Let’s start with “this year in earthquakes” in New Zealand...
Earthquakes: a record-breaking year
This year had many earthquakes, but we are going to focus on the main two magnitude 7.0+ quakes that affected numerous communities: shaking our capital, Wellington, our weary quake-familiar Christchurch. Even our biggest city, Auckland, felt the sway of the East Cape earthquake. You’d be hard pressed to find someone who wasn’t impacted, in some way, by earthquakes in New Zealand this year.
By the numbers, our monitoring network recorded 32,828 earthquakes this year. To give a point of reference, on average we record about 20,000 per year. Our other active year reached 29,000 in 2011. 2016 wins the dubious honour of most earthquakes ever recorded on the GeoNet network (we’ve been around for 15 years). This year we had 122 earthquakes between magnitude 5.0 and 6.0,10 magnitude 6.0-6.9s, and, two magnitude 7.0 plus earthquakes. It’s been a geologically busy year. So let’s get into the earthquakes and their aftershock sequences that were the main contributors.
On the 2nd of September at 4.37 am, an M.7.1 earthquake struck 22 kilometres deep off the northeast coast of New Zealand. Luckily, the damage was minimal on land, although a small tsunami was generated. A strong aftershock sequence continued in the days following. Now, in any other year, the M7.1 would have been the biggest earthquake in New Zealand. But, New Zealand was just getting warmed up.
A little over two months later, at 12.02 a.m., the ground shaking began in North Canterbury, starting near Culverden. In two-and-a-half minutes, the earthquake moved across numerous faults, its seismic energy pooling and then overflowing onto one fault after the other, moving similar to the famous “Bucket Fountain” in Wellington. Along the way, the earthquake ruptured faults, tore through the earth and raised the seabed off Kaikoura. From Christchurch to Wellington to Nelson, the whole part of the upper South Island and Lower North Island were impacted. Thousands of aftershocks have followed since the ground first shook. There is some pretty amazing video, taken by our Julian Thomson and starring Kelvin Berryman. Thanks, Julian and Kelvin!
The M.7.8 Kaikoura earthquake will not go into the global history book of earthquakes because of its magnitude; the Ring of Fire regularly gets that size and much larger earthquakes. What makes it unique is two things: how it ruptured across the faults through the North Canterbury and Marlborough Fault areas and the slow-slip earthquakes triggered by M7.8. While we knew the faults were all there, we had only rarely seen an earthquake behave quite like this one.
Secondly, the slow-slip events or “silent earthquakes” started right after the M7.8 Kaikoura earthquake stopped. Our understanding of slow-slip earthquakes is evolving due to its relatively recent detection in 2002 in New Zealand. We don’t yet fully understand what it means to have slow-slip events triggered by the M.7.8. However, we are cautious as to what this might mean for future earthquakes. We’ve included these events in our probabilities and scenarios for this aftershock sequence. These two unique factors make this an earthquake of significance; New Zealand breaks new ground again!
It can be easy to get carried away by the excitement of the science of the earthquakes. However, the impact of these earthquakes is real and can be very painful for those who experienced it. Earthquakes, especially the large ones like East Cape and Kaikoura, can be anxiety producing; this is normal. Everyone responds to earthquakes differently, so if you are feeling unusually high anxiety due to the earthquakes, there are people here to help you through this time. If you are anxious about the earthquakes and this is affecting your ability to go about your daily life the All Right? Hotline (0800-777-846) is a great resource where you can talk about any anxieties or concerns that you have regarding the earthquakes. Remember to also seek support with friends and family, and to take time out to do things you enjoy.
Tsunamis: the rehearsal and the real thing
This year, we were part of a national Ministry of Civil Defence and Emergency Management-led exercise regarding tsunami called Exercise Tangaroa. This exercise involved the whole nation’s civil defence groups and many other agencies across the country (link). Two days later, at 4 am, we had a striking coincidence with the M7.1 East Cape earthquake, which generated a small tsunami (30 cm). The residents near the East Cape earthquake did the right thing by evacuating immediately to higher ground.
Again, those who evacuated immediately on feeling the long and strong earthquake did the right thing.
If you are on the coast and you feel an earthquake that is long or strong, get gone.
2016 in Volcano Land
We asked our favourite volcanologist at large, Brad Scott, to give us the words for his thoughts on volcanoes in 2016. Here’s the lowdown from Brad:
2016 saw a variety of activity from our active volcanoes, ranging from violent explosive activity to small-scale geysering and a mystery submarine eruption, creating a random pumice raft near Tonga. Also included was volcanic unrest, a hydrothermal eruption and remobilisation of old eruption deposits.
High-intensity rain in January saw debris (sand, clay and rock) left over from the 2012 Te Maari eruptions remobilised by the heavy local rainfall and washed out of the valley below the vents.
