With fracking the problem for me isn't the risk of earthquakes, even if the actual extraction method itself involves fracturing the rock which by logic creates tiny earthquakes.
My issue is the chemicals pumped in under high pressure & the risk of contamination of the water table.
There are well documented cases of drinking water being contaminated with methane gas by fracking in the USA & of flammable water as a result
I'm also shocked by the fact that we are talking about a fossil fuel here when we have over 200-300 years supply of another fossil fuel under our feet which could easily meet the majority of or energy needs for that period & which has much less impact at the point of extraction than shale gas....and that is coal.....yet we keep importing millions of tons of low grade coal from abroad to feed power stations....simply because the government worry about being held to ransom by the miners in the future.
The process of fracking is not dissimilar to how we have been extracting oil offshore for decades, obviously the negative impacts offshore (with regards to the chemicals) are significantly less than when doing it onshore.
Fracking (and its associated side effects) are the result of using the rudimental technique in a new dynamic, what we need is to develop new techniques that are safe and sustainable to use onshore. We can achieve this if enough money is invested in the process, like you say we have centuries worth or resources below our feet, the sooner we recognise that this is a viable option the sooner we can develop the appropriate techniques to extract it safely.