Earthquakes in West Virginia, Arkansas Not Caused by UIC Wells

Natural gas wells drilled horizontally into the Marcellus Shale generally require use of water for fracturing the rock to make it more permeable and produce economic quantities of gas. After fracking, this water often returns from the drill hole laden with dissolved solids that make it unuseful for further fracking. 

Presently, many drillers are recycling the water, using reverse osmosis or some other method.  That leaves a highly concentrated residue that must be disposed somewhere.  Some drillers are putting the frac water into underground injection control (UIC) wells under high pressure. The UIC wells are put far below drinking water aquifers and are sealed off from them, to avoid contamination.

Some question has arisen as to whether the forcing of water into the earth under pressure triggers earthquakes.  Officials in Arkansas think they do, and questions have been raised as to whether disposal activities contributed to earthquakes in BraxtonCounty.  WVU professorTim Carr  says they didn't.