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

点击翻译按钮获取中文摘要

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.