Is fracking to blame for the earthquakes?

Below is one person's explanation for the recent earthquakes in Oklahoma:

The Oklahoma Geological Survey by Austin Holland was published recently, and it states clearly that fracking is one of the causes for earthquakes. When you inject the earth with saltwater to break up the shale beneath the earth, you're creating an instability in the crust that results in sudden and sometimes extreme movement. In other words, the earth sinks a little where the fracking occurs. Doesn't anyone see anything wrong with this? Oil companies are admitting they're damaging the earth, damaging homes, infrastructure, and possibly risking lives...all for the sake of natural gas and oil.

Just to illustrate the point, between 1977 and 2008, there were only 28 earthquakes in Oklahoma: less than 1 per year. Between 2009 and 2010, the state experienced 134 earthquakes: an average of 95 quakes per year. That's a huge difference. And it simply can not be attributed to a fault line or natural causes. Even the British energy company, Cuadrilla Resources, admits that fracking is the most likely cause of increased incidents of earthquakes in the area.