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沿着海底大地测量标志物的最佳位置，以及为确定逆冲断层近海部分沿着滑动的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，陆上大地测量已确定锁定区域几乎完全位于海上，但这些数据缺乏接近性，难以解决变形前沿附近粘滑行为的细节，以及从完全粘滑到稳定滑动的某些组成部分的边界位置。这个为期一年的项目将把现有的断层几何形状模型、断层沿着的锁定行为、陆上GPS数据以及经现场验证的水平和垂直海底大地测量精度纳入弹性/粘弹性模型。利用这一模型结构，将模拟海底大地测量标志物的各种位置，并估计分辨能力，以确定沿卡斯卡迪亚沿着的最低所需阵列配置，以限制逆冲断层上的区域尺度滑动行为。该项目直接有助于GeoPRISMS俯冲周期和变形科学计划的前两个科学目标：是什么决定了俯冲带大地震的规模、位置和频率，以及这与沿沿着俯冲断层观察到的滑动行为的时空变化有何关系？穿过俯冲板块边界的变形在空间和时间上是如何演变的，通过地震周期和超越？这项研究最广泛的影响将是提供一个指南，使用海底大地测量，以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。海底大地测量数据可沿CSZ沿着收集，作为对大推力滑动模型的必要约束，大推力滑动模型主要受地球镜的一部分板块边界观测站的地面GPS矢量的约束。这项研究的结果将有助于指导这一数据收集。

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.