Past earthquakes in southern Colorado studied for links to gas fracking, water disposal

Colorado Independant
By David O. Williams | 08.24.11


Monday’s 5.3-magnitude earthquake southwest of Trinidad in southern Colorado is being called rare but “consistent with the region and historic activity in the area,” and so far no official connection is being made to gas drilling — or hydraulic fracturing — of relatively shallow coal-bed methane gas reserves in the area.

But such a connection to so-called “fracking” and the disposal of fracking fluid in the local gas fields has been investigated by the U.S. Geological Survey (USGS) in the past. A September 2001 swarm of earthquakes prompted a USGS investigation.

“In recent years, a large volume of excess water that is produced in conjunction with coal-bed methane gas production has been returned to the subsurface in fluid disposal wells in the area of the earthquake swarm,” the USGS report reads. “Because of the proximity of these disposal wells to the earthquakes, local residents and officials are concerned that the fluid disposal might have triggered the earthquakes.

“We have evaluated the characteristics of the seismicity using criteria proposed by Davis and Frohlich (1993) as diagnostic of seismicity induced by fluid injection. We conclude that the characteristics of the seismicity and the fluid disposal process do not constitute strong evidence that the seismicity is induced by the fluid disposal, though they do not rule out this possibility.”

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