Collaborative Research: Relationship between plate boundary obliquity, strain accommodation, and fault zone geometry at oceanic-continental transforms: The Queen Charlotte Fault

合作研究：洋-陆转换时板块边界倾斜度、应变调节和断层带几何形状之间的关系：夏洛特皇后断层

• 批准号: 1824165
• 负责人: Emily Roland
• 金额: $ 39.76万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2021-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1824165&HistoricalAwards=false
• 关键词: Collaborative; Research; Relationship; between; plate

Often called the "San Andreas of the North", the Queen Charlotte fault (QCF) system is a strike-slip plate boundary that separates the Pacific and North American tectonic plates offshore western Canada and Southeast Alaska. The QCF is arguably the most active fault of its type in the world: the entire ~900 km offshore length has ruptured in seven M7 earthquakes during the last century and it sustains the highest known deformation rates (50 mm/yr). The fault system represents the largest seismic hazard to southeastern Alaska and Canada outside of Cascadia, and caused Canada?s largest recorded earthquake (M8.1) in 1949. Despite rapid response efforts following M7 earthquakes in 2012 and 2013, first-order questions regarding how the fault system deforms and the processes controlling fault failure during earthquakes remain unanswered due to the lack of modern geophysical imaging. This experiment will be the first comprehensive attempt to characterize this plate boundary at depth on a regional scale. Using seismic energy from marine acoustic and earthquake sources, the project will measure the depth and extent of seismicity, image the fault zone at depth, and determine velocity and thermal structure across the fault. All these data will lead to an improved understanding of this, and other major strike-slip fault systems, for better hazard assessment and earthquake forecasting. The science team is a collaborative, international group of US and Canadian researchers, led by three early-career women. Outreach to local communities will be conducted through a residency at the Sitka Science Center in Alaska and lectures at local high schools and community centers. Compared to convergent continental-oceanic plate boundaries, the time-space evolution of continental-oceanic transform margins is understudied, despite their important role in the planet?s plate tectonic system. Continental-oceanic transform faults are potentially one of the most favorable tectonic settings for subduction initiation due to the juxtaposition of lithospheres of contrasting density and thermal structure -- small degrees of convergence can lead to failure. The QCF system provides an ideal location to investigate how a continental-oceanic transform fault responds to systematically increasing degrees of convergence at the lithospheric scale. The study area includes two potential fault segment boundaries that mark abrupt changes in transpressive deformation mechanisms as suggested by changes in seafloor morphology and shallow seismic reflection structure: strain partitioning and underthrusting in the south transition to highly localized strike-slip deformation in the north. Lack of information on microseismic depths and locations, the deformation history and geometries of faults at depth, and lithospheric velocity structure leave multiple fundamental questions unanswered: Why has the QCF formed where it is, and what is its deformation history? What is the history of PAC underthrusting along the margin and the fate of underthrust material north of the area of maximum convergence? What are the primary physical conditions controlling seismogenesis along oceanic-continental transforms? How are strike-slip and compressive strain accommodated and partitioned over geologic and seismogenic timescales? Using a combined active- and passive-source marine seismic imaging strategy, this research will characterize crustal and uppermost mantle velocity structure, fault zone architecture and rheology, and seismicity. Data will be acquired using long-offset 2D seismic reflection and wide-angle reflection-refraction capabilities of the R/V Marcus G. Langseth and a combined US-Canadian broadband ocean bottom seismometer array of 64 instruments deployed for ~1 year.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.

夏洛特皇后断层（QCF）系统通常被称为“北部的圣安德烈亚斯”，是一个滑雪板边界，将太平洋和北美构造板板分开，加拿大西部和阿拉斯加东南部。 QCF可以说是世界类型中最活跃的断层：上个世纪，整个〜900公里的近海长度在7台M7地震中破裂，并且具有最高已知的变形率（50 mm/yr）。断层系统代表了卡斯卡迪亚以外对阿拉斯加东南部和加拿大的最大地震危险，并在1949年引起了加拿大最大的记录地震（M8.1）。尽管在2012年和2013年M7地震后，迅速的响应努力，但有关在现代遇到的无效的地震中，由于M7地震在2012年和2013年的第一阶问题仍在控制地球上的缺陷失败以及如何控制地球上的缺陷。该实验将是在区域尺度上以深度表征该板块边界的首次全面尝试。使用来自海洋声学和地震来源的地震能量，该项目将测量地震性的深度和程度，图像深度处的断层区域，并确定跨断层的速度和热结构。所有这些数据将导致对此以及其他主要的滑移断层系统的理解，以获得更好的危害评估和地震预测。科学团队是由三名早期职业妇女领导的美国国际团体和加拿大研究人员。将通过阿拉斯加的Sitka科学中心的居住和当地高中和社区中心的讲座进行宣传。与收敛的大陆环境板边界相比，尽管它们在行星板块构造系统中的重要作用，但大陆 - 海洋转化边缘的时空演变仍在研究中。大陆 - 海洋转化断层可能是由于岩石圈的对比密度和热结构并列的最有利的构造设置之一 - 趋同的岩石圈 - 收敛的小程度可能会导致失败。 QCF系统提供了一个理想的位置，以研究大陆环境变换断层如何响应岩石圈尺度下系统地增加的收敛程度。研究区域包括两个潜在的断层段边界，标志着海底形态的变化和浅层地震反射结构的变化所暗示的转染变形机制的突然变化：在南部向北部高度局部的射击滑移变形的南部过渡中的应变分配和张力。缺乏有关微作用深度和位置的信息，深度处的断层的变形历史和几何形状以及岩石圈速度结构留下多个基本问题：为什么QCF形成在哪里，以及其变形史是什么？ PAC在最大收敛范围以北的边缘和估价物质的命运沿线和命运的历史是什么？沿着海洋 - 国际变换控制地震生成的主要物理条件是什么？ 滑滑和压缩应变如何在地质和地震生成时间范围内划分？该研究使用积极的和被动的海洋地震成像策略，将表征地壳和最高地幔速度结构，断层区域结构和流变学以及地震性。 R/V Marcus G. Langseth和美国加拿大的美国加拿大宽带海洋底部地震仪阵列的共同奖励，这些奖项均表现出NSF的合法遗留，将使用NSSF的法定任务和范围，将使用NSSF的法定任务和众多，将使用R/V Marcus G. Langseth的r/v Marcus G. Langseth和共同的64个乐器的综合奖励，这些奖项反映了NSF的合法传教士，该奖项均通过评估了，该奖项均通过评估了，该奖项均表现出智力的范围，并反映了NSF的合法任务，将使用NSSF的法定任务和范围的范围，将使用长期的2D地震反射和广角反射 - 拨款功能获取数据。 标准。