Another Stoke-on-Trent earthquake, magnitude 1.8 occurred yesterday (January 19, 2012) provisionally located near the village of Bagnall, similar to the earthquake on January 11. Above is the recording from Keele University.
If the location of these two events remain this far east, I may have to revise my initial assessment that they are coal mining related since this area is outside the Coal Measures subcrop.
Recent Stoke-on-Trent Earthquakes
View Stoke Quakes in a larger map