When people think about earthquakes, they typically imagine epic disasters that topple buildings and shatter bridges. But in fact, earthquakes are shuddering throughout the Earth’s crust all the time, they’re just too subtle to be felt by you and me. Greg McLaskey, assistant professor in the School of Civil and Environmental Engineering, thinks these tiny tremors are just as important as the large ones, and is interested in learning as much as he can about these vibrations, both large and small, that emanate from our planet’s depths. “I’m interested in earthquakes and sound propagating through solids,” says McLaskey. “Studying sound is the only way we know about earth’s core.”
McLaskey’s academic path actually started right where he is currently--at Cornell’s CEE department, as an undergrad in civil engineering. He then pursued a Masters in structural mechanics and materials at the University of California, Berkeley, followed by a Ph.D. in civil systems. While his degrees were formally in civil engineering “I was actually doing earthquake science,” says McLaskey. “I was studying miniature earthquakes.” He got to really delve into the field as a post doc at the US Geological Survey center in Menlo Park. While there, he created earthquakes in a lab setting using a giant square steel frame containing a 1.5-square-meter block of rock with a fault cut down the middle. The frame squeezes the rock with a million pounds of force, causing this interface within the stone to slip and create seismic waves--just like what happens during a real earthquake.
This is exactly the kind of set-up McLaskey plans to build now that he is a professor at Cornell. Except his model takes things up a notch. “The apparatus I plan to build at Cornell will be capable of applying 7 million pounds to rock that’s three meters long,” says McLaskey. “So it’s going to better simulate the conditions occurring deep within the Earths’ crust.”
Still, while McLaskey is creating a bigger model for his lab, it doesn’t mean he’s only interested in big quakes. “Earthquakes come in all sizes, actually,” he says. “They can of course be as big as magnitude 9, but there are small ones--we’re able to record down to magnitude 1 or 0, but we can’t feel anything smaller than a magnitude 3.” Traditionally, to study the truly tiny quakes, he explains, you have to dig deep into the earth, and in that case scientists might pick up a tremor at magnitude -3. With McLaskey’s new set-up, he can generate mini earthquakes as tiny as -8.
Why bother with such miniscule events? “Part of geophysics is trying to understand how earthquakes scale,” says McLaskey, “and it’s thought that we can learn a lot about the big ones by studying the little ones.” These little ones are caused by something as seemingly insignificant as a tiny rock fracturing into grains of sand; any event on or within the Earth’s surface creates waves of sound that propagate through the Earth. The effects of all these multitudinous shivers? Scientists aren’t sure. One thing is certain--larger disturbances in the Earth’s crust certainly do cause unusual earthquake activity.
“One practical reason we care about this is because of fracking,” says McLaskey, referencing the technique used to drill and pump natural gas out of the ground in multiple areas of the country. “With fracking there are more earthquakes happening in areas where they don’t normally...so a big question is, are these quakes getting triggered by the fracking, or would they have happened anyway.” McLaskey plans to find out once his earthquake model apparatus is up and running.
In addition to studying how vibrations affect the Earth’s crust, McLaskey is looking at how vibrations and sound can affect man-made structures like bridges and buildings. Part of his work in this area involves placing tiny sensors on concrete structures that measure the cracking that occurs over time. His hope is to better understand and predict how these structures respond to the countless vibrations that shake them, and how to assess their true level of safety and soundness.
When he’s not studying earthquakes and vibrations, McLaskey is traversing the many hiking trails that surround Ithaca with his foxhound, or playing washtub bass in a long-distance jug band that he joined while in grad school. While he admits to thinking ‘he’d never be back’ to the area, returning to Ithaca and Cornell suits him. “It’s hard to find a great university in a great small town,” he says.
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