Yoda.
I'm Chelsea Daniels and this is a summer special of the front page the NSID Herald's daily news podcast. Major earthquakes may not be a regular occurrence in New Zealand, but the threat of them is always often in the back of our minds. With a major fault line running through the middle of the country, you only have to look at the events in christ Church and Kaikalder to know the risk they pose.
In May, new modeling.
Was published that highlighted the impact a catastrophic quake could have on this country, including the threat of tsunamis and how prepared we are for such an event. We spoke with doctors Bill Fryer and Matt Gerstenberger from GNS Science to dig into the latest research on our seismic threats. To Bill fry this week, you were on a panel at the Nature Challenge Symposium talking about the Hikui subduction zone. Can you start by explaining what this zone actually means in Layman's terms?
Yeah, sure, quite simply, it's just New Zealand's biggest fault. It's the place where the Pacific and Australian plates collide about five centimeters per year and it hosts some of our largest earthquakes, So.
We often hear of certain fault lines being overdue for a quake.
Is that the case here?
Yeah, maybe I'll hand that question over to Matt Leader of our new National Seismic Hazard Model.
Yeah. So what we do is we look at how often earthquakes have occurred on big or on any fault really in the past, and we have different models of how we understand what that means about the future. So we can look at roughly the inter event times between earthquakes in the past and get an idea of when it is likely to occur in the future. It's pretty hard to say if something's actually overdue. We generally have a range of time when an earthquake might occur within.
Is there any way of actually telling when a quake could happen or is it really just luck.
Of the drawl.
So when we do the National Seismic Hazard Model, this is a model that we use to give probabilistic estimates of shaking that we might see in the next fifty e one hundred years in New Zealand. When we do that, we look at kin the whole range of possible earthquakes
that could occur in New Zealand. So we're looking at all the faults that we know about plus earthquakes that could occur in different places, and that gives us probabilities or likelihoods that shaking might occur in a particular location. But yeah, we cannot predict earthquakes, so we cannot say it's going to occur within the next ten days, but we know pretty well where they're more likely and where they're less likely to occur.
Yeah, can I add onto that mat The work that we presentage at the recent symposium was the result of a National Science Challenge program of work that allowed us to build up on some of the great computational numbers that the National Science Hazard Model has given us and try to explore the way these earthquakes would look when
they do happen. So try to understand the types of differences in earthquakes, not just the rates, but also but that might say about the impacts to New Zealand and the people living, certainly on our coastlines.
And it's really important for planning as well.
I guess the research that I saw regarding the Hikarangi subduction zone planners actually use a kind of worst case scenario right, and that's often what we see in the news and media.
The biggest earthquake that could possibly happen along the Hikarngi is around magnitude possibly a nine, but they think maybe more like eight point seven or so, which is very large, and they only probably happen every thousand years or so.
What is the purpose of saying, Look, if a nine point one quite hit this fault line, tens of thousands of people would die, this many people will be displaced.
What's the purpose of doing that? Do you think?
Perhaps the real utility and trying to come up with scenarios that might be similar to what New Zealand will experience in the future is opportunity to test our response systems, to say, if this happens, what would we do and how could we improve that process? How could we improve what we do to try to limit the damage to New Zealand, to try to improve how we respond as
a nation to it. So by understanding how likely these things are, what they might look like when they happen, and then using that information to forecast impacts, we can test those systems that can improve our outcomes if it does happen in our lifetimes.
The other thing we can do with that type of information, particularly when we start to look across different types of earthquakes that can occur, is we can then look at long term planning, so we can move towards what we would call risk based planning, so you look at the potential earthquakes that could occur, the impacts that those could have, and that allows kind of long term planning for things related to building code and different urban planning type settings.
Generally speaking, how active are our fault lines at the moment? I know over twenty twenty two, twenty twenty three, for instance, there was a series of mini quakes under Lake Topor a magnitude five point six earthquake that struck Topaul last night was felt by thousands of people across the country.
It was horrendous.
Yeah. Yeah, I was flying in bed and not hold bed and up and down and move absolutely skied.
Yeah, it's the biggest fun I felt.
Does that speak to a wider issue here?
