A team of researchers with Southern Methodist University looked at recent bursts of seismic activity in north Texas and found that, as some had suspected, the quakes could be linked to fracking injection wells.

“Because there were no known previous earthquakes, and the located events were close to the two injection wells and near the injection depth, the possibility exists that earthquakes may be related to fluid injection,” authors of the study wrote.

Researchers specifically focused on a string of earthquakes that occurred near Cleburne, Texas during 2009 and 2010. Before 2008, there had never been an earthquake in the Fort Worth Basin of Texas. In 2005, wastewater started being pumped into injection wells in Cleburne.

The process of fracking creates wastewater – a toxic cocktail of chemicals, heavy metals, and radioactive substances. Of course, this toxic waste needs a place to go once the fracking process is complete. Some wastewater ends up in holding ponds, but some is disposed of deep underground.

In July, a paper published in the journal Science associated a 2011 earthquake in Prague, Oklahoma with wastewater injection as well. The Prague earthquake is the largest quake to be linked with fracking wells, and was also deemed an initiating trigger for another quake.

In Youngstown, Ohio last year, a 4.0 magnitude earthquake occurred shortly after wastewater disposal began at a nearby injection well. Scientists quickly determined the cause was the disposal of wastewater from a fracking operation, Scientific American reports.

Last year, the US Geological Survey (USGS) found that, at some locations, the increase in frequency of earthquakes coincided with underground wastewater injection. They note that the number of earthquakes in the central and eastern US has increased considerably over the last few years.

“More than 300 earthquakes above a magnitude 3.0 occurred in the three years from 2010-2012, compared with an average rate of 21 events per year observed from 1967-2000,” a USGS report states.

Just last month, north Texas experienced another string of powerful earthquakes, 15 in one month. Many believe that the quakes are due to fracking wastewater injection processes.

“I’d say it certainly looks very possible that the earthquakes are related to injection wells,” Dr. Cliff Frolich, Associate Director and Senior Research Scientist with the Institute for Geophysics at the University of Texas, said in an interview.

Alisha is a writer and researcher with Ring of Fire. Follow her on Twitter @childoftheearth.