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    Christchurch Earthquake Vs L'Aquila Earthquake
    By Gareth Fabbro | September 7th 2010 09:12 AM | 29 comments | Print | E-mail | Track Comments
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    For those of you who are not geologists, a tuff is a volcanic rock, made up of solidified ash. Hence the pun as my blog title. Actually, my research...

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    With all the fuss surrounding whether the l'Aquila earthquake should have been predicted, the point is often missed that it didn't need to be.  As the recent Christchurch earthquake has shown, a city can survive relatively unscathed without an accurate prediction.  All it takes is proper preparation.

    This is just a quick update to my earlier post on l'Aquila, as the recent Christchurch earthquake demonstrates a point that I didn't emphasise strongly enough there.  The whole "prediction" aspect is a bit of a red herring, everybody knew that an earthquake was going to hit l'Aquila sooner or later.  Regardless of what scientists said about the short-term chances of an earthquake, the town should already have been prepared.  Comparing l'Aquila with Christchurch shows what a difference this preparation can achieve.

    First a bit of background on the two quakes.  The l'Aquila quake was Mw 6.3, at roughly 9 km depth; Christchurch was a Mw 7.1 at a depth of 10 km.  L'Aquila had a population of 73,000, Christchurch 370,000.  From these details, you would expect far more casualties in Christchurch.

    However, this is not the case.  Remarkably, in Christchurch only 2 people suffered serious injuries.  The l'Aquila quake lead to 308 deaths.  How did Christchurch escape so unscathed?

    Earthquake damage in Christchurch. Photo CC-BY Flickr user Benjamin Humphrey
    Earthquake damage in Christchurch.  Photo CC-BY Flickr user Benjamin Humphrey

    There is an element of luck to the low death toll.  The quake happened 4:35 am local time, when most people were sleeping.  A lot of the pictures of damage show areas of the city centre, with fallen masonry on the street.  Had the streets been busy at the time it could have been much worse.  This doesn't, however, explain the discrepancy between l'Aquila and Christchurch, as the l'Aquila quake also took place in the early morning (at 3:32 am local time).

    More importantly, the damage done to buildings in Christchurch was far less than l'Aquila.  The picture above is an isolated example even here you can see in the background undamaged buildings.  The reason for this?  Properly enforced building codes.  Dull though it sounds, building regulations are probably the biggest life saver in an earthquake.  While Italy does have stringent building codes, at least for earthquake-prone areas, many of the buildings in l'Aquila were not built to them.  Organised crime is a big problem in the Italian construction industry, especially in the South.  It appears that rouge builders in l'Aquila cut corners to save money, and the inhabitants paid the price.

    There are other thing that New Zealand does well to cut the impact of earthquakes.  Awareness campaigns make sure that everyone knows what to do in a quake, and mandated government earthquake insurance provides an instant rebuilding fund.  GoodSchist has a nice podcast which expands on this.  All of these obviously contribute, but in my opinion it is the building regulations that are crucial.  It may be cliché, but it is true: Earthquakes don't kill people, falling buildings do.

    Much has been made of the difference in impact of the Christchurch quake with the Haiti quake, and the effect poverty has on expanding the death toll.  However, New Zealand and Italy both have roughly the same GDP per capita, of about $29,000.  The failings of l'Aquila are not due to poverty.  Neither are they due to scientific ignorance.  They are political.  Too little emphasis was placed on ensuring buildings would withstand an earthquake.  This is a lesson every country faced with natural disasters can learn.

    UPDATE: I discuss some of the points raised in comments on a new post here.

    Comments

    As a resident of Christchurch, New Zealand, I appreciate your perspective. I agree that we have our building codes to thank. Many of our older buildings were originally built before our strict building codes, and recently had been forced to undergo earthquake strengthening. There was some complaining at the time about the cost of retrospective strengthening, but those are among the buildings that survived.

    The main areas of damage were: brittle brick buildings that hadn't had earthquake strengthening, and also suburbs nearer the coast on soft sandy soil, due to liquefaction.

