2 November 2010
The Canterbury Earthquake: Images of the distorted railway line
Posted by Dave Petley
Back in September I posted a series of images that I took of the of the surface fault rupture for the 4th September 2010 Mw = 7.1 Canterbury earthquake in New Zealand. Included was this one, taken of a railway line that crossed the fault rupture at the eastern end of the fault near to Rolleston:
Thanks to Malcolm Teasdale of Kiwirail for sending these two images of the state of the track at this site immediately after the earthquake (posted with permission):
The second image is particularly interesting. Note how the rails show high levels of deformation whilst the surrounding ground shows comparatively little. Notice also how the big kink on the left side has pushed the ballast aside and into the track side ditch This has happened on the right side too, but to a lesser extent. The right side bend nearest the camera has pushed the ballast towards the camera.
My initial hypothesis here (I am no expert on railway track deformation) in order to stimulate discussion is that the buckling may be the result of compressional deformation across a broad zone. The compression on the very strong railway line was accommodated when a weak point was found, leading to a comparatively rapid deformation to form the main buckle on the left. This then concentrated stress on both sides of the buckle, allowing the other (right side) bends to form. Can anyone who knows more on this topic comment further?
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
Amazing image!
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I think your theory has merit that this distortion is compressional. I took a look at pictures I have of a number of slides that pulled rail lines in a manner that would be the equivalent of lateral fault displacement and none had the back buckle shown in the picture.
If the offset was purely lateral the track would bend along one or two rail lengths and break (rotate) at the junction between rail lengths. That is what I saw on lateral slides along a line I worked on two years ago. A compression would keep the rail joints together.
Your picture shows that at this locatiopn the lateral off set was not that great as over a distance there was not much off set shown.
Another measure may have been missed. The power lines would be stretched if the off set was primarily lateral and they should be sagging if there was compession.
Thanks as always.
The only power lines I see are in the picture of the train, behind it and perpendicular to the tracks. The poles going along the tracks in all 3 images show no lines on them at all.
you can barely see them but the power lines are there and they are clearly sagging in the last Photo
The track is welded rail and usually clipped in at a neutral temperature of say 60 deg F.
As you can see to the portion of track either side of the disturbance the tie ends are fully bedded in the ballast. When the rail temperatures are above the neutral the rail expands. Lateral movement of the track is prevented by the restraint of the tie ends, the rail plates or seats, the tie spikes or rail clips and as a last resort the slow movement of trains over the track.
In earthquake or in proximity to nearby surface blasting or vibration the gravity forces and passive resistance of the ballast against the tie end, may be reduced to such an extent that the compressive rail stresses are relieved by expansion and lateral shifting. These deformations are typically unwelcome adjuncts to track construction in summer when sudden temperature increases overpower new construction. They are called sun kinks. But blasting and surface ground accelerations induced by seismic loading can and due result in deformation. Note in the first photo the ballast shoulder is shifted with the ties.
Great shots by the way. Second photo shows settlement of the trackbed. Either can result in a nasty wreck in signal territory.
Yeah, it’s a nice problem… It’d be interesting to know how much ‘extra’ track ended up in this section, it seems like a lot, but the angle looking along the tracks could be quite deceptive. I’m also no expert, but to continue the debate, perhaps it’s a result of ground roll accumulating displacement along the line. If the subsurface conditions change here, or the shaking intensity reduced below a threshold, the vertical waves may ‘catch up with each other’ to produce the large displacement, or be ‘frozen’ on the spot (if the section is longer than it appears). The tracks may have ended up laying out sideways under gravity at the end of the main shock.
There was an extra 9meters of track cut out from that area.
Another indication of compressive forces at work is in the fence. The vertical braces in the fence are attached only to the wire, and not to the ground. These braces are inserted between planted fence posts. Along the track where the engine is parked, these braces are vertical, showing that the fence is taut. The fence closer to the deformed track shows slack wire, with the braces tipped at various angles. The possibility that the fence is in poor repair in this single section is very unlikely because the fence encloses a pasture for livestock. Looks like compressive forces worked over the fence.
The last photo was amazing!!!
I’m inclined to believe these photos are the devious works of phtoshop. To get bends of that magnitude would take up an extra couple of metres of track. so i’d expect to see a massive gap in the track. or did this earthquake actually swallow that much land.
