Cite this article as Long, M. D., and J. C. Aragon (2020). Probing the Structure of the Crust and Mantle Lithosphere beneath the Southern New England Appalachians via the SEISConn Deployment, Seismol. Res. Lett. XX, 1–11, doi: 10.1785/0220200163. The eastern margin of North America has been affected by a range of fundamental tectonic processes in the geologic past. Major events include the Paleozoic Appalachian orogeny, which culminated in the formation of the supercontinent Pangea, and the breakup of Pangea during the Mesozoic. The southern New England Appalachians exhibit a particularly rich set of geologic and tectonic structures that reflect multiple episodes of subduction and terrane accretion, as well as subsequent continental breakup. It remains poorly known, however, to what extent structures at depth in the crust and lithospheric mantle reflect these processes, and how they relate to the geological architecture at the surface. The Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) was a deployment of 15 broadband seismometers in a dense linear array across northern Connecticut. The array traversed a number of major tectonic boundaries, sampling across the Laurentianmargin in its western portion to the Avalonian terrane at its eastern end. It also crossed the Hartford rift basin in the central portion of the state. The SEISConn stations operated between 2015 and 2019; data from the experiment are archived at the Incorporated Research Institutions for Seismology Data Management Center and will be publicly available beginning in 2021. A suite of imaging techniques is being applied to SEISConn data, with the goal of providing a detailed view of the crust and mantle lithosphere (including discontinuities, seismic velocities, and seismic anisotropy) beneath the southern New England Appalachians. Results from these analyses will inform a host of fundamental scientific questions about the structural evolution of orogens, the processes involved in continental rifting, and the nature of crustal and mantle lithospheric deformation during subduction, terrane accretion, and continental breakup. Introduction Eastern North America is a passive continental margin that has been shaped by multiple episodes of supercontinent assembly and breakup. The most recent of these cycles encompassed the Appalachian orogeny, which culminated in the formation of the Pangaea supercontinent, as well as subsequent rifting that broke apart Pangaea and formed the present-day Atlantic Ocean basin. Appalachian orogenesis involved several distinct phases over a period of several hundred million years (e.g., Hatcher, 2010). The first phase, the Taconic orogeny, involved the accretion of arc terranes onto the margin of Laurentia (e.g., Karabinos et al., 1998), whereas later phases (the AcadianNeoacadian and Alleghanian orogenies) involved superterrane accretion and continental collision (e.g., Bartholomew and Whitaker, 2010; Hatcher, 2010; Ver Straeten, 2010). Supercontinental breakup was accomplished via a complex set of rifting processes and was accompanied by voluminous magmatism that was associated with the Central Atlantic Magmatic Province (e.g., Schlische et al., 2003). These Mesozoic rifting processes are expressed in a number of abandoned rift basins 1. Department of Geology and Geophysics, Yale University, New Haven, Connecticut, U.S.A.; 