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

近年来，世界上许多地区建立了连续运行的GPS站点，包括位于美国西部的EarthScope的板块边界观测网。在此之前，大多数GPS观测是在调查模式下进行的，在这种模式下，运动被用来在每年或多年的基础上占据标记。这个项目是探索如何从连续的和测量模式的GPS数据中提取长期的板块运动学和随时间变化的信息。科学目标是了解整个卡斯卡迪亚地区缓慢滑动和非火山震动之间的时空关系。PbO和Panga的连续网络正被用来测试卡斯卡迪亚下方的缓慢滑动是否在空间和时间上与非火山地震重合。卡斯卡迪亚南部的慢滑模式与卡斯卡迪亚北部的慢滑模式非常不同，后者的慢滑事件非常规则，规模相似。非火山地震表明，卡斯卡迪亚南部可能存在一些不同的模式，但地震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，将提高垂直分量的信噪比，这对估计卡斯卡迪亚界面上缓滑动的上倾程度至关重要。一个目标是测试非火山震动(NVT)是否与缓慢滑动重合。由于小震的NVT比慢滑更容易观察，它们的重合将有助于圈定缓慢滑动的断层部分。这项工作将为卡斯卡迪亚的慢滑上倾极限设定重要的界限，从而确定慢滑是否延伸到巨型逆冲的锁定部分。这项研究将进一步加深我们对慢滑事件的理解，以及它们应该如何向公众展示。它们是增加还是减少地震风险这个简单的问题还没有得到回答，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.