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After the M7.8 Kaikoura earthquakes, our techs quickly took to the air to put in more temporary sites throughout the Kaikoura Mountains and Southern Alps. The problem with these locations is its remoteness and sustained damaged to cell towers from the earthquake.
Now, when our techs go out into the field, they can only take the most important items with them due to limited space on the helicopters. Our techs are dropped off into the middle of nowhere with few supplies to make these temporary sites. Think “Survivor” but with a radio, some seismographs and a couple of muesli bars. Our techs are able to put in these temporary sites in a matter of hours.
The lack of space has made our techs…become creative in their use of tools. Recently, they realised their antenna needed more height to communicate with base. They cleverly repurposed a spade (used to dig out ground to place the site in) and used electrical tape to put the antenna on the spade. BOOM: instant communication tower. The Spade-tenna© (patent pending) was designed to elevate the antenna in order to increase cellular signal strength in remote locations. This means we don’t lose contact with these sites.
They quickly put up 9 temporary sites since the earthquake stopped shaking, 4 with the clever spade-tenna.
Tim McDougall, one of our techs, said they were proud of their latest innovation but that they are now running out of spades…
A big shout out to our techs because these sites are a critical part of our ongoing monitoring of the M7.8 Kaikoura aftershock sequence. We couldn't be GeoNet without the people looking after our 600 plus monitoring sites throughout New Zealand.
Stress and the earthquakes
Now, I can’t tell you what to feel or how to respond to the earthquakes. But I’ll just share with you what helps me deal with anxiety or nervousness.
1. Understanding the science. Knowing as much as I can about the phenomena comforts me. I try to learn as much as I can.
This leads me to getting to talk about my favourite thing: numbers! Especially measurements (that is data). This earthquake is astounding, with movement along at least 5 separate faults extending around 150 km up the east coast of the South Island with land changes of up to 11 m horizontal and 5 m vertical. Maximum ground shaking of at least 1.3 times the force of gravity at Ward in Marlborough. The tidal gauge that recorded the 2.8 m tsunami at Kaikoura, was uplifted by 90 cm. We recorded the tsunami up to 4 m height at Little Pidgeon Bay. Since the earthquake occurred we have recorded more than 5,500 aftershocks. And these numbers are only a few of the large number of measurements of this earthquake.
And then there are the numbers of regarding the probabilities and further aftershock maps we are publishing. It’s natural to feel anxious about these numbers. Our scientists develop these to understand the potential future. We couldn’t do this even 10 years ago. The ability to have some kind of knowledge about what is possible can help us plan and move forward, as individuals and as a nation.
There is a lot of very good science information going out about this earthquake and not just from GeoNet and GNS Science. The Science Media Centre, QuakeCore, Victoria University of Wellington, NIWA, Massey University, University of Auckland, University of Canterbury, University of Otago, Waikato University, and many others are contributing to the ongoing science response. I want to acknowledge and thank all the scientists working hard around New Zealand right now. It is a great team effort and I’m proud to be a part of it.
Just a quick side comment about the science community and transparency. Anyone can take our data and develop their own models, they don’t have to come to us or other parts of GNS Science. EQC has paid to ensure our data is freely available to anyone who wants it. This means we are completely open about our data. Any praise for GeoNet should also be reflected onto our most steady and supportive funder - EQC, who had the foresight to develop the open data policy at the start of GeoNet in 2001.
So, those are just the quake numbers. Let’s talk about GeoNet numbers. We’ve had 1,300,525 unique visitors to our website and 169,028,688 earthquake notifications have by our app. We thank Fastly, Urban Airship, and AWS for helping us deliver this performance.
2. Prepare, prepare, prepare. What makes me feel more comfortable is being prepared. I know I do feel better if I am prepared. We have emergency supplies (my new house has 10,000 litres of water storage for example). While not everyone can store that much water, there are simple things that everyone can do.
The Ministry of Civil Defence and Emergency Management (MCDEM) are the preparedness experts and we support their message fully. We can’t stop nature from doing its thing and it may not give us notice about what’s going to happen next. BUT we can control how ready we are to respond to nature and bounce back after the event.
During this sequence, we’ve already had two large gales hit central New Zealand. Being prepared comes in handy during storms, floods and all other manner of emergencies too. Please visit www.happens.nz. Our friends at MCDEM (and we are very good friends, having worked so closely together over many years) have put together some great resources on how to be prepared.
