Ruptured land: observations from the air

Before the foul weather set in, a team of GNS Science geologists, Nicola Litchfield and Pilar Villamor, went out on helicopter flights trying to pin down exactly which fault lines ruptured in the Kaikoura Earthquake.  Their observations confirmed what our seismologists have been saying – that this was a very complex earthquake. On their trip they observed several different faults rupturing the land. They mostly followed State Highway 1 as we flew down the east coast of the upper South Island. Roads are very useful markers for telling how much a fault has moved.
 

The trip in their own words:

 

Kekerengu and Waipapa Bay

“The first fault rupture we saw was the Kekerengu Fault. The fault shifted State Highway 1 and the railway line by at least 2.3 m horizontally and 1 m vertically. We followed the fault rupture from the beach inland for 2km to Bluff Station. Here, the earthquake had dislocated hills, fences, roads, buildings and the river bed, some by as much as 10m horizontally. A house was also spectacularly moved off its foundations - the occupants were shaken up, but otherwise okay. This was as far as we flew along this fault so the surface rupture could well have continued past this point.

We continued flying south. At Waipapa Bay the road and railway line were shifted by 1m. Further south, we came to the Hope Fault. From the air it looked like this has offset the road by about 1m. We didn’t follow the Hope Fault inland on this flight, but we’ve heard from other scientists who did fly along here earlier, that they didn’t see any disturbance of the land

 

 

Hundalee, Emu Plains, and The Humps fault zone (yes, someone long ago named a fault 'The Humps')

Then it was on to the Hundalee Fault. Again, we saw the fault had disturbed State Highway 1 and the railway line as well as the beach south of Kaikoura.

We then flew to the epicentre area (The Humps fault zone and Emu Plains) and found some fault ruptures on the north side of the Waiau River, some on previously unknown faults. It was less clear exactly how these faults had moved compared to the others further north, but it looked like some horizontal movement had occurred. At the western end these ruptures had affected some small streams.”

Field trips like this one can only find where fault lines have broken through to the surface. It’s likely that other faults below the surface (or longer lengths of the faults mentioned above) have also moved. Other investigations including satellite images will help to show any subsurface fault movements.

What Next?

Now that the wind and rain have subsided, additional teams are out in the field - they’re hoping to cover areas that Nicola and Pilar didn’t get to.


Fault Map by: Litchfield NJ, Barrell DJA, Begg JG, Benson A, Berryman KR, Clark KJ, Cochran UA, Cox SC, Gasston C, Glassey, PJ, Heron DW, Howarth JD, Langridge RM, Little T, Lukovic B, Nicol A, Pettinga J, Ries WF, Rowland J, Stirling MW, Townsend DB, Upton P, Van Dissen RJ, Villamor, P. 2016. 14th November 2016 Kaikoura Earthquake. Preliminary earthquake geology observations. GNS Science. http:dx.doi.org/10.21420/G2MW2D

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