“We are working on studying many aspects of seismicity,” Holland said.
Hydraulic fracturing, or fracking, can cause small earthquakes for short periods of time, but it does not explain the increase in Oklahoma in recent years, Holland said.
Fracking, a well stimulation technique that is used with high pressure water to crack rock, may have contributed to about 10 percent of earthquakes from 2010 through 2012 and about 10 quakes were 3.0 magnitude or greater, Holland said.
He said fracking did not contribute to the big one Nov. 6, 2011.
Another concern is fluid injection from saltwater disposal wells. Scientists are studying links to earthquakes in Texas and saltwater disposal wells.
Bill Ellsworth, a seismologist at the U.S. Geological Survey’s Menlo Park (Calif.) Science Center, said Arkansas also has had a significant increase in earthquakes in recent years. Links to wastewater disposal and earthquakes is being studied there, he said.
Prague City Manager Jim Greff said he continues to notice more small earthquakes, but nothing like the big one that caused all the damage.
“There are lots of little ones all the time,” Greff said. “Be aware, earthquakes can happen at any time.”
Wakefield said most of the damage has been repaired in the Lincoln County area.
“You’re not seeing as many blue tarps on roofs and houses these days,” he said.