by Timothy Hurst

Was the earthquake the United States Geological Survey is now calling the largest earthquake on record in Oklahoma linked to hydraulic fracturing, or fracking, the widely used but contentious oil and gas production technique which vastly increases the quantity of fossil fuels retrievable in a well?

As of Sunday night, 23 earthquakes have been recorded in central Oklahoma in the last 24 hours. The biggest quake in the latest seismic flurry, the 5.6-magnitude earthquake centered near Sparks, Oklahoma on Saturday night, could be felt as far north as Illinois and Wisconsin.

While most people don't consider Oklahoma to be a hotbed of seismic activity, geological activity in Oklahoma has increased in recent years where earthquakes are occurring with greater frequency and intensity.

According to the Associated Press:

Oklahoma typically had about 50 earthquakes a year until 2009. Then the number spiked, and 1,047 quakes shook the state last year, prompting researchers to install seismographs in the area.

But why?

One hypothesis being floated to explain the increase in the frequency of earthquakes in places like Oklahoma and Arkansas maintains that hydraulic fracturing, or the injection of "developed water" (wastewater) into wells as a disposal method is altering the geological balance in the immediate area of the drilling activity.

In Lincoln County, where most of this weekend's earthquakes were centered, there are 181 injection wells, according to an official from the Oklahoma Corporation Commission, the agency which oversees oil and gas production in the state.

Most scientists say they don't know exactly what is causing the recent uptick in earthquakes in Oklahoma but that fracking likely doesn't generate the kind of long-term geological pressure needed to induce an earthquake.

And one study (pdf) by Oklahoma Geological Survey seismologist Austin Holland found that most of the state's seismic activity was likely not caused by the injection wells which dot the Oklahoma oil fields.

But Holland, who is one of those scientists that doubts the link between fracking and earthquakes, also says more research was needed on the matter and that there may, in fact, be a correlation between fracking and other recent Oklahoma quakes.