Understanding the Chilean earthquake, on the ground and in the lab

One woman gives her personal account of the magnitude 8.8 earthquake in Chile, while two scientists explain what happened and what they've learned from it.
Written by Boonsri Dickinson, Contributing Editor

The magnitude 8.8 earthquake hit Chile, killing more than 700 people. This monster quake is tied for being the 5th strongest earthquake recorded this century.

Just a few days into the disaster, some of the dead bodies have been piled in bags and tossed into makeshift morgues. Troops have been deployed to control looting. Now help is on the way.

Andrea Syrtash was on vacation in Santiago, Chile when the rumble hit. The quake hit offshore, 200 miles from Santiago.

"I was very lucky as I was staying with my friend who is the British Ambassador. The house shook like crazy and it was certainly scary," says Syrtash, an advice columnist and author of upcoming book, 'He's Just Not Your Type (And That's a Good Thing).'

"Ironically I was on vacation to relax before my book comes out since I will be busy with tour. [The earthquake] happened 6 days after we got to Chile. We were very lucky to be in good hands," she says.

The earthquake left her shaking. "I ran out of the bedroom to another room, which is good because part of the ceiling debris ended up on my bed and pillow. Felt like the house was a boat at sea. It was a strange sensation. But actually, I was more scared when it was over," says Syrtash.

And then there were aftershocks.

"The buildings in Santiago are more or less in tact due to strict building codes, so the city almost looks normal. Though many things are closed due to inspections and structural issues. At this point, we are just trying to find a way out as the airport was badly damaged," says Syrtash.

Still, the destruction from the earthquake in Haiti was much worse. Haiti is one of the poorest countries in the region and its poorly constructed buildings left the country in shambles. Also, people living in Haiti were not aware of the risk — the last devastating earthquake occurred there 240 years ago.

Geologist Jian Lin of the Woods Hole Oceanographic Institution agrees. Chile's structures are built better than the buildings in Haiti. And in general, Chileans experience quakes a lot. Even though the energy released in the Chilean earthquake was 500 times greater than Haiti, the strongest shaking zone occurred in the ocean rather than inland as it did in Port-au-Prince, Haiti.

The recent earthquake has been brewing up stress for sometime.  Lin published in 2004 that the 1960 Chile earthquake increased stress on both its northern and southern ends. The rupture zone of Saturday's magnitude 8.8 quake was right next to the northern end of the 1960 earthquake, says Lin.

"This is like you and I are neighbors and the fence in my front yard is connected to the fence in your front yard. If my fence falls down, it will put stress on your fence, making your fence more likely to fall if your fence is also weak," says Lin.

The same kind of earthquake happened in Sumatra, Indonesia in 2004. "I should emphasize that we do not yet have good enough science to say why it took 50 years between two neighboring segments to rupture in Chile, but only 3 months in Sumatra, Indonesia," he says.

The Sumatra earthquake created a tsunami that killed 200,000 people.

On Saturday, some residents of Hawaii were evacuated and others spent the day on mountain tops. They were anticipating a worse case scenario — that a destructive tsunami would wipe away their homes and kill people in its path. However, it turned out to be a no show.

While the tsunami did occur, it didn't create a massive wave like scientists had predicted. The DART buoy resting on the sea floor of Chile did detect a wave underwater. And this is what set off the Pacific Ocean alarm system. Then computer models began to predict what the tsunami would do when it hit Hawaii. The other 30 buoys in the Pacific Ocean also felt the waves, but the waves were expected to be small. While the science catches up, no one really knows how big a tsunami will be until the wave approaches the coastline.

"Such initial estimations based on earthquake data are fast [and happen] within 15 minutes after a quake. But they must be confirmed, calibrated, and modified by oceanographic data recorded by DART buoys and coastal tide gauges as they become available. That is why there were a series of tsunami information messages following Saturday's quake," says Lin.

Harley Benz, the scientist-in-charge at the U.S. Geological Survey's National Earthquake Information Center, says everyone has been asking him why the scientists were wrong about the tsunami. I was guilty of that too.

While the computer models are imprecise, "forecasting the height of tsunamis will only get better because of the quality of data we are collecting after the Sumatra [quake]," says Benz. "It took us days to come up with a slip model in 2004, but we had our first slip model done in a few hours. That's huge progress."

Now, many nations provide agencies like the USGA real time seismologic data. Scientists can now tell where the earthquake occurred, the size of the event, and tell where the slip occurred along the fault.

"We can refine our models of earthquake slips and see how it translates into where the earthquake occurred, so we can describe where the slip occurred. Then we have enough data to be able to watch these things propagate," says Benz.

Regardless, Benz says the earthquake is good for science because we've learned rich lessons since 2004. The ocean base is well instrumented now.

The Chile earthquake ruptured nearly 200 miles of the earth's crust, but scientists don't exactly know how the maximum slip occurred or how to tell for sure if the calm water resting at the sea floor will move and turn into a tsunami.

"The deeper the earthquake, the less likely it is to cause a tsunami," says Benz.

While scientists are excited about the data the Chilean earthquake gave them, it surely gave Syrtash a vacation to remember.

She's still stranded in Chile.

In Syrtash's latest Facebook status update, she writes: "Feel like I'm on the Amazing Race. Airport down so we have changed routes so many times! Heading to a bus station that's still operating in Santiago and hope we can get a bus out to Andes."

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