A 2011 earthquake that was widely felt in Oklahoma and considered “unusual” was likely caused by drilling activities and was not a natural event.
The 5.6-magnitude quake is believed linked to oil drilling waste that was pushed too deeply below ground, according to a scientific team of university academics and federal staff, said The Associated Press (AP). If that were the case, the quake would be the most powerful associated with deep wastewater injections, according to a study just published by the journal Geology.
The waste originated with traditional not hydraulic fracturing—fracking—drilling, said the AP. Oklahoma’s state seismologists say the quake was natural. The quake occurred on November 6 near Prague, Oklahoma. Two people were injured and 14 houses were damaged, said the AP and the quake was felt for hundreds of miles in 14 states, according to the United States Geological Survey (USGS). Experts noted that the earthquake was the largest in that area of the country in decades and the largest in the state.
Geophysicists at the University of Oklahoma, Columbia University and the USGS say that, on November 5, a smaller quake occurred in an old oil well that was used to get rid of wastewater. That well sits along a fault line, said the AP. According to the groups, the smaller quake set off the larger quake, as well as a third, smaller aftershock. The tremors occurred at the wastewater storage location and there was an increase in well pressure, which all point to injections causing the larger quake, the groups said.
That area of Oklahoma was the site of oil drilling as far back as the 1950s; wastewater had been pumped into that area’s disposal wells since 1993. Wastewater is typically pumped more than one mile below ground, the researchers said, wrote the AP.
According to the report, a significant jump in well pressure was seen in 2006. Elizabeth Cochrane, a USGS geophysicist and study co-author, said the increased pressure, due to the injections, is similar to over-blowing a balloon, which weakens the balloon’s skin, wrote the AP. “We have a lot of evidence that certainly leads us to believe” the quake was caused by the injections, said Cochrane. That the injections triggered the earthquake “becomes compelling,” Cochrane noted.
As we previously wrote fracking, might have been the culprit in three Dallas area earthquakes, according to a geophysicist and earthquake expert. As we’ve explained, fracking employs the use of a drill, fresh water, sand—silica—, and a mix of hundreds of chemicals that are shot through an underground horizontal well until it all reaches a bed of shale rock. In Texas, the formation is the Barnett Shale, in northern Texas.
The process releases natural gas. Once fractured, water pressure calms and then internal pressure in the rock creates a so-called “flowback,” in which fracking fluids rise back to the surface, the Environmental Protection Agency (EPA) explained. “That’s dirty water you have to get rid of,” Frohlich told Yahoo News/Life’s Little Mysteries. “One way people do that is to pump it back into the ground.”
We’ve also written that, in the last few years, especially, there has been a rise in seismic activity in areas not typically the site of earthquakes. Underground injection wells for disposing fracking wastewater have been used since the 1960s but only recently has more and more fluid been used in the process. This has created a massive amount of wastewater and a need for more disposal sites.
Previously, USGS researchers did not theorize why disposing of the wastewater underground is responsible for the earthquakes but other studies suggest the briny, salty nature of the drilling fluid causes lubrication of underground rock. If the site of the underground well is near a natural fault line, the wastewater may eventually cause the rocks to move.