Magnitude 6.3 earthquake rocks Christchurch

A post by Chris Rowan[Note: see the bottom of this post for the latest updates and links - last update 26th February]. A few hours ago, Christchurch, the largest city on the South Island of New Zealand, was once again shaken by a large earthquake. The USGS page reports it as a magnitude 6.3, with the rupture occurring just 5 km beneath the surface near the port of Lytellton, only a few kilometres south of Christchurch itself. This is significantly closer that September’s magnitude 7.0 earthquake, which was 45 km to the west; because the energy of seismic waves spreads out and dissipates the further away you are from the rupture point, the shaking experienced in Christchurch today was probably just as, if not more severe, than that experienced in September, even though the quake was smaller in magnitude. The proximity of the rupture, combined with the fact that many buildings in Christchurch had unrepaired damage from September’s earthquake, the timing (in the middle of the day rather than the middle of the night) and the ever-looming spectre of liquefaction, which severely magnifies the effects of shaking, have sadly resulted in collapsed buildings, and at least some casualties. When it comes to the impact on people and infrastructure, earthquake magnitude is only part of the story.

Location and focal mechanism of the Feb 21 2011 M6.3 earthquake near Christchurch. The location and focal mechanism of the September 2010 M7 earthquake are also plotted for reference. Orange dots are >M5.5 aftershocks of today's quake.

The focal mechanism for this earthquake plotted in the figure above, courtesy of the USGS, shows that it is transpressional – a combination of mostly east-west compression, with some right-lateral strike slip motion mixed in – and on a north-south trending fault [update: what I really mean here is more N-S trending than the Darfield fault; as Kim points out in the comments, if my interpretation above is right the actual fault plane is NE-SW oriented]. Superficially, this seems very different from September’s earthquake, which consisted of mainly right lateral motion on an east-west trending fault. However, strike slip on an east-west trending fault and compression on a north-south trending fault are in fact fairly equivalent in tectonic terms – they can be produced by pretty much the same regional tectonic forces. The transpressional deformation in today’s earthquake is fairly consistent with the overall sense of motion across the plate boundary that bisects New Zealand.

Location of Christchurch earthquakes in relation to the plate boundary running through New Zealand.

The other thing worth noting is that today’s rupture occurred in a region of crust that, according to modelling, saw a significant stress change as a result of last September’s earthquake. This seems unlikely to be a coincidence. We’re looking at a grey area between an ‘aftershock’ and a ‘triggered earthquake’, in that the Darfield earthquake probably helped to push the fault that ruptured today over the threshold, but that most of the stress released in this earthquake has been building up since long before six months ago.

Aftershocks and changes in crustal stress due to the Darfield Earthquake in September 2010. Source: Stuff.co.nz

What does this mean for the seismic risks for the residents of Christchurch in the days and months ahead? Well, there are going to be more aftershocks, more than there would have been otherwise. Beyond that, I’m afraid to speculate: I can only hope that there aren’t any more nasty seismic surprises lying in wait beneath the Canterbury Plains, and that Christchurch and New Zealand continue to show their characteristic resilience in the face of this latest disaster. I’ll update this post as necessary, as more concrete information comes in: please feel free to add any relevant links and information in the comments.

Update: 22 Feb 2011

Here’s the shaking recorded by a seismogram close to Wellington, on the Southern North Island, via Shaking Earth:

Click for a larger version. Source: Shaking Earth

From Geonet, you can view a map of reported shaking intensity, coded according to the Modified Mercalli Scale:

Reported shaking from the 21 February Earthquake, according the Mercalii Intensity Scale: 8 - orange; 7 - light orange; 6 yellow; 5 - green; 4 - blue. Source: Geonet

Note how the maximum values are clustered in Christchurch, close to the rupture, and fall away fairly quickly outside it. This contrasts with the shakemap for September, where intense shaking was felt across a much wider region. This shows that yesterday’s magnitude 6.3 quake released much less energy in total than September’s magnitude 7, but due to its location the energy it did release was focussed on a built-up area.