2. Now at Earthquake Science Center, U.S. Geological Survey, Menlo Park, California, U.S.A. *Corresponding author: maureen.long@yale.edu © Seismological Society of America Volume XX • Number XX • – 2020 • www.srl-online.org Seismological Research Letters 1 Data Mine Downloaded from https://pubs.geoscienceworld.org/ssa/srl/article-pdf/doi/10.1785/0220200163/5086943/srl-2020163.1.pdf by Yale University user on 08 July 2020 along eastern North America; the Hartford basin is among the most prominent of these (e.g., Withjack and Schlische, 2005; Withjack et al., 2012). The southern New England Appalachians present a prime opportunity to investigate, within a compact region, the nature of complex structures that have resulted from a complicated history of subduction and terrane accretion (Fig. 1). The bedrock geology of Connecticut expresses the juxtaposition of a variety of terranes, of both continental and volcanic arc affinity and from across the Laurentian and peri-Gondwanan realms. Specifically, proto-North American units are found in the northwestern portion of Connecticut, including Grenville basement rocks up to ∼1:1 Ga old (Fig. 2). A protracted series of subduction-collision events during Appalachian orogenesis resulted in the accretion of various terranes onto proto-North America (e.g., Karabinos et al., 1998; Aleinikoff et al., 2007), including the Avalonian terrane in the southeastern corner of Connecticut (e.g., Wintsch et al., 1992). Later rifting during the Mesozoic modified (and was likely influenced by) these pre-existing structures and formed the Hartford rift basin in the central portion of the state (Fig. 2; e.g., Schlische, 1993). The state of Connecticut thus encompasses widely varied bedrock geology, reflecting a range of subduction, terrane accretion, and rifting processes, within a compact area. For this reason, it can be efficiently sampled with a relatively modest seismic array. The goal of the Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) project is to carry out imaging of the crust and mantle that will inform a set of scientific questions; these questions are related to the formation and preservation of structures in the deep crust and mantle lithosphere. First, we are interested in how episodes of subduction and terrane accretion during Appalachian orogenesis affected crustal and mantle lithospheric structure, as well as whether (and how) present-day deep structure corresponds to surface geology. Second, we are interested in how structure was modified by (failed) rifting during the Mesozoic and how the structure beneath the Hartford rift basin compares with structure across the (ultimately successful) rifted margin of easternNorth America (e.g., Lynner and Porritt, 2017). Third, we wish to understand how the crust and lithospheric mantle were deformed during subduction, terrane accretion, and rifting, and to what extent the signature of this past deformation has been preserved over geologic time. Motivated by these scientific questions, the SEISConn field experiment was carried out across northern Connecticut between 2015 and 2019. The experiment was conceptualized and run by principal investigator (PI) Maureen Long (Yale University), while John Aragon (Yale University) served as project manager and field technician and designed the station layout, to be described later. The deployment