Q&A: Science at quake's ground zero

Professor Tim Little surveys a rupture in the Kekerengu Fault in coastal dunes. The vehicle tracks have been shifted six metres horizontally and two metres vertically. Photo / Rob Langridge

For scientists on the ground in the South Island, trying to understand what has happened to the landscape has been an urgent and testing task. Science reporter Jamie Morton was able to speak briefly with GNS Science earthquake geologist Dr Rob Langridge before he returned to the field today.

What kind of work are you doing on the ground down there?

So several of the faults in the Marlborough and Kaikoura area have ruptured during this very large earthquake and we are on the ground trying to survey the actual displacement or fault movements.

We are starting with some of the really obvious cultural features - the highway, the railway, roads and tracks and things that cross the faults.

We're using GPS surveying equipment to accurately survey the lines.

In many cases, things like highways are very straight, and of course, where they cross the fault, you can measure the straight parts of the highway and see how they've been separated or displaced across the fault.

On the Kekerengu Fault, there has been about five metres of horizontal displacement across the South Island main trunk highway and about two metres of vertical displacement.

So, rather than looking like a normal railway, it now looks like a bit of a rollercoaster ride.

What are some of the challenges you're up against down there?

The land is incredibly shattered, especially when you get up into the hill country and the mountains.

There's a lot of landsliding and damage to the road, but generally, access is quite tough.
Last night, we did actually have a helicopter reconnaissance, so we got to fly around and see some of the faults that are back in the ranges, and the access to those areas is very tough.

There's also been a lot of heavy rain, so there's reactivation of some of the landslide areas, and there's a lot of debris coming down rivers like the Clarence.

Not only is it an active tectonic area, but there are hazards with the material that's coming down off the slopes now.

Is there a sense of urgency to the work you are doing?

There's a focus on the highway because it's liable to be repaired quite quickly.

They are wanting to get the highway as operable as possible towards Kaikoura, so the places that have been displaced by the faults, we want to survey those sites first, and then we'll start mapping those that are cross-cutting farmland and mountain landscapes.
But those are not particularly urgent.

One thing we've talked about is having aerial surveys such as LIDAR and aerial photography, so where it's remote, we can actually start mapping things from digital imagery rather than having to get on the ground at some of these isolated places.

How tough is the work itself? You'd be putting in some long hours, I'm sure.

Yesterday was a very long day.

Today we've been having logistical meetings and we are expecting a southerly coming in later today.

So we'll try to get as much done as we can before it gets really lousy, then we'll come back and consolidate.

We are just staying in Blenheim, which is quite comfortable, and we are away from the main aftershock zone, and from there we are just travelling down the coast.

There are other teams that are coming out from Canterbury University who are mapping the southern end of the zone at the moment and when the inland Kaikoura route is open, people will be looking at the fault deformation close to Kaikoura.

This map - updated today - shows the various fault ruptures and associated quakes around Marlborough following the large 7.8 shake on Monday. Image / GNS Science

As the person normally tasked with overseeing GNS Science's active faults database, what's it been like seeing these ruptures, and the exposure of completely new faults, first hand?

It's very exciting, but at the same time it's so complex that it just blows your mind a bit, especially when you are up in the helicopter and you see the scale of the damage.

There are just some very, very large landslides out there, with lots of land damage in terms of smaller landslides and cracking from the shaking itself.

How are the locals you've met faring?

We've been on the ground in the Kekerengu area and we've been talking to some of the station owners, and we've flown over some of their places.

They've responded quite well, but you can tell there's an underlying level there where they're a little bit shattered emotionally.

But they're being tough and they're getting through it.

Damaged road near Oaro State Highway 1. Photo / NZTA

I think in general, people are happy to talk about it and are happy to be listened to.

From what you've seen down there, what's the big picture in terms of the quake and what drove it?

What we know so far is this is a very big earthquake, and a complex one as well, because it involves multiple faults, from all the way down near Culverden, to all the way up toward Cape Campbell on the Marlborough coast.

It involves many fault movements and it's pretty clear that the coastline has been uplifted as well, because we see rocks and reefs that have been lifted up out of the sea.

The effects of this earthquake are extremely damaging and they have medium to long term impacts on the landscape, the economy, and of course the people.

It's a really major, regional-scale earthquake.