Collaborative Research: A four-dimensional view of deformation in the Eastern Alaska Range - where did the slip on the Denali fault go?

合作研究：阿拉斯加东部山脉变形的四维视图——德纳利断层上的滑动去了哪里？

基本信息

批准号：
1828023
负责人：
Jeff Benowitz
金额：
$ 10.05万
依托单位：
University of Alaska Fairbanks Campus
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-15 至 2021-01-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1828023&HistoricalAwards=false
关键词：
Collaborative Research four dimensional view

项目摘要

The Denali fault in south-central Alaska ruptured in a 7.9 magnitude earthquake in 2002, one of the largest continental strike-slip (horizontal motion of blocks of rocks past each other) earthquakes ever recorded. The event brought attention to this little-studied but major fault, which crosses the trans-Alaska oil pipeline as well as the two main highways in Alaska. Scientists predicted Denali fault earthquakes to have only strike-slip motion, but instead, the 2002 quake started as a thrust (putting one block of rock over another) earthquake and uplifted rocks in the Alaska Range along a previously unknown thrust fault. The unexpected earthquake uplift pattern provided the scientific community additional evidence that thrust faults can siphon lateral motion from the strike-slip Denali fault. If these types of fault interactions persist for millions of years, then determining the amount of thrust faulting next to the Denali fault could help solve a long-lived controversy of how much total displacement has taken place across the Denali fault and explain why the Denali fault is surrounded by large mountains on all sides (forming the Alaska Range). Unraveling the history of thrust faulting and uplift next to the Denali fault will not only help chip away at these intriguing scientific questions but will also inform how significant these faults have been in the past and where the greatest seismic hazards in the Alaska Range are today.To further understand how faults in the region may be transforming lateral slip from the Denali fault into uplift of the Alaska Range, project researchers will install 7 temporary seismometers in this area to record earthquakes and ground motion. By interpreting these seismic signals, the data can produce 3-dimensional CAT-scan type image of where the faults are in the subsurface and the root of the mountains. Project investigators will also conduct geologic mapping studies, which provide a view of where the faults are at the surface. The geologic maps, combined with 3D images of the rocks at depth, will show where major faults exist at depth and if they cut the earth's entire crust. The project will involve several types of isotopic dating methods to determine the timing and rate of motion on these faults. The age information will provide the fourth dimension to the study, time, and will show which faults have been most active in both the distant and recent past. The ultimate goal of the study is to document how faults that have thrust and strike-slip motion connect into the main Denali fault, and what role they play in uplifting the mountain range. The results are important for updating the seismic hazard potential for the oil pipeline, which survived the strike-slip earthquake without breaking but is not engineered to withstand a large thrust earthquake. This project will provide training for students in field methods and laboratory applications and the overall results will be distributed to the public through outreach talks, spoken word performances, and the creation and installation of a highway wayside interpretative sign.The modern and deep time constraints on the horizontal offset history of the Denali Fault have been shown to vary east to west over a distance of ~ 200 km, with as much as 360 km of slip "missing" in the Cenozoic. The potential that the missing slip has been taken up through crustal shortening and/or strike-slip faulting off the main strand of the fault has not been thoroughly investigated. The eastern Alaska Range has significantly thicker crust in an ancient suture zone region compared to neighboring crustal blocks. Preliminary results indicate that a significant component of this crustal thickening occurred since the Oligocene through a combination of high-angle and low-angle thrust faults. This study will test the hypothesis that crustal shortening and thickening could play a major role in reducing the strike-slip component of the Denali fault. An alternate hypothesis is that strike-slip faulting within the suture zone is the important mechanism for bleeding off the slip. Neither of these hypotheses have been fully investigated by previous researchers in this region. To address this research question, project researchers will collect and combine geologic map data, thermochronology, and seismic imaging to determine the mechanisms, timing, and extent of crustal shortening and thickening, and compare that to previously unrecognized strike-slip faulting in the southern Alaska Range suture zone. Seven broadband seismometers, which will be installed over a region of 80 by 30 km (average spacing 15-20 km), will provide a more detailed view of the crustal thickness and intra-crustal discontinuities than the EarthScope Transportable Array can provide. Low-T thermochronometry will include isotopic systems that record cooling from 400 to 65 degrees C, and when combined with sediment tracking (detrital zircons) and structural studies will provide a 4-d analysis of the region's crustal structure. These new results, integrated with existing thermochronology, geochronology, and seismic data, will yield important geologic constraints on how slip dissipates along long-lived transpressive strike-slip faults.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.