    As a resident of Christchurch, New Zealand, I appreciate your perspective. I agree that we have our building codes to thank. Many of our older buildings were originally built before our strict building codes, and recently had been forced to undergo earthquake strengthening. There was some complaining at the time about the cost of retrospective strengthening, but those are among the buildings that survived.

    The main areas of damage were: brittle brick buildings that hadn't had earthquake strengthening, and also suburbs nearer the coast on soft sandy soil, due to liquefaction.

    Fitzgabbro
    Thanks.  I hear reports of some quite spectacular examples of liquifaction, mud volcanoes and the like.
    Not to mention a beautiful shallow previously unknown fault line to explore. The Geologists are loving it.

    Back to the issue of predictability - we always assumed any earthquake in Christchurch would be from the Alpine Fault considerable further away. It was a complete surprise that there was a fault this close to the city - buried under 16,000 years worth of alluvial plains.

    Fitzgabbro
    I think I heard somewhere that roughly half of all major quakes are on unknown faults.  Don't quote me on that though.  Geologically, this new fault may be interesting, but you can (and did in Christchurch) expect large quakes at some distance from the main tectonic features (such as the Alpine Fault).  Every now and then you do get some oddities, like the 1812 New Madrid earthquake that happened about as far away from active deformation as it it possible to get.  Mostly, however, big quakes are focused maybe not on known faults but near known zones of deformation.  Unfortunately these zones can be quite large, for example most of New Zealand is at risk of a major quake.
    You're comparing:
    - a city at sea level and a city at 714m (above 2300 ft)
    - a city built mainly in XX century and a city that has a history from 1254
    - a city where ther are mainly cottages , 1 or 2 floors, with a city with stone building not at street level
    - a city where in the city center people go to work and a city where in the city center people live.

    Say that Aquila collapsed due to organized crime is a very very simple answer.
    Do you read aboyut discussion in Christchurch about building houses in area that are not eligible for that (avonside, new brghton) and so. Why? Even in NZ they are building in very unsafe regions? There is business interest behind?

    Franco,
    Italy

    Fitzgabbro
    I never meant to imply it was organised crime that was at fault, merely that building codes were not followed.  I realise that business interests can be just as reckless as criminals.   All I know is that there have been several prosecutions aimed at builders who did cut corners, but I'm willing to admit I don't know enough about Italian politics to go into the reasons why.

    There are differences between the two cities, other than just building codes, I accept that.  Old buildings are always difficult, as they were built before any regulations were built in.  Christchurch also has some 'heritage' buildings, obviously not as old as the ones in l'Aquila but still built pre-earthquake codes. They were successfully strengthened, as the old buildings in l'Aquila could have been.  Altitude isn't really going to make much difference.

    It may be a simplification, but it really is that simple: building codes save lives.  Compare l'Aquila to Californian earthquakes: the 1994 Mw 6.7 Northridge quake struck LA, a city of well over 3 million people, killed 72; the 1989 Mw 6.9 Loma Prieta quake stuck San Francisco, population 4 million +, killed 63.

    As a geologist I was surprised at how many people died in l'Aquila, especially compared to other quakes of similar size in similarly rich countries.  To me it is obvious that the buildings in l'Aquila were not as strengthened against earthquakes as the could have been, and the Christchurch earthquake is a graphic example of what can be done if the money is spent.  This wasn't meant to be a post about how all Italians (or builders, for that matter) are criminals, merely pointing out that building codes were not strong enough in l'Aquila for whatever reason.  It may be expensive, but - as most Christchurch residents will surely agree - it is worth it in the long run.
    Hello,
    my home was a flat at L'Aquila centre, a 4 stores bulding ended in 1956, in my neightborought has been the worst, I've estimated a 8-10 of population have died (roughly 150 ) in the collapse of 10 buldings greater tha 3 stores built between 1950 and 1970. I can't found anybdy died in homes from 1970, in Italy the first important bulding code have been issued in 1972.
    So you are right, the compliance to building rule is important but L'Aquila had a big quote of old homes, and no law issued after the first of 1972 has forced people to reinfor the old building structure, that was a big polical error.
    The epicentre was really under the citty, only 1 km out of L'Aquila Centre and so a Mw 6.3 maybe also much worse than a 7.1 40 km away..There were no victims 40 km. out of L'Aquila even in very old an very bad homes.
    All the victims and the collapses are very localiced in specific streaps of territory, and never concerns buidings younger than 40 years.
    Hope this can help to understand better the matter of damage comparision.
    kind regards
    angelo

    Fitzgabbro
    Thanks.  It is interesting to know that it was mostly the old buildings that collapsed.

