United Nations Radio

map indicating epicenter of Haiti earthquake

The year 2010 began with two major earthquakes that killed thousands of people in Haiti and Chile. While both caused death, disruption and displacement for millions, the earthquake in Chile was completely different from that of Haiti, says Professor Robert Yeats, retired professor of geosciences at Oregon State University:

Yeats: Yes, it's completely different from Haiti. First of all the Haiti earthquake was on a strike-slip fault which meant that one side of the fault moved side ways or laterally. With the respect to the other, the Haiti earthquake was probably less than 1/500th the size of the Chile earthquake, a magnitude 8.8 and a magnitude 7 the difference is what we call logarithmic, which means a 7 is just much, much weaker than an 8. Eight is much weaker than a nine. And the other thing difference in Haiti is that in Haiti the earthquake struck very close to the city of Port-au-Prince where as in the subduction zone the earthquake was offshore. The other thing that is different about the quakes is the response, is about the countries where they happened. Chile is a developed country and so its got universities, it got seismologists and geologists that have had to deal with earthquakes over a long period of time. Whereas in Haiti the country is so poor they have essentially no scientific backup services. My nderstanding is they didn't even have a course in seismology at any university or higher education in Haiti, so they were completely unprepared academically as well as people just basically living in shantys and shacks, living very close together and so it was a catastrophe waiting to happen. A number of cities around the world that this is certainly true. I happen to recognize this, oh last summer six months ago I am writing a book about active faults of the world and I saw this situation in Haiti with this big strike-slip fault plate boundary fault running so close to Port-au-Prince with at least 2 million people living there. I said this is a time bomb and this is going to go off and it is going to kill hundreds of thousands of people and that exactly what happened.

Narrator: In both countries there were aftershocks. Why do aftershocks occur?

Yeats: Well, it's a good question. The main shock, the big one - it's almost like an echo, the earthquake happens and you move a big block of crust past another block, and so it doesn't do that smoothly - so lots - it's adjusting over time. Aftershocks will continue for years. Some people think they continue for many, many years. And so the earthquake - ah, I think the Japanese discovered this about a century ago - that you have a big earthquake and then you continue to have smaller quakes and they decrease at a rather irregular way, and then you'll sometimes have a six or a seven. But they're not going to be as large as the main shock unless it's a different situation. Now there could be a separate, different earthquake, but I don't have any way of suggesting that this might happen. SEGUE

Narrator: Finally, would you say we are any closer to being able to predict earthquakes?

Yeats: I wish I could answer that yes, but I'll say that a lot of effort has been put on this topic - in fact the whole earthquake programme in the United States in the middle '70s was designed with the idea that if we just put the resources on this that we'd solve this. Basically, it's our version of trying to find a cure for cancer, so a lot of effort has been made by the scientific community, and so far we've had some hints that might work a little bit. The Chinese did successfully forecast an earthquake in 1975 in Manchuria. In fact they've done several, but they're on a specific kind of fault that had a lot of foreshocks - that is the successful prediction. If you had been there two or three days before the earthquake, you would have felt lots and lots of smaller earthquakes, and you would have been calling up people saying, "hey, what's going on, what's happening?" And the people themselves almost drove that prediction and they were really frightened because of all the smallest earthquakes and the same thing happened in Greece a few years ago. But this earthquake - in Haiti earthquake, we don't have any short term ways to predict that that earthquake would happen.

Professor Robert Yeats, retired professor of geosciences at Oregon State University.

Producer: Gerry Adams
Duration: 4'15"