Collaborative Research: Linking slip dynamics to off-fault deformation in strike-slip fault systems

沿着大型断层（如圣安德烈亚斯断层）释放储存的能量，可能会在地震中突然发生。但是，这种储存的能量也可以通过稳定的、周期性的能量释放（被称为“慢地震”），以及断层周围区域的变形来释放。该项目研究了断层移动或“滑动”的变化是否与断层周围区域变形的可观察变化有关。实验室中的物理实验被用来复制圣安德烈亚斯断层系统的各个方面，以分离控制变形的单个因素，并了解断层滑动与变形发生位置之间的关系。了解断层本身和周围区域之间的变形分布是预测区域地震危险的关键。这个多机构项目支持五名学生（高中、本科和研究生水平），并开发新的计算工具来可视化实验结果，以及中学地球科学课程的课程活动。该项目的地质动机源于对加州中部圣安德烈亚斯断层系统两侧的观察，在那里，滑动行为沿着断层的走向发生变化，断层外变形的风格似乎在滑动行为的过渡附近发生变化。然而，自然变形系统是复杂的，很难表明滑移行为与边界变形之间的因果关系。为了简化问题，该项目在实验室中进行了一系列物理实验，控制了边界条件和材料特性。这种方法有助于评估(1)断层外变形模式，(2)地质构造如何发展，(3)系统是否达到稳态几何形状，(4)滑动速率是否影响变形模式，以及(5)某些结构是否可以诊断滑动控制。模型结果可为在岩石圈尺度断层边缘寻找特征构造、论证断层外变形的滑动控制提供指导。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The release of stored energy along large-scale faults, such as the San Andreas fault, can occur abruptly in an earthquake. But this stored energy can also be released via steady, periodic releases of energy known as "slow earthquakes", as well as through deformation in the regions around the fault. This project examines whether changes in how a fault moves or "slips" are linked to observable changes in the deformation of the regions around the fault. Physical experiments in a laboratory are used to replicate aspects of the San Andreas fault system to isolate individual factors controlling deformation and to understand the relationship between how a fault slips and where deformation occurs. Understanding how deformation is distributed between a fault itself and the surrounding regions is critical for forecasting regional earthquake hazards. This multi-institution project supports five students (high school, undergraduate, and graduate levels), and develops new computational tools for visualizing experimental results, along with curricular activities for middle school Earth Science courses.The geological motivation for this project stems from observations from central California, flanking the San Andreas fault system, where slip behavior changes along the strike of the fault, and the style of off-fault deformation appears to change near the transition in slip behavior. However, naturally deforming systems are complicated, and it is difficult to show causation between slip behavior and borderland deformation. To simplify the problem, this project incorporates a series of physical experiments in the laboratory, where boundary conditions and material properties are controlled. This approach facilitates the evaluation of (1) patterns in off-fault deformation, (2) how geologic structures develop, (3) whether the system reaches a steady-state geometry, (4) whether the rate of slip impacts patterns of deformation, and (5) whether certain structures might be diagnostic of slip control. The model results may provide guidelines for characteristic structures to look for in the borderlands of lithospheric-scale faults to demonstrate slip control of off-fault deformation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.