Together, let’s make New Zealand the most prepared country on the planet. Let’s be the people who are ready for anything.
3. Focus on the really important things: relationships. I came home for the first time since the earthquake on Saturday evening, and my cat, Poppy, greeted me at the door with very loud meows. Poppy put her furry face in my shoes for a big whiff (I don’t know why she’d find that comforting) and then demanded cuddles for five minutes. Her small, purring presence helped remind me what is important in life: it’s my relationships. Further, the comfort and support I’ve received from my wife and three daughters, as well as my staff, help me keep all this into perspective. I thank them for their unwavering support.
Are earthquakes scary? They certainly can be. I’m not trying to downplay tragedies or anxiety. I encourage us all to consider what we can do about it. We can’t stop the earth from shaking; more earthquakes will come. If not now, someday. New Zealand’s beautiful mountains were created by earthquakes and uplift. Earthquakes are why, in part, our country exists.
Numbers are great but it's still about people
One more word about our staff. They are tired and they have really worked amazingly hard. Like so many other people working for Civil Defence agencies, the Defence Force, the Police, USAR teams, council workers, infrastructure managers…we are all working very hard for New Zealand, and for you. I need to remind them, and myself, that we are working under extreme conditions with the world still moving underneath our feet. They have my thanks and gratitude.
I just want to share one small anecdote before I sign off. Starting in the early hours of Monday 14 November, our field techs quietly got gear ready, booked helicopters, and were out the door to service and install extra sensors so we could get a better understanding of this quake. Our tech ‘ninjas’ quietly did their jobs. They rarely get the spotlight but our techs are champions. Without them, we wouldn’t have GeoNet.
Dr. Ken Gledhill
6pm, Wednesday 16/11/2016
What has changed since our initial review
Based on our findings and in discussion with international researchers, early indications are that this is one of the most complex earthquakes ever recorded on land. This complexity means we have had to take extraordinary efforts to determine the magnitude, depth, and locations.
The very long time it took for the faults to rupture (over one minute) meant that the standard methods of calculating magnitude were insufficient to capture the full energy released.
Due to the size of the quakes, we’ve gathered data from our entire network of seismic stations. All of these stations would not normally need to be included in magnitude estimates.
Further, our techs at GeoNet went out to several sites which we lost communication with and we have now been able to upload this information, so we have a more complete understanding of the ground deformation and strong-motion data.
Finally, our science teams have been working tirelessly, going up and down the affected areas and measuring the length of faults and how much they moved. Their efforts have provided us with a clearer picture as to the size and length of the ruptures.
Based on all these ongoing efforts, we can say with some confidence that the earthquake was an M7.8. This is consistent with estimates from several other international agencies, specifically the USGS. Their early model provided us important information and we used all our additional data sets to confirm the magnitude.
What this means
The new magnitude just tells us what we think most people who felt the earthquake already know: it was powerful, and went on for a long time over a large distance. It doesn’t change what happened but it does provide us with more knowledge about how significant the event was.
Our recent analysis confirms the complexity of this event. It does not change any of the observations of strong ground motion, fault breaks or GPS recorded movement of the earth’s surface – these are physical observations independent of the magnitude of the earthquake.
We are in the process of revising our probabilities and scenarios based on this new information and should have this released within the next 24 hours.
Good science takes time
Our GeoNet seismic network is robust and records tremors and shakes throughout the country. However, with these very rare large events, it requires time and thought as to what all of this new data means. This earthquake required us to take a different approach and we have been triaging the data to reconcile all the different data sets.
8:30pm, 15th November
With the flooding, earthquakes and tsunami, it feels like Central New Zealand is getting a hammering by our most brutal project manager: nature. And nature has been particularly demanding in the last 48 hours and I just want to share a few of my thoughts about what is going on.
Dr. Ken Gledhill, Director of GeoNet
M7.5 Earthquake: a monster in the making
As a geophysicist, there are a few important things to know about this quake and they are already available in various places and forms. It was a monster quake, one that has shocked us all with its intensity and ferocity. Because of its size it made our world shake strongly but relatively slowly for a very long time. It is a complex, brooding beast we are still trying to understand. Although we published information on it very quickly, please forgive us as we tell you more and revise what we have already told you.
