Earth tides and seismic activity in deep coal mining

Abstract

Deep mining of mineral resources leads to disturbances in the natural state of equilibrium which has formed in the rock mass for hundreds and thousands of years. Hard coal mining with longwall system which is carried out in the Upper Silesia Coal Basin (USCB) in Poland causes deformation of the rock mass. The effect of these are, among other things, the observed seismic tremors which are also called mining tremors. The time of occurrence of these tremors is connected with exceeding the boundary states in the rock mass and releasing a relatively large amount of energy. The observed mining tremors are characterized by energy reaching up to 10*e9J which corresponds to the local magnitude M L = 4.2. In this paper, an attempt was made to relate the time of occurrence of mining tremors with changes in the gravitational load of the rock mass caused by the Earth tides. The statistics of the number of tremors at the time of gravitational loading and unloading of the rock mass indicates that there is a relationship between the time of tremor and Earth tides.