Tellus seismograph records its first earthquake of 2011
by Marie Nesmith
Jan 04, 2011 | 3369 views | 0 0 comments | 8 8 recommendations | email to a friend | print
In the past decade, Tellus Science Museum, formerly known as the Weinman Mineral Museum, has recorded earthquakes across the globe. On loan from Georgia Institute of Technology, its seismograph documents incidents in the Southeast and abroad with magnitudes of at least 3.0 and 7.0, respectively.

Registering a 7.1 on the Richter scale, Sunday's Chilean earthquake was the first seismic activity detected by the Cartersville museum in 2011.

"The earthquake occurred because that part of Chile is very active seismically. It's just like California," Tellus Curator Julian Gray said. "In February, Feb. 27, they had the largest earthquake all year, a 8.8 magnitude earthquake. What's happening is the Nazca plate is the ocean floor of the Pacific in that part of the world [and it] is moving to the east and the South American plate is moving to the west. Those two plates are running into each other. So where they rub together it causes earthquakes.

"So that's why we have the earthquakes there and that's why they have so many there. It's very active seismically, lots of earthquakes, and they're better prepared for it as a result of that. They know that they are in an earthquake prone area so the building structures are built to higher standards."

According to the U.S. Geological Survey, the quake struck 45 miles northwest of Temuco, Chile, at 3:20 p.m. Eastern Standard Time. As of late Sunday, the Associated Press was reporting no fatalities or structural damages resulting from the seismic activity.

"The January 2nd 2011 earthquake occurred at the southern end of the aftershock region of the Mw 8.8 megathrust earthquake of February 27, 2010, and can also be considered an aftershock of that event," the U.S. Geological Survey revealed on its website, www.usgs.gov. "The subduction zone between the Nazca and South America plates has a long history of large megathrust earthquakes, including the largest ever recorded event, an M9.5 shock in 1960, which ruptured a fault mostly to the south of [Sunday's] earthquake."

At Tellus, seismic activity is measured electronically, depicted by a blue line on a computer screen.

"The old style seismograph had this big drum with paper on it and a pin and it would sit there and wiggle back and forth and make little zigzag lines as an earthquake was occurring. We do that electronically now," Gray said. "This is the 21st century, so we use computers and it's on a computer screen. So there's a line that's just going along level and when an earthquake occurs there's a jump and there'll be a sharp spike. So that's what I'm seeing on the screen here. [It] is when the pulse from the earthquake arrived at Tellus. ... It actually helps us learn how far it is to the epicenter and there are different types of seismic waves that we get.

"It's like different frequencies of light. So they arrive at different times. So I got one signal 11 minutes 20 seconds after the earthquake actually occurred. It's several thousand miles and it only took 11 minutes for that signal to get to Tellus. Then another 10 or 12 minutes after that ... another wave arrived, which travels a lot slower, and that one travels along the surface of the Earth. The difference between the arrival times tells us how far that earthquake is. So we can learn the magnitude of the earthquake and the distance to the earthquake from that information. So it's pretty cool. This is just very pure, simple science."

While Tellus' seismograph is a research tool for Georgia Tech, Gray said it is an educational resource for the museum, with seismograms of large quakes being implemented into existing exhibits.

"We have some exhibits in the museum that are related to earthquakes. And if we have something like the Chile earthquake last year [that] was so big ... [we print] out the seismic record and put it up on a panel in the gallery," Gray said. "So if there's anything big like that that happens we try to make a temporary exhibit out of it. But as far as Georgia Tech, there are scientists at Georgia Tech and they've actually loaned us this instrument. We're tied to them through the Word Wide Web.

"They download our data continuously and record it. So ... they have students and professors at Georgia Tech that are studying the seismicity of the South. So they're able to learn something about the crust by the speed at which these seismic waves travel through the crust. It's just like the medical equivalent of a sonogram. It's exactly like that. You have an earthquake and it sends waves through the Earth and it bounces off things in the Earth's interior and we can see that."