Study On The Staged Locking Difference Of Anninghe-Zemuhe-Xiaojiang Fault Zone And The Stress Evolution In Sichuan Yunnan Region

Sichuan-Yunnan region is located in the eastern part of Tibetan Plateau,it is the frontier of the Eurasia and Indian plate collision zone.The new structure and the modern tectonic movement are strong,the frequency of seismic activity is high,the intensity is big,the type is numerous and the distribution is wide,it is the most significant region of the strong earthquake activity in China.According to statistics,in 1500 ~1999 there have been 39 7?7.0 earthquakes,and in 1990 ~1999 there have been 117 M?6.0 earthquakes.In the territory of Sichuan Yunnan region,there are Xianshuihe fault zone,Longmen Shan fault zone,Anninghe-Zemuhe-Xiaojiang fault zone,Red River fault and Lijiang-Xiaojinhe fault.Affected by the Wenchuan earthquake,stress of these faults in Sichuan-Yunnan region have changed,The seismic risk of these faults is to be analyzed.The quasi problem includes two aspects: 1)analyse the activity and locking of Anninghe-Zemuhe-Xiaojiang fault zone 2)Coulomb stress calculation estimate stress perturbation on active faults caused by the great Wenchuan earthquake.We inversed for the slip rate and spatial fault locking of Anninghe-Zemuhe-Xiaojiang fault zone based on a negative dislocation with horizonal GPS velocity data from 1999~2007 and 2009~2014.By using the inversion result and the historical earthquakes,we analyzed the potential of the large earthquake.The result shows the Wenchuan earthquake enhanced the locking of Xiaojiang and the middle segement of Zemuhe,but didn't effect the locking of Anning,the southern and northern segment of Zemuhe.Besides,the northern section of Anninghe,the southern and northern segment of Zemuhe,the southern segment of Xiaojiang are strongly locked before and after the Wenchuan earthquake,the locking depth is more than 20 km.Considering historical earthquakes and the other results,we conclude that these segments are seismogenic faults with large earthquake potential.According to the Wenchuan earthquake slip model of Professor Ji Chen,we simulate the coseismic Coulomb changes and the post seismic Coulomb stress evolution.The results show that: the coseismic Coulomb stress of the southern section of the Minjiang fault and the northeast of Chengdu-Deyang fault increased more than 1bar,the coseismic Coulomb stress of the southern section of Huya fault increased around 1bar,the coseismic Coulomb stress of Daofu-Kangding segment of Xianshuihe fault increased more than 0.06 bar,Coulomb stress of the central segment of Wen County fault increased about 0.07 bar.These regions are seismogenic faults with large earthquake potential.After Wenchuan earthquake,the Coulomb stress of Kangding of Xianshuihe fault,the southern section of Longmen Shan fault zone,the central segment of Wen County fault,the southern section of Minjiang fault,the northeast section of Chengdu Deyang fault is gradually increased,indicating that these regions are seismogenic faults with large earthquake potential.Affected by the Wenchuan earthquake coseismic and postseismic relaxation effect,the Coulomb stress of Kangding segment of Xianshuihe fault and the southern section of Longmen Shan fault showed an increasing trend,suggesting that Wenchuan earthquake played a important role in the promoting of Lushan earthquake and Kangding earthquake.Based on the backslip dislocation,we caculated the interseismic tectonic stress loading rate of the mian faults in Sichuan-Yunnan region.The results showed that interseismic tectonic stress accumulation rate of Xianshuihe fault,Xiaojiang Fault,the Daliangshan fault and the southwest section of Lijiang-Xiaojinhe fault is greater.These regions are seismogenic faults with large earthquake potential.