Tsunami: those who took action did the right thing
In terms of the tsunami, I said it here in the M7.1 East Cape Earthquake. Because we do not have a 24/7 monitoring centre we have to wake people and get them out of bed to look at complex data and make serious calls very quickly. It is not an ideal situation given the past few months and I’d like to change that by getting support for a 24/7 monitoring centre for geohazards. I’m going to be blatant in my campaigning for this, because I think we need a 24/7 monitoring centre to respond to these kinds of events.
But, even with a 24/7, we may still not have been fast enough for people in Kaikoura. The best advice is still: if you are at the coast, and feel a long or strong earthquake, be gone. For those people who took those brave steps in the middle of the night of the tsunami, I applaud your efforts. YOU DID THE RIGHT THING. For people who were further away and waited but left once told to evacuate, YOU ALSO DID THE RIGHT THING. We were lucky the tsunami struck at low tide; high tide could have left more damage than I feel comfortable thinking about.
Moon and earthquake lights
GeoNet only reports on things we can measure. This is why we stick to our knitting: geophysical data. We know that people are really interested in what we think about the supermoon or earthquake lights, but we just don’t have any way to measure their effects using the GeoNet sensors. So, I am just going to leave that topic for other people to discuss.
Kiwis: we’re a unique type of tough
I just want to say a few words about people. This is a painful time. People have died and we mourn with their family and friends. I can only imagine how people are struggling right now in Kaikoura, Ward, and Waiau and the other affected regions. Also, people in Christchurch are experiencing reminders of an earthquake nightmare they might have thought was over, only to realise that sadly, earthquakes are part of the standard operating procedure here in New Zealand. In the Wellington region, we are now experiencing intense flooding, complicating our ability to recover from this earthquake. This combination of hits from nature is exhausting and upsetting.
Damage from the M 7.5 Kaikoura Earthquake
But here is the upshot. One thing I know about us Kiwis, we are prepared, tough, and able to cope with almost anything. It is perfectly acceptable to be scared by this earthquake but we will get through this by doing what I think Kiwis do best: helping each other. We saw this with the Canterbury earthquakes and we are seeing this again. We are also good at taking care of our visitors and our new Kiwis as well.
I can’t relieve anyone’s anxiety about future earthquakes; more will come. What I can say is that preparedness, that old Civil Defence and Emergency Management mantra, is the best solution to being ready for these events. Please visit our friends at the Ministry of Civil Defence and Emergency Management to find out how you can prepare. To learn more about your tsunami evacuation zones and advice, visit your local and regional council. To learn how to keep your china, house and other precious items safe, visit our friends and funders, EQC.
To our GeoNet staff: a huge thank you
Finally, I just want to say a few words about my staff. I’ve been the director for more than a decade and they have never let me or New Zealand down. Their service to New Zealand, science and people, is phenomenal. They really care about what they do. I thank them for their tireless efforts, keeping GeoNet functioning, sleepless nights locating earthquakes or even sending that late night cheeky Tweet. What makes GeoNet a world class geohazards monitoring system is not our instruments (as much as I love the technology), but our people. When people send kind words via social media or emails or phone calls, my staff feel that support deeply, so thank you.
Dr Ken Gledhill
Director, New Zealand GeoNet
Gisborne and Hawke's Bay slow-slip event follows M7.8 Kaikoura Quake (includes Porangahau information, updated 26/11/2016)
Kaikoura Earthquake 2016: Paptea Fault Rupture (Kelvin Berryman explains it all!)
Rapid field reconnaissance indicates that multiple faults have ruptured:
Kekerengu Fault at the coast - appears to have had up to 10m of slip
- Newly identified fault at Waipapa Bay
- Hope Fault - seaward segment - minor movement
- Hundalee Fault
Other faults have also been identified as being involved in the earthquake. In the simplest case an earthquake is a rupture on a single fault plane.
What we are finding in New Zealand is that quite a few of our larger earthquakes involve jumping from rupture on one plane to another in a complex sequence. We first saw that with the Darfield Sept 2010 EQ where multiple segments ruptured together as a single earthquake. We appear to have seen this again overnight.
In terms of what might happen next: The scenarios provide an overview of how we see this earthquake sequence evolving over the next few days to one month. What is on the web page is our best information that we have to hand at the moment. As our science information flows in over the next few days we expect that information may evolve.
