Mining induced seismicity in the North Staffordshire coalfield, England

Abstract

Mining induced seismicity associated with long-wall coal extraction in North Staffordshire, England, has been investigated in order to establish the cause and mechanism of the seismicity. The study shows that seismicity is directly caused by active mining with earth tremor hypocentres moving in unison and in advance of the face. The seismicity does not appear to be directly associated with any of the major faults bounding the mined area. The largest earth tremors have a local magnitude, M L , of approximately 3, and of 711 earth tremors detected on a seismometer network situated in the coalfield, 54 events were sufficiently large to be felt by local residents. The majority of the larger earth tremors have a shear fracture source and are thought to be generated in strata overstressed as a consequence of the interaction of old coal workings with the active coal face. The remaining smaller tremors, which are not felt, have mostly an implosional source mechanism suggesting that they are generated by strata collapse.