Collaborative Research: Causes and Mechanisms of Focused Exhumation Along the Denali Fault, Eastern Alaska Range

合作研究：阿拉斯加东部德纳利断层沿线集中折返的原因和机制

• 批准号: 0952800
• 负责人: Paul Fitzgerald
• 金额: $ 13.99万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-02-01 至 2013-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0952800&HistoricalAwards=false
• 关键词: Collaborative; Research; Causes; Mechanisms; Focused

The 1,200 km long Alaskan Denali Fault system is a major intra-continental right-lateral strike-slip fault system. Since the 2002 Denali earthquake (magnitude 7.9), which initiated along a previously undescribed thrust fault in the eastern Alaska Range, scientists have increasingly focused on how much slip and convergence occurs along this fault system, and where deformation is being accommodated. Mountainous terrain and basins have formed along the Denali fault and the locations and age of formation of these features can be used to constrain the distribution of crustal deformation through time. The eastern Alaska Range, the topographic signature of the eastern Denali Fault, rises dramatically from the tundra (about 200 meters) to sharp glaciated peaks (about 4,000 meters), forming a narrow but high-relief region immediately north of the fault. As the fault continues west, the topography drops significantly, then rises again to form the central Alaska Range, home to Mt. McKinley and Denali National Park. Uplift of the Alaska Range is related to plate tectonic processes associated with subduction and accretion along Alaska's southern margin, but why the uplift is focused along the fault in the eastern Alaska Range is not clear. This research project seeks to understand the thermal history of rocks in the eastern Alaska Range and hence place constraints on regional patterns of exhumation and uplift through time. This will allow evaluation of the relative importance of near-field boundary conditions versus far-field driving forces. The research team is conducting a high-resolution multi-technique thermochronological approach combined with macro-and microstructural work along the eastern Denali Fault. This approach will document variations in exhumation rates during the last 30 million years to understand exhumation patterns in the mountains. Structural studies are focused on the regions with the most extreme exhumation, both in terms of rate and total amount, to understand what controls these patterns. Linking the structural history to exhumation rates will permit the temporal and spatial influence of geodynamic drivers such as changes in Pacific versus North America plate motion, dip of the subducting slab, and the collision of buoyant Yakutat block at the eastern edge of the subduction zone to be evaluated. This study has relevance to fundamental problems of major strike-slip fault systems, including what causes localized exhumation and how strike-slip deformation is transferred into the lower crust. Results will contribute to earthquake hazard prediction in this region by constraining locations of high neotectonic deformation, variations in Denali fault geometry and identification of reverse faults. A better understanding of contributing factors for seismic behavior along the Denali Fault will benefit seismic hazard maps. The Trans-Alaska oil pipeline and future 26 billion dollar Alaska gas pipeline cross the eastern Alaska Range and Denali fault. The pipeline is designed to withstand strike-slip motion, but if the there is a significant dip-slip component the effects could be disastrous.

全长1200公里的阿拉斯加迪纳利断层系是主要的陆内右旋走滑断层系。自 2002 年德纳利地震（7.9 级）沿阿拉斯加山脉东部一条先前未描述过的逆冲断层发生以来，科学家们越来越关注沿该断层系统发生了多少滑动和汇聚，以及在何处适应变形。沿迪纳利断层形成了山地和盆地，这些特征的位置和形成年龄可用于约束地壳变形随时间的分布。阿拉斯加东部山脉是德纳里断层东部的地形特征，从苔原（约 200 米）急剧上升到尖锐的冰川山峰（约 4,000 米），在断层以北形成一个狭窄但地势较高的区域。随着断层继续向西延伸，地势显着下降，然后再次上升，形成阿拉斯加山脉中部，是麦金利山和德纳利国家公园的所在地。阿拉斯加山脉的隆起与阿拉斯加南缘的俯冲和增生相关的板块构造过程有关，但为什么隆起集中在阿拉斯加山脉东部的断层上尚不清楚。该研究项目旨在了解阿拉斯加山脉东部岩石的热历史，从而限制随时间推移的区域折返和隆起模式。这将允许评估近场边界条件与远场驱动力的相对重要性。研究小组正在沿德纳利断层东部开展高分辨率多技术热年代学方法，并结合宏观和微观结构工作。这种方法将记录过去 3000 万年的折返率变化，以了解山区的折返模式。结构研究主要集中在折返率和总量方面最极端的区域，以了解控制这些模式的因素。将构造历史与折返率联系起来将允许地球动力学驱动因素的时间和空间影响，例如太平洋与北美板块运动的变化、俯冲板块的倾角以及俯冲带东缘的浮力雅库塔地块的碰撞，以进行评估。这项研究与主要走滑断层系统的基本问题相关，包括导致局部折返的原因以及走滑变形如何转移到下地壳中。通过限制高新构造变形的位置、德纳里断层几何形状的变化以及反向断层的识别，结果将有助于该地区的地震灾害预测。更好地了解德纳利断层沿线地震行为的影响因素将有助于绘制地震灾害地图。跨阿拉斯加石油管道和未来价值 260 亿美元的阿拉斯加天然气管道穿越阿拉斯加山脉东部和德纳利断层。管道的设计能够承受走滑运动，但如果存在显着的倾滑运动，其影响可能是灾难性的。