Then, it was White Island (Whakaari)’s time. On Wednesday 27 April, a moderate steam and gas-driven eruption occurred at White Island (Whakaari). The eruption ejected the Crater Lake, created a new sub-crater, generated landslides/collapse and excavated some 13 m of the Crater Lake floor. This generated a very energetic blast that covered much of the Main Crater floor and the north-eastern portion of the volcano with some quite festively coloured green tinged ash. This eruption occurred during a period of volcanic unrest. However, we were challenged initially to confirm it had happened. These steam and gas driven eruptions do not give any useful warning.
Mt. Ruapehu’s Crater Lake heated up, cooled back down and then promptly heated up again and then back down again. White Island had another hydrothermal eruption in September and then went back to simmering. Finally, we saw some pretty dramatic geyesing in Rotorua in the lake. The geysers had been pretty quiet for 15 years but decided this was the year to reawaken.
Landslides: slips, slides and the smothering of State Highway One
The newest member of our public information team, Helen Jack, wrote up her thoughts on landslides. Helen is a landslide enthusiast, although she has a fond place in her heart for glaciers as well. She works out of our Dunedin office.
Landslides triggered by earthquakes took the (rather large) cake in 2016. The M5.7 Valentine’s Day earthquake in February rattled down more rocks and cliffs along the eastern Port Hills in Christchurch.
Then, just as our landslides scientists were wrapping up almost six years of work shaken onto their plate by the Christchurch earthquake, the magnitude 7.8 Kaikoura earthquake delivered up an even bigger serving. The earthquake caused over 80,000 landslides throughout North Canterbury, Kaikoura and Marlborough, damaging farmland, smothering State Highway 1 and the Inland Kaikoura Road in many places and damming several rivers. Heavy rainfall events throughout the year brought down landslides in the usual suspects of Haast Pass, Nelson/Tasman, Wellington and the Rimutakas, the Manawatu Gorge, East Cape and Coromandel. Of course, a New Zealand summer wouldn’t be complete without an ex-tropical cyclone or two: In January Victor brought down landslides from East Cape to Tolaga Bay.
While landslides kept road crews very busy, and some property was damaged this year, we continue to be very fortunate that no lives were lost from landslides in 2016, particularly given the amount of landslides caused by the Kaikoura earthquake.
GeoNet turns 15
GeoNet also turned 15 years this year. In 2001, we started as New Zealand’s first national seismological monitoring system. In those 15 years, we’ve grown from a small fledgling network with a handful of online sites to more than 650 monitoring stations around the country, as far north as the Kermadecs and as far south as Antarctica. You can read more about our 15 years of monitoring New Zealand’s geological hazards here.
(Caption: Sara Page, our public information specialist for social media, put the newsletter together detailing all the geological events that GeoNet has monitored in the last 15 years.)
2016: Ground-breaking but New Zealand still unbreakable
It was a challenging year but also inspiring to me about how we all pulled together. So while 2016 was a groundbreaker, it didn’t break us but rather pulled us closer together as a team. This country faced some pretty big challenges, once again, due to seismic forces. And like the devastating events of 2011, people came together and helped out. Volunteers from all over the country came to assist Kaikoura, Ward, Waiau, and other affected communities in North Canterbury, Marlborough and Wellington. It was a terrible year for those communities and people affected by these earthquakes. We support those communities in their ongoing recovery.
For my part, working for GeoNet, I was overwhelmed with the support we received. There were hundreds of “thank you” emails, tweets, and Facebook comments this year from people, which we really appreciate. Further support came from our friends at the Ministry of Civil Defence and Emergency Management, who also work tirelessly this year. We couldn’t have done all the hard work this year without our supporters at EQC, LINZ, DOC, MetService and MBIE.
A couple of brief thank yous are required with a year like this one. Our technical support and services team diligently worked so we didn’t lose service during this challenging time, and our app and software developers helped us provide new and improved services. Our techs worked hard, putting up new temporary sites to better capture every ground movement in North Canterbury and around East Cape. They even found time to innovate with the new ‘Spade-tenna’ (patent pending). We certainly could not have supported GeoNet this year without our team of duty officers. All of these people help support GeoNet. We thank them for their continued service to New Zealand’s geological hazards monitoring network.
2016 was also the year we said goodbye to our manager, Kevin Fenaughty, who had been in charge of public information since the beginning of GeoNet. Kevin left us this year one week before the Kaikoura earthquake for a new job in MCDEM. He sent flowers to say "sorry" but to be honest, we're still a bit grumpy about him leaving. Anyway, if you like our stories, you can thank Kevin because he hired us! So, thank you for your long service, Kev. Also, Natalie Balfour, who was on the public information team for a short but very busy ten months, is now our data management team leader. She did a great job as part of the team but now has another big job in GeoNet. We wish both of them well in their new jobs.
So what will 2017 hold? I’d like to say that 2017 will be more like 2015: mostly harmless. But there are no guarantees; nature is a terrible project manager. Some years it’s almost too much while other years, it’s quiet. One thing we can say is that, at GeoNet, we are taking the lessons learned from 2016 and will continue to improve our network, our website, app, and all our services. We hope for a quiet, calm 2017 but the best thing we can all do is be prepared for whatever happens next.
To find out more here about how to prepare for emergencies, visit our friends at: