Collaborative Research: The Mackenzie Mountains--Deformation and Structure of Active Intraplate Orogenesis from Plate Boundary to Craton

地震活跃的麦肯齐山脉是加拿大亚北极地区的一个神秘山脉，横跨育空地区和西北地区。与大多数山脉不同，麦肯齐位于离最近的（太平洋-北美）板块边界很远的地方，那里是造山应力的发源地。不知何故，压力被转移到几百英里之外相对未变形的育空地区，导致这片积极隆起的山脉与北美内陆古老而坚硬的中心地带相抗衡。该地区是北美最未勘探的地区之一，了解它是更广泛地了解整个阿拉斯加/加拿大构造系统以及它如何形成山脉（包括北美最高的山脉）和产生地震的关键。麦肯齐山脉是当今北美唯一一个活跃变形的山脉，但其内部深处的隆起风格与过去重要的造山活动有相似之处，这些造山活动形成了贯穿北美西部大部分地区的落基山脉科迪勒拉，包括美国的主要省份，落基山脉在科罗拉多州、怀俄明州和蒙大拿州。该项目将通过对深层地质和地震结构的成像，测量正在进行的地表变形，并在完整的地质背景下解释这些新数据，对该地区过去和现在的造山过程产生新的见解。为了做到这一点，科罗拉多州立大学和阿拉斯加大学的学生和教师？费尔班克斯将部署由40个宽带地震仪组成的阵列，以及3个新的连续GPS仪器，在另外25个地点进行活动调查，横贯麦肯齐山脉的荒野中心超过1000公里。该项目将与育空学院（一所两年制学院）合作进行，让本科生参与研究和实地考察，并让他们接触到新的研究机会和职业见解，这些都是育空地区和西北地区学生常见的。此外，我们将首次能够在地震活动性区域附近放置地震仪和GPS仪器，以便更好地定位活动断层区域。虽然该地区人口稀少，但了解这里的地震风险对于保护石油和天然气管道以及矿山废物蓄水池等关键基础设施至关重要。麦肯齐山脉在远离主板块边界（雅库塔地体）的一个区域内活跃变形，而板块边界与山脉之间的区域相对地震较少。麦肯齐山脉的早期隆升表明，继承的岩石圈尺度的地体边界也可能对它们的位置起作用。一个解释麦肯齐山脉异常特征的流行假说（Mazzotti和Hyndman， 2002）是，相对地震带的横向移动是沿着地壳或岩石圈尺度的拆离发生的，在雅库塔凹痕和最终与克拉通的内碰撞之间几乎没有变形。结合地震层析成像和各向异性研究，从GPS获得的地表应变约束将使我们能够测试/完善/反驳板内应力传递的假设，并比以前在这个偏远地区更详细地了解移动岩石圈和克拉通之间相互作用的几何形状和性质。本项目将测试基于这一流行模型的一些预测，涉及：粘度、岩石圈尺度结构、地壳/岩石圈尺度分离的证据、活动岩石圈和克拉通岩石圈之间的过渡、活动带和克拉通之间的应变划分、主要断层（即Tintina断层）的影响和深度范围，以及高热流与火山活动和岩石圈之间通过上地幔结构的联系。作为项目的一个组成部分，研究团队将与育空学院合作，让原住民和其他当地学生参与实地考察、研究和推广，并为该学院的学生提供地球物理职业和科学机会，并提高他们的广泛认识。我们将让阿拉斯加费尔班克斯大学的一名本科生参与实地考察，并鼓励该学生利用这些数据进行本科研究。其他更广泛的机构影响包括与加拿大，法国和澳大利亚的研究合作伙伴的联系，以及与美国地质调查局正在进行的（IRIS（地震学联合研究机构）本科生实习生相关）地震活动分析合作伙伴关系的联系，其中实习生也是最终参与该项目的研究生候选人，以及两名研究生的教育。此外，新的仪器将提供对活动断层和地震危险区域的一级约束，这对于防止工业事故及其相关的环境影响非常重要。最后，我们将把我们的表面波研究整合到我们机构的课堂材料中，并作为IRIS教育和公众推广计划的一部分向公众提供。

The seismically active Mackenzie Mountains are an enigmatic range in the Canadian Subarctic spanning the Yukon and Northwest Territories. Unlike most mountain ranges, the Mackenzies lie far away from the nearest (Pacific-North American) plate boundary where mountain-building stresses originate. Somehow, stress is being transferred for hundreds of miles across the relatively undeformed Yukon Territory to cause this actively uplifting range to fold up against the ancient and rigid heart of interior North America. This region is one of the most geophysically unexplored in all of North America, and understanding it is a key to a broader understanding of the whole Alaskan/Canadian tectonic system and how it forms mountains (including the highest in North America) and generates earthquakes. The Mackenzie Mountain range is the only actively deforming range in of its type in North America today, but its deep interior uplift style has similarities to important past mountain building events that formed the Rocky Mountain Cordillera that runs through much of the North American West, including major provinces of the U.S. Rocky Mountains in Colorado, Wyoming, and Montana. The project will produce new insight into the past and present mountain-building processes of the region by imaging the deep geological and seismic structure and measuring the ongoing surface deformation, and by interpreting these new data in a full geological context. To do this, students and faculty from Colorado State University and the University of Alaska?Fairbanks will deploy an array of forty broadband seismometers, and 3 new continuous GPS instruments augmented with campaign surveys at 25 more sites, transecting the wilderness heart of the Mackenzie Mountains for over 1000 km. This project will be undertaken in partnership with Yukon College, a two-year