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What's up with all the earthquakes?

Q&A: A geophysicist talks about the recent spate of earthquakes, lessons from Charles Darwin and the possibility of volcanoes erupting.

A cracked highway in Mexico; an injured child in Port-au-Prince; the Chilean coastal town of Dichato. (Tomas Bravo/Reuters; Eduardo Munoz/Reuters; Francisco Negroni/GlobalPost)

BUENOS AIRES, Argentina — The quake that hit China Wednesday was the latest in a string of earthquakes in the news lately. Many people are wondering what's going on, so we decided to ask NASA. Eric Fielding is a geophysicist who uses satellites to study earthquakes at the Jet Propulsion Laboratories in California.

GlobalPost: So first question is the one on everybody's mind. What on earth, literally, is going on? What's up with the earthquakes?

Eric Fielding: The most important thing to remember is there are earthquakes all the time, someplace in the world. In a normal year, there are around 16 earthquakes with magnitudes 7 or higher. So far this year we've had six earthquakes like that. So we're well within the expected range for a three or four month period. (See a list of the earthquakes so far this year.)

Is there ever a pattern to a series of earthquakes?

There are certainly cases where one area experiences a sequence of earthquakes over time. The most famous and well studied are the sequences that occurred on the North Anatolian Fault in Turkey. The first one was in 1939 and there was a series of seven major earthquakes, the most recent being the 1999 earthquake that destroyed Izmit, Turkey. They were all along the same fault; each one increased the stress on another section of the fault and caused the next section to go. That's the classic example people use of one earthquake triggering another. There were two earthquakes in 1999, about a month and a half apart.

There was an earthquake that happened in Salta, Argentina, right after the one in Chile. Was that related? The seismic waves would have had to travel through the Andes.

I'd say that was a little further distance than we'd expect. We want to find out more about exactly what happened during that earthquake and how it might be related. We're hoping to get some radar data from that earthquake but we're still waiting for the satellites.

There’s a lot of new information to analyze then?

Lately there's a lot to look at. People like me, who study earthquakes, are getting a little overwhelmed this year. I almost don't want to turn on the news. But the ones we've had this year are more newsworthy. The one in Haiti caused a lot of devastation, the one in Mexico was very close to California. We even felt it here in Los Angeles. The Sumatra earthquake is more expected, they have a magnitude 7 or 8 earthquake every two to three years. The Chile fault line had been identified as overdue for an earthquake and it happened this year.

Are there any lingering questions in your mind with regard to the recent activity? Or do you think it's completely expected, completely normal?

These earthquakes in general are sort of random — sometimes by chance you're going to get a coincidence of several earthquakes in a region like the Pacific Rim in a few months. It's like flipping a coin and getting heads four times in a row. It happens.

Do humans do anything that causes instability or triggers earthquakes?