Indiana University’s Geological Sciences building is home to one of the earliest and longest continuously operating seismograph stations in the Midwest.
The station can record earthquakes locally to earthquakes occurring around the world.
It originally operated near what is now the IU golf course. It was relocated in the 1960s into the then-new Geology Building. It originally operated using a photographic recording system and then was converted into a pen and ink recording system. Along with the analog seismograph station, IU has a broadband digital recording system as well. The station is part of regional and national networks.
The analog seismograph recording station has two components: a bottom drum that rotates about every hour recording distant earthquakes and an upper drum that rotates about every 15 minutes recording nearby earthquakes, said Michael Hamburger, professor emeritus in the Department of Earth and Atmospheric Sciences.
The bottom records earthquakes daily in other parts of the world. The upper drum can record earthquakes too small to feel; it can even record trains, traffic and mining blocks, Hamburger said.
“The recording instrument that you're looking at here is really kind of a historical relic,” he said. “We're one of the last stations that's operating this kind of traditional analog pen and ink recording station.”
The three ink colors represent three components of ground motion. On the left it records vertical motion and the others record horizontal motion: north to south and east to west.
“With the three of them, we can essentially triangulate and figure out the direction that a seismic wave is coming from,” he said. “From the types of the waves, we can get the approximate distance, so that we can kind of get a preliminary estimate of the location of an earthquake even before we're in contact with other seismic stations.”
It’s connected to seismometers, the ground motion sensors, in a vault located in a room across the hall from the seismograph station. The digital instrument also sits beside the older instruments.
Every seismograph station in the world records at the same timescale, Greenwich, England, Hamburger said.
“If you look carefully at the records, you'll see these pronounced little deflections on these records, it's every 60 millimeters. Those are time marks,” Hamburger said. “So each time the clock says a minute has passed, it puts a little deflection in the record that we can use to get precise time.”
The analog seismic station has broad educational and community value, he said. Undergraduate and K-12 students use it to learn about the seismic activity around the world. It can be used to teach about seismic waves, wave propagation and the structure of the interior earth. Hamburger said it’s able to provide a visible record of how the earth was behaving over the 24 hours the analog station records.
“This is a way to make the invisible world visible,” he said, “for students and especially younger students to see this for the first time and to realize that these are actually recordings that are coming from the interior of the Earth. They’re, echoes from an earthquake that happened halfway across the world, and that we can see them and make sense out of them here is kind of a light bulb moment sometimes.”
The data is studied to learn the damage an earthquake may have produced and the local implications. Hamburger said it serves as a reminder that an earthquake across the world is not just a faraway story. Earthquakes can have aftershocks.
“We now, by careful observation of an earthquake in China or an earthquake in Venezuela, can predict how many earthquakes we expect in the weeks to months after an earthquake in California or an earthquake in Indiana,” Hamburger said. “That can help emergency officials know what to expect.”
It’s also used to study volcanoes, landslides or processes associated with active faults. Oil and gas industries also use seismic waves to study the structures that might trap fossil fuels.
Since the analog seismograph records for 24 hours each day, student assistants change the records, Hamburger said.
Hamburger said it’s been a labor of love keeping the analog seismic station running.
Terry Stigall, the building’s electronics technician, has kept the seismic station working since 1981.
It’s become more difficult finding spare parts, she said. Seismograph stations that have shut down have provided spare parts.
The pens on the drums can get damaged or break, she said. Also the analog’s station electronic system can fail due to overheating issues or just natural deterioration.
“If and one of the boards I can't replace, I'll call around everywhere to see if there's something compatible that I could substitute in to make it work,” Stigall said.
Hamburger said they are prioritizing retaining analog records of the major earthquakes with the digital recording available. The digital instrument is helpful when there are earthquakes too small to pick up a signal or too large for the analog instruments to record properly.
“So if you look at a very large earthquake like the Venezuelan earthquakes, these analog instruments actually are not very useful,” Hamburger said. “The pens wildly swing side to side and we can't really use the data very well. That's where these digital instruments come in handy, where they have a much broader range.”
The analog records date back to the 1960s.
