Strength constraints of shallow crustal strata from analyses of mining induced seismicity

Stress redistributions around large underground excavations such as coal mines may lead to failure of the surrounding rock mass. Some of these failure processes were recorded as seismic events. In this paper the different failure processes such as rock mass failure or the reactivation of faults are delineated from the seismic records. These are substantiated by rock mechanical analyses including laboratory strength tests on coal measure rocks obtained from underground drilling. Additionally, shear tests on discontinuities in coal measure rocks (slickensides in shale and rough sandstone joints) were conducted to grasp the possible variation of strength properties of faults. Numerical modeling was employed to evaluate the state of stress at the locations where seismic events did occur.