[ZenGum]

Any large change to the weight on a patch of earth will lead to earthquakes. The (more-or-less solid) crust floats on the (viscous liquid) mantle, and if you build up weight at one point, the crust gradually sinks. This happens a lot at the end of ice ages when the ice caps melt. China's three Gorges Dam has earthquakes every year as it fills and empties. Any large structure causes this.

Good news? These are tiny earthquakes. The only quakes to worry about are continental plate boundaries shifting.

The contamination of ground water, long term, over a wide area, is a very real concern.

How about a ten-year moratorium on new fracking to let us assess the consequences of the fracking done so far? And if it turns out that groundwater is not getting contaminated, we can do more fracking.