I'm not sold on fracking causing earthquakes. Not that I have taken that much interests in it but some pretty smart fellows have said there is proven connection.
Now I don't deal with fracking but I do deal with drilling for both exploration and production. It is very common practice to use drilling fluids pumped into the hole to equalize out pressures. Without this method you would be looking at a blow out.
Drilling 10 miles into a pressurized pocket is like taking a power drill to an atomic bomb. Errors are not easily forgiven.
Edited by DoubleNot7