The Wall of Waiau

BY KATE PEDLEY (UNIVERSITY OF CANTERBURY)
Accessibility: moderate
UC geologists first investigate the fault rupture back in Nov 2016. Photo K Pedley / UC
The 14 November 2016 Kaikōura Earthquake ruptured along over 21 different faults over the north eastern section of the South Island from the epicentre near Waiau, through to offshore Cape Campbell. The Wall of Waiau section of fault scarp along the Leader fault rose to international fame as one of the more visually striking examples of the effects of fault rupture on the landscape.
A pond has formed from displaced drainage. Photo K Pedley / UC
At just after midnight on the 14th November 2016 a magnitude 7.8 earthquake ripped through the countryside of north-eastern South Island. While the human impact effects of earthquakes are indeed sobering, earthquakes are also the vibrations caused by movement of the Earth's tectonic plates that cover the surface of this dynamic planet we call home. Without plate tectonics the islands of New Zealand would still be underwater and we would not have the dramatic and beautiful landscape that is renowned around the world. Fault ruptures like in this event have occurred many times in this region and throughout the South Island over the last 25 million years to slowly build up the mountains we see today.
The fault scarp viewed at this location is around 3.5 m in height.

The geology here is Middle Miocene - Pliocene aged (around 2-15 million years old) Greta Formation, a formation usually dominated by fine-grained marine siltstones, where deposits up to 800 m thick can be found near Waiau township, but also contains conglomerates and sands. The Greta Formation deposits record near-shore marine and some coastal on-land environments as the local region was uplifted out of a shallowing ocean by the ongoing tectonic growth of the Southern Alps (due to tectonic plate collision).
The Wall of Waiau, November 2016. Photo K Pedley / UC
It's a rare opportunity to see "fresh" fault ruptures. The effect of pushing up a block of the ground relative to it's surroundings (and depending on it's geologic properties) creates a fault scarp that is more prone to erosion and will get smoothed over fairly quickly. It has always been a challenge for geologists trying to work out how much and how often a fault has ruptured in the past (and therefore how often it might do so again), when much of it may have been eroded away!
This event moved through the landscape at around 1.8 km per second (over 6000 km per hour!). Therefore this relatively tiny scarp formed incredibly rapidly!

Notice how there is now a pond in front of the scarp - why do you think this has developed? This fault rupture also moved sideways as well as vertically. Can you see any evidence of the sideways movement? It's a lot more subtle to pick up than the obvious vertical movement! HINT: see if you can find any offset sheep tracks or bushes.
Erosion is playing a large role in the evolution of the scarp today. Compare what you see in front of you to the original photos taken just after the earthquake in 2016. How has the scarp changed over time? Have a closer look at the Greta Formation geology that is exposed in the scarp. What is the grainsize of this unit? How soft or hard is it? What effects might physical or chemical weathering have on this unit over time? This unit underlies much of the Woodchester Station land - what hazards might be posed to the landowners and range of activities they might use the land for? Consider effects on forestry, stock, infrastructure, services. How might they be able to reduce or manage the effects?
Directions/Advisory

This site should be paired as a half or full day trip with the Leader River landslide dam (see link), which is also on Woodchester Station. To get to the station turnoff drive approximately 12 km up the Leader Rd from SH1 at the road turnoff to Waiau just before the Leader River.
If coming from Waiau along the Leader Rd, the station entrance is also about 12 km up the road.
The Woodchester Station driveway is windy, narrow, gravel, and 6 km long through to the homestead.
If coming from Christchurch you should allow 2 hours one way travel to get to the homestead.
Make sure all farm gates are left as you find them!!!

While pretty straight forward it would not be recommended for those with weak ankles or balance. Not recommended in wet weather as it can get very boggy!

Accessibility: MODERATE

This is private land and a working highcountry station. Visits are for groups (not individuals) and by prior arrangement only – Please see link below for booking contacts at the facebook site. Groups of no less than 10 people are welcome with a fee of $10 per person for the day visit to the station, payable in person at the homestead when you arrive. School groups are also welcome by arrangement. The landowners, Dave and Rebekah Kelly, will give you instructions on where best to go and park your vehicle for each site.
This is a unique and amazing opportunity to see land evolution in action!

The walk across the grassy paddocks to the Wall from where you park your car near the road takes about 30 minutes and sidles around some steepish hills and rough sheep tracks.

Features
Sedimentary Active Fault Landform Geohazard Active Erosion
Geological Age
Recent! This feature can be precisely dated at just after midnight on 14th November 2016.
Zealandia Evolution Sequence
Pākihi Supergoup: 5 million years ago – present
Links
The Leader River landslide dam GeoTrip: https://secure.geotrips.org.nz/trip.html?id=560&_=1517035138467 Woodchester Station on facebook: https://www.facebook.com/Woodchester/