In September, the largest earthquake in Oklahoma’s history rattled residents of Lincoln County. Oklahoma and southern Kansas have experienced more quakes than usual over the past few years. Geologists say the most likely reason for the rise is increasing extraction of oil and natural gas in the area.
Before 2009, the region typically experienced one or two minor quakes each year. But since then, that number has skyrocketed to more than two per day, says Will Levandowski, a geophysicist with the United States Geological Survey in Colorado.
After engineers extract oil and natural gas from underground reservoirs, they inject wastewater from the process into the ground. That can trigger earthquakes. But not all areas with wastewater injection are having an increase in quakes. Levandowski and his colleagues are studying the differences between the locations. “It might help us understand where earthquakes are more likely,” he says.