The Influence of Fault Geometry on Shallow Frictional Sliding in Subduction Zones

最近对俯冲带浅层断层的观察--一个构造板块俯冲到另一个板块之下--揭示了各种行为。这些包括海啸地震、浅层慢滑事件以及同震快速滑动向海底的延伸。俯冲带如何产生这种范围的断层行为仍然知之甚少。在这里，研究人员调查了断层网络几何形状和摩擦特性对其潜在破裂的影响。他们探索断层之间的相互作用以及与海底的相互作用是否能产生观察到的行为范围。他们采用创新的理论分析和数值模拟相结合的方法。其目标是限制浅层断层行为和大型逆冲地震之间的关系。模拟结果逐渐揭示了地震和海啸的机制。它们有助于评估相关风险。团队开发的代码作为开源与社区共享。该项目还为早期职业科学家提供支持，并为哥伦比亚大学的本科生提供培训。该项目专注于了解俯冲带浅层区域不同类型滑移行为之间的空间和时间关系。研究人员对倾斜逆冲断层上的滑动进行了补充的理论和数值分析，该断层服从速率和状态摩擦。他们使用了一种新技术来包含楔形几何图形的效果，这是浅俯冲区的典型特征。目的是确定断层的滑动稳定性如何通过摩擦和弹性性质以及有效应力与楔形锥角和断层上到沟槽的距离之间的相互作用来控制。该团队还开发并实现了一个在浅俯冲带几何形状的断层网络上滑动的数值模型。该网络由一个主要的板块界面断层和一个单一的伸展逆冲断层组成，该断层分支并与海底相交。该模型用于模拟断层网络上的滑移序列。一个特别的重点是了解浅层断层如何在产生具有不同稳定性特征的事件之间交替，以及这种行为如何影响在锁定带中成核的大型逆冲事件。这些分析将回答有关俯冲带滑动行为的重要问题，包括：断裂带几何形状如何控制逆冲断层的滑动稳定性？浅层滑动事件如何在多个地震旋回的俯冲带断层网络中成核和传播？这项裁决反映了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。

Recent observations of faults in the shallow regions of subduction zones - where one tectonic plate dives under another - have revealed a variety of behaviors. These include tsunami earthquakes, shallow slow slip events, and the extension of fast coseismic slip to the seafloor. How subduction zones produce this range of fault behaviors is still poorly understood. Here, the researchers investigate the effects of fault network geometry and frictional properties on their potential ruptures. They explore whether interactions between faults and with the seafloor can generate the observed range of behaviors. They use a combination of innovative theoretical analysis and numerical simulations. The goal is to constrain the relationships between shallow fault behavior and large megathrust earthquakes. The simulation outcomes unveil gradually the mechanics of earthquakes and tsunamis. They help assessing the associated risks. The codes developed by the team are shared with the community as open source. The project also provides support for an early career scientist and training for an undergraduate student at Columbia University.This project is focused on understanding the spatial and temporal relationships between different types of slip behavior in the shallow region of subduction zones. The researchers conduct complimentary theoretical and numerical analyses of slip on a dipping thrust fault that obeys rate and state friction. They use a new technique to include the effects of the wedge-shaped geometry that is typical of shallow subduction zones. The goal is to determine how sliding stability of the fault is controlled by interactions between frictional and elastic properties and effective stress with the wedge taper angle and distance on the fault from the trench. The team also develops and implements a numerical model for slip on a fault network in a shallow subduction zone geometry. The network consists of a main plate-interface fault with a single splay thrust fault that branches off and intersects the seafloor. The model is used to simulate sequences of slip on the fault network. A special focus is to understand how shallow fault patches can alternate between producing events with different stability characteristics, and how this behavior influences megathrust events that nucleate in the locked zone. These analyses will allow answering important questions about the slip behavior of subduction zones, including: How does fault zone geometry control the sliding stability of thrust faults? How do shallow slip events nucleate and propagate within a subduction zone fault network over multiple seismic cycles?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.