GUY RAZ, host:
RAZ: Joining me now in the studio is NPR's science correspondent Richard Harris.
Richard, you're just back from reporting on the earthquake in Haiti, give us a sense of how much stronger today's quake in Chile was compared to that one Haiti?
RICHARD HARRIS: Well, today's quake was an 8.8 versus a 7.0. And the numbers may not seem that different, but actually, in terms of energy it's enormous. That's about 500 times more energy released in this earthquake in Chile than compared with Haiti. However, that's only one measure. Obviously, the Haitian earthquake did so much damage and there're a couple of reasons for that, one of which is that the energy from that earthquake was very heavily concentrated and it was extremely close to Port-au-Prince - the capital city, so it was very, very close to structures. Many - millions of people were really within intense shaking zones.
This was a much more diffused earthquake. You talk about an epicenter, but you could - I was talking to a geologist who said you should really think of this as sort of like a sausage-shaped thing that ruptured down there. It was very broadly spread out. And so the energy, even though a tremendous amount of energy came out, there wasn't anyone that close by and obviously, there were still deaths and still destruction of property but nothing compared with Haiti where everyone was right on top of that fault and, in fact, where people weren't expecting an earthquake at all. And, of course, we've all heard the stories about how badly constructed Port-au-Prince was.
RAZ: Right. Port-au-Prince.
Mr. HARRIS: Yeah. And it's a very different story in Chile.
RAZ: This same region of Chile was the site of one of the most powerful - the most powerful actually, earthquake in recorded history - this is in 1960 - a 9.5. Explain, what is it about this part of the world that causes these massive quakes?
Mr. HARRIS: Well, what's going on here is essentially, continental drift or plate-tectonics, as the geologists prefer to call it. And basically, what's happening is you've got the Nazca plate, which is under the Pacific Ocean, trying to move East and what's East of it is already South America.
Mr. HARRIS: So it's basically running into South America and it has no place to go but down, so what happens is the continental crust slides underneath, and it's actually the reason that the Andes Mountains exist because over a long period of time, the mountains get pushed up; the crust get's pushed up, so you're seeing the effects of that on a long-term basis. On a short-term basis, what this really means though is that as these stresses accumulate, every so often, the stresses get too much, and bang, something slips underground, large areas, as we saw today sometimes, and you get these tremendous earthquakes.
RAZ: Bigger than anywhere else.
Mr. HARRIS: Well, there are certainly quakes of about this magnitude that have happened. Indonesia wasn't quite this big but it was a very large earthquake. In Alaska - there have been other places where you get large, large earthquakes. But certainly, this is one of the most seismically active parts of the planet.
RAZ: Richard, let me ask you about the tsunami threat. I mean, because obviously, people living in coastal areas along the Pacific had been warned all across the Pacific to evacuate - to go to higher ground. These waves move incredibly fast over these vast distances. Explain why some earthquakes cause, you know, these waves and others don't.
HARRIS: Well, you need an earthquake of a certain magnitude to do this. You need, generally speaking, a really powerful earthquake, such as this one to generate a tsunami. And what's happening is you're basically jolting the seafloor with an earthquake like this. And you can also, by the way, accomplish the same thing with a giant underwater landslide. That's another way you can generate a tsunami. But these earthquake tsunamis are just - you need that super strong jolt. And once you've jolted it, it's just like, you know, dropping, you know, pushing yourself in the bathtub or something. You create a wave, and the wave just takes off and the energy just gets carried across the ocean.
We've been fortunate in this circumstance that basically, Chile is really far away from many of the places that are in danger. So there's been just ample time to warn people that there could be a potential of disaster.
I think what we're also seeing is the good news is that you're not necessarily going to have widespread destruction from this; it came and went through New Zealand without apparent affect, and so on. And so, you know, you don't really know. You can't measure very exactly how a tsunami wave is going to affect things. But at least, we knew that there was a potential.
RAZ: Richard, could an earthquake this big ever hit the U.S.?
HARRIS: Yes, as a matter of fact, it could. There's a very similar circumstances up in the Pacific Northwest around Washington State and Oregon. There have been earthquakes of this nature in the historical record; not that were measured by instruments. But this sort of thing can definitely happen. It has happened in the past and it will inevitably happen in the future, but not necessarily, you know, tomorrow, or a decade, or even a century from now.
RAZ: That's NPR's science correspondent Richard Harris here in the studio with me.
Richard, thanks so much.
HARRIS: My pleasure.
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