The headline and the text of the story don't match. According to the article, the earthquakes were triggered by injection of waste water into geologic layers below the natural gas horizon. This is not hydraulic fracturing ("fracking") of the natural gas-bearing shale unit. The production well produces natural gas and water. The water is removed, piped to a waste water injection well and pumped into the ground, typically into deep saline beds. In Ohio, it is the waste water injection, not the fracking, that is linked to the earthquakes. The waste water disposal is completely separate from the fracking of the production well and the earthquakes would have occurred whether or not fracking was involved in the original well completion. [Right, drill rig. Credit, EPA]
This kind of confusion is contributing to the national frenzy over fracking. There is no fracking going on in Arizona yet I hear all kinds of questions or accusations about the damage it is supposedly doing in the state.