itself was funded mainly by Yale, with some support for field participants that was provided by the U.S. National Science Foundation (NSF), via the Field Experiences for Science Teachers program, to be described later. The analysis of SEISConn data is being supported by the EarthScope and Geophysics programs of NSF. We deployed a linear array of 15 broadband seismometers across northern Connecticut and Rhode Island (Fig. 2), with data collection beginning in August 2015 and ending in August 2019. The instruments recorded data continuously and relied on natural (passive) earthquake sources, recording both teleseismic and regional events, as well as ambient noise that was useful for imaging. The dense station spacing of the experiment (roughly 10 km) allows for unaliased imaging of crustal structure on length scales that are relevant for the complex geology of the area (Fig. 1). The SEISConn array traversed a number of geologic terranes, from Laurentian rocks at its western end to the Avalonian terrane at its eastern end, and it crossed through the Hartford rift basin in its central portion. Instrument Deployment and Details A map of seismic stations that operated as part of the SEISConn experiment is shown in Figure 2. The SEISConn array extended from Lakeville, Connecticut in the west to Chepachet, Rhode Island in the east. The easternmost station location in Rhode Island was chosen to achieve coverage across the Lake Char-Honey Hill fault in eastern Connecticut (Fig. 2), which marks the boundary between Avalonia (to the east) and other peri-Gondwanan terranes (to the west). The station naming convention involved sequential labeling from CS01 at Figure 1. Generalized lithotectonic map of the Appalachian orogen, modified from Murphy et al. (2010), after Hibbard et al. (2006). Box outlines the region targeted by the Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) array, which affords the opportunity to probe the deep structure associated with a number of distinct terrains (as well as the Hartford rift basin, not shown) with a relatively compact seismic array. The color version of this figure is available only in the electronic edition. 2 Seismological Research Letters www.srl-online.org • Volume XX • Number XX • – 2020 Downloaded from https://pubs.geoscienceworld.org/ssa/srl/article-pdf/doi/10.1785/0220200163/5086943/srl-2020163.1.pdf by Yale University user on 08 July 2020 the western end to CS15 at the eastern end. The array aperture was 150 km, and 15 stations were installed, for a nominal station spacing of just over 10 km. We deployed Trillium 120PA broadband seismometers, paired with Taurus digitizer– datalogger, manufactured by Nanometrics, Inc., and owned by Yale University. Data were recorded at 40 Hz sample rate on channels BHE, BHN, and BHZ, and were stored locally on compact flash cards. We began deploying instruments in August 2015, and we installed six stations (CS02, CS03, CS04, CS05, CS13, and CS14) in the summer and fall of 2015. An additional six stations (CS06, CS07, CS08, CS10, CS12, and CS15) were installed in summer 2016, and the remaining three instruments (CS01, CS09, and CS11) were deployed (or, in

中文翻译：

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通过 SEISConn 部署探测新英格兰南部阿巴拉契亚山脉下方地壳和地幔岩石圈的结构

