The geological survey pointed out that Oklahoma has experienced more than 10 magnitude 4.0 or greater earthquakes since the previous record 5.0 El Reno earthquake in 1952.
“This is statistically consistent with the Gutenberg-Richter relationship, which describes the distribution of earthquakes of differing magnitude over time,” the survey wrote in a statement.
The survey also found that water injections began in the area in 1955 and that activity increased until about 2005 and has remained relatively consistent since that time.
“Some researchers have observed that the earthquake activity did not increase over time as injection increased, but rather occurred in a distinct ‘swarm' more typical of a natural event,” the survey said.
The survey also called for further study into the 2011 earthquakes and other seismic activity.
“We have a lot to learn in this arena,” Holland said. “No scientist can say this is how we tell a triggered earthquake from a natural earthquake. There isn't a rigorous scientific finding at this point. Clearly the way we're going to get there is through a lot more data and a lot more research on the subject.”
Keranen said she is not surprised by the differing opinions.
“It's great that we're having this debate and discussion overall,” she said. “That is generally how science progresses: one person states a hypothesis based on good data, and others agree or disagree. I welcome that discussion.”
The journal Geology is published by the Geological Society of America, which has called for public policy changes aimed at reducing greenhouse gasses that many scientists believe contribute to climate change. The Oklahoma Geological Survey, on its website, said its most important objective is “to maximize the ultimate recovery of the energy resources that Nature so generously has bestowed upon us.”
Three outside scientists contacted by The Associated Press said the researchers made a strong case for a likely man-made cause.
“I think they made the case that it is possible; it's probably even more than possible,” said Steve Horton, director of the Center for Earthquake Research and Information at the University of Memphis. “They have a very reasonable conclusion.”
CONTRIBUTING: Business Writer Paul Monies and The Associated Press