JOAN CARTAN-HANSEN, HOST: Scientists study earthquakes using lots of different tools.

One of the most important is the seismograph.

So how do I explain what a seismograph is?

Well, let's start with pizza and football.

[MUSIC] It's game night for the Boise State University football team.

And the area around the stadium is filled with tailgaters.

For these fans, it's all about the pizza, the football, and the science.

For several years, the Boise State geosciences department has tracked how BSU fans shake the ground during a game.

JEFFREY JOHNSON, BOISE STATE UNIVERSITY: What we're observing here is effectively the same thing that we observe when we record normal earthquakes.

There is a source that pushes on the ground.

And then that energy has to travel through the ground in the form of seismic waves.

CARTAN-HANSEN: Johnson uses these tailgating lab sessions to show students how seismographs work.

JOHNSON: So basically what happens is any time the earth shakes, the seismometer can potentially pick it up.

It converts ground motions into small voltages that travel along the coil.

You can see this coil of copper wire right here.

It creates -- it induces as current in that coil because there is a magnet inside that is suspended upon a spring.

When the ground moves, that magnet goes up and down, causes a current, comes up as this wire right here, and we measure that as a voltage, and that goes into our computer.

Right now, we're listening to the earthquakes from bronco stadium, right.

STUDENT: Yeah.

JOHNSON: Bronco stadium is producing tiny little earthquakes as people are cheering on the football team.

STUDENT: Okay.

JOHNSON: But, because we're so close to the source of those microearthquakes, they show upon our monitor.

[CROWD CHEERING] JOHNSON: I can see it right there.

That's the crowd getting all excited about kick-off.

[CROWD CHEERING] JOHNSON: There is the start.

Everyone is roaring.

[CROWD CHEERING] JOHNSON: They are shaking the stadium.

And we are getting those seismic waves.

[CHEERING] [CANNON FIRE] JOHNSON: Oh, there we go.

Right there.

There is some activity from the Boise State Broncos' fans.

This is a non-conventional study.

Usually, we use seismometers to record real earthquakes, and we are listening to human earthquakes.

CARTAN-HANSEN: And what did the data tell these scientists?

Something similar to what they have learned in past years.

JOHNSON: A study that was done in 2009 actually observed the level of seismic noise decreased over the course of the football game.

The first half was a lot more energetic.

Maybe people were less tired.

The second half, perhaps, people were tired or even left the stadium.

CARTAN-HANSEN: Johnson says the study also shows that there is more than one kind of earthquake.

JOHNSON: But you can get a traditional earthquake, such as fault rupturing rock.

That's what we call a tectonic earthquake.

You can get an earthquake from a volcano erupting or from a landslide.

Or in this case, we have little earthquakes produced by people who are yelling and screaming and stomping their feet.

CARTAN-HANSEN: If you want to see where all the earthquakes in the world are happening, check out the united states geological survey map on its website.

You'll find it at earthquakes.usgs.gov/earthquakes /map And if you want to learn more about earthquakes, check out the Science Trek website.

You'll find it at Science Trek dot org.

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