ShakeMap for the M7.5 Kaikoura Earthquake.
A word about the Moon
Some people have raised concerns about a link with the supermoon. In large groups earthquakes exhibit slight associations with lunar cycles, but this is not reliable for forecasting. We have two tides a day throughout New Zealand and at any one place there is no clear association in location. The occurrence of the full moon around the globe does not allow us to say how big, when and where any earthquake might be.
Long term earthquake rates
There were more large earthquakes in a period of several decades prior to about 1950, and it has been relatively quiet since then. Since the M7.8 in July 2009 in Fiordland, that quiet period appears to be over. The reason we had a tsunami generated by an earthquake with an epicentre onshore is that there was deformation further down the fault plane offshore.
Wellington area faults and the subduction interface beneath Wellington are captured in the probability table and the scenarios given there. We do not have any evidence of an impending large earthquake of a similar size in Wellington at this stage but we cannot rule this out. We cannot make a calculation to predict this, but the chance of a further shock in the Wellington area has increased somewhat since the Kaikoura earthquake.
Why were our magnitudes different from the USGS: About magnitude variability
We have changed the New Zealand local magnitude for this earthquake to M7.8.
Felt it? Tell us about it.
Our Felt Detailed report for this earthquake is now available. Please help us by filling out this report to help our long term research programme.
We will be continuing to gather information about this earthquake for some time. We will continue to keep updating information as we learn more about this earthquake.
Be prepared – both physically and mentally
Beyond physical preparedness is the emotional and psychological support for these earthquakes. 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.
Map of the aftershocks associated with the M7.5 Kaikoura Earthquake.
MCDEM have issued a tsunami threat for the initial earthquake. Our tide guages at Kaikoura, Wellington, and Castlepoint have recorded this. Please follow advice regarding tsunami via the Civil Defence website - anyone at the coast on the East Coast of New Zealand move to higher ground.
Thus far there have been approximately 45 aftershocks. It is difficult to predict an aftershock sequence because it is too soon after the initial earthquake to understand the pattern. We need more time and aftershocks to occur so we can get a better picture of what is going on.
Scientific information about the quake
Peak ground accelerations (PGAs) have been recorded up to 0.23g in Wellington. This is similar to the 2013 Lake Grassmere and Cook Strait earthquakes. The PGAs closer to the earthquake will be much larger. We are still working on calculating these values.
Our GPS stations record how land moved in response to the earthquake. Our station at Cape Campbell in Malborough moved two metres north.
Updated at 03:25am More information soon.
About Felt Detailed
This new long-form questionnaire is based on the older Felt reports that you might remember from earthquakes past. However, because we only bring it out for (hopefully) rare larger quakes we’re now able to tailor it for specific earthquakes. For today’s survey we’ve included tsunami related questions. These new questions include asking what you did during and after the shaking, how you like to receive information, and whether you were concerned about a tsunami. We use your valuable insights to better estimate the shaking intensity caused by this earthquake and to better understand the effects of future major earthquakes in New Zealand. These new questions allow us to work with social science researchers to help us better understand how people think and act during earthquakes. We’ve also been able to increase its stability by having it hosted by SurveyMonkey.
We chose SurveyMonkey as our provider for the Felt Detailed because we know it works. The social science team at GNS Science has used it to collect thousands of surveys over the years. We think it should be stable and secure enough to handle all the great information that you’ve got to share. Be aware that this is a very new system and we had to forego a part of our user testing to make it live for this earthquake.
If you felt today's big earthquake, give the new Felt Detailed a go and see what you think. That way you would help us both with the early response (through Felt RAPID) and with the research (through Felt Reports: Detailed). Most of the time, you can stick to clicking a button on Felt Rapid.
P.S. We’ve had a lot of feedback from you guys today about the new felt reporting system not working. Sorry. This was the first big test, and it didn’t perform so well. Why did this happen? Our Google assisted address search was capped at 150,000 searches, and we went over this (Google searches every time you type a single letter into the address bar, so it goes through 150,000 searches quickly!)
Go to Felt Detailed.
National Warning: Tsunami Marine and Beach Threat CANCELLED
Issued at 08:30 NZST 02 September 2016
The Ministry of Civil Defence & Emergency Management (MCDEM) has cancelled the tsunami marine and beach threat warning in place for the North Coast Regions of the North Island of New Zealand.
