固体地球物理学术报告通知-20170908 柳畅 副教授
In order to understand the geodynamic background of the seismic activities across the eastern margin of the Tibetan Plateau, we investigate the stress evolution and crustal deformation process through 3D numerical experiments. We also introduce the method of geodynamic modelling to estimate the recurrence interval of the 2008 Mw7.9 Wenchuan based on the basic physics of earthquakes-stress buildup and release on fault. The inter-seismic stress accumulation and crustal deformation prior to the 2008 Mw7.9 Wenchuan earthquake are simulated through 3D finite element modelling assuming visco-elastic rheology. The co-seismic stress release and the post-seismic stress relaxation of the earthquake are simulated through dislocation source models. We found that the earthquake activities across the eastern margin of the Tibetan Plateau are significantly controlled by the regional crustal rheology, which presents horizontal viscosity contrast between the weak crust of the eastern Tibet and the strong Yangtze craton crust. In this talk I will present my work by answering the following questions related to the seismic activities across the eastern margin the Tibetan Plateau.
1. What is the cause for generation of the 2008 Mw7.9 Wenchuan and 2013 Mw6.6 Lushan earthquakes in the Longmen Shan fault zone?
2. Why did the main shocks locate nearly at the bottom of the upper crust of the Longmen Shan fault zone?
3. Why are earthquakes (Ms > 5.0) active in the eastern Tibetan Plateau but quiescent in the Sichuan Basin?
4. Why did the Longmen Shan fault change motion from thrust in the SW to strike-slip in the NE during the 2008 Wenchuan earthquake?
5. What is the hazard of the seismic gaps in the SW segment of the Longmen Shan fault zone?
6. What is the recurrence interval of the 2008 Mw 7.9 Wenchuan earthquake?