Collaborative Research: A new subsurface framework for the Cascadia subduction zone derived from integrated analyses of the CASIE21 long-offset multi-channel seismic experiment

合作研究：根据 CASIE21 长偏移距多道地震实验的综合分析得出卡斯卡迪亚俯冲带的新地下框架

• 批准号: 2217466
• 负责人: Shuoshuo Han
• 金额: $ 35.43万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2217466&HistoricalAwards=false
• 关键词: Collaborative; Research; new; subsurface; framework

The Cascadia Subduction Zone in the Pacific Northwest is a region of great national interest and growing public awareness because of its high earthquake and tsunami hazard. The Cascadia margin has low levels of recorded seismicity, which reduces what is known of the properties of the earthquake zone. This project aims to identify variations in the structure and properties of the Cascadia margin to better understand the earthquake and tsunami risk to the Pacific Northwest. This project will work with other groups to build a new 3-dimensional picture for the margin. The project will support for four graduate students, two postdoctoral researchers, and three early-career scientists.From June 1 to July 11, 2021, a regional-scale multi-channel seismic study of the Cascadia Subduction Zone was collected using the state-of-the-art long-offset capabilities of the R/V Marcus G. Langseth as part of the CAscadia Seismic Imaging Experiment 2021 (CASIE21). During the expedition, 5,347 km of high quality 12-15 km streamer data were acquired in a 50-75 km spaced grid of seismic lines spanning the margin from the northern Gorda plate at 42°N to the end of subduction offshore Vancouver Island and from ~50 km seaward of the deformation front to near the coastline. This new survey represents the first regional-scale study conducted at Cascadia, spanning most of the subduction zone and filling important gaps in data coverage. This project utilizes the CASIE21 dataset in order to study nearly the whole Cascadia margin and will yield unique insights into three core questions: (1) What is the geometry of the plate interface along the margin, where is significant sediment subduction occurring, and how do plate interface properties including reflectivity and roughness vary along the margin and down dip? How do plate interface properties relate to incoming plate and upper plate structure and megathrust rupture segmentation? (2) How do the structural style and evolution of the upper plate vary along strike and how are they related to megathrust strength, backstops, and fluid migration? (3) How does the lithostratigraphic architecture of the sediment section, and structure, deformation and hydration potential of the shallow-most oceanic crust of the incoming plate associated with bend faulting, distribution of seamounts and propagator shear zones vary along the margin and how do these properties contribute to wedge evolution and megathrust rupture segmentation? This study will result in construction of a new regional-scale structural interpretation of the offshore Cascadia region from seismic images as a primary product along with select studies making use of reflectivity, velocity models, and strain analysis.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.

太平洋西北部的卡斯卡迪亚俯冲带是一个具有高度国家利益和公众意识日益增强的地区，因为卡斯卡迪亚边缘记录的地震活动水平较低，这减少了对地震带特性的了解。该项目旨在识别卡斯卡迪亚边缘的结构和特性的变化，以更好地了解太平洋西北地区的地震和海啸风险。该项目将与其他小组合作，为该边缘构建新的 3 维图像。将支持四名研究生、两名博士后研究人员和三名早期职业科学家。2021年6月1日至7月11日，使用最新状态收集了卡斯卡迪亚俯冲带的区域尺度多道地震研究-R/V Marcus G. Langseth 的艺术长偏移距能力，作为 2021 年 CAscadia 地震成像实验 (CASIE21) 的一部分，在探险期间，5,347。高质量的 12-15 公里拖缆数据是在 50-75 公里间隔的地震线网格中获取的，该网格跨越从北纬 42° 的戈尔达板块北部到温哥华岛近海俯冲结束以及从温哥华岛向海约 50 公里的地震线网格。这项新调查是在卡斯卡迪亚进行的首次区域规模研究，跨越了大部分俯冲带，填补了数据覆盖范围的重要空白。数据集旨在研究几乎整个卡斯卡迪亚边缘，并将对三个核心问题产生独特的见解：（1）沿边缘的板块界面的几何形状是什么，哪里发生显着的沉积物俯冲，以及包括反射率在内的板块界面特性如何变化和粗糙度沿边缘和下倾角变化？板块界面特性与传入板块和上部板块结构以及巨型逆冲断裂分段有何关系？（2）上部板块的结构样式和演化如何沿走向变化以及它们之间有何关系？达到巨大的推力强度， (3) 沉积物剖面的岩石地层结构以及与弯曲断层相关的最浅洋壳的结构、变形和水化潜力如何变化，海山和传播剪切带的分布沿着边缘，这些特性如何有助于楔形演化和巨型逆冲断裂分割？这项研究将根据地震图像构建新的近海卡斯卡迪亚地区的区域尺度结构解释。主要产品以及利用反射率、速度模型和应变分析的精选研究。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。