Based on all available data, the greatest tsunami activity has now passed. However, coasts may still experience unusual, strong currents and sea level fluctuations lasting for several more hours.
At 4:37am today a magnitude 7.1 earthquake struck 100km off the coast of East Cape. The tsunami experts panel is active and is assessing the situation with the Ministry of Civil Defence and Emergency Management (MCDEM).
Shaking was felt throughout the North Island, with nearly 5,000 felt reports reported to GeoNet within the first 20 mins of the earthquake. As at 7:10am there have been 57 aftershocks, the largest, is a magnitude 6.2 quake. Aftershocks can be expected to continue for some time. This morning's quake was preceded by a magnitude 5.7 foreshock at 10:04am yesterday which occurred in the same area. (Note: there is no way to tell if an earthquake is a foreshock, only when the larger quake occurs can we call it a foreshock).
This area is no stranger to large earthquakes. In February 1995 there was a magnitude 7.2 earthquake off the coast of East Cape, further to the south than this morning's earthquake.
If you felt this earthquake, we'd like to learn more about your experience. You can now fill in Felt Detailed here. This longer form felt report takes a bit more time than our Felt Rapid system but it provides valuable information to our scientists about the earthquake.
This will be updated as more information comes to hand, last updated at 4.10 pm.
I’ve worked in or around Civil Defence organisations for over a decade and rarely are the words “no duff” spoken in an exercise. "No duff" means that something real is happening and we need to pause the exercise to respond. Our duty officer returns quickly with the news that, while the earthquake was large, it won’t directly affect New Zealand. We get back to the exercise at hand: the national tsunami Exercise Tangaroa.
Working in Civil Defence Emergency Management exercises can be a strange experience for the uninitiated. There are all kinds of specific terms and acronyms used like CIMS (Coordinated Incident Management System), EOC (Emergency Operation Centre), and CDEM (Civil Defence and Emergency Management). There is good reason for all the acronyms; Civil Defence has developed, partially, out of a military heritage from post-World War 2 and the use of these acronyms helps generate a shared understanding as well as being able to work at speed. But Civil Defence has evolved well past its post WW2 roots; it is now a coordinated group of all first response agencies (Police, Fire, Ambulance) combined with Health, welfare agencies (Red Cross, Salvation Army etc…), lifelines (water, electricity, transport and gas providers) and the coordinating agencies; the local, regional (CDEM groups) and national (Ministry of Civil Defence and Emergency Management). The CDEM structure also includes GeoNet and GNS Science, to provide science advice and information to the responding agencies, specifically MCDEM. And, while CDEM focuses its exercises on agencies, everyone is needed to respond effectively, as seen in Christchurch with the Student Army.
Exercise Tangaroa was a scenario of a large tsunami (M9.1) located in the Kermadec Islands, slightly out of the coverage of the GeoNet sensor network (the writers of exercises can be mean sometimes!). As a regional source tsunami, it means we have little time to determine its impacts before the tsunami hits our shores, unlike the distant source tsunami, where CDEM agencies get hours to carefully plan if evacuations are necessary. However, we still have a role to play in bringing together the Tsunami Experts’ Panel, a group of expert volunteers who assist MCDEM in understanding what the possibility of tsunami impacts are after a large earthquake off the New Zealand coastline. Exercises are always pretty stressful affairs, with miscommunication, misdirection, rumours and systems barely holding up under the pressure. But this is the value of exercising; to see where the gaps are so we can better plan for when the real thing happens. It is stressful, even notionally, working to respond to a pretend tsunami that could have such damaging affects to the people of New Zealand.
Needless to say, we were all pretty tired after Exercise Tangaroa. Imagine our unpleasant surprise when our system detected a large earthquake off the coast of Te Araroa this morning. Our seemingly tireless duty officer sprang into action, shaking off any stress from the day before and quickly refined the earthquake's depth and location. Our duty officer provided us with what we needed; more clarity on the location than our automated system provides. After a brief flurry of media phone calls and social media questions, we have a cup of coffee together, take a breath and prepare ourselves for what Mother Nature may have in store for us next.
