Numerical Simulation on the Special Gravity Fields and Dynamic Response in Longmenshan Orogenic Belt and Adjacent Area
详细信息
- 责任者：Yang Hui (Institute of Geology and Geophysics ; Chinese Academy of Sciences ; Beijing 100029 ; China) ; Teng Jiwen
- 刊名：Chinese Journal of Geophysics
- 出版年：2013
- 卷期：56(1)
- 关键词：重力场 ; gravity field ; 龙门山断裂带 ; Longmenshan Fault Zone
- 页码：p.106-116
- 图表：illus., 2 tables, 44 refs.
- 分类号：0400
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
The Longmenshan orogenic belt is in a very non-isostatic state,which means its crust is in an unstable state.In this paper,2-D Finite Element Method is used with viscoelastic model to study the geodynamical mechanism of gravitational isostasy through the profile across the Songpan-Garze block,Longmenshan faults and Sichuan basin.The results show that:(1) The motion mode of deep materials is much changed by the isostatic adjustment.The interaction effects of the India plate collision and the gravity potential energy cause the dynamics of the sub-vertical downward asthenospheric flow at the bottom of the Longmenshan lithosphere,and lead to the exceptionally steep topography at the eastern Tibetan margin as a result of gravitational buoyancy.(2) The distribution of strain-energy,the rheological structure and other results are calculated numerically,which show that the sections with high risk factors coincide with the areas of the Wenchuan earthquake.The different geophysical structures,as well as the different rheological model on both east and west side of Longmenshan faults zone played important roles in the seismogenic mechanism of the Wenchuan earthquake.(3) We suggest that crustal shortening together with isostatic adjustment,including the rapid erosion-related unloading,is a key component of the geodynamic processes on the eastern Tibetan Plateau margin.
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