So far this year, Oklahoma has had more earthquakes of a magnitude 3.0 or greater than any other state in the country — including California. More than 200, just since January.
This is a new and remarkable phenomenon. Just five years ago, Oklahoma was averaging only two 3.0 earthquakes a year. Now, it's averaging one or two a day.
Scientists are saying that oil and gas-related activity, including fracking and wastewater disposal wells in the state, may be partially to blame.
"We see some cases where there is a pretty clear link between fluid injection and the earthquakes," Austin Holland, a research seismologist at the Oklahoma Geological Survey, told Here & Now's Robin Young.
In other cases, the link is less clear.
"We may be looking at a combination of factors," Holland said. "We can tell that sometimes very large rainfalls or changes in aquifer levels can cause earthquakes. Just the natural changes that occur. We could be looking at a combination of that, combined with changes in the amount of waste water that is disposed of and natural stress changes. There are all sorts of different options that we are looking at and things that might be occurring."
This segment aired on June 24, 2014.