Understanding economic success of unconventional production from shales requires an explanation of the relationship between induced seismicity and hydraulic fracturing. This thesis deals with observing and analyzing synthetic and real microseismic monitoring data acquired during hydraulic fracturing. The thesis is based on observation and analyses of source mechanisms of induced microseismic events that have recently become regularly inverted and interpreted in the oil and gas industry. The results of analyses are interpreted with the geomechanical model of the relationship between hydraulic fracturing and induced seismicity. The study of source mechanisms starts with detailed analyses of spatial distribution of full moment tensor inversion stability. It was mapped based on synthetically computed condition numbers in the vicinity of different monitoring arrays including dense arrays at the surface and sparse arrays with sensors in the boreholes. Stability of inversion was tested under several conditions, mainly dependency on size and geometry of monitoring array and level of noise in the data. In this part of the thesis it is shown that dense surface arrays may provide very stable inversion of source mechanisms which may be interpreted. The study shows that an increasing percentage of non-shear...