    Obviously it is quite a crude comparison between the two quakes, the relationship between the size of the quake and the damage it causes is complex.  Distance to the epicentre plays a part, as does the type of soil/rock that the buildings are built on.  I compared Christchurch to l'Aquila mainly because I had written about it before, and also because the two countries are roughly the same economically speaking.  For a much clearer relationship between building codes and damage, compare Christchurch to Haiti.  There I think the epicentre was also a small distance away from Port au Prince (roughly 20-30km if I remember rightly), and the quake was smaller (6.something I think).  The difference in damage though was astronomical.
    Even in the areas that suffered liquefaction, the newer (post 1930's) buildings did exactly what they were designed to do - they flexed, they "rafted" on the soft ground, they shifted on their foundation, but they stayed intact enough to protect the inhabitants. Yes, the buildings will need replacing, but they can be replaced. Lives can't.

    Well Gareth, spoken like a true mainstream scientist and honestly someone who has no idea about the many benefits of earthquake prediction and a lack of realism as well. Is it not apparent there will never be enough money to rebuilt or retrofit every building around the world? And now in a time of global economic problems you offer little sympathy for the suffering masses. I should like it if you lived in California and found someone you cared about buried in a building with a nice placqard outside that says "enter at your own risk" to insure the building owners are not at fault for injury or deaths inside instead of changing occupancy standards, nor ever requiring retrofitting. So let us blame humanity for a natural disaster!

    You know, it could be said the residents of Christchurch should have expected their earthquake because within 100km of the event a M 7.3 occurred on 9/1/1888 and thus it was way past time, though not on the same fault exactly. And that would mirror what the residents of San Simeon California heard after their quake in 2003, quakes occurred there about every 50 years and it was year 51. But no one told them in San Simeon and no one told them in Christchurh either; but it doesn't mean it couldn't have been done.

    When the day arrives that we start to truly value human life and do whatever it takes to keep people alive, be it prediction when there are to many unsafe structrures, rebuilding or retrofitting then things will be as they should be.

    Petra

    Quentin Rowe
    Hi Petra,

    "You know, it could be said the residents of Christchurch should have expected their earthquake because..."

    Yes, we were expecting it, and yes, we were ready. Just not at this particular day, nor this particular fault, hence the surprise and excitement. When I say 'we' I mean our infrastructure etc. - certainly not me personally.

    We are currently expecting as highly likely in the following days a magnitude 6.1 quake. This is a confident prediction, which unfortunately succeeds in keeping us in a nervous state. Having said that, I still appreciate the knowledge of it's potential eventuality.
    Fitzgabbro
    The main point of my article was not to apportion blame to anyone for what happened in l'Aquila, especially not building owners.  The reasons why the buildings in l'Aquila were not strengthened are probably political very complex.  There are some cases where it is clear-cut, where builders didn't follow the regulations in order to save a little money.

    The point I was trying to make is that it is technically possible to prevent most earthquake deaths.  Why you think pointing that out means I should find someone I care about should be killed in an earthquake I don't know, I was trying to argue that we (be that owners, insurers, governments or "humanity") should strengthen buildings.  I don't know the best way of achieving this, I was just trying to point out the obvious benefits of doing so.
    Quentin Rowe
    Hi Gareth,

    It seems our local council agrees with you. They have decided to upgrade the regulations of commercial heritage buildings from 33% of the regulation requirements to 66%.
    Quentin Rowe
    Hi Garreth,

    I live in the center of Christchurch, and experienced the quake directly. We live in a two storey wooden apartment block, circa 1940's construction. It handled the main quake well, and is handling the constant aftershocks well also. The fact that I can trust the construction of my house is the only things that keeps me sane through the never ending aftershocks.

