关键词: 地震矩, 断裂带, 应变率

Abstract: In this paper,the method for inversing the kinematics parameters of a fault zone from seismic moment tensors is discussed and applied to the study of the present kinematics characteristics of Xianshuihe Fault zone and Fenwei Fault zone. The results show that the Xianshuihe Fault zone extends in the direction of N16癢 and is compressed in the direction of N74癊. The average sinistral motion rate is about 10.9 mm/a. The Fenwei Fault zone extends in N20癢 and is compressed in N78癢 direction. The average dextral motion rate is about 0.24mm/a. Comparing the results mentioned above to the geological information and the GPS results,it is found that the motion directions of fracture zone are basically agreeable,but the slip rate is less than that of the latter two,especially in the Fenwei Fault zone. Three reasons may explain this phenomenon,firstly,the time when the data are collected is different; secondly,all strain energy produced by geological body is assumed to be released by means of the stick slip,instead of creep-slip of the fault; and thirdly there were totally 14 earthquakes of magnitude greater that 5 occurring in the sampled time period,among which there was only one earthquake of maximum over 6 and the largest event is M 6.2. The motion rate of the fault zone calculated from seismic moment tensors is less than the average rate drawn by geological information. This shows that the strain energy of the geological body has not been released completely. So there exists high seismic risk. In addition,the motion rate of the Fenwei Fault zone is less than that of the Xianshuihe Fault zone,indicating that the level of seismicity and the energy released by earthquake of the former is less than that of the latter.

Key words: seismic moment, fault zone, strain rate