Shakemap for the September 2010 M7 Earthquake. Colours as above. Source: Geonet

There are lots of photos coming out of the damage in Christchurch, but this video shot from a helicopter provides a good overview. Obviously some buildings have collapsed completely, but it should be noted that many more structures have remained standing (although many of those will probably be in need of extensive repairs). It is cold comfort to those who have been trapped or injured, or the friends and families of the several hundred casualties, but New Zealand’s stringent building codes have probably once more saved many lives.

At the end of the video I linked to above, there are also some shots of extensive liquefaction caused by the shaking, which probably had a strong influence in the distribution and magnitude of the damage.

Water forced to the surface by liquefaction. Source: TVNZ

Update: 23 Feb 2011

New Zealand’s geologists have once again been doing an excellent job of explaining this earthquake, and the risks going forward, to the media, and through them, the Kiwi public.

There have also been some compelling, often harrowing eyewitness accounts of the earthquake and it’s aftermath:

  • The racing editor of the NZ Herald took ‘a walk through sorrow’ in the centre of Christchurch the evening after the earthquake hit:

    Everywhere I look buildings I have dined in with friends, bars I have visited, banks and shops I have been to are ruined. Not damaged, ruined.

  • A resident of Lyttelton, which was even closer to the epicentre of the quake than Christchurch, in an interview with the Australian Broadcasting Corporation yesterday:

    really 80 per cent of the township, if you like, the heart of Lyttelton, I would say is lying in little pieces.

    Now you’re not talking everything levelled to the ground, but it’s parts of buildings fallen off into the streets. And it’s not just one, it’s every second or third building, you look at it and go, “Well that’s a write off. No business can operate there.”

  • A journalist for the Christchurch paper the Pres, whose headquarters close to the Cathedral was heavily damaged in the earthquake:

    Outside the inner CBD looked like a war zone. Outside on the street strangers were holding each other and crying and gazing bewildered at the gutted ghetto surrounding us.

    (she also describes how one of the many areas overwhelmed by liquefaction “looks like Rotorua“)

Some more photos and videos:

  • supermarket CCTV footage of the moment the earthquake hit shows how the intensity of shaking ramped up over the space of about 10 seconds or so.
  • A dramatic photo from the hills above Christchurch, showing dust rising from the city centre (click for a larger version).

  • Liquefaction on the city streets (see more here):
  • Cracks in the road:

Also worth reading is Dave Petley’s analysis of the reasons why the damage to Christchurch was much more severe than that caused by last September’s larger earthquake. Fortunately, it seems that New Zealand’s Earthquake Commission can cover the costs of further rebuilding. In a similar vein, I’m quoted in this story by the Christian Science Monitor.

Update: 24 Feb 2011

GNS have posted another nice video explaining the different types of seismic waves generated by the earthquake. Part way through, there is a plot of the aftershocks that have continued to rattle Christchurch in the past few days (red dots in the screenshot below – green dots are aftershocks of September’s quake). Most of them are found along a northeast-southwest trending line that probably represents the trace of the fault.

Aftershocks of the magnitude 6.3 earthquake (red) and suggested trace of the rupture (dashed yellow line). Source: GNS

This article in the New Zealand Herald raises the interesting possibility that geological structures in the region may have acted as a ‘seismic lens’, focussing the seismic energy released in the earthquake towards Christchurch. My latest post explains this concept in a bit more detail.

For those involved in the assessment and the communication of seismic hazards, one of the hard lessons coming out of both of the Christchurch earthquakes is that you can’t just focus entirely on the ‘Big Ones’ at large plate boundary faults. Smaller earthquakes on lesser-known or totally unknown faults near a plate boundary zone can be just as dangerous if they run near to, or even underneath a city. The northwest USA is one place where these risks need to be taken seriously: the Cascadia subduction zone poses a major regional seismic (and tsunami) threat, but cities like Portland may also face more local earthquake hazards, as this excellent article points out.

