摘要
After collecting digital seismic waveform records from Sichuan,Yunnan and Chongqing Seismic Telemetry Networks, the authors inverted focal mechanism solutions of moderate and small earthquakes in corresponding regions. On the basis of these results, the mean stress field of five main tectonic zones before and after the Wenchuan Ms 8. 0 earthquake has been worked out. Comparative study on each main tectonic zone before and after the Wenchuan Ms 8. 0 earthquake shows the complicated state of stress field. Local stress disturbance is obvious in south segments of Longmenshan tectonic zone and Xianshuihe tectonic zone before and after the Wenchuan Ms 8. 0 earthquake. That is larger relative changes of stress azimuth disturbance value occurring after the large earthquake. The proportion of reverse dip-slip earthquake decreased apparently in south segments of Xianshuihe tectonic zone and Longmenshan tectonic zone, and middle segment of Huayingshan tectonic zone after the large earthquake. The authors believe that it is a reflection of changes or adjustments of large-scale crustal stress state before and after the Wenchuan Ms 8. 0 earthquake.