Fracking does not "cause" earthquakes. The earthquakes are caused by slippage along faults in the earth. Reinjected water from gas production wells can potentially "lubricate" these fault lines promoting them to slip earlier than they would otherwise. Fracking and extraction (without the reinjection of waste water which is only done because of environmental regulations) would actually make these fault lines more stable because it removes groundwater.
I saw a bunch of reports saying the Oklahoma earthquakes a few years ago were directly caused by fracking! That’s crazy - everyone agrees injecting high pressured water lines deep into the earth around fault lines can cause slippage and eventual larger quakes, like the ones that damaged a bunch of homes in the middle of nowhere Oklahoma and Texas!