    So yes, I can confidently report that it is indeed the building code that saved lives, combined with the time of the quake.

    From the 'inside' of this disaster, it is fascinating to observe what those from the 'outside' perceive. The first thing to note is that all reports focus on the destruction. Reporters stand in front of destroyed buildings, and it seems outsiders get the impression of far more significant destruction, when in fact, the city is mostly intact.

    Brick buildings older than 1931 are the more numerous victims. For stronger modern buildings, liquefaction is the mode of destruction, but fortunately, this is not too widespread.

    For the first time, I get to see a significant disaster, from the inside, after the main interest has died down. I can now understand and emphasise with other earthquake veterans around the world, just how important the psychological effect the aftershocks have on everybody's temperament. By far, this is the worst aspect of the event, after the destruction. It has the effect of removing one's frame of reference, leaving a feeling of being 'ungrounded'. This spills over into sleep patterns, and affects concentration spans. Irritability and fatigue come and go in waves. Apparently we will have to put up with this for months... long after media interest has faded.

    Another aspect to report is hypersensitivity to ultra-low vibrations and movements. Your body becomes a big 'ear', sensitive to frequency and magnitude of all movements. Trucks driving by vibrate the road, which has always been noticeable, but now even cars can be felt through the earth. When sitting still on a sofa, or lying in bed, blood pumping through the body feels like the long wave vibrations that trail behind a big shock. Many of us have become adept at gauging the magnitude of each shock, betting (no dosh) on the outcome. On a larger scale, we can imagine and map out the hitherto unknown fault below us, waking up from it's 16,000 year dormancy, stretching under our city. All this is felt through our legs and feet, and is in a kind of communication with earth on a large scale and can be very impressive. I wonder if elephants feel this way?

    When standing outside during an aftershock, I can hear the entire neighborhood shaking and rattling. I can see the ground move in waves, and would love to be able to see an aerial view of the wave traveling over the land. Soon however, all such fascination will be sobered by the already impacting economic shock to follow.

    It is mostly unspoken here, but we are all so happy nobody was killed! :-)
    Hi Quentin,

    I've been researching PTSD in regard to earthquakes for little more than a decade and the effects can be lifelong, not just immediate. While it may take time or several practice runs before earthquakes to achieve moving past fear, if one can focus on noticing the oddities which are taking place at the time of the quake, provided it's not life threatening, what you'll hear and see if nothing short of amazing in just a few precious seconds.

    I used this method to teach my children not to fear earthquakes and it's been highly effective and it was born out of my first fearful earthquake experience and today I actually look forward to the "ride of a lifetime" unlike most because I'm so captivated by what happens. In a way it's like the whole building or structure becomes a huge musical instrument and while Ma Nature is doing her best dance ever, we mere mortals are missing the best of her coolest moves.

    Just know you survived probably the worst that could happen. I wish you peacefulness and an end to shaking as soon as possible.

    Petra

    Quentin Rowe
    Thanks for that Petra... Actually, I've found the whole experience quite thrilling and exciting, particularly the main shake. Its just that the novelty has worn off! ;-)
    Hi Quentin,

    I'm always excited about whatever shows up, no matter the size. However, I have the worst luck in being there when it happens. From my many trips to Parkfield and walking on the San Andreas Fault or at Olema at the Earthquake Trail along with numerous other locales I could be hired out as a lucky charm to many cities. Perhaps the New Zealanders might wish to invite me as a quake stopper? But if it requires a ride in a helicopter, I'll pass. I went on a geology field trip to Catalina Island some years ago as a guest and what was supposed to be a yacht ride from Long Beach to Catalina was replaced by a helicopter ride. I'll take a serious quake over that any day though I had a terrific time once on land and our fault exporations were marvelous as was the catered lunch. I've learned to make sure when arrangements are made for travel they do not include helicopter rides. LOL

    Petra

    Paul Nicholls of the University of Canterbury, Christchurch, New Zealand has developed this little tool http://www.christchurchquakemap.co.nz/ - along with the geonet website http://www.geonet.org.nz/earthquake/quakes/recent_quakes.html one of the most popular websites in Christchurch this last week.

