Collaborative Research: Taiwan Integrated Geodynamics Research (TAIGER)

克里斯滕森台湾是世界上最活跃的弧陆碰撞的结果(隆升3厘米/年，会聚达8厘米/年)。欧亚板块和南中国海一直向菲律宾海板块的东南西向移动，中国大陆边缘东南部的大洋岩石圈俯冲到位于菲律宾海板块上方的吕宋弧之下。约4 Ma前，欧亚大陆边缘进入俯冲带，发生碰撞造山作用，形成台湾。台湾由代表7个不同构造地层省的平行带组成。碰撞是以倾斜的角度发生的，北部边缘首先碰撞，因此山脉在北部形成，并向南扩散。这种斜碰撞使空间变化被视为时间演化。弧形吸积可以说是后太古宙地球(甚至可能更早)最重要的大陆形成模式。台湾提供了在世界上最活跃的弧形碰撞带研究这些过程的可能性，因为如上所述，由于碰撞的斜向性质，这种碰撞是如何进行的。对于碰撞期间大陆岩石圈发生的变化，PI提出了两个有待检验的端元假说：1)俯冲，壳幔拆离导致地壳共生，同时更深的岩石圈被俯冲；2)它不俯冲，而是在俯冲带内堵塞，导致持续变形，导致岩石圈增厚。碰撞期间大陆岩石圈发生的两个终端成员情景为研究造山的一些最基本问题提供了特别的机会：大陆俯冲在弧陆碰撞中发挥控制作用吗？欧亚大陆岩石圈是否俯冲到台湾以下？-造山运动的一个基本问题是物质平衡。侵蚀、地壳增厚、地幔流量等因素如何定量地相互作用？-造山带如何随时间演化？-地表运动学如何与深部结构相关？-各向异性在空间、横向和垂直方向上如何变化？S裂解方向随深度变化吗？造山带从地表到上地幔的变形是否垂直一致？为了回答这些问题，台湾地质调查局将进行地球物理成像、地震记录和地球动力学综合研究计划，以研究台湾的造山作用。通过结合沿断面的详细的2-D研究和整个区域的3-D图像，可以表征造山带及其演化。数据采集计划包括宽带区域地震和远程地震记录、陆上-近海和陆地折射-反射地震断面、大地电磁测深、岩石物理和重力模拟。板块相互作用的几何形态、地壳形变方式和材料性质将为地球动力学模拟提供新的定量依据。不同的数据集将被整合到一个地球动力学模型中，该模型可以用来测试造山的概念模型。该项目将涉及六个美国机构的合作以及台湾和日本团体的合作和支持。还有一种明显的可能性，那就是大陆科学家中国的参与。该项目的教育影响将是巨大的，将有超过25名来自参与机构的美国和外国学生。此外，“德克萨斯实地教师”计划将有一名高中教师参与记录台湾近海的地震，为德克萨斯州的高中教师开发相关的教学模块。

0409343ChristensenTaiwan is the result of the most active arc-continent collision in the world (uplift of 3cm/yr and convergence of up to 8 cm/yr). The Eurasian plate and the South China Sea have been moving to the SE wrt the Philippine Sea plate, with oceanic lithosphere of the southeast China continental margin subducting beneath the Luzon arc, which sits atop the Philippine Sea plate. Around 4 Ma ago, the margin of Eurasia entered the subduction zone, resulting in collisional orogeny that formed Taiwan. Taiwan consists of parallel belts representing 7 different tectonostratigraphic provinces. The collision is occurring at an oblique angle, with the northern margin colliding first, so that mountains are forming in the North and propagating south. This oblique collision allows spatial changes to be viewed as temporal evolution.Arc accretion is arguably the most important mode of continent formation throughout the post-Archean Earth (perhaps even before). Taiwan offers the possibility of studying these processes in the world's most active arc collision zone with a temporal view of how such collisions progress, due to the oblique nature of the collision as mentioned above. The PIs put forward two end member hypotheses to be tested concerning what is happening to continental lithosphere during the collision: 1) It is subducted, with crust-mantle detachment causing crust to accrete while deeper lithosphere is subducted; 2) It doesn't subduct, but jams up in the subduction zone, leading to continuous deformation resulting in thickening of the lithosphere. The two end-member scenarios for what is happening to continental lithosphere during the collision provide special opportunities to investigate some of the most fundamental questions of mountain building:- Does continental subduction play a controlling role in arc-continent collision? Is the Eurasian continental lithosphere subducting beneath Taiwan?- One of the fundamental issues in orogeny is mass balance. How do factors such as erosion, crustal thickening, mantle flux, etc. interact quantitatively?- How did the orogen evolve through time?- How does surface kinematics relate to deep structure?- How does anisotropy vary in space, laterally and vertically? Do the S-splitting directions change with depth? Is the deformation of the orogen vertically coherent from surface to upper mantle?To answer these questions the PIs will carry out an integrated geophysical imaging, earthquake recording and geodynamic research program to study the Taiwan orogeny. By combining detailed 2-D studies along transects and 3-D images for the whole region, the orogen and its evolution can be characterized. The data acquisition program includes broadband regional seismic and teleseismic recording, onshore-offshore and land refraction-reflection seismic transects, magnetotelluric sounding, petrophysics and gravity modeling. The geometry of the plate interactions, the mode of crustal deformation, and the material properties will provide a new quantitative basis for geodynamic modeling. The various datasets will be integrated into a geodynamic model which can be used to test conceptual models for mountain building.The project will involve collaboration from six US institutions as well as collaboration and support from Taiwanese and Japanese groups. There is also the distinct possibility of the participation of scientists from mainland China. The educational impact of this project will be large, with more than 25 students from the participating institutions, US and foreign. In addition, the "Texas Teacher in the Field" program would involve one high school teacher in recording earthquakes offshore Taiwan, developing related teaching modules for Texas high school teachers.