GO IN DEPTH

Gold Mine Quakes

Gold Mine Quakes Photo Credit: Clipart.com

Recently, scientists literally tapped into a goldmine of earthquake information. You'll hear about it in this Science Update.


Transcript

Studying minor earthquakes with miners. I'm Bob Hirshon and this is Science Update.

Thanks to a science and industry partnership, the gold mines of South Africa are producing a wealth of knowledge for earthquake scientists.

One of them is Penn State University geoscientist Eliza Richardson. She says the gold mines are constantly rumbling with tiny earthquakes.

Richardson:

These are the deepest mines in the world, and they're also the most seismically active in the world. Because they're full of old faults, which would never be active normally, except for the fact that there's mining going on.

All that mining and blasting weakens the areas around the faults, which makes them slip, just like in a major earthquake. To protect their workers from cave-ins, the gold companies have filled their mines with seismic sensors. Now, they're sharing the data with scientists like Richardson, who are using the information to understand how quakes start.

Richardson:

We believe that the physics that governs small earthquakes and large earthquakes is the same. And so the idea is that if you can discover something interesting about how a small earthquake starts, then you'll be able to find out a lot more about the big earthquakes, because there are a lot more small earthquakes than large ones. And because these, particularly the ones in South Africa in the gold mines, are recorded in such detail.

I'm Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

If scientists could only study big earthquakes, they wouldn't learn very much. That's because big quakes–the kind that uproot trees and knock over buildings–are relatively uncommon. And by the time you realize they're happening, it's usually too late.

Fortunately, as Richardson explains, the physics of small quakes is the same as the physics of big quakes. And small quakes are much more common. So if scientists can study a lot of small quakes, they have a better chance of learning how the big ones start.

The problem is that the small quakes can be hard to detect, especially if they happen in faults buried deep beneath the surface of the earth. That's where the seismic instruments installed by the gold mining companies come in handy. By looking at the data from these instruments, Richardson and her colleagues have been able to detect and analyze small, deep earthquakes that you would never even notice if you were standing on the ground above. In fact, the instruments in the gold mines have even detected the smallest earthquakes possible: a magnitude zero on the Richter scale, which is the equivalent of 10 to 12 meters of earth slipping one-tenth of a millimeter.

In some ways, this kind of research is convenient because the scientists don't have to go through the trouble and expense of installing the seismic instruments. So in that sense, the gold from the mines helps finance the research. But Richardson says that piggybacking on the mining companies' data has its drawbacks. Because the instruments weren't designed for scientists by scientists, they don't generate data in a form that's easy for scientists to use. All the mining companies wanted to know is when and where the earthquakes were happening; they didn't plan to study the behavior of the quakes. So a lot of her team's energy is devoted to converting and interpreting the raw data.

Still, she says the sheer number of instruments and the depth at which they're placed makes the effort worthwhile. One of the things her team hopes to learn is how earthquakes interact with each other. In the mines, a small quake in one place often sets off a chain of quakes in the surrounding area. It's believed that larger quakes behave in much the same way. So understanding how and when these little quakes add up could help scientists learn to anticipate when more devastating quakes may strike.

Now try and answer these questions:

  1. What is the original purpose of the seismic instruments in the gold mines?
  2. What are the advantages of using these instruments for scientific research? What are the drawbacks?
  3. What would happen to the research if the mining operations stopped? Look back carefully at the story before you answer.
  4. Can you think of other situations (real or imagined) in which scientists might use data from instruments that were designed for non-scientific reasons? Be specific.

For Educators

The U. S. Geological Survey's Earthquake Hazards Program includes up-to-the minute information on earthquakes, including real-time earthquake maps.

Earthquakes, by NationalGeographic.com's Xpeditions, includes information about the causes and effects of devastating quakes.

The Center for Earthquake Research at the University of Memphis has information, seismic data, links, and more.


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