It is something I’m always being reminded of at GeoNet. Exercising is somewhat reassuring because at least you are aware of when it is coming. In real life, we get no such warning. We don’t know when a damaging tsunami may strike our shores but, if the past is any indicator, we should be as prepared as we can be.
One of our partners, MCDEM (the people who ran Exercise Tangaroa) have put together a great website that can help you prepare for all kinds of emergencies, not just tsunami:
Why is New Zealand so shaky?
What it took to locate earthquakes before GeoNet
Find out what scientists are doing with our earthquake
data and how that impacts New Zealand
GeoNet and EQC's great partnership
At GeoNet we're always trying to improve on our services. We don't have a large team, but we try and stretch what resources we have. So…we've just started a re-design of our website, and we want to make sure we get it right - from the ground up - so it's easy as possible to find the information you want. We'd really love your help in building a better website.
We'd love it if you could complete our online survey - it's mobile friendly too! It has 15 questions, and may take between 10 and 15 minutes. Before we get on to the look and feel of the website, we're starting with the basics - how we structure our webpages. We want to know where you would expect to find information about our various hazards. The survey will be up until midday Monday 29th February.
As a small thank you, one “lucky” survey participant will receive this t-shirt from GeoNet, with our thanks. Yes, it’s an image of a kitten coming out of a volcano. According to one of our volcanologists, it is a “life-changing image”. Note: no New Zealand volcanoes or kittens were harmed in making the t-shirt.
While this t-shirt isn’t very serious, we take improving our website very seriously. So, go on, fill out our survey and be in to get this amazing t-shirt (exchanges are available if you don’t want to be seen rocking a kitten coming out of a volcano t-shirt).
Dr. Ken Gledhill, Director of GeoNet
When I reflect on the last five years, I see the tremendous growth that has occurred for our GeoNet project. Before the earthquakes, we were a little, rarely discussed seismic and volcanic monitoring network, known mainly by scientists, policy makers, hazard analysts and science fans. That all changed after 4 September 2010 and intensified on 22 February 2011 to a level we were not expecting.
Since then, the positives have been many. What we know about earthquakes since 22 February has taken us to new and unexpected directions that we could not have imagined before the earthquake. We now have GeoNet Rapid, which delivers almost immediate information on earthquakes to our users. We now have ‘the GeoNet app’, along with our website and social media platforms. We sent out 2,150,890 push notifications (custom app alerts) on the recent Valentine’s Day earthquake on 14 February 2016. However, it must be cold comfort for the people of Canterbury that the leaps and bounds in the science come from that earthquake that took so much.
I am acutely aware that the costs of this growth have been exceedingly high. The loss of life, the damage to the city, the suffering of people, is almost unimaginable even five years later. So perhaps the greatest learning for me was how people turned to GeoNet for support. I learned that science can sometimes comfort as well as inform.
With every large earthquake that has come since the 22 February 2011, the first consideration we have now is about the people affected and how we can communicate with them. We have become people centred, always learning more about how to provide the latest and most useful information to all our audiences. In this way, we honour the people of Christchurch, who are still teaching us lessons about resilience and enduring strength.
The GeoNet Team
Here is the breakdown of 2015… in terms of geological action for New Zealand.
Volcanoes: Turned down in 2015 but still on “simmer”
Like 2014, volcanic activity was relatively minor in 2015. We had a burst of seismic activity at March but by the end of April, it had gone back to sleep. In August, low gas emissions and seismic activity pulled Mt. Tongariro’s alert level down to 0 on the Volcanic Alert Level (VAL) scale. This was the first time since before the eruptions in 2012 that the level has been back to 0. White Island continued to puff and splutter away, with typical hydrothermal activity and periods of increased tremor continuing throughout the year, but no eruptions. All other volcanoes were quiet. Mt. Ruapehu’s Crater Lake experienced high and low temperatures and a snow and ice avalanche entering and temporarily cooling down areas of the lake by a few degrees. in
What 2016 will bring is unknown but the GeoNet monitoring team continues to keep a close eye on New Zealand volcanoes.
Earthquakes: South Island dominates in Quake Stakes
2015 had a shaky start, with the magnitude 6.0 Wilberforce Earthquake. The South Island continued to dominate in the larger earthquakes stakes, with 6.2 earthquake between Kaikoura and St. Arnaud in late April. The South Island continued to rumble when the 5.8 Matukituki quake, near Wanaka, struck a week later. Fortunately, no major injuries or damage was reported from any of the quakes.
