The quake in Chile also set off a series of small quakes in the Colorado town of Trinidad near the New Mexico state line known for extracting natural gas from coal beds.
In those instances, the triggered seismic activity was followed months later by a moderate quake and researchers say that could be a warning sign of stress on the fault. The triggered events are too small to relieve all the stress and some of that stress can be transferred to nearby faults, making a future larger event more likely, said van der Elst.
Not all sites near injection wells showed increased shaking after a strong distant quake. The team found the most affected areas were places where pumping has been going on for decades.
University of Utah mechanical engineer Sidney Green called the results interesting but “rather speculative” and said they need more study.
If the observations bear out, it could help oil and gas operators know “where it's safe to inject and where it's not,” said Julie Shemeta, a geophysicist and president of Colorado-based MEQ Geo Inc., a consulting company.
Despite a history of man-made quakes near wastewater injection sites, only a small number of the country's 30,000 disposal wells are a problem, said U.S. Geological Survey seismologist William Ellsworth, who published an article in the journal reviewing the state of research.
Ellsworth said fracking does not pose a high risk for triggering quakes strong enough to feel. The largest man-made quake linked to fracking was a magnitude-3.6 in British Columbia in 2009.