科研之友
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摘要
Using a more realistic model of multi-layered viscoelastic media, we examine the effects of the coseismic dislocation and the postseismic viscoelastic relaxation. Then we analyze the interaction between several great earthquakes which occurred in the eastern Bayan Har block, including the 1976 Songpan earthquake sequence, 2008 Wenchuan M-S 8. 0 earthquake, 2013 Lushan M-S 7. 0 earthquake, and the 2017 Jiuzhaigou M-S 7. 0 earthquake. Furthermore, based on the calculation of the Coulomb stress changes caused by these events on the fault planes, we assess the seismic hazard of the major fault in the study area. The results show that there is a correlation between the events of the Songpan earthquake sequence in 1976, the first event may trigger the second one, and the two previous events may trigger the third event. Considering the coseismic and the postseismic effects, the 2008 Wenchuan M-S 8. 0 earthquake might have triggered the 2013 Lushan M-S 7. 0 earthquake, both ruptured the Longmenshan fault zone. The 1976 Songpan earthquake sequence, especially the August 16, 1976 event of magnitude of M-S 7. 2, had contributed to the occurrence of the August 8, 2017 Jiuzhaigou M-S 7. 0 earthquake. When studying the influence of the 2008 Wenchuan earthquake on the 2017 Jiuzhaigou event, we employ different coseismic dislocation models and obtain different results. The resultant Coulomb stress changes on the major fault segments associated with all of the previous events show that, considering the comprehensive influence of all the great events on the surrounding fault zones, the cumulative Coulomb stress increases significantly in the southern segment of the Longmenshan fault zone, the south-central segment of the Xianshuihe fault zone, the northern segment of the Pingwu-Qingchuan fault, the northern segment of the Guanxian-Anxian fault, and the Wenxian fault. And the cumulative Coulomb stress also increased in the eastern segment of the Dongkunlun fault, the western segment of the Diebu-Bailongjiang in the eastern Bayan Har block and the Jinshajiang fault. Comprehensive considering the results of the Coulomb failure stress changes and the existing research results about the great earthquake hazard of the major faults, we should focus more attention on the earthquake hazard in the southern segment of the Longmenshan fault zone, the south-central segment of the Xianshuihe fault zone, the Maqin-Maqu segment of the Dongkunlun fault zone and the Jinshajiang fault.
- 出版日期2017-10
- 单位中国地震局