Update: 26 Feb 2011

ABC News in Australia has posted some striking before and after satellite photos of some of the more heavily damaged areas of Christchurch. I’m especially struck by the amount of debris that has been thrown into the streets even from buildings that are not obviously damaged from above (which doesn’t mean that they’re not) – this is probably mainly from collapsed brick facades. Early estimates suggest that up to a third of buildings in central Christchurch may need to be demolished and rebuilt.

Here’s a map of Christchurch showing the areas that suffered from liquefaction: the northeast of the city seems to have been particularly badly affected.

Liquefaction in Christchurch. Click for enlarged version at source.

On this blog, my latest post addresses the question of whether this earthquake is an aftershock or a triggered earthquake (answer: yes) and takes a very preliminary look at what is in Christchurch’s seismic future.

Categories: earthquakes, focal mechanisms, geohazards, society, tectonics
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Comments (53)

  1. bruce stout says:

    Hi Chris,

    thanks again for your explanations. This North / South fault is news to me. I didn’t even know there was one there. Also, extrapolating a line due north from the epicenter runs pretty damn close to the CBD of Christchurch city. Does this also explain the peak ground velocity felt in the city?

  2. Lanthanide says:

    Likely to be over 100 deaths, possibly up to 200 or so. Lyttleton will be trashed as the quake was right under them, but very little has been seen on the TV news from there so far; doesn’t help that the road links (tunnel, summit road) to there are out.

    I myself was actually in my car stopped at traffic lights for the 6.3, and the 5.8 that followed it 15 minutes later, so I can’t really give a good comparison to how it compared to Septembers, when I was in bed. The maximum acceleration recorded seems to be much higher this time – 188% vs 97% max last time, although the actual shaking period was apparently shorter.

    Most damage seems to be confined to the central city, and most chimney’s probably came down last year. Certainly we haven’t see as much coverage of liquefaction in the suburbs or trashed streets such as Seabreeze Close as we did with the September quake. I guess we’ll see more tomorrow.

    I also think the number of aftershocks this time has been quite a lot more frequent/stronger compared to September. We seem to be getting 5-10 per hour, often with 2 or 3 in the magnitude 4 range (including a 5.0 and 4.8), which seems a lot worse than what I remember from September.

    • Chris Rowan says:

      Interesting. I wonder if the aftershocks are actually more frequent, though – I suspect it might just be they’re closer, so smaller shocks are still causing noticeable shaking.

      • Lanthanide says:

        Yeah, I thought about that after I posted this.

        A large part of it is probably that the aftershocks out in Darfield just felt a lot weaker in CHCH, and what we’re feeling this time is more what they went through out there.

  3. Grant says:

    Chris: Thanks for putting up some of the science, Chris — I can’t really cover the geology myself.

    Lanthanide: Been trying to get more news on Lyttelton myself. (I have family living there.) The tunnel road to Lyttelton is apparently open overnight for the emergency services to use.

  4. John Andrews says:

    Chris,
    is it true that over time since the 1855 Quake that this subduction zone is slowly moving south east – as to the untrained eye it clearly looks like the fracture lines are migrating SE towards the Chatham’s ?

    Are there any dated statistics that support this trend of increased pressure release along this moving plate ?

    best regards

    john

    • Chris Rowan says:

      I don’t think such a clear migratory trend is really supported by the historic data – think, for example, of the Hawke’s Bay earthquake of 1931, or the Gisborne earthquake of a few years ago.

      Over geological timescales, the subduction zone is migrating south along the coast of the South Island, but this is far too slow a process to really affect the patterns of seismicity over the past few decades or centuries.

  5. Kim says:

    Thanks, Chris – if you don’t mind, I’m going to poach figures from this post for class tomorrow/Friday. (And then on Monday, my plate tectonics class is going to discuss triggered EQs…)

  6. Anna says:

    God Bless everyone in Christchurch!!! This is just beyond my imagination what they are experiencing. My friend Joanna cannot even stay home alone at night….I’m sure this is only going to cause more trauma. The psychological problems are going to increase dramatically. To all those who are deceased and their families….I am praying for all of you. And I believe in the power of prayer. If I win the Lotto in NYS I will move everyone in Christchurch to safer ground!!!! I hope other countries….including my own USA will be offering all the assistance possible!!!!!!!!!!

