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

[9014 . 91]将研究俯冲带板块运动学与上盘变形之间的关系。该研究旨在确定活跃俯冲带的增生棱镜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。该研究对认识斜向和正向俯冲带的活动构造过程以及已发掘的俯冲杂岩中记录的构造具有重要意义。弧前区域如何适应活动边缘的辐合是至关重要的，因为这些地区容易发生大震级地震和相关的高应变率，这是人口稠密地区的明显问题。变形的增生棱镜内的应变分布还没有很好地受到观测的约束，而且以前的努力依赖于连续统理论，这些理论还不够普遍，无法解释已知发生在板块边界的块体旋转。对沿俯冲板块边界和上覆不同倾角的俯冲带上的增生棱镜内浅层地震事件的震源机制解进行运动学反演。这种方法可以确定在地壳浅层经历块体旋转的岩石中的大尺度主应变率的方向和相对大小。这种分析最近为了解跨张拉边缘和TFF三联结附近的近地表应变分布提供了重要的见解，但尚未用于正常和斜向俯冲带。除了对理解活动边缘的重要性之外，这项研究还将对解释出土的增生棱柱中记录的时间整合变形历史产生影响，这些棱柱标志着古代俯冲带。

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.