Collaborative Research: Reactivation of Continental Margin Fracture Zones: Insights From Seismicity, Strain Patterns, and Numerical Modeling of Modern and Ancient Orogens

该项目的总体目标是了解与裂谷相关的大陆边缘断裂带有关的地壳结构沿走向的变化如何影响碰撞造山带的演化。数据将从正在进行的台湾和早古生代塔肯碰撞造山带收集，因为现代和古代造山带为了解上地壳下部的运动学提供了机会。应用微极连续介质理论进行应变反演，将从脆性断裂和震源机制两方面揭示台湾部分俯冲断裂带的短期脆性变形特征。由于大陆边缘断裂带的重新激活而产生的长期韧性变形将通过对佛蒙特州和纽约的塔科尼克异形体中暴露的板岩进行有限和增量应变分析来量化。将进行运动学和力学模拟，以综合从两个造山带获得的结果。除了检验运动学模型的可行性外，还将利用力学模型对边界条件和岩石流变性进行限制。尽管山链的高地形发育在碰撞带的上覆构造板块上，但下行构造板块的几何形状可以从根本上控制山区内部的变形模式和隆升历史。断裂带是在碰撞前裂谷作用过程中形成的，与大陆边缘成大角度的断裂带，是下沉大陆地壳的一般特征。它们在碰撞过程中的重新激活预计会产生复杂的三维变形。因此，该项目将有助于该领域正在进行的研究，目的是(1)描述地壳尺度的不均匀如何导致变形岩石在水平方向和垂直方向上的应变分配，以及(2)充分表征地球变形的三维性质--S地壳。此外，现代和古代碰撞带结果的整合将使全球模型的发展成为可能，以帮助解释其他古代碰撞。最终，该项目将促进对影响山链地形发育的因素以及其中地震分布的了解。

The overall goal of this project is to understand how along-strike variations in crustal architecture associated with rift-related continental margin fracture zones affect the evolution of collisional orogenic belts. Data will be collected from the ongoing Taiwan and early Paleozoic Taconic collisional orogenic belts because of the opportunities afforded by modern and ancient orogens for understanding kinematics at lower upper-crustal levels. Short-term brittle deformation will be characterized in the region of the partially subducted fracture zone in Taiwan from brittle faults and earthquake focal mechanisms through the application of micropolar continuum theory to invert for strain. Long-term ductile deformation resulting from the reactivation of continental margin fracture zones will be quantified through finite and incremental strain analysis of slates exposed in the Taconic allochthon of Vermont and New York. Kinematic and mechanical modeling will be undertaken to integrate the results obtained from the two orogenic belts. In addition to testing the viability of kinematic models, the mechanical modeling will be used to put limits on the boundary conditions and rock rheology.Although the high topography of mountain chains develops on the overriding tectonic plate at collisional zones, the geometry of the downgoing tectonic plate can exert a fundamental control on the pattern of deformation within and uplift history of mountainous regions. Fracture zones, which form during precollisional rifting and lie at a high angle to the continental margin, are a general feature of downgoing continental crust. Their reactivation during collision is expected to produce complex, three-dimensional deformation. This project, therefore, will contribute to ongoing research in the field aimed at (1) describing how crustal-scale heterogeneities result in strain partitioning in both the horizontal and vertical directions in a deforming body of rock and (2) fully characterizing the three-dimensional nature of deformation of Earth?s crust. Moreover, the integration of results from modern and ancient collisional zones will enable the development of a global model to aid in the interpretation of other ancient collisions. Ultimately, this project will advance understanding of the factors influencing the topographic development of mountain chains and the distribution of earthquakes within them.