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Determine Patterns of Strain in the Hanging-Wall Rocks at Active Subduction Zones, and to Evaluate These Patterns in the Context of Relative Plate Motions

确定活跃俯冲带上盘岩石的应变模式，并在相对板块运动的背景下评估这些模式

基本信息

批准号：
9901491
负责人：
Jonathan Lewis
金额：
$ 7.2万
依托单位：
Fellowships
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
1999
资助国家：
美国
起止时间：
1999-07-01 至 2003-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=9901491&HistoricalAwards=false
关键词：
Determine Patterns Strain Hanging Wall

项目摘要

9901491LewisThe relation between plate kinematics and hanging-wall deformation at subduction zones will be investigated. The research aims to determine patterns of strain at the base of, and within, accretionary prisms at active subduction zones, and to evaluate these patterns in the context of relative plate motions. This research is important for understanding active tectonic processes at oblique and normal subduction zones as well as the structures recorded in exhumed subduction complexes. How forearc regions accommodate convergence at active margins is fundamentally important because these regions are subject to large magnitude earthquakes and related high strain rates, obvious concerns for populated areas. The distribution of strain within deforming accretionary prisms has not been well constrained by observation, and previous efforts have relied on continuum theories that are not sufficiently general to account for block rotations known to occur at plate boundaries. Kinematic inversions of focal mechanism solutions for shallow seismic events along the subducting plate boundary and within the overlying accretionary prism at subduction zones characterized by varying degrees of obliquity will be performed. This approach enables determination of the orientation and relative magnitudes of the large-scale principal strain rates in rocks experiencing block rotations at shallow crustal levels. Such analyses have recently provided significant insight into near-surface strain distributions at transpressional and transtensional margins and in the vicinity of a TFF triple junction, but have yet to be used at normal and oblique subduction zones. Beyond the importance for understanding active margins, this research will have implications for interpreting the time-integrated deformation histories recorded in the exhumed accretionary prisms that mark ancient subduction zones.

9901491刘易斯将研究板块运动学与俯冲带上盘变形的关系。这项研究的目的是确定活动俯冲带吸积棱柱底部和内部的应变模式，并在相对板块运动的背景下评估这些模式。这一研究对于了解斜向俯冲带和正俯冲带的活动构造过程以及在折返俯冲杂岩中记录的构造具有重要意义。弧前地区如何适应活动边缘的汇聚从根本上说是重要的，因为这些地区容易发生大震级地震和相关的高应变率，这对人口稠密的地区来说是明显的担忧。变形吸积棱柱内的应变分布没有受到观测的很好的约束，以前的努力依赖于连续介质理论，这些理论不够普遍，不足以解释已知的在板块边界发生的块体旋转。将对沿俯冲板块边界和俯冲带上覆吸积棱柱内以不同倾角为特征的浅层地震事件的震源机制解进行运动学反演。这种方法能够确定在地壳浅层经历块体旋转的岩石中大尺度主应变率的方向和相对大小。这类分析最近提供了对扭压和扭张边缘以及TFF三联结附近近地表应变分布的重要洞察，但尚未用于正常和斜向俯冲带。除了了解活动边缘的重要性外，这项研究还将对解释出土的代表古俯冲带的增生棱柱中记录的时间整合形变历史具有重要意义。