Oklahoma residents have been wondering the origin of recent earthquakes. Some blame fracking while others aren’t sure what to blame.

Oklahoma residents have been wondering the origin of recent earthquakes. Some blame fracking while others aren’t sure what to blame.

M. Charles Gilbert, retired professor of the ConocoPhillips School of Geology at the University of Oklahoma, said there are three popular probable explanations to earthquakes in Oklahoma.

One explanation, Gilbert said, is that it is a natural process.

“We’re going all the way from California to the middle of the Atlantic Ocean with our plate, that’s a long distance,” he said. “We can’t expect that it’s actually evenly stressed all the way across.”

Gilbert said another school of thought is that these earthquakes are not out of the ordinary for the region.

“Geological processes go over millions of years’ time,” he said. “In a place like California, you have enough earthquakes where you can plot their frequency against their magnitude and you can see about what the trends are like. In Oklahoma, we’ve only got since about at the earliest 1860.”

Because of the infrequency of the quakes, it is possible that geologists simply don’t have enough data to know if it has always been this way.

“Maybe it’s up and down, up and down, up and down,” Gilbert said. “Some people answer, statistically, we can’t tell whether this is unusual or not. It’s unusual to you and me, but it may not be unusual geologically.”

The third widely-used hypothesis is that the earthquakes are caused by fracking and waste disposal.

Gilbert said that in the early 1960s, there was a U.S. Army facility called the Denver Arsenal.

“It made poisonous things, gases and so on,” he said. “They had a lot of extra junk to get rid of from making these various weapons and poisonous things, so they drilled a well and started pumping the waste down the hole. Unfortunately, earthquakes started occurring.”

Gilbert explained that the facility was pumping millions of gallons a month of waste into the ground. When there was less pumping, there would be less earthquakes, and people began to wonder if there was a connection. Eventually, it was decided the two were related and the facility ceased pumping completely.

“People often ask, ‘well what about fracking?’,” Gilbert said. “It’s not that fracking can’t do something. Fracking is using low volumes of fluid compared to all these other things. The next highest is enhanced oil recovery, where they’re pushing fluids back down into the ground and the most is waste disposal, because you’re putting down sometimes nearly as much as you’re pumping out.”

Gilbert said that there has been a definite increase in what Oklahoma is pumping into the ground.

“When we started producing oil and gas, mostly what was coming out of the ground was nearly 100 percent oil, or maybe 90 percent oil and 10 percent salt water,” he said. “Now, producing in a different way, we’ve used all that up. A lot of our productive wells now might be half oil, half salt water. You can’t dump it on the ground or in the creeks, so you drill disposal wells and pump that stuff back down.”

The Oklahoma Geological Survey said they take the allegations of triggered seismicity very seriously and are assessing that possibility.

“We are currently working on addressing cases in Oklahoma where triggered seismicity has been suggested,” G. Randy Keller, director and state geologist said. “This requires careful examination of a large amount of complex data and does not happen quickly.” 

Keller said the organization is actively working with the Oklahoma Corporation Commission concerning issues of possible triggering.