After May, New Zealand quieted down, with no major earthquakes (more than a 6.0) reported for the rest of the year. As far as the bigger quakes this year, overall, there were 43 quakes that measured more than 5.0. 31 of those 43 were far offshore, in the Kermadec Islands. The North Island was relatively quiet in 2015, with three quakes more than magnitude 5.0 striking on land while the South Island had double this number, with six in 2015.
Generally, 2015 turned out to be quieter than 2014. Total quakes this year was 20,008, which was slightly less than 2014, which had 20,711.
So what does this mean for 2016? Unfortunately, there is no crystal ball to tell us what our Shaky Isles will do next.
Landslides: Triple Threats
This year, our landslide team had a full plate with landslides caused by earthquakes, massive storms and volcanoes. We had three magnitude 6.0 earthquakes this year, as discussed in the previous section, that triggered landslides and slips in their respective areas.
But the serious action came this year from massive storms, including Tropical Cyclone Pam. Pam wasn’t the only storm to grace our shores this year with large storm and rain systems, which created considerable sized floods in the Manawatu region, also generated the largest landslides and slips. We also responded to the rainstorm that affected the Hutt Valley and Kapiti coast in May.
Interestingly, this year, we also had a landslide caused by a volcano! White Island’s activity generated a landslide which required further investigation.
2015 was a busy year but we were fortunate that no one was injured as the land continued to slip and slide away.
Slow-slip earthquakes: when the earth moves very slowly
In 2015, our slow-slip earthquakes didn’t prove very exciting, as there were two slow-slip events that went on without any acknowledgement.
In Manawatu, a slow-slip earthquake started in mid-2014 and continued for the first half of 2015. Land around Manawatu moved up to 15cm to the east, which is about the length of a Crunchie bar.
In June of 2015 there was also a small slow-slip earthquake offshore of Gisborne. Land in this area is very slowly being pushed west by the colliding tectonic plates. However, land movement reversed direction for around a month and our stations moved 5-10 cm to the east. The amount of movement pales in comparison to the previous slow-slip earthquake in the area, where land moved up to 30 cm. This pattern of large slow-slip earthquakes interspersed by one or two smaller ones is a constant pattern for this area since these were discovered in the early 2000s.
Tsunami: long distance water hug from Chile
GeoNet responded to one tsunami last year – generated by a magnitude 8.3 earthquake off the coast of Chile. The tsunami experts panel estimated wave heights between 0.2-1m for much of the East Coast and the Chatham Islands, necessitating the Ministry of Civil Defence and Emergency Management to issue a beach and marine threat, that was in place for nearly 24 hours.
The resulting tsunami was consistent with the panel’s estimates, with the Chatham Islands receiving the largest wave heights – close to 1m. The maximum tsunami height on the East Coast of the mainland was closer to 50cm. Although 50cm doesn’t sound like much, it’s important to remember this is not a single wave, but a surge of water travelling faster than we can run.
Best cam shot of the year:
And that’s it! 2015 was a quieter year than the year before…but we like quiet years. But just because 2015 was quieter, it does not mean that 2016 will be the same.
Here are a few helpful places to get more info about preparing for emergencies:
As announced by Google New Zealand last week, we have been able to distribute our quake information even further thanks to our partnership with Google Public Alerts. Notifications can be received on Android smartphones, or the details found using Google Search or Google Maps on other devices or desktops.
Besides the basic facts, you will also get a map showing the region likely to have been most affected, the likely impacts, and recommended advice from the Ministry of Civil Defence & Emergency Management about what to do during and after an earthquake.
GeoNet is the latest of a number of organisations across the globe that contribute their alerts. These include weather, fire and public safety messages. What these alerts have in common is that they use a messaging standard called CAP (Common Alerting Protocol). Details of GeoNet's quake CAP feed are documented at our new API service. This is our go-to place for all of our services related to web and mobile content – watch it grow! Thanks to our funding agency EQC, these data resources remain free to use by anyone.
Featuring: GeoNet Quake app gets new features, The South Island's shaky start to the year, Ngauruhoe unrest tests the revised volcano alert system, White Island landslide hazard, Strong-motion renewal keeps GeoNet ready, Mystery device emerges at Lauder.
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