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断裂或分离，产生新的海底，这些海底可以加宽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。将西南极半岛与南设得兰群岛分开的布兰斯菲尔德海峡，由于大陆地壳的分离而形成，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，使其成为研究过渡过程的理想场所。以前的海底测绘和实地调查提供了盆地的区域结构;但是，缺乏区域地震研究，记录裂谷作用造成的盆地构造和火山活动。这将是首次对地壳分离最活跃的盆地中心的地震活动和火山结构进行局部规模的研究。新的地震数据将使科学家能够将布兰斯菲尔德海峡目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人领导，美国科学家也参与其中，德国和其他欧洲国家将在一年内监测陆地和海底的地震活动。西班牙进行的一项活跃的地震研究将对可能与地震分布有关的断层和火山结构进行成像。这项研究支持了来自纽约市立大学皇后学院的八名本科生，作为R/V Hesperides上的科学小组成员进行实地考察，并将有助于分析数据。弧后盆地被发现在俯冲环境中，并形成两个阶段，大陆裂谷的初始间隔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非常重要，在弧后裂谷作用使大陆地壳断裂的地方，这与了解被动大陆边缘的形成有关。中央布兰斯菲尔德盆地是不寻常的，因为南设得兰群岛没有最近的弧火山活动，它似乎正在停止俯冲，但这个系统具有广泛的意义，因为它似乎是接近从裂谷到海底扩张的过渡。该奖项将支持由西班牙极地委员会领导的一项国际倡议的美国组成部分，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。其目的是确定整个盆地活动伸展的分布特征，并确定裂谷的火山结构和变形是否与从裂谷向海底扩张过渡的弧后盆地相一致。该实验的美国部分将提供一个由六个水声系泊系统组成的网络，以监测区域地震活动，并提供15个短周期地震仪，以研究该盆地最活跃的火山之一Orca火山的构造和火山地震活动的分布。横跨裂谷的密集多通道地震线的主动地震研究将提供必要的数据，将地震与断层结构联系起来，从而能够对奥卡火山进行断层扫描研究，并深入了解火山结构与裂谷的关系。这项研究将限制整个中央布兰斯菲尔德盆地的活动裂谷的分布，并确定断裂模式和裂谷火山部分的结构是否与裂谷的扩散区或单一扩张中心过渡到洋壳的生产相一致。布兰斯菲尔德盆地是比较研究地震和水声地震位置的理想场所，这将提高对T波信号产生和传播的理解，并有助于将T波研究结果与传统固体地震数据进行比较。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，被认为值得支持和更广泛的影响审查标准。

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

• 发表时间: 2020
• 期刊: Journal of South American earth sciences
• 影响因子: 1.8
• 作者: Alemendros, J.;Wilcock, W.S.D.;Soule, D.;Teixido, T.;Vizcaino, L.;Ardazaz, O.;Granja-Bruña, J. L.;Martin-Jimenez, D.;Yuan, X.;Heit, B.
• 通讯作者: Heit, B.