(also a suspicious shadow caused by nothing on ballast to right of main left kink)
@Fish: that shadow appears to be from one of the power poles along the railway. It just happens to be just outside the left border of the image. In the picture of the train, you can see the same shadow in both ruts and on the ballast, though it gets obscured by the grass.
Besides, looking at the two images shows it’s pretty well authentic. Who’d go to the trouble of photoshopping two images consistently like this?
I agree with Fish…that was the same thing I was thinking as I looked at the pictures. Something would have to give. There would be a gap to make up the extra track…unless it was stretched…which I doubt.
[No, these images are not photoshopped, so please stop this speculation. I have been to the location (the first image) with the earthquake seismologists / fault rupture people who confirmed that the rails were damaged in this way. There were also newspaper reports at the time about this e.g. – http://www.railwaygazette.com/nc/news/single-view/view/kiwirail-recovers-from-earthquake.html and Kiwirail themselves reported the track damage at this location: http://www.kiwirail.co.nz/index.php?mact=News,cntnt01,detail,0&cntnt01articleid=30&cntnt01dateformat=%25d%20-%20%25m%20-%20%25Y&cntnt01returnid=79. Dave]
Several meters of extra rail? Not a bit of it. There is a problem that my high-school physics teacher gave me. If you have a section of rail one mile long that is rigidly anchored at both ends, and it expands by one _inch_, and it buckles in the middle but doesn’t bend (i.e, it bends like a creased sheet of paper), how far is it off the ground at the point where it buckles? The answer, surprisingly, is more than fourteen feet. (take half a mile and half a mile plus half an inch, and use the Pythagorean theorem),
Now, railroads are built with expansion joints, and the sections of rail are considerably less than a mile long, but I would be surprised if it took a compression of more than a foot to produce that amount of displacement.
It’s quite possible for track to buckle like this even without an earthquake, if it gets hot enough and there is insufficient ballast to restrain it; or if it hasn’t been stressed (installed with tension) properly, as mentioned by someone else above.
I’m a railway engineer, I’ve seen it happen.
I cannot help but notice how perfect that sine wave is. Mathematics manifesting itself in the form of natural phenomena.
The rails ‘float’ on the stones. If a large wave on the same plane of the ground (think laying a slinky down and moving one end once quickly side to side) you would get what you see. The extra length is coming from a combination of the steel stretching ,slack being taken up on breaks at the welds of the rail outside the picture.
Amazing photos!! California….anxious of that big one…S.O.S.!!!!!
The shadows on the last picture seem to come from nowhere? The last image in particular has some glaring inconsistencies.
http://www.youtube.com/watch?v=dqq0543JWzI
Yeah, I think it’s shopped. Even without the knowledge that would allow me to speak like the people above, this looks way too extreme to be real. I mean almost 90 degree angles in a track within such short distances? My very simplistic knowledge of how tectonic movement works tells me this isn’t possible. Shopped! You’re not going to get almost 90 degree bends in a track 5 feet apart like that. Tectonic plates are big, not 5 feet wide. I’m drunk, but I still think it’s shopped.
Well Jermsnotagenious, at least you’re candid about the basis of your opinion. Most people convinced by their gut feeling in the face of compelling evidence don’t like to admit the superficiality of the knowledge they based their conclusions upon, so you’re a step in the right direction.
Wow that’s insane…I want to take an old beat up train with no one on it and run it down the track for S&Gs
When discussing the angles in the track, one should be aware that Malcolm’s photos were taken with a tele lens (approx. 135 mm focal length equivalent in 35 mm film, according to the EXIF data).
It should also be noted that this is not a standard gauge railway line, but that the gauge is only 1067 mm.
[for the railway enthusiasts: this is part of the route of the world-famous TranzAlpine train]
Seriously, Its Aliens!
For those that think this is photoshopped? Feel free to fly to Christchurch, NZ and see the damages that created by the Sept 4th 2010 earthquake. You weren’t here to see and feel the magnitude of this earthquake.
AND were you all hidden in a deep cave and not heard of the world news when this happened?
This is for real people.
i acually saw these tarcks and there is no photo shop u people need to understand how bad this was and the horrific damage this has cuased not only to materialistic things but mentally as well this is a true foto
I hadn’t even considered if it was P’shopped or not. I looked again and I doubt it. Why do I think this? 1. Too much trouble to P’shop 2. Rails do this, as explained 3. the shallow angle accentuates the distortions. But, why is the growth trackside different along the damaged section? i.e. green grass instead of brush? All the same, no conspiracy here, move along.
