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

阿拉斯加德纳里断裂系统长1200公里，是一个主要的大陆内右旋走滑断裂系统。2002年的德纳里地震（里氏7.9级）起源于阿拉斯加山脉东部的一条先前未被描述过的逆冲断层，自那以来，科学家们越来越关注沿着这条断层系统发生了多少滑动和收敛，以及在哪里可以容纳变形。德纳里断裂带沿线形成了多山地形和盆地，这些特征的形成位置和年代可以用来约束地壳变形的时空分布。东阿拉斯加山脉是东德纳里断裂带的地形特征，它从苔原（约200米）急剧上升到尖锐的冰川山峰（约4000米），在断裂带的北面形成了一个狭窄但地势高的地区。随着断层继续向西延伸，地形明显下降，然后再次上升，形成阿拉斯加山脉中部，麦金利山和德纳里国家公园的所在地。阿拉斯加山脉的隆升与板块构造过程有关，板块构造过程与阿拉斯加南缘的俯冲和增生有关，但为什么隆升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，从而对挖掘和隆升的区域模式施加限制。这将允许评估近场边界条件与远场驱动力的相对重要性。研究小组正在沿着迪纳利断层东部进行高分辨率的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3000万年中挖掘率的变化，以了解山区的挖掘模式。结构研究的重点是在开掘率和开掘总量上最极端的地区，以了解是什么控制了这些模式。将构造历史与挖掘速度联系起来，可以评估地球动力学驱动因素的时空影响，如太平洋板块与北美板块运动的变化、俯冲板块的倾斜以及俯冲带东部边缘浮力雅库特块体的碰撞。本研究涉及主要走滑断层系统的基本问题，包括局部掘出的原因以及走滑变形如何转移到下地壳。研究结果将有助于该区新构造高变形位置、迪纳里断裂几何形态变化和逆断层识别等方面的地震危险性预测。更好地了解迪纳里断裂带地震行为的影响因素将有助于绘制地震危险图。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里断层。该管道的设计是为了承受走滑运动，但如果存在显著的倾滑成分，其影响可能是灾难性的。

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.