将本文引用为 Long、MD 和 JC Aragon（2020）。通过 SEISConn 部署，Seismol 探测新英格兰阿巴拉契亚山脉南部地壳和地幔岩石圈的结构。水库 莱特。XX, 1–11, doi: 10.1785/0220200163。北美东部边缘在过去的地质过程中受到了一系列基本构造过程的影响。主要事件包括古生代阿巴拉契亚造山运动，最终形成了超大陆盘古大陆，以及中生代盘古大陆的分裂。新英格兰阿巴拉契亚山脉南部展示了一组特别丰富的地质和构造结构，反映了多次俯冲和地体增生，以及随后的大陆分裂。然而，它仍然鲜为人知，地壳和岩石圈地幔深处的结构在多大程度上反映了这些过程，以及它们与地表地质结构的关系。康涅狄格州地下成像结构地震实验 (SEISConn) 是在康涅狄格州北部密集线性阵列中部署 15 个宽带地震仪。该阵列穿越了许多主要的构造边界，在其西部的 Laurentianmargin 到其东端的 Avalonian 地体取样。它还穿过该州中部的哈特福德裂谷盆地。SEISConn 站于 2015 年至 2019 年期间运营；实验数据存档在联合研究机构地震学数据管理中心，并将于 2021 年开始公开。正在对 SEISConn 数据应用一套成像技术，目的是提供新英格兰阿巴拉契亚山脉南部下方地壳和地幔岩石圈（包括不连续性、地震速度和地震各向异性）的详细视图。这些分析的结果将为大量关于造山带结构演化、大陆裂谷过程以及俯冲、地体增生和大陆分裂过程中地壳和地幔岩石圈变形性质的基本科学问题提供信息。介绍 北美东部是一个被动大陆边缘，由多次超大陆组装和分裂形成。最近的这些循环包括阿巴拉契亚造山运动，最终形成了盘古超大陆，以及随后的裂谷分裂了盘古大陆并形成了今天的大西洋盆地。阿巴拉契亚造山运动在数亿年的时间里涉及几个不同的阶段（例如，Hatcher，2010）。第一阶段 Taconic 造山运动涉及弧形地体在 Laurentia 边缘的增生（例如，Karabinos 等，1998），而后期（AcadianNeoacadian 和 Alleghanian 造山运动）涉及超地体增生和大陆碰撞（例如 Bartholomew和惠特克，2010 年；海切尔，2010 年；Ver Straeten，2010 年）。超大陆分裂是通过一系列复杂的裂谷过程完成的，并伴随着与中大西洋岩浆区有关的大量岩浆活动（例如，Schlische 等，2003）。这些中生代裂谷过程表现在一些废弃的裂谷盆地 1. 美国康涅狄格州纽黑文耶鲁大学地质与地球物理系；2. 现在在美国加利福尼亚州门洛帕克市美国地质调查局地震科学中心 *通讯作者：maureen.long@yale.edu © 美国地震学会第 XX 卷 • 编号 XX • – 2020 • www.srl-online.org Seismological Research Letters 1 Data Mine 耶鲁大学用户于 2020 年 7 月 8 日东北部从 https://pubs.geoscienceworld.org/ssa/srl/article-pdf/doi/10.1785/0220200163/5086943/srl-2020163.1.pdf 下载美国; Hartford 盆地是其中最突出的（例如，Withjack 和 Schlische，2005 年；Withjack 等人，2012 年）。新英格兰南部阿巴拉契亚山脉提供了一个绝佳的机会，可以在一个紧凑的区域内进行调查，由俯冲和地体增生的复杂历史导致的复杂结构的性质（图 1）。康涅狄格州的基岩地质表现出各种地体的并置，包括大陆弧和火山弧的亲缘关系，以及横跨劳伦和冈瓦纳大陆地区的地体。具体而言，在康涅狄格州西北部发现了原始北美单元，包括高达 1:1 Ga 的 Grenville 基底岩石（图 2）。阿巴拉契亚造山过程中一系列长期的俯冲碰撞事件导致各种地体增生到原始北美（例如，Karabinos 等人，1998 年；Aleinikoff 等人，2007 年），包括位于美国东南角的阿瓦隆地体康涅狄格（例如，Wintsch 等，1992）。中生代后期的裂谷改造（并可能受其影响）这些先前存在的构造并在该州中部形成了哈特福德裂谷盆地（图 2；例如，Schlische，1993 年）。因此，康涅狄格州涵盖了广泛多样的基岩地质，在一个紧凑的区域内反映了一系列俯冲、地体增生和裂谷过程。因此，可以使用相对适中的地震阵列对其进行有效采样。康涅狄格地下结构成像地震实验 (SEISConn) 项目的目标是对地壳和地幔进行成像，为一系列科学问题提供信息；这些问题与深部地壳和地幔岩石圈结构的形成和保存有关。第一的，我们感兴趣的是阿巴拉契亚造山作用期间的俯冲和地体增生事件如何影响地壳和地幔岩石圈结构，以及当今的深层结构是否（以及如何）对应于地表地质。其次，我们感兴趣的是中生代期间（失败的）裂谷如何改变结构，以及哈特福德裂谷盆地下方的结构如何与北美东部（最终成功）裂谷边缘的结构进行比较（例如，Lynner 和 Porritt，2017） . 第三，我们希望了解在俯冲、地体增生和裂谷过程中地壳和岩石圈地幔是如何变形的，以及这种过去变形的特征在地质时期内保存到什么程度。受这些科学问题的启发，SEISConn 现场实验于 2015 年至 2019 年在康涅狄格州北部进行。该实验由首席研究员 (PI) Maureen Long（耶鲁大学）构思并运行，而 John Aragon（耶鲁大学）担任项目经理和现场技术人员，并设计了车站布局，后文详述。部署本身主要由耶鲁资助，并由美国国家科学基金会 (NSF) 通过科学教师的现场体验计划提供了对现场参与者的一些支持，稍后将进行描述。对 SEISConn 数据的分析得到了 NSF 的 EarthScope 和地球物理学计划的支持。我们在康涅狄格州北部和罗德岛部署了由 15 个宽带地震仪组成的线性阵列（图 2），数据收集从 2015 年 8 月开始，到 2019 年 8 月结束。这些仪器连续记录数据并依赖于自然（被动）地震源，记录远震和区域事件，以及对成像有用的环境噪声。实验的密集站间距（大约 10 公里）允许在与该地区复杂地质相关的长度尺度上对地壳结构进行无混叠成像（图 1）。SEISConn 阵列穿越了许多地质地体，从其西端的劳伦岩石到其东端的阿瓦隆地体，并穿过其中部的哈特福德裂谷盆地。仪器部署和细节 图 2 显示了作为 SEISConn 实验一部分运行的地震台站地图。 SEISConn 阵列从西部的康涅狄格州莱克维尔延伸到东部的罗德岛切帕切特。选择罗德岛最东端的台站位置是为了覆盖康涅狄格州东部的查尔湖 - 蜂蜜山断层（图 2），该断层标志着阿瓦隆尼亚（东面）和其他近冈瓦纳地体（西面）之间的边界）。台站命名约定涉及图 1 中 CS01 的顺序标记。阿巴拉契亚造山带的广义岩石构造图，由 Murphy 等人修改。(2010)，在 Hibbard 等人之后。(2006)。框勾勒出康涅狄格州下方成像结构地震实验 (SEISConn) 阵列的目标区域，这提供了机会以相对相对的方式探测与许多不同地形（以及哈特福德裂谷盆地，未显示）相关的深层结构。紧凑型地震阵列。此图的彩色版本仅在电子版中提供。2 地震研究快报 www.srl-online.org • 第 XX 卷 • 第 XX 号 • – 2020 下载自 https://pubs.geoscienceworld.org/ssa/srl/article-pdf/doi/10.1785/0220200163/5086943/srl- 2020163.1.pdf 耶鲁大学用户于 2020 年 7 月 8 日从西端到东端的 CS15。阵列孔径为 150 公里，安装了 15 个站，标称站间距刚好超过 10 公里。我们部署了 Trillium 120PA 宽带地震仪，搭配 Taurus 数字化仪-数据记录器，由 Nanometrics, Inc. 制造，归耶鲁大学所有。数据以 40 Hz 采样率记录在 BHE、BHN 和 BHZ 通道上，并本地存储在紧凑型闪存卡上。我们于 2015 年 8 月开始部署仪器，并于 2015 年夏季和秋季安装了 6 个站点（CS02、CS03、CS04、CS05、CS13 和 CS14）。