In this guest post University of Auckland Geologist Dr Julie Rowland reflects on the 14 November M7.8 Kaikoura earthquake.
Let’s be clear – it was huge. When you see houses shunted sideways 10 m or lifted up by 8, you know you are dealing with a big one.
The drone imagery and photographs that have been doing the media rounds paint an extraordinary picture of the power of plate tectonics to shape the surface of our land. I was there on day 5 with a small team from the University of Auckland. We had volunteered to help GNS Science map out new ground breaks and capture critical fault displacement data. I’m talking about roads and fence lines that were ripped apart by the rupture – things that get mended quickly. These sorts of features provide important markers for the amount of movement across the fault. This is the data we need to ‘ground truth’ models of what happened and feed in to revised seismic hazard models for the country.
We knew the quake was a big one from its signal on our Geonet seismic and geodetic monitoring network. But, we had no idea it was so complex – the more we looked, the more we saw. Fault after fault after fault had ruptured. My job was to capture data along the Clarence Valley, from the ocean at Waipapa Bay to the broken bridge at top of Clarence Valley Road
In this portion of the rupture, the fault swings inland and instead of being dominated by sideways movement of the sort seen at Kekerengu to the north or Hundalee to the south, the movement across the fault was mostly up. The entire valley is one big squeeze box, with the southwest side ramping up and over the northeast side. River flats used for cropping now have a whopping 6 m+ terrace through them. On one side of the valley hillsides have been shunted up and sideways, bulldozing over farm tracks. On the other side, the uplift has driven collapse of enormous slips, wiping out hectares of good pasture.
Everywhere fences and water supplies for stock and households are ruined.
As astonishing as this event is from a scientific perspective, it is something else completely for the landowners of this valley. It is grief, it is cost and it is work. Here’s the tricky thing – it’s we scientists who are often the first outsiders affected landowners meet after the big shake. In gaining access to property and information we place an additional burden on distressed people.
This carries an enormous responsibility and many challenges – points defined in the excellent New Zealand Natural Hazards Research Management Platform information sheet on ethical guidelines for post-disaster research. This is not a time for scientific exuberance and actually, I didn’t feel like that. I felt far more circumspect. My interactions with landowners defined my experience – from stories of lucky escapes, to the hard decisions needed to get water to troughs so that stock could survive, to the ongoing frustrations of just getting the mail.
What a fantastic bunch of people, with incredible forbearance in what is such a demanding time.