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(和与之相关的地震活动)可以分布在大范围内。基本上有两种基于卫星的观测方法可以准确地监测这种变形。有了全球定位系统(GPS)，我们可以在GPS纪念碑的位置精确地测量地球表面的运动。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InSAR，它使用雷达图像来绘制两个(不频繁的)卫星通过之间的大片土地表面的详细变化。InSAR的一个局限性是它对垂直地面运动最敏感，而垂直地面运动通常是人为的，而不是构造的。该项目旨在弥合GPS和InSAR以高空间和时间分辨率捕捉基本形变过程的能力之间的差距。InSAR探测到的地壳运动受到间歇采样的限制，只能在卫星的视线(LOS)内进行采样。另一方面，GPS对形变场的描述不能达到与InSAR相同的空间分辨率。该项目的目标是利用水平GPS速度显著提高现有长期应变速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。该项目将为长期和随时间变化的水平形变提供有用的基线估计，有助于解释InSAR结果，同时也使大陆形变地区的地球动力学和地震灾害研究取得新的进展。这项工作的重点是太平洋-北美(PA-NA)板块边界地带、地中海和中东以及中亚和东亚。在那里，所有可公开获得的CGPS数据将被分析，并与发布的竞选风格GPS测量结果的长期运动估计相结合。水平速度将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，断层滑移率/向量、震源机制)，以增加对应变样式和局部化的约束。应变速率场随时间变化的改善(最显著的原因是瞬变和震后变形)将仅限于PA-NA板块边界带，那里有大量的CGPS站点。可靠的时变应变率模型(以及相关的扩张和剪切应变变化)很可能针对1-4周的时间窗口被创建，足以捕捉大多数一阶时间变量过程。静态和动态变形结果都将被转换为视距当量，以便与InSAR结果进行一阶比较。对CGPS站点长期运动的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密切相关，并可直接有助于改进危险图。时变应变率模型可能有助于应力传递、地震触发以及最终时变地震危险性的研究。通过该项目，研究生将在GPS数据管理、CGPS时间序列特征和地壳形变建模方面进行培训。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提供，作为科学家和教育工作者的宝贵工具。

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.