Using Geodesy to Separate Transient and Steady Extension in the Basin and Range Province, Western United States

盆岭省是太平洋/北美板块边界变形带的一个组成部分，经历了大地震，可能威胁到内华达州、犹他州、亚利桑那州、爱达荷州和俄勒冈州的社区。 现在可以用空间大地测量方法，如全球定位系统，精确测量800公里宽的省的活动变形，因此现在可以绘制产生引起这些地震的应力的缓慢运动的速率和类型。 然而，最近的地质和地球物理研究对横跨内华达州的变形是如何发生的得出了相互矛盾的结论。 一些大地测量学研究表明，北美板块在内华达州东部是不变形的，而另一些研究则发现了小规模的偶发性变形事件的证据。地质证据表明，最近的正常断层和伸展发生，并大致均匀地分布在全省。 这三种关于北美板块如何变形的不同观点意味着大陆岩石圈伸展的三种极端不同的动力学模式，因此这三种观点不可能都是正确的。 EarthScope板块边界观测站GPS网络的设计是沿着沿着美国50号州际公路，横跨整个盆地和山脉，纬度约为北纬39度。 这些GPS站点现在正在检测内华达州东部的单位数纳应变/年变形率。 因此，PBO准备解决构造大地测量科学中的这一新前沿：板块边界主要元素之间传递变形的缓慢但活跃的领域。 为了区分这三个假设，我们将：1）使用最新的软件和模型处理GPS数据，2）系统地生成大地瞬变目录，3）开发19和20世纪地震粘弹性响应的改进模型，以从GPS时间序列中去除震后瞬变信号，4）估算内华达州东部长期变形的速率和模式，并将这些结果与地质和地震资料进行比较，这些活动的结果将有助于更好地理解活动板块边界的内容物如何变形。 在这样做的过程中，我们将量化驱动地震发生的背景构造变形的速率，模式和风格。 这些比率越来越多地用于指导建筑实践的美国国家地震危险地图。因此，这项工作将对地震的准备工作和未来损失的估计产生直接影响。

The Basin and Range Province is an integral part of the Pacific/North America plate boundary deformation zone, and experiences large earthquakes that can threaten communities in Nevada, Utah, Arizona, Idaho and Oregon. The active deformation of the 800 km wide Province can now be precisely measured with space geodetic methods such as GPS, and thus it is now possible to chart the rates and styles of the slow movements that generate the stresses that cause these earthquakes. However, recent geological and geophysical studies have come to conflicting conclusions about how the deformation across Nevada occurs. Some geodetic studies have suggested that the North American Plate is non-deforming in eastern Nevada, while others have found evidence for episodic, large-scale, but small magnitude deformation events. Geologic evidence suggests that recent normal faulting and extension occurs and is distributed roughly evenly across the Province. These three different views of how the North American plate deforms imply three extremely different dynamic modes of extension of continental lithosphere, and thus it is not possible that all three are correct. The EarthScope Plate Boundary Observatory GPS network was designed with a profile of sites along US Interstate Highway 50, across the entire Basin and Range at a latitude of about 39 degrees N. These GPS sites are now detecting single digit nanostrain/yr deformation rates across eastern Nevada. Therefore PBO is ready to address this new frontier in the science of tectonic geodesy: The slow but active realms that transfer deformation between the major elements of the plate boundary. To distinguish between the three hypotheses we will: 1) process GPS data using the latest software and models, 2) systematically generate a catalog of geodetic transients, 3) develop improved models of the viscoelastic response of 19th and 20th century earthquakes to remove postseismic transient signals from the GPS time series, 4) estimate rates and patterns of long term deformation of eastern Nevada and compare these results to geologic and seismic data.The results of these activities will be an improved understanding of how the contents in active plate boundaries deform. In so doing we will quantify the rate, pattern, and style of background tectonic deformation that drives the occurrence of earthquakes. These rates are increasingly being used in the U.S. National Seismic Hazard Maps that guide building practices. Thus this work will have a direct impact on preparedness for and estimates of future losses from earthquakes.