US: Earthquakes surge in states with Fracking

Earthquake activity is seen to rise in states where hydraulic fracturing is taking place.

Fracking is a drilling method that generates vast amounts of wastewater, which is pumped thousands of feet underground through injection wells. No one knows for certain exactly what happens to the liquids after that.

Scientists wonder whether they could trigger quakes by increasing underground pressures and lubricating faults.

Oklahoma has recorded nearly 250 small-to-medium earthquakes since January, according to statistics kept by the U.S. Geological Survey. That's close to half of all the magnitude 3 or higher earthquakes recorded this year in the continental United States.