Scott Ausbrooks, the geo-hazards and environmental geology supervisor for the Arkansas Geological Survey, explains how an earthquake sensor station buried at Wooly Hollow State Park in Greenbrier works.
GUY — In the moments after a 4.0-magnitude earthquake shook the metal walls of Lynda Harmon's flea market and grocery store just west of town on Arkansas 25, the lifetime Faulkner County resident was thinking about her insurance policy. "Me and many, many more called immediately and got earthquake insurance," Harmon said last Wednesday, the same day the U.S. Geological Survey recorded three more minor quakes centered near her business. "I think everybody is a little anxious either for them to stop or to find out what's causing them. You don't know whether it's going to get bigger or if they're just going to go away."
Geologists expect the quakes will continue for weeks, months or more but that the shaking will stay well beneath disastrous or damaging levels.
But that's only a small comfort for residents in the tiny community of Guy who have had to grow accustomed to the earth moving beneath their feet. The intense increase in seismic activity - many say they can't recall such shaking ever before - has some wishing it would end, others worrying about the big one and still others contemplating the cause.
And it has most everyone talking.
The quakes come up in conversations at Harmon's market multiple times a day as locals check out with clothes, jewelry and groceries. It's the topic of choice at Thunderbirds, the gas station convenience shop where retirees sip coffee and play video gambling. And at City Hall, it's a matter town officials aren't taking lightly.
"It's just an eerie feeling," said Water Superintendent Greg B. Hooten, who wonders if a larger quake than any felt so far could disrupt the city's waterlines. "Some people are worried, some aren't. The biggest thing people are concerned with now is they seem to be getting bigger. And so everybody's waiting to see is the next one going to be bigger than the last."
Scott Ausbrooks is paying particularly close attention. He's the Geo-Hazards and Environmental Geology Supervisor for the Arkansas Geological Survey, which is investigating the temblors and tracking them with its network of seismic stations around the state. A permanent station is buried at Wooly Hollow State Park in Greenbrier, while five temporary stations are deployed elsewhere near Guy to help geologists pinpoint the location of the quake and its depth.
That's critical information in determining whether the shaking is triggered by natural occurrences or manmade work, like natural gas drilling in the area.
Geologists have eliminated most drilling as a possible contributor because, in part, the earthquakes don't correspond to the approximately 3,000 wells in the Fayetteville Shale. But the data from the recent quakes is being used to study saltwater injection mines, a specific type of drilling linked to seismicity in other places across the country and found in mines around Guy. A study of such mining around the Dallas/Forth Worth International Airport found it was a plausible cause for a series of minor quakes in 2008 and 2009. "We have not established that correlation as of yet, but that is something we're looking into," Ausbrooks said recently during a stop at the Wooly Hollow seismic station. "But we also have to keep in mind this is a seismically active area."
Hooten said he met recently with officials from local drilling operations, whom he said presented a pretty strong case that it wasn't their work causing the quakes.
"But they wouldn't come out and say that was not the cause or an effect," Hooten said. "I think there's a link. I don't know. You look at their data and they can make a pretty convincing story it's not from the work they're doing. But I'm sure you could bring in some people who were anti-drilling and -gas and they could probably convince you, too."
Ausbrooks calls the latest quakes a "full-fledged swarm" and likens them to similar activity in Enola that began in 1982.
Back then, the shaking started small, reached as high as a 4.5-magnitude temblor and continued in the form of thousands of aftershocks for more than 6 months.
There's no guarantee the current seismic activity will follow the same pattern, but Ausbrooks said it's a good bet it will. The biggest quake likely to strike the area would be a 5.0, which he said is "right at the threshold" of causing some damage.
Residents should have an emergency kit ready and move valuable, fragile or perhaps dangerous items from precarious positions on shelves. But other than that, it should be business as usual, Ausbrooks said.
"It is unnerving to have the earth move under your feet and I understand that," he said. "But just don't panic."
Panic hasn't been apparent in Guy yet, local residents say, but there are some real concerns.
Harmon said she discusses the shaking with multiple customers a day who question her and each other about whether or not they felt the day's quakes.
She called it more of a conversation than a worry.
"But I think everybody is a little anxious either for them to stop or to find out what's causing them," Harmon said.
Ash Dayani, a manager at the Thunderbirds gas station, said some of the earthquakes feel like a big truck bumping into the house. She said she's "very concerned" about them.
The 4.0 quake woke Dayani and her family up and sent them running from the house as their beds and the walls shook.
"It's just been scary," she said. "There's tremors every night."
Sheila Ruiz has a mobile home between Guy and Quitman. The bigger of the quakes have woken her up with a jolt that didn't cause any damage, but felt as though it was going to.
"It's just for a brief, brief moment and it doesn't last very long," Ruiz said. "But it feels like the trailer is going to tip over."
Steve Wilson, the assistant superintendent at Wooly Hollow State Park, lives with his wife in the park, only about 100 feet from the sensor that records the area's tremors.
Wilson was there when the 4.0 temblor rolled through the region, sounding like a sonic boom, rattling dishes, shaking windows and causing the rafters in the attic to creek under the stress.
Since then, he has felt dozens of the quakes and even been awakened by a few. Wilson said it's to the point he and his wife have gotten used to most of them.
It's not too much of a worry, he said, so long as nothing surpasses the 4.0 quake.
"We hope that's the biggest one we have," Wilson said. "We don't want anything bigger than that."
This article was published October 27, 2010 at 6:30 a.m.
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