The 2016 Kaikoura earthquake was one of the four largest earthquakes to strike mainland New Zealand in 160 years.
Sunday, 27th November 2016
The magnitude 7.8 earthquake which struck 15 km north-east of Culverden at a depth of 15 km at three minutes after midnight on Monday 14th November 2016, was the same size as the three largest earthquakes to strike mainland New Zealand since the magnitude 8.0 quake of 1855. The three previous quakes were all magnitude 7.8 and struck Murchison in 1929, Hawke’s Bay in 1931 and Dusky Sound in 2007.
Quakes of magnitude 7.8 or greater have occurred further off-shore since the 1855 event, most of them in the Kermadec Islands and one quake of magnitude 8.2 in the Puysegur Trench in 1989.
The November 14th earthquake caused extensive damage from North Canterbury to Wellington, isolated many communities in North Canterbury and Marlborough and disrupted electricity supply and road, ferry and rail services. State Highway 1 and the nearby rail link have suffered extensive damage along the South Island’s east coast from Ward to Waiau and it is likely to be months before they are restored. The coastal town of Kaikoura remains isolated by road two weeks after the event, but services are now being restored and supplies have been taken in by army convoy and navy ships.
In the days following the earthquake, tourists and some locals were evacuated from the Kaikoura area by navy vessels from New Zealand, Australia, Canada and the United States of America. Marlborough, which suffered considerable damage during the sequence of 6th magnitude earthquakes in 2013 and 2014, has again sustained damage to infrastructure, housing and commercial buildings.
In Wellington, more than 70 commercial buildings were evacuated in the days following the quake due to earthquake damage. The central business district was effectively closed on Monday 14th to allow buildings to be assessed while strong aftershocks continued to be experienced. As the week progressed and repairs were made, those buildings that had sustained minor damage were able to be reoccupied.
This office building in Molesworth Street will soon be demolished
A seven story parking building in Tory Street is also thought to be at risk of collapse in a strong aftershock, causing the evacuation of several nearby commercial and apartment buildings and a large cinema complex. Plans to temporarily stabilise the structure are being discussed but it is likely to be demolished in the medium term. The building formerly occupied by the Statistics Department has suffered significant damage and has to be demolished.
In Lower Hutt, the Queensgate shopping mall car park and cinema complex are to be demolished because of earthquake damage. 70 of the mall shops remain closed because of the collapse risk as are a nearby supermarket and part of the Angus Inn.
The Earthquake
Seismologists have been working hard to understand this complex event. Initial analysis suggested it was two earthquakes. It was thought that the first quake triggered the second event further north as the fault ruptured. Shaking caused by the two near-simultaneous earthquakes therefore lasted longer ”“ thought to be about 90 seconds near Wellington and over two minutes nearer to the epicentres.
In Wellington, the earthquake was felt to have three distinct components. Shaking from the initial earthquake was felt for some seconds before a gyrating effect was felt. Soon after, the energy released by the second earthquake dramatically increased the shaking. This security video taken at the Titan Cranes depot clearly shows the three stages of the event.
In a statement released on November 16th, GeoNet noted, “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.”
It soon emerged that several separate faults ruptured during the unusual seismic event. Rapid field observations discovered that the Kekerengu Fault had up to 10 metres of slip near the coast. This earthquake fault shifted State Highway 1 and the nearby railway line by at least 2.3 metres horizontally and one metre vertically. There was minor movement on the seaward segment of the Hope Fault which has offset the road by about one metre. The Hundalee Fault also ruptured, the movement extending off the coast into the Kaikoura Canyon. A newly identified fault at Waipapa Bay also moved. Nearer the earthquake epicentre, there is evidence of fault movement in The Humps fault zone and Emu Plains and fault ruptures have appeared on the north side of the Waiau River.
This new information shows how complex this seismic event was, defying the convention that an earthquake is caused by movement of a single fault and the point at which the movement starts is termed the epicentre. The Darfield earthquake of September 2010 was similar, in that it resulted from multiple sections of a long fault rupturing, but was less complex.
