Collaborative Research - Sediment pathways, sedimentation processes, and structural growth along the Tohoku segment of the Japan subduction margin: Role of megathrust earthquakes

合作研究 - 日本俯冲边缘东北段的沉积路径、沉积过程和结构生长：巨型逆冲地震的作用

• 批准号: 1436240
• 负责人: Cecilia McHugh
• 金额: $ 11.9万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1436240&HistoricalAwards=false
• 关键词: Collaborative; Research; Sediment; pathways; sedimentation

While tectonic activity, climate, sea-level fluctuations, and anthropogenic activity are most often cited as important agents that control sediment transport and depositions, the role of earthquakes as agents of sediment dispersal and accumulation at active margins may be underappreciated. The 2011 Tohoku earthquake at the Japan Trench was one of the largest megathrust ruptures this century. Because the Japanese subduction system is exceptionally well instrumented, an unprecedented wealth of data are accumulating that document pre-seismic, co-seismic, and post-seismic conditions, providing the first opportunity to quantify environmental changes resulting from a megathrust earthquake. This project will integrate the analysis of existing sediment cores and geophysical data collected in the rupture area of the 2011 earthquake to unravel the contributions of coseismic sedimentation to the stratigraphy of the Japan Trench slope. The Japan Trench is the focus of a coordinated, long-term research program in Japan, and results from this study will contribute usefully to future investigations as well as strengthen an existing international collaboration. Japanese colleagues have already provided the Principle Investigators with recently acquired geophysical data and invited one of them to participate in two coring cruises. This project will further the development of underwater paleoseismology, an emerging field compared to land-based paleoseismology. Results from this study will be highly societally relevant as they are expected to contribute to the assessment of seismic hazards at the Japan Trench. They will also be applicable to the assessment of seismic hazards at other oceanic trenches, including three GeoPRISMS's focus sites (Cascadia, Aleutian, and New Zealand trenches) and the deep Puerto Rico Trench.The Principle Investigators have already initiated collaboration with Japanese scientists to investigate the 2011 event, due to a previously funded NSF-RAPID grant. One of the Principle Investigators participated in two sediment sampling expeditions to the Japan Trench in 2013 aboard the R/V NATSUSHIMA. The preliminary analysis of 31 piston cores collected across the trench slope suggests that some of them sampled deposits from the 2011 event and from prior events. Close inspection of multibeam bathymetric data also suggests that variations in sediment characteristics along the trench are systematically correlated with variations in the morphology of the small frontal prism, the feature at the lower trench slope that absorbs most of the tectonic deformation. This project aims to further explore these results. Specifically, the combined analysis will address the following two questions:- What are the sedimentary signatures of great earthquakes across a trench slope?- How do seafloor morphology and tectonic structures affect coseismic sediment dispersal and deposition?By analyzing the sedimentary record of past earthquakes and their relation to seafloor morphology and tectonic structures, this project will contribute simultaneously to two distinct fields of geoscience: the characterization of coseismic sedimentary processes at active margins and submarine paleoseismology.

虽然构造活动、气候、海平面波动和人类活动经常被认为是控制沉积物搬运和沉积的重要因素，但地震作为活动边缘沉积物扩散和积累因素的作用可能没有得到充分认识。2011年日本海沟东北地震是本世纪最大的大型逆冲断层之一。由于日本俯冲系统是非常好的仪器，前所未有的丰富的数据积累，记录地震前，同震，和震后的条件，提供了第一次机会，量化环境变化所造成的巨大逆冲地震。该项目将整合对现有沉积物岩心的分析和在2011年地震破裂区收集的地球物理数据，以揭示同震沉积对日本海沟斜坡地层的贡献。日本海沟是日本一个协调的长期研究计划的重点，这项研究的结果将有助于未来的调查，并加强现有的国际合作。日本同事已向主要调查员提供了最近获得的地球物理数据，并邀请其中一人参加两次取芯考察。该项目将进一步发展水下古地震学，这是一个新兴领域相比，陆基古地震学。这项研究的结果将具有高度的社会相关性，因为它们预计将有助于评估日本海沟的地震危险。它们也将适用于评估其他海沟的地震危险，包括GeoPRISMS的三个重点地点（卡斯卡迪亚、阿留申和新西兰海沟）和波多黎各海沟。2013年，其中一名主要调查员参加了在日本海沟进行的两次沉积物取样考察，他们乘坐的是R/V NATSUSHIMA。对在海沟斜坡上收集的31个活塞岩心的初步分析表明，其中一些取样来自2011年事件和以前事件的沉积物。对多波束测深数据的仔细检查还表明，沉积物特性的变化沿着海沟与小额棱柱形态的变化有系统的相关性，小额棱柱是海沟下斜坡的特征，吸收了大部分的构造变形。本项目旨在进一步探索这些结果。具体来说，综合分析将解决以下两个问题：-什么是沉积的大地震跨越沟坡？海底形态和构造结构如何影响同震沉积物扩散和沉积？通过分析过去地震的沉积记录及其与海底形态和构造结构的关系，该项目将同时对地球科学的两个不同领域作出贡献：活动边缘同震沉积过程的特征和海底古地震学。