A magnitude 7.5 earthquake that hit New Zealand near North Canterbury has left two dead and caused extensive damage to infrastructure, with first estimates putting the damage bill in the hundreds of millions.  

The earthquake hit Sunday night and triggered a tsunami warning, which sent thousands of people scrambling to higher ground. Hundreds of aftershocks have followed, with researchers predicting they could continue to pepper the area for months to come. The quake was felt as far afield as Auckland. 

It is the largest earthquake recorded in New Zealand since 2009. 

The worst affected areas are Kaikoura and Marlborough, with Wellington also suffering significant damage. 

The quake has crippled road infrastructure in the region, with road surfaces buckled and landslips cutting off roads in Kaikoura. The town is also without water and sewerage. The Air Force is assisting with assessment of the damage and flying in supplies and personnel to assist. Communication issues have made it difficult to fully assess the extent of the damage and needs of the communities. 

There have also been reports of widespread liquefaction on reclaimed land around Wellington's waterfront, and significant damage to the ferry wharf at Wellington, resulting in the cancellation of inter-island ferry sailings.

The New Zealand Transport Agency (NZTA) says there are many sites affected on State Highways 1 and 7, on both sides of Kaikoura, and inland from Waipara to the Hanmer Springs turnoff and to Springs Junction. 

Neil Walker, Transport Agency Highway Manager, says assessing the sites has been complicated by the threat of continuing aftershocks, along with forecast high winds and heavy rains. 

“We are aware that communities have been cut off by slips and we are working urgently with other agencies such as Police, KiwiRail and local authorities to coordinate efforts ensuring people are transported out of closed areas safely, and roads or alternative routes are open and safe to use as soon as possible.”

Mr Walker says it is too soon to tell how long it will take to assess the damage on all the upper South Island highways. 

“Some have already been assessed and work has been planned for some sections of the highway with less severe damage. Other sites are currently inaccessible by road and/or 4WD and the safety risk needs to be carefully managed both in assessment and in the emergency repair work itself. Transport Agency and council teams are working as fast as we can to reopen highways or find alternative routes to places like Kaikoura.”

'Utter devastation' and need for resilience 

Surveying massive landslips in a Defence Force NH90, Prime Minister John Keys said the damage to the Kaikoura region was worse than he thought, Stuff.co.nz reports. 

"It's just utter devastation, I just don't know...that's months of work," he said.

He estimated the clean-up will run into the hundreds of millions and clearing the debris and blocked roads could take months.

IPWEA NZ President Peter Higgs, who has been working around the clock in his role as a Civil Defence Controller for Gisbourne, says the earthquake again demonstrates the reliance and dependence our communities have on public works infrastructure.

"We who work in this area, need to focus on the resilience of our infrastructure and the 'lifelines' that they deliver," he says. 

"While the public response was excellent in that people heeded the warnings to self-evacuate when a large earthquake was felt, the recovery will take a long time, particularly so in the worst hit areas. It also highlights the limits of our transportation networks – not just road closures, but shipping between the two islands when or ports are damaged." 

Geonet, the group that monitors earthquakes in New Zealand, said it was certain that more earthquakes would be felt in the area, and that it appeared there had been two earthquakes, not one. 

"It looks like we’ve got two separate but related quakes going on. Our reports indicate that the combination of these two quakes lasted two minutes, with the most severe shaking at around 50 seconds. It was widely felt throughout both the North and South Islands. It looks like one was a strike-slip and the other was a thrust fault.  Further, we have received many aftershocks since the start of the quake," Geonet's website reports. 

Geonet has developed three scenarious for how the situation will evolve: . 

Scenario One: Very likely (80% and greater)
A normal aftershock sequence that is spread over the next few months. Felt aftershocks (e.g. M>5) would occur from the M7.5 epicentre near Culverden, right up along the Kaikoura coastline to Cape Campbell over the next few weeks and months. This is the most likely scenario.

Scenario Two: Likely (60% and greater)
In the next month, it would be likely that rupture of earthquakes of about an M6 in the North Canterbury and Marlborough regions will occur, as well as potentially offshore in Southern Cook Strait and offshore Kaikoura.

Scenario Three: Unlikely (less than 40%)
The least likely scenario is that in the next month, (it is unlikely but still possible) there would be rupture of longer known faults (with earthquakes of about M7), in the Marlborough and Cook Strait regions.  

Structural engineers are investigating the integrity of buildings in areas affected by the earthquakes. 

IPWEA Australasia CEO Robert Fuller says he has spoken with members of the IPWEA NZ team. 

"We have been in contact with our NZ Executives; while they are OK, experiencing such a phenomenon is extremely unnerving. I know – I was at the Newcastle earthquake and part of the management recovery team," he says. 

"Yesterday’s sudden earthquake in New Zealand once again reminded us that our jobs as engineering professionals can have a significant impact on the lives of others when such forces of nature are unleashed. 

"When we design to standards and maintain our infrastructure, it is an investment in resilience. You can’t design-out for earthquakes, but you can design and maintain to minimise damage and loss of services."