Seismicity induced by coal mining in Stoke-on-Trent (U.K.)

A series of earth tremors occurring in the area of Stoke-on-Trent during 1975, 1976 and 1977 were investigated with a network of seismometers. The earth tremors were shown to originate from a region above active mineworkings, at depths between 300 and 1000 m. The incidence of earth tremors was far higher during weekdays when coal was being extracted than at weekends. The tremors migrated with the movement of the coal face, but tended to concentrate in zones running across the direction of advance of the coal face. These zones seem to be related to the edges of areas of worked-out coal above the active mineworkings. The cause of many of the tremors is believed to be the interaction between the stress field produced by current mining and the residual stress field surrounding previous workings.