Integrated Geologic and Geodetic Study of Strain Accumulation and Release in the Northern Walker Lane

沃克巷北部应变积累和释放的综合地质和大地测量研究

• 批准号: 0635757
• 负责人: Steven Wesnousky
• 金额: $ 33.49万
• 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: 2007
• 资助国家: 美国
• 起止时间: 2007-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635757&HistoricalAwards=false
• 关键词: Integrated; Geologic; Geodetic; Study; Strain

Pacific-North American right-lateral relative plate motion at the latitude of the San Andreas fault system is approximately 50 mm/yr. Up to one fourth of that motion is accommodated by displacements on faults east of the San Andreas fault system within the Eastern California shear zone and Walker Lane system located in the western Basin and Range province, eastern California and western Nevada. Unlike the San Andreas system, the relative immaturity and complexity of the northern Walker Lane fault system makes the comparison between geodetic and geologic rates difficult. Current data indicate that there is a systematic difference between rates of moment release (obtained from geologic observations of offset markers and paleoseismic investigations), and rates of strain energy accumulation (estimated from geodetic measurement of surface shape change) in the western Basin and Range. The current lack of understanding of this discrepancy may lie in the incompleteness of data on strain release (as seen through structure, physiography, and the spatial and temporal distribution of earthquakes) and the resolution of slip rates based on strain accumulation (as seen by geodesy) in a complex intra-continental setting. This project is an integrated neotectonic and geodetic analysis of the northern Walker Lane in the area between Walker Lake and Lake Tahoe, a region for which the neotectonics data are very minimal. In order to evaluate the difference between budgets of strain accumulation and release a University of Nevada at Reno research team will obtain the most complete measurements to date of these two manifestations of the earthquake cycle in an intra-continental setting. The project uses geodetic data from existing or soon-to-be installed networks (BARGEN, MAGNET, NEARNET, and the EarthScope Plate Boundary Observatory) that will be supplemented with a new geodetic network that uses a semi-continuous observation strategy to obtain roughly three times as many high precision rates as are currently available in the study area. A variety of neotectonic approaches will be used to study the faults bounding the Smith, Mason, Antelope and Bridgeport Valleys and long the Wakuska and Carson lineaments. The scale of the investigation will achieve a maximum in overlap between the strengths of the two disciplines, small enough to obtain a geologic record that is representative, and large enough to resolve variations in the geodetic strain field that can be related to crustal fault patterns. This work is in concert with the goals of EarthScope. Specifically, a complete understanding of the kinematics and mechanics of any plate boundary requires measurements of the rate, style, and evolution of deformation across the entirety of the boundary through geologic time. Results from this study will aid in understanding earthquake hazards in this seismically active region.

圣安地列斯断层系统纬度处的太平洋-北美右旋相对板块运动约为 50 毫米/年。多达四分之一的运动是由东加州剪切带内圣安德烈亚斯断层系以东的断层和位于西部盆地山脉省、加州东部和内华达州西部的沃克莱恩系统的位移所调节的。与圣安德烈亚斯系统不同，沃克莱恩断层系统北部的相对不成熟和复杂性使得大地测量速率和地质速率之间的比较变得困难。目前的数据表明，西部盆地和山脉的力矩释放速率（通过偏移标记的地质观测和古地震研究获得）和应变能积累速率（通过地表形状变化的大地测量估计）之间存在系统差异。目前对这种差异缺乏了解，可能在于复杂大陆内环境中应变释放数据（通过结构、地貌以及地震的时空分布观察）和基于应变积累的滑移率分辨率（通过大地测量学观察）的不完整。该项目是对沃克湖和太浩湖之间地区沃克巷北部的新构造和大地测量进行综合分析，该地区的新构造学数据非常少。为了评估应变积累和发布预算之间的差异，内华达大学里诺分校的研究小组将获得迄今为止大陆内地震周期这两种表现形式的最完整的测量结果。该项目使用来自现有或即将安装的网络（BARGEN、MAGNET、NEARNET 和 EarthScope 板块边界观测站）的大地测量数据，这些数据将辅以新的大地测量网络，该网络使用半连续观测策略，获得的高精度率大约是研究区域目前可用的三倍。将采用各种新构造方法来研究史密斯、梅森、羚羊谷和布里奇波特山谷以及瓦库斯卡和卡森线的断层。调查规模将实现两个学科优势之间的最大重叠，小到足以获得具有代表性的地质记录，大到足以解决可能与地壳断层模式相关的大地应变场的变化。这项工作与 EarthScope 的目标一致。具体来说，要全面了解任何板块边界的运动学和力学，需要测量地质时期整个边界的变形速率、类型和演变。这项研究的结果将有助于了解这个地震活跃地区的地震危害。