Definitely Photoshopped. Check the background shadows of the power poles and the sheep versus the foreground shadows of the equipment and workers in the second photo. The background sun is to the upper left in the photo, whereas the foreground shadows are to the left – more or less (they vary somewhat). The time stamp in the photo information (file properties) has it shot at 11:54 AM local time, but those foreground shadows would suggest late afternoon. There are many other issues, but the shadows are unequivocal.
[This is the last comment suggesting that the image is photoshopped that I will allow. Please stop seeking conspiracies where there are none. This image is not photoshopped. The shadows are long because this location is 43 degrees south of the equator, and the image was taken in the winter. Dave].
Definitely NOT photoshopped. This sort of thing happens not only due to earthquakes, but also due to thermal expansion when sufficient joint gaps have not been left.
The compression usually occurs as a small percentage over a long distance, say several km. Under normal circumstances it is relieved by small gaps, a few mm, between the rails at joints. Because the rail is able to slide in the chairs, it is entirely possible (and very likely) to have all of this compression relieved in a short-distance severe kink like this.
Here is a classic example: http://www.raib.gov.uk/publications/investigation_reports/reports_2010/report062010.cfm
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I think the guy on the right with no pants on did it.
That will buff right out. Just drive over it with a standard issue track-straightener and it’ll be all back to normal in a jiffy.
🙂
in the last picture, if you examine the rails in the distance, it looks almost as if the whole rail set has perhaps shifted(uniformly) to the right. the rail line seems off center on the ballast, maybe by as much as a foot. plus, the dark “traffic stain” on the ballast does not line uip with the tracks anymore. probably my imagination, but does anyone else see this?
ever take a length of garden hose that runs straight across the lawn, and give it a snap, and watch the wave move across it? where the wave “falls” it leaves a buckle/slack. maybe a similar phenomenon happened in this case….
great photos, thanks
living only a few kms from this and the railway workers staying in my hotel they ahve told me that they replaced the track as it was unusable due to the streching of the track
For those that doubt this could be real, do some simple research and you’ll find examples of similar things. JM’s example is just one of many
You need to understand how modern track is constructed. Whereas in the old clickety-clack days of the railway, 60ft lengths of track were bolted together with fishplates with small gaps in cold weather which close up when the rail expands, nowadays, mainline rail in most countries is welded continuously. In the UK, it is “stress free” at around 20 degress (ie is neither in compression or tension so if you cut it around that temperature, nothing happens, colder and it would open up, hotter and your cutting blade would get snagged as it pushed together while cutting.)
SleepyInsomniac says “There would be a gap to make up the extra track…unless it was stretched…which I doubt”, well you can doubt all you like but that is what happens when it is installed and the weather is cold. We use hydraulic systems to pull up the rail (yes, even a put of metal that size can be stretched) to get the right stress in it for when the temperature rises.
Of course as the temp rises over the stress free temp, you get the rails in compression. Something like a ton of force for every degree c. This is not a problem even round bends if you have the ballast in place at the sleeper ends and the track bed is stable. Of course if you wobble the track (like in an earthquake), the ballast looses it stability and any deviation from the straight will result in a sideways force will give a weak point for the stored up stress to be relieved. If the rail gets too hot (UK over 42 degress for 20 degree stress free) it starts to be too much for the ballast to hold and that is when you start getting speed restrictions imposed to reduce the chance that the vibration from a fast train is the catalyst for the buckle (which regular train traveller has not had their summer journey disrupted because of speed restrictions in hot weather).
Stress Free Temperature (SFT) on UK railways is 27C not 20.
I hope they never send you out stressing as a TO :o)
Just a quick note for those suggesting temperature may be the cause of the track distortion: The earthquake occurred at 4:35am on the 4th of September… that’s early spring down there. The air temperature at the time was between 3-4deg C (37-39deg F), and the previous day reached just 12deg C. While the movement of the tracks during the earthquake may have induced some frictional heating, it seems unlikely that the ambient temperature had any effect on the compression of the tracks.
I didn’t suggest that this was thermally caused, only that similar effects have been seen from compression caused by hot weather – which is the usual cause in the absence of earthquakes.
