印度大陆沿喜马拉雅弧形俯冲与青藏高原地壳变形关系的三维有限元模拟

One of the important feature in the India-Asia convergent process is that both the subduction and the collision between the India and the Asia continents are happened along an arcuate boundary fault on the south of the Himalayas , namely the Main Boundary Thrust (MBT). In the northward movement of the India plate, such a unique form of interior boundary must partition the strain, thus causing different effect on crustal deformation along its strike on both sides. However, The details of how the arcuate geometry of the Main Boundary Thrust affects the crustal deformation of the Tibetan plateau is unclear especially in three dimensions.In this proposal, we will build the three-dimensional geometry of the arcuate boundary fault between the India continent and the Himalayas based on available profiles from geophysical investigations. Then, a three-dimensional finite element coda will be developed in which the crustal rheology is treat as viscous-elastic-plastic media, and the boundary fault is treat as a contact interface. Finally, we employ the mechanical modeling technique to explore spatially the slip-rate distribution along the Main Boundary Thrust, and the strain propogation in the crust of the Tibetan plateau related to the arcuate effect of the interior boundary. We believe that such a research should be useful to understand the plate interactions and its mechanics on interior deformation of the continent, and also crucial to explore the possible mechanics of diffusive north-south trending normal faulting in the Tibetan plateau.

印-藏汇聚的一个重要特点是印度大陆向青藏高原的俯冲和碰撞是发生在喜马拉雅前缘的弧形边界带（喜马拉雅主边界冲断层）。在印度大陆向北推挤、契入过程中，这一独特的弧形边界必然会分异应变使它对青藏高原不同部位产生不同效应。然而，在三维空间内该弧形边界到底如何制约青藏高原地壳的变形目前知之甚少。本项目以现有沿喜马拉雅弧深部探测结果为约束来构建该弧形边界断裂在岩石圈层次的三维几何形态，通过开发粘-弹-塑性有限元程序，将该弧形断裂边界用符合摩擦-库仑准则的接触问题描述。基此，应用动力学模拟技术来探讨印度大陆向北推挤过程中应变在该弧形边界断裂上的空间分布特征，以及应变越过该弧形边界断裂后向青藏高原内的扩展方式。该研究对认识板块相互作用中大陆边界几何效应对大陆内部变形动力学制约有重要理论意义，同时对探讨印-藏汇聚过程中青藏高原内部近南北走向弥散性正断层的成因机制以及喜马拉雅主边界断裂地震活动性也具有实际意义