We're here at the top of Wainui Hill and this gives us a fantastic view of
Wellington, Wellington Harbour and the Hutt Valley. And one of the most obvious
striking features of the landscape here is the line of hills on the far side of
the Hutt Valley. It shows us where the Wellington Fault has uplifted the land.
So the Wellington Fault is one of the biggest geological features in the
Wellington region. It is one of New Zealand's greatest geological hazards
because it runs through such a highly populated area. So today we're going to
explore the Wellington Fault. I'm going to take you to a couple of locations
where you can see it up close and see some interesting features. We're going to
go to Upper Hutt and then we'll follow the Hutt Valley down into Wellington to
see the fault in various aspects.
As we come into California Drive we are right on the Wellington Fault and this
strip of grass in the middle of the road is the line of the fault itself and it
was built this way especially to keep the houses from being right on top of
the fault in case it ruptures one day and pulls the houses to pieces. So the
houses are set apart and this is just a really good example of good planning in
a high risk area for earthquakes. We've arrived in California Park in Upper Hutt
and this is probably for me the best place in the Wellington Region to see
the Wellington Fault. Here in California Park there are a few features which
stand out really clearly. First of all the line of the fault - the fault trace or
the fault scarp is really straight and to see that really well what I'm going
to do is pop up this drone into the sky and see if we can trace it right across
the street into the park. A great view of the fault! It's like an absolute straight
line through the park and you can see California Drive how the fault goes
right down the middle of that street.
Now we're going to keep moving across toward Harcourt Park. So we've come
through towards the Hutt River and you can see the footbridge that's going
across the river. Now the Hutt River has actually cut through the Wellington
Fault and there is a cliff on one side but it's all hidden from where I'm
standing by vegetation. So although it's covered with vegetation I can actually
see a kind of clean rock face with a very steep sort of line on the
right-hand side of it which is where the rock types change. So that - right in the
middle of the view - is the Wellington Fault and up above it you can see the
slope of the Wellington F ault going down to one side. So we've come across the
footbridge to Harcourt Park. There you can see the line of the Wellington Fault
along the scarp and over on this side as we come into Harcourt Park we can see
that the ground is going up in steps. So these are also river terraces. Actually
from here I can see one - two - three, at least four of them. Where we're going to
go now is to look at what happens to the river terraces where the fault runs
through them at a right angle. This path through Harcourt Park towards the
playground is right on top of the Wellington Fault and we can see that,
because at the top of the park here you can see how the land on the left-hand
side slopes down towards the right. That's the same fault scarp
that we've seen before. So when we look at the ground on either side of the
fault we can see that it is quite different. This side, on the western side,
we have just flat land and then on the eastern side it's quite slopey.
So here we see the slope coming in towards the fault meeting the path about here
and then up in the distance is the continuation of the slope showing that
it has been offset and uplifted by the Wellington fault. This is telling us that
the Wellington Fault has pushed the land sideways as well as up on one side.
These two terraces have been pushed apart by perhaps 35 metres or so give or take
and that wouldn't have happened in one earthquake. It would be several earthquakes
because we think that the Wellington Fault might move the land
sideways during an earthquake by about five metres.
So we're finished with Harcourt Park now and we're going to go back in the car and drive towards
Wellington with a few stop offs on the way to see how the Wellington Fault
looks in different parts of the landscape down the road.
The Hutt River mostly follows a line right along the Wellington Fault.
Here at Mains Rock we've got a place where we can stand on
some of the rocks that are really really close to the fault, and something that we
can see straight away is that these rocks are really broken. They're
fractured, they're softened up that's because of the crushing effect of the
fault moving multiple times in big earthquakes
and rupturing along its length. So here we are in the Hutt driving along the Hutt
Road and we are actually right beside the Wellington Fault. The road is on the
uplifted side and you can see that the roofs of the houses are lower down.
So the fault is running right through just in front of those houses.
We are now on the top of Wadestown and from here we can look right down on
Thorndon which is the entrance to Wellington and the Wellington Fault runs
right through this entry point to the city. It runs under the motorway, across
the railway, right through the ferry terminal and also over the water supply.
So this means that Wellington is very vulnerable because its main entranceway
for all these transport services and water services is right on top of the
Wellington Fault. And a lot of work has been done by engineers and by planners
to reinforce the infrastructure here, to make it agile and flexible so that there
would be a quick recovery after a big earthquake.
So that train actually is going right across the Wellington Fault right now.
So the Wellington Fault cuts through where the motorway is, just at the point where
the train is going underneath. And you can see those horizontal slabs just at
the top of the motorway pillars and those slabs are called catchers. They're
designed to hold the motorway sections up if the fault were to rupture and
basically pull the ground apart it would stop the the main segments of the
motorway from collapsing down onto the ground.
So our final stop is here at Wright's Hill at the lookout, and it is a stunning
perspective on Wellington. There's the harbour, there's the city and right on the
edge of the harbour you can see the line of the Wellington Fault.
The Western Hills have been lifted up above sea level to about 400 metres high.
The equivalent level is 300 meters below the harbour. So over the life of the
Wellington Fault which might be very roughly a million years or so, there's
been 700 meters of vertical displacement along the Wellington Fault and that will
also translate into several kilometers of horizontal movement with the western
side going to the North and the eastern side being pushed to the South.
So this is our final destination for the tour of the Wellington Fault and it's certainly
worth remembering that we're in an area which has more than one large active
fault in it, and so being prepared for earthquakes, having a plan, having a kit,
going online to look at the best information to be prepared, is definitely
the thing to do if you live in or visit Wellington City