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

大规模断层(如圣安德烈亚斯断层)的储能释放可能在地震中突然发生。但这种储存的能量也可以通过被称为“慢地震”的稳定、周期性的能量释放，以及通过断层周围区域的变形来释放。该项目研究断层移动方式的变化或“滑动”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，以隔离控制变形的个别因素，并了解断层如何滑动和变形发生在哪里之间的关系。了解变形是如何在断层本身和周围地区之间分布的，对于预测地区性地震灾害至关重要。这个多机构项目支持五名学生(高中生、本科生和研究生)，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。该项目的地质动机来自加利福尼亚州中部的观察，圣安德烈亚斯断层系统的侧翼，那里的滑动行为沿断层走向变化，断层外变形的风格似乎在滑动行为的转变附近发生变化。然而，自然变形系统复杂，很难揭示滑动行为与边界变形之间的因果关系。为了简化问题，该项目结合了实验室中的一系列物理实验，在实验室中，边界条件和材料属性受到控制。这种方法有助于评估(1)断层外变形的模式，(2)地质构造如何发展，(3)系统是否达到稳定状态，(4)滑动速度是否影响变形模式，以及(5)某些构造是否可能是滑动控制的诊断。模型结果可能为在岩石圈规模的断层边界寻找特征结构提供指导，以证明断层外变形的滑动控制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.