The media/environmentalists have done a good job of turning the word “frac” into a real boogeyman.
Like has been mentioned many times already the quakes are being caused by the huge volumes of water being disposed into deeper reservoirs that contain dormant fault systems. If the disposal wells are injecting into the deeper horizons they run the risk of being in area where these deeper horizons are located in a fault system area. Not all deep disposal is located in faulted areas. As a result of the increased pressure and possible "lubrication" from water disposal some of these dormant fault systems can be slightly reactivated resulting in the earthquakes being seen. This is a direct result of the exponential increase in production of oil, gas and water from horizontal drilling, mostly from shale reservoirs, that has taken place in the last 5+ years. And yes these wells have to be fraced to produce in commercial quantities. It’s really a large scale manufacturing process now.
The water disposal issue is a very hot topic now and is being studied in depth. I think we will see less and less earthquakes moving forward. But they won’t completely stop.
My bigger issue is the amount of water disposal taking place in medium depth horizons, which typically are not faulted. This is wreaking havoc in the oil field, causing the loss of legacy vertical wells. Major water flows while drilling new wells and holes in casing to existing wells as a result of the huge volumes of water being disposed in an amongst existing wells, have become a real problem from my experience.
If you are on the wrong side of the horizontal game in the Permian (raises hand) as an operator, you're kind of fucked.