    Thankyou for this page. It's sensible reading and I very much appreciate it. Tonight I was looking for info about the quake. I live in the epicenter of the big quake that rocked NZ last Saturday. Apart from a half hour of TV news last Saturday night (after the power came on) I've watched nothing at all. The news is so embellished with destructive images that it annoys me. As Quentin said, the focus is on smashed buildings and gives no indication of the numerous untouched buildings around the smashed one.

    I don't know if we were prepared as a people for the earthquake. I say that because people acted in different ways. I was taught as a child in school to drop and get under cover or crouch behind something and that's what we did. We rolled out of bed and crouched down beside it. Yet many simply stayed in bed and many more ran from the house on to the road. Seems to me that this last action was the riskiest with power lines and trees. Still, it turns out that whatever people did seemed to work because noone was killed.

    Being in the midst of the quake, I find the media an added burden. I mean, I don't need to be stressed more by their exaggerations. Also my family overseas are unnecessarily extremely worried because of what they've seen on the news. I tell them we're fine but it doesn't stop their concern. I guess I'm being ungracious towards TV news since I know they've been an invaluable source of information - but I think they've got to be a little less alarming and a bit more focused on accuracy.

    I've been enjoying the stories from people around me. Everywhere you go, people have a story to share. Nothing extreme; they're very simple and delightful. For example, I went down to the little grocery store in Darfield and bought a block of chocolate. The chocolate supply was almost cleaned out and when I mentioned that to the woman behind the counter, she said parents have been coming in since the quake and buying lots of junk food to please the kids.

    In the days immediately following the quake there was a feeling of peace here. Very strange it was but very real. People were kinder, more aware of each other and very anxious to help. Of course now I'm hearing stories of rat-bags taking advantage of the goodness of others but that's two stories compared to the many many little acts of kindness I've seen in this community. For example, my neighbour went for a drive to see the worst hit areas and he stopped to ask a farmer if he was alright. The farmer said he was fine but they had no water because they had to turn off the mains because the hot water cylinder leaked every time they turned the mains on. My neighbour said he was no plumber but he'd be happy to look at the cylinder. Fortunately they fixed the problem easily by tightening a few screws.

    Regards, Darfield resident

    Fitzgabbro
    Thanks Quentin and Darfield resident.  It is nice to hear some first hand experiences of the quake.  I had noticed that a lot of the pictures of the damage seemed to be of the same few buildings.  I am currently doing fieldwork, so haven't managed to follow much of the news reports, but it doesn't surprise me that they concentrate on the damage, that is what sells newspapers after all.
    "Another aspect to report is hypersensitivity to ultra-low vibrations and movements. Your body becomes a big 'ear', sensitive to frequency and magnitude of all movements." by Quentin
    I was interested to read about this hypersensitivity. I am continuously feeling these vibrations and movements and except for the obvious big tremors, I cannot tell what is real and what is not. It is a most surreal time to be sure....

    I thought of your comments about ground sensitivity Quentin.

    A strange thing happened last weekend. On saturday 11/9 I went for a walk at 8.45am-ish for about an hour. The milk tankers were out in force that day and the ground shook as they rumbled past me. When I got home I was told there been a really good aftershock that shook the house for a bit and made the cat run for dear life. I was stunned - I hadn't felt anything while I was on my walk. I should say, I hadn't felt anything I could definitely say was an earth movement. The aftershock hit at 9am, wasn't that strong - M 4, but was centered in Darfield and was very shallow - that's why it was so keenly felt.

    Interesting what people feel. In the big quake on 4/9/10 our house was literally shaken - like it was a baby rattle and a baby was shaking it. Yet friends in Christchurch report a different movement - like the ground swelling upwards. Turns out it's better to be shaken than riding a wave I guess - no homes, roads or buildings were smashed in the little township of Darfeild. Though to be sure, firemen have been out and about checking and pulling down cracked brick chimneys.

