Geologic Constraints on Fracture Energy of the San Andreas Fault

德克萨斯A M大学的研究人员正在利用对圣安德烈亚斯系统的活动和挖掘断层的结构观测，为地震能量预算提供新的限制。 特别是，工作的重点是表征地震滑动的物理过程，并量化破裂的比破裂能，这是定义为破裂面的形成和摩擦强度损失所消耗的能量。 约束比破裂能对于地震破裂传播动力学模型的建立具有重要意义。该研究涉及详细的现场测绘，采样，光学和电子显微镜和微探针研究活动圣安德烈亚斯断层和圣安德烈亚斯系统的挖掘断层的几个关键表面暴露，以量化断层内的粒度分布和断裂表面积，特别是侧重于断层带内的纳米级颗粒。 正在确定地震断层中颗粒尺寸减小、愈合和颗粒生长的机制。 结果有助于开发天气模型，描述的3-D结构的孕震断层带，并试图将结构/岩石学特征的力学参数重要的地震破裂成核，传播和逮捕。 该项目正在为国家利益的广泛研究计划和倡议做出贡献，例如国家地震减灾计划，南加州地震中心和圣安德烈亚斯断层深度观测站。通过与更广泛的科学界的其他研究人员协调，这项工作的科学效益得到最大限度的发挥。该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灾害和改善减灾工作。

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.