New research has suggested a novel way to measure and potentially predict previously unknown locations that may be prone to earthquakes. The study, led by Professor Jon Waters at the University of Otago, confirms that the region around the New Zealand city of Dunedin was hit by a large-magnitude earthquake 1000 years ago. The team came to their conclusions by studying the genetic properties of kelp uplifted to shorelines during that seismic event – a method that could have domestic and international implications for predicting areas susceptible to earthquakes. Bronnie Wilde spoke to Waters about his findings and unique research method.
Jon Waters is a Professor of Biology at the University of Otago. He is an expert in rates of molecular evolution.
This interview has been edited for clarity and length
Bronnie Wilde: What inspired you to come up with this method of research?
Jon Waters: Everyone saw the [2016] Kaikoura earthquake and how the shore was uplifted there, and all of these kelps and shellfish were sitting there on the rocks drying and dying in the sun and it was such a startling event for us to look at. It made us wonder how this might have happened in the past. There must be examples of this sort of thing elsewhere. So to cut a long story short, we looked around elsewhere in New Zealand and talking to the geologists [we found] there is a big fault just south of Dunedin where there was a big quake around a thousand years ago, but some of the details of that were not worked out.
BW: Is there a history of seismic activity in the area?
JW: Geologists have been looking at what has happened south of Dunedin. There is a major stretch of coast that seems to have been uplifted and you can see evidence of that on the landscape. So the geologists have been looking at what happened there, this fault called the Akatore fault. But we were wondering if that uplift in the region had an effect on the biology around the shore like it had in Kaikoura, so we set out to look at a species of kelp there and looked at its DNA. And we were really amazed to find really strong signature of change that apparently has come from this earthquake about one thousand years ago.
BW: What is this difference between a gradual uplift versus a sudden uplift movement caused by an earthquake?
JW: Well, what we found looking around Kaikoura for instance, [was] that there are some bits of the shore there where things had only come up a little bit, but there were other places where it had come up a long way, places where it had come up several metres that had really ripped everything out in the shore. And so we had an idea of what we might look for and expect to see if there had been a really big earthquake where it had come up a long way, and we are talking about an event a thousand years ago. So if it comes up in small steps then it might affect the biology a bit, but if it came up in one big step that would be a bit like what we have seen in the heavily uplifted parts of Kaikoura. So what we found when we looked at the coast down this way south of Dunedin [was] that there was this complete anomaly, a genetic difference between the kelp populations all along that uplifted shore compared to the populations to the north and south. And genetically it really stuck out like a sore thumb and it could only really be explained by there having been this huge rip-out event and then it got colonised from somewhere else. So the way you can think of it is a bit like a population of humans get ripped out but then [being] replaced from somewhere else altogether. So that is the sort of thing that we are seeing down the coast here.
BW: What are the implications of these findings?
JW: Well the implication is that it really suggests that there was one really major event on this fault about a thousand years ago, rather than being a number of small events. For instance, we know in Dunedin there was an earthquake in 1974, it was medium-sized, it was magnitude five. Small events can happen around here but we weren’t so sure if there could be one big event like this. And what we found was, yes, there was a high magnitude event down the coast [like] something approaching the level of Kaikoura, but really close to Dunedin.
BW: Do you have any estimates as to how large this earthquake might have been?
JW: I am not a geologist but based on the amount of uplift I would say it was a similar sort of event to Kaikoura based on the way it changed the coast. A geologist might say it was a seven or seven point five or something like that, so it is something pretty substantial, something that would really have an effect on Dunedin. Back when this happened there were no people in New Zealand so there was no one around to report it, but if this happens tomorrow, we would certainly know about it.
BW: How would this research help in planning for an earthquake or disaster mitigation?
JW: Well, I think we focus a lot on the big one on the alpine fault that seems to occur every few hundred years and we have got a lot of awareness about that. But I think, as we learnt with Christchurch, sometimes it is a lesser-known fault which is closer to a city that might end up causing more damage. And now we know that we have got a big quake in the past on a fault just near Dunedin, it is the sort of thing that really tells us we need to be prepared for a big one at any time and not just that big one that everyone is focussing on but something on a fault that is closer to Dunedin or another New Zealand city.
BW: Could this research help us identify cities that were previously unknown to be at risk of earthquakes?
JW: Oh, definitely. There is really a possibility to use this sort of tool – and not just in New Zealand – to use the biology as a way of looking at geological change in the past. Because there are some places where the record geologically is not so strong or clear, but to use this tool where we can use DNA of modern populations to look for these sorts of anomalies can really give us a clue into the past. So yeah, we want to extend this more widely.
BW: And what were those advances in genetic science that made this type of experiment possible?
JW: It is just so much more easier now in terms of generating the data that the tools we have we can generate a lot more data a lot more quickly. So we can generate that and we also have stronger tools and computational approaches to analyse the data, so it is all just getting better and quicker. We can look across the whole genome of these populations and we can really get a strong signature and try and put a good time frame on when the changes happen as well.
BW: You mentioned this research could be useful overseas. What are some examples of other places in the world that might be able to use this research?
JW: Well for instance, we have got lots of quakes happening in places like Chile where there have been a number of quakes over the last ten years, but huge ones going back to the 1960s for instance. But geologically they are not all that well-defined and this would really help us to look at those. Other geologically active places like Japan would be another example and even places around the Mediterranean where there were quakes maybe in ancient Roman times where they would use the biology and the geology to try and look at whether things went up or down and that sort of thing. This DNA approach can bring a whole new element to that research and new ways of looking into [earthquakes].
BW: Has this DNA approach been used before elsewhere?
JW: I think we are the first people to look at it in this sort of way, in terms of coastal biology and earthquakes. I think when we use DNA we can look into the distant past and say ‘Hey, there was a huge ice age and it ripped out everything’, so people have looked at that sort of effect but not this really local effect of an earthquake over a few tens of kilometres. So, for us that is a really new approach and it hasn’t really been applied anywhere else before.
BW: What is next for you with this research?
JW: Well, we know of other earthquakes around the New Zealand region and one really interesting one is the Wairarapa quake in 1855. We know around the Wellington region we have got all of these uplifted shores and these were all uplifted in the same sort of way by quakes. And the effects of those ones are really interesting, and it happened more than a century ago so we would like to look at what the effects were of that and it is a really good model because we know the quake happened but can we detect the same sort of thing. So the more we study this sort of process the more we can understand about it.
This interview originally aired on 95bFM’s weekly news and current affairs show The Wire. For more stories like this, click here.
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Disclaimer: The ideas expressed in this discussion reflect the views of the guest and not necessarily the views of The Big Q.
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