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Professor Steve Roecker is part of a team of researchers studying the Tien Shan mountains in Central Asia, considered a geologic puzzle because they exist not at the edge of a tectonic plate, but in the middle of one. Photo by Steve Roecker
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While Troy, like all of New York state, rarely experiences significant seismic activity, Rensselaer is a hive of research activity on the subject. Institute researchers stand at the leading edge of studying both the causes and the effects of earthquakes, examining everything from the physical construction of fault zones to the safe construction of buildings in those zones.
The Geotechnical Centrifuge Center is just one node of earthquake research at Rensselaer. Institute earth scientists have fanned out across the globe to perform significant fieldwork for years, studying faults and earthquake activity from Kyrgyzstan to California and from Indonesia to Oregon. Rensselaer research on earthquakes also engenders interdisciplinary projects: engineers work with computer scientists, and geophysicists collaborate with mathematicians. Earthquakes may be an age-old problem, but the research methods used to understand them are distinctly new.
I Feel the Earth Move
Earthquakes are a product of the motion of the planet’s tectonic plates — the 20 or so large segments of the Earth’s crust slowly moving around the globe — which are responsible for the ongoing rearrangement of the world we see. A head-on collision between tectonic plates, which has happened at the edge of the Indian subcontinent, can produce spectacular features such as the Himalaya mountain range and the recent Kashmir earthquake.
Rensselaer earth scientists have fanned out across the globe to perform significant fieldwork for years, studying faults and earthquake activity from Kyrgyzstan to California and from Indonesia to Oregon.
Tectonic plates do not always meet in this precise fashion, however. When a plate largely supporting an ocean meets a continent-bearing plate, the heavier oceanic plate tends to dive underneath its neighbor, in the process called subduction. And sometimes plates scrape past one another in a lateral motion, as is the case with the San Andreas Fault in California.
Whatever the precise movement, a single earthquake represents the release of tension that accumulates along a fault, where plates move in fits and starts. “It’s like a spring getting loaded,” says Rob McCaffrey, professor of geophysics, who has helped pioneer the use of Global Positioning System (GPS) technology to measure the movements of plates. “The number-one question is how much of the fault will go at one time,” McCaffrey adds. “That determines the magnitude of the earthquake and the duration of its shaking.”
This house, in the Tien Shan mountains in Central Asia, sits at the base of tilted strata. Photo by Steve Roecker
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In geologic time, spanning billions of years, an individual earthquake is a tiny, incremental event. In human terms, however, as Dobry notes, major earthquakes are infrequent (although small ones happen every day around the globe). Yet that is only one reason engineers need to generate their own steady stream of data through simulated quakes.
“With earthquakes, another big problem is, you never know when or where they’re going to happen,” says Tarek Abdoun, assistant professor of civil engineering and associate director of Rensselaer’s centrifuge center. “Whenever you put instruments in a certain area, earthquakes never happen there. But for us, as engineers, to be able to understand a certain phenomenon and design for it, you need to know what is happening. With a centrifuge, you have instrumentation, you can recreate the event, you learn a lot, and now you can improve the design and the foundation of buildings.”
The sheer scale of the planet means researchers still are just beginning to collect earthquake data in many places. In the 1980s, McCaffrey was among the first scientists to use GPS measurements in Indonesia, the site of last year’s catastrophic earthquake. Today, much of McCaffrey’s work involves “measuring the buildup of the energy right now” in complex fault systems in order to develop a detailed picture of fault activity and, eventually, a better sense of which fault segments might be most prone to move in a given period.
Specific earthquake predictions remain an elusive goal. The outlines of tectonic plates might look simple on a world map, but the view from the ground is another matter. Within a fault zone itself, tectonic plates do not just neatly collide or grind past one another, but can shatter into smaller pieces, like a fractured eggshell. The more scientists measure subduction zones, the more they realize how complicated they can be — especially in places like Sumatra.
“It’s not just a simple subduction,” says McCaffrey, who over the years has become something of a specialist in such regions, including Oceania and the Pacific Northwest of the United States. “What New Zealand and Cascadia and Sumatra have in common is that the upper plate in the system is breaking apart and forming these little plates that are moving around independently.” Oregon, for example, sits on a small plate rotating clockwise relative to the rest of the United States. Such intricacies make charting the mechanics of a fault zone much more difficult.
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