Researchers at Columbia University said earthquakes that occur on the other side of the world could create smaller temblors near wastewater injection sites in the United States.
In a study published online Thursday in the journal Science, four researchers from Columbia's Lamont-Doherty Earth Observatory (Nicholas van der Elst, Heather Savage, Katie Keranen and Geoffrey Abers) said an increase in seismic activity in the Midwest "may be related" to wastewater injection wells.
"Areas with suspected anthropogenic earthquakes are also more susceptible to earthquake-triggering from natural transient stresses generated by the seismic waves of large remote earthquakes," the researchers said in an abstract that accompanied the study. "Enhanced triggering susceptibility suggests the presence of critically loaded faults and potentially high fluid pressures.
"Sensitivity to remote triggering is most clearly seen in sites with a long delay between the start of injection and the onset of seismicity and in regions that went on to host moderate magnitude earthquakes within six to 20 months. Triggering in induced seismic zones could therefore be an indicator that fluid injection has brought the fault system to a critical state."
According to reports, the Columbia researchers assert that the 8.8-magnitude earthquake that struck off the coast of Chile in February 2010 triggered smaller quakes in Prague, OK, and in a coalbed methane field of the Raton Basin, located along the Colorado-New Mexico border, just west of Trinidad, CO (see Shale Daily, April 2, 2012).
The researchers also contend that the 9.0-magnitude earthquake that devastated Japan in March 2011 set off a series of smaller earthquakes in Snyder, TX.
In a Friday feature story, the U.S. Geological Survey (USGS) said one of its geophysicists, William Ellsworth, had reviewed the Columbia study and determined that when wastewater disposal wells are drilled near geologic faults and conditions are optimal, earthquakes can result.
"While the disposal process has the potential to trigger earthquakes, not every wastewater disposal well produces earthquakes," the USGS said. "In fact, very few of the more than 30,000 wells designed for this purpose appear to cause earthquakes."
Scientists have linked a dozen small earthquakes in the Barnett Shale in North Texas to wastewater injection wells that support natural gas drilling (see Shale Daily, Aug. 8, 2012). Similarly, an injection well in northeastern Ohio was shut down in early 2012 after a dozen small earthquakes in the region (see Shale Daily, March 12, 2012; Jan. 5, 2012). Arkansas banned disposal wells in a portion of the Fayetteville Shale after quake activity there (see Shale Daily, July 29, 2011; March 4, 2011).
But scientists have disagreed over whether there is a relationship between hydraulic fracturing (fracking) and earthquakes (see Shale Daily, June 20, 2012).
"[Our] studies suggest that the actual fracking process is only very rarely the direct cause of felt earthquakes," the USGS said Friday. "While fracking works by making thousands of extremely small 'micro earthquakes,' they are rarely felt and are too small to cause structural damage. As noted previously, wastewater associated with fracking has been linked to some, but not all, of the induced earthquakes."