    Darfield resident

    Quentin Rowe
    Yes, I've noticed that the hypersensitivity is reduced if I am busy with a task, such as walking or even talking on the phone. We have had quakes in Christchurch in the past, no bigger than 5Mm, of which I have not noticed, and been quite disappointed to miss. I enjoy the feeling of the earth shaking... up to a point. Now, I have had my fair share.

    AS for the direction of the quake, I had a friend report that the big 5.1 aftershock centered near Ferrymead did damage his work premises and had them sent home. The main quake gave minimal damage, but the after shock punched the building upwards, and knocked all their ceiling, conduits and lights to the floor or to hanging. Each quake seems to have a different character, depending on the direction of the waves.

    There we go.. another as I type! My guess is 3.8M
     :-)

    I live approx 20 km from the epicentre of the Christchurch/Darfield earthquake. Our house is wooken and unscathed.

    Even in the picture you show you can see the effects of reinforcement. The brick facade popped off, but the building did not collapse. That's because the walls are not load bearing. I don't think there were any buildings in Christchurch that actually collapsed.

    Load bearing walls also have the pressure of all the weight they are holding up. During an earthquake load bearing walls rupture releasing a lot of energy and literally explode, sending brick shrapnel flying. Christchurch building do not have load bearing walls so the bricks just fall down in a low energy pile. That makes the damage a lot less.

    You can easily do a mini-experiment of the above with wooden blocks or matchboxes etc. Make a stack 10 blocks high and prod it in the middle to make it fall down. Now press down on the top of the stack and prod the wall in the middle. This time the blocks will fly further.

    You can also compare the Christchurch earthquake to the M6.9 Loma Prieta earthquake in the San Fransisco area in 1989. That killed 63 and injured over 3700 people.

    Clearly good building codes and structural engineering are important for surviving earthquakes.

    Nice to hear from you fellow Cantabrians. Went for a drive down telegraph and highfield roads today. In terms of epicenter- THAT was THE place. Road repair crews were there and amazingly, evidence of the quake has gone unless you're a local and know what's different. For example - you know all those images we saw on TV of a road with huge meter deep gashes? - that was highfield rd. Well it's all fixed and the gashes are gone EXCEPT now there's a big hump in the road where before it was perfectly flat. There's a real estate sign nearby which reads "land for sale hilltop views" or something like that. Amazing how fast things are being repaired - not just roads but buildings too. I hope we don't go back to how we were without learning the tremendous lessons here. For one thing I've been VERY busy getting my 72hr kit together. Regards, Darfield resident

    Blessed Mother is here as the Sorrowful Mother, and She has a large sword piercing Her Heart. She says: "Praise be to Jesus."
    ...
    "You have been given a profound sign in the earthquake in the city of Christchurch, New Zealand. The quake left a visible separation in the earth. See in this the sign that a visible and profound separation is at hand in Christ's Church on earth if you do not increase your prayer effort. This separation is now in hearts for the most part - liberal versus traditional. But within this local diocese, it is rising to the surface. This is an underscoring of My call to be recognized under the title of Protectress of the Faith decades ago - a request that was deemed unnecessary."
    ...
    September 15, 2010
    Midnight Service in the United Hearts Field - Feast of Our Lady of Sorrows

    Read all the messages

    Considering what has happened in Christchurch on Feb 22, 2011 perhaps you will revise your article now? Especially considering so called 'earthquake proof' buildings collapsed and other 'non-safe' buildings didn't.

    Fitzgabbro
    I have replied to your comment on the other article in more detail, and I realise I was wrong about some things.  In particular the difference between l'Aquila and Christchurch had a lot more to do with geological variables than I appreciated.

    However, this particular comment is like saying  "My gran has smoked for 60 years and she never caught cancer."  What matters is the most common outcome, not on whether you can find an exception to the rule.  In other words, whether earthquake-resistant buildings are more or less likely to fall down that unprotected ones.