Underground disposal of wastewater from gas production likely triggered a moderate earthquake in Colorado in 2011, the U.S. Geological Survey said on Wednesday in a study that may fuel debate over the impact of the U.S. energy boom. The finding in the Journal of Geophysical Research is the latest research suggesting the injection into wells of wastewater generated by oil and gas extraction can induce earthquakes.

Researchers believe fluids seep into seismic faults and cause them to slip, triggering temblors. The 2011 magnitude 5.3 earthquake in an oil and gas basin spanning the Colorado-New Mexico border was felt in nearby Trinidad, Colorado, where shaking damaged foundations of several homes, said USGS geophysicist and lead study author Bill Barnhart. The basin, which historically produced coal, was not known for being especially quake-prone until extraction of naturally occurring methane gas from coal seams ramped up more than a decade ago, he said.

“We saw a big increase in seismicity starting in 2001, including magnitude 5 earthquakes, in many locations in the basin, and that coincided with a surge in gas production and injection of wastewater,” Barnhart said. The report bolsters previous studies by U.S. seismologists that linked wastewater disposal in underground wells with earthquakes in a handful of states seeing intensified energy production, including Oklahoma and Texas. The largest was a 5.7-magnitude quake that rattled Prague, Oklahoma, in November 2011. The southern Colorado temblor just a few months before was the second largest of such “induced” earthquakes, Barnhart said.

Such reports have fueled charges by hydraulic fracturing critics that wastewater disposal tied to fracking, which uses large volumes of water as well as chemicals to split open rocks and release natural gas, is to blame for an uptick in quakes. Like previous USGS findings, the new research concentrates on the role of wastewater injection in triggering quakes rather than extraction methods, and does not address the wastewater's nature, Barnhart said. “It's the consensus that wastewater injection is leading to some of these larger earthquakes. The composition of the fluid might be a small component, but the fluid itself is the overwhelming factor,” he said.

Scientists suspect the volume of wastewater and how quickly it is injected may influence seismic activity, but that data is not readily available, he said.