My guess is that the displacements were caused by s-waves which cause a sideways displacements. The localized permanency of the dispacement was permitted by poorly compacted ballast which would have allowed the concrete sleepers (ties) to remain displaced after the jostling caused by the initial displacement. Consider the following:
1) The curves look sinusoidal so the compression would be 18% which is very high
2) If the bending was caused by buckling, there would be a single curve. Think about compressing a peice of spaghetti from both ends.
3) Rail steel contains about 0.8% Carbon so it is hard and strong when compared to structural steel at 0.2% C. The increase in strength causes a decrease in elasticity which would inhibit the rails from springing back to their original shape after being deformed. Try to straighten a paper clip after you have bent a straight section 90°.
This is my opinion but I am not a geologist.
Thermal expansion usually happens very slowly. Since this was a mechanical compression – caused by strain in very large rock formations being suddenly relieved – one would expect it to have occurred quickly. It is therefore not surprising that the shape is more complex than for a thermal buckling event.
For example, let’s suppose that the ballast was reasonably stable – it does after all look like well-maintained track, unlike most American examples – and thus resisted the rapid movement of the main buckle. This would have pushed the ends of the buckle in the opposite direction, resultng in a vaguely sinc-shaped wiggle.
for you naysayers, here is an aerial video of the same damage site. was this “photoshopped” as well….?
http://www.youtube.com/watch?v=D2eCjeLaRHk&feature=player_embedded
With the help of the TVNZ video we now know better, where exactly we are: watch the gap in the hedgerow. Here is the satellite view of Google Maps:
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Rolleston,+Canterbury,+New+Zealand&sll=37.0625,-95.677068&sspn=42.901912,56.513672&ie=UTF8&hq=&hnear=Rolleston,+Canterbury,+New+Zealand&ll=-43.576816,172.349718&spn=0.002421,0.005493&t=h&z=18
So, we are 200m away from the Kerrs Rd/West Melton Rd level crossing; the next paved road level crossing is 2.2km to the southeast.
As can be seen in Google Streetview, the track appears to be fixed at these level crossings:
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Rolleston,+Canterbury,+New+Zealand&sll=37.0625,-95.677068&sspn=42.901912,56.513672&ie=UTF8&hq=&hnear=Rolleston,+Canterbury,+New+Zealand&ll=-43.576069,172.343752&spn=0.009622,0.021973&z=16&layer=c&cbll=-43.576001,172.347946&panoid=OeysehUKAyGdV4yzNxvyIw&cbp=13,250.67,,0,27.5
Might this fixing have had any impact on the deformation of the track at this exact place?
My first impression was that this was a strike-slip fault, but the fact that the tracks buckled in both directions implies that the section of track was shortened, not moved side to side. This appears to be a subduction fault, and the areain the foreground was moved towards the background.
Didn’t know earthquakes could create the extra metal that would be needed to make a straight rail into a curvy one like that, with no gaps and no visible stretching.
Either something is very suspect with the images, or we have found a new way to make metal. Can I be the first one to patent the creation of metal by earthquake? I will call it the Canterbury process, after the name of the place where the phenomenon was discovered.
[Nonsense – read the comments above for an explanation as to why the rails have buckled in this way. I will delete any further comments that suggest or imply that these images are photoshopped. Dave]
Hi guys.
Great thread and a very interesting occurance. I am also a Rail engineer and have a couple of comments and a question further to previous posts;
The original post is largely correct about the mechanism for track buckles such as this; the failure occurs as a result of stress build-up across a long section of track but manifests itself at a localised weak spot.
Some posters speculate about the magnitude of the expansion strain; this is a function of the length of continuously welded track (which can be several kilometers) and the difference between the prevailing rail temperature and the “neutral” temperature (the temperate at which the track is neither in compression or tension). The induced strain, as a rule of thumb, is approximately 1mm per 100m per degree Celcius temperature difference (apologies to non metric readers)
Anyhow, I have a question for you guys. The Canterbury earthquake took place at night in the middle of winter so it can be assumed that the air temperature would have been significantly below the neutral temperature as described above. The track would therefore have been in tension immediately prior to the earthquake and a lateral deformation on a straight section would have been impossible.
While I can envisage a scenario whereby seismic activity would vibrate the trackbed to such an extet as to neutralise the restraining capacity of the ballast bed and rail ties, I’m not so sure how it could induce a rail temperature change sufficient to raise the temperature from significantly below neutral to significantly above neutral as would be required to induce a compression failure such as this.
