Collaborative Research: The Tectonic and Magmatic Structure and Dynamics of Back-arc Rifting in Bransfield Strait: An International Seismic Experiment

合作研究：布兰斯菲尔德海峡的构造和岩浆结构以及弧后裂谷动力学：一项国际地震实验

• 批准号: 1744651
• 负责人: William Wilcock
• 金额: $ 51.07万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1744651&HistoricalAwards=false
• 关键词: Collaborative; Research; Tectonic; Magmatic; Structure

One of the fundamental processes in plate tectonics is the rifting or separating of continental crust creating new seafloors which can widen and ultimately form new ocean basins, the latter is a process known as seafloor spreading. The Bransfield Strait, separating the West Antarctic Peninsula from the South Shetland Islands, formed and is presently widening as a result of the separation of continental crust. What is unique is that the system appears to be approaching the transition to seafloor spreading making this an ideal site to study the transitional process. Previous seafloor mapping and field surveys provide the regional structure of the basin; however, there exists a paucity of regional seismic studies documenting the tectonic and volcanic activity in the basin as a result of the rifting. This would be the first local-scale study of the seismicity and structure of the volcanoes in the center of the basin where crustal separation is most active. The new seismic data will enable scientists to compare current patterns of crustal separation and volcanism at the Bransfield Strait to other well-studied seafloor spreading centers. This collaborative international project, led by the Spanish and involving scientists from the U.S., Germany and other European countries, will monitor seismicity for one year on land and on the seafloor. An active seismic study conducted by the Spanish will image fault and volcanic structures that can be related to the distribution of earthquakes. This study supports eight undergraduates from Queens College, CUNY, an ethnically-diverse institution, to conduct field work as members of the scientific party on board the R/V Hesperides and will contribute to the analysis of the data.Back-arc basins are found in subduction settings and form in two stages, an initial interval of continental rifting that transitions to a later stage of seafloor spreading. Studying the transitional process is important for understanding the dynamics and evolution of subduction zones, and in locations where back-arc rifting breaks continental crust, it is relevant to understanding the formation of passive continental margins. The Central Bransfield Basin is unusual in that the South Shetland Islands have lacked recent arc volcanism and it appears subduction is ceasing, but this system has broad significant because it appears to be nearing the transition from rifting to seafloor spreading. This award will support the U.S. component of an international initiative led by the Spanish Polar Committee to conduct a study of the seismicity and volcanic structure of the Central Bransfield Basin. The objective is to characterize the distribution of active extension across the basin and determine whether the volcanic structure and deformation of the rift are consistent with a back-arc basin that is transitioning from rifting to seafloor spreading. The U.S. component of the experiment will contribute a network of six hydroacoustic moorings to monitor regional seismicity and 15 short-period seismometers to study the distribution of tectonic and volcanic seismicity on Orca volcano, one of the most active volcanoes in the basin. An active seismic study across closely spaced multichannel seismic lines across the rift will provide the data necessary to link earthquakes with fault structures enabling a tomography study of Orca volcano and provide insight into how the volcano's structure relates to rifting. This research will constrain the distribution of active rifting across the Central Bransfield Basin and determine whether the patterns of faulting and the structure of volcanic portion of the rift are consistent with a diffuse zone of rifting or a single spreading center that is transitioning to the production of oceanic crust. The Bransfield Basin is an ideal site for a comparative study of seismic and hydroacoustic earthquake locations that will improve the understanding of the generation and propagation of T-wave signals and contribute to efforts to compare the result of T-wave studies with data from traditional solid-earth seismic studies.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.

板块构造的基本过程之一是大陆地壳的裂谷或分离，形成新的海底，新的海底可以扩大并最终形成新的海洋盆地，后者是一个称为海底扩张的过程。布兰斯菲尔德海峡将西南极半岛与南设得兰群岛分隔开来，由于大陆地壳分离而形成，目前正在扩大。独特之处在于该系统似乎正在接近向海底扩张的过渡，这使得这里成为研究过渡过程的理想场所。之前的海底测绘和实地调查提供了该盆地的区域结构；然而，记录盆地因裂谷而发生的构造和火山活动的区域地震研究却很少。这将是对地壳分离最活跃的盆地中心火山的地震活动和结构的首次局部规模研究。新的地震数据将使科学家能够将布兰斯菲尔德海峡当前的地壳分离和火山活动模式与其他经过充分研究的海底扩张中心进行比较。这个国际合作项目由西班牙牵头，由来自美国、德国和其他欧洲国家的科学家参与，将监测陆地和海底的地震活动为期一年。西班牙进行的一项主动地震研究将对可能与地震分布相关的断层和火山结构进行成像。这项研究支持来自纽约市立大学皇后学院（一个种族多元化的机构）的八名本科生作为科学小组成员在 R/V Hesperides 上进行实地工作，并将为数据分析做出贡献。发现了弧后盆地在俯冲环境中并以两个阶段的形式形成，大陆裂谷的初始阶段过渡到海底扩张的后期阶段。研究过渡过程对于了解俯冲带的动力学和演化具有重要意义，而在弧后裂谷破坏大陆地壳的位置，它对于了解被动大陆边缘的形成具有重要意义。中部布兰斯菲尔德盆地的不同寻常之处在于，南设得兰群岛最近没有弧火山活动，而且俯冲似乎正在停止，但该系统具有广泛的意义，因为它似乎正接近从裂谷到海底扩张的过渡。该奖项将支持美国参与由西班牙极地委员会领导的一项国际倡议，对布兰斯菲尔德盆地中部的地震活动和火山结构进行研究。目的是表征整个盆地的活动伸展分布，并确定裂谷的火山结构和变形是否与从裂谷过渡到海底扩张的弧后盆地一致。该实验的美国部分将提供一个由六个水声系泊装置组成的网络，用于监测区域地震活动，并提供 15 个短周期地震仪，用于研究奥卡火山（该盆地最活跃的火山之一）的构造和火山地震活动的分布。对横跨裂谷的间隔紧密的多道地震线进行主动地震研究，将提供将地震与断层结构联系起来所需的数据，从而能够对奥卡火山进行层析成像研究，并深入了解火山结构与裂谷的关系。这项研究将限制布兰斯菲尔德盆地中部活跃裂谷的分布，并确定断层活动模式和裂谷火山部分的结构是否与裂谷扩散区或正在过渡到生产的单一扩张中心一致。洋壳。布兰斯菲尔德盆地是对地震和水声地震位置进行比较研究的理想地点，这将提高对 T 波信号的产生和传播的理解，并有助于将 T 波研究结果与传统固体数据进行比较-地球地震研究。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

BRAVOSEIS: Geophysical investigation of rifting and volcanism in the Bransfield strait, Antarctica

BRAVOSEIS：南极洲布兰斯菲尔德海峡裂谷和火山活动的地球物理调查

• DOI: 10.1016/j.jsames.2020.102834
• 发表时间: 2020-12
• 期刊: Journal of South American Earth Sciences
• 影响因子: 1.8
• 作者: Almendros, J.;Wilcock, W.;Soule, D.;Teixidó, T.;Vizcaíno, L.;Ardanaz, O.;Granja;Martín;Yuan, X.;Heit, B.;et al
• 通讯作者: et al