How do faults grow above dykes?

断层是如何在堤坝上方生长的？

• 批准号: NE/R014086/1
• 负责人: Craig Magee
• 金额: $ 65.39万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FR014086%2F1
• 关键词: How; do; faults; grow; above

Magma travels through Earth's crust to the surface, where it erupts at volcanoes, along vertical paths that have a sheet-like shape (dykes). When dykes are injected, either vertically or laterally, they fracture and push apart the surrounding rock, producing small earthquakes. Continued dyke injection causes fractures to develop into faults, where rock on one side of the crack starts to slip passed the other. Fault slip can pull down and extend or push up rock directly above the dyke, sometimes deforming Earth's surface. Monitoring earthquakes and ground deformation generated by dyke-induced faults can therefore tell us where dykes are injecting, providing us warning of possible eruptions. Studies of injecting dykes and dyke-induced faulting in Ethiopia show that they can also aid continent fragmentation, although these structures have yet to be found along the margins of continents where break-up once occurred. In addition, satellite images of planets (e.g. Mars) indicate that dyke-induced faults deform their surface. It is thus clear that dyke injection and dyke-induced faulting plays and has played a major role in shaping the volcanic and/or tectonic history and surface morphology of Earth and other planets. To understand how dykes and dyke-induced faults control different volcanic, tectonic, and planetary processes, we first need to identify how faults grow above dykes in three-dimensions. However, seismicity and ground deformation related to active dyke injection, which cannot directly be observed, are rarely captured using geophysical techniques and only a small part of a dyke-induced fault can be studied at the surface. Conversely, where ancient dykes are exposed at Earth's surface, erosion of the overlying rocks has often removed dyke-induced faults and the earthquakes that accompanied dyke injection have long-since ceased. To circumvent these problems, many computer and sandbox models have been developed to try and replicate fault growth above dykes. These models have produced numerous hypotheses for dyke-induced fault growth, but without examination of the 3D structure of natural dykes and dyke-induced faults, they cannot be tested. Therefore, despite over 40 years of research, we still do not understand the true 3D structure or evolution of dykes and dyke-induced faults.I have recently identified the first series of ancient dykes and dyke-induced faults to be observed in seismic reflection data, which provide 3D X-ray like images of Earth's subsurface, from the margins of a continent (NW Australia). These data present a unique and exciting opportunity to study the 3D structure of dykes and dyke-induced faults. By measuring offset of sedimentary rocks across faults, which record how slip accumulated, I will be able to test previous model predictions of dyke-induced fault growth. Because the processes driving dyke injection and faulting offshore of NW Australia have long-since ceased, I will also study active dyke-induced faults breaking the surface in Ethiopia. I will specifically use high-resolution, aerial Light Detection and Ranging (LiDAR) images collected in 2009 and 2012 to identify how faults grew and interacted during a single dyke injection event in 2010. Results from these analyses will be used to design of new analogue models that will replicate dyke injection and dyke-induced faulting in 3D, under different tectonic settings (e.g. extension), and using more realistic rock/magma characteristics. This cross-disciplinary research will reveal how faults grow above dykes, raising important implications for our understanding of: (i) how we can use dyke-induced fault activity to assess potential eruptions; (ii) the role dykes and dyke-induced faults play in the break-up of continents; (iii) whether dykes and dyke-induced faults influence the evolution of continental margins, which host most of the world's oil and gas; and (iv) dyke and fault structure beneath the surface of other planets (e.g. Mars).