Tsunami
On-shore earthquakes don’t usually generate tsunami but can cause seiches in harbours, estuaries, lakes and other large bodies of water. A seiche causes water to slosh back and forth across the body of water like a disturbed glass of water.
Initially, the quake was thought to be onshore and of magnitude 6.6 and a tsunami was not anticipated. However, the tide gauge at Kaikoura recorded a sudden drop in sea level soon after the quake and a 2.8 metre tsunami was recorded there. The gauge at Lyttelton recorded a 1 metre tsunami. However, at Little Pigeon Bay on Banks Peninsula a cottage was wrenched off its foundations and the front walls collapsed by a 4 metre wave which travelled 140 metres up the nearby creek.
Uplift
A staggering amount of uplift has been found along the coast of the South Island near Kaikoura. The extent of this is still being determined but initial surveys show that the coastline from 20 km south of Kaikoura to Cape Campbell in Cook Strait has been raised by a half to two metres.
The uplift is not uniform, being about a metre at Kaikoura and about a metre at Cape Campbell. Some sections in-between have shown greater uplift. At Half Moon Bay on the southern side of the Hope Fault, the uplift is over 2 metres. At Waipapa Bay a block has been raised 5.5 metres between two traces of the Papatea Fault.
Lights In the Sky
Several members of the public reported seeing lights, similar to lightning, in the sky at about the time the earthquake was first felt, and video has been published on the internet. Video has also been published showing power lines clashing in Nelson during the earthquake. However, the phenomenon of lights in the sky associated with earthquakes has been reported for centuries.
In New Zealand, it was first reported during the earthquakes in the Wanganui area in the 1840s. Te Papa’s geologist, Hamish Campbell, saw the lights associated with the Kaikoura earthquake and wrote an interesting and entertaining blog about it. This seems to be another scientifically-discounted phenomenon that, with the advent of suitable technology and public access to video recording, will soon take its place as a recognised and researched feature of earthquakes.
Questions and Lessons Learnt
Clearly New Zealand has entered a seismically active period, as have other parts of the Pacific Ocean. After more than 50 years of relative calm, we have experienced a dramatic increase in the number of strong and major earthquakes in the range of magnitude 6 and 7. The last time we experienced a prolonged sequence of large earthquakes was between 1929 and 1942 when New Zealand experienced nine large earthquakes and their aftershocks.
The magnitude 6.7 quake near Gisborne in 2007, the close call with the Dusky Sound quake (also magnitude 7.8) in 2009, the subsequent deadly series of earthquakes in Canterbury, the series of magnitude 6 quakes near Cook Strait in 2013 and 2014, and the magnitude 7.1 quake at East Cape in September should have rung alarm bells. With a great quake (of about magnitude 8) expected on the Alpine Fault the scientific response and assessment seems to be underfunded at a time of increased seismic activity. GeoNet, which determines the size and location of earthquakes and the possible tsunami risk operates on a call-out basis outside office hours. The stress on a seismologist chased out of a deep sleep in the middle of the night to remotely log in and analyse earthquake data to determine the severity and the possibility of a tsunami is immense.
There is talk that the government will fast track a system for sending SMS messages (aka texts) to mobile phones in the event of a tsunami warning. Big deal, but of little use to communities where the mobile network has been taken down by the earthquake. Experience shows that the SMS system struggles to deliver messages when mobile networks are under extreme load ”“ the messages are delayed for hours, arrive in the wrong order and the system gives users erroneous error messages.
The Ministry of Civil Defence has developed a tsunami plan but has still failed to specify a standard for tsunami sirens and their operation. This has been left to local and regional Civil Defence groups. How on earth would someone from the Bay of Plenty recognise a tsunami siren on the Canterbury coast if they sound different from the ones at home? What’s more, after last Monday’s quake some CD groups activated their alarms and others nearby didn’t.
In any case, if the decision to declare a tsunami warning or threat can’t be made because of inadequate scientific input, the existence of warning infrastructure is immaterial. GeoNet now needs to be funded to a 24-hour operation if it is to provide the scientific support for such decisions.
