Collaborative Research: Geodynamic Evolution of an Active Arc-Continent Collision, Eastern Sunda Arc, Indonesia

合作研究：印度尼西亚东巽他弧活动弧大陆碰撞的地球动力学演化

• 批准号: 0337192
• 负责人: Dorothy Merritts
• 金额: $ 5.42万
• 依托单位: Franklin and Marshall College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2006-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337192&HistoricalAwards=false
• 关键词: Collaborative; Research; Geodynamic; Evolution; Active

Arc-continent collision has played a key role in the assembly of continents throughout geologic time and currently poses a significant threat to society as a major source of large earthquakes and explosive volcanic eruptions. However, the fundamental geodynamics of arc-continent collision is poorly understood and lacks quantification. This is due in part to the lack of detailed measurements of deformation patterns at a range of temporal scales, which is only possible from active arc-continent collisions. This study is using a multidisciplinary approach to construct a 3-D mechanical model of the active eastern Sunda arc-continent collision. The aim of the investigation is to measure the accumulation and distribution of strain throughout the collision zone by a combination of methods that sample a wide range of temporal and spatial scales. Oblique collision in the region provides a rare opportunity to examine an evolving orogen at different stages of development. In addition, the abundance of well-preserved flights of uplifted coral terraces fringing most islands provide local and regional strain markers capable of recording deformation patterns over time scales of 10^4 to 10^6 years. This is the temporal range least represented in previous studies of this and other actively deforming plate boundary zones. This project is addressing a series of fundamental geodynamic questions about strain partitioning, such as: where (and how) is plate convergence from the trench transferred to the back arc during progressive arc-continent collision and subduction polarity reversal? Are there discrete lateral-slip faults that link zones of opposing convergence? If so, how does this connective system propagate with the collision? What proportion of the rate of convergence (7-8 cm/yr.) is localized along faults versus ductile structures of the accretionary zone? Is the collision zone segmented into discrete, rigid blocks? If so, what is the nature of the block boundaries and how do they evolve? How is plate boundary reorganization represented at different temporal scales?Integrated geodynamic investigations involving structural geology, geomorphology, and finite element modeling are being used to address these questions. Comparing models with measurements of the GPS velocity field and deformational features, such as active faults and warped coral terraces, demonstrates a variety of tectonic processes that result from the redistribution of deformation into continental regions along preexisting and newly forming geologic structures. This broad transition in rheological behavior between subduction and collision provides new perspectives into differences between continental deformation and rigid-plate tectonics. The distribution of strain away from the trench into the forearc and backarc regions causes the eastern Sunda arc to accrete to the underthrust Australian continental margin and activate new plate boundary segments. Models of this process help better understand these common geodynamic patterns in terms of a time-dependant rheology, and provide a detailed test of theories for the temporal distribution of strain throughout a arc-continent collision zone.

弧大陆碰撞在整个地质时期的大陆组装过程中发挥了关键作用，目前作为大地震和火山爆发的主要来源对社会构成了重大威胁。 然而，人们对弧大陆碰撞的基本地球动力学知之甚少，并且缺乏量化。 部分原因是缺乏对一系列时间尺度变形模式的详细测量，而这只有通过活跃的弧大陆碰撞才能实现。本研究采用多学科方法构建活跃的东部巽他弧大陆碰撞的 3D 力学模型。 研究的目的是通过结合多种时间和空间尺度采样的方法来测量整个碰撞区应变的积累和分布。该地区的斜碰撞为研究处于不同发展阶段的不断演化的造山带提供了难得的机会。此外，大多数岛屿边缘保存完好的隆起珊瑚阶地丰富，提供了能够记录 10^4 至 10^6 年时间尺度变形模式的本地和区域应变标记。 这是之前对该板块边界区域和其他主动变形板块边界区域的研究中最少体现的时间范围。 该项目正在解决一系列有关应变分配的基本地球动力学问题，例如：在渐进的弧大陆碰撞和俯冲极性反转期间，板块汇聚从海沟转移到弧后的位置（以及如何）？是否存在连接相反汇聚区域的离散侧滑断层？ 如果是这样，这个连接系统如何随着碰撞传播？沿断层与增生带延性结构的收敛速度（7-8 厘米/年）的比例是多少？ 碰撞区域是否被分割成离散的刚性块？ 如果是这样，区块边界的本质是什么以及它们是如何演变的？板块边界重组在不同时间尺度上是如何表现的？涉及构造地质学、地貌学和有限元建模的综合地球动力学研究正在被用来解决这些问题。将模型与 GPS 速度场和变形特征（例如活动断层和扭曲的珊瑚阶地）的测量结果进行比较，可以证明由于变形沿着先前存在的和新形成的地质结构重新分布到大陆区域而产生的各种构造过程。 俯冲和碰撞之间流变行为的这种广泛转变为大陆变形和刚性板块构造之间的差异提供了新的视角。远离海沟到弧前和弧后区域的应变分布导致东巽他弧向澳大利亚大陆边缘的逆冲增生并激活新的板块边界段。这一过程的模型有助于更好地理解这些随时间变化的流变学方面的常见地球动力学模式，并为整个弧大陆碰撞带的应变时间分布提供详细的理论测试。