  7. EdK says:

    I imagine that surface waves were much stronger in Christchurch for this quake compared to the M7.1, since the focus was much closer to the city and at a shallower depth. But that’s based on the siesmo class I took a while back now.
    This looks like they were hit with the worst possible combination of factors: structure weakening from the previous large quake and higher intensity shaking (due to quake location) in soil prone to liquefaction.

  8. parclair says:

    I’m repeating this question from Eruptions–

    Bon jour/nuit. I’ve been wondering lately whether or not the combination of Mandelbrot and Chaos mathematics could be used for improving the probabilities of earthquake warning. I know a little about them (Wiki, plus some reading I did when the theories first came out).

    The idea that patterns repeat based on the chemistry and physics of the medium (Mandelbrot), and that things snap in a discontinuous way (chaos) makes me think of basin/range and earthquakes.

    I’m still relearning algebra, and have yet to tackle trig. Perhaps someone out there is aware if any research is being done in this area?

  9. Kim says:

    Is there additional evidence (beyond the focal mechanism) for the N-S trending plane to be the fault? The two smaller earthquakes would make more sense if the fault plane was the NE-SW striking, SE-dipping plane. (That fault plane would also make sense with the topography – the mountainous peninsula south of Christchurch would be in the hanging wall.)

    • Chris Rowan says:

      That is actually the plane I was thinking of as the fault plane, although that’s probably not clear from what I wrote above. I think I was considering the NE-SW or NW-SE fault planes together and just thinking that both are more of a N-S orientation than the E-W trend of the Darfield fault. I’ll amend the text of my post to make this clearer.

      • JC says:

        I found this blog while searching for a fault plane solution for this earthquake. Looking at media photos I have a nasty feeling that the flooding in Bexley, 10 km north of the fault, may partly reflect downthrow on the footwall.

  10. Lanthanide says:

    Interview with Bill Fay (?) from GNS science this morning by the pretty woman on TV that doesn’t understand science. He was saying that it seems this is more of a separate fault from the Greendale one, and therefore your theory of this being a triggered earthquake looks likely.

  11. ddd says:

    Is there no way to predict an earthquake.- some underground science gadget that could prepare th people for the worst., like in the case of the storms & tsunami.——
    Or maybe a connected event like the continuos aftershocks that kept on &on after september shock about?? 60 or more.Could that not have given you a lead about the earths plates going crazy underground??????????and that it was about to explode again with a much higher price tag?–and THAT could hve helped saved lives.Come on scientists,geos,work on this.please I know am asking for a huge chunk of the geological time scales &seismicity ..come on chris — am so sad my words maybe befuddled sorry

    • Chris Rowan says:

      EdK is right – although there have been many attempts over many years to link certain signals from the earth – seismic, electromagnetic, geochemical – to a coming earthquake, any valid signal that is there is swamped by false positives, where you get the same sorts of signals, but no earthquake. It might just be that faults are too complicated to be easily read.

      Also, the comparison to storms and tsunami forecasts is rather unfair, because you can’t predict when and where a hurricane will form any more than you can predict the time and location of an earthquake – there’s just a large enough time gap between a storm’s formation in the oceans and it hitting land to allow you to predict where will be hardest hit, and warn and prepare accordingly. With seismic waves, you don’t have that luxury: almost the moment you detect the earthquake, you’re already being shaken.

