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如何发展将导致更好地了解板块边界的变形。该项目通过调查故障系统的功/能预算来探索故障的演化。一个变形的断层系统将产生或消耗不同类型的能量，包括地球部分隆起的工作？地震释放的能量是地面震动。了解完整的工作预算可以帮助预测新的故障发展。例如，当在系统内具有新断层的能量节省大于创建新断层表面的能量成本时，新断层将发展。本研究探讨了1）理论，2）模拟桌面实验和3）地球上的自然增生楔中的断层的诞生。增生楔形成于俯冲带板块边界，在那里沉积物从下行的海洋板块上刮下来。刮下的沉积物堆积在一个加积楔中，如在俄勒冈州和智利海岸发现的。增生楔非常适合断层生长的研究，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。在其他类型的板块边界，如圣安德烈亚斯断层，岩石有数百万年的历史，活动断层系统受到岩石先前变形的影响。这项研究使用数值模型来探讨各种规模的增生楔内的工作预算。模型将测试理论公式的加积楔增长，模拟桌面沙箱实验进行，并模拟日本南海槽加积楔，其中丰富的数据是从最近和正在进行的调查。这项研究的结果将通过揭示在地球上生长新断层所需的能量来完善对断层生命周期的理解。的地壳和复活老断层。虽然该项目的重点是加积楔，因为在这些设置的材料属性是相对简单的，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，并为活动断层系统的地震事件做好沿着准备。此外，对南海增生系统的数值模拟可能会对该断裂带的未来行为产生深刻的见解，该断裂带在过去曾产生过强烈的地震和毁灭性的海啸。这项建议的一个推广部分将促进在初中和高中课堂上使用桌面沙箱实验。变形沙盒实验有助于为学生带来板块构造的生活和动手和活动的视觉性质激发学生调查地球科学的过程。

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.