Collaborative Research: Constraints on Interseismic Locking near the Trench on the Oregon Segment of the Cascadia Subduction Zone Using Seafloor Geodesy (GNSS-A)

该项目旨在测量北美和胡安德富卡构造板块在卡斯卡迪亚俯冲带之间的相对运动，以帮助量化地震和海啸的危害。 卡斯卡迪亚俯冲带是两个构造板块交界处的一个主要断层，是大地震和海啸的潜在震源。 最近的大地震，如2011年东北地震，已经表明破裂可以延伸到令人惊讶的浅深度，海底的大垂直位移可以产生海啸。 重要的是要了解卡斯卡迪亚俯冲带的情况是否类似，增加了沿着美国西海岸发生大海啸的危险。 确定卡斯卡迪亚的海底是以俯冲板块的速度移动，还是因为断层被局部锁定而减慢，对断层力学的科学理解也很重要。 技术上的挑战是在海底进行这些观测，因为海底既难以接近，又对仪器有腐蚀性。 因此，这项工作需要专门的技术来进行必要的观察。 该项目将支持培训一名研究生和博士后研究员使用海底大地测量技术，并将进一步开发推进海底大地测量所需的工程人力资源和基础设施。将使用全球导航卫星系统声学方法，扩展俄勒冈州近海卡斯卡迪亚俯冲带增生棱柱体上三个现有地点的海底基准的时间序列。 这些海底地点是在前几年建立的，每个地点的勘测次数各不相同，对边缘沿着的四个地点中的三个产生了构造板块速度的初步估计。 在为期两年的项目期间，将使用配备全球导航卫星系统的声波滑翔机进行三次新的调查。 与研究船相比，Wave Glider方法大大降低了调查成本。 除了进行大地测量外，还将探索改进数据处理的新算法，包括旨在减少水柱声速结构造成的偏差和利用多重全球导航卫星系统数据的算法。 最后，将使用弹性边界元模型推断海沟处的运动锁定量，其目标是确定板块锁定是否沿沿着走向变化并与外增生棱镜中的结构特征相关。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

This project aims to measure the relative movement between the North American and Juan de Fuca tectonic plates across the Cascadia Subduction Zone to help quantify the earthquake and tsunami hazards. The Cascadia Subduction Zone, which is represented by a major fault at the interface of two tectonic plates, is a potential source of large earthquakes and tsunamis. Recent large earthquakes, such as the 2011 Tohoku earthquake, have demonstrated that rupture can extend to surprisingly shallow depths, where large vertical displacements of the seafloor can generate a tsunami. It is important to learn if the situation is similar on the Cascadia Subduction Zone, increasing the hazard from a large tsunami along the US west coast. Determining whether the seafloor in Cascadia moves at the subducting plate rate or is slowed because the fault is locked locally is also important to the scientific understanding of the fault mechanics. The technical challenge is to make these observations on the seafloor, which is both difficult to access and corrosive to instrumentation. Thus, this effort requires specialized techniques for making the necessary observations. This project will support the training of a graduate student and postdoctoral fellow in the use of seafloor geodetic techniques, and the project will further develop the engineering human resources and infrastructure needed to advance seafloor geodesy. The time series of seafloor benchmarks at three existing sites on the accretionary prism of the Cascadia Subduction Zone offshore Oregon will be extended using the GNSS-Acoustic method. These seafloor sites were established in previous years with varying numbers of surveys on each, yielding initial estimates of tectonic plate velocities at three of four sites along the margin. Three new surveys will be performed with a GNSS-Acoustic-equipped Wave Glider during the two-year project. The Wave Glider approach greatly reduces the survey cost compared to that undertaken with a research vessel. In addition to undertaking the geodetic surveys, new algorithms will be explored that improve the data processing, including algorithms designed to mitigate biases from the acoustic velocity structure of the water column and by capitalizing on multi-GNSS data. Finally, the amount of kinematic locking at the trench will be inferred using elastic boundary element models, with the goal to identify if plate locking varies along strike and correlates with structural features in the outer accretionary prism.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.