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.

在整个地质时代，弧-陆碰撞在大陆的组合中发挥了关键作用，目前作为大地震和爆炸性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-陆碰撞的基本地球动力学知之甚少，也缺乏量化。这在一定程度上是由于缺乏对时间尺度范围内的变形模式的详细测量，而这只有在活跃的弧-大陆碰撞中才有可能实现。本研究采用多学科方法建立了东巽他弧-大陆活动碰撞的三维力学模型。调查的目的是测量整个碰撞区应变的积累和分布，通过多种方法的组合，采样广泛的时间和空间尺度。该地区的斜向碰撞提供了一个难得的机会来研究在不同发展阶段的演化造山带。此外，在大多数岛屿的边缘，大量保存完好的凸起的珊瑚梯田提供了当地和区域的应变标记，能够记录10^4到10^6年的时间尺度上的变形模式。这个时间范围在以前对这个和其他主动变形的板块边界带的研究中是最少的。该项目解决了一系列关于应变分配的基本地球动力学问题，例如：在渐进弧-大陆碰撞和俯冲极性反转过程中，板块从海沟向弧后转移的位置（以及如何转移的）？是否存在连接相反汇聚带的离散的横向滑动断层？如果是这样，这个连接系统是如何随着碰撞传播的？收敛速度（7- 8cm /年）中沿断层和增生带韧性构造的比例是多少？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？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？包括构造地质学、地貌学和有限元建模在内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（如活动断层和弯曲的珊瑚梯田）的测量结果进行比较，表明了各种构造过程，这些构造过程是由变形沿着先前存在的和新形成的地质构造重新分布到大陆区域造成的。这种俯冲和碰撞之间流变行为的广泛转变为研究大陆变形和刚性板块构造之间的差异提供了新的视角。从海沟向弧前和弧后区域的应变分布导致东巽他弧向逆冲下的澳大利亚大陆边缘增生，并激活了新的板块边界段。这一过程的模型有助于从随时间变化的流变学角度更好地理解这些常见的地球动力学模式，并为整个弧-大陆碰撞区应变的时间分布提供了详细的理论测试。