raoul Island

Fri, 31/03/2017 - 13:53

Blog post edited by Caroline Little

31 March 14.30 pm

HMNZS Canterbury returned to Auckland this morning after a successful voyage to the Kermadec Islands. On board are staff from GNS Science, DOC and NZ Met Service. The GeoNet electronics team and three commercial divers have been upgrading and hardening one of the two tsunami gauge sites on the island, while volcano chemistry team have been sampling the volcano and geothermal features at Green Lake.

The tsunami sensors at Fishing Rock provide real-time sea level data as part of the LINZ tsunami network.  GeoNet technician Kris O’Brien has reported over the weekend the two sensors at Fishing Rock were replaced with new sensors. The new installation is further along the shore platform and provides better protection from the sea. New cable armour which protects the fragile cable from the harsh conditions was installed, with part being re-routed to the new sensor location.  The team also swapped out the satellite communications dish and replaced around 440 kg of batteries.

Dr Bruce Christenson has updated us on the gas and water sampling of springs and fumaroles in the Raoul Caldera. He has noted “overall the system is little-changed since September 2016, although water levels in Green Lake were lower”. The three main fumaroles were sampled as were the two crater lakes. They also sampled the springs in Marker Bay Pool and East Pool. The combination of fumarolic and pool gases, will provide some strong insights into the current hydrothermal system behavior, and provide constraints for modelling and monitoring future activity from the volcano.

GNS Science also had a team visiting Curtis Island to undertake research on the hydrothermal features there.

Installing the new armored cable at Fishing Rock The underwater housing for the tsunami sensors

View Online Caroline Little 2017-03-31T01:53:00Z

Turangi Earthquake swarm update

Fri, 31/03/2017 - 13:13

Blog post edited by Caroline Little

Updated 31 March; 12.30 pm

Yesterday morning, we reported how the swarm activity about 10 km west of Turangi had increased with 249 locatable earthquakes occurring in the previous week. That pulse of activity lead to a M4.5 at 6 km depth later in a day (12.58 pm). This was followed by a more typical aftershock sequence that included three M3+ events and numerous smaller earthquakes. The number of located events in the last week is now 614. The total number of events in the swarm has risen to 1245 since 13 February.

The events are occurring between about 4 and 10 km depth and most are in the 5-8 km depth range. 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. Several active faults are mapped in the GNS Science Active Faults database reflecting the ‘tectonic nature’ of this area. Currently, there are no indications that the earthquakes are related to volcanic activity, being located well away from the active volcanoes.

Earthquake swarms are a common feature of the Taupo Volcanic Zone. Every few years we have one in the greater Turangi area. This one has been ongoing since 13 February and has consisted of two major pulses of activity, with about 20 days between them. This second pulse is stronger with more events. Swarms come in a variety of forms and it is not possible to judge the future easily for them. Some have the stronger phase near the start, others in the middle and some swarms have the stronger activity at the end. We anticipate this one will continue in the short term. As usual, we continue to closely monitor the activity.

Map showing the location of the active faults in the Turangi area Locations of all events in the last week

Seismograph drum plot for last 24 hours

View Online Caroline Little 2017-03-31T01:13:35Z

Earthquake Swarm near Turangi continues

Fri, 31/03/2017 - 11:27

Blog post edited by Brad Scott

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 879 earthquakes in this swarm, the largest event is a M3.8 on 21 February at 9.35 pm. There have only been ten events larger than M3 in the swarm. The number of events per day is variable, typical of swarms. The events are occurring between about 4 and 10 km depth and most are in the 5-8 km depth range. 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.

In the last day the swarm activity has increased with 249 locatable earthquakes occurring. The pulse of activity has included 6 earthquakes larger than M3, ranging from M3.0 to 3.5 in size. The depths remain in the 5-8 km range. The larger events came towards the start of the pulse in the last day and less events and smaller ones have occurred over night. As usual, we continue to closely monitor the activity.

Map showing the location of all the events in the last week Map show the location of all the events to date in the swarm Seismic record for last day showing the decline in activity over night

View Online Brad Scott 2017-03-30T23:27:53Z

Update on slow-slip activity following the Magnitude 7.8 Kaikoura Earthquake

Thu, 30/03/2017 - 09:13

Blog post edited by Caroline Little

Cross-section showing where the slow slip (brown to
yellow patches) is happening at the boundary between
the Australian and
 Pacific Plates.
Bottom right insert 
shows a map view of the slow slip areas.

Some of you will remember the slow-slip events that we observed on the Hikurangi subduction plate boundary following the M7.8 Kaikoura earthquake using the GeoNet GPS network. The Hikurangi subduction zone is where the Pacific Plate and Australian Plate meet beneath the North Island and northern South Island. We thought it was time for an update on what has happened with the slow-slip events since then. 

