Abstract: Principal component analysis （PCA） is used to quickly obtain information on the occurrence of damaged surfaces caused by microseismic activities. The method consists of two parts of the spatial principal component analysis and the spatial-temporal principal component analysis. Firstly，based on the location of microseismic events， an ellipsoid through PCA to describe the shape and aggregation direction of the location event clusterand the occurrence of the fracture surface according to the geometric characteristics of the ellipsoid are obtained. Secondly， sliding a time window covered with a fixed number of events on the event group， the ellipsoid represented by each window can be obtained， and further more， separating the ellipsoids with different directions， the occurrence of the failure surface at different times can be obtained， and then the evolution trend of failure surface can be obtained . According to the mentioned method，using the received microseismic positioning data of a tipical landsliding case of overlying rock mass in goaf induced by a large blasting in Shizhuyuan Tungsten Mine，the analysing results are obtained that the dip of the failure surface is NW319.26°，and the dip angle is 81.62°. It shows the results are similar with the actual occurrence of the sliding surface. The study results show that PCA can be better applied to studying the occurrence of microseismic sources， and can promote the actual applications of microseismic monitoring technology in engineering.

Key words: microseismic monitoring, occurrence of failure surface, focal mechanism, principal component analysis