Deep inside Great Mountain Forest, in the northwest corner of the state, Yale geophysicist Maureen Long kneels down in a grassy clearing to see how her seismology station fared over the long winter.
The station is about the size of a sawhorse. It is topped with two small solar panels, but its main feature — a bowling ball-shaped seismometer — is buried a few feet underground. For months, this gear has been collecting information that will help scientists understand the submerged stories of how North America came to be.
“Connecticut is a place where we can see the result of so many different, fundamental Earth processes,” Long explains. “What we don’t know, quite often, is what those processes looked like deep in the Earth.”
Alongside her is Juan Aragon ’17, a Yale undergraduate who designed the seismology station. He uses a power tool to open the station’s sealed compartment and get at the equipment inside. “All right, the moment of truth!” Aragon says.
Long peers inside, grins and gives a thumbs-up. “Looks pretty good,” she announces. And with that, the real work begins.
This is no casual woods walk, after all. It’s part of an ambitious plan for sussing out deep secrets from planet Earth, via a line of seismometers buried at farms, forests, and backyards across northern Connecticut. The program is called the Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn). By the end of 2016, SEISConn will have 15 compact, broadband seismic stations installed. Once they’re all recording data properly, the gizmos will collect a wealth of seismic information about the crust and upper mantle of Connecticut.
“I tell people it’s like doing a CT scan for the Earth itself,” Long explains. The seismometers in Connecticut will pick up seismic waves from earthquakes that originate far away. By analyzing those waves as they move through rock, geophysicists will be able to create an image of what’s happening miles underground. That, in turn, will offer insight into what’s happening above ground.
“Everything we see on the surface of the Earth is shaped by what goes on under the surface,” Long says. “There’s a school of thought that says life on Earth might not have happened at all without plate tectonics.”
Simply put, plate tectonics is the intricate movement of massive plates located beneath the Earth’s surface. It accounts for the formation of continents and mountain ranges, the occurrence of earthquakes and volcanoes, and a host of geophysical mechanisms. As luck would have it, Connecticut’s geology is a rocky roadmap of subsurface events over hundreds of millions of years.
One example is a Wilson cycle — the process by which continents come together to form supercontinents, then rip apart to form new ocean basins. The Connecticut River Valley is the product of this type of continental rift, formed during the time when today’s Africa and North America split apart from the ancient supercontinent Pangea and created the North Atlantic Oceanic basin.
SEISConn may well get a good look at an entire Wilson cycle, Long says. But first, she and her team of graduate students, undergraduates, and volunteers must install a line of seismic stations across the northern tier of the state. Seven stations went in last year, and the rest are slated for installation this year.
Why northern Connecticut? Long says that part of the state is less developed, with less chance of interference or traffic vibrations that would throw off their readings. Also, northern Connecticut offers a Yale-owned location within the private, Great Mountain Forest. The Yale School of Forestry & Environmental Studies granted Long permission to install a station there.
Of course, that still left 14 more sites to find.
“We started by looking at Google Earth,” Long recalls. “We made a wish list of the spots we wanted. Then we had to see what properties were nearby. We looked for other universities, for farms. Often, people were very receptive. But sometimes, you’re just knocking on doors.”
At the Great Mountain Forest site, Long and her team have no doors to deal with, only dirt roads and dive-bombing barn swallows. In addition to Long and Aragon, the crew includes graduate students Andrea Servali and Neta Bar, and Bar’s husband, Boaz Bar. They do a full survey of the seismology station, including an extensive checklist of maintenance and data retrieval tasks. The station has stored 258 days’ worth of data.
Aragon, for his part, is proud that his station design is holding up to the rigors of New England weather. He wanted the stations to be sturdy, while keeping the data recording apparatus above ground. “Usually, this box is buried,” he says. “You find spiders, snakes, mold, and water in there when you uncover it. This design is more secure and less likely to flood.”
Prior to re-securing the station at Great Mountain Forest, they conduct what is known as a “stomp” test. Essentially, someone needs to hop up and down near the station, while another person makes sure the recorder captures that brief activity.
Boaz Bar volunteers, launching into a forceful, one-man dance routine. “Ladies and gentlemen, we have a successful stomp test,” Long says.
By early afternoon, the team is back on the road, heading west to a YMCA camp in Lakeville. They check in at the camp’s administration building, before driving to the edge of a wooded area with walking trails. At this stop, they bring a more extensive collection of gear, including shovels, saws, tape, and a tool box.
“We should bring the machete, too,” Long says.
They walk a short distance through the trees before coming to the station — one of the first SEISConn units to be installed a year ago. Closer inspection reveals a malfunction in the gear, which sets the whole team into motion. They must diagnose the problem and either do a repair or install new equipment.
Everyone settles in for the duration, understanding it could be weeks or months before they can revisit this location. Every inch of the station will get a thorough inspection, right down to the wiring. There will be trips to the van for more tools and theories about whether the problem is a jostled seismometer or a faulty data recorder.
But it’s nothing Long and her colleagues can’t handle.
“We’re trained geophysicists,” she says. “Now let’s start our checklist.”
– By Jim Shelton
*Source: Yale University