The Ministry of Civil Defence and Emergency Management (MCDEM) needs to dramatically improve its decision-making and communication of tsunami events as well. The “long or strong ”“ get gone” mantra which encourages people in tsunami-risk areas to evacuate without waiting for an official warning has been widely communicated and adopted. However, after the Kaikoura quake the misinformation on the MCDEM website about tsunami risk for people at a distance from the quake’s epicentre dragged on for nearly three hours.
Wild Land has said before, and will say it again. MCDEM needs to stop giving confusing instructions. Don’t run around the country spouting the “long and strong” mantra if your website shows you to be dithering when an event actually occurs. It is simple. In the absence of information, stick to the message that it would be advisable for people in tsunami-prone areas who have felt long or strong shaking to evacuate to higher ground until the situation becomes clearer.
GeoNet staff have put in long hours in the past fortnight gathering information, analysing a vast array of data and trying to keep the public informed. However, its sloppy practice of “updating” old information posts on its website needs to stop. It destroys the audit trail of who said what and at what time. The website’s Content Management System doesn’t automatically apply the date and time of web postings, so it is impossible to know how recent the information is unless the author manually enters a date and time.
With a number of reports being “updated” the website’s news feed is currently a bizarre jumble of stories with some of the stories at the top of the list intermingled with updated entries showing a date that is a week old. This makes it difficult to be sure if an item is current or a database corruption has occurred.
Since its inception, GeoNet’s application for automatically determining the size and location of earthquakes (SeisComp3) has been notorious for its ghost quakes ”“ earthquakes that haven’t occurred, have been given the wrong location or have been assigned the wrong magnitude. At times of intense earthquake activity, as occurred on the Monday morning of the Kaikoura quake, the validated earthquakes are mingled with a stream of unverified information in what resembles a dog’s breakfast. What’s more, important events quickly disappear off the short listings on the website and authoritative information is soon lost to the browsing public.
GeoNet’s headlong rush to become the seismic equivalent of the Twittersphere needs to be reviewed. Is its role to provide clear and concise earthquake information or to flood the web with earthquake data to satisfy adrenaline junkies?
GNS Science has issued only one media statement on its website regarding the Kaikoura earthquake. The state-funded organisation used to issue well-written reports on the findings following a significant earthquake or tsunami event. The gap has been filled by the hastily-written articles on the GeoNet website which are over-written with updates and too often disappear from the website over time. There is a place and an audience for this type of material, but the absence of formally written material is a serious omission.
One thing that can’t be questioned is the dedication of the staff at GNS Science and GeoNet, and the quality of their work. When a large event like this takes place, they put in long hours, travel to remote locations under trying circumstances and embrace the science. The work that is done in New Zealand has attracted students and graduates from many countries, and the organisations are first-class collaborators and contributors. However, like the Ministry of Civil Defence, GeoNet needs to review the state of their public communications – it isn’t working too well.
One question that doesn’t seem to have been asked ”“ Where was TVNZ in the immediate aftermath of the earthquake? Like radio New Zealand, TVNZ has signed an MOU with Civil Defence as one of the two state broadcasters to broadcast information in the event of a significant earthquake or tsunami event. This lardarse organisation, which abdicates its responsibilities at every opportunity, happily broadcast reruns of Emmerdale Farm while the events following the earthquake and a possible tsunami unfolded.
Meanwhile, a state-funded organisation that sticks to its knitting was actually broadcasting with a real human presenter ”“ soon augmented by more real people. Radio New Zealand (RNZ) has been starved of funds by successive governments and has had to shrink its services and shed some of its talented staff over recent years. Nevertheless, it battles on, carrying out as many of its duties as a state-funded broadcaster as its capped budget effectively shrinks year by year.
Having just read the news, RNZ National’s Vicki McKay was calm under fire as the Wellington studio she was in began noisily rocking with the Kaikoura earthquake of 2016. She kept her microphone live as she immediately thought of her audience and what they would need to be doing as the shaking caused by the earthquake gathered momentum.
That showed some grit and should earn her a media award.
[ Compiled from GeoNet and GNS Science media releases ]