When talking about squeezing rocks together, Prof. Gregory McLaskey Ph.D ’05, civil engineering, gets a glimmer in his eyes.
Using the world’s largest rock squeezing machine, McLaskey researches the hidden mechanics of earthquakes — research for which he received the $500,000 National Science Foundation early career award.
The award supports “early-career faculty who have the potential to serve as academic role models in research and education and to lead advances in the mission of their department or organization,” according to the NSF website. The academic work worthy of this award should work toward “integrating education and research.”
He is one of seven Cornell professors that received the award this year.
With both graduate and undergraduate students, McLaskey conducts his research in a room on Cornell’s campus that looks part auto-mechanic shop, part archaeological dig. The machine, which he finished building in 2016, is a platform of two smooth rectangular granite slabs, nearly ten feet wide and 16 feet long, sitting edge to edge to simulate a tectonic fault. Around the edges of the slabs are hydraulic cylinders, capable of applying millions of pounds of force.
Once in motion, one row of hydraulic cylinders applies pressure—up to seven million pounds—to push the slabs together along the fault line. Then, another row of cylinders apply more pressure—up to three and a half million pounds—in the perpendicular direction, to make the plates slip along the fault line.
“The layman might say ‘if the pressure is all the same, the rocks just slip at the same time,’” McLaskey said. But as it turns out, the location of the slip along the artificial fault line changes drastically from simulation to simulation, McLaskey said.
One of the merits of this machine is that it can replicate “slow” earthquakes — ones that register on seismic sensors, but are not felt by anyone on the surface. Slow earthquakes, according to McLaskey, may trigger larger, “fast” earthquakes. The 8.9 magnitude earthquake that hit Japan in 2011, for instance, was preceded by many slow ones, according to McLaskey.
By simulating earthquake forces, McLaskey and his team can make precise calculations about the ways two naturally crashing plates behave thousands of feet beneath beneath the Earth’s surface.
“They may sound the same each time they slip,” McLaskey said, imitating the “booms” made by the simulated earthquake. “But each earthquake is unique.”
At extreme pressure, huge rocks — including those in McLaskey’s machine — become dynamic in their movements, allowing for variation in the location of seismic waves between different quakes. “We’re asking: How is rock deformation linked to shaking?” McLaskey said.
Only large rocks behave with this kind of flexibility, which is why a machine of this size is so valuable to research, according to McLaskey. The location of one slip might suggest where the next slip will occur, and this kind of data aims to better predict where and when earthquakes might hit, as well as anticipate their magnitude.
In light of the outreach aspect of the NSF award, McLaskey is looking at two main issues that apply far outside the lab. The first is the way plates behave when injected with liquid.
This research is relevant to the effects of the oil and gas industry — according to McLaskey, oil and gas companies accrue thousands of gallons of wastewater, and to dispose of it cheaply, inject it into the ground. This process, McLaskey said, has caused many earthquakes in the last decade, including in Arkansas, Oklahoma and Ohio.
Into the slabs of granite and plastic, McLaskey drilled small tunnels which lead to the fault line. While the rocks are under pressure, he pumps water into the holes to observe its ability to trigger earthquakes. This research hopes to give McLaskey and his team a better understanding of how the oil and gas industry can cause unintended earthquakes.
“Another one of my main questions now is, do you really need such a big rock, or can you use different materials at a smaller scale,” McLaskey said.
He is using plastic blocks in similar experiments, hoping to figure out what smaller sized blocks of plastic have the same seismic reactions as the massive granite blocks in the rock squeezing machine.
“If you want to understand tides, you can change the viscosity of the liquid and simulate a day’s worth of waves in a few hours,” McLaskey said. “We don’t know how that scaling works in earthquakes.”
McLaskey’s goal is to be able to apply calculations from crashing plates of a smaller size to the mechanics of larger plates. This would mitigate the barriers to data collection posed by the expense and size of the machine like the one in this lab.
“All awards call themselves awards but are really just funding,” McLaskey said. “This award is about funding, but also about who you are.”