Is it possible that vibration / fatigue loading of the steel could induce such a temperature rise during a seismic event?
The whole point of an earthquake is that bits of ground are moving relative to one another. Thus while the rails were undoubtedly in tension beforehand, the ends of it were moved several metres closer to each other very suddenly, producing a mechanical rather than thermal compression.
Sorry, I’m not a seismologist but I don’t think that is correct. There is no fracturing or deformation in the adjacent ground.
If this deformation has occured elsewhere then the buckle would have to have occured at that point as well once the ballast disengaged from the grounnd.
Ground deformation may have occurred somewhere else along the track line, pushing the rail into itself. The picture only shows the location of where the rail gave way.
I don’t believe temperature compression has anything to do with it. There was a nine meter difference between the track removed and the new track. That’s too much for temperature expansion.
Two similar examples of track displacement occurred during the Alaska quake in April, 1964.
See:
http://www.suite101.com/view_image.cfm/571410
and
http://www.smate.wwu.edu/teched/geology/GeoHaz/eq-transp/eq-transp-05.JPG
Note that both of these examples occurred at stream crossings where the ground is saturated with water.
End
The last photo was amazing!!!
Heat expansion, thats what causes the rail to bend like that. Thats ribbon rail where they weld each rail together. If they didn’t allow for the heat to expand the rail that is what you get. This was the weakest spot with the stone that why it buckle.
I broadly agree with this. However,as per my previous post, the incident occured at night in mid winter. If it happened on a hot day then we would presume that the vibration from the earthquake rendeered the ballast shoulder inneffective (it relies on interlocking stone and gravity to mobilise restraining forces against train and thermal loading).
Having ruled out the “normal” temperature impact, I still contend that the failure might have been caused by external heating of the track related to the earthquake.
Can anyone offer any supporting experience on how this might occur (for example, does an earthquake heat water in buried pipes?) Bear in mind that I estimate that might only need the rail to heat up to about 30C together with seismic vibration to create a substantial bucking risk.
When you look at this, you feel the true force of nature.
[…] in my images from the aftermath of the September 2010 (Darfield) event, which can be found here (the famous railway line images), here (the fault rupture) and here (building […]
Anybody consider that during an earthquake, the ground shifts? When one plate moves over another that distance has to be taken up somewhere. In the softer loam far above, a 2′ shift spread out over a short distance, say a mile, would be entirely unnoticeable; not so for a rigid set of tracks mounted on top of it. Something has to give. I’d wonder if nearby roads also underwent some compression, but unless they were concrete (which needs expansion compression joints anyway) they would also probably be unaffected, asphalt roadbeds being much more compressible than straight lines of steel.
Nice photograph of bent railway track after the Christchurch earthquake in The Hindu (Chennai) http://www.hindu.com/seta/2011/02/24/stories/2011022450071500.htm
Hi everyone, I am an earthquake geologist/geophysicist, so I thought I would contribute my two cents to this discussion…
Neither the temperature, nor the ground shaking that occurred during the earthquake is likely the major contributor to the buckling we see here–rather, it is the permanent deformation of the earth that occurred due to the slip on the fault during the earthquake that caused the tracks to buckle and stay buckled (ground shaking could have temporarily bent and broken the tracks, but to maintain this deformation after the earthquake, you need a permanent deformation, otherwise there would not be any stress on the tracks to maintain this impressive shape).
The focal mechanism of an earthquake is a tool that seismologists use to learn about earthquake deformation. Focal mechanisms record the polarity of the first seismic wave arrivals to the global seismic network array to determine which directions the earth surrounding the fault moved during the earthquake. The focal mechanism from this earthquake (http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usb0001igm/neic_b0001igm_cmt.php) illustrates that there was a large component of compressional deformation in that earthquake (and a little bit of strike-slip, or lateral, offset as well). It is not that the track was lengthened, but rather, that the earth surface uplifted and shortened (and the track length stayed the same, requiring it to buckle).
There are additional methods that we can use, such as INSAR (interferometry of satellite data) that will identify areas that have been uplifted and deformed, and I bet someone out there has already started this analysis for this earthquake.
Similar buckling of train tracks has been observed in other compressional earthquakes–the Kern County, California earthquake in 1952 comes to mind–here’s a link to a photo of the railroad tracks in a tunnel–second row, middle. http://www.kcmuseum.org/stories/storyReader$1461
Thanks for sharing the photos!
