Haiti Considers Future Quakes While Rebuilding
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This is MORNING EDITION, from NPR News. I'm Linda Wertheimer.
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And I'm Renee Montagne.
No one in Haiti wants to think about the next big one, but scientists now studying last month's quake say it could have been worse, and a more damaging quake is likely sooner or later. NPR's Richard Harris reports from Haiti's capital.
RICHARD HARRIS: The quake struck southwest of Port-au-Prince. But in order to understand what could happen next in Haiti, earthquake scientist Eric Calais has headed 30 miles north to the town of Saint-Marc. We pull up at blue-and-white cinderblock building, the local police station.
(Soundbite of ladder being extended)
HARRIS: After a brief conversation with the officer at the counter, the scientific team pulls an extension ladder off the top of its vehicle and leans it up against the station.
OK. Up on the roof.
Professor ERIC CALAIS (Geophysics, Purdue University): Yeah, up on the roof now. We need to find the benchmark.
HARRIS: Calais is looking for a medal disk the size of a dime, which his Haitian colleagues installed here some years ago. After a few minutes of poking around, we find it. Calais then assembles something that looks like across between a radar dish and a Frisbee, and they carefully install it right over the benchmark.
This is a GPS receiver, but far more accurate than your handheld model. With three days of measurements, Calais, from Purdue University, will know the precise location of this spot to within a millimeter - the thickness of a fingernail. And that's important, because he needs to measure how parts of Haiti are moving relative to one another. That's why earthquakes happen here.
Mr. CALAIS: Well, these measurements here are right after the earthquake are important to me, because we still don't understand exactly what happened during the earthquake, and we need to know what the rupture was during the earthquake, how much slip there was at depth.
HARRIS: That is critical in figuring out the risk of future quakes. Rough estimates now are that six miles underground where the quake started, the fault slipped 15 feet. At the surface, the north of Haiti moved about three feet relative to the south. Calais will nail down those numbers once he measures the exact positions of more than 30 of these benchmarks around Haiti.
One thing earthquake scientists have already leaned is that during the January 12th quake, Port-au-Prince caught a break. Most of the energy from the earthquake actually focused to the west, away from the densely populated capital.
Mr. CALAIS: Of course, Port-au-Prince was still hit because seismic waves propagate anyways in all directions, but much less so than if the opposite had happened, the rupture going from west to east.
HARRIS: So if the direction of the energy from this quake had pointed in the other direction, how much worse would it have been for Port-au-Prince?
Mr. CALAIS: Well, it's hard to quantify this, but it could have been, you know, twice worse.
HARRIS: Another break for Port-au-Prince is that all the measurable aftershocks, at least so far, had been centered farther away from town than the original quake. There've been more than 70 so far, and they will continue for months. Just where, nobody can say.
But Port-au-Prince's relative luck won't last forever. The quake apparently shifted more strain onto the eastern segment of the fault, and that runs right through densely populated parts of Port-au-Prince. Seismologists at the U.S. Geological Survey have calculated there's a 2 percent change of a magnitude seven quake on this length of the fault between late January and February 22nd.
Calais doesn't get too excited about that short-term assessment, though the story of two massive quakes here in 1751 isn't exactly comforting.
Mr. CALAIS: There is a history of two earthquakes within essentially a month on this fault. And it could happen again, and it could not happen. This is something we just don't know.
HARRIS: One thing he can say is that the risk to Port-au-Prince is high in the medium term, and that message is now starting to spread throughout Haiti, thanks to the efforts of the country's only earthquake scientist. Back in Port-au-Prince, we ask Claude Prepetit whether he was more concerned about the aftershocks right now or the possibility of another major quake right on the fault that runs through heavily populated areas of Port-au-Prince.
Mr. CLAUDE PREPETIT (Seismologist): (Through translator) I'm concerned about both. A lot of people are sleeping outside, and they want to get back into their house. So we must manage the situation. But also, for the future, we must concerned about it because at any time, the rest of the fault line could move. So we must consider all those criteria when we are rebuilding.
HARRIS: The overwhelming challenge is to figure out how to turn that concern into actions that will eventually make this population safer.
Richard Harris, NPR News, Port-au-Prince.
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