North Canterbury quake explained from a scientist's perspective

What is it like to be part of the team at GNS Science when a big quake hits? Former seismologist Dr Helen Anderson offered to help with the GNS Science and GeoNet response to the Kaikoura earthquake. In the days following the quake, she has been embedded with the GNS Science/GeoNet response teams. She recounts her experience here.

GeoNet scientists are just like you and me - apart from one main difference.

When we leap out of bed and dive for cover all sorts of fear responses are kicking in - fight or flight. GeoNet people are counting seconds, noticing different types of energy waves - and already processing how big and how far away the earthquake is.

On Monday morning, just after midnight, the consensus was "big and quite a way from Wellington".

Time to get on the bike and into work - there's a long day ahead.

At 3pm on Monday I was among about 40 people gathered in the GeoNet ops room at GNS Science's offices in Lower Hutt to discuss what we've learned.

Seismologists, geologists, geodesists, social scientists, tsunami specialists and engineers line the walls as the head of GNS Science's natural hazards group, Gill Jolly, runs us through the agenda on the whiteboard.

Two teams of geologists have just arrived back from helicopter flights over the upper South Island, courtesy of television networks, and their share the observations.

Tens of thousands of quake-triggered landslides have occurred in the Kaikoura back country and in North Canterbury.

Some have dammed rivers.

History shows that 80 per cent of dams that are created in this way fail in the first 12 months.

Some will overtop and stay intact, but we need more information on which ones are most dangerous.

They also report four, and possibly even more, different faults have broken and are showing a multitude of scars on the surface.

They measure a big range of horizontal rupturing from 10m to two metres.

Dr Helen Anderson. Photo / Supplied
Dr Helen Anderson. Photo / Supplied

That is much bigger than expected.

It is quickly apparent that this is a highly complex earthquake rupture.

Possibly one of the most complex on-land ruptures ever seen in New Zealand.

The seismologists are next up.

They report on hundreds of aftershocks spread from Culverden up to Seddon.

There is discussion about the surprisingly complex rupture.

It looks like it started in the south near Culverden and travelled north at 2km-a-second and stopped abruptly near Cape Campbell in Marlborough.

This is a huge rupture by any measure.

The logistics people report on which seismometers and GPS stations have lost or are losing power and there is a sense of urgency in trying to get technicians into the field ahead of an impending storm in central New Zealand.

Flying in 140km/h winds won't be possible.

Ruptures in farmland around Conway near Kaikoura. Photo / SNPA
Ruptures in farmland around Conway near Kaikoura. Photo / SNPA

The geodesists have been starting to model the tide gauge and other GPS data - they are struggling to get a "good solution" for the fault rupture.

Their work will be boosted by the arrival of international satellite data in the coming days.

There's a frustration that getting that takes so long.

The engineers report that they've been in the Wellington CBD since early on Monday morning.

They are able to access some damaged buildings, but others are already closed off.

They report a lot of non-structural damage and some pounding - neighbouring buildings bumping into each other as they sway.

However, the good news is that the recorded shaking levels in buildings is less than the design code.

The tsunami scientists have had a number of meetings earlier in the day and they have just downgraded the tsunami alert so they can stand down.

The marine scientists in the room wonder aloud whether we should be getting a ship with side-scan sonar to the region in the next few days because we'll be losing the chance to get a clean record of the tsunami fault break after that.

A road damaged by the earthquake that struck North Canterbury. Photo / Supplied
A road damaged by the earthquake that struck North Canterbury. Photo / Supplied

Time for a friendly call to NIWA to see if they can help?

Social scientists always bring a different lens and we are all reminded that when we are out and about then our ethical obligation is to help people in distress before we go about our science.

Everybody knows that at some level, but it's a great reminder for those of us who "know" earthquakes that our obligation is understand and empathise with our fellow human beings first.

Honestly communicating what we know - and don't know - is the next big focus and there are at least a dozen media interviews scheduled in the next few hours.

The aim of the scientists is to explain and provide decision-makers with their best understanding of what's going on.

As the meeting breaks up, some people head back to their desks and phones, while others head off to a nearby motel for a few hours kip.

Most have been on deck for 15 hours so far and there's another long night ahead.

The next quake update meeting is scheduled for 9am the following morning.

- NZ Herald

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