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eophysicist Anne Sheehan remembers the days when learning about an earthquake required some serious legwork. As a graduate student at the Massachusetts Institute of Technology (MIT) in the 1980s, when an earthquake of interest struck, she took the train to Harvard where recordings of Earth surface motions (seismic records) were stored on large tapes. She crammed as many as she could into a backpack and then lugged them back to MIT to analyze the data. “It’s hard to imagine a world before the Internet, but we did get things done,” recalls Sheehan. That level of effort to acquire earthquake data seems unimaginable in the age of the Internet, says Sheehan, now director of CIRES’s Solid Earth Sciences Division. Nowadays within seconds of a strike anywhere around the globe, a scientist can get an email or text alert or check out the details of the shake from the U.S. Geological Survey’s website. And this advancement has happened in the blink of an eye in geological time scales, where time measurements are frequently made not in decades, or even millennia, but in millions of years. CIRES and CU’s seismology program was born in 1967, around the time the theory known as plate tectonics was becoming widely accepted. Plate tectonics revealed that the top 100 or so kilometers of our planet are split into a series of rigid plates, like the cracked shell of an egg.

These plates move around due to convection in the underlying mantle, a layer of hot material that can flow like a liquid over geologically long time periods. These plates jostle against each other and temporarily get stuck for tens to hundreds of years until they suddenly break apart, producing earthquakes. Volcanoes are also associated with tectonic plate motions, as magma upwells when plates pull apart or dive down underneath each other. The plate tectonic theory marked a paradigm shift in the field of geology—geologists suddenly understood the link between the location of volcanoes and earthquakes and could explain why Africa and South America looked suspiciously like they had been ripped apart. Sheehan came to CIRES in 1993, and she began to explore a number of questions surrounding the nuances of plate tectonics: Is the Rio Grande Rift, a gash that ripped apart North America from Colorado down to Mexico, still active? What does a fault look like miles below Earth’s surface, a place we will never see with our own eyes? Why are the Rocky Mountains thousands of miles from the edge of a plate, when most mountain chains form near the edges, crumpling upwards from the force of the collision? Technology inspired Sheehan to focus on Colorado when scientists deployed a set of broadband seismometers—instruments that can record a wide range of ground motion—along the state’s Front Range. “The revolution

Seismic Shake-Up

Anne Sheehan programming GPS devices

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Sheehan getting her hands dirty

Spheres: 45th Anniversary Edition  

A periodic magazine covering the broad range of research done at the Cooperative Institute for Environmental Sciences at the University of C...

Spheres: 45th Anniversary Edition  

A periodic magazine covering the broad range of research done at the Cooperative Institute for Environmental Sciences at the University of C...

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