I am a geophysicist and I don't fully buy their explanation. Earthquakes are caused when plates of the earth which are moving relative to one another have built up tension finally build up too much tension and slip. The slipping and moving is what causes the quake.
Fracking or injection wells can't cause things to move like that unless they were already moving or under tension to begin with. Sure the fluids could facilitate the movement but couldn't cause something to move that wasn't trying to move already. In a way if the fracking/injection wells are causing them it might be a good thing because it is relieving stress that might otherwise build up to the point of being a huge quake.
The other thing I find odd is most earthquakes originate pretty deep in the earth. Much deeper than most oil wells. How can fracking or an injection well 5,000' deep cause a quake that originates 5 miles deep?
Earthquake
