Collaborative Research: Geophysical Study of Ongoing Subduction Initiation Along the Matthew-Hunter Trench

合作研究：沿马修-亨特海沟持续俯冲起始的地球物理研究

• 批准号: 2228413
• 负责人: Douglas Wiens
• 金额: $ 53.5万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-11-15 至 2027-10-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2228413&HistoricalAwards=false
• 关键词: Collaborative; Research; Geophysical; Study; Ongoing

Subduction, where one plate plunges downward beneath another plate and produces a volcanic arc on the overriding plate, is a fundamental component of plate tectonics. However, there is little understanding of how subduction begins, largely because there have been no observations of this process happening at the present time. Recent studies show that subduction is just beginning along the Matthew and Hunter Trench, between Vanuatu, New Caledonia, and Fiji in the South Pacific. This project will conduct a pair of scientific cruises to the Matthew-Hunter Subduction Zone to deploy and recover ocean bottom seismographs, as well as gather marine geophysical datasets. The seismic data will be used to image the downgoing plate and magma source regions beneath volcanoes. The cruises will also map the seafloor and make gravity and magnetic measurements that will provide evidence concerning tectonic structures, volcanism, crustal deformation, and ages of subduction initiation processes. This project will be carried out in collaboration with scientists from France and New Caledonia. Subduction initiation may be the most enduring question in terrestrial geodynamics. Most knowledge of subduction initiation comes from the study of past initiation events where some of the volcanic products have been preserved. The lack of present-day examples of subduction initiation that include the classic sequence of forearc magmatism limits the understanding of how these processes occur. However, recent studies show that subduction initiation with accompanying magmatic activity is occurring along the Matthew and Hunter Trench between the New Hebrides Trench and the Fiji Platform. The Matthew-Hunter Subduction Zone thus offers a unique opportunity to study a young subduction zone in the process of formation but sufficiently advanced to create magmatic products. This project will deploy an array of 25 passive ocean bottom seismographs (20 US and 5 French) and carry out a marine geophysical survey to define the slab geometry, seismicity, structure, and mantle flow patterns associated with this developing subduction zone. The seismographs will be deployed along lines to be shot by a collaborative French cruise to take advantage of shallow structure constraints, and the array is designed to image the structure of the forearc, the volcanic Hunter Ridge, and the extensional Monzier Rift. Seismic data will be analyzed using Rayleigh wave tomography from ambient noise and earthquakes, body wave tomography, and shear wave splitting. In addition, an extensive multibeam bathymetric, acoustic backscatter imagery, gravity and magnetic survey will be carried out to identify tectonic structures, regions of recent seafloor volcanism, and magnetic isochrons. Geophysical track spacing will be sufficiently dense to fully map the forearc area and carry out three-dimensional geophysical inversions over the same regions as the main seismograph deployment. This combination of near surface and coincident deeper crustal and mantle imaging will provide powerful constraints for understanding subduction initiation. This project will be carried out in collaboration with investigators from IFREMER and New Caledonia, who have proposed a French cruise currently awaiting scheduling to collect active source seismic data as well as heat flow and fluid samples.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.

俯冲是一个板块向下坠落在另一板下方，并在覆盖板上产生火山弧，是板块构造的基本组成部分。但是，对俯冲的开始几乎没有理解，这主要是因为目前没有观察到这一过程。最近的研究表明，俯冲才始于瓦努阿图，新喀里多尼亚和南太平洋斐济之间的马修和猎人沟。该项目将进行一对科学巡游，前往马修·亨特（Matthew-Hunter）俯冲带，以部署和恢复海洋底部地震仪，并收集海洋地球物理数据集。地震数据将用于图像火山下的下板和岩浆源区域。巡航还将绘制海底，并进行重力和磁性测量，以提供有关构造结构，火山主义，地壳变形以及俯冲起始过程年龄的证据。该项目将与法国和新喀里多尼亚的科学家合作进行。俯冲启动可能是陆地地球动力学中最持久的问题。大多数关于俯冲启动的知识来自对一些火山产品的过去开始事件的研究。俯冲启动的当今示例缺乏包括前臂岩浆的经典序列的限制限制了对这些过程的发生的理解。然而，最近的研究表明，在新的赫布里德斯沟渠和斐济平台之间的马修和猎人沟中，俯冲启动随附随附的岩浆活动。因此，马修·亨特（Matthew-Hunter）的俯冲带提供了一个独特的机会，可以在形成过程中研究年轻的俯冲带，但足够先进以创建岩浆产品。该项目将部署25个被动海洋底部地震仪（20美国和5个法国），并进行海洋地球物理调查，以定义与该发展屈服区相关的板几何，地震性，结构和地幔流动模式。地震仪将沿线部署，以通过协作的法国巡游来拍摄，以利用浅层结构的限制，并且该阵列旨在成像前臂的结构，火山猎人的猎人岭和扩展的Monzier Rift。地震数据将使用来自环境噪声和地震，人体波断层扫描和剪切波分裂的雷利波断层扫描进行分析。此外，将进行广泛的多微光测深，声学反向散射图像，重力和磁调查，以识别构造结构，近期海底火山剂的区域和磁性等音线。地球物理轨道间距将足够致密，可以完全绘制前臂区域，并在与主要地震仪的同一区域上进行三维地球物理反转。近表面和更深层地壳和地幔成像的这种结合将为理解俯冲启动提供强大的限制。该项目将与Ifremer和New Caledonia的调查人员合作进行，他们提议法国巡游目前正在等待安排收集积极的来源地震数据以及热流和流体样品。这奖反映了NSF的法定任务，并认为通过基金会的知识优点和广泛的crietia crietia crietia criperia criperia cribitia cribitia criperia criperia criperia cribitia recectia recectia rection rectuniation。