  12. EdK says:

    ddd,
    The short answer is that while there MAY be precursors before a quake (foreshocks, electromagnetic signals, sudden changes in well-levels) they do not occur reliab;y before each quake. Some may happen and others may not. The between any such precurosrs and quake vary, and sometimes events like a swarm of small earthquakes occur without any association with a larger shock.
    The best that be done is to identify areas at risk and engage in long-term preparedness.
    Its not for a lack of trying.
    Chris can possibly give you a more detailed answer,

  13. bruce stout says:

    I guess we’ll never know now how much of this damage is due to weakening of structures since the Darfield quake and how much to the sheer brute force of this Lyttleton quake but one thing it has done is that it has given my budding confidence that buildings are strong enough now to prevent major loss of life a really big knock. After the M8.8 Chilean quake and the Darfield quake I was thinking we just might be on top of this.. perhaps arrogantly attributing the damage in Haiti to poor building standards .. but if a M6.3 can do this, maybe we’re just not that mighty after all.

    Chris, how rare/frequent are quakes with this sort of peak ground velocity? (They measured 220% g at one place). And a bit of a newbie question: why do soft soils amplify peak ground velocity? I can understand the waves sloshing around a sedimentary basin and interference patterns leading to isolated peaks but is that the same thing?

    • bruce stout says:

      PS: I guess I just woke up a bit gloomy. Have to remind myself that a death toll of 75 for this kind of damage is actually pretty good going, hard as it is to see it like that just now.

  14. Roger Currie says:

    Hi guys , i live at Burrum Heads near Fraser island QLD , where apparantley the sun shines out of Anna Bligh’s rrrrrs , the techtonics blokes at JCU campus in bundaberg , say we are due for a 6. something , anytime , our drama might be tsunami if it happens near Lady Elliott island , which was the last one in the late 1880s .

    Pretty old rocks here , but still cooking deep down , the Hummock at Bargara bundaberg is dormant , we hope . Is it possible to calculate the energy release from the scale ? ie 6.7= x megatonnes of tnt ? or are we talking gigatonnes ?

    What is the groundwater thing?, aquifers being smashed upwards from the waves ?

    We will pray for all the lost ones and thier families , cheers roger

  15. Roger Currie says:

    Christchurch was built on a drained wetland ? , which is why you get liquification under the foundations ?

  16. parclair says:

    @Bruce Stout Here in California, I actually feel MORE confident about the building codes. Given that the structures in CC went through 2 large quakes (with not enough time to really repair from the previous large quake), I’d say that the codes worked.

    The large majority of people got out of the buildings. The buildings worked to preserve life. I’ve always been told ‘never run out of a building during an earthquake’ and from the pictures, I now know why– facade-fall in the streets, but the buildings held.

  17. Billie Jean Crawford says:

    Thanks Chris for all of the information. Best wishes to alll experiencing the quake and after shocks.
    What was the actual time the quake hit for the September quake and also the time for February 21st?
    Thanks again.

  18. David says:

    The unreinforced Masonry did manage to kill people in the streets and still has no place on New Zealand buildings. Other than that the building codes seem to be working, the CBD is of course full of buildings that don’t comply with the building codes since they were grandfathered in. Of course they have known about unreinforced Masonry since at least the 1931 Napier Quake.

    Also Tragic Story of a women and baby she ran outside of the store she was in right into the street and was crushed by the falling masonry.

  19. John P says:

    So which direction were the surface movements, and where, Chris? Some pictures seem to show tension cracks, others compression, and there’s a pic of a sine-wavy ‘pulse’ in some railway tracks like one in the September quake which was explained by someone as follows: the land around the track had absorbed the compression over hundreds of meters without showing a ridge or a thrust fault as you might expect, but the more rigid track had had to shorten at one point. (I can search for the pics and give you links if necessary but you’re prob’ly familiar with them.)

    I find the whole tectonic explanation of NZ (subduction zones to N and S), but a strike-slip fault along the S Island in much the same direction as the subduction zones!) very hard to visualise. Any help would be appreciated. [My life doesn't depend on it but I have a sister living high on a ridge near the Moonlight Fault so I'd like to know whether she should evacuate. And I suppose the answer is at some time in the next 100,000 years she should, but who knows when?]

  20. John P says:

    [Hey, is this running under WordPress? That's my identifying pic from when I was posting on a political site as Jack Aranda!]

