The plot below shows a clear correlation between Cuadrillas fracking operations at Preese Hall Lancashire and sesimic activity in the area.
The small circles are seismic events. By looking at the right hand axes you can see their size.
The blue line shows the volume of water and chemicals injected into the well and out into the fractures created in the shale.
The red line shows the volume of water flowing back out of the well.
There is a clear correlation between the seismic events at Frack stages 2 and again at 4 and 5. These stages caused seismic events at around 2 on the richter scale. These quakes were felt by people up to 10 miles away and caused minor damage to properties on the surface.
The most significant fact about these quakes that is often overlooked is that they caused deformation in Cuadrillas well bore. The steel and concrete was crushed and went from round to oval.
Frack stages 4 and 5 appear quite reckless in their size and timing considering the result of Stage 2 and head scratching that must have ensued in the intervening period. The volume of water that is left in the well can also be deduced by subtracting the flowback effluent from the water injected. More than half remains down there.