Frictional Behavior and Microstructural Evolution of Fault Zones: The Role of Effective Stress and Slip Rate

地震时，断层表面以每秒几厘米到每秒几米的速度滑动。这些滑移率下的摩擦特性在决定地震破裂的关键方面起着重要作用，包括地震应力降、产热和动态破裂扩展模式。然而，人们对动态滑移速度下的摩擦知之甚少。有限的可用数据是在狭窄的条件下收集的，在适合于地震成核的较低速度下，这些数据与摩擦数据库之间存在显著差异。本方案是进行从m/s到微米/s滑移速度的实验室实验。一个重要的目标将是定量地将整个速度范围内的摩擦观测联系起来，并研究将实验室摩擦数据换算成发震断层的问题。裸露的岩石表面和颗粒状断层泥将在一系列正应力和表面条件下进行研究，并根据现有的摩擦理论分析摩擦数据。实验计划的一个主要目标将是确定速度依赖摩擦和摩擦演化（状态）效应的微观力学原因。

MARONE EAR-0001127 During an earthquake, fault surfaces slip at speeds of several cm/s to several m/s. The frictional properties at these slip rates play an important role in determining key aspects of seismic rupture, including earthquake stress drop, heat production, and the mode of dynamic rupture expansion. However, little is known about friction at dynamic slip velocities. The limited available data have been collected under a narrow range of conditions and significant discrepancies exist between these data and the friction database at lower velocities appropriate to earthquake nucleation. This proposal is to conduct laboratory experiments spanning slip speeds from m/s to micron/s. An important goal will be to quantitatively connect friction observations over the entire velocity range and to study the problem of scaling laboratory friction data to seismogenic faults. Bare rock surfaces and granular fault gouge will be studied under a range of normal stresses and surface conditions, and friction data will be analyzed in terms of existing friction theory. A major goal of the experimental program will be to identify the micromechanical causes of velocity-dependent friction and friction evolution (state) effects.