We know through kind of to the last two hundred years, there's quieter times and there's more active times in terms of the number of earthquakes that we may get over a series of decades. You could say, and starting in two thousand and three, it's certainly been a more active time in terms of earthquakes that we've had in the country. We can't say when that's going to end, and maybe that things are starting to quiet down now or maybe
that we continue to stay in this active period. And that's really the reason that we do this research in this type of planning, and so we can understand the potential for what could occur much better and then pass that information on so that that can be included in the tas that are being made.
Can I add man, One thing we can say unequivocally from looking at the last twenty years of activity in New Zealand is New Zealand always has the potential for a big earthquake and tsunami, and we need to be prepared for that. There's never going to be a situation where we go through time where we say, Okay, all the earthquakes are done, I'm finished with that, move on
to something else. And it's this realization that leads us to do things like I just explained, testing the response systems, or to even develop new tools to help us respond things like tsunami early warning, being able to look at waves, monitor tsunami waves before they arrive to our shores, or being able to forecast the extent of strong ground motion, the amount of damaging shaking we might get after these earthquakes happen in the minutes to hours after they do,
so we can try to triage their recoveries and engineers where they need to go to start looking at buildings and rescue crews where they need to go to start dealing with the aftermath of the big events.
So, Matt, you mentioned over the last few years you've been working on the National Seismic Hazard Model. What are some of the risks posed by a major earthquake in New Zealand, like if the Hiccodangi fault raptioned, for example.
Yeah, well, very related to what Bill just said. We know that there can be earthquakes anywhere in the country, so we do have the potential for strong shaking everywhere. There are certain areas that are more likely to have larger earthquakes, and certainly the Hikarangi subduction zone is one of the dominant ones that really controls what we would call the hazard.
So we talk about two things.
We talk about the earthquake hazard and that is kind of the potential for shaking. And then when we talk about the risk, that's really the impact for society, and the National Sizemic Hazard Model really focuses then on the potential for the shaking that gets then passed on to the other information. There are many active faults around the country that have potential for strong shaking.
Yeah. Can I add, Matt that one significant outcome of our national science challenges their resilience to Nature's challenge, is that we developed a framework in which we can use what we know about the faults in New Zealand and what we understand about the physics of how earthquakes actually happen to simulate hundreds of thousands of years of possible earthquakes in New Zealand. This work has led us to understand just a little bit better what might happen in
a big Hickadonki earthquake. And what we've seen from this is that quite commonly when you get the very largest earthquakes, when you think about a magnitude eight plus earthquake that we might have on the subduction interface, we quite commonly have associated activity or triggering of crustal faults. Some of the smaller faults that are very close to that plate interface, and this interaction or communication between the faults that really has given us a bit better idea about what might
happen and how we need to prepare for that. You can well imagine it like happened in twenty sixteen in the kai Quota earthquake. Before the tsunami hit our coasts, there was a tsunami generated. We had over a meter of uplift of some of the coastlines. Some of the coastlines actually rose by over a meter before that wave hits, So you can imagine that the tsunami impact when it does hit, it's going to be different than if that coastline hadn't risen. We started looking for the same type
of behavior in the Hikarongi. So if we get a very large earthquake there in the future, are we going to get the coastline going up? Are we going to get it going down? If so, by how much and how is that going to change the impacts will get from that big earthquake.
Bil, Just to add to our sense of panic, you've actually been working on a tsunami hazard work as well.
Hey, so what more can you tell us about that.
Yeah, Well, first of all, I can tell you, don't panic. Prepare. That's the best thing we can do. The more we understand about these hazards, the more we can prepare for them and make them something that we can live with, coexist with in a smart way. Through the nationale. It's challenge work that I was talking about, and the understanding that these complicated earthquakes have an impact on the tsunami hazard.
We recognize that now is as good a time as ever to try to start putting together all the information we have, making self consistent tsunami hazard maps that we can then carry into inundation, inundations just the flooding we might see from the tsunami itself. And we understand that
when you're very close to the tsunami source. So when you've got a situation like in New Zealand where the megathrust fault is right at us, where the Hikonogy subduction zone is right at us, we know that small scale differences, heterogeneities, or things that make one eight point zero earthquake look like a different earthquake than another eight point zero earthquake,
those things matter for the tsunami inundation. So now we have the opportunity, really for the first time, to provide a realistic hazard map for tsunami inundation that would somehow complement the really globally leading world of the national size Macacert model.
