Geologic Constraints on Fracture Energy of the San Andreas Fault

德克萨斯农工大学的研究人员正在利用对圣安德烈亚斯系统活动断层和出土断层的结构观察，为地震能量收支提供新的约束。特别是，工作的重点是描述地震滑动的物理过程，并量化破裂的比断裂能，它被定义为形成破裂面所消耗的能量和摩擦强度的损失。在模拟地震破裂传播动力学时，约束比破裂能是很重要的。这项研究涉及对圣安德烈亚斯活动断层和圣安德烈亚斯系统出土断层的几个关键表面的详细野外测绘、取样、光学和电子显微镜和微探针研究，以量化断层内的颗粒尺寸分布和断裂面面积，特别是断裂带内的纳米颗粒。地震断层中颗粒尺寸减小、愈合和颗粒生长的机制正在确定中。这些结果有助于建立描述发震断裂带三维结构的天气学模型，并试图将构造/岩石学特征与地震破裂成核、传播和阻止的重要力学参数联系起来。该项目正在为国家利益的广泛研究计划和倡议做出贡献，如国家减少地震风险计划、南加州地震中心和圣安德烈亚斯深度断层观测站。这项工作的科学利益是通过与更广泛的科学界中的其他研究人员协调来最大化的。这项研究为本科生和研究生提供了通过研究进行教育的机会，并解决了地震的基本物理学问题，最终可能有助于减少地震风险和改善减灾。

Researchers at Texas A&M University are using structural observations of active and exhumed faults of the San Andreas system to provide new constraints on the earthquake energy budget. In particular, work focuses on characterizing the physical processes of earthquake slip, and quantifying the specific fracture energy of rupture, which is defined as the energy consumed by the formation of the rupture surface and loss of frictional strength. Constraining the specific fracture energy is important to modeling the dynamics of earthquake rupture propagation. The research involves detailed field mapping, sampling, and optical and electron microscopy and microprobe study of several key surface exposures of the active San Andreas fault and exhumed faults of the San Andreas system to quantify particle size distributions and fracture surface area within the faults, particularly focusing on the nanoscale particles within the fault zones. The mechanisms of particle size reduction, healing and particle growth in seismic faults are being determined. The results contribute to developing synoptic models that describe the 3-D structure of seismogenic fault zones and attempt to relate structural/petrologic characteristics to the mechanical parameters important for earthquake rupture nucleation, propagation, and arrest. The project is contributing to broad research programs and initiatives of national interest, such as National Earthquake Hazard Reduction Program, the Southern California Earthquake Center, and the San Andreas Fault Observatory at Depth. The scientific benefits of this work are maximized through coordination with other researchers in the broader scientific community. The research provides education-through-research opportunities for both undergraduate and graduate students, and addresses the fundamental physics of earthquakes, which ultimately may contribute to reduction of earthquake hazards and improved mitigation.