Spatial Characteristics Of Focal Mechanism And Stress Field In The East Boundary Of Sichuan-Yunnan Block And Its Adjacent Area

The east boundary of Sichuan-yunnan block and its adjacent regions exist several M≥7.0 earthquake empty segments, which has been focus on by the earthquake scholars. This paper proposed researching the focal mechanism and the stress field in the east boundary of Sichuanyunnan block and its adjacent regions, and providing basic data for the long-term earthquake prediction. This article used the seismic waveform data during January 2009 and June 2015, and obtained 188 focal mechanism in the study area by CAP method, and collected 98 centroid moment tensor solutions from the GCMT websit, then obtained the stress field in the study area by the damped regional stress inversion method.By analysising the spatical distribution characteristics of focal mechanism and stress field, we have several knowings as followings: in the study area, the focal mechanism type has a obvious zoning characteristic, along the east boundary of Sichuan-yunnan block,exactly along the Xianshuihe fault,the Anninghe fault,the Zemuhe fault,the Xiaojiang fault and the Daliangshan fault, the focal mechanism type is left-strike slip,while along the Zhaotong fault and the Lianfeng fault, the focal mechanism type is right-strike slip, meanwhile, along the Mabian-yanjin fault, Ebian-yanfeng fault and the east section of Lianfeng fault, the focal mechanism type is thurst or thurst-strike. The spatical distribution of regional stress field show that, from north to sorth along the east boundary of Sichuan-yunnan block,the horizontal direction of principle compressive stress turn from NWW to NW, but the included angle between the maxium principle compressive stress and the trend of the east boundary of Sichuan-yunnan block keep similar. The stress field performance well consistency in the inner part of Sichuan-yunnan block, the east boundary of Sichuan-yunnan blocak and the Daliangshan fault.The stress field performance obvious difference between the Daliangshan fault and the east boundary of the Daliangshan block. The research consider it’s more suitable that the Xianshuihe- daliangshan-xiaojiagn fault should be the east boundary of Sichuan-yunnan block.