From the article:..."
Although it's difficult to attribute earthquakes to a particular cause, it's possible that human activity induced this earthquake, William Yeck, a research geophysicist with the USGS Geologic Hazards Science Center, told Live Science. Since 2014, there has been a significant increase in the rate of earthquakes in north central Oklahoma, the area in which this recent earthquake occurred, he said. The cause of this increase? The injection of wastewater — a byproduct of oil and gas production — into the ground may be to blame.
"The injection of fluids underground can increase underground pressures," he said. "This, in turn, can effectively unclamp faults, allowing them to slip, which results in earthquakes."