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

9901491刘易斯将研究板块运动学与俯冲带上盘变形之间的关系。 这项研究的目的是确定模式的应变在基地，并在活跃的俯冲带，增生棱柱，并评估这些模式的背景下，相对板块运动。 这一研究对于了解斜向俯冲带和正向俯冲带的活动构造过程以及俯冲复合体的构造记录具有重要意义。 弧前地区如何适应活动边缘的会聚是非常重要的，因为这些地区容易发生大规模地震和相关的高应变率，这对人口稠密地区来说是显而易见的问题。 变形增生棱镜内的应变分布没有得到很好的约束观察，以前的努力依赖于连续介质理论，不够一般的帐户块旋转已知发生在板块边界。 将对沿着俯冲板块边界和俯冲带上覆增生棱柱内的浅层地震事件的震源机制解进行运动学反演，俯冲带的特征是不同程度的俯冲。 这种方法能够确定在地壳浅部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。 这种分析最近提供了显着的洞察近地表应变分布在transpressional和transstensional边缘和附近的TFF三重结，但尚未被用于正常和斜俯冲带。 除了了解活动边缘的重要性，这项研究将有意义的解释的时间整合变形的历史记录在挖出的增生棱柱，标志着古老的俯冲带。

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.