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[…] impact on buildings). The impact of a M6 or M7 earthquake could easily be like either of the Canterbury or Christchurch earthquakes depending on the location of the epicenter. A smaller shallow […]
Hi there,
Am I correct i thinking you’re the owner of the brilliant shot of the swayed tracks? I am with a Christchurch film crew making a feature cinema documentary on Christchurch’s experience through these earthquakes and would love to include this photo. We are editing like crazy now so would love to chat asap. Please email me so we can talk! Naturally we would credit you!
Thanks,
Jennifer
[email protected]
[…] funhouse-mirror railroad tracks are a reminder that Mother Nature pretty much laughs at the things we build. What you’re seeing is the aftermath of a recent earthquake in New […]
[…] the site I found this on had many people offering different theories, but I believe that it was caused by a compression […]
Great photo,
Hope you don’t mind that I used it to as a thumbnail to one of my blog posts on Track/Structure Interaction: http://www.beingbrunel.com/track-structure-and-interaction/
Thanks for sharing!
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[…] onGoogle Maps.Via: forbes.com8.Railroad track damage from the Canterbury Earthquake in 2010.Via: blogs.agu.org9.Spanish photographer Chema Madoz uses film in all of his projects. None of his photos are […]
[…] funhouse-mirror railroad tracks are a reminder that Mother Nature pretty much laughs at the things we build. What you’re seeing is the aftermath of a recent earthquake in New […]
[…] Originally Posted by Texheim Plate tectonics. Actually that's not far off: Canterbury earthquake in New Zealand. […]
What happens to a train that’s moving during an earthquake?
The effect of an earthquake on a moving train depends on both the earthquake and the train. The slower the train and the smaller the earthquake, the higher the probability that the train will stay safely on the tracks. The larger the earthquake, the hi…
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[…] is of railway distortion in Canterbury thanks to an earthquake. Engineers and seismologists are still trying to understand what […]
I saw this over on a train track in the Clark county, Wi area and no one seems to g understand! It’s subsidence, underground thermal like activity with earth land slump…might be causing the flooding issues here I wish they would send a ground movement monitor for silent activity that’s spreading across our country! Everything matches what the volcanology terms web site s says on this stuff! Mount Rainer in Washington has puffing smoke and also ash like spurting from fumaroles ( Looks like burnt wood cinders spread out on snow!)side also! You can see this on Satellite land view! (on right side of mountain!)I might be mistaken so something to take note!
On 22 February 2011, at 12:51 pm (lunchtime), Christchurch was struck by a magnitude 6.3 earthquake. The quake was centred 10km south-east of the city at a depth of 5km. 185 people died, 164 people were seriously injured and there was major, widespread damage.
On 22 February 2011, at 12:51 pm (lunchtime), Christchurch was struck by a magnitude 6.3 earthquake. The quake was centred 10km south-east of the city at a depth of 5km. 185 people died, 164 people were seriously injured and there was major, widespread damage. http://www.fencingcompanyokc.com/
The last photo was amazing!!!
The Darfield earthquake fascinates and frustrates me. It was one of those out of the blue large shakes in an area that had no recentzed history of big quakes.
Frustratingly, at the time the seismometer grid in the region was widely spread out, so there is little data to use to look for hints of the build up of stress and strain.
Indeed, previously unknown faults ripped into life that day in what I know (from talking to former students who lived in the area at the time) was a terrifying event.
But even more chilling, from my perspective, was the subsequent seismic activity. If you run a time series of the aftershock activity you can clearly see the
shakes moving NE, out from the ruptured region and up towards Christchurch. It was only a few months later, of course, that the city was hit by a violent M6 that lead to
fatalities and destruction on a scale that hadn’t been experienced in New Zealand for a generation. In hindsight it was pretty much obvious that seismic activity was moving towards
the city, so I’m still amazed that I can find no hints of anybody publishing concerns online in the interval between Darfield and Christchurch.
It’s only since the 2016 M7.8 in the Kaikoura region that I’ve really started getting interested in how we can proactively warn against large shakes but I still shake my head
in disbelief that nobody, even the hysterical doomsayers, never saw the patterns in the aftershocks and realised that they were diffusing up towards a major city.
My interest right now is in the region around Arthur’s Peak, where there’s been a lot of relatively shallow shaking…