Investigating the Partitioning of Vertical Strength within the India-Eurasia Lithosphere using Surface Observations: A Numerical Modeling Approach

板块构造理论在地球物理学领域是革命性的，它解释了板块的运动以及地震和火山的位置。然而，这一理论在大陆边界失效，地震扩展到1000？S的km和显著地形形成。印度板块和欧亚板块的持续碰撞为研究这些区域以及大陆碰撞带变形模式的控制因素提供了一个天然的实验室。在没有岩石圈深度直接采样的情况下，数值模拟可以提供物理上允许的岩石圈性质的界限。了解大陆岩石圈内部强度的变化是评估产生地震和造山力量的基础。本文所获得的结果将对青藏高原形变产生的力、岩石圈内的应力传递、地表观测样本岩石圈性质的深度、上地壳、下地壳和岩石圈地幔之间的强度划分、青藏南部下印度板块的影响以及地球内部对流引起的岩石圈底部流动等方面产生重要影响。该项目将进行三维地球动力学建模，求解Stokes流，以研究欧亚岩石圈内的横向和垂直强度变化。地球物理观测将用于构建印度-欧亚碰撞区的物理精确模型体积，并进行数值模拟，以确定岩石圈强度（垂直和横向）变化对预测的地表变形的影响。在GPS和第四纪断层滑动数据的约束下，将预测的地表速度与观测到的地表变形场进行比较，将区分物理上可行的模型。这项工作将寻求：(1)绘制出欧亚变形岩石圈内允许的垂直强度对比；(2)分离欧亚大陆地区地表观测的深度敏感性；(3)研究变岩石圈厚度和地幔流动对观测地表变形场的影响。

The theory of plate tectonics was revolutionary in the field of geophysics and explained the motion of plates and locations of earthquakes and volcanoes. However, this theory breaks down at continental boundaries where earthquakes extend 1000?s of km and significant topography is created. The ongoing collision of the Indian and Eurasian plate provides a natural laboratory for studying such regions and the factors controlling deformation patterns in continental collisional zones. In the absence of direct sampling of the lithosphere with depth, numerical modeling can provide bounds on physically allowable lithospheric properties. Understanding the variation in strength within the continental lithosphere is fundamental to assessing the forces that generate earthquakes and build mountains. Results obtained within this proposal will have important implications relating to forces generating deformation of the Tibetan Plateau, stress transfer within the lithosphere, the depth to which surface observations sample lithospheric properties, partitioning of strength between upper crust, lower crust and lithospheric mantle, influence of the lower Indian plate beneath southern Tibetan, and flow the base of the lithosphere resulting from convection of the interior of the Earth.This project will perform 3-D geodynamic modeling solving Stokes flow to investigate the lateral and vertical strength variations within the Eurasian lithosphere. Geophysical observations will be used to construct a physically accurate model volume of the India-Eurasian collision zone, and numeric simulations will be performed to determine the effects of variations in lithospheric strength (both vertically and laterally) on predicted surface deformation. Comparisons between predicted surface velocities and the observed surface deformation field, constrained by GPS and quaternary fault slip data, will differentiate between physically viable models. This work will seek to: (1) Map out the allowable vertical strength contrasts within the Eurasian deforming lithosphere; (2) Isolate the depth sensitivity of surface observations within Eurasia; (3) Investigate the influence of variable lithospheric thickness and mantle flow on the observed surface deformation field.