So, here’s what we know now: one slow-slip event has stopped (offshore the east coast of the North Island), and the other one has slowed down (beneath the Kapiti region).  But, the most interesting part of our update is that we have now detected slip occurring on the subduction zone beneath the upper South Island.  All of these slow slips started immediately after the earthquake and are a direct consequence of the magnitude 7.8 Kaikoura earthquake.

The newly discovered upper South Island slip

A swath of new data has revealed that the upper South Island started slowly moving immediately after the Kaikoura Earthquake. This movement was most active during the first month after the earthquake and has slowed down considerably since the start of the year.

Like the slow-slip events in the North Island, most of the land movement we are currently detecting in Marlborough is caused by the subduction plate boundary slipping beneath the upper South Island, where the plates meet about 25km below the Earth’s surface.  Following the Kaikoura earthquake, the plate boundary has slipped up to half a metre — slowly releasing energy over the past few months equivalent to a magnitude 7.3 earthquake. This type of slow slip (often called “afterslip”) typically happens following large earthquakes, either within the zone of earthquake rupture, or in the region immediately surrounding the zone of rupture. New work on what happened during the Kaikoura earthquake (led by GNS Science) was also published last week, which also shows that this same area of the subduction zone may also have moved during the initial M7.8 Kaikoura Earthquake.

We were only recently able to get a full picture of this post-earthquake slip happening on the subduction zone beneath the upper South Island, partly because there are fewer GeoNet continuous GPS sites there. GNS scientists installed new GPS sites after the earthquake and then had to physically go out and retrieve all of the data over time, instead of relying on GeoNet instruments that relay data straight back to us every hour of every day. 

 

East Coast (North Island) slow-slip event

Month-by-month view of the southern slip areas. The first
month has the highest amount of slip, especially in Hawke's
Bay and the upper South Island. 

This slow-slip event involved up to 15 cm of movement offshore on the Hikurangi subduction zone between Gisborne and southern Hawke’s Bay. It took only two weeks to occur, and was mostly finished by the end of November.  Over that period it released enough energy to be equivalent to a magnitude 7.1 earthquake. Slow-slip events on the east coast often trigger small to moderate earthquakes nearby.  There were more than 200 earthquakes associated with this slow slip event off the East Coast of the North Island, including a magnitude 5.5 on 22 November near Porangahau.

Kapiti slow-slip event

The slow-slip event occurring beneath the Kapiti coast and Marlborough Sounds is still trucking along, but at a slightly lower rate compared to immediately after the Kaikoura Earthquake. The tectonic plates have moved past each other by several centimetres since November, and thus far this event has released energy equivalent to a magnitude 7.0 earthquake.  Based on the behaviour of past Kapiti slow-slip events, we expect it to continue for at least a few more months. 

What this all means

Slow-slip events are a relatively newly-recognized phenomena; we’ve only been able to detect them in New Zealand for the last 15 years.  Even though the slow-slip events relieve built-up stress between the tectonic plates without earthquakes, they can transfer stress onto other faults around them. We’ve detected dozens of slow-slip events in the past that haven’t caused large earthquakes, although it is possible that the Cook Strait earthquake sequence in 2013 was triggered by the Kapiti slow slip event, which was occurring at the time.

Because so much slow slip has been happening since the Kaikoura earthquake, our scientists are currently trying to develop new ways to figure out how these slow slips might influence the likelihood of future earthquakes. Our current models suggest that another earthquake of a similar or greater magnitude than the Kaikoura M7.8 has a 5% likelihood within the next year. While 5% is still a small chance, this chance is approximately six times greater than it was prior to the Kaikoura earthquake. We are currently working on updating our calculations based on the new information we have on the slow slip events following the M7.8 earthquake.

As we’ve mentioned previously, we’re aware that these messages could be unsettling, and that’s a very normal reaction. What we do want you to take away from this (and this applies to all New Zealanders, at all times—not only now) is to follow Civil Defence’s advice and make sure that you’re prepared for earthquakes and tsunamis. We know that being prepared makes a real difference in helping you get through an event and recovering afterward. Many of you have already got you and your family prepared, so well done you guys!

Contact Scientist: Laura Wallace

View Online Caroline Little 2017-03-29T21:13:56Z

GeoNet team and GNS scientists depart for Kermadec Islands

Fri, 24/03/2017 - 09:00

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 - 09:21

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 - 15:41

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 - 15:41

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 - 15:40

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 - 15:39

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 - 15:20

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 - 08:42

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