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.

弧形碰撞在整个地质时代的大陆集会中发挥了关键作用，目前，作为大地震和爆炸性火山喷发的主要来源，对社会构成了重大威胁。 然而，弧形碰撞的基本地球动力学知识很少，并且缺乏量化。 这部分是由于缺乏在一系列时间尺度上对变形模式的详细测量，这只有从活跃的弧形碰撞中才有可能。这项研究使用多学科方法来构建活性东部Sunda弧形碰撞的3-D机械模型。 该研究的目的是通过采样各种时间和空间尺度的方法组合来测量整个碰撞区域中应变的积累和分布。该地区的倾斜碰撞提供了一个难得的机会，可以在不同发育阶段检查不断发展的造山基因。此外，大多数岛屿上的大多数山梯露台保存完好的飞行提供了局部和区域应变标记，能够在10^4至10^6年的时间尺度上记录变形模式。 这是对该和其他主动变形板边界区域的先前研究中最少表示的时间范围。 该项目正在解决有关应变分配的一系列基本地球动力学问题，例如：在渐进性弧形碰撞和俯冲极性反转期间，板的收敛（以及如何）是从板块收敛到后弧的？是否存在连接相反收敛区域的离散侧向滑移断层？ 如果是这样，该结缔组织如何与碰撞传播？收敛速率的比例（7-8 cm/yr。）沿断层与增生区的延性结构进行定位？ 碰撞区是否将其分为离散的刚性块？ 如果是这样，块边界的本质是什么？它们如何发展？在不同的时间尺度上表示板边界重组如何使用涉及结构地质，地貌和有限元模型的综合地球动力研究来解决这些问题。将模型与GPS速度场的测量和变形特征进行比较，例如主动断层和扭曲的珊瑚露台，这表明了各种构造过程，这些过程是由于沿着预先存在和新形成的地理结构重新分布在大陆区域中的大陆区域而导致的构造过程。 俯冲和碰撞之间流变行为的这种广泛的过渡为大陆变形和刚性板构造之间的差异提供了新的观点。从沟渠中的应变分布到前臂和后弧后区域导致东部Sunda弧向澳大利亚底层延伸，并激活新的板块边界段。这个过程的模型有助于更好地理解这些常见的地球动力学模式，从时间依赖性流变学方面，并为整个弧形碰撞区域的应变时间分布提供了详细的测试。