Collaborative Research: Laboratory and Theoretical Investigations of the Micro-Mechanical Origins of Rate and State Friction on Tectonic Faults

在地震旋回中，由于地球板块构造运动，构造断层缓慢地积累应力。然后在地震中灾难性地失效。模拟地震周期的关键之一是摩擦定律，它既可以应用于地震的快速动态运动，如断层岩石在摩擦接触中相互摩擦和滑动，也可以应用于地震之间缓慢的应力积累过程，这可能需要数百年的时间。在普林斯顿大学和宾夕法尼亚州立大学之间的这项合作工作中，将在收集滑动界面和断层泥剪切层的超声数据的同时，对摩擦滑动进行异常控制的测量。这项工作对地震危险性评估、地震预报和提高对地震成核的基本认识具有重要的社会意义。速率和状态摩擦定律代表了目前实验室和地震物理数值模拟的最新技术，包括成核、动态破裂和完整的地震周期。然而，我们对摩擦记忆效应和滑移速度依赖关系的理解主要是经验的，这限制了我们将实验室测量应用于地震断层和/或解决与通过实验室测量预测构造断层行为相关的问题的能力。为了解决这些缺点，最近在滑动岩石表面和剪切颗粒状断层泥的超声监测方面取得的进展将为构造断层摩擦行为的物理和微观力学起源提供基本的见解。

In the earthquake-cycle, tectonic faults slowly accumulate stress, due to plate tectonic motion of Earth?s surface, and then fail catastrophically in earthquakes. One of the keys to simulating the earthquake cycle are friction laws that can be applied to both the fast, dynamic motion of earthquakes, as fault rocks rub and slide past one another in frictional contact, and the slow processes of stress accumulation between earthquakes that can take hundreds of years. In this collaborative work between Princeton and Penn State Universities, unusually well-controlled measurements of frictional sliding will be conducted while collecting simultaneous ultrasonic data on the sliding interfaces and sheared layers of fault gouge. The proposed work has important societal implications for seismic hazard assessment, earthquake forecasting, and an improved, fundamental understanding of earthquake nucleation.Rate-and-state friction laws represent the current state-of-the-art in the laboratory and for numerical simulations of earthquake physics, including nucleation, dynamic rupture and the complete seismic cycle. However, our understanding of friction memory effects and slip velocity dependence remains primarily empirical, which limits our ability to apply laboratory measurements to earthquake faults and/or to address the problems associated with predicting the behavior of tectonic faults from laboratory measurements. To address these shortcomings, recent advances in ultrasonic monitoring of sliding rock surfaces and sheared granular fault gouge will provide fundamental insights into the physics and micro-mechanical origins of frictional behavior of tectonic faults.