Wednesday's earthquake on the New Mexico-Colorado line is again raising questions about whether coal-bed methane drilling might be responsible for earthquakes in the area.
Researchers looked into that possibility in 2001, after 12 earthquakes hit in an area near 10 gas wells. Companies had pumped water into the ground in order extract methane from coal bed seams.
However researchers found no proof of a connection and the U-S Geological Survey found that seismic activity actually subsidized as drilling continued.
The agency hasn't determined whether yesterday's magnitude-five quake was related to the 2001 quakes.