The Work Budget of Fault Birth within Accretionary Systems

地球上大多数构造板块的边界都包含复杂的活动断层网络。更好地了解地质断层是如何发展的，将有助于更好地理解板块边界的变形。这个项目通过研究断层系统的功/能量预算来探索断层的演化。变形的断层系统将产生或消耗不同类型的能量，包括地球上抬起的部分？S地壳的工作，以及地震释放的地面震动能量。了解完整的工作预算有助于预测新故障的发展。例如，当在系统中具有新故障所节省的能量大于创建新故障表面的能量成本时，就会出现新故障。这项研究通过1)理论、2)模拟桌面实验和3)地球上的天然吸积楔来检验断层的诞生。在俯冲带板块边界发育吸积楔，在那里沉积物被从向下的大洋板块刮掉。刮掉的沉积物聚集在一个增长的楔形区域内，例如在俄勒冈州和智利海岸附近发现的。吸积楔非常适合于断层生长的研究，因为新的断层在系统的前部发育，在以前从未发生过断层的年轻物质中发育。在其他类型的板块边界，如圣安德烈亚斯断层，岩石已有数百万年的历史，活动断裂系统受到岩石先前变形的影响。这项研究使用数字模型来探索在不同规模的增长楔形内的工作预算。模型将测试增长楔形增长的理论公式，模拟进行的桌面沙箱实验，并模拟日本近海的南开海槽吸积楔形增长，最近和正在进行的研究提供了丰富的数据。这项研究的结果将通过揭示在地球上生长新断层和重新激活旧断层所需的能量来深化对断层生命周期的理解--S地壳。虽然该项目关注的是吸积楔，因为在这些背景下材料性质相对简单，因此其结果应该适用于任何构造板块边界内的断层生长。了解新断层如何以及何时生长，将有助于预测断层行为，并为活动断层系统发生的地震事件做好准备。此外，对南开增生系统的数值模拟可能会对该断裂带未来的行为产生洞察，该断裂带过去曾发生过强烈地震和毁灭性的海啸。该提案的一个外展部分将促进在初中和高中课堂中使用桌面沙盒实验。变形沙盒实验帮助学生将板块构造带入生活，该活动的动手和视觉性质启发学生研究地球科学过程。

Most boundaries of tectonic plates in the Earth contain complex networks of active faults. Better understanding of how geologic faults develop would lead to improved understanding of deformation at plate boundaries. This project explores the evolution of faults by investigating the work/energy budget of the fault system. A deforming fault system will produce or consume different types of energy including the work of uplifting parts of the Earth?s crust and the energy released by earthquakes as ground shaking. Understanding the complete work budget can help predict new fault development. For example, new faults will develop when the energy savings of having the new fault within the system is greater than the energy cost of creating the new fault surface. This study examines the birth of faults within 1) theoretical, 2) analog table top experiments and 3) natural accretionary wedges in the Earth. Accretionary wedges develop at subduction zone plate boundaries where sediments are scraped off of the down-going oceanic plate. The scraped off sediments accumulate within an accretionary wedge, such as found off the coast of Oregon and Chile. Accretionary wedges are well-suited for the study of fault growth because new faults develop at the front of the system within young material that has never before been faulted. At other types of plate boundaries, such as the San Andreas Fault, the rocks are millions of years old and the active fault system is influenced by previous deformation of the rocks. The study uses numerical models to explore the work budget within accretionary wedges of a variety of scales. Models will test theoretical formulations for accretionary wedge growth, simulate table-top sandbox experiments performed, and simulate the Nankai trough accretionary wedge off Japan, for which a wealth of data is available from recent and on-going investigations. The results of the study will refine the understanding of the fault life-cycle by revealing the energy required to both grow new faults in the Earth?s crust and reactivate old faults. While the project focuses on accretionary wedges, because the material properties are relatively simple in these settings, the results should be applicable to fault growth within any tectonic plate boundary. Understanding how and when new faults grow will aid in efforts to predict fault behavior and prepare for earthquake events along active fault systems. Furthermore, the numerical simulation of the Nankai accretionary system may yield insights the future behavior of that fault zone, which has generated strong earthquakes and devastating tsunamis in the past. An outreach component of this proposal will promote the use of table-top sandbox experiments within middle and high school classrooms. The deformational sandbox experiments help bring plate tectonics to life for students and the hands-on and visual nature of the activity inspires students to investigate earth science processes.