college, to engage undergraduates in research and fieldwork, and to expose them to new research opportunities and career insights beyond which are common for students in the Yukon and Northwest Territories. Furthermore, we will, for the first time, be able to emplace seismometers and GPS instruments near the zones of active seismicity, to better locate regions of active faulting. While this area is sparsely populated, understanding seismic risk here is essential for protecting critical infrastructure such as oil and gas pipelines and mine waste impoundments.The Mackenzie Mountains are actively deforming in a zone far inboard from the main plate boundary (Yakutat terrane), while the region between the plate boundary and the mountains is relatively aseismic. Early uplift of the Mackenzie Mountains suggests that inherited lithosphere-scale terrane boundaries may also play a role in their location. A prevailing hypothesis (Mazzotti and Hyndman, 2002) to explain the anomalous characteristics of the Mackenzie Mountains is that lateral transport in the relatively aseismic zone occurs along a crustal or lithospheric-scale detachment, with little deformation between the Yakutat indentor and the eventual inboard collision with the craton. Constraining surface strain from GPS in association with seismic tomography and anisotropy studies will enable us to test/refine/refute this hypothesis for intraplate stress transfer and to understand the geometry and nature of interaction between mobile lithosphere and the craton in much more detail than has been previously possible in this remote area. This project will test a number of predictions based on this prevailing model, related to: viscosity, lithosphere-scale structure, evidence for crustal/lithosphere scale detachment, the transition between mobile and cratonic lithosphere, the partitioning of strain between the mobile belt and craton, and the influences and depth extent of major faults (i.e., the Tintina fault), and the associations between high heat flow and volcanism and lithosphere through upper mantle structure. As an integral part of the project, the research team will partner with Yukon College to incorporate First Nations and other local students in fieldwork, research and outreach, and to contribute to geophysical career and scientific opportunities and broad awareness for students at that institution. We will involve an undergraduate student at University of Alaska Fairbanks with fieldwork and encourage the student to follow this up with undergraduate research using the data. Other institutional broader impacts include links to Canadian, French, and Australian research partners, as well as linking to an ongoing (IRIS (Incorporated Research Institutions for Seismology) undergraduate intern-associated) seismicity analysis partnership with the United State Geologic Survey, where the intern is also a possible candidate for eventual graduate student engagement in this project, and the education of two graduate students. Furthermore, the new instrumentation will provide first-order constraints on regions of active faulting and seismic hazard, important for preventing industrial accidents and their associated environmental impacts. Finally, we will integrate our surface wave research into classroom materials for use at our institutions and to be made publically available as part of an IRIS Education and Public Outreach initiative.