Collaborative Research: Statistical Physics of Fault Behavior - Dynamic Friction, Strain Localization, Comminution, Heat Transfer, and Compaction

地震、滑坡、火山和其他自然灾害都是代价高昂的公共提醒，作为景观和海岸线之美基础的地球物理过程也能够通过突然释放储存的能量造成大规模破坏。这些事件的发生和随后的传播的动力学不稳定性与基础物理学有关吗？摩擦、断裂、加热和压实--颗粒状物质受到地震断层、山坡和火山中存在的极端地球物理条件的影响。该项目旨在开发压力下粒状材料的定量预测模型。基于物理学的方法使该项目能够以一种基于以前的现象学方法无法实现的方式跨越尺度。虽然颗粒材料在自然界和技术中无处不在，但这些系统的基本物理学还没有得到很好的理解。对这些材料进行精确的物理描述，以地球物理变量和实验室观测值为动力，将有助于开发自然现象的预测模型，如地震和山体滑坡，以及食品，制药和建筑行业中出现的技术过程，包括颗粒流，运输，堵塞和包装。对这些系统中的摩擦、变形和失效的不完全理解限制了制造技术的进步以及对自然灾害的预测。从力学，统计物理学，土木工程和地球物理学的综合观点提供了广泛的科学和教育机会，对自然灾害政策和准备以及劳动力的技术培训的影响。该项目的核心是在赞助机构开发并行管道，旨在扩大和支持代表性不足的群体参与STEM领域。活动包括K-12外展，与当地社区学院（圣巴巴拉城市学院和尚潘的帕克兰学院）的合作，以及对本科生和研究生的科学、教育和专业指导。该项目建立了一个定量的，预测性的理论框架，基于非平衡统计热力学，建模的颗粒破碎，温度变化，和颗粒形状的剪切断层泥层的摩擦响应的影响，跨越广泛的速度和正常的应力。通过对岩石力学和岩石物理学社区中获得的砂和断层泥实验数据的定量拟合，验证了理论框架。目标研究包括但不限于以下内容：（Riedel，边界，Y-带）在实验室和断层尺度和这些不同模式之间的滑移的划分;颗粒破碎的动力学及其在断层弱化和断层带结构演化中的作用;热变材料特性和闪光过程在颗粒尺度上对瞬态和稳态摩擦响应的影响;颗粒棱角性对剪切断层泥层体积变化和流变性的影响该项目将定量物理参数与涉及孔隙度、温度、孔隙流体压力和摩擦力的唯象速率和状态定律联系起来。宏观动态过程，包括粘滑，和动态触发的微观机制将被确定。

Earthquakes, landslides, volcanoes, and other natural disasters are costly public reminders that geophysical processes underlying the beauty of landscapes and coastlines are also capable of massive destruction through the sudden release of stored energy. The dynamical instabilities responsible for the onset and ensuing propagation of these events are linked to fundamental physics?friction, fracture, heating, and compaction-- of granular materials subject to extreme geophysical conditions present in earthquake faults, hillsides, and volcanoes. This project aims to develop quantitative, predictive models of granular materials under stress. The physics-based approach enables the project to span scales in a manner that is inaccessible based on previous phenomenological methods. While granular materials are ubiquitous, in both nature and technology, the fundamental physics of these systems is not well understood. Development of a precise, physical description for these materials, motivated by geophysical variables and laboratory observables, will contribute to development of predictive models for natural phenomena, such as earthquakes and landslides, as well as technological processes, including granular flow, transportation, jamming, and packing, that arise in food, pharmaceutical, and construction industries. The incomplete understanding of friction, deformation, and failure in these systems limits progress in manufacturing technologies as well as forecasting natural hazards. Integrating perspectives from mechanics, statistical physics, civil engineering, and geophysics provides a wide range of scientific and educational opportunities, with impact on natural hazards policy and preparedness as well as technical training of the workforce. Central to the project is development of parallel pipelines at the sponsored institutions, aimed at broadening and supporting participation of underrepresented groups in STEM fields. Activities include K-12 outreach, collaboration with local community colleges (Santa Barbara City College and Parkland College in Champaign), and scientific, educational, and professional mentoring of undergraduate and graduate students. This project establishes a quantitative, predictive theoretical framework, based on non-equilibrium statistical thermodynamics, for modeling the influence of grain breakage, temperature variations, and grain shape on the frictional response of sheared gouge layers spanning a wide range of velocities and normal stresses. The theoretical framework is validated by quantitative fits to experimental data on sand and fault gouge obtained in the rock mechanics and geophysics communities. Target investigations include, but are not limited to the following: strain localization patterns (Riedel, boundary, Y-band) at laboratory and fault scales and partitioning of slip between these different modes; dynamics of grain breakage and its role in fault weakening and the evolution of fault zone fabric; effects of thermally-varying material properties and flash processes at the grain scale on transient and steady state frictional response; effect of grain angularity on volume changes and rheology of sheared gouge layers. The project links quantitative physical parameters to phenomenological rate-and-state laws involving porosity, temperature, pore fluid pressure, and friction. Microscopic mechanisms underlying macroscopic dynamic processes, including stick slip, and dynamic triggering will be identified.