And on the Herald podcast tell you why I've Forgotten History? We heard a lot in that about the dangers of that lack of preparation.
The question is if and when that happens again, will it be just a completely overwhelming act of God, or will it be an act of God that actually, if we're UPSPECD a bit we could have prevented.
Are either of you worried about the level of investment as a country we're putting in towards limiting the impact of natural disasters, because we're still hearing stories from Wellington, for instance, about earthquake prone buildings nearly eight years after the Cauculda earthquake.
Yeah, maybe maybe, Matt. I answered that first, then hand over to you. I'm a scientist, not an economist. When I show up at my office each day and I get very passionate about trying to do science that improves the human condition, the politicians and the funding system of it. That's someone else's issue for me, So it's something that I rarely spend time thinking about because I have very little influence on how it's going to play out.
Yeah, I think I would agree with Bill on that. But I do think it's important that there are societal discussions to have about this, that New Zealand needs to think about what it considers important and how it wants to address various things related to natural hazards. And I think it's good that discussions are happening, and I hope those continue to happen.
Well, the fact of the matter is that if one of these natural disasters actually did happen, and the first question would be.
Well, how do we plan for it?
Right, And this is what we're talking about here, This is how we plan for something catastrophic.
Yeah, So it's important that we continue to do the work like both Bill and I are talking about, so we have the best information that we can about what could occur. So when we those decisions do get made in the planning, that they're based on the best science that is really available for that and that can be brought into the wider picture about what the risk tolerance is for the country.
As experts in this area.
How worried are you both about what we've been talking about today.
About the likelihood of a large Hikarangi earthquake. I'm not worried at all. I feel a keen sense of urgency to do as much science as we can to improve how we make it through that big event. But as far as a day to day fear, it's not something I have. We live here, We enjoy this beautiful country. The reason the country is so beautiful is because of these natural processes. It's just something that we need to prepare for, do the best we can to make sure
that our planning processes are in place. We've got our house in order for when it does happen.
Yeah, I think Bill said it very well. I would agree with that. It's not something I worry about on a daily basis. It's something I'm certainly aware of living here and seeing the impact it has on the landscape, and looking at earthquakes around the country, around the world, sorry, and see an impact that those can have. But it's something I think about really in terms of planning and how do we prepare for this, How do we help the country to prepare for that.
You're both experts in your field, and like you said, go to work every day, keen to get stuck into the science. What is something that you're working on or you've read or seen in regards to this issue in New Zealand that really tickles your fancy.
I'd say for me, it's really how do we model the entire Earth as a system. So in the past that hasn't really been done. There's been little individual pieces of say that you could call the earthquake process that's
been looked at it on its own. And where we're heading now, both with the work that I've been leading and the Bill's been leading, is that we're really looking at how New Zealand, and not just New Zealand on its own, but in all the surrounding how that Earth behaves together, how the different faults interact, and how that
changes the whole earthquake process. And that I find that particularly fascinating and it has big implifications for implication, sorry for improving how we model these sorts of things.
Yeah, let me follow in on that too. What's really getting me excited these days is the desire and the possibility I believe now for the first time ever, because of advances in our physical knowledge, advances in computational infrastructure, advances in AI. I think we're now really for the first time able to start looking truly at the multi
peril problem. So not only thinking about earthquakes, not only think about earthquakes and tsunamis, but also earthquakes, tsunamis, landslides, and even coastal processes like storm surge and like the effects of climate change, all within a self consistent model. I think that's what the future is going to look like.
And certainly we need to make sure that the earthquake and tsunami fields follows with advances to allow us to jump in on these large scale models, these large scale realizations that we can make to put everything together, put all of our hazards together, so we can somehow function in a future that we know is going to be drastically affected by climate change.
Yeah, and I think those being on with that, and the more that we can look at these things in a coordinated fashion, have the decisions being made in a coordinated fashion, That's how we're going to get the most benefit for New Zealand.
In the end, Bill, thanks for joining us. That's it for this episode of the Front Page. You can read more about today's stories and extensive news coverage at enzidherld dot co dot nz. The Front Page is produced by Ethan Sills and sound engineer Patti Fox.
I'm Chelsea Daniels. Subscribe to the Front Page on iHeartRadio or wherever you get your podcasts.