2002 年，阿拉斯加中南部的迪纳利断层在一场 7.9 级地震中破裂，这是有记录以来最大的大陆走滑（岩石块彼此水平运动）地震之一。这一事件引起了人们对这一鲜为人知的重大断层的关注，该断层横跨跨阿拉斯加石油管道以及阿拉斯加的两条主要高速公路。科学家预测德纳利断层地震仅具有走滑运动，但相反，2002 年的地震始于逆冲（将一块岩石置于另一块岩石之上）地震，并沿着先前未知的逆冲断层抬升了阿拉斯加山脉的岩石。意外的地震隆起模式为科学界提供了额外的证据，证明逆冲断层可以从走滑德纳利断层虹吸横向运动。如果这些类型的断层相互作用持续数百万年，那么确定德纳里断层附近的逆冲断层数量可能有助于解决长期存在的争议，即跨越德纳利断层发生了多少总位移，并解释了为什么德纳利断层会出现。四面被大山包围（形成阿拉斯加山脉）。解开德纳利断层附近的逆冲断层和隆起的历史不仅有助于解决这些有趣的科学问题，而且还将了解这些断层在过去的重要性以及今天阿拉斯加山脉最大的地震危险在哪里。为了进一步了解该地区的断层如何将德纳里断层的横向滑动转变为阿拉斯加山脉的隆起，项目研究人员将在该地区安装 7 个临时地震仪来记录地震和地面运动。通过解释这些地震信号，数据可以生成断层在地下和山根位置的 3 维 CAT 扫描类型图像。项目研究人员还将进行地质测绘研究，以了解断层在地表的位置。地质图与深层岩石的 3D 图像相结合，将显示深层主要断层的位置以及它们是否切割了整个地壳。该项目将涉及多种同位素测年方法，以确定这些断层运动的时间和速率。年龄信息将为研究提供第四个维度——时间，并将显示哪些断层在遥远的和最近的过去最活跃。该研究的最终目标是记录具有逆冲和走滑运动的断层如何连接到主要的德纳里断层，以及它们在抬升山脉方面发挥的作用。这些结果对于更新石油管道的地震危险潜力非常重要，该石油管道在走滑地震中幸存下来而没有破裂，但其设计不能承受大的逆冲地震。该项目将为学生提供现场方法和实验室应用方面的培训，总体成果将通过外展讲座、口语表演以及高速公路路边解释标志的制作和安装等方式向公众发布。德纳利断层的水平偏移历史已被证明从东到西的变化距离约为 200 公里，在新生代“缺失”了多达 360 公里的滑动。通过地壳缩短和/或断层主链的走滑断层作用来弥补缺失滑移的可能性尚未得到彻底研究。与邻近的地壳块相比，阿拉斯加山脉东部的古代缝合带区域的地壳明显更厚。初步结果表明，自渐新世以来，地壳增厚的一个重要组成部分是通过高角度和低角度逆冲断层的组合发生的。这项研究将检验地壳缩短和增厚可能在减少德纳利断层走滑分量方面发挥重要作用的假设。另一种假设是缝合带内的走滑断层是导致滑移的重要机制。该地区之前的研究人员尚未对这两个假设进行充分研究。为了解决这个研究问题，项目研究人员将收集并结合地质图数据、热年代学和地震成像，以确定地壳缩短和增厚的机制、时间和程度，并将其与阿拉斯加南部以前未被识别的走滑断层作用进行比较范围缝合区。七个宽带地震仪将安装在 80 x 30 公里（平均间距 15-20 公里）的区域内，将提供比 EarthScope 可移动阵列更详细的地壳厚度和地壳内不连续性视图。低温度测温法将包括记录从 400 到 65 摄氏度冷却的同位素系统，与沉积物追踪（碎屑锆石）和结构研究相结合，将提供该地区地壳结构的 4 维分析。这些新结果与现有的热年代学、地质年代学和地震数据相结合，将对滑动如何沿着长期的压性走滑断层消散产生重要的地质约束。该奖项反映了 NSF 的法定使命，并通过使用评估结果被认为值得支持。基金会的智力价值和更广泛的影响审查标准。

项目成果

期刊论文数量（7）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Long distance plutonic relationships demonstrate 33 million years of strain partitioning along the Denali fault

长距离深成关系证明了德纳里断层沿线 3300 万年的应变分配

DOI：
10.1111/ter.12555
发表时间：
2021-12
期刊：
Terra Nova
影响因子：
2.4
作者：
Regan, Sean P.;Benowitz, Jeffrey A.;Waldien, Trevor S.;Holland, Mark E.;Roeske, Sarah M.;O’Sullivan, Paul;Layer, Paul
通讯作者：
Layer, Paul

Tectonic Underplating and Dismemberment of the Maclaren‐Kluane Schist Records Late Cretaceous Terrane Accretion Polarity and ~480 km of Post‐52 Ma Dextral Displacement on the Denali Fault

Maclaren-Kluane 片岩的构造底侵和肢解记录了白垩纪晚期地体增生极性和德纳利断层上约 480 公里的后 52 Ma 右旋位移

DOI：
10.1029/2020tc006677
发表时间：
2021-10
期刊：
Tectonics
影响因子：
4.2
作者：
Waldien, T. S.;Roeske, S. M.;Benowitz, J. A.
通讯作者：
Benowitz, J. A.

Oligocene-Neogene lithospheric-scale reactivation of Mesozoic terrane accretionary structures in the Alaska Range suture zone, southern Alaska, USA

美国阿拉斯加州南部阿拉斯加山脉缝合带中生代地体增生结构的渐新世-新近纪岩石圈规模再激活

DOI：
10.1130/b35665.1
发表时间：
2020-08
期刊：
GSA Bulletin
影响因子：
0
作者：
Waldien, Trevor S.;Roeske, Sarah M.;Benowitz, Jeffrey A.;Twelker, Evan;Miller, Meghan S.
通讯作者：
Miller, Meghan S.

Cenozoic tectono-thermal history of the southern Talkeetna Mountains, Alaska: Insights into a potentially alternating convergent and transform plate margin

阿拉斯加塔尔基特纳山脉南部的新生代构造热历史：洞察潜在的交替聚合和转变板块边缘