Collaborative Research: Structure and Dynamics of the North American Craton - An EarthScope Swath from the Ozarks to the Grenville Front

该项目旨在提高我们对北美稳定大陆内部（大陆中部克拉通台地）岩石圈尺度结构的了解。 该研究区域包括一些世界上最好的克拉通台地岩石圈结构的例子。 具体来说，它横跨奥扎克穹顶和伊利诺伊盆地（包括它们之间的陡峭边界，沿着该边界，前寒武纪/寒武纪不整合面显示出超过 7.5 公里的结构起伏），以及 Rough Creek Graben 和其他主要断层带，包括瓦巴什谷地震带。 它还穿过主要的元古代缝合带和神秘的东部花岗岩-流纹岩省。 该研究旨在解决七个基本构造问题：（1）克拉通内隆起和盆地结构； (2) 北美克拉通地台元古界组合； （3）陆内裂谷、断褶带深部结构； (4)岩石圈对板内地震活动的控制； (5) 大陆中部异常的非造山花岗岩-流纹岩省的深层结构； (6) 构造和岩石圈对“克拉通化”的控制？北美平台； (7) 了解该地区强重力和磁场异常的性质。 该项目的重点是运行以伊利诺伊州盆地为中心的三维、宽带、无源地震阵列。 该阵列嵌入在 Earthscope 可移动阵列中，旨在提供该区域地下结构的增强分辨率。 该实验涉及在 3 年时间内部署 120 个临时地震台，与该地区可移动地震台的运行同时进行；站点占用将分四个不同阶段进行，最多有 60 个同时运行的站点。 所获取的地震数据正在使用各种最先进的地震分析工具进行分析：使用远震 P 波和 S 波的走时断层扫描；波场成像使用行业开发的信号叠加方法来提高信噪比和“迁移”？将推断的震源定位到正确的几何位置；并对这个密集阵列上记录的地震活动进行详细分析，以更好地定位地震源并表征断层。 根据该地区之前的工作估计，在为期三年的现场实验过程中，将记录大约 100 次当地地震和 12,000 次采矿爆炸。 该项目还包含综合教育和外展部分，包括：(1) 在职教师讲习班，旨在扩大了解 EarthScope 科学的大师级教师队伍； (2) 教师研究员计划，将高中科学教师纳入暑期研究团队； (3) 利用与学校、大学预科研究研讨会和国家调查外展计划（实地考察、开放参观、公开演讲）已建立的联系，让学生和公众参与与 EarthScope 相关的活动； (4) 开发“活跃地球”展示材料，用于区域推广，并纳入广泛使用的地球科学入门教科书； (5) 通过本科生研究体验项目吸引本科生参与； （6）研究生教育三所研究型大学。

This project is directed at improving our understanding of the lithosphere-scale structure of North America's stable continental interior (Midcontinent cratonic platform). The study area includes some of the world?s best examples of cratonic platform lithosphere structures. Specifically, it spans the Ozark Dome and the Illinois Basin (including the abrupt boundary between them along which the Precambrian/Cambrian unconformity displays over 7.5 km of structural relief), as well as the Rough Creek Graben and other major fault zones including the Wabash Valley Seismic Zone. It also crosses major Proterozoic sutures and the enigmatic Eastern Granite-Rhyolite province. The study is intended to address seven fundamental tectonic issues: (1) structure of intracratonic uplifts and basins; (2) Proterozoic assembly of the North American cratonic platform; (3) deep structure of intracontinental rifts and fault-and-fold zones; (4) lithospheric controls on intraplate seismicity; (5) deep structure of the midcontinent?s unusual anorogenic granite-rhyolite province; (6) structural and lithospheric controls on ?cratonization? of the North American platform; and (7) understanding the nature of the strong gravity and magnetic-field anomalies in the region. The project is focused on operation of a three-dimensional, broadband, passive seismic array centered over the Illinois Basin. The array is embedded within the Earthscope Transportable Array, and is designed to provide enhanced resolution of subsurface structures in the region. The experiment involves deployment of 120 temporary seismograph stations over a 3-year period coinciding with the operation of the Transportable Array in the area; site occupation will roll in four distinct stages using a maximum of 60 simultaneously operating stations. The acquired seismic data are being analyzed using a variety of state-of-the-art seismic analysis tools: travel-time tomography using teleseismic P and S waves; wave-field imaging using industry-developed methods of stacking signals to improve signal-to-noise ratio and ?migration? of inferred seismic sources to their proper geometric position; and a detailed analysis of seismicity recorded on this dense array, to better locate earthquake sources and characterize faults. Estimates from previous work in the area suggest that approximately 100 local earthquakes and 12,000 mining explosions will be recorded during the course of the three-year field experiment. The project also incorporates an integrated education and outreach component, involving: (1) in-service teacher workshops designed to expand the pool of master teachers knowledgeable about EarthScope science; (2) a teacher Research Fellows program to include high school science teachers in summer research teams; (3) involvement of students and the public in EarthScope-related activities using already established connections with schools, pre-college research symposia, and State Survey outreach programs (field trips; open houses; public presentations); (4) development of material for "Active Earth" displays for regional outreach, and for incorporation in widely used introductory geoscience textbooks; (5) engagement of undergraduate students through a Research Experience for Undergraduates program; and (6) graduate student education three research universities.