Fault Speedometers, Slip Localization, and Slip Complexity on Exhumed Faults

断层上的快速滑动事件导致地震，对全球数百万人构成严重危害。 PI和学生将通过研究高度抛光，非常狭窄的断层，可能是在古代地震快速滑动的产品，调查断层的物理学。该项目的目标是检查犹他州瓦萨奇断层沿着高度抛光的断层表面，以确定产生狭窄断层的机制，并确定这些断层是否在高温下形成。 如果我们能确定高温是高速摩擦过程的结果，我们就可以利用岩石中的证据来确定断层形成的条件和过程。 该小组将对保存下来的断层表面进行实地和实验室调查。 这些数据将有助于约束解释地震如何成核和传播的断层理论模型。 这些模型可以预测断层岩的温度、断层岩的性质和断层带的大小，独立的断层速度计的研制对解释天然地震断层具有重要意义。 从断层相关岩石的结构和成分中建立滑动速率、局部化机制、高分辨率的详细地形和古代断层的运动学是非常困难的，然而这些数据对于地震成核和破裂的约束模型是重要的。 快速滑动的一个可能的指标是狭窄的、高度抛光的和彩虹色的滑动表面。 犹他州的瓦萨奇断层带挖出了许多极其狭窄、高度抛光的滑动面，这些滑动面上覆盖着纳米至微米尺度的赤铁矿或石英。 该小组将使用光学和电子显微镜、成分分析、X射线衍射、全岩地球化学和表面测量方法来检查断层表面和其中的薄彩虹色材料。他们将使用详细的微观化学分析来评估矿物转化、热液或非水蚀变过程以及滑动局部化过程的存在和/或性质。 这项研究的结果将结合起来，以评估这些表面产生地震的可能性。这里提出的分析将记录实验和自然断层面之间的相似性和差异，并与最近的工作在毫米级的下限滑动地震断层，将产生的过程中，启动和传播故障的见解。他们希望利用这些结果来表征毫米级和更小尺度下的凹凸分布，滑动局部化的机制，以及它们与地震引发所需的所谓临界滑动距离的关系。

Rapid slip events on faults resulting in earthquakes pose serious hazards to millions of people globally. The PI and students will investigate the physics of faulting by studying highly polished, very narrow faults that may be the product of fast slip during ancient earthquakes. The goals of this project are to examine highly polished fault surfaces along the Wasatch Fault, Utah, to determine the mechanisms that created the narrow faults and to determine if these faults formed at high temperatures. If we can determine that high temperatures were the result of high-speed frictional processes, we can use the evidence from the rocks to establish the conditions and processes by which faults develop. The team will undertake both field and laboratory investigations of preserved fault surfaces. The data will help constrain theoretical models of faults that explain how earthquakes nucleate and propagate. These models make predictions about the temperatures of fault rocks, the nature of faulted rock, and the size of the faulted zone.The development of independent fault speedometers has great significance for interpreting the natural seismic fault. Establishing the rate of slip, mechanisms of localization, detailed topography at higher resolution, and kinematics of ancient faults from textures and compositions of fault-related rocks is remarkably difficult, and yet these data are important for constraining models of earthquake nucleation and rupture. One possible indicator of rapid slip is a narrow, highly polished and iridescent slip surface. The Wasatch fault zone in Utah exhumed many extremely narrow, highly polished slip surfaces that are coated with nano- to micrometer scale hematite or quartz. The team will examine the fault surfaces and the thin iridescent materials within them using optical and electron microscopy, compositional analyses, X-Ray diffraction, whole-rock geochemistry and surface measurement methods. They will use detailed micro-scale chemical analyses to evaluate the presence and/or nature of mineral transformations, hydrothermal or non-aqueous alteration processes, and the processes of slip localization. The results of this study will be combined to evaluate the likelihood that these surfaces were produced seismically. The analyses proposed here will document similarities and differences between experimental and natural fault surfaces, and in concert with recent work on the mm-scale lower limit of slip on earthquake-producing faults, will yield insights into the processes that initiate and propagate faults. They hope to use the results to characterize the distribution of asperities at the mm and smaller scale, the mechanisms of slip localization, and their relationships to so-called critical slip distances that may be required for the initiation of earthquakes.