Abstract:As a regional,real-time and dynamic monitoring means,the microseismic monitoring technology is quite feasible to forecast several geological hazards,such as rockburst,mine tremor,coal and gas outburst,and so on. And because of the good expandable nature of this technique,it even can prevent and reduce these disasters. The study on the focal mechanism of different hypocenters or seismic sources is the prerequisite and basis for forecasting rockburst by microseismic monitoring technology. Roof structure,especially hard and thick sandstone roof,is one of the main factors leading to the occurrence of rockburst. Based on the analysis of the fracture of hard roof,the equivalent point source model of the tremor or rockburst caused by hard roof is Constructed. According to the model,the seismic displacement equation of hard roof is analyzed by using seismic wave theory. Based on the above analysis,the focal mechanism caused by the rupture of roof is pointed out. The microseismic signals of the fracture of hard roof acquired by the microseismic monitoring system in Sanhejian Mine validate the theoretical analysis results. The results show that by the tensile strength of medium nearby the seismic source,the wave field will generate compression wave in the seismic source and induce tensile fracture at the moment of rock breakage,which is different from the style of failure in the coal pillar and fault. The results can be used to provide theoretical basis to forecast and prevent rockburst caused by hard roof.