The mechanism of small mining tremors from amplitude inversion

A method of inverting seismic wave amplitudes from mining tremors is proposed to reveal their mechanism. A simple shear-implosive model of a mechanism is proposed. The shapes of theoretical and observed radiation patterns are compared in the least squares norm and the parameters describing the shear-slip together with the ratio of implosive and shear dislocations are optimized. The efficiency of the method, even in the case of a small number of stations, is demonstrated by applying it to weak mining tremors from two mine regions in Czechoslovakia.The weak mining tremors are found to be of a predominantly shear mechanism with a clear coincidence of nodal planes to local tectonics, which could imply their tectonic nature.