Potential contributions of Seafloor Geodesy to understanding slip behavior along the Cascadia Subduction Zone

这项研究的目的是确定沿卡斯卡迪亚俯冲带的海底大地测量纪念碑的最佳位置，以及为确定逆冲断层近海部分的滑动性质所需的水平和垂直海底大地测量的频率和持续时间。目前，陆上大地测量已经确定锁定区域几乎完全位于近海，然而这些数据缺乏接近，并且不能很好地解决变形前沿附近的粘滑行为以及从完全粘滑到稳定滑动的某一分量的边界位置。这一为期一年的项目旨在将现有的断层几何模型、沿断层的锁定行为、陆上GPS数据以及经现场验证的水平和垂直海底大地测量的精度同化为弹性/粘弹性模型。使用这个模型结构，将模拟海底大地测量纪念碑的各种放置，并估计分辨率，以确定沿卡斯卡迪亚限制逆冲断层上区域尺度滑动行为所需的最低阵列配置。该项目直接促进了GeoPRISMS科学计划中关于俯冲旋回和变形的前两个科学目标：由什么控制俯冲带大地震的大小、位置和频率，以及这与沿俯冲断层观察到的滑动行为的空间和时间变化有何关系？跨越俯冲板块边界的形变是如何在空间和时间上，通过地震旋回和超越演化的？这项研究的最广泛影响将是为利用海底大地测量更好地量化与卡斯卡迪亚俯冲带内逆冲断层大破裂有关的地震和海啸风险提供指导。可以沿着CSZ收集海底大地测量数据，作为对巨型逆冲滑动模型的必要约束，这些模型主要受地球望远镜的一部分--板块边界观测站的子空GPS矢量的约束。这项研究的结果将有助于指导数据收集。

The purpose of the study is to determine the optimum placement of seafloor geodetic monuments along the Cascadia Subduction Zone and the frequency and duration of horizontal and vertical seafloor geodetic measurements required to resolve the character of slip along the offshore portion of the thrust fault. Presently, onshore geodesy has determined that the locked region lies almost entirely offshore, however these data lack proximity and poorly resolve details of the stick-slip behavior near the deformation front and the location of the boundary from full stick slip to some component of stable sliding. This one-year project to assimilate existing models of fault geometry, locking behavior along the fault, onshore GPS data, and field-proven precisions of horizontal and vertical seafloor geodesy into an elastic/visco-elastic model. Using this model construction, various placements of seafloor geodetic monuments will be simulated and the resolving power estimated to determine the minimum required array configuration along Cascadia to constrain regional-scale slip behavior on the thrust fault. The project contributes directly to the first two science goals in the GeoPRISMS Science plan on Subduction Cycles and Deformation: What governs the size, location and frequency of great subduction zone earthquakes and how is this related to the spatial and temporal variation of slip behaviors observed along subduction faults? And how does deformation across the subduction plate boundary evolve in space and time, through the seismic cycle and beyond? The broadest impact of this study will be to provide a guide towards using seafloor geodesy to better quantify the earthquake and tsunami risk associated with a large rupture of the thrust fault within the Cascadia subduction zone. Seafloor geodetic measurements could be collected all along the CSZ as a needed constraint to models of megathrust slip that are mostly constrained by the sub-aerial GPS vectors from the Plate Boundary Observatory, a part of Earthscope. Results of this study will help guide this data collection.