Improving the Spatial and Temporal Resolution of Strain Rate Models of Continental Deformation

板块构造的一个结果是，在大陆板块边界地带，如东亚和美国西部，构造变形（以及相关的地震活动）可以分布在大面积上。基本上有两种基于卫星的观测方法可以准确监测这种变形。利用全球定位系统（GPS），我们可以精确地测量GPS纪念碑所在地的地球表面运动。在连续GPS（CGPS）测量的帮助下，我们现在可以每天跟踪这些运动（水平和垂直）。另一种方法被称为干涉合成孔径雷达，它使用雷达图像来绘制两次（不经常）卫星经过之间大片土地表面的详细变化。干涉合成孔径雷达的一个局限性是它对垂直地面运动最为敏感，而垂直地面运动通常是人为的而不是构造的。该项目旨在弥补全球定位系统和干涉合成孔径雷达以高空间和时间分辨率捕捉基本变形过程的能力之间的差距。国际合成孔径雷达探测到的地壳运动受到间歇性采样和仅在卫星视线范围内采样的限制。另一方面，GPS衍生的变形场的描述未能实现相同的空间分辨率，获得与干涉合成孔径雷达。该项目的目标是使用水平GPS速度显著提高现有长期应变率张量模型的空间分辨率，并使用连续GPS（CGPS）数据创建额外的时变变形模型。这一项目将提供长期和随时间变化的水平变形的有用基线估计，有助于解释干涉合成孔径雷达结果，同时也有助于在大陆变形地区的地球动力学和地震危险性研究方面取得新的进展。 这项工作的重点是太平洋-北美（PA-NA）板块边界区，地中海和中东，以及中亚和东亚。在那里，所有公开的CGPS数据将被分析，并结合从公布的卫星式GPS测量的长期运动的估计。将水平速度转换为长期变形的连续应变率张量模型。在数据覆盖范围有限的情况下，将包括其他运动学指标（例如，断层滑动速率/矢量、地震震源机制），以便对应变类型和定位进行额外约束。应变率场随时间变化的改善（最明显的是由于瞬变和震后变形）将限于PA-NA板块边界区，在那里CGPS网站是丰富的。可靠的时变应变率模型（和相关的应变和剪切应变的变化）可能会创建1-4周的时间窗口，足以捕捉大多数一阶时变过程。将静态和动态变形结果转换为LOS等效值，以便与干涉合成孔径雷达结果进行一阶比较。CGPS站点的长期运动估计以及应变率结果（张量参数，地图和电影）将在一个专门的门户网站上提供，作为科学家和教育工作者的宝贵工具。长期应变率与预期的地震危险性密切相关，可以直接有助于改善危险图。随时间变化的应变率模型可能有助于应力转移、地震触发和最终随时间变化的地震危险的研究，通过该项目，将对一名研究生进行全球定位系统数据管理、CGPS时间序列特征描述和地壳变形建模方面的培训。从该项目获得的结果（数据和模型）将在一个专门的门户网站上公布，作为科学家和教育工作者的一个宝贵工具。

One consequence of plate tectonics is that in continental plate boundary zones, such as eastern Asia and western United States, tectonic deformation (and the associated earthquake activity) can be distributed over large areas. There are essentially two satellite-based observation methods with which this deformation can be accurately monitored. With the Global Positioning System (GPS) we can precisely measure the Earth's surface motion at the locations of GPS monuments. With the help of continuous GPS (CGPS) measurements, we can now track these motions (horizontal and vertical) on a daily basis. The other methodology is called InSAR, which uses radar images to map detailed changes in the surface of a large swath of land between two (infrequent) satellite passes. A limitation of InSAR is that it is most sensitive to vertical ground motions, which often have anthropogenic instead of tectonic origins. This project aims to bridge the gap between the ability of GPS and InSAR to capture fundamental deformation processes at high spatial and temporal resolution. InSAR-detected crustal motions are limited by being sampled intermittently and only in the satellite's line-of-sight (LOS). On the other hand, GPS-derived descriptions of the deformation field fail to achieve the same spatial resolution that is obtained with InSAR. The goal of project is to significantly improve the spatial resolution of existing secular strain rate tensor models using horizontal GPS velocities, and create additional models of time-variable deformation using continuous GPS (CGPS) data. This project will provide useful baseline estimates of secular and time-dependent horizontal deformation that could aid the interpretation of InSAR results, while also allowing new advances in studies of the geodynamics and seismic hazard of areas undergoing continental deformation. The work is focussed on the Pacific-North America (PA-NA) plate boundary zone, the Mediterranean and Middle East, and central and eastern Asia. There, all publicly available CGPS data will be analyzed and combined with estimates of the secular motions from published campaign-style GPS measurements. The horizontal velocities will be converted to continuous strain rate tensor models of secular deformation. Where data coverage is limited, other kinematic indicators (e.g,, fault slip rates/vectors, earthquake focal mechanisms) will be included for additional constraints on the strain style and localization. Improvements on the temporal variation of the strain rate field (most notably due to transients and postseismic deformation) will be limited to the PA-NA plate boundary zone, where CGPS sites are abundant. Reliable time-variable strain rate models (and associated changes in dilatational and shear strain) can likely be created for 1-4 week time windows, sufficient to capture most first order time-variable processes. Both static and dynamic deformation results will be converted to LOS equivalents for 1st order comparison with InSAR results. Estimates of the secular motions of CGPS sites as well as strain rate results (tensor parameters, maps, and movies) will be made available on a dedicated web portal, as a valuable tool for scientists and educators. Secular strain rates correlate closely with expected seismic hazard and can contribute directly to improving hazard maps. The time-dependent strain rate models may contribute to investigations in stress transfer, earthquake triggering and, ultimately, time-dependent seismic hazard.Through the project, a graduate student will be trained in the management of GPS data, the characterization of CGPS time-series, and crustal deformation modeling. The results (data and models) obtained from this project will be made available on a dedicated web portal, as a valuable tool for scientists and educators.