Collaborative Research: Simultaneous Inversions of GPS Time Series for Kinematics and Transients in Cascadia

近年来，世界上许多地方都建立了持续运行的GPS站点，包括美国西部的Earthscope板块边界观测站网络。在此之前，大多数GPS观测都是在测量模式下进行的，在这种模式下，运动被用于每年或多年的基础上占用标记。该项目旨在探索如何从连续和测量模式的GPS数据中提取长期的板块运动学和随时间变化的变形信息。科学目标是了解整个卡斯卡迪亚缓慢滑动和非火山震颤之间的时空关系。PBO和PANGA的连续网络被用来测试卡斯卡迪亚地下的缓慢滑动是否在空间和时间上与非火山震动一致。南卡斯卡迪亚的慢滑模式与北卡斯卡迪亚的慢滑模式非常不同，北卡斯卡迪亚的慢滑事件非常有规律，而且规模相似。非火山震颤表明，卡斯卡迪亚南部可能存在一些不同的模式，但震颤并不限制慢滑事件的大小。在分析中直接利用时间序列并应用新的GPS处理技术将提高垂向分量的信噪比，这是估计卡斯卡迪亚界面慢滑上倾程度的关键。其中一个目标是测试非火山震动（NVT）是否与缓慢滑动同时发生。由于NVT比慢滑更容易观察到小事件，它们的重合将有助于描绘出缓慢滑动的断层部分。这项工作将为卡斯卡迪亚慢滑的上倾极限提供重要的界限，从而确定慢滑是否会延伸到巨型逆冲构造的锁定部分。这项研究将进一步加深我们对慢滑事件的理解，以及如何将它们呈现给公众。它们是增加还是减少地震危险这个简单的问题还没有答案，但显然很重要。

In recent years continuously operating GPS sites have been established in many parts of the world, including Earthscope's Plate Boundary Observatory network in the western US. Prior to that, most GPS observations were made in survey-mode, where campaigns were used to occupy the marks on a yearly or multi-year basis. This project is to explore how to extract long-term plate kinematics and time-dependent deformation information from both continuous and survey-mode GPS data. The science target is to learn about the spatial and temporal relationship between slow slip and non-volcanic tremor throughout Cascadia. The continuous networks of PBO and PANGA are being used to test whether or not slow slip beneath Cascadia coincides spatially and temporally with non-volcanic tremor. Southern Cascadia has a very different pattern of slow-slip than northern Cascadia where slow-slip events are very regular and similar in size. Non-volcanic tremor suggests that there may be some, but different, patterns in southern Cascadia but tremor does not constrain the sizes of the slow slip events. Utilizing the time series directly in the analyses and applying new GPS processing techniques will enhance the signal-to-noise ratio of the vertical component which is critical in estimating the up-dip extent of slow slip on the Cascadia interface. One goal is to test whether or not non-volcanic tremor (NVT) coincides with slow slip. Since NVT is easier to observe than slow slip for small events, their coincidence will help delineate the portions of faults that slip slowly. The work will place important bounds on the up-dip limit of slow slip at Cascadia and hence whether or not slow slip extends into the locked portions of the megathrust. The research will further our understanding of slow-slip events and how they should be presented to the public. The simple question of whether they increase or decrease the earthquake hazard is not yet answered but is of obvious importance.