Website ScienceDaily.com has an article that demonstrates a link between injection wells (used to dispose of the wastes from fracking).
Based on research carried out at the University of Texas at Austin, and supported by the US Geological Survey, there is a link between waste materials pumped into the ground and small earthquakes (< magnitude 3.0).
The following are extracts from the article, which is here:
Most earthquakes in the Barnett Shale region of North Texas occur within a few miles of one or more injection wells used to dispose of wastes associated with petroleum production such as hydraulic fracturing fluids, according to new research from The University of Texas at Austin. None of the quakes identified in the two-year study were strong enough to pose a danger to the public.
The study by Cliff Frohlich, senior research scientist at the university's Institute for Geophysics, appears this week in the Proceedings of the National Academy of Sciences.
"You can't prove that any one earthquake was caused by an injection well," says Frohlich. "But it's obvious that wells are enhancing the probability that earthquakes will occur."
He found that the most reliably located earthquakes -- those that are accurate to within about 0.9 miles (1.5 kilometers) -- occurred in eight groups, all within 2 miles (3.2 kilometers) of one or more injection wells. Before this study, the National Earthquake Information Center had only identified two earthquake groups in the area strongly associated with specific injection wells. This suggests injection-triggered earthquakes are far more common than is generally recognized.