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横跨育空和西北地区的加拿大亚北极的一个神秘山脉。与大多数山脉不同，麦肯锡山脉远离最近的(太平洋-北美)板块边界，那里是造山压力的源头。不知何故，压力正在相对未变形的育空地区绵延数百英里，导致这一积极抬升的山脉向北美内陆古老而僵硬的心脏靠拢。这一地区是北美地球物理勘探程度最高的地区之一，了解它是更广泛地了解整个阿拉斯加/加拿大构造系统及其如何形成山脉(包括北美最高峰)并引发地震的关键。麦肯齐山脉是当今北美唯一一个活跃变形的山脉，但其深部内部隆起风格与过去形成落基山脉科迪勒拉的重要造山事件有相似之处，落基山脉科迪勒拉贯穿北美西部大部分地区，包括美国落基山脉的科罗拉多州、怀俄明州和蒙大拿州的主要省份。该项目将对该地区过去和现在的造山过程产生新的见解，方法是对深部地质和地震结构进行成像，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。为此，来自科罗拉多州立大学和阿拉斯加大学费尔班克斯分校的学生和教职员工将部署一组40个宽带地震仪，以及3台新的连续GPS仪器，并在另外25个地点进行活动调查，横穿麦肯齐山脉荒野的心脏地带超过1000公里。该项目将与育空学院合作，这是一所两年制的学院，目的是让本科生参与研究和实地考察，并使他们接触到新的研究机会和职业洞察力，这在育空地区和西北地区的学生中是常见的。此外，我们将首次能够在地震活动区附近部署地震仪和GPS仪器，以更好地定位活动断裂区域。虽然这一地区人口稀少，但了解这里的地震风险对于保护石油和天然气管道和矿山废弃库等关键基础设施至关重要。麦肯齐山脉在远离主要板块边界(雅库塔特地体)的内侧区域正在积极变形，而板块边界和山脉之间的区域相对抗震。麦肯齐山脉的早期隆起表明，继承的岩石圈规模的地体边界也可能对它们的位置起到作用。一个解释麦肯齐山脉异常特征的流行假说(Mazzotti和Hyndman，2002)认为，相对无震区的横向运移发生在地壳或岩石圈规模的拆离上，雅库塔特凹陷和最终与克拉通的内侧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来约束GPS的地表应变，将使我们能够测试/完善/驳斥这一板内应力转移假说，并比以前在这个偏远地区更详细地了解可移动的岩石圈和克拉通之间相互作用的几何和性质。该项目将检验基于这一流行模型的若干预测，这些预测涉及：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分配、主要断层(即廷蒂纳断层)的影响和深度程度，以及高热流与火山作用和岩石圈之间通过上地幔结构的联系。作为该项目不可分割的一部分，研究小组将与育空学院合作，将原住民和其他当地学生纳入实地考察、研究和外联，并为该机构的学生提供地球物理职业和科学机会以及广泛的认识作出贡献。我们将邀请阿拉斯加大学费尔班克斯大学的一名本科生进行田野调查，并鼓励该学生利用数据进行本科生研究。其他更广泛的机构影响包括与加拿大、法国和澳大利亚研究伙伴的链接，以及与美国地质调查局正在进行的(IRIS(地震联合研究机构)本科生实习生相关)地震活动分析伙伴关系的链接，其中实习生也可能是最终参与该项目的研究生的候选人，以及两名研究生的教育。此外，新仪器将对活动断层和地震危险区域提供一级约束，这对于防止工业事故及其相关的环境影响非常重要。最后，我们将把我们的面波研究整合到课堂材料中，供我们的机构使用，并作为IRIS教育和公共推广倡议的一部分公开提供。

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.