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

该研究的目的是确定沿卡斯卡迪亚俯冲带海底大地测量纪念碑的最佳位置，以及解决沿逆冲断层近海部分滑动特征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海上，但是这些数据缺乏接近性，并且很难解析变形前沿附近的粘滑行为细节以及从完全粘滑到稳定滑动的某些组成部分的边界位置。该项目为期一年，旨在将现有的断层几何模型、断层锁定行为、陆上GPS数据以及经过现场验证的水平和垂直海底大地测量精度整合到弹性/粘弹性模型中。使用该模型，将模拟海底大地测量纪念碑的各种位置，并估计分辨率，以确定沿卡斯卡迪亚所需的最小阵列配置，以约束逆冲断层的区域尺度滑动行为。该项目直接促进了地球地质系统科学计划中关于俯冲旋回和变形的前两个科学目标：是什么决定了大俯冲带地震的大小、位置和频率，以及这与沿俯冲断层观察到的滑动行为的时空变化有何关系？俯冲板块边界上的变形是如何在空间和时间上、在地震周期中及以后演变的？这项研究最广泛的影响将是为使用海底大地测量学更好地量化与卡斯卡迪亚俯冲带内逆冲断层大破裂相关的地震和海啸风险提供指导。海底大地测量数据可以沿着CSZ收集，作为对大型逆冲滑动模型的必要约束，这些模型主要受到来自板块边界观测站（Earthscope的一部分）的空中GPS矢量的约束。本研究的结果将有助于指导数据的收集。

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.