Collaborative Research: Taiwan Integrated Geodynamics Research

0410227吴台湾是世界上最活跃的弧-陆碰撞的结果（隆升3cm/年，会聚达8 cm/年）。 欧亚板块和南海向菲律宾海板块东南方向移动，中国东南大陆边缘的大洋岩石圈俯冲到菲律宾海板块之上的吕宋弧之下。 大约4 Ma前，欧亚大陆边缘进入俯冲带，导致碰撞造山，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，北方边缘首先碰撞，因此山脉在北方形成，向南传播。 这种倾斜碰撞使得空间变化可以被看作是时间演化。弧吸积可以说是后太古代地球（甚至可能更早）大陆形成的最重要模式。 台湾提供了在世界上最活跃的弧碰撞区研究这些过程的可能性，由于上述碰撞的斜向性质，可以从时间上了解这种碰撞的进展情况。 PI提出了两个端元假说来检验大陆岩石圈在碰撞过程中发生了什么：1）它是俯冲的，壳幔分离导致地壳增生，而更深的岩石圈是俯冲的; 2）它不俯冲，但堵塞在俯冲带，导致持续变形，导致岩石圈增厚。 两个端员的情况下发生了什么大陆岩石圈碰撞提供了特殊的机会，调查一些最根本的问题，山区建设：-大陆俯冲在弧大陆碰撞中发挥控制作用？ 欧亚大陆岩石圈是否正在台湾之下俯冲？天体物理学的基本问题之一是质量平衡。 侵蚀、地壳增厚、地幔通量等因素如何定量地相互作用？造山带是如何随时间演化的？表面运动学与深层结构有何关系？-各向异性在空间上、横向上和纵向上是如何变化的？ S分裂方向随深度变化吗？ 造山带从地表到上地幔的变形是否垂直相干？为了回答这些问题，研究所将进行一项综合地球物理成像、地震记录和地球动力学研究计划，以研究台湾的地壳。 通过结合详细的二维研究沿着断面和三维图像为整个地区，造山带及其演化的特点。 数据采集程序包括宽带区域地震和地震波记录、陆上-海上和陆上折射-反射地震剖面、大地电磁测深、岩石物理和重力模拟。 板块相互作用的几何学、地壳变形模式和物质性质将为地球动力学模拟提供新的定量基础。 各种数据集将被整合到一个地球动力学模型中，该模型可用于测试造山运动的概念模型。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。 中国大陆的科学家也很有可能参加。 该项目的教育影响将是巨大的，超过25名学生来自美国和外国的参与机构。 此外，“德州教师在现场”计划将邀请一位高中教师记录台湾近海的地震，并为德州高中教师开发相关的教学模块。

0410227WuTaiwan 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.