A 4.7-magnitude earthquake that researchers described as the largest in Arkansas in 35 years was recorded late Sunday night near Greenbrier. It was the latest in a swarm of quakes that has bedeviled the region since early last fall.
There were no reports of major damage, though some residents spoke of dislodged screen doors and cracked ceilings. Damage or not, some said this was the longest and scariest quake yet.
“It felt like a real loud thunder, but like 10 times worse than that,” said Kim Bannister, 34, who lives just outside Greenbrier and who, like most in the region, has become somewhat accustomed to earthquakes. “I have felt some of them, but nothing like last night.”
The swarm in central Arkansas has brought dozens of rumblings each week, many of them with magnitudes beyond 2.0.
The situation has garnered national attention because of its possible connection to natural-gas drilling operations in the area. Researchers with the Arkansas Geological Survey have pointed out spatial and temporal relationships between the earthquakes and the use of injection wells, which are used to dispose of the wastewater left over from gas drilling. (Researchers see no such correlation between the quakes and the drilling itself, a process called hydraulic fracturing.)
While a possible connection is being studied, the Arkansas Oil and Gas Commission has imposed an emergency moratorium on the drilling of new injection wells in the area. Wells that were active before the moratorium, which began in December, remain in use.
Determining such a connection is not easy: there have been similar, naturally occurring earthquake swarms in the area in the past. But there is also a growing body of research suggesting that injections wells can induce earthquakes, and there is some circumstantial evidence that this might be happening in Arkansas.
Most of the earthquakes in the latest swarm have been too small to be felt. The worst seemed to have passed after some midsize quakes in October and November, but in the past few weeks, several quakes were recorded with measurements over a 3.0 magnitude.
Sunday’s quake, which occurred around 11 p.m. and was felt in at least five states, surpassed all others recorded in this or any of the previous swarms, said Scott Ausbrooks, a state geological survey researcher.
He said that the fault along which the quakes were occurring could yield an earthquake measuring up to 5.5 magnitude if it were to erupt all at once. But he said that was unlikely.