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(中大陆克拉通地台)岩石圈尺度结构的理解。研究区域包括一些世界上最好的克拉通地台岩石圈结构的范例？S。具体地说，它横跨Ozark穹顶和伊利诺伊盆地(包括它们之间的陡峭边界，前寒武纪/寒武纪不整合显示了超过7.5公里的构造起伏)，以及Rough Creek Graben和包括瓦巴什山谷地震带在内的其他主要断裂带。它还穿越了主要的元古界缝合带和神秘的东部花岗岩-流纹岩省。这项研究旨在解决七个基本构造问题：(1)克拉通内隆起和盆地的结构；(2)北美克拉通地台的元古界组装；(3)陆内裂谷和断褶带的深部结构；(4)岩石圈对板内地震活动的控制；(5)中大陆的深部结构？S异常的非造山花岗岩-流纹岩省；(6)构造和岩石圈对克拉通作用的控制？以及(7)了解该地区强重力和磁场异常的性质。该项目的重点是以伊利诺伊盆地为中心的三维、宽带、被动地震阵列的运行。该阵列嵌入在地球望远镜可移动阵列中，旨在为该地区的地下结构提供增强的分辨率。这项试验涉及在三年期间部署120个临时地震台站，同时在该地区运行可移动阵列；场地占用将分四个不同的阶段进行，最多可同时使用60个地震台站。采集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波的旅行时层析成像；使用行业开发的信号叠加方法进行波场成像，以提高信噪比和偏移？将推断的震源定位到其适当的几何位置；以及详细分析记录在这个密集阵列上的地震活动，以便更好地定位震源和确定断层的特征。对该地区以前工作的估计表明，在为期三年的实地试验过程中，将记录到大约100次当地地震和12000次采矿爆炸。该项目还纳入了一个综合的教育和外联部分，涉及：(1)在职教师讲习班，旨在扩大掌握地球范围科学知识的教师队伍；(2)教师研究研究员方案，将高中科学教师纳入暑期研究小组；(3)利用已建立的与学校的联系、大学前研究座谈会和国家调查外联方案(实地考察；开放参观；公开介绍)，让学生和公众参与与地球范围有关的活动；(4)为“活跃的地球”展示编写材料，用于区域外联，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计划吸引本科生；(6)三所研究型大学的研究生教育。

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.