  21. flow in says:

    why does everyone just accept the ‘alpine fault’ idea? its been a really long time since its moved, and it looks more like the left over of an ancient plate movement.
    is it not more likely that the surface features have ridden northwards, and a causative boundary now lies under the canterbury plains?
    given the massive lump of basalt around mount cook and northwards, this means the long expected ‘big one’ is more likely to occur around the bottom of mt cook and up through the plains, rather than through a now irrelevant scar.

  22. Chris Rowan says:

    @John P: in terms of actual surface motion, the deformation in most places is a response to the seismic waves generated by the earthquake and pumped into the surrounding crust, which, depending on your location relative the the epicentre and the underlying geology, could produce tension or compressional features. It is only where the fault breaks the surface that deformation has to match the motion on the fault plane itself.

    As for the plate boundary, my post on the September earthquake that Bruce links to above provides some more background on how the Alpine fault and the subduction zones to the north and south are different sections of the same plate boundary, where the same overall tectonic movements are accommodated by different structures. The trend of the subduction zones and the Alpine Fault are different (there is a distinct kink to a more SW direction as you move south from the subduction zone off the east coast of the North Island to the strike-slip system on the South Island), but the angle is reduced from what you might expect because the plate motion is oblique to the trend of the subduction zone – it’s a little “strike-slippy”, and there are actually strike slip faults on the North Island behind the subduction zone as a result. One of these ruptured in 1855 in a magnitude 8+ quake, and another runs through Wellington.

    @flow in: while the Alpine Fault has not ruptured since European settlement, there is ample geological evidence that it has ruptured in large (~M8) earthquakes several times in the last couple of thousand years: something I have written about before.

  23. John says:

    I’ve seen a suggestion that one factor in the high accelerations observed may be that the fault movement took place close to the harder rock of the Port Hills. For those not familiar with the area, Banks Peninsula and the Port Hills are an old (millions of years) volcanic area, and the fault movement seems to have taken place between this area and the city. The possibility is that this may have lead to energy being reflected back from the harder rock towards the city, increasing the intensity there. I’m not qualified to decide either way, but it sounds feasible to me.

  24. John P says:

    Thanks Chris. Reflecting after I’d posted the surface movement question, I was starting to wonder if that was the answer.

  25. John P says:

    And thanks Bruce for the link to the deep quakes map. Combing that with Chris’s remark that the subduction is a bit ‘strike-slippy’ I think I can begin to visualise it in 3 dimensions. Though none of it quite explains why the recent focus should be under the Canterbury plains where the homesick Poms built all those beautiful English-looking brick-on-brick buildings.

  26. ken milsom says:

    I do not know much about earthquakes.except that my family and I have lived through two bad ones here in Christchurch.
    I will admit it – I am scared now.People have been talking about this moon man “ken ring”.
    He apparently predicted these two earthquakes and got it right.He has also made a prediction for around the 20th of march for a bigger earthquake to hit here.
    Is the way he predicts earthquakes actually right and true ?
    Please tell me = Are we going to get another one in march ? thanks.

  27. paulie says:

    Great site and posts as always Chris. The previous post from Ken is indicative of how many are feeling in CHCH. The shock of experiencing a smaller M6 aftershock vastly more destructive than the original M7 quake has made the whole thing seem random, chaotic, like angry gods fighting that could explode tomorrow into a M8+ like a bolt from the blue. So everyone here is talking about the phases of the moon/sun man who is predicting the biggest quake of all on March 10th (overlooking the fact that he makes so many predictions that it is statistically inevitable that some are close). The next step will be the Mayor of CHCH sacrificing a white bull somewhere. Hence a couple of questions from someone who, like Ken, knows little about geology:

    1. Would it be not unreasonable to suggest to Ken that, with all the stresses being relieved from the CHCH area fault systems, very shortly CHCH is likely to enter another quiescent phase (perhaps for several thousand years) that will make it perhaps the least likely city to suffer another major local earthquake (Alpine Fault of course is the exception, as it will affect most of the South Island). The irony being that people who decide to leave CHCH are probably moving to places far more likely to experience a large earthquake.

