Physical and Numerical Experiments of Slip Partitioning under Oblique Strike-slip

人们的注意力主要集中在主要走滑断层的主线上，例如加利福尼亚州的圣安德烈亚斯断层，因为它们有可能引发大规模破坏性地震。然而，与这些大断层相关的非走滑运动往往发生在次级断层上，这也可能是2010年海地地震所证明的大地震的来源。导致这些次级断层滑动的构造条件还没有完全了解。该项目采用物理和计算机模拟实验相结合的方法，以更好地了解为什么滑动发生在这些次级断层而不是主断层上。拟议的研究通过以下方式推动预期的社会成果：(1)妇女和残疾人通过支持一名听障女性PI和一名女研究生充分参与STEM；(2)继续指导聋人和听障学生；(3)通过在YouTube上张贴模拟实验的动画和通过网络摄像机播放Google Hangout传输实验来改进STEM教育；(4)通过研究生培训发展具有全球竞争力的STEM工作人员；以及(5)更好地了解断层系统的地震危险性，如圣安德烈亚斯断层。本项目使用物理和数值实验来研究在两种类型的背景下沿着走滑系统的滑动划分，板块倾斜运动和约束弯曲。在这两种背景下，都观察到了沿垂直断层带走滑和沿倾斜断层带斜滑的滑动分割断层，但不同模型的载荷不同。物理实验将测试走滑断层向外发展为边缘次级断层的条件。这些实验探索了滑动划分的控制和阈值，并将量化这些系统中滑动划分的性质。模拟模型利用湿高岭土模拟了一系列斜走滑边界条件，探索了次级收缩断层发育的条件。物理实验数据包括使用数字图像相关测量演变的水平位移场，使用立体成像测量隆起模式的变化，使用压力传感器测量膨胀应力，以及使用红外相机估计断层上的相对水通量。模拟实验的数据将被用来跟踪运动学效率的演变，以测试滑动分区系统是否比非分区系统更有效地适应倾斜收敛。实验的数值模拟将评估滑动分区系统的工作预算，并测试故障系统是否进化以最小化功。各种实验装置的3D数值模拟将提供完整的应力场和应变场，便于计算系统内的完整工作预算。这将提供一些见解，例如，随着断层系统的演化，对重力做功和内部变形之间的权衡提供了见解。这项研究中的物理和数值相结合的研究将在斜向走滑下的滑移分配理论与地质和实验观测之间架起一座重要的桥梁。

Much attention is focused on the main strands of major strike-slip faults, such as the San Andreas Fault in California, for their potential to generate large devastating earthquakes. However, non-strike slip motion associated with these large faults is often accommodated on secondary faults, which may also be the source of large earthquakes as demonstrated in the 2010 Haiti earthquake. The tectonic conditions that cause slip along these secondary faults are not fully understood. This project uses a combination of physical and computer modeling experiments to better understand why slip takes place on these secondary faults rather than the main fault. The proposed research advances desired societal outcomes through: (1) full participation of women and persons with disabilities in STEM through support of a hearing-impaired female PI and a female graduate student; (2) continued mentoring of deaf and hearing-impaired students; (3) improved STEM education through posting of animations from analog experiments on YouTube and web cam broadcast of experiments Google+ Hangouts transmissions; (4) development of a globally competitive STEM workforce through graduate student training; and (5) a better understanding of earthquake hazards along fault systems such as the San Andreas Fault.This project uses physical and numerical experiments to investigate slip partitioning along strike-slip systems within two types of settings, oblique plate motion and restraining bends. Both of these settings are observed to have slip partitioned faults with strike-slip along vertical fault strands and oblique slip along dipping fault strands, but the loading differs between the models. The physical experiments will test the conditions under which strike-slip faults develop outward verging secondary faults. The experiments explore the controls on and thresholds for slip partitioning and will quantify the nature of slip partitioning within these systems. The analog models utilize wet kaolin to simulate a range of oblique strike-slip boundary conditions that explore the conditions for secondary contractional fault development. The physical experiments data include measurements of the evolving horizontal displacement field using digital image correlation, changes in uplift patterns using stereo imaging, measurements of dilational stress using pressure transducers and estimates of relative water flux along faults using an infrared camera. The data from the analog experiments will be used to track the evolution of kinematic efficiency to test if slip partitioned systems accommodate oblique convergence more efficiently than non-partitioned systems. Numerical simulations of the experiments will assess the work budget of the slip partitioned systems and test if the fault systems evolve to minimize work. 3D numerical simulations of the various experimental setups will provide complete stress and strain fields that facilitate calculation of the complete work budget within the system. This will provide insights, for example, on the tradeoffs between work against gravity and internal deformation as the fault system evolves. The combined physical and numerical investigations in this proposed study will provide a critical bridge between theories of slip partitioning under oblique strike-slip and geologic and experimental observations.