Modification of lithospheric structure via subduction, terrane accretion, and rifting: A case study beneath Connecticut

美国东部的基岩地质异常复杂。这种复杂性反映了在地质时期影响北美东部的一系列板块构造过程。这些过程包括超级大陆的形成和分裂，新大陆块在大陆边缘的增生，以及由于俯冲和大陆裂谷而引起的广泛火山活动。康涅狄格州，虽然面积相对紧凑，但代表了研究这一系列基本地球过程的主要机会。这是因为康涅狄格州的地质反映了阿巴拉契亚山脉和盘古大陆形成期间的几个阶段的山脉建设和火山增生，以及后来的盘古大陆分裂和大西洋盆地的形成。该项目将利用部署在康涅狄格州北方的15个地震台站的数据，利用遥远地震的地震波记录，研究该州地壳和地幔的深层结构。该团队将使用这种深层结构的图像来回答有关超级大陆如何形成和分裂的基本问题，以及板块构造过程（如俯冲，裂谷和地幔增生）如何影响地壳和上地幔的演化。该项目包括一个面向高中理科教师的外展项目，让教师们能够花一周时间在野外收集数据，了解康涅狄格州的地质情况，并利用该项目的地震数据开发一个课堂练习。调查人员将分析康涅狄格州地下结构成像地震实验的数据（SEISConn），在康涅狄格州北方密集的线性阵列中部署了15个宽带地震仪。该阵列占据了阿巴拉契亚造山带的一个区域，该区域包括各种各样的吸积构造，以及哈特福德盆地，这是一个由泛大陆分裂造成的中生代裂谷构造。他们将对SEISConn数据应用一套成像技术，重点关注地壳和岩石圈地幔内的不连续结构、地震速度结构和地震各向异性的成像。该项目的动机是三个主要的科学问题：1）在阿巴拉契亚卵子生成过程中的俯冲和俯冲增积事件如何影响地壳和地幔岩石圈结构，以及当今的深部结构如何对应于地表地质？2)地壳和地幔岩石圈的结构如何受到中生代（失败的）裂谷作用的影响，哈特福德裂谷盆地下面的结构与北美东部裂谷边缘（最终成功）的结构相比如何？3)地壳和地幔在俯冲、地幔增生和裂谷作用中是如何变形的？该项目将对SEISConn数据应用一系列分析技术，包括P-to-S和S-to-P接收器函数分析、环境噪声层析成像、波场偏移成像和剪切波分裂。该项目的最后阶段将涉及测试根据地质观测提出的关于过去构造过程的具体假设。该项目将支持耶鲁大学成功的科学教师现场经验（FEST）项目的延续，该项目为康涅狄格州的高中科学教师提供为期一周的现场地震学经验。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The bedrock geology of the eastern United States is extraordinary in its complexity. This complexity reflects a range of plate tectonic processes that have affected eastern North America over geologic time. These processes include the formation and breakup of supercontinents, the accretion of new landmasses onto the continental edge, and widespread volcanic activity due to subduction and continental rifting. The state of Connecticut, though relatively compact in area, represents a prime opportunity to study this range of fundamental Earth processes. This is because Connecticut's geology reflects several phases of mountain building and terrane accretion during the formation of the Appalachian Mountains and the Pangea supercontinent, as well as the later breakup of Pangea and the formation of the Atlantic Ocean basin. This project will use data from an array of 15 seismic stations deployed across northern Connecticut to study the deep structure of the crust and mantle beneath the state, using recordings of seismic waves from distant earthquakes. The team will use images of this deep structure to answer fundamental questions about how supercontinents are formed and break up, as well as how plate tectonic processes such as subduction, rifting, and terrane accretion affect the evolution of the crust and upper mantle. The project includes a component of outreach to high school science teachers, enabling teachers to spend one week in the field collecting data and learning about Connecticut geology, as well as developing a classroom exercise that uses seismic data from the project.The investigators will analyze data from the Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn), a deployment of 15 broadband seismometers in a dense linear array across northern Connecticut. The array occupies a region of the Appalachian Orogen that encompasses a striking variety of accreted terrane structures, as well as the Hartford Basin, a Mesozoic rift structure resulting from the breakup of Pangea. They will apply a suite of imaging techniques to SEISConn data, focusing on the imaging of discontinuity structure, seismic velocity structure, and seismic anisotropy within the crust and lithospheric mantle. The project is motivated by three major science questions: 1) How did episodes of subduction and terrane accretion during Appalachian oogenesis affect crustal and mantle lithospheric structure, and how does present-day deep structure correspond to surface geology? 2) How was the structure of the crust and mantle lithosphere affected by (failed) rifting during the Mesozoic, and how does the structure beneath the Hartford Rift Basin compare to structure across the (ultimately successful) rifted margin of eastern North America? 3) How was the crust and mantle deformed during subduction, terrane accretion, and rifting? This project will apply a range of analysis techniques to SEISConn data, including P-to-S and S-to-P receiver function analysis, ambient noise tomography, wavefield migration imaging, and shear wave splitting. The final phase of the project will involve the testing of specific hypotheses about past tectonic processes that were formulated based on geologic observations. This project will support the continuation of the successful Field Experiences for Science Teachers (FEST) program at Yale, which provides one week of field seismology experience to Connecticut-based high school science teachers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.