    2. Should local geologists have given stronger warnings of the dangers of aftershocks. Most people were aware that there would be aftershocks and that at least one of those likely to be around M6. But most thought that any buildings not toppled by an M7 would be OK in an M6. Of course the reality turned out to be the opposite. Should geologists have been more outspoken on this and sent a clear message that (a) there is a high likelihood of an aftershock at least MM6, and (b) that the aftershocks are trending to east of the original Darfield epicentre (i.e. closer and closer to CHCH/Banks Penninsular), and (c) there is a real possibility that the MM6 quake could be a shallow quake, and (d) because most of the local fault lines are hidden, it is entirely possible that the type of movement could be a dangerous mix of uplift and lateral, and (e) if it happens east of CHCH its effects could be amplified (‘lensing’)… and, put all those together and you’ve got a clear warning for CHCH that an MM6 could be vastly more destructive than the MM7… and until we’re pretty certain the danger has passed people are advised to be very cautious (e.g. no tourists up the top of CHCH cathedral, where 20 or so died when the turret collapsed).

    Are these unreasonable ideas, all with the benefit of hindsight etc. or is there a lesson in here for geologists and the way they describe and predict the situation to communities that have just experienced a major quake?

    • ken milsom says:

      paulie – Thanks for that.For me earthquakes make me feel like I am playing a game of “your numbers up – or is it”.
      I am just an average bloke with a family and a mortgage.And perhaps a too in tune with my feelings.Earthquakes really do scare me.Many people have all ready left Christchurch and I mean thousands have fled.For me it really is not an option.
      I know I am one of many who was in this and I do not want to sound like a wuss.
      But here is my story and I know many many people went thru a lot worse.But for me,telling my story seems to make me feel better,so here it is.

      I was at work at the time.I had been sitting out the back in the yard and one of our trucks had just pulled in.I was sitting there having a smoke and without warning WHAM!
      I knew instantly I needed to get into the open space of the yard and …away from the buildings.I tried to run and twice had my feet pulled out from under me by the cheer force of the shaking – dropping me onto the ground.The second time I went down I checked to see if I was clear of the buildings and the car park on my right came crashing down.As I got up again part of our bulk room came down and directly in front of me a 2 story building came crashing down.
      The noise was like a jumbo jet,The whole thing seemed to take ages to stop.Some of my coworkers and customers had also made it out onto the yard,Some were freaking out,some were crying and some were just shaking with fear.My heart was pounding and I was completely wasted on adrenalin
      .We had another large after shock and some of us sat on the ground.I noticed in the tarmac where there was a crack the ground was actually rocking backwards and forwards,but even more incredible was one side was going one way and the other side was going the opposite way.
      While having a smoke to calm myself and clear my head,I joined up with some coworkers to see if any one was trapped in the fallen part of the car park.There was no one in there,but a few crushed cars and my bike luckily had been parked just past the destruction. I said to one of my workmates that my helmet and keys were upstairs in the cafe.(the cafe was at the other end).
      He simply said “well come on we will run in and get them”.We ran full tit into the store jumping over stock that had fallen down,up the stairs and grabbed my helmet,jacket and keys.Then ran down and out the front door.I ran to my bike down near the crushed part of the car park and got it outside.
      I told other staff that I was off home to check on my family.Turning right down the street i was hit with the impact of devastation.The roads were smashed,there was water and soil liquefaction everywhere.There was building after building after building laying in piles of twisted metal,glass and bricks.There was a guy laying on the pavement mostly berried in bricks,two more people standing near him just shaking there heads.I knew he was dead.
      The roads were flooding and liquefaction was everywhere.The traffic had nearly come to a stand still with the panic.I managed to get home to find my wife not there and I knew she had gone to the school to find my son.
      I parked my bike and ran off towards the school,finding Both my wife and son coming down the road and both uninjured.
      Back home we all told each other our stories.

