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）岩石圈规模结构的认识。研究区域包括一些世界？克拉通台地岩石圈构造的最佳例证。具体来说，它跨越了奥扎克巨丘和伊利诺斯盆地（包括它们之间的突然边界，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地堑和其他主要断裂带，包括沃巴什谷地震带。它还穿过主要的元古代缝合线和神秘的东部花岗岩流纹岩省。研究主要涉及七个基本构造问题：(1)克拉通内隆升和盆地构造；(2)北美克拉通地台元古代组合；(3)陆内裂谷和断褶带的深部构造；(4)岩石圈对板内地震活动的控制作用；(5)中部大陆深部构造？S罕见的造山花岗岩流纹岩省；(6)构造和岩石圈对克拉通化的控制。北美平台；(7)认识该区强重磁场异常的性质。该项目侧重于以伊利诺斯盆地为中心的三维、宽带、被动地震阵列的操作。该阵列嵌入在地球范围可移动阵列中，旨在提高该地区地下结构的分辨率。该实验包括在3年内部署120个临时地震仪站，同时在该地区运行可移动阵列；场地占用将分四个不同阶段进行，同时使用最多60个操作站。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波的走时层析成像；使用行业开发的叠加信号方法进行波场成像，以提高信噪比和偏移量。将推断震源定位到其适当的几何位置；并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表征断层。根据该地区以前的工作估计，在为期三年的实地试验期间，将记录到大约100次当地地震和12,000次采矿爆炸。该项目还包括综合教育和外联部分，包括：(1)在职教师讲习班，旨在扩大了解《地球观测》科学的高级教师队伍；(2)教师研究人员计划，将高中科学教师纳入暑期研究团队；(3)利用与学校、大学预科研究专题讨论会和州调查外展计划（实地考察、开放参观、公开演讲）已经建立的联系，让学生和公众参与与地球镜相关的活动；(4)开发用于区域推广的“活动地球”展示材料，并将其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)三所研究型大学研究生教育。

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.