So you contend that Fracking itself doesn't generate the earthquakes but associated activities do.
That's if what the guys who published the paper are thinking is true. I'm not going to pay to get the full article but I read their article to say that the data to actually test their hypothesis are not available so they used some models to show that the associated activities
potentially cause an increase in earthquake activity.
That's a shame because if all somebody looks at is the title of the paper it'd be reasonable to think that they'd actually shown that the activities did cause the increase in earthquakes.
To go to another level I'll go ahead and say that even if they had the data they referenced as difficult to obtain they could not really unequivocally show a cause and effect relationship because it'd still be observational data. Like it or not you need a controlled experiment to show a cause and effect relationship.
I'm sorry but that's a rule of the scientific method. It's ignored a lot. But it's still a rule.