      And this was mine. Thank you for reading.

      • Alister says:

        Thanks Ken,
        Out Riccarton way it was merely an interesting ride… So it was really a shock to hear then see the devastation. The scale started to sink in when I biked past the Heathcote river – gray with the liquefaction silt, then seeing Hoon Hay road totaly uneven and covered in silt.

        ‘Lensing’ makes sense as our house is the same distance from the epicenter as the city center, but they got clobbered. Should the CTV and PGG building have withstood this quake? We need to know whey they failed.

  28. John P says:

    Short answer, Alister – PGC and CTV were both built before the earthquake codes were fully developed from about 1975 on, and since Chch wasn’t a known danger zone nobody insisted that they must be upgraded or demolished. Hotel GC, which you didn’t ask about, was actually built in stages – 11 more floors added on to the original 15 – amazing! More detail on PGC and Hotel GC at

    http://db.nzsee.org.nz:8080/en/web/chch_2011/report-from-the-field/-/blogs/day-03-field-report%3A-critically-damaged-multi-storey-rc-buildings?_33_redirect=http%3A%2F%2Fdb.nzsee.org.nz%3A8080%2Fen%2Fweb%2Fchch_2011%2Fhome%3Bjsessionid%3DCB1E92AED632919A8AC08503CCB62B06%3Fp_p_id%3D115%26p_p_lifecycle%3D0%26p_p_state%3Dnormal%26p_p_mode%3Dview%26p_p_col_id%3Dcolumn-1%26p_p_col_pos%3D2%26p_p_col_count%3D3

    and click “download the full preliminary report here” near the bottom. Sorry, can’t work out the direct URL for that one.

    As to CTV, I think it was old for a ‘modern’ building anyway but there was a report this morning (NZ and Aust time) that the people demolishing the building next door had punched holes through the walls to support their scaffolding (sorry, can’t find the link at the moment). The inquiry will no doubt consider whether this made the collapse worse or whether, without modern tricks like shear walls, it (with the 100+ people inside) was doomed anyway.

    Th newer buildings seem to have withstood it quite well, though there’s a worrying tale that the internal fire escapes at Forsyth Barr collapsed – see http://www.heraldsun.com.au/news/special-reports/climber-saves-14-from-quake-hit-tower-in-new-zealand/story-fn7z04co-1226012563835

    Everyone will know better in future. I live in Brisbane, which is living proof that most people don’t learn from floods, but engineers and legislators do generally learn from earthquakes. (Though my brother the geotech engineer tells me that architects still try to get away with ‘soft’ ground floors, which sabotages the whole idea of shake-proofing.)

  29. John P says:

    I just cracked the direct URL for the pdf of Weng Kam’s report: http://db.nzsee.org.nz:8080/documents/43301/2fc9b1d3-a52a-4edb-9b8c-018c0368b1ad

  30. Jules says:

    My son raised a valid question for those of us that aren’t in the know how with the whole quake thing. With the Lyttelton fault, can we expect in the future, anytime, another earthquake from the same fault line?

    • Chris Rowan says:

      Yes. But it will take decades or longer for enough stress to build up across the fault for it to rupture again. In the short term, it is possible (although there is no evidence either way at the moment) that there are other, similar faults, that have not ruptured in the past few hundreds of years, under the Canterbury plains.

  31. Aleisha says:

    Hi, I was wondering why weren’t there any tsunamis?

  32. Megan says:

    Because it was centred under the Port Hills, not out to sea.

  33. Joe Momma says:

    LOL 8=D
    PS I <3 u

  34. Vicki Wilkinson says:

    Where can I buy a copy of the photograph taken from the port hills the day of the earthquake? Thanks

  35. Barbara Hansen says:

    Hi from Oregon — Wondering how things are in Christchurch now as you head into summertime. Also wondering if there is consensus on lessons learned from these quakes, in addition to noting that earthquakes can cause earthquakes.
    Best wishes — B.

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