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

利用大地测量学分离美国西部盆岭省的瞬态和稳定延伸

• 批准号: 1053356
• 负责人: William Hammond
• 金额: $ 20.61万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-15 至 2014-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1053356&HistoricalAwards=false
• 关键词: Using; Geodesy; Separate; Transient; Steady

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.

盆岭省是太平洋/北美板块边界变形区的组成部分，发生的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。 现在可以使用 GPS 等空间大地测量方法精确测量 800 公里宽的省份的活动变形，因此现在可以绘制出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于内华达州变形如何发生得出了相互矛盾的结论。 一些大地测量研究表明，北美板块在内华达州东部没有变形，而其他研究则发现了偶发性、大规模但小幅度变形事件的证据。地质证据表明最近发生了正断层和伸展，并且在全省范围内分布大致均匀。 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截然不同的动力模式，因此不可能所有三种都是正确的。 EarthScope 板块边界观测站 GPS 网络是根据美国 50 号州际公路沿线的站点概况设计的，横跨北纬 39 度左右的整个盆地和山脉。这些 GPS 站点现在正在检测内华达州东部的个位数纳米应变/年变形率。 因此，PBO 已准备好解决构造大地测量学中的这一新前沿：在板块边界的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 世纪和 20 世纪地震的粘弹性响应的改进模型，以从 GPS 时间序列中删除震后瞬变信号，4) 估计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结果进行比较 这些活动的结果将加深对活动板块边界内容物如何变形的理解。 在此过程中，我们将量化驱动地震发生的背景构造变形的速率、模式和类型。 这些比率越来越多地用于指导建筑实践的美国国家地震灾害地图。因此，这项工作将对地震未来损失的准备和估计产生直接影响。