Strict Building Code May Explain Lower Chile Toll
MELISSA BLOCK, host:
Several factors mitigated the destructive power of that earthquake. It struck offshore deep down about 21 miles underground. It was centered about 70 miles from the nearest city, Concepcion. By contrast, the earthquake that devastated Haiti was much closer to the earths surface and was very close to the capital, Port-au-Prince. But there is another factor that has kept the loss of life in Chile much lower than in Haiti, and that is much stronger buildings.
Eduardo Kausel specializes in earthquake engineering at MIT and he says the philosophy of building codes has been changing.
Professor EDUARDO KAUSEL (Civil and Environmental Engineering, Massachusetts Institute of Technology): The philosophy of earthquake codes until relatively recently was to prevent the loss of life, in other words to prevent the collapse of buildings or houses. That philosophy now is changing. And in addition to protecting people, we are now also trying to protect the buildings themselves. Because if you have a big earthquake you lose many buildings, you lose many bridges, et cetera, as a result of which the economic impact on the country can be phenomenal actually.
BLOCK: And what would be in those codes exactly? What would they say if you want to design an earthquake-proof building, heres what you have to do? What would it say?
Prof. KAUSEL: Well, you start with the materials and there are choices of materials in Chile. For the most part they use - for high-risk buildings they use concrete, reinforced concrete or reinforced concrete and steel. But on the other hand you have materials which are very poor for an earthquake country, and that would be adobe for example.
BLOCK: We were just hearing about the 15-story building in Concepcion that collapsed. So clearly this is not failsafe, these codes that youre talking about or else that building may have been poorly constructed.
Prof. KAUSEL: That may be so. I saw the video, it was far too poor for me to make an assessment as to why it toppled over. There can be any number of reasons. I mean it may have to do with the foundation, it may have to do with the soil that somehow liquefied or poor construction, poor materials. I mean just by looking very briefly at the video I couldnt really tell.
BLOCK: What did it look like to you, that building?
Prof. KAUSEL: Well, it seemed that it failed at the foundation level because the whole building rotated as a rigid body actually.
BLOCK: When youre designing earthquake proof or earthquake resistant buildings, what are you trying to do? What are you trying to get that building to do when it responds to shaking?
Prof. KAUSEL: Well, you would like to make sure that the building will not fail and youre trying to achieve that by making what the engineers call a ductile -ductility. Ductility is - its very easy to explain. I mean, you take a paper clip and you bend it back and forth, and it doesnt break. On the other hand, you take a piece of chalk, which is brittle, and you bend a little bit and it breaks immediately. So, concrete in principle is also brittle material but by adding adequate amounts of steel you can make it ductile.
BLOCK: When you heard about what had happened and you thought about what would be happening in Chile - which is where you're from - what did you imagine? What did you picture?
Prof. KAUSEL: I was concerned about particularly, the older buildings that predated some of the Chilean seismic codes - I mean, some of the historical buildings. And indeed, if you look in Santiago, most of the damage really happened in the historical part of the city and also some churches that go back to the Spanish colonial times. And those have suffered enormously. On the other hand, modern construction and modern buildings behaved very well. The number of buildings in Santiago is very large. I mean, youre talking of thousands and thousands of buildings. And so when you look at that in perspective, you can see that the Chilean seismic codes have done very well.
BLOCK: Mm-hmm. And what about parts of the world also at high risk for intense earthquakes but where codes are very weak? Where would say the worst - where would you say the problem spots are?
Prof. KAUSEL: Well, the problem spots, for example, in Asia. I mean, youre talking there of Pakistan, Iran, et cetera. I mean, along the Himalayas. I mean, they do also have some seismic codes but obviously theyre difficult to enforce. These are poor countries and theres lots of very poor construction actually.
BLOCK: Eduardo Kausel, thank you very much.
Prof. KAUSEL: Thank you very much for having me here, yeah.
BLOCK: Eduardo Kausel is professor of civil and environmental engineering at MIT.