岩浆穿过地壳到达地表，在那里它沿着垂直的路径在火山口喷发，路径呈片状（岩脉）。当堤坝被垂直或横向注入时，它们会破裂并推开周围的岩石，从而产生小地震。持续的岩脉注入导致裂缝发展成断层，裂缝一侧的岩石开始滑动通过另一侧。断层滑动可以拉下和延伸或推上岩石直接上方的堤坝，有时变形地球表面。因此，监测地震和由堤坝引发的断层引起的地面变形可以告诉我们堤坝在哪里注入，为我们提供可能爆发的警告。对埃塞俄比亚的注入岩脉和岩脉诱发断层的研究表明，它们也有助于大陆的分裂，尽管在曾经发生分裂的大陆边缘沿着尚未发现这些构造。此外，行星（如火星）的卫星图像表明，堤坝引起的断层使其表面变形。因此，很明显，岩脉注入和岩脉诱发的断层作用在塑造地球和其他行星的火山和/或构造历史和表面形态方面发挥了重要作用。为了了解岩脉和岩脉诱发的断层如何控制不同的火山、构造和行星过程，我们首先需要确定断层如何在三维空间中在岩脉上方生长。然而，地震活动和地面变形有关的活动堤坝注入，这不能直接观察到，很少被捕获使用地球物理技术，只有一小部分的堤坝引起的故障可以在表面上进行研究。相反，在地球表面暴露出古代堤坝的地方，覆盖岩石的侵蚀往往会消除堤坝引起的断层，而伴随堤坝注入的地震早已停止。为了规避这些问题，许多计算机和沙箱模型已经开发出来，试图复制断层生长以上的堤坝。这些模型已经产生了许多关于堤坝诱发断层增长的假设，但是如果没有对天然堤坝和堤坝诱发断层的三维结构进行检查，这些假设就无法得到检验。因此，尽管40多年的研究，我们仍然不了解真正的三维结构或堤坝和堤坝诱发断层的演变。我最近确定了第一个系列的古代堤坝和堤坝诱发断层中观察到的地震反射数据，提供了三维X射线像地球的地下图像，从大陆的边缘（澳大利亚西北部）。这些数据为研究堤坝和堤坝诱发断层的三维结构提供了一个独特而令人兴奋的机会。通过测量沉积岩跨越断层的偏移量，记录滑动是如何积累的，我将能够测试以前的模型预测的堤坝引起的断层增长。由于澳大利亚西北部驱动堤坝注入和断层的过程早已停止，我还将研究埃塞俄比亚活跃的堤坝诱发断层。我将特别使用2009年和2012年收集的高分辨率航空光探测和测距（LiDAR）图像，以确定2010年单一堤坝注入事件期间断层如何生长和相互作用。这些分析的结果将用于设计新的模拟模型，这些模型将在不同的构造环境（例如延伸）下，并使用更真实的岩石/岩浆特征，在3D中复制岩墙注入和岩墙引起的断层。这项跨学科研究将揭示断层如何在岩脉上方生长，对我们理解以下内容产生重要影响：（i）我们如何利用岩脉诱发的断层活动来评估潜在的喷发;（ii）岩脉和岩脉诱发的断层在大陆分裂中所发挥的作用;（iii）岩脉和岩脉诱发的断层是否影响大陆边缘的演变，而大陆边缘蕴藏着世界上大部分的石油和天然气;及（iv）其他行星（例如火星）表面下的岩脉及断层构造。

项目成果

Seismic Reflection Data Reveal the 3D Subsurface Structure of Pit Craters

• DOI: 10.1029/2021je007155
• 发表时间: 2021-12
• 期刊: Journal of Geophysical Research: Planets
• 作者: C. Magee;C. Kling;P. Byrne;C. Jackson

Can we relate the surface expression of dike-induced normal faults to subsurface dike geometry?

我们能否将岩脉诱发的正断层的表面表达与地下岩脉几何形状联系起来？

• DOI: 10.1130/g48171.1
• 发表时间: 2020
• 期刊: Geology
• 影响因子: 5.8
• 作者: Magee C

Quantifying Dyke-Induced Graben and Dyke Structure Using 3D Seismic Reflection Data and The Role of Interpretation Bias

使用 3D 地震反射数据量化堤坝诱发的地堑和堤坝结构以及解释偏差的作用

• DOI: 10.55575/tektonika2023.1.2.25
• 发表时间: 2023
• 期刊: Tektonika
• 作者: Magee C

Seismic reflection data reveal the 3D structure of the newly discovered Exmouth Dyke Swarm, offshore NW Australia

地震反射数据揭示了澳大利亚西北部近海新发现的埃克斯茅斯堤群的 3D 结构

• DOI: 10.5194/se-11-579-2020
• 发表时间: 2020
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: Magee C