The following information has been broken down into parts. Each having links for further research.
Earthquakes and Fracking:
Anytime that you drill into the earth, there will be a shift. Depending on the amount, this CAN cause a great shift in the crust/soil. Individuals living near the areas encounter small earthquakes. In some cases, these are unfelt by the public. Fracking, at one time, had only been done in unpopulated areas. More recently, companies have moved towards cities and towns and have extremely increased their drilling.
While fracking injects water and chemicals into the ground, deadly gases are released. There are 800,000 injection wells nationwide in the United States. Nearly 450 earthquakes magnitude 3.0 and larger occurred in four years from 2010-2013, over 100 per year on average, compared with an average rate of 20 earthquakes per year observed from 1970-2000.
In the past year there have been many earthquakes in areas that used to NOT see ANY! If you look at seismic activity in Texas & Oklahoma (just to name a couple) you will see earthquakes near these Fracking zones. There has been talk in the past whether or not companies would begin to use hydraulic fracking near volcanoes.
Fracking and Sinkholes:
Sinkholes can be caused from natural shifts in the land. Though, many regions are seeing an increase in sinkholes. When removing any substance from the earth, a pocket will remain. This pocket will eventually collapse. Depending on the size of the removal is whether or not you will have a crater or just a pothole in the ground. Drilling and mining have been the cause for many years as to why sinkholes are happening. This can range anywhere from Salt mines and Uranium mining.
General Earthquake Information:
Since the first documentation, there has been activity all around the world. Recently, we are encountering more reports of seismic activity being triggered by the hands of mankind. Earthquakes are found to take place before and after volcanic eruptions. This gives researches the ability to monitor and inform the public of hazard possibilities in their area.